JP3263343B2 - Multi air conditioner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-air conditioner comprising a plurality of outdoor units and a plurality of indoor units, and more particularly to an improvement in a startup speed of a small heating capacity operation.

[0002]

2. Description of the Related Art Conventionally, a multi-air conditioner including a plurality of outdoor units and a plurality of indoor units has been developed in order to cope with an increase in capacity of an air conditioner. In this type of multi-air conditioner, gas pipes and liquid pipes connecting each outdoor unit and each indoor unit are integrated into one common pipe due to simplification of piping work.

FIG. 11 is a configuration diagram of a refrigeration cycle of a conventional multi-air conditioner of this type disclosed in, for example, Japanese Patent Application Laid-Open No. 4-93561. As shown in the figure, the outdoor units 1a and 1b are respectively provided with compressors 2a and 2b and a four-way valve 3 respectively.
a, 3b and the outdoor heat exchangers 4a, 4b. Further, the outdoor unit 1b has a check valve 14 on the discharge side of the compressor 2b, and a solenoid valve 15 provided between the outdoor heat exchanger 4b and the connection point 11 of the liquid pipe.

Reference numeral 6 denotes a common gas pipe connecting the outdoor units 1a and 1b and the indoor unit 7, 12 denotes a connection point between the gas pipes exiting the outdoor units 1a and 1b and the common gas pipe 6, and 8 denotes a connection point of the indoor unit 7. A heat exchanger, 9 is an expansion valve, 10 is a common liquid pipe connecting the outdoor units 1a, 1b and the indoor unit 7, and 11 is an outdoor unit 1a, 1b.
It is a connection point between the liquid pipe coming out of the apparatus and the common liquid pipe 10.

[0005] The operation when the heating operation is performed in the refrigeration cycle as described above will be described. The high-temperature and high-pressure gas refrigerant discharged from the compressors 2a and 2b is supplied from the outdoor units 1a and 1b to the heat exchanger 8 of the indoor unit 7 through the gas pipe 6. The heat is condensed and liquefied in the heat exchanger 8 of the indoor unit 7 while applying heat to the indoor side, and after leaving the heat exchanger 8, the pressure is reduced to a low-pressure two-phase refrigerant by the expansion valve 9 in the indoor unit 7. . The low-pressure two-phase refrigerant passes through the liquid pipe 10 and the heat exchanger 4 of the outdoor units 1a and 1b.
a and 4b evaporate and gasify, accumulators 5a and 5b
b and is sucked into the compressors 2a and 2b.

[0006]

Since the conventional air conditioner is configured as described above, when the heating operation is started, the gas pipe 6 cooled by the outside air causes the compressor 2a, 2b to start. The discharged high-temperature and high-pressure gas refrigerant is cooled. When the outside air temperature is low and the operating capacity is small, cooling becomes easier as the temperature of the gas pipe 6 decreases and the flow rate of the refrigerant passing through the gas pipe 6 decreases.

In particular, when the pipes are integrated into one pipe with the increase in the capacity of the multi-air conditioner, the diameter of the pipes is increased in order to prevent a decrease in performance due to a pressure loss in the connected pipes. Therefore, in the small-capacity operation, the cooling portion is increased due to the decrease in the flow rate of the refrigerant and the increase in the number of connected indoor units due to the increase in the capacity, so that the length of the pipe is increased. It will be easier. When the degree of cooling increases, the supplied gas refrigerant is liquefied in the gas pipe 6, and the liquid refrigerant accumulates in the gas pipe 6 and becomes laid down. In such a state, the indoor heat exchanger 8, the liquid pipe 10, the outdoor heat exchangers 4a, 4b
No more refrigerant flows.

For this reason, the refrigerant is sucked into the compressors 2a and 2b on the low pressure side, but the refrigerant discharged from the compressors 2a and 2b does not return, so that the pressure drops. When the low pressure decreases, the flow rate of the compressors 2a and 2b decreases, so that it takes time to start the heating operation. In particular, in the case of small-capacity operation, the problem that a rise time is required becomes prominent.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has a heating time, particularly a heating time, of a multi-air conditioner comprising a plurality of outdoor units and a plurality of indoor units. The purpose is to reduce the start-up time during small capacity operation.

