JP5022920B2 - Air conditioner - Google Patents

Description

  The present invention relates to an air conditioner, and more particularly, to an expansion valve control technique for suppressing a refrigerant overheating state at an evaporator inlet when a heating operation is started.

In general, a refrigerant circuit in which a compressor, an evaporator, an expansion valve, and a condenser are connected by piping is provided, and the opening degree of the expansion valve is controlled based on the refrigerant suction temperature of the compressor and the refrigerant temperature of the evaporator. An air conditioner that performs superheat control is known (see, for example, Patent Document 1).
In this type of air conditioner, the degree of superheat is calculated based on the refrigerant suction temperature detected on the suction side of the compressor and the refrigerant temperature detected at the inlet or intermediate part of the evaporator, and this superheat degree is calculated as the target superheat degree. Thus, the opening degree of the expansion valve is controlled.
JP 2004-36966 A

  By the way, when installing this type of air conditioner in a building or the like, because of the installation space, an outdoor heat exchanger that functions as an evaporator or a condenser, an outdoor unit that has an indoor heat exchanger, and an indoor unit are Often located far away. In this case, since the pipe length of the pipe between the units connecting the outdoor unit and the indoor unit is, for example, 100 m, the pipe length is 100 m. Therefore, when the operation of the air conditioner (particularly the heating operation) is stopped, The refrigerant may fall asleep. For this reason, at the start of operation, it takes time for the refrigerant stagnated in the inter-unit piping to circulate in the refrigerant circuit, and during that time, the refrigerant flowing into the evaporator is in a superheated gas state.

However, in the conventional configuration, the superheat control is executed even when the refrigerant flowing into the evaporator is in a superheated gas state. For this reason, since the expansion valve is controlled so that the refrigerant suction temperature of the compressor further takes the target superheat degree with respect to the refrigerant temperature of the evaporator that is actually in the superheated gas state, When the refrigerant circulation amount that circulates through the refrigerant circuit is further reduced, there is a problem that problems such as an abnormal decrease in the suction pressure of the compressor and poor lubrication of the refrigeration oil occur.
Therefore, an object of the present invention is to provide an air conditioner capable of preventing the occurrence of problems such as an abnormal drop in the suction pressure of a compressor and poor lubrication of refrigerating machine oil at the start of operation.

In order to solve the above-described problems, the present invention includes a refrigerant circuit in which a compressor, an evaporator, an expansion valve, and a condenser are connected by piping, and is based on the refrigerant suction temperature of the compressor and the refrigerant temperature of the evaporator. In the air conditioner that controls the degree of superheat by controlling the opening degree of the expansion valve, whether or not the refrigerant flowing into the evaporator is in a superheated gas state based on the outside air temperature and the refrigerant temperature at the start of operation. When it is determined that the state determining means for determining and the refrigerant flowing into the evaporator are in the superheated gas state, instead of the superheat control, the opening degree of the expansion valve is opened by a predetermined pulse, and the expansion An over-throttle suppression control means for suppressing over-throttle of the valve is provided.
According to this configuration, when it is determined that the refrigerant flowing into the evaporator is in the superheated gas state at the time of starting the operation, the expansion valve opening degree is opened for a predetermined pulse instead of the superheat degree control. Since the control to suppress over-throttle of the valve is performed, the refrigerant circulation amount circulating in the refrigerant circuit can be maintained appropriately, and the superheated gas state at the evaporator inlet can be eliminated, so that the suction pressure of the compressor It is possible to prevent the occurrence of problems such as an abnormal drop in the temperature and poor lubrication of refrigerating machine oil.

  Further, in this configuration, when the state determination unit determines that the refrigerant flowing into the evaporator is not in the superheated gas state during execution of the control for suppressing the over-throttle of the expansion valve, the expansion valve It is also possible to adopt a configuration in which the control to suppress over-throttle is prohibited and the superheat degree control is executed.

