| 摘要 |
PURPOSE:To prevent piston rings from being pressed to rise sections of piston ring grooves by forming escape recesses having the same width as that of locking pin holes on the piston rings and arranging the escape recesses at the position facing the piston ring grooves opposite to the locking pin holes. CONSTITUTION:Two piston ring grooves 8 are formed on the outer periphery of a piston side wall 3, and piston rings 9 are coupled with them respectively by widening abutments 10, 11. Hooking notches 12, 13 are formed on the abutments 10, 11 of the piston rings 9, and they are hooked with locking pins 14 to restrict the piston rings 9 from being rotated in the peripheral direction. In this case, escape recesses 16, 17 are formed respectively at the opposite position to the hooking notches 12, 13 of the said abutments 10, 11. The escape recesses 16, 17 are formed so that the piston rings are not pressed to the pin 14 direction by the rise sections 18 generated by a cutting tool escaping in the locking pin hole 15 direction while forming the piston ring grooves 8. |
