0001]The present invention relates to a method of manufacturing a crankshaft, in particular, to a method for producing a crankshaft by hot forging.
BACKGROUND
[0002]Automobiles, motorcycles, in agricultural machinery or reciprocating engine of a ship or the like, to take out the power converts the reciprocating motion of the piston into rotary motion, the crank shaft 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. 1A is an overall view of which, FIG. 1B is a IB-IB cross section. 1B, the order to facilitate understanding of the shape of the crank shaft, one of the crank arm A7, the counterweight portion W7 integral with the crank arm A7, the pin portions P4 and journal portion connecting with the crank arm portion A7 It is shown by extracting and J4.
[0004]
　Crankshaft 11 illustrated in FIGS. 1A and 1B, mounted on the four-cylinder engine, a crankshaft of a four-cylinder -8 sheets counterweight. As the crankshaft 11 has five journal portions J1 ~ J5,4 one pin portions P1 ~ P4, the front portion Fr, flanges Fl, and, of eight crank arm portion (hereinafter, also referred to as "arm") A1 ~ consisting of 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) has 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 leads the first journal portion J1 of the top flange portion Fl leads 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]
　Pin top PT is the tip of the pin portion, as shown in FIG. 1B, which is the most distant part from the center of the journal portion J4 among the pin P4.
[0007]
　Forged crankshaft having such a shape, generally with the billet raw material. In that billet, billet cross section perpendicular to the longitudinal direction, i.e. transverse cross section is round or square cross-sectional area is constant over the entire length. Hereinafter, the longitudinal direction of the billet or wasteland, "cross section" of the cross section perpendicular to the axial direction of the crankshaft, a cross section parallel to as "longitudinal section". Further, the cross-sectional area of ​​the cross section referred to simply as "sectional area". In the manufacture of forged crankshaft, preforming step, the mold forging step and burr punching process are provided in this order. Further, if necessary, shaping step is provided 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.
[0008]
　Figure 2A ~ Figure 2F is a schematic view for explaining a conventional general forged crankshaft manufacturing process. Figure 2A is a billet of which, Figure 2B roll wasteland, Figure 2C is bent wasteland, Figure 2D rough forged material, Figure 2E shows the finish forged material, Figure 2F forged crankshaft, respectively. Figure 2A ~ Figure 2F show the fabrication process of a crankshaft of the shape shown in FIGS. 1A and 1B.
[0009]
　In the manufacturing method shown in FIGS. 2A ~ Figure 2F, forged crankshaft 11 is manufactured as follows. The sample is heated 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 reduction 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, by excess material flows out from between the parting surface of the mold facing each other, the burr B is formed. 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 FIGS. 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 has 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 integrally. Further, the remaining arm portions, specifically, the second, third, arm portions of the sixth and 7 (A2, A3, A6, A7) has no weight portion, the shape is oval to 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]
　Technology for the production of forged crankshaft, has been proposed. For example, in FIGS. 3 and 4 of WO 2014/038183 (Patent Document 1), is eccentric and fixed journaled for holding sandwich the crude journal portion as a journal portion, a coarse pin portion comprising a pin portion device comprising a pin-type is disclosed. In this apparatus, the moving direction of the fixed journal type and the pin type is the same.
[0017]
　Japanese Patent 2000-94087 (Patent Document 2), a method of manufacturing a crank shaft by die forging by rough stamping processing and finishing beating process is disclosed. In this way, the rough stamping process, the pin-side outer periphery of the pin portion does not form a burr.
[0018]
　The JP 2012-161819 (Patent Document 3), device comprising a journal holding type for holding a part to be a journal portion and a pin portion holding type for holding a part to be a pin portion is disclosed. Pin retentive includes an axial slide, and a radial slide. Therefore, the pin holding type is movable in the axial direction of the mold pressing direction and the material.
CITATION
Patent Document
[0019]
Patent Document 1: WO 2014/038183
Patent Document 2: JP 2000-94087 JP
Patent Document 3: JP 2012-161819 JP
Summary of the Invention
Problems that the Invention is to Solve
[0020]
　As described above, in the finishing beating process, forging using a pair of molds rough forging vertically. At this time, the mold facing the burr of rough forgings to position exists, there is a possibility that burrs portion becomes flaws. Also, when setting the rough forging press apparatus in the finishing beating process, if not stable arrangement of rough forging defects such as scratches are likely to occur. From the above circumstances, a new manufacturing method that can more reduce the occurrence of defects has been desired.
[0021]
　One of the objects of the present invention is to provide a method for producing a forged crankshaft can be further reduced occurrence of flaws.
Means for Solving the Problems
[0022]
　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 which are eccentric with respect to the journal portion, and a plurality of pin portions and a plurality of journal portions a plurality of crank arm portion connecting to a method for manufacturing a forged crankshaft with a. At least one of the plurality of crank arm includes a counterweight unit. Manufacturing method,
　an intermediate containing a plurality of coarse journal portion comprising a plurality of journal portions, and a plurality of coarse pin portion comprising a plurality of pin portions, a plurality of first crude crank arm portion comprising a plurality of crank arm portion, a a preforming step of forming a wasteland from billet,
　a plurality of rough journal portion of the intermediate wasteland while holding the pressure in the vertical direction by a pair of retentive, the axial direction of the holding-type pressing direction and intermediate wasteland final including an intermediate in the axial direction of wasteland by reduction of the intermediate wasteland, second coarse crank arm close to the shape of the crank arm portion than the first roughness crank arm causes decentering the crude pin portion in a direction perpendicular a forming step of forming a rough terrain,
　the final wasteland eccentric direction of the rough pin is arranged parallel to the horizontal direction, to rolling in the vertical direction using a pair of press dies Te including a plurality of journal portions, a plurality of pin portions, and the finishing forging step of forming a finish forged material including a plurality of crank arm portion.
