JPS5874853A - Piston head - Google Patents

Abstract

PURPOSE:To avoid thermal and mechanical stress concentration by subjecting a peripheral angular part including contact face with the metal piston head of a piston cap made of a sintered ceramic material to a chamfering process for making the peripheral angular part a curved form. CONSTITUTION:The peripheral angular part of a piston cap 2 made of a sintered ceramic material is formed into a curved shape by a chamfering process. The curvature radius of the curved face thus formd is designated to a range of 0.5- 5mm., because too small curvature radius makes the chamfering ineffective and also too large curvature radius makes the contact distance with a metal head body too large and also makes the contact area too less, resulting in insufficient fixation. Also, when the contact face between the piston cap 2 and the heat body 1 is roughened to a surface roughness of 1-20S, the holdability of lubricating oil and the efficiency of combustion can be raised. In this way, the concentration of thermal and mechanical stresses can be avoided and a heat-insulating effect with the head body can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piston head used, for example, in a reciprocating engine.

Traditionally, in the piston head of an internal combustion engine such as a reciprocating engine, a head cap made of a ceramic sintered body with low thermal conductivity and good heat resistance is provided on the top of the metal head body, and the head cap is made of a ceramic sintered body with low thermal conductivity and good heat resistance. Efforts are being made to reduce heat loss in the engine to increase output, reduce hydrocarbon emissions, or reduce fuel consumption.

Various shapes are used as the above-mentioned head caps, but in the case of a head cap with an uneven bottom, the mechanical strength of the corner portion is low and cracks may occur due to stress concentration. In addition, such head caps are often fixed to the head body by the so-called casting method, but in this case, 118# ceramic skewers are easier to attach than metal. Because it is extremely small, when the metal material cools and solidifies after casting, the ceramic material is strongly compressed, causing cranks, or even if no cracks occur, compressive stress remains in the ceramic material, especially in these corners. However, the disadvantage was that the mechanical strength was significantly reduced.

The present invention was made in order to eliminate these drawbacks, and the corners of the outer peripheral surface of the piston cap made of a ceramic sintered body, including the contact surface with the piston head body, are chamfered into a single curved shape. It is an object of the present invention to provide a piston head characterized by the following features.

The ceramic sintered body constituting the piston cap of the present invention includes nitrides such as Si, N, AIN, TiN, ZrN, oxynitrides such as 8i, ON, 8iiJON, 8i0. In addition to carbides such as B, O, Tie, and Zre, oxides such as A7 0-%Z rO-1MjAJ, 0°, and carbide sintered bodies such as 8i-N--8i0, MA8 (My-AA!-8i) Yarn and LA
There are S (Ij-AI-8i) type glass ceramics.

According to the present invention, all the corners of the outer thin surface of the piston cap made of these ceramic sintered bodies are chamfered into a curved shape, but if the radius of one skewer of the curved surface is too small, the chamfering effect will be lost. On the other hand, if it is too large, the bonding gap with the head, dowel, etc. will become too large, the contact area with the fixed metal will decrease, and the function of ceramic identification will be lost, so the range of 0.5 to 5 M. It is preferable to

Further, it is desirable that the contact surface of the piston cap with the head body be polished to a surface roughness of 1 to 208. In this case, there is an advantage that not only the retention of lubricating oil is improved but also the combustion efficiency of the entire internal combustion engine is improved.Hereinafter, the present invention will be explained in more detail based on the embodiments shown in the drawings.

1 to 4 are cross-sectional views of the piston head of the present invention. In Figure 1, the metal piston head body l
The corners of the outer circumferential surface, including the abutting surfaces between the piston cap 2 and the piston cap 2 made of the ceramic sintered body, are all chamfered into curved shapes.

In addition, in FIGS. 2 and 3, 3 indicates a metal ring ◎ In the embodiment shown in FIG. In the embodiment shown in FIG. 3, a metal ring 3 is fitted onto the cap 2 and the outside of the head body 1 by shrink fitting.

Further, in FIG. 4, numeral 5 indicates a binding device made by the casting method.

In the piston head of the present invention constructed as described above, the corners of the outer surface of the piston cap made of a ceramic sintered body are processed to face each other in a curved shape, so that thermal radiation to these parts is reduced. Mechanical stress concentration can be avoided.

In addition, since a slight gap is maintained between the metal head body and the head body, this part has a large insulation effect, and this gap absorbs the thermal expansion of the metal, preventing the spread of compressive force to the cap. It has the advantage of being able to

[Brief explanation of drawings]

Figures 1 to 4 are cross-sectional views of embodiments of the present invention. 1... Piston head body 2... Piston cap 3... Metal ring 4... Fastening tool 5... Binding tool (7317) Kengo Patent Attorney Norichika Kensuke (and 1 other person) Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] A piston head consisting of a ceramic sintered piston cap having a bowl-shaped cross section, an inverted bowl shape, or a flat plate is fixed to the top of a metal piston head body, and the piston cap is in contact with the head body. A piston head characterized in that the corners of the outer granite surface including the surface are chamfered into a curved shape.