Technical field
[0001]
　The present invention relates to a method of manufacturing a crank shaft by hot forging.
BACKGROUND
[0002]
　Automobiles, motorcycles, in agricultural machinery or 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]
　1A and 1B are schematic views 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. In the example shown in FIG. 1B, typically referred to as a crank arm A7, the counterweight portion W7 integral with the crank arm A7, the pin P4 and the journal J4 connected to the crank arm A7.
[0004]
　Crankshaft 11 shown in FIGS. 1A and 1B are a crank shaft of a four-cylinder -8 Like counterweight mounted on a 4-cylinder engine. Crankshaft 11 includes five journal portions J1 ~ J5, four pin portions P1 ~ P4, the front portion Fr, and the flange portion Fl, 8 sheets of the crank arm portion (hereinafter, also referred to as "arm") A1 and a ~ A8. The arm A1 ~ A8 is, connecting the journal portion J1 ~ J5 and the pin portion P1 ~ P4, respectively. The arm portions A1 ~ A8 of eight (all) comprises counterweight unit (hereinafter, also referred to as "weight part") the W1 ~ W8 integrally. The front section Fr is provided in the axial direction of the front end of the crankshaft 11, a flange portion Fl is provided on the rear end. The front section Fr will lead to the first journal portion J1 of the top flange portion Fl leads to the fifth journal portion J5 of the last tail.
[0005]
　Hereinafter, when collectively each journal portion J1 ~ J5, pin P1 ~ P4, the arm portions A1 ~ A8, and the weight portion W1 ~ W8, 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".
[0006]
　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 overhangs greatly from the arm portion center plane (plane including the central axis of the journal portion J of the pin portion P).
[0007]
　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 crankshaft of the 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 the steps of clinching the roll forming. Die forging process includes the steps of rough beating and finishing beating.
[0008]
　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 the crankshaft 11 of the shape shown in FIG. 1A and 1B.
[0009]
　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).
[0010]
　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 a crank shaft (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 finishing forging 16, shaped to conform to the 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, rough forging 15 and the finishing forging 16 are both burr B is attached largely around.
[0011]
　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.
[0012]
　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.
[0013]
　Manufacturing process shown in FIGS. 2A ~ Figure 2F is not limited to the crank shaft of a four-cylinder -8 Like counterweight shown in FIG. 1A and 1B, it can be applied to various crankshaft. For example, it can be applied to the crankshaft of a four-cylinder -4 Like counterweight.
[0014]
　4 If the crankshaft of the cylinder -4 sheets counterweight, among eight arm portions A1 ~ A8, a part of the arm portion comprises a weight portion W integrally. For example, the first arm portion A1 of the top eighth arm portions A8 and the center of the two arm portions of the tail (the fourth arm portions A4 and the fifth arm A5) has a weight portion W integrally. Further, the remaining arm portions, specifically, the second, third, arm portions of the sixth and 7 (A2, A3, A6 and A7) is not provided with a weight portion, the shape and oval Become.
[0015]
　In addition, three-cylinder engine, series 6-cylinder engine, V-type 6-cylinder engine, even crankshaft mounted in eight-cylinder engine or the like, the manufacturing process is the same. Incidentally, when the adjustment of the arrangement angle of the pin portion is required, after the burr punching process, twisting process is added.
[0016]
　The main purpose of the pre-forming step is to allocate the volume of the billet. Therefore, the wasteland obtained by preforming, 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 2001-105087 (Patent Document 1), in JP-A-2-255240 (Patent Document 2) and JP-A-10-029032 (Patent Document 3) It is 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]
　Patent Document 3, in the mold forging, discloses a technique for a perpendicular stamping direction (pressing direction) relative to the projecting direction of the weight portion. Accordingly, in Patent Document 3, in the mold forging, and to be able to improve the filling of the material of the weight portion protruding largely from the arm portion center plane. In the technique of Patent Document 3, parting surfaces of the upper and lower molds are arranged at the vertices of the projecting shape of the weight portion, excess material from between the upper and lower molds to flow out as a burr.
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-A 10-029032 JP
Patent Document 4: WO 2014/038183
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, it is possible to perform allocation and offset of the volume of the billet to some extent.
[0022]
　However, 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]
　And 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 techniques can be improved to some extent the filling properties of the weight of the material in the die forging. However, in the technique of Patent Document 3, the material yield decreases as the burr is formed. The material yield by the conventional manufacturing method is not sufficient. Therefore, it is desirable to further improve the material yield.
[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 a plurality of journal portion as a rotational center, a plurality of pin portions eccentric to the journal portion and the journal portion and the connecting pin portion a plurality of crank arm portion When all or part of the crank arm is a manufacturing method of a forged crankshaft comprising a plurality of counterweight unit, the provided integrally.
[0027]
　Method for producing a forged crankshaft, a first preforming step of obtaining initial wasteland from billet, the second preforming step from the initial wasteland obtain an intermediate rough terrain, and the final pre-forming step from the intermediate wasteland obtain the final wasteland, die forging by comprising a finishing forging step of forming a final wasteland to finished size of the crankshaft, a. In the first preforming step, portions to be the pin portion of the billet, and the site of the journal portion, for rolling the axial direction perpendicular to the direction of the billet. Thus, to reduce the cross-sectional area of ​​those sites to form a plurality of flat portions. In the second preforming step, using a first mold pair, to pressure the initial wasteland and the width direction of the flat portion in the pressing direction. From this, smaller than equal to or with eccentricity dimension finishing eccentricity of the portion the pin portion, the thickness of the portion to be a crank arm portion comprising part the counterweight unit, and a counterweight portion integrally but it is larger than the thickness of the finished size. The final pre-molding step, using a second 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, while maintaining the eccentricity of the portion the 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 is reduced to the thickness of the finished 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, with little form burrs can be obtained a final wasteland shape close to the shape of the crankshaft. By finishing forging process, it can shape the shape of the 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 schematic diagram showing an example of the overall shape of the typical forged crankshaft.
FIG 1B] Figure 1B is a IB-IB cross section of Fig. 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 showing the rolling before the situation in the processing flow example of the first pre-forming step is schematically shown.
[Figure 4B] Figure 4B is a longitudinal sectional view schematically showing a situation during rolling completion in the processing flow example of the first preforming step.
[Figure 5A] Figure 5A is a cross-sectional view showing a portion to be a journal portion of the front pressure in the processing flow of the first preforming step.
[Figure 5B] Figure 5B is a cross-sectional view showing a portion to be a journal portion during rolling completion in the processing flow example of the first preforming step.
[Figure 6A] Figure 6A is a cross-sectional view showing a portion to be a pin portion of the front pressure in the processing flow of the first preforming step.
[Figure 6B] Figure 6B is a cross-sectional view showing a portion to be a pin portion at the rolling termination in the processing flow example of the first preforming step.
