The role of thermal expansion valve of automobile air conditioner


Expansion valve, also called throttle valve, is the mai […]

Expansion valve, also called throttle valve, is the main component of automobile air-conditioning refrigeration system and is installed at the entrance of evaporator.

Its function is: throttling and decompressing the high-pressure liquid refrigerant from the receiver dryer, adjusting and controlling the amount of liquid refrigerant entering the evaporator to adapt it to changes in refrigeration load, while preventing the compressor from liquid hammer ( That is, the unevaporated liquid refrigerant is compressed after entering the compressor, which can easily cause damage to the compressor valve plate) and abnormal overheating of the vapor at the outlet of the evaporator.

The thermal expansion valve is a throttling device widely used in refrigeration systems, but the automotive air-conditioning refrigeration system composed of it and the variable displacement compressor has system stability problems in actual use. At-suo Inoue et al. found that there is a system oscillation phenomenon when conducting an experimental study on an automobile air-conditioning refrigeration system composed of a 7-cylinder variable displacement compressor and a thermal expansion valve. M Country GM Company also found the same in the application process of the stepless variable displacement compressor and the thermal expansion valve automobile air-conditioning refrigeration system. We have studied the stability of the automotive air conditioning refrigeration system of the variable displacement compressor and the thermal expansion valve used in a certain vehicle model. In order to analyze the mutual coupling between the variable displacement compressor and the thermal expansion valve parameters in detail, the system is stabilized. It is necessary to deeply understand the dynamic behavior of the thermal expansion valve of the system.

The displacement of the fixed displacement air conditioner compressor increases with the increase of the engine speed. It cannot automatically change the displacement according to the size of the refrigeration load, which has a relatively large impact on the fuel consumption of the engine. Automobile air-conditioning compressor parts are generally controlled by collecting the temperature signal from the outlet of the evaporator. When the temperature reaches the set value, the electromagnetic clutch of the air-conditioning compressor is disconnected and the compressor stops working; when the temperature rises, the electromagnetic clutch is engaged and the compressor Work again. The fixed-displacement air-conditioning compressor is also controlled by the pressure of the air-conditioning refrigeration system. When the pressure in the pipeline is too high or too low, the automobile air-conditioning compressor accessories will also stop working.

Oblique astrolabe

Troubleshooting of water ingress of automobile air-conditioning compressor parts

1. Trouble phenomenon: According to reports, the car's condenser, expansion valve, high and low pressure composite pipe, and dryer have all been replaced with new ones. The refrigerant has been charged and discharged several times. The previous refrigeration effect was not very good, but later it was not refrigerated at all. And the compressor shuts down intermittently. 

2. Inspection and diagnosis: start the engine for inspection, but the compressor will automatically stop after less than 5 minutes. According to past experience, the compressor will stop intermittently in the following situations: excessive refrigerant, failure of the power relay of the electromagnetic clutch of the compressor, failure of the cooling system, failure of the cooling fan, failure of the thermistor, etc.

Due to the loosening of the plug of the air conditioner compressor control circuit, the automobile air conditioner compressor parts cause poor contact, which causes the voltage supplied to the solenoid coil to drop and the current to be unstable. As a result, the electromagnetic clutch of the air conditioner compressor is sometimes engaged and sometimes separated. The clutch and solenoid will be burned out.

The most primitive car air conditioner is only a window ventilation type. Zui’s early car air-conditioning device started in 1927. It only consists of a heater, a ventilating device and an air filter, and it can only heat the interior of the car. To be precise, the history of automobile air-conditioning should begin with the application of refrigeration technology to cars. In the late 1930s, several buses in the country were equipped with air-conditioning devices using refrigeration technology. It was not until the 1960s that automobile air conditioners, which used refrigeration technology as parts of automobile air conditioner compressors, began to gradually become popular. From now on, people's interest in air conditioners for cars has increased year by year, and car air conditioners have become more and more complete and their functions have become more and more comprehensive. Its development can be roughly divided into the following stages: single heating, single air-conditioning, integrated cooling and heating, automatic control, and microcomputer control.

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