JP2014178079A - Air conditioning equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide air conditioning equipment which can improve partial load efficiency and can cause refrigerant of sufficient flow rate to flow through a refrigerant circuit upon the total load operation.SOLUTION: A control device 80 controls operation of a bypass valve 152 and operation of an injection valve 98 such that, when an operation capacity ratio R which represents the ratio of operation capacity to rated capacity upon heating operation is larger than 50%, the bypass valve 152 and the injection valve 98 are closed and such that, when the operation capacity ratio R is 50% or less, the bypass valve 152 and the injection valve 98 are opened.

Description

  The present invention relates to an air conditioner.

  Conventionally, an air conditioner having a two-stage compression mechanism in which two compressors are connected in series is known. Patent Document 1 includes a low-stage compressor and a high-stage compressor, a two-stage compression operation in which both compressors are driven, and a high-stage compressor is stopped and only a low-stage compressor is driven. An air conditioner configured to be switched between single-stage compression operation is disclosed. The air conditioner includes a serial connection pipe that connects a discharge port of a low-stage compressor and a suction port of a high-stage compressor, a discharge pipe that is connected to a discharge port of the high-stage compressor, and a serial connection pipe. And a bypass pipe for connecting the discharge pipe. During the two-stage compression operation, the refrigerant is first compressed by the low-stage compressor. The refrigerant compressed by the low-stage compressor is sucked into the high-stage compressor through the serial connection pipe and further compressed by the high-stage compressor. And the refrigerant | coolant compressed with the high stage side compressor is discharged to discharge piping. On the other hand, during single-stage compression operation, the refrigerant compressed by the low-stage compressor bypasses the high-stage compressor through the bypass pipe. The refrigerant that bypasses the high-stage compressor is discharged as it is into the discharge pipe.

  Patent Document 2 discloses an air conditioner in which a two-stage compression mechanism is configured by a first compression mechanism section and a second compression mechanism section as low-stage side compressors, and a third compression mechanism section as a high-stage side compressor. Disclose. The low stage compressor and the high stage compressor are always connected in series. Further, the connection state between the first compression mechanism unit and the second compression mechanism unit is changed according to the air conditioning state. For example, the first compression mechanism unit and the second compression mechanism unit are connected in series during cooling, and the first compression mechanism unit and the second compression mechanism unit are connected in parallel during heating.

  When the air conditioner has a two-stage compression mechanism, it is efficient by providing a refrigerant pipe (injection pipe) for flowing the gas refrigerant out of the refrigerant flowing out of the condenser to the suction port of the high-stage compression unit. Air-conditioning operation can be performed. The air conditioning apparatuses described in Patent Document 1 and Patent Document 2 are also provided with injection piping.

JP 2007-10282 A JP 2010-156499 A

(Problems to be solved by the invention)

  By the way, COP (Coefficient of performance) has been conventionally used as an index representing the efficiency of an air conditioner. COP represents the cooling / heating capacity with respect to the compressor power (consumed power) during rated operation (COP = cooling / heating capacity during rated operation / compressor power during rated operation). That is, COP only represents the performance during rated operation. In practice, however, the required operating capacity changes due to changes in the outside air temperature. Therefore, in order to perform an evaluation in a state close to actual use, in recent years, APF has been used instead of COP. APF (Annual performance factor) represents the cooling / heating capacity for compressor power (consumed power) when using an air conditioner throughout the year (APF = cooling / heating capacity demonstrated in one year / year) Compressor power consumed).

  Looking at the operating status of the air conditioner throughout the year, the partial load operation (low load operation) time is longer than the rated operation (full load operation) time. Therefore, in order to improve the APF, it is effective to improve the efficiency in partial load operation (partial load efficiency). In this case, the partial load efficiency can be improved by providing a two-stage compression mechanism in the air conditioner and flowing the refrigerant through the injection pipe during the partial load operation.

  Further, since the two-stage compression mechanism is configured by connecting the low-stage compressor and the high-stage compressor in series as described above, even if it has two compression units, The refrigerant discharge flow rate does not increase as compared with the compression mechanism having only the compression portion. Therefore, when the required air-conditioning load becomes large and it becomes necessary to increase the flow rate of the refrigerant in order to increase the operation capacity, for example, the compressor rotational speed must be increased. However, since there is a limit to the increase in the rotational speed of the compressor, it is expected that it is difficult to flow a sufficient flow rate of refrigerant through the refrigerant circuit. In particular, when the compressor is an air conditioner driven by an engine (engine driven air conditioner), the compressor speed depends on the engine speed. For this reason, the compressor speed cannot be increased beyond the upper limit speed of the engine. In other words, the conventional air conditioner having a two-stage compression mechanism can increase the partial load efficiency by flowing the refrigerant through the injection pipe at the time of partial load operation with a small operation capacity, but at the time of full load operation with a large operation capacity. There is a possibility that a refrigerant having a sufficient flow rate (during rated operation) cannot be passed through the refrigerant circuit.

  The present invention can improve the partial load efficiency by flowing the refrigerant through the injection pipe at the time of partial load operation with a small operation capacity, etc., and at a sufficient flow rate at the time of full load operation with a large operation capacity. An object of the present invention is to provide an air conditioner that can flow through the refrigerant circuit.

(Means for solving the problem)
The present invention includes a first compression section that has a first suction port and a first discharge port, sucks gas refrigerant from the first suction port, compresses the sucked gas refrigerant, and discharges the gas refrigerant from the first discharge port, A second compression section having two suction ports and a second discharge port, which sucks the gas refrigerant from the second suction port and compresses the sucked gas refrigerant and discharges it from the second discharge port; and is connected to the first discharge port A first discharge pipe through which the gas refrigerant discharged from the first discharge port flows, a second discharge pipe connected to the second discharge port and through which the gas refrigerant discharged from the second discharge port flows, and a first discharge pipe And a condenser configured to condense the refrigerant flowing in and flowing through the second discharge pipe, an evaporator configured to evaporate the refrigerant flowing out of the condenser, and the condenser and the evaporator The intermediate pipe connecting the A first suction pipe configured to lead to one suction port, a second suction pipe configured to guide the refrigerant flowing out of the evaporator to the second suction port, and a first discharge pipe and a second suction pipe are connected. The bypass pipe, the bypass valve interposed in the middle of the bypass pipe, the injection pipe connecting the intermediate pipe and the bypass pipe, the injection valve interposed in the middle of the injection pipe, and the operating capacity relative to the rated capacity. The bypass valve and the injection valve are closed when the operating capacity ratio representing the ratio is larger than a predetermined threshold, and the bypass valve and the injection valve are opened when the operating capacity ratio is less than the threshold. An air conditioner comprising: a valve control unit that controls the operation of the valve and the operation of the injection valve.

  According to the present invention, when the ratio of the operating capacity to the rated capacity (operating capacity ratio) is greater than the predetermined threshold, that is, when the operating capacity is large, the bypass valve and the injection valve are closed. For this reason, the bypass pipe and the injection pipe are closed. Therefore, the refrigerant discharged from the discharge port of the first compression section to the first discharge pipe flows into the condenser side without flowing into the bypass pipe. Moreover, the refrigerant | coolant discharged to the 2nd discharge piping from the discharge outlet of the 2nd compression part also flows into the condenser side. That is, when the operating capacity is large, the first compression unit and the second compression unit are connected in parallel, and each compression unit discharges the refrigerant. That is, the discharge amount of the refrigerant is doubled as compared with the case where one compressor discharges the refrigerant. For this reason, for example, a sufficient amount of refrigerant can be passed through the refrigerant circuit during full load capacity operation with a large operation capacity.

