JPH11132575A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the reliability of a compressor from lowering due to mixing of liquid refrigerant into gas refrigerant being returned from a gas-liquid separator inserted into a liquid tube back to the compressor through a bypass tube for gas injection. SOLUTION: When the temperature difference between the outlet temperature of a compressor and the condensation temperature of refrigerant drops below a reference level, an on/off valve 14 of bypass piping 13 is closed to stop gas injection. Outlet temperature drops when liquid refrigerant is mixed, and temperature difference between the outlet temperature and the condensation temperature is decreased. When it is compared with a reference temperature difference, the temperature difference can be detected while being distinguished from outlet temperature drop corresponding to variation of operating conditions. Reliability of compressor can be enhanced by stopping gas injection automatically when the liquid refrigerant is mixed based on the detected temperature difference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas pipe for connecting an outdoor heat exchanger and an indoor heat exchanger with a gas-liquid separator interposed therebetween. TECHNICAL FIELD The present invention relates to an air conditioner provided with a bypass pipe for returning air to an air conditioner.

[0002]

2. Description of the Related Art For example, a heating operation in an air conditioner is performed as follows.
This is performed by circulating the refrigerant gas discharged from the compressor from the indoor heat exchanger to the outdoor heat exchanger. At this time,
Heat is absorbed from outside air in the outdoor heat exchanger functioning as an evaporator, and indoor heating is performed by heat radiation in the indoor heat exchanger functioning as a condenser.

[0003] When the outside air temperature is low during the heating operation, it is difficult to obtain a sufficient heating capacity. In such a case,
The gas refrigerant condensed in the indoor heat exchanger and mixed in the liquid refrigerant flowing to the outdoor heat exchanger is separated, and the gas refrigerant is returned to the compressor by gas injection. It will be staged compressed and supplied again to the indoor heat exchanger, thereby improving the overall heating capacity.

In order to perform such gas injection, conventionally, in an air conditioner provided with a compressor having a constant compression capacity, gas-liquid separation is provided in a liquid pipe between an indoor heat exchanger and an outdoor heat exchanger. There is known a device in which a bypass pipe is provided between the gas-liquid separator and the suction side of the compressor, with an on-off valve provided between the gas-liquid separator and the suction side of the compressor.

[0005] In recent years, an air conditioner equipped with a compressor whose compression capacity is variable by inverter control has become mainstream. Also in such an air conditioner, a gas-liquid separator is interposed in the liquid pipe between the indoor heat exchanger and the outdoor heat exchanger as described above, and a bypass for gas injection is provided from the gas-liquid separator. By employing a configuration in which the gas refrigerant is returned to the compressor through the pipe, it becomes possible to perform a heating operation or a cooling operation with increased capacity.

[0006]

However, in an air conditioner equipped with a compressor having a variable compression capacity controlled by an inverter, when a gas injection is performed by providing the above-described gas-liquid separator and the bypass pipe, the gas-liquid separation is performed. There is a problem that a liquid refrigerant is likely to be mixed into a gas refrigerant (hereinafter, referred to as an injection gas) returned from a compressor to a compressor.

That is, in such an air conditioner, a large amount of refrigerant is charged into the refrigerant circuit in anticipation of the required amount of refrigerant circulation at the maximum load. Then, the actual amount of refrigerant circulating greatly fluctuates according to the change in load, and accordingly, the amount of liquid refrigerant in the gas-liquid separator also fluctuates greatly. Therefore, when gas injection is performed when the ratio of the liquid refrigerant in the gas-liquid separator is large, the liquid refrigerant is also easily sucked out of the gas-liquid separator, whereby the liquid refrigerant is contained in the injection gas. A mixed state occurs. When the liquid refrigerant is sucked into the compressor, liquid compression occurs, and if this continues, the reliability of the compressor decreases.

