JP6136403B2 - Air conditioner - Google Patents

Description

  The present invention relates to an air conditioner.

  Conventionally, for example, as shown in Patent Documents 1 to 3, an air conditioner having a two-stage compression mechanism in which two compression units are connected in series is known. According to the air conditioners described in Patent Documents 1 to 3, the gas that has flowed out of the condenser into a portion between the discharge port of the low-stage compression unit and the suction port of the high-stage compression unit that constitutes the two-stage compression mechanism. The refrigerant is injected. Thus, the efficiency of a refrigerating cycle improves by injecting a gas refrigerant.

JP 2010-203287 A JP 2010-156499 A JP 2009-257704 A

(Problems to be solved by the invention)
The efficiency is improved by injecting the gas refrigerant during the heating operation and during the cooling operation. However, gas refrigerant is injected to increase efficiency depending on the air conditioning conditions (heating, cooling), air conditioning load (rated, partial load), the state of the refrigerant flowing in the refrigerant circuit (pressure, temperature), and various conditions of the outside air. The optimum flow rate (injection flow rate) is different. That is, there is an optimum injection flow rate depending on the situation.

  In an air conditioner having a conventional two-stage compression mechanism, the low-stage compression section and the high-stage compression section are driven by the same drive source, so that the respective compressor rotation speeds are the same. For this reason, the pressure (intermediate pressure) in the pipe connecting the discharge port of the low-stage compression unit and the suction port of the high-stage compression unit is fixed, and cannot be controlled. Since the injection flow rate depends on the intermediate pressure, the injection flow rate cannot be changed when the intermediate pressure cannot be controlled. Note that the injection flow rate can be changed by providing a flow rate control valve in the injection pipe through which the gas refrigerant for injection flows and adjusting the opening of the flow rate control valve. However, the maximum value of the flow rate of the gas refrigerant flowing through the injection pipe is determined by the intermediate pressure. Therefore, for example, even when the opening degree of the flow control valve is fully open, if the intermediate pressure is high, the injection flow rate is small, and there may be a situation in which a desired amount of gas refrigerant cannot flow through the injection pipe.

  An object of the present invention is to provide an air conditioner configured to be able to inject a gas refrigerant having an optimum flow rate according to various situations.

(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 The first discharge pipe, the second discharge pipe connected to the second discharge port, the refrigerant flowing through the first discharge pipe and the second discharge pipe are flown in, and the flowed-in refrigerant is condensed. A condenser, an evaporator configured to evaporate the refrigerant flowing out of the condenser, an intermediate pipe connecting the condenser and the evaporator, and configured to guide the refrigerant flowing out of the evaporator to the first suction port; The first suction pipe and the refrigerant flowing out of the evaporator to the second suction port A second suction pipe configured to lead, a series connection pipe connecting the first discharge pipe and the second suction pipe, a first valve member interposed in the middle of the series connection pipe, and a series connection to the intermediate pipe An injection pipe connecting the pipe, a second valve member interposed in the middle of the injection pipe, a flow rate of the gas refrigerant discharged from the first discharge port, and a flow rate of the gas refrigerant discharged from the second discharge port An air conditioner comprising: a flow rate ratio changing unit configured to be able to change a discharge flow rate ratio that is a ratio of

Further, in the air conditioner of the present invention, when the first valve member and the second valve member are opened, the intermediate pressure that is the pressure of the gas refrigerant flowing through the series connection pipe becomes the predetermined optimum intermediate pressure. Ru comprising a control means for controlling the flow rate ratio changing means so.

  According to the present invention, the ratio between the flow rate of the gas refrigerant discharged from the first discharge port of the first compression unit and the flow rate of the gas refrigerant discharged from the second discharge port of the second compression unit by the flow rate changing means. (Discharge flow rate ratio) is changed. When this discharge flow rate ratio is changed when the first compression part and the second compression part are connected in series, the pressure (intermediate pressure) of the gas refrigerant flowing in the series connection pipe is changed. When the intermediate pressure is changed, the flow rate of the refrigerant flowing through the injection pipe (injection flow rate) is also changed. Specifically, the lower the intermediate pressure, the higher the injection flow rate, and the higher the intermediate pressure, the lower the injection flow rate. Thus, according to the present invention, the intermediate pressure can be controlled by the flow rate ratio changing means changing the discharge flow rate ratio. Since the intermediate pressure can be controlled, the injection flow rate can be changed to a desired value in accordance with various situations.

  In addition, when the first valve member and the second valve member are opened, the control means controls the flow rate ratio changing means so that the intermediate pressure becomes a predetermined optimum intermediate pressure, thereby allowing various situations. Accordingly, it is possible to inject a gas refrigerant having an optimum flow rate. In addition, the optimum intermediate pressure corresponds to the optimum injection flow rate in advance so that the flow rate of the refrigerant flowing through the injection pipe becomes an optimum injection flow rate that is predetermined as a flow rate that can increase the refrigeration efficiency during the air conditioning operation. It is good to have been established. By controlling the flow rate ratio changing means so that the intermediate pressure becomes the optimum intermediate pressure determined in this way, the gas refrigerant having the optimum flow rate according to various operating conditions is more reliably ensured from the aspect of improving the efficiency. Can be injected. In this case, the control means may feedback control the flow rate ratio changing means based on the deviation between the optimum intermediate pressure and the actual intermediate pressure.

  The flow rate ratio changing means is configured to change the flow rate of the gas refrigerant discharged from the first discharge port of the first compression unit or the flow rate of the gas refrigerant discharged from the second discharge port of the second compression unit. It is good that it is the flow rate changing means. By changing the discharge flow rate of the first compression unit or the second compression unit, the discharge flow rate ratio can be changed.

In this regard, the flow rate changing means according to the present invention includes a bypass pipe connecting the compression chamber of the second compression section and the second suction port or the compression chamber of the first compression section and the first suction port, and a middle of the bypass pipe. a third valve member which opening control interposed, Ru comprising a. The control means, when the first valve member and the second valve member is open, that controls the opening of the third valve member so that the intermediate pressure is optimized intermediate pressure. According to this, the flow rate of the refrigerant discharged from the discharge port of the second compression unit or the first compression unit is controlled by the control means controlling the opening degree of the third valve member. By controlling the discharge flow rate in this way, the injection flow rate can be controlled according to various situations. Furthermore, in this case, the first compression unit and the second compression unit may be driven by the same drive source. According to this, two compressors can be operated with one drive source, and the discharge flow rate ratio is changed even when the two compressors are operating at the same compressor speed. can do.

  In addition, one of the first compression unit and the second compression unit is driven by the engine, the other of the first compression unit and the second compression unit is driven by the electric motor, and the flow rate changing means is an electric motor, The control means may control the rotation speed of the electric motor. According to this, the flow rate of the refrigerant discharged from the discharge port of the second compression unit or the first compression unit is controlled by the control means controlling the rotation speed of the electric motor. By controlling the discharge flow rate and controlling the intermediate pressure in this way, the injection flow rate can be controlled according to various situations.

It is the schematic which shows the structure of the air conditioner which concerns on 1st Embodiment. In 1st Embodiment, it is a figure which shows the connection structure of a gas engine, and a 1st compression part and a 2nd compression part. It is sectional drawing which shows the arrangement | positioning state of the fixed scroll and turning scroll in the scroll compressor which comprises a 2nd compression part. It is a flowchart which shows the injection flow control routine which the control apparatus which concerns on 1st Embodiment performs. It is a figure which shows the flow of the refrigerant | coolant in a compression unit in case the opening / closing valve for series connection and the injection valve are closing. It is a figure which shows the flow of the refrigerant | coolant in a compression unit in case the on-off valve for series connection is opening. It is a figure showing the refrigerating cycle shown on the ph diagram at the time of flowing a refrigerant into injection piping at the time of heating. It is a figure showing the refrigerating cycle shown on the ph diagram at the time of flowing a refrigerant into injection piping at the time of air conditioning. It is the schematic which shows the structure of the air conditioner which concerns on 2nd Embodiment. It is a figure which shows the connection structure of the gas engine and 1st compression part in 2nd Embodiment. It is a flowchart which shows the injection flow control routine which the control apparatus which concerns on 2nd Embodiment performs.

