CN1818518A - Method of controlling air conditioner for vehicles - Google Patents

Abstract

The present invention relates to a control method of an air conditioner for automobiles, the purpose of which is to variably control the variation of the slant plate inclination angle of a variable capacity swash plate compressor according to the deviation between the target evaporator temperature and the actual evaporator temperature The target control value of the pressure regulator valve, thereby controlling the discharge capacity of the compressor. The control method of the air conditioner for automobiles according to the present invention is characterized in that it includes: the step of calculating the target heat output; the step of calculating the target evaporator temperature; and judging whether it is high-load control or The step of low load control; according to the magnitude of the load, the first compulsory control is performed on the control value of the pressure regulating valve, and then the second normal control is performed. Therefore, in the initial stage of operation of the air conditioner, not only can the actual evaporator temperature quickly reach the target evaporator temperature, but also temperature stability can be ensured.

Description

Control method of air conditioner for automobile

technical field

The present invention relates to a control method of an air conditioner for automobiles, in particular to a control method for an air conditioner for automobiles. According to the temperature deviation between the target evaporator temperature and the actual evaporator temperature, the variable The target control value (Duty) of the pressure regulating valve for the variable slant plate inclination angle of the capacity type swash plate compressor can effectively control the discharge capacity of the compressor.

Background technique

In the variable capacity type swash plate compressor, the pressure of the refrigerant is changed by the pressure regulating valve according to the load, thereby adjusting the inclination angle of the swash plate. Adjusting the inclination angle of the swash plate changes the stroke distance of the piston, thereby adjusting the discharge capacity of the refrigerant; and adjusting the temperature of the evaporator according to the change in the discharge capacity of the refrigerant.

The above-mentioned pressure regulating valve can be divided into an internal control type and an external control type. The structure of this variable capacity swash plate compressor is well disclosed in Japanese Patent Application No. 2001-107854.

In an automobile equipped with an air conditioner having a variable-capacity swash plate compressor as described above, it is necessary to properly operate the air conditioner according to the temperature difference between the actual evaporator temperature and the target evaporator temperature at the initial stage of operation of the air conditioner. The air conditioning unit is running. For example, it goes without saying that in order for the compressor to reach the target evaporator temperature quickly and efficiently and for a good ride, the refrigerant discharge capacity must be adjusted without making a lot of noise.

Japanese Laid-Open Patent No. 2003-200730 discloses a technique of selecting the output of the pressure regulating valve of the variable capacity swash plate compressor for the temperature difference between the actual evaporator temperature and the target evaporator temperature ( Duty, that is, the control value), and then carry out proportional-integral control on the discharge capacity of the compressor.

According to this technique, there is an advantage of rapidly lowering the evaporator temperature. However, when the initial current value of the pressure regulating valve and the actual evaporator temperature are higher than the target value, the actual evaporator temperature is high during the initial operation of the air conditioner. In order to reduce the temperature, the control current value of the pressure regulating valve must be further increased, which will cause the temperature of the evaporator to be too lower than the rated value (Undershoot), and it will take a long time to stabilize the current value to converge.

In addition, Japanese Laid-Open Patent No. 2002-327686 discloses a technique in which the output of the pressure regulating valve is gradually increased from the minimum during the operation of the air conditioner.

According to this technology, there are advantages as follows: by gradually increasing the discharge capacity of the pressure regulating valve from the minimum, it is possible to prevent running shock, improve ride comfort, and improve noise problems; Problem with taking a long time to stabilize to reach the target evaporator temperature.

In addition, in the above-mentioned prior art, etc., there is a problem that the output of the pressure regulating valve is controlled in the same manner irrespective of when a high load is required and when a low load control is required. The convergence and stability of the evaporator temperature is further reduced.

Contents of the invention

The technical problem to be solved by the invention

The object of the present invention is to variably control the target control value of the pressure regulating valve that changes the inclination angle of the swash plate of the variable capacity swash plate compressor according to the temperature deviation between the target evaporator temperature and the actual evaporator temperature. (Duty), and effectively control the discharge capacity of the compressor.

