JP6287631B2 - Manufacturing method of forged crankshaft - Google Patents

Description

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

  In a reciprocating engine such as an automobile, a motorcycle, an agricultural machine, and a ship, a crankshaft is indispensable for converting the reciprocating motion of a piston into a rotational motion to extract power. Crankshafts are roughly classified into those manufactured by die forging and those manufactured by casting. In particular, when high strength and high rigidity are required, the former forged crankshaft having excellent characteristics is often used.

  In general, a forged crankshaft is manufactured by using a billet having a round or square cross-section and a constant cross-sectional area over the entire length as raw materials, and sequentially performing steps of preforming, die forging, deburring, and shaping. Usually, the preforming process includes roll forming and bending processes, and the die forging process includes roughing and finishing processes.

  FIG. 1 is a schematic diagram for explaining a manufacturing process of a conventional general forged crankshaft. A crankshaft 1 (see FIG. 1 (f)) illustrated in the figure is mounted on a 4-cylinder engine and is a crankshaft of a 4-cylinder-8-counterweight. 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 arms that connect the journal portions J1 to J5 and the pin portions P1 to P4, respectively. Part (hereinafter also simply referred to as “arm part”) A1 to A8. The crankshaft 1 has counterweight portions (hereinafter also simply referred to as “weight portions”) W1 to W8 in all eight arm portions A1 to A8.

  Hereinafter, when the journal portions J1 to J5, the pin portions P1 to P4, the arm portions A1 to A8, and the weight portions W1 to W8 are collectively referred to, the reference numerals are “J” for the journal portion and “P” for the pin portion. Also, “A” for the arm portion and “W” for the weight portion. 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, the billet 2 shown in FIG. 1A cut in advance to a predetermined length 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, the billet 2 is rolled with a perforated roll and the volume thereof is distributed in the longitudinal direction while squeezing, thereby forming the roll waste land 3 as an intermediate material (see FIG. 1B). Next, in the bending process, the roll rough ground 3 obtained by roll forming is partially pressed down from the direction perpendicular to the longitudinal direction to distribute the volume thereof, and the bent rough ground 4 as a further intermediate material is formed. (See FIG. 1 (c)).

  Subsequently, in the roughing process, the bent rough ground 4 obtained by bending is press-forged using a pair of upper and lower molds, and a forged material 5 in which the approximate shape of the crankshaft (final product) is formed is formed. (See FIG. 1 (d)). Furthermore, in the finish punching process, the rough forging material 5 obtained by roughing is provided, and the rough forging material 5 is press-forged using a pair of upper and lower dies, and a shape that matches the crankshaft of the final product is formed. The forged material 6 thus formed is formed (see FIG. 1 (e)). At the time of roughing and finishing, surplus material flows out as burrs from between the mold split surfaces of the molds facing each other. For this reason, the rough forged material 5 and the finished forged material 6 both have large burrs (5a, 6a) around the shaped crankshaft.

  In the deburring process, the forged material 6 with the burr 6a obtained by finish punching is held by a die from above and below, and the burr 6a is punched and removed by a blade mold. Thereby, as shown in FIG.1 (f), the forge crankshaft 1 is obtained. In the shaping process, the key points of the forged crankshaft 1 from which burrs have been removed are slightly pressed down from above and below with a mold to correct the dimensional shape of the final product. Here, the essential parts of the crankshaft 1 correspond to, for example, a 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 is applicable not only to the crankshaft of the 4-cylinder-8-counterweight shown in FIG. 1 (f) but also to various crankshafts. For example, the present invention can be applied to a crankshaft of a 4-cylinder-4 counterweight. Here, in the crankshaft of the four-cylinder / four-piece counterweight, among the eight arm portions A, the weight portion W is provided in a part of the arms. For example, the weight part W is provided in the first first arm part A1, the last eighth arm part A8, and the central two arm parts (fourth arm part A4, fifth arm part A5). In addition, the manufacturing process is the same for crankshafts mounted on 3-cylinder engines, in-line 6-cylinder engines, V-type 6-cylinder engines, 8-cylinder engines, and the like. In addition, when adjustment of the arrangement angle of a pin part is required, a twist process is added after a deburring process.

  In recent years, in particular, reciprocating engines for automobiles are required to be lighter in order to improve fuel efficiency. For this reason, the crankshaft, which is a basic part of a reciprocating engine, is also required to be lighter. Examples of conventional techniques for reducing the weight of a forged crankshaft include the following.