[Figure 7A] Figure 7A is a cross-sectional view showing a portion to be a reduction before the web in the processing flow of the first preforming step.
[Figure 7B] Figure 7B is a cross-sectional view showing a portion to be a reduction at the end of the web in the processing flow of the first preforming step.
[FIG. 8A] Figure 8A is a longitudinal sectional view schematically showing the situation at the time of rolling start in the processing flow of the second preforming step.
[Figure 8B] Figure 8B is a longitudinal sectional view schematically showing a situation during rolling completion in the processing flow example of a second preforming step.
FIG 9A] FIG 9A is a cross-sectional view showing a portion to be a reduction at the start of the web in the processing flow of the second preforming step.
[FIG. 9B] FIG 9B is a cross-sectional view showing a portion to be a reduction at the end of the web in the processing flow of the second preforming step.
FIG 10A] FIG 10A is a cross-sectional view showing a portion to be a journal portion during rolling start in the processing flow of the second preforming step.
[FIG. 10B] FIG 10B is a cross-sectional view showing a portion to be a journal portion during rolling completion in the processing flow example of a second preforming step.
FIG 11A] FIG 11A is a cross-sectional view showing a portion to be a pin portion at the rolling start in the processing flow of the second preforming step.
FIG 11B] FIG 11B is a cross-sectional view showing a portion to be a pin portion at the rolling termination in the processing flow example of a second preforming step.
FIG 12A] FIG 12A is a situation before reduction processing flow example of the final pre-forming step is a longitudinal sectional view schematically showing.
[Figure 12B] Figure 12B 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. 12C] FIG 12C 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.
[13] FIG 13 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.
[Figure 14A] Figure 14A is a cross-sectional view showing a rolling before situation in the case of rolling a portion to be the web from the opening side of the concave web processing unit.
FIG 14B] FIG 14B is a cross-sectional view showing a rolling end situation in the case of rolling a portion to be the web from the opening side of the concave web processing unit.
[Figure 15A] Figure 15A is a cross-sectional view showing the situation at the time of rolling start in the processing flow example of partial pressure by the journal processing unit in the second preforming step.
[FIG. 15B] FIG 15B is a cross-sectional view showing the situation at the reduction ended in the processing flow example of partial pressure by the journal processing unit in the second preforming step.
[Figure 16A] Figure 16A is a cross-sectional view showing the situation at the time of rolling start in the processing flow example of partial pressure by the pin processing unit in the second preforming step.
[FIG. 16B] FIG 16B is a cross-sectional view showing the situation at the reduction ended in the processing flow example of partial pressure by the pin processing unit in the second preforming step.
FIG 17A] FIG 17A is a cross-sectional view showing the situation before reduction in the processing flow example of partial pressure by the journal processing unit in the first preforming step.
[Figure 17B] Figure 17B is a cross-sectional view showing the situation at the reduction ended in the processing flow example of partial pressure by the journal processing unit in the first preforming step.
FIG 18A] FIG 18A is a top view schematically illustrating the situation before reduction in the final pre-forming process of the first embodiment.
[Figure 18B] Figure 18B 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.
[Figure 18C] FIG 18C 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.
[19] FIG 19 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. 20A] FIG 20A is a longitudinal sectional view schematically showing a situation before reduction in the final pre-forming process of the second embodiment.
[FIG. 20B] FIG 20B 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. 20C] FIG 20C 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.
[21] FIG 21 is a longitudinal sectional view showing a first mold used in the second preforming step of the third embodiment.
[22] FIG 22 is a longitudinal sectional view showing a first 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 a plurality of journal portions, and a plurality of 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. A plurality of journal portion becomes the center of rotation. A plurality of pin portion is eccentric to the journal portion. 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 billet. 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 of the crank shaft by the die forging.
[0032]
　In the first preforming step, portions to be the pin portion of the billet, and the site of the journal portion, for rolling the axial direction perpendicular to the direction of the billet. Thus, to reduce the cross-sectional area of ​​those sites to form a plurality of flat portions.
[0033]
　In the second preforming step, using a first mold pair, to pressure the initial wasteland and the width direction of the flat portion in the pressing direction. From this gives eccentric portion serving as a pin portion. Its eccentricity is equal to or smaller than the eccentric amount of the finished size. 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 second 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, while maintaining the eccentricity of the portion the 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 is reduced to the thickness of the finished dimensions.
[0035]
　In a typical example, the first mold pair used in the second preforming step, the site becomes a counterweight unit, and site abutting the web processing unit comprising a crank arm comprising a counterweight portion integrally, site abutting pin processing unit comprising a pin portion, and includes a portion abutting journal processing unit serving as a journal portion. Web processing unit, one of the first 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 thereby position the arm processed portion to a concave bottom side, located a wait processing section in a concave open side, the opening width of the weight processing unit, It becomes wider as the distance from the concave bottom.
[0036]
　Then, in the second preforming step, rolling the flat portion by the pin processing unit and the journal processing unit. Thus, the site becomes a counterweight portion, and a portion to be a crank arm portion having an integral counterweight portion deforms push the bottom side of the concave web processing unit.
[0037]
　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, with little form burrs can be obtained a final wasteland shape close to the shape of the crankshaft. By finishing forging process, it can shape the shape of the crankshaft from the final wasteland. From these, it is possible to improve the material yield.
[0038]
　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.
[0039]
　Site in the final pre-molding step, the pressing direction along a direction perpendicular to the axial direction of the intermediate wasteland by the second mold may be the eccentric direction perpendicular to the direction of the site of the pin portion, which is a pin portion or it may be in the eccentric direction.
[0040]
　Hereinafter, a method for manufacturing the forged crankshaft of the present embodiment will be described with reference to the drawings.
[0041]
1. Manufacturing process Example
　forged crankshaft manufacturing method of this embodiment is to subject a plurality of journal portion J as a center of rotation, a plurality of 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. For example, FIG. 1A and 4 cylinders -8 sheets counterweight of the crankshaft 11 shown in FIG. 1B is manufactured object. 4 If the crankshaft of the cylinder -8 sheets counterweight comprises all of the plurality of arm portions A is the weight portion W integrally. Crankshaft such four-cylinder -4 sheets counterweight described above is also manufactured object. 4 If the crankshaft of the cylinder -4 sheets counterweight comprises a portion of the plurality of arm portions A is the weight portion W integrally. The shape of the arm portion without a weight portion is oval shaped.
[0042]
　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. If adjustment of the arrangement angle of the pin portion is required, after the burr punching step may be added torsional step. These series of steps is carried out in hot.
[0043]
　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 the crankshaft 11 of the shape shown in FIG. 1.
