Technical field
[0001]
　The present invention relates to a method of manufacturing a crank shaft by hot forging.
Background technique
[0002]
　Automobiles, motorcycles, in agricultural machinery or reciprocating engine of a ship or the like, in order to convert the reciprocating motion of the piston into rotational movement takes power, the crankshaft is essential. Crankshaft can be produced by die forging or casting. In particular, high strength and high rigidity may be required to the crankshaft, a crankshaft manufactured by die forging (hereinafter, also referred to as "forging crankshaft") is often used.
[0003]
　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, in some cases to carry out the shaping process 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. Crankshaft 1 illustrated in FIG. 1F is mounted on four-cylinder engine, a crankshaft of a four-cylinder -8 sheets counterweight. As the crank shaft 1, the five journal portions J1 ~ J5,4 one pin portions P1 ~ P4, the front portion Fr, flanges Fl, and eight of the crank arm portion (hereinafter, simply 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. Furthermore, eight of all arm A1 ~ A8 are counterweight unit (hereinafter, simply referred to as "weight part") having W1 ~ W8 integrally.
[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.
[0006]
　In the manufacturing method shown in FIGS. 1A ~ FIG 1F, forged crankshaft 1 is manufactured as follows. First, after heating by the induction heating furnace or a gas heating furnace billet 2 of predetermined length, as shown in FIG. 1A, performing roll forming. The roll forming process, for example by squeezing and rolling a billet 2 with grooved rolls, allocate the volume in the longitudinal direction, forming the roll wasteland 3 is an intermediate material (see FIG. 1B). Next, in the bending beating process, partially reduction roll wasteland 3 from a direction perpendicular to a longitudinal direction. Thus, allocating the volume of the roll wasteland 3, it is a further intermediate material bent to shape the wasteland 4 (see FIG. 1C).
[0007]
　Subsequently, the rough beating process, by press forging using a pair of mold wasteland 4 vertically bent to obtain a rough forged material 5 (see FIG. 1D). Its rough forged material 5 is molded to approximate the shape of the 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). Its finish forged material 6 is formed in 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 between the parting surface of the mold facing each other. Therefore, in any of the rough forging 5 and the finishing forging 6 also, burrs B are attached largely around the shape of the crankshaft.
[0008]
　The burr punching step, for example a 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. Thus without burrs forging obtained, burr free 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, among eight arm A, the weight portion W in a part of the arm portion is provided 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) to the weight portion W are provided integrally. Further, the remaining arm portions, specifically, the second, third, arm portions A2, A3, A6 and A7 of the sixth and seventh have no weight portion, the shape is oval (elliptical Jo) and a. 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 recent years, especially reciprocating engines for automobiles, weight reduction is required in order to improve fuel economy. Therefore, also the crank shaft mounted on a reciprocating engine, the weight reduction request is remarkably.
[0014]
　As a conventional technique to reduce the weight of the forged crankshaft, the arm portions having a weight portion integrally, there is a technique of providing a thin portion on the surface of the pin portion. Lightening portion of the concave, from being formed by the die forging, mold division plane perpendicular to the direction, i.e., it extends in the eccentric direction perpendicular to the direction of the pin portion extends to both side surfaces of the arm portions. This technique is disclosed in JP 2009-197929 (Patent Document 1) and Japanese Patent 2010-255834 (Patent Document 2).
[0015]
　The crankshaft is proposed in Patent Document 1, the hollow portions of the concave extends the eccentric direction perpendicular to the direction of the pin portion extends to both side surfaces of the arm portions. In the region of the pin portion side of the axis of at least the journal portion among the thin portion, the depth of the bottom surface of the lightening portion is gradually increased to the journal portion from the pin portion. Further, the bottom surface of the lightening portion is formed along the outer surface of the virtual cylinder. Here, the virtual cylinder extends the pin portion and the arm portion from the junction surface (web) to the joining surfaces of the journal portion and the arm portion (web). Thus, without lowering the rigidity of the crank shaft, and to be able to reduce the weight.
[0016]
　The crankshaft is proposed in Patent Document 2, the thin portion is formed on the surface of the pin portion of the arm portion, the thin portion is recessed in the journal portion to the imaginary line. The virtual line, and the outer peripheral edge of the thrust receiving portion of the pin portion, a straight line passing through the axis of the journal portion between the outer peripheral edge of the thrust receiving portion of the journal portion. Thin portion division surface perpendicular direction of the mold, i.e., extends in the eccentric direction perpendicular to the direction of the pin portion extends to both side surfaces of the arm portions. By providing such a thin wall portion, when a load is applied to the pin by the reciprocating movement of the piston, becomes stress can be dispersed to the arm portion itself is bent, the life of the pin portion can be reduced It is set to. In Patent Document 2, if further providing the hollow portions, and the mass it can also be reduced.
[0017]
　Further, as the prior art to reduce the weight of the forged crankshaft, there is a technique of forming a hole by the punch. This technique is disclosed in JP 2012-7726 JP JP (Patent Document 3) and Japanese Patent 2010-230027 (Patent Document 4).
[0018]
　Patent Documents 3 and 4, is described the arm portion with a hole portion is formed on the surface of the journal portion, the manufacturing method of the crank shaft with the arm is also described. Hole of the arm portion, the straight line connecting the axial center of the axis and the pin portion of the journal portion (hereinafter, also referred to as "arm center line") is molded onto the large recessed deeper toward the pin portion. According to such arm portion can reduce the weight of the volume of the mass of the hole. Weight of the arm leads to weight reduction of the weight portion constituting the arm portion and the pair thus leading to reduction in the overall weight of the forged crankshaft. Further, in both side portions of the pin in the vicinity of the arm portion, since the thickness is maintained thick, rigidity (torsional rigidity and flexural rigidity) is ensured. Here, the side of the arm portions, means side and its peripheral portion in the width direction of the arm portion (eccentric direction perpendicular to the direction of the pin portion).
[0019]
　Thus, while maintaining increasing the thickness of both side portions of the arm portions, if no dent in the surface of the journal portion of the arm portion, can be reduced weight and rigidity ensuring at the same time.
[0020]
　However, forged crankshaft having an arm portion of such unique shape is, in the conventional manufacturing method, it is difficult to manufacture. In die forging process, if an attempt forming a recess in the arm surface, reversed gradient at the site type draft mold recess, since the situation that shaped forging can not escape from the mold it occurs.
[0021]
　To cope with such a situation, in the production method described in Patent Documents 3 and 4, in the die forging process, forming small arm without forming a recess in the arm surface. Then, after the burr punching step, pushing a punch on the surface of the arm portion, forming a recess by traces of the punch.
[0022]
　In the crankshaft shown in Fig. 1F, the shape of the arm portion A and its integral weight portion W is, all the same. In practice, if necessary, for each arm A, which may vary the shape of the arm portion A and its integral weight portion W. This technique is disclosed in JP 2007-71227 JP JP (Patent Document 5) and Japanese Patent 2014-40856 (Patent Document 6).
[0023]
　Patent Document 5, the flywheel is described crankshaft of a four-cylinder -8 Like counterweight mounted to one end. In the crankshaft, the thickness and centroid of the arm as well as the mass of the weight portion is not the same in all of the arm portions, different for each arm. This can ensure the minimum rigidity required for each arm, can reduce the wall thickness at the necessary stiffness is low arm portion, and the result can be achieved weight reduction.
[0024]
　Patent Document 6, the flywheel is described crankshaft for a multi-cylinder engine is mounted on one end. In the crankshaft, bending rigidity and torsional rigidity of the arm portion is higher closer to the flywheel. Further, the bending rigidity and torsional rigidity of the arm portion is different is preferred for each arm portion. Thus, while none of the bending vibration and torsional vibration mitigation, and to be able to reduce the weight.
[0025]
　Thus each arm portion, when the shape of the arm portion and that an integral weight portion is different, depending on its shape, site rigidity required vary within the arm portion. Specifically, there are cases where it is important to ensure the rigidity in the pin portion near the arm portion. Alternatively, in some cases it is important to ensure the rigidity in the journal portion near the arm portion.
CITATION
Patent Literature
[0026]
Patent Document 1: JP 2009-197929 Patent Publication
Patent Document 2: JP 2010-255834 Patent Publication
Patent Document 3: JP 2012-7726 JP
Patent Document 4: JP 2010-230027 Patent Publication
Patent Document 5: JP 2007-71227 JP
Patent Document 6: JP 2014-40856 JP
Summary of the Invention
Problems that the Invention is to Solve
[0027]
　By providing the hollow portions as described in Patent Documents 1 and 2 above on the surface of the pin portion of the arm portion, can be reduced by mass, the rigidity is lowered. Therefore, weight reduction by simple thin portion has a limit in terms of securing the rigidity, it is difficult to meet the demand for further weight reduction.
[0028]
　Further, as described in Patent Documents 3 and 4 above, if forming a hole by the punch on the surface of the arm portion, it is possible to produce a forged crankshaft which attained weight and rigidity ensuring at the same time. However, in this manufacturing method, since the deformation of the entire arm is pushed strongly punch arm portion surface when molding a hole in the arm surface, it requires a great deal of force to push the punch. For this reason, it is necessary to exceptional facilities and the mold for providing a great deal of force to the punch, it is necessary to consider with respect to durability of the punch.
[0029]
　An object of the present invention is to provide a method for producing a forged crankshaft can be obtained forged crankshaft which attained weight and rigidity ensuring at the same time conveniently.
