JP2006170488A - Air conditioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air conditioner capable of being operated corresponding to load with a simple constitution. <P>SOLUTION: This air conditioner 1 comprises two compressors 4, 5, and a suction-side check valve 10 is mounted in a second suction branch pipe 9 of the upper-side compressor 5. Discharge branch pipes 13, 14 of the compressors 4, 5 are constituted to allow refrigerants to flow together after passing through the discharge-side check valves 15, 18. A bypass pipe 16 further extends from the discharge branch pipe 13 of the lower-side compressor 4, and the bypass pipe 16 is connected with the second suction branch pipe 9. An opening and closing valve 17 is mounted in the bypass pipe 16. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an air conditioner capable of two-stage compression.

  Some air conditioners that can be switched between a cooling operation and a heating operation include a compressor in series (for example, see Patent Document 1 and Patent Document 2). In the air conditioner disclosed in Patent Document 1, a low-stage compressor, a high-stage compressor, a condenser, an intercooler, a main throttle device, and an evaporator are sequentially connected by piping. ing.

Moreover, in the air conditioner disclosed in Patent Document 2, a switching device is provided so that air conditioning can be performed by only one of the low-stage compressor and the high-stage compressor. Specifically, in the configuration in which the cooling operation and the heating operation can be switched by switching the four-way valve, a three-way valve is provided in the piping on the suction side of the low-stage compressor, and the refrigerant is not passed through the low-stage compressor. Is piped so that it can be directly introduced into the high stage compressor. Furthermore, a three-way valve is provided in the pipe connecting the low-stage compressor and the high-stage compressor, so that the refrigerant from the low-stage compressor is directly passed through the heat exchanger without going through the high-stage compressor. It is piped so that it can be supplied to The switching device composed of these three-way valve and four-way valve is switched depending on the outdoor air temperature, and three operation cycles are possible.
Japanese Unexamined Patent Publication No. Hei 2-213652 JP 10-1111031 A

However, in the air conditioner disclosed in Patent Document 1, since the low-stage compressor and the high-stage compressor are connected in series, the two compressors are always operated at the same time. In other words, each compressor cannot be operated independently, that is, a single-stage compression operation cannot be performed. If single-stage compression operation is not possible, under high-pressure operation conditions, such as during overload operation, the compressor will stop due to a high-pressure cut, resulting in a decrease in comfort and reliability of the compressor. The sex will be reduced. Also, even under low load conditions such as heating overload and cooling low temperature conditions, the two compressors always operate, so the capacity becomes excessive and the entire system is repeatedly started and stopped, resulting in energy consumption. Efficiency will decrease.
In addition, in an air conditioner as disclosed in Patent Document 2, in addition to the four-way valve used for switching between cooling and heating, a three-way valve is used for switching the refrigerant flow path around each compressor. Therefore, there is a problem that the apparatus configuration becomes complicated. In addition, as the number of valves increases, complicated control is required for switching these valves, resulting in a problem that the cost of the apparatus increases.
The present invention has been made in view of such circumstances, and an object of the present invention is to enable operation in accordance with a load with a simple configuration.

  The invention according to claim 1 of the present invention that solves the above-described problems includes a first compressor, a second compressor, a four-way valve, an outdoor heat exchanger, an outdoor unit having an outdoor decompression means, and an indoor decompression. Means, an air conditioner in which an indoor unit having an indoor heat exchanger is connected by a liquid pipe and a gas pipe, and a suction pipe for sucking refrigerant into the first and second compressors is provided in the first compressor. The first suction branch pipe branches into a second suction branch pipe of the second compressor, and a suction-side check valve for preventing a reverse flow of the refrigerant is provided in the second suction branch pipe. A discharge pipe through which the refrigerant discharged from the first and second compressors flows is a first discharge pipe of the first compressor and a second discharge pipe of the second compressor. Are connected to the four-way valve, and a discharge-side check valve for preventing a refrigerant backflow is provided in the first and second discharge pipes. A bypass branch pipe branches from between the discharge check valve of the first discharge pipe and the first compressor, and the bypass branch pipe is connected to the second suction branch pipe. The air conditioner is characterized in that it is connected between the suction side check valve and the second compressor.

  In this air conditioner, so-called two-stage compression can be performed in which the gas refrigerant discharged from the first compressor is sucked into the second compressor through the bypass branch pipe and further compressed. In this case, the high-pressure gas refrigerant discharged from the second compressor does not flow back to the first compressor through the second discharge pipe by the discharge-side check valve on the first compressor side. . The function of the discharge side check valve is also exhibited when only the second compressor is operated. Also, the gas refrigerant flowing through the bypass branch pipe does not flow back through the second suction branch pipe by the suction side check valve. With this configuration, the refrigerant suction path and the discharge path can be switched as appropriate, and single-stage compression and two-stage compression can be arbitrarily selected.

