JP2007278665A - Air conditioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air conditioner capable of preventing damage of a compressor and of performing highly reliable low outside air temperature cooling operation in a lower temperature environment. <P>SOLUTION: This heat pump type air conditioner performing air conditioning according to a status change of a circulating refrigerant by operating the compressor 11 installed in a refrigerant circuit having an interior electronic expansion valve 22 is provided with a low outside air temperature cooling operation mode. In the low outside air temperature cooling operation mode, if a low pressure below a predetermined value P1 is detected continuously for a predetermined duration t1 during low outside air temperature cooling operation carried out when a low outside air temperature below a predetermined value is detected during cooling operation, operation of the compressor 11 is stopped temporarily and the interior electronic expansion value 22 is fully opened, and after automatic restoration for restarting operation of the compressor 11 under a predetermined condition, the degree of opening of the interior electronic expansion value 22 is reduced when a low pressure inside the compressor 11 is returned to a predetermined pressure. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an air conditioner in which the operable temperature is further reduced in a low outdoor air cooling operation in which a cooling operation is performed in a state where the environmental temperature in which an outdoor unit is installed is low.

2. Description of the Related Art Conventionally, there is known a heat pump type air conditioner that uses a refrigeration cycle to cool or dehumidify a room (air conditioning target) or dehumidify (hereinafter collectively referred to as “air conditioning”). This air conditioner has a configuration in which an indoor unit and an outdoor unit are connected by refrigerant piping and electrical wiring.
In the heat pump type air conditioner described above, a low outdoor air cooling operation in which the cooling operation is performed in a state where the environmental temperature in which the outdoor unit is installed is low may be performed. In the case of such low outdoor air cooling operation, the condensation capacity of the outdoor heat exchanger functioning as a condenser becomes very high even though the refrigerant circulation amount at the start of operation is small. Liquid refrigerant may accumulate inside the outdoor heat exchanger, reducing the amount of refrigerant circulating in the refrigeration cycle and lowering the low pressure side pressure of the compressor to a predetermined value or more. Such a decrease in the low-pressure side pressure is not preferable from the viewpoint of compressor protection. Therefore, there is a restriction on the environmental temperature at which the low outside air cooling operation can be performed, for example, by providing a protection circuit for stopping the compressor to stop the cooling operation.

As measures for preventing the decrease in the low-pressure side pressure generated during the low outdoor air cooling operation described above, the operation of the outdoor fan provided in the outdoor heat exchanger is stopped, or the operation of the outdoor fan is performed more than during normal cooling operation. It is known that the condensation ability is suppressed and optimized by changing to the low-speed rotation side.
In addition, as a measure for preventing a decrease in the low-pressure side pressure generated during the above-described low outside air cooling operation, the opening degree of the electronic expansion valve is set to be larger than that during normal cooling operation when the operation is started, and the refrigerant circulating in the refrigeration cycle easily flows. It is also known to be in a state.

As a specific example of such a low-pressure prevention measure, it is disclosed that the initial opening degree of the electronic expansion valve and the initial air volume of the outdoor fan at the start of the cooling operation are divided into a plurality of regions according to the outside air temperature. In this case, set the electronic expansion valve to a smaller opening in the region where the outside air temperature is lower, set the outdoor fan to a lower air flow, and set the electronic expansion valve to a larger opening in the region where the outside air temperature is lower than a predetermined value. ing. (For example, see Patent Document 1)
Japanese Patent No. 2551238

By the way, according to the above-described prior art, in the low temperature region where the outside air temperature is a predetermined value or less, the electronic expansion valve is set to a large opening and the low outside air cooling operation is performed, so such a state of the large opening is continued. And the circulation amount of the liquid refrigerant becomes excessive. As a result, the liquid refrigerant returns to the compressor of the outdoor unit, so that the compressor is in a liquid compression state, and the lubricating oil concentration in the compressor is diluted by the liquid refrigerant to obtain a sufficient lubrication function. There is concern about disappearing.
Such liquid compression or dilution of lubricating oil concentration is not preferable because it causes damage to the compressor.

Against this background, the problem of compressor breakage is eliminated by suppressing or preventing excessive circulation of the liquid refrigerant that occurs during low-air-air cooling, and highly reliable low-air It is desired to develop an air conditioner that enables cooling operation.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an air conditioner that can prevent a compressor from being damaged and can perform a reliable low outdoor air cooling operation even in a lower temperature environment. To provide an apparatus.

