A hydrostatic traction drive has a steering function, which is implemented via two laterally acting secondary units (traction motors), which are supplied by a common primary unit (pump) in the open circuit. The primary unit is pressure-controlled. The two secondary units are torque-controlled. The affected vehicle is steerable as a function of a steering command by different torque specifications for the two secondary units. Furthermore, a hydrostatic drive for a mobile work machine has working hydraulics in addition to the traction drive. The working hydraulics are also supplied by the primary unit in parallel to the two secondary units.

A working machine is provided, which includes a prime mover, a first traveling pump driven by power of the prime mover to supply operation fluid through a connector fluid tube, a traveling motor including first and second ports connected to the connector fluid tube, the traveling motor configured to be switched in a first speed and a second speed higher than the first speed, a first pressure detector to detect first traveling-pump pressure near the first port, a second pressure detector to detect second traveling-pump pressure near the second port, and a controller configured, with the traveling motor switched in the second speed, to automatically shift down the traveling motor from the second speed to the first speed, when a differential pressure between the first traveling-pump pressure and the second traveling-pump is equal to or more than a deceleration threshold.

A method teaches a control function, preferably a characteristic curve, of a hydrostatic motor of a traction drive of a work machine when in drive mode. The traction drive is provided with the hydrostatic motor and a hydrostatic pump, which is hydraulically connected to the hydrostatic motor. The method includes setting a pivot angle of the hydrostatic motor while taking into account a desired velocity of the work machine when in the drive mode, and checking whether predefined conditions are met. If the predefined conditions are met and a current velocity differs from the desired velocity, the method includes correcting the control function of the hydrostatic motor by taking into account a difference between the desired velocity and the current velocity. At least one value of the corrected control function of the hydrostatic motor is taught during the correcting.

A monitoring system for a travel drive includes a rotational speed sensor of a hydrostatic motor. The rotational speed sensor is configured to determine acceleration. At least one signal from a pressure sensor mounted on at least one working line that connects a pump to the hydrostatic motor of a hydrostatic travel drive is evaluated. The pressure sensor is preferably arranged on at least one working connection of the pump. The system uses the additional pressure signal to evaluate in a reliable manner whether the hydrostatic travel drive generates an unwanted drive torque.

A working vehicle includes: a vehicle body provided with a traveling device; a hydraulic pump including a swashplate configured to change an output of the hydraulic pump according to a swashplate angle; a traveling motor including an output shaft having a rotation speed variable according to the output of the hydraulic pump and capable of transmitting power of the output shaft to the traveling device; an angle detector configured to detect the swashplate angle that is an angle of the swashplate; and a swashplate control unit configured to control the swashplate angle on the basis of control information relating to control of the swashplate angle and an actual swashplate angle that is the swashplate angle detected by the angle detector.

Methods and systems for transmission control are provided. In one example, a transmission system operating method includes maintaining a displacement set-point of a variable displacement hydraulic motor in a hydrostatic assembly within a working zone, where at least a portion of a boundary of the working zone is determined based on a torque constraint of the hydrostatic assembly. The transmission system includes the hydrostatic assembly that includes the hydraulic motor that is hydraulically coupled in parallel with a variable displacement hydraulic pump and a gearbox mechanically coupled to the hydrostatic assembly and including one or more clutches.

A working machine is provided, which includes a prime mover, a first traveling pump driven by power of the prime mover to supply operation fluid through a connector fluid tube, a traveling motor including first and second ports connected to the connector fluid tube, the traveling motor configured to be switched in a first speed and a second speed higher than the first speed, a first pressure detector to detect first traveling-pump pressure near the first port, a second pressure detector to detect second traveling-pump pressure near the second port, and a controller configured, with the traveling motor switched in the second speed, to automatically shift down the traveling motor from the second speed to the first speed, when a differential pressure between the first traveling-pump pressure and the second traveling-pump is equal to or more than a deceleration threshold.

A monitoring system for a travel drive includes a rotational speed sensor of a hydrostatic motor. The rotational speed sensor is configured to determine acceleration. At least one signal from a pressure sensor mounted on at least one working line that connects a pump to the hydrostatic motor of a hydrostatic travel drive is evaluated. The pressure sensor is preferably arranged on at least one working connection of the pump. The system uses the additional pressure signal to evaluate in a reliable manner whether the hydrostatic travel drive generates an unwanted drive torque.

A working machine includes a pair of traveling devices, a pair of traveling motors having a first speed and a second speed higher than the first speed, a pair of traveling pumps to supply operation fluid to the traveling motors, a connector fluid tube connecting the traveling motors and the traveling pumps, a traveling-pump pressure detector to detect a traveling-pump pressure that is pressure generated in the connector fluid tube, a revolving speed detector to detect a prime-mover revolving speed, a third storage to store a second decelerating judgment table representing a relation between the prime-mover revolving speed and a second decelerating judgment pressure, and a controller having: an automatic decelerator portion to perform an automatic deceleration process for reducing a speed of the traveling motor, and a differential pressure calculator portion to calculate a traveling differential pressure between one traveling pump pressure and another traveling pump pressure.

A working machine includes a pair of traveling devices, a pair of traveling motors having a first speed and a second speed higher than the first speed, a pair of traveling pumps to supply operation fluid to the traveling motors, a connector fluid tube connecting the traveling motors and the traveling pumps, a traveling-pump pressure detector to detect a traveling-pump pressure that is pressure generated in the connector fluid tube, a revolving speed detector to detect a prime-mover revolving speed, a third storage to store a second decelerating judgment table representing a relation between the prime-mover revolving speed and a second decelerating judgment pressure, and a controller having: an automatic decelerator portion to perform an automatic deceleration process for reducing a speed of the traveling motor, and a differential pressure calculator portion to calculate a traveling differential pressure between one traveling pump pressure and another traveling pump pressure.