JP2007263443A - Air conditioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To bring out higher heating capability by conducting the control to increase the quantity of a refrigerant sucked in a high stage compressor and a low stage compressor to solve a problem with a prior art wherein it is difficult to individually control a sub-cool quantity in heating a plurality of interior units to cause insufficient capability of individual interior units. <P>SOLUTION: This air conditioner includes a refrigerant circuit having the low stage compressor 1a, the high stage compressor 1b and a plurality of interior units , wherein the air condition further includes: an injection piping 18 diverging from the refrigerant circuit from first and second flow control devices 4A, 4B to be connected to the suction side of the high stage compressor 1b; a second flow control device 6 disposed in the injection piping 18; a third flow control device 13 disposed in the refrigerant circuit to the heat source side heat exchanger 3; a first pressure detecting means 10 for detecting the refrigerant pressure of the refrigerant circuit to the third flow control device 13; and a control device 20 for controlling the opening of the third flow control device 13 based on the detection value of the first pressure detecting means 10. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an air conditioner that allows a part of refrigerant condensed by a condenser to flow between a low-stage compressor and a high-stage compressor.

  Conventionally, an air conditioner of this type is known, for example, described in Patent Document 1 below. The air conditioning apparatus described in Patent Document 1 is shown in FIG. This air conditioner includes a compressor 101 having a first compression chamber 103 and a second compression chamber 104, a use side heat exchanger (condenser) 110, a flow rate control device 111, a gas-liquid separator 125, a flow rate control device 114, And it has the refrigerant circuit which connects the heat-source-unit side heat exchanger (evaporator) 115 by cyclic | annular piping connection. Further, switching means 118 that connects the discharge port 105 of the first compression chamber to the suction port 107 of the second compression chamber and a pipe that communicates with the compressor 101, and the first compression chamber when the compressor 101 is operated in parallel. And a bypass circuit 122 that causes the refrigerant to flow by bypassing 103.

JP-A-5-149634

  In the conventional air conditioner described above, the flow control is performed when there is a difference in height between the outdoor unit and the indoor unit, or when the piping length is long, in a system that individually controls the subcooling amount during heating of a plurality of indoor units. When the pressure between the device 111 and the flow control device 114 increases too much, the pressure difference between the front and rear of the flow control device 111 becomes small, and it is difficult to individually control the heating subcooling amounts of the plurality of indoor units. May lead to insufficient heating capacity. Conversely, if the pressure between the flow control device 111 and the flow control device 114 decreases too much, the amount of refrigerant returning from the valve 124 to the compressor 101 may decrease, leading to insufficient heating capacity.

In addition, when a plurality of indoor units are repeatedly operated and stopped, the compressor is frequently started and stopped, and the gas refrigerant that cannot be condensed in the indoor unit unless the valve 24 is closed for an arbitrary time. Therefore, there is a problem that the discharge temperature of the compressor rises and the operation is not stable.

In order to solve the above-described problems, an air conditioner according to the present invention is connected in parallel with a low-stage compressor and a high-stage compressor that compresses and discharges the refrigerant from the low-stage compressor. A plurality of sets of use side heat exchangers and first flow rate control devices, and a heat source machine side heat exchanger have a refrigerant circuit sequentially connected in an annular shape, and the heat source machine side heat from the first flow rate control device. An injection pipe branched from the refrigerant circuit to the exchanger and connected to the suction side of the high-stage compressor, a second flow rate control device provided in the injection pipe, and the heat source unit from the branch position of the injection pipe A third flow control device provided in the refrigerant circuit to the side heat exchanger, and a first pressure for detecting the refrigerant pressure in the refrigerant circuit from the branch position of the injection pipe to the third flow control device And a flow control device control means for controlling the opening of the third flow control device so that the detection value of the first pressure detection device approaches the control target value of the first pressure detection device. It has a configuration provided.

  According to the air conditioner of the present invention, the refrigerant circuit from the first flow rate control device to the heat source unit side heat exchanger and the suction side of the high stage compressor are injected by the injection pipe having the second flow rate control device. The third flow rate control device is provided in the refrigerant circuit from the branch position of the injection pipe to the heat source unit side heat exchanger, and the refrigerant pressure of the refrigerant circuit from the branch position of the injection pipe to the third flow rate control device is set to the first. And the opening degree of the third flow control device is controlled so that the detected value of the first pressure detecting means approaches the control target value of the first pressure detecting means. When the condensing temperature in the use side heat exchanger is low and the heating capacity is not high, the high flow side compressor is reduced by reducing the opening of the third flow control device and increasing the amount of refrigerant flowing into the injection pipe. And low stage Making it possible to control to increase the amount of refrigerant that sucked into the compressor, it is possible to draw a higher heating capacity.

Embodiment 1 FIG.
Embodiment 1 according to the present invention will be described below.
FIG. 1 shows an example of an overall configuration centering on a refrigerant circuit of an air-conditioning apparatus according to Embodiment 1 of the present invention.
In FIG. 1, this air conditioner heats a low-stage compressor 1a, a high-stage compressor 1b that further compresses and discharges the refrigerant from the low-stage compressor 1a, and a refrigerant flow path of the refrigerant circuit. A four-way valve 2 for switching between cooling and cooling, a set of the use side heat exchanger 5A and the first flow rate control device 4A, and a set of the use side heat exchanger 5B and the first flow rate control device 4B connected in parallel. The gas-liquid separator 14, the third flow rate control device 13, and the heat-source-unit-side heat exchanger 3 have a refrigerant circuit that is pipe-connected in this order.

From the gas-liquid separator 14 arranged in the refrigerant circuit from the first flow rate control devices 4A, 4B to the heat source unit side heat exchanger 3, the injection pipe 18 branches and the low stage side compressor 1a discharge side and the high stage are branched. It is connected to a connecting pipe 22 that connects the side compressor 1b suction side. The pipe end opening 18 a of the injection pipe 18 is disposed at the liquid refrigerant suction position in the gas-liquid separator 14. The injection pipe 18 is provided with a second flow rate control device 6 and a check valve 12. The check valve 12 is arranged in the injection pipe 18 in such a direction that allows the refrigerant to flow only in the direction toward the connection pipe 22. In the injection pipe 18 between the second flow control device 6 and the check valve 12, the refrigerant passing through the heat exchanging portion 7 </ b> B of the injection pipe 18 is transferred from the gas-liquid separator 14 to the heat source unit side heat exchanger 3. For example, a double-pipe type heat exchanger 7 for injection is provided to exchange heat with the refrigerant passing through the heat exchanger 7A of the circuit. The injection pipe 18 between the heat exchanging part 7B of the heat exchanger 7 for injection and the check valve 12 is connected to a refrigerant circuit on the suction side of the low-stage compressor 1a via a connection pipe 19 having the solenoid valve 11. Yes. The refrigerant circuit from the heat exchanger for injection 7 to the third flow rate control device 13 is provided with first pressure detecting means 10 for detecting the refrigerant pressure at that position.