Means for Solving the Problems
[0030]
　Method for producing a forged crankshaft according to an embodiment of the present invention includes a journal portion as a rotational center, and a pin portion which is eccentric with respect to the journal portion, and a crank arm portion connecting the pin portion and the journal portion, the all or part of the crank arm is a manufacturing method of a forged crankshaft and a counterweight portion having integrally. The manufacturing method includes a die forging, and die forging to obtain a forged material molded into the shape of a crankshaft, the first mold pair, the reduction step of reduction of the forging material, the. The forged material is all or a portion of said crank arm having integrally the counterweight unit, having a first excess thickness portion projecting from the outer periphery of the journal portion near the side. Wherein in the reduction step, the reduction deforming said first excess thickness portion by the first mold, thereby overhanging the first excess thickness portion on the pin side.
[0031]
　Wherein the first mold is provided with an inclined surface facing the first excess thickness portion, in the reduction step, it is preferable to deform the first excess thickness portion along the inclined surface.
[0032]
　The manufacturing method includes a burr punching step of removing burrs from the forged material, in the forging step, to obtain the forged material with burrs, in the burr punching process, burrs from the forged material with said burr to obtain a forged material without, in the reduction step, preferably reduction of the forged material without the burr.
[0033]
　In the reduction step, the case of reduction of the forged material without the burr, in the reduction step, the said journal portion near among the pin portion of the surface of the crank arm portion having a first excess thickness portion the surface except at least the regions of the side, preferably maintained by pressing the second mold.
[0034]
　When using the second mold, in the reduction step, following the reduction of the first mold to move the second mold pressing direction of the first mold, said to the crank arm preferably, to maintain the pressing position of the second die in a fixed position.
[0035]
　The first excess thickness portion is preferably protrude from both the sides of the journal portion near.
[0036]
　The reduction step is preferably carried out in the shaping step of correcting the shape of the crank shaft by pressure using a mold.
[0037]
　The forged material, the all or part of the crank arm portion preferably has a second excess thickness portion projecting from the outer periphery of the pin portion near the side. In this case, in the reduction step, the by pressure deforming said second excess thickness portion by the first mold, thereby overhanging the second excess thickness portion to the journal portion.
[0038]
　It said second excess thickness portion is preferably protrude from both the sides of the pin in the vicinity.
Effect of the Invention
[0039]
　Method for producing a forged crankshaft of the present invention, in the die forging process, forming the first excess thickness portion projecting from the outer peripheral side of the vicinity of the journal portion to the arm portion of the forging material. Further, at a reduction process, by overhang the first excess thickness portion on the pin side, increasing the thickness of the side of the journal portion near the arm portion. Therefore, simply compared with the case of providing the hollow portions, together effectively be ensured the rigidity, it is possible to reduce the weight of the depressions of the inner side thereof. Further, since no use of punch, easily performed without requiring a great deal of force.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040]
[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, crank shaft according to the manufacturing method of the present invention, it is a perspective view showing an example of the shape of the pin portion side surface of the arm portion schematically.
[Figure 2B] Figure 2B is a diagram showing the pin portion side surface of the arm unit shown in Figure 2A.
[Figure 2C] FIG 2C is a diagram showing a side of the arm unit shown in Figure 2A.
FIG 2D] FIG 2D is a IID-IID sectional view of Figure 2B.
[Figure 3A] Figure 3A is a crank shaft according to the production method of the present invention, is a perspective view schematically showing an example of the shape of the journal portion surface of a suitable arm.
[Figure 3B] Figure 3B is a diagram showing a journal portion side surface of the arm unit shown in Figure 3A.
FIG 3C] Figure 3C is a IIIC-IIIC sectional view of Figure 3B.
[Figure 4A] Figure 4A is a diagram schematically showing the crank shaft due to manufacturing process, the pin portion side surface of the shape examples of suitable weight without arm portion of the present invention.
[Figure 4B] Figure 4B is a IVB-IVB cross-sectional view of Figure 4A.
[Figure 5A] Figure 5A is a case where the arm portion has a weight portion integrally, is a schematic view showing the reduction step the pin side surface of the previous shape example.
[Figure 5B] Figure 5B is a diagram showing a side of the arm unit shown in Figure 5A.
[Figure 5C] Figure 5C is a VC-VC cross-sectional view of FIG. 5A.
[Figure 6A] Figure 6A is a case where the arm portion has a weight portion integrally a schematic diagram showing a reduction process journal portion surface of the previous shape example.
[Figure 6B] Figure 6B is a VIB-VIB cross-sectional view of FIG 6A.
[Figure 7A] Figure 7A presents weight without arm is a schematic diagram showing a reduction process pin side surface of the previous shape example.
[Figure 7B] Figure 7B is a VIIB-VIIB cross-sectional view of FIG. 7A.
[FIG. 8A] Figure 8A, the arm portions having a weight portion integrally, at the pressing of the second mold in the processing flow example of reduction steps (first exemplary process flow) when folding the first excess thickness portion it is a schematic diagram showing the pin portion side surface of the arm portion.
[Figure 8B] Figure 8B is a schematic diagram showing the pin portion side surface of the arm portion during rolling completion in the first processing flow example.
FIG 9A] FIG 9A is a schematic diagram showing a journal portion side surface of the arm portion during the pressing of the second mold in the first processing flow example.
[FIG. 9B] FIG 9B is a schematic diagram showing a journal portion side surface of the arm portion during rolling completion in the first processing flow example.
FIG 10A] FIG 10A is a schematic side view of the arm portion during the pressing of the second mold in the first processing flow example.
[FIG. 10B] FIG 10B is a schematic side view of the arm portion during rolling completion in the first processing flow example.
FIG 11A] FIG 11A is a cross-sectional view of a journal portion near the time of pressing the second mold in the first processing flow example (XIA-XIA sectional view of FIG. 8A).
FIG 11B] FIG 11B is a cross-sectional view of a journal portion near at reduction completion in the first exemplary process flow (XIB-XIB sectional view of FIG. 8B).
FIG 12A] FIG 12A is a cross-sectional view of the pin portion near the time of pressing the second mold in the first processing flow example (XIIA-XIIA sectional view of FIG. 9A).
[Figure 12B] Figure 12B is a cross-sectional view of the pin portion near the time of reduction completion in the first exemplary process flow (XIIB-XIIB sectional view of FIG. 9B).
FIG 13A] FIG 13A is a cross-sectional view schematically showing a starting point of deformation of the excess thickness portion of the case without the stepped.
FIG 13B] FIG 13B is a cross-sectional view schematically showing a starting point of deformation of the excess thickness portion of the case of providing a step.
[Figure 14A] Figure 14A is a perspective view schematically showing an example of the shape of the pin side surfaces of the arm portions when squeezing the first excess thickness portion.
FIG 14B] FIG 14B is a diagram showing the pin portion side surface of the arm unit shown in FIG. 14A.
FIG 14C] FIG 14C is a diagram showing a side of the arm unit shown in FIG. 14A.
[FIG. 14D] FIG 14D is a XIVd-XIVd sectional view of FIG. 14B.
[Figure 15A] Figure 15A is a perspective view showing a shape example of a suitable arm journal portion side surface of the case of crushing the first excess thickness portion schematically.
[FIG. 15B] FIG 15B is a diagram showing a journal portion side surface of the arm unit shown in FIG. 15A.
[FIG. 15C] FIG 15C is a XVC-XVC sectional view of FIG. 15B.
[Figure 16A] Figure 16A is a schematic diagram showing the pin portion side surface of the shape examples of suitable weight without arm when squeezing the first excess thickness portion.
[FIG. 16B] FIG 16B is a XVIB-XVIB section view of FIG. 16A.
FIG 17A] FIG 17A is a cross-sectional view of a process flow example journal portion near the (second processing flow example) at the time of pressing the second mold reduction step in the case of crushing the first excess thickness portion.
[Figure 17B] Figure 17B is a cross-sectional view of a journal portion near at reduction completion in the second processing flow example.
FIG 18A] FIG 18A is a cross-sectional view of the pin portion near the time of pressing the second die in a second processing flow example.
[Figure 18B] Figure 18B is a cross-sectional view of the pin portion near the time of reduction completion in the second processing flow example.
[FIG. 19A] FIG 19A is the case the pressing direction of the first mold is not perpendicular to the eccentric direction of the pin portion is a schematic diagram showing the pin portion side surface of the arm portion of the front pressure.
[FIG. 19B] FIG. 19B is the case the pressing direction of the first mold is not perpendicular to the eccentric direction of the pin portion is a schematic diagram showing the pin portion side surface of the arm portion during rolling completion.
DESCRIPTION OF THE INVENTION
[0041]
　Hereinafter, a method for manufacturing the forged crankshaft of the present embodiment will be described with reference to the drawings.
[0042]
1. The shape of the crankshaft
　forged crankshaft embodiment is directed includes a journal portion as a rotational center, and a pin portion which is eccentric with respect to the journal portion, and an arm portion connecting the journal portion and the pin portion, the arm portion all or part of the out is and a weight portion having integrally. Such forged crankshaft, for example, can be adopted forged crankshaft shown in FIGS. 2A ~ Figure 4B.
[0043]
　Figures 2A ~ Figure 2D, for a crankshaft according to the production method of the present invention, a schematic diagram showing an example of the shape of the pin portion side surface of the arm portion, FIG. 2A is a perspective view, and FIG. 2B are showing the pin portion-side surface FIG 2C is a diagram, Fig. 2D IID-IID sectional view showing a side surface. In Figure 2A ~ Figure 2D, among the arm portion of the crank shaft, showing extracted only one arm having integrally a weight portion. Incidentally, FIG. 2C is a projection view from the direction indicated by a dotted arrow in Figure 2B. Further, in the present invention, (see symbol T in FIG. 2B) the pin portion P side top side of the eccentric direction of the pin portion, as the weight portion W side bottom side (reference symbol B in FIG. 2B).
