JP4037863B2 - Air conditioner - Google Patents

Description

  The present invention relates to an air conditioner that includes a plurality of indoor units and can be operated by mixing a cooling operation and a heating operation.

  Some air conditioners in which a plurality of indoor units are connected in parallel to one outdoor unit include a cooling / heating switching device between the plurality of indoor units and the outdoor unit. Two connection pipes through which the refrigerant flows from the outdoor unit side are drawn into the cooling / heating switching device, and each of these connection pipes is connected to a connection pipe through which the high-pressure gas refrigerant flows and a connection through which the low-pressure gas refrigerant flows. The pipe is branched into a pipe and a connection pipe through which the liquid refrigerant flows, and each branch pipe after branching is connected to each indoor unit. During the cooling operation, the liquid refrigerant flows into the heat exchanger of the indoor unit to exchange heat, and the low-pressure gas refrigerant is discharged from the indoor unit. During the heating operation, the gas refrigerant flows into the heat exchanger of the indoor unit to exchange heat, and the liquid refrigerant is discharged from the indoor unit. The connection pipe for the high-pressure gas refrigerant and the connection pipe for the low-pressure gas refrigerant are connected to the indoor unit after joining in the cooling / heating switching device, and the connection pipe for the low-pressure gas refrigerant has a first open / close state. A valve is provided, and a second open / close valve is provided in the connection pipe for the high-pressure gas refrigerant.

Here, in order to switch from the heating operation to the cooling operation, when the first on-off valve is opened simultaneously with closing the second on-off valve, the high-pressure gas refrigerant flows into the connection pipe on the low-pressure side, and the high-pressure refrigerant is suddenly reduced Swells and generates noise. In order to prevent the generation of such noise, a capillary tube is connected to the conventional air conditioner so as to bypass both ends of the first on-off valve, and further, both ends of the first on-off valve are bypassed. There is one to which a third on-off valve is connected (for example, see Patent Document 1). When switching from the heating operation to the cooling operation, the second on-off valve is first closed, the third on-off valve is opened, the state is maintained for a predetermined time, and then the first on-off valve is opened. Thereby, a rapid pressure change between the connecting pipes at the time of operation switching is suppressed, and generation of refrigerant noise is prevented.
JP-A-4-347467

However, in such an air conditioner, since it is necessary to provide a capillary tube and a third on-off valve in each of the connection pipes for the low-pressure gas refrigerant, the number of parts increases, and the overall size of the air conditioner increases. This was a cause of high costs. Such a problem becomes particularly noticeable as the number of indoor units increases.
The present invention has been made in view of such circumstances, and an object thereof is an air conditioner configured to prevent a sudden pressure difference when switching from heating operation to cooling operation. This is to prevent an increase in size and cost.

The invention according to claim 1 of the present invention that solves the above-described problems includes a compressor, a four-way valve, an outdoor heat exchanger, a plurality of indoor units, and switching for switching the operation mode of the indoor units to a cooling operation or a heating operation. In an air conditioner in which a cooling / heating switching device including a valve is connected by liquid piping and gas piping, the cooling / heating switching device includes a high pressure gas piping connected to a discharge side of the compressor and a low pressure connected to a suction side of the compressor. A first bypass path having a first pressure reducing means for connecting to the gas pipe and an on-off valve is provided, and the first pressure reducing means has a minimum operating capacity of the indoor unit when performing a cooling operation and a heating operation simultaneously. When the switching valve is opened, the flow path resistance is set so that noise caused by the pressure difference between the low-pressure gas pipe side and the high-pressure gas pipe side is not generated, and the outdoor unit On the discharge side of the compressor A tube, a second pressure reducing means for connecting the compressor suction side of the pipe, a second bypass path having a closing valve is provided, when at least one of the indoor unit switched to the cooling operation from the heating operation, the The first bypass path is opened when the total operating capacity of the plurality of indoor units is less than a predetermined capacity, and the first bypass path and the second when the total operating capacity of the plurality of indoor units is equal to or greater than the predetermined capacity. It was set as the air conditioner characterized by having comprised so that a bypass route might be opened .
In this air conditioner, the pressure difference between the high pressure gas pipe and the low pressure gas pipe is reduced using the first bypass path, and then the switching valve is opened and closed to switch from the heating operation to the cooling operation. Further, a second bypass path is provided, and when these two bypass paths are used, the pressure difference between the high pressure gas pipe and the low pressure gas pipe is further reduced. Furthermore, when the first bypass path is preferentially used and the capacity difference is equal to or greater than a predetermined capacity, the pressure difference between the gas pipes is further reduced by using the second bypass path in combination.