Further, on the discharge side of the high-stage compressor 1b, a second pressure detecting means 8 for detecting the high-pressure refrigerant pressure and a first temperature detecting means 15 for detecting the high-pressure refrigerant temperature are provided. The first flow rate control devices 4A and 4B are provided with throttle opening degree detection means 21A and 21B for detecting the respective opening degrees. Second temperature detection means 16A and 16B are provided in the refrigerant circuit between the use side heat exchangers 5A and 5B and the first flow rate control devices 4A and 4B, respectively. A third temperature detection means 17 for detecting the outdoor temperature is provided outside the outdoor unit. The control device 20 is a device that performs control according to the present embodiment.
In this air conditioner, the compressors 1a and 1b, the four-way valve 2, the heat source device side heat exchanger 3, the gas-liquid separator 14, the control device 20 and the like are arranged in the heat source device. In addition, the set of the first flow control device 4A and the use side heat exchanger 5A is provided in one indoor unit, and the set of the first flow control device 4B and the use side heat exchanger 5B is provided in the other indoor unit. Has been.

  As shown in FIG. 2, the control device 20 includes a general-purpose CPU 23, a memory M, a data bus 24, and the like. The CPU 23 controls the flow rate control device control means 25, the first pressure target value setting means 26, the second pressure target value setting means 27, the third pressure target value setting means 28, and the subcool amount, all of which will be described in detail later. Each function of the detection means 29 and the flow control device closing means 30 is provided. In addition, you may provide the control apparatus 20 which has each said function not in a heat source machine but in any indoor unit.

  Next, the flow of the refrigerant in the refrigerant circuit shown in FIG. 1 will be described with reference to FIG. In the present invention, “cooling only operation” is not directly related, but the cooling operation will be described for reference. The high-temperature and high-pressure gas refrigerant discharged from the low-stage compressor 1a and further compressed and discharged by the high-stage compressor 1b passes through the four-way valve 2 and exchanges heat with outdoor air in the heat source apparatus-side heat exchanger 3. Then, the liquid is condensed and liquefied, and further cooled by the heat exchange section 7A of the heat exchanger 7 for injection via the third flow rate control device 13 which is fully opened. The refrigerant cooled by the heat exchange unit 7A is separated into gas and liquid by the gas / liquid separator 14, and then a part of the refrigerant is depressurized by the first flow control devices 4A and 4B, and the indoor air is used by the use side heat exchangers 5A and 5B. After evaporating and gasifying through heat exchange and passing through the four-way valve 2, it returns to the suction side of the low-stage compressor 1a. On the other hand, a part of the refrigerant separated by the gas-liquid separator 14 is decompressed by the second flow rate control device 6 and exchanges heat with the refrigerant of the heat exchange unit 7A by the heat exchange unit 7B of the heat exchanger 7 for injection. It evaporates and flows into the suction side of the low-stage compressor 1a via the electromagnetic valve 11 in the open state. When the electromagnetic valve 11 is open, the refrigerant does not pass through the check valve 12 due to the pressure state.

On the other hand, in the “heating operation” according to the present embodiment, as shown in FIG. 3, the refrigerant discharged from the high-stage compressor 1 b passes through the four-way valve 2 and then passes through the indoor air in the use-side heat exchangers 5A and 5B. Heat-condensed into condensed liquid and decompressed by the first flow rate control devices 4A and 4B to be in a gas-liquid two-phase state. The refrigerant in the gas-liquid two-phase state is cooled by the heat exchanger 7A of the injection heat exchanger 7 in a state where a part of the gas phase is increased after being separated by the gas-liquid separator 14. After being cooled to the side 7B and depressurized by the third flow rate control device 13, the heat source unit side heat exchanger 3 exchanges heat with outdoor air to evaporate gas, and after passing through the four-way valve 2, the low stage side compressor 1a Return to the suction side. On the other hand, a part of the refrigerant which has been separated by the gas-liquid separator 14 and whose liquid phase has increased is depressurized by the second flow rate control device 6 of the injection pipe 18, and the heat exchange unit 7 B of the injection heat exchanger 7. The refrigerant exchanges heat with the refrigerant in the heat exchanging section 7A to evaporate, and does not pass through the closed solenoid valve 11 but flows into the suction side of the high stage compressor 1b through the check valve 12. In addition, the operation | movement which closes the 2nd flow control apparatus 6 can also be implemented. In this case, the solenoid valve 11 is opened so that the check valve 12 is not vibrated. Further, the detection value of the first pressure detection means 10 can be controlled by controlling the opening of the third flow control device 13. Further, the superheat amount on the discharge side of the high stage compressor 1b can be controlled by controlling the second flow rate control device 6. The superheat amount on the discharge side of the high-stage compressor 1b is a value obtained by subtracting the saturation temperature obtained by conversion from the detection value of the first temperature detection means 15 from the detection value of the second pressure detection means 8. . Further, by controlling the first flow rate control devices 4A and 4B, the subcooling amounts at the outlet portions of the use side heat exchangers 5A and 5B can be controlled. The subcool amounts at the outlets of the use side heat exchangers 5A and 5B are obtained by subtracting the detection values of the second temperature detection means 16A and 16B from the saturation temperature obtained by conversion from the detection value of the second pressure detection means 8, respectively. Value.

Next, an example of the “heating control method” according to the present embodiment will be described with reference to FIG.
In FIG. 4, first, heating operation start or defrosting end is performed (step 1). At this time, the control device 20 sets the first flow rate control devices 4A and 4B to an arbitrary opening degree, fully closes the second flow rate control device 6, and keeps the third flow rate control device 13 fully open. Thus, prior to the start of the heating operation or the return from the defrosting operation to the heating operation, the flow rate control device closing means 30 of the control device 20 keeps the second flow rate control device 6 fully closed, thereby shortening the time. Even when the compressors 1a and 1b are repeatedly started and stopped, the discharge refrigerant temperature of the high-stage compressor 1b due to the inflow of the high-temperature gas refrigerant flowing from the second flow rate control device 6 to the suction side of the high-stage compressor 1b. Can be prevented. Incidentally, the gas refrigerant cannot be sufficiently condensed by the use side heat exchangers 5 </ b> A and 5 </ b> B when the compressor is activated, and the high temperature gas also flows into the second flow rate control device 6. In addition, the third flow rate control device 13 can be fully opened to prevent the compressor capacity from being insufficiently increased due to the low pressure drop after the compressor is started.

