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.

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.

A hydraulic system for a work machine includes a tank to store an operation fluid, a hydraulic device to be operated by the operation fluid, a control valve to control the hydraulic device, a first fluid tube connecting the hydraulic device and the control valve, the first fluid tube being to supply the operation fluid from the control valve to the hydraulic device, a second fluid tube branching from the first fluid tube and connected to the tank, a switch valve provided to the second fluid tube, the switch valve being to control a flow rate of the operation fluid, and an oil cooler provided to the second fluid tube between the switch valve and the tank.

A hydrostatic propulsion drive for a vehicle is disclosed including an electronic control unit and a hydrostatic transmission having a hydraulic pump with an adjustable swept volume and a hydraulic motor with an adjustable swept volume, the hydraulic pump being arranged in a closed hydraulic circuit. The swept volumes of the hydraulic pump and the hydraulic motor are changeable in accordance with a correction factor which is stored in a characteristic diagram and is dependent on the rotational speed and the drive torque of the hydraulic motor, the operating pressure at the hydraulic motor being increased if the correction factor is used. Due to the increased operating pressure, flow-induced pressure drops are reduced by way of volumetric flows, and leakage flows via gaps between moving parts of the hydraulic pump and the hydraulic motor are kept large enough to avoid excessive friction and loss of efficiency.

A hydrostatic propulsion drive for a vehicle is disclosed including an electronic control unit and a hydrostatic transmission having a hydraulic pump with an adjustable swept volume and a hydraulic motor with an adjustable swept volume, the hydraulic pump being arranged in a closed hydraulic circuit. The swept volumes of the hydraulic pump and the hydraulic motor are changeable in accordance with a correction factor which is stored in a characteristic diagram and is dependent on the rotational speed and the drive torque of the hydraulic motor, the operating pressure at the hydraulic motor being increased if the correction factor is used. Due to the increased operating pressure, flow-induced pressure drops are reduced by way of volumetric flows, and leakage flows via gaps between moving parts of the hydraulic pump and the hydraulic motor are kept large enough to avoid excessive friction and loss of efficiency.

A hydraulic system of a work machine includes a first hydraulic device to operate in a first operation mode while pressure of hydraulic oil supplied from a hydraulic pump via a first oil passage is equal to or higher than a first pressure threshold. The hydraulic oil in the first oil passage is to be discharged via a second oil passage. A pilot check valve is provided in the second oil passage and has a pilot port to receive a pilot pressure of the hydraulic oil. The pilot check valve is closed to stop discharging the hydraulic oil in the first oil passage through the second oil passage while the pilot pressure is higher than or equal to the second pressure threshold. The pilot check valve is opened while the pilot pressure is less than the second pressure threshold.

A hydraulic system of a work machine includes a first hydraulic device to operate in a first operation mode while pressure of hydraulic oil supplied from a hydraulic pump via a first oil passage is equal to or higher than a first pressure threshold. The hydraulic oil in the first oil passage is to be discharged via a second oil passage. A pilot check valve is provided in the second oil passage and has a pilot port to receive a pilot pressure of the hydraulic oil. The pilot check valve is closed to stop discharging the hydraulic oil in the first oil passage through the second oil passage while the pilot pressure is higher than or equal to the second pressure threshold. The pilot check valve is opened while the pilot pressure is less than the second pressure threshold.

The invention relates to a method for monitoring a functional state of a pressure-driven actuator which comprises an actuator compartment defined at least in portions by a flexibly deformable wall, the actuator being actuated by applying pressure to the actuator compartment by means of an operating pressure supply, a work process being carried out to actuate the actuator, which process is accompanied by the actuator transitioning from a starting configuration to an end configuration. The pressure the pressure applied to the actuator compartment is measured depending on time by means of a sensor apparatus during the transition from the starting configuration to the end configuration. The invention also relates to a pressure-driven actuator.

The invention relates to a method for monitoring a functional state of a pressure-driven actuator which comprises an actuator compartment defined at least in portions by a flexibly deformable wall, the actuator being actuated by applying pressure to the actuator compartment by means of an operating pressure supply, a work process being carried out to actuate the actuator, which process is accompanied by the actuator transitioning from a starting configuration to an end configuration. The pressure the pressure applied to the actuator compartment is measured depending on time by means of a sensor apparatus during the transition from the starting configuration to the end configuration. The invention also relates to a pressure-driven actuator.

A controller determines a target rotation speed of an engine from an operation amount of an accelerator operating member. The controller determines whether a vehicle is in coasting deceleration. The controller decreases a differential pressure between a first circuit and a second circuit of a hydraulic circuit according to a deviation between an actual rotation speed of the engine and the target rotation speed, or the operation amount of the accelerator operating member when the vehicle is in the coasting deceleration.