Technical field
[0001]
The present invention relates to a method of manufacturing a crank shaft by hot forging.
BACKGROUND
[0002]
Automobiles, motorcycles, the agricultural machine or a reciprocating engine of a ship or the like, in order to convert the reciprocating motion of the piston into rotational movement takes power, the crankshaft is essential. Crankshaft can be produced by die forging or casting. In particular, high strength and high rigidity may be required to the crankshaft, a crankshaft manufactured by die forging (hereinafter, also referred to as "forging crankshaft") is often used.
[0003]
　Figure 1A ~ 1C are schematic view showing a shape example of a typical forged crankshaft. Of these figures, FIG. 1A is a general view, FIG. 1B is a IB-IB cross section, FIG. 1C is a diagram showing the phase of the pin portion. In the example shown in FIG. 1B, typically referred to as a crank arm A1, and the counterweight unit W1 integral with the crank arm A1, the pin P1 and the journal portion J1 connected to the crank arm A1.
[0004]
　Figure 1A ~ FIG forged crankshaft 11 shown in 1C is a forged crankshaft of 3 cylinders -4 Like counterweight mounted on a 3-cylinder engine. Forged crankshaft 11 (hereinafter also referred to as "arm") and four journals J1 ~ J4, and three pin portions P1 ~ P3, the front portion Fr, and the flange portion Fl, 6 sheets of the crank arm and an A1 ~ A6. The arm A1 ~ A6 is, connecting the journal portion J1 ~ J4 and the pin portion P1 ~ P3, respectively. A part of the arm portions of the six arm portions A1 ~ A6 includes counterweight unit (hereinafter, also referred to as "weight part") the W1 ~ W4 integrally. More specifically, the first arm portion A1, the second arm portion A2, the fifth arm A5 and the sixth arm portion A6 is provided with a weight portion W1, W2, W3 and W4 respectively integrally. The third arm portion A3 and the fourth arm A4 is not provided with a weight portion, the shape becomes elliptical.
[0005]
　In the axial direction of the front end of the forged crankshaft 11 front section Fr is provided, the flange portion Fl is provided on the rear end. The front portion Fr leads to the first journal portion J1 of the top flange portion Fl leads to fourth journal portion J4 of the last.
[0006]
　Hereinafter, when collectively each journal portion J1 ~ J4, pin P1 ~ P3, the arm portion A1 ~ A6 and the weight portion W1 ~ W4, the sign, in the journal portion "J", a pin portion "P" , also referred to as "a", "W" in the weight portion in the arm portion. In addition, it summarizes the arm part A and its arm part A and the integral of the weight portion W also referred to as a "web". An oval-shaped arm section A, which does not include the weight portion W is also referred to as "no weight arm part".
[0007]
　As shown in FIG. 1C, 3 one pin portions P1 ~ P3 are arranged offset by 120 ° around the journal portion J. That is, first, second and third pin portions P1, P2 and P3, the first position L1, respectively, is disposed in the second position L2 and the third position L3. First position L1, mutual phase angle of the second position L2 and the third position L3 is 120 °.
[0008]
　As shown in Figure 1B, the width Bw of the weight portion W is greater than the width Ba of the arm portion A. Therefore, the weight portion W is protrudes largely from the arm portion center plane (plane including the central axis of the journal portion of the pin portion P).
[0009]
　When manufacturing the forged crankshaft having such a shape, generally, the billet is used as the starting material. The cross section perpendicular to the longitudinal direction of the billet, i.e. cross-section is round or square. Area of ​​the cross section is constant over the entire length of the billet. As used herein, "cross-section" means a section perpendicular to the axial direction of the longitudinal or forged crankshaft, each wasteland that billet or later. "Longitudinal section" means the longitudinal direction or a cross section parallel to the axial direction. Further, simply referred to as "sectional area" the area of ​​the cross section. Forged crankshaft is manufactured by undergoing the preliminary molding step, the mold forging step and burr punching process in that order. Further, if necessary, through the shaping process after the burr punching process. Usually, preforming step includes a roll forming process and the bending beating process. Die forging step includes a rough beating process and finishing beating process.
[0010]
　Figure 2A ~ Figure 2F is a schematic view for explaining a conventional general forged crankshaft manufacturing process. Of these figures, FIG. 2A shows the billet. Figure 2B shows a role wasteland. Figure 2C shows the bending wasteland. Figure 2D shows the rough forging. Figure 2E shows a finished forging. Figure 2F shows the forged crankshaft. Note that FIG. 2A ~ Figure 2F shows a series of steps in the case of producing a forged crankshaft 11 shown in FIG. 1A ~ FIG 1C.
[0011]
　Referring to FIGS. 2A ~ Figure 2F, explaining the manufacturing method of forging the crank shaft 11. First, after heating by a heating furnace a predetermined length billet 12 as shown in FIG. 2A, performing roll forming and bending beating in this order in the preforming step. In roll forming, squeeze rolling a billet 12 by using, for example, grooved roll. Thus, allocating the volume of the billet 12 in the axial direction to obtain a roll wasteland 13 is an intermediate material (see FIG. 2B). Then, the bent stamped, partially press pressure roll wasteland 13 from the axial direction perpendicular to the direction. Thus, allocating the volume of the roll wasteland 13, it is a further intermediate material bending obtain wasteland 14 (see FIG. 2C).
[0012]
　Subsequently, the rough beating process, by forging using a pair of molds bending wasteland 14 vertically to obtain a rough forged material 15 (see FIG. 2D). On its rough forging 15, roughly in the shape of the forged crankshaft (final product) is shaped. Furthermore, the finishing beating process, by forging using a pair of molds in a vertical rough forged material 15 to obtain a finish forged material 16 (see FIG. 2E). Its finish forged material 16, the shape that matches the forged crankshaft of the final product is shaped. When these rough beating and finishing beating, excess material flows out from between the parting surface of the mold facing each other, the remaining material becomes a burr B. Therefore, around the rough forging 15 and the finishing forging 16, either, burr B is attached increases.
[0013]
　The burr punching step, for example, the finish forged material 16 with burrs while maintaining across the pair of molds, punching burrs B by blade type. Accordingly, the burr B is removed from the finishing forging 16, no burr forging is obtained. Burr without forging is substantially the same shape as the forged crankshaft 11 shown in FIG. 2F.
[0014]
　The shaping step, slightly rolling a die key points of burrs without forging from above and below, to correct the burr without forging the dimensions of the final product. Here, the key point of burrs without forging, for example, a journal portion J, the pin portion P, the front portion Fr, the shaft portion such as a flange portion Fl, more arm portions A and the weight portion W. Thus, forged crankshaft 11 is produced. In the case of producing a forged crankshaft of 3 cylinders -4 Like counterweight, for adjusting the arrangement angle of the pin portion (120 ° phase angle) after the burr punching process, is that the twisting step is added .
[0015]
　Manufacturing process shown in FIGS. 2A ~ Figure 2F are not limited to forging the crank shaft of the three-cylinder -4 Like counterweight shown in FIG 1A ~ FIG 1C, it can be applied to a variety of forged crankshaft. For example, the same as that of the manufacturing process, can be produced forged crankshaft of 3 cylinders -6 Like counterweight, 4-cylinder engine, series 6-cylinder engine, V-type 6-cylinder engine, a forged crankshaft mounted in eight-cylinder engine or the like .
[0016]
　The main purpose of the pre-forming step is to allocate the volume of the billet. Therefore, the wasteland obtained by preforming step, is hardly shaped shape forged crankshaft. By thus allocating the volume of billet preforming step can reduce the formation of burrs at the die forging process in a subsequent step, thereby improving the material yield. Here, the material yield is meant forged crankshaft to the volume of the billet ratio of the volume (final product) (percentage).
[0017]
　Technology for the production of forged crankshaft, for example, JP-A-2001-105087 (Patent Document 1), JP-A-2-255240 (Patent Document 2) and JP 62-244545 (Patent Document 3) It disclosed. Patent Document 1 discloses a preformed method using the upper mold and the lower mold comprising a pair. In its preliminary molding method, when the reduction of the workpiece rod-shaped with the upper and lower molds, with extended portions of the workpiece to offset successive portions in a part thereof with respect to the axis. Thereby, as the Patent Document 1, because it can implemented extend and bend simultaneously possible to reduce the capital investment.
[0018]
　Preforming method of Patent Document 2, instead of the roll forming of a conventional two-pass, using a high-speed roll equipment 4 pass. In that pre-molding method, the cross-sectional area of ​​the roll wasteland, weight part of the forged crankshaft (final product) is determined in accordance with the distribution of the cross-sectional area of ​​the arm portion and the journal portion. Accordingly, in Patent Document 2, and it can be improved material yield.
[0019]
　Preforming method of Patent Document 3, by at least two dies move relative to pressure in a state sandwiching the billet. Material in the axial and radial directions is distributed by the rolling of the dice. Thus, axially asymmetric wasteland in accordance with the general shape of a forged crankshaft is molded. In Patent Document 3, and the axially asymmetric wasteland are obtained only preforming method described above, can be immediately proceeds to die forging.
CITATION
Patent Document
[0020]
Patent Document 1: JP 2001-105087 Patent Publication
Patent Document 2: JP-A 2-255240 Patent Publication
Patent Document 3: JP 62-244545 Patent Publication
Patent Document 4: WO 2014/091730
Summary of the Invention
Problems that the Invention is to Solve
[0021]
　In the manufacture of forged crankshaft, as described above, to improve the material yield and reduce the formation of burrs is desired. Wherein in the preformed method described in Patent Document 1, the distribution of the volume of the billet, part comprising a pin portion (hereinafter, also referred to as "pin-corresponding portion") can be somewhat eccentrically of.
[0022]
　However, the eccentric and the volume of distribution of the pin corresponding portion is insufficient, in the die forging in a subsequent step, large burrs with the shaping of the pin portion is formed. Furthermore, in the preforming method of Patent Document 1, at the site where the web, and the volume of the portion to be a weight portion, and the volume of the portion to be an arm portion provided with a weight portion integrally, allocation of not been studied. Therefore, in the die forging process in a subsequent step, in the weight portions projecting largely from the arm portion center plane, filling material is insufficient, it tends to occur underfill. To prevent the underfill weight portion may conveniently may be increased to excess volume in wasteland. However, in this case, the material yield is reduced. In the following, the site where the weight portion, also referred to as "weight equivalent part". The arm section provided integrally with the weight portion to become the site (except for the weight portion), also referred to as "arm-corresponding portion". It summarizes the weight equivalent portion and the arm portion corresponding also referred to as a "web-corresponding portion".
[0023]
　The preforming method of Patent Document 2 can not be eccentric pin portion corresponding. This is because due to the roll forming. Therefore, large burrs in shaping the pin portion by die forging in a later step are formed. Further, in the patent document 2 of the preform method, not be the volume distribution between the weight equivalent portion and the arm portion corresponding web corresponding section. This is because due to the roll forming. Therefore, in the die forging process in a subsequent step, filling material of the weight portion becomes insufficient. As a result, likely to occur missing meat.
[0024]
　According to the patent document 3 technology can be carried out without forming burrs, of the eccentric and the billet of the pin portion corresponding volume of distribution somewhat. However, will need a dedicated equipment rolling, it can not be carried out easily. Further, eccentricity and volume of distribution of the pin corresponding portion is insufficient, in the die forging in a subsequent step, large burrs with the shaping of the pin portion is formed.
[0025]
　An object of the present invention is to provide a method for producing a forged crankshaft can improve material yield.
Means for Solving the Problems
[0026]
　Method for producing a forged crankshaft according to an embodiment of the present invention includes four journals as the center of rotation, eccentric with respect to the journal portion, a first position of the phase angle is 120 °, the second position and the comprises a three pin portions which are arranged in three positions, a plurality of crank arm connecting the journal portion and the pin portion, and a plurality of counterweight unit comprising all or part of the crank arm is integrally, the a method for producing a forged crankshaft.
