Abstract: Provided is a work vehicle capable of satisfying a user's demand to brake performance in a flexible manner. A wheel loader 1 comprises a controller 5 storing a plurality of control characteristics each of which is set such that a brake valve control pressure Pi of a solenoid proportional valve 45 increases as a pedal angle ? of a brake pedal 43 increases, and under the condition where a pedal angle ? is equal to or less than a predetermined pedal angle ?, an increase rate of the brake valve control pressure Pi with respect to the pedal angle ? varies. In a case where the pedal angle ? detected by a potentiometer 33 is equal to or less than the predetermined pedal angle ?th, the controller 5, calculates the brake valve control pressure Pi based on the selected one control characteristic.

Abstract: The operability can be improved when the rotational speed of the engine is low and the working device actuator and the steering actuator are operated in a combined manner, while the configuration of prioritizing the operation of the steering actuator is maintained. A control device (70) included in a wheel loader (1) determines whether a working device (4) is in load lifting operation or not based on the pressure that is between a working device directional switching valve (44) and an orifice (45) and is detected by a pressure sensor (71), and reduces the opening area of a steering control valve (37) when determining that the rotational speed of an engine (14) detected by a rotational speed sensor (72) is equal to or less than a predetermined threshold (Ns) and a working device is in the load lifting operation.

Abstract: The operability can be improved when the rotational speed of the engine is low and the working device actuator and the steering actuator are operated in a combined manner, while the configuration of prioritizing the operation of the steering actuator is maintained. A control device (70) included in a wheel loader (1) determines whether a working device (4) is in load lifting operation or not based on the pressure that is between a working device directional switching valve (44) and an orifice (45) and is detected by a pressure sensor (71), and reduces the opening area of a steering control valve (37) when determining that the rotational speed of an engine (14) detected by a rotational speed sensor (72) is equal to or less than a predetermined threshold (Ns) and a working device is in the load lifting operation.

Abstract: A hydraulic drive system (1) including a meter-in compensator (37) and a bleed-off compensator (42) comprises a plurality of sensors (64 to 68), a controller (62), and an outlet pressure switching valve (61). The controller (62) determines whether or not the state of a wheel loader (2) which is detected based on the signals output from the sensors (64 to 68) meets a predetermined steering limiting condition. When the controller (62) determines that the state of the wheel loader (2) meets the steering limiting condition, it outputs a command signal to the outlet pressure switching valve (61). The outlet pressure switching valve (61) reduces the flow rate of the hydraulic oil flowing to steering cylinders (18L, 18R), in response to the command signal in such a manner that the flow rate becomes lower than that corresponding to the operation amount of a handle of a steering device (35).

Abstract: In a hydraulic drive system, hydraulic oil discharged from an actuator pump is supplied to an actuator via an actuator drive circuit. In the hydraulic drive system, the hydraulic oil discharged from a fan pump is supplied to a cooling fan motor via a fan drive circuit, and the cooling fan motor rotates a cooling fan at a rotational speed corresponding to the flow rate of the hydraulic oil supplied to the cooling fan motor. A merge circuit connects the actuator drive circuit and the fan drive circuit to each other to cause the hydraulic oil flowing through the actuator drive circuit to merge into the hydraulic oil flowing through the fan drive circuit. When the merge condition is satisfied, the controller controls the merge circuit to connect the actuator drive circuit and the fan drive circuit to each other.

Abstract: A hydraulic control device includes: a hydraulic pump connected in parallel to steering and boom cylinders; a steering control valve that controls the direction of operating oil flowing through the steering cylinders; a boom control valve that connects the hydraulic pump to a tank when the valve is at a neutral position and controls the direction of the oil flowing through the boom cylinders when the valve is at an offset position; a meter-in pressure compensator that increases flow rate of the oil flowing through a variable restrictor of the steering control valve in accordance with pressure in front of and behind the restrictor; and a bleed-off pressure compensator that decreases flow rate of the oil flowing through the boom control valve in accordance with the increase in pressure of the oil flowing through the steering cylinders to maintain the predetermined pressure of the oil in the steering control circuit.