Another object of the present invention is: according to the magnitude of the above-mentioned temperature deviation, the first forced control is performed on the target control value of the above-mentioned pressure regulating valve, and then the second normal control is performed, thereby making the evaporator temperature quickly reach the target evaporator temperature, and reach the target evaporator temperature stably without fluctuation.

Technical solutions for solving problems

Invented scheme

In order to achieve the above object, the control method of the automobile air conditioner of the present invention is characterized in that it includes the following steps: calculating the target heat output; calculating the target evaporator temperature; and discharging heat according to the above target, The step of judging whether it is high-load control or low-load control; according to the above load, after the first forced control of the control value (Duty) of the pressure regulating valve of the variable capacity swash plate compressor, the second normal control is performed. control steps.

According to the present invention, it is preferable that, when it is determined that the high load control is performed, the forced control is initially maintained at a maximum set value, and then decreased at a constant rate of change.

Preferably, the maximum set value of the control value of the pressure regulating valve is within the range of 70-100%.

In addition, it is preferable that in the process of the above-mentioned forced control, after the above-mentioned control is kept at the maximum set value, when the temperature difference between the actual evaporator temperature and the target evaporator temperature is below the specified temperature difference, the temperature is reduced by a certain rate of change. Smaller than the above control value. In addition, it is preferable that the timing of switching from the forced control to the normal control is the timing when the absolute value of the temperature difference between the actual evaporator temperature and the actual evaporator temperature before a predetermined time is equal to or less than a predetermined value.

According to the present invention, when the low load control is determined, it is preferable that the forced control forcibly maintains the control value at the minimum set value for a predetermined time. In addition, preferably, the control minimum setting value of the control value of the pressure regulating valve is within the range of 0 to 40%.

In addition, it is preferable that the normal control of the pressure regulating valve is proportional-integral (PI) control or proportional-integral-derivative (PID) control.

In addition, it is preferable that the above-mentioned normal control controls the above-mentioned control value by changing a control coefficient set in accordance with the magnitude of the load. Preferably, the control coefficient is set to have a magnitude proportional to an absolute value of a temperature deviation between the actual evaporator temperature and the target evaporator temperature. In addition, it is preferable that the control coefficient is set to a maximum setting value when the absolute value of the temperature deviation is equal to or greater than a predetermined value.

In addition, it is preferable that in the step of calculating the target evaporator temperature, the user sets the target indoor temperature of the vehicle, and the vehicle indoor temperature, the vehicle outdoor temperature, and the amount of sunlight are detected by a sensor set at a predetermined position of the vehicle. And input these values, calculate the target discharge temperature of the air conditioner outlet (Vent) according to the above-mentioned target indoor temperature, vehicle indoor temperature, vehicle outdoor temperature, and sunshine amount, input the maximum evaporator temperature, and calculate the target discharge temperature of the above-mentioned outlet and The maximum evaporator temperature is compared to calculate the target evaporator temperature.

Furthermore, in the step of inputting the maximum evaporator temperature, the maximum evaporator temperature is calculated based on the temperature of the air flowing into the evaporator when the compressor is driven at a minimum, and the temperature is input.

Moreover, preferably, in the step of comparing the target discharge temperature with the maximum evaporator temperature, when the target discharge temperature at the outlet is lower than the maximum evaporator temperature, the target discharge temperature is set as the target evaporator temperature; when the above target If the discharge temperature is higher than the maximum evaporator temperature, the maximum evaporator temperature is set as the target evaporator temperature.

Furthermore, preferably, after the step of detecting and inputting the vehicle interior temperature, vehicle exterior temperature, and sunlight amount by a sensor provided at a predetermined position of the vehicle, a step of calculating the outlet target exhaust heat is further included.