  Further, the over-throttle suppression control means may be configured to open the opening of the expansion valve by the predetermined pulse every predetermined time.

  According to the present invention, when it is determined that the refrigerant flowing into the evaporator is in the superheated gas state when the operation is started, the expansion valve opening degree is opened for a predetermined pulse instead of the superheat degree control. Since the control to suppress over-throttle of the valve is performed, the refrigerant circulation amount circulating in the refrigerant circuit can be maintained appropriately, and the superheated gas state at the evaporator inlet can be eliminated, so that the suction pressure of the compressor It is possible to prevent the occurrence of problems such as an abnormal drop in the temperature and poor lubrication of refrigerating machine oil.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a circuit diagram showing a refrigerant circuit in an air conditioner to which an embodiment of a refrigeration apparatus according to the present invention is applied.
1 includes an outdoor unit 20, an indoor unit 30, and a control device 40. An outdoor refrigerant pipe 21 of the outdoor unit 20 and an indoor refrigerant pipe 31 of the indoor unit 30 are connected to a gas pipe 51 and a liquid pipe. Are connected via a unit-to-unit pipe 53. Although FIG. 1 shows a configuration including one indoor unit 30, the configuration is not limited thereto, and a configuration in which a plurality of indoor units 30 are connected in parallel to the inter-unit piping 53 may be employed. .

  The outdoor unit 20 is installed outdoors, and a compressor 22 is disposed in the outdoor refrigerant pipe 21. A sub-accumulator 23 and a main accumulator 24 are provided on the suction side of the compressor 22, and a four-way valve is provided on the discharge side. The outdoor heat exchanger 26, the receiver tank 27, and the expansion valve 28 are sequentially arranged on the four-way valve 25 side. An outdoor fan 55 (FIG. 2) that blows air toward the outdoor heat exchanger 26 is disposed adjacent to the outdoor heat exchanger 26. Further, a bypass pipe 29A that bypasses the sub-accumulator 23 and the compressor 22 is provided on the outlet side of the main accumulator 24, and the bypass pipe 29A is provided on the discharge side of the compressor 22 when the operation of the compressor 22 is stopped. A pressure equalizing valve 29B that is opened to equalize the pressure on the suction side is disposed.

In addition, a first outdoor temperature sensor 26A that measures the refrigerant inlet / outlet temperature (refrigerant temperature) C1 of the outdoor heat exchanger 26 is disposed at the connection port on the receiver tank 27 side of the outdoor heat exchanger 26, and outdoor heat exchange is performed. A second outdoor temperature sensor 26 </ b> B that measures an intermediate refrigerant temperature (refrigerant temperature) C <b> 2 at the position is disposed at a substantially central portion of the vessel 26. The first outdoor temperature sensor 26A measures the liquid refrigerant temperature C1 that flows out of the outdoor heat exchanger 26 during the cooling operation and flows into the outdoor heat exchanger 26 during the heating operation. On the other hand, the second outdoor temperature sensor 26B measures the refrigerant temperature C2 in the gas-liquid mixed state in the outdoor heat exchanger 26, that is, the refrigerant evaporation temperature during the heating operation and the refrigerant condensing temperature during the cooling operation.
In the present embodiment, an outdoor air temperature sensor 26 </ b> C that measures the outdoor air temperature TO is disposed in the vicinity of the outdoor heat exchanger 26, and a compressor is connected to the inlet side of the main accumulator 24 via the main accumulator 24. An accumulator temperature sensor 24 </ b> A that measures the refrigerant suction temperature TS sucked into 22 is disposed.

