Switchable orifice solenoid with plate valve for an anti-lock brake system

Abstract

A switchable solenoid valve is disposed between the master cylinder port and the wheel caliper port for an anti-lock brake system. The switchable solenoid valve includes a valve housing, a valve seat that includes a center orifice and a plurality of perimeter bores, and an axially moveable valve plate and tappet for sealing against the valve seat. The switchable solenoid valve is movable between a normally open position, a closed position and an intermediate position that occurs when the brake system is in anti-lock mode. In the open position, both the valve plate and tappet are spaced away from the valve seat to allow unrestricted pressure fluid flow between the master cylinder and the wheel caliper. When the solenoid valve is moved in to the closed position, the valve plate is in face-to-face engagement with the valve seat to seal the perimeter bores while the tappet is simultaneously sealingly engaged with the center orifice. When the brake system is in anti-lock mode, the valve is switched into the intermediate position and the valve plate remains sealed against the valve seat due to a pressure difference between the master cylinder port and the wheel caliper port, while the tappet moves partially away the center orifice to permit restricted fluid flow to flow between the master cylinder port and the wheel caliper port.