JP5436331B2 - Crankshaft manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing a crankshaft, and more particularly to a technique for forming a hollow hole in a crankpin portion of a crankshaft.

  A crankshaft of an internal combustion engine includes a journal shaft portion. A crankpin portion parallel to the journal shaft portion is connected by an arm portion. The arm portion is formed with a counterweight portion, and the formation position of the counterweight portion with respect to the journal shaft portion is on the opposite side of the connecting portion of the crankpin portion.

  In the crankshaft, from the viewpoint of improving fuel efficiency, a hollow hole may be formed in the crankpin portion to reduce the weight. Even when the hole is formed in the crankpin portion, the rigidity of the crankshaft is hardly affected. Therefore, it is preferable to form the hole in the crankpin portion. As a method for forming the hole, a cutting method, a method of forming a crank pin with a pipe material and joining it to the crankshaft main body, and the like can be considered. However, both methods complicate the process and increase the manufacturing cost. Here, in order to reduce the manufacturing cost, it is effective to form the crankshaft body and form the hole by forging. However, since the crankshaft has a complicated shape as described above, the conventional forging Then, it is difficult to form the hole at the same time as forming the crankshaft.

  That is, in conventional forging, the upper and lower molds of the mold move in the press ram direction to constrain the object to be molded, and the material is filled in the closed mold cavity to obtain the target shape of the material. (For example, patent document 1). When forming a crankshaft by such forging, the arrangement of the crankshaft on the mold must be such that its axial direction is perpendicular to the direction of movement of the press ram. It is difficult to insert into the crankpin portion from the axial direction of the shaft. For this reason, in conventional forging, hot flashing multi-step molding is generally used. In this case, the crankpin part and the arm part are in a solid state so that the upper and lower molds of the mold to be used can be divided, and a slip-off gradient from the mold is formed at these parts.

  As described above, in forging using a closed type structure, it is difficult to form a hole in the crankpin portion. Therefore, the hole is formed without forcing the crankshaft in the closed space after forging and molding trim. Is going.

  Specifically, for example, when the holes 13A and 13B are formed in the crankshaft 10 shown in FIG. 9, as shown in FIG. 10 (A), one arm portion 12 (see FIG. 9) for connecting the crankpin portion 13 is formed. One surface of the rightmost arm portion 12) is brought into contact with the lower mold 1 (shaded portion in the figure), and the punch 2 is inserted into the crankpin portion 13 from the upper surface side of the other arm portion 12. The holes 13A and 13B are formed independently by inserting the punch 2; however, when the hole 13B is formed, interference with a portion adjacent to the arm portion 12 occurs. From the diagonal direction (the direction of the broken line arrow in FIG. 9). In this case, the trace may remain in the contact part with the lower mold | type 1 in one surface of the arm part 12 (rightmost arm part 12 of FIG. 9).

JP 2003-343592 A

  However, in the method shown in FIG. 10A, since the radial direction (arrow direction) of the crankpin portion 13 is free as shown in FIG. 10B, the holes 13A and 13B are provided in the crankpin portion 13. If formed, the dimensional accuracy is lowered. Specifically, in the crankpin portion 13, surface sink marks are generated in the axial direction of the crankpin portion 13 at the opening end surfaces of the holes 13 </ b> A and 13 </ b> B, and material is formed in the radial direction of the crankpin portion 13 (arrow direction in the figure). It will spread. For this reason, it is necessary to perform balance correction by forming a plurality of holes (not shown) in the outer periphery of the counterweight portion of the arm portion 12.

  Therefore, it is conceivable to perform coining using a forging device that moves in a direction perpendicular to the moving direction of the press ram, using a preformed body that has been molded in a shape that can be applied to the upper and lower split molds in advance. . However, this lateral molding technique cannot improve the dimensional accuracy by forming the hole.