  Patent Documents 1 and 2 describe an arm part in which a hole is formed on the surface on the journal part side, and also describe a method of manufacturing a crankshaft having this arm part. The hole portion of the arm portion is formed on a straight line connecting the axis center of the journal portion and the axis center of the pin portion (hereinafter also referred to as “arm portion center line”), and is deeply recessed toward the pin portion. In the arm part described in the same document, the volume of the hole part is reduced in weight. The weight reduction of the arm portion leads to a reduction in the weight of the weight portion paired with the arm portion, which in turn leads to a weight reduction of the entire forged crankshaft. Further, since the arm portion disclosed in the same document is maintained thick at both side portions in the vicinity of the pin portion sandwiching the arm portion center line, rigidity (torsional rigidity and bending rigidity) is also ensured.

  In this way, if the surface of the arm part on the journal part side is provided with a dent while maintaining the thickness of both side parts of the arm part, it is possible to reduce the weight and ensure the rigidity at the same time.

  However, it is difficult to manufacture a forged crankshaft having such a uniquely shaped arm portion by a conventional manufacturing method. In the die forging process, if a dent is to be formed on the surface of the arm portion, the die cutting gradient of the die at the dent portion becomes a reverse gradient, and a situation occurs in which the molded forging material cannot be removed from the die. .

  In order to cope with such a situation, in the manufacturing methods described in Patent Documents 1 and 2, in the die forging process, the arm portion is formed to be small without forming a recess on the surface of the arm portion. Further, after the deburring step, a punch is pushed into the surface of the arm portion, and a dent is formed by the trace of the punch.

JP 2012-7726 A JP 2010-230027 gazette

  Certainly, according to the manufacturing methods described in Patent Documents 1 and 2, it is possible to form a dent on the surface of the arm portion on the journal portion side while maintaining a large thickness on both sides of the arm portion. . Thereby, the forged crankshaft which aimed at weight reduction and rigidity ensuring simultaneously can be manufactured.

  However, in this manufacturing method, in order to form a dent on the surface of the arm portion, the punch is strongly pressed into the surface of the arm portion to deform the entire arm portion, so that a great force is required for pushing the punch. For this reason, a special equipment configuration for applying a great force to the punch is required, and consideration is also required for the durability of the punch.

  The objective of this invention is providing the manufacturing method of the forge crankshaft which can obtain the forge crankshaft which aimed at weight reduction and rigidity ensuring simultaneously easily.

  A method for manufacturing a forged crankshaft according to an embodiment of the present invention includes a journal part serving as a rotation center, a pin part eccentric with respect to the journal part, and a crank arm part connecting the journal part and the pin part. It is a manufacturing method of a forged crankshaft. The manufacturing method includes a die forging step, a deburring step, and a surplus portion bending step. In the die forging step, a finished forged material with burrs in which the shape of the crankshaft having a surplus portion protruding from the outer periphery is formed on the outer periphery of each side portion in the vicinity of the pin portion of the crank arm portion is formed. In the deburring step, burrs are removed from the finished forged material formed in the die forging step. In the surplus portion bending step, the roll is pressed against the surplus portion of the crank arm portion while moving the roll along the eccentric direction of the pin portion against the crankshaft formed by removing the burr in the deburring step. Accordingly, the surplus portion of the crank arm portion is bent toward the surface of the crank arm portion on the journal portion side.

  In the manufacturing method, in the surplus portion bending step, the surface of the crank arm portion on the journal portion side excluding at least the regions on both sides is held by pressing the first mold. Is preferable.

  In the above manufacturing method, the surplus portion of the finish forged material formed in the die forging step protrudes from an outer periphery in a range from the both side portions of the crank arm portion to a top portion in the eccentric direction of the pin portion. It can be.

  In the above manufacturing method, the surplus portion bending step is preferably performed in a shaping step of correcting the shape of the crankshaft by pressing with a mold.

  According to this invention, the surplus part which protrudes locally is formed in the outer periphery of the both sides of an arm part, and this surplus part which protrudes locally is bent by pressing of a roll. Thereby, it becomes possible to form a dent in the surface of the arm part on the journal part side while keeping the thickness of both side parts of the arm part thick. For this reason, in the obtained forged crankshaft, weight reduction and rigidity ensuring can be achieved simultaneously. At the time of manufacture, it is sufficient to bend the surplus portion protruding locally by pressing the roll, so that it can be easily performed without requiring a great deal of force.

