JP2001324017A - Manufacturing method for piston pin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a piston pin to be tapered and rounded only by cold forging. SOLUTION: A hole 13 having an inside diameter larger than the inside diameter of a hollow hole 11 is formed through a stepped part 12 in both end parts (both ends in the longitudinal direction) in the axial direction of a piston pin blank 10, and the wall thickness of both axial end parts of the piston pin blank 10 is made smaller than that of the other part. Subsequently, cold forging is performed to taper and round the corner parts at both axial ends of the piston pin blank 10. Thus, plastic deformation is caused only at both axial end parts of the piston pin blank 10, and no deformation is caused in the other part, so that the inside diameter of the hollow hole 11 may not be reduced, and burr may not be caused in the outer peripheral surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a piston pin used for connecting a piston and a connecting rod in a reciprocating internal combustion engine used for an automobile, an agricultural machine, an aircraft, and the like. More specifically, the present invention relates to a method for manufacturing a piston pin which has excellent workability and can reduce manufacturing cost.

[0002]

As this type of piston pin, for example, a piston pin blank 50 having a hollow hole 51 formed by cold forging a steel bar or a bar steel (see FIG. 6).
Is known. This piston pin is tapered or rounded at the corners at both axial ends (longitudinal ends) of the piston pin in order to assemble it smoothly when assembling the piston and connecting rod. I have.

As a method of manufacturing a piston pin having such a tapered or round shape, for example, machining is performed on a piston pin blank 50 to finish the entire length to a desired size, and at the corners at both ends in the axial direction, FIG. 8 is provided, or a radius 53 is provided as shown in FIG. 8, and thereafter, necessary heat treatment and finish grinding of the outer diameter are performed.

[0004] However, in this manufacturing method by machining, there is a problem that the number of cutting and grinding processes is large and the manufacturing cost rises.

On the other hand, as shown in FIGS. 9 and 10, a piston pin blank 50 is set on a die 56 composed of an upper die 54 and a lower die 55, and the upper die 54,
The radius R provided on each of the lower molds 55 is
A method is known in which the blank is transferred to both corners in the axial direction of the blank 50 (the corners at both ends in the axial direction of the piston pin blank 50 are plastically deformed along the radius R), and the piston pin is finished to the required overall length. Have been.

However, when the piston pin is manufactured by cold forging, the material at the corners at both ends in the axial direction of the piston pin blank 50 is excessive, and the extra material is obtained in the process of plastically deforming the piston pin blank 50. As a result, the inner diameter of the hollow hole 51 of the piston pin blank 50 is reduced, and the outer periphery of the piston pin blank 50 corresponds to the gap 57 between the mating surfaces of the upper mold 54 and the lower mold 55. A bar 58 is formed at the surface. For this reason, it is necessary to machine the outer peripheral surface of the piston pin blank 50 and the inner peripheral surface of the hollow hole 51 after cold forging to remove the burr 58 and return the reduced hollow hole to its original inner diameter. However, there is a problem in that these machining processes are troublesome as compared with the machining processes performed by the above-described method of manufacturing the piston pin, and rather increase the manufacturing cost.

The present invention has been made in view of the above circumstances, and has as its object to provide a method of manufacturing a piston pin only by plastic working without requiring finishing by machining such as cutting and grinding. .

[0008]

In order to achieve the above object, the present invention provides a piston pin having a hollow hole for connecting a piston and a connecting rod, the piston pin having both ends in the axial direction (both longitudinal ends). In the method for manufacturing a piston pin, in which a corner portion is rounded or tapered by plastic working, in a piston pin manufacturing method, a piston pin is processed in advance so that a wall thickness at both axial end portions is smaller than a wall thickness of another portion. The present invention is characterized in that a blank is used, and corner portions at both axial ends of the piston pin / blank are rounded or tapered by plastic working.