[0044]
　In the first preforming step, out of the billet 22 is a workpiece, a plurality of parts comprising a pin portion (hereinafter, also referred to as "pin-corresponding portion"), and a plurality of sites comprising a journal portion (hereinafter, "Journal equivalent reducing the cross-sectional area in each part "also referred to). Along with this, a plurality of flat portions 23a in the billet. Flat portion 23a is formed at a position of the pin corresponding portion and the journal portion corresponding. Flat portion 23a, as shown in FIGS. 5B and 6B described later, a large pressure direction perpendicular to the direction of the width Bf than the thickness ta of the pressing direction. Such volume obtain initial wasteland 23 which are distributed in the. The first pre-forming step, for example, can be used reducer roll or cross rolls. The first preforming step can also be carried out according to the processing flow example of using the third mold described below.
[0045]
　In the second preforming step, to further distribute the volume, the initial rough terrain 23 to pressure using a first mold pair. The pressing direction at that time is the width direction of the flat portion 23a. Thus, the intermediate wasteland 24 without burrs can be obtained. In 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). Further, eccentricity of the pin corresponding portion of the intermediate wasteland 24 is the same as the eccentricity of finished size. The eccentricity of the finished size means the eccentricity of the pin portion of the forged crankshaft. For details of the second preforming step, described below.
[0046]
　The final pre-molding step, using a second mold, which pressure the 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, while maintaining the eccentricity of the pin corresponding part, it is reduced to the 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. Eccentricity of the pin corresponding portion of the final wasteland 25, unchanged from the eccentricity of the pin corresponding portion of the intermediate wasteland 24 is the same as the eccentricity of finished size. Finally preforming step, for example, can be used forming apparatus described 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.
[0047]
　In the finishing forging step, as in the conventional finishing beating process described above, forming the final wasteland 25 to finished size of the crank shaft by the die forging. Specifically, a pair of molds are used up and down. The final wasteland 25, the pin corresponds 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. Thus, with the outflow of surplus material formed burrs B, finishing forging 26 with burr can be obtained. The finishing forging 26, shaped to conform to the crankshaft of the final product is shaped. Since the final wasteland 25 approximate the shape of the crankshaft is shaped, when subjected to forging the final wasteland 25 in the finishing forging process, it is possible to minimize the formation of burrs B.
[0048]
　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.
[0049]
　Incidentally, Patent Document 4, the molding apparatus for molding materials for striking finishing the crude material rough shape of the crankshaft is shaped has been proposed. 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.
[0050]
　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.
[0051]
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 a prior reduction conditions, FIG. 4B is a longitudinal sectional view showing the state at the pressure ends.
[0052]
　5A and 5B are a cross-sectional view showing a portion (journal equivalent portions) serving as a journal portion. Of these figures, FIG. 5A shows a prior reduction conditions, Figure 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.
[0053]
　6A and 6B are a cross-sectional view showing a portion (pin portion corresponding) comprising a pin portion. Of these figures, FIG. 6A shows a prior reduction conditions, Figure 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.
[0054]
　7A and 7B are a cross-sectional view showing a portion to be a web (web corresponding section). Of these figures, FIG. 7A shows a prior reduction conditions, Figure 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.
[0055]
　FIG 4A ~ FIG 7B, showing a billet 22 having a cross section of the round, and a third mold 30 of a pair in upper and lower. The third die 30 is provided with a third upper die 31, and a third lower die 32. To facilitate understanding of the situation, 5B, in FIGS. 6B and 7B, the third upper die 31 before reduction, together with a third lower die 32 and the billet 22 are also shown by two-dot chain line, the journal equivalent portions It shows a central axial position C by a circle of black. A pair of third mold 30 includes a pin portion corresponding abutting pin processing unit, and, abutting journal processing portion and a journal portion corresponding.
[0056]
　Journal processing unit, as shown by a thick line in FIG. 5A, the upper die journal processing portion 31a provided in the third upper die 31, and consists of a lower mold journal processing portion 32a provided on the third 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.
[0057]
　Pin processing unit, as shown by a thick line in FIG. 6A, the upper die pin processing unit 31b provided in the third upper die 31, and consists of the lower die pin processing unit 32b provided in the third 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 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.
[0058]
　In the first pre-forming step, as shown in FIG. 4A, in a state of being separated from the third upper die 31 is raised a third upper die 31 of the third lower die 32, the billet 22 and the third upper die 31 disposed between the third lower die 32. When from this state to lower the third upper die 31, the pin corresponding portion is accommodated in a concave of the upper die pin processing unit 31b, the journal corresponding portion is accommodated in a concave of the upper die journal processing portion 31a of the billet 22 . Further lowering the third upper die 31, upper die pin processing unit 31b and the lower die pin processing unit 32b billet 22 and the upper mold journal processing portion 31a and the lower mold journal processing section 32a, is pressure, pressure has been site sectional area of ​​the decrease. As a result, the flat portion 23a as shown in FIGS. 5B and 6B is formed. In cross-section of the flat portion 23a, the width Bf is greater than the thickness ta (see FIG. 5B and FIG. 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. After completion of the reduction by the third mold 30, to raise the third upper die 31, take out the processed billet 22 (initial wasteland 23).
[0059]
　By adopting such a processing flow example, as to pressure the pin-corresponding portion and the journal portion corresponding, material is moved in the axial direction of the billet. Thereby, the material flows into the web corresponding section between the pin corresponding portion and a journal portion corresponding. As a result, it is possible to obtain an initial wasteland volume is distributed in the axial direction.
[0060]
　Further, according to the processing flow example shown in FIGS. 4A ~ Figure 7B, in the process of lowering the third 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, closed section is formed by the upper die pin processing unit 31b and the lower die pin processing unit 32b. 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. Thus, no burr is formed between the third upper die 31 and the third lower die 32. Therefore, it improves the material yield, can facilitate the distribution of axial volume.
[0061]
　When using the third mold pair 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 the third mold. Also, for adjusting the shape of the web corresponding section (dimension) may be pressure by partially third mold 30 the web corresponding section (see FIGS. 7A and 7B). For example, as the width Bb of the web corresponding section is the same as the width Bf of the flat portion may be pressure by partially third mold the web corresponding section.
[0062]
3. Processing flow example of a second preforming process
　diagram 8A ~ Figure 11B 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.
[0063]
　9A and 9B are a cross-sectional view showing a portion to be a web (web corresponding section). 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.
[0064]
　10A and 10B are a cross-sectional view showing a portion (journal equivalent portions) serving as a journal portion. Among these drawings, 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.
[0065]
　11A and 11B are a cross-sectional view showing a portion (pin portion corresponding) comprising a pin 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.
