JPH10141134A - Piston for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of seizure and reduce friction. SOLUTION: A piston 1 is provided with a ring land 3 on the side of top surface part 2 and a skirt part 4 contiguous to the part 3. The skirt part has an apron part 8 at which a piston hole 10 is opened. At the ring land part 3 an oil ring groove 7 is formed. In the groove 7 positioned at an upper side of the skirt part on the thrust side continuous to the apron part 8, an oil hole 13 is formed. The oil hole 13 is formed to extend partially in its circumferential edge 13a to the side of the skirt part 4 passing through a side surface of the groove T and reach a bottom surface of the groove 7.

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, and more particularly to a piston capable of preventing seizure and reducing friction.

[0002]

2. Description of the Related Art A piston for an internal combustion engine is arranged in a cylinder with a predetermined gap, and reciprocates in the cylinder. At this time, since the connecting rod supports the piston in a tilted state, the piston reciprocates while being pressed against the inner surface of the cylinder by the side force.

In the above-mentioned motion state, if the side force is large and the lubrication between the piston and the inner surface of the cylinder is not good, seizure may occur.

Therefore, in order to keep the lubrication state between the piston and the inner surface of the cylinder in a good state and prevent seizure, for example, Japanese Utility Model Laid-Open Publication No. 1-71157 discloses a method in which a lower surface of an oil ring groove is notched. A piston having an oil hole reaching the bottom of the oil ring groove has been proposed.

In the above conventional piston, an oil hole reaching the bottom of the oil ring functions as an oil reservoir, and a lubricating oil film is formed between the piston and the inner surface of the cylinder to prevent seizure. And

[0006]

However, the oil hole of the prior art is formed above the apron portion (side cut portion) connecting the pin boss portion and the skirt portion.

For this reason, the lubricating oil (engine oil) discharged from the oil hole escapes to the apron portion in the gravitational direction without contributing to the formation of an oil film on the skirt when the piston reciprocates vertically. As a result, the expected lubricating effect may not be obtained.

The present invention has been devised in view of such conventional circumstances, and has as its object to provide a piston for an internal combustion engine capable of preventing seizure and reducing friction. I do.

[0009]

In view of the above, the invention according to claim 1 includes a ring land portion on the crown surface side and a skirt portion following the ring land portion, and a piston pin hole is formed in the skirt portion. An apron portion is formed, and in the piston for an internal combustion engine in which an oil ring groove is formed in the ring land portion, in an oil ring groove located above a thrust side skirt portion following the apron portion, A part of the periphery extends to the skirt portion side beyond the side surface of the oil ring groove, and an oil hole whose bottom surface reaches the bottom surface of the oil ring groove is formed. It has a configuration.

Further, the invention according to claim 2 has a configuration in which, in the structure of the invention according to claim 1, the axis of the piston pin hole is offset to the anti-thrust side with respect to the axis of the piston. It has a configuration.

According to a third aspect of the present invention, in the configuration of the first aspect of the present invention, a part of a peripheral edge is provided in the oil ring groove at a position substantially symmetric with the oil hole with respect to the axis of the piston. Extends to the skirt portion side beyond the side surface of the oil ring groove, and has a configuration in which a through hole penetrating through the inner peripheral side of the piston is formed.

According to a fourth aspect of the present invention, in the configuration of the first aspect of the invention, the axis of the piston pin hole is offset on the anti-thrust side with respect to the axis of the piston. On the other hand, in the oil ring groove at a position substantially symmetric to the oil hole, a part of the peripheral edge extends to the skirt portion side beyond the side surface of the oil ring groove, and a through hole is formed to penetrate the inner peripheral side of the piston. It is. It has a configuration.

According to the present invention, since the oil hole is formed in the oil ring groove located above the skirt portion on the thrust side, the oil hole functions as a lubricating oil (engine oil) reservoir, and the piston and the cylinder A good lubricating oil film is formed on the contact surface with the inner surface, seizure is advantageously prevented, and friction is reduced.

At this time, since the oil hole is formed in the oil ring groove located above the skirt portion,
The oil discharged from the oil hole during the reciprocating sliding of the piston can effectively lubricate the skirt without escaping to the apron.

Accordingly, a piston for an internal combustion engine that can prevent seizure and reduce friction can be obtained.

Further, since a part of the peripheral edge a of the oil hole extends to the skirt side beyond the side surface of the oil ring groove, the oil taken in the oil ring groove is efficiently stored in the oil hole. be able to.

Further, since the bottom surface of the oil hole is formed so as not to penetrate the inner peripheral side of the piston beyond the bottom surface of the oil ring groove, the volume of the oil hole increases, and a large amount of oil is contained in the oil hole. Can be stored.

