JPS6128822B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piston having a cavity in its head forming a combustion chamber of an internal combustion engine.

Conventionally, metal materials, particularly aluminum alloys, have been mainly used as materials for this type of piston.
However, although such materials are lightweight and have excellent heat resistance, they do not have anything noteworthy from the perspective of improving combustion performance.

For this reason, there is a type in which the inner wall of the cavity is made of a ceramic member, and the outer periphery is cast with the piston base material through a reinforcing material made of a metal material with a small coefficient of thermal expansion (see Utility Model Application No. 79910/1983). ).

However, even with this method, it is difficult to effectively absorb deformation due to the difference in thermal expansion coefficient between the ceramic member and the piston base material with the reinforcing material made of metal. Since they are subjected to large explosion pressures, there were problems in terms of durability, such as the possibility of peeling from the joint between the two.

The present invention was made in order to solve these conventional problems, and the present invention is made by using asbestos or glass fiber as the main component over the entire surface between the ceramic member constituting the cavity inner wall and the metal piston base material. This cushioning material can sufficiently effectively absorb deformation due to the difference in thermal expansion coefficient between the ceramic member and the piston base material, and can also absorb explosion pressure well, so it has excellent durability. An object of the present invention is to provide a piston for an internal combustion engine, which has features such as excellent performance and improved yield because no precision is required in the shape and dimensions of the buffer material layer during manufacturing.

The present invention will be explained below based on embodiments shown in the drawings.

In FIG. 1, a piston 1 can freely reciprocate up and down within a cylinder liner 3 of a cylinder block 2, and has an intake port 6 and an intake valve 7 in a combustion chamber 5 formed between the head of the piston 1 and the cylinder head 4. By compressing the intake air absorbed through the compressed air and igniting the fuel injected from the injection nozzle 8 into the compressed air, the piston 1 is pushed down by the explosion pressure, and the piston 1 is pushed down through the piston 9, the connecting rod 10, etc. Get the output.

A plurality of annular grooves 11 provided on the outer periphery of the piston 1
A compression ring and an oil ring 12 are fitted inside to prevent compressed gas from leaking from the combustion chamber 5 into the crankcase.

According to the present invention, the piston 1 having such a configuration is formed as follows. A cavity 20 provided at the head of the piston 1 and forming a part of the combustion chamber 5 is formed of a cylindrical ceramic member 21, and the entire outer circumference is covered with a cushioning material layer mainly composed of asbestos material or glass fiber. 41 is sandwiched between them and cast-molded with a metal material 22 such as an aluminum alloy. Ceramic members have good heat resistance, so they prevent cracks in the inner wall of the cavity when the temperature rises. With this configuration, the temperature drop inside the cavity formed by the highly insulating ceramic member 21 is suppressed, the ignitability of the heating material is improved, the ignition delay period is shortened, knocking is reduced, and engine noise is reduced. It is also possible to reduce the amount of fuel and improve startability.

Further, the buffer material layer 41 is capable of stress deformation, and can effectively absorb deformation due to the difference in thermal expansion coefficient between the ceramic member 21 and the metal material 22 during casting and engine operation, and can also absorb explosion pressure. Due to the effective damping, the overall durability of the piston is significantly improved compared to conventional pistons. Furthermore, since no precision is required in the shape and dimensions of the cushioning material layer during manufacturing, the yield is improved.

2 and 3 show a modification of the previous embodiment. That is, the outer peripheral surface of the ceramic member 21A is tapered downward (FIG. 2), or the collar 31 is extended from the outer peripheral surface of the ceramic member 21B (FIG. 3). Both the taper and the brim prevent the metal material 22 and the ceramic members 21A, 21B from peeling off, and the boundary layer between the ceramic and metal may buckle due to the difference in thermal expansion or other mechanical stress. To make the peeling phenomenon that easily occurs less likely to occur.

FIG. 4 shows that in the above embodiment, the ceramic members 21, 21A, 21B are all formed into a vessel shape with a predetermined thickness from the inside of the cavity, whereas the entire piston head is formed of a ceramic member 51 and a cushioning material layer 41 is formed. It is shown that it is cast with a metal material 52 through it. In this case, the conventional compression ring is abolished and 1
Alternatively, the plurality of annular protrusions 51a can be connected to the ceramic member 51.
The combustion chamber 5 and the crankcase are integrally formed so as to protrude, thereby providing a gas seal between the combustion chamber 5 and the crankcase. Annular protrusion 51a
When a plurality of finely spaced ceramics are provided, it functions as a labyrinth seal (Fig. 4, 51a'). In this way, the thermal expansion coefficient of ceramic is significantly lower than that of metal materials (approximately 1/7 that of aluminum alloy). If the annular protrusion 51a is formed by precision machining, thermal deformation of the piston head and the annular protrusion 51a is extremely small, and the structure is small enough to provide sufficient gas sealing without using a separate compression ring. This allows the gap to be maintained. Therefore, mechanical loss due to friction between the compression ring and the cylinder liner can be reduced, and the net output of the engine can be increased.

It is possible to reduce the weight of the piston by making the outer diameter of the metal material 52 including the skirt portion smaller than that of the ceramic member 51 of the piston head, and it is also possible to integrally mold the entire piston from ceramic material.

As described above, according to the present invention, in a piston having excellent thermal sinterability and having a cavity formed of a highly insulating ceramic member, asbestos or glass fiber is mainly contained between the ceramic member and the piston base material made of a metal material. Since the cushioning material layer is provided, it is possible to effectively absorb the deformation difference due to thermal and other mechanical stress differences between the ceramic and metal, preventing damage to both, and significantly increasing durability.
Effects such as improved production efficiency, improved yield, and cost reduction can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing the inside of a cylinder of an internal combustion engine using the piston according to the present invention, FIGS. 2 and 3 are vertical cross-sectional views showing a modified form of the piston,
FIG. 4 is a longitudinal sectional view of a piston showing another embodiment. 1... Piston, 20... Cavity, 21, 21
A, 21B, 51... Ceramic member, 22, 52
...Metal material, 41...Buffer material layer.

Claims (1)

[Claims] 1. The inner wall of the cavity is made of a ceramic member,
In a piston for an internal combustion engine that is cast and molded in a piston base material made of a metal material, a buffer material layer mainly composed of asbestos or glass fiber is provided over the entire surface between the ceramic member and the piston base material. A piston for an internal combustion engine characterized by: 2. A piston for an internal combustion engine according to claim 1, characterized in that the ceramic member is formed into a vessel shape. 3. The piston for an internal combustion engine according to claim 2, wherein the outer peripheral surface of the vessel-shaped ceramic member is cylindrical. 4. A piston for an internal combustion engine according to claim 2, wherein the outer circumferential surface of the vessel-shaped ceramic member has a peel-preventing shape such as a downwardly expanding taper or a flange, and the outer circumferential surface of the ceramic member is cast-molded with a metal material. 5. The piston for an internal combustion engine according to claim 1, wherein the piston head including the cavity is mainly made of ceramic, and the lower part including the skirt with a buffer layer interposed therebetween is made of metal. 6. The piston for an internal combustion engine according to claim 5, wherein the outer diameter of the piston head is larger than the outer diameter of the lower part. 7. A piston for an internal combustion engine according to claim 5 or 6, wherein the outer periphery of the piston head is integrally formed with one or more annular protrusions serving as a gas seal ring.