The invention according to claim 2 is the air conditioner according to claim 1, characterized in that the first compressor has a larger capacity than the second compressor.
In this air conditioner, when the first compressor is operated as a low-stage compressor when the two-stage compression is performed, the compressor capacity of the first compressor is increased, so that the gas refrigerant is efficiently used. Boosts well.

The invention according to claim 3 is the air conditioner according to claim 1 or 2, wherein only the first compressor is operated, only the second compressor is operated, and A control unit that switches between a mode in which both the first and second compressors are operated simultaneously is provided.
In this air conditioner, in addition to the two-stage compression operation, a compressor having an appropriate capacity can be selected in stages according to the load, and the operation can be performed efficiently.

The invention according to claim 4 is the air conditioner according to claim 1 or 2, wherein the branch pipe is provided with an open / close valve.
In this air conditioner, when the on-off valve is closed, the flow of the gas refrigerant from the discharge side of the first compressor toward the suction side of the second compressor can be prohibited. By providing the on-off valve in this way, the parallel compression mode can be implemented.

According to a fifth aspect of the present invention, in the air conditioner according to the fourth aspect, a mode in which only the first compressor is operated, a mode in which only the second compressor is operated, and the on-off valve is opened. The air conditioner further comprises a control unit that switches between a mode in which both the first and second compressors are operated simultaneously and a mode in which the on-off valve is closed and both the compressors are operated. The machine performs single-stage compression using the first compressor or the second compressor at low load or during standard operation, and under conditions where the compression ratio is large, such as low outside air temperature conditions for heating. Then, the on-off valve is opened to perform two-stage compression. Further, when a compression function is required, such as at high loads, the on-off valve is closed and single-stage compression is performed in parallel by two compressors.

The invention according to claim 6 is the air conditioner according to any one of claims 1 to 5, wherein at least one of the first compressor and the second compressor is included. The compressor is a variable capacity compressor.
In this air conditioner, when single-stage compression is performed with one compressor, the compressor capacity can be controlled according to the load. Moreover, the compression ratio in each compressor is optimized at the time of two-stage compression by changing the capacity.

  According to the present invention, the bypass branch pipe connecting the discharge side of the first compressor and the suction side of the second compressor, and the reverse flow of the refrigerant from the bypass branch pipe toward the suction side of the first compressor Since there is a suction side check valve to prevent and a discharge side check valve to prevent backflow from the discharge side of one compressor to the discharge side of the other compressor, it is not necessary to control switching of the three-way valve In addition, single-stage compression and two-stage compression can be selectively performed, and it is possible to select an appropriate operation cycle according to the operation state. Furthermore, since the number of switching valves can be reduced, the cost of the apparatus can be reduced. In addition, when an on-off valve is provided in the branch pipe, general parallel compression in which two compressors are operated together becomes possible. If the capacity of the first compressor is made larger than the capacity of the second compressor or the capacity of the second compressor is made variable, it becomes possible to cope with various load changes and energy. Consumption efficiency can be improved, and at the time of two-stage compression, the compression ratio in each compressor can be optimized, so that operation efficiency and reliability can be improved.

The best mode for carrying out the invention will be described in detail with reference to the drawings.
As shown in FIG. 1, the air conditioner 1 is composed of an outdoor unit 2 and an indoor unit 3. The outdoor unit 3 includes two compressors, a low-stage compressor 4 that is a first compressor and a high-stage compressor 5 that is a second compressor. The high-stage compressor 5 is a variable capacity compressor that has a smaller capacity than the low-stage compressor 4 but can change its capacity.
A suction pipe 6 is connected to the suction side of each compressor 4, 5. The suction pipe 6 branches at a branch point 7 into a first suction branch pipe 8 and a second suction branch pipe 9. The first suction branch pipe 8 is connected to the suction side of the low stage compressor 4, and the second suction branch pipe 9 is connected to the suction side of the high stage compressor 5. A suction side check valve 10 is provided in the second suction branch pipe 9. The suction-side check valve 10 is set so as to allow the refrigerant to flow in the direction toward the high-stage compressor 5 but not to allow the refrigerant to flow in the opposite direction.