According to a second aspect of the present invention, in the air conditioner according to the first aspect, a discharge pressure sensor for detecting a discharge pressure is provided on the discharge side of the compressor, and the suction for detecting the suction pressure on the suction side of the compressor A pressure sensor is provided, and calculation means is provided for calculating a pressure difference between the internal pressure of the high-pressure gas pipe and the internal pressure of the low-pressure pipe from the detected values of the discharge pressure sensor and the suction pressure sensor.
In this air conditioner, the pressure difference between the high-pressure gas pipe and the low-pressure gas pipe is calculated from the output of the pressure sensor, and the opening and closing control of the bypass path is performed accordingly.

According to a third aspect of the present invention, in the air conditioner according to the second aspect , when the at least one indoor unit is switched from the heating operation to the cooling operation, a pressure difference between the discharge pressure and the suction pressure of the compressor is predetermined. The first bypass path is opened when the pressure is less than the pressure, and the first bypass path and the second bypass path are opened when the pressure difference is equal to or greater than the predetermined pressure.
In this air conditioner, the second bypass path is used in combination according to the pressure difference to reduce the pressure difference between the gas pipes.

According to a fourth aspect of the present invention, in the air conditioner according to the third aspect , after opening the first bypass path and the second bypass path, a pressure difference between the discharge pressure and the suction pressure of the compressor is increased. When the pressure is equal to or higher than the predetermined pressure, the operation capacity of the compressor is reduced.
In this air conditioner, when the pressure difference cannot be sufficiently reduced only by the first and second bypass paths, the pressure difference between the high pressure gas pipe and the low pressure gas pipe is reduced by reducing the operating capacity of the compressor. Let

The invention according to claim 5 is the air conditioner according to claim 1, wherein the compressor is a compressor capable of capacity control by bypassing a high-pressure side and a low-pressure side of a compression chamber. And
In this air conditioner, the compressor bypasses the compression chamber on the high pressure side and the compression chamber on the low pressure side, thereby reducing the operating capacity. As a result, the pressure difference between the high pressure gas pipe and the low pressure gas pipe is reduced. Decrease.

  According to the present invention, one bypass path that can connect the high-pressure gas pipe and the low-pressure gas pipe is provided in each of the cooling / heating switching device and the outdoor unit, and therefore, by appropriately using these two bypass paths. The pressure difference between the switching valves when switching from the heating operation to the cooling operation can be reduced. Compared to the case where a bypass path is provided for each indoor unit as in the prior art, the apparatus configuration is simplified, and the apparatus can be reduced in size and cost. In addition, if the first bypass path on the refrigerant switching device side is set so as to match the combination that minimizes the operating capacity of the indoor unit, noise can be prevented when the operating capacity is small or when the pressure difference is small. Further, by using the second bypass path on the outdoor unit side in combination, it is possible to prevent noise even when the operation capacity is large or the pressure difference is large. Furthermore, by appropriately controlling the discharge pressure of the compressor, it is possible to prevent the generation of noise even when the operating capacity is larger or the pressure difference is larger.

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 according to this embodiment includes one outdoor unit 2, and the outdoor unit 2 includes a high-pressure gas pipe 3, a liquid pipe 4, and a low-pressure gas pipe 5. A plurality of indoor units 6 are connected in parallel to form an indoor unit group 7. Although FIG. 1 shows the case where the number of indoor units 6 is six, any number of indoor units 6 such as ten or twelve units can be connected.

  The outdoor unit 2 has a compressor 10. The compressor 10 is a variable capacity compressor. Such a compressor 10 is configured to be able to bypass the high-pressure side compression chamber and the low-pressure side compression chamber inside the compression chamber, and can reduce the capacity stepwise in accordance with the opening degree of the bypass. Is preferred. The discharge pipe 11 of the compressor 10 is connected via an oil separator 12 to a first port 13A of a four-way valve 13 that is a switching valve.