In addition, it is preferable that the step of calculating the target heat output is calculated based on the target indoor temperature of the vehicle input by the user, the indoor temperature of the vehicle input from a sensor installed at a predetermined position of the vehicle, the outdoor temperature of the vehicle, and the amount of sunlight. Perform calculations.

Furthermore, it is preferable that when it is determined that the above-mentioned low load control is performed, the control value of the above-mentioned pressure regulating valve is set to the minimum, and the temperature of the cooling water is measured to determine whether it is below the set cooling water temperature. If the above-mentioned cooling water If the temperature is below the set cooling water temperature, set the opening of the temperature regulating door to the maximum heating position.

Description of drawings

FIG. 1 is a cross-sectional view showing an example of a variable capacity type swash plate compressor;

Fig. 2 is a system configuration diagram for realizing the control method of the automobile air conditioner of the present invention;

Fig. 3 is a flow chart showing the control method of the automobile air conditioner of the present invention;

Fig. 4 is a flowchart showing the steps of setting a target evaporator temperature;

Fig. 5 is a graph showing the relationship between the time of high load control, the control value of the pressure regulating valve and the temperature of the evaporator;

Fig. 6 is a graph showing the relationship among the time accompanying the low load control, the control value of the pressure regulating valve, and the temperature of the evaporator.

Description of reference symbols

100 variable capacity inclined plate compressor

160 pressure regulating valve

240 temperature adjustment door

300 control unit

320 outside temperature sensor

330 evaporator temperature sensor

340 interior temperature sensor

350 sunlight sensor

360 cooling water temperature sensor

Detailed ways

The features and advantages of the present invention will be more clearly understood through the following detailed description based on the accompanying drawings. First of all, the terms and words used in this specification and claims should be based on the principle that the inventor uses the best method to describe his own invention and can properly define the concept of the term, so that the meaning and meaning of the technical idea consistent with the present invention can be defined. concept explained.

FIG. 1 shows an example of a variable capacity type swash plate compressor 100 . The variable capacity swash plate compressor 100 includes: a cylinder block (Cylinder Block) 110, which forms a plurality of cylinder bores 112 (Cylinder Bore) in the longitudinal direction along concentric circles; a plurality of pistons (Piston) 114, which are inserted into the cylinder Each cylinder bore 112 of the column 110; the front housing 120, which is connected to the front of the cylinder column 110, and forms the crank chamber 122 inside; the rear housing 130, which is connected to the rear of the cylinder column 110, and has a A refrigerant suction chamber 132 and a refrigerant discharge chamber 134 are formed; a drive shaft 140 is supported throughout the above-mentioned front shell 120 and cylinder column 110 ; and a rotor (Rotor) 142 is formed together with the drive shaft 140 inside the above-mentioned crank chamber 122 Rotation; Swash plate 144, which is movably arranged around the above-mentioned drive shaft 140, its edge is connected with each piston 114 in such a way that the piston 114 moves back and forth, and one side of the edge is hinged with the rotor 142; valve unit (Valve Unit) 150, which is interposed between the cylinder column 110 and the rear shell 130, sucks the refrigerant from the refrigerant suction chamber 132 into the cylinder bore 112, and discharges the compressed refrigerant from the cylinder bore 112 to the refrigerant discharge chamber 134; and an externally controlled pressure regulating valve 160, which is arranged in the above-mentioned rear shell 130 so as to adjust the opening degree of the refrigerant return flow path connecting the above-mentioned refrigerant discharge chamber 134 and the crank chamber 122, and to adjust the relative drive of the swash plate 144 The inclination angle of the shaft 140.

