JPH09100912A - Piston for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To combine the reduction of weight and hammering sound of a piston. SOLUTION: A piston wall between a pin boss part 2 and a skirt part 3 is eliminated to reduce the weight of a piston, and both skirt parts 3 are connected to the pin boss part 2 by a strut member 6, formed of metal smaller in a coefficient of thermal expansion than piston base material, so as to reduce piston hammering sound and to improve the rigidity of the skirt parts.

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 striking sound reducing structure thereof.

[0002]

2. Description of the Related Art In order to reduce the weight of a piston, a short skirt structure in which the axial length of the skirt is shortened, or a structure in which the piston wall between the pin boss and the skirt is removed or a hole is formed in the wall is adopted. Has been done. However, in the case of the piston wall removal structure or the hollowed-out hole structure, in order to prevent the rigidity of the skirt portion from being lowered, a structure is used in which the lower end of the skirt portion is connected to the lower end of the pin boss portion by a reinforcing rib extending in the piston circumferential direction (for example, Japanese Patent Laid-Open No. 2-2
No. 04665).

[0003]

A clearance (clearance) is provided between the skirt portion and the cylinder bore for allowing the piston to slide and forming an oil film to prevent seizure. The existence of the piston causes the piston to tilt, and the side surface of the piston hits the cylinder bore to generate a hammering sound. In particular, in the short skirt structure, the piston tilt becomes large and the tapping sound also becomes large. Further, in the structure in which the skirt portion and the pin boss portion are connected by the reinforcing rib, the clearance between the skirt portion and the cylinder bore must be large so as to absorb the difference in thermal expansion between the reinforcing ribs after warming up and immediately after starting. Therefore, the hammering sound of the piston immediately after starting becomes loud. As a result, with the conventional structure, it has been extremely difficult to achieve both weight reduction and piston hammering noise reduction. An object of the present invention is to provide a piston for an internal combustion engine that can achieve both reduction of piston striking sound and weight reduction of the piston.

[0004]

The piston of the present invention that achieves the above object is as follows. A piston for an internal combustion engine in which a piston wall between a pin boss portion and a skirt portion is removed, wherein both skirt portions are connected to the pin boss portion by strut members made of metal having a coefficient of thermal expansion smaller than that of a piston base material.

In the above piston of the present invention, since both skirts are connected to the pin bosses by the strut members, the rigidity of the skirts can be maintained and the weight can be reduced without lowering the rigidity. Further, since the strut member is made of a material having a smaller coefficient of thermal expansion than the piston base material, the clearance between the skirt and the bore for absorbing the difference in thermal expansion before and after warm-up can be made smaller than before, and the piston striking can be reduced. The sound can be reduced. Therefore, it is possible to achieve both weight reduction and reduction of piston hammering noise.

[0006]

1 and 2 show a first embodiment of the present invention, and FIGS. 3 and 4 show a second embodiment of the present invention. Portions common to both embodiments are given the same reference numerals in both embodiments. First, the first of the present invention,
The structure and operation of the parts common to the second embodiment will be described with reference to FIGS. 1 and 2, for example. The piston 1 for an internal combustion engine of the embodiment of the present invention has a substantially circular piston top portion 4
And a pair of pin boss portions 2 extending downward from the piston top portion 4 and a pair of skirt portions 3 extending downward from the piston top portion 4. A line connecting the pair of pin boss portions 2 through the center of the piston and a line connecting the pair of skirt portions 3 through the center of the piston are orthogonal to each other, and the direction connecting the pair of skirt portions 3 is the thrust anti-thrust of the piston. Direction. A piston pin hole 5 is provided in the pin boss portion 2, and a piston pin is mounted in the piston pin hole 5 (not shown).

The length of the skirt portion 3 in the piston axial direction is short (shorter than the radius of the piston) to form a short skirt piston. Further, the skirt portion 3 and the pin boss portion 2 are not connected in the circumferential direction of the piston by the piston base material, and the wall between the skirt portion 3 and the pin boss portion 2 is removed. Due to this short skirt structure and non-connection structure, the weight is significantly reduced compared to the conventional piston.