[0044]
　Arm A having a weight portion W, as shown in FIGS. 2A ~ Figure 2D, of the pin portion P side of the surface, inside the area At both side portions Ac and Ad in the vicinity journal portion J, has a recess. Further, protruding on both sides Ac and Ad are pin portion P side of the vicinity of the journal portion J, their sides Ac and Ad the thickness as compared to the thickness of the recess is thick. Here, the side is meant the side and the periphery thereof in the width direction of the arm portion A (eccentric direction perpendicular to the direction of the pin portion), in other words, it means the end portions in the width direction of the arm portion A .
[0045]
　Such arm A, like the arm portion having no hollow portions, side portions Ac and Ad the thickness in the vicinity of the journal portion J is maintained thick. Moreover, resulting in depressions on the surface of the pin portion P side is formed. A crank shaft provided with the arm portion A can be made lighter by indentation of the pin portion P side surface of the arm portion A. In addition, both side portions Ac and Ad the thickness of the journal portion J vicinity of the arm portion A, by being maintained as the arm portions having no hollow portions, it is possible to secure the rigidity. In other words, both side portions Ac and Ad the thickness of the journal portion J vicinity of the arm portion A, compared with the thickness of the recess, by a thick, it is possible to secure the rigidity.
[0046]
　Here, the present inventors have found was examined for rigidity, while the inner region At a thickness smaller effect on the rigidity, is clearly to be greater influence on the rigidity sides Ac and Ad in the thickness in the width direction became.
[0047]
　Specifically, in the case of providing the hollow portions as described in Patent Documents 1 and 2 above on the surface of the pin portion of the arm portion extends lightening portions of concave up both sides of the width direction. Therefore, since it becomes thinner sides Ac and Ad in the thickness in the width direction, the rigidity is lowered. In contrast, the crankshaft according to the present embodiment, recessed pin portion P side surface is provided only in the middle of both sides. Furthermore, since both side portions Ac and Ad in the thickness in the width direction is thick is maintained as the arm portions having no hollow portions, a decrease in rigidity can be suppressed. As a result, according to the crankshaft of the present embodiment, simply compared with the case of providing the hollow portions, the rigidity can be efficiently ensured, achieving further weight reduction by expanding recessed inner sides Ac and Ad can.
[0048]
　Sides Ac and a thicker portion of Ad of the journal portion J vicinity, in order to ensure the rigidity effectively, contain a range extending in the center of the journal portion from the bottom side of the outer edge of the pin thrust portion (not shown) It is preferred. Here, the pin thrust portion, provided on the pin side surface of the arm portion, a portion for limiting movement of the connecting rod in the thrust direction.
[0049]
　Journal portion J vicinity of both side portions Ac and Ad in the inner region At of the shape (shape of the bottom of the recess), as shown in FIG. 2D, is preferably convex such swelling is the center in the width direction. In other words, the thickness of the inner area At is preferably gradually reduced as the distance from the center in the width direction. Shape of the bottom of the recesses for the center in the width direction is inflated such convex, rigidity can be further improved in particular the bending stiffness.
[0050]
　Subsequently, the shape of the journal portion J side surface of the arm portion A having a weight portion integrally, illustrating the preferred embodiments thereof.
[0051]
　Figures 3A ~ 3C are crank shaft according to the manufacturing method of the present invention, a schematic view showing a shape example of a journal portion side surface of a suitable arm, FIG. 3A is a perspective view, Figure 3B is a journal portion surface shows, FIG. 3C is a IIIC-IIIC sectional view.
[0052]
　Arm A having a weight portion W, as shown in FIGS. 3A ~ Figure 3C, among the journal portion J-side surface, has a recess inside the region As the side portions Aa and Ab of the pin portion near P is preferable. Further, both side portions Aa and Ab of the pin portion near P is overhanging the journal portion J side, the thickness of their sides Aa and Ab are, compared to the thickness of the recess, is preferably thick.
[0053]
　Thus, the thickness of the side portions Aa and Ab of the pin portion near P is, like the arm with no lightening portion is maintained thick. Moreover, resulting in depressions on the surface of the journal portion J side. Therefore, the rigidity can be secured by the thickness maintained on both sides Aa and Ab of the pin portion near the P. In other words, by both side portions Aa and Ab of the pin portion near P is thicker than the inner region As, can ensure rigidity. Further, it is possible to further weight reduction by indentation of the journal portion J side surface.
[0054]
　Pin portion P near the sides Aa and Ab of the shape of the inner area As (bottom shape of the recess), as shown in FIG. 3C, is preferably convex such swelling is the center in the width direction. In other words, the thickness of the inner region As, preferably gradually reduced as the distance from the center in the width direction. Shape of the bottom of the recesses for the center in the width direction is inflated such convex, rigidity can be further improved in particular the bending stiffness.
[0055]
　Subsequently, the arm portions having no weight portion, i.e., the weight without arm, illustrating the preferred embodiments thereof.
[0056]
　4A and 4B, the crank shaft by the manufacturing method of the present invention, is a schematic view showing a shape example of a suitable weight without arm, shows the Figure 4A the pin side surfaces, Figure 4B IVB-IVB it is a cross-sectional view. In Figure 4A and 4B, among the arm portion of the crank shaft, showing extracted only one weight without arm.
[0057]
　As shown in FIGS. 4A and 4B, the weight without arm A, similarly to the arm portion having integrally a weight portion shown in FIG. 2A ~ Figure 2D, of the pin portion P side of the surface, near the journal portion J It preferred of the inner region At the sides Ac and Ad, have a dent. Further, protruding on both sides Ac and Ad are pin portion P side of the vicinity of the journal portion J, their sides Ac and Ad the thickness as compared to the thickness of the recess, is preferably thick. In this case, the thickness of the side portions Ac and Ad of the journal portion J vicinity of the arm portion A, by maintaining as arm without a conventional lightening portion can ensure rigidity. In other words, by sides Ac and Ad of the journal portion J vicinity of the arm portion A is thicker than the recess can ensure rigidity. Further, it is possible to further reduce the weight of the recess of the pin portion P side surface of the arm portion A.
[0058]
　Like the arm having integrally a weight portion, even in the weight without arm A, the journal portion J vicinity of both side portions Ac and Ad in the inner region At of the shape (shape of the bottom of the recess), as shown in FIG. 4B is preferably a convex shape as swelling is the center in the width direction. Shape of the bottom of the recesses for the center in the width direction is inflated such convex, rigidity can be further improved in particular the bending stiffness.
[0059]
　Further, although not shown, the weight without arm A, the view of the 3A ~ weight portion shown in Figure 3C as with the arm portion having an integral, of the journal portion J-side surface, the pin portion P on both sides of the vicinity preferably it has a recess inside the region As parts Aa and Ab. Further, both side portions Aa and Ab of the pin portion near P is overhanging the journal portion J side, the thickness of their sides Aa and Ab are, compared to the thickness of the recess, is preferably thick. In this case, the thickness of the side portions Aa and Ab of the pin portion near P of the arm A, by maintaining as arm having no hollow portions can ensure rigidity. In other words, by both side portions Aa and Ab of the pin portion near P of the arm portion A is thicker than its inner region As, can ensure rigidity. Further, it is possible to further reduce the weight of the recess of the journal portion J side surface of the arm portion A.
[0060]
　As the arm portions having a weight portion shown in FIG. 3C integrally, in weight without arm A, (bottom shape of the recess) shape of the inner region As the side portions Aa and Ab of the pin portion near P in the width direction preferably a central swells like convex of the. Shape of the bottom of the recesses for the center in the width direction is inflated such convex, rigidity can be further improved in particular the bending stiffness.
[0061]
　Method for producing a forged crankshaft of the present embodiment is a reduction step of rolling the forged material, increasing the thickness of the side of the journal portion near the arm portion having a weight portion integrally. Further, at a reduction process may be further increased thickness of the side of the pin portion near the arm portion having a weight portion integrally. Further, at a reduction process, the arm portions having no weight portion, either one or both sides and the journal portion near the side of the pin portion near may be increased in thickness. For the arm portion shape of the reduction step prior to the crankshaft, illustrating a case where a weight portion integrally, and a case where no weight portion sequentially.
[0062]
　FIGS. 5A ~ 5C are for the case where the arm portion has a weight portion integrally a schematic view showing a shape example of a reduction step prior to the pin side surface, FIG. 5A shows the pin side surfaces, 5B is a diagram showing a side, FIG. 5C is a VC-VC cross-sectional view. In Figure 5A ~ FIG 5C, among the arm portion of the crank shaft, showing extracted only one arm having integrally a weight portion. Incidentally, FIG. 5B is a projection view from the direction indicated by a dotted arrow in FIG. 5A.
[0063]
　As shown in FIGS. 5A ~ FIG 5C, the arm A having a weight portion W, before the reduction step, among the pin portion P side of the surface, the inner region At both side portions Ac and Ad in the vicinity journal portion J, having a surface shape that matches the shape of the bottom of the recess after the reduction step. Its surface shape extending smoothly to the region on both sides Ac and Ad in the vicinity journal portion J. Accordingly, both side portions Ac and Ad the thickness in the vicinity of the journal portion J is smaller than the thickness after reduction process.
[0064]
　The arm portion A having a weight portion W are respectively on both side portions Ac and the outer periphery of the Ad near the journal portion J having a first excess thickness portion Aca and Ada. A first excess thickness portion Aca and Ada protrudes along the width direction from both side portions Ac and the outer periphery of the Ad near the journal portion J. First the excess thickness portion Aca and Ada shown in FIGS. 5A ~ 5C are a plate-like, is provided along the sides Ac and the outer periphery of the Ad near the journal portion J. The thickness of the first excess thickness portion Aca and Ada as compared to both side portions Ac and Ad in the thickness of the base, or is thin comparable.
