JPH0518464A - Piston pin supporting structure of internal combustion engine - Google Patents

Abstract

PURPOSE:To provide a lightweight piston without impairing the strength around clip fitting groove of a pin boss by forming clip grooves with the whole in approx. C-form while the land is left on the head side of a piston. CONSTITUTION:A left and a right clip groove 28, 29 are so formed that the whole assumes an approx. C-forms while the land 40 is left on the head side of a piston 13. In the piston pin 27 supporting structure, the thickness of the wall 13A between a ring groove 14 and the place where clip grooves are formed remains the same as any conventional arrangement even though pin holes 23, 24 are shifted toward the ring groove 14, i.e., to the head side of the piston, by an amount leaving the land 40. Accordingly the pin hole 23 can be shifted toward the ring groove 14, i.e., to the piston head side, while the strength around the clop grooves can be kept about the same as the conventional, and thereby the piston 13 be constructed in light weight.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Generally, in an internal combustion engine intended for high output in a high rotation range, a piston receives a large amount of explosive energy in an explosive combustion stroke and a reciprocating member including a piston, a connecting rod, etc. Much more inertial force is applied. This force also acts on the pin boss and the piston pin supported by the pin boss. For this reason, the pin boss or the like needs to be strong enough to resist such inertial force.

By the way, a retaining ring such as a circlip is fitted to the inner circumference of the pin boss to regulate the axial movement of the piston pin. In that case, since the clip fitting groove is formed in the pin boss, the strength around the pin boss may be reduced. As means for countering such a decrease in strength, for example, as shown in FIG. 6, the clip fitting groove 1 is arranged so as to avoid the lower part of the ring groove 2 and be displaced inward of the piston 3 from that, or as shown in FIG. As shown in 7,
By widening the space between the center of the pin hole 4 of the piston 3 and the ring groove 2, the wall thickness W of the wall 5 existing between the clip fitting groove 1 and the ring groove 2 is ensured to be a necessary amount. It is possible.

[0004]

However, all the above-mentioned means have the following problems. That is, in the former case, the length of the piston pin 7 becomes shorter as the clip 6 is displaced inward of the piston 3, and as a result, the catching margin L between the piston pin 7 and the pin boss 8 becomes smaller. In the latter case, the total weight of the piston 3 increases as the total height of the piston 3 increases. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a piston pin support structure for a piston in an internal combustion engine, in which the weight of the piston can be reduced without reducing the strength around the clip fitting groove of the pin boss. To do.

[0005]

[Means for Solving the Problems] The clip groove is formed so as to have a substantially C-shape as a whole while leaving a land portion on the head side of the piston.

The clip groove is formed by leaving the unprocessed land portion on the ring groove side without extending over the entire circumference of the pin hole, so that the pin hole is formed by the amount corresponding to the land portion. Even if it shifts to the groove, that is, to the piston head side, the thickness of the wall between the portion where the ring groove and the clip groove are formed is the same as the conventional one.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an internal combustion engine having a so-called elliptic piston will be described below with reference to the drawings. In FIGS. 1 and 2, a cylinder hole 10 having an oval cross section is formed in a cylinder block 10, and a piston 13 having an oval cross section is also slidably fitted in the cylinder hole 12. As shown in FIG.
As shown in FIG.
Ring grooves 14, 15 and 16 are formed in the second and third ring grooves 15 and 16 and a pressure ring 17 is also formed in the first and second ring grooves 15 and 16, respectively.
Oil rings 18 are fitted in the ring grooves 14, respectively.

Inside the piston 13, right and left ends and intermediate pin bosses 19, 20 and 21, 2 are arranged along the major axis direction.
2 are integrally formed, and pin holes 23, 24 and 25 formed in the pin bosses 9, 20 and 21, 22 are formed.
The piston pin 27 is laid sideways through the 26. The pin holes 23 and 24 of the left and right pin bosses 19 and 20 are provided with specially shaped clip grooves 28 and 29, which will be described later in detail. 30 are fitted and these snap rings 30
Engages with both end faces of the piston pin 27 to prevent axial sliding thereof.

The piston pin 27 has two connecting rods 3
The small ends of 1a and 31b are connected, and the large ends of these connecting rods 31a and 31b are connected to the crankshaft 32. Incidentally, 33a and 33b are other connecting rods connected to the crankshaft 32, and these are the cylinder block 1
It is connected to a piston in another cylinder block (not shown) arranged in a V-shape.