  On the other hand, when the operating capacity ratio is equal to or less than a predetermined threshold, that is, when the operating capacity is small, the bypass valve and the injection valve are opened. When the bypass valve is opened, the refrigerant compressed by the first compression unit passes through the bypass pipe and is sucked into the second compression unit from the suction port of the second compression unit. That is, when the operating capacity is small, the first compression unit and the second compression unit are connected in series. Further, when the injection valve is opened, the refrigerant flowing out of the condenser flows through the injection pipe. The refrigerant that has flowed through the injection pipe flows from the injection pipe to the bypass pipe, and is further sucked into the second compression section. As described above, the partial load efficiency can be increased by injecting the refrigerant during the partial load operation in which the operation capacity is equal to or less than the predetermined threshold. Further, when the operation capacity is small, the flow rate of the refrigerant flowing through the refrigerant circuit is not so large. For this reason, even if the compression parts are connected in series, a sufficiently necessary amount of refrigerant can be passed through the refrigerant circuit.

  In the present invention, the “operating capacity” represents a capacity (amount of heat) required for the air conditioner according to the air conditioning load, and its unit is kW. The operating capacity can be determined based on, for example, the difference between the room temperature and the set temperature in the case of indoor air conditioning, the outside air temperature, the pressure or temperature of the refrigerant flowing in the refrigerant circuit, and the like.

  The valve control unit may control the opening degree of the injection valve based on the pressure of the refrigerant flowing in the bypass pipe when the operation capacity ratio is equal to or less than the threshold value. According to this, when the 1st compression part and the 2nd compression part are connected in series, the opening degree of the injection valve is controlled based on the pressure (intermediate pressure) of the refrigerant flowing in the bypass pipe, thereby the injection. The flow rate of the refrigerant flowing in the pipe is optimized. For this reason, the efficiency at the time of the partial load driving | operation whose operating capacity ratio is below a predetermined threshold value can be improved more.

  The threshold value is preferably 50%. The partial load operation time with an operation capacity ratio of 50% or less accounts for more than half of the operation time of the air conditioner throughout the year. Therefore, when the operating capacity ratio is 50% or less, the efficiency when the operating capacity ratio is 50% or less can be increased by connecting the two compression parts in series and flowing the refrigerant through the injection pipe, thereby increasing the APF. Can be improved.

  The air conditioner of the present invention may include a sub heat exchanger for heating and evaporating the refrigerant flowing through the injection pipe. The air conditioner according to the present invention may be an engine-driven air conditioner including an engine that drives the first compression unit and the second compression unit. And in a sub heat exchanger, it is good to heat-exchange the cooling water (engine cooling water) which cooled the engine, and the refrigerant | coolant which flows through injection piping. In this case, the valve control unit may control the operation of the bypass valve and the operation of the injection valve so that the bypass valve and the injection valve are opened when the operating capacity ratio during heating is equal to or less than the threshold value. According to this, the efficiency at the time of the partial load operation during the heating operation and the operation capacity ratio of 50% or less can be increased.

It is the schematic which shows the structure of the air conditioner which concerns on this embodiment. It is a flowchart which shows the valve control routine performed in order that a control apparatus may control operation | movement of a bypass valve and an injection valve during heating operation. It is a figure which shows the flow of the refrigerant | coolant in a compression unit in the case of heating operation in the state which the bypass valve and the injection valve have closed. It is a figure showing the refrigerating cycle shown on the ph diagram in the case of heating operation in the state where a bypass valve and an injection valve are opened. It is a figure showing the refrigerating cycle shown on the ph diagram in case the air conditioner is performing heating operation in the state where the bypass valve and the injection valve are closed. It is a figure showing the refrigerating cycle shown on the ph diagram in the case of heating operation in the state where the bypass valve and the injection valve are opened. It is a flowchart which shows the opening degree control routine which a control apparatus performs in order to control the opening degree of an injection valve. It is a partial schematic sectional drawing of the scroll compressor used by this embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram illustrating a configuration of an air conditioner 1 according to the present embodiment. The air conditioner 1 is an engine-driven air conditioner that is driven by a gas engine EG. As shown in FIG. 1, this air conditioner 1 includes a compression unit 10, indoor heat exchangers 20A and 20B installed indoors, an outdoor heat exchanger 30 installed outdoors, and an expansion valve that expands the refrigerant. 40, a four-way selector valve 50, an accumulator 60 for separating the refrigerant into a gas and liquid, a sub heat exchanger 70, a control device 80, and a gas engine EG.

  The compression unit 10 includes a first compression unit 11 and a second compression unit 12. The first compression unit 11 and the second compression unit 12 are driven by the driving force of the gas engine EG. The first compression unit 11 has a first suction port 11a and a first discharge port 11b, sucks refrigerant from the first suction port 11a, compresses the sucked refrigerant, and discharges the refrigerant from the first discharge port 11b. The second compression unit 12 has a second suction port 12a and a second discharge port 12b. The second suction unit 12 sucks refrigerant from the second suction port 12a and compresses the sucked refrigerant and discharges it from the second discharge port 12b.

  One end of the first discharge pipe 131 is connected to the first discharge port 11b, and one end of the second discharge pipe 132 is connected to the second discharge port 12b. The other end of the first discharge pipe 131 and the other end of the second discharge pipe 132 merge at point A in FIG. 1 and are connected to one end of the first pipe 91. Also, one end of the first suction pipe 141 is connected to the first suction port 11a, and one end of the second suction pipe 142 is connected to the second suction port 12a. The first suction pipe 141 and the second suction pipe 142 meet at point B in FIG. 1 and are connected to one end of the fifth pipe 95.

  The first discharge pipe 131 and the second suction pipe 142 are connected by a bypass pipe 151. A bypass valve 152 is interposed in the middle of the bypass pipe 151. An intermediate pressure sensor 153 is attached to the bypass pipe 151. The intermediate pressure sensor 153 detects the pressure (intermediate pressure) Pm of the gas refrigerant flowing through the bypass pipe 151.

  A first check valve 161 is interposed in the middle of the first discharge pipe 131. The first check valve 161 allows the flow of the refrigerant from the first discharge port 11b of the first compression unit 11 toward the point A and blocks the flow of the refrigerant in the opposite direction. Further, a second check valve 162 is interposed in the middle of the second suction pipe 142. The second check valve 162 allows the refrigerant flow from the point B toward the second suction port 12a of the second compression unit 12, and blocks the refrigerant flow in the opposite direction.

  A temperature sensor 171 is attached in the middle of the second suction pipe 142 at a position downstream of the portion where the bypass pipe 151 communicates (on the second suction port 12a side). The temperature sensor 171 detects the temperature Ts of the gas refrigerant sucked into the second compression unit 12 from the second suction port 12a through the second suction pipe 142.

