JPH09303555A - Piston - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reliability of a piston. SOLUTION: The end edges 122 and 132 opposing to the pin holes 121 and 131 of a pin bosses 12 and 13 which are formed at the inner side of a piston 11 are inclined to separate each other as withdrawing from the top surface 111 of the piston. At the positions 16 and 17 at the end edges 122 and 132 at the piston top surface 111 side, recesses 18 and 19 for stress dispersion are provided. The recesses 18 and 19 for stress dispersion are formed by cutting in the redial direction of the pin holes 121 and 131 from the pin holes 121 and 131, so as to cross with the end edges 122 and 132. The wall surfaces 181 and 191 of the recesses 18 and 19 for stress dispersion connecting to the pin holes 121 and 131 are made in curved surfaces reversing at the bottom side of the pin holes 121 and 131.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston having a pair of pin bosses formed inside a piston and having a piston pin penetrating through the pin hole.

[0002]

2. Description of the Related Art An example of this type of piston for an internal combustion engine is disclosed in Japanese Utility Model Laid-Open No. 6-22549. As shown in FIG. 7, the piston pin 14 penetrating through the pin holes 121 and 131 of the pair of pin bosses 12 and 13 formed inside the piston 10 causes the explosion pressure in the piston top surface 101 due to the explosion in the piston cylinder. receive. This explosion pressure is transmitted to the piston rod 15 via the piston 10 and the piston pin 14.

[0003]

During the transmission of the explosion pressure, the piston pin 14 is flexibly deformed as shown by the chain line. The bending deformation of the piston pin 14 is caused by the pin holes 121, 1
A strong local hit is provided between the piston pin 14 and the portions 16 and 17 on the piston top surface 101 side of the opposed edges 122 and 132 of 31. This local contact is in a state of striking linearly strongly, and a strong tensile stress concentrates on the above-mentioned site. This concentrated tensile stress causes a crack starting from the portions 16 and 17.

An object of the present invention is to prevent the occurrence of the above-mentioned cracks and improve the reliability of the piston.

[0005]

To this end, according to the first aspect of the present invention, a stress-dispersing concave portion is provided at a portion of the pair of pin bosses formed inside the piston on the side of the top surface of the piston at the opposing edge of the pin holes. It was

The piston pin flexibly deformed due to the explosion in the piston cylinder hits strongly against the piston top surface side portion of the end edge of the pin hole, but the stress distribution concave portion distributes the tensile stress generated by the hit. This action of dispersing the tensile stress prevents the occurrence of cracks at the above-mentioned site.

According to the second aspect of the present invention, the stress-dispersing recess is formed by cutting the pin hole in the radial direction of the pin hole so as to intersect with the end edge, and the wall surface of the stress-dispersing recess that is continuous with the pin hole is defined as the pin hole. The curved surface is inverted on the back side.

The opening edge of the stress dispersion concave portion on the peripheral surface of the pin hole has a substantially U shape. When the piston pin flexibly deformed due to the explosion in the piston cylinder hits strongly against the piston top surface side portion of the end edge of the pin hole, the stress dispersion concave portion is expanded and deformed. The curved surface shape of the inverted portion of the substantially U-shaped wall surface contributes to the dispersion of the stress due to the expansion deformation.

According to the third aspect of the present invention, the wall surfaces of the stress-dispersing concave portions that are inclined with respect to each other and in which the facing edges are inclined so as to be separated from each other as they move away from the piston top surface,
The shape is such that it expands as it goes away from the inner wall surface of the stress distribution recess for the pin hole, and it is closer to the opposing stress distribution recess side in the longitudinal direction of the piston pin than the portion of the end edge opposite to the piston top surface. A concave portion for stress dispersion was provided at the position.

Generally, the piston is formed by molding, but the inclination of the end edge, the shape of the wall surface of the stress dispersion concave portion connected to the pin hole, and the position of the stress dispersion concave portion are set for the stress dispersion. It becomes possible to mold the recess.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. The same components as those in FIG. 7 are designated by the same reference numerals.

As shown in FIG. 1A, the pin holes 121, 13 of the pin bosses 12, 13 formed inside the piston 11 are
Opposing edges 122 and 132 of 131 are inclined so as to be separated from each other as the distance from the piston top surface 111 increases. As shown in FIG. 1 (b), each edge 122, 13
In portions 16 and 17 of the piston 2 on the piston top surface 111 side, stress dispersion recesses 18 and 19 are provided.

