JP6424643B2 - Method of manufacturing forged crankshaft - Google Patents

Description

  The present invention relates to a method of manufacturing a crankshaft by hot forging.

  In reciprocating engines such as automobiles, motorcycles, agricultural machines, and ships, a crankshaft is essential in order to convert the reciprocating motion of the piston into rotational motion and extract power. The crankshaft can be manufactured by die forging or casting. In particular, when high strength and high rigidity are required for the crankshaft, a crankshaft manufactured by die forging (hereinafter, also referred to as "forged crankshaft") is often used because of its excellent properties.

  Generally, forged crankshafts are made of billets as raw materials, and the billets have a round or square cross section and a constant cross-sectional area over the entire length. In the manufacture of forged crankshafts, a preforming step, a die forging step, a deburring step and a shaping step are provided in that order. Usually, the preforming process includes the steps of roll forming and bending, and the die forging process includes the steps of roughing and finishing.

  FIG. 1 is a schematic view for explaining a conventional general forged crankshaft manufacturing process. The crankshaft 1 (see FIG. 1 (f)) illustrated in the figure is a crankshaft of a four-cylinder eight-piece counterweight mounted on a four-cylinder engine. The crankshaft 1 has five journal portions J1 to J5, four pin portions P1 to P4, a front portion Fr, a flange portion Fl, and eight crank arm portions (hereinafter, also simply referred to as "arm portions") A1. To A8. The arm parts A1 to A8 connect the journal parts J1 to J5 and the pin parts P1 to P4, respectively. In addition, all the eight arm portions A1 to A8 integrally include counterweight portions (hereinafter, also simply referred to as "weight portions") W1 to W8.

  Hereinafter, when the journals J1 to J5, the pins P1 to P4, the arms A1 to A8, and the weights W1 to W8 are collectively referred to, the reference numerals are “J” in the journal and “P” in the pins. Also described as “A” in the arm part and “W” in the weight part. The pin portion P and a pair of arm portions A (including the weight portion W) connected to the pin portion P are collectively referred to as "slow".

  In the manufacturing method shown in FIG. 1, the forged crankshaft 1 is manufactured as follows. First, a billet 2 having a predetermined length as shown in FIG. 1A is heated by an induction heating furnace or a gas atmosphere heating furnace, and then roll forming is performed. In the roll forming step, for example, by rolling and squeezing the billet 2 using a hole-shaped roll, the volume is distributed in the longitudinal direction, and the roll stock 3 as an intermediate material is formed (see FIG. 1B). Next, in the bending process, the roll stock 3 is partially pressed from the direction perpendicular to the longitudinal direction. Thereby, the volume of the roll waste 3 is distributed, and the bending waste 4 which is a further intermediate material is formed (see FIG. 1 (c)).

  Subsequently, in the roughing process, the forged material 5 is obtained by press-forging the bending rougher 4 up and down using a pair of molds (see FIG. 1D). The rough forging material 5 is formed into an approximate shape of a crankshaft (final product). Furthermore, in the finish casting process, the rough forged material 5 is press-forged using a pair of molds up and down to obtain the finish forged material 6 (see FIG. 1E). The finish forging 6 is shaped to match the crankshaft of the final product. At the time of these roughing and finishing, excess material flows out as burrs from between the mold parting faces of the molds facing each other. For this reason, in each of the rough forging material 5 and the finish forging material 6, the burrs B are largely attached around the formed crankshaft.

  In the deburring step, the burr B is punched out and removed by the blade type in a state in which the finish forged material 6 with burrs is sandwiched and held by, for example, a pair of dies. Thereby, a burrless forged material is obtained, and the burrless forged material has substantially the same shape as the forged crankshaft 1 shown in FIG. 1 (f).

  In the shaping process, a key portion of the burr-free forging material is slightly pressed down from above and below by a mold, and the burr-free forging material is corrected to the dimensional shape and shape of the final product. Here, the essential parts of the burr-free forging material correspond to, for example, the shaft portion such as the journal portion J, the pin portion P, the front portion Fr, the flange portion Fl, and the arm portion A and the weight portion W. Thus, the forged crankshaft 1 is manufactured.

  The manufacturing process shown in FIG. 1 can be applied not only to the four-cylinder eight-piece counterweight crankshaft shown in FIG. 1 (f) but also to various crankshafts. For example, it can be applied to a four-cylinder four-piece counterweight crankshaft.

  In the case of a four-cylinder / four-piece counterweight crankshaft, the weight portion W is integrally provided on a part of the eight arm portions A1 to A8. For example, the weight portion W is integrally provided on the first arm portion A1 at the top, the eighth arm portion A8 at the rear end, and the two arm portions in the center (the fourth arm portion A4 and the fifth arm portion A5). Further, the remaining arm portions, specifically, the second, third, sixth and seventh arm portions (A2, A3, A6, A7) do not have weight portions, and the shape is oval Become. Below, the arm part which does not have a weight part is also called "oblong arm part."

  In addition, even in the case of a crankshaft mounted on a three-cylinder engine, in-line six-cylinder engine, V-type six-cylinder engine, eight-cylinder engine, etc., the manufacturing process is the same. In addition, when adjustment of the arrangement | positioning angle of a pin part is required, a twisting process is added after a burr removal process.

  In recent years, weight reduction has been required for reciprocating engines, especially for automobiles, in order to improve fuel consumption. For this reason, the demand for weight reduction is also increasing for crankshafts mounted on reciprocating engines.

  As a conventional technique for reducing the weight of a forged crankshaft, there is a technique of providing a concave lightening portion on the surface of the pin portion side in an arm portion integrally having a weight portion. The concave lightening portion is formed by die forging, and thus extends in a direction perpendicular to the parting surface of the mold (the die surface), that is, in the direction perpendicular to the eccentric direction of the pin portion. Patent documents 1 and 2 are concerned with this technology.

