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. When the high strength and high rigidity are required to the crankshaft, a crankshaft manufactured by die forging (hereinafter, also referred to as "forging crankshaft") is often used.
[0003]
　In general, raw materials forged crankshaft is billets. In that billet cross section is round or square, is constant cross-sectional area over the entire length. Manufacturing process of forging the crank shaft includes a pre-molding step, the mold forging step and burr punching process. If necessary, shaping step is added after the burr punching process. Usually, preforming step includes the steps of stamping and bending roll forming, die forging step comprises the steps of rough beating and finishing beating.
[0004]
　Figure 1A ~ FIG. 1F is a schematic diagram for explaining a conventional general forged crankshaft manufacturing process. Figure 1A is a billet, Figure 1B is a roll wasteland, Figure 1C the bending wasteland, Figure 1D rough forged material, FIG. 1E finish forged material, FIG. 1F shows crankshaft (final product), respectively. Forged crankshaft 1 illustrated in FIG. 1F is mounted on four-cylinder engines. Part crankshaft 1 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, simply referred to as "arm" ) provided with A1 ~ A8, 8 sheets of counterweight portion (hereinafter, simply also referred to as "weight part") W1 ~ W8, a. The arm A1 ~ A8 is, connecting the journal portion J1 ~ J5 and the pin portion P1 ~ P4, respectively. Also, all of the arm portions A1 ~ A8 has a weight portion W1 ~ W8 integrally respectively.
[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. Together a pair of arm portions A (including the weight portion W) which leads to the pin portion P and the pin portion P is also referred to as "slow".
[0006]
　In the manufacturing method shown in FIGS. 1A ~ FIG 1F, forged crankshaft 1 is manufactured as follows. First, after heating the billet 2 of predetermined length, as shown in FIG. 1A by a heating furnace (e.g., an induction heating furnace or gas heating furnace or the like), and roll forming. The roll forming process, for example, rolling a billet 2 with grooved rolls, thereby reducing the cross-sectional area in a part of the length of the billet 2. Thus, allocating the volume of the billet 2 in the longitudinal direction to obtain a roll wasteland 3 is an intermediate material (see FIG. 1B). Next, in the bending beating process, the roll wasteland 3 partially pressure from a direction perpendicular to a longitudinal direction, thereby decentering the part of the length of the roll wasteland 3. Thus, allocating the volume of the roll wasteland 3, it is a further intermediate material bending obtain wasteland 4 (see FIG. 1C).
[0007]
　Subsequently, the rough beating process, obtained by pressing forging, rough forged material 5 with bent wasteland 4 a pair of molds (upper and lower dies) (see FIG. 1D). Rough forged material 5 obtained has the approximate shape of a crank shaft (final product). Furthermore, the finishing beating process, by press forging using a pair of molds rough forged material 5 up and down to obtain a finish forged material 6 (see FIG. 1E). Resulting finish forged material 6 has a shape that matches the crankshaft of the final product. When these rough beating and finishing beating, surplus material, the burrs to flow out from the gap between the upper and lower molds. Therefore, none of the rough forging 5 and the finishing forging 6, has a large burr B around.
[0008]
　The burr punching step, for example, the finish forged material 6 with burrs while maintaining across the pair of molds, punching burrs B by blade type. Thus, to remove the burr B from the finish forged material 6 to obtain the burrs without forging. Burr without forging is substantially the same shape as the forged crankshaft 1 shown in FIG. 1F.
[0009]
　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, a front portion Fr and the axial portion, such as flange portion Fl, more arm portions A and the weight portion W. Thus, forged crankshaft 1 is manufactured.
[0010]
　Manufacturing process shown in FIGS. 1A ~ FIG 1F is not limited to the crank shaft of a four-cylinder -8 Like counterweight shown in Fig. 1F, it can be applied to various crankshaft. For example, it can be applied to the crankshaft of a four-cylinder -4 Like counterweight.
[0011]
　4 If the crankshaft of the cylinder -4 sheets counterweight, a portion of the arm portion A of the eight arm portions A having a weight portion W integrally. For example, the first arm portion A1 of the top eighth arm portions A8 and two arm portions of the center of the last (fourth arm A4, the fifth arm A5) has a weight portion W. Further, the remaining arm portions, specifically, the second arm portion A2, the third arm A3, the arm portion A7 of the arm A6 and the seventh sixth has no weight portion. In the following, an arm portion which does not have the weight portion, also referred to as a "no weight arm part".
[0012]
　In addition, three-cylinder engine, series 6-cylinder engine, even crankshaft mounted in V-type 6-cylinder engine and 8-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.
[0013]
　In the manufacture of such forging crankshaft, by reducing the outflow of burrs in the mold forging, it is desirable to improve the material yield. Here, the material yield, the volume of the forged crankshaft (final product) means a proportion (percentage) occupying the volume of the billet. The material yield is at preforming, by promoting the distribution of the volume, can be improved.
[0014]
　Technology related preformed, JP 2001-105087 (Patent Document 1), is described in JP-A 2-255240 (Patent Document 2) and JP 62-244545 (Patent Document 3).
[0015]
　Patent Document 1, preforming method using a pair of upper and lower molds are described. In that pre-molding method, when the reduction of the workpiece rod-shaped with the upper and lower molds, while reducing the cross-sectional area by extending a portion of the workpiece, slide the other portion continuous to a portion while to the eccentric move. In such Patent Document 1 preforming method according to, and from can be implemented extend and bend simultaneously, can provide a small preformed method of capital investment.
[0016]
　The preform according to Patent Document 2, instead of the roll forming of a conventional two-pass, using a high-speed roll equipment 4 pass. In its preformed, the cross-sectional area of ​​the roll wasteland, the weight portion of the forged crankshaft (final product), be determined in accordance with the distribution of the cross-sectional area of ​​the arm portion and the journal portion has been proposed. Accordingly, in Patent Document 2, and it can be improved material yield.
[0017]
　The preform according to Patent Document 3, to allocate the volume by cross rolling method in the axial direction and the radial direction, obtaining axially asymmetric intermediate material. The cross rolling method, reduction of the round bar material with two dice, allocating the volume by rolling action of the dies.
CITATION
Patent Document
[0018]
Patent Document 1: JP 2001-105087 Patent Publication
Patent Document 2: JP-A 2-255240 Patent Publication
Patent Document 3: JP 62-244545 Patent Publication
JP 4: WO2014 / 038183 Patent Publication
Summary of the Invention
Problems that the Invention is to Solve
[0019]
　In the manufacture of forged crankshaft, as described above, to reduce the outflow of burrs in the mold forging, it is desired to improve the material yield. The material yield by promoting the distribution of volumes in the preform can be improved.