In order to solve the above problems, the present invention employs the following means.
An air conditioner according to the present invention is a heat pump type air conditioner that performs air conditioning by operating a compressor provided in a refrigerant circuit provided with an electronic expansion valve to change the state of refrigerant circulating.
When a low pressure equal to or lower than a predetermined value (P1) is continuously detected for a predetermined time (t1) during a low outside air cooling operation in which a low outside air temperature is detected that is less than a predetermined value during cooling operation, the operation of the compressor is temporarily stopped. The opening of the electronic expansion valve is fully opened, and the opening of the electronic expansion valve is reduced when the low pressure pressure of the compressor recovers to a predetermined pressure after the automatic return to resume the operation of the compressor under a predetermined condition. The present invention is characterized in that a low outside air cooling operation mode is provided.

  According to such an air conditioner, when a low-pressure pressure equal to or lower than a predetermined value (P1) is continuously detected for a predetermined time (t1) during low-air cooling operation in which a low outside air temperature less than a predetermined value is detected during cooling operation, After the automatic operation of stopping the operation of the compressor to fully open the opening of the electronic expansion valve and restarting the operation of the compressor under a predetermined condition, the low pressure of the compressor is restored to the predetermined pressure. Since the low-air-air cooling operation mode in which the opening degree of the electronic expansion valve is throttled at the time is provided, the low pressure of the refrigeration cycle rises toward the equal pressure when the compressor is stopped and the electronic expansion valve is fully opened. . After detecting this pressure increase and automatically returning the compressor operation, it is confirmed that the low pressure has risen to the predetermined low pressure and the opening of the electronic expansion valve is reduced. Thus, the circulation amount of the liquid refrigerant can be prevented from becoming excessive. Therefore, even when the outside air temperature becomes lower, the low outside air temperature cooling operation can be continued without stopping the compressor.

In the above invention, in the low outside air temperature cooling operation mode, the operation of the compressor is stopped and the electronic expansion valve is operated when a low pressure equal to or lower than a predetermined value (P1) is continuously detected for a predetermined time (t1). Operation of the compressor after the elapse of a predetermined time (t3) from the point of time when the operation is stopped and the low pressure pressure equal to or higher than the predetermined value (P2) is continuously detected for a predetermined time (t2) from the operation stop phase. The electronic expansion valve is set to the initial opening degree when the low pressure pressure equal to or greater than the predetermined value (P2) is detected after the elapse of a predetermined time (t4) from the restart of the operation of the compressor, and the compression It is preferable to include an electronic expansion valve control stage for returning to normal electronic expansion valve control after a lapse of a predetermined time (t5) from the restart of operation of the machine.
In the electronic expansion valve control step, when a low pressure equal to or higher than a predetermined value (P2) is not recovered after a predetermined time (t4) has elapsed since the resumption of operation of the compressor, a predetermined time (t5) from the resumption of operation of the compressor. ) After the elapse of time, the electronic expansion valve may be set to the initial opening and returned to the normal electronic expansion valve control.

According to the present invention described above, since the operation in the low outside air cooling operation mode suppresses or prevents the excessive circulation amount of the liquid refrigerant that has occurred during the low outside air cooling, the problem of the compressor breakage due to liquid compression or poor lubrication can be avoided. Can be solved. For this reason, at the time of low outside air cooling operation, the compressor can be prevented from being damaged due to liquid compression or poor lubrication, and is highly reliable even in a lower outside air temperature environment such as about -15 ° C. Driving becomes possible.
Moreover, such a low outdoor air cooling operation mode can be easily realized by changing the software of the outdoor control unit. Therefore, the cost is low as compared with a hardware change in which new equipment is added to the air conditioner.

Hereinafter, an embodiment of an air-conditioning apparatus according to the present invention will be described with reference to the drawings.
FIG. 3 is an explanatory diagram showing an example of the overall configuration of the multi-type air conditioner. This multi-type air conditioner includes an outdoor unit 10 and a plurality of indoor unit units 20 connected to the outdoor unit 10 (in FIG. 3, the configuration in the case of two indoor unit units is displayed). It is provided and configured. The indoor unit 10 and the outdoor unit 20 are connected by a refrigerant pipe 30 through which a refrigerant flows, electric wiring (not shown), and the like.