[0065]
　6A and 6B, the case where the arm portion has a weight portion integrally a schematic view showing a shape example of a reduction step before the journal portion surface, FIG. 6A shows a journal portion surface, FIG. 6B is VIB-VIB cross-sectional view.
[0066]
　As described above, the arm portion A having a weight portion W, together with increasing the thickness of the side portions Aa and Ab of the pin portion near P, preferably formed indentations in the surface of the journal portion J side. In this case, the arm portion A having a weight portion W, of the journal portion J-side surface, the inner region of the side portions Aa and Ab of the pin portion near P, a bottom shape of the recess after the reduction step (final product) with a matching surface profile. Its surface shape extending smoothly to the area of ​​both side portions Aa and Ab of the pin portion near the P. Thus, the thickness of the side portions Aa and Ab are thinner than the thickness after reduction process.
[0067]
　Further, on both side portions Aa and Ab of the pin portion near P, the second excess thickness portion Aaa and Aba projecting from each of the outer periphery are formed. The second excess thickness portion Aaa and Aba is a plate-like, is provided along the outer circumference of the both side portions Aa and Ab of the pin portion near the P. The thickness of the second excess thickness portion Aaa and Aba as compared to the thickness of the side portions Aa and Ab of the root thereof, or is a thin comparable.
[0068]
　7A and 7B, the weight no arm is a schematic diagram showing a shape example of reduction steps before the pin side surface, FIG. 7A shows the pin side surfaces, Figure 7B VIIB-VIIB cross section it is.
[0069]
　As described above, in the weight without arm part A, together with increasing the thickness of the side portions Ac and Ad of the journal portion J vicinity preferable to form the depressions on the surface of the pin portion P side. In this case, the weight without arm A before reduction step, like the arm portion A having a weight portion W of FIG 5A ~ FIG 5C, of ​​the pin portion P side of the surface, both side portions in the vicinity of the journal portion J Ac and in the inner area At of Ad, with a surface shape that matches the shape of the bottom of the recess after the reduction step. Also has a side portions Ac and respective first excess thickness portion Aca and Ada the outer periphery of the Ad near the journal portion J, a first excess thickness portion Aca and Ada are near the journal portion J of the side portions Ac and Ad projecting from the outer periphery.
[0070]
　As described above, in the weight without arm part A, together with increasing the thickness of the side portions Aa and Ab of the pin portion near P, preferably formed indentations in the surface of the journal portion J side. In this case, the reduction step prior to the weight without arm A, similarly to the arm A having a weight portion W, of the journal portion J-side surface, the inner region of the both side portions of the pin portion near P, after reduction step having a surface shape that matches the shape of the bottom of the recess (final product) (not shown). Further, a second excess thickness portion Aaa and Aba on the outer circumference of the both side portions Aa and Ab of the pin portion near P, the outer circumference of the second excess thickness portion Aaa and Aba is a pin portion near the P side portions Aa and Ab protruding from.
[0071]
2. Method for producing a forged crankshaft
　production method of forging the crank shaft of the present embodiment includes a die forging step and a reduction step in that order. As in the first example process described later, during the die forging process and the reduction process, it may be added burr punching process. Alternatively, as in the second step example below, as a step after the reduction step, it may be added burr punching process. Alternatively, as in the third step examples described later, in the burr punching step, it is also possible to carry out rolling steps.
[0072]
　As pre-process for die forging process, for example, can be added to pre-forming step. During the die forging process and the reduction process, when adding a burr punching step, as a step after the reduction step, for example, you can add shaping step. Alternatively, the shaping step, it is also possible to carry out rolling steps. Incidentally, when the adjustment of the arrangement angle of the pin portion is required, during the burr punching step and the shaping step, twisting step is added. These steps are all carried out in a series between heat.
[0073]
[First Step Example
　for step example of adding a burr punching process during die forging step and the reduction step are described below.
[0074]
　Preforming step, for example, it is constituted by a bending beating step and roll forming step. The roll forming process and bending beating process, and allocating the volume of billet (raw), forming a wasteland bending.
[0075]
　In the die forging process, obtain a forged material with burrs which are molded into the shape of a crank shaft. Its the forging, for example, similarly to the burr without forging shown in FIG 5A ~ FIG 5C, the journal portion J, the shape of the pin portion P and the arm portion A is molded. Further, the forged material, the arm A having a weight portion W integrally has a first excess thickness portion Aca and Ada projecting from the outer peripheral side Ac and Ad in the vicinity journal portion J. Forging, the arm portion A, may have a second excess thickness portion Aaa and Aba projecting from the outer peripheral side Aa and Ab of the pin portion near the P.
[0076]
　Such obtain forging die forging process, the rough stamping process and finishing beating step can be configured by providing in that order.
[0077]
　Type draft die forging step, the site corresponding to the inner region At both side portions of the pin portion P side surface of the arm portion and the first excess thickness portion Aca, either a portion corresponding to the Ada, not reversed gradient. Therefore, none of die forging the rough stamping and finishing beating can be performed without any problem to obtain a forged material.
[0078]
　For the same reason, the as shown in Figure 3A ~-3C or FIGS. 6A and 6B, the arm A having a weight portion W, together with increasing the thickness of the side portions Aa and Ab of the pin portion near P, journal may form a dent in section J-side surface, inverse gradient is not generated. Further, in the weight without arm part A, together with increasing the thickness of the side portions Ac and Ad in the vicinity journal portion J, may form a recess in the surface of the pin portion P side, inverse gradient is not generated. Further, the weight without arm part A, together with increasing the thickness of the side portions Aa and Ab of the pin portion near P, may form a recess in the surface of the journal portion J side, inverse gradient is not generated. In these cases, none of the die forging of rough-handed and finishing strike, carried out without any trouble.
[0079]
　The burr punching process, a forging material with a burr in a state for example held by sandwiching by a pair of molds, by punching burrs, removing burrs from forged material. Thus, it is possible to obtain a burr free forging.
[0080]
　The reduction step, reduction of the resulting burrs without forging the first mold pair. At that time, by deforming the first excess metal portion and reduction in a first mold, thereby overhanging the first excess thickness portion to the pin portion of the arm portion. Thus, at the sides of the journal portion near the arm portion, increasing the thickness. Also, if no burr forging having a second excess thickness portion, when the pressure causes overhang the second excess thickness portion at the journal portion of the arm portion. Thus, at the sides of the pin portion near the arm portion, increasing the thickness. The processing flow of the reduction process will be described later.
[0081]
　Further, in the shaping step, by reduction of burrs without forging a pair of molds, to correct the geometry of the final product. As described above, the reduction step can be carried out in the shaping step. Because it employs a conventional manufacturing step similar reduction step is preferably carried out in the shaping step.
[0082]
　If necessary to adjust the arrangement angle of the pin portion, after the burr punching step (prior to the shaping step) to adjust the placement angle of the pin portion at the twisting step. By this process, in the manufacturing method of the forged crankshaft of the present embodiment, to obtain a forged crankshaft.
[0083]
Second Step Example
　as a step after the reduction step, the step example of adding a burr punching step, discussed below.
[0084]
　As pre-process for die forging process, it can be added to the first step example the same preforming step. In the die forging process, obtain a forged material with burrs which are molded into the shape of a crank shaft. Its forging, as in the first step example, has a first excess thickness portion. Forging may further comprise a second excess thickness portion. Die forging step for obtaining such forging is equivalent to rough beating process of a conventional manufacturing process.
[0085]
　The reduction step, reduction of the resulting burrs with forging the first mold pair. At that time, by deforming the first excess metal portion and reduction in a first mold, thereby overhanging the first excess thickness portion to the pin portion of the arm portion. Further, if the forging material having a second excess thickness portion, when the pressure causes overhang the second excess thickness portion at the journal portion of the arm portion. In addition, when the pressure in the first mold, molding a burr with forging to shape that matches the final product. Reduction step in this case corresponds to finishing beating process of a conventional manufacturing process.
[0086]
　In the subsequent burr punching step, the forging material after reduction step, by removing the burr as in the first step example, obtaining a burr free forging. If necessary, after the burr punching step may be carried out shaping step. Further, when the adjustment of the arrangement angle of the pin portion is required, after the burr punching step (prior to the shaping step) to adjust the placement angle of the pin portion at the twisting step.
[0087]
[Third Step Example
　In burr punching step, the process example in carrying out the reduction step will be described below.
[0088]
　As pre-process for die forging process, it can be added to the first step example the same preforming step. In die forging step, as in the first step example, to obtain a forged material with burrs which are molded into the shape of a crank shaft. Die forging process, the rough stamping process and finishing beating step can be configured by providing in that order. Its forging, as in the first step example, has a first excess thickness portion. Forging may further comprise a second excess thickness portion.
[0089]
　When carrying out the burr punching process at a reduction process, to retain the forged material with burrs across the first mold pair. At that time, the reduction of the forged material with burrs, by deforming the first excess thickness portion, thereby overhang the first excess thickness portion to the pin portion of the arm portion. Further, if the forging material having a second excess thickness portion, together, to overhang the second excess thickness portion at the journal portion of the arm portion. Then, while holding the forged material in a first mold pair, by punching burrs with a knife type, to remove the burrs from the forging. If necessary, after the burr punching step may be carried out shaping step. Further, when the adjustment of the arrangement angle of the pin portion is required, after the burr punching step (prior to the shaping step) to adjust the placement angle of the pin portion at the twisting step.