  A discharge pressure sensor 172 is attached in the middle of the first pipe 91 connected to the first discharge pipe 131 and the second discharge pipe 132 at the point A. The discharge pressure sensor 172 detects the pressure (discharge pressure) Pd of the gas refrigerant flowing through the first pipe 91. Further, a suction pressure sensor 173 is attached in the middle of the fifth pipe 95 connected to the first suction pipe 141 and the second suction pipe 142 at the point B. The suction pressure sensor 173 detects the pressure (suction pressure) Ps of the gas refrigerant flowing through the fifth pipe 95.

  The other end of the first pipe 91 is connected to the four-way switching valve 50. As shown in FIG. 1, the four-way switching valve 50 has four ports (a first port 51, a second port 52, a third port 53, and a fourth port 54). The four-way switching valve 50 has a heating connection state in which the first port 51 is connected to the second port 52 and the third port 53 is connected to the fourth port 54, and the first port 51 is connected to the third port 53 and The connection state can be switched to the cooling connection state in which the second port 52 is connected to the fourth port 54. The first pipe 91 is connected to the first port 51 of the four-way switching valve 50. One end of the second pipe 92 is connected to the second port 52. One end of a third pipe 93 is connected to the third port 53, and one end of a fourth pipe 94 is connected to the fourth port 54.

  The other end of the second pipe 92 branches, the indoor heat exchanger 20A is connected to one branch pipe, and the indoor heat exchanger 20B is connected to the other branch pipe. Each branch pipe is provided with flow control valves 21A and 21B. The outdoor heat exchanger 30 is connected to the other end of the third pipe 93. The indoor heat exchangers 20A and 20B and the outdoor heat exchanger 30 are connected by an intermediate pipe 96. The indoor heat exchangers 20A and 20B allow the refrigerant to flow into the interior from the second pipe 92 or the intermediate pipe 96, and exchange heat between the refrigerant and the ambient air. The outdoor heat exchanger 30 allows the refrigerant to flow into the inside from the intermediate pipe 96 or the third pipe 93, and allows the refrigerant and the outside air to exchange heat. As can be seen from FIG. 1, the expansion valve 40 is interposed in the middle of the intermediate pipe 96. The expansion valve 40 expands the refrigerant passing therethrough.

  The other end of the fourth pipe 94 is connected to the accumulator 60. The accumulator 60 gas-liquid separates the refrigerant that has flowed there. The gas refrigerant out of the refrigerant gas-liquid separated by the accumulator 60 flows through the fifth pipe 95.

  Further, as shown in FIG. 1, one end of the injection pipe 97 communicates with a portion near the indoor heat exchangers 20A and 20B than a portion in the middle of the intermediate pipe 96 where the expansion valve 40 is interposed. To do. The other end of the injection pipe 97 communicates with the bypass pipe 151. That is, the intermediate pipe 96 and the bypass pipe 151 are connected by the injection pipe 97. An injection valve 98 is interposed in the middle of the injection pipe 97. The injection valve 98 is a flow rate adjusting valve with a variable opening. Accordingly, the flow rate of the refrigerant flowing through the injection pipe 97 is changed by changing the opening degree of the injection valve 98. A sub heat exchanger 70 is interposed in the middle of the injection pipe 97. The refrigerant flowing through the injection pipe 97 flows into the sub heat exchanger 70. The refrigerant flowing into the sub heat exchanger 70 exchanges heat with the cooling water that has cooled the gas engine EG. The sub heat exchanger 70 evaporates liquid refrigerant among the refrigerant flowing through the injection pipe 97.

  The control device 80 inputs information detected by each sensor (temperature sensor 171, intermediate pressure sensor 153, discharge pressure sensor 172, suction pressure sensor 173, etc.). The control device 80 is electrically connected to the bypass valve 152 and the injection valve 98, and controls the open / closed state and the opening degree of the bypass valve 152 and the injection valve 98 based on information input from various sensors.

  Next, the air conditioning operation (heating operation, cooling operation) of the air conditioner 1 will be briefly described. First, the heating operation will be described. During heating, the four-way switching valve 50 is brought into a heating connection state. When the compression unit 10 operates during heating, the high-pressure gas refrigerant compressed by the compression unit 10 is discharged to the first pipe 91. The high-pressure gas refrigerant discharged to the first pipe 91 enters the four-way switching valve 50 from the first port 51. Since the first port 51 of the four-way selector valve 50 is connected to the second port 52 and the second port 52 is connected to the second pipe 92 during heating, the four-way selector valve 50 enters the four-way selector valve 50 from the first port 51. The high-pressure gas refrigerant exits the four-way switching valve 50 from the second port 52 and flows through the second pipe 92 and flows into the indoor heat exchangers 20A and 20B. The high-pressure gas refrigerant that has flowed into the indoor heat exchangers 20A and 20B is condensed by discharging heat to the indoor air while flowing through the indoor heat exchangers 20A and 20B. At this time, the indoor air is warmed by the heat discharged from the high-pressure gas refrigerant, and the room is heated.

  The refrigerant that is condensed by discharging heat to the room air partially liquefies and flows out of the indoor heat exchangers 20A and 20B, and flows through the intermediate pipe 96. Then, the pressure is reduced so as to be easily evaporated by being expanded by the expansion valve 40, and then flows into the outdoor heat exchanger 30. The refrigerant flowing into the outdoor heat exchanger 30 evaporates by taking heat of the outside air while flowing through the outdoor heat exchanger 30.

  The refrigerant that has evaporated the heat of the outside air partially vaporizes and flows out of the outdoor heat exchanger 30 and flows through the third pipe 93. The four-way switching valve 50 enters from the third port 53. During heating, the third port 53 of the four-way selector valve 50 is connected to the fourth port, and the fourth port 54 is connected to the fourth pipe, so that the refrigerant entering the four-way selector valve 50 from the third port 53 is The four-way switching valve 50 exits the fourth port 54 and flows to the fourth pipe 94. Then, it flows into the accumulator 60 from the fourth pipe 94. In the accumulator 60, the refrigerant is separated into a liquid refrigerant and a low-pressure gas refrigerant. Then, only the low-pressure gas refrigerant flows through the fifth pipe 95 and returns to the compression unit 10.

  Next, the cooling operation will be described. During cooling, the four-way switching valve 50 is brought into a cooling connection state. When the compression unit 10 operates during cooling, the compressed high-pressure gas refrigerant is discharged from the compression unit 10 to the first pipe 91. The high-pressure gas refrigerant discharged to the first pipe 91 enters the four-way switching valve 50 from the first port 51. During cooling, the first port 51 of the four-way switching valve 50 is connected to the third port, and the third port 53 is connected to the third pipe 93. Therefore, the gas that has entered the four-way switching valve 50 from the first port 51 The refrigerant exits the four-way switching valve 50 from the third port 53, flows through the third pipe 93, and flows into the outdoor heat exchanger 30. The high-pressure gas refrigerant that has flowed into the outdoor heat exchanger 30 discharges heat to the outside air and condenses while flowing through the outdoor heat exchanger 30.