  In Patent Document 1, the outer periphery of a virtual cylindrical body connecting the joint surfaces of each of the pin portion and the journal portion to the web, at least in the region closer to the pin portion than the axial center of the journal portion. It has been proposed that the depth is gradually increased from the pin side to the journal side along the surface. As a result, the mass can be reduced without lowering the rigidity of the crankshaft.

  In Patent Document 2, an imaginary line passing through the axis of the journal portion is assumed between the outer peripheral edge of the thrust receiving portion of the pin portion and the outer peripheral edge of the thrust receiving portion of the journal portion. A thin-walled portion is formed in the arm portion between the imaginary line and the axis of the journal portion, and the thin-walled portion is perpendicular to the parting surface of the mold, ie, in the direction perpendicular to the eccentric direction of the pin portion. It extends over the entire width. By providing such a thin portion, when a load is applied to the pin portion by the reciprocating motion of the piston, the arm portion itself can be flexed to disperse the stress, and the life of the pin portion can be prolonged. And According to Patent Document 2, the mass can also be reduced by further providing a lightening portion.

JP, 2009-197929, A JP, 2010-255834, A

  As described above, forged crankshafts are required to be reduced in weight. If a lightening portion as described in Patent Documents 1 and 2 is provided on the pin portion side surface of the arm portion, the mass can be reduced but the rigidity is reduced. For this reason, the weight reduction by a lightening part has a limit from a viewpoint of securing rigidity, and it is difficult to meet the demand for further weight reduction.

  An object of the present invention is to provide a method of manufacturing a forged crankshaft which can obtain a forged crankshaft which can simultaneously achieve weight reduction and securing of rigidity.

  A manufacturing method of a forged crankshaft according to an embodiment of the present invention includes: a journal portion serving as a rotation center; a pin portion eccentric to the journal portion; and a crank arm portion connecting the journal portion and the pin portion In the method for manufacturing a forged crankshaft, the forged crankshaft has a counterweight portion integrally with all or part of the crank arm portion, and in the manufacturing method, the shape of the crankshaft is formed. Forming a forged material with burrs, removing the burrs from the forged material with burrs, deburring the forged material with no burrs, and using the forged materials without burrs with a pair of first dies A pressing step of pressing a second mold into the surface of the pin portion side to form a recess in a crank arm portion integrally having the counterweight portion after pressing; And in the mold forging step, in the crank arm portion integrally having the counterweight portion, a first excess thickness portion protruding from the outer periphery is further formed on the outer periphery of each side portion in the vicinity of the journal portion; In the process, when the burr-free forging material is pressed down, the first excess thickness portion is crushed with the first mold to increase the thickness of both side portions in the vicinity of the journal portion, and the concave portion is used as the pin. It shape | molds between the said both sides of the said journal part vicinity among the part side surfaces.

  The pressing step is carried out in a shaping step of correcting the shape of the crankshaft by pressure reduction using a mold.

  In the method for manufacturing a forged crankshaft according to the present invention, in the die forging step, the first surplus portion projecting from the outer periphery of both side portions in the vicinity of the journal portion of the arm portion is formed into a forged material. Further, in the pushing step, by crushing the first excess thickness portion, the thickness of both side portions in the vicinity of the journal portion of the arm portion is increased, and accordingly, the first recessed portion is formed inside the both side portions. Furthermore, in the pushing step, the second mold is pushed into the pin portion side surface of the arm portion, and a recess is formed between both side portions in the vicinity of the journal portion.

  The method of manufacturing a forged crankshaft according to the present invention can secure rigidity more efficiently than in the case of providing a hollow portion by increasing the thickness at both side portions near the journal portion of the arm portion. Moreover, weight reduction can be achieved by the formation of the first recess and the recess.

FIG. 1 is a schematic view for explaining a conventional general forged crankshaft manufacturing process. FIG. 2 is a schematic view showing an example of the shape of the pin portion side surface of the arm portion in the crankshaft targeted by the present invention, wherein FIG. 2 (a) is a perspective view and FIG. 2 (b) is the pin portion side surface , (C) is a side view, and (d) is an I-I sectional view. FIG. 3 is a schematic view showing an example of the shape of the surface on the side of the journal of the arm in the crankshaft targeted by the present invention, wherein FIG. 3 (a) is a perspective view, and FIG. 3 (b) is the surface on the journal side. FIG. 12C is a sectional view taken along the line II-II. FIG. 4 is a schematic view showing an example of the shape of an oval arm portion of a crankshaft targeted by the present invention, wherein FIG. 4 (a) is a view showing a surface on a pin portion side, and FIG. It is III sectional drawing. FIG. 5 is a schematic view showing an example of the shape of the pin portion side surface before the pressing step for the arm portion integrally having the weight portion, and FIG. 5 (a) is a view showing the pin portion side surface, FIG. Is a side view, and (c) is a cross-sectional view taken along the line IV-IV. FIG. 6 is a schematic view showing an example of the shape of the surface on the side of the journal part before the pushing process for the arm having the weight integrally, and FIG. 6 (a) shows the surface on the journal side, FIG. ) Is a V-V cross-sectional view. FIG. 7 is a schematic view showing an example of the shape of the pin portion side surface before the pressing step for the oval arm portion, and FIG. 7 (a) is a view showing the pin portion side surface, and FIG. 7 (b) is VI. FIG. 6 is a cross-sectional view taken along line VI of FIG. FIG. 8 is a schematic view showing the pin portion side surface of the arm portion in the processing flow example of the pushing step, and FIG. 8 (a) shows the holding time, FIG. 8 (b) shows the drawing end, FIG. Indicates when pressing is complete. FIG. 9 is a schematic view showing the surface on the side of the journal of the arm in the processing flow example of the pushing process, wherein FIG. 9 (a) shows the holding time, FIG. 9 (b) shows the drawing end, FIG. Indicates when pressing is complete. FIG. 10 is a schematic view showing the side of the arm portion in the processing flow example of the pushing step, and FIG. 10 (a) shows the holding time, FIG. 10 (b) shows the pressing end, and FIG. Indicates FIG. 11 is a cross-sectional view of the position of the journal portion in the processing flow example of the pushing process, and FIG. 11 (a) shows the holding time, FIG. 11 (b) shows the drawing end, and FIG. . FIG. 12 is a cross-sectional view of the pin position in the process flow example of the pushing process, and FIG. 12 (a) shows the holding time, FIG. 12 (b) shows the drawing end, and FIG. . Fig. 13 is a cross-sectional view of the position of the journal in the case of using the sixth mold. Fig. 13 (a) shows the holding time, Fig. 13 (b) shows the pressing end, Fig. 13 (c) shows the pressing end Show.