  Next, it is determined whether 10 minutes have elapsed since the start of compressor operation or the end of defrosting (step 2). When this condition is satisfied, the second flow control device 6 is opened to a predetermined opening, and the third flow control device 13 is throttled to a predetermined opening (step 3). Thereafter, the control target value of the first pressure detection means 10 and the control target value of the discharge superheat amount of the high stage compressor 1a are set (step 4). An arbitrary target value is set at the initial stage of control. Thereafter, the flow rate control device control means 25 of the control device 20 controls the opening degree of the third flow rate control device 13 according to the control target value of the first pressure detection means 10 set in step 4, and the higher stage side. The second flow rate control device 6 is controlled in accordance with the discharge superheat amount target value of the compressor 1a (step 5). After 1 minute has elapsed since the previous setting of the target value in step 4 (step 5), the control target value and the discharge superheat amount target value of the first pressure detection means 10 are reset. In the present embodiment, the control target value of the first pressure detector 10 and the control target value of the discharge superheat amount of the high stage compressor 1a are set simultaneously. It may be performed at the timing.

  The target value of the first pressure detection means 10 in step 4 is, for example, the first value when the difference obtained by subtracting the detection value of the first pressure detection means 10 from the detection value of the second pressure detection means 8 is less than 2 MPa. When the target value of the pressure detection means 10 is 1.4 MPa and the difference obtained by subtracting the detection value of the first pressure detection means 10 from the detection value of the second pressure detection means 8 is 2 MPa or more and less than 4 MPa, the first value When the target value of the pressure detection means 10 is 1.7 MPa and the difference obtained by subtracting the detection value of the first pressure detection means 10 from the detection value of the second pressure detection means 8 is 4 MPa or more, the first pressure detection means A target value of 10 is set to 2.0 MPa. Accordingly, when it is determined that the differential pressure across the first flow rate control devices 4A and 4B is small, the target value of the first pressure detection means 10 is lowered, and the differential pressure across the first flow rate control devices 4A and 4B is reduced. If it is determined that the flow rate is large, the target value of the first pressure detection means 10 is increased, and the second flow rate control device 6 passes through the control range of all the first flow rate control devices 4A and 4B. The amount of refrigerant can be increased as much as possible. Note that the target value of the first pressure detecting means 10 may be set in advance to an arbitrary value that is within the controllable range of the first flow rate control devices 4A and 4B.

The target value of the compressor discharge superheat amount of the high-stage compressor 1b in step 4 is, for example, changing the inverter power supply frequency (compressor frequency) indicating the capacity change of the low-stage compressor 1a and the high-stage compressor 1b. To change. For example, when the compressor frequency is 70 Hz or more, the target value of the compressor discharge superheat amount is 10, and when the compressor frequency is 40 Hz or more and less than 70 Hz, the target value of the compressor discharge superheat amount is 30, When the compressor frequency is less than 40 Hz, the target value of the compressor discharge superheat amount is set to 50. In this embodiment, the compressor frequencies of the low-stage compressor 1a and the high-stage compressor 1b are controlled in the same way. However, as another embodiment, the low-stage compressor 1a and the high-stage compressor 1b are used at different compressor frequencies. The side compressor 1b may be operated.

  As described above, the air conditioner according to the first embodiment is configured to control the flow rate control device of the control device 20 so that the detection value of the first pressure detection means 10 approaches the control target value of the first pressure detection means 10. Since the control means 25 controls the opening degree of the third flow rate control device 13, the third flow rate control device is used when the condensation temperature in the use side heat exchanger 3 is low and the heating capacity is not high. The amount of refrigerant flowing into the injection pipe 18 can be increased by narrowing the opening 13. Thereby, it is possible to control to increase the amount of refrigerant sucked into the high-stage compressor 1b and the low-stage compressor 1a, and higher heating capacity can be extracted. That is, when the detection value of the first pressure detection means 10 is increased too much, the pressure difference between the first flow control device 10 and the first flow control device 10 becomes small, and the plurality of first flow control devices 4A and 4B can be individually controlled. It is possible to prevent problems such as disappearance. Conversely, it is possible to prevent the heating capacity of the entire system from being lowered due to the detection value of the first pressure detection means 10 being too low.

  Further, in this air conditioner, the flow rate control device closing means 30 of the control device 20 has the second flow rate prior to the start of the low stage compressor 1a and the high stage compressor 1b or the return from the defrosting operation to the heating operation. Since the control device 6 is closed in advance, it is possible to prevent a problem that it is not possible to reach an operation state in which sufficient heating performance can be exhibited.

In this air conditioner, the gas-liquid separator 14 is provided in the refrigerant circuit between the first flow control devices 4A and 4B and the third flow control device 13, and the liquid refrigerant separated by the gas-liquid separator 14 is supplied. Since it is made to flow from the injection pipe 18 to the suction side of the high-stage compressor 1b, a large amount of refrigerant can flow into the suction side of the high-stage compressor 1b, and the refrigerant discharged from the compressor The amount can be increased.

Further, the air conditioner is configured such that a refrigerant passing through the injection pipe 18 and a refrigerant circuit between the gas-liquid separator 14 and the third flow control apparatus 13 are connected to the injection pipe 18 from the second flow control device 6. Since the injection heat exchanger 7 for exchanging heat with the passing refrigerant is provided, an efficient heating operation can be performed.

In the present embodiment, the control target value of the first pressure detection means 10 is set by the flow control device control means 25 with the detection value of the second pressure detection means 8 and the detection value of the first pressure detection means 10. However, as another embodiment, the apertures of the first flow control devices 4A and 4B of a plurality of indoor units are detected by the throttle aperture detection means 21A and 21B, respectively. The first pressure target value setting means 26 of the device 20 selects the maximum opening from the detected opening, and determines the control limit of the first flow control devices 4A and 4B based on the selected maximum opening. Thus, the control target value of the first pressure detection means 10 may be set and changed in the memory M.
As described above, the control target value of the detection value of the first pressure detection means 10 is set and changed based on the maximum opening detection value selected from the detected opening amounts of the first flow control devices 4A and 4B. By doing so, it is possible to control the detection value of the first pressure detection means 10 while confirming whether or not the first flow control devices 4A and 4B can be controlled. Thereby, the flow capacity of the 2nd flow control device 6 can be increased as much as possible within the range which all the 1st flow control devices 4A and 4B can control, and heating capacity can be increased.

Further, as another embodiment, the subcool amount detection means 29 of the control device 20 detects the subcool amounts of the first flow control devices 4A and 4B of the plurality of indoor units, respectively, and the second pressure target value of the control device 20 is detected. The setting means 27 changes the control target value of the first pressure detection means 10 to the memory M by determining the control limit of the first flow control devices 4A and 4B based on the detected maximum detected value of the subcool amount. It doesn't matter if you do.
In this way, the control target value of the detection value of the first pressure detection means 10 is changed based on the maximum opening detection value selected from the detected subcool amounts by the first flow control devices 4A and 4B. By doing so, it is possible to control the detection value of the first pressure detection means 10 while confirming whether or not the first flow control devices 4A and 4B can be controlled. As a result, it is possible to perform the control for increasing the heating capacity by increasing the flow rate of the second flow rate control device 6 as much as possible within the controllable range of all the first flow rate control devices 4A and 4B. It becomes.