  In order to solve the above problem, the present inventor has proposed to perform side forming by forging on a preformed crankshaft that is set smaller than the shape of the cavity of the mold that is the upper and lower split mold ( Japanese Patent Application No. 2009-027047). Specifically, the shape of the crankshaft preform is set to be smaller than the shape of the mold cavity, and in lateral molding by forging, the punch is inserted into the crankpin portion of the preform, The material of the preform is filled in to obtain a molded product. In this case, by setting the mold cavity to a shape corresponding to the target shape of the molded product, a molded product having the target shape can be obtained by forging.

  However, since the shape of the crankshaft preform is set to be smaller than the shape of the mold cavity, the placement of the preform in the mold is between the preform and the mold cavity. There is clearance. For this reason, the molded product obtained by the side molding is deformed, and there is a possibility that the target shape cannot be obtained with high accuracy.

  Therefore, an object of the present invention is to provide a crankshaft manufacturing method capable of accurately obtaining a target shape of a molded product by lateral molding by forging.

  As a result of examining the deformation of the molded product by forging in a mode in which a clearance exists between the preform and the mold cavity, the present inventor has obtained the following knowledge. 7A and 7B show the deformation state of the molded product that occurs when side molding by forging is performed in a mode in which a clearance exists between the preform 40 and the cavity of the mold 31. FIG. It is a figure for demonstrating, Comprising: (A) is the state before insertion of the punch 32 by forging, (B) is a side view showing the state after insertion of the punch 32 by forging.

  When the shape of the crankshaft preform is set to be smaller than the shape of the mold cavity, as shown in FIG. 7A, in the arrangement of the preform 40 in the mold 31, the preform 40 is formed. There is a clearance between the mold and the cavity of the mold 31. When the punch 32 is inserted into the crankpin portion 43 of the preform 40 in such a state, a hole 43A is formed in the crankpin portion 43 as shown in FIG. The material of the preform 40 is filled to obtain a molded product, but the molded product is deformed.

  In the deformation of the molded product, it has been found that the journal shaft portion 41 moves away from the crankpin portion 43 in the direction perpendicular to the reference axis. In the case of a four-cylinder engine, when the punches 32 are inserted on both sides of all the crankpin portions 43, each portion of the journal shaft portion 41 is perpendicular to the crankpin portion 43 with respect to the crankpin portion 43 (see FIG. 8). It has been found that the journal shaft portion 41 is lowered in the coaxiality of the journal shaft 41. In addition, the area | region X of FIG. 8 is an area | region containing the arm part 42 and the crankpin part 43 of FIG. 7 (A), (B). The symbol S in FIG. 8 is the actual axis of the molded product, and the coaxiality is the amount of deviation of the actual axis S that should be on the same straight line as the reference axis with respect to the reference axis.

  Therefore, in the design stage of the preform, by determining the shape of the preform in anticipation of the deformation of the molded product, even in a mode in which there is a clearance between the preform and the mold cavity The present inventors have found that the coaxiality of the journal shaft can be improved and have completed the present invention.

  A crankshaft manufacturing method according to the present invention is a crankshaft manufacturing method including a journal shaft portion and a crankpin portion parallel to the journal shaft portion. A crankshaft preform is placed in the cavity of the lower mold and the preform is forged. In the preforming, the shape of the crankshaft preform is smaller than the cavity shape. In forging, by inserting a punch into the crankpin part, a hole is formed in the crankpin part, and the material of the preform is filled in the cavity. The distance of the vertical movement of the reference axis with respect to the crank pin portion of the journal shaft portion is acquired in advance, and based on the amount of separation movement, And determining the Jo.

  In the crankshaft manufacturing method of the present invention, a crankshaft preform is forged using a mold that can be divided into an upper mold and a lower mold. In this case, the crankshaft preform is formed smaller than the shape of the mold cavity used for forging. In forging, the material of the molded product is filled into the mold by inserting a punch into the crankpin portion.

