Gm Global Technolgoy Operations, Inc.

Harry Fackenthal

Carl A Lentz

James C Polak

Walter Eric Palmer

Robert H Schaefer

A retarder and friction brake system having vehicle service brakes and a shaft brake unit having a hydrodynamic retarder and friction brake. Manual brake controls provide for initial brake apply of the brake unit and then apply of the service brakes or independent apply of the service brakes. The brake unit has a dual chamber, hydrodynamic retarder with opposed bladed stators and a central rotor member having opposed bladed rotors mounted between the stator members for limited axial movement and rotation with a drum fixed to the shaft, and a friction brake having plates located concentrically within the retarder chambers on opposite sides of the rotor and splined to the drum and stators and a brake apply motor. In response to brake demand, the brake controls provide air pressure proportional to brake demand to the brake apply motor and fluid pressure proportional to brake demand and, in a low speed range limited to lower values with decreasing speed, to a brake chamber to provide a release pressure on the brake apply motor and flow through the constant restriction cooling passages in the brake plates to the retarder chambers for retarder braking and pumping through a cooler to provide with increasing speed in the low speed range, decreasing friction braking and increasing retarder braking having a total value proportional to brake demand, and in the higher speed range low friction braking and high retarder braking having a total value proportional to brake demand and increasing in a substantially straight line with increasing speed.

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Indianapolis, IN, United States of America

Harry Fackenthal