Effect of the invention
[0023]
　According to the manufacturing method of the forged crankshaft of the present invention, it can be further reduced occurrence of flaws.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024]
[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 used in the manufacturing process of the conventional general forged crankshaft.
[Figure 2B] Figure 2B is a schematic diagram showing a roll wasteland in a conventional typical forged crankshaft manufacturing process.
[Figure 2C] FIG 2C is a schematic diagram showing a wasteland bending in a conventional typical forged crankshaft manufacturing process.
FIG 2D] FIG 2D is a schematic diagram showing a rough forged material in a conventional typical forged crankshaft manufacturing process.
FIG 2E] FIG 2E is a schematic view showing the finishing forging material in a conventional typical forged crankshaft manufacturing process.
FIG 2F] FIG 2F is a schematic view showing a forged crankshaft in a conventional typical forged crankshaft manufacturing process.
[Figure 3A] Figure 3A is a schematic diagram showing an example of a billet used in the manufacturing method of this embodiment.
[Figure 3B] Figure 3B is a schematic diagram showing an example of an initial wasteland produced by the production method of this embodiment.
FIG 3C] Figure 3C is a schematic diagram showing an example of an intermediate wasteland produced by the production method of this embodiment.
[Figure 3D] Figure 3D is a schematic diagram showing an example of a final wasteland produced by the production method of this embodiment.
FIG 3E] Figure 3E is a schematic diagram showing an example of a finishing forging produced by the production method of the present embodiment.
FIG 3F] Figure 3F is a schematic diagram showing an example of a forged crankshaft produced by the production method of this embodiment.
[Figure 4A] Figure 4A is a longitudinal sectional view schematically showing a pre-reduction in an example of a step of the pre-forming step.
[Figure 4B] Figure 4B is a longitudinal sectional view schematically showing a time reduction completion in an example of a step of the pre-forming step.
[Figure 5A] Figure 5A is a longitudinal sectional view schematically showing a time reduction start in an example of another process of preforming step.
[Figure 5B] Figure 5B is a longitudinal sectional view schematically showing a time reduction completion of an example of another process of preforming step.
[Figure 6A] Figure 6A is a longitudinal sectional view showing a state before the start of an example of a molding process schematically.
[Figure 6B] Figure 6B is a longitudinal sectional view showing a state of an example of a molding process schematically.
[Figure 6C] Figure 6C is a longitudinal sectional view schematically showing the state at the end of an example of a molding process.
[Figure 7A] Figure 7A is a top view of a horizontal section schematically showing the state before the start of an example of a molding process.
[Figure 7B] Figure 7B is a top view of a horizontal section schematically showing the end state of an example of a molding process.
[FIG. 8A] Figure 8A is a diagram showing a journal portion and a fixed-retentive in the vicinity in the state before the start of an example of a molding process.
[Figure 8B] Figure 8B is a diagram showing a journal portion and a fixed-retentive in the vicinity in the state at the end of an example of a molding process.
FIG 9A] FIG 9A is a diagram showing the rough pin and pin eccentric in the vicinity in the state before the start of an example of a molding process.
[FIG. 9B] FIG 9B is a diagram showing the rough pin and pin eccentric in the vicinity at the end of the state of one example of a molding process.
FIG 10A] FIG 10A is a diagram showing a first coarse arm portion and the fixed-retentive in the vicinity in the state before the start of an example of a molding process.
[FIG. 10B] FIG 10B is a diagram showing a second coarse arm portion and the fixed-retentive in the vicinity in the state at the end of an example of a molding process.
[11] FIG 11 is a graph schematically showing the relationship between the axial reduction process and the pin eccentric step in the molding process.
FIG 12A] FIG 12A is a longitudinal sectional view schematically showing a molding apparatus in a state at the start of the molding process.
[Figure 12B] Figure 12B is a longitudinal sectional view schematically showing a molding apparatus in a state during the molding step.
[FIG. 12C] FIG 12C is a longitudinal sectional view schematically showing a molding apparatus in the return status of the molding process.
FIG 13A] FIG 13A is a cross-sectional view schematically showing a molding apparatus in a state at the start of the molding process.
FIG 13B] FIG 13B is a cross-sectional view schematically showing a molding apparatus in a state during the molding step.
[FIG. 13C] FIG 13C is a cross-sectional view schematically showing a molding apparatus in the return status of the molding process.
[14] FIG 14 is a graph schematically showing the operation of each unit of the molding apparatus in the molding process.
DESCRIPTION OF THE INVENTION
[0025]
　Embodiments of the present invention will be described below. As will be described by way of example embodiments of the present invention in the following description, the present invention is not limited to the examples described below.
[0026]
　(Method of manufacturing a forged crankshaft)
　the production method of the present embodiment, a plurality of journal portions serving as the center of rotation (the journal portion J), a plurality of pin portions which are eccentric with respect to the journal portion J (the pin portion P) a method for producing a forged crankshaft having a plurality of crank arm portion connecting the plurality of pin portion P and a plurality of journal portions J and (arm a), a. At least one of the plurality of crank arm includes a counterweight unit W. The manufacturing method of this embodiment, the preliminary molding step, molding step, and a finishing forging process.
[0027]
　Examples of forged crankshaft produced in the present embodiment include the above-described example. All of the plurality of crank arm portion A may comprise a counterweight unit W, only a part of the plurality of crank arm portion A may comprise a counterweight unit W.
[0028]
　Preforming step, a plurality of rough journal portion comprising a plurality of journal portions J, a plurality of coarse pin portion comprising a plurality of pin portion P, a plurality of the plurality of crank arm A first rough crank arm a step of forming an intermediate wasteland billet containing. Preforming step may include a plurality of steps. There is no limitation to the preforming step, may be used known methods. For example, it may be used preforming process described in the Background section.