  The refrigerant condensed by exhausting heat to the outside air is partially liquefied and flows out of the outdoor heat exchanger 30 and flows through the intermediate pipe 96. Then, the pressure is reduced so as to be easily evaporated by expansion by the expansion valve 40, and then flows into the indoor heat exchangers 20A and 20B. The refrigerant flowing into the indoor heat exchangers 20A and 20B evaporates by taking the heat of the indoor air while flowing through the indoor heat exchangers 20A and 20B. At this time, the refrigerant removes heat from the room air, thereby cooling the room air and cooling the room.

  The refrigerant that has evaporated the heat of the indoor air is partially vaporized, flows out of the indoor heat exchangers 20A and 20B, and flows through the second pipe 92. The four-way switching valve 50 enters from the second port 52. During cooling, the second port 52 of the four-way switching valve 50 is connected to the fourth port 54, and the fourth port 54 is connected to the fourth pipe 94, so that the four-way switching valve 50 enters from the third port 53. The refrigerant exits the four-way switching valve 50 from the fourth port 54 and flows to the fourth pipe 94. Then, it flows into the accumulator 60 from the fourth pipe 94. In the accumulator 60, the refrigerant is separated into a liquid refrigerant and a low-pressure gas refrigerant. Then, only the low-pressure gas refrigerant flows through the fifth pipe 95 and returns to the compression unit 10.

  Thus, during heating, the indoor heat exchangers 20A and 20B serve as condensers, and the outdoor heat exchanger 30 serves as an evaporator. On the other hand, during cooling, the outdoor heat exchanger 30 becomes a condenser, and the indoor heat exchangers 20A and 20B become condensers. In the present embodiment, a portion where the refrigerant discharged from the compression unit 10 flows until returning to the compression unit 10 is referred to as a refrigerant circuit. Therefore, the refrigerant discharged from the compression unit 10 flows through the refrigerant circuit and returns to the compression unit 10. Air conditioning (cooling and heating) is performed by the refrigerant flowing through the refrigerant circuit.

  During the heating operation, the control device 80 controls operations (open / closed state and opening degree) of the bypass valve 152 and the injection valve 98. FIG. 2 is a flowchart showing a valve control routine executed by the control device 80 to control the operation of the bypass valve 152 and the injection valve 98 during the heating operation. This routine is executed at predetermined minute intervals during the heating operation.

  When the valve control routine is activated, the control device 80 first calculates the operating capacity ratio R in step 10 (hereinafter, step is abbreviated as S) in FIG. The operating capacity ratio R represents a percentage of the ratio (V / Vmax) of the operating capacity V (kW) to the rated capacity Vmax (kW) of the air conditioner (the capacity may be referred to as capacity). The operating capacity V is the operating capacity (capacity) required of the air conditioner 1 according to the air conditioning load (heating load). For example, when the operating capacity ratio R is 50%, the air conditioner 1 is operated so as to exhibit an operating capacity of 50% of the rated capacity. The operating capacity V is calculated based on the discharge pressure Pd detected by the discharge pressure sensor 172, the suction pressure Ps detected by the suction pressure sensor 173, the temperature of the air-conditioned space, the set temperature, and the like.

  Next, the control device 80 determines whether or not the calculated operating capacity ratio R is 50% or less (S11). When the operating capacity ratio R exceeds 50% (S11: No), the control device 80 proceeds to S13 and outputs a closing operation signal to the bypass valve 152 and the injection valve 98. As a result, the bypass valve 152 and the injection valve 98 are closed. Note that when the bypass valve 152 and the injection valve 98 are already closed, the bypass valve 152 and the injection valve 98 are kept closed. The control device 80 ends the control routine after outputting the closing operation signal to the bypass valve 152 and the injection valve 98 in S13.

  FIG. 3 is a diagram illustrating the flow of the refrigerant in the compression unit 10 when the bypass valve 152 and the injection valve 98 are closed. When the bypass valve 152 and the injection valve 98 are closed, the bypass pipe 151 and the injection pipe 97 are closed.

  In this case, the refrigerant flowing through the fifth pipe 95 branches at point B into a refrigerant flowing through the first suction pipe 141 and a refrigerant flowing through the second suction pipe 142. The refrigerant flowing through the first suction pipe 141 is sucked into the first compression unit 11 from the first suction port 11a, is compressed inside the first compression unit 11, and is discharged from the first discharge port 11b of the first compression unit 11. It is discharged into the pipe 131. The refrigerant discharged from the discharge port 11b of the first compression unit 11 to the first discharge pipe 131 goes to the point A in FIG.

  On the other hand, the refrigerant flowing through the second suction pipe 142 is sucked into the second compression unit 12 from the second suction port 12a, is compressed inside the second compression unit 12, and is discharged from the second discharge port 12b of the second compression unit 12. It is discharged to the 2-discharge pipe 132. The refrigerant discharged to the second discharge pipe 132 goes to point A in FIG.

  The refrigerant discharged from the first compression section 11 to the first discharge pipe 131 and the refrigerant discharged from the second compression section 12 to the second discharge pipe 132 merge at a point A and flow to the first pipe 91, and further switch in four directions. It flows into the indoor heat exchangers 20A and 20B (condenser) through the valve 50 and the second pipe 92. That is, when the operating capacity ratio R exceeds 50%, that is, at the time of high partial load operation or full load operation where the required operating capacity is large, the first compression unit 11 and the second compression unit 12 are connected in parallel. The compressor part discharges the refrigerant.

  When both compression parts are driven in a state where the first compression part 11 and the second compression part 12 are connected in parallel, the compression volume of the refrigerant gas (the refrigerant in the compression part) compared to the case where there is only one compression part. (Excluded volume of gas) is doubled. Therefore, the amount of refrigerant gas discharged from the compression unit 10 in a single compression process is large. Accordingly, since a sufficient amount of refrigerant can flow from the compression unit 10 into the refrigerant circuit, it is possible to avoid the occurrence of insufficient air conditioning capacity due to the insufficient refrigerant flow rate.

  Moreover, when it is judged that the operating capacity ratio R is 50% or less in S11 of FIG. 2 (S11: Yes), the control device 80 advances the process to S12. When the operating capacity ratio R is 50% or less, for example, the flow control valve 21B is closed, and the partial load operation is performed such that the refrigerant does not flow into the indoor heat exchanger 20B and the refrigerant flows only into the indoor heat exchanger 20A. This is the case. In such a case, the controller 80 outputs an opening operation signal to the bypass valve 152 and the injection valve 98 in S12. As a result, the bypass valve 152 and the injection valve 98 are opened. In addition, when the bypass valve 152 and the injection valve 98 are already opened, the bypass valve 152 and the injection valve 98 are kept open. The control device ends the control routine after outputting an opening operation signal to the bypass valve 152 and the injection valve 98 in S12.