  Here, since there is a clearance between the preform and the cavity of the mold, when filling the material in the mold, the journal shaft is separated from the crankpin in the direction perpendicular to the reference axis. There is a risk of movement. However, in the crankshaft manufacturing method of the present invention, in the design of the preform, the vertical movement amount of the reference axis with respect to the crankpin portion of the journal shaft portion by punch insertion in forging is acquired in advance, and the separation movement is performed. Since the shape of the preform is determined based on the amount, even if the above-described deformation of the molded product occurs in the side molding by forging, such deformation can be offset. Therefore, since the coaxiality of the journal shaft can be improved, the target shape of the molded product can be obtained with high accuracy.

  In addition, it is possible to reduce the weight by forming a hollow hole in the crankpin portion, and to improve the dimensional accuracy of the crankshaft by forging in the closed space as described above. Therefore, it is not necessary to perform balance correction such as forming a plurality of holes in the counterweight portion. In addition, when the hole is formed by general machining, the opening corner of the hole has an edge shape. Therefore, in order to avoid stress concentration on the part, a finishing process is separately performed by hand work or the like. However, in the crankshaft manufacturing method of the present invention, the opening corner of the hole has a curved shape due to the deformation resistance of the material during forging, so there is no need to perform a conventional finishing process.

  The crankshaft manufacturing method of the present invention can employ various configurations. For example, in forging, the punch is inserted on both sides of the crankpin portion at the same time, and holes are formed on both sides of the crankpin portion. In forming the hole portion, one hole portion is closer to the bottom surface than the other hole portion. A mode in which the area is set wide and shallow from the surface of the crankpin portion can be used.

  In this aspect, the punch is inserted into both sides of the crankpin portion at the same time in the forging in the closed space, so that the deformation of the hole portion that has occurred in the conventional hole formation (the hole portion due to the insertion of the other punch) It is possible to prevent deformation of the hole shape, generation of surface sinks, and burrs in the vicinity of one formed hole during formation. Thereby, dimensional accuracy can be further improved. Therefore, it is possible to prevent an increase in manufacturing cost due to an increase in balance correction such as forming a plurality of holes in the counterweight portion.

  Also, after the hole is formed in the crankpin as described above, the crankpin hole in the center of the crankpin is connected to the journal shaft hole in the center of the journal shaft between the arms. When processing the oil flow path, in the formation of the hole, one of the holes is set to have a larger bottom surface area and a shallower depth from the surface of the crankpin than the other hole. By arranging such irregularly shaped holes as appropriate according to the oil flow path, an oil flow path sufficient for oil supply can be formed with the shortest linear distance. Further, in this case, since the deformation does not occur when the hole is formed as described above, there is no defect in the processing of the oil passage.

  According to the crankshaft manufacturing method of the present invention, not only can the weight be reduced by forming a hole in the crankpin portion, but the target shape of the molded product can be obtained with high accuracy by forging, etc. The effect of can be obtained.

It is a conceptual diagram showing the forging apparatus used with the manufacturing method of the crankshaft of one Embodiment concerning this invention, and is a perspective view showing the lower mold | type of a forging apparatus. It is a figure for demonstrating hole part formation by the manufacturing method of the crankshaft of one Embodiment which concerns on this invention. It is a conceptual diagram showing the forging apparatus used with the manufacturing method of the crankshaft of one Embodiment which concerns on this invention, and is the sectional side view of the A-A 'line of FIG. 1 showing the schematic structure of a forging apparatus. It is a conceptual diagram for demonstrating the manufacturing method of the crankshaft of one Embodiment which concerns on this invention. It is a sectional side view showing the state where the molded product of the crankshaft of one embodiment concerning the present invention deformed by punch insertion by forging. BRIEF DESCRIPTION OF THE DRAWINGS The schematic structure of the crankshaft of one Embodiment which concerns on this invention is represented, (A) is a sectional side view of a crankshaft, (B) is a bottom view of the hole part to the one side of a crankpin part, (C) is a crank. It is a bottom view of the hole part to the other side of a pin part. (A), (B) is for demonstrating the deformation | transformation state of the molded article which arises when the side molding by forging is performed in the aspect in which a clearance exists between the preform and the mold cavity. It is a figure, (A) is the state before the punch insertion by forging, (B) is a sectional side view showing the state after the punch insertion by forging. It is a top view showing the state which the molded article deform | transformed by the punch insertion by forging. It is a figure for demonstrating the conventional method of the hole formation in a crankpin part. (A), (B) is a figure for demonstrating the problem of the conventional method of the hole formation to a crankpin part.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 and 3 are conceptual diagrams showing a forging device 100 used in side forming of a crankshaft manufacturing method according to an embodiment of the present invention. FIG. 3 is a view for explaining hole formation by the forging device 100 shown in FIGS. FIG. 1 is a perspective view showing a lower mold of the forging device 100. 3 is a side cross-sectional view taken along the line A-A ′ of FIG. In FIG. 3, illustration of each part (especially metal mold | die 103) of the forging apparatus 100 is simplified.

