JPH03142030A - Forming method for piston pin - Google Patents

Abstract

PURPOSE:To prevent the overlapping of pierced part and the generation of end surface burr and to improve the quality of the piston pin by forming one side by one side the tapered parts which are to be formed at both sides of the inside of piston pin with cold forging. CONSTITUTION:The piston pin 1 whose wall thinned bole 2 is pre-worked from both sides with cold forging is inserted to the die hole 3a of the die 3, and one side of the piston pin 1 is supported with the pin sleeve 4, 8 and the marking pin 5a, 5b, and the forming pin is inserted in the wall thinned hole 2 from the other side of the piston pin and the tapered part 7 is formed. Next, the other end side is worked with the same method. Therefore, the overlapping of the pierced part and the generating of burrs of the end surface are prevented and the working of high quality without variation is obtained, and the strength is improved without the breaking of fiber flow.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for forming a piston pin, and more specifically to a method for reducing the weight of the piston pin by thinning the inner diameter thereof.

(Prior Art) Conventionally, in order to reduce the weight of this type of piston pin, the inner diameter of the piston pin has been thinned out. As shown in the figure, the taper part 12.12 was formed by cutting the machining allowance 11, but this increased the number of cutting processes, resulting in higher costs, and the fiber flow cut caused by cutting, resulting in a decrease in strength. There was the problem of inviting.

Therefore, as a countermeasure against these problems, the applicant has recently developed a piston pin in which inner diameter tapered portions 13 are simultaneously formed by cold forging on both sides of the inner diameter of a piston pin 10 formed in advance by cold forging, as shown in FIG. I tried the molding method.

(Problem to be Solved by the Invention) However, in the forming method in which the taper portions 13° 13 are simultaneously formed on both sides of the inner diameter of the piston pin 10 by the cold forging method as described above, the hole formed by the tip of the forming pin is Folds 15 are likely to occur in the pierced portion of the piston pin 14, burrs 16 are generated on the end surface of the piston pin 10, and dimensions are insufficient for the predetermined length of the piston pin, resulting in poor material yield, etc. There was a problem.

The present invention was proposed in view of the above-mentioned problems, and
By forming the tapered parts on both sides of the inner diameter of the piston pin on each side by cold forging, it is possible to prevent the pierced part from folding in and the end face from cracking, thereby obtaining a high-quality piston pin with no dimensional variations. The object of the present invention is to provide a method for forming a piston pin.

(Means for Solving the Problems) In order to achieve this object, the present invention involves inserting a piston pin with a hollow hole formed from both sides by a cold forging method into a mold hole of a die. One end side is supported by a bottle sleeve and a marking pin, a formed bottle is pushed into the hollow hole from the other end side of the piston pin to form a tapered part, and then the other end side which has been processed is supported by a bottle sleeve and a marking pin. This is characterized in that the taper portion is formed by supporting the piston pin with the piston pin and pushing the molding pin into the hollowed-out hole on the unprocessed side of the piston pin again.

(Function) As described above, in the piston pin forming method according to the present invention,
Since tapered portions are formed on each side of the inner diameter of the piston pin by cold-timber forming, a high-quality piston pin can be molded by preventing folding of the pierced portion and cracking of the end surface.

(Example) Hereinafter, a method of forming a piston pin according to the present invention will be explained in detail based on FIGS. 1 to 3.

FIGS. 1 to 3 are cross-sectional views showing the process of forming a piston pin according to the present invention. The piston pin 1 is preliminarily formed with hollow holes 2.degree. 2 from both sides by cold forging.

The piston pin 1 is inserted into the mold hole 3a of the die 3 as shown in FIG. mark the piercing part 2a with the marking pin 5
It is supported by the tip of a.

Next, the forming pin 6 is inserted into the lightening hole 2 from the other end side of the piston pin 1, and by pushing it with a predetermined pressing force, the forming pin 6 is inserted into the lightening hole 2 with a taper corresponding to the tapered surface 6a of the forming bottle 6. Section 7 is formed.

Next, as shown in FIG. 3, the molding bottle 6 and the piston pin 1 are pulled out from the mold hole 3a of the die 3, reversed and inserted into the mold hole 3a of the die 3 again, and the end surface of the processed piston pin 1 is It is supported by a bottle sleeve 8 that serves as a stopper, and a marking pin 5b having approximately the same shape as the taper portion 7 of the piston pin 1 is inserted and supported in order to suppress deformation of the inner diameter.

Then, in the same manner as described above, the forming pin 6 is inserted into the hollow hole 2 from the unprocessed side of the piston pin 1, and is pushed in with a predetermined pressing force to form the tapered portion 7 in the hollow hole 2.

(Effects of the Invention) As explained above, according to the method for forming a piston pin according to the present invention, a piston pin having lightening holes formed on both sides by cold forging in advance is inserted into a mold hole of a die, and the piston pin is One end of the pin is supported by a bottle sleeve and a marking pin, and a formed bottle is pushed into the hollow hole from the other end of the piston pin to form a tapered part, and then the other end that has been processed is made into a bottle sleeve. The taper part is formed by supporting the piston pin with a marking pin and pushing the molding bottle into the hollowed-out hole on the unprocessed side of the piston pin again to form the tapered part. You can't get high quality.

Further, unlike the conventional cutting process, there is no need for a cutting process and there is no fiber flow cutting, so the strength of the piston pin can be improved and the yield of material can be improved.

[Brief explanation of the drawing]

1 to 3 are cross-sectional views showing the process of forming a piston pin according to the present invention. FIG. 1 is a cross-sectional view showing the piston pin before forming the taper portion, and FIG. Fig. 3 is a forming process diagram for forming a tapered part on the opposite side of the piston pin, Fig. 4 is a cross-sectional view showing the cutting state of the piston pin in a conventional piston pin forming method; FIG. 5 is a sectional view showing simultaneous molding of a piston pin attempted by the applicant. 1... Piston pin, 2... Lightening hole, 2a...
Earring part, 3...Gui, 3a...Mold hole, 4.8...
- Pin sleeve, 5a, 5b... marking pin, 6... molded pin, 7... taper part.

Claims (1)

[Claims] A piston pin with holes made in advance from both sides by cold forging is inserted into the mold hole of the die, one end of the piston pin is supported by a pin sleeve and a marking pin, and the piston pin is thinned from the other end. Push the molded pin into the punched hole to form a tapered part, then support the other end of the piston pin with the pin sleeve and marking pin, and push the molded pin again into the punched hole on the unprocessed side of the piston pin. A method for forming a piston pin, characterized in that a tapered portion is formed by.