FIG. 1 is a schematic diagram for explaining a manufacturing process of a conventional general forged crankshaft. 2A and 2B are schematic views showing the shape of the crankshaft arm portion before shaping in the first embodiment of the present invention, where FIG. 2A is a perspective view and FIG. 2B is a view from the journal portion side. FIG. 4C is a top view, and FIG. 4D is a cross-sectional view taken along line AA. 3A and 3B are schematic views showing the shape of the arm portion of the crankshaft after shaping in the first embodiment of the present invention, where FIG. 3A is a perspective view and FIG. 3B is a view from the journal portion side. FIG. 4C is a top view, and FIG. 4D is a cross-sectional view along the line BB. FIG. 4 is a schematic diagram showing an example of roll operation in the shaping process of the first embodiment of the present invention, where FIG. 4A is a front view showing a state before shaping, and FIG. Sectional drawing which shows a state, The figure (c) is a front view which shows the state after shaping. FIG. 5 is a top view schematically showing an operation example of the first mold in the shaping process of the first embodiment of the present invention. FIG. 5 (a) shows a state in which the first mold is pressed. (B) shows the state after shaping, respectively. FIG. 6 is a schematic view showing the shape of the arm portion of the crankshaft before shaping according to the second embodiment of the present invention. FIG. 6 (a) is a front view when viewed from the journal portion side, and FIG. 6 (b). Is a top view. FIG. 7 is a schematic view showing the shape of the arm portion of the crankshaft after shaping according to the second embodiment of the present invention. FIG. 7 (a) is a front view when viewed from the journal portion side, and FIG. 7 (b). Is a top view. FIG. 8 is a schematic diagram showing an example of roll operation in the shaping process of the second embodiment of the present invention, where FIG. 8A is a front view showing a state before shaping, and FIG. Sectional drawing which shows a state, The figure (c) is a front view which shows the state after shaping. FIG. 9 is a side view schematically showing an operation example of the first mold in the shaping process of the second embodiment of the present invention. FIG. 9A shows a state in which the first mold is pressed. (B) shows the state after shaping, respectively. FIG. 10 is a cross-sectional view schematically showing a configuration example in the case of using a barrel-type roll.

  The manufacturing method of the forged crankshaft of this invention can employ | adopt 1st Embodiment and 2nd Embodiment. The first embodiment and the second embodiment differ in the shape of the arm portion of the forged crankshaft. Specifically, in the first embodiment, as shown in FIG. 2 to be described later, in the arm portion A of the forged crankshaft before shaping, the surplus portions (Aaa, Aba) is provided. On the other hand, in the second embodiment, as shown in FIG. 6 described later, in the arm part A of the forged crankshaft before shaping, the top part of the pin part in the eccentric direction from both side parts (Aa, Ab) of the crank arm part. Surplus portions (Aaa, Aba, Aca) are provided in a range up to Ac (hereinafter also referred to as “pin top portion”).

  Below, the manufacturing method of the forged crankshaft of this invention is divided and demonstrated to 1st Embodiment and 2nd Embodiment.

[First Embodiment]
In the first embodiment, the manufacturing process shown in FIG. 1 can be adopted. That is, the first embodiment includes the steps of preliminary forming (roll forming and bending), die forging (roughing and finishing), deburring, and shaping. Each process of pre-forming, die forging, deburring and shaping is performed hot.

1. FIG. 2 is a schematic diagram showing the shape of the arm portion of the crankshaft before shaping in the first embodiment of the present invention. FIG. 2 (a) is a perspective view, and FIG. 2 (b) is a perspective view. When viewed from the journal side, the front view, FIG. 10C is a top view, and FIG.

  3A and 3B are schematic views showing the shape of the arm portion of the crankshaft after shaping in the first embodiment of the present invention, where FIG. 3A is a perspective view and FIG. 3B is a view from the journal portion side. FIG. 4C is a top view, and FIG. 4D is a cross-sectional view along the line BB.

  2 and 3, one of the crankshaft arm portions (including the weight portion) is representatively extracted, and the remaining crankshaft arm portions are omitted.

  In the arm part A after shaping according to the first embodiment, in other words, in the arm part A of the forged crankshaft that is the final product, both side parts (Aa, Ab) near the pin part P are journals as shown in FIG. It swells to the part J side, and the thickness of those both sides (Aa, Ab) is made thick. Furthermore, the arm part A has a dent in the area | region As inside a both-sides part (Aa, Ab) among the surfaces by the side of the journal part J.