Further, a discharge pipe 11 is connected to the discharge side of each of the compressors 4 and 5. The discharge pipe 11 has a first discharge pipe 13 connected to the discharge side of the low stage side compressor 4 and a second discharge pipe 14 connected to the discharge side of the high stage side compressor 5. The 1 discharge piping 13 and 14 is comprised so that it may join. A discharge side check valve 15 is provided in the first discharge pipe 13. The discharge-side check valve 15 allows the refrigerant to flow in the direction from the low-stage compressor 4 toward the junction 12, but does not allow the refrigerant to flow in the direction to flow backward to the low-stage compressor 4. Is set to Further, a bypass pipe 16 branches from between the discharge side check valve 15 and the low stage side compressor 4. The bypass pipe 16 is connected to the second suction branch pipe 9 on the higher stage side compressor 5 side than the suction side check valve 10, and in the bypass pipe 16, an on-off valve 17 made of an electromagnetic valve is provided. Is provided.
The second discharge pipe 14 is connected to the discharge side of the high stage compressor 5. A discharge-side check valve 18 is provided in the second discharge pipe 14. The discharge-side check valve 18 allows the refrigerant to flow in the direction from the high-stage compressor 5 toward the junction 12, but does not allow the refrigerant to flow in the direction toward the high-stage compressor 5. Is set to

  Further, the discharge pipe 11 is connected to the first port 20 a of the four-way valve 20. In FIG. 1, the first port 20 a communicates with the second port 20 b, and the second port 20 b is connected to the indoor heat exchanger 22 of the indoor unit 3 via a pipe 21. Furthermore, one end of a pipe 23 that is a liquid pipe is connected to the indoor heat exchanger 22, and an expansion valve 24 is provided on the one end side of the pipe 23 and in the indoor unit 3. . The other end of the pipe 23 is led to the outdoor unit 2 and connected to the outdoor heat exchanger 26 via the expansion valve 25. Furthermore, a pipe 27 is connected to the outdoor heat exchanger 26, and this pipe 27 is connected to the third port 20 c of the four-way valve 20. In FIG. 1, the third port 20c communicates with the fourth port 20d, and the aforementioned suction pipe 6 is connected to the fourth port 20d. The piping configuration in FIG. 1 corresponds to the heating operation. During the cooling operation, which will be described later, the four-way valve 20 is switched so that the first port 20a and the third port 30c communicate with each other. 20b communicates with the fourth port 20d.

  In addition, the outdoor unit 2 is provided with a control unit 28, which controls the compressors 4, 5, switches the on-off valve 17 and the four-way valve 20, and opens the expansion valves 24, 25. I am in charge of adjusting the degree.

Next, the operation of this embodiment will be described.
The air conditioner 1 is controlled by the control unit 28 into a single-stage compression mode in which only one of the first compressor and the second compressor is operated, a two-stage compression mode, and a parallel compression mode. You can switch and drive.

  In the single-stage compression mode, the compressors 4 and 5 are appropriately selected according to the load, such as when the heating is overloaded or when the cooling is at a low temperature. For example, when only the high stage side compressor 5 is operated in the single stage compression mode, the low stage side compressor 4 is stopped and the on-off valve 17 is closed. As shown by the arrows in FIG. 2, during heating, the gas refrigerant discharged from the high-stage compressor 5 passes through the junction 12 from the second discharge pipe 14 and is guided to the four-way valve 20. At this time, since the discharge-side check valve 15 is present in the first discharge pipe 13, the refrigerant does not flow back to the low-stage compressor 4. Therefore, the refrigerant is supplied from the four-way valve 20 to the indoor heat exchanger 22 through the pipe 21. The liquid refrigerant formed by heat exchange in the indoor heat exchanger 22 is discharged to the pipe 23, decompressed by the expansion valves 24 and 25, and supplied to the outdoor heat exchanger 26. The liquid refrigerant becomes a gas refrigerant by heat exchange in the outdoor heat exchanger 26, is discharged from the pipe 27, passes through the four-way valve 20, and is led to the suction pipe 6. In the intake pipe 6, it passes through the branch point 7, passes through the second intake branch pipe 9, and is sucked into the high-stage compressor 5. Thereafter, the refrigerant circulates through the above-described path. In addition, since the on-off valve 17 is closed, the refrigerant does not flow into the discharge side of the low-stage compressor 4 from the bypass pipe 16.