As another embodiment, the third pressure target value setting means 28 is based on the difference between the detection value by the second pressure detection means 8 and the detection value by the first pressure detection means 10. It is also possible to change the setting of the control target value of the detection means 10 in the memory M.
Thus, if the control target value of the first pressure detection means 10 is changed by the difference between the detection value of the first pressure detection means 10 and the detection value of the second pressure detection means 8, the first The flow rate control devices 4A and 4B can be controlled within a controllable range, and a decrease in heating capacity can be prevented.

Embodiment 2. FIG.
The second embodiment according to the present invention will be described below.
FIG. 5 shows an example of the overall configuration centering on the refrigerant circuit of the air-conditioning apparatus according to Embodiment 2 of the present invention. 6, 7, and 8 show operation states during the cooling / heating operation in the air conditioner of FIG. 5, FIG. 6 is an operation state diagram of only cooling or heating, and FIG. 7 is a simultaneous cooling / heating operation. FIG. 8 is an operation state diagram showing a heating main operation (when the heating operation capacity is larger than the cooling operation capacity), and FIG. 8 is an operation showing a cooling main operation (when the cooling operation capacity is larger than the heating operation capacity) in the simultaneous cooling and heating operation. It is an operation state diagram. In this embodiment, a case where three indoor units are connected to one heat source unit will be described, but the same applies to the case where two or four or more indoor units are connected.
In FIG. 5, A is a heat source machine. B, C, and D are indoor units connected in parallel as will be described later, and have the same configuration. E is a first branch 70, a fourth flow rate controller 73, a second branch 71, a first gas-liquid separator 72, a first heat exchanger 79, a fifth, which will be described in detail later. It is a repeater with a built-in flow rate control device 75.

  1a is a variable-capacity low-stage compressor, 1b is a variable-capacity high-stage compressor that further compresses and discharges the refrigerant from the low-stage compressor 1a, and 2 is a refrigerant circuit of the air conditioner. Four-way valve for switching the refrigerant flow direction, 3 is a heat source machine side heat exchanger, 64 is an accumulator, 80 is a heat source machine side fan that blows outdoor air to the heat source machine side heat exchanger 3, and 27 is a refrigerant flow direction The switching valve 8 for limiting the pressure is a second pressure detecting means provided on the discharge side of the high stage compressor 1b, and the heat source unit A is constituted by these. 5 is a use side heat exchanger provided in the three indoor units B, C, D, 66 is a first connecting pipe with a large diameter connecting the four-way valve 2 of the heat source unit A and the relay E, 66b, 66c , 66d connect the use side heat exchanger 5 of the indoor units B, C, and D and the relay E, respectively, the first connection pipe on the indoor unit side corresponding to the first connection pipe 66, and 67 the heat source The second connection pipes 67b, 67c, and 67d, which have a smaller diameter than the first connection pipe 66, are connected to the indoor units B, C, and D, respectively. The use side heat exchanger 5 and the relay E are connected via the first connection pipe 66. The second connection pipe on the indoor unit side corresponding to the second connection pipe 67, 68 is the indoor unit side. Three-way connection of the first connection pipes 66b, 66c, 66d to the first connection pipe 66 side or the second connection pipe 67 side in a switchable manner The valve 4 is connected to the vicinity of each use side heat exchanger 5 and is a first flow control device that is controlled by the superheat amount during cooling on the outlet side of the use side heat exchanger 5 and by the subcool amount during heating. Are connected to the second connection pipes 67b, 67c, 67d on the indoor unit side. 70 is a first three-way switching valve 68, 68, 68 that connects the first connection pipes 66b, 66c, 66d on the indoor unit side to the first connection pipe 66 side or the second connection pipe 67 side so as to be switchable. , 71 is a second branching section made up of the second connecting pipes 67b, 67c, 67d and the second connecting pipe 67 on the indoor unit side, and 72 is a second branching pipe provided in the middle of the second connecting pipe 67. The gas phase part is connected to the first valve 8 a of each three-way switching valve 68, and the liquid phase part is connected to the second branch part 71.

73 is a fourth flow control device that can be opened and closed, such as an electric expansion valve, disposed between the first gas-liquid separator 72 and the second branch portion 71, and 74 is the second branch portion 71. The first bypass pipe connecting the first connecting pipe 66 and the first connecting pipe 66, 75 is a fifth flow control device such as an electric expansion valve provided in the middle of the first bypass pipe 74, and 76 is the first bypass pipe. 74 is provided on the downstream side of the fifth flow rate control device 75 provided in the middle of 74, and exchanges heat with the downstream portion of the second connection pipe 67 from the fourth flow rate control device 73. The heat exchanging part 79 is provided downstream of the second heat exchanging part 76 provided in the middle of the first bypass pipe 74, and is a part upstream of the fourth flow rate control device 73 of the second connecting pipe 67. The first heat exchanging units 50c, 50c, and 50d that exchange heat with each other These are seventh check valves provided in the middle of the second connection pipes 67b, 67c, 67d on the indoor unit side of the second branch part 71, and are connected to the indoor unit side from the second connection pipe 67. Refrigerant refrigerant flow is allowed only to the second connection pipes 67b, 67c, and 67d. Reference numeral 51 denotes a downstream portion of the seventh check valves 50c, 50c, 50d provided in the middle of the second connection pipes 67b, 67c, 67d on the indoor unit side of the second branch part 71 and the second connection pipe 67. Is a second bypass pipe that connects the downstream side of the fourth flow control device 73 and the upstream side of the second heat exchange unit 76 provided in the middle of the second bypass pipe 51. The pipes connected to the indoor unit side second connection pipes 67b, 67c, and 67d and the pipes connected to the second connection pipe 67 in the second bypass pipe 51 join in the middle. 52 c, 52 c, 52 d are connected to the second connection pipe 67 in the second bypass pipe 51 by pipes connected to the indoor unit side second connection pipes 67 b, 67 c, 67 d in the middle of the second bypass pipe 51. This is an eighth check valve provided upstream from the portion that joins the piping to be connected, and allows refrigerant flow only from the second connection piping 67b, 67c, 67d on the indoor unit side to the second connection piping 67. .