  Thus, the arm part A after shaping maintains the thickness of both side parts (Aa, Ab) thick, and has a recess formed on the surface on the journal part J side. For this reason, the forged crankshaft by 1st Embodiment can achieve weight reduction by the dent of the arm part A surface. In addition, it is possible to ensure rigidity by maintaining the thickness of both side portions (Aa, Ab) of the arm portion A.

  On the other hand, as shown in FIG. 2, the arm part A before shaping matches the final product shape after shaping in the area As inside the both side parts (Aa, Ab) of the surface on the journal part J side. Have a dent to do. The indentation smoothly extends to the regions on both sides (Aa, Ab) of the arm part A. Thereby, as for the arm part shape, the thickness of both sides (Aa, Ab) is thinner than the thickness of the final product after shaping.

  Furthermore, the surplus part (Aaa, Aba) which protrudes from the said outer periphery is formed in the both outer peripheral parts (Aa, Ab) of the arm part A, respectively. The surplus portions (Aaa, Aba) are plate-like and are provided along the outer periphery of both side portions (Aa, Ab) of the arm portion A. The thickness of the surplus portion (Aaa, Aba) is comparable or thin compared to the thickness of both side portions (Aa, Ab) at the base.

2. As described above, the first embodiment includes the steps of preforming, die forging, deburring, and shaping, and all the steps are performed in series. In addition, when adjustment of the arrangement angle of a pin part is required, a twist process is added between the deburring process and the shaping process.

  In the first embodiment, in the same manner as in the conventional manufacturing method shown in FIG.

  Next, in the die forging process (rough punching and finish punching), a finished forged material with burrs is formed from the bent rough ground. At this time, the shape of the arm portion of the crankshaft is as shown in FIG. Specifically, as described above, the arm part A of the crankshaft has a recess formed on the surface of the journal part J, and plate-shaped surplus parts (Aaa, Aba) are formed on the outer periphery of both side parts (Aa, Ab). Is done. The indentation smoothly spreads to the areas on both sides (Aa, Ab) of the arm part A, and the thickness of the surplus part (Aaa, Aba) is the same as the thickness of both sides (Aa, Ab) at the base. Moderate or thin.

  Both rough and finish die forging are performed by press forging using a pair of upper and lower dies. A mold engraving portion reflecting the shape is engraved in a mold used for mold forging. The die cutting gradient of the mold engraving portion does not become a reverse gradient in any of the portion corresponding to the dent on the surface of the arm portion and the portion corresponding to the surplus portion (Aaa, Aba) on the outer periphery of the arm portion. For this reason, die forging can be performed without any problem.

  Subsequently, in the deburring step, the forged crankshaft is obtained by punching and removing the burrs from the finished forged material with burrs. The crankshaft obtained through the deburring process has an arm portion having the shape shown in FIG. 2, and surplus portions (Aaa, Aba) are formed on the outer periphery of both side portions (Aa, Ab) of the arm portion A. ing.

  And it transfers to a shaping process. In the shaping process of the first embodiment, a pair of upper and lower dies are used in the same manner as in the conventional general shaping process. In addition, the first mold is used together with the roll.

  FIG. 4 is a schematic diagram showing an example of roll operation in the shaping process of the first embodiment of the present invention, where FIG. 4A is a front view showing a state before shaping, and FIG. Sectional drawing which shows a state, The figure (c) is a front view which shows the state after shaping. In the figure, the shaping mold and the first mold are not shown. FIG. 2B is a cross-sectional view of the X position showing a state when the roll 11 passes through the X position of FIG.

  FIG. 5 is a top view schematically showing an operation example of the first mold in the shaping process of the first embodiment of the present invention. FIG. 5 (a) shows a state in which the first mold is pressed. (B) shows the state after shaping, respectively. In the figure, illustration of the shaping mold and the roll is omitted.

  A mold engraving portion is engraved in the shaping mold (not shown), and the portion of the final product shape of the crankshaft shown in FIG. 3 excluding the arm portion A (example) is engraved in the mold engraving portion. : The shape of the journal portion J and the pin portion P) is reflected. Since the shaping mold accommodates the roll, the part corresponding to the arm part A is largely opened in the eccentric direction of the pin part P. Furthermore, since the shaping die accommodates the first die, a portion corresponding to the depression on the surface of the arm portion A on the journal portion J side is opened.