[0008] Even if the ratio of the liquid refrigerant in the gas-liquid separator is maximized, the compressor may be provided with a large-capacity gas-liquid separator so that a sufficient gas refrigerant phase exists therein. Although it is possible to prevent the liquid refrigerant from flowing back, the provision of such a large-capacity gas-liquid separator increases the size of the apparatus and increases the cost of the apparatus.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described problems, and has as its object to suppress the state of liquid compression in a compressor during gas injection without providing a large-capacity gas-liquid separator. An object of the present invention is to provide an air conditioner that can improve the reliability of the air conditioner.

[0010]

Therefore, an air conditioner according to a first aspect of the present invention provides a refrigerant circulation circuit by connecting an outdoor heat exchanger 8 and an indoor heat exchanger to a compressor 1 having a variable compression capacity by an inverter 1a. And a gas-liquid separator 11 is interposed in the liquid pipes 10 and 12 between the outdoor heat exchanger 8 and the indoor heat exchanger, and the gas-liquid separator 11 is connected to the suction side of the compressor 1. Between,
An air conditioner provided with a gas injection bypass pipe 13 for returning gas refrigerant in a gas-liquid separator 11 to the compressor 1 and an on-off valve 14 for opening and closing a flow path through the bypass pipe 13. When the temperature difference between the discharge temperature of the compressor 1 and the condensation temperature of the refrigerant circulating in the refrigerant circuit becomes smaller than the reference temperature difference, the gas for closing the on-off valve 14 to stop gas injection. The injection monitoring control means 15 is provided.

In the air conditioner having the above structure, the temperature difference between the discharge temperature of the compressor 1 and the condensing temperature of the refrigerant (hereinafter referred to as discharge side temperature difference) is monitored by the gas injection monitoring control means 15 during gas injection. Then, when the discharge-side temperature difference becomes smaller than the reference temperature difference, control is performed to close the on-off valve 14 that opens and closes the flow path of the bypass pipe 13 and stop gas injection.

That is, when liquid refrigerant is mixed into the injection gas, the discharge temperature of the compressor 1 decreases. However, the discharge temperature depends on the operating frequency of the compressor 1 by the inverter 1a, that is, whether the compression capacity is large or small. It fluctuates greatly depending on operating conditions such as temperature and room temperature. For this reason, it is difficult to determine, simply by detecting a drop in the discharge temperature, whether this is due to a change in operating conditions or due to the mixing of liquid refrigerant into the injection gas.

On the other hand, the discharge side temperature difference is a predetermined temperature difference (reference temperature difference) because when the discharge temperature decreases in accordance with a change in the operating conditions, the condensing temperature also changes to some extent. It is held above. On the other hand, when the discharge temperature is lowered due to the mixing of the liquid refrigerant into the injection gas, the condensing temperature does not change much. Therefore, the discharge-side temperature difference at this time is smaller than the above-described reference temperature difference.

Therefore, by comparing the discharge-side temperature difference with the reference temperature difference, it is possible to determine that the liquid refrigerant has been mixed into the injection gas, and based on this determination result, the gas injection is stopped. By doing so, the liquid compression state in the compressor 1 can be quickly stopped. Accordingly, the compressor 1 can be operated with the reliability ensured without providing a gas-liquid separator having an excessive capacity.

An air conditioner according to a second aspect is characterized in that the reference temperature difference is determined based on the operating frequency of the compressor 1 by the inverter 1a.

That is, the discharge-side temperature difference when the liquid refrigerant is not mixed in the injection gas has a correlation with the operating frequency of the compressor 1 such that the lower the temperature, the smaller the difference.

For this reason, for example, when the above-mentioned reference temperature difference is uniformly determined without depending on a change in the operating frequency, the reference temperature difference is set to a smaller value based on the discharge-side temperature difference when the operating frequency is low. Value will be set. At this time, for example, even when the liquid refrigerant is mixed during the gas injection at a high operating frequency and the discharge side temperature difference is gradually reduced, this temperature difference is maintained at the above-mentioned reference temperature difference. The time until it becomes smaller than that is detected becomes longer.