A cylinder head 34 is fitted on the upper part of the cylinder block 11 via a gasket, and a combustion chamber wall 35 formed on the lower surface of the cylinder head 34 and an upper surface of the piston 13 form a combustion chamber 36. .. In the combustion chamber 36 above the piston 13, four intake valves 37 are provided in one half portion in the short axis direction along the longitudinal direction and in the other half portion in the short axis direction in the longitudinal direction. Four exhaust valves are provided along each of them, and recesses 39a and 39b are formed on the upper surface of the piston 13 for avoiding interference with the intake and exhaust valves 37 and 38 (FIG. 3). reference).

The structure of the clip grooves 28, 29 formed in the pin holes 23, 24 of the left and right pin bosses 19, 20 will be described. The left and right clip grooves 28 and 29 have the same structure. Here, the left clip groove 28 is used.
Will be described and the description of the other side will be omitted. Clip groove 28
Is formed so as to have a substantially C-shape as a whole, except for the land portion 40 on the head side of the piston 13. Further, the distance M from the outer end of the pin hole 23 to the center of the clip groove 28
Is set to be smaller than the depth N of the ring grooves 14, 15, 16. That is, the position of the clip groove 28 is determined so that the clip groove 28 overlaps the ring groove 14 when viewed from the upper surface or the lower surface. In the figure, Z indicates a cutter for processing the clip groove 28. In this way, by using the cutter Z having a diameter smaller than that of the pin hole 23 and leaving the unprocessed portion on the upper portion, the land portion can be easily formed.

According to the piston pin support structure having the above structure, however, the land portions 40 are left on the side of the ring groove 14 in order to form the clip grooves 28 and 29 without extending over the entire circumference of the pin holes 23 and 24. Since it is formed by
Even if the pin holes 23 and 24 are displaced toward the ring groove 14 side, that is, the piston head side by the amount of 0 left, the thickness of the wall 13A between the portion where the ring groove 14 and the clip groove are formed is It is the same as the one (value shown by W in FIG. 7). Therefore, the pin hole 23 can be displaced to the ring groove 14, that is, the piston head side while maintaining the strength around the clip groove to the same level as the conventional one, so that the weight of the piston 13 can be reduced.

In addition, the distance M from the outer ends of the pin holes 23 and 24 to the centers of the clip grooves 28 and 29 is defined by the ring groove 14
Is set to be smaller than the depth N of the clip groove 2, and the clip groove 2 is placed at a position overlapping the ring groove 14 when viewed from the upper surface or the lower surface.
8 is formed, it is possible to use a piston pin having a length similar to that of the conventional one shown in FIG.
The problem shown in the example of FIG. 6 in which the catching margin between the piston pin and the pin boss is shortened does not occur. In addition,
In the above embodiment, an example in which the present invention is applied to a so-called elliptical piston is described, but the present invention is not limited to this, and the present invention can of course be applied to one using a normal circular piston.

[0013]

As described above, according to the present invention, since the clip groove is formed so as to have a substantially C-shape as a whole, leaving the land portion on the head side of the piston, the land portion is formed. Even if the pin hole is shifted to the ring groove, that is, the piston head side by the amount of the above, the wall thickness from the place where the clip groove is formed to the ring groove can be made approximately the same as the conventional one. Therefore, the weight of the piston can be reduced while maintaining the strength around the clip groove to the same level as the conventional one.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a plan view of the piston of the same embodiment.

3 is a cross-sectional view taken along the line AA of FIG.

FIG. 4 is an enlarged cross-sectional view of a main part of the same embodiment.

5 is a cross-sectional view taken along the line BB of FIG.

FIG. 6 is a cross-sectional view showing a conventional example.

FIG. 7 is a cross-sectional view showing a conventional example.

[Explanation of symbols]

 10 Cylinder Block 12 Cylinder Hole 13 Piston 14 Ring Groove 15 Ring Groove 16 Ring Groove 19 Pin Boss 20 Pin Boss 23 Pin Hole 24 Pin Hole 27 Piston Pin 28 Clip Groove 29 Clip Groove 30 Retaining Ring (Clip) 40 Land Part

Claims (1)

Claim: What is claimed is: 1. A pair of pin bosses are provided on opposite sides of a piston slidably fitted into a cylinder hole of a cylinder block, and a piston pin is inserted sideways into the pin holes formed in the pin boss. , One end of a connecting rod connected to the crankshaft is rotatably connected to the piston pin, and a clip groove is formed in the inner circumference of the pin hole of the pair of pin bosses, and the clip groove engages with the end portion of the piston pin. In an internal combustion engine in which a retaining ring for preventing the piston pin from sliding in the axial direction is fitted, the clip groove is generally C-shaped, leaving a land portion on the head side of the piston. A piston pin support structure for a piston in an internal combustion engine, the structure being formed as follows.