(First embodiment)
A first embodiment of the present invention will be described 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. As shown in FIG. 1, the air conditioner 1 includes a compression unit 10 for compressing a gas refrigerant, indoor heat exchangers 21A and 21B installed indoors for exchanging heat between the refrigerant and indoor air, Installed in the outdoor heat exchanger 22 for exchanging heat between the refrigerant and the outside air, a heating expansion valve 23A and a cooling expansion valve 23B for expanding the refrigerant, a four-way switching valve 24, and a first gas-liquid separating refrigerant. The gas-liquid separator 25 and the second gas-liquid separator 26, a sub heat exchanger 27 for exchanging heat between the refrigerant and the engine cooling water, a control device 30, and a gas engine 40 are provided.

  The compression unit 10 includes a first compression unit 11 and a second compression unit 12. In the present embodiment, the first compression unit 11 and the second compression unit 12 are driven by the driving force of the gas engine 40. FIG. 2 is a diagram showing a connection configuration between the gas engine 40 and the first compression unit 11 and the second compression unit 12. As shown in FIG. 2, the gas engine 40 has an output shaft 41, and power is output to the outside from the output shaft 41. A first pulley 42 and a second pulley 43 are attached to the output shaft 41 so as to be rotatable coaxially with the output shaft 41.

  Further, the first compression unit 11 includes a first suction port 11 a, a first discharge port 11 b, and an input shaft 111. A third pulley 112 is attached to the input shaft 111 so as to be rotatable coaxially with the input shaft 111. A clutch 113 is interposed in the middle of the input shaft 111. The belt BT1 is wound between the third pulley 112 and the first pulley 42. Therefore, the power of the gas engine 40 is transmitted to the input shaft 111 via the output shaft 41, the first pulley 42, the belt BT1, and the third pulley 112. The 1st compression part 11 act | operates because the input shaft 111 rotationally drives. When the first compression unit 11 is operated, gas refrigerant is sucked into the first compression unit 11 from the first suction port 11a, and the sucked gas refrigerant is compressed in the compression chamber in the first compression unit 11, and compressed gas. The refrigerant is discharged from the first discharge port 11b.

  The second compression unit 12 includes a second suction port 12a, a second discharge port 12b, and an input shaft 121. A fourth pulley 122 is attached to the input shaft 121 so as to be rotatable coaxially with the input shaft 121. A clutch 123 is interposed in the middle of the input shaft 121. The belt BT <b> 2 is wound between the fourth pulley 122 and the second pulley 43. Therefore, the power of the gas engine 40 is transmitted to the input shaft 121 via the output shaft 41, the second pulley 43, the belt BT2, and the fourth pulley 122. The 2nd compression part 12 act | operates because the input shaft 121 rotationally drives. When the second compression unit 12 is operated, the gas refrigerant is sucked into the second compression unit 12 from the second suction port 12a, and the sucked gas refrigerant is compressed in the compression chamber in the second compression unit 12 and compressed gas. The refrigerant is discharged from the second discharge port 12b.

  Thus, in this embodiment, both the 1st compression part 11 and the 2nd compression part 12 are driven by one drive source (gas engine 40). For this reason, since the output shaft 111 of the first compressor 11 and the output shaft 121 of the second compressor 12 rotate in synchronization with the rotation of the output shaft 41 of the gas engine 40, the compressor of the first compressor 11 The rotational speed and the compressor rotational speed of the second compressor 12 are the same. Accordingly, the compressor speed of each compressor can be changed by changing the engine speed, but the speed of each compressor cannot be set to a different speed.

  As shown in FIG. 1, one end of the first discharge pipe 131 is connected to the first discharge port 11b of the first compression section 11, and one end of the second discharge pipe 132 is connected to the second discharge port 12b. The refrigerant discharged from the first discharge port 11b flows through the first discharge pipe 131. The refrigerant discharged from the second discharge port 12b flows through the second discharge pipe 132. The other end of the first discharge pipe 131 and the other end of the second discharge pipe 132 merge at a point A in FIG. 1 and are connected to one end of the first pipe 51. 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 55.

  The first discharge pipe 131 and the second suction pipe 142 are connected by a series connection pipe 151. A series connection opening / closing valve 152 is interposed in the series connection pipe 151. Further, an intermediate pressure sensor 153 is attached to the series connection pipe 151. The intermediate pressure sensor 153 detects the pressure (intermediate pressure) Pm of the gas refrigerant flowing through the serial connection 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 serial connection 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 51 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 51. Further, a suction pressure sensor 173 is attached in the middle of the fifth pipe 55 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 55.

  A bypass pipe 181 is connected to the second compression unit 12. The bypass pipe 181 is connected to the second suction port 12 a of the second compression unit 12 through the second suction pipe 142. A bypass valve 182 having a variable opening is interposed in the middle of the bypass pipe 181. In the present embodiment, both the first compressor 11 and the second compressor 12 are scroll compressors. As is well known, the scroll compressor includes a fixed scroll and a turning scroll that rotates eccentrically without rotating with respect to the fixed scroll. Here, the scroll compressor used for the 2nd compression part 12 is demonstrated easily.

  FIG. 3 is a cross-sectional view showing an arrangement state of the fixed scroll 124 and the orbiting scroll 125 in the scroll compressor constituting the second compression unit 12. When the second compression unit 12 is activated, the orbiting scroll 125 does not rotate with respect to the fixed scroll 124 in the order of (a) → (b) → (c) → (d) → (e) in FIG. The core rotates. As shown in FIG. 3, a compression chamber is formed by a space surrounded by the fixed scroll 124 and the orbiting scroll 125. Further, two suction holes 12 c and 12 c communicating with the suction port 12 a of the second compression unit 12 are formed in the bottom plate of the fixed scroll 124. The suction holes 12c and 12c are formed at positions that open to the two compression chambers A1 and A2 formed on the outer side of the space surrounded by the fixed scroll 124 and the orbiting scroll 125. Therefore, the gas refrigerant sucked from the suction port 12a is first introduced into the outer compression chambers A1 and A2 as shown in FIG. Further, one discharge hole 12 d that communicates with the discharge port 12 b of the second compression unit 12 is formed in the bottom plate of the fixed scroll 124. The discharge hole 12 d is formed near the center of the fixed scroll 124.

  As the orbiting scroll 125 rotates eccentrically without rotating with respect to the fixed scroll 124 in the order of (a), (b), (c), (d), and (e) of FIG. The volume is gradually reduced to increase the pressure of the gas refrigerant in the compression chambers A1 and A2, and the position gradually moves from the outer position to the center position. Then, as shown in FIG. 3 (e), when the compression chamber moves to the portion where the discharge hole 12d is opened, the gas refrigerant in the compression chamber is discharged from the discharge port 12b through the discharge hole 12d.

  Further, two bypass holes 12e and 12e are formed in the bottom plate of the fixed scroll 124. The bypass holes 12e and 12e are opened at positions inside the suction holes 12c and 12c. A bypass pipe 181 communicates with the bypass holes 12e and 12e. That is, the bypass pipe 181 connects the second suction port 12 a of the second compression unit 12 and the compression chamber in the second compression unit 12. Therefore, when the bypass valve 182 is open, the bypass holes 12e and 12e communicate with the second suction port 12a (suction holes 12c and 12c) via the bypass pipe 181. For this reason, the pressure in the compression chamber in which the bypass holes 12e and 12e are opened is substantially equal to the suction pressure. That is, while the bypass holes 12e and 12e are open in the compression chamber, the gas refrigerant in the compression chamber is basically not compressed. After the communication between the bypass holes 12e and 12e and the compression chamber is blocked, the gas refrigerant in the compression chamber is compressed. In FIG. 3, since the bypass holes 12e and 12e are open to the compression chambers A1 and A2 between FIGS. 3A to 3C, the gas refrigerant in the compression chambers A1 and A2 is not compressed. Since the bypass holes 12e and 12e do not open to the compression chambers A1 and A2 at the time of FIG. 3D, the gas refrigerant in the compression chambers A1 and A2 starts to be compressed. That is, the bypass pipe 181 connects the compression chamber and the second suction port during the period from the start of compression of the refrigerant in the compression chamber to the middle of the compression, and the connection between the compression chamber and the second suction port thereafter until the end of the compression. It connects to the 2nd compression part 12 so that it may be intercepted. Further, when the bypass valve 182 is closed, the gas refrigerant in the compression chambers A1 and A2 is compressed from the point of FIG.

