JPH10288083A - Piston for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piston for an internal combustion engine wherein weight can be lightened, noise and seizure by a piston slap can be prevented. SOLUTION: A piston 1 is provided with a ring land part 3 continued to a crown surface part 2, pin boss part 6 formed in a lower side of this ring land part 3, piston pin hole 7 formed in this pin boss part 6, and a skirt part 4 continued to this ring land part 3. The skirt part 4 is provided only in a region almost at a right angle relating to an axial line X1 of the piston pin hole 7. The skirt part 4 and the pin boss part 6 are connected by a reinforcing beam. In a plane or in the vicinity thereof including the axial line of the piston pin hole, a maximum diametric part 9 with the piston in the largest diameter is formed. Respectively in a side nearer the ring land part 3 than this maximum diametric part 9 and a side distant from the ring land part 3, a curved part 10 is formed, where the diameter of the piston 1 is gradually decreased in a manner of quadratic curve from the largest diameter.

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 reducing the weight and preventing noise and seizure due to piston slap.

[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 while changing from a state in which the connecting rod is inclined rightward to a state in which the connecting rod is inclined leftward, the piston reciprocates while being pressed against the inner surface of the cylinder by a rightward or leftward side force. become.

In the above-described motion state, when the side force changes its direction, the piston moves from one side to the other side, and may collide with the inner surface of the cylinder to generate a piston slap, which may cause noise.

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.

In order to prevent noise and seizure caused by the piston slap of the piston, Japanese Patent Laid-Open No.
No. 85405 discloses that a skirt portion of a piston includes a curved portion whose diameter increases in a quadratic curve as it goes downward, a maximum diameter portion connected to the curved portion, and a lower portion connected to the maximum diameter portion. And a taper portion having a tapered portion whose diameter decreases linearly linearly as the position of the piston becomes smaller, and the inclination angle of the tapered portion is set to a predetermined angle.

[0006]

In recent years, for the purpose of reducing the weight of a piston, a skirt portion is formed only in a region substantially perpendicular to the axis of a piston pin hole formed in a pin boss portion. The development of a piston in which a pin boss is connected with a reinforcing beam is being pursued.

According to the study of the inventor, in the lightweight piston, since the rigidity of the skirt portion is increased by the reinforcing beam, as shown in the conventional example, it is larger than the maximum diameter portion near the piston pin hole. It has been found that a shape (tapered shape) in which the lower diameter decreases linearly linearly does not provide a sufficient countermeasure effect.

The present invention has been devised in view of such conventional circumstances, and provides a piston for an internal combustion engine which can be reduced in weight and which can prevent noise and seizure due to piston slap. With the goal.

[0009]

SUMMARY OF THE INVENTION In view of the above, according to the first aspect of the present invention, a ring land portion following a crown surface, a pin boss formed below the ring land, and a pin boss formed on the pin boss. A piston pin hole, and a skirt portion following the ring land portion, wherein the skirt portion is
In a piston for an internal combustion engine formed only in a region substantially perpendicular to the axis of the piston pin hole formed in the pin boss portion, and the skirt portion and the pin boss portion are connected by a reinforcing beam, the axis of the piston pin hole is A maximum diameter portion where the diameter of the piston is the largest is formed in or near the plane including, on each of the side closer to the ring land portion and the side farther from the ring land portion than the maximum diameter portion,
The configuration is such that a curved portion is formed in which the diameter of the piston gradually decreases in a quadratic curve from the maximum diameter.

According to a second aspect of the present invention, in the configuration of the first aspect, the curved portion closer to the ring land portion than the maximum diameter portion is closer to the ring land portion than the maximum diameter portion. It is configured to have a curvature smaller than that of the curved portion on the far side.

According to such a configuration, the piston is incorporated and operated in a cylinder of the engine (not shown), and reciprocates while being pressed against the inner surface of the cylinder by the right or left side force.