During the cooling operation, the control unit 28 (see FIG. 1) switches the four-way valve 20 to connect the first port 20a and the third port 20c, and connects the second port 20b and the fourth port 20d. Communicate. As a result, the gas refrigerant discharged from the high-stage compressor 5 is supplied to the outdoor heat exchanger 26 from the third port 20d of the four-way valve 20 in the direction opposite to the arrow in FIG. Then, it becomes liquid refrigerant by heat exchange, and is decompressed by the expansion valves 24 and 25 and then supplied to the indoor heat exchanger 22. And after it becomes a gas refrigerant | coolant by heat exchange with the indoor heat exchanger 22, it is suck | inhaled by the high stage side compressor 5 through the suction piping 6 from the 2nd port 20b.
In such a single-stage compression mode, by using the high-stage compressor 5 having a small capacity, the start / stop of the compressor is reduced under a low load condition, so that the energy consumption efficiency is improved. Furthermore, since the capacity of the high stage side compressor 5 is changed according to the load, the energy consumption efficiency is further improved.

The two-stage compression mode is used at the time of high compression ratio operation such as a heating low temperature condition, and both compressors 4 and 5 are operated with the on-off valve 17 opened. As shown in FIG. 3, the gas refrigerant discharged from the low-stage compressor 4 is guided to the second intake branch pipe 9 through the bypass pipe 16. At this time, since the suction side check valve 10 prevents the refrigerant from flowing back, the refrigerant is sucked into the high stage compressor 5. The high-temperature and high-pressure gas refrigerant further compressed by the high-stage compressor 5 is guided to the four-way valve 20 through the discharge pipe 11. At this time, since the discharge-side check valve 15 is present in the first discharge pipe 13, the gas refrigerant does not flow back to the high-stage compressor 5. Further, since this gas refrigerant is higher in pressure than the gas refrigerant discharged from the low stage side compressor 4, the gas refrigerant on the low stage side compressor 4 does not directly flow into the junction 12. During heating, the refrigerant returns from the four-way valve 20 through the indoor heat exchanger 22, the expansion valves 24 and 25, and the outdoor heat exchanger 26 to the suction pipe 6 while performing heat exchange. Then, the refrigerant is sucked into the low-stage compressor 4 from the first suction branch pipe 8. In the first intake branch pipe 8, the high-stage compressor 5 side is at a higher pressure than the suction-side check valve 10, so that the gas refrigerant passes through the suction-side check valve 10 and is compressed to the high-stage side. It does not flow directly into the machine 5.
In such a two-stage compression mode, the low-pressure gas refrigerant is compressed once by the low-stage compressor 4 and then led to the high-stage compressor 5 to perform compression again, so the compression ratio must be increased. Even under operating conditions, the compression ratio for each of the compressors 4 and 5 can be lowered, and the operating efficiency can be improved. Further, the reliability can be improved.

In the parallel compression mode, for example, it is used at the time of large capacity operation in which the connection capacity of the indoor unit 3 is 130%, and both the compressors 4 and 5 are operated with the on-off valve 17 closed. As shown in FIG. 4, the gas refrigerant discharged from both the compressors 4 and 5 joins at the joining point 12 and is guided to the four-way valve 20. At this time, since the on-off valve 17 is closed, the gas refrigerant discharged from the low-stage compressor 4 is not sucked into the high-stage compressor 5. Further, as described above, due to the presence of the discharge side check valves 15 and 18, the gas refrigerant discharged from the one compressor 4 or 5 does not flow backward to the discharge side of the other compressor 4 or 5. During heating, the gas refrigerant passes from the four-way valve 20 through the indoor heat exchanger 22, the expansion valves 24 and 25, and the outdoor heat exchanger 26, and returns to the suction pipe 6 while performing heat exchange. Then, the gas refrigerant is branched at the branch point 7, sucked into the low-stage compressor 4 from the first suction branch pipe 8, and sucked into the high-stage compressor 5 from the second suction branch pipe 9.
In this parallel compression mode, since the two compressors 4 and 5 are operated in parallel, the amount of refrigerant circulated is larger than in the single-stage compression mode with one unit. Can be improved. Further, since the high-stage compressor 5 is of a variable capacity type, it is possible to ensure an appropriate capacity corresponding to the load even when the load is small or the load is large. In addition, when load is small, energy consumption efficiency can be improved.

