| 摘要 |
PROBLEM TO BE SOLVED: To ensure radiation performance from the upper portion of a piston to a cylinder bore while maintaining a friction reducing effect between the piston and the cylinder bore by a spacer. SOLUTION: The spacer 14 is fitted inside the water jacket 13 formed to surround the periphery of the cylinder bore 12a of a cylinder block 11 in an internal combustion engine. For this reason, the cylinder bore 12a is thermally insulated by regulating a flow of cooling water in the water jacket 13 by the use of the spacer 14. Thereby, friction between the cylinder bore 12a and a piston 18 can be reduced by thermally expanding the cylinder bore 12a. When the piston 18 is situated in the maximum side-pressure generating position, the upper edge of the spacer 14 is situated between piston rings 19-21 and the skirt part 18b of the piston 18, respectively. For this reason, the heat dissipation performance of the upper portion of the piston 18 can be secured by: reducing the sliding resistance as a result of enlarging the diameter of the cylinder bore 12a by covering a portion of the cylinder bore 12a, which corresponds to the outer side of the skirt part 18b in a radial direction, by the use of the spacer 14; and concurrently avoiding the coverage of the outside of the piston rings 19-21 in the radial direction by the use of the spacer 14. COPYRIGHT: (C)2011,JPO&INPIT
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