[0029]
　Molding process, in a state in which each of the plurality of coarse journal portion of the intermediate wasteland and held by pressure in the vertical direction by a pair of retentive perpendicular direction (horizontal direction to the axial direction of the holding-type pressing direction and intermediate wasteland by rolling the intermediate wasteland in the axial direction of the intermediate wasteland crude pin portion causes eccentric to), the closer the shape of the crank arm a (crank arm portion a of the forged crankshaft) than the first roughness crank arm a step of forming a final wasteland containing 2 crude crank arm portion. Hereinafter, the first coarse crank arm portion and a second coarse crank arm portion respectively, may be referred to as a "first rough arm portion" and "second coarse arm".
[0030]
　Retentive includes a fixed holding type which does not move in the axial direction of the intermediate wasteland, and a movable holding type which moves in the axial direction of the intermediate wasteland. Moving retentive moves axially while holding the rough journal portion. Molding step can be carried out by using the holding type and pin eccentric. Pin eccentric is a type that is decentered crude pin portion is movable in the direction of eccentricity of the pin portion.
[0031]
　In the molding process, the crude pin portion of the same only the intermediate rough terrain and the eccentric amount of the pin portion of the forged crankshaft (final product) may be eccentric. Alternatively, the amount by coarse pins of the intermediate wasteland may be eccentrically close to the eccentricity of the pin portion of the forged crankshaft. In this case, after the step (e.g. finishing forging step), further decentering the crude pin portion.
[0032]
　Finishing forging process, the final wasteland eccentric direction is arranged parallel to the horizontal direction of the rough pin portion, by reduction in the vertical direction by using a pair of press dies, a plurality of journal portions J, a plurality of a step of forming a pin portion P, and finishing forging including a plurality of crank arm a. Therefore, the journal portion of the finishing forging, the pin portion, and the shape of each part of the crank arm is substantially the same as those in the form of a forged crankshaft (final product). Incidentally, finish forging, it may optionally be subjected to twisting step. In a case of performing twisting process after the entire shape of the finished forging, not necessarily the same as the overall shape of the forged crankshaft. If you do not twist process, the shape of the finished forging may be substantially the same as the shape of the forged crankshaft except burrs.
[0033]
　The pair of press dies, using a press mold the shape of the finished forging is engraved. There is no particular limitation on the finishing forging process, may be used known methods.
[0034]
　Burr finishing forging, it can be removed by performing after the forging process finishing burr punching step of removing the burrs. There is no particular limitation to the burr punching step may be a known burrs Bleeding.
[0035]
　The manufacturing method of this embodiment may optionally after finishing the forging step (e.g. after burr punching step) may be performed shaping step. If adjustment of the arrangement angle of the pin portion is required, after the finish forging step (e.g. after burr punching step) may be performed twisting process. Twisting step, and the above-mentioned preforming step, forming step and finishing forging steps are all carried out in a series between heat.
[0036]
　In the production method of the present embodiment, the molding step may be carried out as burrs final wasteland is formed by outflow of Yozai the parting surface of the holding type extending in a horizontal direction. In the production method of the present embodiment, in either case the molding process and finishing forging process, intermediate wasteland or final wasteland is molded in a state in which the eccentric direction of the rough pin is arranged parallel to the horizontal direction . Therefore, even if the molding process as burr is formed is performed, it is possible to suppress in the finishing forging, the journal portion, a winding flaw at the site where there is a volume difference as the pin portion and the crank arm .
[0037]
　In the molding step, the crude front portion as the front part Fr of forged crankshaft, rough flange portion serving as a flange portion Fl of forged crankshaft, and, burrs may have formed on at least one moiety selected from the crude pin portion .
[0038]
　In the molding process, after end of the eccentricity of the crude pin portion may end the pressure of the intermediate wasteland in the axial direction. According to this configuration, it is possible to suppress the volume flow to the pin side of the crank arm from the counterweight unit can be easily secured the volume of the counter weight portion.
[0039]
　In the molding process, before the end of the eccentricity of the crude pin portion may end the pressure of the intermediate wasteland in the axial direction. According to this configuration, it is possible to mold the shape of Pinshoruda portion of the final wasteland more shape close to finishing forging, sit is more stable to the press-type final wasteland finishing forging process.
[0040]
　In the molding process, the end of the eccentricity of the crude pin portion at the same time, may end the pressure of the intermediate wasteland in the axial direction. According to this configuration, it is possible to suppress the volume flow to the pin side of the crank arm from the counterweight unit can be easily secured the volume of the counter weight portion. Further, since the short time of the molding process, thereby improving the production efficiency of the forging crankshaft.
[0041]
　Reduction of the intermediate wasteland in the axial direction in the molding step may be performed by a hydraulic cylinder. By using the hydraulic cylinder, the pressure of intermediate wasteland in the axial direction, it is easy to control independently of the eccentricity of the coarse pin portion.
[0042]
　Eccentricity of crude pin portion in the molding step may be performed using a wedge mechanism. For example, eccentricity of the coarse pin portion in the molding step may be performed using a fixed wedge on the bolster base. Eccentricity of crude pin portion can be carried out using a pin eccentric to move the wedge mechanism. For more information about the pin eccentric later.
[0043]
　Hereinafter, a method for manufacturing the forged crankshaft of the present embodiment will be described with reference to the drawings.
[0044]
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 connecting the parts P and a plurality of arm portions a (counter arm). At least one of the plurality of arm portions A includes a weight portion W (counterweight unit). In one example of the manufacturing method of this embodiment, the crank shaft of a four-cylinder -8 Like counterweight shown in FIGS. 1A and 1B is manufactured. Further, in another example, a crank shaft or the like of the four-cylinder -4 sheets counterweight described above is manufactured.
