JPH0234516Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to the structure of a bearing between a ceramic piston and a piston pin in which the piston body is made of ceramic, and particularly relates to the structure of a sleeve interposed therebetween. be.

[Prior Art] Generally, sufficient lubrication is required between the piston pin hole and the piston pin to prevent wear and seizure, and it is also necessary to avoid stress concentration as much as possible to ensure sufficient strength. There is.

In order to deal with such problems, traditionally,
A floating bush is inserted between the piston pin hole and the piston pin to ensure lubrication (1986-
83648), inserting a bearing alloy material to prevent wear (Utility Model Application No. 56-167757), and enlarging the piston pin hole inward to avoid stress concentration at the inner end of the piston pin hole. Opened (Utility Model Publication No. 56-113141),
A proposal has been made to form the upper surface of the piston pin hole into a tapered shape (Utility Model Application No. 54-97509).

[Problem to be solved by the invention] However, when the piston body is made of ceramic, ceramic is a material with extremely poor elasticity, so the force from the piston pin causes a large amount of damage to the end of the piston pin hole. Stress concentration will occur, and in the worst case, there is a risk that the ceramic in that area will break. Furthermore, due to the difference in thermal expansion between the ceramic and the piston pin shaft material, there is a problem that the clearance between the piston pin hole and the piston pin cannot be maintained, which may cause seizure of the piston pin.

In order to solve the above-mentioned problems with ceramic pistons, the present invention aims to alleviate the stress concentration applied to the end of the piston pin hole, and to ensure sufficient clearance between the piston pin and the piston pin for smooth rotation. The purpose is to provide a sleeve structure that allows for

[Means for Solving the Problems] The piston pin bearing sleeve of the present invention, which meets this objective, consists of a cylindrical metal sleeve interposed between the piston pin hole of the ceramic piston and the piston pin, and has an axial end surface. It has a groove cut in the axial direction and extends all the way in the circumferential direction, and is made of a low thermal expansion material.

[Function] By inserting a sleeve with such a structure, the stress applied to the piston pin hole is reduced due to the stress relaxation ability of metal, which is much higher than that of ceramic, and the groove provided on the end surface allows the sleeve end to be The bending rigidity of the groove side wall of the piston pin hole is reduced, and the end of the groove side wall can be elastically deformed in the radial direction when subjected to a radial load, so the stress generated on the inner surface of the piston pin hole is reduced, and the edge of the piston pin hole stress concentration is significantly alleviated. In addition, since the sleeve itself is made of a low thermal expansion material, the bearing clearance between it and ceramic, which is also a low thermal expansion material, does not change significantly due to temperature changes, and an appropriate clearance is maintained. rotation is ensured.

[Embodiments] Hereinafter, preferred embodiments of the piston pin bearing sleeve of the present invention will be described with reference to the drawings.

1 and 2 show the structure of a piston pin bearing sleeve according to an embodiment of the present invention. In the figure, 1 is the main body of a ceramic piston made of ceramic material. A piston pin hole 3 is provided in the left and right piston pin boss portions 2 of the ceramic piston 1, and a metal piston pin 4 is inserted into the piston pin hole 3.

A cylindrical sleeve 5 is interposed between the piston pin hole 3 and the piston pin 4 of the ceramic piston 1. The sleeve 5 is made of a low thermal expansion metal material (for example, invar, invar, etc.). As shown in FIG. 2, the sleeve 5 has a groove 6 cut in the axial direction and extending all the way around the circumference in the axial end surface 5a (both end surfaces in the case of this embodiment). ing. In this embodiment, the cross-sectional shape of the groove 6 is approximately U-shaped, and in particular, the groove side surface 6a on the piston pin hole 3 side is
Piston pin hole 3 as it approaches the end face of sleeve 5
It is formed in a tapered shape that approaches the sides.

Note that the depth of the cut of the groove 6 may be appropriately set according to the range in which the rigidity is desired to be weakened, as will be described later.

The operation of the piston pin bearing sleeve configured as described above will be explained below.

A force P is applied to the piston pin 4 as a reaction force of the explosive force, etc.
, and stress is generated between the sleeve 5 and the ceramic piston 1.

Figure 3 shows the distribution of vertical stress on the piston side in the conventional structure without a sleeve.
The figure shows a comparison of the vertical stress distribution according to the present invention. As shown in the figure, in the case of the conventional structure, the piston body material is ceramic, which is a material with extremely poor elasticity, resulting in extreme stress concentration at the end of the piston pin hole 3 (especially at the inner end in the axial direction). arise. Therefore, the maximum stress Pmax becomes large, and as mentioned above, in the worst case, the ceramic will break.

However, according to the present invention, since the sleeve 5 is interposed, first, the stress value applied to the piston pin hole 3 is reduced due to the stress relaxation ability of the metal material, which is much higher than that of ceramic. Further, by providing the groove 6 in the sleeve end surface 5a, the bending rigidity of that portion is reduced and elastic deformation in the radial direction becomes possible. In particular, piston pin hole 3
The elastic deformation of the side wall of the groove 6 on the piston pin hole 3 side is effective in alleviating the stress concentration. By making the wall thickness of this side wall small, the bending rigidity of that part is weakened over a certain width from the end face of the side wall (however, since the wall is continuous in the circumferential direction, it deforms more easily toward the end face, and (If the width is separated, there will be almost no deformation), the force applied from that part to the piston pin hole 3 side is suppressed to a small level, and as a result, the stress distribution applied to the piston pin hole 3 is averaged as shown in Figure 4. become the direction. That is, although the total load is the same, the load is concentrated at the ends and is averaged over the entire load surface. Therefore, the maximum stress Pmax applied to the piston pin hole 3 is also kept low, and stress concentration at the end is avoided. In particular, by tapering the groove surface 6a on the side of the piston pin hole 3, the elastic deformation of the axial end of the groove side wall becomes large, so that stress concentration is effectively alleviated.

[Effect of the invention] Therefore, according to the invention, a sleeve having a groove cut in the axial direction and extending over the entire length in the circumferential direction at the end is interposed between the ceramic piston and the piston pin. As a result, it is possible to alleviate stress concentration at the end of the piston pin hole, and it is possible to significantly increase the possibility of putting ceramic pistons into practical use. That is, stress concentration at the joint between the ceramic and metal piston pin, which is considered to be the biggest problem with heat shield pistons, can be avoided.

In addition, by using a low thermal expansion material for the sleeve, the clearance between the ceramic piston and the sleeve can be kept approximately constant over the low and high temperature range, ensuring smooth rotation and preventing seizure. This effect can also be obtained.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a piston incorporating a piston pin bearing sleeve according to an embodiment of the present invention;
Fig. 2 is an enlarged partial sectional view of the device shown in Fig. 1, Fig. 3 is a stress distribution diagram of the conventional piston pin hole, and Fig. 4 is a stress distribution diagram of the piston pin hole by the device of Fig. 1. be. 1... Ceramic piston, 3... Piston pin hole, 4... Piston pin, 5... Sleeve, 5
a...End face, 6...Groove, 6a...Groove side surface on the piston pin hole side, Pmax...Maximum stress.

Claims (1)

[Scope of utility model registration request] It consists of a cylindrical metal sleeve inserted between the piston pin hole and the piston pin of a ceramic piston, and has a groove cut in the axial direction on the axial end face and extending all the way in the circumferential direction,
A piston pin bearing sleeve characterized in that it is made of a low thermal expansion material.