KR20060053225A - Method for controlling air conditioner of vehicle - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for an air conditioner for a vehicle, wherein a target control value (Duty) for a pressure regulating valve for changing a swash plate inclination angle of a variable displacement swash plate type compressor is obtained. It is aimed at controlling the discharge capacity of a compressor by controlling variably according to the magnitude | size of.

The control method of the automotive air conditioner of the present invention includes the steps of calculating a target discharge heat amount; Calculating a target evaporator temperature; Determining high load control or low load control from the target discharge heat; In addition, the control value (Duty) for the pressure regulating valve of the variable displacement swash plate type compressor is primarily characterized in that it comprises the step of controlling normally after the forced control according to the magnitude of the load. Therefore, the control value for the pressure regulating valve of the compressor is first forcedly controlled according to the magnitude of the load determined as the target discharge heat amount, and then the second normal control is performed so that the actual evaporator temperature is set at the initial stage of the air conditioner operation. Not only can the temperature be reached quickly, but temperature stability can be ensured.

Air Conditioning, Air Conditioning, Air Conditioning Control, Compressor, Variable Capacity, Swash Plate Slope, Pressure Control

Description

Control method of vehicle air conditioner {METHOD FOR CONTROLLING AIR CONDITIONER OF VEHICLE}

1 is a cross-sectional view showing an example of a variable displacement swash plate compressor.

2 is a system configuration diagram for performing a control method of the vehicle air conditioner according to the present invention.

3 is a flowchart illustrating a control method of the vehicle air conditioner according to the present invention.

4 is a flowchart showing a step of setting a target evaporator temperature.

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

6 is a graph showing the relationship between the time according to the low load control, the pressure regulating valve control value and the evaporator temperature.

<Explanation of symbols for the main parts of the drawings>

100: variable displacement swash plate compressor, 160: pressure control valve,

240: temperature control door, 300: control unit,

320: evaporator temperature sensor, 330: outside temperature sensor,

340: in-vehicle temperature sensor, 350: solar radiation sensor,

360: coolant temperature sensor.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method of an air conditioner for a vehicle. In particular, a target control value (Duty) for a pressure regulating valve for changing a swash plate inclination angle of a variable displacement swash plate type compressor is a temperature between a target evaporator temperature and an actual evaporator temperature. The present invention relates to a control method for an automotive air conditioner that can be controlled variably in accordance with the magnitude of a deviation, so that the discharge capacity of the compressor can be efficiently controlled.

In the variable displacement swash plate compressor, the inclination angle of the swash plate can be adjusted by varying the pressure of the refrigerant by the pressure control valve according to the load. By changing the stroke distance of the piston by adjusting the inclination angle of the swash plate, the discharge capacity of the refrigerant can be adjusted, and the evaporator temperature is adjusted according to the change of the discharge capacity of the refrigerant.

The pressure regulating valve can be divided into an internal control type and an external control type. The structure of such a variable displacement swash plate compressor is well disclosed in Japanese Patent Laid-Open No. 2001-107854.

In a vehicle equipped with an air conditioner having a variable displacement swash plate compressor as described above, the air conditioner must be properly operated in accordance with the temperature difference between the actual evaporator temperature and the target evaporator temperature at the beginning of operation of the air conditioner. For example, the compressor has to reach the target evaporator temperature quickly and effectively, and the ride capacity of the refrigerant must not be reduced, and the discharge capacity of the refrigerant must be adjusted under the condition that noise is not greatly generated.

In Japanese Laid-Open Patent Publication No. 2003-200730, after selecting the output (Duty, ie, control value) of the pressure regulating valve of the variable displacement swash plate compressor with respect to the temperature difference between the target evaporator temperature and the actual evaporator temperature, the discharge capacity of the compressor is determined. Techniques for proportional-integral control are disclosed.

According to this technique, there is an advantage that the evaporator temperature drops quickly, but when the initial current value of the pressure regulating valve and the actual evaporator temperature are higher than the target value, the temperature of the evaporator is lowered because the actual evaporator temperature is high during the initial operation of the air conditioner. In order to increase the control current value of the pressure regulating valve, there is a problem that the evaporator temperature is excessively undershooted, and the settling time is long until the current value falls and converges.