  On the other hand, the indoor unit 30 is configured by arranging an indoor heat exchanger 32 in an indoor refrigerant pipe 31. An indoor fan 56 (FIG. 2) that blows air to the indoor heat exchanger 32 is disposed adjacent to the indoor heat exchanger 32. In addition, a first indoor temperature sensor 32A that measures the refrigerant inlet / outlet temperature (refrigerant temperature) E1 of the indoor heat exchanger 32 is disposed at the connection port on the liquid pipe 52 side of the indoor heat exchanger 32, and indoor heat exchange is performed. A second indoor temperature sensor 32 </ b> B that measures an intermediate refrigerant temperature (refrigerant temperature) E <b> 2 at the position is disposed at a substantially central portion of the vessel 32. The first indoor temperature sensor 32A and the second indoor temperature sensor 32B have substantially the same functions as the first outdoor temperature sensor 26A and the second outdoor temperature sensor 26B described above.

The outdoor refrigerant pipe 21 and the indoor refrigerant pipe 31 are connected via an inter-unit pipe 53, so that the main accumulator 24, the sub accumulator 23, the compressor 22, the four-way valve 25, the outdoor heat exchanger 26, and the receiver tank 27 are connected. The expansion valve 28 and the indoor heat exchanger 32 are sequentially connected, and the main accumulator 24 is further connected to the indoor heat exchanger 32 via the four-way valve 25, so that a loop-like refrigerant circuit 15 in which the refrigerant flows is configured.
The control device 40 controls the operation of the outdoor unit 20 and the indoor unit 30. Specifically, the compressor 22, the four-way valve 25, the expansion valve 28, the pressure equalizing valve 29B, and the outdoor fan 55 (FIG. 2) of the outdoor unit 20. And the indoor fan 56 (FIG. 2) of the indoor unit 30 is each controlled. An operation unit (for example, a remote controller) 57 for remotely operating the air conditioner 10 is connected to the control device 40. In this embodiment, the control device 40 is housed in the casing of the outdoor unit 20 and operated. The unit 57 is provided in the indoor unit 30.

Next, the configuration of the control device 40 will be described.
FIG. 2 is a block diagram illustrating a functional configuration of the control device 40.
The control device 40 includes an EEPROM 41 that stores a control program, control data, and the like, a CPU 42 that controls the entire air conditioner 10 based on the control program and the like in the EEPROM 41, and a RAM 43 that temporarily stores various data. And a transmission / reception unit 44 that communicates with the operation unit 57, and an interface 45 that transmits and receives signals to and from each unit of the air conditioning apparatus 10.

  The control device 40 is connected to the first outdoor temperature sensor 26A, the second outdoor temperature sensor 26B, the first indoor temperature sensor 32A, the second indoor temperature sensor 32B, the accumulator temperature sensor 24A, and the outdoor air temperature sensor 26C via the interface 45. It is connected and configured to be able to acquire temperature data at each location. And if the operation part 57 is operated, the control apparatus 40 will control the four-way valve 25, the compressor 22, the expansion valve 28, the outdoor fan 55, and the indoor fan 56, respectively.

Specifically, when the cooling operation is set through the operation unit 57, the control device 40 switches the four-way valve 25 to the cooling side, and the refrigerant flows as indicated by solid arrows as shown in FIG. The outdoor heat exchanger 26 functions as a condenser, and the indoor heat exchanger 32 functions as an evaporator to enter a cooling operation state, and the indoor heat exchanger 32 cools the room.
On the other hand, when the heating operation is set, the control device 40 switches the four-way valve 25 to the heating side, the refrigerant flows as indicated by the wavy arrow, the indoor heat exchanger 32 becomes the condenser, and the outdoor heat exchange. The unit 26 functions as an evaporator and enters a heating operation state, and the indoor heat exchanger 32 heats the room. Further, the control device 40 variably controls the operation frequency of the compressor 22 based on the difference between the set temperature set by the operation unit 57 and the room temperature.
Further, the control device 40 determines the refrigerant suction temperature TS of the compressor 22 measured by the accumulator temperature sensor 24A and the refrigerant temperature of the evaporator (the refrigerant inlet temperature measured by the first indoor temperature sensor 32A of the indoor heat exchanger 32 during the cooling operation). E1, during heating operation, the degree of superheat is controlled based on the refrigerant inlet temperature C1) measured by the first outdoor temperature sensor 26A of the outdoor heat exchanger 26, and the opening degree of the expansion valve 28 is controlled.