Therefore, by setting the reference temperature difference for each operation frequency based on the above-mentioned correlation, for example, the state of mixing of the liquid refrigerant when the operation frequency is high can be detected more quickly. By stopping the injection, the reliability of the compressor 1 is further improved.

According to a third aspect of the present invention, the reference temperature difference is further determined based on the ambient temperature around the heat exchanger on the side of the outdoor heat exchanger 8 and the indoor heat exchanger that functions as a condenser. It is characterized by having.

That is, the outdoor heat exchanger 8 functions as a condenser during the cooling operation, and the indoor heat exchanger functions as the condenser during the heating operation. The higher the ambient temperature in these heat exchangers, the greater the difference in discharge-side temperature. Therefore, by setting the reference temperature difference based on the correlation with the ambient temperature around the heat exchanger on the condenser side, the occurrence of the liquid refrigerant mixing state in the injection gas can be determined even more quickly. Therefore, the reliability of the compressor 1 is further improved.

In the air conditioner of the fourth aspect, the reference temperature difference is further determined based on the ambient temperature around the heat exchanger on the side of the outdoor heat exchanger 8 and the indoor heat exchanger that functions as an evaporator. It is characterized by having.

That is, the evaporation temperature in the indoor heat exchanger during the cooling operation and the evaporation temperature in the outdoor heat exchanger 8 during the heating operation also change in accordance with the level of the ambient temperature, as described above. Change. Therefore, by setting the reference temperature difference based on the correlation with the ambient temperature around the heat exchanger on the evaporator side, the occurrence of the mixed state of the liquid refrigerant is determined more quickly. The reliability of the compressor 1 is improved.

[0023]

Next, a specific embodiment of the air conditioner of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a refrigerant circuit diagram showing a configuration inside an outdoor unit in a separate type air conditioner. As shown
A compressor 1 is installed in the outdoor unit, and a discharge pipe 2 of the compressor 1 and a suction pipe 4 provided with accumulators 3, 3 are connected to a four-way switching valve 5, respectively. . The compressor 1 has an inverter 1a for controlling the rotation speed, that is, the compression capacity.

The four-way switching valve 5 is connected to a first gas pipe 6 at one switching port and a second gas pipe 7 to the other switching port. An outdoor heat exchanger 8 is connected to the second gas pipe 7.
A first liquid pipe 10 provided with an electric expansion valve 9 as a pressure reducing mechanism, a gas-liquid separator 11, and a second liquid pipe 12 provided with an electric expansion valve 9 'are sequentially connected. ing.

Although not shown, an indoor unit equipped with an indoor heat exchanger is connected between the end of the second liquid pipe 12 and the end of the first gas pipe 6 through a communication pipe. Thus, a refrigerant circulation circuit is formed in which the refrigerant discharged from the compressor 1 passes through the outdoor heat exchanger 8 and the indoor heat exchanger and is returned to the compressor 1.

That is, when the compressor 1 is operated with the four-way switching valve 5 located at the switching position shown by the solid line in the figure, the refrigerant discharged from the compressor 1 circulates along the solid line arrow in the figure,
At this time, while the outdoor heat exchanger 8 functions as an evaporator and absorbs heat from the outside, the indoor heat exchanger functions as a condenser, and the heat is radiated to perform indoor heating.

On the other hand, by switching the four-way switching valve 5 from the above,
By circulating the refrigerant discharged from the compressor 1 along the dashed arrow in the drawing, a cooling operation is performed in which the outdoor heat exchanger 8 functions as a condenser and the indoor heat exchanger functions as an evaporator.

The gas-liquid separator 11 interposed between the first liquid pipe 10 and the second liquid pipe 12 is further connected to an intermediate port of the compressor 1 by a bypass pipe 13. An opening / closing valve 14 composed of an electromagnetic valve is interposed in 13.