[0027]
　Method for producing a forged crankshaft, a first preforming step of obtaining initial wasteland from the workpiece made of the billet or stepped material, a second preforming process from initial wasteland obtain an intermediate wasteland, the final wasteland from the intermediate wasteland including the final preform to obtain a finishing forging step of forming a final wasteland to finished size forged crankshaft by die forging, a. In the first preforming step, using a first mold pair, portions serving as the pin portion of the workpiece, and a portion to be a journal portion, for rolling the axial direction perpendicular to the direction of the workpiece. Accordingly, while decreasing the cross-sectional area of ​​those sites to form a plurality of flat portions, to eccentric portion serving as a second pin portion arranged in the second position of the flat portion, and a second pin portion eccentricity of portion which becomes smaller than equal to or with eccentricity dimension finishing. In the second preforming step, using a second mold, which pressure the initial wasteland and the eccentric direction perpendicular to the direction of the site of the second pin portion in the pressing direction. Accordingly, the eccentrically to the first pin portion become sites and the third third pin portion become sites in opposite directions, which is arranged at a position disposed in the first position. The first and third eccentric weight portion serving as a pin portion is finished dimensions eccentricity (√3) / 2 equal to or smaller than a, the site becomes a counterweight unit, and a counterweight portion integrally the thickness of the portion to be a crank arm provided is larger than the thickness of the finished size. The final pre-molding step, using a third mold, and pressure of the intermediate wasteland from the axial direction perpendicular to the direction of the intermediate wasteland, further comprising: a crank arm portion comprising part the counterweight unit, and a counterweight portion integrally the portion to be, for reduction of the axial direction of the intermediate wasteland. Thus, first, while maintaining the eccentricity of the portion the second and third pin portion, the site becomes a counterweight portion, and the thickness of the portion to be a crank arm portion having an integral counterweight unit, finishing It is reduced to the thickness of the dimensions.
Effect of the invention
[0028]
　Method for producing a forged crankshaft according to an embodiment of the present invention, the first preforming step and the second preforming step, without forming burrs, to obtain an intermediate wasteland distribution of axial volume was enhanced it can. The intermediate wasteland the volume of the volume and the arm corresponding portion of the weight portion corresponding web corresponding section is appropriately distributed. Therefore, even in the final pre-molding step, it is possible to obtain with little formation of burrs, the final wasteland shape close to the shape of the forged crankshaft. By finishing forging process, it can shape the shape of the forged crankshaft from the final wasteland. From these, it is possible to improve the material yield.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029]
[Figure 1A] Figure 1A is a shape example of a typical forged crankshaft an overall view schematically showing.
FIG 1B] Figure 1B is a IB-IB cross section of Fig. 1A.
[Figure 1C] Figure 1C is a diagram showing a phase of the pin portion for forging the crank shaft of Figure 1A.
[Figure 2A] Figure 2A is a schematic diagram showing a billet in the conventional manufacturing process.
[Figure 2B] Figure 2B is a schematic diagram showing a roll wasteland in the conventional manufacturing process.
[Figure 2C] FIG 2C is a schematic diagram showing a wasteland bending in the conventional manufacturing process.
FIG 2D] FIG 2D is a schematic diagram showing a rough forged material in a conventional manufacturing process.
FIG 2E] FIG 2E is a schematic view showing the finishing forging at the conventional manufacturing process.
FIG 2F] FIG 2F is a schematic view showing a forged crankshaft in a conventional manufacturing process.
[Figure 3A] Figure 3A is a schematic diagram showing a billet in a manufacturing process of the present embodiment.
[Figure 3B] Figure 3B is a schematic diagram showing an initial rough terrain in the production process of the present embodiment.
FIG 3C] Figure 3C is a schematic diagram showing an intermediate wasteland in the production process of the present embodiment.
[Figure 3D] Figure 3D is a schematic view showing a final wasteland in the manufacturing process of the present embodiment.
FIG 3E] Figure 3E is a schematic diagram showing a finishing forging in the production process of the present embodiment.
FIG 3F] Figure 3F is a schematic view showing a forged crankshaft in the production process of the present embodiment.
[Figure 4A] Figure 4A is a longitudinal sectional view schematically showing a situation reduction at the start of the processing flow of the first preforming step.
[Figure 4B] Figure 4B is a longitudinal sectional view schematically showing a reduction at the end of the status of the processing flow of the first preforming step.
[Figure 5A] Figure 5A is a cross-sectional view showing a portion to be a pin portion arranged in the second position when pressure starts processing flow example of the first preforming step.
[Figure 5B] Figure 5B is a cross-sectional view showing a portion to be a pin portion arranged in the second position when pressure end of the working flow of the first preforming step.
[Figure 6A] Figure 6A is a cross-sectional view showing a portion to be a journal portion during rolling start of the processing flow of the first preforming step.
[Figure 6B] Figure 6B is a cross-sectional view showing a portion to be a journal portion during pressure end of the working flow of the first preforming step.
[Figure 7A] Figure 7A is a cross-sectional view showing a portion to be the web at pressure starts processing flow example of the first preforming step.
[Figure 7B] Figure 7B is a cross-sectional view showing a portion to be the web at pressure end of the working flow of the first preforming step.
[FIG. 8A] Figure 8A is a longitudinal sectional view schematically showing a situation reduction at the start of the processing flow of the second preforming step.
[Figure 8B] Figure 8B is a longitudinal sectional view schematically showing a situation reduction at the end of the processing flow of the second preforming step.
FIG 9A] FIG 9A is a cross-sectional view showing a portion to be a pin portion which is disposed in the third position when pressure starts processing flow example of a second preforming step.
[FIG. 9B] FIG 9B is a cross-sectional view showing a portion to be a pin portion which is disposed in the third position when pressure end of the working flow of the second preforming step.
FIG 10A] FIG 10A is a cross-sectional view showing a portion to be a pin portion arranged in the second position when pressure starts processing flow example of a second preforming step.
[FIG. 10B] FIG 10B is a cross-sectional view showing a portion to be a pin portion arranged in the second position when pressure end of the working flow of the second preforming step.
FIG 11A] FIG 11A is a cross-sectional view showing a portion to be a journal portion during rolling start of the processing flow of the second preforming step.
FIG 11B] FIG 11B is a cross-sectional view showing a portion to be a journal portion during pressure end of the working flow of the second preforming step.
FIG 12A] FIG 12A is a cross-sectional view showing a portion to be the web at pressure starts processing flow example of a second preforming step.
[Figure 12B] Figure 12B is a cross-sectional view showing a portion to be the web at pressure end of the working flow of the second preforming step.
FIG 13A] FIG 13A is a cross-sectional view showing a portion to be a weight without arm portion during rolling start of the processing flow of the second preforming step.
FIG 13B] FIG 13B is a cross-sectional view showing a portion to be a weight without arm portion during pressure end of the working flow of the second preforming step.
[14] FIG 14 is a schematic diagram illustrating the eccentricity of the first pin corresponding portion and the third pin-corresponding portion.
[Figure 15A] Figure 15A is a situation before reduction processing flow example of the final pre-forming step is a longitudinal sectional view schematically showing.
[FIG. 15B] FIG 15B is a longitudinal sectional view schematically showing a situation during the bottom dead center reaches the upper mold in the processing flow example of the final pre-molding step.
[FIG. 15C] FIG 15C is a longitudinal sectional view schematically showing the status of the mobile end in the axial direction in the processing flow example of the final pre-molding step.
[16] FIG 16 is a schematic diagram showing the orientation of the intermediate wasteland clamping direction by the upper and lower molds in the final pre-molding step, it is a view of the intermediate wasteland from the axial direction.
FIG 17A] FIG 17A is a cross-sectional view showing a rolling before situation when the pressure from the opening side of the lower mold the web processing unit of the concave in the second preforming step.
[Figure 17B] Figure 17B is a cross-sectional view showing a rolling end situation in the case of reduction from the second pre-forming step at the opening side of the lower mold the web processing unit concave.
FIG 18A] FIG 18A without forming a closed cross section by the pin processing unit in the second preforming step, a cross-sectional view showing the state pressure at the start of the case of rolling a pin-corresponding portion.
[Figure 18B] Figure 18B, without forming a closed cross section by the pin processing unit in the second preforming step, a cross-sectional view showing a rolling end situation in the case of rolling a pin-corresponding portion.
[FIG. 19A] Figure 19A without forming a closed cross section by the journal processing unit in the second preforming step, a cross-sectional view showing the situation at the start pressure when the pressure journal equivalent portions.
[FIG. 19B] FIG 19B, without forming a closed cross section by the journal processing unit in the second preforming step, a cross-sectional view showing a rolling end situation in the case of rolling a journal equivalent portions.
[FIG. 20A] FIG 20A is a cross-sectional view showing the situation before reduction processing flow example of partial pressure by the journal processing unit in the first preforming step.
[FIG. 20B] FIG 20B is a cross-sectional view showing a reduction at the end of the status of the processing flow example of partial pressure by the journal processing unit in the first preforming step.
[21] FIG 21 is a schematic view showing a shape example of a stepped material.
[FIG. 22A] FIG 22A is a top view schematically illustrating the situation before reduction in the final pre-forming process of the first embodiment.
[FIG. 22B] FIG 22B is a top view schematically illustrating the situation at the time the bottom dead center reaches the upper mold in the final pre-forming process of the first embodiment.
[FIG. 22C] FIG 22C is a top view schematically showing the status of the mobile end in the axial direction in the final pre-forming process of the first embodiment.
[23] FIG 23 is a schematic view showing a mold clamping direction and the posture of the intermediate wasteland by the upper and lower molds in the final pre-forming process of the embodiment 1, it is a view of the intermediate wasteland from the axial direction.
[FIG. 24A] FIG 24A is a schematic diagram showing an initial rough terrain in the manufacturing process of the second embodiment.
[FIG. 24B] FIG 24B is a schematic diagram showing an intermediate wasteland in the manufacturing process of the second embodiment.
[FIG. 24C] FIG 24C is a schematic view showing a final wasteland in the manufacturing process of the second embodiment.
[FIG. 25A] FIG 25A is a longitudinal sectional view schematically showing a situation before reduction in the final pre-forming process of the second embodiment.
[FIG. 25B] FIG 25B is a longitudinal sectional view schematically showing a situation during the bottom dead center reaches the upper mold in the final pre-forming process of the second embodiment.
[FIG. 25C] FIG 25C is a longitudinal sectional view schematically showing the movement at the end of the status of the axial direction of the final pre-forming process of the second embodiment.
FIG. 26 is a longitudinal sectional view showing a second mold used in the second preforming step of the third embodiment.
[27] FIG 27 is a longitudinal sectional view showing a second mold used in the second preforming step of the third embodiment.
DESCRIPTION OF THE INVENTION
[0030]
　Method for producing a forged crankshaft according to an embodiment of the present invention includes four journals, and three pin portions, a plurality of crank arm portion, and a plurality of counterweight portion, the manufacturing method of forging the crank shaft with a is there. The four journals becomes the center of rotation. Three pin portions are eccentric with respect to the journal portion, the phase angle is a first position of 120 °, are arranged in the second position and the third position. A plurality of crank arm portion connects the journal portion and a pin portion. A plurality of counterweight portion is all or a portion of the crank arm is provided integrally.
[0031]
　Method for producing a forged crankshaft includes a first preforming step, a second preforming step, and a final pre-molding step, and finish forging step. First preforming step, obtain an initial wasteland from the workpiece made of the billet or stepped material. Second preforming step, obtaining the intermediate wasteland from the initial wasteland. Last preforming step, to obtain a final wasteland from the intermediate wasteland. Finishing forging process, shaping the final wasteland to finished size forged crankshaft by die forging.
[0032]
　In the first preforming step, using a first mold pair, portions serving as the pin portion of the workpiece, and a portion to be a journal portion, for rolling the axial direction perpendicular to the direction of the workpiece. Accordingly, while decreasing the cross-sectional area of ​​those sites to form a plurality of flat portions, giving the eccentric portion to be a second pin portion arranged in the second position of the flat portion. Eccentricity of portion which becomes the second pin portion is equal to or smaller than the eccentric amount of the finished size.
