JPS5925883B2 - Piston manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piston manufacturing method for machining a crank pin insertion hole with high precision.

FIGS. 1 and 2 are views showing a "ball joint type piston" disclosed in Utility Application No. 56-37614 previously filed by the present applicant.

As can be seen from FIG. 1, a spherical seat 3 is provided in the concave portion 2 of the piston body 1, and a spherical portion 5 formed at one end of the connecting rod 5 is slidably fitted into this spherical seat 3. There is.
At the other end of the connecting rod 5, there is formed a cylindrical ring T in which a crank pin insertion hole 16 is eccentrically bored as shown in FIG. That is, the end surface of the ring T has a regular hexagonal outer shape, and the crank pin insertion hole 6 has a distance from its center axis 8 to each side surface 9a, 9b, 9c, etc. of the ring 7, in other words, the crank pin insertion hole 6 The distances obtained by adding different values of Δa to Δf to the radius γ are set to be different. Therefore, the piston stroke length X (
(see Figure 1), the sides 9a, 9b, 9c
. . . Select one side surface that matches the required stroke length X, bring the connecting rod 4 into contact with this side surface, and connect the ring □ and the connecting rod 4 by welding. Since the above-mentioned stroke length
Next processing is in progress. However, since the vicinity of the welded part of the ring T is affected by heat, the metal structure of the inner peripheral surface of the crank pin insertion hole 6 remains the same in the part that is not affected by heat, whereas the metal structure is affected by heat. The mechanical properties, particularly the hardness, of the parts significantly increased or decreased due to annealing effects, solution treatment effects, quenching effects, etc., and the machining characteristics of the above-mentioned secondary processing were also affected by the above-mentioned heat on the inner peripheral surface of the crank pin insertion hole 6. The difference between the part and the part that is not affected by heat is very large, and as a result, the machining accuracy and roundness deteriorate, causing various problems. The present invention has been made in consideration of the above circumstances, and the ring has a double structure of a main ring part and an auxiliary ring part, thereby avoiding the heat effect caused by welding and performing secondary processing for stroke length adjustment. It is an object of the present invention to provide a piston manufacturing method that can improve accuracy.

Hereinafter, the present invention will be explained based on examples with reference to the drawings.

FIG. 3 shows the ring 7 portion of the ball joint type piston obtained by the present invention, and this ring T portion is the main ring portion 10 formed into a cylindrical body whose end surface has a regular hexagonal outer shape.
The main ring part 10 is formed with an auxiliary ring part 12 whose cross section is press-fitted into a regular hexagonal through hole 11 and whose end face is a regular hexagon.

The auxiliary ring 12 is provided with a crank pin insertion hole 6 having a center axis substantially common to the center axis 13 of the auxiliary ring 12 (in the direction perpendicular to the plane of the paper in FIG. 3). The inner diameter of the crank pin insertion hole 6 is made smaller by the adjustment of the stroke length X, which will be described later. The central axis 14 of the regular hexagonal outer shape of the main ring portion 10 and the central axis 13 are eccentric by an eccentric amount E. In addition, the auxiliary ring portion 12
Each side 15a15b15c...2
A is each side surface 9a, 9b of the main ring portion 10, respectively.
, 9c...

The connecting rod 4 is connected by welding to any one of the side surfaces 9a, 9b, 9c, . . . of the main ring portion 10 that satisfies the required stroke length X. Further, the ball joint type piston obtained according to the present invention is completely the same as that shown in FIGS. 1 and 2 except for the ring 7 portion, so a description thereof will be omitted. Next, the piston manufacturing method of the present invention will be explained. First, the spherical portion 5 is connected to one end of the connecting rod 4 by, for example, resistance welding. Next, select the side surface that satisfies the required stroke length X from the side surfaces 9a, 9b, 9c, etc. of the main ring portion 10 to the other end of the connecting rod 4, and weld it in the same manner as the spherical portion 5. . At this time, main ring part 1
The vicinity of the welded part of 0 is affected by heat. Then, the auxiliary ring part 12 is press-fitted into the through hole 11 of the main ring part 10. The auxiliary ring portion 12 is not affected by heat due to welding at all and has a uniform metal structure. Thereafter, the crank pin insertion hole 6 after secondary processing is opened at a predetermined distance Z on the extension of the axis of the connecting rod 4 from the center of the spherical part 5 and is perpendicular to the end face of the auxiliary ring part 12. The position of the imaginary straight line serving as the central axis is determined by a jig (not shown). (As mentioned above, the inner diameter of the crank pin insertion hole 6 initially drilled in the auxiliary ring portion 12 is formed to be small, and the center axis of the crank pin insertion hole 6 at this time and the (The central axes of the crank pin insertion hole 6 do not necessarily coincide.) Therefore,
Using the virtual straight line determined by the jig as the center axis, cutting is performed using, for example, a boring machine to enlarge the diameter to a predetermined diameter. Furthermore, finishing machining is performed by internal diameter honing. Next, the spherical portion 5 attached to the connecting rod 4 is fitted and held in the spherical seat 3 by caulking the thin wall portion 16 of the spherical seat 3. At this time, a dimensional error occurs due to caulking, so the actual stroke length X is measured and corrected by cutting off the end surface 17 of the piston body 1 by the amount of error with respect to the required stroke length X. As described above, in the piston manufacturing method of the present invention, the ring welded to the connecting rod has a double structure of the main ring part and the auxiliary ring part, and the main ring part is first connected to the connecting rod by welding, and then the main ring part The auxiliary ring part is fitted to the auxiliary ring part, and then the crank pin insertion hole is secondary-machined so that the auxiliary ring part satisfies the predetermined stroke length, which can avoid the heat effects caused by welding. The machining accuracy, especially the roundness, of the crank pin insertion hole can be improved.

In the above embodiments, the auxiliary ring part is fitted into the main ring part by press fitting, but it may also be fitted by shrink fitting.

Further, in the above embodiment, the ball joint type piston is based on Utility Application No. 56-37614 by the present applicant, but without being limited to this, a ring having a crank pin insertion hole is connected to a connecting rod by welding. The present invention can be applied to any type of piston, without being limited to ball joint type pistons, as long as it has a structure that In addition, various changes can be made without departing from the gist of the present invention.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway side view of a conventional ball joint type piston, Fig. 2 is an enlarged view of the ring of the ball joint type piston in Fig. 1, and Fig. 3 is a ball joint obtained by the manufacturing method according to the present invention. FIG. 2 is an enlarged view of the main parts of the piston. 1: Connecting rod, 6: Crank pin insertion hole, 10: Main ring part, 11: Through hole, 12: Auxiliary ring part.

Claims (1)

[Scope of Claims] 1. A piston manufacturing method characterized by comprising the following configuration. (a) A process of connecting one end of the connecting rod by welding to the outer surface of the cylindrical main ring part that has a through hole into which the auxiliary ring part is fitted. (b) Fitting the auxiliary ring portion into the through hole of the main ring portion connected to the connecting rod. (c) Forming a crank pin insertion hole that satisfies the required stroke length in the auxiliary ring part fitted to the main ring part.