JPH03177757A - Air conditioner - Google Patents

Abstract

PURPOSE:To improve the utilization of heat exchangers by making it possible to change one of the heat exchangers connected in parallel with one another over to an evaporator and a condenser. CONSTITUTION:When a gas pipe of a heat exchanger 22 is allowed to communicate to the suction pipe of a compressor 21 by a three-way valve 9, the heat exchanger 22 works as an evaporator, and simultaneous operations that evaporate refrigerants having different evaporation temperatures are carried out by a heat exchanger 12 and the heat exchanger 22. In this case, both heat exchanger have different evaporation temperatures if their heat absorption sources are different from each other, while their evaporation temperatures become equal if their heat absorption sources are equal, by a check valve 3a provided on the way of a bypass 2 connecting the suction pipe 16 of a compressor 11 with the suction pipe 26 of the compressor 21. When the gas pipe of the heat exchanger 22 is allowed to communicate to a branched passage 29 by the three-way valve 9, the heat exchanger 22 works as a con denser, and simultaneous condensation operations can be carried out by the heat exchanger 22 and a heat exchanger 32. In this case, both heat exchangers have different condensation temperatures if their heat radiation sources are different from each other, while their condensa tion temperatures become equal if their heat radiation sources are equal, by a check valve 3b provided on the way of the outlet pipe of the compressor 21.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an air conditioner in which a pair of a heat exchanger and a compressor connected in series are arranged in parallel in a refrigerant circuit. Concerning measures to improve equipment utilization and operational efficiency.

(Prior Art) Conventionally, as disclosed in, for example, Japanese Utility Model Publication No. 18933/1983, a first compressor (a+) and a first heat exchanger (b
l) and the first pressure reducing valve (cl) are connected in series by the first piping (dl), and the first compressor (a;'), the second heat exchanger (bl) and the second pressure reducing valve (C2) are connected in series. 2nd piping (dl)
and a third heat exchanger (b3) is interposed in the third pipe (d3), and the third heat exchanger (b3) and the second heat exchanger (b3) are connected in series to the third pipe (d3). The first and second piping (d+) so that the exchanger (bl) functions as an evaporator.

(dl) in parallel, each heat exchanger (b
An air conditioner that can maintain the evaporation pressures at + ) and (bz ) at different values corresponding to different heat absorption sources, and can perform the dehumidifying function without reducing the so-called refrigeration efficiency EER. This is a known technique.

(Problem to be Solved by the Invention) However, in the above conventional system, each heat exchanger (b+
), (b1), each heat exchanger (b+) has the advantage of being able to set the evaporation pressures of (bl) to different values.

There is a problem in that the overall operating efficiency cannot necessarily be made sufficiently high depending on the state of the heat absorption source (bl).

Also, 1st. Since the second heat exchangers (bl) and (bz) are both fixed so that they can only function as evaporators, they cannot be fully utilized, so the advantage of having two compressors is There aren't many. That is, for example, if the second heat exchanger (BL) is a heat storage coil placed in a heat storage tank, it can only be used to store cold heat, and a separate coil is required to extract cold heat. becomes. On the other hand, those that store warm heat can only be used to extract the stored warm heat, and there is a problem in that a separate coil is required to store the warm heat.

The present invention has been made in view of the above, and its purpose is to improve the utilization of heat exchangers by allowing one of the heat exchangers connected in parallel to be switched between an evaporator and a condenser. In addition, when simultaneous evaporation or simultaneous condensation is performed in each heat exchanger, the operational efficiency can be improved by taking measures to change the evaporation temperature or condensation temperature according to changes in the heat absorption or heat radiation source. The aim is to improve the

(Means for Solving the Problems) In order to achieve the above object, the first means for solving the problems is as shown in FIG.
(11), a first heat exchanger (12) and the first heat exchanger (12) disposed in sequence on the suction side of the first compressor (11);
) are connected in series through the first pipe (14), and the second compressor (21) and the m2 compressor (21
) and a second heat exchanger (22) arranged sequentially on the suction side of the second heat exchanger (22) and a second flow rate control valve (23) for the second heat exchanger (22) are connected in series by a second pipe (24). , a third heat exchanger (32) and a third flow control valve (33) for the third heat exchanger (32) are connected in series by a third pipe (34), On the other hand, the above 1. Second piping (14)
, (24) are connected in parallel with each other.