[0010]

A multi-air conditioner according to the present invention comprises a plurality of outdoor units having a compressor, an outdoor heat exchanger and an accumulator, and a plurality of indoor units having an indoor heat exchanger and a decompression device. If the operating capacity of the indoor unit is small during the heating operation, the operation is stopped and the common gas piping connecting the outdoor unit and the indoor unit, the common liquid piping connecting the outdoor unit and the indoor unit, and the gas piping A bypass circuit is provided in the outdoor unit whose communication with the liquid pipe is interrupted, and supplies a liquid refrigerant in an accumulator of the outdoor unit to an outdoor heat exchanger of another operating outdoor unit.

Further, the bypass circuit is provided between the accumulator of the outdoor unit whose operation is stopped and the liquid pipe of another outdoor unit which is operating.

Further, the bypass circuit is provided between the accumulator of the outdoor unit whose operation is stopped and the liquid piping of the outdoor unit communicating with the common liquid piping.

[0013] Further, there is provided another bypass circuit for flowing high-pressure gas from the high-pressure side communicating with a common gas pipe of the outdoor unit whose operation is stopped to the accumulator of the outdoor unit.

Further, one end of the bypass circuit is connected to the bottom of the accumulator of the outdoor unit whose operation is stopped.

Further, one end of the bypass circuit is inserted from the top or the side of the accumulator of the outdoor unit whose operation is stopped, and reaches the bottom of the accumulator.

[0016] The present invention further includes a flow control valve provided in the bypass circuit for controlling the flow rate of the refrigerant in the bypass circuit, and a control device for controlling the flow control valve.

Further, the control device controls to open the flow control valve simultaneously with the start of the heating operation.

Further, the control device controls the flow control valve to be opened after a lapse of a predetermined time after the heating operation is started.

Further, the control device controls the flow control valve to be opened when the low pressure of the refrigeration cycle of the air conditioner becomes lower than a certain value after the heating operation is started.

Further, the control device controls the opening degree of the flow control valve,
The liquid refrigerant is controlled to an appropriate constant value so that the liquid refrigerant evaporates completely in the outdoor heat exchanger of another outdoor unit during operation, and the liquid refrigerant evaporating in the outdoor heat exchanger does not decrease.

Further, the control device sets the opening of the flow control valve to
The superheat degree of the refrigerant at the outlet of the outdoor heat exchanger of another outdoor unit during operation is controlled to be a constant value.

The control device controls the flow control valve so that the flow control valve is closed after a predetermined time required for starting the heating operation after the flow control valve is opened.

Further, the bypass circuit is used as a liquid bypass circuit for returning the high-pressure liquid to the low-pressure side and suppressing the high-pressure rise when the high pressure of the refrigeration cycle rises transiently during the cooling operation.

Further, the bypass circuit used as the liquid bypass circuit is provided with a heat exchanger for exchanging heat between the two-phase refrigerant after the liquid refrigerant bypassed by the flow control valve and the high-pressure liquid.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. Here, description will be made assuming that two outdoor units are connected. The gas pipe and the liquid pipe connecting the outdoor unit and the indoor unit are one common gas pipe,
It is assumed that they are collected in a liquid pipe.

FIG. 1 is a view showing an example of an embodiment of the present invention, and is a configuration diagram of a refrigeration cycle of a multi-air conditioner. In the figure, 1a and 1b are outdoor units, 2a and 2b are compressors of each outdoor unit, 3a and 3b are four-way valves of each outdoor unit, and 6 is a common gas pipe connecting the outdoor units 1a and 1b and the indoor unit 7. , 12 is a connection point between a gas pipe exiting from the outdoor units 1a and 1b and a common gas pipe 6, 8 is an indoor heat exchanger of the indoor unit 7,
9 is an expansion valve of the indoor unit 7, 10 is a common liquid pipe connecting the outdoor units 1a and 1b and the indoor unit 7, and 11 is an outdoor unit 1a and 1b.
Connection point between the liquid pipe coming out of the pipe and the common liquid pipe 10, 4a,
4b is an outdoor heat exchanger of the outdoor units 1a and 1b, and 5a and 5b are accumulators of the outdoor units 1a and 1b.

