An external control type fan clutch device has an electromagnet fixed to a rotating shaft. The electromagnet is energized to activate a valve member formed of a plate spring and an armature and provided to a drive disk or a sealed housing to externally control opening and closing an oil circulating flow passage (oil supply port). The valve member is structured so that the armature attached to the plate spring of the valve member is divided into a plurality of pieces in the direction from the base end side to the oscillating end side of the plate spring to provide a plurality of bend points of the plate spring.

A torque transmission system (20) for transmitting torque from a prime mover (22) along a drivetrain includes a clutch device (28) configured to accept a torque input from the prime mover, an intermediate pulley (32), a belt (30) operatively engaged between the clutch device and the intermediate pulley, an angle gearbox (36) configured to change a spatial orientation of torque transmitted between an input and an output of the angle gearbox, a driveshaft (34) operably engaged between the intermediate pulley and the angle gearbox, and an output device (38) configured to accept a torque output from the angle gearbox. The clutch device is located upstream from the intermediate pulley and the angle gearbox along the drivetrain.

A clutch device for a clutch system has an input member that rotates at a first speed. A friction drive system is disposed between the input member and an output member. The clutch device is selectively movable by a fluid actuator assembly, between an engaged position in which the friction drive system drives the output member to rotate at the first speed, and a disengaged position in which a viscous drive system rotates the output member at a second speed slower than the first speed. A variable viscous fluid supply assembly includes a viscous fluid storage chamber, a valve, and a valve actuator that selectively drives the valve to move between an open position and a closed position to control an amount of viscous fluid available to the viscous drive system, thereby varying the second speed.

A fan drive for a working vehicle includes a speed shift unit and a fan in series to the speed shift unit. The speed shift unit includes a clutch unit and is configured to discretely provide a first non-zero speed ratio and a second non-zero speed ratio. The clutch unit is configured to alternatively connect the first or the second non-zero speed ratio to the fan.

An engine cooling system includes a liquid-to-air heat exchanger having an associated fan and a pump forcing convection and a controller communicating with the fan and the pump, the controller increasing fan speed in response to a first gradient in heat transfer rate to power exceeding a second gradient in heat transfer rate to power for increasing pump speed, and increasing pump speed when the second gradient is greater than the first gradient. The controller may increase the pump speed in response to a desired increase in heat transfer rate. The first gradient may be based on a gradient in heat transfer rate to air flow from a map of heat exchanger performance. The second gradient may be based on a gradient in heat transfer rate to coolant from a map of heat exchanger performance.