The secret of pure electric vehicle air conditioning

For pure electric vehicle air conditioners, the power source comes from an electric motor, replacing the traditional belt drive. The motor is generally assembled with the compressor and driven coaxially to form a fully enclosed structure. When the DC power from the battery pack passes through the inverter to power the air conditioner compressor drive motor, the air conditioner motor drives the compressor to rotate, thereby forming a refrigeration cycle and producing a refrigeration effect. By adjusting the motor speed to change the compressor speed, the air conditioning compressor displacement and cooling capacity can be flexibly controlled.

Advantages: simple structure, high reliability and low failure rate. When it comes to the choice of compressor type, pure electric vehicles use scroll compressors. Compared with other types (such as swash plate type, crank connecting rod type, vane type and other compressors), the scroll type has many advantages such as small vibration, low noise, long service life, light weight, high speed, high efficiency, small size, etc. This advantage is more in line with the air conditioning requirements of electric vehicles.

scroll compressor

The scroll compressor is mainly composed of a fixed scroll and a movable scroll of the same linear shape, two scrolls that mesh with each other. They are installed 180° offset from each other (that is, the phase angle differs by 180°). The fixed scroll is fixed on the frame, and the movable scroll is directly driven by the electric motor, but it cannot rotate and can only revolve around the fixed scroll with a small radius of rotation.

When the driving motor rotates to cause the movable scroll to revolve, the refrigerant gas is sucked into the peripheral part of the fixed scroll through the filter element. As the drive shaft rotates, the movable scroll rotates according to the trajectory in the fixed scroll, causing the movable scroll and the fixed scroll to rotate. Six cavities are formed in which the volume gradually decreases from outside to inside. The refrigerant gas is gradually compressed in the six-month crescent-shaped compression cavity composed of the moving and fixed scrolls. The compressed refrigerant gas is passed from the center hole of the fixed plate through the valve plate. Continuous discharge.

During the entire working process of the compressor, all working chambers gradually become smaller from the outside to the inside and are in different compression conditions, thereby ensuring that the scroll compressor can continuously inhale, compress and discharge air. Although the scroll compressor discharges a small amount of refrigerant each time, its discharge volume is 27 to 30 cubic centimeters, but because its movable scroll can rotate up to 9000 to 13000 r/min, its total displacement is sufficient Large, it can meet the needs of vehicle air conditioning and refrigeration. Of course, the power consumption of the compressor is also large, up to 4~7KW.

A complete pure electric vehicle air conditioning system mainly includes: compressor, evaporator, condenser, heater core, water tank, intercooler, oil cooler, HVAC pipeline assembly, HVAC shell expansion valve, control unit and other components. Because the refrigeration principle is the same as that of fuel vehicle air conditioners, we will not go into details here. Today we will just take a look at its special feature---the heating air supply for pure electric vehicles!

There are three common types of warm air supply sources: heat pump type, PTC electric heater type, and waste heat + auxiliary PTC type. Due to space limitations, we only explain PTC electric heaters.

PTC is a direct heating resistance material that generates heat when energized, which can be used for air conditioning heating. For example, some electric vehicle air conditioners have 8 PTC heating elements inside. The air conditioner driver supplies battery high-voltage power to each element. The power can reach 300~600W, which is used to heat cold air or coolant. In order to improve the efficiency of the heater, water is often used as the heating medium. The water is heated and sent to the radiator of the air conditioning duct, and then blown by the fan to the cabin or the windshield to increase the temperature and humidity inside the cabin. Remove frost from windshield.

Temperature and resistance characteristics of TC elements. When the component is first powered on, its resistance will slowly decrease as the temperature increases, which means that its calorific value is low at room temperature. When the temperature exceeds the "Curie temperature", the resistance value will increase stepwise as the temperature increases. The temperature of the blown gas can reach 85℃, which can fully meet the requirements of air conditioning and heating. When the temperature is higher than 85℃, the PTC resistance becomes, and the actual performance is that it automatically stops working.