A rotary electrohydraulic actuator includes a direct drive hydraulic motor having an output shaft through opening that is concentric with a rotational axis of a rotor of the hydraulic motor. The actuator includes a power plant mounted on the hydraulic motor via a manifold. The power plant includes an electric motor driven hydraulic pump. Operation of the electric motor causes the hydraulic pump to supply pressurized fluid to the hydraulic motor. The power plant is compactly mounted to the manifold so that a longitudinal axis of the electric motor is parallel to and spaced apart from the rotational axis of the hydraulic motor.

In a drive unit which has an axial piston pump and an electronic control unit, the axial piston pump is pivoted with a method in which pressure-reducing valves which act in opposition to one another are suddenly energized. Since in this respect no orifices are provided in the adjustment device, a so-called initiation jump of the excited current gives rise to a sudden reduction in the assigned actuating pressure or the actuating pressure difference formed therefrom. Then, a zero crossover jump of the excited current or of the excited currents is carried out in order to overcome the centering spring and therefore ensure a continuous zero crossover of the axial piston pump. Furthermore, a hydrostatic traction drive includes such a drive unit.

In a drive unit which has an axial piston pump and an electronic control unit, the axial piston pump is pivoted with a method in which pressure-reducing valves which act in opposition to one another are suddenly energized. Since in this respect no orifices are provided in the adjustment device, a so-called initiation jump of the excited current gives rise to a sudden reduction in the assigned actuating pressure or the actuating pressure difference formed therefrom. Then, a zero crossover jump of the excited current or of the excited currents is carried out in order to overcome the centering spring and therefore ensure a continuous zero crossover of the axial piston pump. Furthermore, a hydrostatic traction drive includes such a drive unit.

A variable drive system of a power system is disclosed. The variable drive system may include an engine gearset to transfer power from an engine output of an engine to a variable input driveshaft of the variable drive system. The variable drive system may include a generator gearset to transfer power, generated by the engine, to a generator driveshaft of a generator. The variable drive system may include a variable drive, coupled to the variable input driveshaft, to enable a gear ratio between engine output and the generator driveshaft to be adjustable, the variable input driveshaft being offset from at least one of the engine output or the generator driveshaft. The variable drive system may include a direct drive clutch to bypass variable power transfer through the variable drive and enable direct power transfer from the engine output to the generator driveshaft.

A hydraulic transaxle comprises an axial piston hydraulic pump having a variable displacement, and a transaxle casing incorporating the hydraulic pump. The hydraulic pump includes a movable swash plate and a pair of trunnion shafts. The transaxle casing includes a pair of side walls, and includes a pair of casing holes each of which penetrates each of the side walls between an inside and an outside of the transaxle casing. The pair of trunnion shafts are passed through the respective casing holes. The swash plate is formed with a pair of swash plate holes in the respective side portions facing the respective side walls in the inside of the transaxle casing. Proximal end portions of the respective trunnion shafts are inserted into the respective swash plate holes. A distal end portion of one of the trunnion shafts projects from the corresponding casing hole to the outside of the transaxle casing.

A hydraulic transaxle comprises an axial piston hydraulic pump having a variable displacement, and a transaxle casing incorporating the hydraulic pump. The hydraulic pump includes a movable swash plate and a pair of trunnion shafts. The transaxle casing includes a pair of side walls, and includes a pair of casing holes each of which penetrates each of the side walls between an inside and an outside of the transaxle casing. The pair of trunnion shafts are passed through the respective casing holes. The swash plate is formed with a pair of swash plate holes in the respective side portions facing the respective side walls in the inside of the transaxle casing. Proximal end portions of the respective trunnion shafts are inserted into the respective swash plate holes. A distal end portion of one of the trunnion shafts projects from the corresponding casing hole to the outside of the transaxle casing.

An electric actuator for use with a variable drive apparatus is disclosed herein. The electric actuator has a rotary design incorporating a magnetic field sensor chip disposed on a circuit board to sense the rotational orientation of the magnetic field of a cylindrical diametric magnet positioned on the end of a control shaft of a hydrostatic drive unit. The circuit board includes a microprocessor, electric motor power control and CAN Bus communication capability. The gear housing of the electric actuator features an integral end cap to accommodate mounting of the electric motor to enable a compact design.

An example hydrostatic transmission includes (i) a motor section having a motor interface; (ii) a pump section configured to generate fluid flow, where the pump section comprises a pump interface having a first pump port to provide fluid flow therethrough and a second pump port to receive returning fluid flow therethrough; and (iii) an interface block coupled to the motor interface and coupled to the pump interface so as to couple the pump section to the motor section, where the interface block includes internal fluid passage to facilitate fluid communication between the pump section and the motor section.

An example hydrostatic transmission includes (i) a motor section having a motor interface; (ii) a pump section configured to generate fluid flow, where the pump section comprises a pump interface having a first pump port to provide fluid flow therethrough and a second pump port to receive returning fluid flow therethrough; and (iii) an interface block coupled to the motor interface and coupled to the pump interface so as to couple the pump section to the motor section, where the interface block includes internal fluid passage to facilitate fluid communication between the pump section and the motor section.

A return-to-neutral mechanism for a hydrostatic transmission configured to return a control member of a pump to neutral after the control member has been moved toward a forward or reverse position. The return-to-neutral mechanism includes a stop member mountable to a housing, a control arm for moving the control member, and a spring for engaging the control arm and stop member to bias and return the control arm to neutral after being released from forward or reverse positions. The stop member may have an opening for receiving a fastener for mounting to the housing, and the opening may be configured to permit adjustment of the stop member along at least two transverse directions to preload the spring at the neutral position. The control arm may have abutments for moving legs of the spring, and the abutments may have recessed and protruding portions for receiving and containing the spring legs.