JPH05172001A - Piston for internal combustion engine - Google Patents

Abstract

PURPOSE:To perform cooling of a pin boss part and side wall part and to prevent overheat deterioration of oil by forming a recessed part in a periphery of an opening end part in the outer periphery side of a piston pin hole, and communicating this recessed part with a hollow part inside a piston and a lower part of the piston. CONSTITUTION:In a piston 10, a hollow part 24 for an oil sump is formed of a head part 12, a shelf part 22 hung from a lower face thereof, a side wall part and the like. In a periphery of an opening end part in the outer periphery side of a piston pin hole 20 penetrating a pin boss part 18, a recessed part 28 depressed more than the outer periphery part is formed. A first passage 36 is formed in a side wall part to communicate the recessed part 28 with the hollow part 24. A second passage 40 for communicating the recessed part 28 with a space in the lower part of the piston 10 is formed in a wall 34 under the recessed part 28. The pin boss part 18 and a side wall part are cooled by oil flowing through the respective passages 36, 40 from the hollow part 24, and the oil is cooled at a cylinder bore surface so as to prevent overheat and deterioration.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a piston for an internal combustion engine.

[0002]

2. Description of the Related Art A piston cooling structure for cooling a piston by spraying oil into the top of the piston or the space inside the piston is known (for example, Japanese Utility Model Publication 55-106).
348). In the conventional piston cooling structure, the oil is sprayed from the inside of the piston to the inner surface of the piston to cool the piston.

[0003]

However, the piston cooling structure in which the piston is cooled only from the inner surface has the following problems. I. The piston cannot be cooled uniformly. In particular, since the thickness around the pin boss portion is large and a large amount of heat from the combustion chamber is conducted through the top of the piston, the temperature tends to be high. If the temperature around the pin boss part becomes locally high, the knock limit will be reduced, and noise due to a large clearance with the cylinder bore,
This causes an increase in friction. B. Further, since the oil drops only after coming into contact with the piston, the oil is easily overheated by the piston, and the heat deterioration of the oil is accelerated.

It is an object of the present invention to provide a piston for an internal combustion engine which enables the piston to be cooled more uniformly, including the pin boss portion, which has been difficult to cool in the past, and which can suppress the thermal deterioration of the oil itself. is there.

[0005]

According to the invention, the above object is achieved by the following piston of an internal combustion engine. That is, in a piston for an internal combustion engine having a hollow portion to which oil is supplied inside the piston, a recessed portion that is recessed from the piston outer peripheral surface is formed around the opening end portion of the piston pin hole on the piston outer peripheral side, and the recessed portion is A first passage communicating with the hollow portion of the piston and a second passage communicating with the lower portion of the piston.
And a passage for the internal combustion engine piston.

[0006]

In the piston of the internal combustion engine of the present invention described above,
The oil supplied to the hollow part cools the top of the piston,
Then, the pin boss portion and the sidewall portion, which have been difficult to cool in the past, are cooled through the first passage portion, and at the same time, the pin boss portion and the sidewall portion are cooled by the contact with the cylinder bore cooled by the engine cooling water. Return to the oil pan through the passage 2. Therefore, the entire piston can be cooled, and deterioration due to overheating of oil can be prevented.

[0007]

1 to 4 show a preferred embodiment of a piston for an internal combustion engine according to the present invention. 1 to 4, the piston 10 includes a disk-shaped head portion 12 and a head portion 12 which is located at a position orthogonal to the piston pin axial direction.
A pair of skirt portions 14 extending downward from the side wall portion 16, a sidewall portion 16 located in the piston pin axial direction portion extending downward from the head portion 12, and a sidewall portion 16 located in the piston pin axial direction portion and integrally formed. It has a pin boss portion 18. A piston pin hole 20 is provided in the pin boss portion 18.
Has penetrated.

Head portions 1 are provided on both sides of the piston pin shaft center.
A pair of shelves 22 are provided that hang down from the lower surface of 2, and bend in the axial direction of the piston pin at the lower end of the hanging wall, and extend to the vicinity of the small end outer surface of the connecting rod (not shown). However, there is a slight gap between the tip of the lower wall of the shelf 22 and the outer surface of the connecting rod. The hanging wall of the shelf 22 is located inside the piston from the skirt portion 14 in the thrust-anti-thrust direction portion of the piston. A space surrounded by the pair of shelves 22, the head portion 12, the sidewall portion 16, and the connecting rod small end forms a hollow portion 24 for storing oil. An oil supply hole 26 is formed in the lower wall of the shelf 22 that constitutes the lower wall of the hollow portion 24, and the oil injected upward from below the piston enters the hollow portion 24 from the oil supply hole 26. enter.

Around the opening end of the piston pin hole 20 on the outer peripheral side of the piston, a recess 2 recessed from the outer peripheral surface of the piston is formed.
8 is formed. The recess 28 is vertically below the piston ring groove 30 and the oil ring groove 32, and is separated from the space below the piston by a recess lower wall 34. The recesses 28 are on the left and right of the piston pin hole 20 in the left-right direction of the piston pin axis.