Next, superheat degree control is demonstrated. In addition, this embodiment demonstrates the case where the air conditioning apparatus 10 is heating-operating.
The control device 40 is based on the refrigerant suction temperature TS of the compressor 22 measured by the accumulator temperature sensor 24A and the refrigerant inlet temperature C1 measured by the first outdoor temperature sensor 26A of the outdoor heat exchanger 26 functioning as an evaporator. The superheat degree SH is calculated. Specifically, this superheat degree SH is calculated by the following equation.
SH = TS-C1
Then, the control device 40 compares the calculated superheat degree SH with a predetermined target superheat degree SHtgt (for example, 2.0 degrees), and determines which is greater.
In this determination, the calculated superheat degree SH is compared with a predetermined target superheat degree SHtgt,
SH <SHtgt
If it is determined that, the control device 40 reduces the opening of the expansion valve 28, that is, controls the expansion valve 28 in the closing direction.
On the other hand, the calculated superheat degree SH is compared with a predetermined target superheat degree SHtgt,
SH> SHtgt
If it is determined that, the control device 40 increases the opening degree of the expansion valve 28, that is, controls the expansion valve 28 to open.
In addition, the control device 40
SH = SHtgt
If it is determined that, the current opening degree of the expansion valve 28 is maintained.
Thereby, since the opening degree of the expansion valve 28 is controlled so that the calculated superheat degree SH approaches the predetermined target superheat degree SHtgt, an appropriate heating operation is performed.

By the way, in this embodiment, the air conditioning apparatus 10 is arrange | positioned at high-rise buildings, such as a building, and the outdoor unit 20 and the indoor unit 30 are arrange | positioned far apart. According to this, since the pipe length of the inter-unit pipe 53 connecting the outdoor unit 20 and the indoor unit 30 is a long pipe of, for example, 100 m, during the operation stop of the air conditioner 10, Coolant may stagnate inside.
In particular, since the inter-unit piping 53 is cooled with the outside air in winter, the refrigerant is likely to sleep in the inter-unit piping 53. Therefore, when the heating operation is started, the refrigerant that has stagnated in the inter-unit piping 53 becomes the refrigerant. It takes time to circulate through the circuit 15, and during that time, the refrigerant flowing into the outdoor heat exchanger 26 tends to be in a superheated gas state.
For this reason, in this embodiment, at the time of starting the heating operation, the over-throttle suppression control for suppressing the opening degree of the expansion valve 28 from being excessively throttled and preventing the superheated gas refrigerant from flowing into the outdoor heat exchanger 26. Is executed.

Next, the operation of this embodiment will be described. FIG. 3 is a flowchart showing an operation procedure of the present embodiment.
First, the control device 40 determines whether or not a first predetermined time (150 seconds in the present embodiment) has elapsed since the start of the heating operation (step S1). The first predetermined time is a time until the temperature measured by each temperature sensor is stabilized in order to reliably determine whether or not the superheated gas refrigerant is flowing into the outdoor heat exchanger 26. Thereby, it is prevented that the superheated gas refrigerant is flowing into the outdoor heat exchanger 26 based on an erroneous measurement value.
In this determination, when the first predetermined time has not elapsed since the start of operation (step S1: No), the process proceeds to step S7, and the superheat control described above is executed. On the other hand, when the first predetermined time has elapsed from the start of operation (step S1: Yes), it is considered that the temperature measured by each temperature sensor is stable, and thus the process proceeds to step 2.

