|Explore Topics of Radiator Fan Clutch
We all know what the function of a clutch in our vehicle is, i.e. to engage and disengage one part of the system to the other part. Main clutch in our vehicle is used to engage and disengage the transmission with the engine.Cooling fan clutch is a mechanical or electrical device which engages and disengages the radiator fan with the engine. As engine starts operating, the fan clutch also starts rotating. At lower temperature of engine, fan clutch is partially engaged and so it rotates at slow speed and when engine temperature increases beyond critical value, fan is fully engaged and rotates at high speed.
So how would a clutch know about the engine temperature so that it can engage accordingly with the radiator fan?
Fan clutch is actually controlled by a bimetallic coil which is sensitive to temperature changes.The basic function of fan clutch is to rotate the radiator fan at high speed when engine temperature is higher and rotate at slower speed when engine temperature is below the critical value.
When engine is idling or operating at lower temperature the fan clutch is partially engaged with radiator fan and as soon as the engine temperature increases beyond certain predetermined value, the fan clutch engages completely to draw more amount of air on the radiator to effectively cool the coolant flowing around the engine. By providing this type of arrangement engine is running at optimum temperature to get highest efficiency.
Construction of the Radiator Fan Clutch:
Fan clutch constitutes of fluid reservoir, bimetallic coil, arm shaft and pump plate.
It’s a small tank or reservoir in which silicone fluid which circulates in the clutch assembly is reserved.
This is the coil which can be used as thermal switch in fan clutch. Bimetallic consists of number of coils which have different thermal expansion; it measures the temperature of engine and accordingly allows the circulation of fluid.
The bimetallic coil is connected to the arm shaft in such a way that as the temperature rises; the shaft moves the arm to allow more fluid to pass through it in the pump plate.
Pump plate consists of wipers on it and there are holes for the fluid to flow in front of the wipers. Thus pump plate controls the flow of fluid in the working chamber.
Working of Radiator Fan Clutch
The working of fan clutch is very simple. When engine temperature increases, the temperature of bimetallic coil also increases. As bimetallic coil is connected to the arm shaft, with the increase in temperature of bimetallic coil the shaft moves the arm allowing the opening for pump plate. This opening permits the fluid to flow in the working chamber from the reservoir. The holes in front of wiper allow silicone to circulate in the fan clutch. With the increase in temperature, the arm uncovers the hole more allowing more silicone to flow through it. High pressure areas are developed in front of wiper due to difference in speed of clutch plate and pump plate which forces the silicone back in the reservoir.The fan clutch is said to be fully engaged when silicone in working chamber completely fills the grooves in clutch body and clutch plate.The continuous action of wipers reduces the amount of silicone in the grooves and so the speed of fan is reduced. The setting of bimetallic coil decides the temperature of engagement and disengagement of fan clutch.