As a key component of the automotive thermal management system, the electronic water pump plays an important role in the intelligent control of the temperature of the automotive subsystems, ensuring the safe and reliable operation of the subsystems, and reducing energy consumption. This paper introduces the basic structure, principle, advantages and disadvantages of mainstream electronic water pumps, analyzes its different application requirements in major systems such as internal combustion engines, new energy pure electric vehicle drive systems, and power battery thermal management, and analyzes the application and technology of electronic water pumps. Development trends are inferred.

Electronic water pump is a key component in the automotive cooling system. It is mainly used in the main cooling system of the internal combustion engine, the turbocharger cooling circuit and the air intake intercooling system. It is also used in the drive system of new energy vehicles and the thermal management system of the power battery. The use of intelligently controlled electronic water pumps in the above systems can enable the temperature of the cooling system to be closed-loop controlled according to real-time working conditions, and reduce energy consumption while ensuring the reliability of the cooled components.

1 The mainstream structure, principle and advantages and disadvantages of electronic water pumps
The electronic water pump is composed of three basic parts: hydraulic machinery, motor and motor controller. According to its fluid sealing structure, it is mainly divided into dry type and wet type electronic water pump. The hydraulic mechanical part and the motor part of the dry electronic water pump are separated independently and connected by a shaft. The water pump and the motor are sealed and isolated by rotating dynamic seals. The motor casing, water pump casing and motor controller casing are connected as a whole, and the motor drives The impeller of the water pump rotates. The wet electronic water pump is designed with a sealed thin-walled bushing between the rotor and the stator of the motor, and the rotor of the motor is integrated with the impeller of the water pump. When working, the rotor of the motor is immersed in the fluid medium, the magnetic field generated by the stator coil penetrates the thin-walled bushing and the magnetic field of the permanent magnet of the rotor forms a loop, driving the rotor and impeller to rotate, and the motor controller is installed next to the motor.

2. Application of electronic water pump technology in internal combustion engines
2.1 Application of internal combustion engine main cooling water pump
At present, the main cooling water pump of most internal combustion engines is a mechanical pump, which is installed at the front end of the engine. The driving force is provided, and the water pump and the crankshaft rotate synchronously according to a fixed transmission ratio. The disadvantage of this design is that the speed of the water pump can only rise and fall synchronously with the speed of the engine. When the engine needs to warm up quickly at low temperature, it does not need a large coolant flow, but the water pump cannot run at a low speed. However, when the engine is under low-speed and high-load conditions, a large flow of liquid cooling is required, and the water pump cannot run at high speed at this time. When driving at low load and high speed, the air cooling effect is good, and a large coolant flow is not required, but at this time the water pump is running at high speed. In order to ensure a reliable cooling effect under special working conditions such as low speed and heavy load, the mechanical pump must be designed with relatively high power. However, under most non-special working conditions, the pump operates with excess power, resulting in unnecessary energy consumption.

Because of these deficiencies in mechanical water pumps, electronic water pumps are gradually being applied to the main engine cooling system. The speed of the electronic coolant pump is no longer directly related to the engine. The electronic control unit (ECU) collects parameters such as engine speed, load, and water temperature through sensors, and compares them with the calibrated optimal water temperature under corresponding working conditions to control the water pump speed. Realize closed-loop control of liquid temperature. Its advantage is that it can control the operating temperature of the engine in the optimal range, thereby improving the thermal efficiency of the engine and reducing fuel consumption, while achieving rapid warm-up under low temperature conditions. The speed of the electronic water pump is independently controlled, and it does not need to run at full power when it is not the maximum cooling demand. The maximum power and average operating power of the electronic water pump are much lower than those of the mechanical water pump.

The power of the electronic water pump is mainly distributed between 50 and 600 W. For cars equipped with ordinary generators and ordinary 12 V batteries, the power consumption and current of this power section are still too large. The electric energy that drives the water pump is generated by the generator driven by the engine, and the multi-stage conversion of energy brings about a large loss of efficiency. And because the electronic water pump involves technologies in multiple fields such as electronics, software, motors, and hydraulic machinery, it is very difficult, and the failure of the water pump will also lead to serious consequences of engine damage, so its reliability is extremely high. Previously, only a few international auto parts companies had mature technologies and products. These factors made the application cost of the main cooling electronic water pump very high and it was difficult to popularize it.

As cars become more efficient at recovering energy to generate electricity during braking, the recovered electricity is most suitable for driving accessories such as water pumps. After years of research and development, some auto parts companies have also launched a series of cost-effective electronic main water pump products, which are now supporting mainstream auto manufacturers. After solving the power consumption and cost problems of the water pump, the electronic water pump for main cooling of the engine will quickly become popular due to its unique advantages.