[0066]
　FIG 8A ~ FIG 11B, showing the initial wasteland 23 obtained in the first preforming step described above, the first mold 40 of a pair in upper and lower. The first mold 40 includes a first upper die 41, and a first lower die 42. To facilitate understanding of the situation, 9B, FIG. 10B and 11B, the first upper die 41 at the pressure start, with the first lower mold 42 and the initial rough terrain 23 are also shown by two-dot chain line, the journal corresponding the axis position C parts shown by a circle of black. The first mold pair 40, embryonic web corresponding section of wasteland 23 and the upper mold web processing unit 41c abuts and the lower mold web processing unit 42c, the pin-corresponding portion and the upper die pin processing unit 41b and the lower die pin working in contact with parts 42b, and includes a journal portion corresponding upper die journal processing portion 41a and the lower mold journal processing portion 42a abuts.
[0067]
　Cross-sectional shape of the web processing unit, as shown by a thick line in FIG. 9A, is concave as a whole lower die web processing unit 42c. The other of the upper mold web processing unit 41c is planar. 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.
[0068]
　Web processing portion of the recessed (lower in FIG. 9A-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. 9A, 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.
[0069]
　In the second preforming step, as described above, larger than the thickness dimension finished thickness of the web corresponding section. 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 arm portion and the weight portion thereof arm portions is provided integrally).
[0070]
　Journal processing unit, as shown by a thick line in FIG. 10A, the upper die journal processing portion 41a provided in the first upper die 41, and consists of a lower mold journal processing portion 42a provided on the first lower mold 42. Upper die journal processing section 41a is concave, can accommodate the whole of the flat portion of the initial wasteland 23. Lower die journal processing unit 42a 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 the entire flat portion of the initial wasteland 23.
[0071]
　Pin processing unit, as shown by a thick line in FIG. 11A, the upper die pin processing unit 41b provided in the first upper die 41, and consists of the lower die pin processing unit 42b provided in the first lower mold 42. Upper die pin processing unit 41b is a concave, can accommodate the whole of the flat portion of the initial wasteland 23. Lower die pin processing unit 42b is provided on the tip surface of the projection. Note that either one of the upper die pin processing unit 41b and the lower die pin processing unit 42b and the concave is not particularly limited. In other words, the lower die pin processing unit 42b may be concave capable of accommodating the entire flat portion of the initial wasteland 23.
[0072]
　In the second preforming step, as shown in FIG. 8A, in a state of being separated from the first upper die 41 is raised the first upper die 41 of the first lower mold 42, the initial wasteland 23 first upper die 41 When placed between the first lower die 42. 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.
[0073]
　From this state lowers the first upper die 41. Then, as shown in FIGS. 10A and FIG. 11A, the flat part of the initial wasteland 23 is accommodated in a concave of the upper die journal processing unit 41a and a concave of the upper die pin processing unit 41b. At this time, as shown in FIG. 9A, the web corresponding section, without contacting the bottom surface of the web processing unit, the majority of the web corresponding section is disposed in the weight processing unit 42e of the webs processing unit 42c.
[0074]
　Further lowering the first upper die 41, it closed section by the upper mold pin processing unit 41b and the lower die pin processing unit 42b is formed. Also, it closed section by the upper mold journal processing portion 41a and the lower mold journal processing portion 42a is formed. In this state, when the reach the bottom dead center further lowers the first upper die 41, the entire flat portion of the inside of the upper die pin processing unit 41b and the lower die pin processing unit 42b is pressure. Further, the overall flat portion of the inside of the upper mold journal processing portion 41a and the lower mold journal processing portion 42a is pressure. Thus the flat part of the initial wasteland 23 is rolling by the first mold 40, as a result, the cross-sectional area decreases in the journal equivalent portions and the pin-corresponding portion. Accordingly, the material became surplus flows into the arm portion corresponding to flow in the axial direction, the distribution of the volume progresses. Further, the center of gravity of the pin corresponding portion moves in eccentric direction of the pin portion (see arrows hatched in FIG. 1B). The eccentricity of the pin corresponding portion is smaller than equal to or eccentric amount of finished size. Eccentricity of the pin portion corresponding is less than the amount of eccentricity of the finishing size, the eccentricity of the finished size with die forging after the final pre-molding step.
[0075]
　Planar web processing portion among the web processing unit (FIG. 9A and the upper in Fig. 9B-type web processing unit 41c) is not pressed against the web corresponding section, with the pressure of the first mold 40, the web corresponding section It is pushed into the bottom side of the concave lower mold web processing unit 42c. The pushing is generated with the pressure of the journal corresponding portion and the pin corresponding portion located 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.
[0076]
　When forming a weight equivalent portion by such a weight processing unit 42e, the front and rear in the axial direction of the weight portion corresponding upper mold pin processing unit 41b and the lower die pin processing unit 42b, and the upper mold journal processing portion 41a and the lower die journal processing portion 42a is present. In this case, the site of the upper of the upper die pin processing unit 41b upper portion (the portion enclosed by an ellipse D1 of FIG. 8B) of the (circular portion enclosed by D2 in FIG. 8B), and the upper mold journal processing unit 41a is the axis of the material It acts as a partition for limiting the direction of flow. Therefore, it is not that the material flows out from the weight equivalent portion in the axial direction. Further, as described above, since no pressing planar web processing unit (FIG. 9A and the upper mold web processing unit 41c in Fig. 9B) in the web corresponding section, the material to the weight equivalent portion from the pin corresponding portion and the journal equivalent portions It can be promoted from flowing. Furthermore, without flow out surplus material as a burr, it is possible to secure a weight equivalent portion.
[0077]
　After completion of the reduction by the first mold 40 to raise the first upper die 41, take out the processed initial wasteland 23 (intermediate wasteland 24). In intermediate wasteland thus obtained, thickness of the web corresponding section is greater than the thickness of the finished size.
[0078]
　According to a second preforming step, the material to flow from the pin corresponding portion and the journal portion corresponding to the web corresponding section. This allows allocating the volume in the axial direction. Furthermore, the web corresponding section moves inside the arm processing unit and weight processing unit, narrows in concave bottom side, widens in concave opening side. For this reason, the volume in the web equivalent portion is properly distributed. As a result, in the final pre-molding step and finishing forging process in a subsequent step, it can suppress the underfill occurs in the weight unit. Further, it is possible to reduce the excess material provided to the weight equivalent portion, thereby improving the material yield.
[0079]
　In this processing flow example, to accommodate the flat portion in a concave of the upper die pin processing unit 41b and a concave of the upper die journal processing unit 41a. Thereafter, closed section is formed by the upper die pin processing unit 41b and the lower die pin processing unit 42b, it closed section by the upper mold journal processing portion 41a and the lower mold journal processing portion 42a is formed. Since the flat portion in this state is pressure, there is no burr is formed between the first upper die 41 first lower die 42. Therefore, it improves the material yield, the flow of material from the pin corresponding portion and the journal portion corresponding to the web corresponding section is further promoted.