  In a crankshaft production line, for example, a steel material as a raw material is cut to obtain a billet, and then the billet is preformed by forging. In the preforming, a preformed product is obtained by performing a crushing process, a roughing process, a finishing process, and a trimming process. Next, a punch is inserted into the crankpin portion of the preform by forging to perform side molding, thereby forming a hole in the crankpin portion and filling the material of the preform into the cavity. Get the molded part of the shaft. Subsequently, after cooling the molded product, a product is obtained by appropriately performing processing and surface treatment on the molded product.

  In the present embodiment, in the design of the preformed product, the vertical movement amount of the reference axis line with respect to the crank pin portion of the journal shaft portion by the punch insertion in the side molding is acquired in advance, and the preliminary movement amount is determined based on the separation movement amount. Determine the shape of the molded product. For example, in determining the shape of a preformed product, the preforming used for obtaining the distance of movement based on the distance in the vertical direction of the reference axis with respect to the crank pin portion of the journal shaft portion of the preformed product based on the amount of movement of separation. Set smaller than the product. Thus, the shape preform is put into the forging apparatus 100 shown in FIGS. 1 and 3, and side molding is performed.

  The forging device 100 is an example of a device to which the crankshaft manufacturing method of the present invention is applied, and is a device for obtaining a four-cylinder crankshaft. As shown in FIG. 3, the forging device 100 includes, for example, a press bolster 101, and a press ram 102 is supported on the press bolster 101. A mold 103 is disposed between the press bolster 101 and the press ram 102.

  The mold 103 includes a lower mold 103A, an upper mold 103B, and side forming punches 111p to 118p (hereinafter abbreviated as punches 111p to 118p). The upper mold 103B is provided so as to be movable with respect to the lower mold 103A. A reference numeral 104 in FIG. 3 denotes a load adjusting unit (such as a hydraulic unit, an air pressure unit, or a spring unit) that adjusts an initial load on the upper mold 103B. When the volume of the preform 200 is larger than the set value, the upper mold 103B moves in the opening direction (upward direction) according to the molding pressure in the mold 103.

  The mold 103 is provided with a crankshaft preform 200. The preform 200 includes a journal shaft portion 211, and a crankpin portion 213 parallel to the journal shaft portion 211 is connected to the journal shaft portion 211 by an arm portion 212. A counterweight portion 212A is formed on the arm portion 212, and the formation position of the counterweight portion 212A with respect to the journal shaft portion 211 is on the opposite side of the connecting portion of the crankpin portion 213.

  The punches 111p to 118p are provided so as to be movable in a direction perpendicular to the moving direction of the upper mold 103B. Specifically, the punches 111p and 112p are movable with respect to the inside of the mold 103 along punch holes 111a to 118a formed in the side portion of the mold 103.

  The punches 111p to 118p include a cam mechanism that moves into the mold 103 in conjunction with the movement of the press ram 102. As shown in FIG. 3, the cam mechanisms 111 and 112 for moving the punches 111p and 112p include cams 111c and 112c and cam drivers 111d and 112d for driving the cams 111c and 112c. In addition, since the cam mechanism of the punches 113p to 118p has substantially the same configuration and action as the punches 111p and 112p, description and illustration thereof are omitted below.