[0020]
　As in the manufacturing process shown in FIGS. 1A ~ FIG 1F, there is a case where preforming consists roll forming and bending beating. In this case, the following method is considered to promote the distribution of the volume.
(1) In roll forming reduces the cross-sectional area at the site of the journal portion among the billet.
(2) followed, in the bending beating, a portion comprising a pin portion, and is eccentric to the site side to be the weight portion of the portion to be the arm portion partly by reduction with a set of weight portion connected with the pin portion .
[0021]
　In the following, "Journal equivalent part" a portion to be a journal portion, "pin-corresponding portion" a portion to be a pin portion, a pair of arm portions connected with the pin-corresponding portion and the pin portion corresponding (site a weight portion "slow-corresponding portion" a portion serving as a containing), a portion to be an arm section having a weight section is also referred to as "wait there arm equivalent portion".
[0022]
　However, in the above method, the larger reducing the cross-sectional area of ​​the journal portion corresponding in roll forming, when to decenter the slow portion corresponding bending beating, material flow to the journal corresponding portion becomes unavoidable from the slow-corresponding portion. By the material flow, flaws around the journal equivalent portions (so-called, overlies scratches) sometimes occurs. Further, the material flow inhibits the distribution of volumes in the preform. These, if preformed consists roll forming and bending beating, and reduction of the cross-sectional area of ​​the journal associated section in the roll forming, the eccentricity of the slow associated section in the bending beating is not sufficient. Therefore, it has been desired to be further promoted the distribution of the volume.
[0023]
　Wherein in the preformed method described in Patent Document 1, when the pressure in the pair of upper and lower molds, while reducing the cross-sectional area in a portion of the workpiece rod-shaped, is decentered other portion. However, since the simultaneously eccentrically with reduced cross-sectional area by the pair of upper and lower molds, reduction amount and the amount of eccentricity of the cross-sectional area is not sufficient. Therefore, it has been desired to be further promoted the distribution of the volume.
[0024]
　Wherein in the preformed method described in Patent Document 2, since it is roll forming, it can not be offset a portion of the billet. Therefore, the roll wasteland obtained, it is necessary to further apply a clinched like. In this case, as described above, reduction and eccentricity of the cross-sectional area is not sufficient.
[0025]
　Wherein in the preformed described in Patent Document 3, to allocate the volume by cross rolling method in the axial and radial directions. The cross rolling method, rather than a press machine used in bending stamped or die forging or the like, using special equipment. Also, the cross rolling method, it is difficult to process a plurality of locations at the same time, for example, a plurality of journal equivalent portions and a plurality of the slow portion corresponding order, so that the processing. For this reason, the die is increased in size. From these, the equipment cost is increased.
[0026]
　An object of the present invention, while suppressing an increase in facility cost, by facilitating the distribution of volumes in preforming is to provide a method for producing a forged crankshaft can improve material yield.
Means for Solving the Problems
[0027]
　Method for producing a forged crankshaft according to an embodiment of the present invention includes a plurality of journal portion as a rotational center, and a plurality of pin portions eccentric to the plurality of journal portions, said plurality of said plurality of journal portions a plurality of crank arm portion connecting the pin portion, a method of manufacturing a forged crankshaft with a. At least one of the plurality of crank arm part is arm portion there weight having a counterweight portion. The manufacturing method, by rolling the first part is a part of the length of the rod-like member by the first mold pair, and reduction steps to reduce the cross-sectional area of ​​said first portion, said being pressure first 1 site while held by the first mold includes an eccentric step of decentering the second portion of the rod-shaped member by a second mold. It said second portion is at least part of the portion excluding the first region in one of the bar-like member. The eccentric direction of the second mold, the pressing direction by the first mold, and, respectively a direction perpendicular to the longitudinal direction of the bar-like member.
Effect of the invention
[0028]
　According to the production method of the present invention for producing a forged crankshaft, the second portion to be eccentric, the material flow to the first part held is pressure can be suppressed. Therefore, allocation of volumes is promoted, thereby improving the material yield. The manufacturing method of the present invention can be carried out using a press machine. Therefore, it is possible to suppress the increase in equipment cost.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029]
[Figure 1A] Figure 1A is a schematic diagram showing the billet in conventional general forged crankshaft manufacturing process.
FIG 1B] Figure 1B is a schematic diagram showing a roll wasteland in a conventional typical forged crankshaft manufacturing process.
[Figure 1C] Figure 1C is a schematic diagram showing a wasteland bending in a conventional typical forged crankshaft manufacturing process.
[Figure 1D] Figure 1D is a schematic diagram showing a rough forged material in a conventional typical forged crankshaft manufacturing process.
FIG 1E] FIG. 1E is a schematic diagram showing a finishing forging material in a conventional typical forged crankshaft manufacturing process.
[FIG. 1F] FIG. 1F is a schematic diagram showing a crankshaft in a conventional typical forged crankshaft manufacturing process.
[Figure 2A] Figure 2A is a longitudinal sectional view showing a time reduction start in the processing flow example by reduction steps and the eccentric step.
[Figure 2B] Figure 2B is a longitudinal sectional view showing a time reduction completion in the processing flow example by reduction steps and the eccentric step.
[Figure 3A] Figure 3A is a top view showing a time reduction completion in the processing flow example by reduction steps and the eccentric step.
[Figure 3B] Figure 3B is a top view showing a time eccentric ends in the processing flow example by reduction steps and the eccentric step.
[Figure 4A] Figure 4A is a side view showing a rod-like member at the reduction ended in the processing flow example by reduction steps and the eccentric step.
[Figure 4B] Figure 4B is a top view of a rod-like member shown in Figure 4A.
[Figure 4C] Figure 4C is a IVC-IVC sectional view of Figure 4A.
[FIG. 4D] FIG. 4D is a IVD-IVD sectional view of Figure 4A.
[Figure 5A] Figure 5A is a side view showing a rod-like member at the eccentric ends in the processing flow example by reduction steps and the eccentric step.
[Figure 5B] Figure 5B is a top view of a rod-like member shown in FIG. 5A.
[Figure 6A] Figure 6A is a longitudinal sectional view showing a time reduction start in the processing flow example of using the third mold.
[Figure 6B] Figure 6B is a longitudinal sectional view showing a time reduction completion in the processing flow example of using the third mold.
[Figure 7A] Figure 7A is a top view showing a time reduction completion in the processing flow example of using the third mold.
[Figure 7B] Figure 7B is a top view showing a time eccentric ends in the processing flow example of using the third mold.