  FIG. 4 is a diagram illustrating the flow of the refrigerant in the compression unit 10 when the bypass valve 152 and the injection valve 98 are opened. When the bypass valve 152 and the injection valve 98 are opened, the first discharge port 11b of the first compression unit 11 and the second suction port 12a of the second compression unit 12 communicate with each other through the bypass pipe 151. For this reason, the 1st compression part 11 and the 2nd compression part 12 are connected in series. In this case, the first compressor 11 is a low-stage compressor, and the second compressor 12 is a high-stage compressor. Accordingly, the refrigerant flowing through the fifth pipe 95 flows from the point B through the first suction pipe 141 and is first sucked into the first compression unit 11. The refrigerant absorbed by the first compression unit 11 is compressed to the intermediate pressure and then discharged to the first discharge pipe 131. The refrigerant discharged to the first discharge pipe 131 flows through the bypass pipe 151 and further enters the second suction pipe 142. Then, the air is sucked into the second compression unit 12, compressed to a high pressure by the second compression unit 12, and then discharged to the second discharge pipe 132. Then, it flows from the point A to the first pipe 91. Thus, at the time of low partial load operation where the operation capacity ratio R is 50% or less, the first compression unit 11 and the second compression unit 12 are connected in series, and the refrigerant is compressed in two stages by the compression unit 10.

  In addition, since the injection valve 98 is opened, the bypass pipe 151 and the intermediate pipe 96 are communicated with each other through the injection pipe 97. For this reason, a part of the refrigerant flowing out from the indoor heat exchangers (condensers) 20A, 20B flows through the injection pipe 97. And heat exchange with engine cooling water is performed by passing through the sub heat exchanger 70 interposed in the middle of the injection piping 97. As a result, the liquid refrigerant of the refrigerant flowing through the injection pipe 97 evaporates.

  The gas refrigerant that has passed through the sub heat exchanger 70 flows from the injection pipe 97 to the bypass pipe 151. Then, it merges with the gas refrigerant whose pressure has been increased to the intermediate pressure by the first compression unit 11, and is sucked into the second compression unit 12.

  Thus, according to the present embodiment, the first compression unit 11 and the second compression unit 12 are connected in parallel at the time of high partial load operation or full load capacity operation in which the operation capacity ratio R exceeds 50%. At the time of low partial load operation in which the operating capacity ratio R is 50% or less, the first compression unit 11 and the second compression unit 12 are connected in series, and a gas is interposed between the first compression unit 11 and the second compression unit 12. The refrigerant is injected.

  FIG. 5 shows a case where the air conditioner 1 is performing a heating operation in a state where the bypass valve 152 and the injection valve 98 are closed, that is, in a state where the first compression unit 11 and the second compression unit 12 are connected in parallel. It is a figure showing the refrigerating cycle shown on the ph diagram. In FIG. 5, the low-pressure gas refrigerant immediately before being supplied to the compression unit 10 is represented by a position indicated by a point A. When the refrigerant is supplied to the compression unit 10 and compressed, the low-pressure gas refrigerant represented by the position indicated by the point A changes to a high-temperature high-pressure gas refrigerant represented by the position indicated by the point B. The amount L of change in specific enthalpy when the state of the refrigerant changes from the position indicated by point A to the position indicated by point B corresponds to the work amount (compressor power) of the compression unit 10.

  Further, the high-temperature and high-pressure gas refrigerant represented by the position indicated by the point B is condensed by the indoor heat exchangers 20A and 20B, thereby changing to the low-temperature and high-pressure liquid refrigerant represented by the position indicated by the point C. The change Φ of the specific enthalpy when the refrigerant changes its state from the position shown at point B to the position shown at point C is the heat exchange amount actually exchanged by the indoor heat exchangers 20A, 20B, that is, the air conditioner 1 It corresponds to the heating capacity (operating capacity) exhibited. Efficiency is represented by the ratio of L to Φ (Φ / L).

  Further, when the low-temperature high-pressure liquid refrigerant represented by the position indicated by the point C is expanded by the expansion valve 40, the state changes to the low-temperature low-pressure gas-liquid two-phase refrigerant represented by the position indicated by the point D. Then, the low-temperature low-pressure gas-liquid two-phase refrigerant represented by the position indicated by the point D is evaporated in the outdoor heat exchanger 30, thereby changing the state to the low-pressure gas refrigerant indicated by the point A. The heating operation is continued by repeating such a refrigeration cycle.

  FIG. 6 shows a heating operation in a state where the bypass valve 152 and the injection valve 98 are opened, that is, in a state where the first compression unit 11 and the second compression unit 12 are connected in series and the refrigerant flows through the injection pipe 97. It is a figure showing the refrigerating cycle shown on the ph diagram in the case where it is carrying out. In FIG. 6, the low-pressure gas refrigerant immediately before being supplied to the compression unit 10 is represented by a position indicated by a point A. The refrigerant represented by the position indicated by the point A is first compressed by the first compression unit 11, thereby changing its state to the medium pressure gas refrigerant represented by the position indicated by the point B 1. The amount of change L1 of the specific enthalpy when the state of the refrigerant changes from the position indicated by the point A to the position indicated by the point B1 corresponds to the work amount (compression power) of the first compression unit 11.

  In addition, the refrigerant compressed by the first compression unit 11 is merged with the gas refrigerant flowing from the injection pipe 97 in the bypass pipe 151, and at this time, the refrigerant is cooled by the gas refrigerant flowing from the injection pipe 97. Specific enthalpy is reduced. Therefore, the state of the medium-pressure gas refrigerant represented by the position indicated by the point B1 changes to the position indicated by the point B2 by joining with the refrigerant from the injection pipe 97. That is, the temperature slightly decreases while the pressure does not change.

  In addition, the intermediate pressure gas refrigerant represented by the position indicated by the point B2 is then compressed by the second compression unit 12, thereby changing its state to the high temperature and high pressure gas refrigerant represented by the position indicated by the point B3. The amount of change L2 of the specific enthalpy when the state of the refrigerant changes from the position indicated by the point B2 to the position indicated by the point B3 corresponds to the work amount (compression power) of the second compression unit 12.

  Further, the high-temperature high-pressure gas refrigerant represented by the position indicated by the point B3 is condensed in the indoor heat exchangers 20A and 20B, thereby changing to the low-temperature high-pressure liquid refrigerant represented by the position indicated by the point C. When the refrigerant changes its state from the position indicated by point B3 to the position indicated by point C, the change Φ of the specific enthalpy is the heat exchange amount actually exchanged by the indoor heat exchangers 20A and 20B, that is, the air conditioner 1 It corresponds to the heating capacity (operating capacity) exhibited. Efficiency is expressed by L1, L2 and Φ.

  Further, a part of the low-temperature high-pressure liquid refrigerant represented by the position indicated by the point C flows to the injection pipe 97 at the position of the point C ′ where the pressure is slightly reduced due to the pressure loss when flowing through the intermediate pipe 96. The refrigerant that has flowed into the injection pipe 97 is heated and evaporated by heat exchange in the sub heat exchanger 70, and then merges with the refrigerant discharged from the first compression section 11 (the refrigerant represented by the position indicated by the point B1). To do. On the other hand, the refrigerant that does not flow into the injection pipe 97 is expanded by the expansion valve 40, so that the state changes from the position indicated by the point C 'to the low-temperature low-pressure gas-liquid two-phase refrigerant indicated by the position indicated by the point D. Then, the low-temperature low-pressure gas-liquid two-phase refrigerant represented by the position indicated by the point D is evaporated in the outdoor heat exchanger 30, thereby changing the state to the low-pressure gas refrigerant indicated by the point A. The heating operation is continued by repeating such a refrigeration cycle.