  In particular, in the shaping step of the first embodiment, the roll 11 and the first die 20 are used in addition to the shaping die. Each of the roll 11 and the first mold 20 is independent of the shaping mold and is accommodated in an open portion of the shaping mold.

  As shown in FIG. 4, the roll 11 has a substantially cylindrical shape, and is rotatably supported by a holder (not shown). The roll 11 can move back and forth along the center line of the arm portion A of the crankshaft (the eccentric direction of the pin portion P). The roll 11 is moved back and forth by a hydraulic cylinder or the like connected to the holder. Such rolls 11 are provided so as to make a pair in the vertical direction, and the rotation shafts of the rolls 11 are arranged substantially parallel to the outer surfaces of both side portions (Aa, Ab) of the arm portion A (FIG. )reference).

  On the other hand, a mold engraving portion having a shape corresponding to the depression on the surface of the arm portion is engraved in the first mold 20. The 1st metal mold | die 20 can be moved forwards or backwards so that it may contact or separate with respect to the dent of the arm part surface. The forward / backward movement of the first mold 20 is performed by a hydraulic cylinder or the like connected to the first mold 20.

  The shaping process using such a shaping mold, the roll 11 and the first mold 20 is performed as follows. First, the crankshaft after deburring is housed in the mold engraving portion of the lower shaping mold. At this time, both the roll 11 and the first mold 20 are in a retracted state separated from the crankshaft, and the arm part A is completely restrained by the mold including the surplus parts (Aaa, Aba) on the outer periphery of the arm part. It has not been.

  From this state, the upper shaping die is moved toward the lower shaping die. As a result, the shaft portion (e.g., journal portion J, pin portion P, front portion Fr, flange portion Fl) of the crankshaft and further the weight portion W are slightly pressed down and corrected to the dimensional shape of the final product.

  After the pressure reduction by the shaping die, the first die 20 is advanced, and the first die 20 is pressed against the surface of the arm portion A on the journal portion J side as shown in FIG. At this time, the 1st metal mold | die 20 is pressed against the surface of the recessed area | region As except the area | region of both sides (Aa, Ab) among the surfaces by the side of the journal part J of the arm part A. FIG.

  Next, the roll 11 is moved along the eccentric direction of the pin portion (see the hatched arrows in FIG. 4A). In that case, first, the outer peripheral surface of the roll 11 and the site | part of the pin top part Ac side of surplus parts (Aaa, Aba) contact, and the roll 11 is pressed against the site | part. When the roll 11 is further moved, the portion of the surplus portion (Aaa, Aba) on the pin top portion Ac side is deformed along the outer peripheral surface of the roll 11 and is gradually bent toward the surface on the journal portion J side. . When the roll 11 is further moved, the surplus portions (Aaa, Aba) are bent in order along the eccentric direction of the pin portion from the pin top portion Ac side. Finally, all of the surplus portions (Aaa, Aba) are bent toward the surface on the journal portion J side (see FIG. 4C).

  Thereby, both side parts (Aa, Ab) of the arm part A project toward the surface on the journal part J side by the volume of each surplus part (Aaa, Aba). In this way, as shown in FIG. 3, a crankshaft is obtained in which the thickness of both side portions (Aa, Ab) of the arm portion A is increased and the surface of the arm portion A on the journal portion J side is recessed. It is done.

  Further, when the roll is pressed, the arm portion A is restrained by the first mold 20 being pressed against the recessed region As on the surface of the journal portion J, so that the shape of the recessed region As is stabilized. . Furthermore, both side portions (Aa, Ab) of the arm portion A are projected toward the journal portion J by pressing the roll, and the projecting shape is precisely formed by the first mold 20.

  After the pressing of the roll is completed, the roll 11 and the first mold 20 are retracted from the arm portion A, and then the upper shaping mold is raised and the crankshaft is taken out.

  As described above, according to the first embodiment, it is possible to form a dent on the surface of the arm portion A on the journal portion J side while maintaining the thickness of both side portions (Aa, Ab) of the arm portion A thick. . For this reason, 1st Embodiment can manufacture the forge crankshaft which aimed at weight reduction and rigidity ensuring simultaneously.

  Moreover, 1st Embodiment forms the surplus part (Aaa, Aba) which protrudes locally on the outer periphery of the both sides (Aa, Ab) of the arm part A, This surplus part (Aaa) which protrudes locally , Aba) is bent by the roll 11. For this reason, the first embodiment does not require a great deal of force and can be easily performed.

