| 摘要 |
PURPOSE:To improve the strength of a lower rail member and to improve sealing ability through prevention of the occurrence of self-vibration by a method wherein the thickness of the lower rail member with which an oil scratch ring is formed is increased to a value higher than that of an upper rail member. CONSTITUTION:A compact ring 1 comprises a piston body 2, and a piston 8 coupled to a connecting rod 7. A seal ring 10 of a piston ring 6 and an oil scratch ring 11 are engaged internally of a number of grooves 3-5 formed circumferentially of the head part of the piston body 2. The oil scratch ring 11 is formed with upper and lower rail members 12 and 13 and a spacer member 14 held between the nip formed thereby. In this case, a thickness t2 of the lower rail member 13 is increased to a value higher than a thickness t1 of the upper rail member 12. This constitution improves rigidity of the lower rail member 13, prevents the occurrence of self-vibration even when support thereby is rendered partially ineffective, and improve sealing ability. |
