Application of DC brushless water pump in electric vehicle
The DC brushless water pump of pure electric vehicle has higher requirements on structure and performance than the general water pump; The working environment of the automobile water pump is relatively poor. It is necessary to be able to prevent vibration, moisture and heat. In particular, there are higher requirements for the stability and reliability of the new energy electric vehicle water pump. In addition, the environmental protection and energy conservation of the filter water pump should also be considered;
The magnet of the DC brushless water pump and the impeller are injection molded into one to form the magnetic rotor of the motor. There is a direct injection molded shaft sleeve in the middle of the rotor. The shaft sleeve is high wear-resistant graphite fixed in the rotor body. The stator and circuit board of the motor are encapsulated in the pump body with epoxy resin adhesive. There is a cavity between the stator and the rotor. The pump body cavity is connected with the motor rotor cavity. The motor rotor cavity is completely isolated from the motor stator and motor control, The rotating shaft is made of high finish and high-strength zirconia. The shaft connects the motor with the pump body and is produced by the cavity free vacuum perfusion integrated process. Therefore, it does not need to be equipped with traditional mechanical shaft seal and shaft lubricating oil, so it is completely sealed and leak proof.
The torque of the motor drives the permanent magnet (rotor) to work through the magnetic field generated by the coil on the silicon steel sheet (stator). The magnet is magnetized at n (n is an even number) level to make the magnet parts form a complete coupled magnetic system. When the magnetic pole generated by the stator coil is opposite to the magnetic pole of the magnet, that is, the displacement angle between the two magnetic poles Φ= 0, at this time, the magnetic energy of the magnetic system is the lowest; When the magnetic poles are rotated to opposite poles, that is, the displacement angle between the two magnetic poles Φ= 2 π /n, at this time, the magnetic energy of the magnetic system is the maximum. After removing the external force, because the magnetic poles of the magnetic system repel each other, the magnetic force will restore the magnet to the lowest magnetic energy state. Then the magnet moves and drives the magnetic rotor to rotate; The driving force of the impeller of the DC brushless water pump is the brushless DC motor.
The driving force for the rotation of the impeller of the dc brushless water pump of the pure electric vehicle is the brushless DC motor. The brushless DC motor is the power core of the dc brushless water pump. The dc brushless water pump is powered by the brushless DC motor, so as to realize the conversion of mechanical energy into hydraulic energy; The water pump is an important component of the engine cooling system. Its function is to pump the coolant to make the coolant flow rapidly in the cooling water channel of the engine, so as to take away the heat generated during engine operation and maintain the normal operating temperature of the engine. The impeller is the core of the pump. The movement of the impeller itself is very simple, but it rotates with the magnetic rotor. However, due to the action of the blade, the movement of the liquid in the impeller is very complex; On the one hand, it is involved with the rotation of the impeller, and on the other hand, it is continuously thrown out of the rotating impeller under the driving of the blade, that is, the movement relative to the impeller. Therefore, the outer diameter of the impeller, the height and angle of the impeller blade, and the clearance with the water pump shell directly affect the performance of the water pump. The automobile water pump is mainly the main component of the forced circulation of the automobile cooling system.
In the cylinder block of the automobile engine, there is a water channel for cooling water circulation, which is connected with the radiator (commonly known as the water tank) in the front of the automobile through the water pipe to form a large water circulation system. A water pump is installed at the upper outlet of the engine, which is driven by the fan belt to pump out the hot water in the water channel of the engine cylinder block and pump in the cold water. There is also a thermostat next to the water pump. When the car is just started (cold), it does not open, so that the cooling water does not pass through the water tank, but only circulates in the engine (commonly known as small circulation). When the temperature of the engine reaches more than 80 ℃, it is opened, the hot water in the engine is pumped into the water tank, and the cold air when the car moves forward blows through the water tank to take away heat. Basically, it works like this. The DC brushless water pump is electronically commutated without the use of carbon brushes. Both the magnet rotor and the stator silicon steel sheet have multi-level magnetic fields. When the magnet rotor rotates an angle relative to the stator, it will automatically change the direction of the magnetic poles, so that the rotor will always maintain the same level of repulsion, so that the brushless DC magnetic isolation pump has high speed and efficiency. The stator and rotor of the pure electric vehicle DC brushless water pump are completely isolated, It completely avoids the liquid leakage problem of the traditional motor type dc brushless water pump. Moreover, it can be fully submersible and completely waterproof, effectively improving the service life and performance of the pump. Therefore, the DC brushless water pump does not need water pump bearings, nor lubrication with grease, nor sealing gaskets and oil seals, reducing mechanical wear, reducing power consumption, and improving the service life.
Working principle of DC brushless water pump for pure electric vehicle
The ultimate purpose of the dc brushless water pump of pure electric vehicle is to timely emit part of the heat absorbed by the heated parts of the vehicle, so as to ensure the normal operation of the engine at the most appropriate temperature. When the power is turned on, the water pump operates to drive the impeller to rotate. The coolant in the water pump is driven by the impeller to rotate together. Under the action of centrifugal force, it is thrown to the edge of the water pump shell, and a certain pressure is generated at the same time, and then flows out of the water outlet or water pipe. The pressure at the center of the impeller decreases because the coolant is thrown out. The coolant in the water tank is sucked into the impeller through the water pipe under the pressure difference between the water pump inlet and the center of the impeller to realize the reciprocating circulation of the coolant. The bearing supporting the brush water pump shaft shall be lubricated with grease, so it is necessary to prevent the coolant from leaking into the grease to cause grease emulsification, and also to prevent the coolant from leaking. The sealing measures to prevent leakage of water pump include water seal and sealing gasket. The water seal pair seal ring and the shaft are installed between the impeller and the bearing through interference fit, and the water seal static seal seat is tightly against the housing of the water pump, so as to achieve the purpose of sealing the coolant. The water pump housing is connected with the engine through a sealing gasket and supports moving parts such as bearings. There is also a drain hole on the water pump housing, which is located between the water seal and the bearing. Once the coolant leaks through the water seal, it can be discharged from the drain hole to prevent the coolant from entering the bearing cavity and damaging the bearing lubrication and component corrosion. If there is still coolant leakage after the engine is stopped, it indicates that the water seal has been damaged; The DC brushless water pump has different design structure and production process; No carbon brush is worn, and the pump body and motor are integrated, so the above sealing and leakage proof conditions do not exist.
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