Delayed rear brake application in electro-hydraulic (EHB) braking systems

摘要

A vehicle electro-hydraulic braking system of the type which can operate in a brake-by-wire mode wherein hydraulic pressure from an electric pump is applied to wheel brake actuators in proportion to the driver's braking demand DD as sensed electronically at a brake pedal (12, fig 1), wherein the pressure demand RBD for rear brake actuators (16b, fig 1) is arranged to be delayed until at least one of two conditions has been fulfilled, namely (a) the pressure FBD of at least one front brake actuator (16a, fig 1) has reached a predetermined pressure PSBmin/SB, (eg. 2 bar) and/or (b) a predetermined time delay threshold TSBmax/SB has been exceeded (eg. 100-300ms) and/or wherein delivery to the fluid brakes is limited to a predetermined value that is relatively low with respect to that for the front brakes (eg. 10% of front brake delivery). In emergency, a master cylinder mechanically coupled to the brake pedal can supply fluid directly to front brake actuators in a push-through mode via digital valves (30a, 30b, fig 1).