[0080]
　As will be described later, in the second preforming step, the partial pressure by the upper mold pin processing unit 41b and the lower die pin processing unit 42b, may prevent the formation of burrs. Also, the partial pressure by the upper mold journal processing portion 41a and the lower mold journal processing unit 42a, may prevent the formation of burrs.
[0081]
4. Processing flow example of the final preform process
　diagram 12A ~ FIG. 12C, the processing flow example of the final pre-forming step is a longitudinal sectional view schematically showing. Of these figures, FIG. 12A shows a prior reduction conditions. Figure 12B shows the situation at the time of arrival bottom dead center of the upper die. Figure 12C shows the situation at the end axial movement. Figure 13 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 12A ~ FIG 12C, showing an intermediate wasteland 24 obtained in the second preforming step described above, the second mold 51 of a pair in upper and lower, an upper plate 52 and a lower plate 53. The second mold 51 is provided with a second upper die 60, and a second lower die 70. The second 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 second lower mold 70 is supported on the lower plate 53. The lower plate 53 is fixed to the base of the press machine (not shown).
[0082]
　To rolling the web corresponding section in the axial direction of the intermediate wasteland 24, second upper die 60 and a second lower die 70 is divided into a plurality of members. Members constituting the second upper die 60 and a second lower die 70 are arranged along the axial direction of the intermediate wasteland 24. The second upper die 60 and a second lower die 70 are respectively provided with a fixed journal type member 61 and 71, a plurality of movable journaled member 62 and 72, and a plurality of pin-shaped members 63 and 73.
[0083]
　Fixing journaled member 61 and 71, (a portion to be the third journal portion) central journal equivalent portions among the intermediate wasteland 24, and is disposed at a position including a web portion corresponding to lead to the journal corresponding portion. Fixing journaled member 61 and 71, relative to the upper plate 52 and lower plate 53, which is immovable.
[0084]
　Movable journaled member 62 and 72, the journal corresponding portion other than the center within the intermediate wasteland 24 (first, second, portion which becomes the fourth and fifth journal portion), and a web corresponding section leading to the journal corresponding portion It is arranged at a position including a. The movable journaled member 62 and 72 of the front end is also present at the position of the portion to be the front. Rear of the movable journal type member 62 and 72 of the end is also present at the position of the portion the flange. Movable journaled member 62 and 72, on the upper plate 52 and lower plate 53 is movable an axial direction of the intermediate wasteland 24 in a direction toward the fixed journal type member 61 and 71.
[0085]
　Pin-shaped member 63 and 73 are respectively disposed in positions of the pin corresponding portions among the intermediate wasteland 24. Pin-shaped member 63 and 73, on the upper plate 52 and lower plate 53 is movable an axial direction of the intermediate wasteland 24 in a direction toward the fixed journal type member 61 and 71. Pin-shaped 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.
[0086]
　Thus second upper die 60 and a second lower die 70 is made of a member, each type engraved portion (reference numeral 61a in FIG. 12A, 62a, 63a, 71a, see 72a and 73a) are formed. Its mold engraving portion, are reflected approximate shape of a crank shaft (final product).
[0087]
　In the final preforming step, as shown in FIG. 12A, in a state of raising the second upper die 60, to place the intermediate wasteland 24 between the second upper die 60 and the second lower die 70. At that time, the intermediate wasteland 24, pin-corresponding portion is disposed in a posture such as to line up in the vertical plane (see FIG. 13). From this state, to lower the second upper die 60. Then, the intermediate wasteland 24 is pressure from the axial direction perpendicular to the direction of the intermediate wasteland 24 (FIGS. 12A ~ 13 in the vertical direction) by the second upper die 60 and a second lower die 70. Thus, the journal corresponding part and the pin corresponding portion of the intermediate wasteland 24 is pressure, approximate the shape of the journal portion and the pin portion is shaped.
[0088]
　Further, the movable journal type member 62 and 72, as well as a pin-type member 63 and 73, is moved to a axial direction of the intermediate wasteland 24 in a direction toward the fixed journal type member 61 and 71. This movement can be implemented, for example, by the wedge mechanism or a hydraulic cylinder.
[0089]
　Movable journaled member 62 and 72, and with the axial movement of the pin-shaped members 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 pin corresponding portion is maintained the same as the eccentricity of finished size.
[0090]
　After completion of the reduction by the second mold 51, it raises the second upper die 60, take out the processed intermediate wasteland 24 (final wasteland).
[0091]
　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.
[0092]
　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.
[0093]
　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.
[0094]
5. The volume distribution of the web corresponding section
　volume distribution in 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) can be adjusted. For example, to change the opening width of the arm processed portion may be or the arm machining portion and the inclined surface.
[0095]
　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.
[0096]
　14A and 14B are cross-sectional views illustrating a case where reduction portion to be a web (the web corresponding section) from the opening side of the concave web processing unit. Of these figures, FIG. 14A shows a prior reduction conditions, FIG. 14B shows the situation at pressure exit. 14A and 14B, in the view 9A and 9B, is modified shallow depth of the concave of the web processing unit.
[0097]
　The processing flow example shown in FIGS. 14A and 14B, similarly to the processing flow example shown in FIG. 9A and 9B, 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 reduction by the first mold 40, pressed against the planar upper mold web processing unit 41c is on the side surface of the opening side of the web corresponding section 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.
[0098]
　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. 9B). In this case, the soft reduction by the material from escaping a site that is not in contact with the mold.
[0099]
6. Preferred embodiments such as
　in terms of improving the filling property of the weight of the material in the process later in the second preforming step, the thickness of the web corresponding section of the intermediate wasteland t1 (mm), the ratio finished size t0 (mm) (t1 in / t0), it 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.
[0100]
　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.
[0101]
　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.
[0102]
　From the viewpoint of reducing burrs to be formed in a later step, the cross-sectional area of the pin corresponding portion of the intermediate wasteland Sp2 (mm 2 cross-sectional area of the pin portion of) the forged crankshaft (final product) Sp0 (mm 2 ratio) ( Sp2 / Sp0 in), 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.
[0103]
　As described above, in the second preforming step, when forming the weight equivalent portion by weight processing unit 42e, the site of the upper of the upper portion and the upper mold journal processing portion 41a of the upper die pin processing unit 41b is a material axis It acts as a partition for limiting the direction of flow. To increase this effect, the concave of the upper die pin processing unit 41b and a concave of the upper die journal processing section 41a, the opening width becomes important that the narrowing (Bp: see FIG. 10A: FIG. 11A see, Bj) . On the other hand, when the opening width Bj opening width Bp and concave of the upper die journal processing portion 41a of the concave of the upper die pin processing unit 41b is too narrow, the load in a subsequent step increases.