[0090]
3. Process flow example of a reduction process
　in the reduction process, as described above, by reduction of the excess thickness portion by the first mold, increasing the thickness at the side of the arm portion. Variation of this excess thickness portion is a bending or crushing.
[0091]
First processing flow example]
　First, the processing flow example when folding the excess thickness portion at a reduction process (first process flow example). The first exemplary process flow is a processing flow of the reduction step in the first step example.
[0092]
　Figure 8A ~ 12B, for the arm portions having a weight portion integrally, is a schematic diagram showing a processing flow example when bending the first excess thickness portion at a reduction process. 8A and 8B of which illustrates the pin portion side surface of the arm portion, FIG. 8A when pressing the second die, Figure 8B shows the time of reduction completion. Further, FIGS. 9A and 9B show a journal portion side surface of the arm portion, FIG. 9A when pressing the second die, Figure 9B shows the time of reduction completion. FIG 8A ~ Figure 9B, a burr without forging 30, vertically shows a first mold 10 of the pair, to facilitate the understanding of the drawings, the second mold to be described later, the third mold and Osamu not shown in the drawings of the ingredients.
[0093]
　10A and 10B are views showing a side of the arm portion, FIG. 10A shows time pressing of the second mold, FIG. 10B is a time reduction ends, respectively. FIG 10A and 10B, the burr without forging 30, and the second die 22 during pressing, the third mold 23, shown a jig 26, for easy understanding of the drawing, the 1 not shown in the drawings of the mold. Further, in the FIG. 10A, showing a second mold 22 during retraction by a two-dot chain line.
[0094]
　11A and 11B are cross-sectional views of the vicinity of a journal portion (see FIG. 8A) a 2 XIA-XIA sectional view when the pressing of the mold 11A, 11B is XIB-XIB section at reduction End a diagram (see FIG. 8B). FIG 11A and 11B, shows a burr without forging 30, the first mold 11 and 12 of the pair, and a second mold 22.
[0095]
　12A and 12B are cross-sectional views of a pin portion near (see FIG. 9A) the 2 XIIA-XIIA sectional view when the pressing of the mold 12A, 12B is XIIB-XIIB section at reduction End a diagram (see FIG. 9B). FIG 12A and 12B, shows a burr without forging 30, the first mold 11 and 12 of the pair, and a third mold 23.
[0096]
　The reduction step, using the first mold 10 of the pair. The first mold 10 is composed of an upper mold 11 and the lower mold 12, the upper die 11 and lower die 12 are engraved respectively Carving unit. Its mold engraving unit, part of the final product shape of the crankshaft is reflected. Specifically, the arm portions having a weight portion integrally, for bending the first excess thickness portion Aca and Ada, the shape of the vicinity of the journal portion among the both side portions of the arm portions is reflected in the mold engraved portion. Also, sites contributing to bending of the first excess thickness portion within the mold engraved portion has an inclined surface 11a and 12a facing the first excess thickness portion. The inclined surfaces 11a and 12a is inclined a first excess thickness portion as guided to toward the pin side surface (see FIG. 11A).
[0097]
　Also, if further include a second excess thickness portion Aaa and Aba arm portion having a weight portion integrally, for bending the second excess thickness portion, the shape of the pin portion near the mold engraving of the sides of the arm portion It is further reflected in the department. Also, sites contributing to bending of the second excess thickness portion within the mold engraved portion has a second excess thickness portion facing the inclined surfaces 11b and 12b. The inclined surfaces 11b and 12b is inclined a second excess thickness portion as guided to toward the journal portion surface (see FIG. 12A).
[0098]
　Although not shown, if further include a first excess thickness portion Aca and Ada in weight without arm, to bend the first excess thickness portion, the shape of the vicinity of the journal portion is mold engraving of the sides of the arm portion It is further reflected in the department. Also, sites contributing to bending of the first excess thickness portion within the mold engraved portion has an inclined surface facing the first excess thickness portion. The inclined surface is inclined the first excess thickness portion as guided to toward the pin side surface.
[0099]
　When further providing a second excess thickness portion Aaa and Aba in weight without arm, to bend the second excess thickness portion, the shape of the pin in the vicinity is further reflected in the mold engraved portion among the both side portions of the arm portions . Also, sites contributing to bending of the second excess thickness portion within the mold engraved portion has an inclined surface facing the second excess thickness portion. The inclined surface is inclined a second excess thickness portion as guided to toward the journal portion surface.
[0100]
　When carrying out the reduction step in shaping step, the arm shape other than both side portions of the above are further reflected in the mold engraved portion. The shape of such a journal portion and the pin portion is also reflected in the mold engraved portion.
[0101]
　However, as shown in FIGS. 11A and 11B, the first mold 11 and 12, a portion corresponding to the inner region At both side portions of the pin portion P side surface of the arm portion A is opened. The open portion may accommodate a second mold 22. The second mold 22, the mold engraved portion is engraved, in its mold engraved portions, recessed shape of the pin portion P side surface of the arm portion A is reflected. The second mold 22 is independent of the first die 10, it is possible to move forward and backward to or spaced apart or in contact against the inner region At both side portions of the arm portion surface.
[0102]
　Here, the second die 22 is positioned between the arm portions adjacent the arrangement space becomes narrow. Therefore, the second mold 22, as shown in FIGS. 10A and 10B, a configuration may be adopted for coupling the jig 26 which is movable along the eccentric direction of the pin portion. This configuration will be described in detail below.
[0103]
　To realize the forward and backward movement of the second die 22, the second die 22 is movably held along the guiding direction by the guide member (not shown) (see the solid line arrows in FIG. 10A). The second die 22 may be connected to the jig 26 in a slidable state along the sliding direction (see broken line arrows in FIG. 10A). Jig 26 is connected to the hydraulic cylinder or the like, is movable along the eccentric direction of the pin portion with its operation (see arrows hatched in FIG. 10A).
[0104]
　Thus connecting the jig 26 and the second die 22, the jig 26 is accompanied to move along the eccentric direction of the pin portion, when retracted from the position at the time of pressing the second mold 22 is moves along the section leading to the position in the guide direction (see the solid line arrow in drawing). At that time, the second die 22 is moved relative to the sliding direction (see dashed arrows in the figure) with respect to the jig 26.
[0105]
　The second mold 22, in addition to the forward and backward movement of the above, it may be movable in the pressing direction of the first mold 10. Movement in the pressing direction of the second die 22 are appropriately executed by means such as a spring or a hydraulic cylinder. Means for moving to the pressing direction is provided separately from the drive source for reciprocating movement.
[0106]
　When providing the second excess thickness portion to the arm portion having integrally a weight portion, the first mold 10, as shown in FIGS. 12A and 12B, the inner area of ​​both sides of the journal portion J side surface of the arm portion A portion corresponding to as is opened. The open portion may accommodate a third mold 23. The third mold 23, the mold engraved portion is engraved, in its mold engraved portions, recessed shape of the journal portion J side surface of the arm portion A is reflected. The third mold 23 is capable of forward and backward movement, the forward and backward movement is realized by the operation such as a hydraulic cylinder coupled. The third mold 23, like the second mold may be movable in the pressing direction of the first mold 10.
[0107]
　Although not shown, in the case of providing the first excess thickness portion to the weight without arm, the first mold 11 and 12, a portion corresponding to the inner region At both side portions of the pin portion P side surface of the arm portion A It is released. The open portion may accommodate a fourth mold similar to the second die 22 mentioned above. Also, when providing the second excess thickness portion to the weight without arm, the first mold 11 and 12, a portion corresponding to the inner region As on both sides of the journal portion J side surface of the arm portion A is opened. The open portion may accommodate a fifth mold similar to the third mold 23 described above.
[0108]
　An example of a process flow of the reduction step of the present embodiment using such first mold 10 will be described. First, by separating the upper mold 11 and the lower mold 12 of the first mold 10, placing the burrs without forging 30 after burr removal between the upper mold 11 and the lower mold 12 in that state. When using a second die to fifth mold, prior to placing the burrs without forging 30 is retracted by retracting the second mold to fifth die.
[0109]
　Next, the case of using the second mold to fifth mold, is advanced to the second die to fifth die respectively, as shown in FIG. 10A, 11A and 12A, is pressed against the respective surfaces of the arm portions A . Thus, to retain the respective surfaces of the arm portions A, respectively. However, among the surfaces of the arm portion, the first surplus meat portion Aca and Ada are on both sides of the journal portion near the region provided, both sides of the pin portion near provided a second excess thickness portion Aaa and Aba for the region, not pressing any of the second mold to fifth die (see FIGS. 11A and 12A). Holding by pressing a mold in those areas, since it is impossible to increase the thickness at both sides of the journal portion and near the pin vicinity.
[0110]
　In this state, it is moved so that the upper mold 11 and the lower mold 12 of the first mold 10 are in close proximity, and more specifically, to lower the upper die 11 to the bottom dead center. Thus, burr free forging 30 is reduction by the first mold 10. During the reduction, as shown in FIG. 11B, bent toward the pin portion P side surface of the arm portion A along the first excess thickness portion Aca and Ada the inclined surface of the mold engraved portion of the first mold 10 , the overhang of the first excess thickness portion Aca and Ada the pin portion P side. As a result, both side portions Ac and Ad the thickness of the journal portion J vicinity of the arm portion is increased. Therefore, the crankshaft resulting thickness becomes thicker at both side portions Ac and Ad of the journal portion J vicinity of the arm portion.
[0111]
　Similarly, in the case of providing a second excess thickness portion to the arm portion having a weight portion integrally, upon reduction, the journal portion J side surface of the first mold 10 and the second excess thickness portion Aaa and Aba arm portion A bent towards. Thereby, overhang the second excess thickness portion Aaa and Aba the journal portion J side, increasing the thickness at both side portions Aa and Ab of the pin portion near the P.