In addition, Japanese Laid-Open Patent Publication No. 2002-327686 discloses a technique for gradually controlling the output of a pressure regulating valve from the minimum to the largest when the air conditioner is operated.

According to this technique, by controlling the discharge capacity of the compressor gradually from the minimum, the starting shock (Shock) is prevented to improve the riding comfort and noise problem, but the stable time until reaching the target evaporator temperature is long. There is a problem.

Further, in the above prior arts, by controlling the output of the pressure regulating valve in the same way regardless of whether high load control is required for the compressor and low load control is required, convergence to the target evaporator temperature and There is a problem inevitably deteriorating the stability.

An object of the present invention, by varying the target control value (Duty) for the pressure regulating valve for changing the swash plate inclination angle of the variable displacement swash plate compressor according to the magnitude of the temperature deviation between the target evaporator temperature and the actual evaporator temperature The purpose is to efficiently control the discharge capacity of the compressor.

Another object of the present invention is to control the target control value for the pressure regulating valve according to the magnitude of the temperature deviation, and then to control the secondary normally, so that the evaporator temperature reaches the target evaporator temperature quickly. In addition, to achieve a stable reach without vibration (Fluctuation).

In order to achieve the above object, the control method of the automotive air conditioner according to the present invention includes the steps of calculating a target discharge heat; Calculating a target evaporator temperature; Determining a high load control or a low load control from the target discharge heat amount; And forcibly controlling the control value (Duty) of the pressure regulating valve of the variable displacement swash plate compressor primarily according to the magnitude of the load, and then controlling the secondary normally.

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

The maximum set value for the control value of the pressure regulating valve is preferably 100 to 70%.

Further, in the forced control process, after the control value is maintained at the maximum set value, when the difference between the actual evaporator temperature and the target evaporator temperature is less than a predetermined temperature difference, it is preferable to reduce the control value to a constant rate of change. Further, the time point at which the forced control is switched to the normal control is preferably a time point at which the absolute value of the temperature difference between the actual evaporator temperature and the actual evaporator temperature before the predetermined time is equal to or less than the predetermined value.

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

Further, the normal control for the pressure regulating valve is preferably proportional-integral (PI) control or proportional-integral-derived (PID) control.

In addition, it is preferable that the said normal control sets the said control value by the control coefficient set variable according to the magnitude | size of a load. The control coefficient is preferably set to have a magnitude proportional to the absolute value of the temperature deviation between the actual evaporator temperature and the target evaporator temperature. Further, the control coefficient is preferably set to the maximum set value when the absolute value of the temperature deviation is more than a predetermined value.

In the calculating of the target evaporator temperature, the user sets a target indoor temperature of the vehicle, detects and inputs the vehicle indoor temperature, the vehicle outdoor temperature, and the solar radiation amount from a sensor installed at a predetermined position of the vehicle, and the target indoor temperature. Calculates the target discharge temperature of the air conditioner vent based on the vehicle indoor temperature, the vehicle outdoor temperature, and the amount of insolation, inputs the maximum evaporator temperature, compares the target discharge temperature of the vent with the maximum evaporator temperature It is preferred to be made to calculate.

In addition, the step of inputting the maximum evaporator temperature is preferably made to calculate and input the maximum evaporator temperature according to the air temperature introduced into the evaporator during the minimum driving of the compressor.

Further, in the step of comparing the target discharge temperature and the maximum evaporator temperature, if the target discharge temperature is lower than the maximum evaporator temperature, the target discharge temperature is set to the target evaporator temperature, and if the target discharge temperature is higher than the maximum evaporator temperature, the maximum evaporator temperature is set. It is desirable to set the target evaporator temperature.

The method may further include calculating a vent target discharge capacity after detecting and inputting the vehicle indoor temperature, the vehicle outdoor temperature, and the solar radiation amount from a sensor installed at a predetermined position of the vehicle.

The calculating of the target discharge heat amount may be calculated by the target indoor temperature of the vehicle input by the user, the vehicle indoor temperature, the vehicle outdoor temperature, and the solar radiation input from a sensor installed at a predetermined position of the vehicle.