[0104]
　These, in the case of employing the processing flow example shown in FIG. 8A ~ Figure 11B, the opening width Bp of the concave of the upper die pin processing unit 41b (mm), the diameter Dp of the pin portion of the forged crankshaft (final product) the ratio to (mm), preferably 0.5 to 1.5. The opening width Bj concave upper mold journal processing section 41a (mm) is a ratio to forging the crank shaft diameter of the journal portion of the (final product) Dj (mm), that a 0.5-1.5 preferable.
[0105]
　The processing flow example of the aforementioned second preforming step, to the reduction of the initial wasteland 23 (pars). State that when the pressure, the state of closed cross section by the upper mold journal processing portion 41a and the lower mold journal processing portion 42a are formed, the closed section by the upper mold pin processing unit 41b and the lower die pin processing unit 42b is formed to. This prevents formation of burrs. By partial pressure journal equivalent portions by the upper mold journal processing portion 41a and the lower mold journal processing unit 42a, it may prevent the formation of burrs. In addition, by partial reduction pins corresponding portion by the upper die pin processing unit 41b and the lower die pin processing unit 42b, it may be prevented from flowing out of the burr.
[0106]
　15A and 15B are cross-sectional views illustrating a processing flow example of partial pressure by the journal processing unit in the second preforming step. Of these figures, FIG. 15A shows the situation at the time of rolling start, Fig. 15B shows the situation at pressure exit. 15A and upper die journal processing portion 41a and the lower mold journal processing unit 42a shown in FIG. 15B, a modification of the shape of FIG. 10A and the upper mold journal processing portion 41a and the lower mold journal processing unit 42a shown in FIG. 10B is there. In the upper mold journal processing portion 41a and the lower mold journal processing unit 42a shown by a thick line in FIG. 15A, the upper die journal processing section 41a is concave capable of housing the entirety of the flat portion of the initial wasteland 23. The lower mold journal processing unit 41a is provided on the tip surface of the projection. Upper die journal processing portion 41a and the lower mold journal processing unit 42a is provided with a relief portion 41f and 42f at both ends in the width direction, the escape portion 41f and 42f extends in the width direction.
[0107]
　According to the upper mold journal processing portion 41a and the lower mold journal processing unit 42a, along with the descent of the first 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 lowering of the first 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 to flow in the axial direction is distributed. At that time, part of the material, but flows into the escape portion 41f and 42f, are part of the escape portion 41f and 42f do not contact with the flat portion. Therefore, the flat portion is partially pressure, burrs are not formed.
[0108]
　Incidentally, by applying the configuration shown in FIGS. 16A and 16B will be described later in the journal processing unit, by partial reduction of the journal equivalent portions may prevent the formation of burrs. In view of promoting the distribution of the volume, in a state of forming a closed cross section by the upper mold journal processing portion 41a and the lower mold journal processing unit 42a, it is preferable to pressure the entire flat portion. Further, in view of preventing the material in the gap of the upper mold and the lower mold begins to bite, to partial pressure by the upper mold journal processing portion 41a and the lower mold journal processing unit 42a is preferred.
[0109]
　16A and 16B are cross-sectional views illustrating a processing flow example of partial pressure by the pin processing unit in the second preforming step. Of these figures, FIG. 16A shows the situation at the time of rolling start, Fig. 16B shows the situation at pressure exit. Upper die pin processing unit 41b and the lower die pin processing unit 42b shown in FIGS. 16A and 16B, a modification of the shape of FIG. 11A and the upper mold pin processing unit 41b and the lower die pin processing unit 42b shown in FIG. 11B is there. In the upper die pin processing unit 41b and the lower die pin processing unit 42b shown by a thick line in FIG. 16A, the upper die pin processing unit 41b is a concave majority capable of accommodating the flat portion of the initial wasteland 23. The lower mold pin processing unit 42b is concave. The depth of the upper die pin processing unit 41b is deeper than the bottom die pin processing unit 42b.
[0110]
　According to the upper die pin processing unit 41b and the lower die pin processing unit 42b, with the downward movement of the first upper die 41, the majority of the flat portion of the initial wasteland 23 is housed in a concave of the upper die pin processing unit 41b that. In this state, when the further lowering of the first upper die 41, upper die pin processing unit 41b is the flat portion abuts, followed lower mold pin processing unit 42b portion comes into contact with the flat portion. At that time, the upper die pin processing unit 41b and the lower die pin processing unit 42b are both partially and abut flat portion. In other words, flat portion at the periphery of the parting surfaces do not abut the pin processing unit. Therefore, without forming burrs, it can flow the material web corresponding section from the pin corresponding unit. It is also possible to decenter the pin corresponding portion.
[0111]
　Incidentally, it was applied to the pin processing unit configured as shown in FIGS. 15A and 15B described above, by partial reduction pins corresponding portion may prevent the formation of burrs. In view of promoting the distribution of the volume, in a state of forming a closed cross section by the upper mold pin processing unit 41b and the lower die pin processing unit 42b, preferably rolling the entire flat portion. In view of preventing chewing out, for partial pressure by the upper mold pin processing unit 41b and the lower die pin processing unit 42b is preferred.
[0112]
　In the first preforming step described above, using the third mold 30, to pressure the whole circumference of the billet. State that when the pressure, the state of closed cross section by the upper mold journal processing portion 31a and the lower mold journal processing portion 32a are formed, the closed section by the upper mold pin processing unit 31b and the lower die pin processing unit 32b is formed to. This prevents formation of burrs. By partial pressure journal equivalent portions 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.
[0113]
　17A and 17B are cross-sectional views illustrating a processing flow example of partial pressure by the journal processing unit in the first preforming step. Of these figures, FIG. 17A shows a prior reduction conditions, FIG. 17B shows the situation at pressure exit. Upper die journal processing portion 31a and the lower mold journal processing unit 32a shown in FIG. 17A and 17B, a modification of the FIG. 5A and shape of the upper die journal processing portion 31a and the lower mold journal processing unit 32a shown in FIG. 5B . As shown by thick lines in FIG. 17A, both of the upper mold journal processing portion 31a and the lower mold journal processing portion 32a, a concave, are of the same depth.
[0114]
　According to such a journal processing unit, with the descent of the third upper die 31, the deepest portion of the upper mold journal processing portion 31a and the lower mold journal processing portion 32a abuts against the billet 22. In this state, further lowering the third upper die 31, upper die journal processing portion 31a and the lower mold journal processing portion 32a are both partially billet and abut. 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. 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 journal processing unit, preferably reduction of the entire billet.
[0115]
　Pin processing unit of the third mold, although not shown, FIG. 17A and employs the same configuration as the journal processing unit shown in FIG. 17B, may be partially pressure the billet. In view of promoting the distribution of the volume, as shown in FIG. 6A and 6B, in a state of forming a closed cross section by the pin processing unit, preferably reduction of the entire billet.