According to this embodiment, since the discharge side check valves 15 and 18 are provided on the discharge side of the compressors 4 and 5, when operating only one compressor 4 or 5, one compressor 4 or 5 is operated. The gas refrigerant discharged from 5 does not flow backward to the other compressors 4 and 5. Therefore, it is possible to selectively use each of the compressors 4 and 5 without performing a conventional valve switching operation.
Further, since the bypass pipe 16 for supplying the gas refrigerant from the first discharge pipe 13 of the low stage side compressor 4 to the suction side of the high stage side compressor 5 is provided, two-stage compression using both compressors 4 and 5 is provided. Is possible. In this case, since the suction side check valve 10 is provided in the second suction branch pipe 9 on the high stage side compressor 5 side, the gas refrigerant discharged from the low stage side compressor 4 is prevented from flowing back. The Therefore, it is possible to perform the two-stage compression without performing the conventional valve switching operation.
Furthermore, since the on-off valve 17 is provided in the bypass pipe 16, it is possible to prevent the gas refrigerant from flowing into the bypass pipe 16 by closing the on-off valve 17 when performing parallel compression. When the compressors 4 and 5 are operated together, it is possible to switch between the two-stage compression mode and the parallel compression mode. The on-off valve 17 is less expensive than a three-way valve and is easy to control, so that the device cost can be kept low.
Further, since the capacity of the high-stage compressor 5 is set smaller than the capacity of the low-stage compressor 4, the refrigerant can be efficiently compressed during the two-stage compression.

Note that the present invention can be widely applied without being limited to the above-described embodiment.
For example, in the above-described embodiment, the second compressor 5 on the high stage side is a variable capacity type and the low stage side is a constant speed type, so the first compressor 4 that is a constant speed machine on the low stage side. However, when the first and second compressors 4 and 5 are a combination of constant speed machines having different capacities, only the first compressor 4 is operated. A compressed mode is implemented.
When the on-off valve 17 is not provided in the bypass pipe 16, it is possible to implement either the first single-stage compression mode or the two-stage compression mode.
The low stage compressor 4 may be a variable capacity compressor. In this case, the high-stage compressor 5 may be a constant capacity compressor, or both compressors 4 and 5 may be variable capacity types.

It is a figure which shows the system configuration | structure of the air conditioner in embodiment of this invention. It is a figure which shows the circulation path of a refrigerant | coolant when implementing single stage compression. It is a figure which shows the circulation path of a refrigerant | coolant when implementing two-stage compression. It is a figure which shows the circulation path | route of a refrigerant | coolant when implementing parallel compression.

Explanation of symbols

1 Air conditioner 4 Low stage compressor (first compressor)
5 High-stage compressor (second compressor)
6 Suction pipe 8 Suction branch pipe (One suction branch pipe)
9 Inhalation branch pipe (the other inhalation branch pipe)
10 Suction side check valve 11 Discharge pipe 13 Discharge branch pipe (one discharge branch pipe)
14 Discharge branch (the other discharge branch)
15, 18 Discharge side check valve 16 Bypass piping 17 On-off valve 20 Four-way valve 22 Indoor heat exchanger 24 Expansion valve (indoor pressure reducing means)
25 Expansion valve (outdoor pressure reducing means)
26 Outdoor heat exchanger 28 Control unit

Claims (6)

A first compressor, a second compressor, a four-way valve, an outdoor heat exchanger, an outdoor unit having outdoor decompression means, an indoor unit having decompression means and indoor heat exchanger, a liquid pipe and a gas pipe In the air conditioner connected with
The suction pipe for letting the first and second compressors suck the refrigerant branches into a first suction branch pipe of the first compressor and a second suction branch pipe of the second compressor. The second suction branch pipe is provided with a suction-side check valve for preventing the refrigerant from flowing backward,
As for the discharge piping through which the refrigerant discharged from the first and second compressors flows, the first discharge piping of the first compressor and the second discharge piping of the second compressor merge. A discharge side check valve for preventing back flow of the refrigerant is provided in each of the first and second discharge pipes, connected to the four-way valve later, and the discharge side check valve of the first discharge pipe and the A bypass branch pipe branches from between the first compressor and the bypass branch pipe is connected between the suction-side check valve of the second suction branch pipe and the second compressor. An air conditioner characterized by   The air conditioner according to claim 1, wherein the first compressor has a capacity larger than that of the second compressor.   A controller that switches between a mode in which only the first compressor is operated, a mode in which only the second compressor is operated, and a mode in which both the first and second compressors are operated simultaneously; The air conditioner according to claim 1 or 2, characterized by the above.   The air conditioner according to claim 1 or 2, wherein the bypass branch pipe is provided with an on-off valve.   A mode in which only the first compressor is operated, a mode in which only the second compressor is operated, a mode in which the on-off valve is opened and both the first and second compressors are operated simultaneously; The air conditioner according to claim 4, further comprising a controller that closes the on-off valve and switches between modes in which both the compressors are operated. 6. The compressor according to claim 1, wherein at least one of the first compressor and the second compressor is a variable capacity compressor. 6. Air conditioner.

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