| 摘要 |
PROBLEM TO BE SOLVED: To provide a vehicular hydraulic master cylinder capable of quickly increasing a hydraulic pressure from an initial stage of a brake operation while preferably keeping an operational feeling of an initial stage of the brake operation.SOLUTION: A first seal groove 14b has a cylinder hole opening lateral surface 14g formed with a flat surface intersecting a cylinder shaft, a cylinder hole bottom part lateral surface 14e and a seal groove bottom surface 14h in parallel to the cylinder shaft. A primary cup 16 includes a base part 16a, an inner circumferential lip part 16b and an outer circumferential lip part 16c, and the outer circumferential lip part 16c provides an annular raised part 16e, the top part of which is abutted on a cylinder hole inner circumferential surface 11d on a top end side outer circumferential surface. Upon the assembling, an outer circumferential surface 16g from an edge part 16f of the base part side of the raised part 16e to the base part 16a gets to an inclination surface, the diameter of which gradually increases and a clearance E1 between the cylinder hole inner circumferential surface 11d and an outer circumferential surface of a piston 14 gets smaller than a clearance E2 between an outer circumferential surface of the base part 16a and the cylinder hole inner circumferential surface 11d.SELECTED DRAWING: Figure 1 |