Reference numeral 32 denotes a third check valve provided between the heat source device side heat exchanger 3 and the second connection pipe 67, and only from the heat source device side heat exchanger 3 to the second connection pipe 67. Allow refrigerant flow. Reference numeral 33 denotes a fourth check valve provided between the four-way valve 2 and the first connection pipe 66, and allows the refrigerant to flow only from the first connection pipe 66 to the four-way valve 2. Reference numeral 34 denotes a fifth check valve provided between the four-way valve 2 and the second connection pipe 67, and permits refrigerant flow only from the four-way valve 2 to the second connection pipe 67. Reference numeral 35 denotes a sixth check valve provided between the heat source machine side heat exchanger 3 and the first connection pipe 66, and the refrigerant flows only from the first connection pipe 66 to the heat source machine side heat exchanger 3. Is acceptable. The third, fourth, fifth, and sixth check valves 32, 33, 34, and 35 constitute a flow path switching device 40. The flow path switching device 40 circulates the refrigerant only from the refrigerant outlet side of the condenser to the second connection pipe 67 side during the operation in which the heat source unit side heat exchanger 3 becomes a condenser, and from the first connection pipe 66. During operation in which the refrigerant is circulated only to the four-way valve 2 side and the heat source apparatus side heat exchanger 3 is an evaporator, the refrigerant is circulated only from the first connection pipe 66 to the refrigerant inflow side of the evaporator and the four-way valve 2. The refrigerant is circulated only to the second connection pipe 67 side. Reference numeral 85 denotes a third pressure detecting means provided between the first branch part 70 and the fourth flow control device 73, and 86 denotes the fourth flow control device 73 and the first flow control device 4. It is the 4th pressure detection means provided between. Reference numerals 15 and 16 denote first and second temperature detection means provided at both ends of each use-side heat exchanger 5, and the second temperature detection means 16 is connected to the first flow control device 4 side. The first temperature detection means 15 is connected to the other end.

In addition, the heat source device side heat exchanger 3 has the same heat transfer area as the first heat source device side heat exchanger 41 and the first heat source device side heat exchanger 41 connected in parallel to each other. A first electromagnetic on-off valve 44 provided at one end of the heat source machine side heat exchanger 42, the heat source machine side bypass path 43, the first heat source machine side heat exchanger 41 connected to the four-way valve 2; A second electromagnetic opening / closing valve 45 provided at the other end of the heat source device side heat exchanger 41 and a third electromagnetic valve provided at one end of the second heat source device side heat exchanger 42 connected to the four-way valve 2. The on-off valve 46, the fourth electromagnetic on-off valve 47 provided at the other end of the second heat source unit side heat exchanger 42, and the fifth electromagnetic on-off valve 48 provided in the middle of the heat source unit side bypass passage 43. It is constituted by. Reference numeral 8 denotes a second pressure detection means provided in the middle of the pipe connecting the four-way valve 2 and the discharge portion of the high-stage compressor 1b. Reference numeral 80 denotes a heat source machine side blower that controls the heat exchange capacity of the heat source machine side heat exchanger 3. The first connection pipe 66 is provided with the high-pressure side of the gas-liquid separator 14 and the injection heat exchanger 7. The gas-liquid separator 14 and the pipe 22 between the high-stage compressor 1b and the low-stage compressor 1a are injection pipes 18 having the low pressure side of the second flow control device 6 and the heat exchanger 7 for injection. It is connected. Further, the third flow control device 13 and the first pressure detection means 10 are provided in the pipe 40 a including the sixth check valve 35. Further, the heat source machine A is a flow rate control device that controls the opening of the third flow rate control device 13 so that the detection value of the first pressure detection means 10 approaches the control target value of the first pressure detection means 10. A control device 20 having the function of the control means 25 is provided.

Operation | movement of the air conditioning apparatus of Embodiment 2 comprised in this way is demonstrated. First, the case of “only cooling operation” will be described with reference to FIG.
That is, as indicated by solid line arrows in the figure, the high-temperature and high-pressure refrigerant gas discharged from the low-stage compressor 1a and further compressed and discharged by the high-stage compressor 1b passes through the four-way valve 2 and passes through the heat source machine side. After the heat exchanger 3 exchanges heat with the outdoor air blown by the heat source blower 80 with variable air flow, it is condensed and liquefied, and then the third check valve 32, the second connection pipe 67, the first air The liquid separation device 72 and the fourth flow rate control device 73 are passed in this order, and further passed through the second branch portion 71 and the second connection pipes 67b, 67c, and 67d on the indoor unit side to the indoor units B, C, and D. Inflow. And the refrigerant | coolant which flowed into each indoor unit B, C, D is pressure-reduced to low pressure by each 1st flow control device 4 controlled by the superheat amount of each utilization side heat exchanger 5 exit, and each utilization side heat | fever The exchanger 5 exchanges heat with room air, evaporates and gasifies, and cools the room. And the refrigerant | coolant which became this gas state is the 1st connection piping 66b, 66c, 66d by the side of an indoor unit, the three-way switching valves 68, 68, 68, the 1st branch part 70, the 1st connection piping 66, a heat source The refrigerant circulation cycle sucked into the low-stage compressor 1a through the gas-liquid separator 14, the fourth check valve 33, the four-way valve 2, and the accumulator 64 of the machine A is configured, and the cooling operation is performed.

At this time, the first port 8a of the three-way switching valve 68 is closed, and the second port 8b and the third port 8c are closed. In this case, since the first connection pipe 66 is at a low pressure and the second connection pipe 67 is at a high pressure, the third check valve 32 and the fourth check valve 33 are necessarily circulated. Note that the third flow rate control device 13 is not fully closed. In addition, during this cycle, a part of the refrigerant that has passed through the fourth flow control device 73 enters the first bypass pipe 74 and is reduced to a low pressure by the fifth flow control device 75, and the second heat exchange unit 76. Thus, heat exchange is performed with the refrigerant before the flow path in the downstream portion of the fourth flow control device 73 is separated, and further with the refrigerant flowing into the fourth flow control device 73 at the first heat exchange portion 79. The refrigerant that has evaporated and exchanged heat enters the fourth check valve 33 of the heat source device A through the first connection pipe 66, and is sucked into the low-stage compressor 1a through the four-way valve 2 and the accumulator 64. On the other hand, the refrigerant in the second branch portion 71 that has been heat-exchanged by the first and second heat exchange portions 79 and 76 and has been sufficiently cooled and subcooled passes through the seventh check valves 50b, 50c, and 50d. Then, the air flows into the indoor units B, C, and D that are going to be cooled. Here, the capacity and heat source of the compressors 1a and 1b with variable capacity so that the evaporation temperature in each use-side heat exchanger 5 and the condensation temperature in the heat source apparatus-side heat exchanger 3 become a predetermined target temperature. By controlling the air volume of the air blower 80, the target cooling capacity can be obtained in each of the indoor units B, C, and D. The second flow control device 6 is fully closed so that the refrigerant does not flow to the injection pipe 18.

