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 control system for monitoring a torque converter in a machine is disclosed. The control system includes a first speed sensor associated with a driving shaft of the torque converter. The first sensor is configured to measure an input speed of the torque converter. The control system further includes a second speed sensor associated with an output shaft of the torque converter. The second sensor is configured to measure an output speed of the torque converter. The control system further includes a processing module adapted to calculate a speed ratio based on the signals received from the first speed sensor and the second speed sensor. The control system further includes an output module adapted to provide indication for a seized condition of a one way clutch in the torque converter based on the speed ratio.

A control system for monitoring a torque converter in a machine is disclosed. The control system includes a first speed sensor associated with a driving shaft of the torque converter. The first sensor is configured to measure an input speed of the torque converter. The control system further includes a second speed sensor associated with an output shaft of the torque converter. The second sensor is configured to measure an output speed of the torque converter. The control system further includes a processing module adapted to calculate a speed ratio based on the signals received from the first speed sensor and the second speed sensor. The control system further includes an output module adapted to provide indication for a seized condition of a one way clutch in the torque converter based on the speed ratio.

A hydrostatic transmission includes a pump running surface and a motor running surface connected by internal porting formed in a housing member. A valve is disposed in the housing and connects a sump formed by the housing and the internal porting. A trunnion includes a first arm engaged to a swash plate to rotate the swash plate to vary the output of the pump, and a second arm which rotates with the first arm, the second arm having an operative end that is capable of opening the valve to permit a hydraulic connection between the internal porting and the sump through the valve bore when the trunnion is rotated to a predetermined position.

A hydrostatic transmission includes a pump running surface and a motor running surface connected by internal porting formed in a housing member. A valve is disposed in the housing and connects a sump formed by the housing and the internal porting. A trunnion includes a first arm engaged to a swash plate to rotate the swash plate to vary the output of the pump, and a second arm which rotates with the first arm, the second arm having an operative end that is capable of opening the valve to permit a hydraulic connection between the internal porting and the sump through the valve bore when the trunnion is rotated to a predetermined position.

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.

An automatic transmission where the control portion controls the adjustment solenoid valve so that the circulation hydraulic pressure equals to a second circulation hydraulic pressure higher than the first circulation hydraulic pressure when the rotational speed difference between the output rotational speed of the fluid transmission device and the rotational speed of the driving source is more than the predetermined rotational speed.

An automatic transmission where the control portion controls the adjustment solenoid valve so that the circulation hydraulic pressure equals to a second circulation hydraulic pressure higher than the first circulation hydraulic pressure when the rotational speed difference between the output rotational speed of the fluid transmission device and the rotational speed of the driving source is more than the predetermined rotational speed.

A bi-directional pump connected to a motor by a pair of supply/discharge lines; a regulator changes the bi-directional pump tilting angle; and a controller controls the regulator based on a turning signal outputted from a turning operation valve. At the turning acceleration, at which the signal increases, the controller calculates a motor flow rate passing through the motor and an instruction flow rate determined based on the turning signal. If the instruction flow rate is greater than a reference flow rate obtained by adding a predetermined value to the motor flow rate, the controller controls the regulator so the bi-directional pump tilting angle is adjusted to a tilting angle realizing the reference flow rate. If the instruction flow rate is not greater than the reference flow rate, the controller controls the regulator so the bi-directional pump tilting angle is adjusted to a tilting angle realizing the instruction flow rate.