  As shown in FIG. 6, when the bypass valve 152 is opened and the first compression unit 11 and the second compression unit 12 are connected in series, the refrigerant is compressed in two stages in the compression process. The refrigerant state at the start of the second stage compression (point B2) is different from the refrigerant state at the end of the first stage compression (point B1). Specifically, the temperature of the refrigerant at the start of the second stage of compression is lowered by the refrigerant flowing in from the injection pipe 97 to be lower than the temperature of the refrigerant at the end of the first stage of compression. Therefore, an isentropic line passing through the point (B2) representing the refrigerant state at the start of the second stage compression and an isentropic line passing through the point (B1) representing the refrigerant state at the end of the first stage compression. Is different. In this case, as can be seen from FIG. 6, the pressure increase gradient with respect to the specific enthalpy in the second stage compression process is larger than the pressure increase gradient with respect to the specific enthalpy in the first stage compression process. The greater the pressure rise gradient, the less compression power. That is, the compressor power L2 at the time of the second compression can be greatly reduced by the cooling effect by the refrigerant gas injection.

  In the case shown in FIG. 6, the efficiency of the air conditioner 1 is represented by L1, L2, and Φ. Further, the compressor power L2 of the second compressor 12 is considerably smaller than the compressor power L1 of the first compressor 11 because the pressure difference is smaller. If more refrigerant is compressed in the second compressor 12, more refrigerant can be compressed with less compressor power, and efficiency can be improved. That is, the efficiency can be improved by flowing more refrigerant through the injection pipe 97.

  Further, the case shown in FIG. 6 is a case where the operating capacity ratio R is 50% or less. That is, the efficiency is improved during low partial load operation with a small operation capacity V. When the operation status of the air conditioner is viewed throughout the year, the low partial load operation time in which the operation capacity ratio R is 50% or less accounts for more than half of the total operation time. According to this embodiment, since the efficiency when the operating capacity ratio R is 50% or less is increased, the APF can be greatly improved.

  On the other hand, at the time of high partial load operation or rated operation (full load operation) in which the operating capacity ratio R exceeds 50%, the first compression unit 11 and the second compression unit 12 are connected in parallel, so that the discharge from the compression unit 10 The flow rate of the refrigerant to be increased can be increased. For this reason, when the operation capacity V is large, a sufficient amount of refrigerant can be flowed to the refrigerant circuit, and the occurrence of insufficient air conditioning capacity due to the insufficient refrigerant flow rate can be avoided.

  By the way, if the flow rate (injection flow rate) of the refrigerant flowing through the injection pipe 97 is increased, generally an improvement in efficiency can be expected. In addition, if the intermediate pressure Pm is too high, the injection flow rate is reduced, so the power reduction effect of the first compression unit 11 is reduced. Therefore, there exists an injection flow rate and an intermediate pressure Pm that can increase the efficiency most. In this embodiment, when the operating capacity ratio R is 50% or less, the control device 80 controls the opening degree of the injection valve 98 based on the magnitude of the intermediate pressure Pm, so that the optimum refrigerant flow rate according to the situation. Is allowed to flow through the injection pipe 97. FIG. 7 is a flowchart showing an opening degree control routine executed by the control device 80 in order to control the opening degree of the injection valve 98. This opening degree control routine is executed at every minute interval when the control device 80 outputs an opening operation signal to the injection valve 98.

  When the opening degree control routine is activated, the control device 80 first calculates the target intermediate pressure Pm * in S21 of FIG. The target intermediate pressure Pm * is the pressure of the refrigerant flowing through the bypass pipe 151 that is set so as to maximize the efficiency. That is, the optimum value of the intermediate pressure Pm viewed from the efficiency is the target intermediate pressure Pm *. This target intermediate pressure Pm * is calculated based on the required air conditioning load, suction pressure Ps, and discharge pressure Pd. In the present embodiment, a target intermediate pressure table showing the relationship among the target intermediate pressure Pm *, the required load amount, the suction pressure Ps, and the discharge pressure Pd is stored in the control device 80 in advance. In S21, the control device 80 selects an optimum target intermediate pressure Pm * from the target intermediate pressure table based on the required load amount, the suction pressure Ps, and the discharge pressure Pd.

  Next, the control device 80 calculates the superheat degree ΔTs (° C.) of the refrigerant sucked into the second compression unit 12 (S22). The degree of superheat ΔTs can be obtained from the temperature detected by the temperature sensor 171 (the temperature of the refrigerant sucked into the second compressor 12) Ts and the intermediate pressure Pm detected by the intermediate pressure sensor 153. This degree of superheat ΔTs indicates how far the refrigerant represented by the position of point B2 in FIG. 6 is away from the saturated vapor pressure curve. As the degree of superheat ΔTs is smaller, the refrigerant is closer to saturated vapor and is more likely to get wet. As the degree of superheat ΔTs increases, the state of the refrigerant is further away from the saturated vapor pressure curve and is less likely to get wet.

  Subsequently, the control device 80 determines whether or not the current intermediate pressure Pm is less than the target intermediate pressure Pm * (S23). When the intermediate pressure Pm is equal to or higher than the target intermediate pressure Pm * (S23: No), the control device 80 proceeds to S25 to determine whether or not the intermediate pressure Pm is larger than the target intermediate pressure Pm *. If the intermediate pressure Pm is not greater than the target intermediate pressure Pm * (S25: No), this means that the intermediate pressure Pm is equal to the target intermediate pressure Pm *. In this case, the control device 80 ends this routine. On the other hand, when it is determined in S25 that the intermediate pressure Pm is larger than the target intermediate pressure Pm * (S25: Yes), the control device 80 outputs an opening degree decrease signal to the injection valve 98 (S27). As a result, the opening degree of the injection valve 98 is reduced, the flow rate of the refrigerant flowing through the injection pipe 97 is reduced, and the intermediate pressure Pm is reduced. The control device 80 then ends this routine.

  If it is determined in S23 that the intermediate pressure Pm is less than the target intermediate pressure Pm * (S23: Yes), the control device 80 proceeds to S24, and determines whether or not the degree of superheat ΔTs is greater than 5 ° C. Judging. When the degree of superheat ΔTs is 5 ° C. or less (S24: No), this indicates that the refrigerant sucked into the second compression unit 12 is in a state close to saturated steam. In this case, in order to prevent the wet refrigerant from being sucked into the second compression unit 12, the control device 80 advances the process to S 27 and outputs an opening degree decrease signal to the injection valve 98. As a result, the opening degree of the injection valve 98 is decreased, the flow rate of the refrigerant flowing through the injection pipe 97 is decreased, and the intermediate pressure Pm is decreased. Further, since the cooling of the refrigerant sucked into the second compression unit 12 is suppressed by the decrease in the injection flow rate, an extreme decrease in the degree of superheat ΔTs is suppressed, and as a result, the wet refrigerant is sucked into the second compression unit 12. Is effectively prevented. Thereafter, the control device 80 ends this routine.

  When it is determined in S24 that the degree of superheat ΔTs is greater than 5 ° C. (S24: Yes), the control device 80 outputs an opening degree increase signal to the injection valve 98 (S26). As a result, the opening degree of the injection valve 98 is increased, and the flow rate of the refrigerant flowing through the injection pipe 97 is increased. Thereafter, the control device 80 ends this control routine.