The outdoor unit 10 includes a compressor 11 that compresses and delivers a refrigerant, a four-way valve 12 that switches a circulation direction of the refrigerant, an outdoor heat exchanger 13 that exchanges heat between the refrigerant and the outside air, and a heating operation. The main components are an outdoor electronic expansion valve 14 that functions as a throttle mechanism, a receiver 15 and an accumulator 16 that control the outlet refrigerant of the condenser, and an outdoor control unit 17 that performs various operation controls.
In addition, the indoor unit 10 is provided with other devices such as an outdoor fan, a service valve, and a strainer (not shown).

In the outdoor unit 10 described above, sensors for detecting the temperature, pressure, etc. of the refrigerant and inputting them to the outdoor control unit 17 are provided at appropriate positions.
Among these, as temperature sensors for detecting the refrigerant temperature, a discharge pipe temperature sensor 18a, an outdoor heat exchange temperature sensor 18b, a suction pipe temperature sensor 18c, and a dome temperature sensor 18d are provided. Furthermore, an outdoor temperature sensor 18e is provided as a temperature sensor for detecting the temperature of the outdoor environment air (hereinafter referred to as “outdoor air”) in which the outdoor unit 10 is installed. A high pressure sensor 19a and a low pressure sensor 19b are provided as pressure sensors for detecting the refrigerant pressure.

The indoor unit 20 has a configuration in which equipment such as an indoor fan (not shown) is housed in the casing, in addition to the indoor heat exchanger 21, the indoor electronic expansion valve 22 that functions as a throttle mechanism during cooling operation, and the indoor control unit 23. Is done.
The indoor unit 20 is provided with appropriate sensors for detecting the temperature of the refrigerant and the intake air for each unit and inputting the detected temperature to the indoor control unit 23. The illustrated indoor unit 20 includes three indoor heat exchange temperature sensors 24a, 24b, and 24c that detect the refrigerant temperature, and a suction temperature sensor 25 that detects the intake air temperature.
The indoor unit 20 guides indoor air sucked by an indoor fan to the indoor heat exchanger 21 and passes it through the room, and the conditioned air heat-exchanged with the refrigerant supplied from the outdoor unit 10 described above is indoors. It is configured to blow out.

And the air conditioning apparatus mentioned above is the low outdoor air cooling operation selected when the outdoor control part 17 of the outdoor unit 10 detects the low outdoor air temperature below predetermined value (for example, set to about 5 degreeC) at the time of cooling operation. Has a mode. This low outside air operation mode is a control program for cooling operation formed in the outdoor control unit 17, and the low pressure sensor 19b disposed on the suction side of the compressor 11 has a low pressure (PSL) equal to or less than a predetermined value P1. Is selected when a predetermined time t1 is detected continuously.
In this low outside air operation mode, the compressor 11 is stopped once, the opening degree of the indoor electronic expansion valve 22 is fully opened, and after the automatic return when the operation of the compressor 11 is resumed by satisfying a predetermined condition, 11 is an operation control in which the opening degree of the indoor electronic expansion valve 22 is reduced from the fully open position when the low pressure of 11 is recovered to the predetermined pressure P2.

Below, the effect | action of the air conditioning apparatus comprised as mentioned above is divided and demonstrated in each case at the time of air_conditionaing | cooling operation and heating operation.
First, the air conditioning operation during the cooling operation will be described together with the refrigerant flow indicated by arrows in the drawing. In addition, the cooling operation and the heating operation are selectively switched according to the flow direction of the refrigerant that is changed by the operation of the four-way valve 12.
In this cooling operation, the refrigerant converted into a high-temperature and high-pressure gas by the compression of the compressor 11 passes through the four-way valve 12 and is led to the outdoor heat exchanger 13. In the outdoor heat exchanger 13, the high-temperature and high-pressure gas-phase refrigerant exchanges heat with the outdoor air, so that the high-temperature and high-pressure gas refrigerant dissipates heat to the outdoor air and is condensed and liquefied. As a result, the high-temperature and high-pressure gas refrigerant becomes a high-temperature and high-pressure liquid refrigerant, and this liquid refrigerant passes through the outdoor electronic expansion valve 14 and the receiver 15 that are fully opened during the cooling operation, and then passes through the refrigerant pipe 30 and the indoor unit. 20 is supplied.