  When the first mold 20 is pressed against the surface of the arm part A, the first mold 20 is not pushed any further, so that the force for holding the first mold 20 is small. Moreover, when pressing the 1st metal mold | die 20 on the surface of the arm part A, in shaping the final shape of the arm part A by pressing of the roll 11, it will only bend the surplus part (Aaa, Aba). . For this reason, it can prevent that the influence of bending arises in other parts, such as a journal part.

  Further, in the first embodiment, since the surplus portions (Aaa, Aba) on the outer periphery of the arm portion are bent in the shaping process, it is not necessary to change the conventional manufacturing process. However, the bending of the surplus portions (Aaa, Aba) on the outer periphery of the arm portion may be performed in a step different from the shaping step as long as it is after the deburring step.

[Second Embodiment]
The second embodiment is based on the first embodiment described above and changes the shape of the arm portion of the forged crankshaft.

1. 6. Shape of Crankshaft Arm Part FIG. 6 is a schematic diagram showing the shape of the crankshaft arm part before shaping in the second embodiment of the present invention. FIG. 6A is a front view when viewed from the journal part side. The figure and the figure (b) are top views.

  FIG. 7 is a schematic view showing the shape of the arm portion of the crankshaft after shaping according to the second embodiment of the present invention. FIG. 7 (a) is a front view when viewed from the journal portion side, and FIG. 7 (b). Is a top view.

  In the arm part A after shaping in the second embodiment, in other words, in the arm part A of the forged crankshaft that is the final product, as shown in FIG. 7, both side parts (Aa, The thickness of Ab) is increased, and a recess is provided in the region As on the surface of the journal portion J. Further, the arm portion after shaping according to the second embodiment is thick even in a continuous range from both side portions (Aa, Ab) to the pin top portion Ac in addition to both side portions (Aa, Ab).

  As described above, the shaped arm portion A is continuously thick in the range from the both side portions (Aa, Ab) to the pin top portion Ac, and has a depression formed on the surface on the journal portion J side. Yes. For this reason, the forged crankshaft by 2nd Embodiment can achieve weight reduction by the dent of the arm part A surface. In addition, it is possible to ensure rigidity by maintaining the thickness of both side portions (Aa, Ab) of the arm portion A.

  Here, stress concentration tends to occur in the pin fillet portion, which is a joint between the pin portion P and the arm portion A. For this reason, the pin fillet portion is often subjected to quenching by high frequency induction heating for the purpose of improving fatigue strength. At this time, since the pin top portion Ac of the arm portion A is adjacent to the pin fillet portion to which quenching is performed, there is a possibility that a crack will occur if a certain thickness is not ensured. The forged crankshaft according to the second embodiment is excellent in resistance to fire cracking because the pin top portion Ac of the arm portion A is thick when quenching is applied to the pin fillet portion.

  On the other hand, as shown in FIG. 6, the arm part before shaping according to the second embodiment is a region inside the both side parts (Aa, Ab) and the pin top part Ac on the surface on the journal part J side of the arm part A. As has a dent that matches the final product shape after shaping. The indentation smoothly extends to both side portions (Aa, Ab) of the arm portion A and the pin top portion Ac. Thereby, as for the arm part shape, the thickness of both side parts (Aa, Ab) and the pin top part Ac is thinner than the thickness of the final product after shaping.

  Furthermore, surplus portions (Aaa, Aba, Aca) projecting from the outer periphery are formed on the outer periphery of the range in the range from both side portions (Aa, Ab) of the arm portion A to the pin top portion Ac. The surplus portions (Aaa, Aba, Aca) are plate-like, and are provided along the outer periphery in a range from both side portions (Aa, Ab) of the arm portion A to the pin top portion Ac.

  The thickness of the surplus portion (Aaa, Aba) is comparable or thin compared to the thickness of both side portions (Aa, Ab) at the base. Further, the thickness of the surplus portion Aca is comparable to or thinner than the thickness of the pin top portion Ac of the arm portion A.

2. Manufacturing method of forged crankshaft The process of 2nd Embodiment is the same as that of said 1st Embodiment. That is, a crankshaft is obtained by a die forging process and a deburring process, and the arm part of the crankshaft before shaping is shaped as shown in FIG. The crankshaft of the final product (after shaping) is obtained from the deburred crankshaft by a shaping process, and the arm portion of the crankshaft of the final product is shaped as shown in FIG.