  The four-way valve 13 can switch the flow path by switching control of a control device (not shown). In FIG. 1, the first port 13A and the second port 13B are connected, and the third port 13C Although the fourth port 13D is connected, it is also possible to connect the first port 13A and the third port 13C and connect the second port 13B and the fourth port 13D. is there. A pipe 14 is connected to the second port 13B of the four-way valve 13, and a bypass pipe 15 is connected in the middle of the pipe 14, and the bypass pipe 15 is composed of an electromagnetic valve in order. After the first on-off valve 16 and the check valve 17 are provided, they are connected to the high-pressure gas pipe 3. The check valve 17 is set so as to prevent the backflow of the gas refrigerant from the high-pressure gas pipe 3 side.

  Further, a first pipe 18 and a second pipe 19 are connected to the pipe 14. The first pipe 18 is provided with an outdoor heat exchanger 21 and connected to the pipe 22. The second pipe 19 is provided with an outdoor heat exchanger 23 and connected to the pipe 22. The pipe 22 is provided with an expansion valve 24 and is connected to the liquid pipe 4 via a receiver tank 25. Further, the piping 22 is provided with a bypass piping 50 that bypasses the expansion valve 24. In the bypass pipe 50, a solenoid valve 51 as a flow rate adjusting valve and a check valve 52 are connected in series. The bypass pipe 50 exits from the first and second outdoor heat exchangers 21 and 23 during cooling operation or the like. Liquid refrigerant can bypass the expansion valve 24 through these bypass pipes 50, and the bypass pipe 50 is closed during heating operation or the like so that the refrigerant can pass through the expansion valve 24.

  The high pressure gas pipe 3 is connected to the third port 13C of the four-way valve 13. The high-pressure gas pipe 3 is provided with a reverse valve 26 between the connection point to the third port 13 </ b> C and the junction point of the bypass pipe 15. The check valve 26 is set so as to prevent the backflow of the gas refrigerant from the indoor unit 6 side. Further, a pipe 30 is connected to the fourth port 13D, and this pipe 30 is connected to the suction pipe 32 of the compressor 10 via the accumulator 31 after joining the low-pressure gas pipe 5. Here, the discharge pipe 11 of the compressor 10 is provided with a discharge pressure sensor 33A, and the suction pipe 32 is provided with a suction pressure sensor 33B. The outputs of these sensors 33A and 33B are connected to a control device 34 that controls the air conditioner 1. The control device 34 is a calculation means for calculating a pressure difference between the pressure of the high-pressure gas pipe 3 and the pressure of the low-pressure gas pipe 5 according to the detection results of the sensors 33A and 33B, and switching for controlling the opening and closing of the valves. It functions as a control means.

The high-pressure gas pipe 3, the liquid pipe 4, and the low-pressure gas pipe 5 extending from the outdoor unit 2 toward the indoor unit 6 are connected to the indoor units 6 after branching in the cooling / heating switching device 35.
The branch pipe 3A of the high-pressure gas pipe 3 is provided with a heating switching valve 36 composed of an electromagnetic valve. The branch pipe 5A of the low-pressure gas pipe 5 is provided with a cooling switching valve 37 made of an electromagnetic valve. These branch pipes 3 </ b> A and branch pipes 5 </ b> A join one by one and are connected to one end side of the indoor heat exchanger 38 of the indoor unit 6. The branch pipe 4 </ b> A of the liquid pipe 4 is provided with an expansion valve 39 in the indoor unit 6 and is connected to the other end side of the indoor heat exchanger 38.

  Further, the cooling / heating switching device 35 includes a branch point outdoor unit 2 branching from the high pressure gas pipe 3 to each branch pipe 3A, and a branch point outdoor unit 2 branching from the low pressure gas pipe 5 to each branch pipe 5A. A first bypass path 40 is provided. The first bypass path 40 has a pipe 41 that connects the high-pressure gas pipe 3 and the low-pressure gas pipe 5, and the pipe 41 includes a first bypass on-off valve 42 and a first pressure reducing means from the high-pressure gas pipe 3 side. A certain capillary tube 43 is provided. The first bypass opening / closing valve 42 may be any pressure-reducing mechanism that can be fully closed. For example, an electronic expansion valve (electric expansion valve) that can be fully closed can be used. From the viewpoint of reducing the pressure difference between the high-pressure gas pipe 3 and the low-pressure gas pipe 5, the capillary tube 43 preferably has a large flow path area and can ensure a large flow rate. From the viewpoint of suppressing the noise of the gas refrigerant flowing through 40, it is desirable that the flow path resistance is as large as possible. Therefore, in this embodiment, the indoor unit 6 has a minimum operating capacity at the time of simultaneous cooling and heating, that is, one indoor unit 6 that is performing cooling operation and one indoor unit 6 that is performing heating operation. The flow path resistance and the like are set so that no noise is generated when the high pressure gas refrigerant is passed through the first bypass path 40 in the case of one unit.