The liquid refrigerant introduced into the indoor unit 20 is depressurized by passing through the indoor electronic expansion valve 22 and is sent to the indoor heat exchanger 21 as a low-temperature and low-pressure liquid refrigerant. This liquid refrigerant exchanges heat with air in the air-conditioning target space (hereinafter referred to as “room air”) in the indoor heat exchanger 21 and absorbs heat from the room air. As a result, the indoor air is cooled to cool air, and the refrigerant itself evaporates to become a low-temperature and low-pressure gaseous refrigerant.
This gaseous refrigerant is returned to the outdoor unit 10 through the refrigerant pipe 30 and is again sucked into the compressor 11 from the four-way valve 12 via the accumulator 16, and hence the air is repeatedly changed in the same process. Circulate the refrigeration cycle of the harmony device.

Next, the heating operation will be briefly described. This heating operation is performed by operating the four-way valve 12 from the cooling operation described above to switch the refrigerant circulation direction.
The refrigerant made into a high-temperature and high-pressure gas by the compression of the compressor 11 passes through the four-way valve 12 and the refrigerant pipe 30 and is guided to the indoor unit 20 as indicated by broken line arrows in the drawing. This gaseous refrigerant exchanges heat with indoor air when passing through the indoor heat exchanger 21 of the indoor unit 20 to radiate heat. By this heat radiation, the indoor air is heated to become warm air, and the gaseous refrigerant is condensed to become a high-temperature and high-pressure liquid refrigerant. The liquid refrigerant passes through the indoor electronic expansion valve 22 and the refrigerant pipe 30 that are fully opened during the heating operation, and is returned to the outdoor unit 10.

The liquid refrigerant flowing in the outdoor unit 10 is decompressed when passing through the outdoor electronic expansion valve 14, and thereby flows into the outdoor heat exchanger 13 as a low-temperature and low-pressure liquid refrigerant.
The liquid refrigerant flowing into the outdoor heat exchanger 13 exchanges heat with outdoor air when passing through the heat exchanger, absorbs heat, evaporates, and becomes a low-temperature and low-pressure gaseous refrigerant. Since this gaseous refrigerant passes through the four-way valve 12 and the suction muffler 16 and is sucked into the compressor 11, it circulates through the refrigeration cycle of the air conditioner while repeating state changes in the same process.

Next, the operation control in the low outside air cooling operation mode of the above-described air conditioner will be described in detail based on FIG. 1 and FIG.
In the low outside air cooling operation mode, when the detected value of the outside air temperature detected by the outside air temperature sensor 18e is a low temperature lower than a predetermined value during the cooling operation, as shown in step S1 of FIG. The detection value of the low pressure sensor 19b that detects the low pressure is monitored. As a result, the low pressure sensor 19b detects a low pressure equal to or lower than the predetermined value P1, and when the low pressure detection state continues for a predetermined time t1, it is determined that the low pressure abnormality has been detected, and the normal cooling operation control is changed to the low outside air cooling operation mode. The operation control switched to is executed.
Here, as an example of the predetermined value P1 and the predetermined time t1, the predetermined value P1 is a low pressure of about 0.08 MPa, and the predetermined time t1 is about 15 seconds.

Such a low-pressure abnormality causes the condensation capacity of the outdoor heat exchanger 13 to be higher than necessary due to the low outside air temperature, and the condensed liquid refrigerant accumulates in the outdoor heat exchanger 13, so that the refrigerant circulation rate in the refrigeration cycle is remarkably high. It is generated by decreasing.
For this reason, if the low-pressure abnormality detection mentioned above is made, after progressing to the following step S2 and stopping the operation of the compressor 11, it progresses to the next step S3 and the indoor electronic expansion valve 22 is fully opened. Here, when there are a plurality of indoor unit units 20, the indoor electronic expansion valve 22 that is fully opened is assumed to be installed in the indoor unit unit 20 that is in operation, and the indoor unit unit 20 that is stopped is fully closed. Is maintained as it is.

Further, in order to reduce the condensation capacity of the outdoor heat exchanger 13, the operation of an outdoor air fan (not shown) provided in the outdoor heat exchanger 13 is switched to stop or low speed rotation.
In this way, when the low pressure sensor 19b detects a low pressure equal to or lower than the predetermined value P1 for a predetermined time t1, the operation of the compressor 11 is stopped and the opening degree of the indoor electronic expansion valve 22 is fully opened. This completes the shutdown phase.

  By continuing the operation stop state of the compressor 11 after the operation stop phase described above, the refrigerant pressure in the refrigeration cycle passes through the indoor electronic expansion valve 22 in which the gas refrigerant is fully opened and is directed to the pressure equalization pressure of the refrigerant. Rise. For this reason, in step S4, when a low pressure equal to or higher than the predetermined value P2 set to a value lower than the pressure equalizing pressure is continuously detected for a predetermined time t2, the operation is resumed because the pressure rises smoothly toward the pressure equalizing pressure. The process proceeds to the next step S5.