In the closed vessel-shaped gas-liquid separator 11, the first liquid pipe 10 and the second liquid pipe 12 are connected to the gas-liquid separator 1.
1, while the bypass pipe 13 opens at a position near the upper wall of the gas-liquid separator 11.
Thus, for example, the refrigerant that has flowed into the gas-liquid separator 11 from the second liquid pipe 12 during the heating operation, if a gas component is mixed therein, is converted into a gas phase and a liquid phase.
The liquid refrigerant is separated into upper and lower parts in the inside, and the separated liquid refrigerant is supplied to the first liquid pipe 10. Also, during the cooling operation, similarly, the refrigerant from the first liquid pipe 10 is vertically separated into a gas phase and a liquid phase in the gas-liquid separator 11, and the separated liquid refrigerant is separated into the second liquid pipe. 12.

On the other hand, the gas refrigerant separated upward in the gas-liquid separator 11 is returned to the compressor 1 through the bypass pipe 13 if the above-mentioned on-off valve 14 is opened, and this gas refrigerant is The gas refrigerant returned from the accumulator 3 is compressed and discharged by the compressor 1 (hereinafter, the on-off valve 14 is opened and the gas in the gas-liquid separator 11 is passed through the bypass pipe 13). Compressor 1
The operation of returning gas to gas is called gas injection.)

By performing the above gas injection, a heating operation or a cooling operation with an increased refrigerating capacity can be performed as described above. However, in the operation using such gas injection, when the amount of the liquid refrigerant in the gas-liquid separator 11 increases and the liquid level approaches the opening end of the bypass pipe 13, the bypass pipe 13 The liquid refrigerant is likely to be mixed into the gas refrigerant returned to the compressor 1 through the compressor. When the refrigerant mixed with the liquid refrigerant is returned to the compressor 1, liquid compression occurs in the compressor 1. If the liquid compression state continues, the reliability of the compressor 1 decreases.

Therefore, in the present embodiment, the entire air conditioner is monitored, and while the compression capacity of the compressor 1, that is, the rotational speed thereof is determined in accordance with the load, frequency control is performed.
Apart from an air conditioning control device (not shown) for controlling the heating operation or the cooling operation, a gas injection monitoring and control device (gas injection monitoring and control means) is provided to prevent the reliability of the compressor 1 from being reduced due to the above-described gas injection. 15 is further provided.

The monitoring and control by this device 15 is performed by the compressor 1
A discharge temperature sensor 16 attached to the discharge pipe 2 to detect the discharge temperature of the outdoor heat exchanger 8, and an outdoor temperature sensor attached to the outdoor heat exchanger 8 to detect the condensation temperature or the evaporation temperature in the outdoor heat exchanger 8. A heat exchanger temperature sensor 17, an outside air temperature sensor 18 disposed near the outdoor heat exchanger 8 for detecting the outside air temperature, and an evaporating temperature or a condensing temperature in the above-mentioned indoor heat exchanger. Each detected temperature signal from an indoor heat exchanger temperature sensor 19 attached to the indoor heat exchanger and a room temperature sensor 20 arranged near the indoor heat exchanger for detecting room temperature, and compression by the inverter 1a. This is performed based on the operating frequency of the machine 1. Hereinafter, the control procedure will be described with reference to FIG.

When the air-conditioning operation is started by the air-conditioning control device, at the same time, the monitoring control by the gas injection monitoring and control device 15 is started.
First, as an initial setting, a timer for preventing erroneous detection described later is reset (step S1). Next, it is determined whether or not the on-off valve 14 provided in the bypass pipe 13 is ON, that is, whether or not the on-off valve 14 is in an open state in order to perform gas injection through the bypass pipe 13. (Step S2).

If the on-off valve 14 is off, step S
The process returns from step 2 to S1, and the processing of steps S1 and S2 is repeated. As a result, a standby state is established until the on-off valve 14 is turned ON. When the operating frequency of the compressor 1 controlled according to, for example, a change in the air conditioning load exceeds a predetermined frequency, the air conditioning control device performs an ON operation of the on-off valve 14, thereby starting gas injection. Then, this is determined in step S2, and the process proceeds from step S2 to S3.