[0116]
7. Other embodiments
Embodiment 1]
　FIGS. 18A ~ FIG. 18C is a top view schematically showing the final pre-molding step in a manufacturing method of the first embodiment. Of these figures, FIG. 18A shows a prior reduction conditions. Figure 18B shows the situation at the time of arrival bottom dead center of the upper die. Figure 18C shows the situation at the end axial movement. Figure 19 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 ~ Figure 17B, the form of the second mold are different to be used in the final pre-molding step. The other configuration is the same as the above embodiment. In order to facilitate the understanding of the situation, FIG. 18A ~ FIG 18C, showing a second lower die 70 of the second upper die 60 and a second lower die 70 constituting the second mold 51. FIG 18A, shows an outline of the intermediate wasteland 24 by broken lines. Figure 18B and Figure 18C shows no burrs.
[0117]
　In the above embodiment, as shown in FIGS. 12A and 13, the intermediate wasteland 24, in position as the pin corresponding portion are arranged in a vertical plane, it is disposed on the second lower die 70. Therefore, as shown in FIG. 12B, if the second upper die 60 by the downward movement of the second upper die 60 is a second lower die 70 transgressions clamping journal equivalent portions and the pin corresponding portion of the pin portion corresponding eccentric It is rolling along the direction.
[0118]
　In contrast, in Embodiment 1, as shown in FIGS. 18A and 19, the intermediate wasteland 24, the pin corresponds portions in position as aligned in a horizontal plane, it is disposed on the second lower die 70. Therefore, as shown in FIG. 18B, if the second upper die 60 by the downward movement of the second upper die is a second lower die 70 transgressions clamping journal equivalent portions and the pin corresponding portion, the eccentric direction of the pin corresponding portion It is under pressure from the perpendicular direction.
[0119]
　Thus, in the final pre-forming process of the first embodiment, the posture of the intermediate wasteland 24, pin-corresponding portion is position as aligned in a horizontal plane. This attitude, as well as the final wasteland posture of after finishing the forging step is. 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.
[0120]
[Embodiment 2]
　FIGS. 20A ~ FIG 20C is a longitudinal sectional view schematically showing a final pre-molding step in the manufacturing method of the second embodiment. Of these figures, FIG. 20A shows a prior reduction conditions. Figure 20B shows the situation at the time of arrival bottom dead center of the upper die. Figure 20C shows the situation at the end axial movement. Manufacturing method of Embodiment 2 is different from the embodiment shown in above FIG 3A ~ Figure 17B, the form of the 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. Posture of the intermediate wasteland 24 in the final pre-molding step, the pin-corresponding portion is position as aligned in a vertical plane.
[0121]
　As shown in FIG. 20A, the eccentric amount of the pin corresponding portion of the intermediate wasteland 24 is smaller than the eccentricity of the finished size. In the second preforming step, so as to be smaller than the eccentricity dimension finishing eccentricity of the pin corresponding portion, 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 FIGS. 20B and 20C, 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, eccentricity of the pin corresponding portion of the final wasteland 25 is smaller than the eccentricity of the finished size.
[0122]
　Next, in the finish forging step, the final wasteland 25, the pin corresponds portions in position as aligned in a horizontal plane, it is disposed on the second lower die 70. The forging is performed by the lowering of the second upper die 60. Here, in the final rough terrain 25 stages which are disposed on the second lower die 70, the pin corresponding portion of the final wasteland 25 is offset from the pin portion engraving portion formed on the second lower die 70. This is because less than eccentricity dimension finishing eccentricity of the pin corresponding portion of the final wasteland 25. Even in such a state, the second upper die 60 by contacting the pin-corresponding portion, the pin-corresponding portion is pushed into the engraving portion pin portion of the second lower die 70 to be lowered. Thus, the pin portion is obtained became eccentricity of finished size.
[0123]
　However, from the viewpoint of ensuring the filling of the material to the pin portion engraving unit, eccentricity E3 pins corresponding portion of the final wasteland 25 (mm), the eccentricity of the finished size (amount of eccentricity of the pin portion of the forged crankshaft ) in the ratio E0 (mm) (E3 / E0 ), preferably less than 1.0 (1.0-Dp / 2 / E0) above. 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 cross-sectional area of the pin corresponding portion of the final wasteland 25 Sp3 (mm 2 ), the cross-sectional area of the pin portion of the forged crankshaft Sp0 (mm 2 in ratio) (Sp3 / Sp0), 0.7 or 1 it is preferable to be .5 or less, more preferably to 0.75 to 1.1.
[0124]
　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.
[0125]
[Embodiment 3]
　FIGS. 21 and 22 is a longitudinal sectional view showing a first 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 ~ Figure 17B, the form of the first mold used in the second preforming step is different.
[0126]
　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 first upper die 41 of the first lower mold 42, the initial wasteland 23 is disposed on the first lower mold 42. As described above, in the second preforming step, to the eccentric pin portion corresponding. Second initial wasteland 23, the lower mold pin processing unit 42b for processing the third pin corresponding portion projects than the lower mold journal processing unit 42a. Therefore, placing initial wasteland 23 to the first lower mold 42, the initial wasteland 23 is supported at two points by two lower mold pin processing unit 42b. Further, the upper die pin processing unit 41b is disposed on the end side of the initial waste land 23 than the lower mold pin processing unit 42b. In this state, when the first mold 40 is under pressure the initial wasteland 23, fulcrum lower mold pin processing unit 42b, the upper die pin processing unit 41b as the power point, load is applied to the initial wasteland 23. Thus, the bending moment acts on the initial wasteland 23. If the bending moment acting on the initial wasteland 23 is excessively large, the initial wasteland 23 is curved. When the first upper die 41 in a state where the initial wasteland 23 is bent to reach the bottom dead center, the position of the initial wasteland 23 first mold 40 is under pressure is deviated from a predetermined position. That is, the pin processing unit of the first mold 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.
[0127]
　Referring to FIGS. 21 and 22, the manufacturing apparatus of the third embodiment, a fourth upper die 91 and a fourth lower mold 92 in place of the upper die pin processing unit 41b and the lower die pin processing unit 42b. The fourth upper die 91 and a fourth lower die 92, the first mold 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 the first lower die 42 arranged initial wasteland 23, initial wasteland 23 is not supported by the fourth lower die 92. Initial wasteland 23 is supported on a plurality of lower mold journal processing unit 42a. Area in which a plurality of lower mold journal processing unit 42a supports the initial wasteland 23 is wider than the area in which the fourth lower die 92 supports the initial wasteland. In this state, when the first mold 40 is under pressure the initial wasteland 23, journal equivalent portions are equally pressure. In other words, hardly load the initial wasteland 23 is loaded. Therefore, the bending moment in the initial rough terrain 23 is less likely to act.
