Automobile Industry

Vacuum Technology in the Production Process of Automobile Air Conditioning

Usually, automotive air conditioners are composed of compressors and electronically controlled clutches, evaporators, condensers, liquid receiver dryers, thermal expansion valves and control systems. The current automobile air conditioner mainly uses R134a refrigerant as the refrigerant. After being compressed by the compressor, it expands adiabatically in the evaporator to reduce the air temperature in the car.

R134a refrigerant is an environmentally friendly refrigerant, which is non-destructive to the ozone layer, has good safety performance, and is non-flammable, non-toxic and non-irritating. But it is prone to chemical reactions with water molecules to form highly corrosive hydrogen chloride gas. Also, compressors for R134a refrigerant require the use of synthetic lubricating oil, which is hygroscopic and automatically absorbs water vapor from the air.

The absorbed water vapor molecules are then dissolved in the oil, increasing the water content of the lubricating oil. Therefore, the air-conditioning system using R134a refrigerant must be thoroughly dried before filling the refrigerant, otherwise the water vapor molecules remaining in the system will react with R134a to form hydrogen chloride gas, which will cause serious corrosion to the metal parts of the air-conditioning system.

In the general refrigerant filling process of automobile air conditioning system, vacuuming is the most critical step. Vacuuming is not only to remove the gas in the air conditioning system, but more importantly, to remove the moisture in the system by vacuuming. Because the boiling point of water at atmospheric pressure is 100°C, under low pressure in a vacuum state, even room temperature of 20°C can make water boil. Therefore, the vacuum can quickly evaporate the moisture in the system, so as to achieve the purpose of completely drying the air conditioning system.

In the vacuum state, different pressures correspond to different degrees of drying of the system. In general, the lower the vacuum pressure, the drier the system will be. However, the longer the evacuation time is required to bring the system to lower pressures. During the vacuuming process of the air conditioner, most of the time is used to dry the system.

The automotive refrigerant vacuum filling machine is generally composed of a vacuum system, a refrigerant input control and pressurization system, a refrigerant filling and metering system, and an electronic control system. It can complete the vacuuming, leak detection, precise dosing of refrigerants, etc.

Automobile refrigerant vacuum filling machines can generally be divided into two types: fixed type and accompanying type. Since the span of each station on the automobile assembly line is relatively large, each vehicle usually has to move 3-8m during the refrigerant filling process. The mobile filling machine can move with the car during the filling process, and automatically return to the starting position when the filling is completed. The fixed filling machine allows the filling joint and filling pipeline to move with the car, and the filling machine itself is fixed in one position. Walk-behind filling machines are generally suitable for relatively fast production takt, but are relatively expensive. Stationary dosing machines can only be used for slower production cycles, but are relatively inexpensive.

With the acceleration of the production speed of the automobile production line, the vacuuming of the air-conditioning system and the refrigerant filling have been separated into two independent steps to complete. Only in this way can there be a long enough time for vacuuming and drying, and at the same time, the production cycle can be shortened.

Another direction of the development of refrigerant filling equipment is to achieve zero emission during refrigerant filling, that is to say, when the filling gun is separated after each filling, the system cannot have excess refrigerant leaking into the atmosphere.


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