  Hereinafter, a method of manufacturing the forged crankshaft according to the present embodiment will be described with reference to the drawings.

1. Shape of Crankshaft The forged crankshaft targeted by the present embodiment includes a journal portion as a rotation center, a pin portion eccentric to the journal portion, and an arm portion connecting the journal portion and the pin portion. Further, the forged crankshaft has a weight portion integrally with all or a part of the arm portions. For example, a forged crankshaft shown in FIGS. 2 to 4 can be employed as such a forged crankshaft.

  FIG. 2 is a schematic view showing an example of the shape of the pin portion side surface of the arm portion in the crankshaft targeted by the present invention, wherein FIG. 2 (a) is a perspective view and FIG. 2 (b) is the pin portion side surface , (C) is a side view, and (d) is an I-I sectional view. In the figure, among the arm portions of the crankshaft, only one arm portion having a weight portion is extracted and shown, and the arm portions of the remaining crankshafts are omitted. In addition, the figure (c) is a projection figure from the direction shown by the broken line arrow of the figure (b). In the present invention, the pin portion P side in the eccentric direction of the pin portion is on the top side (see symbol T in FIG. 7B), and the weight portion W is on the bottom side (see symbol B in FIG. ).

  As shown in the figure, the arm portion A integrally including the weight portion W has the first recessed portion At inside the both side portions (Ac, Ad) in the vicinity of the journal portion J in the surface on the pin portion P side. Have. Further, both side portions (Ac, Ad) in the vicinity of the journal portion J bulge toward the pin portion P, and the thickness of the both side portions (Ac, Ad) is thicker than the thickness of the first hollow portion At. Here, the side portions (Ac, Ad) mean the side surfaces of the arm portion A in the width direction (the direction perpendicular to the eccentric direction of the pin portion) and its peripheral portion, in other words, the width direction of the arm portion A Means the end.

  Further, a concave portion Au is provided on the surface of the arm portion A on the side of the pin portion P, more specifically, on the bottom surface of the first hollow portion At. The recess Au is disposed between both sides (Ac, Ad) near the journal J, that is, between one side Ac and the other side Ad. The concave portion Au has a curved surface shape, and can be, for example, a spherical surface, an elliptical surface, or a paraboloid surface. The position in the width direction of the recess Au can be, for example, the center of both sides (Ac, Ad).

  As described above, since the arm portion A has the first recessed portion At and the recessed portion Au on the surface on the side of the pin portion P, the forged crankshaft targeted by the present embodiment can achieve weight reduction. Further, since the thickness of both side portions (Ac, Ad) in the vicinity of the journal portion J of the arm portion A is maintained thick, the forged crankshaft targeted by the present embodiment can secure rigidity. The reason is explained below.

  When the present inventors examined the rigidity, the thickness of the inner side (between) of the both sides (Ac, Ad) has little influence on the rigidity, but the thickness of the both sides (Ac, Ad) has an influence on the rigidity. It became clear that it was big. Specifically, in the case where the lightening portions as described in Patent Documents 1 and 2 described above are provided on the pin portion side surface of the arm portion, the concave lightening portions penetrate to both side surfaces in the width direction of the arm portion. . As a result, the thickness of both side portions (Ac, Ad) in the vicinity of the journal portion J also becomes thin, so the rigidity is reduced. In addition, rigidity here means torsional rigidity.

  On the other hand, in the forged crankshaft targeted by the present embodiment, the first depression At is formed inside the both sides (Ac, Ad) in the vicinity of the journal J, and the recess Au is formed in both sides (Ac, Ad). Molding between). For this reason, since the thickness of both side parts (Ac, Ad) can be maintained thick, the fall of the rigidity of a forged crankshaft can be controlled. As a result, according to the forged crankshaft according to the present embodiment, as compared with the case where the lightening portion is provided, the rigidity is efficiently ensured, and further weight reduction is achieved by forming the concave portion Au together with the first hollow portion At. Can be

  The thick portions of both sides (Ac, Ad) in the vicinity of the journal portion J range from the bottom outer edge of the pin thrust portion (not shown) to the center of the journal portion from the viewpoint of efficiently securing rigidity. It is preferable to include. Here, the pin thrust portion is a portion that is provided on the pin portion side surface of the arm portion and that restricts the movement of the connecting rod in the thrust direction.

  In the manufacturing method of the embodiment described later, the thickness of the both side portions (Ac, Ad) is increased by crushing the first surplus portion protruding from the both side portions (Ac, Ad) in the vicinity of the journal portion J. In this case, from the viewpoint of securing the stability of deformation at the time of crushing, the first depression At at the surface on the side of the pin P corresponds to a portion where the thickness of both sides (Ac, Ad) near the journal J is thick, It is preferable to arrange so that the thickness may correspond to the range of the thick part. The presence of the first recess At immediately in close proximity to both sides at the time of crushing makes it easy to deform only the side only from the first recess At, specifically, only the both sides and the first surplus portion. It is because it becomes possible.

  It is preferable that a portion of the recessed portion Au be located directly behind the journal portion J, and it is more preferable that the recessed portion Au be located entirely behind the journal portion J. Thereby, it is possible to further suppress the reduction in the rigidity of the forged crankshaft while reducing the weight.