[0033]
　In the second preforming step, using a second mold, which pressure the initial wasteland and the eccentric direction perpendicular to the direction of the site of the second pin portion in the pressing direction. Accordingly, the eccentrically to the first pin portion become sites and the third third pin portion become sites in opposite directions, which is arranged at a position disposed in the first position. First and eccentricity of portion which becomes a third pin portion finishing dimension eccentricity (√3) / 2 equal to or than the smaller. Site the counterweight unit, and the thickness of the portion to be a crank arm comprising a counterweight portion integrally, is larger than the thickness of the finished size.
[0034]
　The final pre-molding step, using a third mold, and pressure of the intermediate wasteland from the axial direction perpendicular to the direction of the intermediate wasteland, further comprising: a crank arm portion comprising part the counterweight unit, and a counterweight portion integrally the portion to be, for reduction of the axial direction of the intermediate wasteland. Thus, first, while maintaining the eccentricity of the portion the second and third pin portion, the site becomes a counterweight portion, and the thickness of the portion to be a crank arm portion having an integral counterweight unit, finishing It is reduced to the thickness of the dimensions.
[0035]
　In a typical example, if the workpiece is stepped material, the cross-sectional area of ​​the portion to be the site and journal portion comprising a pin portion, the crank arm comprises part a counterweight unit, and a counterweight portion integrally compared to the total cross-sectional area of ​​the sites where the parts, small.
[0036]
　The first mold pair used in the first preforming step portion abutting pin processing unit comprising a pin portion, and includes a portion abutting journal processing unit serving as a journal portion. In the first preforming step, by the pin processing unit and the journal processing unit, to form a flat portion by rolling the workpiece.
[0037]
　The second mold pair used in the second preforming step includes site the counterweight unit, and a portion which abuts against the web processing unit comprising a crank arm having integrally the counterweight unit. Web processing unit, one of the second mold pair comprises a portion abutting arm processing unit comprising a crank arm portion, and a portion abutting the weight processing unit serving as a counterweight unit. Arm processing unit and weight processing unit is generally concave, and, together with the arm processed portion in a concave shape of the bottom side is positioned, the weight processing unit in a concave open side is positioned. The opening width of the weight processing unit is wider as the distance from the concave bottom surface.
[0038]
　Then, in the second preforming step, as the decentering a portion serving as the first and third pin portion, the site becomes a counterweight portion, and a portion to be a crank arm portion having integrally a counterweight portion, concave deforming push of the bottom side of the web processing unit.
[0039]
　According to the manufacturing method of this embodiment, the first preforming step and the second preforming step, without the formation of burrs, it is possible to obtain the intermediate wasteland distribution of axial volume was promoted. The intermediate wasteland is (portion to be a weight portion, and the weight portion portion to be an arm portion provided integrally) web corresponding section weight equivalent portion at a volume and arm corresponding portion (weight portion of (a portion to be the weight portion) the volume of the arm portion provided integrally (excluding the weight portion) and a site) are appropriately distributed. Therefore, even in the final pre-molding step, it is possible to obtain with little formation of burrs, the final wasteland shape close to the shape of the forged crankshaft. By finishing forging process, it can shape the shape of the forged crankshaft from the final wasteland. From these, it is possible to improve the material yield.
[0040]
　Preferably, in the second preforming step, the weight equivalent portion and the arm a substantial portion when deforming push the bottom side of the concave web processing unit, the weight equivalent portion and the opening side of the web processing unit concave arm equivalent portion to distribute the volume and pressure from.
[0041]
　Site in the final pre-molding step, the pressing direction along a direction perpendicular to the axial direction of the intermediate wasteland by the third mold may be a eccentric direction of the portion which becomes the second pin portion, which is a second pin portion it may be eccentric direction perpendicular to the direction of.
[0042]
　Hereinafter, a method for manufacturing the forged crankshaft of the present embodiment will be described with reference to the drawings.
[0043]
1. Manufacturing process Example
　forged crankshaft manufacturing method of this embodiment is directed includes four journals J serving as a rotation center, and three pin portion P which is eccentric with respect to the journal portion J, the journal portion J and the pin portion a plurality of arm portions a connecting the P, all or part of the arm portion a and a plurality of weight portions W provided integrally. Three pin portions P1, P2 and P3, the first position L1, are arranged in the second position L2 and the third position L3. Hereinafter, it refers to a pin portion disposed in a first position L1 to as first pin portion P1. The pin portion arranged in the second position L2 also referred to as a second pin portion P2. The pin portion disposed in the third position L3 also referred to as a third pin portion P3. First position L1, mutual phase angle of the second position L2 and the third position L3 is 120 °. For example, forged crankshaft 11 of the three-cylinder -4 Like counterweight shown in FIG 1A ~ FIG 1C is manufactured object.
[0044]
　The manufacturing method of this embodiment includes a first preforming step, a second preforming step, and a final pre-molding step, and a finishing forging process. As a step after finishing the forging process, it may be added to the Bali punching process. If necessary, after the burr punching step may be added shaping step. Adjusting the arrangement angle of the pin portion can be carried out in the finishing forging process. Alternatively, add a step twisting after the burr punching step may be performed to adjust the arrangement angle of the pin portion at the twisting step. These series of steps is carried out in hot.
[0045]
　Figure 3A ~-3F are schematic views for explaining an example of a process of manufacturing the forged crankshaft of the present embodiment. Of these figures, FIG. 3A shows the billet. Figure 3B shows the initial wasteland. Figure 3C shows an intermediate wasteland. Figure 3D shows the final wasteland. Figure 3E shows the finish forged material. Figure 3F shows the forged crankshaft. Note that FIG. 3A ~-3F show a series of steps in the case of producing a forged crankshaft 11 having a shape shown in FIG. 1A ~ FIG 1C. Right diagram of FIG. 3B ~ FIG. 3D, the portion comprising a journal portion (hereinafter, also referred to as "journal equivalent portions") first with respect to the center of the site to be the second and third pin portion (hereinafter, "first pin equivalent unit ", also referred to as a" second pin corresponding portion "and the" third pin corresponding portion ") indicating the position of PA1, PA2 and PA3. Right diagram of FIG. 3E and 3F show a first position of the second and third pin portions P1, P2 and P3 with respect to the center of the journal portion. On the right side of the diagram of FIG. 3B ~ FIG 3D, illustrating a first position L1 ~ third position L3 of the pin portion of the forged crankshaft as a final product in phantom.
[0046]
　In the first preforming step, rolling the workpiece by using the first mold. The pressing direction at that time is the axis perpendicular to the direction of the workpiece. In this example, the billet 22 is used as the workpiece. Thus, among the billet 22, crushed three pins corresponding portions and four journal equivalent portions, reducing the cross-sectional area at their sites. Accordingly, the plurality of flat portions 23a are formed in the billet 22. Flat portion 23a is formed at a position of the pin corresponding portion and the journal portion corresponding.
[0047]
　In the first preforming step, of the flat portion 23a, it is decentered along the second pin corresponding part PA2 to the pressing direction. By this way the pin corresponding portion and the journal portion corresponding to is squeezed, the initial wasteland 23 is obtained volume is allocated. Here, the decentering amount of the second pin portion corresponding initial wasteland 23, equal to or less than the amount of eccentricity of the finished size. The eccentricity of the finished size means the eccentricity of the pin portion of the forged crankshaft. First preforming step, for example, can be carried out in accordance with the processing flow example below.
[0048]
　In the second preforming step, to further distribute the volume, the initial rough terrain 23 to pressure using a second mold pair. The pressing direction at that time is the eccentric direction perpendicular to the direction of the second pin portion corresponding PA2. Thus, the intermediate wasteland 24 is obtained. In intermediate wasteland 24, first pin portion corresponding PA1 and a third pin portion corresponding PA3 is eccentrically along the pressing direction. However, the eccentric direction of the eccentric direction and the third pin portion corresponding PA3 of the first pin portion corresponding PA1 is opposite to each other. That is, in the intermediate wasteland 24, a first pin portion corresponding PA1 the phase angle between the second pin corresponding part PA2 is 90 °. A third pin corresponding portion PA3 the phase angle between the second pin corresponding part PA2 is 90 °. Further, the first pin portion corresponding PA1 the phase angle between the third pin equivalent part PA3 is 180 °.
[0049]
　The first and the eccentric amount of the third pin corresponding portion of the intermediate wasteland 24, the eccentricity of the finished size (√3) / 2 equal to or less than a. Further, in the intermediate wasteland 24, (see FIG. 3C) thickness t1 in the axial direction of the web corresponding section is greater than the thickness of the finished size t0 (see Fig. 3F). The thickness t0 of the finished size, meaning arm portion and the axial thickness of the weight portion of the forged crankshaft (final product). The details of the second preforming step, described below.
[0050]
　The final pre-molding step, using a third die and pressure intermediate wasteland 24 from an axial direction perpendicular to the direction of the intermediate wasteland 24. Furthermore, the reduction of the web corresponding section of the intermediate wasteland 24 from the axial direction of the intermediate wasteland 24. Thus, first, while maintaining the phase angle and the amount of eccentricity of the second and third pin portion corresponding PA1, PA2 and PA3, reduced to a thickness dimension finished thickness of the web corresponding section. As a result, the final wasteland 25 is obtained an approximate shape of the forged crankshaft is shaped. Finally preforming step, for example, can be applied to molding apparatus disclosed in Patent Document 4. However, when using this apparatus, the mold members for holding the pin corresponding portion will not be moved so as to further eccentric pin substantial portion. It will be described later processing flow example of the final pre-molding step.
[0051]
　In the finishing forging, molding the final wasteland 25 to finished size forged crankshaft by die forging. Specifically, a pair of molds are used up and down. The final wasteland 25, the first and third pins corresponding portions PA1 and PA3 are in position as aligned in a horizontal plane, it is arranged on the lower mold. The forging is performed by the lowering of the upper die. That is, the pressing direction of the forging is the eccentric direction of the second pin portion corresponding PA2. Thus, with the outflow of surplus material formed burrs B, finishing forging 26 with burr can be obtained. The finishing forging 26, shaped to match the forged crankshaft of the final product is shaped. Since the approximate shape of a forged crankshaft final wasteland 25 is shaped, in the finishing forging process, it is possible to minimize the formation of burrs B.
[0052]
　In addition, in the finishing forging process, the first pin portion corresponding PA1 is the eccentric direction of the second pin portion corresponding PA2 pushed in the opposite direction, it reaches the first position L1. The third pin corresponding portion PA3 and eccentric direction of the second pin portion corresponding PA2 pushed in the opposite direction, it reaches the third position L3. Thus, the first, mutual phase angle of the second and third pin portions P1, P2 and P3 becomes 120 °.
[0053]
　The burr punching step, for example, the finish forged material 26 with burrs while maintaining across the pair of molds, punching burrs B by blade type. Thus, burr B is removed from the finishing forging 26. As a result, forged crankshaft 21 (final product) is obtained.
[0054]
　Incidentally, Patent Document 4, the molding apparatus has been proposed in which the coarse shape of the forged crankshaft molding material for out finishing the crude material was shaped. The crude material, a round billet obtained by subjecting repeat reducing rolling and clinched like. Further, in a later step, the material for finishing beating, finish forging and burr punching is performed in this order.
[0055]
　In the production method of the present embodiment, instead of reducing rolling and bending out in the manufacturing process of Patent Document 4 employs a first preforming step and the second preforming step. The final pre-forming process of this embodiment corresponds to the molding with the molding device of Patent Document 4. However, when using this apparatus, the mold members for holding the pin corresponding portion will not be moved so as to further eccentric pin substantial portion.
[0056]
2. Processing flow example of the first pre-forming step
　diagrams 4A ~ Figure 7B is a schematic diagram showing a processing flow example of the first preforming step. Of these figures, FIG. 4A is a longitudinal sectional view showing the situation at the time of rolling start, Fig. 4B is a longitudinal sectional view showing the state at the pressure ends.
[0057]
　5A and 5B are a cross-sectional view showing a portion to be a pin portion arranged in the second position (second pins corresponding portion). Of these figures, FIG. 5A shows the situation at the time of rolling start, Fig. 5B shows the situation at pressure exit. Incidentally, FIG. 5A is a VA-VA sectional view of FIG. 4A, FIG. 5B is a VB-VB cross-sectional view of FIG 4B.
