Automobile air conditioning device is also called automobile air conditioner for short. It is used to adjust and control the temperature, humidity, air cleanliness and air flow in the car compartment to the best state, provide passengers with a comfortable riding environment and reduce travel fatigue; create good working conditions for drivers, and play an important role in ensuring safe driving. It generally includes a refrigeration device, a heating device and a ventilation device. This combined device makes full use of the limited space inside the car, has a simple structure and is easy to operate. It is an internationally popular modern automobile air conditioning system.
6 Key components: automotive air conditioner compressors
▪ Classification of automotive air conditioner compressors
▪ Special requirements for automotive air conditioner compressors
▪ Compressor maintenance
1、Development
With the rapid growth of the automobile industry and the increase in export trade, the automobile parts industry has also achieved qualitative development. Automobile air conditioning has become a necessary component for automobile riding comfort. As of August 2024, the domestic automobile air conditioning installation rate is 100% in China, and automobile air conditioning devices have become important functional components in automobiles.
As the world's major air compressor production base, my country has basically formed a complete range of automobile air conditioning production systems with large, medium and small matching. The annual production of automobile air conditioners in China in 2023 is about 35.46 million units (approximate data), which can not only fully meet the needs of the development of my country's automobile industry production, but also some enterprises have the ability to enter the international market.
Although the Chinese automobile air conditioning market has great potential, it also faces severe challenges. The rise in global raw material prices has brought huge cost pressure to the industry; in terms of products, the production of air conditioners for trucks and some special vehicles is relatively small, and market demand cannot be met; in terms of technology, the development trend of energy conservation and environmental protection has brought new challenges to the industry. With the vigorous development of China's automobile industry, consumers will pay more attention to the safety, stability, comfort, entertainment, accessibility and energy conservation and emission reduction of automobiles in the future. Some new automobile air-conditioning products that are more in line with energy-saving and environmental protection requirements will be more popular; in terms of technological development trends, automobile air-conditioning will develop towards environmentally friendly air-conditioning, green air-conditioning, small energy-saving, comfortable and automated directions.
2. Air conditioner type
1) According to the driving mode, it can be divided into: independent type (a dedicated engine drives the compressor, with large cooling capacity and stable operation, but high cost, large size and weight, mostly used in large and medium-sized buses) and non-independent type (the air conditioner compressor is driven by the car engine, the cooling performance is greatly affected by the engine operation, the stability is poor, and it is mostly used in small buses and cars).
2) According to the air conditioner performance, it can be divided into: single function type (the cooling, heating, and ventilation systems are installed separately, operated separately, and do not interfere with each other, mostly used in large buses and trucks) and integrated cooling and heating type (cooling, heating, and ventilation share the same blower and air duct, and are controlled on the same control panel. When working, it can be divided into a combination type in which cold and warm air work separately and a mixed temperature control type in which cold and warm air can work at the same time. Cars mostly use mixed temperature control type).
3) According to the control mode, it can be divided into: manual type (control the temperature, wind speed, and wind direction by turning the function keys on the control panel) and electric control pneumatic adjustment (using a vacuum control mechanism, when the air conditioner function key is selected, the temperature and air volume can be automatically controlled within the preset temperature).
4) According to the adjustment method, it is divided into: fully automatic adjustment (using calculation and comparison circuit, through sensor signals and pre-adjustment signals to control the adjustment mechanism to automatically adjust the temperature and air volume) and microcomputer-controlled fully automatic adjustment (using microcomputer as the control center to achieve all-round and multi-functional optimal control and adjustment of the air environment in the car)
3、Air conditioning arrangement
Different types of air conditioning systems have different layouts. The most widely used air conditioning system in cars today is the integrated cooling and heating air conditioning system. Its layout is to assemble the evaporator, warm air radiator, centrifugal blower, operating mechanism, etc. together, which is called the air conditioning assembly.
4、Air conditioning composition
Modern air conditioning systems are composed of refrigeration systems, heating systems, ventilation and air purification devices and control systems.