For example, the depth of the concave portion Au can be 0.5 mm or more and the thickness of the arm portion or less, and the maximum diameter of the concave portion Au can be equal to or less than the diameter of the journal portion. In addition, from the viewpoint of reducing the force required to press the second mold, the depth D (mm) of the recess Au is made shallow and the area S (mm ² ) of the recess Au is set to secure the weight reduction effect. It is preferable to widen. Specifically, it is preferable to set D / (S) ^1/2 to (3π) ^−1/2 or less. In this case, the angle θ1 (see FIG. 2C) of the tangent of the recess Au can be set to, for example, 60 ° or less, which also reduces the force required for pushing. In addition, the risk of chewing can be reduced.

  Then, the preferable aspect is demonstrated about the shape of the journal part J side in the arm part A which has a weight part integrally.

  FIG. 3 is a schematic view showing an example of the shape of the surface on the side of the journal of the arm in the crankshaft targeted by the present invention, wherein FIG. 3 (a) is a perspective view, and FIG. 3 (b) is the surface on the journal side. FIG. 12C is a sectional view taken along the line II-II.

  The arm portion A integrally including the weight portion W has a second recessed portion As inside the both sides (Aa, Ab) in the vicinity of the pin portion P in the surface on the journal portion J side, as shown in the figure. Is preferred. Further, both sides (Aa, Ab) in the vicinity of the pin portion P bulge toward the journal portion J, and the thickness of the both sides (Aa, Ab) is thicker than the thickness of the second depression As. Is preferred. In this case, while the rigidity is maintained by maintaining the thickness of both sides (Aa, Ab) in the vicinity of the pin portion P, further weight reduction can be achieved by the second recessed portion As.

  Then, the preferable aspect is demonstrated about the arm part which does not have a weight part integrally, ie, an oval arm part.

  FIG. 4 is a schematic view showing an example of the shape of an oval arm portion of a crankshaft targeted by the present invention, wherein FIG. 4 (a) is a view showing a surface on a pin portion side, and FIG. It is III sectional drawing. In the figure, among the arm portions of the crankshaft, only one oval arm portion is extracted and shown, and the arm portions of the remaining crankshafts are omitted.

  As shown in the figure, the oval arm portion A is, like the arm portion integrally including the weight portion shown in FIG. It is preferable to have a first depression At at the inside of Ad). Further, both sides (Ac, Ad) in the vicinity of the journal J bulge toward the pin P, and the thickness of both sides (Ac, Ad) is thicker than the thickness of the first depression At. Is preferred. In this case, while maintaining rigidity by maintaining the thickness of both side portions (Ac, Ad) of the arm portion A in the vicinity of the journal portion J, further weight reduction is achieved by the first hollow portion At of the pin portion P side surface of the arm portion A. be able to.

  Although the illustration is omitted, the oval arm portion A, like the arm portion integrally having the weight portion shown in FIG. It is preferable to have a second recess (not shown) inside of. Further, both side portions (Aa, Ab) in the vicinity of the pin portion P swell toward the journal portion J side, and the thickness of the both side portions is preferably thicker than the thickness of the second hollow portion. In this case, while maintaining rigidity by maintaining the thickness of both sides (Aa, Ab) in the vicinity of the pin portion P, further weight reduction can be achieved by the second depression portion on the surface on the journal portion J side.

  Subsequently, before the pushing step, in other words, the shape of the crankshaft (the burr-free forging material) after the burr removing step, the arm portion integrally having the weight portion and the oval arm portion will be described in order.

  FIG. 5 is a schematic view showing an example of the shape of the pin portion side surface before the pressing step for the arm portion integrally having the weight portion, and FIG. 5 (a) is a view showing the pin portion side surface, FIG. Is a side view, and (c) is a cross-sectional view taken along the line IV-IV. In the figure, among the arm portions of the crankshaft, only one arm portion having a weight portion is extracted and shown, and the arm portions of the remaining crankshafts are omitted. In addition, the figure (b) is a projection figure from the direction shown by the broken line arrow of the figure (a).

  As shown in the figure, in the arm portion A integrally including the weight portion W, the inner regions of both side portions (Ac, Ad) in the vicinity of the journal portion J in the surface of the pin portion P side are the first after the pressing step. It has a shape that matches the bottom of the recess. However, since the recess is not provided in the inner region of both sides (Ac, Ad) near the journal portion J, the region where the recess is provided is excluded. Further, in the area of both sides (Ac, Ad) near the journal portion J, the shape of the inner area is smoothly spread. Thereby, the thickness of the both sides (Ac, Ad) of journal part J vicinity is thinner than the thickness after a pushing process.

  In addition, the arm portion A integrally including the weight portion W has a first surplus portion (Aca, Ada) on the outer periphery of both side portions (Ac, Ad) in the vicinity of the journal portion J. The first surplus portion (Aca, Ada) protrudes in the width direction of the arm portion A from the outer periphery of both side portions (Ac, Ad) in the vicinity of the journal portion J. Further, the first surplus portions (Aca, Ada) are plate-like, and are provided along the outer periphery of both sides (Ac, Ad) near the journal portion J. The thickness of the first surplus portion (Aca, Ada) is comparable to or thinner than the thickness of both sides (Ac, Ad) of the root.

  FIG. 6 is a schematic view showing an example of the shape of the surface on the side of the journal part before the pushing process for the arm having the weight integrally, and FIG. 6 (a) shows the surface on the journal side, FIG. ) Is a V-V cross-sectional view. In the figure, in the arm portion A integrally including the weight portion W, the thickness of both sides (Aa, Ab) in the vicinity of the pin portion P is maintained thick and the second recessed portion As is formed on the surface on the journal portion J side. An example of the shape in the case of

  In this case, of the surface on the journal portion J side, the inner regions on both sides in the vicinity of the pin portion P are shaped to match the bottom surface of the second depression As as after the pressing step (final product). Further, in the area of both sides (Aa, Ab) in the vicinity of the pin portion P, the shape of the inner area is smoothly spread. Thereby, the thickness of the both sides (Aa, Ab) of pin part P vicinity is thinner than the thickness after a pushing process.