Rotation Unit According to the variable capacity swash plate compressor 100 described above, when the electromagnetic clutch 146 is energized, the power of the engine E is transmitted to the drive shaft 140 through the electromagnetic clutch 146 , thereby rotating the swash plate 144 . The rotation of the swash plate 144 sequentially moves the plurality of pistons 114 and the like back and forth. When the piston 114 retreats relative to the above-mentioned cylinder bore 112 (that is, during the suction stroke), the suction side of the valve unit 150 is opened due to the pressure drop inside the cylinder bore 112, so that the cylinder bore 112 and the suction chamber communicate with each other. The agent is sucked into the cylinder bore 112 from the suction chamber. In addition, when the piston 114 advances toward the cylinder bore 112 side (that is, during the compression stroke), the refrigerant sucked into the cylinder bore 112 is compressed due to an increase in the pressure inside the cylinder bore 112, and at the same time, the discharge side of the valve unit 150 is compressed. Opening allows the cylinder bore 112 and the refrigerant discharge chamber 134 to communicate with each other, thereby discharging compressed refrigerant from the cylinder bore 112 into the refrigerant discharge chamber 134 .

In addition, according to the load, the opening of the refrigerant recovery passage connecting the refrigerant discharge chamber 134 and the crank chamber 122 is adjusted by the pressure regulating valve 160, and the inclination angle of the swash plate 144 is changed, thereby increasing the discharge capacity of the refrigerant. changes. That is, when the output (Duty, current value) to the pressure regulating valve 160 is maximum, the more the swash plate 144 is inclined relative to the drive shaft 140 side, the longer the stroke distance of the piston 144 is, and the refrigerant discharge capacity is increased. When the output to the pressure regulating valve 160 is minimum, the inclination of the swash plate 140 is changed so that the stroke distance of the piston 114 is shortened, thereby reducing the discharge capacity of the refrigerant.

FIG. 2 shows an automotive air conditioner employing the above-described variable capacity swash plate compressor 100 .

As shown in Figure 2, the above-mentioned air conditioning device comprises: an air conditioning box 210; a blower 220, which is arranged on the inlet side of the above-mentioned air conditioning box 210; an evaporator 200, which is built in the above-mentioned air conditioning box 210, and the refrigerant passes through the Heating core 230, which is refrigerated in the above-mentioned air-conditioning box 210, and cooling water is supplied from the engine E to the heating core 230; temperature adjustment door 240, which adjusts the opening of the cold air passage and the hot air passage of the air passing through the above-mentioned evaporator 200 the compressor 100, which sucks the refrigerant from the above-mentioned evaporator 200, and then discharges it; the condenser 170, which condenses the refrigerant supplied from the above-mentioned compressor 100, and then discharges it; the receiving dryer 180, which receives The dryer 180 performs gas-liquid separation of the refrigerant supplied from the condenser 170 ; Symbols 212, 214, and 216 represent exits, respectively, and numerals 212d, 214d, and 216d represent doors for adjusting the openings of the exits 212, 214, and 216, respectively.

On the other hand, the drive output to the following three components is controlled by the control unit 300: the electromagnetic clutch 146 that transmits the power of the engine E to the compressor 100 in a continuously interrupted manner, and the electromagnetic clutch 146 for adjusting the inclination angle of the swash plate 144 The driving output of the pressure regulating valve 160 for controlling the discharge capacity of the compressor 100 and the actuator 310 for regulating the opening degree of the temperature regulating door 240 . That is, the control unit 300 controls the actuator ( Actuator) 310 output voltage; and by changing the inclination angle of the swash plate 144 relative to the drive shaft 140 to change the discharge capacity of the compressor 100 to control the output current value of the pressure regulating valve 160.

In FIG. 2, unexplained symbols: 320, an evaporator temperature sensor, 330, an outside temperature sensor, 340, an interior temperature sensor, 350, a solar radiation sensor, and 360, a cooling water temperature sensor. Detection signals of these sensors are input into the control unit 300 .

The control method of the automobile air conditioner of the present invention will be described below.

As shown in FIG. 3 , when the air conditioner is operated, signals from various sensors such as the evaporator temperature sensor 320 , the outside temperature sensor 330 , the inside temperature sensor 340 , the solar radiation sensor 350 , and the cooling water temperature sensor 360 are input. to the control unit 300 (step S100).