[FIG. 8A] Figure 8A is a side view showing a rod-like member at the reduction ended in the processing flow example of using the third mold.
[Figure 8B] Figure 8B is a top view of a rod-like member shown in Figure 8A.
FIG 9A] FIG. 9A is a side view showing a rod-like member at the eccentric ends in the processing flow example of using the third mold.
[FIG. 9B] FIG 9B is a top view of a rod-like member shown in Figure 9A.
FIG 10A] FIG 10A is a cross-sectional view showing a prior reduction in the configuration example using a wedge mechanism.
[FIG. 10B] FIG 10B is a cross-sectional view showing a time reduction completion in the configuration example using a wedge mechanism.
[FIG. 10C] FIG 10C is a cross-sectional view showing the operation of the second die in the configuration example using a wedge mechanism.
[11] FIG 11 is a top view showing an example of a rough forging is formed by die forging step.
FIG 12A] FIG 12A is a schematic diagram showing another example of a forged crankshaft produced by the production method of this embodiment.
[Figure 12B] Figure 12B is a schematic diagram showing an example of reduction by rod-shaped member in a manufacturing process of forging the crank shaft shown in FIG. 12A.
[FIG. 12C] FIG 12C is a schematic diagram showing an example of a wasteland 52 obtained by decentering the rod-like member shown in FIG. 12B.
FIG 13A] FIG 13A is a schematic diagram showing another example of a pressure by rod-shaped member in a manufacturing process of forging the crank shaft shown in FIG. 12A.
FIG 13B] FIG 13B is a schematic diagram showing another example of a wasteland 52 obtained by decentering the rod-like member shown in FIG. 13A.
[Figure 14A] Figure 14A is a schematic diagram showing another example of a forged crankshaft produced by the production method of this embodiment.
FIG 14B] FIG 14B is a schematic diagram showing an example of reduction by rod-shaped member in a manufacturing process of forging the crank shaft shown in FIG. 14A.
FIG 14C] FIG 14C is a schematic diagram showing another example of a wasteland 52 obtained by decentering the rod-like member shown in FIG. 14B.
DESCRIPTION OF THE INVENTION
[0030]
　It will be described below embodiments of the present invention. In the following description, will be described by way of example embodiments of the present invention, the present invention is not limited to the examples described below.
[0031]
　Manufacturing method of the present embodiment is a method for producing a forged crankshaft. Its forged crankshaft, a plurality of journal portion J as a center of rotation, a plurality of pin portion P which is eccentric with respect to a plurality of journal portions J, a plurality of connecting the plurality of journal portions J and a plurality of pin portion P comprising a crank arm portion a, a. At least one of the plurality of crank arm portion A is arm AW there weight having a counterweight portion W. Manufacturing method of the present embodiment includes an eccentric step and reduction step.
[0032]
　Reduction step, by reduction of the first portion is a part of the length of the rod-like member by the first mold pair, it is a step of reducing the cross-sectional area of ​​the first portion. With the first portion is held by being pressure by the first mold, the next eccentric step is performed.
[0033]
　Rod-like member which is rolling at a reduction step is a member made of a material of the forged crankshaft. The said rod-like member, it is possible to use a material called as the above-described billet.
[0034]
　The pressure step, to the first site may be pressure once, the first region a plurality of times (e.g., twice) may be pressure. An example of when the first site is rolling twice is carried out as follows. First, the pressure of the first round, to rolling the first part of the rod-like member. This reduction, the cross section of the first part, together with the shortening in the pressing direction, extend in a direction perpendicular to both the longitudinal direction of the pressing direction and the rod-like member. In the next second round of pressure, the rod-like member rotate 90 °, to pressure the first site again. For example, if the cross section of the rod-shaped member is round, the cross-section becomes elliptical shape by pressure of the first round. Reduction of the second round is performed in a state in which direction is disposed so that the vertical direction (direction of gravity) of the major axis of the elliptical cross-section. By thus performing a reduction of two, it is possible to greatly reduce the cross-sectional area of ​​the first portion.
[0035]
　Eccentric step, a first portion which is pressure while holding the first mold, a step of decentering the second portion of the rod-like member by the second mold. The second portion is at least part of the region excluding the first region among the bar-like member. That is, some or all of the sites except the first site among the bar-like member is a second site. In one example, all of the sites that are sandwiched between the first portion and second portion.
[0036]
　Eccentric direction of the second mold (eccentric direction of the eccentric steps), reduction of the first mold direction (pressing direction in pressure step), and, respectively a direction perpendicular to the longitudinal direction of the rod. According to this arrangement, without receiving influence of the material movement of the first mold and the longitudinal direction, it is possible to arbitrarily set the eccentricity of the second mold. In a typical example, the pressure step, the first mold is moved in the vertical direction, the second mold is moved mainly in a horizontal direction in an eccentric step.
[0037]
　The second portion may include a weight there arm corresponding portion AWC the weight there arm AW. In weight there arm AW, the weight portion W is eccentric to the opposite side of the pin portion P which arm AW There the weight are in contact. Since the weight portion W has a large volume, it is preferable to eccentric eccentric step arm corresponding portion AWC there weight becomes the weight there arm AW.
[0038]
　In weight there arm AW, counterweight unit W is eccentric in a direction opposite to the pin portion P which weight there arm AW contacts. When the second site comprises an arm portion corresponding AWC there weight, the manufacturing method of the present embodiment may satisfy the following condition (1). According to the following eccentric steps, it facilitates the formation of the weight portion W in the subsequent steps and improve the material yield.
(1) in an eccentric step, it is decentered in a direction corresponding to the second portion to the eccentric direction of the counterweight unit W.
[0039]
　Here, "a direction corresponding to the eccentric direction of the counterweight portion W", when the twisting process is not provided after the equal to the eccentric direction of the counterweight unit W. On the other hand, if the twisting step is provided after "direction corresponding to the eccentric direction of the counterweight portion W" refers to the direction closer to the eccentric direction of the counterweight unit W.
[0040]
　When the second site comprises an arm portion corresponding AWC there weight, the manufacturing method of the present embodiment, the following (2) and / or (3) Conditions may further meet the.
(2) the first site comprises a portion to be the journal portion J.
Including (3) a second site, the pin portion corresponding to the pin portion P, and the weight there arm equivalent portion AWC.
[0041]
　In condition (2), the first site may include all of the journal equivalent portions. In that case, it is possible to decenter the second portion without eccentric journal equivalent portions in an eccentric step.
[0042]
　Manufacturing process meeting the above (3) condition (e.g. (conditions 2) and (3)), the following (4) and (5) Conditions may further meet the.