  When the bypass valve 182 is closed, the compression chambers A1 and A2 are compressed from the time shown in FIG. For this reason, the flow rate of the refrigerant discharged from the discharge port 12b is large. On the other hand, when the bypass valve 182 is open, the compression chambers A1 and A2 are compressed from the midpoint (the time shown in FIG. 3D), so the compression volume is small. For this reason, the flow rate of the refrigerant discharged from the discharge port 12b is small. That is, the 2nd compression part 12 of this embodiment is constituted so that the discharge flow rate of a refrigerant is variable. Further, the discharge flow rate of the second compression unit 12 can be changed by changing the magnitude of the opening degree α of the bypass valve 182. When the bypass valve 182 is closed, the discharge flow rate of the second compression unit 12 is maximum (Qmax), and when the bypass valve 182 is fully open, the discharge flow rate of the second compression unit is minimum (Qmin). . Therefore, as the opening degree α increases from the state where the bypass valve is closed (opening degree α = 0), the discharge flow rate decreases from Qmax, and the discharge flow rate becomes Qmin when fully opened.

  As shown in FIG. 1, the other end of the first pipe 51 is connected to the four-way switching valve 24. As shown in FIG. 1, the four-way switching valve 24 has four ports (a first port 241, a second port 242, a third port 243, and a fourth port 244). The four-way switching valve 24 has a heating connection state in which the first port 241 is connected to the second port 242 and the third port 243 is connected to the fourth port 244, the first port 241 is connected to the third port 243, and The connection state can be switched to the cooling connection state in which the second port 242 is connected to the fourth port 244. The first pipe 51 described above is connected to the first port 241 of the four-way switching valve 24. One end of the second pipe 52 is connected to the second port 242. One end of the third pipe 53 is connected to the third port 243, and one end of the fourth pipe 54 is connected to the fourth port 244.

  The other end of the second pipe 52 branches, the indoor heat exchanger 21A is connected to one branch pipe, and the indoor heat exchanger 21B is connected to the other branch pipe. Each branch pipe is provided with flow control valves 211A and 211B, respectively. The number of indoor heat exchangers may be one or three or more. The outdoor heat exchanger 22 is connected to the other end of the third pipe 53. The indoor heat exchangers 21A and 21B and the outdoor heat exchanger 22 are connected by an intermediate pipe 56. The indoor heat exchangers 21 </ b> A and 21 </ b> B allow refrigerant to flow into the interior from the second pipe 52 or the intermediate pipe 56 and to exchange heat between the refrigerant and the indoor air. The outdoor heat exchanger 22 allows the refrigerant to flow into the inside from the intermediate pipe 56 or the third pipe 53, and allows the refrigerant and the outside air to exchange heat.

  The intermediate pipe 56 includes a heating intermediate pipe 56A and a cooling intermediate pipe 56B that branch at the point C in FIG. 1 and merge at the point D when viewed from the direction toward the outdoor heat exchanger 22 from the indoor heat exchangers 21A and 21B. Have. A heating check valve 591 and a heating expansion valve 23A are interposed in the heating intermediate pipe 56A. The heating check valve 591 allows the flow of the refrigerant in the heating intermediate pipe 56A from the point C to the point D and blocks the flow in the opposite direction. The heating expansion valve 23A expands the refrigerant passing therethrough.

  A cooling check valve 592, a pressure reducing valve 593, a second gas-liquid separator 26, and a cooling expansion valve 23B are interposed in the cooling intermediate pipe 56B. The cooling check valve 592 allows the flow of the refrigerant in the cooling intermediate pipe 56 </ b> B from the point D to the point C and blocks the flow in the opposite direction. The pressure reducing valve 593 depressurizes the refrigerant flowing through the cooling intermediate pipe 56B. The second gas-liquid separator 26 gas-liquid separates the refrigerant flowing through the cooling intermediate pipe 56B, flows the gas refrigerant to the cooling injection pipe 57B described later, and flows only the liquid refrigerant to the cooling intermediate pipe 56B. The cooling expansion valve 23B expands the refrigerant passing therethrough.

  In addition, as shown in FIG. 1, between the portion in the middle of the heating intermediate pipe 56 </ b> A where the heating expansion valve 23 </ b> A is interposed and the portion where the heating check valve 591 is interposed. The one end of the heating injection pipe 57A communicates with this portion. A sub heat exchanger 27 is provided in the middle of the heating injection pipe 57A. The refrigerant flowing through the heating injection pipe 57A flows into the sub heat exchanger 27. The refrigerant flowing into the sub heat exchanger 27 exchanges heat with the cooling water that has cooled the gas engine 40. The sub heat exchanger 27 evaporates liquid refrigerant out of the refrigerant flowing through the heating injection pipe 57A.

  Further, one end of the cooling injection pipe 57B communicates with the second gas-liquid separator 26. The other end of the heating injection pipe 57 </ b> A and the other end of the cooling injection pipe 57 </ b> B merge at a point E in FIG. 1 to form a single injection pipe 57 and communicate with the series connection pipe 151. That is, the intermediate pipe 56 and the serial connection pipe 151 are connected by the injection pipe 57. An injection valve 19 is interposed in the middle of the injection pipe 57.

  The other end of the fourth pipe 54 is connected to the first gas-liquid separator 25. The first gas-liquid separator 25 gas-liquid separates the refrigerant that has flowed there. The gas refrigerant out of the refrigerant gas-liquid separated by the first gas-liquid separator 25 flows through the fifth pipe 55.

  The control device 30 is configured by a microcomputer having a CPU, a ROM, and a RAM. The control device 30 inputs information detected by each sensor (temperature sensor 171, intermediate pressure sensor 153, discharge pressure sensor 172, suction pressure sensor 173, etc.), and operates the air conditioner 1 based on the input information (for example, The engine speed of the gas engine 40 is controlled. To do. The control device 30 is connected to the on-off valve 152 for series connection, the bypass valve 182, and the injection valve 19, and controls the open / close state and opening of these valves 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. In the heating operation, the four-way selector valve 24 is brought into the heating connection state. When the compression unit 10 (the first compression unit 11 and the second compression unit 12) is activated during the heating operation, the high-pressure gas refrigerant compressed by the compression unit 10 is discharged to the first pipe 51. The high-pressure gas refrigerant discharged to the first pipe 51 enters the four-way switching valve 24 from the first port 241. During heating, the first port 241 of the four-way switching valve 24 is connected to the second port 242, and the second port 242 is connected to the second pipe 52, so that the four-way switching valve 24 enters the first port 241. The high-pressure gas refrigerant exits the four-way switching valve 24 from the second port 242, flows in the second pipe 52, and flows into the indoor heat exchangers 21A and 21B. The high-pressure gas refrigerant that has flowed into the indoor heat exchangers 21A and 21B is condensed by discharging heat to the indoor air while flowing through the indoor heat exchangers 21A and 21B. 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 has been exhausted and condensed into the indoor air is partially liquefied and flows out of the indoor heat exchangers 21A and 21B, flows through the intermediate pipe 56, and further flows into the heating intermediate pipe 56A from the position indicated by point C. Then, the pressure is reduced so as to be easily evaporated by being expanded by the heating expansion valve 23 </ b> A, and then flows into the outdoor heat exchanger 22. The refrigerant flowing into the outdoor heat exchanger 22 evaporates by taking the heat of the outside air while flowing through the outdoor heat exchanger 22.