In step S3, it is determined whether the operation mode is the cooling mode. If the operation mode is the cooling mode, then in step S4, the discharge temperature detected by the discharge temperature sensor 16 and the outdoor heat exchanger temperature The outdoor heat exchanger temperature detected by the sensor 17, that is, the temperature difference Tc from the condensing temperature is compared with a cooling reference temperature difference Ac to be described later. If Tc is equal to or greater than Ac, the process returns to step S1.
If there is no change in each determination result in S4, steps S1 to S4
The process of S4 is repeated, and the gas injection operation is continued.

If it is determined in step S4 that the temperature difference Tc has fallen below the reference temperature difference Ac during the repetition of the above-described processing, that is, during the continuation of the gas injection operation, the time counting by the timer is performed. It is started (step S5), and then, through step S6 for determining whether or not the time measured by this timer has reached a predetermined time t _OV ,
The process returns to step S2. Therefore,
Thereafter, if there is no change in the determination results in steps S2 to S4 and S6, the processes in steps S2 to S6 are repeated until the time measured by the timer reaches the predetermined time t _OV .

Then, in step S6, a predetermined time t
_When it is determined that the _OV has elapsed, that is, the state where the temperature difference Tc between the discharge temperature and the outdoor heat exchanger temperature is smaller than the cooling reference temperature difference Ac has continued for a predetermined time t _OV ,
The process shifts from step S6 to S7, and in this step S7, an OFF signal for closing the on-off valve 14 is output to the air conditioning control device, whereby control for turning off the gas injection operation is performed. .

If the temperature difference Tc becomes larger than the reference temperature difference Ac before the predetermined time t _OV elapses, the process returns from step S4 to S1, and the timer is reset in step S1. After being performed, the above processing is repeated. This prevents erroneous detection when the decrease in the temperature difference Tc is temporary, such as when noise is mixed into the detected temperature signal, and the gas injection operation is continued.

On the other hand, when the operation mode started by the air conditioning control device is the heating mode, steps S1 to S1 are executed.
The process proceeds from step S3 to step S8. After the operation mode is determined in step S8, in step S9, the discharge temperature and the indoor heat exchanger temperature detected by the indoor heat exchanger temperature sensor 19, that is, Also in this case, a process of comparing the temperature difference Tw with the temperature of the heat exchanger on the side functioning as a condenser with a heating reference temperature difference Aw described later is performed.

When the temperature difference Tw is smaller than Aw, the process proceeds from step S9 to step S5, whereby the temperature difference between the discharge temperature and the indoor heat exchanger temperature is obtained in the same manner as described above. When the state where Tw is smaller than Aw continues for the predetermined time t _OV , step S7
In, an OFF signal to the on-off valve 14 is output, and gas injection is stopped.

It should be noted that in the discrimination of the operation mode in steps S3 and S8 in FIG. 2, when the operation mode is neither cooling nor heating, for example, during defrost operation, steps S8 to S8 are executed.
1 is performed, so that steps S1 to S
3. It becomes a standby state by repeating S8.

As described above, according to the above control,
The temperature difference Tc · Tw between the discharge temperature of the compressor 1 and the condensing temperature is compared with the reference temperature difference Ac · Aw, and Tc · Tw is Ac · A.
When it becomes smaller than w, the gas injection is stopped.

That is, if liquid refrigerant is mixed into the injection gas during gas injection, the work energy of the compressor 1 is consumed for evaporating the liquid refrigerant. As a result, the discharge temperature of the compressor 1 decreases. descend. By the way, since the discharge temperature of the compressor 1 fluctuates greatly according to the operating frequency of the compressor by the inverter 1a and the operating conditions such as the outside air temperature and the room temperature, simply detecting a decrease in the discharge temperature is not enough for the operation. It is difficult to determine whether the change is due to a change in conditions or due to mixing of a liquid refrigerant into the injection gas.