  Further, the arm portion A has second surplus portions (Aaa, Aba) on the outer circumferences of both side portions (Aa, Ab) in the vicinity of the pin portion P. The second excess thickness portions (Aaa, Aba) protrude in the width direction of the arm portion A from the outer periphery of both side portions (Aa, Ab) in the vicinity of the pin portion P. The second excess thickness portions (Aaa, Aba) are plate-like, and are provided along the outer periphery of both side portions (Aa, Ab) near the pin portion P. The thickness of the second surplus portion (Aaa, Aba) is comparable to or thinner than the thickness of both sides (Aa, Ab) of its root.

  FIG. 7 is a schematic view showing an example of the shape of the pin portion side surface before the pressing step for the oval arm portion, and FIG. 7 (a) is a view showing the pin portion side surface, and FIG. 7 (b) is VI. FIG. 6 is a cross-sectional view taken along line VI of FIG. In the figure, in the oval arm portion A, while maintaining the thickness of both side portions (Ac, Ad) in the vicinity of the journal portion J, a shape example in the case of forming the first recessed portion At on the surface on the pin portion P side. Indicates

  In this case, as in the case of the arm portion A integrally including the weight portion W in FIG. 5, the inner regions of both side portions (Ac, Ad) in the vicinity of the journal portion J in the surface on the pin portion P side And the bottom surface of the first recess of the Further, on both sides (Ac, Ad) in the vicinity of the journal J, as in the case of the arm A having the weight W integrally shown in FIG. 5, there are first surplus portions (Aca, Ada).

  As described above, in the oval arm portion A, it is preferable to maintain the thickness of both side portions (Aa, Ab) in the vicinity of the pin portion P thick and to form the second recessed portion As on the surface on the journal portion J side. . In this case, as in the case of the arm portion A integrally including the weight portion W in FIG. 6, the inner region of both sides in the vicinity of the pin portion P in the surface on the journal portion J side is the second recessed portion after the pushing step. The shape matches the bottom of the (not shown). Further, on both sides (Aa, Ab) in the vicinity of the pin portion P, second excess thickness portions (Aaa, Aba) are provided similarly to the arm portion A integrally including the weight portion W of FIG.

2. Method of Manufacturing Forged Crankshaft The method of manufacturing a forged crankshaft of the present embodiment includes a die forging step, a deburring step, and a pushing step in that order. As a pre-process of the die forging process, for example, a pre-forming process can be provided. For example, a shaping process can be provided as a post-process of the pressing process. Moreover, a pushing process can also be implemented at a shaping process. In addition, when adjustment of the arrangement | positioning angle of a pin part is required, a twisting process is added between a burr removal process and a shaping process. All of these steps are carried out in series in hot.

  The preforming process can be configured by a roll forming process and a bending process. In the roll forming process and the bending process, the volume of billet (raw material) is distributed to form a bending waste.

  In the die forging process, a burred forged material in which the shape of a crankshaft is formed from a bending waste is obtained. For example, the shapes of the journal portion J, the pin portion P and the arm portion A are formed on the burred forged material by die forging as in the case of the burrless forged material shown in FIGS. Further, the forged material with burrs has first excess thickness portions (Aca, Ada) on the outer periphery of both side portions (Ac, Ad) near the journal portion J in the arm portion A integrally including the weight portion W.

  A die forging process for obtaining such a burred forged material can be configured by providing a roughing process and a finishing process in this order. The die-cutting slope of the die forging process does not become reverse slope at any of a portion corresponding to the surface on the pin portion P side of the arm portion and a portion corresponding to the first excess thickness portion (Aca, Ada). For this reason, it is possible to perform the rough forging and the finish forging die without any trouble, and it is possible to obtain a forged material with a burr.

  In the deburring process, for example, the burr is removed from the forged material in a state in which the forged material with burrs is sandwiched between a pair of molds. Thereby, a burr-free forging material can be obtained.

  In the pressing step, the burr-free forging material is pressed down by the pair of first dies. At that time, the first excess thickness portion is crushed by the first mold, and the thickness of both side portions in the vicinity of the journal portion of the arm portion is increased. Thereafter, in a state in which the burr-free forging material is pressed down by the pair of first dies, the second die is pushed into the surface of the pin portion side in the arm portion integrally having the weight portion to form the recess. The concave portion is formed on the pin portion side surface of the arm portion between both sides in the vicinity of the journal portion. Details of such a pushing process will be described later.

  In the shaping process, the burr-free forging material is pressed down with a pair of molds to correct it to the dimensional shape of the final product. As mentioned above, the pressing process can also be performed in the shaping process. Since a manufacturing process similar to that of the prior art can be employed, it is preferable to carry out the pressing process in the shaping process. When the pressing process is performed in the shaping process, the burr-free forging material is corrected when the burr-free forging material is pressed by the first mold.

  If it is necessary to adjust the placement angle of the pin portion, the placement angle of the pin portion is adjusted in the twisting process. According to such a process, the manufacturing method of the forged crankshaft of the present embodiment obtains a forged crankshaft.

3. Example of Processing Flow of Pushing Step FIGS. 8 to 12 are schematic views showing an example of a processing flow of the pushing step. Among them, FIG. 8 shows the pin portion side surface of the arm portion, and FIG. 8A shows the time of holding, FIG. 8B shows the time of completion of the reduction, and FIG. Further, FIG. 9 shows the surface of the arm portion on the side of the journal portion, and FIG. 9 (a) shows the time of holding, FIG. 9 (b) shows the end of pressure reduction, and FIG. FIGS. 8 and 9 show a burr-free forging material 30 and a pair of first dies 10 at the top and bottom, and the second dies and jigs are omitted to facilitate understanding of the drawings. Further, the burr-free forging material 30 is shown by extracting only one arm portion having a weight portion integrally in the arm portions.