  A part of the refrigerant evaporated by taking the heat of the outside air is vaporized and flows out of the outdoor heat exchanger 22 and flows through the third pipe 53. Then, the four-way switching valve 24 enters from the third port 243. During heating, the third port 243 of the four-way switching valve 24 is connected to the fourth port 244, and the fourth port 244 is connected to the fourth pipe 54, so that the four-way switching valve 24 enters the third port 243. The refrigerant flows from the fourth port 244 through the four-way switching valve 24 to the fourth pipe 54. Then, it flows into the first gas-liquid separator 25 from the fourth pipe 54. In the first gas-liquid separator 25, 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 55 and returns to the compression unit 10.

  Next, the cooling operation will be described. In the cooling operation, the four-way switching valve 24 is brought into a cooling connection state. When the compression unit 10 is activated during the cooling operation, the compressed high-pressure gas refrigerant is discharged from the compression unit 10 to the first pipe 51. The high-pressure gas refrigerant discharged to the first pipe 51 enters the four-way switching valve 24 from the first port 241. During cooling, the first port 241 of the four-way switching valve 24 is connected to the third port 243, and the third port 243 is connected to the third pipe 53, so that the four-way switching valve 24 enters the first port 241. The gas refrigerant exits the four-way switching valve 24 from the third port 243, flows through the third pipe 53, and flows into the outdoor heat exchanger 22. The high-pressure gas refrigerant that has flowed into the outdoor heat exchanger 22 is condensed by discharging heat to the outside air while flowing through the outdoor heat exchanger 22.

  The refrigerant that is condensed by exhausting heat to the outside air is partially liquefied and flows out of the outdoor heat exchanger 22 and flows through the intermediate pipe 56, flows into the cooling intermediate pipe 56B from the position indicated by point D, and is decompressed by the pressure reducing valve 593. After that, it flows into the second gas-liquid separator 26. The second gas-liquid separator 26 separates the refrigerant into a gas refrigerant and a liquid refrigerant. Of the separated refrigerant, only the liquid refrigerant further flows through the cooling intermediate pipe 56B. Then, the pressure is reduced so as to be easily evaporated by being expanded by the cooling expansion valve 23B, and then flows into the indoor heat exchangers 21A and 21B. The refrigerant that has flowed into the indoor heat exchangers 21A and 21B evaporates by taking the heat of the indoor air while flowing through the indoor heat exchangers 21A and 21B. 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 room air partially vaporizes and flows out of the indoor heat exchangers 21A and 21B and flows through the second pipe 52. Then, the four-way switching valve 24 enters from the second port 242. During cooling, the second port 242 of the four-way switching valve 24 is connected to the fourth port 244, and the fourth port 244 is connected to the fourth pipe 54, so that the four-way switching valve 24 enters the third port 243. The refrigerant flows from the fourth port 244 through the four-way switching valve 24 to the fourth pipe 54. Then, it flows into the first gas-liquid separator 25 from the fourth pipe 54. In the first gas-liquid separator 25, 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 55 and returns to the compression unit 10.

  Thus, during heating, the indoor heat exchangers 21A and 21B serve as condensers and the outdoor heat exchanger 22 serves as an evaporator. On the other hand, during cooling, the outdoor heat exchanger 22 becomes a condenser, and the indoor heat exchangers 21A and 21B 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 air conditioning operation of the air conditioner 1, the control device 30 executes an injection flow rate control routine shown in FIG. When this injection flow rate control routine is started, the control device 30 first calculates the operating capacity ratio R in step 11 of FIG. 4 (hereinafter, step is abbreviated as S). 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 based on the temperature Ts detected by the temperature sensor 171, 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. Is calculated.

  Next, the control device 30 determines whether or not the calculated operating capacity ratio R is 50% or less (S12). When the operating capacity ratio R exceeds 50% (S12: No), the control device 30 proceeds to S21 and outputs a closing operation signal to the series connection on-off valve 152, the injection valve 19 and the bypass valve 182. (S16). As a result, the series connection on-off valve 152, the injection valve 19 and the bypass valve 182 are closed. (If already closed, keep it closed). The control device 30 ends the control routine after outputting a closing operation signal to each valve in S21.

  FIG. 5 is a diagram showing the flow of the refrigerant in the compression unit 10 when the series connection on-off valve 152 and the injection valve 19 are closed. The flow of the refrigerant is represented by a dotted arrow in the figure.

  When the series connection on-off valve 152 and the injection valve 19 are closed, the series connection pipe 151 and the injection pipe 57 are closed. In this case, the refrigerant flowing out of the evaporator and flowing through the fifth pipe 55 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 guided to the first suction port 11a and is sucked into the first compression unit 11 from the first suction port 11a. Then, after being compressed inside the first compression unit 11, it is discharged from the first discharge port 11 b of the first compression unit 11 to the first discharge pipe 131. The refrigerant discharged from the discharge port 11b of the first compressor 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 guided to the second suction port 12a and is sucked into the second compression unit 12 from the second suction port 12a. Then, after being compressed inside the second compression unit 12, it is discharged from the second discharge port 12 b of the second compression unit 12 to the second 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 the point A and enter the first pipe 51, and then condense. Flows into the vessel. 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. For this reason, the amount of refrigerant discharged from the compression unit 10 in a single compression process is large. Therefore, since a sufficient amount of refrigerant can flow from the compression unit 10 into the refrigerant circuit, the refrigerant flow rate is insufficient when the operation capacity is large (for example, when the operation capacity ratio R exceeds 50%). The occurrence of insufficient air conditioning capacity can be avoided.

  Moreover, when it is judged that the operating capacity ratio R is 50% or less in S12 of FIG. 4 (S12: Yes), the control device 30 advances the process to S13. When the operation capacity ratio R is 50% or less, for example, the flow control valve 211B is closed, and partial load operation is performed such that the refrigerant does not flow into the indoor heat exchanger 21B and the refrigerant flows only into the indoor heat exchanger 21A. This is the case. In such a case, the control device 30 outputs an opening operation signal to the series connection on-off valve 152 in S13. As a result, the series connection on-off valve 152 is opened. (If already opened, keep it open).

  When the series connection on-off valve 152 is opened, the first discharge pipe 131 and the second suction pipe 142 are connected by the series connection pipe 151. Therefore, 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 via the serial connection pipe 151. FIG. 6 is a diagram showing the refrigerant flow in the compression unit 10 in this case. The flow of the refrigerant is represented by a dotted arrow in the figure.

  When the series connection on-off valve 152 is opened, the first compression unit 11 and the second compression unit 12 are connected in series via the series connection pipe 151. 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 out of the evaporator and flowing through the fifth pipe 55 flows from the point B through the first suction pipe 141, is guided to the first suction port 11a, and is sucked into the first compression unit 11 from the first suction port 11a. The The refrigerant sucked into the first compression section 11 is increased to a predetermined pressure and discharged from the first discharge port 11b to the first discharge pipe 131. The refrigerant discharged to the first discharge pipe 131 flows through the serial connection pipe 151, enters the second suction pipe 142, and is guided to the second suction port 12a. Then, the air is sucked into the second compression unit 12 from the second suction port 12a and is compressed to a high pressure by the second compression unit 12. The refrigerant compressed to a high pressure is discharged from the second discharge port 12b to the second discharge pipe 132. Then, it flows into the 1st piping 51 from the point A, and flows in into a condenser. 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. Further, since the refrigerant can flow through the series connection pipe 151, the refrigerant can be introduced from the injection pipe 57 into the series connection pipe 151 by opening the injection valve 19. That is, when the operating capacity ratio R is 50% or less, the efficiency can be improved by injecting the refrigerant gas.

After outputting the opening operation signal to the series connection on-off valve 152 in S13, the control device 30 outputs the opening operation signal to the injection valve 19 (S14). Thereby, the injection valve 19 is opened (when the valve is already opened, the state is maintained). When the injection valve 19 is opened, the refrigerant flowing through the injection pipe 57 flows into the series connection pipe 151. Next, the control device 30 determines whether the current operation of the air conditioner 1 is a heating operation or a cooling operation (S15). In the case of the heating operation, the control device 30 advances the process to S16. On the other hand, in the case of the cooling operation, the control device 30 advances the process to S17. In S16, control device 30 calculates optimal injection flow rate Q _opt based on the heating injection table. On the other hand, in S17, the control device 30 calculates the optimum injection flow rate _Qopt based on the cooling injection table. The optimum injection flow rate Q _opt is an optimum value determined in advance as the flow rate of the refrigerant flowing through the injection pipe 57 in order to increase the refrigeration efficiency during the air conditioning operation.

