Patent ID: 6276137
Filing Date: 2001-08-21
Classification: B60T

Abstract:
A brake master cylinder comprising, in combination:a cylinder defining a bore;a primary piston in the bore having a primary seal thereon;a secondary piston in the bore downstream of the primary piston in the direction of brake activation and having a primary seal and a secondary seal thereon;a primary pressure chamber defined in the bore between the primary seal on the primary piston and the secondary seal on the secondary piston and being in fluid communication with a first brake;a secondary pressure chamber defined in the bore downstream of the primary seal on the secondary piston and being in fluid communication with a second brake;an intermediate chamber defined in the bore between the primary seal on the secondary piston and the secondary seal on the secondary piston;the cylinder having a primary bypass opening downstream of the primary seal on the primary piston with the primary piston in an inactivated position, a primary compensation opening upstream of the primary bypass opening and the primary seal on the primary piston, a secondary bypass opening downstream of the primary seal on the secondary piston with the secondary piston in an inactivated position, and a secondary compensation opening upstream of the secondary bypass opening and the primary seal on the secondary piston, each of the primary and secondary bypass openings and the primary and secondary compensation openings communicating with the reservoir;the primary seal on the primary piston passing over the primary bypass opening with activation of the primary piston from its inactivated position;the primary seal on the secondary piston passing over the secondary bypass opening with activation of the secondary piston from its inactivated position;the secondary piston having an axial fluid flow passage with a primary check valve permitting fluid flow only out of the axial fluid flow passage into the primary pressure chamber and a secondary check valve permitting fluid flow only out of the axial fluid flow passage into the secondary pressure chamber;a cross flow passage in the secondary piston intersecting the axial fluid flow passage between the primary and secondary check valves to communicate the axial fluid flow passage with the intermediate chamber and thus with the reservoir through the secondary compensation opening, anda filter element carried by the secondary piston in the path of brake fluid flowing through the axial flow passage so as to prevent particles from being carried by the brake fluid to either of the primary and secondary check valves, the filter element being an internal filter element disposed in the axial fluid flow passage and spanning the intersection thereof with the cross flow passage.