  The outdoor unit 2 is provided with a second bypass path 45 that can connect the discharge pipe 11 and the suction pipe 32. The second bypass path 45 includes a pipe 46, a second bypass on-off valve 47 disposed on the pipe 46 from the discharge pipe 11 side, and a capillary tube 48 serving as a second decompression unit. The second bypass on-off valve 47 may be any pressure-reducing mechanism that can be fully closed. For example, an electronic expansion valve (electric expansion valve) that can be fully closed can be used.

  Next, the operation of this embodiment will be described. In the air conditioner 1, a cooling operation in which all of the plurality of indoor units 6 are cooled, a heating operation in which all of the indoor units 6 are heated, and a cooling / heating mixed operation in which the cooling operation and the heating operation are mixed for each indoor unit 6. And can be implemented. In the case of the cooling and heating mixed operation, the cooling main operation or the heating main operation can be mainly performed. The cooling main operation is an operation in which the cooling operation is dominant, that is, the total value of the evaporation capacity of the indoor unit group 7 is larger than the total value of the condensation capacity. The heating main operation is an operation in which the heating operation is dominant, that is, the total value of the condensation capacity of the indoor unit group 7 is larger than the total value of the evaporation capacity.

  First, when cooling all the indoor units 6, the first port 13A and the second port 13B of the four-way valve 13 are connected, and the third port 13C and the fourth port 13D are connected. The electromagnetic valve 51 of the bypass pipe 50 is opened. In the cooling / heating switching device 35, all the heating switching valves 36 are closed, and all the cooling switching valves 37 are opened. The high-pressure gas refrigerant from the compressor 10 passes through the outdoor heat exchangers 21 and 23 from the four-way valve 13 to become liquid refrigerant, passes through the branch pipe 4A from the liquid pipe 4 via the bypass pipe 50, and is expanded by the expansion valve 39. After being depressurized, the refrigerant flows into each indoor heat exchanger 38, where the room is cooled by heat exchange to become a low-pressure gas refrigerant, and is compressed from the branch pipe 5A through the low-pressure gas pipe 5 and from the accumulator 31 through the suction pipe 32. Inhaled by the machine 10.

  During the cooling main operation, the four-way valve 13 remains the same as the cooling operation, the first on-off valve 16 of the bypass pipe 15 is opened, and the electromagnetic valve 51 of the bypass pipe 50 is closed. As illustrated in FIG. 2, when the three indoor units 6A, 6B, and 6C are in the cooling operation and the indoor unit 6D is in the heating operation, the cooling / heating switching device 35 has the indoor units 6A, 6B, and 6C side. The cooling switching valve 37 and the heating switching valve 36 on the indoor unit 6D side are opened, and the other switching valves 36 and 37 are all closed. The refrigerant discharged from the compressor 10 is condensed by the outdoor heat exchangers 21 and 23 through the first and second ports 13A and 13B of the four-way valve 13, and the expansion valve 24 and the receiver tank 25 are used as high-pressure liquid refrigerant. Is supplied from the liquid pipe 4 to the indoor unit 6C side, depressurized by the expansion valve 39 and evaporated by the indoor heat exchanger 38, thereby cooling the room and further passing through the low-pressure gas pipe 5 as low-pressure gas. Circulated to the suction side. Further, a part of the refrigerant discharged from the compressor 10 and passing through the four-way valve 13 passes through the bypass pipe 15 and flows into the compressor 6D from the high-pressure gas pipe 3 and is condensed in the indoor heat exchanger 38 so that the room. After heating, the refrigerant is supplied to the liquid pipe 4 via the expansion valve 39, merged with the refrigerant supplied to the indoor unit 6C that performs the cooling operation, and supplied to the cooling, and then passes from the low-pressure gas pipe 5 through the suction pipe 32. It is sucked into the compressor 10.

