JP4384336B2 - Piston pin manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a piston pin used to connect a piston and a connecting rod in a reciprocating internal combustion engine used in an automobile, an agricultural machine, an aircraft, and the like. The present invention relates to a method for manufacturing a piston pin that can reduce manufacturing costs.
[0002]
[Problems to be solved by the invention]
As this type of piston pin, for example, a piston pin manufactured by using a piston pin blank 50 (see FIG. 6) having a hollow hole 51, which is formed by cold forging bar steel and bar steel, is known. This piston pin is tapered and rounded at the corners at both ends in the axial direction (both ends in the length direction) so that the piston pin and connecting rod can be assembled smoothly. Yes.
[0003]
As a method of manufacturing a piston pin with a taper or a radius in this manner, for example, the piston pin blank 50 is machined to finish the entire length to a desired dimension, and the corner portions at both ends in the axial direction are as shown in FIG. 8 is provided with a taper portion 52 or a round 53 as shown in FIG. 8, and then necessary heat treatment and finish grinding of the outer diameter are performed.
[0004]
However, this manufacturing method by machining has a problem that the number of cutting and grinding processes is large and the manufacturing cost increases.
[0005]
On the other hand, as shown in FIGS. 9 and 10, the piston pin blank 50 is set on a die 56 composed of an upper die 54 and a lower die 55, and is provided on the upper die 54 and the lower die 55 by cold forging. The rounded portion R is transferred to both ends in the axial direction of the piston pin / blank 50 (the angular portions at both ends in the axial direction of the piston pin / blank 50 are plastically deformed along the rounded portion R) and required for the piston pin. There is a known method of finishing the entire length.
[0006]
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 extra, and the extra material is in the process of plastic deformation of 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 at the outer peripheral surface portion of the piston pin / blank 50 corresponding to the gap 57 between the mating surfaces of the upper die 54 and the lower die 55. Bar 58 is generated. For this reason, after cold forging, 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 to remove the burr 58 and return the reduced hollow hole to the original inner diameter. However, these machining processes are troublesome as compared with the machining process performed by the above-described piston pin manufacturing method, and there is a problem that the manufacturing cost increases.
[0007]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method of manufacturing a piston pin only by plastic working without requiring finishing by machining such as cutting and grinding.
[0008]
[Means for Solving the Problems]
To achieve the above object, the present invention provides a piston pin having a hollow hole for connecting a piston and a connecting rod, and is rounded or tapered by plastic working at the corners at both ends in the axial direction (both ends in the length direction) of the piston pin. In the manufacturing method of the piston pin, the piston pin blank, which has been processed in advance so that the thickness at the axial end portions is thinner than the thickness of the other portion, is used. The corners at both ends in the axial direction of the blank are rounded or tapered by plastic working.
[0009]
As a method of forming a piston pin blank to be processed into a piston pin before the plastic processing, the thickness at the axial end portions (longitudinal end portions) is thinner than the thickness at other portions. A method in which holes having an inner diameter larger than the inner diameter of the hollow hole are formed in advance on both ends in the axial direction of the piston pin / blank via a stepped portion, and the inner diameter of the smallest diameter portion is gradually reduced to the inner diameter of the hollow hole. The method of forming an equal taper hole in advance, a hole having an inner diameter larger than the inner diameter of the hollow hole through the stepped portion, the inner diameter of the largest diameter portion is equal to the inner diameter of the hole, and the inner diameter of the smallest diameter portion is There is a method in which a tapered hole having the same inner diameter is formed in advance.
[0010]
According to the method of the present invention, the thickness of the piston pin blank at both end portions in the axial direction (both end portions in the length direction) is made thinner than the other portions. Even if it is rounded or tapered by plastic processing, it is necessary to let excess material escape from the corner as in the conventional case where the wall thickness at the axial end of the piston pin blank is equal to the wall thickness at the other part. However, plastic deformation is only at the corners, and 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 are generated on the outer peripheral surface. It is not.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described below with reference to the accompanying drawings.
[0012]
1 to 5 show an embodiment of the piston pin manufacturing method of 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 view for explaining a process of plastic working (cold forging) of the piston pin / blank shown in FIG. 1, wherein the piston pin / blank is placed in a die. FIG. 5 is a diagram for explaining the process of plastic working (cold forging) of the piston pin / blank shown in FIG. It is explanatory longitudinal cross-sectional view of the state which chamfered the corner | angular part of an axial direction both ends (it attached | subjected the round).
