Abstract: The present invention is directed to a retarder control system for protection against transmission overspeed. The system operates in conjunction with a rotatable input member and an output member that is rotatable relative to the input member. A torque transfer device is operatively connected between the relatively rotatable input and output members. Specifically, a piston assembly is operated by an input control chamber that selectively receives pressurized hydraulic fluid which effects translation of the piston assembly to actuate the torque transfer device and thereby effect a driving connection between the relatively rotatable input and output members. The present system is adapted to control a hydrodynamic retarder assembly having a work cavity to receive hydraulic fluid. The retarder input valve assembly is supported from one of the relatively rotatable members selectively to deliver pressurized hydraulic fluid from the input control chamber to the retarder cavity.

Abstract: A retarder control embodying the concepts of the present invention utilizes a spool valve having a spool valve member axially translatable between an on- and an off-position. A spring is employed to bias the spool valve member toward its off-position. A torque converter, a cooler and a retarder each have an input and an output that are ported through the spool valve. The retarder is selectively ported to a hydraulic return through the spool valve, and a modulating solenoid may be employed to feed pressurized hydraulic fluid against the spool valve member not only to move the spool valve member against the spring toward its on-position but also to regulate the axial translation of the spool valve member in order to control the pressure at the retarder discharge that is also ported through the spool valve. A cooler communicates directly with the converter when the spool valve member is in its off-position.

Abstract: An electronically controlled hydrodynamic retarder interconnects with the output shaft of a vehicle transmission to selectively apply a braking torque thereto. The retarder includes a solenoid valve, the operating duty cycle of which controls the retarder capacity and resultant braking torque. A control unit, interconnecting the transmission and the retarder, regulates the duty cycle of the solenoid valve to regulate the retarder operation as a function of excessive deceleration or overheating, while also regulating such operation during downshift to assure efficient, effective, and comfortable operation of the transmission/retarder. The retarder is adaptive to accommodate variations resulting from age, wear, and the like.

Abstract: An accumulator and relay valve is operable to isolate a fluid operated electric switch from the transient pressure pulses present at the output of a pulse-width-modulated pressure control valve. The accumulator and relay valve is further operable to control a minimum pressure level that is communicated from the pressure control valve to the switch.

Abstract: A hydraulic retarder is disposed to receive fluid as directed by a flow valve to selectively retard vehicle motion. The flow valve responds to an operator controlled modulator valve to direct fluid from a cooler which is supplied from a torque converter to the hydraulic retarder upon a request by the operator. A modulator valve is also effective to control the pressure of the fluid exiting the cooler and entering the retarder.