  When all the indoor units 6 are operated for heating, the first port 13A and the third port 13C of the four-way valve 13 are connected, and the second port 13B and the fourth port 13D are connected. . In the cooling / heating switching device 35, all the heating switching valves 36 are opened, and all the cooling switching valves 37 are closed. The high-pressure gas refrigerant from the compressor 10 passes through the high-pressure gas pipe 3 from the four-way valve 13 and flows into each indoor heat exchanger 38 through the branch pipe 3A, where the room is heated by heat exchange and becomes liquid refrigerant. From the branch pipe 4A through the liquid pipe 4, the first and second outdoor heat exchangers 21, 23 become gas refrigerant. At this time, the liquid refrigerant does not flow into the bypass pipe 50 due to the presence of the check valve 52. The low-pressure gas refrigerant discharged from the first and second outdoor heat exchangers 21 and 23 passes through the second port 13B and the fourth port 13D of the four-way valve 13 and passes from the suction pipe 32 to the compressor 10. Inhaled.

  During the heating main operation, the four-way valve 13 remains the same as in the heating operation, and the first on-off valve 16 of the bypass pipe 15 is closed. As illustrated in FIG. 3, when the indoor unit 6A performs a cooling operation and the indoor units 6B, 6C, and 6D perform a heating operation, the cooling / heating switching device 35 includes a cooling switching valve 37 on the indoor unit 6A side, The switching valve 36 for heating on the indoor units 6B, 6C, and 6D side is opened, and the other switching valves 36 and 37 are all closed. The refrigerant discharged from the compressor 10 is supplied to the high-pressure gas pipe 3 via the check valve 26 via the first and third ports 13A and 13C of the four-way valve 13, and further, the heating switching valve of the cooling / heating switching device 35. The air is supplied from 36 to the indoor heat exchanger 38 of the indoor unit 6B, where it is condensed to heat the room and sent to the high-pressure liquid pipe 4 via the expansion valve 39. Here, a part of the refrigerant sent to the high-pressure liquid pipe 4 is supplied to the indoor unit 6 </ b> A, and is evaporated in the indoor heat exchanger 38 to cool the room, passes through the low-pressure gas pipe 5, and the compressor 10. Inhaled. The remaining refrigerant sent to the high-pressure liquid pipe 4 is also returned to the outdoor unit 2 side, evaporates in the outdoor heat exchangers 21 and 23 through the receiver tank 25 and the expansion valve 24, and the third and third of the four-way valve 13. 4 is sucked into the compressor 10 through the ports 13C and 13D.

  In addition, when performing the operation in which the load of cooling / heating is balanced, as exemplified when the number of cooling operations and the number of heating operations among the plurality of indoor units 6 are the same, for example, the outdoor air temperature is When the temperature is low, the four-way valve 13 on the outdoor unit 2 side is the same as that in the heating-main operation, the first on-off valve 16 of the bypass pipe 15 is also closed, and the indoor unit 6 side is adjusted to the cooling / heating operation. The switching valves 36 and 37 are opened and closed in the same manner as in the cooling / heating main operation. In this case, the refrigerant discharged from the compressor 10 is first supplied to the indoor unit 6 that performs the heating operation through the first and third ports 13A and 13C of the four-way valve 13 via the high-pressure gas pipe 3 and the cooling / heating switching device 35. Then, it is used for indoor heating by condensing, and then supplied to the indoor unit 6 that performs cooling operation via the high-pressure liquid pipe 4 in the cooling / heating switching device 35 and then used for indoor cooling by evaporating. The gas pipe 5 is sucked into the compressor 10. Conversely, when the outdoor air temperature is high, the balance operation can be performed with the same connection as in the cooling main operation. If the connection is made in the same manner as in the main operation of either cold or warm according to the outdoor temperature, the cooling load increases when the outdoor temperature is high, or conversely the heating load is low when the outdoor temperature is low. Even if it increases, it is possible to promptly shift to the cooling main operation or the heating main operation without switching the four-way valve 13.