(4) In the pressure step, reducing the cross-sectional area of the pin corresponding portion by rolling a pin-corresponding portion of the rod by a pair of third mold.
(5) in an eccentric step, while holding the pin corresponding portion by the third mold, it is decentered pin corresponding portion while moving the third mold by a second die.
[0043]
　In one throws including weight portion W, and the pin portion P and the weight portion W is eccentric in the opposite direction. Therefore, in the manufacturing method satisfies the condition (3) (e.g., (2) and (condition 3)), in a step after the eccentric step, is decentered opposite the direction of the arm portion corresponding there weight pins corresponding portion it becomes necessary. In that case, the manufacturing method of the present embodiment may satisfy the conditions of the following (6) and (7).
(6) the production method of the present embodiment further includes a die forging step for forming a rough forged material by following the eccentric step, die forging a wasteland formed by an eccentric step.
(7) In die forging step, by die forging the second portion, the coarse pin portion comprising a pin portion P, and formed in the direction opposite to the eccentric direction of the second site in an eccentric step.
[0044]
　Rough forging are formed by die forging step has a shape substantially equal or, close to it the shape and the shape of the final product forged crankshaft. When performing die forging step of (6) and (7), burr rough forging may be formed. It has been made sufficient volume distribution in an eccentric step in the manufacturing method of this embodiment. Therefore, even when the burr is generated in the forging step, it is possible to reduce the amount of burrs as compared with the conventional manufacturing method.
[0045]
　In the production method satisfies the condition (3) (e.g. (conditions 2) and (3)), the pin corresponds section may be eccentric in steps other than die forging step.
[0046]
　Hereinafter, an example of a method for manufacturing the forged crankshaft of the present embodiment will be described with reference to the drawings. The embodiments described below are exemplary, at least a portion of the configuration in the following embodiment, can be replaced with the above-described configuration.
[0047]
1. Manufacturing process Example
　forged crankshaft manufacturing method of this embodiment is the subject connects the journal portion J which is a rotation center, and the pin portion P which is eccentric with respect to the journal portion J, the journal portion J and the pin portion P It comprises an arm section a, a. Some or all of the arm portion A is provided with a weight portion W. The manufacturing method of this embodiment, for example, can be directed to a crankshaft of a four-cylinder -8 Like counterweight shown in FIG 1F. It is also possible to target the crankshaft of a four-cylinder -4 sheets counterweight above. Alternatively, it is also a three-cylinder engine, to be directed to a crankshaft mounted in series 6-cylinder engine, V-type 6-cylinder engine or an eight-cylinder engine or the like.
[0048]
　Method for producing a forged crankshaft of the present embodiment includes a reduction step, an eccentric step. The pressure step, pressure in the longitudinal direction of the part (first portion) of the rod-like member by a first mold pair, reducing the cross-sectional area of ​​the part. The eccentric step, while holding the first site that was pressure by the first mold, the second mold, is decentered longitudinal part of the rod-shaped member (second part). Thereby promoting the distribution of the volume of the rod. Details of pressure steps and the eccentric step, described below.
[0049]
　Processing consisting of rolling steps and the eccentric step of the present embodiment corresponds to preforming of the conventional manufacturing process, and more specifically, corresponds to a preformed consisting roll forming and bending beating. Roll forming and bending beating is carried out respectively by a different equipment, but in the manufacturing method of this embodiment, the processing consisting of rolling steps and the eccentric steps, as described below, can be carried out in a single press machine.
[0050]
　Rod-like member is a workpiece, for example, can be a billet. Alternatively, it can be an initial wasteland with reduced cross-sectional area in a part of the length. Its initial wasteland, for example, obtained by performing the roll forming or the like billets.
[0051]
　After preforming, for example, similarly to the manufacturing process shown in FIG. 1D ~ Figure 1F, it can be added to the die forging process and burr punching process, if necessary, add shaping step after the burr punching process. Die forging step may be comprised of rough stamped and finishing beating. Incidentally, when the adjustment of the arrangement angle of the pin portion is required, after the burr punching process, twisting process is added. These steps are all carried out in a series between heat.
[0052]
　Alternatively, as a step after the preforming, it may be added step of processing the molding apparatus described in WO2014 / 038183 (Patent Document 4). Patent Document 4, the molding apparatus for molding materials for striking finish from a crude material roughness shape of the crankshaft is shaped is proposed. As a crude material, using a wasteland obtained by reduction steps and the eccentric step. In this case, after the step of processing by the above forming apparatus, it may be added finishing forging step and burr punching step may be to add a shaping step as needed. These steps are all carried out in a series between heat.
[0053]
2. Reduction step and the eccentric step
　for processing flow example by reduction steps and the eccentric step will be described with reference to the drawings. This processing flow example is directed to the crankshaft of a four-cylinder -8 sheets counterweight.
[0054]
　Figure 2A ~ Figure 5B is a schematic diagram showing a processing flow example by reduction steps and the eccentric step. Figures 2A and 2B of which is a longitudinal sectional view, Fig. 2A when pressure starts, Figure 2B shows the time reduction ends, respectively. FIG 2A and FIG 2B is omitted, the rod-like member 51 (billet), shows a first mold 10 of the pair, to facilitate the understanding of the drawings, the second mold to be described later.
[0055]
　3A and 3B, a top view, FIG. 3A shows the time reduction completion, Figure 3B a time eccentric ends respectively. FIG 3A and 3B, the first upper die 11 of the rod-shaped member 51, wasteland 52, first mold 10 of the pair, and show a second die 20. To facilitate understanding of the drawings, in FIGS. 3A and 3B, respectively hatching first upper die 11 and second die 20 is subjected.
[0056]
　FIGS. 4A ~ 4D are schematic views showing the rod-like member at the reduction completion, 4A is a side view, Figure 4B is a top view, FIG. 4C IVC-IVC sectional view, FIG. 4D is a IVD-IVD sectional view is there. Further, FIGS. 5A and 5B are schematic views illustrating an eccentric end of the rod-like member (wasteland 52), FIG. 5A is a side view, FIG. 5B is a top view. The bottom of FIG. 5B, with different parts of wasteland 52, to indicate the correspondence between each part of the forged crankshaft (final product) shows the shape of a forged crankshaft 1 in phantom.
[0057]
　In this processing flow example, the first die 10 of the pair is constituted by a first upper die 11 and the first lower die 12. The first upper die 11 is fixed to the upper base plate of the press (not shown), the first lower die 12 is fixed to the lower base plate of the press (not shown).