Next, the control unit 300 calculates the target heat output (step S110). The above-mentioned target heat emission can be calculated based on the target indoor temperature of the vehicle input by the user, the vehicle indoor temperature detected by the sensors 330 , 340 , and 350 installed at predetermined positions on the vehicle, the vehicle outdoor temperature, and the amount of sunlight.

Next, the target evaporator temperature is calculated by the control unit 300 (step S120).

The aforementioned target evaporator temperature can be calculated through the steps shown in FIG. 4 , that is, the user sets the target indoor temperature (step S121 ). Next, the vehicle indoor temperature, the vehicle outdoor temperature, and the amount of sunlight detected by the sensors 330, 340, and 350 installed at predetermined positions of the vehicle are input into the control unit 300 (step S122). Next, the target discharge temperatures of the outlets 212, 214, and 216 of the air conditioner are calculated based on the target indoor temperature, the vehicle indoor temperature, the vehicle outdoor temperature, and the amount of sunlight (step S124). After that, the maximum evaporator temperature is input (step S125). Furthermore, the target discharge temperature of the said outlet 212, 214, 216 is compared with the said maximum evaporator temperature (step S126), and the target evaporator temperature is selected (step S127).

In addition, it is preferable that the step of inputting the maximum evaporator temperature is to calculate and input the maximum evaporator temperature based on the temperature of the air flowing into the evaporator 200 when the compressor 100 is driven at a minimum.

In addition, preferably, in the step of comparing the target discharge temperature with the above-mentioned maximum evaporator temperature, when the target discharge temperature is lower than the maximum evaporator temperature, the target discharge temperature is set as the target evaporator temperature; when the target When the discharge temperature is higher than the maximum evaporator temperature, the maximum evaporator temperature is set as the target evaporator temperature.

In addition, after the step of detecting and inputting the vehicle indoor temperature, the vehicle outdoor temperature, and the amount of sunlight by the sensors 330, 340, and 350 installed at predetermined positions of the vehicle (step S122), the control system for the exit 212, Step 214, 216 of calculating the target discharge heat, and then calculating the target discharge temperature of the outlets 212, 214, 216 based on the above-mentioned target discharge heat (step S124).

As described above, after the target evaporator temperature is calculated, it is determined whether it is high-load control or low-load control based on the above-mentioned target exhaust heat (step S130). For example, when the outside air temperature is above 30°C, it can be judged as high load control, and the judgment of the magnitude of this load can be set according to an appropriate standard.

According to the present invention, according to the size of the above load, the control value of the pressure regulating valve 160 is subjected to the first forced control and the second normal control. The specific process is as follows.

First, when it is determined to be high-load control, as shown in FIGS. 3 and 5, in the above-mentioned forced control, the control value of the above-mentioned pressure regulating valve 160 is initially maintained at the maximum setting value (step S140), and then made to Decrease at a certain rate of change (step S160).

The above-mentioned maximum set value can be set, for example, within a range of 70 to 100%, more preferably within a range of 80 to 90%.

In addition, in the above-mentioned high load control process, it is judged whether the temperature difference between the actual evaporator temperature and the target evaporator temperature is below the set temperature difference (step S150). Preferably, after the above-mentioned control value is kept at the maximum set value, when the difference between the actual evaporator temperature and the target evaporator temperature is below the specified temperature difference (for example, 5°C), then decrease at a certain rate of change above control values.

In addition, the time point of switching from the above-mentioned forced control to the normal control refers to the time point when the actual evaporator temperature detected by the evaporator temperature sensor 320 is in a stable state, and it is preferable that the actual evaporator temperature (Tn) is within the specified time (Δt, The time point when the absolute value of the temperature difference of the actual evaporator temperature (Tn-1) before 2.7 seconds) is below a predetermined value (for example, 0.3).

Also, it is preferable that the above-mentioned general control is proportional-integral control or proportional-integral-derivative control.