[0013]
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, for example, by cold forging a steel bar or a bar steel, and has an inner diameter larger than the inner diameter of the hollow hole 11 via a stepped portion 12 at both ends in the axial direction (both ends in the length direction). Each of the holes 13 is formed.
[0014]
Due to the holes 13, the thickness of both end portions in the axial direction of the piston pin blank 10 becomes thinner than the thickness of the other portions. The inner diameter of the hole 13 (thickness P at both ends in the axial direction of the piston pin blank 10) and the depth S of the hole 13 (see FIG. 4) are formed at the corners at both ends in the axial direction of the piston pin blank 10. It is determined from the size of R 14 (see FIG. 5). When the radius 14 is increased, the inner diameter and depth S of the hole 13 are increased, or the depth S is made constant and the inner diameter is increased, or the inner diameter is made constant and the depth S is increased.
[0015]
Next, a method for manufacturing a piston pin by cold forging the piston pin blank 10 will be described with reference to FIGS.
[0016]
A die 20 used for cold forging is composed of an upper die 21 and a lower die 22, and cavities 23 and 24 having diameters slightly larger than the diameter of the piston pin blank 10 are formed in the upper die 21 and the lower die 22. Each of the cavities 23 and 24 is formed with a rounded portion R at the corner. The die 20 is not different from that used in the conventional manufacturing method.
[0017]
First, as shown in FIG. 4, the piston pin blank 10 is inserted into the cavity 24 of the lower mold 22. As a result, the substantially lower half of the piston pin blank 10 is accommodated in the cavity 24. Next, when the upper die 21 is lowered with respect to the lower die 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 die 21 during this lowering process. Further, when the upper die 21 is lowered to the lower limit position with a predetermined pressure with respect to the lower die 22, the shaft of the piston pin blank 10 follows the rounded portion R of the cavities 23 and 24 as shown in FIG. The corner portions at both ends in the direction are chamfered by plastic deformation (the rounds 14 are attached), and the entire length of the piston pin blank 10 is formed to a predetermined length L.
[0018]
At the time of cold forging, plastic deformation occurs at both ends in the axial direction of the piston pin blank 10, but plastic deformation does not occur at other portions. Therefore, there is no possibility that the inner diameter of the hollow hole 11 is reduced, or burrs are generated on the outer peripheral surface of the piston pin blank 10 (location 25 corresponding to the gap between the mating surfaces of the upper die 21 and the lower die 22). After the end of the cold forging, the piston pin blank 10 taken out from the die 20 can be used as it is as a piston pin without finishing.
[0019]
In this embodiment, as described above, the piston pin can be manufactured only by cold forging the piston pin blank 10.
[0020]
Since the manufactured piston pin has chamfered corners at both ends in the axial direction (with rounds 14), the piston pin can be smoothly inserted into the mounting holes of the piston and the connecting rod. The connecting work with the connecting rod is performed efficiently. In addition, the axial stress of both ends of the piston pin is not subject to any shear stress, and even if chamfering is performed after the wall thickness is reduced (even if the radius is 14), there is no problem and no chamfering is performed. Therefore, it is possible to reduce the weight as compared with a piston pin (not provided with a radius 14).
[0021]
FIG. 2 shows a modified example of the piston pin blank 10 shown in FIG. 1. Instead of the holes 13, taper holes 15 are formed at both ends in the axial direction of the piston pin blank 10 by, for example, cold forging. Yes. The tapered hole 15 is coaxial with the hollow hole 11, has a maximum diameter at both ends in the axial direction of the piston pin blank 10, and gradually decreases in inner diameter 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 depth of the tapered hole 15 are determined by the size of chamfering, and when chamfering is large, the maximum diameter and depth are increased, or either the maximum diameter or depth is increased.
[0022]
Due to the tapered hole 15, the thickness of both end portions in the axial direction of the piston pin blank 10 becomes thinner than the thickness of the other portions.