  Punches 111p and 112p are provided on the side surfaces of the cams 111c and 112c on the inner side of the mold 103. The side surfaces of the cams 111c and 112c on the outside of the mold 103 are inclined surfaces. The lower surfaces of the cam drivers 111d and 112d are inclined surfaces arranged at a predetermined interval with respect to the inclined surfaces of the cams 111c and 112c in the initial state. The cam drivers 111d and 112d descend as the press ram 102 moves downward. When the lower surfaces of the cam drivers 111d and 112d come into contact with the inclined surfaces of the cams 111c and 112c, the inclined surfaces slide with each other.

  The cam mechanisms 111 and 112 are provided with retracting members 111s and 112s. After the side molding by the punches 111p and 112p at the bottom dead center of the press ram 102 is completed, when the cam drivers 111d and 112d are raised along with the movement to the top dead center by the press ram 102, the side molding punches 111p and 112p are The retraction members 111s and 112s are retreated to the outside of the mold 103 and return to the initial position.

  By using such a cam mechanism, for example, the punches 111p and 112p and the punches 113p and 114p are inserted simultaneously on both sides of the crankpin portion 213 shown in FIG. 1, and then the punches 115p and 116p are inserted and The punches 117p and 118p are inserted simultaneously. FIG. 2 shows a form in which punches 111p and 112p are inserted on both sides of the crankpin portion 213. FIG. When the punches 111p to 118p are inserted in one process from the top dead center to the bottom dead center of the press ram 102, for example, a technique for preventing interference between punches proposed by the present applicant in Japanese Patent Application No. 2009-27050 is used. Is preferred.

  A crankshaft preform 200 is disposed in the mold 103 of the forging device 100. In the arrangement of the preformed product 200, the axial direction of the journal shaft portion 211 is perpendicular to the moving direction of the press ram 102. The insertion direction of the punches 111P to 118p is set to a direction in which the collision of the adjacent arm portion with the counterweight portion is avoided. For example, the angle from the vertical direction to the axial direction of the central portion of the crankpin portion 213 is 45 degrees. It is preferable to do.

  The crankshaft manufacturing method of the present embodiment using the forging device 100 as described above will be described mainly with reference to FIGS. First, the crankshaft preform 200 is placed on the lower mold 103 </ b> A of the mold 103. Subsequently, when the press ram 102 moves downward from the top dead center, the punches 111p and 112p and the punches 113p and 114p are simultaneously inserted into both sides of the crankpin portion 213, and then the punches 115p and 116p are inserted. And the punches 117p and 118p are simultaneously inserted. Thereby, the hole part formation to the both sides of each crankpin part 213 of the preform 200 is performed simultaneously. After such hole formation, the crankshaft is released from the mold 103.

  In this embodiment, the preform 200 is previously formed smaller than the crankshaft target shape (that is, the shape of the mold cavity). In forging, the preforms 200 are closed by the mold 103 and the side molding punches 111p to 118p are inserted into the crankpin portions of the preforms 200 to form holes in the crankpin portions. The mold 103 can be filled with the material of the preform 200.

  FIG. 4 is a conceptual diagram for explaining the crankshaft manufacturing method of the present embodiment, and shows a case where a hole is formed by one punch P. FIG. In FIG. 4, the downward arrow indicates the restraining pressure direction from the mold 103 to the preform 200, and the upward arrow in FIG. 4 indicates the filling direction of the preform 200. As shown in FIG. 4, when the preform 200 molded smaller than the cavity shape is placed in the cavity of the mold 103, there is a clearance between the preform 200 and the cavity. Can be filled into the preform 200 by inserting it into the preform 200.

  Here, at the design stage of the preform, the vertical movement amount of the reference axis line with respect to the crank pin portion 213 of the journal shaft portion 211 by the insertion of the punch P in the side forming as described above is acquired in advance, Based on the amount of separation movement, the shape of the preform 200 is determined. Since the shape of the preform 200 is determined in anticipation of the deformation of the molded product at the design stage of the preform 200 as described above, the material filling of the preform 200 is performed by inserting the punch P as shown in FIG. Even if deformation occurs in the obtained molded product, such deformation can be offset. Therefore, since the coaxiality of the journal shaft portion 211 can be improved, the target shape of the crankshaft molded product can be obtained with high accuracy.

