JP2010201495A - Method for manufacturing connecting rod, and coining die apparatus used therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a connecting rod capable of increasing the cross-section secondary moment of a rod part by the coining operation, and achieving the high buckling strength of the rod part. <P>SOLUTION: When manufacturing a connecting rod by executing the coining operation to a hot-forged material 10B, a sealed closing type coining die 40 having an upper forming die 46, a lower forming die 52 and a pair of right and left side forming dies 58, 60 is used as a coining die of a rod part 20. During the coining operation, the rod part 20 is vertically held by the upper and lower forming dies 46, 52, the rod part 20 is held in the right-to-left direction by the pair of side forming dies 58, 60. The rod part 20 is simultaneously pressed from four faces of the upper and lower faces and the right and left faces to execute the work-hardening by imparting the shape correction and the strain of the rod part 20. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a connecting rod and a coining type apparatus used therefor.

  As a manufacturing method of a connecting rod (connecting rod) that connects a piston and a crankshaft and transmits the force received by the piston to the crankshaft, a manufacturing method by forging has been conventionally used.

FIG. 10 shows an example of a conventional connecting rod.
In the figure, reference numeral 10 denotes a connecting rod. The connecting rod 10 has a large end 12 having a large end hole 14 in the center, a small end 16 having a small end hole 18 in the center, and the large end 12 and the small end. 16 and a flange portion 20 that connects 16 to each other.

  Here, as shown in FIG. 12 (B), the flange portion 20 includes a pair of left and right ribs 22A and 22A protruding up and down at the left and right ends, and a connecting portion that connects the ribs 22A in the left and right direction at the upper and lower intermediate portions. 24A, and the cross-sectional shape is substantially I-shaped.

In the forging process for manufacturing the connecting rod, first, a rough shape of the connecting rod is obtained by hot forging.
FIG. 11 shows an example of a hot forging process for obtaining the rough shape.
Here, the process of crushing the longitudinal intermediate portion of the heated rod-shaped material (steel material) 1 is performed in the step (I), and then the whole is further deformed into a flat shape in the step (II) (step (II)). ).
Thereafter, the crushing step (III) and the roughing step (IV) are followed by the main forming step (V), where the rough shape of the connecting rod is formed.
Subsequently, in the step (VI), the large end hole 14 and the small end hole 18 are punched, and further, the burr removing step (VII) is performed, the burr 2 is removed, and the hot forging material 10B is obtained. .
In the main molding in the step (V), the work is sandwiched and pressed between the upper molding die and the lower molding die to perform molding.
In this hot forging, the temperature of the workpiece after deburring is about 1000 ° C.
In a conventional connecting rod manufacturing method by forging, coining is performed in the cooling process after hot forging.

This coining process is mainly intended to correct the shape of the large end part 12, the small end part 16, and the flange part 20, but there are cases where the reinforcement to the flange part 20 is performed.
The connecting rod 10 is required to have a strong buckling strength at the flange portion 20, and for that reason, conventionally, the flange portion 20 is formed in a substantially I-shaped cross section, and the buckling strength is imparted to the flange portion 20 due to the effect of the shape. ing.
In the coining process, the flange portion 20 is further strengthened by work hardening by imparting strain.

However, the coining process in the conventional manufacturing method has caused various problems as shown below.
FIG. 12 (A) shows the cross-sectional shape of the flange 20B in the rough shaped material after hot forging, that is, the hot forged material 10B.
As shown in the figure, the hot forging material 10B is formed by pressing the workpiece between the upper mold and the lower mold in the step (V) of FIG. Due to the draft of the molding die and the lower molding die, the rib 22B has a bulging portion 26B having a shape in which the protruding amount to the left and right outwards increases from the upper and lower ends toward the center.
In the drawing, 28B indicates an inclined surface forming the inclined shape of the bulging portion 26B.

Further, inside the rib 22B, there is a curved portion 30B that forms a curved shape inward and leftward and rightward from both upper and lower ends of the rib 22B toward the connecting portion 24B.
In the figure, 32B represents the curved surface of the bending portion 30B.
Here, the angle θ of the inclined surface 28B is 7 to 10 °, for example, and the curved surface 32B is a curved surface having a radius of 5 mm, for example.

