JPS60132051A - Piston of internal-combustion engine - Google Patents

Abstract

PURPOSE:To improve the cooling effect on the top of a piston and recover oil smoothly by inclining a cavity in the back of the top of the piston such that the center side of piston is in the upper position and the peripheral end side in the lower position to open oil holes inclined downward. CONSTITUTION:The top 11 of a piston 10 is formed in the back with a cavity 12. The cavity 12 is formed slantly such that the ceiling 13 and the bottom 14 have respectively the piston center side on the upper position and the peripheral end on the lower position. The bottom 14 is provided with an oil supply hole 16 and an oil exhaust hole 17 in the neiborhood of the peripheral end. An oil hole 20 is provided from an oil ring groove 19 on the outer peripheral surface of the piston slantly downward to the interior of the piston 10. Thus, when vertical acceleration is applied to the piston, oil in the cavity 10 moves along the ceiling 13 and bottom 14 while being recovered from the oil ring groove through the oil hole 20 smoothly.

Description

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

Conventional technologyIncreasing the compression ratio is effective in improving fuel efficiency in internal combustion engines, but in order to suppress the knocking that tends to occur when the compression ratio is increased, cooling oil is sprayed onto the piston from the back side. Various piston cooling structures for cooling the piston have been proposed. In one of these cooling structures, in order to increase the cooling effect, a hollow part is formed on the back surface of the top of the piston, cooling oil is supplied to this hollow part, and the oil is stored in the hollow part, so that the piston can move up and down. A piston with a hollow part has also been proposed in which oil is splashed onto the ceiling surface of the hollow part to cool the top of the piston.

In order to efficiently cool the top of this piston with a hollow part, the oil must be circulated in the hollow part so as to sufficiently wet the ceiling surface, and the old and new oil must be replaced efficiently. It is desirable to have this done.

In order to meet this demand, for example, as shown in FIG. 1, the ceiling surface 4 of the hollow part 3 formed on the back surface of the top 2 of the piston 1 is formed into an inclined surface, so that the inertia of oil due to the vertical movement of the piston 1 is A piston that circulates oil along a ceiling surface 4 is known.

However, in such a conventional piston with a hollow part, since the ceiling surface 4 is inclined, the height of the peripheral end of the hollow part 3 becomes low, and the volume of that part becomes small. Therefore, oil tends to fill up in that area, and the flow of the oil is impaired due to stagnation caused by the filling, and there is a possibility that it becomes 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 peripheral end of the hollow part 3, is filled with oil as described above, the supply of oil from the oil jet 6 to the hollow part 3 becomes insufficient. Therefore, there was a problem in that it became difficult to efficiently replace old and new oil.

In addition, since the oil hole 8 provided to collect oil from the oil ring groove 7 of the piston 1 is opened in the horizontal direction, the oil adhering to the back surface of the hollow part 3 is pressed against the outlet part of the oil hole 8. There is also the problem that oil recovery is likely to deteriorate and oil consumption may increase.

Purpose of the Invention In order to solve the above-mentioned problems, the present invention improves the cooling effect of the top of the screw by making the oil in the hollow part undergo sufficient circulation movement and efficiently replacing the oil. At the same time, the purpose is to smoothly recover oil from the oil hole and reduce oil consumption.

Structure of the Invention The piston of the internal combustion engine of the present invention that meets this objective has a ceiling surface and a bottom surface of a hollow portion formed on the back surface of the top of the piston.
The piston is formed on an inclined surface so that the center side of the piston is on the upper side and the peripheral side is on the lower side, and the oil oar, which is drilled inward from the oil ring groove of the screw, is opened diagonally downward. It consists of slanted holes.

Effect of the Invention In such a piston, by slanting the oil hole, interference between the oil hole and the bottom side of the hollow portion can be easily avoided structurally, and the bottom surface of the hollow portion can be easily sloped in the same way as the ceiling surface. The height of the peripheral end of the hollow portion is also high. Therefore, the volume of the hollow part is made sufficiently large even at the peripheral end, which prevents oil from filling up and stagnation.Furthermore, since both the ceiling and bottom surfaces are sloped, the oil is absorbed by the vertical movement of the piston. Good circulation is achieved throughout the hollow space due to inertial force. As a result, the entire ceiling surface of the hollow space is also sufficiently wetted.

In addition, since the height of the circumferential edge of the hollow part is increased, the vicinity of the oil supply hole in the hollow part will not be filled with oil, and the oil from the oil jet will smoothly flow into the hollow part, allowing old and new oil to be efficiently exchanged. Can be replaced often.

Furthermore, since the oil hole is opened diagonally, it is difficult for oil adhering to the back surface of the piston to pass through the oil hole to the oil ring side, and oil from the oil ring groove can be smoothly collected.

Effects of the invention Therefore, by circulating oil over the entire ceiling surface in the hollow space and efficiently replacing old and new oil,
The cooling effect of the piston top can be sufficiently enhanced, the occurrence of knocking can be suppressed, and fuel efficiency can be improved by improving the compression ratio in the engine output direction.

Further, since oil can be smoothly recovered from the oil ring groove through the oil hole, it is possible to reduce oil leakage toward the combustion chamber side, thereby reducing oil consumption.

Embodiments Below, 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 the figure, 10 indicates the entire piston. A hollow portion 1 is provided on the back side of the top portion 11 of the piston 1O.
2 is formed.