  Further, in the forging in the closed space of the mold 103, the punches 111p and 112p are simultaneously inserted into both sides of the crank pin portion 213, the punches 113p and 114p are simultaneously inserted, and the punches 115p and 116p are simultaneously inserted. The punches 117p and 118p are inserted simultaneously. As a result, deformation of the hole that has occurred in the conventional hole formation (deformation of the hole shape near one formed hole when the hole is formed by inserting the other punch, surface sink, Generation) can be prevented, so that the dimensional accuracy can be further improved.

  After the formation of the holes as described above, as shown in FIG. 6, the crankpin hole 223 at the center of the crankpin 213 of the obtained molded product and the center of the journal shaft 211 between the arms 212. The oil passage 223 connecting the journal shaft hole 221 is processed. Here, in order to set the oil flow path 223 to the shortest straight distance, in the hole formation, the hole 213L (one hole) has a bottom area smaller than the hole 213M (the other hole). The depth from the surface of the crankpin portion 213 is set wide and shallow.

  By arranging the holes 213L and 213M having such irregular shapes as shown in FIG. 6 so as not to overlap the processing position of the oil flow path 223, the oil flow path 223 sufficient for oil supply can be formed with the shortest linear distance. Can be formed. Further, in this case, no deformation occurs during the formation of the holes 213L and 213M as described above, so that there is no defect in the processing of the oil flow path 223.

  As described above, in the present embodiment, it is possible to reduce the weight by forming the hollow holes 213L and 213M in the crankpin portion 213, and it is possible to reduce the weight of the molded product at the design stage of the preform 200. Since the shape of the preform 200 is determined in anticipation of deformation, the coaxiality of the journal shaft portion 211 can be improved. Therefore, the target shape of the molded product of the crankshaft can be obtained with high accuracy. As a result, it is possible to prevent an increase in manufacturing cost due to an increase in the number of holes for balance correction such as processing a plurality of drill holes in the counterweight portion 212A.

  In particular, since the hole 213L has a larger bottom area than the hole 213M and is set shallower from the surface of the crankpin part 213, the oil flow path 223 having the shortest linear distance can be secured, There is no defect in the processing.

  DESCRIPTION OF SYMBOLS 103 ... Mold, 103A ... Lower mold, 103B ... Upper mold, 111P-118P, P ... Side punch (punch), 200 ... Crankshaft preform, 211 ... Shaft shaft part, 212 ... Arm part, 213 ... Crank pin part, 213L ... Hole part (one hole part), 213M ... Hole part (the other hole part), 111p, 112p, P ... Punches for side molding (punch)

Claims (2)

In a method for manufacturing a crankshaft comprising a journal shaft portion and a crankpin portion parallel to the journal shaft portion,
Preforming the crankshaft;
Forging the preform by placing the crankshaft preform in a mold cavity comprising a split upper mold and a lower mold,
In the preforming, the shape of the crankshaft preform is smaller than the shape of the cavity,
In the forging, a hole is formed in the crankpin portion by inserting a punch into the crankpin portion, and a material for the preform is filled in the cavity to obtain a crankshaft molded product. ,
In the design of the preform, the vertical movement distance of the reference shaft line of the journal shaft portion with respect to the crankpin portion by the punch insertion in the forging is acquired in advance, and the preforming is performed based on the separation movement amount. A method of manufacturing a crankshaft characterized by determining a shape of a product. In the forging, the punch is inserted simultaneously on both sides of the crankpin portion, holes are formed on both sides of the crankpin portion,
2. The crankshaft according to claim 1, wherein in forming the hole portion, one of the hole portions is set to have a larger bottom surface area and shallower than a surface of the crankpin portion than the other hole portion. Manufacturing method.

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