How does the viscous fan clutch work?

Working principle: silicon oil fan clutch, using silicon oil as medium, using silicon oil shear force to transfer torque. The space between the front cover of the fan clutch and the driven plate is the oil storage chamber, where the high viscosity silicone oil is stored.

The key sensing component is the spiral bimetal temperature sensor on the front cover, which can control the valve plate to control the silicone oil to enter the working chamber and connect the drive shaft and fan.

When the engine load increases and the coolant temperature increases, the high temperature air flow blows on the bimetal temperature sensor, which causes the bimetal plate to heat and deform, driving the driving pin between the valve plates and the control valve plate to deflect by an angle. When the air temperature exceeds a certain temperature, the oil inlet hole is opened, and the silicone oil in the oil storage cavity enters the working cavity through the hole. The torque on the active plate is transmitted to the clutch housing through the shear stress of silicon oil, which drives the fan to rotate at high speed.