  FIG. 10 is a view showing the side surface of the arm portion, and FIG. 10 (a) shows the time of holding, FIG. 10 (b) shows the time of end of pressing, and FIG. The figure shows the burr-free forging material 30, the second die 22, and the jig 26, and the first die is not shown to facilitate understanding of the drawing.

  11A and 11B are cross-sectional views of the position of the journal portion, where FIG. 11A is at the time of holding (the position VII-VII in FIG. 8A) and FIG. The VIII-VIII position) and the figure (c) show the end of pressing (IX-IX position in FIG. 8C). The figure shows a burr-free forging material 30, a pair of first molds 10, and a second mold 22.

  12A and 12B are cross-sectional views of the pin portion position, where FIG. 12A is at the time of holding (X-X position of FIG. 9A) and FIG. (XI-XI position), the same figure (c) shows the end of pushing (XII-XII position in FIG. 9 (c)). The figure shows a burr-free forging material 30, a pair of first molds 10, and a third mold 23.

  In the pushing step, a pair of first molds 10 is used. The first mold 10 can be composed of an upper mold 11 and a lower mold 12, and in the upper mold 11 and the lower mold 12, mold engraving portions are engraved respectively. The mold engraving portion reflects a part of the final product shape of the crankshaft. Specifically, in the arm portion A integrally including the weight portion W, in order to crush the first surplus portion (Aca, Ada), both sides (Ac, Ad) of the arm portion A in the vicinity of the journal portion J are The shape is reflected in the mold engraving section.

  In addition, when the second surplus portion (Aaa, Aba) is provided on the arm portion A integrally including the weight portion W, the pin portion of the arm portion A is pressed to crush the second surplus portion (Aaa, Aba). The shapes of both sides (Aa, Ab) near P are further reflected in the mold engraving.

  Although illustration is omitted, in the case of providing the first excess thickness portion in the oval arm portion A, the shape of both side portions in the vicinity of the journal portion J of the arm portion A is mold engraving in order to crush the first excess thickness portion. It is further reflected in the department. In addition, when the second excess thickness portion is provided in the oval-shaped arm portion A, the shape of both side portions in the vicinity of the pin portion P of the arm portion A is further reflected in the mold engraving portion in order to crush the second excess thickness portion. Be done.

  When the pressing step is performed in the shaping step, in order to correct the burr-free forging material to the dimensional shape of the final product, for example, the arm portion shape other than the above-mentioned both side portions is further reflected in the mold engraving portion. Further, the shapes of the journal portion J and the pin portion P are also reflected in the mold engraving portion. On the other hand, when the shaping process is not performed in the pressing step, in order to hold the burrless forged material by pressing down using the first mold in the process of pressing the second mold, for example, the shapes of the journal portion and the pin portion Is further reflected in the type engraving department.

  However, as shown in FIG. 11, the first mold (11, 12) is at least a portion of the surface of the arm portion A on the side of the pin portion P, in order to prevent the die-cutting slope from becoming reverse. The part which becomes a hollow part is open. The second mold 22 may be accommodated in the opened portion, and a sixth mold (not shown) described later may be further accommodated. The second mold 22 is engraved with a mold engraving, and the shape of the recess Au is reflected in the mold engraving. Further, the second mold 22 is independent of the first mold (11, 12), and can move back and forth with respect to the surface of the arm portion A on the side of the pin portion P.

  Here, the second mold 22 is disposed between the adjacent arm portions, and the arrangement space thereof is narrowed. Therefore, as shown in FIG. 10, the second mold 22 may be connected to a jig 26 movable along the eccentric direction of the pin portion. This configuration will be described in detail below.

  In order to realize the back and forth movement of the second mold 22, the second mold 22 is movably held along the guiding direction (see the solid arrow in the same figure) by the guide member (not shown). In addition, the second mold 22 is connected to the jig 26 in a slidable state along the sliding direction (see the broken arrow in the same drawing). The jig 26 is connected to a hydraulic cylinder or the like, and can move along the eccentric direction of the pin portion (refer to the hatched arrow in the same figure) in accordance with the operation.

  By connecting the jig 26 and the second mold 22 in this manner, as the jig 26 moves along the eccentric direction of the pin portion, the second mold 22 is guided in the guiding direction (the solid arrow in FIG. Move along the reference). At that time, the second mold 22 moves relative to the jig 26 in the sliding direction (see the broken arrow in the same drawing).

  When the second excess thickness portions (Aaa, Aba) are provided on the arm portion A integrally including the weight portion W, the first mold (11, 12) is formed of the journal portion J of the arm portion A as shown in FIG. The part corresponding to the 2nd hollow part of the side surface is open. Thereby, it is possible to prevent the die-cutting slope from being reverse. The third mold 23 may be accommodated in the opened portion. A mold engraving portion is engraved in the third mold 23, and the shape of the second depression portion As is reflected in the mold engraving portion. The third mold 23 can move back and forth, and the back and forth movement is realized by the operation of a hydraulic cylinder or the like connected thereto.

  The third mold 23 may be movable in the pressing direction of the first mold 10. The movement of the third mold 23 in the rolling direction is performed separately from the drive source of the forward and backward movement using appropriate means such as a spring or a hydraulic cylinder.

  Although illustration is omitted, in the case where the oval-shaped arm portion is provided with the first excess thickness portion, a portion of the first mold corresponding to the first hollow portion on the pin portion side surface of the arm portion is opened. In the opened portion, a fourth mold similar to the above-described third mold may be accommodated. Moreover, when providing a 2nd excess thickness part in an oval-shaped arm part, the site | part corresponding to the 2nd hollow part of the surface by the side of the journal part of an arm part is open | released. In the opened portion, a fifth mold similar to the above-described third mold may be accommodated.

