The device and principle of operation of the air conditioner compressor
Car device,  Vehicle electrical equipment

The device and principle of operation of the air conditioner compressor

A car air conditioner is a rather complex and expensive system. It provides air cooling in the passenger compartment, so its breakdown, especially in summer, causes a lot of inconvenience for drivers. A key component in an air conditioning system is the air conditioning compressor. Let's take a closer look at its structure and principle of operation.

How does air conditioning work in a car?

It is difficult to imagine a compressor in isolation from the entire system, therefore, first, we will briefly consider the principle of operation of the air conditioning system. The device of a car air conditioner does not differ from the device of refrigeration units or household air conditioners. It is a closed system with refrigerant lines. It circulates through the system, absorbing and releasing heat.

The compressor does the main job: it is responsible for circulating the refrigerant through the system and divides it into high and low pressure circuits. The highly heated refrigerant in the gaseous state and under high pressure flows from the supercharger to the condenser. Then it turns into a liquid and passes through a receiver-drier, where water and small impurities come out of it. Next, the refrigerant enters the expansion valve and the evaporator, which is a small radiator. There is a throttling of the refrigerant, accompanied by a release of pressure and a decrease in temperature. The liquid again turns into a gaseous state, cools and condenses. The fan drives the cooled air into the vehicle interior. Further, the already gaseous substance with a low temperature goes back to the compressor. The cycle repeats again. The hot part of the system belongs to the high pressure zone, and the cold part to the low pressure zone.

Types, device and principle of operation of the compressor

The compressor is a positive displacement blower. It starts its work after turning on the air conditioner button in the car. The device has a permanent belt connection to the motor (drive) through an electromagnetic clutch, which allows the unit to be started when needed.

The supercharger draws in gaseous refrigerant from the low pressure area. Further, due to compression, the pressure and temperature of the refrigerant increases. These are the main conditions for its expansion and further cooling in the expansion valve and evaporator. A special oil is used to increase the service life of the compressor components. Part of it remains in the supercharger, while the other part flows through the system. The compressor is equipped with a safety valve that protects the unit from overpressure.

There are the following types of compressors in air conditioning systems:

  • axial piston;
  • axial piston with a rotating swash plate;
  • bladed (rotary);
  • spiral.

The most widely used are axial-piston and axial-piston superchargers with an inclined rotating disc. This is the simplest and most reliable version of the device.

Axial piston supercharger

The compressor drive shaft drives the swash plate, which in turn drives the pistons in the cylinders to reciprocate. The pistons move parallel to the shaft. The number of pistons may vary depending on the model and design. There can be from 3 to 10. Thus, the tact of work is formed. The valves open and close. Refrigerant is sucked in and discharged.

The power of the air conditioner depends on the maximum compressor speed. Performance often depends on engine speed. The fan speed range is from 0 to 6 rpm.

To remove the dependence of the compressor on the engine speed, compressors with variable displacement are used. This is achieved by using a rotating swash plate. The angle of inclination of the disc is changed by means of springs, which adjusts the performance of the entire air conditioner. In compressors with fixed axial discs, regulation is achieved by disengaging and closing the electromagnetic clutch.

Drive and electromagnetic clutch

The electromagnetic clutch provides communication between the running engine and the compressor when the air conditioner is turned on. The clutch consists of the following components:

  • belt pulley on the bearing;
  • electromagnetic coil;
  • spring loaded disc with hub.

The motor drives the pulley by means of a belt connection. The spring-loaded disc is connected to the drive shaft, and the solenoid coil is connected to the supercharger housing. There is a small gap between the disc and the pulley. When the air conditioner is turned on, the electromagnetic coil creates a magnetic field. The spring loaded disc and the rotating pulley are connected. The compressor starts up. When the air conditioner is turned off, the springs move the disc away from the pulley.

Possible malfunctions and compressor shutdown modes

As already mentioned, air conditioning in a car is a complex and expensive system. Its “heart” is the compressor. The most frequent breakdowns of the air conditioner are associated with this particular element. Problems can be:

  • malfunction of the electromagnetic clutch;
  • failure of the pulley bearing;
  • refrigerant leaks;
  • fuse blown.

The pulley bearing is heavily loaded and often fails. This is due to his constant work. A breakdown can be identified by an unusual sound.

It is the air conditioning compressor that does most of the mechanical work in the air conditioning system, so it often fails. This is also facilitated by bad roads, malfunctioning of other components, and improper operation of electrical equipment. Repair will require special knowledge and skills. Better to contact a service center.

There are also some modes in which the compressor is turned off, provided by the system:

  • very high (above 3 MPa) or low (below 0,1 MPa) pressure inside the supercharger and lines (shown by pressure sensors, threshold values ​​may differ depending on the manufacturer);
  • low air temperature outside;
  • excessively high coolant temperature (above 105˚C);
  • the evaporator temperature is less than about 3˚C;
  • throttle opening more than 85%.

To more accurately determine the cause of the malfunction, you can use a special scanner or contact a service center for diagnostics.

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