  FIG. 8 is a schematic diagram showing an example of roll operation in the shaping process of the second embodiment of the present invention, where FIG. 8A is a front view showing a state before shaping, and FIG. Sectional drawing which shows a state, The figure (c) is a front view which shows the state after shaping. In the figure, the shaping mold and the first mold are not shown. FIG. 2B is a cross-sectional view of the Y position showing a state when the roll 12 passes through the Y position of FIG.

  FIG. 9 is a side view schematically showing an operation example of the first mold in the shaping process of the second embodiment of the present invention. FIG. 9A shows a state in which the first mold is pressed. (B) shows the state after shaping, respectively. In the figure, illustration of the shaping mold and the roll is omitted.

  In the shaping process of the second embodiment, the shaping mold and the first mold 20 used in the first embodiment are used. Further, the roll 12 shown in FIG. 8 is rotatable and is along the center line of the crankshaft arm portion A (the eccentric direction of the pin portion P), like the roll 11 used in the first embodiment. Advancing and retreating is possible.

  Unlike the roll 11 used in the first embodiment, the shape of the roll 12 shown in FIG. 8 is a truncated cone shape. Further, the roll 12 shown in FIG. 8 is movable up and down, in other words, in a direction perpendicular to the center plane of the arm portion A of the crankshaft (see the broken line arrow in FIG. 8A). The up and down movement of the roll 12 can be realized by, for example, a slider and an urging means (for example, a spring) that urges the roll 12 toward the arm surface central surface. Here, the “center surface of the arm part A” is a plane including the axis of the journal part and the axis of the pin part.

  In the shaping process of the second embodiment, the first die 20 is advanced after the press pressure by the shaping die as in the first embodiment. Thereby, as shown in FIG. 9A, the first mold 20 is pressed against the surface of the arm portion A on the journal portion J side.

  Next, the roll 12 is moved along the eccentric direction of the pin portion (see the hatched arrows in FIG. 8A). In that case, the site | part of the periphery of the pin top part Ac and the outer peripheral surface of the roll 12 contact first among surplus parts (Aaa, Aba, Aca), and the roll 12 is pressed against the site | part. When the roll 12 is further moved along the eccentric direction, the peripheral portion of the pin top portion Ac is deformed along the outer peripheral surface of the roll 12 and is gradually bent toward the surface on the journal portion J side. When the roll 12 is further moved along the eccentric direction, the surplus portions (Aaa, Aba, Aca) are sequentially bent from the periphery of the pin top portion Ac to both side portions (Aa, Ab). In the process, the roll 12 moves up and down along the outer peripheral shapes of the pin top portion Ac and both side portions Aa of the arm portion A. Finally, all the surplus portions (Aaa, Aba, Aca) are bent toward the surface on the journal portion J side.

  As a result, both side portions (Aa, Ab) of the arm portion A and the surplus portion Aca of the pin top portion Ac are directed toward the surface on the journal portion J side by the volume of each surplus portion (Aaa, Aba, Aca). Overhang. For this reason, in the obtained crankshaft, as shown in FIG. 7, the thickness in the continuous range from both side portions (Aa, Ab) of the arm portion A to the pin top portion Ac is increased. Further, a recess is formed on the surface of the arm part A on the journal part J side.

  According to the second embodiment as described above, the thickness of the range from the both side portions (Aa, Ab) of the arm portion A to the pin top portion Ac is continuously increased, while the journal portion J side of the arm portion A is maintained. It becomes possible to form a dent on the surface. Thereby, 2nd Embodiment can aim at weight reduction and rigidity ensuring simultaneously in the forge crankshaft obtained, and can further improve the resistance with respect to a burning crack.

  In the second embodiment, surplus portions (Aaa, Aba, Aca) projecting locally are formed on the outer periphery of the arm portion A, and the surplus portions (Aaa, Aba, Aca) are bent by a roll. For this reason, the second embodiment does not require a great deal of force and can be easily performed.

  Of course, the second embodiment can achieve the same effects as the first embodiment.

  The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the first mold 20 is not always necessary. If precise dimensional accuracy of the arm part A is not required, both sides of the arm part A can be obtained by bending the surplus part (Aaa, Aba) on the outer periphery of the arm part with a roll without the first mold 20 ( This is because a recess can be formed on the surface of the arm portion A on the journal portion J side while maintaining the thickness of Aa, Ab) to be large.