[0112]
　Folding is not shown, in the case of providing the first excess thickness portion to the weight without arm part, upon pressure, toward the first excess thickness portion to the pin portion P side surface of the arm portion A in the first mold 10 . Thereby, overhang the first excess thickness portion to the pin portion P side, increasing the thickness at the both sides of the journal portion J vicinity of the arm portion. Also, when providing the second excess thickness portion to the weight without arm part, upon pressure, a second excess thickness portion by the first mold 10 bent toward the journal portion J side surface of the arm portion A. Thereby, overhang the second excess thickness portion to the journal portion J side, increasing the thickness at both side portions of the pin portion near the P.
[0113]
　When carrying out the reduction step in shaping step further correct the shape of the crankshaft during the reduction, the final product shape.
[0114]
　Subsequently, by separating the upper die 11 of the first mold and the lower mold 12, and more specifically, to raise the upper die 11 to the top dead center. When using a second die to fifth mold, before giving to separate the upper die 11 and the lower mold 12, to retract the second mold to fifth die is retracted, respectively. In a state of being spaced apart an upper die 11 and the lower mold 12, unloading the processed burrs without forging 30.
[0115]
　According to the manufacturing method of forging the crank shaft of the present embodiment, the arm unit A having a weight portion integrally, while increasing the thickness of the side Ac and Ad in the vicinity journal portion J, the pin portion P side It can be provided a recess on the surface to become. Therefore, the production method of the forged crankshaft of the present embodiment, it is possible to produce a forged crankshaft which attained weight and rigidity ensuring at the same time.
[0116]
　A method of manufacturing a forged crankshaft of the present embodiment, the first die 10 bends the first excess thickness portion Aca and Ada. Or, as described later, crushing by the first mold 10 pushes the first excess thickness portion Aca and Ada. Thus, increasing the thickness of the side Ac and Ad of the journal portion near the arm portion. Therefore, the production method of the forged crankshaft of the present embodiment, simply performed without requiring a great deal of force.
[0117]
　The arm portion A shown in FIGS. 2A ~ Figure 2D, a range of providing a recess in the pin portion P side surface is the same as the range sides Ac and Ad the thickness in the vicinity of the journal portion J of the thick portion. Here, the range means a range of the eccentric direction of the pin portion. Range providing the recess on the pin portion P side surface, and scope sides Ac and Ad the thickness in the vicinity of the journal portion J of the thick portions, may be different. Bent from the viewpoint of reliably performing, recess of the pin portion P side surface, depending on both sides Ac and a thicker portion of the Ad near the journal portion J, to arranged to coincide with that it has a thickness of the thick portions It is preferred.
[0118]
　The first mold 10 has excess thickness portions Aaa, Aba, if having an inclined surface abutting the Aca and Ada, the angle of the inclined surface alpha (see FIG. 11A) is preferably in the 3 ~ 20 °. Here, the angle α of the inclined surface, the angle of parting surfaces and the inclined surface is formed. By the angle α of the inclined surface and 3 ° or more, it can facilitate folding, dent shape during bending can be suppressed from being deformed. Further, by setting the angle α of the inclined surface and 20 ° or less, the thickness of both side portions of the arm portion by folding easily be secured, it can promote secure and lightweight rigid.
[0119]
　From the viewpoint of promoting folding arm unit of the pre-reduction step preferably has variations of the excess thickness portions, i.e. the starting point of bending.
[0120]
　13A and 13B are sectional views showing a starting point of bending schematically, the case of FIG. 13A is not provided with a step as a starting point, FIG. 13B shows a case of providing a step at the starting point. 13A and 13B are both a cross-sectional view at a position corresponding to the VC-VC position of Figure 5A. FIG 13A and 13B, shows the sectional shape of the arm portion A of the previous reduction step in the vicinity of the journal portion J. Arm A shown in FIGS. 13A and 13B are both prior reduction step of the pin portion P side of the surface, the inner region At both side portions Ac and Ad in the vicinity journal portion J, after the reduction step recess with the bottom surface shape as the matching surface shape. Gradient (°) in its inner region At is made continuously increases with the distance from the arm portion center plane (see symbol S in FIG. 13A). Its surface shape spreads to the region on both sides Ac and Ad in the vicinity journal portion J. Its gradient in the region of both side portions Ac and Ad (°) is constant.
[0121]
　Here, the slope (unit: °, reference θa and .theta.b), the surface of the arm portion is an angle formed between the axis perpendicular to the plane of the journal portion. The arm portion center plane is a plane containing the axis of the axis and the pin portion of the journal portion.
[0122]
　Arm A shown in FIG. 13A comprises an origin O on the surface of the pin portion P side. In its origin O, relationship between the distance and slope from the arm center plane is discontinuous. If you have such an origin O, first becomes excess thickness portion Aca and Ada is bend easily folded at the origin O, folding can facilitate, that the dent shape during bending deformation can be suppressed.
[0123]
　Distance d1 from the arm portion center plane to the origin O (Unit: mm, see FIG. 13A), the distance from the arm portion center plane up to the base of the first excess thickness portion Aca and Ada (point B) d2 (unit: mm, preferably smaller than see Figure 13B). Thus, only the portion of the side surface of the arm portion from the origin O is easily bent, a dent shape at the time of bending can be suppressed from being deformed. Here, the root of the first excess thickness portion Aca and Ada (point B) is a root of the first excess thickness portion Aca and Ada in the surface of the journal portion J side of the arm portion A, for example, the outer edge of the journal thrust portion It can be set to. In this case, the distance d2 is, for example, a radius (mm) of the journal thrust portion.
[0124]
　Origin O gradient θa at arm center plane side (°) is preferably less origin gradient θb in the side surface of the arm portion (°). Thus, since the thickness of the first excess thickness portion is thinner, portion of the arm portion center plane side of the origin O is hardly deformed. Therefore, only the portion of the side surface of the arm portion from the origin O is easily bent, can facilitate folding, dent shape during bending can be suppressed from being deformed.
[0125]
　In the origin O of the bending, as shown in FIG. 13B, it may be formed a step by reducing the thickness stepwise. This also only the portion of the side surface of the arm portion from the origin O is easily bent, can facilitate folding, dent shape during bending can be suppressed from being deformed.
[0126]
[Second processing flow example]
　When performing the in crush deformation of the first excess thickness portion at a reduction process, is described shape and process flow example of a crank shaft (second processing flow example) below. The shape and the processing flow example of the crankshaft when the crushing, since if the basic structure for folding the above are the same, appropriately omitted the description of the common portions will be mainly described different parts.
[0127]
　If crushing the first excess thickness portion, compared to the case where the shape of the side surface of the arm portion is bent, different. This will be described below with reference to the drawings.
[0128]
　Figure 14A ~ FIG 14D is a schematic diagram showing an example of the shape of the pin side surfaces of the arm portions when squeezing the first excess thickness portion, FIG. 14A is a perspective view, FIG. 14B is showing the pin portion-side surface FIG 14C is a view showing a side, FIG. 14D is a XIVd-XIVd sectional view. The shape of the pin portion P side surface of the arm portion A shown in FIG. 14A ~ FIG 14D is the same as the arm portion A shown in FIG. 2A ~ Figure 2D. When collapsing, as shown in FIG. 14D, the journal portion J side in the vicinity among the arm portion A, without tilting, which is substantially parallel to the arm center plane.
[0129]
　Figure 15A ~ 15C are a schematic view showing a shape example of a journal portion side surface of a suitable arm when squeezing the first excess thickness portion, FIG. 15A is a perspective view, Figure 15B is a journal portion surface shows, FIG 15C is a XVC-XVC sectional view. The shape of the journal portion J side surface of the arm portion A shown in FIG. 15A ~ 15C are the same as the arm portion A shown in FIG. 3A ~ Figure 3C. When collapsing, as illustrated in FIG. 15C, the pin portion P near the sides of the arm A is without tilting, which is substantially parallel to the arm center plane.
[0130]
　16A and 16B are schematic views showing a shape example of a suitable weight without arm when squeezing the first excess thickness portion, FIG. 16A shows the pin side surfaces, FIG. 16B XVIB-XVIB it is a cross-sectional view. The shape of the pin portion P side surface of the arm portion A shown in FIGS. 16A and 16B are the same as the arm portion A shown in FIG. 4A and 4B. When collapsing, as illustrated in FIG. 16B, the journal portion J side in the vicinity of the arm portion A, without tilting, which is substantially parallel to the arm center plane.
[0131]
　As described above, the weight without arm A, the view of 15A ~ weight portion shown in Figure 15C similar to the arm portion having an integral, of the journal portion J side surface of the pin portion near the P side portions Aa and Ab preferably has a recess in the inner region As. For crushing, in weight without arm A, the side surface in the vicinity of the journal portion J, without tilting, is substantially parallel to the arm center plane.
[0132]
　From the viewpoint of promoting the deformation of the first excess thickness portion during crushing, the arm portion before reduction step preferably has variations of the excess thickness portions, i.e. the origin of the crushing. Origin of crushing includes a starting point of bending as shown in FIG. 13A and 13B, the same form can be adopted.
[0133]
　When the crushing is the origin O of the arm portions around side slope .theta.a (°) is preferably in the range from origin gradient .theta.b (°) or more at the side face of the arm portion (see FIG 13A). Thus, since the thickness of the first excess thickness portion is thickened, the site of the arm portion side surface is less likely to deform the journal portion side from the origin O. Therefore, the site of the side surface of the arm portion from the origin O can be flared to stably pin side.