14 is a check valve provided on the discharge side of the compressor 1b, 15 is a solenoid valve provided between the outdoor heat exchanger 4b and the connection point 11 of the liquid pipe, and 16 is a liquid refrigerant of the accumulator 5b. Is a bypass circuit for supplying to the outdoor heat exchanger 4a, 17 is a flow control valve for controlling the flow rate in the bypass circuit 16, and 18 is a control device for controlling the opening of the flow control valve 17.

FIG. 2 is a diagram showing an example of the embodiment of the present invention, and is a diagram showing a connection between the bypass circuit 16 and the accumulator 5b. As shown in the drawing, one end of the bypass circuit 16 is inserted from below the accumulator 5b.

Next, the operation of the heating operation during the stable operation in this embodiment will be described. First, the case where the operation capacity of the indoor unit 7 is large and both the outdoor unit 1a and the outdoor unit 1b operate will be described. When performing the heating operation, the four-way valve 3
a and 3b are connected in the solid line direction in FIG. The solenoid valve 15 is opened, and the flow control valve 17 is controlled to be fully closed so that the refrigerant does not flow into the bypass circuit 16.

The flow of the refrigerant in this case is as follows.
The high-pressure, high-temperature refrigerant gas discharged from the compressors 2a, 2b passes through the four-way valves 3a, 3b, and the refrigerant discharged from the outdoor units 1a, 1b merges at the connection port 12 of the gas pipe. The gas refrigerant supplied to the indoor unit 7 through the common gas pipe 6 is condensed and liquefied in the indoor heat exchanger 8 of the indoor unit 7, and then decompressed by the expansion valve 9 of the indoor unit 7, and is a low-pressure two-phase refrigerant. Becomes After the low-pressure two-phase refrigerant passes through the common liquid pipe 10, the connection point 11 of the liquid pipe
Is distributed to the outdoor units 1a and 1b. The two-phase refrigerant distributed to the outdoor units 1a and 1b is vaporized and gasified by the outdoor heat exchangers 4a and 4b, and then is drawn into the compressors 2a and 2b through the accumulators 5a and 5b.

On the other hand, the operation of the heating operation when the operation capacity of the indoor unit 7 is small will be described. Since the operation is the small capacity operation, the outdoor unit 1a operates and the outdoor unit 1b stops. When performing the heating operation, the four-way valves 3a and 3b are connected in the solid line direction in FIG. The solenoid valve 15 is closed, and the flow control valve 17 is controlled to be fully closed so that the refrigerant does not flow through the bypass circuit 16.

The flow of the refrigerant in this case is as follows.
The high-pressure, high-temperature refrigerant gas discharged from the compressor 2a flows into the gas pipe 6 through the four-way valve 3a. Here, the outdoor unit 1
In b, high pressure is applied to the four-way valve 3b, but is closed by the check valve 14, so that high pressure is not applied to other parts.

The gas refrigerant supplied to the indoor unit 7 through the gas pipe 6 is condensed and liquefied by the indoor heat exchanger 8 of the indoor unit 7, and then decompressed by the expansion valve 9 to become a low-pressure two-phase refrigerant. After the low-pressure two-phase refrigerant passes through the liquid pipe 10, the outdoor units 1a and 1b
However, since the solenoid valve 15 is closed, the refrigerant does not flow to the outdoor unit 1b, and the refrigerant flows only to the outdoor unit 1a. The two-phase refrigerant that has flowed into the outdoor unit 1a is vaporized and gasified by the outdoor heat exchanger 4a, and then is drawn into the compressor 2a through the accumulator 5a.

Next, the operation in the cooling operation of this embodiment will be described. The operating capacity of the indoor unit 7 is large, and the outdoor unit 1
a, the case where the outdoor unit 1b operates together will be described. When performing the cooling operation, the four-way valves 3a and 3b are connected in a direction indicated by a dotted line in FIG. In addition, the solenoid valve 15 is opened, and the flow rate control valve 17 prevents the refrigerant from flowing through the bypass circuit 16.
Controlled to fully closed.