[0058]
　6A and 6B are a cross-sectional view showing a portion (journal equivalent portions) serving as a journal portion. Of these figures, FIG. 6A shows the situation at the time of rolling start, Fig. 6B shows the situation at pressure exit. Note that FIG. 6A is a VIA-VIA sectional view of FIG. 4A, FIG. 6B is a VIB-VIB cross-sectional view of FIG 4B.
[0059]
　7A and 7B are a cross-sectional view showing a portion to be a web (web corresponding section). Of these figures, FIG. 7A shows the situation at the time of rolling start, Fig. 7B shows the situation at pressure exit. Note that FIG 7A is a VIIA-VIIA cross-sectional view of FIG. 4A, FIG. 7B is a VIIB-VIIB cross-sectional view of FIG 4B.
[0060]
　FIG 4A ~ FIG 7B, showing a billet 22 having a cross section of the round, and a first mold 30 of a pair in upper and lower. The first mold 30 includes a first upper die 31, and a first lower die 32. To facilitate understanding of the situation, FIG. 5A ~ FIG 7B, illustrating a central axial position C of the journal portion corresponding in circle black. Figure 5B, FIG. 6B and 7B, shown together first upper die 31 at the pressure started, the first lower die 32 and the billet 22 by the two-dot chain line. The first die 30 of the pair is provided with a pin corresponding portion abutting pin processing unit, and, abutting journal processing portion and a journal portion corresponding.
[0061]
　Pin processing unit, as shown by a thick line in FIG. 5A, the upper die pin processing unit 31b provided in the first upper die 31, and consists of the lower die pin processing unit 32b provided in the first lower die 32. Upper die pin processing unit 31b is a concave, it is possible to accommodate a billet 22. Lower die pin processing unit 32b of the first lower mold 32 is provided on the tip surface of the projection. Note that either one of the upper die pin processing unit 31b and the lower die pin processing unit 32b and the concave is not particularly limited. In other words, the lower die pin processing unit 32b may be concave capable of accommodating billet 22.
[0062]
　The first and third pins corresponding portion abutting the pin processing unit is similar to the second pin corresponding portion abutting the pin processing unit as shown in FIGS. 5A and 5B. However, in the pressing direction, the position of the first and third pins corresponding portion abutting the pin processing unit is different from the position of the second pin corresponding portion abutting pin processing unit (see FIG. 4A and FIG. 4B).
[0063]
　Journal processing unit, as shown by a thick line in FIG. 6A, the upper die journal processing portion 31a provided in the first upper die 31, and consists of a lower mold journal processing portion 32a provided on the first lower die 32. Upper die journal processing section 31a is concave, it is possible to accommodate a billet 22. Lower die journal processing unit 32a is provided on the tip surface of the projection. Note that either one of the upper mold journal processing portion 31a and the lower mold journal processing portion 32a and the concave is not particularly limited. That is, the lower mold journal processing portion 32a may be concave capable of accommodating billet 22.
[0064]
　In the first preforming step, in a state of being separated from the first upper die 31 is raised the first upper die 31 of the first lower mold 32, while a billet 22 of the first upper die 31 and the first lower die 32 It is placed. When from this state to lower the first upper die 31, as shown in FIG. 5A, the pin corresponding portion of the billet 22 is accommodated in a concave of the upper die pin processing unit 31b. Further, as shown in FIG. 6A, the journal equivalent portions is accommodated in the concave of the upper die journal processing unit 31a. Further lowering the first upper die 31, upper die pin processing unit 31b and the lower die pin processing unit 32b, and the upper mold journal processing portion 31a and the lower mold journal processing unit 32a, the billet 22 is pressure. Therefore, the cross-sectional area of ​​the pin corresponding portion and the journal portion corresponding decreases. As a result, the flat portion 23a as shown in FIGS. 5B and 6B is formed.
[0065]
　The position of the second pin corresponding portion abutting pin processing unit among the pin processing unit and the journal processing unit, as shown in FIG. 4A, the position of the first and third pins corresponding portion abutting the pin processing unit and different. Therefore, the second pin corresponding portion eccentrically along the rolling direction while being deformed. The eccentricity of the second pin corresponding section, is smaller than or equal to the eccentricity of the finished size. After completion of the reduction by the first die 30 raises the first upper die 31, take out the processed billet 22 (initial wasteland 23).
[0066]
　By adopting such a processing flow example, as the cross-sectional area of ​​the pin corresponding portion and the journal portion corresponding to pressure the pin-corresponding portion and the journal portion corresponding decreases, the material of the pin corresponding portion and the journal equivalent portions, moves in the axial direction of the billet 22. Thus, the material part to be the weight without arm portion between the pin corresponding portion and a journal portion corresponding (hereinafter, also referred to as "no weight arms corresponding portion") and flows into the web corresponding section. As a result, it is possible to obtain the initial wasteland 23 volume is distributed in the axial direction.
[0067]
　Further, in the process of lowering the first upper die 31, the opening of the concave of the upper die pin processing unit 31b is blocked by the lower die pin processing unit 32b, the upper die pin processing unit 31b and the lower die pin processing unit 32b closed section is formed (see FIG. 5A and FIG. 5B). The opening of the concave of the upper die journal processing portion 31a, closed by the lower mold journal processing unit 32a, closed section by the upper mold journal processing portion 31a and the lower mold journal processing portion 32a is formed (FIG. 6A and FIG. see 6B). Thus, there is no burr is formed between the first upper die 31 and the first lower die 32. Therefore, it improves the material yield, can facilitate the distribution of axial volume.
[0068]
　In the first pre-forming step, as described below, by partial reduction of the journal corresponding portion by the journal processing unit may prevent the formation of burrs. In addition, by partial reduction pins corresponding portion by the pin processing unit may prevent the formation of burrs.
[0069]
　In the first preforming step, from the viewpoint of promoting the distribution of axial volume, it may not be pressure on the web corresponding section by a first mold. Also, for adjusting the shape of the web corresponding section (dimension) may be pressure by partially first mold a web corresponding section (see FIGS. 7A and 7B).
[0070]
　Further, no weight arms corresponding unit, for adjusting its shape (dimension) may be pressure by partially the first mold.
[0071]
　In cross-section of the flat portion 23a, the width Bf of the pressing direction and perpendicular direction may be larger than the pressing direction thickness ta. For example, the cross-sectional shape of the flat portion 23a is elliptical or oval shape (see FIGS. 5B and 6B). The dimensions of width Bf and the thickness ta of the flat portion 23a may be different in the journal equivalent portions and the pin-corresponding portion.
[0072]
3. Processing flow example of a second preforming process
　diagram 8A ~ Figure 13B is a schematic diagram showing a processing flow example of a second preforming step. Of these figures, FIG. 8A is a longitudinal sectional view showing the situation at the time of rolling start, Fig. 8B is a longitudinal sectional view showing the state at the pressure ends.
[0073]
　9A and 9B are a cross-sectional view showing a portion to be a third pin portion (third pin corresponding portion). Of these figures, FIG. 9A shows the situation at the time of rolling start, Fig. 9B shows the situation at pressure exit. Incidentally, FIG. 9A is a IXA-IXA cross-sectional view of FIG. 8A, FIG. 9B is a IXB-IXB sectional view of FIG. 8B.
[0074]
　10A and 10B are a cross-sectional view showing a portion to be a second pin portion (second pin corresponding portion). Of these figures, FIG. 10A shows the situation at the time of rolling start, Fig. 10B shows the situation at pressure exit. Note that FIG. 10A is an XA-XA cross-sectional view of FIG. 8A, FIG. 10B is a XB-XB cross section of FIG. 8B.
[0075]
　11A and 11B are a cross-sectional view showing a portion (journal equivalent portions) serving as a journal portion. Of these figures, FIG. 11A shows the situation at the time of rolling start, Fig. 11B shows the situation at pressure exit. Note that FIG. 11A is a XIA-XIA sectional view of FIG. 8A, FIG. 11B is a XIB-XIB section view of FIG. 8B.
[0076]
　12A and 12B is a cross-sectional view showing a portion to be a web (web corresponding section). Of these figures, FIG. 12A shows the situation at the time of rolling start, Fig. 12B shows the situation at pressure exit. Note that FIG. 12A is a XIIA-XIIA section view of FIG. 8A, FIG. 12B is a XIIB-XIIB section view of FIG. 8B.
[0077]
　13A and 13B are cross-sectional views showing a portion the weight without arm portion (wait without arm equivalent portion). Of these figures, FIG. 13A shows the situation at the time of rolling start, Fig. 13B shows the situation at pressure exit. Note that FIG. 13A is a XIIIA-XIIIA sectional view of FIG. 8A, FIG. 13B is a XIIIB-XIIIB sectional view of FIG. 8B.
[0078]
　FIG 8A ~ FIG 13B, showing the initial wasteland 23 obtained in the first preforming step described above, and a second die 40 of a pair in upper and lower. The second mold 40 includes a second upper die 41, and a second lower die 42. To facilitate understanding of the situation, FIG. 9A ~ FIG 13B, showing a central axial position C of the journal portion corresponding in circle black. Further, FIG. 9B, FIG. 10B, FIG. 11B, FIG. 12B and 13B, also shown a second upper die 41 at the pressure started, the second lower mold 42 and the initial wasteland 23 by a two-dot chain line. A pair of second mold 40, the pin portion corresponding abutting pin processing unit 41b of the initial wasteland 23, 42b, 41f and 42f, the journal corresponding portion abutting journal processing portion 41a and 42a, and the web corresponding section and those comprising a upper die web processing unit 41c and the lower mold web processing unit 42c in contact.
[0079]
　Pin processing unit, the upper die pin processing unit 41b provided in the second upper die 41, 41f, and the lower die pin processing unit 42b provided in the second lower mold 42, consisting of 42f (bold line in FIG. 9A and 10A see section). Upper die pin processing unit 41b, 41f is concave, it is possible to accommodate a flat portion of the initial wasteland 23. Note that either the upper die pin processing unit 41b, 41f and the lower die pin processing unit 42b, any of 42f concave, not particularly limited. In other words, the lower die pin processing unit 42b, or may be a concave 42f is capable of accommodating billet.
[0080]
　In a third pin portion corresponding, as indicated by a thick line in FIG. 9A, the upper die pin processing unit 41b of the second upper die 41, is concave capable of housing a flat portion of the initial wasteland 23. Lower die pin processing unit 42b of the second lower mold 42 is provided on the tip surface of the projection. On the other hand, in the second pin portion corresponding, as indicated by a thick line in FIG. 10A, the lower die pin processing unit 42f of the second lower mold 42 is concave. Upper die pin processing unit 41f of the second upper die 41 is provided on the tip surface of the projection.
[0081]
　In the pressing direction and a pressing direction perpendicular to the direction (eccentric direction of the second pin portion corresponding) position of the second pin corresponding portion abutting pin processing unit shown in FIGS. 10A and 10B, in FIGS. 9A and 9B different from the position of the third pin portion corresponding abutting pin processing unit shown. Further, in the pressing direction, the position of the first pin portion corresponding abutting pin processing unit is different from the third pin portion corresponding to the position of the abutting pin processing unit.
[0082]
　Journal processing unit, as shown by the bold line in FIG. 11A, the upper die journal processing portion 41a provided in the second upper die 41, and consists of a lower mold journal processing portion 42a provided in the second lower die 42. Upper die journal processing section 41a is concave, it is possible to accommodate a flat portion of the initial wasteland 23. Lower die journal processing portion 42a of the second lower mold 42 is provided on the tip surface of the projection. Note that either one of the upper mold journal processing portion 41a and the lower mold journal processing portion 42a and the concave is not particularly limited. That is, the lower mold journal processing portion 42a may be concave capable of accommodating flat portion of the initial wasteland.