After calculating the optimum injection flow rate Q _opt in S16 or S17, the control device 30 determines the optimum intermediate pressure Pm _opt based on the optimum injection flow rate Q _opt . (S18). The optimum intermediate pressure Pm _opt is a pressure necessary for setting the flow rate of the refrigerant flowing through the injection pipe 57 to the optimum injection flow rate Q _opt . Subsequently, the control device 30 feedback-controls the opening degree α of the bypass valve 182 based on the optimum intermediate pressure Pm _opt (S19). As a result, the intermediate pressure Pm is maintained at the optimum intermediate pressure Pm _opt . Thereafter, the control device 30 ends this routine.

By executing the injection flow rate control routine as described above, the control device 30 opens the series connection on-off valve 152 and the injection valve 19 and opens the bypass valve 182 when the operating capacity ratio R is 50% or less. The degree α is controlled. By controlling the opening degree α, the injection flow rate Q is controlled so as to coincide with the optimal injection flow rate Q _opt . Here, the improvement in efficiency by injection will be described separately for heating operation and cooling operation.

(Heating injection)
During heating and when the injection valve 19 is open, a part of the refrigerant flowing through the heating intermediate pipe 56A after being condensed by the indoor heat exchangers 21A and 21B flows into the heating injection pipe 57A. The refrigerant flowing into the heating injection pipe 57A exchanges heat with the engine coolant in the sub heat exchanger 27. As a result, the liquid refrigerant is evaporated. Then, the gas refrigerant that has flowed out of the sub heat exchanger 27 flows into the serial connection pipe 151 through the injection pipe 57, and is further sucked into the second compression section 12 from the second suction port 12 a of the second compression section 12.

  FIG. 7 is a diagram showing the refrigeration cycle shown on the ph diagram when the refrigerant flows through the injection pipe 57 during heating as described above. In FIG. 7, 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 57 in the serial connection pipe 151, but at this time, the refrigerant is cooled by the gas refrigerant flowing from the injection pipe 57. This reduces the specific enthalpy. Accordingly, 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 57. 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 and high-pressure gas refrigerant represented by the position indicated by the point B3 is condensed in the indoor heat exchangers 21A and 21B, thereby changing to the low-temperature and 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 21A and 21B, that is, the air conditioner 1 It corresponds to the heating capacity (operating capacity) exhibited. Efficiency is expressed by L1, L2 and Φ.

  In addition, the injection pipe 57 (heating injection pipe 57A) is located at a point C ′ where a part of the low-temperature high-pressure liquid refrigerant represented by the position indicated by the point C has slightly reduced pressure due to pressure loss when flowing through the intermediate pipe 56. ). The refrigerant that has flowed into the injection pipe 57 is heated and evaporated by heat exchange in the sub heat exchanger 27, and then merges with the refrigerant discharged from the first compression unit 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 57 is expanded by the heating expansion valve 23A, 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 22, 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. 7, when the on-off valve 152 for series connection 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 into the injection pipe 57 to be lower than the temperature of the refrigerant at the end of the first stage of compression. For this reason, the isentropic line passing through the point (B2) representing the state of the refrigerant at the start of the second stage compression and the isentropic line passing through the point (B1) representing the state of the refrigerant at the end of the first stage compression. Is different. In this case, as can be seen from FIG. 7, 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 compression 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. 7, the efficiency of the air conditioner 1 is represented by L1, L2, and Φ. Further, the compression power L2 of the second compression unit 12 is considerably smaller than the compression power L1 of the first compression unit 11. Therefore, if the flow rate of the refrigerant flowing through the injection pipe 57 is increased to such an extent that the second compression unit 12 does not perform the wet operation, and more refrigerant is compressed in the second compression unit 12, more refrigerant can be obtained with less compression power. It can be compressed, and the efficiency can be increased. That is, at the time of heating, the efficiency can be increased by flowing more refrigerant through the injection pipe 57 in order to reduce the compression power.

(Cooling injection)
During cooling and when the injection valve 19 is open, the refrigerant condensed in the outdoor heat exchanger 22 and flowing through the cooling intermediate pipe 56B flows into the second gas-liquid separator 26, and the gas refrigerant, liquid refrigerant, Separated. Only the gas refrigerant flows into the injection pipe 57 (cooling injection pipe 57B). The gas refrigerant flowing through the injection pipe 57 flows into the serial connection pipe 151 and is further sucked into the second compression section 12 from the second suction port 12a of the second compression section 12.

  FIG. 8 is a diagram illustrating the refrigeration cycle shown on the ph diagram when the refrigerant is caused to flow through the injection pipe 57 during cooling. In FIG. 8, 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.

  In addition, the refrigerant compressed by the first compression unit 11 is merged with the gas refrigerant flowing from the injection pipe 57 in the serial connection pipe 151, but at this time, the refrigerant is cooled by the gas refrigerant flowing from the injection pipe 57. This reduces the specific enthalpy. Accordingly, 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 57. 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. When the high-temperature high-pressure gas refrigerant represented by the position indicated by the point B3 is condensed in the outdoor heat exchanger 22, the refrigerant is changed to a low-temperature high-pressure liquid refrigerant represented by the position indicated by the point C. Further, the low-temperature high-pressure liquid refrigerant represented by the position indicated by the point C is depressurized by the pressure reducing valve 593, whereby the state changes to the gas-liquid two-phase refrigerant represented by the position of the point C1. This gas-liquid two-phase refrigerant flows into the second gas-liquid separator 26 and is gas-liquid separated. The gas refrigerant that has been gas-liquid separated by the second gas-liquid separator 26 flows through the injection pipe 57 and merges with the refrigerant discharged from the first compression unit 11 (the refrigerant represented by the position indicated by the point B1). The liquid refrigerant separated from the gas-liquid separator 26 by the second gas-liquid separator 26 is transferred to the liquid state indicated by the point C2, and then expanded by the cooling expansion valve 23B. The state changes to a gas-liquid two-phase refrigerant. Then, the low-temperature low-pressure gas-liquid two-phase refrigerant represented by the position indicated by the point D is evaporated in the indoor heat exchangers 21A and 21B, so that the state changes to the low-pressure gas refrigerant indicated by the point A. The amount of change Φ of the specific enthalpy when the state of the refrigerant changes from the position indicated by the point D to the position indicated by the point A is the heat exchange amount actually exchanged by the indoor heat exchangers 21A and 21B, that is, the air conditioner 1 Corresponds to the cooling capacity (operating capacity) exhibited. The cooling operation is continued by repeating such a refrigeration cycle.

  During cooling, the gas refrigerant separated by the second gas-liquid separator 26 out of the refrigerant flowing out of the outdoor heat exchanger 22 does not contribute to air conditioning even if it flows into the indoor heat exchangers 21A and 21B. Therefore, by passing the gas refrigerant flowing out of the outdoor heat exchanger 22 through the injection pipe 57 and leading to the serial connection pipe 151, it is possible to prevent wasteful refrigerant from flowing into the indoor heat exchangers 21A and 21B. The refrigeration efficiency can be improved by cooling the refrigerant compressed by the two compression units 12. Further, the refrigerant flowing out of the outdoor heat exchanger 22 is separated into gas and liquid, and only the liquid refrigerant is passed through the cooling expansion valve 23B, whereby the enthalpy of the refrigerant evaporated in the evaporator can be lowered, and thereby the indoor heat The evaporation capability (Φ) in the exchangers 21A and 21B can be increased. That is, in the cooling injection according to the present embodiment, the refrigerant is gas-liquid separated by the second gas-liquid separator 26 in order to improve the evaporation capability in the evaporator (indoor heat exchangers 21A and 21B).