In order to prevent the rigidity of the skirt portion 3 from decreasing due to the non-coupling structure, both skirt portions 3 are provided with strut members 6.
Is connected to the pin boss portion 2. The strut member 6 is made of a metal having a coefficient of thermal expansion smaller than that of the piston base material, and is partially surrounded by the skirt portion 3 and the pin boss portion 2. The strut member 6 extends in an in-plane direction orthogonal to the axial direction of the piston pin hole 5 at a portion between the skirt portion 3 and the pin boss portion 2 and applies thrust and anti-thrust force from the skirt portion 3 to the pin boss portion 2. Is transmitted to the pin boss portion 2 to receive a part of the force. The piston base material is made of aluminum alloy, and the strut member 6 is made of titanium alloy, iron, stainless steel, or the like. A minimum clearance is provided between the skirt portion 3 and the cylinder bore surface to allow the piston 1 to slide even after warming up, and the cylinder bore surface is lubricated with oil.

Regarding the operation of the common portion, the weight of the piston 1 is reduced by the short skirt structure and the wall removing structure between the skirt portion 3 and the pin boss portion 2. Further, the rigidity of the skirt portion 3 is prevented from being lowered by the connecting structure of the strut members 6. Since the strut member 6 is made of a metal having a coefficient of thermal expansion smaller than that of the piston base material, the clearance between the skirt portion 3 and the cylinder bore can be maintained at a small value even in the most contracted state before warming up, and piston striking noise can be suppressed. .

Next, the structure peculiar to each embodiment of the present invention,
I will explain about the action. In the first embodiment of the present invention, as shown in FIGS. 1 and 2, the strut member 6 is composed of a single member. The strut member 6 extends in an arc shape at the lower end of the one skirt portion 3, extends from one circumferential end of the one skirt portion 3 to the lower portion of the one pin boss portion 2, passes below the piston pin hole 5, and The one pin boss portion 2 extends to the lower end of the other skirt portion 3, and the lower end of the other skirt portion 3 extends from one end in the circumferential direction to the other end in the circumferential direction,
The other end of the other skirt extends from the other end in the circumferential direction to the lower part of the other pin boss, passes below the piston pin hole 5, and extends from the other pin boss 2 to the lower end of the one skirt 3. It extends to the other end of the direction. The strut member 6 has a strip plate shape, and the width direction of the strip plate is oriented in the skirt portion 3 in a direction parallel to the piston axis center, and the width direction of the strip plate is orthogonal to the piston axis center between both skirt portions 3. It is directed in the in-plane direction. This strip can be easily formed by pressing.

The peculiar operation of the first embodiment of the present invention is that the strut member is light in weight because of the band plate structure and easy to mold, and the strut member 6 is exposed between the pin boss portion 2 and the skirt portion 3. Therefore, even after warming up, the oil mist can always cool, the difference in thermal expansion of the strut members 6 before and after warming up can be kept small, and the effect of suppressing the piston tapping sound is great.

In the second embodiment of the present invention, as shown in FIGS. 3 and 4, the strut member 6 includes the pin boss portions 2
It consists of two members, one on each side. Each strut member 6 is a plate whose width is substantially the same as the total height of the skirt portion 3 and which extends in the longitudinal direction from one circumferential end portion of one skirt portion 3 to one circumferential end portion of the other skirt portion 3.
The intermediate portion has a cylindrical portion 6a formed by punching. The cylindrical portion 6a is concentric with the piston pin hole 5 and has a larger diameter than the piston pin hole 5.

Regarding the peculiar function of the second embodiment of the present invention, since the skirt portion 3 is connected to the pin boss portion 2 through the strut member 6 over the entire height thereof, the reinforcing effect is great and the piston pin hole is also provided. Since 5 is reinforced by the cylindrical portion 6a of the strut member 6, the difference in thermal expansion between the piston pin holes 5 before and after warm-up can be kept small, and the clearance between the piston pin and the piston pin hole 5 can be made small, so that the piston posture is good. That is, the piston tapping noise can be further suppressed as a result.

[0014]

According to the present invention, since both skirt portions are connected to the pin boss portion by the strut member made of a metal having a smaller coefficient of thermal expansion than the piston base material, the skirt rigidity is maintained and the piston wall is lightened by removing the piston wall. It is possible to reduce the piston tapping noise by reducing the difference in thermal expansion between the time of load operation and before and after starting. As a result, it is possible to achieve both weight reduction and reduction of piston tapping noise.

[Brief description of the drawings]

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

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view of a piston for an internal combustion engine according to a second embodiment of the present invention.

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

[Explanation of symbols]

 1 Piston 2 Pin Boss Section 3 Skirt Section 5 Piston Pin Hole 6 Strut Member 6a Cylindrical Section

Claims (1)

[Claims] 1. A piston for an internal combustion engine in which a piston wall between a pin boss portion and a skirt portion is removed, wherein both skirt portions are connected to the pin boss portion by a strut member made of a metal having a thermal expansion coefficient smaller than that of a piston base material. An internal combustion engine piston.