Heat-insulating piston structure
First Claim
1. A heat-insulating piston structure comprising:
- a piston skirt adapted to be moved reciprocatingly in a cylinder liner and having an upper end wall;
a piston head having a mounting portion to be fixed to said upper wall of said piston skirt and formed out of a material the coefficient of thermal expansion of which is substantially equal to that of a ceramic material;
a ring consisting of a ceramic material and adapted to be fixed in a pressed state to the upper surface of said piston skirt by setting said piston head on said piston skirt;
a thin plate portion of a small thickness consisting of a ceramic material, joined at its outer circumferential portion to said ring and constituting a surface member exposed to a combustion gas; and
a heat-insulating member sealed in a hollow space defined by the upper surface of said piston head, the lower surface of said thin plate portion and a part of the inner circumferential surface of said ring.
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Accused Products
Abstract
The heat-insulating piston structure according to the present invention is formed by fixing a piston head, which consists of a material the coefficient of thermal expansion of which is substantially equal to that of a ceramic material, to a piston skirt, and setting a thin, flat plate portion of a ceramic material on the whole of the flat surface of the piston head which is on the side of a combustion chamber via a heat-insulating member. Accordingly, the piston can be formed so that it has excellent heat-insulating characteristics and high thermal resistance, deformation resistance and corrosion resistance. Especially, the thin plate portion of a ceramic material, which is exposed to a combustion gas, can be formed to the smallest possible thickness to reduce the thermal capacity thereof greatly. Therefore, the temperature of the wall of the combustion chamber varies easily with that of the combustion gas (in other words, the amplitude of the temperature of this wall becomes large). Consequently, a difference between the temperature of the thin plate portion of a ceramic material and those of the gases (combustion gas and suction air) becomes small momentarily, so that the heat transfer rate of the thin plate portion decreases. This causes a decrease in the quantity of heat which the suction air receives from the wall surface. As a result, the suction air smoothly enters the combustion chamber without being expanded therein. This enables the suction efficiency and cycle efficiency to be improved.
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Citations
23 Claims
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1. A heat-insulating piston structure comprising:
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a piston skirt adapted to be moved reciprocatingly in a cylinder liner and having an upper end wall; a piston head having a mounting portion to be fixed to said upper wall of said piston skirt and formed out of a material the coefficient of thermal expansion of which is substantially equal to that of a ceramic material; a ring consisting of a ceramic material and adapted to be fixed in a pressed state to the upper surface of said piston skirt by setting said piston head on said piston skirt; a thin plate portion of a small thickness consisting of a ceramic material, joined at its outer circumferential portion to said ring and constituting a surface member exposed to a combustion gas; and a heat-insulating member sealed in a hollow space defined by the upper surface of said piston head, the lower surface of said thin plate portion and a part of the inner circumferential surface of said ring. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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Specification