The ceiling surface 13 and bottom surface 14 of the hollow part 12 are connected to the piston 1.
When viewed in the vertical direction X of O, the screw is formed into an inclined surface so that the center side of the screw is on the upper side and the peripheral end side is on the lower side. Therefore, the hollow portion 12 as a space defined by the ceiling surface 13 and the bottom surface 14 is formed as an inclined space such that the center side of the piston is on the upper side and the peripheral end side is on the lower side. Further, in this embodiment, the ceiling surface 13 and the bottom surface 14 are formed as substantially parallel surfaces, and the interval therebetween is set to be appropriately wide over the entire area from the center of the piston to the circumferential edge of the hollow portion. In addition, an oil supply hole 16 for guiding oil from the oil jet 15 into the hollow part 12 is formed in the bottom surface 14 of the hollow part 12 at a position near the peripheral end of the hollow part 12, and at a position opposite to the oil supply hole 16. An oil discharge hole 17 is provided.

A piston ring groove 18 and an oil ring groove 19 are carved on the outer peripheral surface of the piston 1O. An oil hole 20 is formed from the oil ring groove 19 to penetrate inward of the piston 10. The oil hole 2O is constituted by an inclined hole that opens diagonally downward inside the piston 10.

In this embodiment, the lower wall of the hollow portion 12 is molded integrally with the piston 10, but as shown in FIG. A hollow lower wall may be formed.

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, and in the upper half of the vertical movement, the piston 10 is subjected to downward acceleration, and in the lower half, the piston 10 is accelerated. 10 is subjected to upward acceleration. Therefore, when upward acceleration is acting on the piston 1O, an inertial force acts on the oil in the hollow part 12 to move it downward relative to the piston 1O, and a downward acceleration is applied to the piston 10. When active, the inertia saw moves in the opposite direction. Therefore, due to the inertial force of the oil caused by the vertical movement of the piston 10, the oil in the hollow part 12 tries to be pressed alternately against the ceiling surface 13 side and the bottom surface 14 side of the hollow part 12; When it fills up, the movement of this oil is stopped.

However, in the present invention, since the oil hole 2O is formed diagonally, even if the position of the bottom surface 14 at the peripheral end of the hollow portion 12 is lowered, the oil hole 2O and the bottom surface 14 can be easily connected structurally. interference can be avoided. Therefore, the spatial height of the peripheral end of the hollow part 12 can be made high, and the volume of the hollow part 12 can be made sufficiently large even at the peripheral end. the result,
Sufficient volume is ensured throughout the hollow portion 12, and the entire area is prevented from being filled with oil.

Therefore, when downward acceleration is acting on the piston 1O, the oil in the hollow part 12 is splashed up by its inertia, and the oil pressed against the ceiling surface 13 moves along the inclined ceiling surface 13 toward the center of the piston. The water flows towards the ceiling and wets the entire ceiling surface 13. and,
When the direction of acceleration of the piston 1O is reversed, the oil is moved toward the bottom surface 14, flows down along the inclined bottom surface 14 due to its inertia, and is discharged from the oil discharge hole 17. That is, the oil in the hollow part 12 is moved up and down by the vertical movement of the piston 1O, as shown by the arrow in FIG.
It is discharged while being circulated within 2. Of this circulating flow,
The flow along the tempura bowl surface 13 sufficiently wets the entire ceiling surface 13, and the top of the piston 10 is effectively cooled.

Furthermore, by ensuring a sufficient height and sufficient volume at the circumferential end of the hollow portion 12, oil is prevented from filling and staying in the vicinity of the oil supply hole 16. Therefore, oil from the oil jet 15 can easily flow into the hollow part 12.
The oil in the hollow portion 12 is swept away toward the discharge hole 17, and the old and new oil are smoothly exchanged.

In addition, since the oil hole 2○ is diagonally drilled,
Oil adhering to the back surface of the piston becomes difficult to enter the oil hole 20 along the back surface of the piston, and also becomes difficult to rise along the oil hole 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.

As is clear from the above description, according to this embodiment, the ceiling surface of the hollow part can be sufficiently wetted over the entire surface, and the oil in the hollow part can be efficiently replaced, and the piston top can be sufficiently cooled. This has the effect of increasing the As a result, the occurrence of knocking can be suppressed, and the engine output and fuel efficiency can be improved.

Further, the oil from the oil ring groove can be smoothly recovered through the oil hole, and the amount of oil leaking into the combustion chamber can be suppressed, thereby achieving the effect that oil consumption can be kept small.

[Brief explanation of the drawing]

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. 6 is a vertical cross-sectional view of a device showing a modification of the device of the second embodiment. 1O...Piston 11...Top 12...Hollow part 13...Ceiling surface 14...Bottom surface 15...Oil Jet 16...Oil supply hole 17...Oil discharge hole 19...Oil ring groove 2O...Oil hole 21...Piston body 22・・・・・・Plate-1-

Claims (1)

[Claims] (1) In a piston for an internal combustion engine in which a hollow part for oil cooling is formed on the back surface of the top of the piston, the ceiling and bottom surfaces of the hollow part are inclined so that the center side of the piston is on the upper side and the peripheral end side is on the lower side. 1. A piston for an internal combustion engine, characterized in that the oil hole is formed from an oil ring groove of the piston toward the inside of the piston and is formed with an inclined hole that opens diagonally downward.