[0134]
　Figure 17A ~ FIG. 18B is a schematic diagram showing a processing flow example when crushing the first excess thickness portion at a reduction process. 17A and 17B of which is a cross-sectional view of the vicinity journal portion, FIG. 17A when pressing the second die, Figure 17B shows the time reduction completion. FIG 17A and 17B, shows a burr without forging 30, the first mold 11 and 12 of the pair, and a second mold 22.
[0135]
　18A and 18B are cross-sectional views of a pin portion near Figure 18A when pressing the second die, Figure 18B shows the time reduction completion. FIG 18A and FIG. 18B, showing a burr without forging 30, the first mold 11 and 12 of the pair, and a third mold 23.
[0136]
　Second processing flow example when crushed shown in FIGS. 17A ~ FIG. 18B, when bending of the aforementioned (first processing flow example), the basic configuration is the same. Therefore, in the processing flow example when crushing, shows a pin portion side surface, since it becomes the same as FIGS. 8A and 8B, it is omitted. Further, it shows a journal portion side surface, since it becomes the same as FIGS. 9A and 9B, is omitted. Shows a side of the arm portions also, since it is the same as FIGS. 10A and 10B, is omitted. Incidentally, FIG. 17A corresponds to a cross-sectional view of the XIA-XIA position of FIG. 8A, FIG. 17B is a cross-sectional view of XIB-XIB position of FIG 8B. Further, FIG. 18A corresponds to a cross-sectional view of a XIIA-XIIA position of FIG. 9A, FIG. 18B is a cross-sectional view of the XIIB-XIIB position in FIG 9B.
[0137]
　Even when crushed, the upper die 11 and the lower mold 12 constituting the first mold 10, respectively Carving portion engraved. Further, the arm portion having a weight portion integrally, for crushing the first excess thickness portion, the shape of the vicinity of the journal portion is reflected in the mold engraved portion among the both side portions of the arm portions. Site contributes to the crushing of the first excess thickness portion within the mold engraved portion without tilting, it is substantially parallel to the parting plane. If the weight portion provided further second excess thickness portion to the arm portion having an integral, in the case of providing the first excess thickness portion to the weight without arm portion, and any case of providing a second excess thickness portion to the weight without arm But sites contribute to crushing, without tilting, it is substantially parallel to the parting plane.
[0138]
　When rolling the burrs without forging 30 by the first mold 10, as shown in FIG. 17B, crushing the first excess thickness portion Aca and Ada. Accordingly, it deformed into a shape along the first excess thickness portion Aca and Ada the mold engraved portion of the first mold 10, thereby overhanging the first excess thickness portion Aca and Ada the pin portion P side. As a result, both side portions Ac and Ad the thickness of the journal portion J vicinity of the arm portion is increased. Therefore, the crankshaft resulting thickness becomes thicker at both side portions Ac and Ad of the journal portion J vicinity of the arm portion.
[0139]
　When providing the second excess thickness portion to the arm portion having integrally a weight portion, during rolling, crushing in the first mold 10 pushes the second excess thickness portion Aaa and Aba. Thus, a second excess thickness portion Aaa and Aba allowed overhang the journal portion J side along the mold engraved portion of the first mold 10, thereby increasing the thickness at both side portions Aa and Ab of the pin portion near the P.
[0140]
　Although not shown, if further include a first excess thickness portion to the weight without arm part, upon pressure, crushing the first excess thickness portion by the first mold 10. Thereby, overhang the first excess thickness portion to the pin portion P side, increasing the thickness at the both sides of the journal portion J vicinity of the arm portion. Also, if further include a second excess thickness portion to the weight without arm part, upon pressure, crushing the first mold 10 pushes the second excess thickness portion. Thereby, overhang the second excess thickness portion Aaa and Aba the journal portion J side, increasing the thickness at both side portions of the pin portion near the P.
[0141]
　The arm portion A shown in FIGS. 14A ~ FIG 14D, the range of providing a recess in the pin portion P side surface is the same as the range sides Ac and Ad the thickness in the vicinity of the journal portion J of the thick portion. Range providing the recess on the pin portion P side surface, and scope sides Ac and Ad the thickness in the vicinity of the journal portion J of the thick portions, may be different. From the viewpoint of ensuring the stability of the deformation during the crushing, dents of the pin portion P side surface, depending on both sides Ac and a thicker portion of Ad of the journal portion J vicinity consistent with that it has a thickness of the thick portions preferably arranged to have. Only side portion than recessed by crushing recess in the immediate vicinity of both sides during exists, specifically, because only the side portions and the first excess thickness portion is easily deformable.
[0142]
4. Preferred embodiments such as
　a crank shaft (final product) is arm portion having a weight portion integrally (hereinafter, also referred to as "Weighted arm") when provided with a plurality of, in forging, all of the first excess thickness of the weight with the arm portion parts may have a portion of the weight with the arm portion may have a first excess thickness portion. Weighted arm providing the first excess thickness portion is, for example, flexural rigidity and torsional rigidity is required in the arm portion, based on the rigidity required site can be appropriately determined.
[0143]
　Yes crankshaft having an arm portion with a plurality of weights in (final product), the case of providing a second excess thickness portion to the weight with the arm portion of the forging material, all of the weight with the arm portion of forging a second excess thickness portion may be a part of the weight with the arm portion may have a second excess thickness portion. Further, as shown in Figure 5A, may be the arm part with the same weights have both a first excess thickness portion and the second excess thickness portion, Weighted arm with another weight having a first excess thickness portion arm attached may have a second excess thickness portion. Weighted arm providing a second excess thickness portion, for example, flexural rigidity and torsional rigidity is required in the arm portion, based on the rigidity required site can be appropriately determined.
[0144]
　Arm without a plurality of weight portion crankshaft comprising (weight without arm) in (final product), when providing the first excess thickness portion to the weight without arm forging, weight without arm forging good all of which may have a first excess thickness portion, a portion of the weight without arm portion may have a first excess thickness portion. Weight without arm providing the first excess thickness portion is, for example, flexural rigidity and torsional rigidity is required in the arm portion, based on the rigidity required site can be appropriately determined.
[0145]
　Yes crankshaft comprising a plurality of weights without arm in (final product), the case of providing a second excess thickness portion to the weight without arm forging, all of the weight without arm of forging a second excess thickness portion may be a part of the weight without arm portion may have a second excess thickness portion. Further, as shown in FIG. 7A, may be the same weight without arm part has both a first excess thickness portion and the second excess thickness portion, another weight and weight without arm having a first excess thickness portion None arm portion may have a second excess thickness portion. Weight without arm providing a second excess thickness portion, for example, flexural rigidity and torsional rigidity is required in the arm portion, based on the rigidity required site can be appropriately determined.
[0146]
　As in the previous example of the shape and the processing flow example, Weighted arm portion may have first the excess thickness portion (Aca, Ada) on both sides of the journal portion near (sides Ac and Ad) or, first the excess thickness portion (Aca, Ada) may have on one side of the journal portion near (Ac or Ad). Even if the Weighted arm has a first excess thickness portion on one side (Ac or Ad) of the journal portion near, by overhang the first excess thickness portion to the pin portion, reduction It can increase the thickness at one side of the arm portion after step. Therefore, while lighter, it can ensure rigidity. Sides of the journal portion near providing the first excess thickness portion is, for example, flexural rigidity and torsional rigidity is required in the arm portion, based on the rigidity required site can be appropriately determined.
[0147]
　The second excess thickness portion to the weight with the arm portion is in the vicinity of the pin portion side (Aa, Ab) (Aaa, Aba), then a as described above in the shape example and exemplary process flow, both sides (both sides it may have the Aa and Ab), or may have on one side (Aa or Ab). Even if the Weighted arm has a second excess thickness portion on one side of the pin portion near (Aa or Ab), whereby overhang the second excess thickness portion at the journal portion, pressure It can increase the thickness at one side of the arm portion after step. Therefore, while lighter, it can ensure rigidity. Side of the pin portion near providing a second excess thickness portion, for example, flexural rigidity and torsional rigidity is required in the arm portion, based on the rigidity required site can be appropriately determined.
[0148]
　The first excess thickness portion to journal the vicinity of the side of the weight without arm (Ac, Ad) (Aca, Ada), then a as described above in the shape example and exemplary process flow, both sides (both sides Ac and Ad) to may have, or may have on one side (Ac or Ad). Even if the weight without arm portion has a first excess thickness portion on one side (Ac or Ad) of the journal portion near, by overhang the first excess thickness portion to the pin portion, reduction It can increase the thickness at one side of the arm portion after step. Therefore, while lighter, it can ensure rigidity. Sides of the journal portion near providing the first excess thickness portion is, for example, flexural rigidity and torsional rigidity is required in the arm portion, based on the rigidity required site can be appropriately determined.
[0149]
　The second excess thickness portion to the side (Aa, Ab) of the pin portion near the weight without arm (Aaa, Aba), then a as described above in the shape example and exemplary process flow, both sides (both sides may have the Aa and Ab), it may have on one side (Aa or Ab). Even if the weight without arm portion has a second excess thickness portion on one side of the pin portion near (Aa or Ab), whereby overhang the second excess thickness portion at the journal portion, pressure It can increase the thickness at one side of the arm portion after step. Therefore, while lighter, it can ensure rigidity. Side of the pin portion near providing a second excess thickness portion, for example, flexural rigidity and torsional rigidity is required in the arm portion, based on the rigidity required site can be appropriately determined.