As described above, the main purpose of the heating injection is to improve the efficiency by reducing the compression power, whereas the main purpose of the cooling injection is to improve the efficiency by increasing the evaporation capacity. For this reason, even when the injection cycle is used, the optimum value of the flow rate of the refrigerant flowing through the injection pipe 57 (the optimum injection flow rate Q _opt ) differs between heating and cooling. Generally, the optimum value of the flow rate of the refrigerant flowing through the injection pipe 57 during heating injection is larger than the optimum value of the flow rate of the refrigerant flowing through the injection pipe 57 during cooling injection. Therefore, in the present embodiment, at the time of heating injection calculates the optimum injection rate Q _opt based on heating the injection table, at the time of cooling the injection to calculate the optimum injection rate Q _opt based on cooling injection table. Each injection table is configured, for example, as a map in which the optimal injection flow rate Q _opt is made to correspond to the temperature Ts, the discharge pressure Pd, the suction pressure Ps, the required air conditioning load, etc., and the optimal injection with reference to the map The flow rate Q _opt is selected.

Further, the injection flow rate Q is determined by the pressure (intermediate pressure) Pm of the refrigerant flowing in the series connection pipe 151. If the intermediate pressure Pm is low, the differential pressure ΔP between the refrigerant pressure in the injection pipe 57 and the pressure of the refrigerant in the serial connection pipe 151 increases, so the injection flow rate Q increases. On the other hand, if the intermediate pressure Pm is high, the differential pressure ΔP decreases, so the injection flow rate Q decreases. That is, the injection flow rate Q can be controlled by controlling the intermediate pressure Pm (more precisely, the differential pressure ΔP). Therefore, in the present embodiment, the control device 30 calculates the optimum intermediate pressure Pm _opt for flowing the refrigerant having the optimum injection flow rate Q _opt through the injection pipe 57 in S18 of FIG. In this case, for example, the optimum intermediate pressure Pm _opt can be calculated based on the optimum injection flow rate Q _opt with reference to a map that associates the injection flow rate Q with the intermediate pressure Pm.

Note that the control device 30 replaces the process of S16 with the heating intermediate pressure in which the temperature Ts, the discharge pressure Pd, the suction pressure Ps, the required air conditioning load, and the like correspond to the optimum intermediate pressure Pm _opt during heating. Based on a table or the like, the optimum intermediate pressure Pm _opt may be directly determined without calculating the optimum injection flow rate Q _opt . Similarly, the control device 30 replaces the process of S17 with the cooling intermediate pressure in which the temperature Ts, the discharge pressure Pd, the suction pressure Ps, the required air conditioning load, and the like correspond to the optimum intermediate pressure Pm _opt at the time of cooling. Based on a table or the like, the optimum intermediate pressure Pm _opt may be directly determined without calculating the optimum injection flow rate Q _opt . In this case, the process of S18 can be omitted.

  The intermediate pressure Pm is determined by the ratio (discharge flow ratio) QR (= Q2 / Q1) between the discharge flow rate Q1 of the first compression unit 11 and the discharge flow rate Q2 of the second compression unit 12. When the discharge flow rate Q2 of the second compression unit 12 is smaller than the discharge flow rate Q1 of the first compression unit 11 (when the discharge flow rate ratio QR is small), the suction from the second compression unit 12 by the refrigerant from the first compression unit 11 Since the mouth 12a side is pressurized, the suction pressure (that is, the intermediate pressure Pm) of the second compression unit 12 increases. On the other hand, when the discharge flow rate Q2 of the second compression unit 12 is larger than the discharge flow rate Q1 of the first compression unit 11 (when the discharge flow rate ratio QR is large), the refrigerant on the suction port 12a side of the second compression unit 12 is discharged. Since it is pulled toward the outlet 12b, the suction pressure (that is, the intermediate pressure Pm) of the second compression unit 12 is reduced. That is, the intermediate pressure Pm can be controlled by controlling the discharge flow rate ratio QR.

Further, the discharge flow rate ratio QR is determined by the opening degree α of the bypass valve 182 interposed in the bypass pipe 181 connected to the second compression unit 12. When the opening degree α is increased, the discharge flow rate Q2 of the second compression unit 12 is decreased, so that the discharge flow rate ratio QR is decreased. On the other hand, when the opening degree α is decreased, the discharge flow rate Q2 of the second compression unit 12 is increased, so that the discharge flow rate ratio QR is increased. That is, the bypass pipe 181 and the bypass valve 182 are discharge flow ratio changing means, and the discharge flow ratio QR can be controlled by controlling the opening degree α of the bypass valve 182. From these, it can be seen that the intermediate pressure Pm can be controlled by controlling the opening degree α, and hence the injection flow rate Q can be controlled. Therefore, in the present embodiment, the opening degree α is feedback-controlled based on the optimum intermediate pressure Pm _opt in S19 of FIG. In this case, a deviation ΔPm (= Pm _opt −Pm) between the current intermediate pressure Pm and the optimum intermediate pressure Pm _opt is calculated, and feedback control is performed by outputting a control signal to the bypass valve 182 so that the deviation ΔPm approaches zero. Is done. Therefore, according to the present embodiment, the opening degree α of the bypass valve 182 is feedback-controlled so that the intermediate pressure Pm becomes the optimum intermediate pressure Pm _opt and the discharge flow rate ratio QR is set to a desired flow rate ratio. A gas refrigerant having an optimum flow rate can be caused to flow through the injection pipe 57 depending on conditions. As a result, the refrigeration efficiency can be increased particularly during partial load operation where the operation capacity ratio is 50% or less.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. In the said 1st Embodiment, although the 1st compression part 11 and the 2nd compression part 12 demonstrated both the air conditioners 1 comprised so that it might drive synchronously with the one gas engine 40, in this embodiment. Only the first compression unit 11 is driven by the gas engine 40. The 2nd compression part 12 is an electric compressor driven with an electric motor.

  FIG. 9 is a schematic diagram illustrating a configuration of the air conditioner 2 according to the present embodiment. As with the air conditioner 1 according to the first embodiment, the air conditioner 2 according to the present embodiment includes the compression unit 10, the indoor heat exchangers 21A and 21B, the outdoor heat exchanger 22, the heating expansion valve 23A, and A cooling expansion valve 23B, a four-way switching valve 24, a first gas-liquid separator 25 and a second gas-liquid separator 26, a sub heat exchanger 27, a control device 30, and a gas engine 40 are provided. Among these, the configuration other than the compression unit 10 and the control device 30 is the same as the configuration shown in the first embodiment.

  As shown in FIG. 9, the compression unit 10 according to this embodiment includes a first compression unit 11 and a second compression unit 612. The first compression unit 11 is driven by the driving force of the gas engine 40. FIG. 10 is a diagram illustrating a connection configuration between the gas engine 40 and the first compression unit 11. As shown in FIG. 10, the gas engine 40 has an output shaft 41 from which power is output to the outside. A first pulley 42 is attached to the output shaft 41 so as to be rotatable coaxially with the output shaft 41.

  The first compression section 11 has an input shaft 111, and a third pulley 112 is attached to the input shaft 111 so as to be rotatable coaxially with the input shaft 111. A clutch 113 is interposed in the middle of the input shaft 111. A belt BT <b> 1 is wound between the third pulley 112 and the first pulley 42. Therefore, the power of the gas engine 40 is transmitted to the input shaft 111 via the output shaft 41, the first pulley 42, the belt BT1, and the third pulley 112.

  Moreover, as shown in FIG. 9, the 2nd compression part 612 has the 2nd suction port 612a and the 2nd discharge port 612b. The air conditioner 2 of the present embodiment includes an electric motor 62, and the electric motor 62 is connected to the second compression unit 612. The second compression unit 612 operates when the electric motor 62 is driven. In the present embodiment, the first compressor 11 and the second compressor 12 are scroll compressors, but other compressors may be used.

  The control device 30 is configured by a microcomputer having a CPU, a ROM, and a RAM. The control device 30 inputs information detected by each sensor (temperature sensor 171, intermediate pressure sensor 153, discharge pressure sensor 172, suction pressure sensor 173, etc.) and operates the air conditioner 2 based on the input information (for example, The engine speed of the gas engine 40 is controlled. To do. The control device 30 is electrically connected to the series connection on-off valve 152 and the injection valve 19, and controls the open / close state of these valves. Further, the control device 30 is also electrically connected to the electric motor 62 and controls the rotation speed of the electric motor 62. Other configurations of the present embodiment are the same as those described in the first embodiment. Therefore, the same components as those described in the first embodiment are denoted by the same reference numerals, and a specific description thereof is omitted.