The flow of the refrigerant in this case is as follows.
The high-pressure, high-temperature refrigerant gas discharged from the compressors 2a, 2b passes through the four-way valves 3a, 3b, is condensed and liquefied in the outdoor heat exchangers 4a, 4b, and the high-pressure liquid refrigerant is supplied to the liquid pipe 10. Thereafter, the pressure is reduced by the expansion valve 9 of the indoor unit 7 to become a two-phase refrigerant, and then evaporated and gasified by the indoor heat exchanger 8 of the indoor unit 7, and the gas pipe 6, the four-way valves 3a and 3b, the accumulator 5
a and 5b are drawn into the compressors 2a and 2b.

Here, looking at the difference between the heating operation and the cooling operation, the two-phase refrigerant exists in the liquid pipe 10 in the heating operation, while the liquid refrigerant exists in the liquid pipe 10 in the cooling operation. Therefore, surplus refrigerant is generated in the heating operation as compared with the cooling operation, and this refrigerant exists in the accumulators 5a and 5b in the form of a liquid refrigerant. In the present invention, the rising speed of the heating operation is improved by utilizing the excess liquid refrigerant.

Next, the operation at the time of starting the heating operation when the operating capacity of the indoor unit is small will be described. Since the operation is the small capacity operation, the outdoor unit 1a operates and the outdoor unit 1b stops. When performing the heating operation, the four-way valves 3a and 3b are connected in the solid line direction in FIG. The solenoid valve 15 is closed, and the flow control valve 17 is controlled by the control device 18 to an opening degree at which a suitable amount of refrigerant flows through the bypass circuit 16. In addition, since the refrigerant lays down in the outdoor units 1a and 1b before the start, the liquid refrigerant exists in the outdoor heat exchangers 4a and 4b and the accumulators 5a and 5b.

The flow of the refrigerant in this case is as follows.
The high-pressure, high-temperature refrigerant gas discharged from the compressor 2a flows into the gas pipe 6 through the four-way valve 3a. The refrigerant gas flowing into the gas pipe 6 is cooled and liquefied in the middle of the gas pipe 6, and the refrigerant stagnates in the gas pipe 6. Therefore, the refrigerant does not flow downstream of the indoor heat exchanger 8 of the indoor unit 7. Compressor 2
In the case of a, the gas refrigerant discharged from the compressor 2a merely goes around the refrigeration cycle and does not return to the compressor 2a just by sucking the gas refrigerant, so that the suction pressure of the compressor 2a, that is, the low pressure of the refrigeration cycle decreases.

On the other hand, since the inside of the accumulator 5b is in a state of gas-liquid equilibrium, the pressure becomes the saturation pressure of the temperature around the outdoor unit 1b. On the other hand, the operating outdoor unit 1a attempts to evaporate the refrigerant in the outdoor heat exchanger 4a, so that the low pressure of the refrigeration cycle is lower than the saturation pressure of the temperature around the outdoor unit 1a.

Therefore, the pressure of the accumulator 5b becomes higher than the low pressure of the refrigeration cycle,
The liquid refrigerant in b is supplied to the outdoor heat exchanger 4a of the outdoor unit 1a by the bypass circuit 16. Since the liquid refrigerant supplied to the outdoor heat exchanger 4a evaporates and gasifies, it functions to prevent a decrease in the low pressure of the refrigeration cycle. Therefore, a decrease in the low pressure can be prevented, and a decrease in the flow rate of the gas refrigerant discharged from the compressor 2a is improved, so that the increase in the high pressure of the refrigeration cycle is accelerated. When the high pressure rises quickly, the refrigerant temperature in the indoor heat exchanger 7 rises quickly, so that the heating operation starts up quickly.

FIG. 3 is a diagram showing a change in the high pressure of the refrigeration cycle after starting the heating operation in the present embodiment. It can be understood that the rise of the high pressure of the refrigeration cycle and the rise of the heating operation are earlier than in the conventional air conditioner.