A branch line (29) bypass-connects the discharge pipe of the second compressor (21) and the gas pipe of the second heat exchanger (22).
) and the second gas heat tube of the second heat exchanger (22) with 'M42
a connection switching mechanism (9) that selectively connects the suction pipe of the compressor (21) to the branch path (29); and the suction pipe of the first compressor (11) and the second compressor (21). Bypass passage (2) that connects the suction pipe of the refrigerant so that the refrigerant can be bypassed.
and a first compressor (11
) and a first check valve (3a) that allows refrigerant to flow only from the suction pipe side of the second compressor (21) to the suction pipe side of the second compressor (21), and the branch at the discharge pipe of the second compressor (21). Road (29)
A second check valve (3b) is provided on the downstream side of the connection part with the second compressor (21) and allows only the flow of refrigerant from the second compressor (21) side.

As shown in FIG. 2, the second solution, in addition to the first solution, switches the refrigeration cycle between the first heat exchanger (12) and the third heat exchanger (32). A main cycle switching mechanism (7) is provided.

A third solution is to arrange a plurality of third heat exchangers (32) in the second solution, and each third heat exchanger (32) is arranged in a plurality.
2) A sub-cycle switching mechanism (8), . . . is provided for switching the gas pipes of . . . to selectively communicate with the discharge line (37) and the suction line (36).

(Function) With the above configuration, in the invention of claim (1), the gas pipe of the second heat exchanger (22) is connected to the suction pipe of the second compressor (21) by the connection switching mechanism (9). When switched to , the second heat exchanger (22) becomes an evaporator, and the refrigerant is simultaneously evaporated at different evaporation temperatures in the first heat exchanger (12) and the second heat exchanger (22). Evaporation operation is performed. At that time, the suction pipe of the first compressor (11) and the second compressor (21)
A first check valve (
3a), so the exchanger (12),
In (22), when the heat absorption sources are equal, the evaporation temperatures differ, and when the heat absorption sources change and become equal, the evaporation temperatures naturally become equal.

In addition, the connection switching mechanism (9) connects the second heat exchanger (22).
When the gas pipe is switched to communicate with the branch line (29), the second heat exchanger (22) functions as a condenser and the second
Simultaneous condensation operation in which the refrigerant is condensed simultaneously in the heat exchanger (22) and the third heat exchanger (32) becomes possible. In that case,
Since the second check valve (3b) is provided in the discharge pipe of the second compressor (21), when the heat radiation sources of the heat exchangers (22) and (32) are different, the radiation is performed at different condensation temperatures. When the heat sources change and become equal, operation is performed at equal condensing temperatures.

In other words, simultaneous evaporation operation indoors and at the heat absorption source;
Alternatively, simultaneous condensing operation can be performed indoors and at the heat radiation source, improving the usability of the second heat exchanger (22), and at the same time, the evaporation temperature can be adjusted according to changes in the heat absorption source or heat radiation source. Or, the condensing temperature is naturally adjusted to improve operational efficiency.

In the invention of claim (2), the main cycle switching mechanism (7) switches the first cycle. Third heat exchanger (12).

(32) is alternately switched between the evaporator and the condenser, making heating and cooling operation possible indoors.
By using the second heat exchanger (22), it is possible to absorb heat from a heat absorption source and radiate heat to a heat radiation source during air-conditioning operation, and in addition to the effect of the invention of claim (1), the use of the heat exchanger performance will be significantly improved.

In the invention of claim (3), in addition to the effect of the invention of claim (3), the plurality of third heat exchangers (32 ),...
The evaporator and condenser are alternately switched, and depending on the indoor air conditioning demand, it is possible to individually switch between cooling and heating operations indoors.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

FIG. 1 shows a refrigerant piping system of an air conditioner according to a first embodiment of the present invention, in which (11) is a first compressor whose operating frequency is variably adjusted by a first inverter (15);
) is placed on the suction pipe side of the first compressor (11), and is a first heat exchanger that functions as an evaporator, an outdoor heat exchanger (
13) is a first electric expansion valve as a first flow control valve for the outdoor heat exchanger (12), and each of the above-mentioned devices (11).