The stress-dispersing recesses 18 and 19 are provided at the end edge 12.
It is formed by cutting from the pin holes 121 and 131 in the radial direction of the pin holes 121 and 131 so as to intersect with 2, 132. Stress-dispersing recess 1 connected to the pin holes 121 and 131
The wall surfaces 181, 191 of 8, 19 have pin holes 121, 13
It is a curved surface that is inverted on the back side of 1. That is, the pin hole 1
Stress-dispersing recesses 18, 19 on the peripheral surfaces of 21, 131
The opening edges 183 and 193 are substantially U-shaped.

The stress-dispersing recess 18 is opposed to the stress-dispersing recess 1 in the longitudinal direction of the piston pin 14 in the longitudinal direction of the piston pin 14 rather than the portion 20 of the end edge 122 opposite to the piston top surface 111.
It is located near the 9 side. Similarly, the stress dispersion recesses 19
Is closer to the opposing counterpart stress dispersion recess 18 side in the longitudinal direction of the piston pin 14 than the portion 21 of the end edge 132 opposite to the piston top surface 111. And
Stress dispersion recesses 18 and 1 connected to the pin holes 121 and 131
The wall surfaces 181 and 191 of the inner wall surface 181, 191 of the inner wall surface 182, 192 of the recesses 18, 19 for stress dispersion with respect to the pin holes 121, 131, respectively.
The shape is such that it expands as it moves away from it.

When the explosion pressure acts on the piston top surface 111, the piston pin 14 is flexibly displaced as shown by a chain line in FIGS. Due to this bending displacement, the stress-dispersing concave portions 18 and 19 are expanded and deformed as shown by a chain line.

A curve E in FIG. 4 is a stress dispersion concave portion 18, 1.
9 shows the tensile stress generated in the portions 16 and 17 when 9 is present. The curve D represents the tensile stress generated in the portions 16 and 17 when the stress dispersion recesses 18 and 19 are not provided. The horizontal axis represents the position from the position P1 in the circumferential direction of the pin holes 121 and 131 shown in FIG. 2 to the position P2. Position Q1, Q
2 indicates the positions of the opening edges 183 and 193. The vertical axis represents tensile stress.

The following effects are obtained in the first embodiment. (1-1) Piston pin 1 flexed and deformed by explosive pressure
4 strongly hits the portions 16 and 17 of the end edges 122 and 132 of the pin holes 121 and 131 on the piston top surface 111 side. At this time, the stress-dispersing concave portions 18 and 19 are expanded and deformed as shown by a chain line in FIGS. 2 and 3, and the peripheral surface of the piston pin 14 is in contact with the expanded and deformed opening edges 183 and 193. . Therefore, the presence of the stress-dispersing recesses 18 and 19 increases the contact ratio between the peripheral surface of the piston pin 14 and the end edges 122 and 132 as compared with the case where the stress-dispersing recesses 18 and 19 are not present, and the curve E of FIG. The tensile stress is dispersed as shown by. This action of dispersing the tensile stress prevents the occurrence of cracks in the portions 16 and 17 on the piston top surface 111 side. As a result, the reliability of the piston 11 is improved. (1-2) The wall surfaces 181 and 191 of the stress-dispersing recesses 18 and 19 connected to the pin holes 121 and 131 are attached to the pin holes 121 and 13, respectively.
In the configuration in which the curved surface is inverted on the inner side of 1, the curved surface shapes of the inverted portions 184 and 194 of the substantially U-shaped wall surfaces 181 and 191 contribute to the dispersion of the stress associated with the expansion deformation of the stress distribution recesses 18 and 19. To do. (1-3) The wall surfaces 181 and 191 of the stress dispersion recesses 18 and 19 connected to the pin holes 121 and 131 are the pin holes 121 and 1, respectively.
The inner wall surface 18 of the stress dispersion recesses 18 and 19 with respect to 31
The shape is such that it spreads away from 2,192. The stress-dispersing recesses 18 and 19 having such an expanded shape
Is for the purpose of stress distribution of the opposing partner in the longitudinal direction of the piston pin 14 in the longitudinal direction of the end portions 122, 132 of the end edges 122, 132 which are inclined so as to separate from each other as they move away from the piston top surface 111. It is provided at a position close to the recess side. Therefore, the stress dispersion concave portion 1
The mold portions corresponding to the stress-dispersing recesses 18, 19 can be extracted in the direction of the central axis L of the piston 11 from 8, 8, and the piston 11 can be formed by molding together with the stress-dispersing recesses 18, 19. Stress dispersion recess 18,
The structure capable of molding 19 does not require the formation of the stress dispersion recesses 18 and 19 after molding the piston 11,
The manufacturing process of the piston 11 is simplified. In addition, the molding of the stress-dispersing recesses 18, 19 is performed by molding the stress-dispersing recesses 18, 19
Results in high precision formation.

