Failure Analysis Of Fan Clutch-The 3 most important aspects
Do You Know These Methods? Don’T Be Afraid Of Generator Failure
2021-12-18
coolant-lamp
Why does the coolant light come on when servicing the urea injection unit?
2021-12-18

Why does the coolant light come on when servicing the urea injection unit?

  • Fan control of the cooling system is essential if the diesel engine is to maintain optimum operating temperature. At present, most domestic heavy trucks use silicone clutch fans. Truck drivers will inevitably encounter problems such as the fan not turning during the driving process. This is when many truck drivers choose to lock the fan clutch. Is this the right thing to do? This must not be feasible.
  • Here I will briefly introduce the working principle of silicone oil fan clutch so that truckers can deepen their understanding of the routine fan clutch failure, and then avoid some wrong operations, regulate driving and bring better benefits to themselves.
Clutch

Principle Of Silicone Oil Fan Clutch

  • Different from ordinary rigid fans, a silicone oil fan clutch uses silicone oil as the medium and uses silicone oil shear viscosity to transmit torque. The space between the front cover of the fan clutch and the driven plate is an oil storage chamber, where high-viscosity silicone oil is stored.

  • The key sensing component is the spiral bimetallic sheet temperature sensor on the front cover. It senses heat and deforms to control the valve plate, so as to control the silicone oil to enter the working chamber and connect the drive shaft with the fan.

  • When the temperature is low, the control valve does not open, and the silicone oil in the oil storage chamber cannot flow into the working chamber at this time. There is no silicone oil in the working chamber, the torque on the driving plate cannot be transmitted to the driven plate, and the clutch is in a disengaged state.

Clutch
  • When the engine load increases and the coolant temperature increases, the high-temperature air flow blows on the bimetallic temperature sensor, causing the bimetallic plate to be heated and deformed, driving the valve plate drive pin and the control valve plate to deflect an angle. When the air temperature exceeds a certain temperature, the oil inlet hole is opened, and the silicone oil in the oil storage chamber enters the working chamber through this hole. The torque on the driving plate is transmitted to the clutch housing through the shear stress of silicone oil to drive the fan to rotate at high speed.

Function Of Silicone Oil Fan Clutch

  • Due to the changes of environmental conditions and operating conditions, the thermal condition of the engine changes at all times. Therefore, the cooling intensity of the engine must be adjusted at any time. For example, in summer, when the engine works at low speed and heavy load and the coolant temperature is very high, the fan should rotate at high speed to increase the cooling air volume and enhance the heat dissipation capacity; In cold winter, when the coolant temperature is low, it becomes meaningless for the fan to continue to work. It not only consumes engine power in vain but also produces great noise.
  • In many areas of the north, if the temperature is below 10 ℃ for more than 100 days, the actual engine cooling fan will do useless work, and the fuel consumed will be a very serious waste. This also explains why the clutch cannot be locked.
Clutch

Frequent Fault Analysis

  1. The spiral bimetallic sheet temperature sensor is broken, resulting in the nonrotation of the fan.
  2. The fatigue failure of the spiral bimetallic sheet temperature sensor leads to high-temperature sensing conditions, which leads to the fan can not work in time and affects the engine performance.
  3. The oil storage chamber and working chamber are not tightly sealed, and the loss of silicone oil affects the torque transmission.
Solution
  • Firstly, the locked fan clutch will lose a lot of power. It is understood that the power required by the rigidly connected cooling fan accounts for 3-5% of the engine power, and the fuel consumption is very amazing.

  • Secondly, silicone oil can play a certain buffer role. Even in the engaged state, the speed of the fan is smaller than that of the drive shaft, which will cause a great impact on the connection. The diameter of the heavy truck fan is very large, and the inertia is also large. The fan rotates with the engine, and the engine starts and stops very quickly, which will cause a strong impact on the connection of the fan clutch. Under the inertia for a long time, If the situation is serious, the fan will fall and the water tank may be damaged, which should not be underestimated.

  • With the progress of science and technology, the fan design of the cooling system has also experienced great changes, from the earliest rigid fan to the silicone oil clutch fan, and then to the advanced electromagnetic clutch fan and electronic silicone oil clutch fan.
Postscript:

If you choose to drive a truck, you must learn to operate. The engine is the core component of the truck, and the fan, as the cooling system, plays a vital role in the working efficiency of the engine.

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