(12) and (13) are sequentially connected in series through a first pipe (14) so that refrigerant can flow therethrough. Also, (21)
(22) is a second compressor (21) whose operating frequency is variably adjusted by a second inverter (25);
A regenerative heat exchanger as a second heat exchanger is disposed on the suction side of the regenerative heat exchanger and is disposed in a heat storage tank (not shown) that stores water as a heat storage medium; (23) is the regenerative heat exchanger; vessel(
22) as a second flow rate control valve for each of the above-mentioned devices (21), (22), (23).
) are sequentially connected in series through a second pipe (24) so that refrigerant can flow therethrough. On the other hand, (32) is an indoor heat exchanger that is a third heat exchanger that functions as a condenser, and (33) is an indoor electric expansion valve that is a third flow rate regulating valve. 33) are connected in series through a third pipe (34) so that refrigerant can flow therethrough. Then, the first pipe (34) is connected to the third pipe (34). Second piping (14).

(24) are connected in parallel to each other, and the main refrigerant circuit (
1) is configured.

The gas pipe of the regenerative heat exchanger (22) and the second
The second discharge pipe (27), which is the discharge pipe of the compressor (21), is connected to the second discharge pipe (27) by a branch passage (29), and the branch passage (29) and the gas pipe of the regenerative heat exchanger (22) are connected. The gas pipe of the regenerative heat exchanger (22) is connected to the connection part of the second compressor (
A heat storage three-way switching valve (9) is provided as a connection switching mechanism that selectively connects the second suction pipe (26), which is the suction pipe (21), to the branch path (29).

That is, when the heat storage three-way switching valve (9) switches to the solid line side in the figure, the gas pipe of the heat storage heat exchanger (22) communicates with the second suction pipe (26), and the heat storage heat exchanger (22) evaporates. On the other hand, when the heat storage three-way switching valve (9) switches to the broken line side in the figure, the gas pipe of the heat storage heat exchanger (22) switches to the branch path (
29) to the second discharge pipe (27), so that the regenerative heat exchanger (22) functions as a condenser.

Furthermore, the first suction pipe (16), which is the suction pipe of the first compressor (11), and the second suction pipe (26), which is the suction pipe of the second compressor (21), are bypassed by a bypass path (2). connected from the first suction pipe (16) to the second suction pipe (26)
By bypassing and circulating the refrigerant to the side, it is possible to stop the first compressor (11) and operate the two heat exchangers (12) and (22) only with the second compressor (21). ,
Close the heat storage electric expansion valve (23) and close the outdoor heat exchanger (12).
It is also possible to operate only the compressors (11) and (21) with two compressors (11) and (21).

Here, as a feature of the present invention, the bypass path (2) allows only the flow of refrigerant from the first suction pipe (16) side to the second suction pipe (26) side in the bypass path (2). A functional first check valve (3a) is interposed, while a first discharge pipe (27) is provided downstream of the junction (28) with the bypass pipe (29). A second check valve (3b) is provided that prevents the refrigerant from flowing from the second compressor (21) side and only allows the refrigerant to flow from the second compressor (21) side.

Therefore, in the invention of claim (1), the regenerative heat exchanger (
Since the second heat exchanger (22) can be switched between the evaporator and the condenser by the heat storage three-way switching valve (connection switching mechanism) (9), the heat storage heat exchanger (22) can be switched to the heat storage tank. It can be used for heat storage and for recovering heat from the heat storage tank. For example, when storing warm heat in a heat storage tank, the heat storage three-way switching valve (9) is switched to the side shown by the broken line in the figure. The refrigerant discharged from the second compressors (11) and (21) is transferred to the indoor heat exchanger (
32) and the regenerative heat exchanger (22) side, and the indoor heat exchanger (32) side performs heating operation, while the refrigerant condenses on the regenerative heat exchanger (22) side and becomes the heat storage medium of the heat storage tank. Simultaneous operation of heating and storage of warm heat becomes possible. Also,
By switching the heat storage three-way valve (9) to the solid line side in the figure and making the heat storage heat exchanger (22) and the outdoor heat exchanger (12) each function as an evaporator, it is possible to perform the heat storage heat recovery heating operation. This makes it possible to improve the usability of the second heat exchanger (22).

In that case, the 29 heat exchangers (12) and (22) are connected to the first compressor (11) and the second compressor (21), respectively.
The first suction pipe (16) is operated to function as an evaporator, and the second suction pipe (16) is connected to the bypass passage (2) connecting between the first suction pipe (16) and the second suction pipe (26). 26
) is provided with the first check valve (3a) that only allows the refrigerant to flow through the heat exchangers (12) and (22). Can drive. In other words, since the heat absorption sources are different between the outdoor heat exchanger (12) and the regenerative heat exchanger (22), there is a risk that the coefficient of performance will deteriorate if the number of compressors is operated. (12).

