A hydrostatic transmission system includes a fluid-driven motor and an integrated pump assembly connected to the fluid-driven motor to provide fluid to operate the fluid-driven motor. The integrated pump assembly includes a pump with at least one fluid driver comprising a prime mover and a fluid displacement assembly to be driven by the prime mover such that fluid is transferred from a first port of the pump to a second port of the pump. The pump assembly also includes two valve assembles to isolate the pump from the system. The hydrostatic transmission system also includes a controller that establishes at least one of a speed and a torque of the at least one prime mover to exclusively adjust at least one of a flow and a pressure in the hydrostatic transmission system to an operational set point.

An expansion tank includes a tank body mounted inside a housing forming a sump, where the tank body defines an internal expansion volume. A fluid inlet tube on the tank body has an upper end open to the sump and a lower end open to the internal expansion volume. A single 2-way check valve is located at the lower end of the tube, and fluid enters the expansion volume when the pressure in the sump exceeds the pressure in the expansion volume by a first predetermined amount, and fluid exits the expansion volume to the sump when the pressure in the expansion volume exceeds the pressure in the sump by a second predetermined amount. The check valve may be a combination duckbill valve and umbrella valve. The tank body may include a cover on which the inlet tube is formed.

A traveling hydraulic stepless transmission (HST), ensures stopping of a vehicle on a slope under high load conditions, maintains stopping the vehicle on flat ground under low load conditions, and enables smooth starting from a stop. The HST includes a neutral check valve (NCV) and an internal damping system (IDS). The NCV includes a first orifice that opens a first oil passage to a transaxle case when a pressure in the first oil passage is equal to or less than a predetermined pressure, and that connects the second oil passage to the transaxle case when a pressure in a second oil passage is equal to or less than the predetermined pressure. The IDS includes second orifices that connect a high pressure side of the oil passages to the transaxle case when a discharge rate of the hydraulic pump is equal to or less than a predetermined discharge rate.

A traveling hydraulic stepless transmission (HST), ensures stopping of a vehicle on a slope under high load conditions, maintains stopping the vehicle on flat ground under low load conditions, and enables smooth starting from a stop. The HST includes a neutral check valve (NCV) and an internal damping system (IDS). The NCV includes a first orifice that opens a first oil passage to a transaxle case when a pressure in the first oil passage is equal to or less than a predetermined pressure, and that connects the second oil passage to the transaxle case when a pressure in a second oil passage is equal to or less than the predetermined pressure. The IDS includes second orifices that connect a high pressure side of the oil passages to the transaxle case when a discharge rate of the hydraulic pump is equal to or less than a predetermined discharge rate.

A hydraulic fluid expansion tank is located inside a housing of a drive device and includes an upper check valve and a lower check valve in communication with a sump located within the drive device and an internal volume of the expansion tank. The tank may also include a vent opening in communication with a vent of the drive device that is in communication with atmospheric pressure.

A hydrostatic transmission system includes a fluid-driven motor and an integrated pump assembly connected to the fluid-driven motor to provide fluid to operate the fluid-driven motor. The integrated pump assembly includes a pump with at least one fluid driver comprising a prime mover and a fluid displacement assembly to be driven by the prime mover such that fluid is transferred from a first port of the pump to a second port of the pump. The pump assembly also includes two valve assembles to isolate the pump from the system. The hydrostatic transmission system also includes a controller that establishes at least one of a speed and a torque of the at least one prime mover to exclusively adjust at least one of a flow and a pressure in the hydrostatic transmission system to an operational set point.

A system having a primary machine, a hydraulic machine, and a frequency converter disposed in an assembly casing. The system further includes a cooling circuit, suitable for a same coolant to traverse a plurality of ducts suitable for cooling the primary machine, the frequency converter, and the hydraulic machine.

A hydrostatic transmission for a traction drive includes a first hydraulic machine that is coupled to a drive machine and that has an adjustable displacement volume and a second hydraulic machine that is fluidically connected to the first hydraulic machine and that is coupled to a drive output of the traction drive. At the first hydraulic machine, a control pressure acts in the direction of an enlargement of its displacement volume and a working pressure of the second hydraulic machine acts in the opposite direction. The hydrostatic transmission further includes a control device that varies the control pressure to influence a torque of the second hydraulic machine. The control device stores a characteristic map by which a setpoint control pressure is determined as a function of a setpoint torque and a displacement volume of the second hydraulic machine so as to regulate the torque of the second hydraulic machine.

A hydrostatic transmission for a traction drive includes a first hydraulic machine that is coupled to a drive machine and that has an adjustable displacement volume and a second hydraulic machine that is fluidically connected to the first hydraulic machine and that is coupled to a drive output of the traction drive. At the first hydraulic machine, a control pressure acts in the direction of an enlargement of its displacement volume and a working pressure of the second hydraulic machine acts in the opposite direction. The hydrostatic transmission further includes a control device that varies the control pressure to influence a torque of the second hydraulic machine. The control device stores a characteristic map by which a setpoint control pressure is determined as a function of a setpoint torque and a displacement volume of the second hydraulic machine so as to regulate the torque of the second hydraulic machine.

A hydraulic fluid expansion tank is located inside a housing of a drive device. The expansion tank comprises a siphon tube in communication with a sump located within the drive device and also comprises a vent opening in communication with a vent of the drive device that is in communication with atmospheric pressure. The fluid expansion tank is positioned and restrained within the drive device without the use of fasteners.