[0009] The piston pin processed into the piston pin
As a method of forming a blank at both ends in the axial direction (both ends in the longitudinal direction) thereof before plastic working, for example, a method of forming the blank at both ends in the axial direction of the piston pin blank is used. In addition, a method in which a hole having an inner diameter larger than the inner diameter of the hollow hole is previously formed through the step portion, and a method in which a taper hole is previously formed in which the inner diameter is gradually reduced and the inner diameter of the minimum diameter portion is equal to the inner diameter of the hollow hole And a hole having an inner diameter larger than the inner diameter of the hollow hole via the step portion, and a tapered hole having an inner diameter of the maximum diameter portion equal to the inner diameter of the hole and an inner diameter of the minimum diameter portion equal to the inner diameter of the hollow hole. There is a method of forming in advance.

According to the method of the present invention, the thickness of the piston pin blank at both ends in the axial direction (both ends in the longitudinal direction) is made thinner than the other portions. Even if the corners are rounded or tapered by plastic working, extra material is added to the corners as in the conventional case where the thickness at the axial end portions of the piston pin blank is equal to the thickness at other portions. There is no need to escape from the plastic part, plastic deformation is only at the corners, there is no risk of plastic deformation in other parts, as a result, the inner diameter of the hollow hole of the piston pin blank is reduced, and burrs occur on the outer peripheral surface There is no danger.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings.

1 to 5 show one embodiment of a method for manufacturing a piston pin according to the present invention. 1 is a longitudinal sectional view of a piston pin blank used in the method of the present invention, FIG. 2 is a longitudinal sectional view showing a modification of the piston pin blank shown in FIG. 1, and FIG. 3 is a piston pin blank shown in FIG. FIG. 4 is a longitudinal sectional view showing another modified example of FIG. 4, and FIG. 4 is a view for explaining a process of plastic working (cold forging) of the piston pin blank shown in FIG. FIG. 5 is a view for explaining a process of plastic working (cold forging) of the piston pin blank shown in FIG. 1, and FIG. It is an explanatory longitudinal cross-sectional view of a state where corner portions at both ends in the axial direction are chamfered (with a radius).

In this embodiment, a piston pin blank 10 having a hollow hole 11 shown in FIG. 1 is used. The piston pin blank 10 is manufactured by, for example, cold forging a steel bar or a steel bar, and has an inner diameter larger than the inner diameter of the hollow hole 11 at both ends in the axial direction (both ends in the length direction) through a step portion 12. Are formed respectively.

Due to the holes 13, the thickness of the piston pin blank 10 at both axial ends is smaller than the thickness of the other portions. Inner diameter of hole 13 (piston pin / blank 1
0, and the depth S of the hole 13 (see FIG. 4) is the size of the radius 14 (see FIG. 5) formed at the corners at both axial ends of the piston pin blank 10. Determined by If the radius 14 is large, the hole 13
The inner diameter and the depth S are increased, or the inner diameter is increased while the depth S is constant, or the depth S
To increase.

Next, a method of manufacturing a piston pin by cold forging the piston pin blank 10 will be described with reference to FIGS.

The die 20 used for cold forging is an upper die 2
1 and a lower mold 22, and cavities 23 and 24 having diameters slightly larger than the diameter of the piston pin blank 10 are formed in the upper mold 21 and the lower mold 22, respectively, at the bottom of the cavities 23 and 24. A rounded portion R is formed at each corner. The dies 20 are not different from those used in the conventional manufacturing method.

First, as shown in FIG.
The blank 10 is inserted into the cavity 24 of the lower mold 22. As a result, substantially the lower half of the piston pin blank 10 fits in the cavity 24. Next, when the upper mold 21 is lowered with respect to the lower mold 22 by a hydraulic cylinder (not shown) or the like, the upper half of the piston pin blank 10 is accommodated in the cavity 23 of the upper mold 21 in the course of this lowering. When the upper die 21 is further lowered to a lower limit position with a predetermined pressure with respect to the lower die 22, the shaft of the piston pin blank 10 is aligned with the radius R of the cavities 23 and 24 as shown in FIG. The corners at both ends in the direction are chamfered by plastic deformation (with a radius 14),
The entire length of the piston pin blank 10 is formed to a predetermined length L.