2.2 Application of electronic water pump in turbocharger cooling circuit
Due to the high-temperature exhaust gas and high-speed rotation of the turbocharger, the temperature at the turbine end will reach above 600°C, while the working temperature of the sealing ring needs to be controlled below 230°C, and the bearing needs to be controlled below 150°C, otherwise the turbocharger will be damaged quickly , so efficient cooling is key. Turbochargers are generally designed with a liquid cooling circuit, but after the engine stops, the mechanical main water pump will also stop working. Without cooling of the circulating liquid, heat soaking will cause damage to the bearings, shafts and seals of the turbocharger. To solve this problem, a 15-30 W auxiliary electronic water pump is generally configured in the turbocharger cooling circuit to continue to provide cooling for the supercharger after the engine is shut down.

2.3 Application of electronic water pump in air intake intercooling circuit
Due to the high-temperature heat conduction at the turbine end of the turbocharger and the heat generated by the compression of the air, the temperature of the air passing through the turbocharger compressor can reach 150°C, while the temperature of the air entering the engine should generally be controlled below 50°C. Compressed air is used to cool the air, and the current mainstream technology uses liquid cooling plus air cooling to cool the intake air. In a supercharged engine equipped with a mechanical main water pump, a small electronic water pump of 30-60 W is often configured in the liquid cooling circuit of the intercooler to control the intake air temperature. The electronic water pump is used in the air intake and intercooling system, which can solve the cooling demand of the turbocharger through the layout of the pipeline. In engines using external exhaust gas recirculation (EGR) technology, the liquid cooling circuit of the EGR cooler is generally connected in parallel with the intake air intercooling circuit to achieve exhaust gas cooling.

2.4 Internal combustion engine thermal management system based on electronic water pump
After the engine uses the electronic main water pump, it can realize the shutdown cooling function. On this basis, the thermal management system is equipped with an electronically controlled valve group that can control the flow direction and flow of the cooling circuit, so as to realize the matching of the needs of each cooling circuit, and does not need to be equipped with multiple The water pump can better meet the thermal management needs of various parts of the engine. At present, General Motors has used this technology on the CSS series of new engines. However, its thermal management system and electronic water pump are designed and arranged separately and connected by pipelines. The integrated design of pump and valve can save installation pipelines, optimize layout space and reduce pipeline interfaces, which is conducive to cost reduction. It will become the development trend of engine thermal management technology in the future.

3 Application of electronic water pump technology in new energy electric vehicles
The application of electronic water pumps in electric vehicles is mainly the liquid cooling circuit of the drive system and the liquid cooling circuit of the power battery. The drive system includes a drive motor, a motor controller and a reducer. The drive motor generates a lot of heat when it is running under heavy load, and the high-power device IGBT in the motor controller will also generate a lot of heat. Excessive temperature will reduce the efficiency of the motor and electric control. drop, temperature runaway can lead to serious consequences of rapid burnout. In order to ensure good lubrication in the high-speed reducer, it is also necessary to control the temperature of the lubricating oil through the heat exchanger. Therefore, the driving system is generally designed with a liquid cooling circuit, and the temperature of the cooling liquid is generally required to be controlled within 90°C. The general power of the  small electronic coolant pump used in this system is 40-60 W.

The lithium-ion power battery of an electric vehicle will generate heat during charging and discharging, especially during fast charging and high-power discharging. The discharge performance and cycle life are reduced, and thermal runaway may also cause the power battery to spontaneously ignite. Therefore, the power battery is designed with a thermal management system of liquid circulation. In the liquid circulation circuit, there is a heat exchanger for heat exchange with the air conditioning system, an electric heater for heating the liquid, and an electronic water pump to drive the liquid circulation, which can realize the power battery. The temperature of the power battery is controlled at 10-55°C, the temperature of the liquid in the battery thermal management system is generally lower than 50°C, and the power of the mini electronic water pump is generally 50-120 W.

There are also components such as chargers, inverters and DC transformers in electric vehicles, which also need to use liquid cooling systems. Due to the large difference in the control temperature range of the drive system and battery thermal management, the same cooling system cannot be used, so more than two electronic water pumps are generally used. The difference between the electronic water pump used for electric vehicles and the electronic water pump used for internal combustion engines is that the temperature of the working medium of the internal combustion engine water pump can reach 120 °C, and the ambient temperature can reach 150 °C, and its high temperature reliability requirements are extremely high. The electric vehicle water pump not only needs to work when the car is running, but also during the charging process, and its service life is required to be higher.