1)、Ventilation system: Its function is to ensure indoor ventilation when the car is driving, that is, to continuously rush fresh air into the car interior to drive out dust, carbon dioxide and harmful gases from the engine. In the cold winter, fresh air should also be heated to ensure that the indoor temperature is suitable.
2)、Heating system: Its function is to heat the air in the car interior or the fresh air entering the car interior from the outside to achieve the purpose of heating and dehumidification.
3)、Refrigeration system: Its function is to reduce the temperature in the car when the ambient temperature outside the car is high, so that passengers feel cool and comfortable.
4）Air purification system: Its function is to filter the introduced air, continuously remove the dirty gas in the car interior, and keep the air in the car clean.
5）Control system: The control system is mainly composed of electrical components, vacuum pipelines and operating mechanisms. On the one hand, it is used to control the temperature and pressure of the cooling and heating systems, and on the other hand, it is used to manipulate the temperature, air volume and flow direction of the air in the car to improve the various functions of the air conditioning system.
Car air conditioning is generally composed of a compressor, an electronically controlled clutch, a condenser, an evaporator, an expansion valve, a receiver dryer, a pipe (hoses), a condensing fan, a vacuum solenoid valve (vacuum solenoid), an idler and a control system. Car air conditioning is divided into high-pressure pipelines and low-pressure pipelines. The high-pressure side includes the compressor output side, high-pressure pipelines, condensers, receiver dryers and liquid pipelines; the low-pressure side includes evaporators, accumulators, return air pipelines, compressor input sides and compressor oil pools.
Receiver dryer - is actually a device for storing refrigerant and absorbing refrigerant moisture and impurities. On the one hand, it is equivalent to the fuel tank of a car, replenishing refrigerant for the extra space of leaked refrigerant. On the other hand, it is like an air filter, filtering out impurities mixed in the refrigerant. The liquid receiver dryer is also equipped with a certain amount of silica gel to absorb moisture.
Condenser and evaporator - although they are called differently, their structures are similar. They are devices that are covered with metal sheets for heat dissipation on a row of winding pipes to achieve heat exchange between the outside air and the substances in the pipes. The condensation of the condenser refers to the heat dissipation of the refrigerant in its pipes from gas to liquid. Its principle is similar to that of the engine's cooling water tank (the only difference is that the water in the water tank is always in liquid), so it is often installed in the front of the car, together with the water tank, to enjoy the cool breeze from the front. In short, the condenser goes to where it is cool so that it can dissipate heat and condense. The evaporator is just the opposite of the condenser. It is the place where the refrigerant changes from liquid to gas (that is, evaporates) and absorbs heat.
5、Key components: automotive air conditioning compressor
In a vapor compression refrigeration device, the compressor is one of its main components. The role of the compressor in the compression refrigeration system is to pressurize the gaseous refrigerant and then send it to the condenser for cooling and condensation. The compressor provides power for the operation of the refrigeration system, so it consumes work.
There are two types of compressors used in vapor compression refrigeration systems: one is speed type, such as centrifugal type. The other is volumetric type. In automotive air conditioning refrigeration systems, volumetric compressors are currently used.
Classification of automotive air conditioning compressors
1. Volumetric compressors can be divided into reciprocating piston type (referred to as reciprocating type) and rotary piston type (referred to as rotary type) according to their structure.
Reciprocating and rotary types are used in automotive air conditioning devices to varying degrees. The reciprocating type was the first to come out and is still widely used today (for example: BOCK, BITZER compressors). As far as reciprocating compressors are concerned, they are more mature in technology, have accumulated rich experience in production and use, have low material requirements, are easy to process, and are low in cost. It can adapt to a wider range of pressure and cooling capacity, and has high thermal efficiency. The disadvantage is that due to the reciprocating movement of the piston, the dynamic balance performance is poor, which limits the increase in the compressor speed, the structure is complex, there are many vulnerable parts, and the maintenance workload is large. The rotary compressor has a rotating working volume and no reciprocating mechanism, so it has good dynamic balance performance, stable operation, small vibration, and high efficiency within its suitable working range. In addition, the rotary compressor has a simple structure, small size, light weight, few parts, and high reliability. However, the rotary compressor has a small displacement and is generally used in air-conditioning systems with small cooling capacity, such as car air-conditioning systems.