Next, the case of “only heating operation” will be described with reference to FIG. That is, as indicated by a dotted arrow in the figure, the high-temperature and high-pressure refrigerant gas discharged from the low-stage compressor 1a and further compressed and discharged by the high-stage compressor 1b passes through the four-way valve 2 to The check valve 34, the second connection pipe 67, the first gas-liquid separator 72, the first branch section 70, the three-way switching valve 68, and the first connection pipes 66b, 66c, 66d on the indoor unit side. In this order, the air flows into each of the indoor units B, C, and D, exchanges heat with room air, condenses, and heats the room. And the refrigerant | coolant which became this state passes each 1st flow control device 4 controlled by the subcooling amount of each utilization side heat exchanger 5 exit, and 2nd connection piping 67b, 67c, 67d on the indoor unit side. Flow into the second branch portion 71, merge after passing through the eighth check valves 52 b, 52 c, 52 d, and the fourth flow rate control device 73 and the second flow rate in the middle of the second connection pipe 67. It enters between the heat exchangers 76 and passes through the fifth flow control device 75. Here, the refrigerant is further depressurized by the first flow rate control device 4 or the fifth flow rate control device 75 to a gas-liquid two-phase of intermediate pressure. Then, the refrigerant reduced to the intermediate pressure is reduced in pressure by the third flow control device 13 of the pipe 40a from the first connection pipe 66 through the gas-liquid separator 14 of the heat source machine A, and becomes a low-pressure refrigerant. It flows into the heat source apparatus side heat exchanger 3 from the stop valve 35, heat-exchanges with the outdoor air ventilated by the heat source apparatus side fan 80 with variable ventilation volume here, and evaporates to be in a gas state. The refrigerant in a gas state constitutes a refrigerant circulation cycle that is sucked into the low-stage compressor 1a through the four-way valve 2 and the accumulator 64, and performs a heating operation.

At this time, in the three-way switching valve 68, the second port 8b is closed, and the first port 8a and the third port 8c are opened. At this time, the refrigerant inevitably flows to the fifth check valve 34 and the sixth check valve 35 because the first connection pipe 66 has a low pressure and the second connection pipe 67 has a high pressure. In addition, the seventh check valves 50b, 50c, and 50d are closed because the second connection pipes 67b, 67c, and 67d on the indoor unit side have a higher pressure than the second connection pipe 67. Here, the capacity of the compressors 1a and 1b with variable capacity and the heat source machine side so that the condensation temperature in each use side heat exchanger 5 and the evaporation temperature in the heat source machine side heat exchanger 3 become predetermined target temperatures. By controlling the amount of air blown from the blower 80, the target heating capacity of each indoor unit can be obtained. Further, a part of the liquid refrigerant separated by the gas-liquid separator 14 is decompressed by the second flow rate control device 6, and after heat exchange by the injection heat exchanger 7, the low-stage compressor 1 a and the high-stage compressor are compressed. It flows into the piping 22 between the machines 1b. The control method of the detection value of the first pressure detection means 10 is the same as that of the first pressure detection means 10 shown in the first embodiment.

Next, the case of “heating main” in the simultaneous cooling and heating operation will be described with reference to FIG. That is, as indicated by a dotted arrow in the figure, the high-temperature and high-pressure refrigerant gas discharged from the low-stage compressor 1a and further compressed by the high-stage compressor 1b is discharged from the four-way valve 2 and the fifth reverse valve. It is sent to the relay machine E through the stop valve 34 and the second connection pipe 67, passes through the first gas-liquid separator 72, the first branch part 70, the three-way switching valve 68, and the first on the indoor unit side. It passes through the connection pipes 66b and 66c in this order, flows into the indoor units B and C to be heated, and heats the indoor air in the use side heat exchanger 5 to be condensed and liquefied to heat the room. Then, the condensed and liquefied refrigerant passes through each first flow rate control device 4 controlled by the subcooling amount at each use-side heat exchanger B, C outlet, is slightly decompressed, and flows into the second branch portion 71. The second connection pipe 67 passes through the second bypass pipe 51 including the eighth check valves 52 b and 52 c, and is cooled by the second heat exchange unit 76. A part of the refrigerant cooled by the second heat exchange section 76 passes through the seventh check valve 50d and the second connection pipe 67d on the indoor unit side and enters the indoor unit D to be cooled. After the pressure is reduced by the first flow rate control device 4 controlled by the superheat amount at the outlet of the use side heat exchanger 5, heat is exchanged by the use side heat exchanger 5 to evaporate into a gas state to cool the room. Then, it flows into the first connection pipe 66 through the three-way switching valve 68.

On the other hand, the remainder of the refrigerant cooled by the second heat exchange unit 76 is set so that the pressure difference between the detected pressure of the third pressure detecting means 85 and the detected pressure of the fourth pressure detecting means 86 falls within a predetermined range. After passing through the fifth flow control device 75 to be controlled, the second heat exchange unit 76 exchanges heat with the refrigerant that has come out of the heating indoor units B and C, evaporates, and passes through the cooling indoor unit D. And the sixth check valve 35 on the side of the heat source machine after the pressure is reduced from the first connection pipe 66 to the low pressure by the third flow rate control device 13 of the pipe 40a through the gas-liquid separator 14 of the heat source machine A. It flows into the heat exchanger 3, where it exchanges heat with the outdoor air blown by the heat source machine side blower 80 with variable ventilation volume, and evaporates into a gas state. At this time, the capacities of the compressors 1a and 1b whose capacity is variable so that the evaporating temperature of the cooling indoor unit D and the condensing temperature of the heating indoor units B and C become a predetermined target temperature, and the air flow rate of the heat source side fan 80 And the first, second, third and fourth electromagnetic valves 44, 45 at both ends of the first and second heat source side heat exchangers 41 and 42 in the heat source side heat exchanger 3 The refrigerant which adjusts the heat transfer area by opening and closing 46 and 47 and opens and closes the electromagnetic on-off valve 48 of the heat source unit side bypass passage 43 and flows through the first and second heat source unit side heat exchangers 41 and 42. By adjusting the flow rate, an arbitrary amount of heat exchange can be obtained in the heat source unit side heat exchanger 3, and the target heating capacity or cooling capacity can be obtained in each of the indoor units B, C, and D. Thereafter, the refrigerant constitutes a refrigerant circulation cycle that is sucked into the low-stage compressor 1a through the four-way valve 2 and the accumulator 64, and performs heating main operation.

