A hydraulic retarder and control composed of an accumulator, for rapid filling of the retarder; a pulse valve, for controlling fluid flow to and from the accumulator; a regulator valve, for limiting the inlet pressure to the retarder; and a pair of check valves, for preventing fluid flow from the retarder to a pressure source and from the retarder to the accumulator. The pulse valve is controllable to provide rapid filling of the retarder, while the regulator valve will direct fluid from a secondary source to the retarder and control the pressure at the retarder inlet. The accumulator is filled from the main pressure source, between retard requests, at a rate that does not disturb the main transmission pressure level. One of the check valves and the pulse valve prevent the fluid in the accumulator from returning to the system other than when a retard request is present.
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. To the contrary, the cooler communicates directly with the retarder when the spool valve member is in the on-position. First and a second reaction sub-chambers are disposed in opposition against the spool valve member. A spring is received within the first reaction sub-chamber. A modulating solenoid effects continuous communication of pressurized hydraulic fluid to the second reaction sub-chamber when the spool valve member in its on-position, and a conduit selectively communicates pressurized hydraulic fluid to the first reaction chamber.
A hydrodynamic retarder control apparatus includes two valve spools, one, a retarder control valve, functions as a relay valve to control the on/off operation of a hydrodynamic retarder and the other, a regulator valve, functions to control the regulation of pressure at the hydrodynamic retarder. During abnormal periods of operation of the regulator valve, the retarder control valve will also function as a pressure control valve thereby limiting the maximum pressure at the hydrodynamic retarder.
In one aspect of this invention, a system and process for controlling a fluid actuated retarder is disclosed. This includes an input mechanism and an electronic controller for receiving a signal from the input mechanism, including a value for a desired retarder control level. Also, there is a proportional solenoid valve that is actuated by the electronic controller. The proportional solenoid control valve is operatively connected to a proportional retarder spool valve and the proportional retarder spool valve is operatively connected to a fluid actuated retarder.
