JPH06101566A - Piston for internal combustion engine - Google Patents

Abstract

PURPOSE:To cause a piston to fully abut on the inner peripheral surface of a cylinder along its overall length in the vertical direction by causing a top and second land to have their profiles inclined along the inclination of the profile of the upper end of a skirt portion. CONSTITUTION:A land portion 11 and a skirt portion 12 are discontinuously formed and a plurality of lands 23-25 are formed on the outer periphery of the land portion 11 and partitioned by a plurality of ring grooves 21, 22. The skirt portion 12 has a single skirt surface 32, 33 along the vertical direction. Of the plurality of lands 23-25, at least the top land 23 and the second land 24 have their profiles inclined along the inclination of the profile of the upper end of the skirt portion 12. Therefore, the top land 23 and the second land 24, both of which have their profiles inclined, stabilize the behavior of a piston, and the skirt surface 32, 33 is so wide that pressure applied to the surface can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston for an internal combustion engine.

[0002]

2. Description of the Related Art As a prior art relating to the present invention, for example, a "piston" disclosed in GB2164419A is disclosed.
There is. This prior art will be described with reference to FIG. 3. The piston 70 has a discontinuous land portion 71 and a skirt portion 72, and they are connected to each other by a support portion 73. Ring grooves 71a, 71 are formed on the outer periphery of the land portion 71.
b, 71c are processed and formed, and lands 71d, 71e, 7 are formed.
1f and 71g are divided. On the other hand, the skirt portion 72 is divided into skirt surfaces 72a and 72b.

In such a piston 70, since the skirt portion is divided and discontinuous, the skirt surfaces 72a, 72a when the piston is mounted on the engine and operated.
In order to secure an oil film on b, the outer surface of the piston 70 needs to have a profile as shown in FIG. That is,
The skirt surfaces 72a and 72b are respectively provided with a profile 74.
Skirt surface 72a, 7 as a barrel shape like a, 74b
An oil film is easily formed and retained on 2b. However, in the case of such profiles 74a and 74b, matching is difficult, and the contact area with respect to the cylinder surface decreases, so that the surface pressure rises, and conversely it becomes difficult to hold the oil film. As a result, the skirt surface 72
Scratch wear is likely to occur on a and 72b. Further, the profile has to be stepped over the entire axial length of the piston 70, and the posture of the piston 70 in the cylinder becomes unstable.

Another conventional technique in which the land portion and the skirt portion are divided is the "piston for internal combustion engine" disclosed in Japanese Patent Laid-Open No. 62-225753.

[0005]

Therefore, in the present invention, stabilization of the behavior of the piston is a technical subject.

[0006]

The technical means of the present invention taken to solve the above-mentioned technical problems of the present invention is such that the land portion and the skirt portion are formed discontinuously and the land portion outer periphery is formed. In a piston for an internal combustion engine in which a plurality of lands are defined by a plurality of ring grooves, the skirt portion has a single skirt surface in the vertical direction, and at least the top land and the second land of the plurality of lands are profiled. That is, the inclination of is continuous with the inclination of the profile at the upper end of the skirt.

[0007]

According to the above-mentioned technical means of the present invention, a skirt portion having a single skirt surface in the vertical direction, and a top land and a second land having a profile inclination continuous with the inclination of the profile at the upper end of the skirt portion are provided. The behavior of the piston is stabilized, and the skirt surface is wide and the surface pressure can be kept low.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the technical means of the present invention will be described below with reference to the accompanying drawings.

A piston 1 for an internal combustion engine shown in FIGS. 1 and 2.
0 has a land portion 11 and a skirt portion 12 which are formed discontinuously, and has a support portion 14 and a support portion 14 around the pin boss 13, respectively.
They are integrally connected via 15 and 16. Land part 1
In FIG. 1, a plurality of ring grooves 21 and 22 are formed on the outer circumference of the No. 1 and piston rings (not shown) are respectively inserted therein. The ring groove divides the outer periphery of the skirt portion 12 into the top land 23, the second land 24, and the third land 25. On the other hand, in the skirt portion 12, skirt surfaces 32 and 33 are formed so as to be line-symmetric with respect to the axis of the pin hole 31, and the skirt surfaces 32 and 33 are formed.
Is not divided in the vertical direction of the piston and is single.

The piston 10 is formed by casting and then is finished by cutting the outer surface and the like. The profiles of the top land 23, the second land 24, the third land 25 and the skirt surface 32 (33) are shown in FIG. , P
1, P2, P3 and P4. Also, for comparison with the prior art, J1, J2 and J3 show the profiles of the land of the prior art. In FIG. 1, the profile is drawn at a higher magnification for easier understanding. First, the profile P of the skirt surface 32 (33)
Describing No. 4, the central portion is vertical and serves to enhance the posture retention with respect to a cylinder surface (not shown) and reduce the surface pressure. However, the upper and lower ends of the profile P4 are slightly curved inward of the piston 10, and the piston 1
The oil film retention is improved during the actual operation of 0. On the other hand, of the profiles P1, P2, P3 of the land portion 11, at least the slopes of the profiles P1, P2 of the top land 23 and the second land 24 are made continuous with the slope of the upper end of the profile P4 of the skirt surface 32 (33). ing. By setting the profiles P1 and P2 in this way, the land portion 11 can easily hit the cylinder, and the posture of the piston 10 in the cylinder can be further stabilized. Compared with the conventional profiles J1 and J2,
You can see how this looks. The profile of the third land 25 may be the conventional profile J3, or may be the profile P3 continuous with the inclination of the upper end of the profile P4 of the skirt surface 32 (33).
A resin coat may be applied to the top land 23, the second land 24, the third land 25, and the skirt surface 32 (33).

[0011]

As described above, in the piston for an internal combustion engine of the present invention, the skirt has a single skirt surface in the vertical direction, and the inclination of the profile of at least the top land and the second land is the inclination of the profile at the upper end of the skirt. Since it is continuous with the piston, it can hit the inner peripheral surface of the cylinder well over the entire length in the vertical direction of the piston, and the behavior is very stable. At the same time, the oil film retainability is improved and the piston does not seize.

[Brief description of drawings]

FIG. 1 is a partial sectional view of a piston for an internal combustion engine according to an embodiment of the present invention and a profile of an outer surface of the piston.

FIG. 2 shows a bottom view of FIG.

FIG. 3 shows a cross-sectional view of a prior art piston and a profile of the outer piston surface.

[Explanation of symbols]

 10 piston for internal combustion engine, 11 land part, 12 skirt part, 21, 22 ring groove, 23 top land, 24 second land, 25 third land, 32, 33 skirt surface.

Claims (1)

[Claims] 1. A piston for an internal combustion engine in which a land portion and a skirt portion are discontinuously formed, and a plurality of lands are defined by a plurality of ring grooves on the outer periphery of the land portion, wherein the skirt portion is a vertical direction. Has a single skirt face,
In addition, the piston for an internal combustion engine, wherein at least the profile of each of the top land and the second land of the plurality of lands is continuous with the profile of the profile at the upper end of the skirt portion.