  In the conventional coining method shown in FIG. 12C, the hot forging material 10B is formed by using the upper forming die 34 and the lower forming die 36 in the same manner as the main forming in the step (V) in hot forging. The coining process is performed by pinching up and down, and the upper and lower molds 34 and 36 are used to deform the upper and lower ends of the ribs 22B of the hot forged material 10B with vertical pressing force. A flange 20 having a cross-sectional shape as shown in FIG.

In such coining processing, a part of the material escapes along the joint of the upper mold 34 and the lower mold 36, thereby generating burrs 3 there.
Also in this coining process, in order to remove the upper mold 34 and the lower mold 36, the rib 22A has a bulging portion 26A indicated by the oblique lines in FIG. 12C after the coining process, Further, the rib 22A has a curved portion 30A inside.

In such a conventional manufacturing method, the yield of the material is deteriorated due to the generation of burrs 3, and a deburring process for removing the generated burrs 3 is required separately.
In addition, the generation of burrs 3 and the bulging portion 26A and the curved portion 30A reduce the strain applied to the flange portion 20, and therefore the degree of work hardening due to the distortion is reduced, and the flange portion 20 is It cannot be strengthened sufficiently.

  In order to increase the buckling strength of the flange portion 20, it is important to make the secondary moment of section as large as possible in order to increase the deformation resistance against the bending moment. However, the bulging portion 26A and the bending portion 30A described above are important. Since most of the meat is located near the connecting portion 24A that is the center of bending, the contribution to the secondary moment of the cross section is small, and the buckling strength of the flange portion 20 can be sufficiently increased by the shape effect of the cross section. Can not.

  Ideally, the cross-sectional shape of the flange portion 20 is an I-shape as indicated by a halftone dot in FIG. 12 (C). For this purpose, the distal end portion farthest from the connecting portion 24A of the rib 22A is used. Although it is necessary to make the wall thickness as thick as possible, in the case of the conventional manufacturing method, it is difficult to realize such a cross-sectional shape.

  Further, in the conventional manufacturing method, the distortion during the coining process is concentrated on the burr 3 portion, and not only the distortion is uniformly applied to the other part of the cross section, but also the burr 3 in which the distortion is concentrated is generated thereafter. Therefore, the work hardening by applying strain cannot be sufficiently achieved, and therefore the strength of the flange 20 cannot be sufficiently improved by the work hardening.

In addition, there exist some which were disclosed by the following patent document 1, patent document 2, and patent document 3 regarding the method of manufacturing a connecting rod by forge processing.
However, those disclosed in Patent Document 1, Patent Document 2, and Patent Document 3 cannot solve the problems of the present invention, and those disclosed in these Patent Documents are different from the present invention.

Japanese Patent Laid-Open No. 2005-14080 JP 2006-31980 A JP 2006-31978 A

  In the present invention, against the background as described above, when producing a connecting rod by forging, the cross-section secondary moment of the buttock can be effectively increased by coining, and the buckling strength of the buttock is increased by the shape effect. It can be made high strength, can be imparted with a lot of distortion evenly during processing, can fully demonstrate the strength improvement by work hardening, and can eliminate burr removal processing after coining processing, Another object of the present invention is to provide a connecting rod manufacturing method capable of increasing the yield of the material and a coining type apparatus used therefor.

  Thus, claim 1 relates to a method for manufacturing a connecting rod, and first, a rough shape of a connecting rod having a large end portion and a small end portion and a flange portion connecting the large end portion and the small end portion is formed by hot forging. Then, in the manufacturing method of a connecting rod in which the hot forging material having the rough shape is subjected to coining to manufacture a connecting rod, as a coining mold of the flange portion, the axial direction of each hole of the large end portion and the small end portion An upper mold and a lower mold that are arranged so as to be relatively movable so as to face each other and a pair of left and right side molds that are arranged so as to be relatively movable so as to be opposed to the left and right; A coining mold that closes and closes the inside in a closed state is used, and during the coining process, the upper and lower molds are used to clamp the collar part up and down, and the pair of side molds sandwich the collar part left and right. Press the upper and lower and left and right 4 Pressurized simultaneously, and performs the work hardening due to the shape correction and distortion imparting of 該桿 portion by deformation due to pressurizing.