In addition, when it is determined that the low load control, the control value of the pressure regulating valve is set to the minimum, and it is determined whether the temperature of the cooling water temperature is lower than the set cooling water temperature by measuring the cooling water temperature. It is desirable to set the opening degree to the maximum heating position.

The features and advantages of the present invention will become more apparent from the following detailed description based on the accompanying drawings. Prior to this, the terms or words used in the present specification and claims are based on the principle that the inventor can appropriately define the concept of terms in order to explain the invention in the best way. It should be interpreted as meanings and concepts corresponding to

1 shows an example of a variable displacement swash plate compressor 100. The variable displacement swash plate compressor 100 includes: a cylinder block (110) having a plurality of cylinder bores (112) formed in a longitudinal direction along a concentric circle; A plurality of pistons (Piston, 114) inserted into each cylinder bore (112) of the cylinder block (110); A front housing 120 coupled to the front of the cylinder block 110 to form a crank chamber 122 therein; A rear housing 130 coupled to the rear of the cylinder block 110 to form a refrigerant suction chamber 132 and a refrigerant discharge chamber 134 therein; A drive shaft (140) supported over the front housing (120) and the cylinder block (110) and intermittently receiving the power of the engine (E) by the electromagnetic clutch (146); A rotor (Rotor 142) rotating together with the drive shaft 140 in the crank chamber 122; A swash plate 144 which is installed to be movable around the drive shaft 140 and whose edge is coupled to each piston 114 so as to advance and retract the piston 114, and one side of which is hinged to the rotor 142; Interposed between the cylinder block 110 and the rear housing 130, the refrigerant is sucked into the cylinder bore 112 from the refrigerant suction chamber 132 and compressed into the refrigerant discharge chamber 134 from the cylinder bore 112. A valve unit 150 for discharging the refrigerant; In addition, the rear housing 130 is installed to adjust the inclination angle of the swash plate 144 with respect to the drive shaft 140 by adjusting the opening degree of the refrigerant return flow path connecting the refrigerant discharge chamber 134 and the crank chamber 122. It includes an externally controlled pressure regulating valve (160).

According to the variable displacement swash plate compressor 100 as described above, when power is applied to the electromagnetic clutch 146, the power of the engine E is transmitted to the drive shaft 140 through the electromagnetic clutch 146. The swash plate 144 rotates. Rotation of the swash plate 144 causes the plurality of pistons 114 to move forward and backward sequentially. At the time of retraction of the piston 114 from the cylinder bore 112 (that is, during the suction stroke), the suction side of the valve unit 150 is opened by the pressure drop inside the cylinder bore 112, and the cylinder bore 112 is opened. And the suction chamber communicate with each other, the refrigerant is sucked into the cylinder bore 112 from the suction chamber. When the piston 114 moves toward the cylinder bore 112 (that is, during the compression stroke), the refrigerant sucked into the cylinder bore 112 is compressed by an increase in the pressure inside the cylinder bore 112, thereby Since the discharge side of the unit 150 is opened and the cylinder bore 112 and the refrigerant discharge chamber 134 communicate with each other, the compressed refrigerant is discharged from the cylinder bore 112 to the refrigerant discharge chamber 134.

In addition, the inclination angle of the swash plate 144 is changed by adjusting the opening degree of the refrigerant return flow path connecting the refrigerant discharge chamber 134 and the crank chamber 122 by the pressure regulating valve 160 according to the load. The discharge capacity is varied. That is, when the output (Duty, current value) to the pressure regulating valve 160 is the maximum, as the swash plate 144 is inclined toward the drive shaft 140, the stroke distance of the piston 114 is increased, the discharge capacity of the refrigerant is increased Increases. 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, so that the discharge capacity of the refrigerant is reduced.

2 shows a vehicle air conditioner to which the variable displacement swash plate compressor 100 as described above is applied.