[0045]
　Figure 3A ~-3F are schematic views for explaining an example of a process of manufacturing the forged crankshaft of the present embodiment. In the example described in FIGS. 3A ~ Figure 3F, a crank shaft of the shape shown in FIG. 1 is manufactured. Figure 3A is a billet, Figure 3B shows the initial wasteland, Figure 3C intermediate wasteland, Figure 3D final wasteland, Figure 3E finish forged material, Figure 3F forged crankshaft (final product), respectively.
[0046]
　First, of the billet 22 is a workpiece, a portion comprising a pin portion (hereinafter, also referred to as "pin-corresponding portion") and the site of the journal portion (hereinafter, also referred to as "journal equivalent portions") reduces the cross-sectional area of ​​the It is allowed to form a small part 23a the cross-sectional area. This gives an initial wasteland 23 shown in Figure 3B. This step, for example, may be used reducer roll and cross roll.
[0047]
　Next, in order to further distribute the volume, the initial wasteland 23 pressure by the pair of press dies, to form an intermediate wasteland 24. There is no particular limitation to the reduction method can be applied a known method. Intermediate wasteland 24 includes a rough journal portion 24j of the journal portion J, a coarse pin portion 24p as the pin portion P, the first coarse arm portion 24a of the arm portion A (first coarse crank arm portion), a front portion Fr become rough front part 24FR, and includes a rough flange portion 24fl which the flange portion Fl, the.
[0048]
　Forming an intermediate wasteland 24 from the billet 22 is a pre-molding process. Process described in FIGS. 3B and 3C is only an example, it may be formed intermediate wasteland by other processes. It will be described in detail later preforming step.
[0049]
　Next, the molding process. In the molding step, to form the final wasteland 25 from the intermediate wasteland 24. As shown in FIG. 3D, the final wasteland 25 includes close to the shape of the arm portion A than the first roughness arm portion 24a second coarse arm 25a (second rough crank arm). The final wasteland 25, crude pin portion 25p, rough journal portion 25j, crude front portion 25Fr, and the crude flange portion 25 fL. For details of the molding process will be described later.
[0050]
　In the finishing forging step, as in the conventional finishing beating step, the die forging. By the finishing forging process to form the finished forging 26 from the final wasteland 25. As shown in FIG. 3E, finishing forging 26 includes a plurality of journal portions J, a plurality of pin portions P, and a plurality of arm portions A (omitted portion of the code). In FIG. 3E, an example is shown in which a burr B is formed in the finishing forging process. It will be described in detail later finishing the forging process.
[0051]
　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, to remove the burr B from the finish forged material 26. Accordingly, forged crankshaft 21 (final product) is obtained as shown in FIG. 3F. Since about the name of each part of the forged crankshaft 21, described in FIG. 1A and 1B, a description thereof will be omitted.
[0052]
2. One example of a pre-forming step
　diagrams 4A ~ Figure 5B is a schematic diagram showing an example of a preforming process. 4A and 4B show a process for forming an initial wasteland 23 shown in Figure 3B. 5A and 5B illustrate a process of forming an intermediate wasteland 24 shown in FIG. 3C.
[0053]
　FIG 4A, the billet 22 cross-section is round, showing a pair of press dies 30 above and below. Pressing die 30 includes an upper die 31 and a lower mold 32. The upper die 31 and lower die 32 has a shape for forming the initial wasteland 23 from the billet 22.
[0054]
　First, as shown in FIG. 4A, placing the billet 22 between the upper die 31 and lower die 32. In this state, by rolling the billet 22 lowers the upper die 31, to reduce the cross-sectional area of ​​the pin corresponding portion and the journal portion corresponding, to form a small part 23a the cross-sectional area. In this manner, a initial wasteland 23. In the initial wasteland 23, the cross section of the cross-section and journal corresponding portion of the pin corresponding portion are each elliptical. The long axis of their oval, extending in a direction perpendicular to the plane of Figure 4B.
[0055]
　Next, as shown in FIGS. 5A and 5B, a pair of press dies 40 above and below, press molding the initial wasteland 23. Press die 40 includes an upper die 41 and lower die 42. Upper die 41 and lower die 42 has a shape for forming the intermediate wasteland 24 from the initial wasteland 23.
[0056]
　First, as shown in FIG. 5A, place the initial wasteland 23 between the upper die 41 and lower die 42. At this time, it is performed in a state where the long axis of the elliptical cross section of the pin corresponding portion and the journal equivalent portions are arranged in parallel vertically extending (pressing direction). That is, the long axis of the cross section of the pin corresponding portion and the journal portion corresponding elliptical, it is arranged in a vertical direction parallel to the direction of the plane of FIG. 5A. In other words, the initial wasteland 23 formed by the press die 30, rotated 90 ° around the axis of the initial waste land 23 is disposed in the press mold 40.
[0057]
　Then, lowering the upper mold 41 an initial wasteland 23 pressure, thereby forming an intermediate wasteland 24. Intermediate wasteland 24, crude journal portion becomes journal portion J 24j, crude pin becomes the pin portion P 24p, first coarse arm portion 24a of the arm portion A (first coarse crank arm portion), a front portion Fr crude front part 24FR, and the crude flange portion 24fl which the flange portion Fl (see Fig. 3C). Crude pin portion 24p, to the crude journal portion 24j, is slightly eccentric to the eccentric direction of the pin portion P. The axial length of the intermediate wasteland 24, the axial direction of the forged crankshaft as a final product longer than the length.
