Meritor WABCO -- Products -- System Saver Air Dryers

Meritor WABCO’s Hydraulic Power Brake (HPB) is a braking and vehicle control system for business class trucks (classes 4 through 7) and buses that are equipped with hydraulic brakes. HPB provides:

Full power brake performance.
Braking control functions: Anti-Lock Braking (ABS), Automatic Traction Control (ATC) and Electronic Brake force Distribution (EBD).
Optional Parking Brake Control.

The HPB system has two main components:

Hydraulic compact unit (HCU) which consists of two independent electric motors driving two pump systems, two accumulators, a dual circuit fluid reservoir with integrated filters, pressure relief valves, solenoid valves and a dual circuit relay valve. The HCU is mounted to the vehicle frame rail.
Dual circuit master cylinder.

The HCU is activated each time the ignition is turned on, or whenever the driver steps on the brake pedal. If the system is equipped with the optional power park brake feature, the HCU supplies the energy to release and control the service and park brakes.

During normal operation, the ECU actuates two separate power drivers for the electric motors, keeping the pressure level within the desired limits.

When the brake pedal is applied, the master cylinder provides pressure equal to the pedal force. That pressure is sent from the accumulators to the appropriate brakes. When the pedal is released brake fluid returns from the brake calipers to the reservoir, and line pressure is reduced to zero.

For ABS, wheel pressure is individually modulated by eight integrated ABS solenoid valves in the ECU. For ATC, the normally closed ATC solenoid valve in the ECU is actuated and hydraulic energy is supplied to the sensed wheel. At the same time, the normally open ATC valve is actuated to prevent fluid flow back into the reservoir. The brake pressure is then modulated by the corresponding ABS solenoid valves.

For unparalleled stopping distance capabilities, combine HPB with the Meritor® Quadraulic™ hydraulic disc brake. Learn more about the Meritor® Quadraulic™ hydraulic disc brake.