  According to a second aspect of the present invention, in the first aspect, the rough shape in the hot forged material is a pair of left and right ribs protruding vertically at the left and right end portions, and a connecting portion for connecting the ribs in the left-right direction at the upper and lower intermediate portions And the left and right outer surfaces of the ribs have a bulging shape that increases in the amount of protrusion in the left and right outer direction from the upper and lower ends toward the upper and lower intermediate portions. The lateral molding die pressurizes the bulging portion inward in the left-right direction and molds.

  According to a third aspect of the present invention, in the second aspect of the present invention, the pair of side molding dies are formed by molding the outer surface of the rib having the bulging portion into a straight shape in the vertical direction.

  According to a fourth aspect of the present invention, in any one of the second and third aspects, the rough shape of the hot forged material has a curved shape inward from the upper and lower ends of the rib toward the connecting portion, In the coining process, the upper mold and the lower mold compress and deform the upper and lower ends of the rib in the vertical direction, and pressurize and deform the curved curved portion to deform the connecting portion in the horizontal direction. The rib is shaped to have a straight shape in the vertical direction except for the root portion to the connecting portion.

  The present invention relates to a coining mold apparatus used in the above manufacturing method, and the coining mold apparatus is arranged so that the upper mold, the lower mold and the left and right molds are arranged so as to be movable relative to each other. And a pair of left and right side molds arranged in a possible manner, and the inside is hermetically closed when closed as a whole. In addition to pressing up and down, the pair of side molds clamps the collar part to the left and right, presses the collar part simultaneously from the four sides of the top and bottom, and left and right. It is characterized by performing work hardening by shape correction and distortion application.

Effects and effects of the invention

  As described above, when manufacturing the connecting rod by forging, the present invention first performs the coining after forming the rough shape of the connecting rod by hot forging. It has an upper mold, a lower mold, and a pair of left and right side molds arranged so as to be opposed to the left and right, and the inside is closed when the whole is closed. Using a coining die that closes, the upper and lower molds clamp the hot forged heel part up and down, and the pair of side molds squeeze the heel part left and right. The part is pressurized simultaneously from the top, bottom, left and right surfaces, and the shape of the heel part is corrected and the work is hardened by applying distortion by deformation caused by the pressurization.

  According to the manufacturing method of the present invention, burrs are not generated at the time of coining, unlike the conventional manufacturing method, thereby improving the material yield, and thereafter deburring for deburring. This process can be omitted.

  In addition, in the manufacturing method of the present invention, unlike the case where the hot forging material is pressed up and down with only a pair of upper and lower molds, burrs are generated by letting the material escape between the upper and lower molds. Since it is not necessary to perform the hot forging in a pair of lateral molds, and the hot forging material is laterally pressed simultaneously with the upper and lower pressures of the lower mold, The material can be sufficiently wound up to the tip side of the surface, whereby the tip portion can be made sufficiently thick, and the cross-sectional secondary moment of the collar portion can be increased. The buckling strength of the part can be effectively increased.

  In addition, in order not to generate burrs in which strain is concentrated, it is possible to impart a large amount of strain at the time of coining over the entire cross section of the buttock, and it is possible to sufficiently draw out work hardening due to the strain, The buckling strength of the buttocks can be further increased by work hardening.

According to the present invention, the buckling strength of the buttocks can be effectively increased due to the effect of the cross-sectional shape in the buttocks and work hardening, so the same buckling strength is used using the same material. In this case, the cross-sectional area of the cross section of the flange portion can be reduced, and the flange portion of the connecting rod can be reduced in size.
As a result, the amount of material used can be reduced, the cost can be reduced, and the weight of the connecting rod can be reduced by downsizing the collar portion.
In addition, when the cross-sectional areas of the cross sections are the same, it is possible to use an inexpensive material having a lower strength as the material to be used, and the cost required for the material can be reduced.