[0058]
　Such pair of first mold 10, and pressure the part of the length of the rod-shaped member 51 (billet), the first portion 51a (hereinafter, also referred to as "reduction unit") to reduce the cross-sectional area of ​​the. In this processing flow example, the site to be site (journal equivalent portions) and the front portion of the journal portion (hereinafter, also referred to as "front-corresponding portion") is the pressure portion 51a (see FIGS. 5A and 5B).
[0059]
　The first upper die 11 and the first lower mold 12 has respective concave mold engraved part to pressure the pressure portion 51a of the above. Cross-sectional shape of the mold engraving unit is, for example, a parabolic or semi-elliptical shape.
[0060]
　The first mold 10, the longitudinal part of the rod-shaped member 51 is largely opened. More specifically, the first mold 10, portions that are not pressure (hereinafter, also referred to as "non-pressure portion") range corresponding to is opened. In this processing flow example, the range corresponding to the site of the pin portion (pin equivalent part) and a set of weights there arm corresponding portion to connect with the pin corresponding portion (portion to be an arm section having a weight section) is opened . That is, the range corresponding to the slow-corresponding portion is opened. Furthermore, the site comprising a flange portion (hereinafter, also referred to as "flange corresponding portion") range corresponding to also open.
[0061]
　At least a portion of their open range, the second die 20 is disposed. By its second die 20, the second die 20 presses against which the second portion 51b among the bar-like member 51 (hereinafter also referred to as "eccentric portion") is eccentrically. As the eccentric portion 51b is at least part of the non-pressure portion. In this processing flow example, the eccentric portion 51b is a slow-corresponding portion of the non-pressure portion (a flange corresponding portion and the slow-corresponding portion). The second mold 20, pressure by the first mold 10 direction, and is movable along the respective perpendicular direction of the longitudinal direction of the rod-shaped member 51 (see arrows hatched in FIG. 3B) .
[0062]
　Reduction step and the eccentric step can be performed as follows using the first mold 10 and second mold 20 described above.
[0063]
　With the operation of the press, is separated from the first upper die 11 and the first lower mold 12, on the first lower mold 12, the cross-sectional shape for mounting the rod-shaped member 51 is circular. At that time, the second die 20, in order to prevent interference of the rod 51 is retracted.
[0064]
　Subsequently, the pressure step, lowers the first upper die 11 with the operation of the pressing machine, the rod-like member 51 is brought into contact with the first upper die 11, to start the reduction of the first mold 10 (Fig. 2A reference). Further lowering the first top die 11, the pressure of the first die 10, the cross-sectional area decreases in the longitudinal direction of the part of the rod-shaped member 51 (the above-mentioned pressure portion 51a). To reach a bottom dead center further lowers the first upper die 11, and ends the pressure (see Fig. And Fig. 2B 3A). As a result, the cross-sectional shape of the pressure portion 51a is deformed into a flat shape from the circular shape (see FIG. 4D).
[0065]
　In reducing cross-sectional area at a reduction unit 51a, the material of the pressure portion 51a, without flowing as burrs, it flows into the non-pressure portion. Thus, increased cross-sectional area in a non-pressure portion of the foregoing, the volume of the rod-shaped member 51 is distributed in the longitudinal direction (see FIGS. 4A ~ Figure 4D).
[0066]
　The eccentric step, by maintaining the position of the first upper die 11 to the bottom dead center, pinching and holding the pressure portion 51a of the rod 51 in the first mold 10 of the pair. In this state, by moving the second mold 20 is pressed against the rod-shaped member 51 (see FIG. 3B), is decentered eccentric portion 51b of the above (see FIG. 5B). Thereby promoting the distribution of the volume. In this way, wasteland 52 shown in FIGS. 5A and 5B are formed.
[0067]
　After eccentric completion, it retracts the second die 20, thereby raising the first top die 11. In this state, the wasteland 52 is taken out to be conveyed to a subsequent step.
[0068]
　In such a processing flow example can be adopted a method of manufacturing a forged crankshaft of the present embodiment, the reduce the cross-sectional area of ​​pressure portion 51a by the first mold 10 at a reduction step, the second die 20 in an eccentric step decentering the eccentric portion 51b. Therefore, it facilitates the allocation of volume.
[0069]
　Further, the eccentric step, since the first die 10 to hold the pressure portion 51a of the rod 51, can suppress the material flow to the pressure portion 51a from the eccentric portion 51b. Therefore, even when greatly reduced cross-sectional area of ​​the pressure portion 51a at a reduction step, it can be prevented from occurring overlies flaws in eccentric step. These as well, it can facilitate the distribution of the volume.
[0070]
　The method for producing a forged crankshaft of the present embodiment as is because it can facilitate the allocation of volume at preforming, it is possible to reduce the outflow of burrs in rough beating and finishing beating a subsequent step, thereby improving the material yield.
[0071]
　As described above, the pressure of the first mold 10 of the pair, can be achieved by a press machine. Operation of the second die 20, for example, below the wedge mechanism, or can be realized by a hydraulic cylinder or the like. Therefore, the reduction step and the eccentric step, can use existing presses, special equipment like a cross rolling method is required. Therefore, it is possible to suppress the increase in equipment cost.
[0072]
　Also, as in the processing flow example described above, in one stroke of the press machine (1 reciprocates), it is possible to perform the reduction step and the eccentric step. Thus, while maintaining or improving the manufacturing efficiency can be improved material yield.
[0073]
　As in this processing flow example, the first portion 51a which is pressure by a first mold (pressure unit) includes a journal portion corresponding, second portion 51b which is decentered by a second mold (eccentric portion), the pin preferably containing a substantial portion, and wait there arm equivalent portion. Thus, in preforming, it is possible to reduce the cross-sectional area of ​​the journal portion corresponding, it is possible to decenter the slow-corresponding portion. Accordingly, it further facilitates the distribution of the volume of the preliminary molding.
[0074]
　Arm portion corresponding eccentric portion 51b is there pin corresponds section and weight, that is, including the slow-corresponding portion, it is preferable to decentering the eccentric portion 51b at a portion side of the weight portion (opposite side of the pin corresponding portion) (see FIG. 5B ). Here, the crank shaft (final product), as compared to the cross-sectional area of ​​the pin portion, when the cross-sectional area of ​​the weight portion is large in many cases. If brought into eccentric eccentric portion 51b in this case site side as a weight portion, while suppressing the volume of the pin corresponding portion can be secured the volume at the site to be the weight section. As a result, it is possible to improve the material yield.