  Here, the operation when switching from the heating operation to the cooling operation will be described with reference mainly to the flowchart of FIG. 4 and the timing chart of FIG. FIG. 5 illustrates the control of the compressor 10, the bypass paths 40 and 45, and the switching valves 36 and 37, and the change in the system pressure of the air conditioner 1 that changes accordingly. The high pressure indicates the pressure of the gas refrigerant in the high pressure gas pipe 3, and the low pressure of the system pressure indicates the pressure of the gas refrigerant in the low pressure gas pipe 5. These pressures are detected by the discharge pressure sensor 33A and the suction pressure sensor 33B, respectively.

  First, during a heating operation (step S1), when a command to switch to a cooling operation is issued (step S2), the total capacity of the indoor unit 6 or the pressure difference between the high pressure gas pipe 3 and the low pressure gas pipe 4 is acquired. When the total capacity of the indoor unit 6 is equal to or larger than the predetermined capacity or the pressure difference is equal to or larger than the predetermined value (No in Step S3), the first bypass opening / closing valve 42 of the first bypass path 40 is opened (Step S4A). As a result, the high-pressure gas refrigerant in the high-pressure gas pipe 3 flows into the low-pressure gas pipe 5 in the first bypass path 40, and the pressure of the high-pressure side gas refrigerant decreases as in the system pressure shown as an example in FIG. The gas refrigerant rises and the difference between the two becomes small.

  Further, the second bypass opening / closing valve 47 of the second bypass path 45 is opened (step S5), and the high-pressure gas refrigerant flows into the low-pressure gas pipe 5 through the second bypass path 45. As a result, as illustrated in FIG. 5, the pressure of the gas refrigerant on the high pressure side of the system pressure decreases, the gas refrigerant on the low pressure side increases, and the difference between the two decreases further. After the pressure difference of the system is decreased to less than a predetermined value, the heating switching valve 36 is closed (step S8), then the cooling switching valve 37 is opened (step S9), and the above-described cooling operation is started.

  On the other hand, when the total capacity of the indoor unit 6 is less than the predetermined value or the pressure difference is less than the predetermined value in step S3 (Yes in step S3), the first bypass opening / closing valve 42 of the first bypass path 40 is opened. (Step S4B), the process proceeds to step S8. This is because the capacity difference or the pressure difference is originally small, so that the pressure difference before and after the cooling switching valve 37 is small enough to prevent the generation of noise simply by opening the first bypass path 40.

  In performing such control, the predetermined value serving as the determination threshold and the design value of the first bypass path 40 are, for example, two units that are the minimum unit of the cooling and heating mixed operation when twelve indoor units 6 are provided. When the cooling switching valve 37 is opened under the condition that each of the indoor units 6 is in the cooling operation and the heating operation, the pressure difference or capacity at which no noise is generated becomes a predetermined value. In addition, the flow path area, length, and shape of the first bypass path 40, particularly the capillary tube 43, are designed so that no noise is generated due to the capacity difference and the pressure difference.

  Here, since the compressor 10 of the air conditioner 1 is a variable capacity type, the control may be performed so that the process does not proceed from step S5 to step S8, but proceeds to step S8 after passing through step S6 and step S7. That is, when the system pressure difference is equal to or larger than the predetermined value in step S5 (No in step S6), the capacity of the compressor 10 is decreased (step S7). This further reduces the pressure difference in the system pressure of FIG. If the system pressure difference is less than the predetermined value in step S6 and the capacity of the compressor 10 is changed in step S7, the pressure condition in step S3 and the pressure condition in step S6 are the same. Things have been applied.

  In this embodiment, since the first bypass path 40 is provided in the cooling / heating switching device 35 as means for connecting the high-pressure gas pipe 3 and the low-pressure gas pipe 5, a bypass is provided for each cooling switching valve 37 as in the prior art. Compared with the case where the device is provided, the device configuration can be simplified, and the device can be reduced in size and cost. Since the second bypass path 45 having the same configuration is provided on the outdoor unit 2 side in addition to the first bypass path 40, the first bypass path is as in the case where many indoor units 6 are operating. Even if only 40 cannot reduce the pressure difference in a short time, the pressure difference can be reduced by cooperating both bypass paths 40 and 45, and the generation of noise can be prevented. Moreover, if comprised in this way, the 1st bypass path 40 can be designed so that a noise may not generate | occur | produce when a capacity | capacitance difference is small or a pressure difference is small. Further, since the discharge pressure sensor 33A and the suction pressure sensor 33B on the compressor 10 side are used for obtaining the pressure difference, each bypass path 40, while controlling the discharge pressure of the compressor 10, is used. 45 can be controlled.