The manufacturing method of claim 2 has a pair of left and right ribs that protrudes up and down at the left and right end portions, and a connecting portion that connects the ribs in the left and right directions at the upper and lower intermediate portions. The bulging shape of the shape that increases the amount of protrusion to the left and right outwards as the left and right outer surfaces of the ribs go from the upper and lower ends to the middle part, and at the time of coining processing after hot forging, a pair of side forming dies According to the manufacturing method of claim 2, the material is sufficiently moved to the tip end side of the rib by pressurization (clamping pressure) by the side molding die. And the tip end portion of the rib can be formed thick.
As a result, the cross-sectional secondary moment of the collar can be effectively increased, and distortion due to processing can be effectively and evenly applied to the collar.

  In this case, the pair of side molding dies can mold the collar portion so that the outer side surface of the rib has a straight shape in the vertical direction after processing (Claim 3).

According to a fourth aspect of the present invention, the rough shape of the hot forged material is formed into a shape having a curved portion that is curved inwardly from the upper and lower ends of the rib toward the connecting portion. The upper and lower ends of the rib are compressed and deformed in the vertical direction with the molding die, and the curved portion is pressurized and deformed to form the connecting portion in a plate shape in the left-right direction, and the inner side surface of the rib is the root portion to the connecting portion. In the manufacturing method according to claim 4, it is possible to make the collar shape closer to an I-shape, and the cross section of the collar part is secondary. The moment can be increased even more effectively.
Moreover, the distortion by processing can be applied equally and more, and the strength improvement by work hardening can be further enhanced.

  Next, a fifth aspect of the present invention relates to a coining mold apparatus used for forming the collar portion in the coining process. The coining mold apparatus includes an upper mold and a lower mold which are disposed so as to be opposed to each other in the vertical direction. A mold and a pair of left and right side molding dies arranged to be movable relative to the left and right, and the whole is closed and the inside is hermetically closed. By pressing the heel part up and down with the lower mold, pressing the heel part left and right with a pair of side molds, and simultaneously pressing the heel part from the upper and lower and left and right surfaces, It is designed to perform work hardening by correcting the shape of the buttocks and imparting distortion. By using the coining type apparatus of claim 5, the manufacturing method of claims 1 to 4 is preferably carried out. Can do.

It is the figure which showed the connecting rod obtained by the manufacturing method of one Embodiment of this invention. It is a principal part plane sectional view of the coining type device used for the embodiment. It is explanatory drawing of the principal part process of the coining process in the embodiment. It is explanatory drawing of the process following FIG. It is explanatory drawing of the process following FIG. It is explanatory drawing of the process following FIG. It is the figure which compared and showed the shape of each collar part of the hot forging material and the connecting rod in the same embodiment. It is the figure which showed the manufacturing process of the connecting rod in an Example. It is explanatory drawing of the test method of buckling strength. It is the figure which showed an example of the conventional connecting rod. It is process explanatory drawing in the case of hot forging. FIG. 11 is a cross-sectional view of a flange portion of the connecting rod and hot stepped construction material of FIG. 10 and an explanatory diagram of conventional coining processing.

Next, embodiments of the present invention will be described in detail with reference to the drawings.
In FIG. 1, 10 shows the shape of the connecting rod obtained by the manufacturing method of this embodiment.
In the figure, 10 is a connecting rod, 12 is a large end having a circular large end hole 14 in the center, 16 is a small end having a circular small end hole 18 in the center, and 20 is a large end 12 and a small end. It is a collar part connecting the part 16.

  As shown in the partially enlarged view of FIG. 1, the flange portion 20 has a pair of left and right ribs protruding vertically at the left and right ends (up and down when the axes of the large end hole 14 and the small end hole 18 are in the vertical direction). 22 and a connecting portion 24 for connecting the rib 22 in the left-right direction at the upper and lower intermediate portions, and the cross-sectional shape is substantially I-shaped.

