Abstract: A reservoir assembly for a vehicle hydraulic braking system includes two chambers (2, 3) for the storage of hydraulic fluid. The reservoir assembly is provided with a structure for increasing the effective volume of one of the chambers (2), for example a bellows (12) or a bucket (30), and which may be operable in conjunction with the fitting of a filler cap (17) to seal a filler opening (5) for that chamber. This enables a volume of fluid to be accommodated in a chamber of increased volume, thereby substantially eliminating the possibility of volume in excess of a given volume from overflowing from the chamber (2, 3). When the reservoir assembly is installed in a vehicle braking system of a brake-by-wire electro-hydraulic type (EMB) having a first power circuit (51), and a second back-up hydrostatic circuit (60), the one chamber (2) supplies fluid to the hydrostatic circuit, and the other chamber (3) supplies fluid to the power circuit.

Abstract: An hydraulic braking system of the brake-by-wire type has an hydraulic pressure source comprising an hydraulic accumulator adapted to be charged by a pump. An accumulator isolating valve is so positioned and biased to correspond to the direction of flow from the accumulator to a solenoid-operated proportional valve. The valve is biased into a closed position in opposition to the flow from the pump to the accumulator.

Abstract: A compliance unit (8) for use in an hydraulic braking system is disclosed which is adapted to absorb hydraulic fluid from a master cylinder (1) during normal braking and, in the event that a fault in the braking system is detected the unit is adapted to return fluid to the master cylinder (1). The compliance unit (8) therefore effectively decreases its compliance in the event of a fault. The unit (8) may comprise a pair of pistons (14, 15) working in a stepped bore against a first and second biasing force, with a third variable biasing force provided to cancel out the second biasing force during normal operation to provide an increased compliance.