[0128]
　Further, the first mold 40 of the third embodiment, 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 unit 42a, the initial of the fourth lower die 92 pressure of wasteland 23 is started. Therefore, during rolling of the pin corresponding portion, the journal portion corresponding initial wasteland 23 is pressure by the upper mold journal processing portion 41a and the lower mold journal processing unit 42a. That is restrained journal equivalent portions of the initial wasteland 23 by the upper mold journal processing portion 41a and the lower mold journal processing unit 42a.
[0129]
　In short, the fourth lower die 92 is independently elevating and the journal equivalent portions of the initial wasteland 23 is rolling with simultaneous or preceding the pin corresponding portion, by an initial wasteland during rolling of the pin corresponding portion 23 but difficult to bend. Thus, the initial wasteland 23 that is volume allocation, because it is rolling at a predetermined position of the first mold 40, underfill, etc. to an intermediate wasteland after reduction is less likely to occur. The same applies to the fourth upper die 91. That is, the manufacturing apparatus of the third embodiment, the first, fourth upper die 91 for rolling the fourth pin corresponding portion, a fourth gold a fourth lower die 92 for rolling the second, third pin corresponding portion equipped with a type 90.
[0130]
　Description will be given of a configuration of the first mold 40 and the fourth mold 90 according to the third embodiment. Fourth mold 90, in order to independently elevating the fourth upper die 91 and a fourth lower die 92, and a control mechanism. Control mechanism, for example a die cushion, a hydraulic cylinder.
[0131]
　Referring to FIG. 21, the control mechanism will be described a die cushion 81. The first 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 first 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 first lower mold 42. After the upper mold journal processing portion 41a and 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.
[0132]
　Referring to FIG. 22, 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 first 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 first lower mold 42. After the upper mold journal processing portion 41a and 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.
[0133]
　Also the control mechanism in either case the die cushion or hydraulic cylinders, the timing of the fourth lower mold 92 protrudes from the first 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.
[0134]
　The same applies to the fourth upper die 91. Therefore, detailed description of the fourth upper die 91 will be omitted.
[0135]
　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. For example, oval-shaped arm portion without a weight portion (hereinafter, also referred to as "weight without arm".) Crankshaft having a (e.g. 4-cylinder -4 sheets counterweight of the crankshaft) in the case of producing the even, first preforming step of the above embodiments, the second preforming step, and a final pre-molding step can be applied. In this case, the molding of the weight without arm corresponds to the molding of the web in those processes. In intermediate wasteland obtained by the second preforming step, the site to be weight without arm portion (hereinafter, also referred to as "wait without arm equivalent portion".) In the axial thickness of the can be greater than the thickness of the finished size to good, it may be the same as the thickness of the finished size. When the thickness of the weight without arm equivalent portion of the intermediate wasteland is greater than the thickness of the finished size, the final preforming step, the weights without arm corresponding portion is pressure from the axial direction, reduced to the thickness dimension its thickness finish It is. Same as the thickness is finished size of the weight without arm equivalent portion of the intermediate wasteland, the final preforming step, the weights without arm corresponding unit is not under pressure from the axial direction, it is maintained in the thickness dimension its thickness finish that.
Industrial Applicability
[0136]
　The present invention can be effectively utilized in the production of forged crankshaft mounted in a reciprocating engine.
DESCRIPTION OF SYMBOLS
[0137]
　21 forged crankshaft
　22 billet
　23 initial wasteland
　23a flat portion
　23b web corresponding opening side of the side surface
　24 intermediate wasteland
　25 Last wasteland
　26 finishing forging
　30 third mold
　31 third upper die
　31a upper die journal processing section
　31b upper die pin processing unit
　32 third lower mold
　32a under type journal processing portion
　32b lower die pin processing unit
　40 first mold
　41 first upper die
　41a upper die journal processing section
　41b upper die pin processing unit
　41c upper die web processing unit
　41f escape part
　42 the first lower die
　under 42a-type journal processing portion
　42b lower die pin processing unit
　42c under type web processing unit
　42d arm processing unit
　42e weight processing unit
　42f escape portion
　51 second mold
　52 upper plate
　53 lower plate
　60 second upper die
　61 fixed journal type member
　62 movable journaled member
　63 pin-type member
　70 the second lower mold
　71 fixed journal type member
　72 movable journaled member
　73 pin-type member
　90 fourth mold
　91 fourth upper die
　92 fourth lower die
　A, A1 ~ A8 crank arm portion
　J, J1 ~ J5 journal portion
　P, P1 ~ P4 pin portion
　W, W1 ~ W8 counterweight part
　B Bali

The scope of the claims
[Requested item 1]
　A plurality of journal portion as a rotational center, and a plurality of pin portions eccentric to the journal portion, and a plurality of crank arm portion connecting the pin portion and the journal portion, said all of the crank arm or a part is a method for producing a forged crankshaft and a plurality of counterweight portion provided integrally,
　the manufacturing method includes
　a first preforming step of obtaining initial wasteland from billet,
　to obtain an intermediate wasteland from the initial wasteland a second preforming step,
　and the final preform to obtain the final wasteland from the intermediate wasteland,
　by die forging anda finishing forging step of forming said final wasteland to finished size of the crank shaft,
　the first preformed in step portion serving as the pin portion of said billet, and the portion serving as the journal portion, in the axial direction perpendicular to the direction of the billet By lower, the decrease the cross-sectional area of each part to form a plurality of flat portions,
　wherein in the second preforming step, using a first mold of the pair, and the width direction of the flat portion in the pressing direction wherein by rolling the initial rough terrain, the eccentric amount of the portion to be a pin portion is finished is smaller than equal to or eccentric amount of size, portions serving as the counterweight unit, and integrated with the counterweight unit Te the thickness of the portion to be a crank arm portion becomes larger than the thickness of the finished size, including in
　the in the final pre-molding step, using a second mold, the axial direction perpendicular to the direction of said intermediate wasteland said intermediate wasteland and pressure from the further portion becomes the counterweight unit, and a portion serving as the crank arm having integrally the counterweight unit, the axial direction of the intermediate wasteland By rolling the while maintaining the eccentricity of the portion serving as the pin portion, the portion serving as the counterweight unit, and the thickness of the portion to be the crank arm having integrally the counterweight unit, finished size reduced to a thickness, the production method of the forged crankshaft.
[Requested item 2]
　A method of manufacturing a forged crankshaft according to claim 1,
　in the final pre-molding step, the pressing direction along a direction perpendicular to the axial direction of the intermediate wasteland by the second mold, and the pin portion a eccentric direction perpendicular to the direction of the site, the production method of the forged crankshaft.