[0083]
　Web processing unit, as shown by a thick line in FIG. 12A, the upper die web processing unit 41c provided in the second upper die 41, and consists of a lower mold the web processing unit 42c provided in the second lower die 42. Cross-sectional shape of the web processing unit, as shown by a thick line in FIG. 12A, one of the upper die web processing unit 41c and the lower mold web processing unit 42c is generally concave. For example, as shown in FIG. 12A, a concave as a whole lower die web processing portion 42c of the second lower mold 42, the other of the upper mold web processing portion 41c of the second upper die 41 is a flat. Incidentally, either one of the upper mold web processing unit 41c and the lower mold web processing unit 42c and the concave can be appropriately set in accordance with the shape of the forged crankshaft.
[0084]
　Web processing portion of the recessed (lower in FIG. 12A type web processing unit 42c) abuts site the arm portion (arm portion corresponding) and 42d arm processing section abutting, portion a weight portion (weight equivalent portion) having a weight processing section 42e. Arm processing unit 42d is located on the bottom side of the concave lower mold web processing unit 42c, the weight processing unit 42e is positioned at the opening side of the concave lower mold web processing unit 42c. The opening width Bw of the weight processing unit 42e is wider as the distance from the bottom surface of the concave lower mold web processing unit 42c. For example, as shown in FIG. 12A, the weight processing unit 42e, the both side surfaces are both inclined surfaces. Further, 42d arm processing unit, both sides are parallel, an opening width Bw is constant. Incidentally, both sides of 42d arm processing unit may not be exactly parallel, allowing a slight slope.
[0085]
　In the second preforming step, larger than the thickness t0 of the dimension finishing the axial thickness t1 of the web corresponding section (see Figures and Figure 3C 3F). Therefore, the axial length of the upper die web processing unit 41c and the lower mold web processing unit 42c is greater than the thickness of the finished size of the web (the weight portion and the arm portion provided with the weight portion integrally).
[0086]
　In the second preforming step, in a state of being separated from the second upper die 41 is raised the second upper die 41 and the second lower mold 42, the initial rough terrain 23 and the second upper die 41 of the second lower mold 42 It is placed between. At that time, as the width direction of the flat portion (the major axis direction in the case of an ellipse) is the pressing direction, the initial wasteland 23, arranged in a posture rotated 90 ° around the axis from the state at the end of the first preforming step It is. Therefore, the pressing direction by the second die 40 is made eccentric direction perpendicular to the direction of the second pin portion corresponding.
[0087]
　From this state to lower the second upper die 41. Then, FIG. 9A, is housed in FIGS. 10A and 11A, the upper die pin processing unit 41b of the upper mold journal processing portion 41a and the recessed flat portion of the concave initial wasteland 23 and the lower die pin processing unit 42f . At this time, as shown in FIG. 12A, the web corresponding section, without contacting the bottom surface of the lower mold the web processing unit 42c, the web corresponding section mostly the weight processing unit 42e of the lower die web processing unit 42c It is placed in.
[0088]
　Further lowering the second upper die 41, in the third pin portion corresponding, closed section by the upper mold pin processing unit 41b and the lower mold pin processing unit 42b is formed (see FIG. 9A). In the second pin portion corresponding, it closed section formed by the upper die pin processing unit 41f and the lower die pin processing unit 42f (see FIG. 10A). Also, it closed section by the upper mold journal processing portion 41a and the lower mold journal processing portion 42a is formed (see FIG. 11A). In this state, when the reach the bottom dead center to further lower the second upper die 41, the flat portion of the inside of the upper die pin processing unit 41b and the lower mold pin processing unit 42b (third pin equivalent part) is pressure is, inside of the flat portion of the lower die pin processing unit 42f and the upper die pin processing unit 41f (second pin corresponding portion) is pressure. Also, the flat portion of the inside of the upper die journal processing portion 41a and the lower mold journal processing portion 42a is pressure. Flat portion of the initial wasteland 23 in this manner is pressure by the second mold, as a result, the cross-sectional area decreases in the journal equivalent portions and the pin-corresponding portion. Accordingly, the material became surplus to flow in the axial direction and flows into the web corresponding section, the allocation of volume progresses.
[0089]
　The third pin corresponding portion eccentrically along the pressing direction. First pin corresponding portion is eccentric to the opposite side of the third pin corresponding portion along the pressing direction. The eccentricity of the first and third pins corresponding portion equal to or smaller than the amount of eccentricity (√3) / 2 of the finished size. On the other hand, the second pin corresponding portion is located in the pressing direction and the direction perpendicular, not eccentric. Therefore, the amount of eccentricity of the second pin corresponding section remains the same or smaller than the eccentric amount of the finished size.
[0090]
　Figure 14 is a schematic diagram illustrating the eccentricity of the first pin corresponding portion and the third pin-corresponding portion. Figure 14 is a view as viewed from the axial direction of the forged crankshaft. Referring to FIG. 14, the phase difference between the second position L2 to the first position L1 and the second pin portion first pin portion of the forged crankshaft is disposed in the three-cylinder engine is disposed is 120 °. However, the first pin portion corresponding position PA1 intermediate wasteland obtained in the second preforming step the phase difference between the second pin portion corresponding position PA2 is 90 °. Therefore, the first pin portion corresponding in die forging after the final preforming step, to further eccentric to the axis position C of the journal equivalent portions. Accordingly, in the forged crankshaft as a final product, the phase difference between the first position L1 and the second position L2 is a 120 °.
[0091]
　Eccentricity of the first pin portion (finished size) is the distance DL between the axis C and the center of the journal portion of the first position L1. Therefore, the axis position C of the journal portion, when the center position PA1 of the first pin portion corresponding, and a right triangle consisting of the center of the first position L1 virtual, eccentricity of the first pin portion corresponding in the second preforming step the amount DL1 is eccentricity DL of the first pin portion (√3) / 2 equal to or less than a. Larger eccentric amount DL1 of the first pin portion corresponding than (√3) / 2 of eccentricity DL of the first pin portion, difficult to be eccentric in the subsequent step a first pin portion corresponding to the first position L1 it is. This is because must be decentered pressing direction with the first pin corresponding portion along a direction not parallel (horizontal direction in FIG. 14) to the first position L1. In the case the eccentricity DL1 of the first pin portion corresponding smaller than (√3) / 2 of eccentricity DL of the first pin portion, later in the die forging process or the like, the eccentricity DL1 of the first pin portion corresponding It is eccentric to (√3) / 2 of eccentricity DL of the first pin portion. Third pin corresponding portion is the same. For the second pin corresponding portion is smaller than the eccentricity dimension eccentric amount finish, the second pin corresponding portion in the die forging process after the final pre-molding step, with respect to the axial center position C of the journal portion corresponding further eccentrically Te.
[0092]
　Planar web processing portion among the web processing unit (FIG. 12A and the upper in Fig. 12B type web processing unit 41c) is not pressed against the web corresponding section, the web corresponding section of the concave lower mold web processing unit 42c It is pushed to the bottom side. The pushing is generated with the pressure of the first and third pins corresponding portions positioned before and after the web corresponding section (deformation). During pushing, the web corresponding section is deformed along 42d arm processing unit described above and the weight processing unit 42e. That is, the width of the web corresponding section, narrows in a concave bottom side (arm equivalent portion), it widens in concave opening side (weight equivalent portion). Further, the side surface 23b on the opening side of the web corresponding section, cross-sectional shape is an arc shape.
[0093]
　After completion of the reduction by the second die 40 raises the second upper die 41, take out the processed initial wasteland 23 (intermediate wasteland 24). In intermediate wasteland 24 thus obtained, thickness of the web corresponding section is greater than the thickness of the finished size.
[0094]
　According to a second preforming step can be eccentric without forming burrs, the first and third pins corresponding portions, respectively. Moreover, by flowing the material web corresponding section from the pin corresponding portion can allocate the volume in the axial direction. If necessary, if the flow of material to the web corresponding section from the journal equivalent portions, thereby also allocate volume in the axial direction.
[0095]
　In the second preforming step, for adjusting the weights without arm equivalent portion of the shape (dimension) may be pressure by partially second die 40 to wait without arm corresponding section (see FIGS. 13A and 13B). Also, if it is desired to flow into the material to wait without arm equivalent portion, it is not necessary to pressure the wait without arm corresponding portion by the second mold 40.
[0096]
4. Processing flow example of the final preform process
　diagram 15A ~ 15C are the processing flow example of the final pre-forming step is a longitudinal sectional view schematically showing. Of these figures, FIG. 15A shows a prior reduction conditions. Figure 15B shows the situation at the time of arrival bottom dead center of the upper die. Figure 15C shows the situation at the end axial movement. Figure 16 is a schematic diagram showing the orientation of the intermediate wasteland clamping direction by the upper and lower molds in the final pre-molding step, it is a view of the intermediate wasteland from the axial direction. Note that in FIG. 15A-FIG. 15C, the actual second pin corresponding portions will be positioned in front or back of the first and third pins corresponding unit, for convenience, shows the first to third pins corresponding unit on the same surface .
[0097]
　FIG 15A ~ FIG 15C, showing an intermediate wasteland 24 obtained in the second preforming step described above, a pair of third mold 51 up and down, the upper plate 52 and a lower plate 53. The third mold 51 is provided with a third upper die 60, and a third lower die 70. The third upper die 60 is supported on the upper plate 52. The upper plate 52 moves up and down by the actuation of the press ram (not shown). The third lower die 70, it is supported on the lower plate 53. The lower plate 53 is fixed to the base of the press machine (not shown).
[0098]
　To rolling the web corresponding section in the axial direction of the intermediate wasteland 24, third upper die 60 and the third lower die 70 is divided into a plurality of members. Members constituting the third upper die 60 and the third lower die 70 is arranged along the axial direction of the intermediate wasteland 24. The third upper die 60 and the third lower die 70, respectively, and the fixing pin-type member 64 and 74, a plurality of stationary journal type member 61 and 71, a plurality of movable journaled member 62 and 72, a plurality of movable pins and a mold member 63 and 73.
[0099]
　Fixing pin mold member 64 and 74 is arranged at a position of the second pin portion corresponding to the center among the intermediate wasteland 24. Fixing pin mold member 64 and 74, relative to the upper plate 52 and lower plate 53, which is immovable.
[0100]
　Fixing journaled member 61 and 71 are disposed before and after the axial direction of the fixed pin-type member 64 and 74. In other words, the fixed journal type member 61 and 71, the second weight without leading to pin equivalent part arm corresponding portion, second and third journal equivalent portions leading to its weight without arm equivalent portion among the intermediate wasteland 24, and its It is arranged at a position including a web portion corresponding to lead to a journal portion corresponding. Fixing journaled member 61 and 71, relative to the upper plate 52 and lower plate 53, which is immovable.
[0101]
　Movable pin mold member 63 and 73 are disposed at positions of the first and third pins corresponding portions among the intermediate wasteland 24. Movable pin mold member 63 and 73, on the upper plate 52 and lower plate 53, in the direction toward the stationary pin-type member 64 and 74 a axial direction of the intermediate wasteland 24 (fixed journal type member 61 and 71) it is movable. Movable pin mold member 63 and 73, relative to the upper plate 52 and lower plate 53, which is immovable in a direction other than the axial direction.
[0102]
　Movable journaled member 62 and 72, first and fourth journal equivalent portions among the intermediate wasteland 24, and are arranged at a position including a web portion corresponding to lead to the journal corresponding portion. Incidentally, the front side of the movable journal type member 62 and 72 is also present at the position of the portion to be the front. Movable journaled member 62 and 72 of the rear side, also present at the location of the site where the flange. Movable journaled member 62 and 72, on the upper plate 52 and lower plate 53, in the direction toward the stationary pin-type member 64 and 74 a axial direction of the intermediate wasteland 24 (fixed journal type member 61 and 71) it is movable.
[0103]
　Such third upper die 60 and the third lower die 70 made of members, each type engraved portion (reference numeral 61a in FIG. 15A, 62a, 63a, 64a, 71a, 72a, see 73a and 74a) are formed ing. Its mold engraving portion, are reflected approximate shape of forged crankshaft (final product).
