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 work vehicle includes an engine, a speed changing apparatus that includes a hydrostatic stepless speed changing mechanism and is configured to subject motive power transmitted from the engine to speed changing and output the motive power, a travelling apparatus configured to travel on the motive power received from the speed changing apparatus, a speed detector configured to detect a speed of the travelling apparatus, a pressure detector configured to detect a hydraulic pressure in a closed circuit of the hydrostatic stepless speed changing mechanism, and a controller.

Provided is a work vehicle capable of attaining a maximum vehicle speed specification value set in advance for each vehicle body even in the case where a device constituting an HST traveling drive system has deteriorated over time. In a wheel loader 1 equipped with an HST traveling drive system, a controller 5 is configured to, in the case where a detection pressure value P is equal to or less than a switching pressure value Ps corresponding to a switching point in the HST motor 42 between a maximum displacement volume qmax and a minimum displacement volume qmin, and a detection vehicle speed value V is less than an upper limit vehicle speed specification value Vmaxs, limit the minimum displacement volume qmin of the HST motor 42 to a first minimum displacement volume value qmin1 less than a minimum displacement volume specification value qmins that is associated with the upper limit vehicle speed specification value Vmaxs.

A work vehicle includes a power source, a travel device, a power transmission device, and a control device. The power transmission device includes a hydrostatic continuously variable transmission having a relief valve capable of setting a relief pressure, and is configured to transmit power of the power source to the travel device. The control device includes a relief pressure setting unit configured to set the relief pressure of the relief valve in accordance with a target output value of the travel device.

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 hydrostatic assembly includes a pressure medium with a variable viscosity and a control device through which at least one process variable or state variable of the hydrostatic assembly is open-loop or closed-loop controlled as a function of the viscosity. The hydrostatic assembly further includes a temperature sensing device configured to sense a temperature of the pressure medium.

A hydraulic work machine is provided in which left and right hydraulic motors are driven independently of each other by two hydraulic pumps and in which an anomaly of any of the left and right track devices can be detected with high accuracy. The hydraulic work machine includes a first pressure sensor 13 configured to detect a first pump pressure that is a delivery pressure of a first hydraulic pump 11 and a second pressure sensor 23 configured to detect a second pump pressure that is a delivery pressure of a second hydraulic pump 21. When a controller 2 decides, from detection results of a travel operation detector 5 and work operation detectors 3 and 4, that a work implement 103 is not operated but travel operation devices 6 and 7 are operated and besides left and right track devices 50 and 60 are straightly traveling, the controller 2 calculates an anomaly decision evaluation value based on a pressure difference value obtained by subtracting one from the other of the first pump pressure and the second pump pressure and decides, based on a result of comparison between the anomaly decision evaluation value and a predetermined decision reference value 84, that one of the left and right track devices has an anomaly.

A counter balance valve (71L) is located between a directional control valve (23) and a hydraulic motor (32L) and provided on the way of a pair of supply/discharge lines (25A, 25B). The counter balance valve (71L) allows a spool (72L) to be displaced axially based on a pressure difference between the supply/discharge lines (25A, 25B). The counter balance valve (71L) includes a communicating passage (73L) for communicating the supply/discharge lines (25A, 25B) when the displacement of the spool (72L) exceeds a predetermined amount (X.sub.CM), based on a pressure difference between the supply/discharge lines (25A, 25B). The communicating passage (73L) is provided in the spool (72L) of the counter balance valve (71L).

A method of diagnosing a hydrostatic transmission system includes defining an initial charge pressure of a charge pump at a defined operating position of a primary pump. The primary pump is controlled to operate at the defined operating position. A current charge pressure from the charge pump is sensed when the primary pump is operating at the defined operating position. A pressure difference between the initial charge pressure of the charge pump and the current charge pressure of the charge pump is calculated and correlated to a system state of health of the hydrostatic transmission system.

In some implementations, a controller may obtain, during an event, pressure data regarding an amount of pressure of fluid associated with a component of the machine. The controller may obtain, during the event, flow data regarding a flow of the fluid associated with the component of the machine. The controller may determine, based on the pressure data and the flow data, an amount of wear of a track of the machine. The controller may perform an action based on the amount of wear of the track of the machine.