Furthermore, the above-mentioned target evaporator temperature and actual evaporator temperature mean the temperature of the air discharged through the evaporator or the temperature of the evaporator itself, but either temperature may be used as required.

As mentioned above, in the high-load control process, after the control value of the pressure regulating valve 160 is kept at the maximum, the forced control is performed with a certain rate of change decreasing. After that, when the actual evaporator temperature is lower than The reason why normal control is performed at the target evaporator temperature is that the actual evaporator temperature can quickly reach the target evaporator temperature in consideration of the quick effect of the heating device. For example, in the process of high load control, if the normal control time point is set as the time point when the actual evaporator temperature is higher than the target evaporator temperature, it will cause discomfort to the passengers, and the time for the actual evaporator temperature to reach the target evaporator temperature Increase.

On the other hand, when it is determined that the low load control is performed, as shown in FIG. The magnitude of the load value, the control coefficient can be set variably, and normal control is performed (step S180). It is preferable that the above-mentioned general control does not produce a situation below the rated value.

Preferably, the time to keep the control value at the minimum set value is, for example, 1 minute or less. In addition, the aforementioned minimum setting value may be set within a range of 0 to 40%, more preferably within a range of 30 to 40%.

In addition, during the above-mentioned low load control process, the cooling water temperature can be additionally measured by the cooling water temperature sensor 360 to determine whether the temperature is below the set cooling water temperature (step S210 ). When the cooling water temperature is below the set cooling water temperature, as shown in FIG. 2 , the opening of the temperature regulating door 240 is set at the maximum heat supply position (ie, the hot gas passage closed position). That is, the discharge temperature of the air is prevented from being lowered due to the lower cooling water temperature. In addition, when the cooling water temperature is above the set cooling water temperature, the temperature adjustment door 240 is controlled at a normal position.

In the process as described above, when the low load control is performed, the evaporator temperature can stably reach the target evaporator temperature without fluctuation. It can be realized more effectively by adjusting the opening degree of the temperature adjustment door 240 .

Also, preferably, the normal control in the above low load control process is proportional-integral control, or proportional-integral-derivative control.

Furthermore, it is preferable that in the above-mentioned high-load control or low-load control process, when performing normal control, the control coefficient that can be changed according to the size of the load is proportional gain, integral gain or differential gain according to the control method. . In addition, it is preferable that the above-mentioned control coefficient is set in such a manner that it has a value proportional to the absolute value of the temperature deviation between the actual evaporator temperature and the target evaporator temperature; In this case, it is preferable to set the control coefficient to the maximum setting value. The reason for this is that, when the above-mentioned temperature deviation is large, the above-mentioned control coefficient is set smaller to quickly reach the target evaporator temperature, and when the above-mentioned temperature deviation is small, the above-mentioned control coefficient is set smaller, In order to achieve the target evaporator temperature stably without fluctuation.

The effect of the invention

According to the control method of the automobile air conditioner of the present invention constituted as described above, according to the load size determined from the target heat output, the flow rate and the adjustment method for adjusting the refrigerant return from the refrigerant discharge chamber 134 to the crank chamber 122 are adjusted. The control value of the pressure regulating valve 160 that adjusts the inclination angle of the swash plate 144 performs the first forced control, and then performs the second normal control, so that during the operation of the air conditioner, not only the actual evaporator temperature can be quickly reached The target evaporator temperature can be ensured, and the stability of the temperature can be ensured, so that the comfortable driving of the car can be realized.