[0104]
　In the final preforming step, as shown in FIG. 15A, in a state of increasing the third upper die 60, to place the intermediate wasteland 24 between the third upper die 60 and the third lower die 70. At this time, as shown in FIG. 16, the intermediate wasteland 24, the first and third pins corresponding portions PA1 and PA3 are disposed in a posture such as to line up in a vertical plane. That is, the intermediate wasteland 24, the eccentric direction of the second pin portion corresponding PA2 is arranged in a posture such that the horizontal direction. From this state, it lowers the third upper die 60. Then, the intermediate wasteland 24 is pressure from the axial direction perpendicular to the direction of the intermediate wasteland 24 (vertical direction) by a third upper die 60 and the third lower die 70 (see FIG. 15B). Thus, the journal corresponding portion of the intermediate wasteland 24, pin-corresponding portion, and the weight without arm corresponding portion is rolling, the journal portion, the approximate shape of the pin portion and weight without arm part is shaped.
[0105]
　Further, the movable journal type member 62 and 72, and the movable pin mold member 63 and 73, is moved to a axial direction of the intermediate wasteland 24 in a direction facing the fixed pin-type member 64 and 74. This movement can be implemented, for example, by the wedge mechanism or a hydraulic cylinder.
[0106]
　Movable journaled member 62 and 72, and with the axial movement of the movable pin mold member 63 and 73, the web corresponding section of the intermediate wasteland 24 is rolling in the axial direction of the intermediate wasteland 24. Thus, reduced to a thickness dimension finish thickness of the web corresponding section, the approximate shape of the arm portion and the weight portion is shaped. At that time, the pin corresponding portion does not move in the direction of eccentricity. In other words, eccentricity of the first and third pins corresponding section, the eccentricity of (√3) of finished size / 2 to be the same maintained. Eccentricity of the second pin corresponding portion is maintained the same as the eccentricity of finished size.
[0107]
　After completion of the reduction by the third mold 51, to raise the upper mold 60 to take out the processed intermediate wasteland 24 (final wasteland).
[0108]
　According to such end preforming step, since the reduction of the web corresponding section in the axial direction, with the weight portion, it can improve the filling of the material can suppress the underfill occurs. Further, since it is excellent in filling property of the material of the weight portion, without substantially forming a burr, it is possible to obtain a final wasteland.
[0109]
　According to the manufacturing method of this embodiment, the first preforming step and the second preforming step described above, without forming burrs, it is possible to obtain an intermediate wasteland. Therefore, it is possible to improve the material yield.
[0110]
　Further, according to the manufacturing method of this embodiment, the first preforming step and the second preforming step can facilitate the distribution of axial volume. In other words, it is possible to reduce the cross-sectional area of ​​the pin corresponding portion and the journal portion corresponding, can increase the cross-sectional area of ​​the web corresponding section. In the second preforming step can be the width of the web corresponding section, narrowing in the arm corresponding section, wider at the weight equivalent portion. That is, it is possible to properly distribute the volume in the web corresponding section. Therefore, in the final pre-molding step of post-process, to suppress the formation of burrs can be shaped to approximate the shape of the forged crankshaft. Since the approximate shape of the forged crankshaft using a final wasteland that is shaped, in the finishing forging process, it is possible to minimize the formation of burrs. These can improve the material yield.
[0111]
5. The thickness and volume distribution of the web corresponding section
　in the second preforming step may be thicker than the thickness dimension finished thickness of the weight without arm equivalent portion. In this case, in the final preforming step, to the reduction of weight without arm corresponding portion in the axial direction of the intermediate wasteland. Therefore, the fixed journal type member 61 and 71 used in the final pre-molding step is changed to the movable journaled member.
[0112]
　In the second pre-forming process described above, the second mold having a web processing unit is used. However, the second preforming step is not limited to such a configuration. For example, in the second preforming step, similarly to the first preforming step, without reduction of the web corresponding section, the material may be allowed to flow into the pin-corresponding portion and the journal portion corresponding.
[0113]
　When using a second mold having a web processing unit, the volume distribution of the web corresponding section according to the second preforming step, by appropriately changing the shape of the arm processing unit in response to the shape of the forged crankshaft (final product) Accordingly, it is possible to adjust. For example, to change the opening width of the arm processed portion may be or the arm machining portion and the inclined surface. Incidentally, if the arm processing portion and the inclined surface, can be extracted processed initial wasteland from the second mold (intermediate wasteland) smoothly after reduction completion.
[0114]
　The shape of the weight of the forged crankshaft (final product) is different. For example, overhanging large weight portion in the width direction, sometimes the length of the eccentric direction of the pin portion is smaller. In such a case, in the second preforming step, it is effective to change the shape of the weight processing unit. The shape change of the weight processing unit, for example, to adjust the angle of the inclined surface may be or curved a weight processing unit. Further, by rolling the web corresponding section from the opening side of the concave web processing unit may allocate the volume by weight equivalent portion.
[0115]
　17A and 17B are cross-sectional views showing a case in which pressure from the opening side of the lower mold the web processing unit of the concave site as a web (web corresponding section). Of these figures, FIG. 17A shows a prior reduction conditions, FIG. 17B shows the situation at pressure exit. In Figure 17A and 17B, compared to the view 12A and 12B, a shallow depth of the concave lower mold web processing unit 42c.
[0116]
　The processing flow example shown in FIGS. 17A and 17B, similarly to the processing flow example shown in FIG. 12A and 12B, the web corresponding section is pushed into the bottom side of the concave lower mold web processing unit 42c, a concave lower mold deformed along the web processing unit 42c. In addition, since the small depth of the concave lower mold web processing unit 42c, the end of the pressure by the second die 40, the planar upper mold web processing unit 41c on the side surface of the opening side of the web corresponding section pressing It is. Thus, the web corresponding section is pressure from the opening side of the concave lower mold web processing unit 42c, decreases with the length of the eccentric direction width increases. As a result, the volume in the weight equivalent portion is allocated.
[0117]
　When such that reduction of the side surface of the opening side of the web corresponding section, from the viewpoint of preventing the material from flowing into the web corresponding section is inhibited, it is preferred to carry out the soft reduction. Soft reduction, for example, be achieved by reduction of the part of the opening side of the side surface 23b of the web corresponding section (see FIG. 12B). In this case, the soft reduction by the material from escaping a site that is not in contact with the mold.
[0118]
6. Another aspect of the second preforming step
　in the above second preforming step, rolling pins corresponding portion in a state of forming a closed cross section by the upper mold pin processing unit and the lower die pin processing unit. However, if burrs been formed, without forming a closed cross section by the pin processing unit may pressure the pin-corresponding portion.
[0119]
　18A and 18B, without forming a closed cross section by the pin processing unit, a cross-sectional view showing a case in which pressure pins corresponding portion. Of these figures, FIG. 18A shows the situation at the time of rolling start, Fig. 18B shows the situation at pressure exit. The shape of the upper die pin processing unit 41b and the lower die pin processing unit 42b shown in FIGS. 18A and 18B is different from the shape of FIG. 9A and the upper die pin processing unit 41b and the lower die pin processing unit 42b shown in FIG. 9B. 18A and the lower die pin processing unit 42b of the upper die pin processing unit 41b and the second lower die 42 of the second upper die 41 shown in FIG. 18B are both concave. The depth of the upper die pin processing unit 41b of the second upper die 41 is deeper than the bottom die pin processing unit 42b of the second lower die 42.
[0120]
　According to the upper die pin processing unit 41b and the lower die pin processing unit 42b, with the descent of the second upper die 41, mostly second upper third pin corresponding portion of the initial wasteland 23 (pars) It is housed in the upper die pin processing unit 41b of the mold 41. In this state, further lowering the second upper die 41, a third pin portion corresponding (flat part) is eccentrically along the pressing direction. At that time, the lower mold pin processing unit 42b of the upper die pin processing unit 41b and the second lower die 42 of the second upper die 41 are both partially pins corresponding portion and abuts. In other words, the upper die pin processing unit 41b and the lower die pin processing unit 42b does not contact with the pin corresponding portion at the periphery of the parting surface. Further, the material flows out in the axial direction with the eccentric pin portion corresponding pin-corresponding portion is narrowed cross-sectional area is decreased. Therefore, it is possible to narrow without forming burrs, it causes an eccentric pin portion corresponding.
[0121]
　If you want to promote the distribution of the volume in the second preforming step, preferably rolling pins corresponding portion in a state of forming a closed cross section by the first and second pin processing unit. In view of preventing chewing out, preferably rolling pin substantial portion partially by the pin processing unit. When carrying out the partial pressure in order to prevent the formation of burrs, as the shape of the pin processing unit may use the shape of the journal processing portion shown in FIGS. 19A and 19B will be described later.
[0122]
　In the second preforming step described above, the journal equivalent portions are also pressure in a state of forming a closed cross section by the upper mold journal processing portion and the lower mold journal processing unit. However, if burrs are formed, without forming a closed cross section by the journal processing unit may pressure the journal equivalent portions. For example, as the shape of the journal processing unit may use the shape of the pin processing unit shown in FIG. 18A and FIG. 18B.
[0123]
　19A and 19B, without forming a closed cross section by the journal processing unit, a cross-sectional view showing a case in which reduction of the journal equivalent portions. Of these figures, FIG. 19A shows the situation at the time of rolling start, Fig. 19B shows the situation at pressure exit. The shape of the upper mold journal processing portion 41a and the lower mold journal processing unit 42a shown in FIGS. 19A and 19B is different from the shape of the Figure 11A and the upper mold journal processing portion 41a and the lower mold journal processing unit 42a shown in FIG. 11B. In the upper mold journal processing portion 41a and the lower mold journal processing unit 42a shown in FIGS. 19A and 19B, the upper die journal processing portion 41a of the second upper die 41, a total of can accommodate a recessed flat portion of the initial wasteland 23 there (thick line see Figure 19A). The lower mold journal processing portion 42a on the arc of the second lower mold 42 is provided on the tip surface of the projection (thick line see Figure 19A). Upper die journal processing portion 41a and the lower mold journal processing unit 42a is provided with a relief portion 41g and 42g on both ends in the width direction, the escape portion 41g and 42g extends in the width direction.
[0124]
　According to the upper mold journal processing portion 41a and the lower mold journal processing unit 42a, along with the descent of the second upper die 41, the entire flat portion of the initial wasteland 23 is housed in a concave of the upper die journal processing section 41a that. In this state, when the further lower the second upper die 41, upper die journal processing portion 41a is flattened portion abuts, followed lower mold journal processing portion 42a and comes into contact with the flat portion. The flat portion with the abutment sectional area decreases is rolling, the material volume flows in the axial direction is distributed. At that time, part of the material, but flows into the escape portion 41g and 42g, a portion of the relief portion 41g and 42g do not abut against the flat portion. Therefore, the flat portion is partially pressure, burrs are not formed.
[0125]
　If you want to promote the distribution of the volume in the second preforming step is preferably pressure journal equivalent portions while forming a closed cross section by the upper mold journal processing portion and the lower mold journal processing unit. In view of preventing chewing out, to partially pressure journal equivalent portions by the upper mold journal processing portion and the lower mold journal processing unit is preferred.
[0126]
7. Another aspect of the first preforming step
　in the above first preforming step, using the first mold 30 to form a closed cross section by the upper mold journal processing portion 31a and the lower mold journal processing unit 32a. Further, to form a closed cross section by the upper mold pin processing unit 31b and the lower die pin processing unit 32b. In this state, the pressure the entire circumference of the journal corresponding portion and the pin corresponding portion of the billet. This prevents formation of burrs. By partially rolling the journal equivalent portions by the journal processing unit may prevent the formation of burrs. Further, by rolling the pin corresponding portion partially by the pin processing unit may prevent the formation of burrs.
[0127]
　20A and FIG. 20B is a cross sectional view showing a processing flow example of partial pressure by the journal processing unit in the first preforming step. Of these figures, FIG. 20A shows a prior reduction conditions, FIG. 20B shows the situation at pressure exit. The shape of the upper mold journal processing portion 31a and the lower mold journal processing unit 32a shown in FIGS. 20A and 20B is different from the shape of the Figure 6A and the upper mold journal processing portion 31a and the lower mold journal processing unit 32a shown in FIG. 6B. As indicated by a bold line in FIG. 20A, both of the upper mold journal processing portion 31a and the lower mold journal processing portion 32a, a concave, a same depth.
