Patent ID: 7003954
Filing Date: 2006-02-28
Classification: B60T

Abstract:
1. A master cylinder apparatus comprising: a tandem-type master cylinder adapted to be connected to wheel cylinders through fail-safe valves; and a stroke simulator for ensuring a desired stroke of a brake pedal upon receiving a brake fluid introduced from a primary-side fluid pressure chamber formed in the master cylinder, wherein: the tandem-type master cylinder comprises: a cylinder body; a primary piston and a secondary piston arranged in an axial direction of the cylinder body and being capable of sliding movement in the cylinder body; the primary-side fluid pressure chamber, which is defined between the primary piston and the secondary piston; a secondary-side fluid pressure chamber defined between the secondary piston and the cylinder body; a first circumferential groove and a second circumferential groove formed in an inner surface of a bore of the cylinder body, the first circumferential groove and the second circumferential groove being spaced apart from each other in the axial direction of the cylinder body; a first cup seal provided in the first circumferential groove and adapted to seal an outer circumferential surface of the primary piston; a second cup seal provided in the second circumferential groove and adapted to seal an outer circumferential surface of the secondary piston; a first return spring provided in the primary-side fluid pressure chamber so as to bias the primary piston in a direction for retraction; a second return spring provided in the secondary-side fluid pressure chamber so as to bias the secondary piston in the direction for retraction; and a limiting means provided in the cylinder body so as to limit a retracted position of the secondary piston.