VISCOUS FAN Operation (Cooling system)

VISCOUS FAN Operation

Description To engage and disengage the fan drive the bi-metal coil senses air temperature behind the radiator. When The viscous drive unit for the engine cooling fan, a pre-determined temperature is reached, the coil provides a means of controlling the speed of the fan opens a valve (5) which allows fluid to enter the drive relative to the running temperature of the engine. The area and, due to centrifugal force, circulates to the viscous unit is a type of fluid coupling, which drives annular drive area. the fan blades by means of ’silicone fluid’. There are two sets of annular grooves (3), one in the drive clutch and the other in the drive body, a specific clearance being provided between the two sets of

grooves.

1. Input (drive) member
2. Output (driven) member
3. Sensing mechanism (bi-metal coil)

The fan drive has to be engaged only periodically, between 5% and 10%, during normal operating conditions, because the engine is cooled by ram air for most of the time.

Viscous unit disengaged (engine at normal running temperature)

10. Fluid reservoir

1. Input (drive) member
2. Output (driven) member
3. Running clearance
4. Pump plate
5. Valve (closed)
6. Sensing mechanism (bi-metal coil)
7. Fluid seal
8. Bearing, input member
9. Fluid chamber