A hydrodynamic machine comprising: a toroidal working chamber including a first bladed wheel and a second bladed wheel arranged concentrically with the first bladed wheel; and an electrohydraulic system including an open loop unit and a and closed loop control unit, a working medium accumulator, a pump operable to pump a working medium from the working medium accumulator into the toroidal working chamber, a heat exchanger, a valve operable to switch between a first position, the first position being a non-braking position, and a second position, the second position being a braking position, and a line system operable to allow the pump to pump the working medium in both the first position and the second position into the working chamber.

A controllable hydrodynamic retarder system for a transmission including an electronic controller unit (ECU) for selecting and controlling brake torque by adjusting a retarder outlet pressure is described. The system can include an algorithm to calculate a retarder outlet pressure set point or tables or brake torque curves or profiles to allow the ECU to calculate or look up the functional relationships between the retarder RT outlet pressure, a vehicle or rotor speed, and a brake torque curve selected by the operator to provide the selected RT outlet pressure. The systems disclosed can also include a cooling system or utilize a vehicles engine cooling system. In one embodiment, the cooler can be shared between a transmission and the controllable retarder and can be adjusted to accommodate cooling requirements. The ECU can also make adjustments to the RT outlet pressure to address short term and long term RT overheating protection independent of the cooling system.

A controllable hydrodynamic retarder system for a transmission including an electronic controller unit (ECU) for selecting and controlling brake torque by adjusting a retarder outlet pressure is described. The system can include an algorithm to calculate a retarder outlet pressure set point or tables or brake torque curves or profiles to allow the ECU to calculate or look up the functional relationships between the retarder RT outlet pressure, a vehicle or rotor speed, and a brake torque curve selected by the operator to provide the selected RT outlet pressure. The systems disclosed can also include a cooling system or utilize a vehicles engine cooling system. In one embodiment, the cooler can be shared between a transmission and the controllable retarder and can be adjusted to accommodate cooling requirements. The ECU can also make adjustments to the RT outlet pressure to address short term and long term RT overheating protection independent of the cooling system.

A vehicle may include rear ground traction members, front ground traction members, a rear drive system to drive the rear ground traction members, a continuously variable speed front drive system to drive the front ground traction members and a controller. The variable speed front drive system may include a hydraulic pump, a hydraulic motor driven by the hydraulic pump and operably coupled to the front ground traction members by a planetary gear assembly. The planetary gear assembly may include a sun gear coupled to and driven by the hydraulic motor, a ring gear operably coupled to the rear ground traction members and a planet carrier carrying planet gears intermeshing between the ring gear and the sun gear. The planet carrier has an output shaft operably coupled to the front ground traction members. At least one sun brake is actuatable by the controller to retard rotation of the sun gear.

A vehicle may include rear ground traction members, front ground traction members, a rear drive system to drive the rear ground traction members, a continuously variable speed front drive system to drive the front ground traction members and a controller. The variable speed front drive system may include a hydraulic pump, a hydraulic motor driven by the hydraulic pump and operably coupled to the front ground traction members by a planetary gear assembly. The planetary gear assembly may include a sun gear coupled to and driven by the hydraulic motor, a ring gear operably coupled to the rear ground traction members and a planet carrier carrying planet gears intermeshing between the ring gear and the sun gear. The planet carrier has an output shaft operably coupled to the front ground traction members. At least one sun brake is actuatable by the controller to retard rotation of the sun gear.

There is provided a hydraulic system for a vehicle. The hydraulic system has a hydraulic rotary actuator assembly rotationally coupled to a road wheel of the vehicle. The hydraulic rotary actuator assembly has a first operating mode, wherein a rotation of the road wheel causes the hydraulic rotary actuator assembly to pump a fluid from a fluid supply system. The hydraulic system further has a variable restrictor assembly coupled to the hydraulic rotary actuator assembly in the vehicle. The variable restrictor assembly controls a flow of the fluid flowing from the hydraulic rotary actuator assembly, to brake the rotation of the road wheel on a ground surface. The hydraulic system further has a variable restrictor controller coupled to the variable restrictor assembly. The variable restrictor controller controls the variable restrictor assembly, so as to enable a variation of a rate of braking of the road wheel on the ground surface.

There is provided a hydraulic system for a vehicle. The hydraulic system has a hydraulic rotary actuator assembly rotationally coupled to a road wheel of the vehicle. The hydraulic rotary actuator assembly has a first operating mode, wherein a rotation of the road wheel causes the hydraulic rotary actuator assembly to pump a fluid from a fluid supply system. The hydraulic system further has a variable restrictor assembly coupled to the hydraulic rotary actuator assembly in the vehicle. The variable restrictor assembly controls a flow of the fluid flowing from the hydraulic rotary actuator assembly, to brake the rotation of the road wheel on a ground surface. The hydraulic system further has a variable restrictor controller coupled to the variable restrictor assembly. The variable restrictor controller controls the variable restrictor assembly, so as to enable a variation of a rate of braking of the road wheel on the ground surface.

A method of operating a drive-train (1) of a motor vehicle, which has a drive aggregate (2), a transmission (3) with a hydrodynamic torque converter (4), an engine brake device (6) and a drive output (5). The engine brake device (6) which is activated when the drive-train (1) is operating in an overdrive mode, during a coasting process, before carrying out an overdrive downshift, when the turbine rotational speed (n_tu) of the torque converter (4) is lower than the engine idling rotational speed (n_mot_LL) of the drive aggregate (2). The engine brake device (6) is deactivated at a point in time chosen such that, when the overdrive downshift is carried out, a load change in the drive-train (1) is avoided.

A magnetorheological fluid brake and a control method therefor. When braking is not required, the brake does not work, and no field coils are energized. When braking is required and the brake receives a retarding braking signal, a field coil module is energized, the current is gradually increased, an oil port is gradually closed, and a back pressure inside the brake is also gradually increased, thereby gradually increasing a braking force so as to achieve a braking effect. By using the characteristics of a pump and the characteristics of a valve for the magnetorheological fluid, the viscosity of the magnetorheological fluid is adjusted, such that a back pressure is generated in a pump body, which in turn imposes a braking torque on a shaft, thereby performing braking.

A magnetorheological fluid brake and a control method therefor. When braking is not required, the brake does not work, and no field coils are energized. When braking is required and the brake receives a retarding braking signal, a field coil module is energized, the current is gradually increased, an oil port is gradually closed, and a back pressure inside the brake is also gradually increased, thereby gradually increasing a braking force so as to achieve a braking effect. By using the characteristics of a pump and the characteristics of a valve for the magnetorheological fluid, the viscosity of the magnetorheological fluid is adjusted, such that a back pressure is generated in a pump body, which in turn imposes a braking torque on a shaft, thereby performing braking.