[0058]
3. An example of a molding process
　diagram 6A ~ FIG 6C, 7A and 7B are schematic views showing an example of a molding process. A state before the start of FIGS. 6A and 7A the molding step, Fig. 6B is a state in an example of the forming process, FIG. 6C and FIG. 7B is a schematic view showing a state at the end of the molding process. 6A and 6B are a longitudinal sectional view through line VIA-VIA of FIG. 7A. Specifically, in FIG. 7A, a vertical section which connects the center line of the intermediate wasteland 24. 6C is a longitudinal sectional view through line VIC-VIC in FIG. 7B. Figure 7A is a top view showing a horizontal cross section along line VIIA-VIIA in FIG. 6A. Figure 7B is a top view showing a horizontal cross section along line VIIB-VIIB in FIG. 6C. More specifically, FIGS. 7A and 7B, slightly more parting surface of the holding die 60 is a cross-sectional view of the lower. For ease of understanding, FIGS. 6A ~ FIG 6C, 7A and 7B, shows the contour of an intermediate wasteland 24 and final wasteland 25 by a thick dotted line. Further, FIG. 7A and 7B, illustrates a portion of a contour of the later-described wedge receiving member 72a by the thin dotted line.
[0059]
　Referring to FIG. 6A, in the molding step, using retentive 60 and pin eccentric 71. Retentive 60 includes stationary retentive 61, movable holding die 62, the front-side holding type 63, and the flange side holding type 64. The mechanism for moving these types will be described later. Each of these types, including the upper and lower molds. That is, the holding die 60 is a pair of retentive (lower retentive 60a and upper retentive 60b). Specifically, the fixed holding tool 61 includes a stationary retentive 61b is fixed retentive 61a and the upper mold is a lower mold. Movable holding die 62 includes a movable holding mold 62a is lower die and a movable holding mold 62b is an upper mold. Front retentive 63 includes a front side holding type 63b is a front side holding type 63a and an upper mold is the lower mold. Flange side retentive 64 includes a flange-side holding type 64a is lower die and a flange-side holding type 64b is an upper mold. Pin eccentric 71 includes a pin eccentric 71a is lower die, and a pin eccentric 71b is an upper mold.
[0060]
　Lower mold, is disposed on the bolster base 102a to be described later. Upper mold is supported by the die cushion base 104 to be described later, it moves in the vertical direction along with the movement of the die cushion base 104.
[0061]
　Retentive 60 is the type that holds a rough journal portion 24j. Of retentive 60, stationary retentive 61 does not move in the axial direction of the intermediate wasteland 24. On the other hand, the movable holding die 62, the front-side holding type 63 and the flange side holding type 64, is movable in the axial direction of the intermediate wasteland 24. Pin eccentric 71 is a type which eccentric crude pin 24p, which is movable in the axial direction perpendicular to the direction of the pressing direction and intermediate wasteland 24 of the holding die 60. And each holding mold 60 and the pin eccentric 71, the first coarse arm portion is formed and has a recess 60c and recess 71c for forming a space disposed (FIG. 6A).
[0062]
　First, as shown in FIGS. 6A and 7A, it is placed intermediate wasteland 24 on the mold bottom. In this case, placing the intermediate wasteland 24 so that the direction to decenter the crude pin 24p is the axis perpendicular to the direction of the pressing direction and intermediate wasteland 24 of the holding die 60. In the stage before the start of the molding process, each type are spaced axially of wasteland.
[0063]
　Next, the die cushion base 104 is lowered over the mold, and holds the pressure respectively in the vertical direction of the rough journal portion 24j by a pair of retentive 60. As shown in FIG. 6B, rough journal portion 24j is fixed by the holding mold 60. Crude journal portion 24j held by the fixed holding tool 61 does not move in the horizontal direction.
[0064]
　Then, with the rough journal portion 24j is held, along with the decentering crude pin 24p, for rolling the intermediate wasteland 24 in the axial direction of the intermediate wasteland 24. These result, as shown in FIGS. 6C and 7B, the final wasteland 25 is formed. Hereinafter, sometimes referred to the step of decentering the crude pin portion 24p and the pin eccentric step, it may be referred to a process of reduction of the intermediate wasteland 24 in the axial direction as the axial pressure process.
[0065]
　Pin eccentric step is carried out by moving the pin eccentric 71 in a direction perpendicular to and axially intermediate wasteland 24 in a direction perpendicular (i.e., horizontal direction) with respect to the pressing direction of the retaining mold 60. In one example of this embodiment, the moving direction of the two pins eccentric 71 at both ends, and the moving direction of the middle two pins eccentric 71 is opposite the direction (see arrows in FIG. 7A). As shown in FIG. 7B, the pin eccentric 71a moves by being pushed by the wedge receiving member 72a. Similarly, as shown in FIG. 6C, even pin eccentric 71b located above, moves pushed by in the same direction as the pin eccentric 71a on the wedge receiving member 72b will be described later.
[0066]
　In before the start of the molding process state (state of FIG. 6A and FIG. 7A), the crude journal portion 24j and a cross section of the fixed holding tool 61 in the vicinity, schematically shown in Figure 8A. At the return status of the molding process (the state of FIG. 6C and FIG. 7B), the crude journal portion 25j and a cross section of the fixed holding tool 61 in the vicinity, schematically shown in FIG. 8B. These figures are a cross-sectional view perpendicular to the axial direction of the intermediate wasteland, stationary retentive 61 shows only a part. For ease of understanding, FIG. 8A and 8B, is a vertical line passing through the center of the coarse journal portion 24j and the crude journal portion 25j, indicating the center line JCT. Similarly, FIG. 9A, described below, FIG. 9B, in FIGS. 10A and 10B,, indicates the center line JCT. However, the position of the center line JCT in FIGS 9A ~ FIG. 10B, only schematic illustration for ease of understanding.