Subsequently, the control device 40 determines whether or not a second predetermined time (10 minutes in the present embodiment) has elapsed from the start of operation (step S2). The second predetermined time is a time set as sufficient to execute the above-described over-throttle suppression control. This over-throttle suppression control is effective to be executed at the start of operation, and even if the superheat degree control is executed after the second predetermined time has elapsed from the start of operation, the outdoor heat exchanger 26 is overheated. There is little risk of gas refrigerant flowing in.
In this determination, when the second predetermined time has elapsed from the start of operation (step S2: Yes), it is considered that the air conditioner 10 has been stably operated, and the process proceeds to step S7. Execute control.

On the other hand, if the second predetermined time has not elapsed since the start of operation (step S2: No), the control device 40 uses the outdoor air temperature TO measured by the outdoor air temperature sensor 26C and the outdoor heat exchanger functioning as an evaporator. Based on the refrigerant inlet temperature C1 measured by the first outdoor temperature sensor 26A of 26, the temperature difference T1 between the outside air temperature TO and the refrigerant inlet temperature C1 is larger than the first reference temperature (5 ° C. in the present embodiment). That is,
T1 = TO-C1> 5 ° C.
It is determined whether or not the condition is satisfied (step S3). Here, when the refrigerant flowing into the outdoor heat exchanger 26 is in the superheated gas state, the refrigerant temperature in the superheated gas state rises, so that the refrigerant inlet temperature C1 approaches the outside air temperature TO. For this reason, it is possible to easily determine whether or not the refrigerant flowing into the outdoor heat exchanger 26 is in the superheated gas state by comparing the outside air temperature TO and the refrigerant inlet temperature C1. In the present embodiment, the control device 40, the first outdoor temperature sensor 26A, and the outdoor temperature sensor 26C function as a state determination unit.
In this determination, when the difference temperature T1 between the outside air temperature TO and the refrigerant inlet temperature C1 is larger than 5 ° C. (step S3: Yes), the control device 40 determines that the refrigerant flowing into the outdoor heat exchanger 26 is superheated gas. It is determined that the liquid refrigerant is not circulated normally, and over-throttle suppression control described later is prohibited (step S4), the process proceeds to step S7, and the above-described superheat degree control is executed.

On the other hand, when the difference temperature T1 between the outside air temperature TO and the refrigerant inlet temperature C1 is 5 ° C. or less (step S3: No), the control device 40 determines that the difference temperature T1 is smaller than the first reference temperature. It is determined whether or not the temperature is 3 ° C. or less (step S5). These first reference time and second reference time are set by experiment.
In this determination, when the difference temperature T1 between the outside air temperature TO and the refrigerant inlet temperature C1 is 3 ° C. or less (step S5: Yes), the control device 40 executes overthrottle suppression control (step S6). Specifically, the control device 40 controls the expansion valve 28 so as to open a predetermined pulse P (30 pulses in the present embodiment) from the initial opening pulse P0. In this case, as shown in FIG. 4, it is desirable to perform control so as to open by a predetermined pulse P every predetermined time t (in this embodiment, 30 seconds). According to this configuration, when it is determined that the refrigerant flowing into the outdoor heat exchanger 26 is in the superheated gas state when the heating operation is started, the opening degree of the expansion valve 28 is set to a predetermined value instead of the superheat degree control. In order to perform control to suppress the over-throttle of the expansion valve 28 by opening the pulse P, the liquid refrigerant that has passed through the opened expansion valve 28 flows into the outdoor heat exchanger 26, and at the inlet of the outdoor heat exchanger 26. The overheated gas state can be eliminated. For this reason, the refrigerant | coolant circulation amount which circulates through the refrigerant circuit 15 can be maintained appropriately, and generation | occurrence | production of malfunctions, such as abnormal fall of the suction pressure of the compressor 22, and the lubrication failure of refrigeration oil, can be prevented.
Further, in this configuration, since the expansion valve 28 is gradually opened, a large amount of liquid refrigerant is prevented from flowing into the outdoor heat exchanger 26 at a stretch, so that the liquid refrigerant is prevented from returning to the compressor 22. Is done. Further, in this configuration, since the above steps S1 to S5 are determined every time the expansion valve 28 is opened by the predetermined pulse P, which control of the superheat degree control and the overthrottle suppression control is appropriate for the expansion valve 28. It is determined each time. For this reason, the valve control of the expansion valve 28 can be executed with high accuracy. Furthermore, in this configuration, an appropriate amount of refrigerant circulates in the refrigerant circuit 15 at an early stage due to the control for suppressing over-throttle as compared with the case of only the superheat degree control, and therefore the indoor heat exchanger 32 during the heating operation. Since the high-temperature and high-pressure liquid refrigerant is immediately supplied to the user, the user can immediately get a feeling of hot air. In the present embodiment, the control device 40 functions as an overdrawing suppression control unit.