The sidewall portion 16 is formed with a first passage 36 which communicates the inside and outside of the piston. The first passage 36 communicates the recess 28 and the hollow portion 24. The first passages 36 are provided on both the left and right sides of the connecting rod small end, below the oil ring groove 32 so as not to reach the ring land 38, and above the lower wall of the shelf 22 forming the hollow portion 24. First passage 36
The provision of the above allows the oil supplied to the hollow portion 24 to pass through the first passage 36 and exit to the concave portion 28. The oil in the recess 28 contacts the inner surface of the cylinder bore.

A second passage 40 is formed in the recess lower wall 34 to connect the recess 28 and the space below the piston. The second passage 40 is formed, for example, by notching the recess lower wall 34 from the outer peripheral side toward the inner peripheral side. Therefore, even when the oil passes through the second passage 40, the oil can contact the inner surface of the cylinder bore.

Next, the operation will be described. The oil injected from below the piston to above (including diagonally above)
The oil enters into the hollow portion 24 through the oil supply hole 26 of the shelf 22 inside the piston. The oil repeatedly hits the ceiling and the lower wall of the hollow portion 24 during the reciprocating motion of the piston in the vertical direction, and uniformly cools the head portion 12 of the piston almost entirely.

The oil in the hollow portion 24 is transferred to the first passage 36.
Is discharged to the concave portion 28 through Oil is the first passage 3
The sidewall portion 16 and the pin boss portion 18 are effectively cooled when passing through 6 and in the recess 28.
Conventionally, since there are no holes or recesses such as the first passage 36 and the recess 28 of the present invention around the pin boss portion, and since the pin boss portion is thick, a large amount of heat flows and the periphery of the pin boss portion is locally high in temperature. However, in the present invention, since the first passage 36 and the recessed portion 28 are provided, the pin boss portion 18 and the sidewall portion 16 are also sufficiently cooled, the generation of a locally high temperature portion is suppressed, and the piston 10 is entirely formed. Can be cooled uniformly.

When the piston has a locally high temperature portion, the piston is distorted and the clearance between the piston and the cylinder bore must be increased in order to escape the thermal deformation. However, when the temperature is uniform, the posture of the piston is maintained. It is easy and noise and friction can be reduced.

The oil discharged into the recess 28 contacts the inner surface of the cylinder bore over a wide area when the piston moves up and down. Since the inner surface of the cylinder bore is always cooled from the inside of the cylinder block by the engine cooling water flowing through the water jacket formed in the cylinder block, the oil is also cooled and the oil is prevented from being overheated.

In the conventional piston cooling device which blows only on the inner surface of the piston and cools the piston from only the inner surface side, the oil heated by the piston heated from the combustion chamber is not heated but is cooled. Although there is a risk of overheating of the oil and deterioration of the oil in the piston that locally becomes hot, in the present invention, since the oil contacts the inner surface of the cylinder bore and is cooled, overheating of the oil is prevented.

The oil discharged to the recess 28 passes through the second passage 40, drops below the piston, and is returned to the oil pan. Even when passing through the second passage 40, the oil contacts the inner surface of the cylinder bore and is cooled, so that the temperature rise of the oil can be suppressed to a low level. The oil returned to the oil pan is pumped up by a pump and is again sent to each part of the engine for lubrication and cooling.

[0018]

According to the present invention, a concave portion recessed from the outer peripheral surface of the piston is formed around the opening end portion of the piston pin hole on the outer peripheral side of the piston, and the concave portion is formed by the hollow portion formed in the piston and the first passage. Since it communicates with the space below the piston through the second passage, the oil that passes through the first passage and goes out to the recess can cool the pin boss portion and sidewall portion, which was difficult to cool in the past, and the entire piston It can be cooled more uniformly than before. As a result, the knock limit can be extended to improve performance, improve the piston posture, reduce noise and friction, and reduce the heat load on the equipment around the piston (connecting rod, piston pin, piston ring). Therefore, the reliability can be improved.

Further, since the oil contacts the surface of the cylinder bore and is cooled when passing through the recess and the second passage, it is possible to prevent overheating of the oil and deterioration of the oil.

[Brief description of drawings]

FIG. 1 is a front view of a piston for an internal combustion engine according to an embodiment of the present invention as seen in a piston pin axial direction.

FIG. 2 is a cross-sectional view of the piston of FIG. 1 taken along a plane orthogonal to the piston pin axial direction.

3 is a cross-sectional view of the piston of FIG. 1 taken along a plane parallel to the piston pin axial direction.

FIG. 4 is a bottom view of the piston of FIG.

[Explanation of symbols]

 10 piston 12 head part 14 skirt part 16 sidewall part 18 pin boss part 20 piston pin hole 22 shelf 24 hollow part 26 oil supply hole 28 recess 30 piston ring groove 32 oil ring groove 34 recess lower wall 36 first passage 38 ring land 40 Second passage

Claims (1)

[Claims] 1. In a piston for an internal combustion engine having a hollow portion into which oil is supplied, a recessed portion that is recessed from the piston outer peripheral surface is formed around the opening end portion of the piston pin hole on the piston outer peripheral side, The piston for an internal combustion engine, wherein the concave portion has a first passage communicating with the hollow portion of the piston and a second passage communicating with a lower portion of the piston.