2. The driving mode of automobile air-conditioning compressors can be divided into two types according to their driving source, non-independent and independent.
The non-independent type is driven by the main engine of the car to drive the compressor. This driving mode is suitable for models where the main engine of the car has surplus power and the compressor power is not too large, such as cars, vans, engineering vehicles, etc. This driving mode occupies a small space and is easy to maintain. However, since the compressor consumes part of the power of the main engine, it will affect the acceleration performance of the vehicle, and the cooling capacity of the air-conditioning device will change with the change of vehicle speed.
Independent type (or auxiliary type), that is, an engine is configured separately to drive the compressor. Since a dedicated drive machine is set up separately, the driving of the car and the cooling effect of the air-conditioning device do not affect each other. However, this driving method takes up a certain amount of space in the car, is costly, noisy, and the maintenance of the auxiliary engine is complicated, so the application range is not wide.
Whether it is driven by the main engine or the auxiliary engine, the automobile air-conditioning compressor adopts the open type, that is, the power input end of the compressor main shaft extends out of the body and is connected to the drive machine through a pulley. The shaft is equipped with a shaft seal at the part extending out of the body to prevent the refrigerant from leaking.
Special requirements for automobile air-conditioning compressors
The dynamic characteristics of automobile operation and the changing external environment put forward some special requirements for the performance and structure of automobile air-conditioning compressors, which are manifested in:
1. Good low-speed performance is required, requiring the compressor to have a large cooling capacity and high efficiency when the automobile engine is low speed and no-load.
2. The input power is low when the car is driving at high speed, which not only saves fuel consumption, but also reduces the power consumption of the engine for air conditioning and improves the power performance of the car itself.
3. The compressor should be small and lightweight, which can save space in the car, be easy to install, and save material and fuel consumption.
4. It should be able to withstand the test of harsh operating conditions and have high reliability and durability. At idle speed, the temperature in the car engine compartment is sometimes as high as 80℃ and the condensing pressure is high, which requires the compressor to withstand high temperature and high pressure and limited overload. There are always bumps and vibrations when the car is driving on the road, which also requires the compressor to have good shock resistance and minimize the leakage of refrigerant.
5. Do not have an adverse effect on the car. The compressor is required to run smoothly, with low vibration and noise, and the impact of start-stop on engine speed is small, and the starting torque is small.
Compressor maintenance
First, check whether the refrigerant is sufficient. It can be estimated by feeling the temperature difference between the inlet and outlet pipes of the dryer, or by testing through the manifold pressure gauge.
Secondly, the dust and dirt in the air outlet and the cab should be cleaned regularly. This not only helps the beauty of the car, but also is beneficial to the health of the driver and passengers.
Third, regularly check whether the liquid level of the refrigerant in the air conditioning system is normal. There are several ways to check the liquid level, but the most common and simplest method is to use the peephole of the dryer.
Fourth, check whether the compressor belt is in good condition. If the belt surface is shiny on the side where it contacts the pulley groove, and there is a "squeaking" noise when the air conditioner is started, it means that the belt is seriously slipping and the belt and pulley should be replaced; if the belt is too loose, it should be adjusted, otherwise it will easily cause poor cooling of the air conditioning system.
Fifth, check whether there are oil stains on the hoses and pipe joints of the air conditioning system. If leakage is found, consult the maintenance department in time for a solution.
In addition, when the car air conditioner is used for the first time after the season change, it is best to sterilize and deodorize the air conditioning system. This is because the air conditioning system will breed fungi and mold if it is "vacated" for a long time. It not only makes the air emit an unpleasant musty smell, but also is harmful to the health of the people in the car. This work can be done at the repair shop, or you can buy a special spray for sterilization and deodorization and handle it yourself.