[0150]
　As described above, the arm portion A having a weight portion W may have a first excess thickness portion Aca and Ada on both sides Ac and Ad journal vicinity. In this case, the pressure step, as shown in FIGS. 10A ~ FIG 11B, the arm portion A having a weight portion is W, the area of ​​both sides Ac and Ad in the vicinity journal portion J among the surface of the pin portion P side at least excluding the surface, preferably maintained by pressing the second mold 22. Thus, it is possible to finish the recessed shape of the pin portion P side surface of the arm portion A precise. However, as in the second and third step example, if burr attached to the forging material to be subjected to the reduction step, the second mold 22 is not applicable.
[0151]
　The arm portion A having a weight portion W has a first excess thickness portion (Aca, Ada) may have one of the journal portion near the side Ac and Ad. In this case, the both side portions Ac and the outer peripheral of the pin portion P side surface of the first excess thickness portion is the arm part A except at least the regions of the side projecting out of the Ad near the journal portion J, the second die 22 preferably held by the pressing. Thus, it is possible to finish the recessed shape of the pin portion P side surface of the arm portion A precise.
[0152]
　When using the second mold 22 at a reduction process, the second die 22 to follow the pressure of the first die 10 is moved in the pressing direction of the first mold 10, the second die to the arm portion A preferably, to maintain the 22 pressing position of the fixed position. Thus, it is possible to finish more precisely the recess shape of the pin portion P side surface.
[0153]
　In the arm portion having integrally a weight portion, the mold forging step, further forming a second excess thickness portion of the foregoing, in the reduction step, to deform the second excess thickness portion in the first mold, the pin portion near P It is preferable to increase the thickness at one or both sides (Aa and Ab). Thus, while ensuring the rigidity, it is possible to further reduce the weight. In this case, in view of finishing the recessed shape of the journal portion J side surface precision, it is preferable to use a third mold described above. However, as in the second and third step example, If there is a burr on the forging material to be subjected to the pressing process, the third mold can not be applied.
[0154]
　In weight without arm part, in the die forging process, first the excess thickness portion to further shape the above, the reduction step, the first mold to deform the first excess thickness portion, the journal portion J vicinity of the side (Ac and preferably increase the thickness at one or both Ad). Thus, while ensuring the rigidity, it is possible to further reduce the weight. In this case, in view of finishing the recessed shape of the pin portion P side surface precision, it is preferable to use a fourth mold described above. However, as in the second and third step example, If there is a burr on the forging material to be subjected to the pressing process, the fourth mold can not be applied.
[0155]
　Further, in the weight without arm part, in the die forging step, the second excess thickness portion is further shaped to the foregoing, the reduction step, to deform the second excess thickness portion in the first mold, the pin portion P near the sides is preferable to increase the thickness at one or both of (Aa and Ab). Thus, while ensuring the rigidity, it is possible to further reduce the weight. In this case, in view of finishing the recessed shape of the journal portion J side surface precision, it is preferable to use a fifth mold described above. However, as in the second and third step example, If there is a burr on the forging material to be subjected to the pressing process, the fifth mold can not be applied.
[0156]
　When using a second die to fifth mold, pressed against the second die to fifth die on the surfaces of the arm portions A. Second die to fifth mold only hold the surface of the arm portion A, because there is no pushing force required for pressing the second die to fifth mold small.
[0157]
　First and second processing flow example described above, the shift both directed to a crankshaft mounted in a four-cylinder engine, the crankshaft, each eccentric direction arm portion of the pin portion at equal intervals of 180 ° to. When shifting equally spaced Thus 180 °, both of the arm portions, is pressure from the eccentric direction perpendicular to the direction of the pin portion by the first mold. In this case, the pressing direction of the first mold is perpendicular with the axial direction of the crankshaft.
[0158]
　However, the pressing direction of the first mold is not limited to the eccentric direction perpendicular to the direction of the pin portion. For example, in the case of a crankshaft mounted in three-cylinder engine, the eccentric direction of the pin portion is shifted at regular intervals of 120 ° or 60 ° for each arm portion. In this way, the production of a crank shaft, not shifted at equal intervals of 180 °, there is a case of adjusting the arrangement angle of the pin portion by adding twisting process. In some cases, to adjust beating finished the placement angle of the pin portion. For example, the adjustment of the arrangement angle of the pin portion in a first step example when performed in twisting process, the pressing direction of the first mold at a reduction process, the eccentric direction perpendicular to the direction of the pin portion in a part of the arm portion not not. To explain the situation in this case will be described below.
[0159]
　19A and 19B are schematic views showing the pin portion side surface of the arm portion when the pressing direction of the first mold is not perpendicular to the eccentric direction of the pin portion, FIG. 19A shows a prior reduction, Figure 19B It shows the time pressure end. Crankshaft having an arm portion A shown in FIG. 19A and FIG. 19B is a crank shaft mounted on a three-cylinder engine, the arrangement angle of the pin portion P is shifted at regular intervals of 120 °. Therefore, in the reduction step, the eccentric direction of the portion of the pin portion P is 30 ° inclined from the horizontal direction. Accordingly, the pressing direction of the first mold 10 (Fig. 19A in and 19B vertically) is a 60 ° offset direction from the eccentric direction of the pin portion P.
[0160]
　Thus also the pressing direction of the first mold 10 is a case where not the eccentric direction perpendicular to the direction of the pin portion P, can be applied a method of manufacturing a forged crankshaft of the present embodiment. That is, first the excess thickness portion by the first mold 10 (Aca, Ada) or second excess thickness portion (Aaa, Aba) by deforming the can increase the thickness of the side portions of the arm portions. Accordingly, the pressing direction of the first mold, first the excess thickness portion by the first mold 10 (Aca, Ada) or second excess thickness portion (Aaa, Aba) thickness on both sides of the arm portion by deforming the as long as it can increase without limit.
Industrial Applicability
[0161]
　The present invention can be effectively utilized in the production of forged crankshaft mounted in a reciprocating engine.
DESCRIPTION OF SYMBOLS
[0162]
　1: Forged crankshaft, J, J1 ~ J5: journal
　portion, P, P1 ~ P4: pin, Fr: the front
　section, Fl: flange portion, A, A1 ~ A8: crank
　arm, W, W1 ~ W8: counterweight
　unit, Aa, Ab: the sides of the pin in the vicinity of the arm
　portion, Aaa, Aba: second excess thickness
　portion, Ac, Ad: the side of the journal portion near the arm
　portion, Aca, Ada: first excess material
　part, As: inner area of both sides of the journal portion surface of the arm
　portion, at: inner region of the both side portions of the pin portion side surface of the arm portion,
　10: first mold, 11: upper die, 11a, 11b: the inclined
　surface, 12: lower die, 12a, 12b: inclined surface 22: second
　mold 23: third mold, 26: jig, 30: no burrs forging

The scope of the claims
[Claim 1]
　Counter and a journal portion as a rotational center, and a pin portion which is eccentric with respect to the journal portion, and a crank arm portion connecting the pin portion and the journal portion, all or a portion of said crank arm portion has integrally a method of manufacturing a forged crankshaft comprising a weight portion, and
　the production method,
　by mold forging, and die forging to obtain a forged material molded into the shape of a crankshaft,
　the first mold pair, anda reduction step of rolling the forged material,
　the forging material is all or a portion of said crank arm having integrally the counterweight unit, protruding from the outer periphery of the journal portion near the side has a first excess thickness portion which,
　in the reduction step, the reduction deforming said first excess thickness portion by the first mold causes overhang the first excess thickness portion to the pin portion The method of forging the crank shaft.
[Claim 2]
　The method of manufacturing a forged crankshaft according to claim 1,
　wherein the first mold, the first comprising the excess thickness portion and the opposed inclined surface,
　with the pressure step, the inclined surface of the first excess thickness portion It is deformed along the production method of the forged crankshaft.
[Claim 3]
　The method of manufacturing a forged crankshaft according to claim 1 or 2,
　the manufacturing method includes a burr punching step of removing burrs from the forged material,
　and in the forging step, to obtain the forged material with burrs ,
　wherein the burr punching process, to obtain a forged material without burrs from the forged material with the burr,
　and in the reduction step, the reduction of the forging material without the burr method of forging the crank shaft.
[Claim 4]
　The method of manufacturing a forged crankshaft according to claim 3,
　wherein the pressure step, the side portions of the journal portion near among said pin portion of the surface of the crank arm portion having a first excess thickness portion at least excluding the surface area, it is held by the pressing of the second mold, the production method of the forged crankshaft.
[Claim 5]
　The method of manufacturing a forged crankshaft according to claim 4,
　in the reduction step, following the reduction of the first mold to move the second mold pressing direction of the first mold, the crank maintaining the pressing position of the second mold into the arm portion in a fixed position, the production method of the forged crankshaft.
[Claim 6]
　The method of manufacturing a forged crankshaft according to any one of claims 1 to 5,
　wherein the first excess thickness portion respectively protrude from both the sides of the journal portion near method of forging the crank shaft .
[Claim 7]
　The method of manufacturing a forged crankshaft according to any one of claims 1 to 6,
　wherein the reduction step, the reduction using a metal mold carried by shaping step of correcting the shape of the crankshaft, the forged crankshaft Production method.
[8.]
　The method of manufacturing a forged crankshaft according to any one of claims 1 to 7,
　wherein the forging, the all or part of the crank arm portion, protruding from the outer periphery of the pin portion near the side a second excess thickness portion which,
　in the reduction step, the reduction deforming said second excess thickness portion by the first mold, thereby overhanging the second excess thickness portion to the journal portion, method for producing a forged crankshaft.
[Claim 9]
　The method of manufacturing a forged crankshaft according to claim 8,
　wherein the second excess thickness portion respectively protrude from both the sides of the pin in the vicinity, the production method of the forged crankshaft.