Claims (17)

1. A control method for an automotive air conditioner, characterized in that it comprises the following steps: A step of calculating the target heat output; the step of calculating the target evaporator temperature; The step of judging whether it is high-load control or low-load control based on the above-mentioned target to discharge heat; According to the magnitude of the above load, the first forced control is performed on the control value of the pressure regulating valve of the variable capacity swash plate compressor, and then the second normal control is performed. 2. The method for controlling an air conditioner for an automobile according to claim 1, wherein when it is determined that the high-load control is performed, the control value is initially kept at a maximum set value during the forced control. , and then decrease it with a certain rate of change. 3. The method of controlling an air conditioner for an automobile according to claim 2, wherein the maximum set value is within a range of 70 to 100%. 4. The control method of the air conditioner for automobiles according to claim 2, characterized in that: during the forced control process, when the temperature difference between the actual evaporator temperature and the target evaporator temperature is below a specified temperature difference, the above-mentioned The control value decreases from the maximum set value at a certain rate of change. 5. The control method of an automotive air conditioner according to claim 1, wherein the time point of the normal control is when the absolute value of the temperature difference between the actual evaporator temperature and the target evaporator temperature is below a predetermined value. point. 6. The method of controlling an air conditioner for an automobile according to claim 1, wherein when it is determined that the low load control is performed, the forced control forcibly keeps the control value at a minimum setting for a predetermined time. value. 7. The control method of an automobile air conditioner according to claim 6, wherein the minimum set value is in the range of 0 to 40%. 8. The control method of an automotive air conditioner according to claim 1, wherein the normal control of the pressure regulating valve is proportional-integral control or proportional-integral-derivative control. 9. The control method of an automobile air conditioner according to claim 1, wherein in said normal control, said control value is set by a control coefficient which is set to vary according to a magnitude of a load. 10. The control method of an automotive air conditioner according to claim 9, wherein the control coefficient is set in such a manner that it has a value proportional to the absolute value of the temperature deviation between the actual evaporator temperature and the target evaporator temperature. set up. 11. The control method of an automotive air conditioner according to claim 10, wherein the control coefficient is set to a maximum setting value when the absolute value of the temperature deviation is greater than or equal to a predetermined value. 12. The control method of an air-conditioning device for an automobile according to claim 1, wherein in the step of calculating the target evaporator temperature, the user sets the target indoor temperature of the vehicle, and is determined by the stipulations set in the vehicle. The position sensor detects the vehicle indoor temperature, the vehicle outdoor temperature, and the amount of sunlight and inputs these values, and calculates the target discharge temperature at the outlet of the air conditioner based on the above-mentioned target indoor temperature, vehicle indoor temperature, vehicle outdoor temperature, and sunlight amount, and inputs the maximum For the evaporator temperature, the target evaporator temperature is calculated by comparing the target discharge temperature at the outlet with the maximum evaporator temperature. 13. The control method of an automotive air conditioner according to claim 12, characterized in that in the step of inputting the maximum evaporator temperature, the maximum evaporator temperature is determined according to the temperature of the air flowing into the evaporator at the minimum driving time of the compressor. Do the math and enter that temperature. 14. The control method of an automotive air conditioner according to claim 12 or 13, characterized in that: when the target discharge temperature of the outlet is lower than the maximum evaporator temperature, the target discharge temperature is set as the target evaporator temperature ; When the target discharge temperature of the above outlet is higher than the maximum evaporator temperature, set the maximum evaporator temperature as the target evaporator temperature. 15. The method of controlling an air conditioner for an automobile according to claim 12, characterized in that in the step of detecting and inputting the temperature inside the vehicle, the temperature outside the vehicle, and the amount of sunlight by a sensor installed at a predetermined position of the vehicle After that, a step of calculating the outlet target heat dissipation is further included. 16. The control method of an air conditioner for automobiles according to claim 1, wherein in the step of calculating the target heat output, the vehicle is installed at a predetermined position of the vehicle according to the target indoor temperature of the vehicle input by the user. Calculate the vehicle interior temperature, vehicle exterior temperature, and sunshine amount input from the sensor. 17. The method for controlling an air conditioner for an automobile according to claim 1, wherein when it is determined that the low load control is performed, the control value of the pressure regulating valve is set to the minimum, and the temperature of the cooling water is measured. And judge whether it is below the set cooling water temperature, if the above cooling water temperature is below the set cooling water temperature, then the opening degree of the temperature regulating door is set to the maximum heating position.

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