In step S5, when the predetermined time t3 has further passed from the time when the predetermined time t2 has passed, it is determined that the low pressure is in a stable pressure state that is not supported for restarting the operation of the compressor 11, and the operation of the compressor 11 is performed. Resume. In this way, the automatic return stage for resuming the operation of the compressor 11 is completed after the elapse of the predetermined time t3 from the time when the low pressure pressure equal to or greater than the predetermined value P2 is continuously detected for the predetermined time t2 from the operation stop stage.
Here, as an example of the predetermined value P2 and the predetermined times t2 and t3, the predetermined value P2 is a low pressure of about 0.2 MPa higher than P1, the predetermined time t2 is about 10 seconds, and the predetermined time t3 is about 3 minutes.

  After the automatic return stage described above, in step S6, when the low pressure pressure equal to or higher than the predetermined value P2 is detected again after the predetermined time t4 has elapsed since the restart of the operation of the compressor 11, the opening degree of the indoor electronic expansion valve 22 is reduced from the fully open position. The initial opening is set to proceed to the next step S7. In this step S7, after a predetermined time t5 has elapsed since the restart of the operation of the compressor 11 by the automatic return, the normal electronic expansion valve control is maintained to keep the degree of superheat constant. The predetermined time t5 provided here is a time for confirming that a stable operation without support for normal control is continued.

In this way, when a low pressure greater than or equal to the predetermined value P2 is detected after the elapse of the predetermined time t4 from the restart of the operation of the compressor 11, the indoor electronic expansion valve 22 is set to the initial opening, and the predetermined operation from the restart of the operation of the compressor 11 is performed. By returning to the normal electronic expansion valve control after the elapse of time t5, the electronic expansion valve control stage in the low outside air cooling operation mode is completed. That is, the completion of the electronic expansion valve control stage described here means the end of the low outside air cooling operation mode.
Here, the initial opening degree of the indoor electronic expansion valve 22 is an opening degree that is set when a normal cooling operation is started, and is usually about 20% of the fully opened state. As an example of the predetermined times t4 and t5, the predetermined time t4 is about 1 minute, and the predetermined time t5 is about 3 minutes.

  The low outside air cooling operation mode described above is effective when the cooling operation of the air conditioner is started in a state where the outside air temperature is low, or when the liquid refrigerant accumulates in the outdoor heat exchanger 13 after the operation is temporarily stopped. is there. That is, once the cooling operation is stopped and the indoor electronic expansion valve 22 is fully opened, the low pressure sensor 19b detects the process in which the refrigerant pressure in the refrigeration cycle rises to the equal pressure, and compression is performed at a predetermined low pressure P2. The operation of the machine 11 is resumed, and after confirming that the indoor electronic expansion valve 22 is maintained at the initial opening and that stable cooling operation can be continued, the routine proceeds to normal cooling operation.

Therefore, even if the amount of circulating refrigerant is small, after the flow of refrigerant circulating in the refrigeration cycle is stabilized, the low outside air cooling operation can be continued, and the liquid refrigerant generated at the time of low outside air cooling can be maintained. Excessive circulation can be suppressed or prevented. Further, the compressor 11 is prevented from being damaged due to liquid compression or poor lubrication due to the low outside air cooling operation, and the highly reliable low outside air cooling operation is performed even in a low temperature environment such as an outside air temperature of about −15 ° C. Is possible.
The addition of such a low outdoor air cooling operation mode eliminates the need for hardware changes and modifications such as adding new equipment to the air conditioner, and reduces the cost by simply changing the software of the outdoor control unit 17. realizable.
Further, the low outside air cooling operation mode described above prevents the liquid refrigerant from returning to the compressor 11 during the low outside air cooling operation without the accumulator 16 installed on the suction side of the compressor 11. This enables reliable operation that avoids damage to the machine.

Next, a modified example of the above-described low outside air cooling operation mode will be described based on the time chart shown in FIG.
This modification is different from the above-described embodiment in the control of the electronic expansion valve control stage, and is the same control before this electronic expansion valve control stage. Therefore, only the electronic expansion valve control stage will be described below, and the description for the control before that will be omitted.

