VEHICLE BRAKING APPARATUS

摘要

A vehicle braking apparatus (10) having a service braking section (12) and a wheel lock control (ABS) section (14). Under certain conditions the wheel lock control section may not be able to generate sufficient pressure to operate the vehicle wheel brakes when the master cylinder (20) output pressure has been isolated therefrom. When such conditions occur, the displacement piston (106) of the ABS section moves to open a check valve (122,200) which connects master cylinder output pressure to the vehicle wheel brake (30) even though the ABS section has isolated it from that wheel brake. The check valve is a two-stage orifice valve arrangement which provides orifice control of master cylinder pressure during initial brake actuation and provides two stage valve opening action when the master cylinder output pressure is to be delivered to the wheel brake to actuate that brake irrespective of the attempted control of the wheel brake by the ABS section of the vehicle brake apparatus. This therefore effectively returns the vehicle braking apparatus to service braking until the vehicle operator releases the vehicle braking apparatus.