TROY, Mich., (March 16, 2005) – Commercial vehicle components supplier ArvinMeritor and Meritor WABCO Vehicle Control Systems announced has unveiled a new Premium Hydraulic Braking System for medium-duty truck and bus applications.

The package, available immediately in North America, includes Meritor WABCO’s Hydraulic Power Brake (HPB) — the next-generation of its hydraulic actuation and anti-lock braking system (ABS) — and the Meritor Quadraulic hydraulic disc brake. Combined, these two brake technologies offer unparalleled stopping and performance capabilities, the companies said in a conference call to trucking journalists.

Drivers, the companies say, will appreciate pedal feel similar to that of a passenger car, while fleets and owner-operators will benefit from longer lining life, fewer aftermarket parts and single-source shopping.

The HPB is a braking and vehicle control system for vehicles in classes 4-7, providing three important functions:

— It does not require the use of an external source to provide power assist to achieve a low pedal effort as required in a conventional hydraulic braking system.

— Includes brake control functions, including ABS, automatic traction control (ATC), and electronic brake force distribution (EBD); and optional auto-apply electronic parking brake control.

The hydraulic energy required to actuate the brakes and control these functions is stored in hydraulic accumulators. When the vehicle’s ignition is turned on, internal pumps are activated and fill both accumulators with pressurized hydraulic brake fluid. When the brake pedal is applied, the small master cylinder provides a hydraulic signal to the relay valve.

Proportional to that signal, ArvinMerior explains, the accumulators provide pressure to the brake calipers. When the pedal is released, brake fluid returns to the reservoir from the brake calipers. For ABS and ATC activation, pressure at the wheel is individually modulated by ABS and ATC solenoid valves in the hydraulic modulator assembly. When required, hydraulic pressure is supplied and released to the appropriate foundation brake to achieve the desired functional effect.

“The enhanced stopping performance delivered by the new HPB is accomplished through faster reaction time when compared to other available hydraulic braking systems,” said Alan Korn, chief engineer, Meritor WABCO. “This improved reaction time is a direct result of the stored energy in the accumulators, which are features distinct to this system.”

EBD (electronic brake force distribution) is another key development of the HPB system. According to the companies, this function provides constant review of the vehicle’s load status and monitoring of each wheel end. Based on wheel slip observed by the HPB system during braking, braking forces at the axles are automatically adjusted to achieve a balanced, efficient use of the brakes. This allows the vehicle to adjust for consistent brake feel independent of the load, ArvinMeritor says.

The Quadraulic disc brake — designed to package within the 19.5 x 6.75 inch and 22.5 inch wheel sizes, and available in two piston sizes (4 x 64 mm and 4 x 70 mm) — uses a fixed caliper, eliminating concerns often associated with rail slider or pin slider designs.

When lining changes are required, only the lining retention bolt needs to be removed and the new linings can be dropped into the caliper. An absence of caliper swing due to the fixed caliper design allows for the brake hose to remain untouched during the lining replacement process eliminating the possibility of hose damage, according to the companies.