As shown in FIG. 4, the refrigeration cycle of this embodiment is provided with a bypass circuit 19 connecting the high pressure side and the low pressure side of the outdoor unit 1b, and a solenoid valve 20 for opening and closing the bypass circuit 19. Is also good. When the heating operation is started, when the flow rate control valve 17 is opened, the solenoid valve 20 is opened so that the refrigerant flows through the bypass circuit 19, so that the high pressure of the refrigeration cycle can be applied to the accumulator 5b. When the high pressure of the refrigeration cycle is applied to the inside of the accumulator 5b, the differential pressure between the pressure of the accumulator 5b and the low pressure of the refrigeration cycle increases as compared with the case where no high pressure is applied. It becomes easy to be supplied to the container 4a. Therefore, it becomes easier to prevent a decrease in the low pressure of the refrigeration cycle, and the heating operation starts up earlier.

The timing of opening the flow control valve 17 may be not at the same time as the start of the heating operation but after a certain time has elapsed after the start of the heating operation. Immediately after the heating operation is started, the low pressure is not drawn so much, and the outside air temperature and the outdoor heat exchanger 4a of the outdoor unit 1a
Since the temperature difference from the temperature of the refrigerant in the
Even when the liquid refrigerant is supplied to the outdoor heat exchanger 4a of the outdoor unit 1a from the above, the amount of evaporation of the liquid refrigerant is small, and the effect of preventing the lowering of the low pressure of the refrigeration cycle is small.

After a certain period of time has elapsed since the start of the heating operation, when the flow control valve 17 was opened, a low pressure was drawn to some extent, and the temperature difference between the outside air temperature and the refrigerant temperature in the outdoor heat exchanger 4a of the outdoor unit 1a increased. The outdoor unit 1 from the bypass 16
All the liquid refrigerant supplied to the outdoor heat exchanger 4a evaporates, and a sufficient effect of preventing a decrease in the low pressure of the refrigeration cycle can be achieved.

Next, regarding the opening of the flow control valve 17, if the opening of the flow control valve 17 is too large than an appropriate value, a large amount of liquid is supplied to the outdoor heat exchanger 4 a of the outdoor unit 1 a through the bypass 16. Since the refrigerant is supplied, the liquid refrigerant cannot be completely evaporated in the outdoor heat exchanger 4a, and the liquid refrigerant is stored in the accumulator 5a. If such a situation is left, the accumulator 5a overflows, and the liquid refrigerant is sucked into the compressor 2a, and the compressor 2a may be damaged by liquid compression.

When the opening of the flow control valve 17 is smaller than an appropriate value, the amount of the liquid refrigerant evaporated in the outdoor heat exchanger 4a is small, and the effect of suppressing the lowering of the low pressure is reduced. Therefore, the opening of the flow control valve 17 is set to a predetermined constant value so as to be an appropriate opening, the amount of the liquid refrigerant from the bypass 16 is too large, the liquid does not return to the accumulator 5a, and the outdoor heat exchanger 4
The control is performed so that the amount of the liquid refrigerant evaporating at a is large and the effect of suppressing the lowering of the low pressure is sufficiently obtained.

The degree of opening of the flow control valve 17 may be controlled so that the degree of superheat of the refrigerant at the outlet of the outdoor heat exchanger 4a is constant. In this case, the degree of superheat of the refrigerant is, for example, 5
Set to ° C. If the degree of superheat is 5 ° C., the liquid does not return to the accumulator 5a.
The state in which the liquid refrigerant overflows at a is avoided. If the degree of superheat is 5 ° C., the outdoor heat exchanger 4a
This indicates that a certain degree of evaporation, that is, gasification of the liquid refrigerant, is being performed, so that the amount of the liquid refrigerant that evaporates is large, and a sufficient effect of suppressing a decrease in low pressure can be obtained.

Next, if the flow control valve 17 is opened and remains as it is, any excess refrigerant originally existing in the accumulator 5b of the outdoor unit 1b moves toward the outdoor unit 1a. 1a increases, the accumulator 5a overflows, and the compressor 2
There is a possibility that the liquid refrigerant is sucked into a and the compressor 2a is damaged by liquid compression. Therefore, after the heating operation is started, a certain time required for the heating operation to start is determined, and during that time, the flow control valve 17 is opened and then the flow control valve 17 is controlled to close. In the present embodiment, a gas pipe and a liquid pipe that connect the outdoor unit and the indoor unit are one common gas pipe,
Although the description has been made assuming that the gas pipes and the liquid pipes connecting the outdoor unit and the indoor unit are combined into a plurality of common pipes as shown in FIG. Can be.