During cold forging, piston pin blank 10
Plastic deformation occurs at both ends in the axial direction, but no plastic deformation occurs at other portions. Therefore, there is no danger that the inner diameter of the hollow hole 11 is reduced, and that burr does not occur on the outer peripheral surface of the piston pin blank 10 (a portion 25 corresponding to the gap between the mating surfaces of the upper die 21 and the lower die 22). After the completion of the cold forging, the piston pin blank 10 taken out of the die 20 can be used as a piston pin as it is without performing finishing.

In this embodiment, the piston pin can be manufactured only by cold forging the piston pin blank 10 as described above.

The manufactured piston pin is chamfered at both corners in the axial direction (with a radius 14).
As a result, the piston and the connecting rod can be smoothly inserted into the mounting holes, and the connection work between the piston and the connecting rod can be efficiently performed. In addition, there is essentially no stress applied to both ends of the piston pin in the axial direction. Even if the wall is thinned and chamfered (even with the radius 14), there is no problem.
The weight can be reduced as compared with the piston pin without chamfering (without the radius 14).

FIG. 2 shows a modification of the piston pin blank 10 shown in FIG. 1. Instead of the holes 13, tapered holes 15 are formed at both ends in the axial direction of the piston pin blank 10 by, for example, cold forging. Has formed. This tapered hole 15 is coaxial with the hollow hole 11 and has a piston pin
The maximum diameter is at both ends in the axial direction of the blank 10, and the inner diameter gradually decreases toward the central portion of the piston pin blank 10. The minimum diameter portion of the tapered hole 15 is substantially equal to the inner diameter of the hollow hole 11. The maximum diameter and the depth of the tapered hole 15 are determined by the size of the chamfer. When the chamfer is large, the maximum diameter and the depth are increased, or one of the maximum diameter and the depth is increased.

Due to the tapered hole 15, the thickness of the piston pin blank 10 at both axial ends is smaller than the thickness of the other portions.

The piston pin blank 10 having the tapered hole 15 can also be worked into a piston pin by performing cold forging as shown in FIGS. Also in this case, plastic deformation occurs at both axial ends of the piston pin blank 10 in the process of cold forging,
No plastic deformation occurs in other parts. Therefore, there is no possibility that the inner diameter of the hollow hole 11 is reduced or burrs are formed on the outer peripheral surface of the piston pin blank 10, and after the cold forging, it can be used as a piston pin as it is without finishing. Can be.

FIG. 3 shows another modification of the piston pin blank 10 shown in FIG. 1. Instead of the hole 13, a hole is formed at both axial ends of the piston pin blank 10 by, for example, cold forging. 16 are formed. Each of the holes 16 has a hole portion 17 having an inner diameter larger than that of the hollow hole 11, and is continuous with the hole portion 17, and has a maximum diameter equal to the inner diameter of the hole portion 17, toward the central portion of the piston pin blank 10. And a tapered hole portion 18 formed so that the inner diameter is gradually reduced. The minimum diameter portion of the tapered hole portion 18 is substantially equal to the inner diameter of the hollow hole 11.

Due to the holes 18, the thickness of the piston pin blank 10 at both axial ends is smaller than the thickness of the other portions.

In the case of the piston pin blank 10 having the hole 16, similarly to the case of the piston pin blank 10 shown in FIGS. 1 and 2, the piston pin can be manufactured by performing cold forging. No need for finishing.

In the above embodiment, the corners at both ends in the axial direction of the piston pin blank 10 are chamfered (R 14
) Is shown, but a taper may be provided instead of the radius 14.

The present invention is characterized in that a piston pin blank 10 having a smaller thickness at both ends in the axial direction than other portions is used.
The blank 10 is not limited to those shown in FIGS.

[0029]

As described above, according to the present invention,
Prior to plastic working, the piston pin blank is pre-processed so that the wall thickness at both ends in the axial direction is smaller than the wall thickness of the other parts. The piston pin can be manufactured by adding, and it is not necessary to perform finishing machining after cold forging. Also, the manufacturing cost is lower than when manufacturing piston pins from piston pin blanks only by machining, or when manufacturing cold-forged piston pins and blanks and then finishing them by machining to manufacture piston pins. Can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a piston pin blank used in the method of the present invention.