  On the other hand, when the temperature difference T1 between the outside air temperature TO and the refrigerant inlet temperature C1 is larger than 3 ° C. (step S5: No), the control device 40 moves the process to step S7 and executes the superheat degree control described above. To do. Here, for example, in a scene where the circulation amount of the liquid refrigerant increases, by setting the second reference temperature to be lower than the first reference temperature, it is possible to quickly shift from over-throttle suppression control to superheat degree control. The liquid return to the compressor 22 due to the opening of the expansion valve 28 can be minimized.

Next, the control device 40 determines whether or not an operation stop instruction is issued through the operation unit 57 (step S8). In this determination, if there is no operation stop instruction (step S8: NO), the process returns to step S1, and the processes of steps S1 to S8 are repeatedly executed.
On the other hand, when there is an operation stop instruction (step S8: Yes), the control device 40 cancels the prohibition of over-throttle suppression control in step S4 (step S9) and stops the operation and ends the process. .

  According to the present embodiment, the air that performs superheat control by controlling the opening degree of the expansion valve 28 based on the refrigerant suction temperature TS of the compressor 22 and the refrigerant inlet temperature C1 of the outdoor heat exchanger 26 that functions as an evaporator. In the conditioning apparatus, when the heating operation is started, it is determined whether or not the refrigerant flowing into the outdoor heat exchanger 26 is in an overheated gas state based on the outside air temperature TO and the refrigerant inlet temperature C1, and the outdoor heat exchanger 26 is determined. When it is determined that the refrigerant flowing into the superheated gas state is in the superheated gas state, instead of the superheat control, the opening degree of the expansion valve 28 is opened by a predetermined pulse P, and control for suppressing over-throttle of the expansion valve 28 is performed. For example, when the outdoor unit 20 and the indoor unit 30 are connected by a long inter-unit pipe 53, the refrigerant stagnates inside the inter-unit pipe 53 while the operation of the air conditioner 10 is stopped. Even so, the liquid refrigerant flowing through the opened expansion valve 28 flows into the outdoor heat exchanger 26 due to the control for suppressing over-throttle of the expansion valve 28, so that the superheated gas state at the inlet of the outdoor heat exchanger 26 Can be eliminated. For this reason, the refrigerant | coolant circulation amount which circulates through the refrigerant circuit 15 can be maintained appropriately, and generation | occurrence | production of malfunctions, such as abnormal fall of the suction pressure of the compressor 22, and the lubrication failure of refrigeration oil, can be prevented.

  Further, according to the present embodiment, when the control device 40 determines that the refrigerant flowing into the outdoor heat exchanger 26 is not in the superheated gas state during execution of the control for suppressing the overthrottle of the expansion valve 28. In addition to prohibiting the control for suppressing the over-throttle of the expansion valve 28 and executing the superheat control, the opening degree of the expansion valve 28 is appropriately controlled by this superheat control, and the heating operation of the air conditioner is properly controlled. Can continue. Furthermore, since control for suppressing over-throttle of the expansion valve 28 is prohibited, an appropriate amount of refrigerant circulates in the refrigerant circuit 15, thereby preventing liquid return to the compressor 22.