  In the electronic expansion valve control stage of this modified example, when the low pressure pressure not less than the predetermined value P2 is not recovered after the elapse of the predetermined time t4 from the restart of the operation of the compressor 11, the indoor electronic expansion is performed after the elapse of the predetermined time t5 from the operation restart of the compressor 11. The valve 22 is set to the initial opening and the normal electronic expansion valve control is restored. That is, when the predetermined time t5 has elapsed since the resumption of the operation of the compressor 11 after the automatic return stage, the opening degree of the indoor electronic expansion valve 22 is increased even if the low pressure does not increase to the predetermined value P2. It is throttled from full open and set to the initial opening, and it returns to normal electronic expansion valve control that keeps the degree of superheat constant.

As described above, the electronic expansion valve control in the low outdoor air cooling operation mode is performed by setting the indoor electronic expansion valve 22 to the initial opening degree and returning to the normal electronic expansion valve control after the elapse of the predetermined time t5 from the restart of the operation of the compressor 11. The steps may be completed to end the low outside air cooling operation mode.
Even in such a control, after the flow of the refrigerant circulating in the refrigeration cycle is stabilized, the low outside air cooling operation can be continued, and the excessive circulation of the liquid refrigerant generated during the low outside air cooling is suppressed or prevented. It is possible to prevent the compressor 11 from being damaged due to liquid compression or poor lubrication caused by the low outside air cooling operation, and a highly reliable low outside air cooling operation can be performed even in a lower temperature environment such as about −15 ° C. It becomes possible.

  Note that the present invention is not limited to the above-described embodiment, and for example, is applied to an air conditioner having a configuration in which one outdoor unit and one indoor unit are provided and one electronic expansion valve is provided in the refrigerant circuit. It can be appropriately changed within a range not departing from the gist of the present invention.

It is a figure which shows the time chart of the low outdoor air cooling operation mode as one Embodiment of the air conditioning apparatus which concerns on this invention. It is a flowchart of the low external air cooling operation mode shown in FIG. It is a figure which shows the structural example of the air conditioning apparatus which concerns on this invention. It is a time chart which shows the modification of the low outside air cooling operation mode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Outdoor unit 11 Compressor 12 Four-way valve 13 Outdoor heat exchanger 14 Outdoor electronic expansion valve 17 Outdoor control part 18e Outdoor temperature sensor 19a High pressure sensor 19b Low pressure sensor 20 Indoor unit 21 Indoor heat exchanger 22 Indoor electronic expansion valve 23 Indoor control unit

Claims (3)

In a heat pump type air conditioner that performs air conditioning by operating a compressor provided in a refrigerant circuit provided with an electronic expansion valve to change the state of refrigerant circulating,
When a low pressure equal to or lower than a predetermined value (P1) is continuously detected for a predetermined time (t1) during a low outside air cooling operation in which a low outside air temperature is detected that is less than a predetermined value during cooling operation, the operation of the compressor is temporarily stopped. The opening of the electronic expansion valve is fully opened, and the opening of the electronic expansion valve is reduced when the low pressure pressure of the compressor recovers to a predetermined pressure after the automatic return to resume the operation of the compressor under a predetermined condition. An air conditioner characterized in that a low outside air cooling operation mode is provided. The low outside temperature cooling operation mode is:
An operation stop stage of stopping the operation of the compressor and fully opening the opening of the electronic expansion valve when a low pressure of a predetermined value (P1) or less is continuously detected for a predetermined time (t1);
An automatic return step of restarting the operation of the compressor after the elapse of a predetermined time (t3) from the time when the low pressure pressure equal to or higher than the predetermined value (P2) is continuously detected for a predetermined time (t2) from the operation stop phase;
When a low pressure greater than or equal to a predetermined value (P2) is detected after a lapse of a predetermined time (t4) from the restart of operation of the compressor, the electronic expansion valve is set to an initial opening degree, and a predetermined time ( t5) an electronic expansion valve control stage for returning to normal electronic expansion valve control after elapse;
The air conditioning apparatus according to claim 1, comprising:   In the electronic expansion valve control step, if the low pressure pressure equal to or higher than the predetermined value (P2) is not recovered after a predetermined time (t4) has elapsed since the resumption of operation of the compressor, the predetermined time (t5) from the resumption of operation of the compressor. The air conditioning apparatus according to claim 2, wherein after the elapse of time, the electronic expansion valve is set to an initial opening degree and returned to normal electronic expansion valve control.

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