JPH057097B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method of coupling a ball and a shaft,
The present invention relates to a ball-shaft coupling structure and method suitable for, for example, a ball joint for an internal combustion engine or a piston device.

[Background of the invention]

Piston devices are widely used in automobile compressors and the like, as disclosed in, for example, Japanese Patent Laid-Open No. 55-96377. As shown in FIG. 1 of the above-mentioned publication, the structure consists of a piston part that reciprocates within the cylinder, and a piston rod that mechanically connects the piston part and the swing drive plate.

In the above configuration, since the piston rod mainly performs reciprocating motion, most piston rods are made of steel and have a spherical pair. In the case of a spherical pair like this, it is usually molded in one piece by casting, or
The only method available was to form the ball portion and shaft portion separately from steel and then join them together by welding. However, in the case of casting, it is necessary to cut and polish at least the ball portion in a subsequent process, resulting in extremely low productivity and high costs.

On the other hand, in the case of parts in which the ball part and shaft part were formed separately and joined by welding, it was difficult to achieve the same dimensional accuracy as in the previous example, even though it was easier to mold each part, making it unsuitable for mass production. .
Furthermore, even if a light metal such as aluminum is used for the shaft in order to reduce weight, current welding technology is unreliable in joining aluminum and steel materials, making it almost impossible to put it to practical use.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a ball-shaft coupling method that has good dimensional accuracy and is excellent in mass productivity.

[Summary of the invention]

In the present invention, the mounting hole provided toward the center of the ball is formed with a material that is softer than the material of the ball, and has an enlarged diameter stepped portion at the tip having dimensions approximately equal to the diameter and depth of the mounting hole. Then, a force perpendicular to the upper surface of the enlarged diameter stepped portion of the shaft is applied by a pressing die to locally plastically deform the material of the enlarged diameter stepped portion in the radial direction. This method of connecting a ball and a shaft is characterized in that a tension force is applied between the two, and then the two are connected by cold forming.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 shows a method of connecting balls and shafts in a piston device for an automobile compressor. In the figure, a ball 1 is made of steel, and a mounting hole 1A with a depth of several mm is formed from its outer periphery toward the center, and the hole diameter is the diameter of the tip of a shaft 2 made of aluminum material. The outer shape of the portion 21 is approximately the same. Here, the shaft 2 is made of at least a softer material than the ball material, and is easily plastically deformed during joining, which will be described later, and is designed to maintain the accuracy of the ball by not applying more than necessary plastic deformation pressure to the ball. On the other hand, since it has a paired structure, the ball 3 is arranged on the opposite side of the shaft 2 as well, and is fitted in the same manner.

The mounting holes 1A formed in the balls 1 and 3 are machined using a lathe or the like, and an annular W groove 1B (see FIG. 2) is formed in the middle of the inner peripheral surface thereof. The enlarged diameter stepped portion 21 of the shaft 2 is fitted into the mounting hole 1A, and the outer peripheral portion 2A of the shaft 2 is locally plastically deformed around the annular groove 1B, thereby creating a tension force around the annular groove and between the two. It is firmly connected.

Next, the method of connecting the ball and shaft according to the present invention will be explained with reference to FIG.

First, as shown in FIG. 3, a pair of hollow molds 4,
After the shaft 2 is held in a sandwiched manner by the shaft 2, the mounting hole 1A of the ball 1 is fitted into the enlarged diameter stepped portion 21 of the shaft 2, and they are inserted and placed together into the cylindrical receiving mold 5. On the other hand, a hemispherical hole 5A, which is equal to the spherical surface of the ball, is provided at the center of the bottom surface of the receiving mold 5, and receives the ball 1.

Further, the press molds 4, 41 have male teeth 4A, 41A at the peripheral edge of the lower end surface along the inner diameter thereof, and are arranged so as to fill the gap between the mounting hole 1A of the ball 1 and the shaft 2. The connection between the ball 1 and the shaft 2 is achieved by lowering the press molds 4, 41, and the male teeth 4A, 41
A locally presses the entire circumference of the upper surface 2B of the enlarged diameter stepped portion 21 vertically. Then, the compressed material locally plastically flows at right angles to the pressing direction, and the tensile force of the material flowing around the protrusion created by the formation of the annular W groove 1B and in the gap between the shaft tip and the mounting hole is exerted. They are also rigidly connected.

After the connection of one ball is completed, press molds 4, 41
The combined shafts 2 are then removed, turned over, and combined in the same working order as described above.

The piston device thus obtained is advantageous when joining dissimilar metals, and it is possible to join balls and shafts made of any metal, making it ideal for weight reduction.

Further, the mounting hole 1A provided in the ball 1 is provided facing the central axis, and the enlarged diameter stepped portion 21 of the shaft 2 is fitted therein, and the upper surface 21B of the enlarged diameter stepped portion 21 is connected to the press mold 4. , 41 concentrically and locally, and is plastically deformed in the radial direction and is bonded to the ball's mounting hole 1A, so no more bonding pressure is applied to the outer periphery of the ball than necessary, and product accuracy is improved. This makes it suitable for mass production. As for the joining method, since the joining members are plastically deformed by cold pressing, the joining is extremely effective regardless of the material used. In the above embodiment, the annular W groove 1B was formed on the inner peripheral surface of the mounting hole 1A of the ball 1, but the surface may be roughened by electrical discharge machining instead, or the mounting hole may be roughened by cutting. In some cases, the roughness of the cut surface is sufficient. However, if sufficient strength is required, it is reasonable to form grooves while cutting.

Further, in the embodiment, the connection of steel material and aluminum material has been described in the form of a pair of spherical surfaces, but only one side may be spherical, and the constituent materials may be a combination of steel material and steel material. However, in the case of steel materials, either the mounting hole or the shaft should be carburized.
A simple and effective method is to let it harden.
Therefore, if the outer circumference of the shaft is carburized,
The ball is joined by plastic deformation around the mounting hole. In this case, a carburized layer is usually formed on the ball surface, and the same effect on bonding can be expected.

〔Effect of the invention〕

According to the present invention, there is provided a method for connecting a ball and a shaft with good dimensional accuracy, excellent mass productivity, and strong connection.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is an exploded perspective view of a piston device, FIG. 2 is a half-longitudinal cross-sectional view showing the process of joining the parts in FIG. 1, and FIG. FIG. 1...Ball, 2...Shaft, 1A...Mounting hole, 1
B...Annular groove, 4A, 41A...Male teeth, 21...Enlarged diameter stepped portion, 2B...Upper surface of enlarged diameter stepped portion.

Claims (1)

[Scope of Claims] 1. A mounting hole provided toward the center of the ball has an enlarged diameter step formed of a material softer than the material of the ball and having dimensions approximately equal to the diameter and depth of the mounting hole at the tip. Fitting the enlarged diameter stepped portion of the shaft with the attached portion formed thereon, and then applying a force perpendicular to the upper surface of the enlarged diameter stepped portion of the shaft using a press die;
A method for joining a ball and a shaft, comprising locally plastically deforming the material of the diameter-enlarging stepped portion in the radial direction to apply tension between the two, and then joining the two by cold forming. 2. The ball and shaft according to claim 1, characterized in that the mounting hole has an annular unevenness on its inner circumferential surface, and the shaft that has been plastically deformed is tightly coupled at the unevenness. How to combine.