On the other hand, when the discharge temperature lowers due to a change in the operating conditions, the condensing temperature also changes to some extent, so that the temperature difference between the discharge temperature and the condensing temperature (hereinafter referred to as the discharge side temperature difference) is obtained. , Is maintained at or above a predetermined temperature difference (reference temperature difference). On the other hand, when the discharge temperature decreases due to the mixing of the liquid refrigerant into the injection gas, the condensing temperature hardly changes.Therefore, the discharge-side temperature difference is reduced as the discharge temperature decreases. It becomes a value smaller than the reference temperature difference obtained.

Therefore, in the present embodiment, it is determined that the liquid refrigerant has been mixed into the injection gas by comparing the discharge-side temperature difference with the reference temperature difference, and the gas injection is performed based on the determination result. Control to stop. As a result, the liquid compression state in the compressor 1 can be quickly stopped, and its reliability can be maintained and improved.

In the present embodiment, the cooling reference temperature difference Ac and the heating reference temperature difference Aw are determined based on the operating frequency Hz of the compressor 1 by the inverter 1a and the room temperature Ti detected by the room temperature sensor 20. , Outside temperature sensor 18
From the outside air temperature To around the outdoor heat exchanger 8 detected at
Based on the following equations (1) and (2), step S4
9 is calculated each time the processing in step 9 is executed. Ac = a × Hz + b × (Ti-27 ° C.) + C × (To-35 ° C.) + D (1) Aw = g × Hz + h × (Ti-20 ° C.) + I × (To-7 ° C.) + J (2) (A, b, c, d, g, h, i, j are positive constants)

That is, when the liquid refrigerant is not mixed into the injection gas, the discharge-side temperature difference Tc · Tw is:
First, there is a correlation with the operating frequency of the compressor 1 that the lower the frequency, the smaller the operating frequency.

Therefore, in the above equations (1) and (2), each of the first
In the section, a calculation term that increases and decreases in proportion to the operating frequency Hz is provided, and thereby, by setting a reference temperature difference for each operating frequency Hz, for example, the mixing state of the liquid refrigerant when the operating frequency is high Therefore, the gas injection is stopped on the basis of the result of the determination, whereby the reliability of the compressor is further improved.

Further, the temperature difference on the discharge side has a correlation with the ambient temperature around the heat exchanger on the side functioning as a condenser such that the higher the temperature, the greater the difference.

That is, the outdoor heat exchanger 8 functions as a condenser during the cooling operation, and the indoor heat exchanger functions as a condenser during the heating operation. As the temperature is higher, condensation in these heat exchangers is less likely to occur, and accordingly, the discharge temperature and the condensing temperature change, and the discharge-side temperature difference increases.

Therefore, based on the correlation between the ambient temperature around the heat exchanger functioning as a condenser and the temperature difference on the discharge side,
In the formula (1), the third term is provided in the third term, and in the formula (2), the second term is provided with a calculation term for increasing or decreasing according to the level of the ambient temperature.

The discharge-side temperature difference also has a correlation with the ambient temperature around the heat exchanger on the side functioning as an evaporator, as the temperature is higher.

That is, during the cooling operation, the indoor heat exchanger
During the heating operation, the outdoor heat exchangers 8 each function as an evaporator. However, the higher the ambient temperature (the room temperature during the cooling operation and the outside air temperature during the heating operation) in these heat exchangers, the higher the temperature.
Evaporation becomes easier in these heat exchangers, and the discharge-side temperature difference increases accordingly.

Therefore, based on the correlation between the ambient temperature around the heat exchanger functioning as an evaporator and the temperature difference on the discharge side,
In the expression (1), the second term is provided, and in the expression (2), the third term is provided with an operation term that increases or decreases according to the level of the ambient temperature.

By using the function composed of these calculation terms to determine the reference temperature difference Ac · Aw while calculating it sequentially, it is possible to quickly and surely detect the occurrence of the mixed state of the liquid refrigerant in the injection gas. This makes it possible to perform operation utilizing gas injection as much as possible without impairing the reliability of the compressor 1.

