ANTI-LOCK BRAKE PRESSURE MODULATOR

摘要

A brake pressure modulator includes a housing having a bore in which a piston is slidably movable and divides the bore into an outlet chamber communicating with the master cylinder and an outlet chamber communicating with the wheel brakes. A passage in the piston connects the inlet and outlet chambers to permit free fluid communication between the master cylinder and the wheel brakes during normal brake actuation. A plunger operatively associated with a fluid motor extends sealingly through the housing and into the outlet chamber. Brake fluid pressure in the outlet chamber urges the plunger outwardly of the outlet chamber and the fluid motor into engagement of the housing to support the plunger against movement by the brake pressure from a normal position. A valve arrangement is provided to close the passage in the piston upon movement of the plunger from the normal position by a pressure differential acting on the fluid motor in response to a sensed incipient wheel lock condition. Further movement of the plunger forcibly moves the piston to decrease the volume of the inlet chamber and increase the volume of the outlet chamber so that the brake fluid pressure communicated to the wheel brake is decreased. The fluid motor reciprocates the plunger and piston to cyclically release and reapply the brakes. Upon termination of the sensed wheel condition the plunger and fluid motor return to the normal position separated against movement by the brake pressure by engagement with the housing.