In this embodiment, the outer side surface 33 of the rib 22 has a straight shape in the vertical direction (the inclination angle is 0 degree with respect to the vertical direction), and the inner side surface 35 also excludes a part of the root portion of the connecting portion 24. Thus, it has a straight shape in the vertical direction (however, the inclination angle is slightly inclined at 3 degrees).
Further, the root portion has a curved shape inwardly from the upper and lower ends of the rib 22 toward the connecting portion 24. However, the curved portion 30 has a small shape, and the curved surface 29 on the surface has an arc shape with a small radius R (here, 3 mm).
On the other hand, the connecting portion 24 has a plate shape in which the upper surface and the lower surface form a straight shape in the left-right direction.

In the manufacturing method of the connecting rod 10 according to this embodiment, the rod-shaped material (steel material) 1 of FIG. 11 is converted into the steps (I), (II), (III), (IV), (V), (VI), FIG. Hot forging is performed through each step (VII), and then coining is performed on the hot forged material having a rough shape.
Coining is performed in the cooling process after hot forging. In particular, the temperature at which the strength can be effectively increased by coining is in the range of 350 ° C to 600 ° C.
2 to 6 show the configuration of a coining type apparatus used in the coining process.

As shown in FIG. 3, the coining type device 40 includes an upper holding die 42 and a lower holding die 44.
The upper holding mold 42 includes an upper mold 46 for molding the flange portion 20, an upper hold pin 48 that fits downward into the large end hole 14 to position and restrain the large end hole 14, and the small end hole 18. The upper hold pins 50 that are fitted downward to position and restrain the small end holes 18 are held downward.

  On the other hand, the lower holding die 44 is positioned opposite to the lower molding die 52 and the upper hold pin 48 for forming the flange portion 20 and is fitted upward into the large end hole 14 from the lower side to cooperate with the upper hold pin 48. It is positioned opposite to the lower hold pin 54 and the upper hold pin 50 that act to position and restrain the large end hole 14, and is fitted upward into the small end hole 18 from below to position and restrain the small end hole 18. The lower hold pins 56 are held in a state of protruding upward.

  The lower holding die 44 is also formed with a pair of left and right side forming dies 58 and 60 for forming the flange portion 20, the large end portion 12 and the small end portion 16 and the front and rear end portions of the large end portion 12, respectively. The end molding die 62 (see FIG. 2) for use and the end molding die 64 for molding the front-rear direction end portion of the small end portion 16 are similarly held in a state of protruding upward.

Here, the pair of side molds 58 and 60 and the pair of end molds 62 and 64 are held by the lower holding mold 44 so as to be movable in the horizontal direction in the figure.
The pair of side molds 58 and 60 together with the upper mold 46 and the lower mold 52 for molding the collar part 20 hermetically closes the inside in the cross section of the collar part 20 by clamping.
Further, the side molds 58 and 60, the end molds 62 and 64, the upper mold 46, and the lower mold 52 form a molding space 70 (see FIG. 2) that is hermetically sealed inside in a clamped state. To do.

  A male taper surface 66 is provided on the outer surface of each of the side molds 58 and 60 and the end molds 62 and 64, while a female taper surface 68 having the same inclination angle is formed on the upper holding mold 42. When the upper holding mold 42 is lowered, the pair of side molding dies 58 and 60 and the end molding dies 62 and 64 are moved downward by the guiding action of the male taper surface 66 and the female taper surface 68. It can be moved inward simultaneously in conjunction with each other. However, the side molds 58 and 60 and the end molds 62 and 64 can be moved by hydraulic pressure, pneumatic pressure or the like without depending on the guide action of the tapered surfaces 66 and 68.

In the coining process using the coining mold apparatus 40 having the above configuration, the lower mold 52 is first moved by air pressure, hydraulic pressure, etc. in the state where the upper holding mold 42 is lifted as shown in FIG. The hot forging material 10 </ b> B having a rough shape shown in FIG. 7A is placed on the lower mold 52 and lowered together with the lower mold 52. FIG. 3I shows the state at this time.
The shape of the hot forged material 10B is the same as that shown in FIG.