[0128]
　According to the upper mold journal processing portion 31a and the lower mold journal processing unit 32a, along with the descent of the first upper die 31, the deepest portion of the upper mold journal processing portion 31a and the lower mold journal processing unit 32a is the billet 22 It abuts. In this state, further lowering the first upper die 31, upper die journal processing portion 31a and the lower mold journal processing portion 32a are both abuts partially billet 22. In other words, the upper die journal processing portion 31a and the lower mold journal processing section 32a does not contact with the billet 22 at the periphery of the parting surface. Therefore, without forming burrs can be formed flat portions reduces the cross-sectional area.
[0129]
　If you want to promote the distribution of the volume, the as shown in Figure 6A and 6B, in a state of forming a closed cross section by the journal processing unit, preferably reduction of the entire billet. In view of preventing chewing out, the as shown in Figure 20A and FIG. 20B, it is preferable to rolling the billet partially in the journal processing unit.
[0130]
　Pin processing unit of the first die 30, although not shown, FIG. 20A and employs the same configuration as the journal processing unit shown in FIG. 20B, the billet may be partially pressure of. In view of promoting the distribution of the volume, as shown in FIG. 5A and 5B, in a state of forming a closed cross section by the pin processing unit, preferably reduction of the entire billet. In view of preventing chewing out, to pressure the billet partially by the pin processing unit it is preferred.
[0131]
8. Preferred embodiments such as
　in terms of reducing the burr formed in the step after the cross-sectional area of the pin corresponding portion of the intermediate wasteland Sp2 (mm 2 ) is forged crankshaft sectional area of the pin portion (final product) Sp0 (mm 2 ) the ratio (Sp2 / Sp0) for, preferably 0.7 to 1.9. From the same viewpoint, the cross-sectional area of the pin corresponding portion of the initial wasteland Sp1 (mm 2 ) is forged crankshaft sectional area of the pin portion (final product) Sp0 (mm 2 in ratio) (Sp1 / Sp0), 0 . preferably 9 to 1.9.
[0132]
　The amount of decentering the second pin corresponding portion by first preforming step (mm), i.e. the initial wasteland 23, the second pin corresponding portion of the intermediate wasteland 24 and final wasteland 25 eccentricity Ea (mm), the eccentricity of the finished size preferably in the amount (amount of eccentricity of the pin corresponding portion of the forged crankshaft) E0 (mm) of 20% or more. More preferably at least 50% of the eccentricity E0 of finished size, and most preferably 100% of the eccentricity E0 of finished size. If less than eccentricity E0 of eccentricity Ea finish dimension of the second pin portion corresponding, it is necessary to the second pin corresponding portion by the finishing forging after the final pre-shaping step further eccentric. For this reason, it may be a flaw occurs. In the above embodiments, a case is the same (100%) and the eccentric amount E0 dimensions eccentricity Ea of the second pin portion corresponding finishing.
[0133]
　The amount of decentering the first and third pins corresponding portion by the second preforming step, i.e., the amount of eccentricity of the first and third pins corresponding portion of the intermediate wasteland 24 and final wasteland 25 Eb (mm), the eccentricity of the finished size the amount E0 (mm) of (√3) are preferably the same or smaller than a / 2. In the above embodiment, a case where eccentricity Eb of the first and third pins corresponding portion is the same as (√3) / 2 of eccentricity E0 of finished size. However, from the viewpoint of ensuring the filling of the material to the pin portion engraving unit, first and eccentricity Eb of the third pin portion corresponding final wasteland 25, the ratio eccentricity E0 of finished size (Eb / (( in √3) / 2 × E0)) , preferably in the (1.0-Dp / 2 / ( (√3) / 2 × E0)) or more. Here Dp means the diameter of the pin portion of the finished size (the diameter of the pin portion of the forged crankshaft). From the same viewpoint, the first and third cross-sectional area of the pin portion corresponding Spb final wasteland 25 (mm 2 ) is forged sectional area of the pin portion of the crank shaft Sp0 (mm 2 ratio) ((Spb) / Sp0) in, preferably to 0.7 or more and 1.5 or less, more preferably to 0.75 to 1.1.
[0134]
　From the viewpoint of improving the filling property of the weight of the material in a later step, in the second preforming step, the thickness of the web corresponding section of the intermediate wasteland 24 t1 (mm), the ratio finished size t0 (mm) (t1 / t0 ) in may preferably be 1.1 or more, more preferably 1.5 or more. On the other hand, when the ratio (t1 / t0) is greater than 3.5, bulge deformation area of ​​the material surface is increased, the dimensional accuracy of the arm portion outer periphery may be reduced. Therefore, it is preferable to the ratio of (t1 / t0) and 3.5 or less.
[0135]
　From the standpoint of preventing underfill weight portion while ensuring the filling property of the weight of the material in a later step, the cross-sectional area of the web corresponding section of the intermediate wasteland Sw2 (mm 2 ), the web of forged crankshaft (final product) the cross-sectional area Sw0 (mm 2 in ratio) (Sw2 / Sw0), preferably 0.3 to 0.9. From the same viewpoint, the initial cross-sectional area of the web corresponding section of wasteland Sw1 (mm 2 ) is forged crankshaft webs of the cross-sectional area of the (final product) Sw0 (mm 2 in ratio) (Sw1 / Sw0), 0.2 it is preferable to and ~ 0.8. Here, the cross-sectional area Sw1 web corresponding section, the cross-sectional area of the arm portion corresponding the sum of the cross-sectional area of the weight portion corresponding. Further, the cross-sectional area of the web Sw0 is a cross-sectional area of the weight portion, the weight portion is the sum of the cross-sectional area of the arm portion provided integrally.
[0136]
　From the viewpoint of reducing burrs to be formed in a later step, the cross-sectional area of the journal portion corresponding intermediate wasteland Sj2 (mm 2 cross-sectional area of the journal portion of) the forged crankshaft (final product) Sj0 (mm 2 ratio) ( Sj2 / Sj0 in), preferably 1.0 to 1.9. From the same viewpoint, the cross-sectional area of the journal portion corresponding initial wasteland Sj1 (mm 2 ) is forged crankshaft cross-sectional area of the (final product) Sj0 (mm 2 in ratio) (Sj1 / Sj0), 1.2 ~ 1 It is preferable to a .9.
[0137]
　In the manufacturing process examples shown in FIG. 3A ~ Figure 3F, although the workpiece and billet 22 may be a stepped element with the workpiece.
[0138]
　Figure 21 is a schematic view showing a shape example of a stepped material. In stepped material 27 shown in FIG. 21, similarly to the initial wasteland 23 shown in FIG. 3B, the pin corresponding portion and the journal equivalent portions are narrowed as compared with the web portion corresponding. That is, the cross-sectional area of ​​the pin corresponding portion and the journal portion corresponding is smaller than the cross-sectional area of ​​the web corresponding section. Stepped material 27 is different from the initial wasteland 23 shown in FIG. 3B, no eccentric none of the pin corresponding portion. Stepped material 27, for example, it can be molded using a reducer roll or cross rolls.
[0139]
　When such a stepped material workpiece, in the first preforming step, to the reduction of the stepped material by a first mold of a pair of above. Specifically, pressure pins corresponding portion by the pin processing unit, and further reduce the cross-sectional area of ​​the pin corresponding portion to form a flat portion. In addition, reduction of the journal corresponding portion by the journal processing unit, to form a flat portion to further reduce the cross-sectional area of ​​the journal portion corresponding. Further, decentering the second pin corresponding portion.
[0140]
9. Other embodiments
Embodiment 1]
　FIGS. 22A ~ FIG 22C is a top view showing schematically a final pre-molding step in a manufacturing method of the first embodiment. Of these figures, FIG. 22A shows a prior reduction conditions. Figure 22B shows the situation at the time of arrival bottom dead center of the upper die. Figure 22C shows the situation at the end axial movement. Figure 23 is a schematic view showing a mold clamping direction and the posture of the intermediate wasteland by the upper and lower molds in the final pre-forming process of the embodiment 1, it is a view of the intermediate wasteland from the axial direction. Manufacturing method of Embodiment 1, as compared to the embodiment shown above in FIG. 3A ~ 21, the form of the third mold used in the final pre-molding step is different. The other configuration is the same as the above embodiment. In order to facilitate the understanding of the situation, FIG. 22A ~ FIG 22C, a third lower die 70 of the third upper die and a third lower die 70 constituting the third mold 51. FIG 22A, shows an outline of the intermediate wasteland 24 by broken lines. Figure 22B and Figure 22C shows no burrs.
[0141]
　In the above embodiment, as shown in FIGS. 15A and 16, the intermediate wasteland 24 is a position as the first and third pins corresponding portions PA1 and PA3 are arranged in a vertical plane, on the third lower die 70 It is placed in. Therefore, as shown in FIG. 15B, when the third upper die 60 by the downward movement of the third upper die 60 is a third lower die 70 transgressions clamping journal equivalent portions and the pin corresponding portion, the first and third It is rolling along the eccentric direction of the pin corresponding portions PA1 and PA3.
[0142]
　In contrast, in Embodiment 1, as shown in FIGS. 22A and 23, the intermediate wasteland 24 is a position as the first and third pins corresponding portions PA1 and PA3 are arranged in a horizontal plane, the third lower die 70 It is placed on top of. Therefore, as shown in FIG. 22B, the third upper die by lowering the third upper mold and is the third lower die 70 transgressions clamping journal equivalent portions and the pin corresponding portion, the first and third pins corresponding eccentric direction perpendicular to the direction of the parts PA1 and PA3 are rolling from (eccentric direction of the second pin portion corresponding PA2).
[0143]
　Thus, in the final pre-forming process of the first embodiment, the posture of the intermediate wasteland 24, the first and third pins corresponding portions PA1 and PA3 are position as aligned in a horizontal plane. The attitude is the same as the final wasteland posture of after finishing the forging step. Therefore, the position of the burr formed at the final pre-molding step, the position of the burr formed in the finishing forging process, coincide. Therefore, even burrs are formed at the final pre-molding step, the burr, be with burrs which are formed in the finishing forging process, is removed in the subsequent burr punching process.
[0144]
[Embodiment 2]
　FIGS. 24A ~ FIG 24C is a schematic view for explaining an example of a process of manufacturing the forged crankshaft of the second embodiment. Of these figures, FIG. 24A shows the initial wasteland. Figure 24B shows the intermediate wasteland. FIG. 24C shows the final wasteland. Figure 25A ~ FIG 25C is a longitudinal sectional view schematically showing a final pre-molding step in the manufacturing method of the second embodiment. Of these figures, FIG. 25A shows a prior reduction conditions. Figure 25B shows the situation at the time of arrival bottom dead center of the upper die. Figure 25C shows the situation at the end axial movement. Manufacturing method of Embodiment 2 is different from the embodiment shown in above FIG 3A ~ 21, the form of the initial wasteland 23 obtained in the first preforming step is different. Form of intermediate wasteland 24 obtained in the second preforming step is different. Moreover, the form of the final wasteland 25 obtained in the final preforming process is different. The other configuration is the same as the above embodiment. The final position of the intermediate wasteland 24 of the preliminary molding step, the first and third pins corresponding portion is position as aligned in a vertical plane.
[0145]
　As shown in FIGS. 24B and FIG. 25A, the amount of eccentricity of the second pin portion corresponding PA2 intermediate wasteland 24 is smaller than the eccentricity of the finished size. Eccentricity of the first and third pins corresponding portions PA1 and PA3 are of eccentricity of finished size (√3) / less than 2. In the first pre-forming step, as the amount of eccentricity of the second pin portion corresponding PA2 is such eccentricity, the initial wasteland 23 is molded (see FIG. 24A). In the second preforming step, as the amount of eccentricity of the first and third pins corresponding portions PA1 and PA3 is such eccentricity, the intermediate wasteland 24 is molded. Then, in the final pre-forming step, similarly to the above embodiments, the pin corresponding portion does not move in the direction of eccentricity. Therefore, as shown in FIG. 24C, FIG. 25B and FIG. 25C, the eccentricity of the pin corresponding portion of the final wasteland 25 is unchanged and the eccentric amount of the pin corresponding portion of the intermediate wasteland 24. In other words, the amount of eccentricity of the second pin portion corresponding final wasteland 25 is smaller than the eccentricity of the finished size. Eccentricity of the first and third pins corresponding portions PA1 and PA3 are of eccentricity of finished size (√3) / less than 2.
