A method is used to control a hydrostatic drive including a drive machine, a hydraulic pump coupled to the drive machine, and a hydraulic motor coupled to the hydraulic pump via a hydraulic working circuit. In the method, at least one of multiple manipulated variables of the hydrostatic drive is ascertained and set, in the course of a precontrol, from a specified setpoint value for at least one of the controlled variables, including a pressure in the hydraulic working circuit, a speed of the hydraulic pump, and an output variable of the hydrostatic drive. In the method, the remaining controlled variables and/or manipulated variables are automatically updated.

A method is used to control a hydrostatic drive including a drive machine, a hydraulic pump coupled to the drive machine, and a hydraulic motor coupled to the hydraulic pump via a hydraulic working circuit. In the method, at least one of multiple manipulated variables of the hydrostatic drive is ascertained and set, in the course of a precontrol, from a specified setpoint value for at least one of the controlled variables, including a pressure in the hydraulic working circuit, a speed of the hydraulic pump, and an output variable of the hydrostatic drive. In the method, the remaining controlled variables and/or manipulated variables are automatically updated.

A travel control device is provided with hydraulic pumps of a variable capacity type that are driven by an engine; hydraulic motors that are driven by discharged oil from the hydraulic pumps; traveling devices that are rotation-driven by the hydraulic motors; a travel operation lever that is operated so as to instruct a traveling operation; a first control valve for generating a charged hydraulic pressure by adjusting the discharged oil from a charge pump and a second control valve for generating a capacity control hydraulic pressure in accordance with the operation of the travel operation lever. The first control valve is designed to pressure-adjust and generate a charged hydraulic pressure in accordance with the rotation speed of the engine, and the hydraulic pump is subjected to a variable capacity control process by a capacity control hydraulic pressure that is pressure-adjusted and generated by the second control valve.

A travel control device is provided with hydraulic pumps of a variable capacity type that are driven by an engine; hydraulic motors that are driven by discharged oil from the hydraulic pumps; traveling devices that are rotation-driven by the hydraulic motors; a travel operation lever that is operated so as to instruct a traveling operation; a first control valve for generating a charged hydraulic pressure by adjusting the discharged oil from a charge pump and a second control valve for generating a capacity control hydraulic pressure in accordance with the operation of the travel operation lever. The first control valve is designed to pressure-adjust and generate a charged hydraulic pressure in accordance with the rotation speed of the engine, and the hydraulic pump is subjected to a variable capacity control process by a capacity control hydraulic pressure that is pressure-adjusted and generated by the second control valve.

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.

In one aspect, a method for adjusting torque limits for a work vehicle may include controlling, with a computing device, an operation of an engine of the work vehicle such that a torque output of the engine is maintained at or below a baseline engine torque limit. The method may also include receiving, with the computing device, an input associated with a current hydraulic power requirement of a hydraulic system of the work vehicle, and adjusting, with the computing device, a torque limit for the engine from the baseline engine torque limit to an adjusted engine torque limit based on the current hydraulic power requirement of the hydraulic system. In addition, the method may include controlling, with the computing device, the operation of the engine such that the torque output of the engine is maintained at or below the adjusted engine torque limit.

In one aspect, a method for adjusting torque limits for a work vehicle may include controlling, with a computing device, an operation of an engine of the work vehicle such that a torque output of the engine is maintained at or below a baseline engine torque limit. The method may also include receiving, with the computing device, an input associated with a current hydraulic power requirement of a hydraulic system of the work vehicle, and adjusting, with the computing device, a torque limit for the engine from the baseline engine torque limit to an adjusted engine torque limit based on the current hydraulic power requirement of the hydraulic system. In addition, the method may include controlling, with the computing device, the operation of the engine such that the torque output of the engine is maintained at or below the adjusted engine torque limit.

The work vehicle includes: a clutch device including a forward-travel clutch and a backward-travel clutch configured to cause, when being in an engagement state, the work vehicle to travel in a forward travel direction and a backward travel direction; a forward-backward travel instruction device configured to instruct the work vehicle to travel in the forward travel direction or the backward travel direction; a clutch state detection device configured to detect whether the forward-travel clutch and the backward-travel clutch are each in the engagement state; and a torque restriction section configured to restrict a maximum absorbing torque of the hydraulic pump to be low when a restriction condition holds, the restriction condition including a condition that a traveling direction of the work vehicle, which corresponds to an engagement state of the clutch device, and a traveling direction of the work vehicle, which is instructed by the forward-backward travel instruction device are opposite to each other.

A work machine includes a relief valve that is installed in a hydraulic line that forms a closed circuit between a hydraulic pump and a hydraulic motor, and sets a relief pressure of the hydraulic line; a braking device that brakes a traveling device attached to the hydraulic motor; and an operation mechanism that operates the braking device. When a traveling speed of the traveling device is equal to or more than a predetermined threshold, the relief pressure is changed from a first pressure that is a pressure before a braking operation is performed by the operation mechanism to a second pressure that is lower than the first pressure.

A work machine includes a relief valve that is installed in a hydraulic line that forms a closed circuit between a hydraulic pump and a hydraulic motor, and sets a relief pressure of the hydraulic line; a braking device that brakes a traveling device attached to the hydraulic motor; and an operation mechanism that operates the braking device. When a traveling speed of the traveling device is equal to or more than a predetermined threshold, the relief pressure is changed from a first pressure that is a pressure before a braking operation is performed by the operation mechanism to a second pressure that is lower than the first pressure.