Electronic water pump structure and working principle
If the engine temperature is too high, the lubricating ability of the engine fuel will decrease, which will lead to aggravated wear of the parts. If the temperature reaches a certain value, it will cause serious failures such as engine cylinder scuffing or burning of tiles, and eventually the engine will be burned and scrapped.
The water pump is an important component of the automobile engine cooling system. Its main function is to drive the coolant circulation, absorb the excess heat of the engine and transfer it to the outside air through the heat sink to avoid excessive engine temperature.
There are two types of water pumps: traditional mechanical water pumps and electronic water pumps. Traditional engines generally use a mechanical water pump, which drives the water pump bearing and impeller to rotate through the pulley. The coolant in the water pump is driven by the impeller to rotate together, and is thrown to the edge of the water pump shell under the action of centrifugal force, and at the same time generates a certain pressure. Then flow out from the outlet or water pipe. The pressure at the center of the impeller decreases due to the coolant being thrown out, and the coolant in the water tank is sucked into the impeller through the water pipe under the action of the pressure difference between the pump inlet and the center of the impeller to realize the reciprocating circulation of the coolant.
The traditional mechanical water pump works based on the engine speed, which leads to the need for a large power to drive even in cold start and low load high speed conditions with low demand for flow, and the cooling capacity provided at this time is far greater It is not based on the actual demand of the engine, and it needs a lot of power to drive, which will cause the decline of the engine's power performance and economy.
The working principle of the electronic water pump is as follows: ECU (electronic control unit) adjusts the size of the duty cycle through PWM (pulse width modulation) according to the feedback signal such as water temperature, and transmits the signal to the controller inside the electronic water pump. The size controls the rotation of the motor, thereby driving the rotation of the impeller rotor, thereby realizing the circulation of the coolant.
The electronic water pump can precisely control the flow according to the cooling device's demand for coolant. With the development of science and technology and the high requirements for fuel efficiency, the application of electronic water pumps is increasing. At present, hybrid and new energy engines on the market have begun to use electronic water pumps.The electronic water pump is composed of pump casing, impeller, sealing ring, motor casing, electrical plug, motor assembly, bearing, rotor, controller, controller seat, back cover, fixing bolts, etc.
The ECU adjusts the duty ratio through PWM according to the feedback signal such as water temperature, and the controller connects the wiring harness through the electrical plug, and then controls the motor to drive the impeller and rotor according to the duty ratio, thereby realizing the coolant circulation and ensuring the precise flow of the coolant. control; the sealing ring is to ensure the tightness between the pump casing and the motor casing, the controller seat and the back cover; the pump casing, the motor casing, and the back cover are to seal the internal components of the electronic water pump in a dust-free environment to ensure that the electronic the working reliability of the water pump .
Features of electronic water pumps
▶ Provide timely and appropriate cooling capacity, low energy consumption and high efficiency, realize precise control of coolant flow according to water temperature and other information, reduce coolant flow distance and reduce water pump displacement by about 60%.
▶ To reduce friction, the electronic water pump is driven by electricity. Compared with the mechanical water pump, which is driven by an accessory belt, the friction work is reduced. The NEDC (New European Driving Cycle, which is the European endurance test standard) cycle can reduce fuel consumption by about 2%.
▶ Accelerate warm-up. For hybrid engines, due to frequent start and stop, a faster warm-up speed is required. Since the displacement of the electronic water pump can be controlled in real time, reducing the coolant flow rate during cold start can speed up warm-up and reduce fuel consumption and emission effects.
▶ The service life is longer, and the continuous working time is more than 20,000 hours.
▶ The risk of water leakage is greatly reduced. The impeller of the mechanical water pump is press-fitted on the water pump bearing with an interference fit, while the integrated magnetic impeller of the electronic water pump is driven by the magnetic core installed in the water pump shell, so that the water chamber and The separation of the exterior removes the water seal, reducing frictional losses and the risk of water leaks.
▶ Flexible control methods (PWM, bus).
▶ Multiple working protections (over temperature, over voltage, over current, etc.)
Electronic water pump failure mode and failure cause
The water temperature rises abnormally, and the performance of the electronic water pump decreases. Performance degradation can occur for two reasons:
▶The interference design between the impeller assembly and the hollow shaft is too small, resulting in unreliable connection between the impeller and the hollow shaft, and the impeller slipping, resulting in substandard impeller speed and reduced pump performance;
▶The design of the anti-rotation structure of the inlay is unreasonable, resulting in slipping between the inlay and the injection impeller, resulting in substandard impeller speed and reduced pump performance.
▶ The speed of the electronic water pump sometimes stops, and finally drops to zero and stops working. The reasons for the water pump not working are summarized in the following 5 points:
- 1.The chip or electronic device fails, and the thickness of the copper foil does not meet the design requirements, causing the copper foil to burn when the temperature rises;
- 2.Waterproof and breathable valve sealing ring material selection is unreasonable, aging in the extreme environment, resulting in unqualified air tightness, water vapor entering the dry area, short circuit of the water pump, and the water pump stops working;
- 3.The design of the welding area between the controller reed and the enameled wire is unreasonable, and the strength of the contact section is not enough, which leads to the breakage of the reed and the enameled wire, and the water pump cannot work;
- 4.There is no glue between the capacitors at the controller or between the capacitors and the bracket, so the capacitors only rely on the welding support between the pins and the reeds. Under vibration conditions, the capacitors shake as a whole, causing the pins to be fatigued and broken by cyclic loads , causing the pump speed to drop to zero;
- 5.Unreasonable selection of heat dissipation glue leads to the expansion of heat dissipation glue and produces a large number of voids, which makes the PCB (printed circuit board) unable to dissipate heat normally, resulting in overheating failure.