[0075]
　From the viewpoint of further facilitating the distribution of the volume of the preliminary molding pressure portion 51a preferably includes a front portion corresponding is more preferable. If forged crankshaft comprises a weight without arm part, from the viewpoint of further facilitating the distribution of the volume of the preliminary molding pressure portion 51a is more preferably includes a portion to be a weight without arm.
[0076]
　The pressure step, pressure pins corresponding portion by a pair of third mold, reducing the cross-sectional area of ​​the pin corresponding portion is preferred. In this case, the eccentric step, while holding the pin corresponding portion by the third mold, the second mold, the pin corresponding portion while moving the third mold it is sufficient to eccentricity. For processing flow example in the case of using a third die, with reference to the drawings.
[0077]
　FIGS. 6A ~ FIG 9B is a schematic diagram showing a processing flow example of using the third mold. 6A and 6B of which is a longitudinal sectional view, FIG. 6A when pressure starts, Figure 6B shows the time reduction ends, respectively. Further, FIGS. 7A and 7B are a top view, FIG. 7A shows the time reduction completion, Figure 7B the time eccentric ends respectively. FIG 6A ~ FIG 7B, as compared with FIG. 2A ~ Figure 3B described above, the third mold 30 in the pair is added. To facilitate understanding of the drawings, in FIGS. 7A and 7B, the first upper die 11, respectively hatching second die 20 and third upper die 31 is subjected.
[0078]
　8A and 8B are schematic views showing the rod-like member at the reduction ended in the processing flow example of using the third mold, FIG. 8A is a side view, FIG. 8B is a top view. Further, FIGS. 9A and 9B are schematic views showing the rod-like member at the eccentric ends in the processing flow example of using the third mold (wasteland 52), FIG. 9A is a side view, FIG 9B is a top view.
[0079]
　In this processing flow example, the third die 30 of the pair, and a third upper die 31 and the third lower die 32. The third upper die 31 is held on the upper base plate of the press (not shown), a third lower die 32 is held in the lower base plate of the press (not shown). Thus, in pressure step, with the operation of the press machine, pressure by the third mold 30 pins corresponding portion 51c from the same direction as the pressing direction of the first mold 10. The third upper die 31 and the third lower die 32 are both pressure by the first mold 10 direction, and, (see arrow hatched in FIG. 7B) the longitudinal direction of the respective perpendicular direction of the rod-like member 51 It is held movably in along. Along with this movement, in an eccentric step, it is eccentric pins corresponding portion 51c. In this way wasteland 52 is formed.
[0080]
　The third upper die 31 and the third lower die 32 has respective concave mold engraved part to pressure the pin-corresponding portion 51c. Cross-sectional shape of the mold engraving unit is, for example, a parabolic or semi-elliptical shape.
[0081]
　The third in the pressure step in the case of using the mold 30, with the operation of the press, the first upper die 11 is lowered a third upper die 31, the bottom dead center of the first top die 11 and the third upper die 31 until to reach (see FIG. 6B and FIG. 7A). At that time, the first die 10, pressure portion 51a of the rod 51 (journal equivalent portions and the front portion corresponding) is rolling, the cross-sectional area of ​​those sites is reduced. In addition, the third mold 30, and pressure pins corresponding portion 51c of the rod 51, the cross-sectional area of ​​the pin corresponding portion 51c is reduced. As a result, the cross-sectional shape of the pin corresponding portion 51c of the rod 51, similarly to the journal corresponding portion shown in FIG. 4D, is deformed into a flat shape from a circular shape.
[0082]
　A first upper die 11 and the third upper die 31 need not necessarily be lowered simultaneously. For example after the first upper die 11 is lowered to the bottom dead center before, the third upper die 31 may be lowered. By doing so, that the material to be extruded is rolling material and the third upper die 31 to be extruded is pressure in the first upper die 11 in the axial direction interfere with each other, it must load increases there are effects such as suppressing.
[0083]
　The eccentric step, by maintaining the position of the first upper die 11 and the third upper die 31 to the bottom dead center, holds the journal equivalent portions and the front corresponding portion of the rod-shaped member 51 in the first mold 10 of the pair , it holds the pin corresponding portion 51c of the rod 51 in a pair of third mold 30. In this state, moving the second mold 20, by pressing the rod-like member 51, is decentered eccentric portion 51b (the pin corresponding portion 51c and the weight there arm equivalent portion) (see FIG. 7B). At that time, since the pin corresponding portion 51c is held by the third mold 30 of a pair, between the pin corresponding portion 51c of the second die 20 and the rod member 51, third die 30 is interposed. Along with pressing the second die 20, third die 30 is a pin corresponding portion 51c of the rod 51 while moving eccentrically. In this way wasteland 52 is formed.
[0084]
　By using this way the third mold 30 in the pair, in a state of reduced cross-sectional area of ​​the pin portion corresponding 51c, it is possible to eccentric pins corresponding portion 51c. Further, the eccentric step, since the holding pins corresponding portion 51c by a pair of third mold, prevents the wait there material from the arm portion corresponding to the pin corresponding portion 51c is to flow. Therefore, it is possible to further facilitate the distribution of the volume.
[0085]
　Operation of the second die 20, for example, below the wedge mechanism, or can be realized by a hydraulic cylinder or the like. With operating the second mold reliably synchronized with reciprocation of the press, from the viewpoint of realizing a high speed operation, it is preferable to operate the second die by the wedge mechanism. Hereinafter, a configuration example of a case of operating the second die by the wedge mechanism will be described with reference to the drawings.
[0086]
　Figure 10A ~ FIG. 10C is a cross-sectional view schematically showing a configuration example of a case of operating the second die by the wedge mechanism, Figure 10A before rolling, at Figure 10B is pressure ends, FIG. 10C is a second showing the mold of the operation, respectively. FIG 10A ~ FIG 10C, showing a portion of the press 40, the rod-like member 51 (billet), and the first mold 10 of the pair, and the second die 20, and a wedge 44. Press 40 includes a bed 43, an upper base plate 41 to reciprocate vertically, a lower base plate 42, the elastic member 45 and a (eg, a spring). Lower base plate 42 is vertically movably held on the bed 43 via the elastic member 45.
[0087]
　The first upper die 11 of the first mold 10 is fixed to the upper base plate 41, the first lower die 12 is fixed to the lower base plate 42. The second mold 20 is a movable state along a (horizontal direction in this configuration example) rolling direction perpendicular to the direction of the first mold, is held in the lower base plate 42. The part of the bottom surface of the second die 20, and an inclined surface 20a, the height of the inclined surface 20a is higher as the distance from the first die 10. The wedge 44 extends in the vertical direction, the lower end of the wedge 44 is fixed to the bed 43. The upper surface of wedge 44 is an inclined surface 44a, the height of the inclined surface 44a is higher as the distance from the first die 10.
