| 摘要 |
PURPOSE:To prevent gouging between a cavity forming member and a cylinder to enhance the durability of the cylinder, by forming the cavity forming member with a diameter smaller than that of the piston body, and as well, by fitting the cavity forming member in a through-hole formed in the substantially center section of the top surface of the piston body. CONSTITUTION:A piston body 2 is rotatably attached to a connecting rod 7 by means of a piston pin 6. Further, a cavity forming member 3 in which a recessed combustion chamber cavity 4 is formed is pivotally supported to the piston pin 6 through an attaching hole 9 formed in the leg section 8 of the cavity forming member 3. In this arrangement, the cavity forming member 3 is formed in a bottomed cylinder shape having a diameter smaller than that of the piston body 2, and the cylindrical section 2a of the cavity forming member 3 is fitted in a through-hole 1a formed in the substantially center section of the top surface of the piston body 2 so that the top surface of the cavity forming member 3 is made substantially flush with the top surface of the piston body 2. With this arrangement, the cavity forming member 3 is never made into contact with the inner wall of a cylinder even by vibration so that it causes no gouging between the cavity forming member 3 and the cylinder.
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