| 摘要 |
<p>PROBLEM TO BE SOLVED: To improve formability and profitability while preventing effectively failure caused by biting of cup seal under generation of high liquid pressure by forming beveling of a specified size on the top end side surface outer circumferential rim of a piston in a liquid operated master cylinder for a vehicle and the like. SOLUTION: In a liquid operated master cylinder for the rear wheel disk brake device in a motorcycle, a cylinder hole 7 is arranged so as to open the bottom end thereof, and a piston 8 is fit in fluidsealing relation and movably through a cup seal 10. The cup seal 10 and a retainer 11 are arranged on the top end surface 8d of a piston 8 in which a liquid operated chamber 9 is formed between the cylinder hole 7 upper wall and the piston 8, and a reset spring 12 is contractedly arranged between the retainer 11 and the cylinder hole 7 upper wall. In the diameter of the piston 8, an upper flange 8b is formed slightly smaller than that of a main body part 8a, and also the outer circumferential rim of the upper end surface 8d of the upper flange 8b is formed in a circular arc shape of a beveling radial diameter R 0.6mm to 1.2m.</p> |