Embodiment 2 Next, another example of the embodiment of the present invention will be described with reference to the drawings. In the present embodiment, the refrigerant circuit is arranged as shown in FIG. 1 similarly to the first embodiment, and the connection between the bypass circuit 16 and the accumulator 5b is connected to one end of the bypass circuit 16 inserted from above the accumulator 5b as shown in FIG. The liquid refrigerant at the bottom of the accumulator 5b can be made to flow.

The operation of the present embodiment is the same as that of the first embodiment, except that the pipe at one end of the bypass circuit 16 can be inserted from above the accumulator 5b as shown in FIG. The degree of freedom is increased, and the accumulator 5b can be disposed at the bottom of the outdoor unit 1b.

Further, as shown in FIG. 7, one end of the bypass circuit 16 inserted from the side of the accumulator 5b may be configured to allow the liquid refrigerant at the bottom of the accumulator 5b to flow.
Also in this case, the degree of freedom in installing the accumulator 5b can be improved.

Embodiment 3 FIG. Next, another example of the embodiment of the present invention will be described with reference to the drawings. FIG. 8 is a diagram showing another example of the embodiment of the present invention, and is a configuration diagram of a refrigeration cycle of an air conditioner. The third embodiment differs from the first and second embodiments in the arrangement of the bypass circuit 16. One end of the bypass circuit 16 is arranged between the liquid pipe connection point 11 of the outdoor unit 1b and the solenoid valve 15. In this case, as in the first embodiment, when the liquid refrigerant of the accumulator 5b is caused to flow through the bypass circuit 16 during the heating small capacity operation, the liquid refrigerant of the accumulator 5b flows through the bypass circuit 16 as indicated by the arrow in FIG. Since the air is supplied to the outdoor heat exchanger 4a of the outdoor unit 1a via the connection point 11 of the pipe, the heating operation can be started earlier as in the first embodiment. By arranging the bypass circuit 16 in this way, the bypass circuit 16 can be formed as a closed circuit in the outdoor unit 1b, and the number of pipes connecting the outdoor units is reduced, so that the work for installing the outdoor unit is simplified. Is done.

The bypass circuit 16 and the accumulator 5
The connection method of b is the same as in the first and second embodiments.
The same effect can be obtained in any case of FIG.

The bypass circuit 16 can be used as a liquid bypass circuit for returning the high-pressure liquid at the outlet of the outdoor heat exchanger 4b used as a condenser when the outdoor unit 1b is performing the cooling operation to the low-pressure side.

When used as a liquid bypass circuit, as shown in FIG.
After squeezing at 7, the heat exchanger 21 can exchange heat with the high-pressure liquid refrigerant to form a circuit for recovering the latent heat of the bypassed liquid refrigerant.

When the liquid bypass circuit is provided, when the ambient temperature of the outdoor unit is high during the cooling operation and the high pressure of the refrigeration cycle rises transiently, the rise of the high pressure can be suppressed by the liquid bypass, and the compressor can be protected. It becomes possible.

When a circuit for recovering the latent heat of the bypassed liquid refrigerant by exchanging heat with the high-pressure liquid refrigerant in the heat exchanger 21 is provided, the gas pipe 6 can be cooled without impairing the cooling capacity.
The flow rate of the refrigerant flowing through the gas pipe 6 can be reduced, so that the pressure loss in the gas pipe 6 can be reduced and the performance degradation due to the pressure loss can be suppressed.

When the bypass circuit 16 is also used as a liquid bypass circuit during the cooling operation, the bypass circuit 1
It is more preferable to use the connection between the accumulator 5 and the accumulator 5b as shown in FIG. 10 than the connection as shown in FIG. When the liquid bypass is used in the connection method as shown in FIG. 2, the refrigerant returned from the liquid bypass blows up the liquid in the accumulator 5b and is sucked into the suction of the compressor 2b. There is a risk of causing breakage. As shown in FIG. 10, by laying the connection port of the bypass circuit 16 on the accumulator 5b side, it is possible to prevent the liquid in the accumulator 5b from being blown up when used as a liquid bypass.