According to the third and fourth aspects of the present invention, the through-hole is formed in the oil ring groove at a position substantially symmetrical with the oil hole, so that excess oil flows through the piston through the through-hole. , And is advantageously prevented from increasing the consumption of oil.

Further, since a part of the periphery of the through hole extends to the skirt portion side beyond the side surface of the oil ring groove, oil taken in the oil ring groove can be efficiently passed through the through hole. Can be collected.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a plan view of a piston for an internal combustion engine showing an embodiment of the present invention.
Is a side view. In the figure, a piston for an internal combustion engine denoted by reference numeral 1 has a crown surface portion 2 at the uppermost end in FIG. 1, a ring land portion 3 following the crown surface portion 2, and a ring land portion 3
And a skirt portion 4 following the skirt portion.

In this embodiment, three piston ring grooves 5, 6, 7 are formed in the ring land portion 3, and two piston ring grooves 5, 6 located on the crown surface 2 side. In the compression ring groove, the piston ring groove 7 formed adjacent to the skirt portion 4 is an oil ring groove.

Reference numeral 8 denotes an apron portion formed on the skirt portion 4. Reference numeral 9 denotes a pin boss portion formed so as to protrude from the apron portion 8 toward the inner peripheral side of the skirt portion 4. The apron portion 8 and the pin boss portion Numerals 9 are formed so as to face both sides of the axis Y1 of the piston 1 (axial center line) (see FIG. 3).

The pin boss portion 9 is formed with a piston pin hole 10 whose both ends are open to the apron portion 8. The piston pin hole 10 has its axis (axial line) X1 aligned with the axis Y1 of the piston 1. It is formed so as to be substantially at right angles to it. The axis X1 of the piston pin hole 10 is offset from the axis Y1 of the piston 1 on the side opposite to the thrust, as shown in FIG.

A piston pin 11 is inserted into the piston pin hole 10, and a connecting rod 12 is connected to the piston pin 11.

An oil hole 13 is formed in the oil ring groove 7 located above the skirt portion 4 on the thrust side following the apron portion 8. The oil hole 13 has a part of a peripheral edge 13 a extending to the skirt portion 4 side beyond the side surface 7 a of the oil ring groove 7, and a bottom surface 13 b formed in the oil ring groove 7.
And is formed so as not to penetrate the inner peripheral side of the piston 1. The oil hole 1
3 are formed in this embodiment (see FIGS. 3 and 4).

In the oil ring groove 7 at a position substantially symmetrical to the oil hole 13 with respect to the axis Y1 of the piston 1, that is, in the oil ring groove 7 located above the skirt portion 4 on the anti-thrust side, A through hole 14 penetrating through the inner peripheral side of the piston 1 is formed. The through hole 14 has a peripheral edge 1
A portion of 4a extends toward the skirt portion 4 beyond the side surface 7a of the oil ring groove 7. In this embodiment, three through holes 14 are formed (see FIGS. 3 and 4).

In FIG. 2, Y2 is a line passing through the axis X1 of the piston pin hole 10 and parallel to the axis Y1 of the piston 1. In FIG. 3, X2 is the piston 1
Are parallel to the axis X1 of the piston pin hole 10.

According to such a configuration, the piston 1 operates by being incorporated in an engine (not shown).

When an engine (not shown) is operated, the piston 1 behaves as shown in FIG. 5 during the compression and expansion strokes. In FIG. 5, Y0 indicates the axis (axial line) of the cylinder.

That is, before the top dead center of the compression stroke, as shown in FIG. 5 (a), the piston 1 applies a compressed gas pressure Fg (specifically, the sum of the compressed gas pressure and the inertia force of the piston 1). Receive. Since the pressure Fg is decomposed into a force Fc and a thrust force Ft to the inclined connecting rod 12, the piston 1 receives the thrust force Ft, and moves in contact with the cylinder inner surface c on the anti-thrust side.

When the piston 1 approaches the top dead center, the pressure Fg of the compressed gas increases and the inclination angle of the connecting rod 12 decreases, so that the thrust force Fg increases.
t becomes smaller. For this reason, the piston 1 shown in FIG.
As shown in (b), a moment M is generated, the skirt rotates counterclockwise around the lower end B of the skirt as a fulcrum, and the upper end A of the skirt on the thrust side comes into contact with the cylinder inner surface c on the thrust side. In this state, the piston 1 enters the explosion stroke.

After the top dead center, the inclination of the connecting rod 12 is reversed, so that the direction of the thrust force Ft changes, and the piston 1 generates a moment M as shown in FIG. It rotates clockwise with the point A as a fulcrum, and the side surface on the thrust side contacts the cylinder inner surface c on the thrust side.

Thereafter, the piston 1 moves in contact with the cylinder inner surface c on the thrust side during the expansion stroke.