At this time, the second port 8b of each three-way switching valve 68 connected to the indoor units B and C is closed, and the first port 8a and the third port 8c are opened, so that the three-way switching valve is connected to the indoor unit D. The first port 8a of 68 is closed, and the second port 8b and the third port 8c are open. The refrigerant inevitably flows to the fifth check valve 34 and the sixth check valve 35 because the first connection pipe 66 has a low pressure and the second connection pipe 67 has a high pressure. At this time, the fourth flow control device 73 is closed. Further, since the second connection pipes 67b and 67c on the indoor unit side have higher pressure than the second connection pipe 67, the seventh check valves 50b and 50c are closed. Moreover, since the pressure of the second connection pipe 67d on the indoor unit side is lower than that of the second connection pipe 67, the eighth check valve 52c is closed. Due to the presence of the first and eighth check valves 50 and 52, the cooling indoor unit D is in a state where the refrigerant that has passed through the heating indoor units B and C does not pass through the second heat exchanging unit 76 and is not sufficiently subcooled. Is prevented from flowing into. Further, a part of the liquid refrigerant separated by the gas-liquid separator 14 is decompressed by the second flow rate control device 6, and after the heat exchange by the injection heat exchanger 7, the low-stage compressor 1 a and the high-stage compressor It flows into the piping 22 between 1b. The control method of the detection value of the first pressure detection means 10 is the same as the control method of the first pressure detection means 10 shown in the first embodiment.

Next, the case of the “cooling main” operation in the simultaneous cooling and heating operation will be described with reference to FIG. That is, as indicated by solid line arrows in the figure, the refrigerant gas discharged from the low-stage compressor 1a and further compressed and discharged by the high-stage compressor 1b passes through the four-way valve 2 to the heat source machine side heat exchanger. In this state, heat is exchanged with the outdoor air blown by the heat source side blower 80 with variable air flow, and a high-temperature and high-pressure state of gas-liquid two-phase is obtained. Here, the capacities of the compressors 1a and 1b having variable capacities and the air volume of the heat source side fan 80 are adjusted so that the evaporation temperature and the condensation temperature in the use side heat exchanger 5 become predetermined target temperatures, And the 1st, 2nd, 3rd, 4th electromagnetic on-off valve 44, 45, 46, 47 of the both ends of the 1st, 2nd heat source side heat exchanger 41, 42 in the heat source side heat exchanger 3 is shown. The heat transfer area is adjusted by opening and closing and the flow rate of the refrigerant flowing through the first and second heat source side heat exchangers 41 and 42 is adjusted by opening and closing the electromagnetic on-off valve 48 of the heat source side bypass path 43. As a result, the heat source unit side heat exchanger 3 can obtain an arbitrary amount of heat exchange, and each of the indoor units B, C, and D can have a target heating capacity or cooling capacity. Thereafter, the gas-liquid two-phase high-temperature and high-pressure refrigerant is sent to the first gas-liquid separator 72 of the relay E through the third check valve 32 and the second connection pipe 67. Here, the gas-liquid two-phase refrigerant is separated into a gas refrigerant and a liquid refrigerant, and the separated gas refrigerant is in the order of the first branch portion 70, the three-way switching valve 68, and the first connection pipe 66d on the indoor unit side. Then, the air flows into the indoor unit D to be heated, and heat is exchanged with the indoor air in the use side heat exchanger 5 to be condensed and liquefied to heat the room.

After that, the first flow control device 4 controlled by the subcooling amount at the outlet of the use side heat exchanger 5 is passed through the first flow rate control device 4 to be slightly depressurized and flows into the second branch portion 71, and includes the eighth check valve 52d. The second connection pipe 67 flows into the downstream portion of the fourth flow rate control device 73 through the second bypass pipe 51. On the other hand, the liquid refrigerant separated by the first gas-liquid separation device 72 is controlled by the detection pressure of the third pressure detection means 85 and the detection pressure of the fourth pressure detection means 86. It passes through the refrigerant from the heating indoor unit D and is cooled by the second heat exchange unit 76. Then, a part of the refrigerant cooled by the second heat exchange unit 76 passes through the seventh check valves 50b and 50c and the second connection pipes 67b and 67c on the indoor unit side to be cooled. After flowing into B and C and depressurizing by each first flow rate control device 4 controlled by the superheat amount at the outlet of each use side heat exchanger 5, heat is exchanged by each use side heat exchanger 5 and evaporated. The gas then enters the gas state, cools the room, and flows into the first connection pipe 66 through the three-way switching valve 68.
On the other hand, the remaining refrigerant cooled by the second heat exchange unit 76 is controlled so that the pressure difference between the detected pressure of the third pressure detecting means 85 and the detected pressure of the fourth pressure detecting means 86 falls within a predetermined range. The second heat exchanging unit 76 and the first heat exchanging unit 79 exchange heat through the fifth flow control device 75 and evaporate, and then the refrigerant from the cooling indoor units B and D and the connection pipe 66 are used. Air and heat blown by the heat source machine side blower 80 of variable amount of air flow from the sixth check valve 35 to the heat source machine side heat exchanger 3 through the gas-liquid separator 14 of the combined heat source machine A. It exchanges and evaporates and it will be in a gas state. Such a refrigerant circulation cycle is configured, and a cooling main operation is performed.

At this time, the first port 8a of the three-way switching valve 68 connected to the indoor units B and C is closed, the second port 8b and the third port 8c are opened, and the second port 8b of the indoor unit D is In the closed state, the first port 8a and the third port 8c are opened. The refrigerant inevitably flows into the third check valve 32 and the fourth check valve 33 because the first connection pipe 66 has a low pressure and the second connection pipe 67 has a high pressure. Further, since the second connection pipes 67b and 67c on the indoor unit side are lower in pressure than the second connection pipe 67, the eighth check valves 52b and 52c are closed. Since the second connecting pipe 7d on the indoor unit side has a higher pressure than the second connecting pipe 67, the seventh check valve 50c is closed. Due to the presence of the first and eighth check valves 50 and 52, the cooling indoor unit D in a state where the refrigerant that has passed through the heating indoor units B and C does not pass through the second heat exchange unit 76 and is not sufficiently subcooled. Is prevented from flowing into. The second flow control device 6 is fully closed so that the refrigerant does not flow to the injection pipe 18.

While the air conditioner according to the second embodiment is capable of simultaneously operating cooling and heating in a plurality of indoor units by a plurality of switching valves and check valves, the flow control device control means 25 of the control device 20 includes: The opening degree of the third flow rate control device 13 is controlled so that the detection value of the first pressure detection means 10 approaches the control target value of the first pressure detection means 10. Therefore, the same excellent effect as that of the first embodiment can be obtained.