[0088]
　When adopting such a configuration example, the pressure step, the first upper die 11 with the descent of the upper base plate 41 is lowered. Accordingly, the first die 10 of the pair, rod-like member 51 is pressure. Spring constant and the like of the elastic member 45, since it is suitably adjusted based on the load that is added to the lower base plate 42 at a reduction process, elastic member 45 of the reduction process is not much shrink. Therefore, since almost no lowering the lower base plate 42 at a reduction process, the second die 20 hardly moves in the horizontal direction.
[0089]
　Further lowering the upper base plate 41, and the parting surface of the first upper die 11, and the parting surface of the first lower mold 12 abuts reduction is completed (see FIG. 10B). After reduction completed and further lowering the upper base plate 41, the load to be added to the lower base plate 42, greatly increased compared to the reduction process, it contracts the elastic member 45 (see FIG. 10C). Accordingly, the first upper die 11, a first lower die 12 and second die 20 is lowered. At that time, the inclined surface 20a of the second mold 20 is pressed on the inclined surface 44a of the wedge 44, (see arrow hatched in FIG. 10C) in which the second die 20 is moved to the horizontal direction. Thus, the second die 20 is pressed against the rod-shaped member 51, a portion of the rod 51 eccentrically. Thus employing a wedge mechanism, it is possible to operate the second mold with the reciprocating motion of the upper base plate 41.
[0090]
　In the configuration example using the above-described processing flow example and a wedge mechanism, after completion of the reduction by the first mold 10 of a pair, to initiate the eccentricity of the second die 20. In the method of manufacturing the forged crankshaft of the present embodiment, at the end of pressure by the first mold 10 of a pair may start the eccentricity of the second die 20. That is, the end of the pressure step may initiate eccentric step.
[0091]
　When starting eccentric step late in the reduction step, the first moving distance of the mold at the start of the eccentric step preferably set to less than 75% to 100%. Here, the moving distance of the first mold is a distance that one of the first upper die or the first lower mold has moved relative to the other (mm), the time reduction start 0%, at pressure ends It is referred to as 100%. If the moving distance of the first mold at the start of the eccentric step 75% or more, holding the rod-like member 51 according to the first die 10 becomes sufficient, and the type engraved portion of the first upper die 11 and the first since the mold space formed by the mold engraved portion of the lower mold 12 is sufficiently narrow, it can be reliably suppressed material flow to pressure portion from the eccentric portion.
[0092]
　In terms of reducing equipment load, similarly to the configuration example using a processing flow example and the wedge mechanism described above, after the reduction step completion, preferably starts eccentric step. This is because the energy reduction in the first die, the energy for the horizontal movement of the second mold is required at the same time, because the equipment capacity is increased.
[0093]
　In the configuration example using the above-described processing flow example and a wedge mechanism, of the second die 20, a rod-like member 51 abutting portions of the shape as the plane shape, as a result, step-like level difference S and a reduction unit 51a It is formed at the boundary between the eccentric portion 51b (see FIG. 5B). The height of the step S is the eccentric amount of the eccentric portion 51b. In the method of manufacturing the forged crankshaft of the present embodiment, at the boundary between the pressure portion 51a and the eccentric portion 51b may be eliminated the step S. That may be gradually changing the eccentricity around the boundary between the pressure portion 51a and the eccentric portion 51b. For example, by changing the shape of the second die 20 (site in contact with the rod-like member 51 equivalents) as appropriate, can eliminate the step S.
[0094]
　The processing flow example described above, reduction of the first mold 10 direction, and, along each perpendicular direction of the longitudinal direction of the rod-shaped member 51 (see arrows hatched in FIG. 3B and FIG. 7B), the second to move the mold 20. Moving direction of the second die 20, i.e., a direction to decenter the eccentric portion 51b of the rod-like member, for example, may be appropriately set according to the shape of the forged crankshaft (product shape).
[0095]
　May be die forging under the conditions of the above-described the wasteland formed by the eccentric step (7). For example, in die forging step, the second portion of wasteland 52 (eccentric portion 51b) by die forging shown in Figure 5B, the crude pin portion comprising a pin portion P, opposite to the eccentric direction of the eccentric portion 51b it may be formed in the direction. The rough forged material 53 formed by such die forging step shown in FIG. 11. Figure 11 is a top view of the rough forging 53, the arrangement direction of the rough forging 53 in FIG. 11, are the same as the arrangement direction of wasteland 52 in Figure 5B.
[0096]
　Rough forging 53 of FIG. 11 is obtained by die forging the wasteland 52 shown in Figure 5B. Rough forging 53, coarse arm corresponding to the journal portion J1 crude journal corresponding to ~ J5 J1 '~ J5', crude pin portion corresponding to the pin P1 ~ P4 P1 '~ P4', the arm portions A1 ~ A8 part A1 '~ A8', crude counterweight unit corresponding to counterweight portions W1 ~ W8 W1 '~ W8', rough front portion Fr corresponding to the front portion Fr ', and the crude flange Fl corresponding to the flange portion Fl 'including. In each throw, and the eccentric direction of the eccentric direction and the coarse counterweight portion of the crude pin portion opposite. That is, the eccentric direction of the coarse counterweight portion, the eccentric direction of the rough pin coarse arm having the rough counterweight unit is in contact is reversed.
[0097]
　Die forging to form a rough forged material 53 from wasteland 52 may be performed by a general die forging burr B occurs. Even if the burr B is caused by performing an eccentric step of moving the material to the counterweight unit W side in advance, thereby improving the material yield. The rough forged material 53, a predetermined process (for example, finishing forging step and burr punching step) by subjecting to, it is possible to obtain a forged crankshaft 1 shown in dotted line in FIG. 9B. It is also possible to similarly die forging the wasteland 52 shown in FIG. 9B.
[0098]
　In the above example, it illustrated for forged crankshaft of a four-cylinder -8 sheets counterweight. As described above, the manufacturing method of this embodiment can be used for the production of other forged crankshaft. For example, it can be used in the production process of forged crankshaft including an arm portion A having no weight portion W. As such an example, an example of manufacturing a forged crankshaft of a four-cylinder -4 Like counterweights will be described with reference to FIGS. 12A ~ FIG 12C.
[0099]
　Figure 12A is a top view of a forged crankshaft 1 of a four-cylinder -4 Like counterweight. In forged crankshaft 1 shown in FIG. 12A, the arm portions A1, A4, A5, and A8 each have a weight portion W1, W4, W5, and W8. The other arm portion has no weight portion, the cross section is, for example, elliptical.
