| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a structure preventing damage due to galling between an inner circumferential face 11d of a shell 10 and a piston 20 without causing any increase in a cost. SOLUTION: In a seal mounting groove 21 of the piston 20, a seal member 50 constructed of a T-ring and backup rings 60 and 60 axially arranged on both sides of the seal member 50 are held, and the inner circumferential face 60b in each of the backup rings 60 is brought into tight contact with a groove bottom 21a of the seal mounting groove 21, while the outer circumferential face 60c is brought into tight contact with the inner circumferential face 11d of the shell 10 and provided with a required thickness in a axial direction for increasing radial rigidity in comparison with the seal member 50. Consequently, the backup ring 60 is provided with a bearing function to reduce inclination when the piston 20 is moved in the axial direction.</p> |