Next, a second embodiment shown in FIG. 5 will be described. The same components as those in the first embodiment are denoted by the same reference numerals. In this embodiment, the stress dispersion recesses 18, 1
The reversal portions 184 and 194 of 9 enter the inner side of the pin holes 121 and 131 more than the portions 20 and 21 of the end edges 122 and 132 on the side opposite to the piston top surface 111. Then, the cutout grooves 22 and 23 in which the expanded shapes of the stress dispersion recesses 18 and 19 are extended in the direction of the central axis L of the piston 11 as they are are the end edges 122 and 132 on the side opposite to the piston top surface 111. 20 and 21 are formed.
The presence of the grooves 22 and 23 means that the stress-dispersing recesses 18 and 19
It is possible to pull out the mold part corresponding to the direction of the central axis L of the piston 11.

The following effects are obtained in the second embodiment. (2-1) The same effect as in the first embodiment can be obtained. (2-2) Pin hole 12 relating to the stress dispersion recesses 18 and 19
The amount of penetration of 1,131 into the back side is large, and the contact ratio between the piston pin 14 and the opening edges 183, 193 when the stress dispersion recesses 18, 19 are expanded and deformed is larger than that in the first embodiment. Will also be higher.

Next, a third embodiment shown in FIG. 6 will be described. The same components as those in the first embodiment are denoted by the same reference numerals. In this embodiment, the stress dispersion recesses 24, 2
5, the inner wall surfaces 241 and 251 are pin holes 121 and 13
The curved surface smoothly connects to the wall surface 242 connected to 1. The other configurations of the stress-dispersing recesses 24 and 25 are the same as those of the first embodiment.

The following effects can be obtained in the third embodiment. (3-1) The same effect as the first embodiment can be obtained. (3-2) In the configuration in which the inner wall surfaces 241 and 251 of the stress distribution recesses 24 and 25 with respect to the pin holes 121 and 131 are curved surfaces that are inverted, the curved surface shapes of the inner wall surfaces 241 and 242 correspond to the stress distribution recesses 24 and 25. It contributes to the dispersion of stress associated with the expansion deformation.

[0022]

As described in detail above, according to the present invention, since the stress dispersion concave portion is provided at the piston top surface side portion at the opposing edges of the pin holes of the pair of pin bosses formed inside the piston, The tensile stress generated at the edge due to the explosion pressure is dispersed to prevent the occurrence of cracks at the site, and the excellent effect of improving the reliability of the piston is achieved.

[Brief description of drawings]

FIG. 1 shows a first embodiment, in which (a) is a side sectional view.
(B) is a perspective view of a main part.

FIG. 2 is an enlarged sectional view taken along line AA of FIG.

FIG. 3 is a diagram showing the shape and expansion deformation of a stress dispersion recess.

FIG. 4 is a graph showing tensile stress.

FIG. 5 is a side sectional view showing a second embodiment.

FIG. 6 is an enlarged cross-sectional view of an essential part showing a third embodiment.

FIG. 7 is a side sectional view showing a conventional piston.

[Explanation of symbols]

11 ... Piston, 111 ... Piston top surface, 12, 13 ...
Pin bosses, 121, 131 ... Pins, 122, 132 ... Edges, 14 ... Piston pins, 18, 19, 24, 25 ... Stress dispersion recesses, 181, 191 ... Wall surfaces, 182, 192
… The inner wall.

Claims (3)

[Claims] 1. A piston for penetrating a piston pin into a pair of pin holes of a pin boss formed inside the piston, wherein a stress-dispersing concave portion is provided at a portion on the piston top surface side of the opposing edge of the pin hole of each pin boss. The piston provided. 2. The stress-dispersing recess is formed by cutting from the pin hole in the radial direction of the pin hole so as to intersect with the end edge, and the wall surface of the stress-dispersing recess that is continuous with the pin hole is on the inner side of the pin hole. The piston according to claim 1, wherein the piston has a curved surface that is inverted by. 3. The opposed edges are inclined so as to be separated from each other as they move away from the top surface of the piston, and the stress dispersion concave portion is formed at a position closer to the piston than the top surface of the end edge of the piston. The wall surface of the stress-dispersing recess, which is located near the opposing stress-dispersing recess side in the longitudinal direction of the pin and is continuous with the pin hole, widens away from the inner wall surface of the stress-dispersing recess with respect to the pin hole. And the piston according to claim 2.