As shown in FIG. 2, the air conditioning apparatus includes an air conditioning case 210 and a blower 220 installed at an inlet side of the air conditioning case 210; An evaporator (200) embedded in the air conditioning case (210) through which a refrigerant is passed by the compressor (100); A heater core 230 installed in the air conditioning case 210 and supplied with coolant from the engine E; A temperature control door 240 for adjusting the degree of opening of the cold air passage and the warm air passage for the air passing through the evaporator 200; A compressor (100) for sucking and discharging the refrigerant from the evaporator (200); A condenser (170) for condensing and discharging the refrigerant supplied from the compressor (100); A receiver dryer (180) for gas-liquid separation of the refrigerant supplied from the condenser (170); In addition, the expansion valve 190 is formed by throttling the refrigerant supplied from the receiver dryer 180 to the evaporator 200. Reference numerals 212, 214, and 216 denote vents, respectively, and reference numerals 212d, 214d, and 216d denote doors for adjusting the opening degrees of the vents 212, 214, and 216, respectively.

On the other hand, the pressure control valve 160 for controlling the discharge capacity of the compressor 100 by adjusting the inclination angle of the electromagnetic clutch 146 and the swash plate 144 to intermittently transfer the power of the engine (E) to the compressor (100). ) And the actuator 310 for adjusting the opening degree of the temperature control door 240 is controlled by the control unit 300. That is, the control unit 300 applies or cuts power to the electromagnetic clutch 146 and turns the temperature control door 240 to the heater core 230 side flow path or the bypass channel bypassing the heater core 230. The output voltage to the actuator 310 is controlled, and the output current value to the pressure regulating valve 160 is controlled to change the inclination angle of the swash plate 144 with respect to the drive shaft 140 to increase or decrease the discharge capacity of the compressor 100. .

In FIG. 2, reference numeral 320 denotes an evaporator temperature sensor, 330 denotes an external temperature sensor, 340 denotes an in-vehicle temperature sensor, 350 denotes an insolation sensor, and 360 denotes a coolant temperature sensor, and a detection signal for these is a control unit 300. Is entered.

Next, a control method of the vehicle air conditioner according to the present invention will be described.

As shown in FIG. 3, when the air conditioner is operated, the control unit 300 includes the evaporator temperature sensor 320, the vehicle temperature sensor 330, the vehicle temperature sensor 340, the solar radiation sensor 350, and the coolant temperature sensor. Signals from various sensors such as 360 are input to the control unit 300 (S100).

Next, a target discharge heat amount is calculated by the control unit 300 (S110). The target discharge heat amount may be calculated by the target indoor temperature of the vehicle input by the user and the vehicle indoor temperature, the vehicle outdoor temperature, and the solar radiation amount detected and input from the sensors 330, 340, 350 installed at predetermined positions of the vehicle. .

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

The target evaporator temperature may be calculated through the steps as shown in FIG. 4. That is, the user sets the target indoor temperature (S121). Next, the vehicle indoor temperature, the vehicle outdoor temperature, and the amount of insolation are sensed by the sensors 330, 340, and 350 installed at predetermined positions of the vehicle and input to the control unit 300 (S122). Next, the target discharge temperature of the vents 212, 214, 216 of the air conditioner is calculated based on the target indoor temperature, the vehicle indoor temperature, the vehicle outdoor temperature, and the amount of insolation (S124). Next, the maximum evaporator temperature is input (S125). Next, the target discharge temperature of the vents 212, 214, and 216 is compared with the maximum evaporator temperature (S126) to select a target evaporator temperature (S127).

In addition, the step of inputting the maximum evaporator temperature is preferably made to calculate and input the maximum evaporator temperature according to the air temperature introduced into the evaporator during the minimum driving of the compressor.

Further, in the step of comparing the target discharge temperature and the maximum evaporator temperature, if the target discharge temperature is lower than the maximum evaporator temperature, the target discharge temperature is set to the target evaporator temperature, and if the target discharge temperature is higher than the maximum evaporator temperature, the maximum evaporator temperature is set. It is desirable to set the target evaporator temperature.

Further, after detecting and inputting the vehicle indoor temperature, the vehicle outdoor temperature, and the solar radiation amount from the sensors 330, 340, 350 installed at predetermined positions of the vehicle (S122), the target discharge of the vents 212, 214, 216 is performed. Computing the amount of heat may be further included, and after that, the target discharge temperature of the vents 212, 214, and 216 may be calculated (S124) based on the target discharge heat amount.

As described above, after the target evaporator temperature is calculated, the high load control or the low load control is determined from the target discharge heat amount (S130). For example, when the outside temperature is 30 ℃ or more can be determined by the high load control, the determination of the size of such a load can be set on an appropriate basis.