  When the control device 80 executes such an opening degree control routine, the intermediate pressure Pm and the flow rate of the refrigerant flowing through the injection pipe 97 are optimized during the low partial load operation where the operation capacity ratio R is 50% or less.

  In the present embodiment, an efficient scroll compressor is used for the first compression unit 11 and the second compression unit 12. FIG. 8 is a partial schematic cross-sectional view of the scroll compressor used in the present embodiment. A scroll compressor 100 shown in FIG. 8 includes a compression chamber 110 that compresses refrigerant gas, a first passage 101 and a second passage 102 that supply refrigerant gas to the compression chamber 110, and refrigerant gas compressed in the compression chamber 110. And a third passage 103 for discharging to the outside. The first passage 101 and the second passage 102 communicate with the suction ports (11a, 12b) of the compressor. The third passage 103 communicates with the discharge ports (11b, 12b) of the compressor.

  In general, a scroll compressor has two independent compression chambers formed between both wraps (both scrolls) from the outer peripheral side along with the eccentric rotation of the turning wrap (turning scroll) with respect to the fixed wrap (fixed scroll). Move to the inner circumference. The volume of the compression chamber is gradually reduced in the process of moving toward the inner periphery. Then, when the compression chamber has moved substantially to the center, the compression chamber (compression chamber 110c in FIG. 8) communicates with the discharge ports (11b, 12b) via the third passage 103, so that the refrigerant in the compression chamber Is discharged to the outside. Also, the two compression chambers (compression chambers 110a and 110b in FIG. 8) formed on the outer periphery communicate with the first passage 101 and the second passage 102 at a certain timing. At this time, since the compression chambers and the suction ports (11a, 12a) are communicated with each other, the refrigerant is supplied to these compression chambers. That is, the refrigerant is supplied to the outer compression chambers 110a and 110b via the first passage 101 and the second passage 102, and moves from the outer peripheral side to the inner peripheral side while the volume of these compression chambers is gradually reduced. As a result, the refrigerant inside these compression chambers is gradually compressed. When the compression chamber approaching the center communicates with the discharge port via the third passage 103, the refrigerant gas in the compression chamber is discharged from the discharge port.

  As can be seen from FIG. 8, reed valves 104 and 104 are attached in the middle of the first passage 101 and the second passage 102. The reed valves 104 and 104 permit the flow of the refrigerant gas flowing in the direction from the suction port ((11a or 12a) toward the compression chamber 110, and block the flow of the refrigerant gas flowing in the opposite direction. For this reason, the backflow of the refrigerant gas in the first passage 101 and the second passage 102 is prevented.

  Since the scroll compressor is configured such that the internal compression chamber is intermittently connected to the discharge port and the suction port, pressure pulsation occurs at the timing when the compression chamber is connected to the discharge port and the suction port. When this pressure pulsation is transmitted to the injection pipe 97, the flow rate of the refrigerant flowing through the injection pipe 97 varies. Therefore, in order to optimize the injection flow rate, pressure pulsation and back flow must be suppressed. In this regard, the scroll compressor 100 used in the present embodiment is provided with a reed valve in the middle of a passage (first passage 101, second passage 102) connecting the suction port and the compression chamber. Therefore, when this scroll compressor 100 is used for the second compression unit 12, the pressure pulsation is transmitted to the refrigerant flowing through the injection pipe 97 communicating with the suction port 12a of the second compression unit 12, and the backflow is suppressed. . As a result, the injection flow rate can be optimized.

  As described above, the air conditioner 1 of the present embodiment has the first suction port 11a and the first discharge port 11b, and sucks the gas refrigerant from the first suction port 11a and compresses the sucked gas refrigerant. The first compression unit 11 that discharges from the first discharge port 11b, the second suction port 12a, and the second discharge port 12b, and sucks the gas refrigerant from the second suction port 12a and compresses the sucked gas refrigerant to Connected to the second compression section 12 that discharges from the two discharge ports 12b and the first discharge port 11b, and to the first discharge pipe 131 through which the gas refrigerant discharged from the first discharge port 11b flows, and to the second discharge port 12b The second discharge pipe 132 through which the gas refrigerant discharged from the second discharge port 12b flows, the refrigerant flowing through the first discharge pipe 131 and the second discharge pipe 132 are introduced, and the refrigerant that has flowed in is condensed. Condenser (indoor heat exchangers 20A and 20B during heating operation), an evaporator configured to evaporate refrigerant flowing out of the condenser (outdoor heat exchanger 30 during heating operation), condenser and evaporation An intermediate pipe 96 connected to the evaporator, a first suction pipe 141 configured to guide the refrigerant flowing out of the evaporator to the first suction port 11a, and a refrigerant flowing out of the evaporator to the second suction port 12a The constructed second suction pipe 142, the bypass pipe 151 connecting the first discharge pipe 131 and the second suction pipe 142, the bypass valve 152 interposed in the middle of the bypass pipe 151, the intermediate pipe 96 and the bypass An injection pipe 97 for connecting the pipe 151, an injection valve 98 interposed in the middle of the injection pipe 97, a bypass valve 152 and an injection valve 98. And a control unit 80 as a valve control unit for controlling the work. The control device 80 also closes the bypass valve 152 and the injection valve 98 when the operating capacity ratio R representing the ratio of the operating capacity to the rated capacity during heating operation is larger than 50%, and the operating capacity ratio R is 50%. The operation of the bypass valve 152 and the operation of the injection valve 98 are controlled so that the bypass valve 152 and the injection valve 98 are opened at the following times.

  According to the air conditioner 1 of the present embodiment, when the operation capacity is large during heating operation, specifically, when high partial load operation or full load capacity operation in which the operation capacity ratio R exceeds 50% is performed. The 1st compression part 11 and the 2nd compression part 12 are connected in parallel, and each compression part discharges a refrigerant. Thereby, compared with the case where one compression part discharges a refrigerant | coolant, the discharge amount of a refrigerant | coolant is doubled. For this reason, the discharge amount of the refrigerant increases. As a result, a sufficient amount of refrigerant can be passed through the refrigerant circuit when the required operating capacity is large.

  On the other hand, when heating operation is being performed and the operation capacity is small, specifically, when performing a low partial load operation with an operation capacity ratio R of 50% or less, the first compression unit 11 and the second compression unit 12 are connected in series. Is done. Further, when the injection valve 98 is opened, the refrigerant flowing out of the indoor heat exchangers 20A and 20B flows through the injection pipe 97. The refrigerant that has flowed through the injection pipe 97 flows from the injection pipe 97 to the bypass pipe 151 and is further sucked into the second compression unit 12. The efficiency can be improved by injecting the refrigerant in this way. That is, the efficiency can be improved when the operating capacity is small. Further, when the operation capacity is small, the flow rate of the refrigerant flowing through the refrigerant circuit is not so large. For this reason, even if the compression parts are connected in series, a sufficiently necessary amount of refrigerant can be passed through the refrigerant circuit.

  In general, the partial load operation time in which the operation capacity ratio R is 50% or less often occupies half or more of the operation time of the air conditioner throughout the year. Therefore, when the operating capacity ratio R is 50% or less, the APF can be greatly improved by increasing the efficiency by connecting the two compression parts in series and flowing the refrigerant through the injection pipe 97.