  An example of the processing flow of the pushing process of the present embodiment using the first mold 10 and the second mold 22 will be described. First, the second mold 22 is retracted and retracted, and the upper mold 11 and the lower mold 12 of the first mold 10 are separated. When the third to fifth molds are used, the third to fifth molds are also retracted and retracted. In this state, the burr-free forging material 30 is disposed between the upper mold 11 and the lower mold 12.

  Next, when using the third to fifth molds, the third to fifth molds are respectively advanced and pressed onto the surfaces of the arm portion A (see FIGS. 10A and 12A). ). Thereby, each surface of arm part A is held, respectively. However, of the surface of the arm portion, the regions on both sides near the journal J provided with the first excess thickness and the regions on both sides near the pin P provided with the second excess thickness There is no pressing of any of the third to fifth molds. If the mold is pressed against and held in these areas, it becomes impossible to increase the thickness on both sides near the journal and near the pin.

  In this state, the upper mold 11 and the lower mold 12 of the first mold 10 are moved close to each other, and more specifically, the upper mold 11 is lowered to the bottom dead center. Thereby, the burr-free forging material 30 is pressed down by the first mold 10. At that time, as shown in FIG. 11 (b) etc., the first surplus portion (Aca, Ada) is crushed to have a shape along the mold engraving portion of the first mold 10, and on the pin portion P side. Make it overhang. As a result, the thickness of both sides (Ac, Ad) in the vicinity of the journal J of the arm increases. For this reason, the thickness of the obtained crankshaft is increased at both side portions (Ac, Ad) near the journal portion J of the arm portion.

  Similarly, in the case where the second excess thickness portion is provided in the arm portion integrally having the weight portion, the second excess thickness portions (Aaa, Aba) are crushed by the first mold 10 during the pressing and the journal portion J side The thickness is increased at both side portions (Aa, Ab) in the vicinity of the pin portion P (see FIG. 12 (b) and the like).

  Although the illustration is omitted, when the first extra thickness portion is provided in the oval arm portion, the first extra thickness portion is crushed by the first mold 10 to be protruded to the pin portion P side during reduction. The thickness is increased on both sides near the journal J of the arm. When the second excess thickness portion is provided in the oval arm portion, the second excess thickness portion is crushed by the first mold 10 to be protruded to the journal portion J side during the reduction, and the vicinity of the pin portion P is obtained. Increase the thickness on both sides of the

  When the pressing process is performed in the shaping process, the shape of the crankshaft is corrected during pressure reduction to obtain a shape in which the recess is removed from the final product.

  Subsequently, in a state where the burr-free forging material 30 is pressed down by the upper mold 11 and the lower mold 12 of the first mold 10, that is, in a state of being sandwiched and held by the first mold 10, the second mold 22 is advanced Let As a result, the second mold 22 is pressed into the middle of both side portions (Ac, Ad) of the pin portion P side surface of the arm portion A, more specifically, to the bottom surface of the first hollow portion At, Au is formed (see FIG. 11 (c) etc.).

  After molding the recess Au, the second mold 22 is retracted and retracted. When using the third to fifth molds, the third to fifth molds are also retracted and retracted respectively. Subsequently, the upper mold 11 and the lower mold 12 of the first mold 10 are separated, and more specifically, the upper mold 11 is raised to the top dead center. In that state, the processed burr-free forging material is carried out.

  According to the manufacturing method of the forged crankshaft of this embodiment, in the arm portion A integrally including the weight portion, the pin portion is maintained while maintaining a large thickness of both side portions (Ac, Ad) in the vicinity of the journal portion J. It is possible to provide the first recess At and the recess Au on the surface on the P side. For this reason, the manufacturing method of the forged crankshaft of this embodiment can manufacture the forged crankshaft which aimed at weight reduction and rigidity ensuring simultaneously.

  In the pressing step, it is also conceivable to use a punch whose shape is a cylindrical shape, or a cylindrical punch having a conical portion at its tip, instead of the second mold 22. However, punches are not suitable because they require a great deal of force for pushing, and the equipment load and the life of the punch become problems. From the viewpoint of reducing the force required to press the second mold 22, the shape of the mold engraving portion of the second mold is preferably a convex curved surface, for example, a spherical shape, an elliptical surface, or a paraboloid of revolution. It can be planar.

  It is preferable that an angle θ2 (see FIG. 10A) formed by the pressing direction of the second mold 22 and the surface (bottom surface of the first recess At) where the recess Au is formed be an acute angle. If the angle θ2 is an acute angle, the degree of processing per unit pressing amount decreases, so that the force required to press the second mold 22 can be further reduced. This effect is remarkable when θ2 is 70 ° or less. On the other hand, if θ2 is less than 30 °, excessive deformation (such as shearing) to scrape the surface on which the recessed portion Au is formed (the bottom of the first depression At) may not be obtained, and the desired deformation may not be obtained. There is. From these, it is more preferable to set θ2 to 30 to 70 °. Here, the pressing amount means the moving amount (mm) of the second mold in the pressing direction.

  It is preferable to use the above-mentioned sixth mold from the viewpoint of precisely finishing the first hollow portion At on the pin portion P side.

  Fig. 13 is a cross-sectional view of the position of the journal in the case of using the sixth mold. Fig. 13 (a) shows the holding time, Fig. 13 (b) shows the pressing end, Fig. 13 (c) shows the pressing end Show. This figure is obtained by adding a sixth mold 24 to FIG.

  A mold engraving portion is engraved in the sixth mold 24, and the shape of the first hollow portion At is reflected in the mold engraving portion. However, as shown in FIG. 13, in the surface of the pin portion P side of the arm portion A of the sixth mold 24, at least a portion to be the recessed portion Au is opened. The second mold 22 described above is accommodated in the opened portion.