[0023]
Also in the case of the piston pin blank 10 having the tapered hole 15, as shown in FIGS. 4 and 5, it can be processed into a piston pin by performing cold forging. Also in this case, plastic deformation occurs at both ends in the axial direction of the piston pin blank 10 during the cold forging process, but plastic deformation does not occur at other portions. Therefore, there is no possibility that the inner diameter of the hollow hole 11 is reduced or burrs are generated on the outer peripheral surface of the piston pin / blank 10, and it is used as it is as a piston pin without finishing after cold forging. Can do.
[0024]
FIG. 3 shows another modification of the piston pin / blank 10 shown in FIG. 1. Instead of the holes 13, holes 16 are respectively formed at both ends in the axial direction of the piston pin / blank 10 by cold forging. Forming. Each hole 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. The maximum diameter is equal to the inner diameter of the hole portion 17, and toward the central portion of the piston pin blank 10. It consists of a tapered hole portion 18 formed so that the inner diameter is successively reduced. The minimum diameter portion of the tapered hole portion 18 is substantially equal to the inner diameter of the hollow hole 11.
[0025]
Due to the holes 18, the thickness of both end portions in the axial direction of the piston pin blank 10 becomes thinner than the thicknesses of the other portions.
[0026]
In the case of the piston pin blank 10 having the holes 16, the piston pin can be manufactured by cold forging as in the case of the piston pin blank 10 shown in FIGS. There is no need to apply.
[0027]
In the above embodiment, the case where the corners at both ends in the axial direction of the piston pin blank 10 are chamfered (the rounds 14 are attached) is shown, but it is needless to say that a taper may be provided instead of the rounds 14. .
[0028]
The present invention is characterized in that it uses a piston pin blank 10 whose thickness at both axial end portions is thinner than that of the other portions, and is shown in FIGS. 1 to 3 as a piston pin blank 10. It is not limited to things.
[0029]
【The invention's effect】
As described above, according to the present invention, the piston pin blank is processed in advance so that the wall thickness at both ends in the axial direction is thinner than the wall thickness of the other part before plastic processing. Therefore, the piston pin can be manufactured with a round shape (taper) only by plastic processing, and it is not necessary to perform finishing machining after cold forging. Compared to manufacturing piston pins from piston pins / blanks only by machining, or when piston pins / blanks are cold-forged and then machined to produce 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 modified example of the piston pin blank shown in FIG.
FIG. 3 is a longitudinal sectional view showing another modified example of the piston pin blank shown in 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 explaining a state in which the piston pin blank is set in a die. .
FIG. 5 is a view for explaining the process of plastic working (cold forging) of the piston pin blank shown in FIG. 1, and the corner portions at both ends in the axial direction of the piston pin blank are surfaced by the rounding of the die. It is a description longitudinal cross-sectional view of the state which took and rounded.
FIG. 6 is a longitudinal 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.
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 showing a state in which the piston pin blank is set in a die.
10 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 sectional view showing a state in which burrs are generated in the process of cold forging.
[Explanation of symbols]
10 Piston Pin / Blank 18 Tapered Hole 11 Hollow Hole 20 Die 12 Step 21 Upper Die 13, 16 Hole 22 Lower Die 14 R 23, 24 Cavity 15 Taper Hole R R 17 Portion

Claims (3)

In the manufacturing method of the piston pin, the piston pin having a hollow hole for connecting the piston and the connecting rod is rounded or tapered by plastic working at the corners at both ends in the axial direction of the outer periphery of the piston pin.
By forming cylindrical holes having an inner diameter larger than the inner diameter of the hollow hole at both ends in the axial direction of the piston pin / blank in advance, the thickness of both ends in the axial direction of the piston pin / blank can be reduced at other portions. It is characterized by using a piston pin blank that has been processed in advance to be thinner than the wall thickness of , and applying a round or taper to the corners at both ends in the axial direction of the piston pin blank by plastic processing. Manufacturing method of piston pin. In the piston pin manufacturing method according to claim 1,
Adjacent to the cylindrical bore, equal to the inner diameter of the maximum diameter portion is the inner diameter of the cylindrical bore, the inner diameter of the minimum diameter portion is equal to the inner diameter of the hollow hole, a tapered hole formed in advance, the piston Pin manufacturing method. In the manufacturing method of the piston pin according to claim 1 or 2 ,
The method of manufacturing a piston pin, wherein the plastic working is cold forging.

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