Abstract: The automotive air conditioning system is a device that implements refrigeration, heating, ventilation and air purification of the air in the cabin. It can provide passengers with a comfortable riding environment, reduce the fatigue of the driver and improve the safety of driving. Air-conditioning units have become one of the hallmarks for measuring the completeness of a car's function. The automobile air conditioning system is composed of a compressor, an air conditioner blower, a condenser, a liquid storage dryer, an expansion valve, an evaporator and a blower. This paper mainly introduces the principle of the automobile air conditioner blower. Key words: blower control principle As global warming and people's requirements for the riding environment increase, more and more cars are equipped with air conditioning systems. According to statistics, 78% of the cars sold in the US and Canada in 2000 have been air-conditioned, and now it is conservatively estimated to be at least 90%. In addition to giving people a comfortable ride environment, car air conditioners. As a reader of a car user, you should understand the principle and make the emergency situation more effective and quicker. 1 How the working principle of automotive refrigeration system
The working principle of automotive air conditioning refrigeration system
1. The working principle of automotive air conditioning refrigeration system
Automatic refrigeration of automotive air conditioning refrigeration system, compression, heat release, The four processes of throttling and endothermic are composed. (1) Compression process: The compressor sucks in the low-temperature and low-pressure refrigerant gas at the outlet of the evaporator, compresses it into a high-temperature and high-pressure gas, and then delivers it to a condenser. The main function of this process is to compress the pressurization to make the gas easy to liquefy. During the compression process, the state of the refrigerant does not change, but the temperature and pressure are continuously increased to form a superheated gas. (2) Exothermic process: The high temperature and high pressure superheated refrigerant gas enters the condenser (heat sink) to exchange heat with the atmosphere. Due to the pressure and temperature decrease, the refrigerant gas condenses into a liquid and releases a large amount of heat. The role of this process is to remove heat and condense. The condensing process is characterized by a change in the state of the refrigerant, that is, from a gaseous state to a liquid state under the condition of constant pressure and temperature. The condensed refrigerant liquid is a high pressure high temperature liquid. The refrigerant liquid is too cold, and the degree of supercooling is greater, and the ability to evaporate and absorb heat during evaporation is greater, and the better the refrigeration effect, that is, the cooling capacity is correspondingly increased. (3) Throttling process: The high-pressure high-temperature refrigerant liquid is throttled by the expansion valve to reduce the temperature and pressure, and the expansion device is removed by the mist (fine droplets). The function of this process is to reduce the temperature of the refrigerant and reduce the pressure. The high temperature and high pressure liquid rapidly change into a low temperature to resist the liquid, so as to facilitate the heat absorption, control the cooling capacity and maintain the normal operation of the refrigeration system. (4) Endothermic process: the mist-like refrigerant liquid after being cooled and depressurized by the expansion valve enters the evaporator, so the boiling point of the refrigerant is much lower than the temperature inside the evaporator, so the refrigerant liquid evaporates in the evaporator. Boil into a gas. During the evaporation process, the surrounding heat is absorbed in a large amount, and the temperature inside the vehicle is lowered. The low temperature and low pressure refrigerant gas then flows out of the evaporator and waits for the compressor to be inhaled again. The endothermic process is characterized by a change in the state of the refrigerant from a liquid state to a gaseous state, at which time the pressure is constant, that is, a change in this state is made during the constant pressure process. 2. Automobile air conditioning refrigeration system generally consists of a compressor, a condenser, a liquid storage dryer, an expansion valve, an evaporator and a blower. As shown in Figure 1, copper pipes (or aluminum pipes) and high-pressure rubber pipes are connected between the components to form a closed system. When the cold system is operating, the different states of the refrigeration memory circulate in this closed system, and each cycle has four basic processes: (1) Compression process: the compressor draws in the low temperature pressure-resistant refrigeration at the outlet of the evaporator. The gas is compressed into a high temperature and high pressure gas to remove the compressor. (2) Exothermic process: The high temperature and high pressure superheated refrigerant gas enters the condenser, and the refrigerant gas condenses into a liquid due to a decrease in pressure and temperature, and a large amount of heat is released. (3) Throttling process: After the refrigerant liquid having a higher temperature and pressure passes through the expansion device, the volume becomes larger, the pressure and temperature drop sharply, and the expansion device is eliminated in the form of a mist (fine droplets). (4) Endothermic process: The misty refrigerant liquid enters the evaporator, so that the boiling point of the refrigerant is much lower than the temperature inside the evaporator, so the refrigerant liquid evaporates into a gas. The surrounding heat is absorbed in a large amount during the evaporation process, and then the low-temperature low-pressure refrigerant vapor enters the compressor again. 2 The working principle of the blower
