A hydraulic system in of a work machine includes a hydraulic pump to supply pilot hydraulic oil in a hydraulic oil reservoir. A travel pump is to drive a travel motor according to a pilot pressure of the pilot hydraulic oil. A target pilot pressure of the pilot hydraulic oil is input through a travel operation device to control, according to the target pilot pressure, the pilot pressure supplied from the hydraulic pump to the travel pump. A pilot oil path connects the travel operation device and the travel pump to supply the pilot pressure to the travel pump. A drain oil path is divided from the pilot oil path. A pressure adjustment valve is provided in the drain oil path to adjust the pilot pressure to be less than the target pilot pressure when a condition is satisfied.

The invention relates to a system (2) for controlling a disengageable hydraulic transmission (1) for a vehicle, involving the circulation and the pressurisation of a transmission fluid, said system (2) comprising: means (21) for collecting information relative to the operation of the hydraulic transmission (1) since the last time the transmission was serviced, means (22) for estimating an ageing state of the transmission fluid based on the information collected, and means (23) for controlling the disengageable hydraulic transmission (1) as a function of the estimated ageing state.

The present invention relates to a system for assisting the driving of a vehicle comprising at least one hydraulic machine forming a pump (19), at least one hydraulic machine forming an engine (130, 140) and an open hydraulic circuit (100) extending through a tank (13) and comprising a suction duct (11) extending from the tank (13) to an inlet of the pump (19), a supply duct (15) extending from the outlet of the pump (19) to the inlet of the engine (130, 140) and a return duct (122) extending from the outlet of the engines (130, 140) to the tank (13), characterised in that at least one of the engines (130, 140) is an engine that can disengage the clutch, and in that the system comprises an element forming a restriction (180) and creating a loss of charge over the return duct and a means (190, 192) adapted for connecting to the engine casing, the part of the return duct (122) located upstream of the element forming a restriction (180) and for applying to the engine casing, from the return duct (122), a pressure lower than the pressure of this return duct.

A hydrostatic travel drive includes a hydraulic pump for the purpose of supplying pressure medium to a hydraulic motor of the travel drive that can be coupled to an output, which pump can be coupled to a drive machine. The hydraulic pump has an actuating cylinder with at least one cylinder chamber and a swept volume which can be adjusted via the actuating cylinder, and at least one electrically activatable pressure valve via which the cylinder chamber can be charged with an adjustingly active actuating pressure. The travel drive further includes device via which a pressure of the hydraulic pump can be limited by means of influencing the actuating pressure.

In one aspect, a method is provided or braking a work vehicle including an engine and a hydrostatic drive system including a hydraulic pump configured to be rotationally driven by the engine and a hydraulic motor fluidly coupled with the hydraulic pump through a closed hydraulic loop of the hydrostatic drive system. The hydraulic pump may be configured to fluidly drive the hydraulic motor. The method may include receiving an operator request to reduce a ground speed of the work vehicle. The method may include monitoring a fluid temperature of a hydraulic fluid associated with the closed hydraulic loop and automatically controlling at least one of a pump displacement of the hydraulic pump or a motor displacement of the hydraulic motor based on the operator request and the monitored fluid temperature to adjust hydrostatic braking of the work vehicle and thereby reduce the ground speed of the work vehicle.

In one aspect, a method is provided or braking a work vehicle including an engine and a hydrostatic drive system including a hydraulic pump configured to be rotationally driven by the engine and a hydraulic motor fluidly coupled with the hydraulic pump through a closed hydraulic loop of the hydrostatic drive system. The hydraulic pump may be configured to fluidly drive the hydraulic motor. The method may include receiving an operator request to reduce a ground speed of the work vehicle. The method may include monitoring a fluid temperature of a hydraulic fluid associated with the closed hydraulic loop and automatically controlling at least one of a pump displacement of the hydraulic pump or a motor displacement of the hydraulic motor based on the operator request and the monitored fluid temperature to adjust hydrostatic braking of the work vehicle and thereby reduce the ground speed of the work vehicle.

A device for controlling a gear ratio of a hydrostatic mechanical power-split transmission comprises an input switch (1) which, when rotated, produces a particular transmission characteristic and, at the same time, limits the maximum pressure. The selected position of the input switch (1) selects a particular maximum pressure curve from a large number of stored maximum pressure curves.

A device for controlling a gear ratio of a hydrostatic mechanical power-split transmission comprises an input switch (1) which, when rotated, produces a particular transmission characteristic and, at the same time, limits the maximum pressure. The selected position of the input switch (1) selects a particular maximum pressure curve from a large number of stored maximum pressure curves.

A hydrodynamic clutch having an input side and an output side, the rotational motions of which are coupled to one another with a hydraulic fluid. A method for determining the degree of filling of the hydrodynamic clutch with fluid including steps of periodically sensing a fluid temperature of the hydraulic fluid, determining the thermal output supplied to the clutch on the basis of the temperature, determining a lambda value on the basis of the thermal output and determining the degree of filling on the basis of the lambda value.

A hydrodynamic clutch having an input side and an output side, the rotational motions of which are coupled to one another with a hydraulic fluid. A method for determining the degree of filling of the hydrodynamic clutch with fluid including steps of periodically sensing a fluid temperature of the hydraulic fluid, determining the thermal output supplied to the clutch on the basis of the temperature, determining a lambda value on the basis of the thermal output and determining the degree of filling on the basis of the lambda value.