FIG. 2 is a longitudinal sectional view showing a modification of the piston pin blank shown in FIG.

FIG. 3 is a longitudinal sectional view showing another modification of the piston pin blank shown in FIG.

FIG. 4 is a view for explaining a process of plastic working (cold forging) of the piston pin blank shown in FIG. 1 and is a longitudinal sectional view illustrating a state where the piston pin blank is set in a die. .

FIG. 5 is a view for explaining a process of plastic working (cold forging) of the piston pin blank shown in FIG. 1, wherein corners at both ends in the axial direction of the piston pin blank are formed by round chamfering of a die. It is an explanatory longitudinal cross-sectional view of a state where a radius is taken.

FIG. 6 is a vertical sectional view of a piston pin blank used to manufacture a conventional piston pin.

7 is a longitudinal sectional view of a piston pin manufactured by machining the piston pin blank of FIG. 6;

FIG. 8 is a longitudinal sectional view of another piston pin manufactured by machining the piston pin blank of FIG. 6;

9 is a view for explaining a process of manufacturing a piston pin by cold forging the piston pin blank of FIG. 6, and is an explanatory longitudinal sectional view in a state where the piston pin blank is set in a die.

10 is a view illustrating a process of manufacturing a piston pin by cold forging the piston pin blank of FIG. 6,
It is explanatory sectional drawing of the state in which the burr | flash generate | occur | produced in the process of cold forging.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Piston pin blank 18 Tapered hole part 11 Hollow hole 20 Die 12 Step part 21 Upper die 13, 16 holes 22 Lower die 14 R 23, 2
4 Cavity 15 Tapered hole R radius 17 Hole

Continued on the front page (72) Inventor Takao Inagaki 117 Shimizu Toyoba, Toyoyama-cho, Nishi-Kasugai-gun, Aichi Prefecture No. 606 Shato Toyoyama F-term (reference) 3J044 AA18 BA03 BC19 DA09 EA10 4E087 AA10 BA20 CA11 CB03 EC01 HA61 HB02

Claims (5)

[Claims] 1. Manufacture of a piston pin for connecting a piston and a connecting rod, wherein a piston pin having a hollow hole is rounded or tapered by plastic working at corners at both axial ends of the piston pin. In the method, using a piston pin blank pre-processed so that the wall thickness at both ends in the axial direction is smaller than the wall thickness of the other parts, at the corners at both ends in the axial direction of the piston pin blank, A method of manufacturing a piston pin, wherein a radius or a taper is provided by plastic working. 2. The method for manufacturing a piston pin according to claim 1, wherein a hole having an inner diameter larger than the inner diameter of the hollow hole is formed in advance at both ends in the axial direction of the piston pin blank via a step. A method of manufacturing a piston pin, wherein the thickness of both ends in the axial direction of the piston pin blank is made smaller than the thickness of other parts. 3. The method for manufacturing a piston pin according to claim 1, wherein the inner diameter of the piston pin blank is gradually reduced at both axial ends, and the inner diameter of the smallest diameter portion is equal to the inner diameter of the hollow hole. A method of manufacturing a piston pin, characterized in that the thickness of both ends in the axial direction of the piston pin blank is made thinner than the thickness of other portions by forming a tapered hole in advance. 4. The method for manufacturing a piston pin according to claim 1, wherein: at both axial ends of the piston pin blank, a hole having an inner diameter larger than the inner diameter of the hollow hole via a step portion; The inner diameter of the diameter portion is equal to the inner diameter of the hole, and the inner diameter of the smallest diameter portion is equal to the inner diameter of the hollow hole. A method for manufacturing a piston pin, characterized in that the wall thickness is made smaller than the wall thickness of other parts. 5. The method of manufacturing a piston pin according to claim 1, wherein the plastic working is cold forging.