Abstract: A hydraulic drive system includes a pump, a steering actuator, a loading/unloading apparatus actuator, a drive device, a relief valve, and an input unit. The drive device: flows hydraulic oil from the pump to the loading/unloading apparatus actuator when an operating tool is operated; flows the hydraulic oil from the pump to the steering actuator when a steering has become an operated state from a non-operated state regardless of an operation of the operating tool; and causes the hydraulic oil from the pump to be discharged to a tank via the relief valve to increase the torque of an engine when an increase instruction is inputted to the input unit and the steering is in a non-operated state.

Abstract: A hydraulic drive system (1) including a meter-in compensator (37) and a bleed-off compensator (42) comprises a plurality of sensors (64 to 68), a controller (62), and an outlet pressure switching valve (61) The controller (62) determines whether or not the state of a wheel loader (2) which is detected based on the signals output from the sensors (64 to 68) meets a predetermined steering limiting condition. When the controller (62) determines that the state of the wheel loader (2) meets the steering limiting condition, it outputs a command signal to the outlet pressure switching valve (61). The outlet pressure switching valve (61) reduces the flow rate of the hydraulic oil flowing to steering cylinders (18L, 18R), in response to the command signal in such a manner that the flow rate becomes lower than that corresponding to the operation amount of a handle of a steering device (35).

Abstract: In a hydraulic drive system, hydraulic oil discharged from an actuator pump is supplied to an actuator via an actuator drive circuit. In the hydraulic drive system, the hydraulic oil discharged from a fan pump is supplied to a cooling fan motor via a fan drive circuit, and the cooling fan motor rotates a cooling fan at a rotational speed corresponding to the flow rate of the hydraulic oil supplied to the cooling fan motor. A merge circuit connects the actuator drive circuit and the fan drive circuit to each other to cause the hydraulic oil flowing through the actuator drive circuit to merge into the hydraulic oil flowing through the fan drive circuit. When the merge condition is satisfied, the controller controls the merge circuit to connect the actuator drive circuit and the fan drive circuit to each other.

Abstract: A hydraulic drive system includes a pump, a steering actuator, a loading/unloading apparatus actuator, a drive device, a relief valve, and an input unit. The drive device: flows hydraulic oil from the pump to the loading/unloading apparatus actuator when an operating tool is operated; flows the hydraulic oil from the pump to the steering actuator when a steering has become an operated state from a non-operated state regardless of an operation of the operating tool; and causes the hydraulic oil from the pump to be discharged to a tank via the relief valve to increase the torque of an engine when an increase instruction is inputted to the input unit and the steering is in a non-operated state.

Abstract: A hydraulic control device includes: a hydraulic pump connected in parallel to steering and boom cylinders; a steering control valve that controls the direction of operating oil flowing through the steering cylinders; a boom control valve that connects the hydraulic pump to a tank when the valve is at a neutral position and controls the direction of the oil flowing through the boom cylinders when the valve is at an offset position; a meter-in pressure compensator that increases flow rate of the oil flowing through a variable restrictor of the steering control valve in accordance with pressure in front of and behind the restrictor; and a bleed-off pressure compensator that decreases flow rate of the oil flowing through the boom control valve in accordance with the increase in pressure of the oil flowing through the steering cylinders to maintain the predetermined pressure of the oil in the steering control circuit.

Abstract: A steering system, in a state where a first steering means is not operated, a third signal pressure output means outputs a third signal pressure in response to a second signal pressure fed to the third signal pressure output means, and feeding and discharging control means operates based in the third signal pressure, while in a state where the first steering means is operated, the third signal pressure output means stops outputting of the third signal pressure regardless of whether or not the second signal pressure is fed to the third signal pressure output means, and the feeding and discharging control means operates based on the first signal pressure.

Abstract: A steering system, in a state where a first steering means is not operated, a third signal pressure output means outputs a third signal pressure in response to a second signal pressure fed to the third signal pressure output means, and feeding and discharging control means operates based in the third signal pressure, while in a state where the first steering means is operated, the third signal pressure output means stops outputting of the third signal pressure regardless of whether or not the second signal pressure is fed to the third signal pressure output means, and the feeding and discharging control means operates based on the first signal pressure.