Here, immediately after passing through the top dead center, a side force due to the largest thrust force Ft acts on the side surface of the piston 1 on the thrust side, and the piston 1 becomes severe against seizure. Become.

Therefore, according to the present invention, the oil hole 13 is formed in the oil ring groove 7 located above the skirt portion 4 on the thrust side, so that the oil hole 13 serves as a lubricating oil (engine oil) reservoir. Function. Therefore, on the thrust side where the large side force acts, a good lubricating oil film is formed on the contact surface between the piston 1 and the cylinder inner surface c, and seizure is advantageously prevented and friction is reduced.

At this time, since the oil hole 13 is formed in the oil ring groove 7 located on the upper side of the skirt portion 4, the oil discharged from the oil hole 13 when the piston 1 slides in the reciprocating manner is reduced to the apron portion. 8, the skirt portion 4 can be effectively lubricated.

Therefore, the piston 1 for an internal combustion engine that can prevent seizure and reduce friction can be obtained.

Further, a part of the peripheral edge 13a of the oil hole 13 exceeds the side surface 7a of the oil ring groove 7 and the skirt 4
Since it extends to the side, the oil taken in the oil ring groove 7 can be efficiently stored in the oil hole 13.

Further, since the bottom surface 13b of the oil hole 13 is formed so as not to penetrate the inner peripheral side of the piston 1 beyond the bottom surface 7b of the oil ring groove 7, the volume of the oil hole 13 becomes large. A large amount of oil can be stored in the oil hole 13.

Further, since the through-hole 14 is formed in the oil ring groove 7 at a position substantially symmetric with the oil hole 13, surplus oil is supplied from the thrust side where a large thrust force does not act during the expansion stroke of the piston 1. Through the through-hole 14, it passes through the inner peripheral side of the piston 1 and is collected in an iorpan (not shown). This can advantageously prevent an increase in oil consumption.

The through hole 14 has a peripheral edge 14a.
Of the oil ring groove 7 extends to the skirt portion 4 side beyond the side surface 7a of the oil ring groove 7, so that the oil taken into the oil ring groove 7 can be efficiently recovered through the through hole 14.

Although the embodiment has been described with reference to the drawings, the specific configuration is not limited to this embodiment, and can be changed without departing from the gist of the invention.
For example, one oil hole 13 and one through hole 14 may be formed, or four or more oil holes 13 and four or more through holes may be formed. Further, the cross-sectional shapes of the oil holes 13 and the through holes 14 are not limited to circular shapes, and various shapes can be adopted.

[0044]

As described in detail above, according to the present invention, it is possible to obtain a piston for an internal combustion engine capable of preventing seizure and reducing friction.

[Brief description of the drawings]

FIG. 1 is a plan view of an internal combustion engine piston according to an embodiment of the present invention.

FIG. 2 is also a side view.

FIG. 3 is a sectional view taken along the line BB of FIG. 2;

FIG. 4 is a sectional view taken along line CC of FIG. 3;

FIG. 5 is a diagram illustrating the behavior of the piston in a state before the top dead center of the compression stroke (a), a state near the top dead center (b), and a state past the top dead center (c).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piston 2 Crown surface part 3 Ring land part 4 Skirt part 7 Oil ring groove 8 Apron part 10 Piston pin hole 13 Oil hole 14 Through hole X1 Axis line of piston pin hole Y1 Axis line of piston

Claims (4)

[Claims] 1. A ring land portion on a crown surface side, and a skirt portion following the ring land portion. An apron portion having a piston pin hole is formed in the skirt portion, and the apron portion is formed on the ring land portion. Is a piston for an internal combustion engine having an oil ring groove formed therein. In the oil ring groove located above the thrust skirt portion following the apron portion, a part of the periphery extends beyond the side surface of the oil ring groove. An oil hole extending toward the bottom of the piston and having a bottom surface reaching the bottom surface of the oil ring groove. 2. The piston for an internal combustion engine according to claim 1, wherein an axis of said piston pin hole is offset to an opposite thrust side with respect to an axis of said piston. 3. An oil ring groove having a position substantially symmetrical to an oil hole with respect to an axis of the piston, a portion of a peripheral edge of the oil ring groove extends toward a skirt portion beyond a side surface of the oil ring groove, and an inner periphery of the piston is formed. 2. The piston for an internal combustion engine according to claim 1, wherein a through-hole penetrating the side is formed. 4. An oil ring groove wherein the axis of the piston pin hole is offset to the thrust side with respect to the axis of the piston and which is substantially symmetrical with the oil hole with respect to the axis of the piston. 2. A part of the oil ring groove extends to the skirt portion side beyond the side surface of the oil ring groove, and a through-hole penetrating the inner peripheral side of the piston is formed.
A piston for an internal combustion engine according to the above.