A working machine includes a prime mover, a hydraulic pump driven by power of the prime mover, a cooler including a cooling fan rotated by either the power of the prime mover or hydraulic fluid delivered from the hydraulic pump, and a controller configured or programmed to perform a reduction control for reducing a target fan rotation speed that is a target rotation speed of the cooling fan in response to reduction of an actual prime mover rotation speed that is an actual rotation speed of the prime mover, and to perform, after the reduction control, a restoration control for restoring the target fan rotation speed. The controller is configured or programmed to make a difference between a reduction rate of the target fan rotation speed in the reduction control and an increase rate of the target fan rotation speed in the restoration control.

Provided is a technique for improving the cooling efficiency of a vehicle heat exchange system configured to cool a cooling liquid discharged from each of a plurality of heat sources. The vehicle heat exchange system comprises a high-temperature side radiator unit and a low-temperature side radiator unit, the high-temperature side radiator including: a first high-temperature side radiator that faces a first fan and is connected to a high-temperature side discharge pipe; a second high-temperature side radiator that faces a second fan and is connected to a high-temperature side supply pipe; and a high-temperature side connection pipe for supplying the cooling liquid from the first high-temperature side radiator to the second high-temperature side radiator, and the low-temperature side radiator unit including: a first low-temperature side radiator that is arranged to face the second high-temperature side radiator on the upstream side of the cooling air flow, and is connected to a low-temperature side discharge pipe; a second low-temperature side radiator that is arranged to face the first high-temperature side radiator on the upstream side of the cooling air flow, and is connected to a low-temperature side supply pipe; and a low-temperature side connection pipe for supplying the cooling liquid from the first low-temperature side radiator to the second low-temperature side radiator.

Provided is a work machine capable of notifying that maintenance is necessary due to continuation of clogging in a cooling device or decrease in cooling performance. A wheel loader 1 including a radiator 31 and an oil cooler 32 comprises a controller 5, 5A configured to determine a clogging continuation state of the radiator 31 or the oil cooler 32. The controller 5, 5A determines whether clogging is occurring in the radiator 31 or the oil cooler 32 based on outside air temperature AW and cooling water temperature CW or hydraulic oil temperature HW, determines whether the clogging continues based on a clogging occurrence ratio R1, R2 while an engine 30 is operating, and outputs a notification command signal for providing the alarm buzzer 61 and the user management system 62 with a command to notify that maintenance is necessary when it is determined that the clogging continues.

An outdoor unit has a frame that carries a ground grooming or working implement, a traction drive, and a cooling fan, all of which comprises loads on a prime mover. A power management controller automatically reduces an operational speed of the traction drive when prime mover droop is present. The cooling fan cools two cooling fluids. The controller stores data representing variable fan speeds for cooling each cooling fluid in both normal and above normal temperature ranges and for use when prime mover droop is present. The controller uses the highest fan speed required for cooling the cooling fluids in the normal range unless the droop fan speed is lower in which case the lower droop fan speed is used but only to the extent that the lower droop fan speed is not lower than the highest fan speed required for cooling the cooling fluids in the above normal temperature range.

To curb temperature rises in a control device for a supercharger and extend the life of the control device for the supercharger, a work vehicle includes a variable geometry supercharger with variable boost pressure, and a working device driven by pressure oil discharged from a working hydraulic pump, the work vehicle further including: a supercharger control device adapted to control the supercharger; a temperature detection device adapted to detect temperature of the supercharger control device; and a main control device adapted to limit at least one of maximum rotational speed of an engine and maximum vehicle speed of the work vehicle in case the temperature of the supercharger control device is above a predetermined temperature as compared to case the temperature of the supercharger control device is below the predetermined temperature.

Provided is a work machine capable of notifying that maintenance is necessary due to continuation of clogging in a cooling device or decrease in cooling performance. A wheel loader 1 including a radiator 31 and an oil cooler 32 comprises a controller 5, 5A configured to determine a clogging continuation state of the radiator 31 or the oil cooler 32. The controller 5, 5A determines whether clogging is occurring in the radiator 31 or the oil cooler 32 based on outside air temperature AW and cooling water temperature CW or hydraulic oil temperature HW, determines whether the clogging continues based on a clogging occurrence ratio R1, R2 while an engine 30 is operating, and outputs a notification command signal for providing the alarm buzzer 61 and the user management system 62 with a command to notify that maintenance is necessary when it is determined that the clogging continues.

The invention relates to a drive system for a working machine, the drive system including: a gearbox; an internal combustion engine having an engine output shaft; a power takeoff coupled to the engine output shaft; a torque converter having an input shaft operatively coupled to the engine and an output shaft operatively coupled to the gearbox; a hydraulic cooling fan; a hydraulic fan pump coupled to the power takeoff and connected to the hydraulic fan via a first hydraulic valve. The drive system further includes: a hydraulic motor coupled to the gearbox and configured to provide power to the gearbox for vehicle propulsion, wherein the hydraulic motor is coupled to the hydraulic fan pump via a second hydraulic valve and arranged to receive power from the hydraulic fan pump. The invention further relates a method for controlling the described drive system.

The invention relates to a drive system for a working machine, the drive system including: a gearbox; an internal combustion engine having an engine output shaft; a power takeoff coupled to the engine output shaft; a torque converter having an input shaft operatively coupled to the engine and an output shaft operatively coupled to the gearbox; a hydraulic cooling fan; a hydraulic fan pump coupled to the power takeoff and connected to the hydraulic fan via a first hydraulic valve. The drive system further includes: a hydraulic motor coupled to the gearbox and configured to provide power to the gearbox for vehicle propulsion, wherein the hydraulic motor is coupled to the hydraulic fan pump via a second hydraulic valve and arranged to receive power from the hydraulic fan pump. The invention further relates a method for controlling the described drive system.

A control method for a fan of a work vehicle includes supplying, when an engine is started, a first current to a solenoid of a variable relief valve such that the hydraulic fluid flows by a first flow rate, supplying, when a rotational speed of the engine becomes larger than a first rotational speed threshold value, a second current larger than the first current to the solenoid such that the hydraulic fluid flows by a second flow rate smaller than the first flow rate to reduce the rotational speed of the fan, and supplying, when the rotational speed of the engine becomes larger than a second rotational speed threshold value that is larger than the first rotational speed threshold value, a current to the solenoid to change the rotational speed of the fan, the current corresponding to a temperature of liquid flowing in the work vehicle.

The work vehicle includes an engine, a radiator; a hydraulic pump; a cooling fan that blows a cooling air to the radiator; a hydraulic motor which is driven by a pressure oil delivered from the hydraulic pump, and rotates the cooling fan; a directional control valve that switches a flow direction of the pressure oil from the hydraulic pump to rotate the hydraulic motor in forward and reverse directions; and a controller that controls the directional control valve so as to cause the repetitive operation of the forward and reverse rotation of the cooling fan to be performed at predetermined time intervals, in which the controller reduces the time intervals more than a normal time initially set when a relationship between the outside air temperature detected by the outside air temperature sensor and the refrigerant temperature detected by the refrigerant temperature sensor satisfies a predetermined condition.