[0067]
　In before the start of the molding process state (state of FIG. 6A and FIG. 7A), the crude pin portion 24p and a cross section of the pin eccentric 71 in the vicinity, schematically shown in Figure 9A. At the return status of the molding process (the state of FIG. 6C and FIG. 7B), the crude pin portion 25p and a cross section of the pin eccentric 71 in the vicinity, schematically shown in FIG. 9B. These figures are a cross-sectional view perpendicular to the axial direction of the intermediate wasteland. As is clear from the position of the center line JCT crude journal portion shown in FIGS. 9A and 9B, coarse pin portion of FIG. 9B 25p is eccentric. As shown in FIG. 9A, the pin eccentric 71 has a space in which crude pin 24p is located.
[0068]
　In before the start of the molding process state (state of FIG. 6A and FIG. 7A), a first coarse arm portion 24a and a cross section of the fixed holding tool 61 in the vicinity, schematically shown in FIG. 10A. At the return status of the molding process (the state of FIG. 6C and FIG. 7B), the second coarse arm 25a and a cross section of the fixed holding tool 61 in the vicinity, schematically shown in FIG. 10B. These figures, in a cross-sectional view perpendicular to the axial direction of the intermediate wasteland 24, and the crude arm portion of the fixed holding tool 61 is formed, part of the space to be arranged, that is, a view showing a cross section of the recess 60c. As shown in FIG. 10A, retentive 60 has a space in which the first coarse arm portion 24a is disposed. Material with the axial pressure moves to the space. As a result, the second coarse arm portion 25a having a shape close to the shape of the arm portion A is formed than the first roughness arm portion 24a. As shown in FIGS. 10A and 10B, the cross-sectional area of ​​the second coarse arm 25a is larger than the cross-sectional area of ​​the first coarse arm portion 24a.
[0069]
　Referring to Figure 6A, the axial pressure process, the front-side holding type 63 and the flange side holding type 64, carried out by moving to both approaches. At this time, the front-side holding type 63 and the flange side retentive 64 moves in the axial direction of the intermediate wasteland 24.
[0070]
　In the molding step, burrs final wasteland 25 may be formed. In the production method of the present embodiment, as described below, placing direction of the final wasteland 25 in the finish forging step is the same as the mounting direction of the intermediate wasteland 24 in the forming step having a pin eccentrically process. That is, none of the pins eccentric steps and finishing forging process, the eccentric direction of the rough pin 24p and 25p are arranged parallel in the horizontal direction. Therefore, even out burr parting surface of the holding die 60 extending in the horizontal direction (the surface facing the lower mold and the upper mold) in the molding process, avoided that cause flaws occurred at the burr finishing forging process It is.
[0071]
　On the other hand, the placing direction of wasteland at pin eccentric step in the placing direction and the 90 ° different conventional manufacturing method of wasteland in the finish forging step, the burrs comes into parting surface of the mold pin eccentric step, final there is a possibility that the cause of defects in the product. If the placing direction different 90 °, burrs formed on the parting surface of the mold in the pin eccentricity process, because in the next finishing forging process, are placed in the press mold a position facing.
[0072]
　The timing of pin eccentricity steps and axial reduction process in the molding step will be described with reference to FIG. 11. 11, the horizontal axis represents the progress of the entire process (time) and the vertical axis represents the progress of each process. Here, the progress of the pins eccentric step, when the moving distance to the final position of the coarse pin portion of the pin eccentric step was 100% means the ratio of the movement distance of the rough pin portion. The progress of the axial reduction step, the final reduction rate in the axial direction of the intermediate wasteland in the axial direction reduction process when the (distance shorter in the axial direction) was set to 100%, reduction of the axial direction of the intermediate wasteland It means the ratio of.
[0073]
　The solid line 1 in FIG. 11, ends at the same time the axial reduction step of the pin eccentric process shows the case where ends. Each dotted line 2a and the dotted line 2b of Figure 11, the axial rolling process before the end of the pin eccentric process shows the case where ends. Dashed line 3 in FIG. 11, the axial reduction step after the pin eccentric step is completed indicates the case where ends.
[0074]
　In the conventional manufacturing method and the moving direction of the pin eccentric to the moving direction of the holding type is the same vertical movement of the pin eccentric may act as a force for opening the mold the retentive. In other words, chewing out of the material there is a risk that occurs in such a journal-type cracking portion. Therefore, in the conventional manufacturing method, in order to lower the risk of out chewing material, to terminate the axially reduction step before the pin eccentric step is completed it was important. In contrast, in the manufacturing method of this embodiment, the moving direction of the pin eccentric 71 is horizontal and perpendicular to the axial direction of the pressing direction of the retaining type 60 (vertical direction) and the intermediate wasteland 24. Therefore, movement of the pin eccentric is hardly acts as a force to open the mold a retentive, low bite out risk of the material in such a journal-type cracking portion. Therefore, in the manufacturing method of this embodiment, after end of the termination at the same time or pin eccentric process of pin eccentricity process, even to end the axial reduction step can be suppressed risk of out chewing increases.
[0075]
　However, the manufacturing method of the present embodiment, does not exclude that end the axial rolling process before the end of the pin eccentricity process. If Exit Exit axial reduction step before the pin eccentric step, at pin eccentricity process flow of the material of the intermediate wasteland 24 is not easily suppressed. Since the rough pin portion Pinshoruda portion 25p of the final wasteland 25 formed (Fig. 3D) hardly occurs underfill easily precisely forms a coarse pin portion 25p vicinity shape. Thus, it is possible to mold the shape of Pinshoruda portion of the final wasteland more shape close to finishing forging, sit is more stable to mold the final wasteland finishing forging process.
[0076]
　As an example of a molding apparatus used in the molding process, the structure of the molding apparatus 100, schematically shown in FIGS. 12A and 13A. For ease of understanding, unnecessary portions in the description is omitted or simplified illustration, and further hatching of the portion of the device. Figure 12A shows parallel longitudinal section in the axial direction of the intermediate wasteland 24. Figure 13A shows a cross-section perpendicular to the axial direction of the intermediate wasteland, specifically, it illustrates a cross section of a portion of the pin eccentric 71 schematically. 12A and 13A shows a state before the start of the molding process.