  Since the basic flow of the refrigerant during the air-conditioning operation (heating operation and cooling operation) of the air-conditioning apparatus 2 according to the present embodiment is the same as the flow described in the first embodiment, the specific description thereof is omitted. .

  During the air conditioning operation of the air conditioner 2, the control device 30 performs the injection flow rate control shown in FIG. When the injection flow rate control routine is activated, the control device 30 first calculates the operating capacity ratio R in S31 of FIG. Next, it is determined whether or not the calculated operating capacity ratio R is 50% or less (S32). When the operating capacity ratio R exceeds 50% (S32: No), the control device 30 advances the process to S41 and outputs a closing operation signal to the series connection on-off valve 152 and the injection valve 19. As a result, the series connection on-off valve 152 and the injection valve 19 are closed. (If already closed, keep it closed). The control device 30 ends the control routine after outputting the closing operation signal to each valve in S41.

  In addition, when it is determined in S32 of FIG. 11 that the operating capacity ratio R is 50% or less (S32: Yes), the control device 30 proceeds to S33 and sends an open operation signal to the series connection on-off valve 152. Output. As a result, the series connection on-off valve 152 is opened. (If already opened, keep it open).

Next, the control device 30 outputs an opening operation signal to the injection valve 19 (S34). Thereby, the injection valve 19 is opened (when the valve is already opened, the state is maintained). When the injection valve 19 is opened, the refrigerant flowing through the injection pipe 57 flows into the series connection pipe 151. Next, the control device 30 determines whether the current operation of the air conditioner 1 is a heating operation or a cooling operation (S35). In the case of the heating operation, the control device 30 advances the process to S36. On the other hand, in the case of the cooling operation, the control device 30 advances the process to S37. In S36, control device 30 calculates optimal injection flow rate Q _opt based on the heating injection table. On the other hand, in S37, the control device 30 calculates the optimum injection flow rate Q _opt based on the cooling injection table.

After calculating the optimum injection flow rate Q _opt in S36 or S37, the control device 30 determines the optimum intermediate pressure Pm _opt based on the optimum injection flow rate Q _opt . (S38). Subsequently, the control device 30 feedback-controls the rotational speed β of the electric motor 62 based on the optimum intermediate pressure Pm _opt (S39). As a result, the intermediate pressure Pm is maintained at the optimum intermediate pressure Pm _opt . Thereafter, the control device 30 ends this routine.

  When the controller 30 executes the injection flow rate control routine as described above, when the operating capacity ratio R is 50% or less, the series connection on-off valve 152 and the injection valve 19 are opened, and the motor of the electric motor 62 is The rotational speed β is controlled.

As described in the first embodiment, the injection flow rate Q can be controlled by controlling the intermediate pressure Pm. The intermediate pressure Pm is determined by a ratio (discharge flow ratio) QR (= Q2 / Q1) between the discharge flow rate Q1 of the first compression unit 11 and the discharge flow rate Q2 of the second compression unit 612. The discharge flow rate ratio QR is determined by the rotational speed β of the electric motor 62 in the present embodiment. When the rotation speed β decreases, the discharge flow rate QR decreases because the discharge flow rate of the second compressor 12 decreases. On the other hand, when the rotation speed β increases, the discharge flow rate Q2 of the second compression unit 12 increases, so the discharge flow rate ratio QR increases. That is, the electric motor 62 is a discharge flow rate ratio changing unit, and the discharge flow rate ratio QR can be controlled by controlling the rotation speed β of the electric motor 62 (the compressor rotation speed of the second compression unit 12). From these, it can be seen that the intermediate pressure Pm can be controlled by controlling the motor rotational speed β (or the compressor rotational speed of the second compressor 12), and hence the injection flow rate Q can be controlled. Therefore, in the present embodiment, feedback control of the motor rotational speed β is performed based on the optimum intermediate pressure Pm _opt in S39 of FIG. In this case, a deviation ΔPm (= Pm _opt −Pm) between the current intermediate pressure Pm and the optimum intermediate pressure Pm _opt is calculated, and feedback control is performed by outputting a control signal to the electric motor 62 so that the deviation ΔPm approaches zero. Is done. Therefore, according to this embodiment, the discharge flow rate ratio QR is desired by feedback-controlling the motor rotational speed β (or the compressor rotational speed of the second compressor 12) so that the intermediate pressure Pm becomes the optimum intermediate pressure Pm _opt. By setting to the flow rate ratio, the gas refrigerant having the optimum flow rate can be caused to flow through the injection pipe 57 in accordance with the operating conditions. As a result, the refrigeration efficiency can be increased particularly during partial load operation where the operation capacity ratio is 50% or less.

  As described above, the air conditioners 1 and 2 according to the first and second embodiments have the first suction port 11a and the first discharge port 11b, and suck the gas refrigerant from the first suction port 11a and the sucked gas. The first compressor 11 that compresses the refrigerant and discharges it from the first discharge port 11b, the second suction ports 12a and 612a, and the second discharge ports 12b and 612b, and the gas refrigerant from the second suction ports 12a and 612a. The second compressors 12 and 612 for sucking and compressing the sucked gas refrigerant and discharging them from the second discharge ports 12b and 612b, the first discharge pipe 131 connected to the first discharge port 11b, and the second discharge port 12b, 612b connected to the second discharge pipe 132, the first discharge pipe 131 and the second discharge pipe 132 through which the refrigerant flowing in and a condenser configured to condense the refrigerant that flows in (heating operation) Is an indoor heat exchanger 21A, 21B, an outdoor heat exchanger 22 during cooling operation, and an evaporator configured to evaporate refrigerant flowing out of the condenser (outdoor heat exchanger 22 during heating operation, during cooling operation). Is an indoor heat exchanger 21A, 21B), an intermediate pipe 56 connecting the condenser and the evaporator, a first suction pipe 141 configured to guide the refrigerant flowing out of the evaporator to the first suction port 11a, A second suction pipe 142 configured to guide the refrigerant flowing out of the evaporator to the second suction ports 12a and 612a, a series connection pipe 151 connecting the first discharge pipe 131 and the second suction pipe 142, and a series connection An on-off valve 152 for series connection interposed in the middle of the pipe 151, an injection pipe 57 for connecting the intermediate pipe 56 and the series connection pipe 151, and an injection interposed in the middle of the injection pipe 57 The discharge flow rate ratio QR, which is the ratio of the flow rate Q1 of the gas refrigerant discharged from the first valve 11 and the first discharge port 11b and the flow rate Q2 of the gas refrigerant discharged from the second discharge ports 12b and 612b. And a flow rate ratio changing means (bypass pipe 181, bypass valve 182, electric motor 62) configured to be able to

Further, the air conditioners 1 and 2 of the first and second embodiments have an intermediate pressure which is the pressure of the gas refrigerant flowing in the series connection pipe 151 when the series connection on-off valve 152 and the injection valve 19 are open. A control device 30 is provided for controlling the flow rate ratio changing means so that the pressure Pm becomes a predetermined optimum intermediate pressure Pm _opt .

  According to the air conditioners 1 and 2 according to the first and second embodiments, the discharge flow rate ratio QR is controlled by the flow rate change means when the first compression unit 11 and the second compression units 12 and 612 are connected in series. By doing so, the intermediate pressure Pm can be controlled. For this reason, the injection flow rate Q can be changed according to various operating conditions.

Further, when the series connection on-off valve 152 and the injection valve 19 are opened, the control device 30 controls the flow rate ratio changing means so that the intermediate pressure Pm becomes a predetermined optimum intermediate pressure Pm _opt. Thus, it is possible to inject a gas refrigerant having an optimum flow rate according to various operating conditions such as heating operation and cooling operation. Further, the optimum intermediate pressure Pm _opt is set so that the flow rate of the refrigerant flowing through the injection pipe 57 becomes an optimum injection flow rate Q _opt that is predetermined as the flow rate of the refrigerant flowing through the injection pipe 57 in order to increase the refrigeration efficiency during the air conditioning operation. Therefore, it is possible to inject a gas refrigerant having an optimum flow rate according to various operating conditions more reliably in terms of increasing efficiency.

