EV AC Cooling System Center - Air Conditioning Compressor

  Automobile air-conditioning compressor is the heart of automobile air-conditioning refrigeration system, which plays the role of compressing and transporting refrigerant vapor.

According to different working principles, air conditioner compressors can be divided into fixed displacement compressors and variable displacement compressors.

·Fixed displacement compressor

The displacement increases proportionally with the increase of the engine speed, it cannot automatically change the power output according to the cooling demand, and it has a relatively large impact on the engine fuel consumption.

·variable displacement compressor

The power output can be automatically adjusted according to the set temperature. The air conditioning control system does not collect the temperature signal of the air outlet of the evaporator, but controls the compression ratio of the compressor according to the pressure change signal in the air conditioning pipeline to automatically adjust the temperature of the air outlet. During the whole process of refrigeration, the compressor is always working.

  According to different working methods, compressors can generally be divided into reciprocating type and rotary type. Common reciprocating compressors include crankshaft connecting rod type and axial piston type. Common rotary compressors include rotary vane type and scroll type. Crankshaft connecting rod type and axial piston type are the first and second generation compressor forms, which are widely used in large-displacement vehicles. But the current mainstream is rotary vane and vortex type.

·Rotary Vane Compressor

There are two types of cylinder shapes for rotary vane compressors: round and oval. In a circular cylinder, there is an eccentric distance between the main shaft of the rotor and the center of the cylinder, so that the rotor is close to the suction and exhaust holes on the inner surface of the cylinder. In an elliptical cylinder, the major axis of the rotor coincides with the center of the ellipse. The blades on the rotor divide the cylinder into several spaces. When the main shaft drives the rotor to rotate for one revolution, the volume of these spaces changes continuously, and the volume and temperature of the refrigerant vapor also change in these spaces. Rotary vane compressors do not have suction valves because the vanes do the job of sucking in and compressing the refrigerant.

   If there are 2 blades, there are 2 exhaust processes for one rotation of the main shaft. The more blades, the less fluctuations in the compressor's discharge. As the third-generation compressor, the volume and weight of the rotary vane compressor can be made small, and it is easy to arrange in a narrow engine compartment, with low noise and vibration and high volumetric efficiency. However, the rotary vane compressor requires high machining accuracy and high manufacturing cost.

·scroll compressor

4th generation compressor

The scroll compressor structure is mainly divided into two types: dynamic and static and double revolution. At present, dynamic and static applications are the most common. Its working parts are mainly composed of a moving turbine and a static turbine. The structures of the moving and static turbines are very similar. They are both composed of an end plate and an involute spiral protruding from the end plate. The two are eccentrically arranged and have a phase difference. 180°, the static turbine is stationary, while the moving turbine is driven by the crankshaft to eccentrically rotate and translate under the constraint of a special anti-rotation mechanism, that is, there is no rotation, only revolution.

Advantages of scroll compressors

The scroll compressor has many advantages: the compressor is small in size and light in weight, and the eccentric shaft driving the moving turbine can rotate at high speed. Because there is no suction valve and discharge valve, the scroll compressor operates reliably, and it is easy to realize variable speed movement and variable displacement technology. Multiple compression chambers work at the same time, the gas pressure difference between adjacent compression chambers is small, the gas leakage is small, and the volumetric efficiency is high. Due to its advantages of compact structure, high efficiency and energy saving, micro-vibration, low noise and working reliability, the scroll compressor has been more and more widely used in the field of small-scale refrigeration, and has therefore become one of the main directions of compressor technology development.

Anti-rotation structure

In order to prevent the rotation of the scroll air conditioner compressor, the anti-rotation mechanism of the conventional electric scroll compressor includes a steel ball and socket type, a cross slip ring type, and a cylindrical pin ring type. At present, the cross slip ring type and cylindrical pin type are commonly used. The steel ball and socket anti-rotation mechanism is a circular motion, with many parts and complex structure, high cost and high noise, so it is rarely used.

The cross-slip ring anti-rotation mechanism is reciprocating, with low noise and stable low speed. But the power consumption is large, and it is not suitable for high-speed movement; (27CC-34CC) (currently Highly, Hunan Beite, Zhengzhou Yuebo use this mechanism) cylindrical pin ring type is the current anti-rotation mechanism for mainstream electric scroll compressors , but there is sliding friction between the cylindrical pin and the ring, which affects the parts

The precision requirement is higher, and the production cost is higher. And there will be friction and gnawing between the cylindrical pin and the ring, resulting in the failure of the anti-rotation mechanism. (Tesla-Halla, Sanden, Shanghai Guangyu)

Common failure causes

As a high-speed rotating working part, the air conditioner compressor has a relatively high probability of failure. Common failures include abnormal noise, leakage and failure to work.

(1) Abnormal sound There are many reasons for the abnormal sound of the compressor. For example, the electromagnetic clutch of the compressor is damaged, or the internal wear of the compressor is serious, etc., which can cause abnormal noise.

(2) Leakage Refrigerant leakage is the most common problem with air conditioning systems. The part where the compressor leaks is usually at the junction of the compressor and the high and low pressure pipes, where it is usually troublesome to check because of the installation location. The internal pressure of the air conditioning system is very high. When the refrigerant leaks, the compressor lubricating oil will be lost, which will cause the air conditioning system to stop working.

operation or poor lubrication of the compressor. There are pressure relief protection valves on air conditioner compressors. The pressure relief protection valves are usually for one-time use. After the system pressure is too high for pressure relief, the pressure relief protection valves should be replaced in time.

(3) Not working There are many reasons why the air conditioner compressor does not work, usually because of related circuit problems. It is possible to preliminarily check whether the compressor is damaged by directly supplying power to the electromagnetic clutch of the compressor.