According to the present invention, according to the magnitude of the load, the control value for the pressure regulating valve 160 is forcibly controlled first, and then the control coefficient is variably set according to the magnitude of the load to control normally. The specific process is as follows.

First, when it is determined that the high load control, as shown in Figures 3 and 5, the forced control, the control value for the pressure regulating valve 160 initially maintains the maximum set value (S140), after It is made to reduce the control value to a constant rate of change (S160).

The maximum set value can be set, for example, in the range of 100 to 70%, more preferably in the range of 90 to 80%.

Further, in the high load control process, it is determined whether the temperature difference between the actual evaporator temperature and the target evaporator temperature is less than or equal to the set temperature difference (S150). After the control value is maintained at the maximum set value, it is preferable to reduce the control value to a constant rate of change when the difference between the actual evaporator temperature and the target evaporator temperature is less than or equal to a predetermined temperature difference (eg, 5 ° C.).

In addition, the time point at which the forced control is switched to the normal control is a time point at which the actual evaporator temperature sensed by the evaporator temperature sensor 320 is stable, and the actual evaporator temperature Tn and a predetermined time Δt, for example, 2.7 seconds. It is preferable that the absolute value of the temperature difference with respect to the actual evaporator temperature Tn-1 before) is a predetermined value (for example, 0.3) or less.

Further, the normal control is preferably proportional-integral control or proportional-integral-derived control.

The target evaporator temperature and the actual evaporator temperature mean an air temperature discharged through the evaporator or a temperature of the evaporator itself, and any one of them may be applied if necessary.

As described above, in the high load control process, the control value for the pressure regulating valve 160 is kept to the maximum and then forcedly controlled to decrease at a constant rate of change, and then the normal control is performed while the actual evaporator temperature is lower than the target evaporator temperature. This is to allow the actual evaporator temperature to reach the target evaporator temperature quickly in consideration of the cooling fastness. For example, in the course of high load control, when the normal control point is set to the time when the actual evaporator temperature is higher than the target evaporator temperature, discomfort is created for the occupant, and the time for which the actual evaporator temperature reaches the target evaporator temperature becomes long.

On the other hand, if it is determined that the low load control, as shown in Figure 6, the forced control to forcibly maintain the control value of the pressure regulating valve 160 to the minimum set value for a predetermined time (S200), the load of The control coefficient is variably set according to the size to control normally (S180). It is preferable that the said normal control is made so that undershoot may not generate | occur | produce.

The time for maintaining the control value at the minimum set value is preferably 1 minute or less. In addition, the minimum set value may be set in the range of 0 to 40%, more preferably 30 to 40%.

In addition, in the low load control process, the cooling water temperature may be additionally measured by the cooling water temperature sensor 360 to determine whether the cooling water temperature is lower than the set cooling water temperature (S210). When the coolant temperature is lower than the set coolant temperature, as shown in FIG. 2, the opening degree of the temperature control door 240 is set to the maximum heating position (ie, the warm passage closed position). In other words, the discharge temperature of the air is prevented from being lowered due to the low cooling water temperature. When the coolant temperature is equal to or higher than the set coolant temperature, the temperature control door 240 is controlled to the normal position.

When low load control is performed in the above-described process, the actual evaporator temperature can be stably reached at the target evaporator temperature without vibration. This can be more effectively achieved by adjusting the opening degree to the temperature control door 240.

Further, it is preferable that the normal control in the low load control process is also proportional-integral control or proportional-integral-derived control.

Further, in the high load control or low load control process, the control coefficient that is variably applied according to the size of the load when performing normal control is proportional gain and integral gain according to the control method. Or differential gain. In addition, the control coefficient is preferably set to have a magnitude proportional to the absolute value of the temperature deviation between the actual evaporator temperature and the target evaporator temperature, when the absolute value of the temperature deviation is a predetermined value or more, the maximum set value It is preferable.