As described above, the lower the operating frequency, the smaller the temperature difference on the discharge side when there is no liquid refrigerant mixed in the injection gas. In the range, the change in the temperature difference on the discharge side due to the mixing of the liquid refrigerant cannot be sufficiently determined, and erroneous detection may occur. Therefore, in the present embodiment, the control for determining and determining the reference temperature difference Ac · Aw based on the functional expressions (1) and (2) is as follows:
For example, the operation is performed in an operation range of 30 Hz or more, and in the region below the operation frequency, the air-conditioning control device uniformly controls the gas injection OFF.
However, during operation at a low frequency, the amount of the refrigerant circulating in the refrigerant circuit is small and the flow velocity is low, so that the liquid level of the liquid refrigerant in the gas-liquid separator 11 is low and stable. For this reason, there is almost no possibility that the liquid refrigerant will be sucked out to the bypass pipe 13. Therefore, when the operation is performed at a low frequency, the gas injection ON operation can be performed on the contrary.

Although the specific embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and can be implemented with various modifications within the scope of the present invention. For example, in the above, a separate type air conditioner in which one indoor unit is connected to an outdoor unit has been described as an example, but a multi-type air conditioner configured by connecting a plurality of indoor units to an outdoor unit is also described. The present invention can be applied.

[0060]

As described above, in the air conditioner according to the first aspect of the present invention, by comparing the temperature difference between the discharge temperature of the compressor and the condensation temperature of the refrigerant with the reference temperature difference, It is determined whether or not the liquid refrigerant has been mixed into the gas refrigerant returned through the pipe, whereby control for automatically stopping gas injection is performed, so that the occurrence of liquid compression in the compressor is suppressed, and Reliability can be maintained and improved.

In the air conditioners of the second to fourth aspects, the reference temperature difference is determined based on the operating frequency of the compressor by the inverter and the outside air temperature / room temperature, so that the liquid refrigerant can be mixed more quickly and. It is possible to reliably detect, and it is possible to further maintain and improve the reliability of the compressor.

[Brief description of the drawings]

FIG. 1 is a refrigerant circuit diagram additionally showing a control block diagram of a configuration inside an outdoor unit of an air conditioner according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a procedure of gas injection monitoring control in the air conditioner.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Compressor 1a Inverter 2 Outdoor heat exchanger 10 1st liquid pipe 11 Gas-liquid separator 12 2nd liquid pipe 13 Bypass piping 14 On-off valve 15 Gas injection monitoring control device (gas injection monitoring control means)

Claims (4)

[Claims] An outdoor heat exchanger (8) and an indoor heat exchanger are sequentially connected to a compressor (1) having a variable compression capacity by an inverter (1a) to form a refrigerant circulation circuit, and an outdoor heat exchanger. Liquid pipe (10) (1) between (8) and the indoor heat exchanger
A gas-liquid separator (11) is interposed in 2), and the gas refrigerant in the gas-liquid separator (11) is compressed between the gas-liquid separator (11) and the suction side of the compressor (1). An air conditioner provided with a bypass pipe (13) for gas injection returned to the compressor (1) and an on-off valve (14) for opening and closing a flow path through the bypass pipe (13), (1)
When the temperature difference between the discharge temperature of the refrigerant and the condensation temperature of the refrigerant circulating in the refrigerant circuit becomes smaller than the reference temperature difference,
Gas injection monitoring control means (15) for closing the on-off valve (14) to stop gas injection
An air conditioner comprising: 2. The method according to claim 1, wherein the reference temperature difference is calculated by an inverter (1a).
The air conditioner according to claim 1, wherein the air conditioner is determined based on an operating frequency of the compressor (1). 3. The method according to claim 1, wherein the reference temperature difference is further determined based on an ambient temperature around the heat exchanger on the side of the outdoor heat exchanger (8) and the indoor heat exchanger that functions as a condenser. The air conditioner according to claim 2, wherein 4. The method according to claim 1, wherein the reference temperature difference is further determined based on an ambient temperature around the heat exchanger on the side of the outdoor heat exchanger (8) and the indoor heat exchanger that functions as an evaporator. The air conditioner according to claim 3, wherein