[0146]
　Next, in the finish forging step, the final wasteland 25, the first and third pins corresponding portions in position as aligned in a horizontal plane, is arranged on the lower mold. The forging is performed by the lowering of the upper die. Here, at the stage of final wasteland 25 is placed on the lower mold, the second pin corresponding portion of the final wasteland 25 has emerged from the pin portion engraving portion formed on the lower mold. This is because less than the amount of eccentricity of the second eccentric amount of the pin portion corresponding finishing dimensions of the final wasteland 25. Even in such a state, the upper die descends into contact with the second pin portion corresponding, the pin corresponding portion is pushed into the pin portion for engraving portion of the lower die. Therefore, the second pin portion which became the eccentric amount of the finishing size is obtained.
[0147]
　Further, at the stage of final wasteland 25 is placed on the lower mold, the first and third pins corresponding portion of the final wasteland 25 is offset from the pin portion engraving portion formed on the lower mold. This is because less than the final first and the eccentric amount of the third pin portion corresponding wasteland 25 finishing dimension eccentricity of (√3) / 2. Even in such a state, the upper mold descends by contacting the first and third pins corresponding section, these pins corresponding portion is pushed into the engraving portion pin portions of the lower mold. Thus, the first and third pin portion became eccentricity of finished size is obtained.
[0148]
　A second mold used in the final pre-forming process of the second embodiment may be applied to the second mold forms such as the embodiment 1.
[0149]
[Embodiment 3]
　FIGS. 26 and 27 are sectional views showing a second mold used in the second preforming step of the third embodiment. Second preliminary molding step of the third embodiment, as compared with the embodiment shown in above FIG 3A ~ 21, the form of the second mold used in the second preforming step is different.
[0150]
　In Embodiment 1 and 2 above, there is a possibility that the following problems arise. Referring to FIG. 8A, in a state of being separated from the second upper die 41 and the second lower mold 42, the initial wasteland 23 is disposed on the second lower die 42. As described above, in the second preforming step, thereby decentering the first pin corresponding portion, and a third pin portion corresponding. Lower die pin processing unit 42h for processing the first pin portion corresponding initial wasteland 23 protrudes from the lower mold journal processing unit 42a. Therefore, placing initial wasteland 23 to the second lower mold 42, the initial wasteland 23 tilts. In this state, when the second die 40 under pressure the initial rough terrain 23, for initial wasteland 23 is inclined, easy initial wasteland 23 moves in the axial direction. The initial wasteland 23 during pressure moves, the position of the initial wasteland 23 second mold 40 is pressure is deviated from a predetermined position. That is, the pin processing unit of the second die 40 may occur a situation such that reduction of the web corresponding section of the initial wasteland 23. Therefore, the intermediate wasteland after reduction, may underfill or the like is generated.
[0151]
　Referring to FIGS. 26 and 27, the manufacturing apparatus of the third embodiment, a fourth lower mold 92 in place of the lower die pin processing unit 42h. The fourth lower mold 92, and the second die 40 can be raised and lowered independently. Before reduction of the initial wasteland 23, fourth lower die 92 is disposed at the same height as or lower the lower die journal processing unit 42a. That is, the fourth lower mold 92 does not protrude from the lower mold journal processing unit 42a. Therefore, before rolling start, even if the initial wasteland 23 disposed on the second lower mold 42, the initial wasteland 23 is kept substantially horizontally.
[0152]
　Further, in Embodiment 3, after the reduction start of the initial wasteland 23 by reduction and simultaneous or lower mold journal processing portion 42a of the initial wasteland 23 by the lower mold journal processing portion 42a, pressure of the initial wasteland 23 according to the fourth lower mold 92 is started It is. Therefore, during rolling of the first pin portion corresponding upper mold journal processing portion 41a, the journal portion corresponding initial wasteland 23 is pressure by the lower mold journal processing unit 42a. That is restrained journal equivalent portions of the initial wasteland 23 upper die journal processing portion 41a, the lower mold journal processing unit 42a.
[0153]
　In short, since the journal equivalent portions of it and initial wasteland 23 fourth lower die 92 is independently elevator is reduction in the pin portion corresponding simultaneously with or prior, during rolling of the pin corresponding portions initial wasteland 23 axially difficult to move in. Thus, the initial wasteland 23 that is volume allocation, because it is rolling at a predetermined position of the second die 40, underfill, etc. to an intermediate wasteland after reduction is less likely to occur. The same applies to the third pin portion corresponding. That is, the manufacturing apparatus of Embodiment 3 includes a fourth lower die 92 for rolling a first pin portion corresponding, the fourth mold 90 consisting of the fourth upper die 91. for rolling a third pin portion corresponding.
[0154]
　Description will be given of a configuration of the second die 40 and the fourth mold 90 according to the third embodiment. Fourth mold 90, in order to independently lower the pin processing unit includes a control mechanism. Control mechanism, for example a die cushion, a hydraulic cylinder.
[0155]
　Referring to FIG. 26, the control mechanism will be described a die cushion 81. The second lower mold 42 is supported on the bolster base 82 via the die cushion 81. Die cushion 81 has a buffering function. The fourth lower mold 92 is supported on the bolster base 82 via the pin base 83. When the second lower mold 42 starts to pressure the initial wasteland 23, the buffering function of the die cushion 81, a fourth lower mold 92 starts to protrude from the second lower die 42. Upper die journal processing unit 41a, after the lower mold journal processing portion 42a is in contact journal equivalent portions of the initial wasteland 23 abutting simultaneously or equivalent, as the fourth lower die 92 abuts the pin corresponding portion of the initial wasteland 23 die cushion 81 is set. Thus, the pin corresponding portion of the initial wasteland 23 is pressure after starting pressure simultaneously or journal equivalent portions and journal equivalent portions.
[0156]
　Referring to FIG. 27, the case control mechanism is a hydraulic cylinder 84. Hydraulic cylinder 84 can raise and lower the fourth lower die 92. The fourth lower mold 92 is supported on the bolster base 82 via a hydraulic cylinder 84. When the second lower mold 42 starts to pressure the initial wasteland 23, the hydraulic cylinder 84 is actuated, the fourth lower mold 92 starts to protrude from the second lower die 42. Upper die journal processing unit 41a, after the lower mold journal processing portion 42a is in contact journal equivalent portions of the initial wasteland 23 abutting simultaneously or equivalent, as the fourth lower die 92 abuts the pin corresponding portion of the initial wasteland 23 hydraulic cylinder 84 is set. Thus, the pin corresponding portion of the initial wasteland 23 is pressure after starting pressure simultaneously or journal equivalent portions and journal equivalent portions.
[0157]
　Also the control mechanism in either case the die cushion or hydraulic cylinders, the timing of the fourth lower mold 92 protrudes from the second lower mold 42 is appropriately set. That is, the pin corresponding portion of the initial wasteland 23 may be pressure at the same time as the reduction of the journal equivalent portions. Pin equivalent unit may be reduction in the period from after the start pressure of the journal portion corresponding to pressure completion. Pin equivalent unit may be pressure after completion pressure journal equivalent portions.
[0158]
　The same applies to the fourth upper die 91. Therefore, detailed description of the fourth upper die 91 will be omitted.
[0159]
　In addition, the present invention is not limited to the above embodiments, without departing from the scope of the present invention, it is needless to say various modifications are possible.
Industrial Applicability
[0160]
　The present invention can be effectively utilized in the production of forged crankshaft mounted in reciprocating engine 3 cylinders.
DESCRIPTION OF SYMBOLS
[0161]
　21 forged crankshaft
　22 billet
　23 initial wasteland
　23a flat portion
　23b web corresponding section of the opening side of the side surface
　24 intermediate wasteland
　25 Last wasteland
　26 finish forged material
　27 stepped material
　30 first mold
　31 first upper die
　31a upper die journal machining part
　31b upper die pin processing unit
　32 first lower mold
　32a under type journal processing portion
　32b lower die pin processing unit
　40 the second mold
　41 and the second upper die
　41a upper die journal processing section
　41b upper die pin processing unit (third pin equivalent
　part) 41c upper die web processing unit
　41f upper die pin processing unit (second pin equivalent
　part) 41 g relief portion
　42 the second lower mold
　42a under type journal processing unit
　42b under type pin processing unit (third pin corresponding
　portion) 42c lower die web processing unit
　42d arm processing unit
　42e weight processing unit
　42f lower die pin processing unit (second pin equivalent
　part) 42 g escape portion
　51 third mold
　52 upper plate
　53 the lower plate
　60 third upper die
　61 fixed journal type member
　62 movable journaled member
　63 movable pin mold member
　64 fixing pin mold member
　70 third lower die
　71 fixed journal type member
　72 movable journaled member
　73 movable pin mold member
　74 fixing pin mold member
　90 fourth mold
　91 fourth upper die
　92 fourth lower die
　A, A1 ~ A6 crank arm portion
　J, J1 ~ J4 journal portion
　P, P1 ~ P3 pin portion
　W, W1 ~ W4 counterweight unit
　PA , PA1 ~ PA3 pin corresponding section
　B Bari

The scope of the claims
[Requested item 1]
　Four journals as the center of rotation, the eccentric to the journal portion, a first position of the phase angle is 120 °, and three pin portions which are arranged in the second position and the third position, the a plurality of crank arm portion connecting the pin portion and the journal portion, all or a portion of said crank arm is a method for producing a forged crankshaft comprising a plurality of counterweight unit, the provided integrally,
　the manufacturing method,
　a first preforming step of obtaining initial wasteland from the workpiece made of the billet or stepped material,
　a second preforming step of obtaining an intermediate wasteland from the initial wasteland,
　to obtain a final wasteland from the intermediate wasteland final a preforming step,
　it includes a finishing forging step of forming said final wasteland to finished size of the forged crankshaft by die forging, and
　in the first preforming step, single Using a first mold, the portion serving as the pin portion of the workpiece, and a portion serving as the journal portion, by pressure from the axial direction perpendicular to the direction of the workpiece, each sites while forming a plurality of flat portions reduces the cross-sectional area of the site, is eccentric portion serving as a second pin portion arranged in said second position of said flat portion, and the second pin portion eccentricity becomes smaller than equal to or eccentric amount of finished size of,
　and in the second preforming step, using a second mold, the eccentric direction perpendicular to the direction of the part to be the second pin portion by rolling the initial wasteland in the pressing direction, eccentric to the first first pin portion become site and the third third pin portion become sites in opposite directions, which is disposed in a position which is disposed in a position is, portions to be the first and third pin portion Sites of eccentricity finishing smaller than equal to or an eccentric amount of (√3) / 2 dimension, the said crank arm having integrally the site becomes counterweight part, and the counterweight unit thickness, greater than the thickness of the finished size of
　the said final preform step, using a third mold, and pressure of the intermediate wasteland the axial direction perpendicular to the direction of the intermediate wasteland, further wherein the counterweight site the parts, and the portion serving as the crank arm having integrally the counterweight unit, by rolling in the axial direction of the intermediate wasteland, the first, the portion to be the second and third pin portion while maintaining the eccentricity, the said crank arm portion comprising part serving as the counterweight unit, and the counterweight unit integrally The position of the thickness, is reduced to the thickness of the finished size, the production method of the forged crankshaft.
[Requested item 2]
　A method of manufacturing a forged crankshaft according to claim 1,
　wherein the final in preforming step, said third axis direction and the pressing direction along the vertical direction of the by die intermediate wasteland, the second pin portion become a eccentric direction of the site, the production method of the forged crankshaft.