  Furthermore, by making the compressor 10 variable capacity type, it becomes possible to reduce the pressure difference even in the compressor 10, and the pressure difference of the system is not sufficiently reduced even in the first and second bypass paths 40 and 45. In this case, by adjusting the discharge pressure in the compressor 10, it is possible to prevent the generation of noise during operation switching.

Note that the present invention can be widely applied without being limited to the above-described embodiment.
For example, the compressor 10 is preferably a variable capacity type that can easily reduce the pressure difference, but an inverter type can also be used. In this case, in step S7 shown in FIG. 4, the pressure difference is reduced by lowering the frequency and lowering the rotational speed of the motor.

It is a system configuration figure of the air harmony device concerning an embodiment of the invention. It is a figure explaining the flow of the refrigerant at the time of cooling main operation. It is a figure explaining the flow of the refrigerant at the time of heating main operation. It is a flowchart explaining the process at the time of switching from heating operation to cooling operation. It is a timing chart at the time of switching from heating operation to cooling operation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Air conditioner 2 Outdoor unit 3 High pressure gas piping 4 Liquid piping 5 Low pressure gas piping 6 Indoor unit 13 Four-way valve 21, 23 Outdoor heat exchanger 33A Discharge pressure sensor 33B Suction pressure sensor 34 Control device (calculation means)
35 Cooling / heating switching device 40 First bypass path 42 First bypass on-off valve 43 Capillary tube (first decompression means)
45 Second bypass path 47 Second bypass on-off valve 48 Capillary tube (second decompression means)

Claims (5)

Air in which a compressor, a four-way valve, an outdoor heat exchanger, a plurality of indoor units, and a cooling / heating switching device including a switching valve for switching the operation mode of the indoor units to cooling operation or heating operation are connected by liquid piping and gas piping In the harmony machine,
The cooling / heating switching device has a first bypass path having a first pressure reducing means for connecting a high pressure gas pipe connected to the discharge side of the compressor, a low pressure gas pipe connected to the suction side of the compressor, and an on-off valve. The first pressure reducing means includes the low-pressure gas pipe side and the high-pressure gas even when the switching valve is opened when the operating capacity of the indoor unit when performing the cooling operation and the heating operation at the same time is minimized. The flow resistance is set so that noise caused by a pressure difference with the pipe side does not occur, and the outdoor unit includes a discharge side pipe of the compressor and a suction side pipe of the compressor. A second bypass path having a second pressure reducing means for connecting the two and the on-off valve is provided , and when the at least one indoor unit is switched from the heating operation to the cooling operation, the total operation capacity of the plurality of indoor units is predetermined. If the capacity is less than Open bypass passage, an air conditioner, wherein the sum of the operating capacity of the plurality of indoor units is configured to open the first bypass passage and the second bypass passage when the above predetermined capacity. A discharge pressure sensor for detecting a discharge pressure is provided on the discharge side of the compressor, a suction pressure sensor for detecting a suction pressure is provided on the suction side of the compressor, and the detection values of the discharge pressure sensor and the suction pressure sensor are respectively 2. The air conditioner according to claim 1, further comprising calculation means for calculating a pressure difference between an internal pressure of the high-pressure gas pipe and an internal pressure of the low-pressure pipe. When switching at least one indoor unit from a heating operation to a cooling operation, when the pressure difference between the discharge pressure and the suction pressure of the compressor is less than a predetermined pressure, the first bypass path is opened, and the pressure difference is The air conditioner according to claim 2 , wherein the air conditioner is configured to open the first bypass path and the second bypass path when the pressure is higher than the pressure. After opening the first bypass path and the second bypass path, the operating capacity of the compressor is decreased when the pressure difference between the discharge pressure and the suction pressure of the compressor is equal to or higher than the predetermined pressure. It is comprised, The air conditioner of Claim 3 characterized by the above-mentioned.   2. The air conditioner according to claim 1, wherein the compressor is a compressor capable of capacity control by bypassing a high pressure side and a low pressure side in a compression chamber.

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