According to the control method of the vehicle air conditioner according to the present invention configured as described above, the pressure for adjusting the inclination angle of the swash plate 144 by adjusting the flow rate of the refrigerant returning from the refrigerant discharge chamber 134 to the crank chamber 122 By forcibly controlling the control value for the control valve 160 according to the magnitude of the load determined as the target discharge heat, and then controlling the secondary normally, the actual evaporator temperature is set to the target evaporator temperature at the beginning of the air conditioner operation. Not only can it be reached quickly, but also the temperature stability can be secured, so that comfortable driving can be achieved.

Claims (17)

Calculating a target discharge heat amount; Calculating a target evaporator temperature; Determining a high load control or a low load control from the target discharge heat amount; And, Controlling the pressure (Duty) of the pressure regulating valve of the variable displacement swash plate compressor firstly according to the magnitude of the load and then controlling the second normally Control method of a vehicle air conditioner, characterized in that comprises a. The method of claim 1, And, if it is determined that the high load control is made, the forced control is performed such that the control value is initially maintained at the maximum set value and subsequently reduced to a constant rate of change. The method of claim 2, The maximum set value is a control method for a vehicle air conditioner, characterized in that 100 ~ 70%. The method of claim 2, And in the forcing control process, when the temperature difference between the actual evaporator temperature and the target evaporator temperature is equal to or less than a predetermined temperature difference, the control value is reduced from the maximum set value to a constant rate of change. The method according to any one of claims 1 to 4, The time point of the normal control is a control method of an automotive air conditioner, wherein an absolute value of a temperature difference between an actual evaporator temperature and an actual evaporator temperature before a predetermined time is equal to or less than a predetermined value. The method of claim 1, And if it is determined that the low load control, the forced control, the control method of the automotive air conditioner, characterized in that for maintaining the control value to a minimum set value for a predetermined time. The method of claim 6, The minimum set value is a control method for a vehicle air conditioner, characterized in that 0 to 40%. The method of claim 1, Normal control for the pressure regulating valve is a proportional-integral (PI) control or proportional-integral-derivative (PID) control method of the automotive air conditioner. The method of claim 1, The said normal control is a control method of the air conditioning apparatus for automobiles characterized by setting the said control value by the control coefficient set variable according to the magnitude | size of a load. The method of claim 9, And 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. The method of claim 10, And the control coefficient is set to a maximum set value when the absolute value of the temperature deviation is equal to or greater than a predetermined value. The method of claim 1, Computing the target evaporator temperature, the user sets the target indoor temperature of the vehicle, detects and inputs the vehicle indoor temperature, the vehicle outdoor temperature and the solar radiation amount from a sensor installed at a predetermined position of the vehicle, the target indoor temperature, the vehicle The target discharge temperature of the air conditioner vent is calculated according to the indoor temperature, the vehicle outdoor temperature, and the amount of insolation, the maximum evaporator temperature is input, and the target evaporator temperature is determined by comparing the target discharge temperature of the vent with the maximum evaporator temperature. Control method for a vehicle air conditioner, characterized in that the calculation is made. The method of claim 12, The step of inputting the maximum evaporator temperature, the control method of the vehicle air conditioner, characterized in that the input to calculate the maximum evaporator temperature according to the air temperature flowing into the evaporator during the minimum driving of the compressor. The method according to claim 12 or 13, When the target discharge temperature of the vent is lower than the maximum evaporator temperature, the target discharge temperature is set to the target evaporator temperature, and when the target discharge temperature is higher than the maximum evaporator temperature, the maximum evaporator temperature is set to the target evaporator temperature Control method of the device. The method of claim 12, And after calculating and inputting a vehicle indoor temperature, a vehicle outdoor temperature, and an insolation amount from a sensor installed at a predetermined position of the vehicle, calculating a vent target discharge heat amount. Way. The method of claim 1, The calculating of the target discharge heat amount may be calculated based on a target indoor temperature of a vehicle input by a user, a vehicle indoor temperature, an outdoor temperature of a vehicle, and solar radiation input from a sensor installed at a predetermined position of the vehicle. Control method of air conditioning unit. The method of claim 1, When it is determined that the low load control, the control value of the pressure regulating valve is set to the minimum, and it is determined whether the temperature of the cooling water temperature is below the set cooling water temperature by measuring the cooling water temperature. Control method of a vehicle air conditioning apparatus, characterized in that the setting to the maximum heating position.

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