[0077]
　Forming apparatus 100 includes plates (forming apparatus main body) 101, bolster base 102, the die cushion cylinder (telescopic mechanism) 103, the die cushion base 104, a hydraulic cylinder (horizontal cylinder) 105 and the pin eccentricity for the wedge 106,. Plate 101 includes a lower plate 101a and the upper plate 101b. Bolster base 102 includes a lower bolster base 102a and an upper bolster base 102b (base).
[0078]
　Bolster base 102 is supported by the plate 101. Die cushion base 104 is supported on the bolster base 102b via the die cushion cylinder 103. Die cushion cylinder 103 is not Chijimara the pressure and the load required to hold the rough journal portion, a cylinder shrinks when applied all the load by the plate 101.
[0079]
　Hydraulic cylinder 105 is a cylinder for rolling the intermediate wasteland 24 in the axial direction. Forming apparatus 100 shown in FIG. 12A comprises a hydraulic cylinder 105 for both coarse front portion 24fr side and rough flange portion 24fl side. By two hydraulic cylinders 105, which pressures the opposite ends of the intermediate wasteland 24 in the axial direction of the intermediate wasteland 24.
[0080]
　Each retentive 60a and lower pin eccentric 71a downward, and is disposed on the bolster base 102a. Each upper retentive 60b and upper pin eccentric 71b, is supported by the die cushion base 104. For example, those types are suspended by fittings protruding from the die cushion base 104 (L-bracket). Of retentive 60, movable holding die 62, the front-side holding type 63 and the flange side holding type 64, is movable in a direction parallel to the axial direction of wasteland.
[0081]
　Referring to FIG. 13A, the wedge 106 of the pin eccentric penetrates the die cushion base 104. Therefore, the wedge 106 is moved independently of the die cushion base 104. The wedge 106 includes an inclined surface. The wedge 106 is fixed to the bolster base 102b. Plate 101b is a plate pressing the retentive 60b through the die cushion cylinder (telescopic mechanism) 103.
[0082]
　End of the pin eccentric 71a is connected to the wedge receiving member 72a. More specifically, the pin eccentric 71a, as in the axial direction of the intermediate wasteland 24 relatively movable with respect to the wedge receiving member 72a, an end portion of the pin eccentric 71a is connected to the wedge receiving member 72a and has (see Figures and Figure 7A 7B). As shown in FIG. 13A, the wedge receiving member 72a is provided with an inclined surface facing the inclined surface of the wedge 106. Similarly, the ends of the pins eccentric 71b is also connected to a wedge receiving member 72b. More specifically, as the axial direction of the intermediate wasteland relatively movable with respect to the wedge receiving member 72b, the ends of the pins eccentric 71b is connected to the wedge receiving member 72b. Wedge receiving member 72b is provided with an inclined surface facing the inclined surface of the wedge 106.
[0083]
　Wedge receiving members 72a and 72b are movable only in the eccentric direction of the pin. On the other hand, the pin eccentric 71a, in addition to the eccentric direction of the pin, is also movable in the axial direction of the intermediate wasteland. Similarly, pin eccentric 71b, in addition to the eccentric direction of the pin, is also movable in the axial direction of the intermediate wasteland. Since the pin eccentric 71 to move in the axial direction of the intermediate wasteland, wedge receiving member 72a (and the wedge receiving member 72b), as shown in FIG. 7A, has a shape extending in the axial direction of the intermediate wasteland.
[0084]
　Between the upper and lower molds of the molding device 100 in the state of FIG. 12A and FIG. 13A, place the intermediate wasteland 24. Intermediate wasteland 24, the eccentric direction of the rough pin 24p is arranged to be parallel to the horizontal direction. With such an arrangement, the mass is distributed in the horizontal direction, it is easy to take a horizontal mass balance. As a result, a stable attitude of the arranged intermediate wasteland 24, it is possible to suppress occurrence of molding failure in the molding step.
[0085]
　In the molding step, by lowering the plate 101 and the holding of rough journal portion 24j, and a pin eccentric step. Further, in the molding step, the axial reduction step by driving the hydraulic cylinder 105.
[0086]
　Referring to FIG. 12A, with the descent of the plate 101b, also lowered in the vertical direction bolster base 102b and supported above the mold to it. And retentive 60a and retentive 60b is by retentive 60b is lowered to contact the crude journal portion 24j is held in the holding mold 60 is pressure. It shows a state in the molding step in FIGS. 12B and 13B. Figures 12B and 13B are sectional views of the same portion as FIG. 12A and FIG. 13A.
[0087]
　When the holding type 60a and retentive 60b lowers the further plate 101b while abutting, die cushion cylinder 103 is contracted. The die cushion cylinder 103, cylinder retracts by the load due to the plate 101b is used. By die cushion cylinder 103 retracts, the position of the die cushion based 104 unchanged, wedge 106 of pin eccentric continues to descend.
[0088]
　Referring to FIG. 13B, the wedge 106 is lowered, the inclined surface of the wedge 106 presses the inclined surface of the wedge receiving members 72a and 72b. As a result, the wedge receiving members 72a and 72b are moved to the pin eccentric direction. Along with this, the pin eccentric 71a and 71b are moved to the pin eccentric direction.
[0089]
　Referring to FIG. 12B, 2 one hydraulic cylinder 105, a front-side holding type 63 and the flange-side holding type 64 rolling both as close. Along with this, the moving retentive 62 and pin eccentric 71, moves closer to the center of the fixed holding tool 61 in the axial direction of the intermediate wasteland. By the above operation, the pin eccentric 71, the axial direction of the pressing direction and the intermediate wasteland retentive 60 moves in both directions perpendicular direction.