After the hot forging material 10B is set in the coining die device 40 in this way, the upper holding die 42 in the raised position is lowered to the bottom dead center.
At this time, the upper mold 46 and the upper hold pins 48 and 50 held by the upper holding mold 42 are both lowered.

  Further, in the pair of side forming dies 58 and 60 and the pair of end forming dies 62 and 64 held on the lower holding die 44, the male tapered surfaces 66 are fitted into the female tapered surfaces 68 of the upper holding die 42. As the upper holding mold 42 is lowered, each of the upper holding molds 42 moves inward in conjunction with the lowering movement of the upper holding mold 42 by the cam action of the tapered surface, and the upper holding mold 42 is lowered to the bottom dead center. As a result, the upper molding die 46, the lower molding die 52, the pair of side molding dies 58, 60, and the pair of end molding dies 62, 64 are closed and the molding space 70 closed and sealed inside is formed. Form.

At this time, as shown in the partially enlarged view of FIG. 5, the upper mold 46 and the lower mold 52 pinch the flange 20B up and down, and the pair of side molds 58 and 60 sandwich the flange 20B right and left. Then, the flange portion 20B is simultaneously pressed from the upper, lower, left and right surfaces to deform it, and is formed into the cross-sectional shape shown in FIG. 7B.
The cross-sectional shape of the collar part 20 shown in FIG. 7B is the same as the cross-sectional shape of the collar part 20 shown in the partially enlarged view of FIG.

That is, by this coining process, the shape of the collar portion 20 is such that the outer surface of the pair of ribs 22 has a straight shape in the vertical direction, and the inner surface has a straight shape in the vertical direction except for the root portion of the connecting portion 24. Further, the connecting portion 24 is formed into a plate shape in the left-right direction.
Further, the base portion of the connecting portion 24 in the rib 22 is formed as a curved portion 30 whose inner surface partially forms an arc-shaped curved surface 29 having a predetermined curvature.
The shape of each molding surface of the upper mold 46, the lower mold 52, and the pair of side molds 58, 60 is such a shape.
Thereafter, the upper forming die 46 and the upper holding pins 48 and 50 are raised together with the upper holding die 42, whereby the processed connecting rod 10 is taken out (see FIG. 6).

When forming the flange 20, the upper mold 46 and the lower mold 52 compress and deform the upper and lower ends of the rib 22 in the vertical direction, and compress and deform the curved portion 30B of the hot forged material 10B. The material is moved along with the deformation, and finally the cross-sectional shape of the flange portion 20 is changed to the cross-sectional shape shown in FIG.
For example, the processing rate of the cross section of the flange 20 at that time is about 10%.
At this time, unlike the conventional processing method, no burr is generated in the flange portion 20.

  This coining process has the meaning of correcting the shape of the collar part 20 and performing work hardening by imparting strain, but at the same time, slightly compressing the large end part 12 and the small end part 16, The shape correction of the portion 12 and the small end portion 16 is also performed.

  Note that the upper hold pins 48 and 50 that are held by the upper holding die 42 and move downward together with the upper holding die 42 reach the bottom dead center when the upper holding die 42 reaches the bottom dead center. The large end hole 14 and the small end hole 16 are respectively positioned together with the lower holding pins 54 and 56 that are respectively fitted downward into the small end hole 18 and are previously fitted upward into the large end hole 14 and the small end hole 16. It is restrained to a fixed state and functions to prevent the hot forging material 10B from being displaced during pressure processing.

Here, each of the lower hold pin 54 and the upper hold pin 48 is half-inserted into the large end hole 14 and abuts each other at the central position in the vertical direction of the large end hole 14.
Similarly, each of the lower hold pin 56 and the upper hold pin 50 is half-inserted into the small end hole 18 and abuts each other at the vertical center position of the small end hole 18.