By changing the evaporation temperature of (22), the coefficient of performance can be improved. In addition, if the amount of heat stored in the heat storage tank changes and the difference in heat absorption sources becomes less, each heat exchanger (12), (2
Since the evaporation temperatures of 2) naturally become the same value, the air conditioner can be operated with high operating efficiency.

For example, as in the conventional system shown in FIG.
) to (32) (the evaporation temperature for the evaporator and the condensation temperature for the condenser) change as shown in the states (1) to (3) shown in Table 1 below.

In that case, in the above state I, both the first compressor (11) and the second compressor (21) will be operated with a high coefficient of performance by changing the evaporation temperature, but in state II, Since the second compressor (21) forcibly takes warm heat from the heat storage tank which has almost no heat source, the coefficient of performance deteriorates and the overall operating efficiency decreases. However, in the circuit configuration shown in FIG. 1 above, the regenerative heat exchanger (
When the evaporation temperature of 22) tries to fall below the evaporation temperature of the outdoor heat exchanger (12), the refrigerant is bypassed from the first suction pipe (16) to the second suction pipe (26), so the evaporation temperature of both becomes lower than that of the outdoor heat exchanger (12). be equal.

Table 2 In other words, the operating conditions are as shown in Table 2 above.

In other words, by providing a bypass path (2) for circulating refrigerant between each suction pipe (16) and (26), and providing a check valve (3) in the bypass path (2), the regenerative heat exchanger ( As long as there is a sufficient heat source for heat storage heat exchanger (22),
While the evaporation temperature on the 2) side is increased, when the heat source of the heat storage tank decreases, the evaporation temperature is naturally maintained at the same evaporation temperature, improving the overall operating efficiency.

Similarly, the regenerative heat exchanger (22) and the outdoor heat exchanger (32)
When performing simultaneous condensing operation with the heat exchangers (
When the difference between the heat radiation sources of 22) and (32) is large, for example, while the water temperature in the heat storage tank is low, the second check valve (3b) maintains the difference in condensation temperature, while increasing the heat stored in the heat storage tank. When the difference in the heat radiation sources disappears, the refrigerant flows through the second check valve (3b), and the condensing temperatures of the heat exchangers (22) and (32) naturally become equal, allowing the device to operate. Increased efficiency.

Furthermore, depending on changes in operating conditions, when the amount of refrigerant to be circulated is not required, by stopping the first compressor (11), only the second compressor (21) can operate the two heat exchangers, that is, the outdoor heat exchanger. Heat exchanger (12) and regenerative heat exchanger (22)
), as well as a regenerative heat exchanger (
22) is not used and the required capacity is large, the heat storage electric expansion valve (23) is closed and one heat exchanger, that is, the outdoor heat exchanger (12) is used as the compressor (11). ).

(21) can also be operated with each such heat exchanger (12), (22) and compressor (11).

By changing the connection relationship with (21), efficient operation can be achieved in response to changes in operating conditions.

In the above embodiment, the second heat exchanger (22) is a regenerative heat exchanger, but if the second heat exchanger (22) is a heat exchanger using exhaust heat recovery, for example, an outdoor heat exchanger ( 12) The evaporation is carried out at a higher evaporation temperature different from that of 12).

Further, in the above embodiment, the first heat exchanger (12) is an outdoor heat exchanger, but the first heat exchanger (12) can also be an indoor heat exchanger. In that case, while operating the air conditioner, the connection of the heat storage three-way switching valve (9) is switched to the solid line side in the figure, and the refrigerant is evaporated in the heat storage heat exchanger (22), thereby storing cold heat in the heat storage tank. In this case, when the heat absorption sources are different, operation is performed at different evaporation temperatures, while when the heat absorption sources are changed and become equal, the evaporation temperatures are naturally adjusted to be equal. In addition, by switching the heat storage three-way switching valve (9) connection to the dashed line side in the figure and condensing the refrigerant in the heat storage heat exchanger (22), the stored cold heat can be used to perform the cold storage heat recovery cooling operation. At that time, while there is sufficient cold storage heat in the heat storage tank, the second check valve (3b) closes the first discharge pipe (
17) side to the second discharge pipe (27) side is blocked, and the condensing temperature of the storage heat exchanger (22) is operated in a state lower than the condensing temperature of the outdoor heat exchanger (12). In addition, when the amount of stored cold heat decreases, the condensation temperatures of the two are automatically adjusted to be equal, and the effect of improving operating efficiency can be obtained.