[0100]
　In the manufacture of forged crankshaft 1 shown in FIG. 12A, it performs the reduction step and the eccentric step described above. Figure 12B is a side view corresponding to FIG. 4A, showing the shape of the reduction step at the end of the rod 51. The pressure step, the first portion (pressure portion 51a) is pressure. Reduction unit 51a in this example is no weight arms corresponding portion, and includes a journal portion corresponding, it may further comprise at least a portion of the pin portion corresponding.
[0101]
　In the next eccentric step, as shown in FIG. 12C, to form a wasteland 52 by decentering the second portion (eccentric portion 51b). Figure 12C is a top view corresponding to FIG. 5B. Eccentric portion 51b in this example includes a wait there arm equivalent portion. In this way, the wasteland 52 for producing forged crankshaft 1 (4-cylinder -4 Like counterweight) obtained.
[0102]
　For another example of producing a forged crankshaft 1 of a four-cylinder -4 Like counterweight shown in FIG. 12A, it will be described with reference to FIGS. 13A ~ FIG 13B. In this example, performing a reduction step and the eccentric step described above.
[0103]
　Figure 13A is a side view corresponding to FIG. 4A, showing the shape of the reduction step at the end of the rod 51. The pressure step, the first portion (pressure portion 51a) is pressure. The first part of this example is no weight arms corresponding portion, and comprise a portion of the journal equivalent portions may further comprise at least a portion of the pin portion corresponding. The first portion, of the journal equivalent portions, does not include a portion to be a journal portion J3.
[0104]
　In the next eccentric step, as shown in FIG. 13B, by decentering the second portion (eccentric portion 51b), to form a wasteland 52. Figure 13B is a top view corresponding to FIG. 5B. Eccentric portion 51b of the example, the weight there arm equivalent portion, and includes a journal portion corresponding to the journal portion J3. In this way, the wasteland 52 forged crankshaft 1 of a four-cylinder -4 Like counterweights obtained.
[0105]
　An example of manufacturing a forged crankshaft of 3 cylinders -4 Like counterweights will be described with reference to FIGS. 14A ~ FIG 14C. Figure 14A is a top view of a forged crankshaft 1 of 3 cylinders -4 Like counterweight. In forged crankshaft 1 shown in FIG. 14A, the arm portions A1, A2, A5, and A6 each have a weight portion W1, W2, W5, and W6. Arm portions A3 and A4 has no weight portion, the cross section is, for example, elliptical. Pin P2 between the arm portion A3 and the arm portion A4 is eccentric in a direction perpendicular to the paper surface.
[0106]
　In the manufacture of forged crankshaft 1 shown in FIG. 14A, it performs the reduction step and the eccentric step described above. Figure 14B is a side view corresponding to FIG. 4A, showing the shape of the reduction step at the end of the rod 51. The pressure step, the first portion (pressure portion 51a) is pressure. Reduction unit 51a in this example comprises weight without arm equivalent portion, the pin portion corresponding sandwiched weight without arm equivalent portion, and the journal equivalent portions.
[0107]
　In the next eccentric step, as shown in FIG. 14C, by decentering the second portion (eccentric portion 51b), to form a wasteland 52. Figure 14C is a top view corresponding to FIG. 5B. Eccentric portion 51b of the example, the weight there arm equivalent portion, and includes a pin portion corresponding sandwiched arm corresponding portion there weight. In this way, wasteland 52 forged crankshaft 1 of 3 cylinders -4 Like counterweight is obtained.
Industrial Applicability
[0108]
　The present invention can be effectively utilized in the production of forged crankshaft mounted in a reciprocating engine.
DESCRIPTION OF SYMBOLS
[0109]
　1: Forged crankshaft
　10: first mold, 11: first upper mold, 12: first lower mold, 20: second
　mold, 20a: inclined surface 30: third mold, 31: third upper type 32: third lower
　die, 40: press 41: upper base plate, 42: lower base
　plate, 43: bed, 44: wedge, 44a: inclined surface, 45: elastic
　member, 51: rod-like member, 51a: the first portion (pressure
　portion), 51b: second portion (eccentric
　portion), 51c: a pin portion sites (pin equivalent
　part), 52: wasteland
　a, A1 ~ A8: crank arm, B: Bari,
　J, J1 ~ J5: journal portion, P, P1 ~ P4: pin part, Fr: the front
　section, Fl: flange portion, W, W1 ~ W8: counterweight section

The scope of the claims
[Requested item 1]
Forging and a plurality of journal portion as a rotational center, and a plurality of pin portions eccentric to the plurality of journal portions, and a plurality of crank arm connecting the said plurality of journal portions of the plurality of pin portions a method of manufacturing a crankshaft,
　at least one of said plurality of crank arm is the arm part there weight having a counterweight portion,
　said manufacturing method,
　the longitudinal direction of the rod-like member by the first mold pair by rolling the first part is a part, and reduction steps to reduce the cross-sectional area of the first portion,
　while maintaining the pressure by said first portion by said first die, said rod-like member wherein an eccentric step of decentering the second portion by a second mold, a
　second portion, at least a portion of the sites except the first site is one of the bar-like member There,
　the eccentric direction of the second mold, the first mold by the pressing direction, and the respectively perpendicular directions of the longitudinal direction of the rod-like member, the manufacturing method of the forged crankshaft.
[Requested item 2]
　A method of manufacturing a forged crankshaft according to claim 1,
　wherein the second site, comprising said weight there arm corresponding portion becomes weight there arm portion, the manufacturing method of the forged crankshaft.
[Requested item 3]
　A method of manufacturing a forged crankshaft according to claim 2,
　in the weight there arm portion, the counterweight portion, said said pin portion weight there arm portion is in contact is eccentric in the opposite direction,
　the in eccentric step, is decentered said second portion in a direction corresponding to the eccentric direction of the counterweight unit, the production method of the forged crankshaft.
[Requested item 4]
　A method of manufacturing a forged crankshaft according to claim 2 or 3,
　wherein the first site comprises a site serving as the journal portion,
　the second portion is a pin corresponding portion serving as the pin portion, and, the wait there comprises an arm portion corresponding method for producing a forged crankshaft.
[Requested item 5]
　A method of manufacturing a forged crankshaft according to claim 4,
　in the pressure step, reducing the cross-sectional area of the pin corresponding portion by rolling the pin corresponding portion of the rod-shaped member by a pair of third mold is,
　the eccentric step, while holding the pin corresponding portion by the third mold, the decentering of the pins corresponding portion while moving the third mold by a second die, forged crankshaft Production method.