JPH0433984B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a piston cooling structure for an internal combustion engine, and more particularly to a piston for an internal combustion engine having a hollow portion for cooling the piston on the back surface of the top.

[Conventional technology]

Increasing the compression ratio is effective in improving fuel efficiency in internal combustion engines, but in order to suppress the occurrence of knocking that tends to occur when increasing the compression ratio, cooling oil is sprayed onto the piston from the back side. Various cooling structures for cooling pistons have been proposed.

One of the piston cooling structures is to form a hollow part on the back surface of the top of the piston in order to increase the cooling effect.
There is also a piston with a hollow part that supplies cooling oil to this hollow part, stores the oil in the hollow part, and uses the vertical movement of the piston to splash the oil onto the ceiling of the hollow part to cool the top of the piston. Proposed.

In order to efficiently cool the top of the piston in this hollow piston, it is desirable to circulate oil so as to sufficiently wet the interior of the hollow, especially the ceiling surface, and to efficiently replace old and new oil.

In order to meet this demand, for example, as shown in FIG. A piston is known that moves the ceiling surface 4 along the ceiling surface 4.

[Problem to be solved by the invention]

However, in such a conventional piston with a hollow part, since the ceiling surface 4 is inclined,
The height of the outer periphery of the hollow part 3 becomes lower, and the volume of that part becomes smaller. Therefore, there is a problem in that the outer peripheral portion is likely to be filled with oil, and the flow of oil is impaired due to accumulation due to the filling, making it difficult to generate a sufficient circulating flow on the ceiling surface 4 side.

Moreover, if the vicinity of the oil supply hole 5, which is normally provided near the outer circumference of the hollow part 3, is filled with oil as described above, the oil will be discharged from the oil jet 6 to the hollow part 3.
There is a problem in that the supply of oil becomes insufficient and it becomes difficult to efficiently replace old and new oil.

The present invention has focused on the above-mentioned problems, and an object of the present invention is to provide a piston for an internal combustion engine that allows sufficient circulation movement of the oil in the hollow part and allows efficient oil replacement in the hollow part. shall be.

[Means to solve the problem]

A piston for an internal combustion engine according to the present invention in accordance with this purpose has a piston for an internal combustion engine in which a hollow part for cooling the piston is formed on the back surface of the top of the piston, and the center part is larger than the outer circumferential part. An oil supply hole formed on an upward slope, and provided with an oil supply hole on the outer periphery of the bottom of the hollow part through which oil from the oil jet can flow, as well as an oil discharge hole for discharging oil that has flowed into the hollow part. Consists of.

[Effect]

In the piston of an internal combustion engine configured in this way, the ceiling and bottom surfaces of the hollow part are formed as inclined surfaces with the center located above the outer periphery. It becomes possible to increase the height to the surface. Therefore, the vicinity of the oil supply hole in the hollow part is not filled with oil, the oil from the oil jet flows smoothly into the hollow part, and old and new oil are efficiently exchanged.

In addition, since both the ceiling and bottom surfaces of the hollow section are formed as inclined surfaces, when the piston moves downward, the oil in the hollow section is collected in the center along the ceiling surface due to inertial force, and the piston When moving upward, the oil in the hollow part will be diffused along the bottom surface to the outer periphery due to inertial force.
As a result, the oil is circulated well throughout the hollow portion, promoting heat exchange between the piston and the oil, thereby increasing the cooling effect of the piston.

〔Example〕

Hereinafter, preferred embodiments of the piston for an internal combustion engine of the present invention will be described with reference to the drawings.

FIG. 2 shows a piston for an internal combustion engine according to an embodiment of the present invention. In FIG. 2, 10 indicates the entire piston. A hollow portion 12 is formed on the back side of the top portion 11 of the piston 10 .

The ceiling surface 13 of the hollow portion 12 is formed into an inclined surface that is inclined with respect to the vertical direction X of the piston 10 so that the center portion 13a is upward and the outer peripheral portion 13b is downward. As described above, the bottom surface 14 of the hollow portion 12 is located at the center portion 1 with respect to the vertical direction X of the piston 10.
4a is on the top and the outer peripheral part 14b is on the bottom. That is, the hollow portion 12 has a substantially U-shaped cross section.

In this embodiment, the ceiling surface 13 and the bottom surface 14 are
They are substantially parallel, and the distance between them is set to be appropriately wide over the entire area from the center of the piston to the circumferential edge of the hollow portion.

An oil supply hole 16 for allowing oil from the oil jet 15 to flow into the hollow portion 12 and an oil discharge hole 17 for discharging the oil that has flowed into the hollow portion 12 are provided on the outer peripheral portion 14b of the bottom surface 14 of the hollow portion 12. ing. The oil discharge hole 17 is located on the opposite side of the oil supply hole 16.

A piston ring groove 18 and an oil ring groove 19 are formed on the outer peripheral surface of the piston 10. An oil hole 20 is formed from the oil ring groove 19 and extends inwardly through the piston 10. The oil hole 20 is constituted by an inclined hole that opens diagonally downward inside the piston 10.

Note that in this embodiment, the lower wall of the hollow portion 12 is formed integrally with the piston 10;
As shown in FIG. 3, a plate 22 separate from the piston body 21 may be used to constitute the hollow lower wall.