Next, regarding the second embodiment according to the invention of claim (2),
This will be explained based on FIG. FIG. 2 shows the configuration of an air conditioner according to a second embodiment, and in addition to the configuration shown in FIG. 1 above,
The outdoor four-way switching valve (7) is the main connection switching mechanism that switches the refrigeration cycle between the outdoor heat exchanger (12), which is the first heat exchanger, and the indoor heat exchanger (32), which is the third heat exchanger. is arranged, and by switching the outdoor four-way switching valve (7), the gas pipe of the outdoor heat exchanger (12) and the indoor heat exchanger (32) are connected.
) gas pipe (16) and the first suction pipe (16). The second discharge pipe (17) and the second discharge pipe (27) are alternately communicated with each other. That is, when the outdoor four-way switching valve (7) is switched to the solid line side in the figure, the indoor heat exchanger (32) becomes a condenser and heating operation is performed, while the outdoor four-way switching valve (
7) is switched to the dashed line side in the figure, the indoor heat exchanger (32) becomes an evaporator and cooling operation is performed. here,
During heating operation, heating and cold storage heat simultaneous operation or cold storage heat recovery cooling operation are performed at different condensation temperatures or evaporation temperatures depending on the operating conditions, as in the invention of claim (1) above. .

On the other hand, during cooling operation, when the heat storage three-way switching valve (9) is switched to the broken line side, the refrigerant is condensed in the heat storage heat exchanger (22) and the outdoor heat exchanger (12), thereby storing cold heat in the heat storage tank. Cooling storage and heat recovery cooling operation is carried out, and when the heat absorption sources are different, the evaporation temperatures are different, and when the heat absorption sources are changed and become equal, the evaporation temperatures are naturally adjusted to the same value, improving operational efficiency. .

Therefore, in the invention of claim (2), the above claim (1)
) In addition to the effects of the invention, it is possible to perform cooling operation indoors as necessary, and simultaneous operation of cooling and cold storage heat, cooling operation with cold storage heat recovery, and in that case, other heat exchange The condensing temperature or evaporation temperature can be naturally adjusted according to the change in the size of the heat absorption source or heat radiation source with the vessel (12) or (32), and the operational efficiency can be improved. .

Next, the invention of claim (3) will be explained based on FIG. 3. FIG. 3 shows the configuration of an air conditioner according to a third embodiment, which includes two indoor heat exchangers (32) in addition to the configuration of the air conditioner shown in FIG. 2 above.

(32) are arranged in parallel in the refrigerant circuit (1), and furthermore, on the gas pipe side of each indoor heat exchanger (32), (32),
29 indoor four-way switching valves (29) serve as sub-cycle switching mechanisms that switch the gas pipes of each indoor heat exchanger (32), (32) to selectively communicate with the discharge line (37) and the suction line (36). 8) (8) are arranged respectively. That is, each indoor heat exchanger (32), (32) is made to function as a condenser or an evaporator in response to changes in indoor demand, so that heating and cooling operations can be performed individually. In addition, (CA), ... are all capillary tubes interposed between the - connection boat of each four-way switching valve <7), (8), and (8) and the suction line (36). be.

In the invention of claim (3), in addition to the effect of the invention of claim (2), the heating and cooling operation can be switched individually according to changes in air conditioning demand in each room, and in this way, the indoor Even when total requirements change in a complex manner, the first
．． Second heat exchanger (12).

Natural adjustment of the evaporation temperature or condensation temperature of (22), each heat exchanger (12), (22) and each compressor (11),
It becomes possible to change the connection relationship with (21) or the number of operating units, resulting in a significant improvement in overall operating efficiency.

In each of the above embodiments, the connection switching mechanism was configured with the heat storage three-way switching valve (9), but the connection switching mechanism also included the second suction pipe (26) (or second discharge pipe (27)) and the branch path 2
It goes without saying that the connection of the gas pipes of the second heat exchanger (22) can be changed by interposing an on-off valve in each of the heat exchangers (9) and switching the opening and closing of the valve.