The blower on the car is usually a centrifugal blower. The centrifugal blower works similarly to the centrifugal fan, except that the air compression process usually passes through several The working impeller (or several stages) is carried out under the action of centrifugal force. The blower has a rotor that rotates at a high speed. The blades on the rotor drive the high-speed movement of the air. The centrifugal force causes the air to flow in the involute-shaped casing along the involute to the fan outlet, and the high-speed airflow has a certain wind pressure. The new air is replenished by the center of the casing. Theoretically speaking, the pressure-flow characteristic curve of the centrifugal blower is a straight line, but due to the frictional resistance loss inside the fan, the actual pressure and flow characteristic curve gradually decreases with the increase of the flow rate, and the corresponding centrifugal The power-flow curve of the fan rises as the flow increases. When the fan is running at a constant speed, the operating point of the fan will move along the pressure-flow characteristic curve. The operating point of the fan is not only dependent on its own performance, but also depends on the characteristics of the system. When the pipe network resistance increases, the pipeline performance curve will become steeper. The basic principle of fan adjustment is to obtain the required working condition by changing the performance curve of the fan itself or the external pipe network characteristic curve. Therefore, some intelligent systems are installed in the car to help the car operate normally at low speed, medium speed and high speed. 3 Control principle of blower 2.1 Automatic control When the "automatic" switch of the air conditioning control panel is pressed, the air conditioner computer automatically adjusts the rotational speed of the blower according to the air temperature required to be output. When the air flow direction is selected in the "face" or "double flow direction", and the blower is in the low speed state, the blower speed will vary within the limit range according to the intensity of the sunlight. (1) Operation of low speed control During the low speed control, the air conditioner computer disconnects the base voltage of the power transistor, and the power transistor and the super high speed relay are also disconnected. The current flows from the blower motor to the blast air resistance, and then the iron is applied to make the motor run at a low speed. The air conditioner computer has the following seven parts: 1 battery, 2 ignition switch, 3 heater relay, 4 blower motor, 5 blower resistor , 6 power triode, 7 temperature fuse, 8 air conditioner computer, 9 high speed relay. (2) Operation of medium speed control During the medium speed control, the power transistor is assembled with a temperature fuse which protects the transistor from overheating damage. The air conditioner computer changes the base current of the power transistor by changing the blower drive signal to achieve the purpose of wirelessly controlling the blower motor speed. (3) Operation of high-speed control During high-speed control, the air conditioner computer disconnects the base voltage of the power transistor, its connector is grounded with No. 40, and the high-speed relay is turned on, and current flows from the blower motor. The high speed relay, then to the ground, allows the motor to rotate at high speed. 2.2 Preheating In the automatic control state, a temperature sensor fixed to the lower part of the heater core detects the temperature of the coolant and performs warm-up control. When the coolant temperature is below 40 °C and the automatic switch is turned on, the air conditioner computer turns off the blower to prevent cold air from escaping. Conversely, when the coolant temperature is above 40 °C, the air conditioner computer activates the blower and rotates it at a low speed. From this point on, the blower speed is automatically controlled in accordance with the calculated air flow rate and the required output air temperature. The preheating control referred to above exists when the air flow direction is selected at the "bottom" or "dual flow direction". 2.3 Delayed airflow control (only for cooling) The delay airflow control is based on the temperature inside the cooler detected by the evaporator temperature sensor. Delayed airflow control prevents hot air from being accidentally discharged from the air conditioner. This delay control operation is only performed once when the engine is started and meets the following conditions: 1 compressor operation; 2 blower control is in "automatic" state (automatic switch is open); 3 air flow is controlled in "face" state ; Adjust to “Face” by face switch, or set to “Face” status in automatic control; 4 The temperature inside the cooler is higher than 30 °C. The operation of the delayed air flow control is as follows: Even when the above four conditions are all satisfied and the engine has been started, the blower motor cannot be started immediately. The blower motor is 4 seconds apart, but the compressor must be switched on and the engine is started. The evaporator must be cooled with coolant gas. After 4s, the blower motor starts, running at low speed in the first 5s, and in the last 6s, the blower motor gradually accelerates until high speed. This operation prevents the hot, hot air from suddenly expelling from the vents. Conclusion The perfect automotive computer-controlled air conditioning system can automatically adjust the temperature, humidity, cleanliness, grace and ventilation of the air inside the vehicle, and make the air inside the vehicle flow at a certain speed and direction. To provide passengers with a good riding environment, to ensure that passengers are in a comfortable air environment under various external climates and conditions, and to prevent frost on the window glass, so that the driver maintains a clear view for safety. Driving provides basic guarantees.