In the reciprocating sliding motion of the piston, when the side force changes its direction, the piston moves from one side to the other side, and may collide with the inner surface of the cylinder to generate a piston slap, which may cause noise. ,Also,
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. According to the present invention, these can be advantageously solved.

That is, in the piston of the present invention, a maximum diameter portion is formed on or near a plane including the axis of the piston pin hole, and a portion closer to the ring land portion and farther from the ring land portion than the maximum diameter portion is formed. Each has a curved portion in which the diameter of the piston gradually decreases in a quadratic manner from the maximum diameter.

Therefore, when the direction of the side force changes and the piston comes into contact with the inner surface of the cylinder, the piston comes into gentle contact with the curved portion. Thereby, the piston slap is alleviated, and the generation of noise is prevented.

[0015] Further, since the curved portion is formed on the side farther from the ring land portion than the maximum diameter portion (the lower end side of the skirt portion), lubricating oil (engine oil) supplied from the oil pan is formed between the piston and the piston. It will be easily taken in between the cylinder inner surface. This facilitates formation of an oil film on the contact surface between the piston and the inner surface of the cylinder, thereby preventing seizure.

In particular, according to the second aspect of the invention,
Since the curved portion farther from the ring land portion than the maximum diameter portion (the lower end side of the skirt portion) is formed with a large curvature (small radius of curvature), lubricating oil is more effectively applied between the piston and the cylinder. It becomes possible to take in.

Therefore, a piston for an internal combustion engine that can be reduced in weight and that can prevent noise and seizure due to piston slap can be obtained.

[0018]

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, in which the shape of a skirt portion is exaggerated, and FIG. 2 is a view taken in the direction of arrow A in FIG.

The piston for an internal combustion engine indicated by reference numeral 1 in the figure is made of an aluminum alloy material.
, An uppermost crown surface portion 2, a ring land portion 3 following the crown surface portion 2, and a skirt portion 4 following the ring land portion 3. The ring land portion 3 has three piston ring grooves 5 in this embodiment.
Is formed.

Reference numeral 6 denotes a pin boss formed below the ring land 3, and the pin boss 6 is formed to face both sides of the axis Y1 of the piston 1 (FIG. 2).
reference). The pin boss portion 6 is formed with a piston pin hole 7 penetrating therethrough. The piston pin hole 7 is formed such that its axis (axial line) X1 is substantially perpendicular to the axis Y1 of the piston 1. I have.

The skirt portion 4 is formed only in a region substantially perpendicular to the axis X1 of the piston pin hole 7 formed in the pin boss portion 6, and is not formed in the remaining portion. That is, the skirt portion 4 is not formed in the direction of the axis X1 of the piston pin hole 7. As a result, the weight of the piston 1 is reduced because the skirt portion 4 is not formed in the direction of the axis X1 of the piston pin hole 7.

The skirt 4 and the pin boss 6 are connected by a reinforcing beam 8. The reinforcing beam 8 extends from the outer peripheral side of the pin boss 6 in a direction substantially perpendicular to the axis X1 of the piston pin hole 7, and its upper end is connected to the ring land 3.

The diameter of the piston 1 is a maximum diameter on or near a plane including the axis X1 of the piston pin hole 7, and the diameter of the ring land 3 is larger than the maximum diameter 9.
On the side closer to (the upper end side of the skirt portion 4) and on the side farther from the ring land portion 3 (the lower end side of the skirt portion 4), the size is gradually reduced in a quadratic curve from the maximum diameter.

That is, a maximum diameter portion 9 where the diameter of the piston 1 is maximum is formed on or near a plane including the axis X1 of the piston pin hole 7, and the maximum diameter portion 9 is formed.
The diameter of the piston 1 on the side closer to the ring land portion 3 (the upper end side of the skirt portion 4) and on the side farther from the ring land portion 3 (the lower end side of the skirt portion 4), A gradually decreasing curved portion 10 is formed.