  The shape and configuration of the roll are not limited to the shape and configuration of the roll shown in FIG. 4 or the shape and configuration of the roll shown in FIG. In the present invention, for example, a barrel-shaped roll (hereinafter also referred to as “barrel-type roll”) may be used.

  FIG. 10 is a cross-sectional view schematically showing a configuration example in the case of using a barrel-type roll. In the drawing, one pin portion P and a pair of arm portions (A1, A2) located at both ends of the pin portion P are extracted from the crankshaft. The barrel type roll 13 shown in the figure has a first tapered surface 13a and a second tapered surface 13b. Both the first taper surface 13a and the second taper surface 13b have a smaller outer diameter as they move away from the central position in the rotation axis direction. In this case, since the shaping mold accommodates the roll, the space between the pair of arm portions is largely opened in the eccentric direction of the pin portion P together with the portions corresponding to the pair of arm portions.

  In the shaping process using the barrel-type roll 13 having such a shape, the surplus portion of the first arm portion A1 is bent by the first tapered surface 13a, and the second arm portion A2 surplus portion is formed by the second tapered surface 13b. Bend. Thus, if a barrel type roll is used, the surplus part of a pair of arm part can be bent simultaneously.

  Specifically, in the first embodiment, a truncated cone-shaped roll or a barrel-type roll can be used without being limited to a substantially cylindrical roll. Moreover, in 2nd Embodiment, it is not limited to a truncated cone-shaped roll, A substantially cylindrical roll or a barrel-type roll can be used.

  In the present invention, the movement of the roll in the direction perpendicular to the center plane of the arm portion can be appropriately set according to the shape of the roll and the shape of the arm portion. Specifically, in the first embodiment, the roll is not limited to the case where the roll cannot move in the direction perpendicular to the arm portion center plane, and the roll in the direction perpendicular to the arm portion center plane is the same as in the second embodiment. May be movable.

  On the other hand, in the second embodiment, the roll 12 that is movable in the direction perpendicular to the arm center plane is used as the roll. However, as in the first embodiment, the roll 12 moves in the direction perpendicular to the arm section center plane. You may use the roll without. In this case, the portion around the pin top portion Ac in the surplus portion cannot be bent, but if measures such as appropriately changing the shape around the pin top portion Ac formed in the die forging process are taken, the crankshaft The resistance to fire cracking can also be maintained without adversely affecting the function and the like.

  The present invention can be effectively used for manufacturing a forged crankshaft to be mounted on any reciprocating engine.

1: Forged crankshaft, J, J1-J5: Journal part, P, P1-P4: Pin part,
Fr: front part, Fl: flange part, A, A1 to A8: crank arm part,
W, W1-W8: Counterweight part, Aa, Ab: Side part of arm part,
Ac: Pin top part of the arm part,
As: Inner region of both side portions on the journal side surface of the arm portion,
Aaa, Aba, Aca: surplus part,
11-13: Roll, 13a: 1st taper surface, 13b: 2nd taper surface,
20: First mold

Claims (4)

A forging crankshaft manufacturing method comprising: a journal part serving as a rotation center; a pin part eccentric with respect to the journal part; and a crank arm part connecting the journal part and the pin part,
The manufacturing method is
A die forging step of forming a finished forging material with a burr in which the shape of a crankshaft having a surplus portion projecting from the outer periphery is formed on the outer periphery of each side portion of the crank arm portion in the vicinity of the pin portion;
A deburring process for removing burrs from the finished forged material formed in the die forging process;
By pressing the roll against the extra portion of the crank arm portion while moving the roll along the eccentric direction of the pin portion against the crankshaft formed by removing the burrs in the deburring step, And a surplus portion bending step of bending the surplus portion toward the journal portion side surface of the crank arm portion. In the manufacturing method of the forged crankshaft of Claim 1,
In the surplus part bending step, a forged crankshaft manufacturing method of holding at least the surface of the crank arm part on the journal part side excluding the regions on both sides by pressing a first die. . In the manufacturing method of the forged crankshaft of Claim 1 or 2,
The forged crankshaft manufacturing method, wherein the surplus portion of the finish forged material formed in the die forging step protrudes from an outer periphery in a range from the both side portions of the crank arm portion to a top portion in the eccentric direction of the pin portion. . In the manufacturing method of the forged crankshaft in any one of Claims 1-3,
The method of manufacturing a forged crankshaft, wherein the surplus part bending step is performed in a shaping step of correcting the shape of the crankshaft by press reduction using a mold.

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