(Effects of the Invention) As explained above, according to the invention of claim (1), the first. The second heat exchanger is connected to the first heat exchanger. A pair of sets connected in series on the suction side of the second compressor are connected in parallel to the third heat exchanger, and the gas pipes of the second heat exchanger are connected to the discharge pipe and suction pipe of the second compressor. In addition, the suction pipe of the first compressor and the suction pipe of the second compressor are connected by a bypass, and refrigerant flows from the suction pipe side of the first compressor into the bypass passage. A first check valve is provided that allows only
Since the second check valve that only allows the flow of refrigerant from the second compressor side is provided in the discharge pipe, by making the second heat exchanger function as both the evaporator and the condenser, the second check valve can function as both the evaporator and the condenser. a simultaneous evaporation operation in which the evaporation temperature of the refrigerant is naturally adjusted in accordance with changes in the heat absorption source in the second heat exchanger; In the third heat exchanger, a simultaneous condensing operation in which the condensing temperature of the refrigerant is naturally adjusted according to changes in the heat radiation source is possible, and therefore the usability and operating efficiency of the heat exchanger can be improved.

According to the invention of claim (2), in the invention of claim (1), the refrigeration cycle is alternately switched between the first heat exchanger and the third heat exchanger, so that heating and storage of heat can be achieved. Simultaneous heating operation, storage heat recovery heating operation.

Simultaneous cooling and cold storage heat operation and cold storage heat recovery cooling operation can be performed, and therefore, in addition to the effect of the invention of claim (1), the usability of the heat exchanger can be significantly improved.

According to the invention of claim (3), in addition to the invention of claim (3), a plurality of third heat exchangers are arranged, and the gas pipe of each third heat exchanger is connected to a discharge line and a suction line. Since the switch is made to selectively communicate with the
In addition to the effects of the invention, each third heat exchanger can be individually switched between evaporation operation and condensation operation.

[Brief explanation of drawings]

1 to 3 show embodiments of the present invention, and FIG. 1 is a first embodiment of the present invention.
FIG. 2 is a refrigerant piping system diagram showing the configuration of the air conditioner according to the second embodiment. FIG. 3 is the refrigerant piping system diagram showing the configuration of the air conditioner according to the second embodiment. 3
1 is a refrigerant piping system diagram showing the configuration of an air conditioner according to an example. FIG. 4 is a refrigerant piping system diagram showing the configuration of a conventional air conditioner. 1 Main refrigerant circuit 3a First check valve 3b Second check valve 7 Outdoor four-way switching valve (main cycle switching mechanism) 8 Indoor four-way switching valve (sub-cycle switching mechanism) 9 Heat storage three-way switching valve (connection switching mechanism) 11.21 1st. Second compressor 12 Outdoor heat exchanger (first heat exchanger) 22 Regenerative heat exchanger (second heat exchanger) 32 Indoor heat exchanger (third heat exchanger) 13 Outdoor electric expansion valve (first flow rate adjustment valve) 23 Heat storage electric expansion valve (second flow rate control valve) 33 Indoor electric expansion valve (third flow ffi control valve) 14°24°4 1st to 3rd piping 29 Branch path diagram

Claims (3)

[Claims] (1) A first compressor (11), a first heat exchanger (12) disposed in sequence on the suction side of the first compressor (11), and the first
A first flow rate control valve (13) for the heat exchanger (12) is connected in series with the first pipe (14), and sequentially connected to the second compressor (21) and the suction side of the second compressor (21). The second heat exchanger (22) to be arranged and the second flow rate control valve (23) for the second heat exchanger (22) are connected in series with the second pipe (24), while the third heat exchanger (32) and a third flow rate control valve (33) for the third heat exchanger (32) are connected in series by a third pipe (34), and the first, A branch line (29) connecting the second pipes (14) and (24) in parallel with each other and bypass-connecting the discharge pipe of the second compressor (21) and the gas pipe of the second heat exchanger (22). )
and the gas pipe of the second heat exchanger (22) is connected to the second compressor (21).
) and a connection switching mechanism (9) that selectively connects the suction pipe of the first compressor (1
a bypass passage (2) connecting the suction pipe of 1) and the suction pipe of the second compressor (21) so that the refrigerant can be bypassed; a first check valve (3a) that allows refrigerant to flow only from the suction pipe side of the second compressor (21) to the suction pipe side of the second compressor (21);
1), a second check valve (3b) is provided on the downstream side of the connection with the branch path (29) and allows flow of refrigerant only from the second compressor (21) side. An air conditioner characterized by: (2) Main cycle switching mechanism (7) that switches the refrigeration cycle between the first heat exchanger (12) and the third heat exchanger (32)
) The air conditioner according to claim (1). (3) A plurality of third heat exchangers (32) are arranged,
A sub-cycle switching mechanism (8), . . . that switches the gas pipes of the third heat exchangers (32), . The air conditioner according to claim 2, further comprising: an air conditioner.