  Each of the upper hold pin 48, the lower hold pin 54, the upper hold pin 50, and the lower hold pin 56 has a chamfered outer peripheral surface at each end, and the entire circumference is between the large end hole 14 and the small end hole 18. An annular minute gap is formed at an intermediate position in the vertical direction.

  When the hot forming mold is worn and, as a result, the volume of the workpiece during coining increases, the excess meat moves in the longitudinal direction in the molding space 70 during processing, and the large end holes 14, The small end hole 18 can flow and move into an annular gap formed between the upper hold pins 48 and 50 and the lower hold pins 54 and 56.

  In this case, fine burrs are generated around the inner periphery of the large end hole 14 and the small end hole 18 in the processed product, but the large end hole 14 and the small end hole 18 are then finished by cutting. Therefore, the burrs generated at that time are also removed at the same time, and no special processing for deburring is required.

Using JIS S55C, the connecting rod 10 was manufactured by performing hot forging and subsequent coining by the process shown in FIG.
Specifically, the hot forging process from steps (I) to (V) in FIG. 11 at 1200 ° C., and the subsequent steps (VI) and (VII) were punched and deburred.
Thereafter, in a cooling process by natural cooling, coining was performed at 600 ° C. and a processing rate of 10% with respect to the flange 20, and then naturally cooled to room temperature.
For comparison, coining using a conventional coining mold apparatus for forming the collar part 20 using only the upper mold 34 and the lower mold 36 was also performed.

  8 (A) and 8 (A) show the cross-sectional shape of the flange 20B of the rough shaped material (hot forged material) 10B after hot forging, and (B) and (B) show the flange 20 of the connecting rod 10 of this embodiment. (B) and (C) respectively show the cross-sectional shape of the flange portion 20A of the connecting rod 10A of the comparative example using the conventional coining type.

Here, the cross-sectional shape of the flange portion 20B shown in (B) and (A), the cross-sectional shape of the flange portion 20 in (B) and (B), and (B) of the flange portion 20A of the connecting rod 10A of the comparative example in (C). The cross-sectional shapes are the same as those shown in FIGS. 7A and 7B and FIGS. 12A and 12B, respectively.
In addition, the connecting rod 10 of the present embodiment and the connecting rod 10A of the comparative example have the same cross-sectional shape other than the collar portion, such as the shapes of the large end portion 12 and the small end portion 16.

The connecting rod 10 of the present example obtained above and the connecting rod 10A of the comparative example were subjected to a buckling test (the contents of the buckling test will be described later), and the buckling strength of each of the flange portions 20 and 20A was measured.
The results are shown in Table 1.
In Table 1, the value of the moment of inertia of the cross section is shown as a relative value when the value of the connecting rod 10A of the comparative example is 1.
As shown in Table 1, the connecting rod 10 of this example has a buckling strength value of about 50 MPa higher than the connecting rod 10A of the comparative example.

This is because, in the case of the connecting rod 10 of the present embodiment, the secondary moment of section is higher than that of the connecting rod 10A of the comparative example, and the deformation resistance to the bending moment is increased in shape, that is, the shape is increased in strength. Furthermore, in the case of the connecting rod 10 of the present embodiment, the effective strain amount of the flange portion 20 is increased as compared with the connecting rod 10A of the comparative example, and the strain distribution is equalized over the entire cross section, so that This is due to the increased strength.
In addition, in order to clarify the effect by the difference in shape based on the change of a shaping | molding die here, the said coining process is performed at 600 degreeC with little influence of work hardening.

<Buckling test method>
As shown in FIG. 9A, fixing pins 72 and 74 are fitted in the large end hole 14 and the small end hole 18, respectively, and the fixing pins 72 and 74 are moved close to each other at a constant speed. The flanges 20 and 20A are compressed and deformed, and the load at the point at which the displacement-load curve in FIG. 9B is bent is obtained from the load and displacement values output at that time, and this is defined as the buckling load. A value obtained by dividing the load by the cross-sectional area of the flange portions 20 and 20A was determined as the buckling strength (stress).