It is a refrigerant circuit figure of the air harmony device concerning Embodiment 1 of the present invention. It is a block diagram which shows schematic structure of the control apparatus of the air conditioning apparatus which concerns on Embodiment 1 of this invention. It is a flowchart of the refrigerant | coolant of the operation state which concerns on Embodiment 1 of this invention. It is a figure of the flowchart which shows the process sequence of control of Embodiment 1 of this invention. It is a refrigerant circuit figure of the air conditioning apparatus which concerns on Embodiment 2 of this invention. It is a refrigerant | coolant flowchart which shows the driving | running state only of the air_conditioning | cooling or heating which concerns on Embodiment 2 of this invention. It is a flowchart of the refrigerant | coolant which shows the operation state of the heating main body which concerns on Embodiment 2 of this invention. It is a flowchart of the refrigerant | coolant which shows the driving | running state of the cooling main body which concerns on Embodiment 2 of this invention. It is a refrigerant circuit figure of the conventional air conditioning apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a Low stage side compressor, 1b High stage side compressor, 2 Four-way valve, 3 Heat source side heat exchanger, 4, 4A, 4B 1st flow control device, 5, 5A, 5B Use side heat exchanger, 6 2nd flow control device, 7 heat exchanger for injection, 8 2nd pressure detection means, 9 3rd pressure detection means, 10 1st pressure detection means, 11 solenoid valve, 12 check valve, 13 3rd 14 gas-liquid separator, 15 first temperature detection means, 16A, 16B second temperature detection means, 17 third temperature detection means, 18 injection pipe, 18a pipe end opening, 20 control apparatus, 21A, 21B Aperture opening degree detection means, 25 Flow rate control device control means, 26 First pressure target value setting means, 27 Second pressure target value setting means, 28 Third pressure target value setting means, 29 Subcool amount detection Means, 30 Flow control device closing means, 40 flow path switching device, 64 accumulator, 66 first connection piping, 67 second connection piping, 70 first branch portion, 71 second branch portion, 73 fourth flow control device , 74 1st bypass piping, 75 5th flow control apparatus.

Claims (8)

A low-stage compressor, a high-stage compressor that compresses and discharges refrigerant from the low-stage compressor, a plurality of sets of a use-side heat exchanger and a first flow rate controller connected in parallel, and a heat source A refrigerant circuit sequentially connected to the machine-side heat exchanger in an annular manner, and is branched from the refrigerant circuit from the first flow rate control device to the heat source machine-side heat exchanger to suck the high-stage compressor Injection pipe connected to the side, a second flow rate control device provided in the injection pipe, and a third flow rate control device provided in the refrigerant circuit from the branch position of the injection pipe to the heat source side heat exchanger A first pressure detecting means for detecting a refrigerant pressure in the refrigerant circuit from the branch position of the injection pipe to the third flow rate control device, and a detected value of the first pressure detecting means as the first pressure. Inspection An air conditioning apparatus characterized in that it comprises a flow control device controlling means for controlling the opening of the flow control device to the third to approach the control target value of the means. The throttle opening degree detecting means for detecting the opening degree of each of the plurality of first flow control devices, and the control target value of the first pressure detecting means is set based on the maximum value among the detected plurality of opening degrees. 2. The air conditioner according to claim 1, further comprising first pressure target value setting means for changing. Subcool amount detection means for detecting subcool amounts by the plurality of first flow control devices respectively, and setting change of the control target value of the first pressure detection means based on the maximum value among the detected plurality of subcool amounts The air conditioner according to claim 1, further comprising second pressure target value setting means. Based on the difference between the second pressure detection means for detecting the refrigerant pressure on the discharge side of the high stage compressor and the detection value by the second pressure detection means and the detection value by the first pressure detection means. The air conditioner according to claim 1, further comprising third pressure target value setting means for changing the setting of the control target value of one pressure detection means. A low-stage compressor, a high-stage compressor that compresses and discharges refrigerant from the low-stage compressor, a plurality of sets of a use-side heat exchanger and a first flow rate controller connected in parallel, and a heat source A refrigerant circuit sequentially connected to the machine-side heat exchanger in an annular manner, and is branched from the refrigerant circuit from the first flow rate control device to the heat source machine-side heat exchanger to suck the high-stage compressor Prior to returning from the start-up or defrosting operation to the heating operation of the low-stage compressor and the high-stage compressor, the injection pipe connected to the side, the second flow rate control device provided in the injection pipe, An air conditioner comprising: a flow control device closing means for closing the second flow control device in advance. A low-stage compressor, a high-stage compressor that compresses and discharges refrigerant from the low-stage compressor, a plurality of sets of indoor-side heat exchangers and first flow rate controllers connected in parallel, and a heat source A refrigerant circuit sequentially connected to the machine-side heat exchanger in an annular manner, and is branched from the refrigerant circuit from the first flow rate control device to the heat source machine-side heat exchanger to suck the high-stage compressor An injection pipe connected to the side, a second flow rate control device provided in the injection pipe, and a gas-liquid separation device provided at a branch position of the injection pipe in the refrigerant circuit. A pipe end opening is arranged at the liquid refrigerant suction position in the gas-liquid separator, and the liquid refrigerant separated by the gas-liquid separator is passed through the injection pipe and the second flow rate controller. An air conditioning apparatus characterized by being configured so as to flow into the suction side of the high-stage compressor. A refrigerant that passes through the injection pipe to the injection pipe from the second flow rate control device to the suction side of the high-stage compressor, and a refrigerant that passes through a refrigerant circuit from the branch position of the injection pipe to the heat source side heat exchanger; The air conditioner according to claim 6, further comprising an injection heat exchanger for heat exchange. A low-stage compressor, a high-stage compressor that compresses and discharges the refrigerant from the low-stage compressor, a four-way valve, a heat source apparatus-side heat exchanger, an accumulator, a heat source apparatus, an indoor heat exchanger, and A plurality of indoor units composed of a first flow control device or the like and connected in parallel are connected via a first connection pipe and a second connection pipe, and the use side heat exchange of the plurality of indoor units A first branch section that connects at least one of the units to the first connection pipe or the second connection pipe in a switchable manner, and the rest of the use-side heat exchangers of the plurality of indoor units. A pipe having a fourth flow rate control device is connected between the second branch portion connected to the second connection pipe via a flow rate control device, and the second branch portion and the first connection are connected. Connected to the pipe with a bypass pipe having a fifth flow control device, During operation in which the source-side heat exchanger is a condenser, the refrigerant is circulated only from the refrigerant outlet side of the condenser to the second connection pipe side and from the first connection pipe to the four-way valve side only. The refrigerant is circulated only from the first connection pipe to the refrigerant inflow side of the evaporator during the operation in which the heat source apparatus side heat exchanger is an evaporator and the four-way valve is connected to the second connection pipe side. In the air conditioner having the flow path switching device for circulating the refrigerant only in the first pipe, an injection pipe branched from the first connection pipe and connected to the suction side of the high-stage compressor, and a first pipe provided in the injection pipe 2, a third flow rate control device provided in the pipe of the flow path switching device from the branch position of the injection pipe to the heat source machine side heat exchanger, A first pressure detecting means for detecting a refrigerant pressure in the refrigerant circuit from the branch position of the jet pipe to the third flow rate control device, and a detected value of the first pressure detecting means as the first pressure detecting means. An air conditioner comprising flow rate control device control means for controlling the opening of the third flow rate control device so as to approach the control target value.

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