The air conditioner 1 according to the first embodiment includes a bypass pipe 181 that connects the compression chamber of the second compression unit 12 and the second suction port 12a, and an opening degree control that is interposed in the middle of the bypass pipe 181. A possible bypass valve 182 is provided. The bypass pipe 181 is connected between the compression chamber and the second suction port 12a during the period from the start of compression of the gas refrigerant in the compression chamber of the second compression unit 12 to the middle of the compression. It connects to the 2nd compression part 12 so that connection with a room and the 2nd inlet 12a may be intercepted. Then, the control device 30 feedback-controls the opening α of the bypass valve 182 so that the intermediate pressure Pm becomes the optimum intermediate pressure Pm _opt when the series connection on-off valve 152 and the injection valve 19 are open. . The flow rate of the refrigerant discharged from the second discharge port 12b of the second compression unit 12 so that the flow rate of the refrigerant flowing through the injection pipe 57 becomes the optimum injection flow rate Q _opt by the control device 30 controlling the opening degree α. Is controlled. By controlling the discharge flow rate in this way, the injection flow rate can be controlled according to various situations.

  Moreover, according to the said 1st Embodiment, the 1st compression part 11 and the 2nd compression part 12 are driven by the same drive source (gas engine 40). For this reason, two compressors can be operated by one drive source, and even when the two compressors are operating at the same compressor speed, discharge can be performed by adjusting the opening degree α. The flow rate ratio QR can be changed.

In the air conditioner 2 according to the second embodiment, the first compressor 11 is driven by the gas engine 40 and the second compressor 12 is driven by the electric motor 62. And the control apparatus 30 feedback-controls the rotation speed (beta) of the electric motor 62 so that the flow volume of the refrigerant _| coolant which flows through the injection piping 57 may turn into the optimal injection flow volume _Qopt . The control device 30 controls the motor rotational speed β so that the flow rate of the refrigerant flowing through the injection pipe 57 becomes the optimum injection flow rate Q _opt so that the refrigerant discharged from the second discharge port 12b of the second compression unit 12 The flow rate is controlled. By controlling the discharge flow rate in this way, the injection flow rate can be controlled according to various situations.

  Further, according to the second embodiment, the intermediate pressure Pm can be controlled without providing special means such as the bypass pipe 181 and the bypass valve 182 as in the first embodiment. Moreover, since the drive source of the 1st compression part 11 and the drive source of the 2nd compression part 12 differ, each compression part can be driven independently. For this reason, for example, when a scroll compressor is used as the compression unit, the pressure pulsation can be canceled by shifting the generation timing of the pressure pulsation generated in each compressor. For this reason, loss of compression work due to pressure pulsation is reduced.

  Furthermore, according to the second embodiment, since the second compression unit 612 is an electric compressor, even when the operation of the first compression unit 11 is impossible due to a shortage of fuel in the gas engine, the power from a commercial power source or the like The operation of the air conditioner can be continued by operating the second compression unit 612 by supplying power. In addition, the running cost can be reduced by increasing the driving ratio of the second compression unit 612 at night or the like when electric power is cheaper than gas.

As mentioned above, although embodiment of this invention was described, this invention should not be limited to the said embodiment. For example, in the first and second embodiments, the configuration in which the discharge flow rate of the second compression unit 12 is changed in order to change the discharge flow rate ratio QR has been described. However, the discharge flow rate of the first compression unit 11 is changed. Alternatively, both the discharge flow rate of the first compression unit 11 and the discharge flow rate of the second compression unit 12 may be changed. In the first and second embodiments, an example in which the optimum injection flow rate is calculated with reference to the heating injection table or the cooling injection table and the optimum intermediate pressure Pm _opt is determined based on the calculated optimum injection flow rate has been described. However, the optimum intermediate pressure Pm _opt may be determined without calculating the optimum injection flow rate Q _opt based on various information such as heating / cooling, discharge pressure Pd, suction pressure Ps, and required air conditioning load. Further, in order to change the discharge flow rate of the first compression unit 11 and / or the second compression unit 12, the compression unit is configured so that the volume (exclusion volume) of the compression chamber in the compression unit can be changed according to the situation. May be. For example, when using a compressor having a mechanism for reciprocating the piston by rotating the swash plate (swash plate type compressor), the displacement volume can be reduced by changing the reciprocating stroke of the piston by changing the inclination angle of the swash plate. You may use the compressor comprised so that it could change in the air conditioner of this invention. Thus, the present invention can be modified without departing from the gist thereof.

DESCRIPTION OF SYMBOLS 1, 2 ... Air conditioning apparatus, 10 ... Compression unit, 11 ... 1st compression part, 11a ... 1st suction port, 11b ... 1st discharge port, 12,612 ... 2nd compression part, 12a, 612a ... 2nd suction port 12b, 612b ... second discharge port, 12c ... suction hole, 12d ... discharge hole, 12e ... bypass hole, 131 ... first discharge pipe, 132 ... second discharge pipe, 141 ... first suction pipe, 142 ... second Inlet piping, 151 ... Series connection piping, 152 ... Series connection on-off valve (first valve member), 153 ... Intermediate pressure sensor, 171 ... Temperature sensor, 172 ... Discharge pressure sensor, 173 ... Suction pressure sensor, 181 ... Bypass piping (Flow rate ratio changing means, flow rate changing means), 182 ... Bypass valve (flow rate ratio changing means, flow rate changing means, third valve member), 19 ... Injection valve (second valve member), 21A, 21B ... Indoor heat exchanger (Steamed , 22) outdoor heat exchanger (condenser, evaporator), 23A ... expansion valve for heating (condenser, evaporator), 23B ... expansion valve for cooling, 24 ... four-way switching valve, 25 ... first DESCRIPTION OF SYMBOLS 1 gas-liquid separator, 26 ... 2nd gas-liquid separator, 27 ... sub heat exchanger, 30 ... control apparatus (control means), 40 ... gas engine, 51 ... 1st piping, 52 ... 2nd piping, 53 ... 3rd piping, 54 ... 4th piping, 55 ... 5th piping, 56 ... Intermediate piping, 56A ... Intermediate piping for heating, 56B ... Intermediate piping for cooling, 57 ... Injection piping, 57A ... Heating injection piping, 57B ... Cooling injection Piping 62, electric motor (flow ratio changing means, flow changing means, electric motor), 593 ... pressure reducing valve, Pd ... discharge pressure, Pm ... intermediate pressure, Pm _opt ... optimum intermediate pressure, Ps ... suction pressure, Q ... injection flow rate , _{Q o t ...} optimum injection rate, QR ... discharge flow rate ratio, R ... operation capacity ratio, alpha ... opening, beta ... motor speed

Claims (2)

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;
A second discharge pipe connected to the second discharge port;
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 series connection pipe connecting the first discharge pipe and the second suction pipe;
A first valve member interposed in the middle of the series connection pipe;
An injection pipe connecting the intermediate pipe and the series connection pipe;
A second valve member interposed in the middle of the injection pipe;
A flow rate ratio changing unit configured to change a discharge flow rate ratio which is a ratio of a flow rate of the gas refrigerant discharged from the first discharge port and a flow rate of the gas refrigerant discharged from the second discharge port. When,
When the first valve member and the second valve member are opened, the flow rate ratio is changed so that the intermediate pressure, which is the pressure of the gas refrigerant flowing in the series connection pipe, becomes the predetermined optimum intermediate pressure. Control means for controlling the means ,
The flow rate changing means includes a bypass pipe that connects the compression chamber of the second compression section and the second suction port or the compression chamber of the first compression section and the first suction port, and is interposed in the middle of the bypass pipe. A third valve member mounted on the opening controllable,
The control means controls the opening of the third valve member so that the intermediate pressure becomes the optimum intermediate pressure when the first valve member and the second valve member are opened. apparatus. The air conditioner according to claim 1,
An air conditioner in which the first compression unit and the second compression unit are driven by the same drive source.

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