  Further, according to the present embodiment, the opening degree of the control device 40 and the expansion valve 28 is released by a predetermined pulse P (30 pulses) every predetermined time t (30 seconds). By preventing a large amount of liquid refrigerant from flowing into the heat exchanger 26 at once, the liquid refrigerant is prevented from returning to the compressor 22. Further, each time the expansion valve 28 is opened by a predetermined pulse P, it is determined each time whether the expansion valve 28 is suitable for the superheat control or the overthrottle suppression control. It can be executed with high accuracy.

Although one embodiment of the present invention has been described above, the present invention is not limited to this. For example, in the present embodiment, the refrigerant flowing into the outdoor heat exchanger 26 is likely to be in a superheated gas state when the heating operation is started. Therefore, the heating operation is illustrated as an example, but the present invention is not limited thereto. Of course, the above-described control for suppressing over-throttle at the start of the cooling operation may be applied. In this case, the control device 40, the first indoor temperature sensor 32A, and the outside air temperature sensor 26C function as state determination means.
In the present embodiment, the first outdoor temperature sensor 26A disposed on the inlet side of the outdoor heat exchanger 26 is used as a sensor for measuring the refrigerant temperature of the outdoor heat exchanger 26. However, the present invention is not limited to this. Instead, the second outdoor temperature sensor 26B provided at an intermediate position of the outdoor heat exchanger 26 may be used.
Moreover, although the case where this invention was applied to the air conditioning apparatus 10 provided with the one outdoor unit 20 and the one indoor unit 30 was illustrated in this embodiment, the air provided with an arbitrary number of outdoor units and indoor units, respectively. The harmony device can be widely applied.

It is a figure which shows the circuit structure of the air conditioning apparatus of this embodiment. It is a figure which shows the function structure of a control apparatus. It is a flowchart which shows operation | movement of embodiment. It is a figure which shows the opening degree control of the expansion valve in each control.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Air conditioning apparatus 15 Refrigerant circuit 20 Outdoor unit 22 Compressor 24 Main accumulator 24A Accumulator temperature sensor 25 Four-way valve 26 Outdoor heat exchanger 26A 1st outdoor temperature sensor (state discrimination means)
26C Outside air temperature sensor (state discrimination means)
28 expansion valve 29A bypass pipe 29B pressure equalizing valve 30 indoor unit 32 indoor heat exchanger 40 control device (state determination means, over-throttle suppression control means)
C1 Refrigerant inlet temperature SH Superheat degree TO Outside air temperature TS Refrigerant suction temperature P Predetermined pulse t Predetermined time

Claims (3)

A refrigerant circuit in which a compressor, an evaporator, an expansion valve, and a condenser are connected by piping is provided, and the degree of superheat is controlled by controlling the opening degree of the expansion valve based on the refrigerant suction temperature of the compressor and the refrigerant temperature of the evaporator. In an air conditioner that performs control,
State determination means for determining whether or not the refrigerant flowing into the evaporator is in an overheated gas state based on the outside air temperature and the refrigerant temperature at the start of operation;
When it is determined that the refrigerant flowing into the evaporator is in a superheated gas state, instead of the superheat control, the opening degree of the expansion valve is opened by a predetermined pulse to suppress overthrottle of the expansion valve. An air conditioner characterized by comprising over-throttle suppression control means. During execution of control for suppressing over-throttle of the expansion valve,
When the state determination means determines that the refrigerant flowing into the evaporator is not in the superheated gas state, the control for inhibiting the expansion valve from being overthrown is prohibited and the superheat degree control is executed. The air conditioning apparatus according to claim 1, wherein   The air conditioner according to claim 1 or 2, wherein the over-throttle suppression control means opens the opening of the expansion valve by the predetermined pulse every predetermined time.

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