The operation of the piston of the internal combustion engine constructed in this manner will be described below.

The vertical movement of the piston 10 is the rotational movement of the crankshaft converted into a reciprocating movement via the connecting rod; in the upper half of the vertical movement, the piston 10 receives downward acceleration, and in the lower half, the piston 10 receives downward acceleration. 10 is subjected to upward acceleration. Therefore, when upward acceleration is acting on the piston 10, an inertial force acts on the oil in the hollow portion 12 so that the oil tends to move downward relative to the piston 10. Further, when downward acceleration is acting on the piston 10, an inertial force acts on the oil in the hollow portion 12, which tends to move upward relative to the piston 10.

Therefore, when downward acceleration is acting on the piston 10, the oil in the hollow portion 12 is splashed up by its inertia, and the oil pressed against the ceiling surface 13 is moved along the inclined ceiling surface 13. The water then flows toward the center of the hollow part 12, and wets the entire ceiling surface 13. Then, when the direction of the acceleration of the piston 10 is reversed, the oil is pressed against the bottom surface 14 side, and due to its inertial force, it flows out along the inclined bottom surface 14 to the outer periphery of the hollow part 12, and the oil drains into the oil discharge hole 17. is discharged from.

In this way, the oil in the hollow part 12 is circulated in the hollow part 12 by the vertical movement of the piston 10, as shown by the arrow in FIG.
It is discharged from 7. Of this circulating flow, the ceiling surface 1
3, the ceiling surface 13 is sufficiently wetted over the entire surface, and the top of the piston 10 is effectively cooled.

Further, by ensuring a sufficient height of the outer circumferential portion of the hollow portion 12 and a sufficient volume of the outer circumferential portion, oil is prevented from filling and accumulating in the vicinity of the oil supply hole 16. Therefore, the oil from the oil jet 15 easily flows into the hollow part 12, and the oil in the hollow part 12 is swept away toward the discharge hole 17, thereby smoothly replacing old and new oil.

Further, since the oil hole 20 is diagonally formed, oil adhering to the back surface of the piston is difficult to enter into the oil wheel 20 through the back surface of the piston, and is also difficult to rise along the oil wheel 20. Therefore, oil is difficult to reach the oil ring groove 19 side, and oil can be smoothly collected from the oil ring groove 19 side. As a result of smooth oil recovery, the amount of oil leaking from the cylinder bore surface through the oil ring and piston ring into the combustion chamber is suppressed.

〔Effect of the invention〕

According to the present invention, the ceiling surface and the bottom surface of the hollow part for piston cooling formed on the back surface of the top of the piston are formed into inclined surfaces whose center part is inclined upwardly than the outer peripheral part, and the outer periphery of the bottom face of the hollow part Since the hollow part is provided with an oil supply hole through which oil can flow from the oil jet and an oil discharge hole through which oil that has flowed into the hollow part is discharged, the following effects can be obtained.

(1) When the piston moves downward, the oil in the hollow part can be collected along the ceiling surface at the center of the hollow part, and when the piston moves upward, the oil collected in the center of the hollow part can be collected in the center of the hollow part. It can be diffused to the outer periphery within the hollow along the bottom surface.

Thereby, it becomes possible to circulate the oil that has flowed into the hollow portion from the oil supply hole and to discharge it from the oil discharge hole. Therefore, heat exchange between the piston and the oil can be promoted, and the piston cooling effect can be enhanced.

(2) Since the bottom surface of the hollow part is an inclined surface, it is possible to make the height from the bottom surface to the ceiling surface on the outer peripheral surface of the hollow part higher than when the bottom surface is flat. As a result, even if the oil supply hole is disposed on the outer periphery of the hollow portion, the vicinity of the oil supply hole will not be filled with oil, and oil can be sufficiently supplied to the hollow portion. As a result, the exchange efficiency of old and new oil is increased,
The piston cooling effect can be further enhanced.

(3) In this way, since the piston cooling effect can be enhanced, the occurrence of knocking can be suppressed, and the engine output and compression ratio can be improved to improve fuel efficiency.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of an embodiment of a conventional piston with a hollow portion, FIG. 2 is a longitudinal cross-sectional view of a piston for an internal combustion engine according to an embodiment of the present invention, and FIG. 3 is a longitudinal cross-sectional view of an apparatus for forming a hollow portion. FIG. 7 is a longitudinal cross-sectional view of a device showing a modification of the device of the second embodiment. 10...Piston, 11...Top, 12...Hollow part, 13...Ceiling surface, 14...Bottom surface, 15...
Oil jet, 16...Oil supply hole, 17...
...Oil drain hole, 22...Plate.

Claims (1)

[Claims] 1. In a piston for an internal combustion engine in which a hollow part for cooling the piston is formed on the back surface of the top of the piston, the ceiling and bottom surfaces of the hollow part are formed into inclined surfaces with the center located above the outer circumferential part, and the hollow part A piston for an internal combustion engine, characterized in that an oil supply hole through which oil from an oil jet can flow is provided on the outer periphery of the bottom surface of the piston, and an oil discharge hole through which oil that has flowed into the hollow part is discharged is provided.