The curved portion 10 closer to the ring land portion 3 than the maximum diameter portion 9 has a smaller curvature (radius of curvature) than the curved portion 10 farther from the ring land portion 3 than the maximum diameter portion 9. Large). That is, the curvature of the curved portion 10 on the side closer to the ring land portion 3 is gentler than that of the curved portion 10 on the side farther from the ring land portion 3, and the reduction amounts a and b from the maximum diameter at each end are smaller. , The reduction amount a is formed larger than the reduction amount b (see FIG. 2).

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

At this time, the connecting rod (not shown) supports the piston 1 while changing from a state in which the connecting rod is inclined rightward to a state in which the connecting rod is inclined leftward, so that the piston 1 is attached to the inner surface of the cylinder by a rightward or leftward side force. It will slide back and forth while being pressed.

In the above-mentioned motion state, when the side force changes its direction, the piston 1 may move from one side to the other side, colliding with the inner surface of the cylinder to generate a piston slap, which may cause noise. If the side force is large and the lubrication condition between the piston 1 and the inner surface of the cylinder is not good, seizure may occur. In the present invention, these are advantageously solved.

That is, in the piston 1 of the present invention, the maximum diameter portion 9 is formed on or near the plane including the axis X1 of the piston pin hole 7, and the side closer to the ring land portion 3 than the maximum diameter portion 9 and the ring A curved portion 10 in which the diameter of the piston 1 gradually decreases in a quadratic curve from the maximum diameter is formed on each side far from the land portion 3.

For this reason, when the direction of the side force changes and the piston 1 comes into contact with the inner surface of the cylinder, the piston 1 comes into gentle contact with the curved portion 10. Thereby, the piston slap is reduced, and the generation of noise is reduced.

The curved portion 1 is located farther from the ring land portion 3 than the maximum diameter portion 9 (the lower end of the skirt portion 4).
By forming 0, lubricating oil (engine oil) supplied from an oil pan (not shown) is easily taken in between the piston 1 and the cylinder inner surface. This facilitates formation of an oil film on the contact surface between the piston 1 and the inner surface of the cylinder, thereby preventing seizure.

In particular, the curved portion 10 on the side farther from the ring land portion 3 than the maximum diameter portion 9 (the lower end side of the skirt portion 4) is formed with a large curvature (small radius of curvature). Lubricating oil can be more effectively taken into the cylinder.

Therefore, the piston 1 for the internal combustion engine which can be reduced in weight and can prevent noise and seizure due to the piston slap can be obtained.

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 spirit of the invention.
For example, it is possible to arbitrarily select whether to offset the axis X1 of the piston pin hole 7 toward the thrust side or the opposite thrust side of the piston 1.

[0036]

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

[Brief description of the drawings]

FIG. 1 is a plan view of a piston for an internal combustion engine according to an embodiment of the present invention, in which the shape of a skirt portion is exaggerated.

FIG. 2 is a view in the direction of arrow A in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piston 2 Crown surface part 3 Ring land part 4 Skirt part 6 Pin boss part 7 Piston pin hole 8 Reinforcement beam 9 Maximum diameter part 10 Curved part X1 Axis line of piston pin hole

Claims (2)

[Claims] 1. A ring land portion following a crown surface portion, a pin boss portion formed below the ring land portion, a piston pin hole formed in the pin boss portion, and a skirt portion following the ring land portion. Wherein the skirt portion is formed only in a region substantially perpendicular to the axis of the piston pin hole formed in the pin boss portion, and the skirt portion and the pin boss portion are connected by a reinforcing beam. In the piston, a maximum diameter portion where the diameter of the piston is maximized is formed on or near a plane including the axis of the piston pin hole, and is farther from the ring land portion than the maximum diameter portion and closer to the ring land portion. A piston for an internal combustion engine, characterized in that a curved portion is formed on each of the sides so that the diameter of the piston gradually decreases in a quadratic curve from the maximum diameter. 2. The curved portion closer to the ring land portion than the maximum diameter portion has a smaller curvature than the curved portion farther from the ring land portion than the maximum diameter portion. The piston for an internal combustion engine according to claim 1.