  According to the present embodiment as described above, burrs are not generated at the time of coining, unlike the conventional manufacturing method, thereby improving the yield of the material, and thereafter, deburring for deburring. The punching process can be omitted.

  Moreover, according to this embodiment, the cross-sectional secondary moment of the collar part 20 can be enlarged, and the buckling strength of the collar part 20 can be made high by the shape effect.

  Further, in order not to generate burrs in which distortion is concentrated, it is possible to impart a large amount of distortion during the coining process over the entire cross section of the flange 20, and work hardening due to the distortion can be sufficiently extracted. The buckling strength of the flange portion 20 can be further increased by work hardening.

Although the embodiment of the present invention has been described in detail above, this is merely an example.
For example, in the above embodiment, the shape of the outer surface of the rib 22 is a straight shape in the vertical direction. However, in some cases, it is possible to apply coining to a shape in which the middle part in the vertical direction is recessed inward in the horizontal direction. is there. Alternatively, the collar portion 20 can be coined with the upper and lower molding dies and the pair of left and right lateral molding dies in various other shapes. It can be implemented and configured in the form and form added.

DESCRIPTION OF SYMBOLS 10 Connecting rod 10B Hot forging material 12 Large end part 14 Large end hole 16 Small end part 18 Small end hole 20 Ridge part 22 Rib 24 Connection part 40 Coining type | mold apparatus 46 Upper shaping | molding die 52 Lower shaping | molding die 58,60 Side shaping die 70 Molding space

Claims (5)

A rough shape of a connecting rod having a large end portion and a small end portion and a flange portion connecting the large end portion and the small end portion is first formed by hot forging, and then coining is performed on the hot forging material having the rough shape. In the manufacturing method of the connecting rod which manufactures the connecting rod by applying
As the coining mold of the collar part, the upper mold, the lower mold, and the left and right facing relative movements are arranged so as to be relatively movable in the axial direction of the holes of the large end and small end. Use a coining mold that has a pair of left and right side molds arranged in a possible manner, and that is closed in its entirety when closed as a whole.
In the coining process, the upper and lower molds are used to clamp the flange part up and down, and the pair of side molding molds are used to clamp the flange part left and right, so that the flange part is vertically and laterally separated from four surfaces. A method of manufacturing a connecting rod, wherein pressurization is performed at the same time, and work hardening is performed by correcting the shape of the buttocks and applying distortion by deformation accompanying the pressurization. In Claim 1, the rough shape in the hot forged material has a pair of left and right ribs protruding vertically at the left and right end portions, and a connecting portion for connecting the ribs in the left and right direction at the upper and lower intermediate portions, and The left and right outer surfaces of the rib have a bulging shape that increases the amount of protrusion in the left and right outer direction from the upper and lower ends toward the upper and lower intermediate part,
In the coining process, the pair of side molding dies pressurizes the bulging portion inward in the left-right direction and molds the connecting rod.   3. The method of manufacturing a connecting rod according to claim 2, wherein the pair of side forming dies are formed by forming the outer surface of the rib having the bulging portion into a straight shape in the vertical direction.   The rough shape of the hot forging material according to any one of claims 2 and 3, wherein the rough shape of the hot forged material is curved inwardly from the upper and lower ends of the rib toward the connecting portion, and during the coining process, The molding die and the lower molding die compressively deform the upper and lower end portions of the rib in the vertical direction and pressurize and deform the curved curved portion to deform the connecting portion into a plate shape in the lateral direction. A method for manufacturing a connecting rod, wherein the side surface is formed into a vertical shape excluding a base portion to the connecting portion. A coining mold apparatus used for forming the collar portion in the coining process according to any one of claims 1 to 4,
It has an upper mold, a lower mold, and a pair of left and right side molds, which are arranged so as to be movable relative to each other, and are entirely closed. The inside is sealed and closed in the state,
In the coining process, the upper and lower molds are used to clamp the collar part up and down, and the pair of side molding molds are used to sandwich the collar part from side to side. A coining type apparatus characterized in that it is subjected to work hardening by correcting the shape of the buttocks and applying strain by deformation caused by the pressurization.

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