  The sixth mold 24 can move back and forth, and the back and forth movement is realized by, for example, an operation of a hydraulic cylinder or the like connected thereto. The sixth mold 24 may be movable in the pressure reduction direction of the first mold 10 (the direction perpendicular to the eccentric direction of the pin portion). The movement of the sixth mold 24 in the rolling direction is performed, for example, using an appropriate means such as a spring or a hydraulic cylinder separately from the drive source for the forward and backward movement. In the pressing step, the sixth mold 24 may move forward and backward as in the case of the third to fifth molds described above.

  When using such a 6th metal mold | die 24, the pin part side surface of an arm part is hold | maintained by pressing of the 6th metal mold | die 24 in a pushing process. However, of the pin portion side surface of the arm portion, the region of both sides in the vicinity of the journal portion provided with the first excess thickness portion does not press the sixth mold 24. When the sixth mold is pressed against and held in the area, it is impossible to increase the thickness on both sides in the vicinity of the journal portion.

  When holding the pin-part-side surface of the arm part with the sixth mold, the pressure of the first mold (11, 12) is followed in order to finish the first depression At at the pin part P more precisely. It is preferable to move the sixth mold 24 in the direction of pressure reduction of the first mold (11, 12) and maintain the pressing position of the sixth mold 24 on the arm portion at a fixed position.

  In the arm portion having the weight portion integrally, in the die forging step, the above-mentioned second excess thickness portion is further formed, and in the pressing step, the second excess thickness portion is crushed with the first mold and both sides in the vicinity of the pin portion Preferably, the thickness of the part is increased. Thereby, the weight can be further reduced while securing the rigidity. In this case, it is preferable to use the above-mentioned third mold from the viewpoint of precisely finishing the concave shape of the surface on the journal side.

  In the oval-shaped arm part, in the die forging step, the above-mentioned first extra thickness part is further formed, and in the pressing process, the first extra thickness part is crushed with the first mold, and the thickness of both sides near the journal part It is preferable to increase the Thereby, the weight can be further reduced while securing the rigidity. In this case, it is preferable to use the above-mentioned fourth mold from the viewpoint of precisely finishing the concave shape on the surface on the pin portion side.

  Further, in the oval arm portion, in the die forging step, the above-mentioned second excess thickness portion is further formed, and in the pressing step, the second excess thickness portion is crushed with the first mold, and both side portions in the vicinity of the pin portion It is preferable to increase the thickness of Thereby, the weight can be further reduced while securing the rigidity. In this case, it is preferable to use the above-mentioned fifth mold from the viewpoint of precisely finishing the concave shape on the surface on the journal side.

  The processing flow examples shown in FIGS. 8 to 12 are directed to a crankshaft mounted on a four-cylinder engine, and in the crankshaft, the eccentric direction of the pin portion is shifted at equal intervals of 180 ° for each arm portion. In this case, in the case of shifting at an equal interval of 180 °, any arm portion is pressed down by the first mold from the direction perpendicular to the eccentric direction of the pin portion. In this case, the pressing direction of the first mold is also perpendicular to the axial direction of the crankshaft.

  However, the reduction direction by the first mold is not limited to the direction perpendicular to the eccentric direction of the pin portion. For example, in the case of a crankshaft mounted on a three-cylinder engine, the eccentric direction of the pin portion is shifted at equal intervals of 120 ° or 60 ° for each arm portion. As described above, when not shifting at an equal interval of 180 °, the rolling direction by the first mold does not become perpendicular to the eccentric direction of the pin portion at a part of the arm portions. Even in this case, the manufacturing method of the forged crankshaft of the present embodiment can be applied. That is, the thickness of the both sides of the arm can be increased by crushing the first surplus portion with the first mold. Therefore, the reduction direction by the first mold is not limited as long as the thickness of the both sides of the arm can be increased by crushing the first excess thickness portion with the first mold.

  The present invention can be effectively used for the manufacture of forged crankshafts mounted on reciprocating engines.

1: Forged crankshaft, J, J1 to J5: Journal section, P, P1 to P4: Pin section,
Fr: front part, Fl: flange part, A, A1 to A8: crank arm part,
W, W1 to W8: counter weight section,
Aa, Ab: the side portion near the pin portion of the arm portion,
Aaa, Aba: second excess, Ac, Ad: side of the arm near the journal,
Aca, Ada: 1st surplus, As: 2nd hollow, At: 1st hollow,
Au: recess, 10: first mold, 11: upper mold, 12: lower mold, 22: second mold,
23: 3rd mold, 24: 6th mold, 26: Jig, 30: Forgings without burrs

Claims (2)

A manufacturing method of a forged crankshaft comprising: a journal portion serving as a rotation center; a pin portion eccentric to the journal portion; and a crank arm portion connecting the journal portion and the pin portion,
The forged crankshaft has a counterweight portion integrally with all or part of the crank arm portion,
The manufacturing method is
A die forging process for obtaining a burred forged material in which a shape of a crankshaft is formed;
Deburring process for obtaining a burrless forged material by removing burrs from the burred forging material;
After pressing down the burr-free forging material with a pair of first molds, in a crank arm section integrally having the counterweight section, the second mold is pushed into the surface of the pin section side to form a recess Process, and
In the die forging step, the crank arm portion having the counterweight unit integrally, on both sides of each outer peripheral is a portion located on both sides of the journal portion of the end portion in the width direction of the crank arm, the Further forming a first surplus portion projecting from the outer periphery,
In the push-step, when the reduction of the burr without forging squashed said first excess thickness portion in the first mold, with increasing thickness of the both side portions,
A forged crank, in which the recess is formed on the pin portion side surface closer to the journal portion side than the end on the journal portion side of the pin portion and between the side portions having an increased thickness. Axis manufacturing method. In the method of manufacturing a forged crankshaft according to claim 1,
The method of manufacturing a forged crankshaft, wherein the pushing step is performed in a shaping step of correcting the shape of the crankshaft by pressure reduction using a mold.

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