[0090]
　Figure 12C and Figure 13C, showing the state of the molding apparatus 100 at the end of the molding process. Figures 12C and 13C are cross-sectional views of the same portion as FIG. 12A and FIG. 13A.
[0091]
　In the state shown in FIG. 12C and FIG. 13C, the eccentricity of the downward and coarse pin portion 24p with it the wedge 106 has been completed. Furthermore, with the hydraulic cylinder 105, pressure of the intermediate wasteland 24 in the axial direction is completed. In this state, the mold adjacent the axial direction of the final wasteland 25 (each type constituting a holding mold 60, and the pin eccentric 71) is in contact.
[0092]
　If pin eccentric direction is the vertical direction, the mechanism therefor, it is necessary to place above and below the mold. In such a case, the height of the device is increased. On the other hand, the method of the present embodiment, since the pin eccentric direction is horizontal, can avoid such problems. Therefore, the method of the present embodiment, it is possible that the height be carried out in low compact device.
[0093]
　14, movement of the upper plate 101b, the movement of the die cushion base 104, pin eccentricity, and the axial pressure is a diagram schematically showing an example of each timing. The horizontal axis shows the progress of the entire process (time course). Figure 14 begins a pin eccentric axial pressure simultaneously shows an example in which axial pressure is completed before the pin eccentricity is completed. The start and end timing of pin eccentricity, wedge 106, it can be changed by altering the like shape of the wedge receiving members 72a and 72b. Alternatively, it is also possible to move the pin eccentric 71 by an actuator such as a hydraulic cylinder. In this case, the timing of the movement of the pin eccentric 71 can be freely set independently of the timing of the other steps. Therefore, the degree of freedom of the molding process, it is possible to form a more quality higher final wasteland 25.
[0094]
　As described above, the final wasteland 25 (see FIG. 3D) is formed. Crude journal portion 25j of the final wasteland 25, crude pin 25p, and the second coarse arm portion 25a, as compared with those of the intermediate wasteland 24, the journal portion J of the final product, the pin portion P, and close to the arm portion A shape having.
[0095]
4. An example of a finishing forging process
　in the finishing forging process, using a pair of press dies, and the axial direction of eccentricity and final wasteland 25 of the rough pin 25p for rolling the final wasteland 25 in a direction perpendicular. This reduction, to form the finished forged material 26 including a plurality of journal portions J, a plurality of pin portions P, and a plurality of crank arm portion A (see FIG. 3E). Finishing forging process can be performed using a known apparatus. The press mold used in this case, it is possible to use a general press die.
[0096]
　In the production method of the present embodiment, placing direction of the final wasteland 25 in the finish forging step is the same as the mounting direction of the intermediate wasteland 24 and final wasteland 25 in the molding process. That is, in either case the molding process and finishing forging process, intermediate wasteland or final wasteland is eccentric direction of the rough pin portion is molded in a state of being arranged parallel to the horizontal direction. Therefore, even out burr parting face of the holding type in the molding process, the burrs can be prevented from generating the defects entrainment in the finishing forging process.
Industrial Applicability
[0097]
　The present invention is applicable to the production of forged crankshaft.
DESCRIPTION OF SYMBOLS
[0098]
　21: Forged crankshaft
　22: Billet
　24: Intermediate wasteland
　25: Last wasteland
　26: Finishing forging
　60: retentive, 71: pin eccentric
　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

WE CLAIM

A plurality of journal portion as a rotational center, forged crank comprising a plurality of pin portions which are eccentric, and a plurality of crank arm connecting the said plurality of pin portions of the plurality of journal portions relative to said journal portion a method of manufacturing a shaft,
　wherein at least one of the plurality of crank arm includes a counterweight portion,
　said manufacturing method,
　a plurality of rough journal portion serving as the plurality of journal portions, and said plurality of pin portion a plurality of coarse pin portion comprising a plurality of first crude crank arm portion as a plurality of crank arm portion, and the preforming step to form an intermediate wasteland billet containing,
　said plurality of coarse journal portion of the intermediate wasteland in a state of holding by pressure in the vertical direction respectively by a pair of retentive, the direction perpendicular to the axial direction of the pressing direction and the intermediate wasteland of the retentive By rolling the intermediate wasteland in the axial direction of the intermediate wasteland with decentering the crude pin portion, final including a second crude crank arm close to the shape of the crank arm portion than the first rough crank arm a forming step of forming a rough terrain,
　the said final wasteland eccentric direction of the rough pin is arranged parallel to the horizontal direction, by reduction in the vertical direction by using a pair of press dies, said plurality of journal portion, the plurality of pin portions, and a manufacturing method of forging the crank shaft; and a finishing forging step of forming a finish forged material including a plurality of crank arm portion.
[Requested item 2]
　Said final wasteland perform the forming step as burr is formed, the production method of the forged crankshaft according to claim 1 by flowing out the Yozai the parting surface of the retentive extending horizontally.
[Requested item 3]
　In the forming step, the after end of the eccentricity of the coarse pin, ends the pressure of the intermediate wasteland to the axial direction, the production method of the forged crankshaft according to claim 1 or 2.
[Requested item 4]
　In the forming step, the before the end of the eccentricity of the coarse pin, ends the pressure of the intermediate wasteland to the axial direction, the production method of the forged crankshaft according to claim 1 or 2.
[Requested item 5]
　In the molding step, the ends of the eccentric of the crude pin portion at the same time, to end the reduction of the intermediate wasteland to the axial direction, the production method of the forged crankshaft according to claim 1 or 2.
[Requested item 6]
　Reduction of the intermediate wasteland to the axial direction in the molding step is performed by a hydraulic cylinder,
　the eccentricity of the coarse pin portion rows with a fixed wedge on the base to push the holding mold through the expansion mechanism dividing method for producing a forged crankshaft according to any one of claims 1 to 5.