  Further, the control device 80 according to the present embodiment executes an opening degree control routine when the operating capacity ratio R during heating operation is 50% or less, and controls the opening degree of the injection valve 98 based on the intermediate pressure Pm. doing. More specifically, the control device 80 calculates the target intermediate pressure Pm * that maximizes the efficiency when the operating capacity ratio R during heating operation is 50% or less, and the actual intermediate pressure Pm is the target intermediate pressure Pm. The opening degree of the injection valve 98 is controlled so as to approach the intermediate pressure Pm *. By executing such opening degree control, the partial load operation can be performed most efficiently.

  Further, the control device 80 calculates the superheat degree ΔTs of the refrigerant sucked into the second compression unit 12 when the operation capacity ratio R during the heating operation is 50% or less, and the superheat degree ΔTs is 5 ° C. or less. In some cases, the opening degree of the injection valve 98 is controlled so that the injection flow rate decreases. By controlling the injection valve 98 in this way, it is possible to prevent the damp refrigerant from being sucked into the second compression unit 12.

  Further, the air conditioner 1 of the present embodiment includes a sub heat exchanger 70 for heating and evaporating the refrigerant flowing through the injection pipe 97, and cooling water (engine) that has cooled the gas engine EG with the sub heat exchanger 70. (Cooling water) and the refrigerant flowing through the injection pipe 97 are subjected to heat exchange. Thus, the refrigerant to be injected can be evaporated by making good use of the exhaust heat of the engine.

  Further, the scroll compressor 100 used in the present embodiment includes a suction port (11a, 12a) through which refrigerant gas is sucked, a discharge port (11b, 12b) through which refrigerant gas is discharged, and a compression chamber formed inside. 110 (110a, 110b, 110c), a suction side passage (first passage 101, second passage 102) connecting the compression chamber 110 (110a, 110b) and the suction port, a compression chamber 110 (110c), and a discharge port A reed valve that is provided in the discharge-side passage (third passage 103) and the suction-side passage and that allows the refrigerant to flow from the suction port to the compression chamber 110 (110a, 110b) and blocks the opposite flow. 104. The presence of the reed valve 104 prevents the pressure pulsation generated in the scroll compressor 100 from being transmitted to the refrigerant flowing through the injection pipe 97. Therefore, the injection flow rate can be optimized, thereby improving the efficiency.

  As mentioned above, although embodiment of this invention was described, this invention should not be limited to the said embodiment. For example, in the above embodiment, the first compression unit 11 and the second compression unit 12 are connected in series and refrigerant is injected into the injection pipe 97 during the partial load operation during the heating operation and the operation capacity ratio R is 50% or less. Although it is configured to flow, the first compression unit 11 and the second compression unit 12 are connected in series and injected during partial load operation during the cooling operation and the operation capacity ratio R is equal to or less than a predetermined threshold (for example, 50%). You may comprise so that a refrigerant | coolant may flow in the piping 97. FIG. In this case, instead of evaporating the refrigerant in the sub heat exchanger 70, the refrigerant flowing out of the condenser (outdoor heat exchanger) is separated into liquid refrigerant and gas refrigerant by the gas-liquid separator, and the separated gas refrigerant is separated. It suffices to configure such that only the gas flows through the injection pipe 97. In the above embodiment, whether the first compression unit 11 and the second compression unit 12 are connected in parallel or in series is switched depending on whether the operation capacity ratio R is 50% or less. The threshold value is not limited to this. For example, the first compression unit 11 and the second compression unit 12 may be switched in parallel or in series depending on whether or not the operating capacity ratio R is 60% or less. Moreover, as a compression part to which this invention is applied, a scroll compressor may be sufficient and a compressor other than that may be sufficient. Thus, the present invention can be modified without departing from the gist thereof.

DESCRIPTION OF SYMBOLS 1 ... Air conditioning apparatus, 10 ... Compression unit, 11 ... 1st compression part, 11a ... 1st suction port, 11b ... 1st discharge port, 12 ... 2nd compression part, 12a ... 2nd suction port, 12b ... 2nd discharge Outlet, 131 ... first discharge pipe, 132 ... second discharge pipe, 141 ... first suction pipe, 142 ... second suction pipe, 151 ... bypass pipe, 152 ... bypass valve, 153 ... intermediate pressure sensor, 171 ... temperature sensor 172 ... Discharge pressure sensor, 173 ... Suction pressure sensor, 20A, 20B ... Indoor heat exchanger (condenser, evaporator), 21A, 21B ... Flow control valve, 30 ... Outdoor heat exchanger (evaporator, condenser)
40 ... expansion valve, 50 ... four-way switching valve, 60 ... accumulator, 70 ... sub heat exchanger, 80 ... control device (valve control unit), 91 ... first pipe, 92 ... second pipe, 93 ... third pipe, 94: Fourth piping, 95: Fifth piping, 96: Intermediate piping, 97: Injection piping, 98: Injection valve, 100: Scroll compressor, 101: First passage, 102: Second passage, 103: Third passage 104, reed valve, 110, compression chamber, EG, gas engine, Pd, discharge pressure, Ps, suction pressure, Pm, intermediate pressure, Pm, target intermediate pressure, R, operating capacity ratio, V ... operating capacity, Vmax ... Rated capacity, ΔTs ... degree of superheat

Claims (3)

A first compression section that has a first suction port and a first discharge port, sucks gas refrigerant from the first suction port, compresses the sucked gas refrigerant, and discharges the gas refrigerant from the first discharge port;
A second compression section that has a second suction port and a second discharge port, sucks gas refrigerant from the second suction port, compresses the sucked gas refrigerant, and discharges it from the second discharge port;
A first discharge pipe connected to the first discharge port, through which the gas refrigerant discharged from the first discharge port flows;
A second discharge pipe connected to the second discharge port, through which the gas refrigerant discharged from the second discharge port flows;
A condenser configured to condense the refrigerant flowing in and flowing in the refrigerant flowing through the first discharge pipe and the second discharge pipe;
An evaporator configured to evaporate the refrigerant flowing out of the condenser;
An intermediate pipe connecting the condenser and the evaporator;
A first suction pipe configured to guide the refrigerant flowing out of the evaporator to the first suction port;
A second suction pipe configured to guide the refrigerant flowing out of the evaporator to the second suction port;
A bypass pipe connecting the first discharge pipe and the second suction pipe;
A bypass valve interposed in the middle of the bypass pipe;
An injection pipe connecting the intermediate pipe and the bypass pipe;
An injection valve interposed in the middle of the injection pipe;
The bypass valve and the injection valve are closed when an operation capacity ratio representing a ratio of the operation capacity to the rated capacity is larger than a predetermined threshold value, and when the operation capacity ratio is less than the threshold value, the bypass valve And a valve control unit for controlling the operation of the bypass valve and the operation of the injection valve so that the injection valve is opened,
An air conditioner. The air conditioner according to claim 1,
The said valve control part is an air conditioner which controls the opening degree of the said injection valve based on the pressure of the refrigerant | coolant which flows through the said bypass piping, when the said operation capacity ratio is below the said threshold value. In the air conditioner according to claim 1 or 2,
An air conditioner in which the threshold is 50%.

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