[0059]

According to the multi-air conditioner of the present invention,
When the operation capacity of the indoor unit is small during the heating operation, the heating unit is provided with a bypass circuit that supplies the liquid refrigerant in the accumulator of the outdoor unit that is stopped to the outdoor heat exchanger of the other outdoor unit that is operating. The start-up speed of operation can be increased.

Also, the operation of the bypass circuit is stopped by providing a bypass circuit between the accumulator of the outdoor unit whose operation is stopped and the liquid pipe of the outdoor unit communicating with the common liquid pipe. Since a closed circuit can be formed in the outdoor unit, and the number of pipes connecting the outdoor units is reduced, the work for installing the outdoor unit is simplified.

Further, by providing another bypass circuit for flowing the high-pressure gas from the high-pressure side communicating with the common gas pipe of the outdoor unit whose operation is stopped to the accumulator of the outdoor unit, the liquid refrigerant of the accumulator is operated during the operation. The outdoor unit can be easily supplied to the outdoor heat exchanger, the lowering of the low pressure of the refrigeration cycle is suppressed, and the rise of the heating operation is accelerated.

Further, by inserting one end of the bypass circuit from the top or the side of the accumulator of the outdoor unit during operation stop to reach the bottom of the accumulator, the degree of freedom of installation of the accumulator of the outdoor unit during operation stop is improved. Can be improved.

Further, the control device controls the flow control valve to be opened after a lapse of a predetermined time after the start of the heating operation, so that all of the liquid refrigerant supplied from the bypass circuit to the outdoor heat exchanger of the outdoor unit in operation is operated. It is possible to sufficiently evaporate and sufficiently prevent the lowering of the low pressure of the refrigeration cycle.

In addition, the control device controls the flow control valve to be opened when the low pressure of the refrigeration cycle falls below a certain value after the heating operation is started, so that the effect of preventing the reduction of the low pressure of the refrigeration cycle can be sufficiently achieved. Can be fulfilled.

Further, the controller sets the opening of the flow control valve to an appropriate value so that the liquid refrigerant does not completely evaporate in the outdoor heat exchanger of the other outdoor unit during operation and the amount of the liquid refrigerant evaporated in the outdoor heat exchanger does not decrease. By controlling to a constant value, the amount of liquid refrigerant from the bypass circuit is too large and the liquid refrigerant does not overflow in the accumulator of another outdoor unit during operation,
In addition, the amount of the liquid refrigerant evaporated in the outdoor heat exchanger of the other outdoor unit during operation is large, and a sufficient effect of suppressing a decrease in low pressure can be obtained.

Further, the controller controls the opening degree of the flow control valve so that the degree of superheat of the refrigerant at the outlet of the outdoor heat exchanger of the other outdoor unit being operated becomes a constant value. Liquid does not return to the accumulator of the outdoor unit.

After the control device opens the flow control valve,
By controlling the flow control valve to close after a certain period of time necessary to start the heating operation, the amount of surplus refrigerant present in the outdoor unit during operation increases, the accumulator overflows, and the liquid refrigerant is sucked into the compressor. There is no danger of compressor damage due to liquid compression.

Further, when the high pressure of the refrigeration cycle rises transiently during the cooling operation, the bypass circuit is used as a liquid bypass circuit that returns the high pressure liquid to the low pressure side and suppresses the rise of the high pressure. When the outdoor unit ambient temperature is high and the high pressure of the refrigeration cycle rises transiently, the rise of the high pressure can be suppressed by the liquid bypass, and the compressor can be protected.

Further, by providing the bypass circuit with a heat exchanger for exchanging the two-phase refrigerant with the high-pressure liquid after squeezing the liquid refrigerant bypassed by the flow control valve, pressure loss in the gas pipe can be reduced. Performance degradation due to loss can be suppressed.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an embodiment of the present invention, and is a configuration diagram of a refrigeration cycle of a multi-air conditioner.

FIG. 2 is a diagram illustrating an example of an embodiment of the present invention, and is a diagram illustrating a method of connecting a bypass circuit and an accumulator.

FIG. 3 is a diagram illustrating an example of the embodiment of the present invention, and is a diagram illustrating a rise in high pressure in a heating start operation of the air-conditioning apparatus.

FIG. 4 is a diagram illustrating an example of an embodiment of the present invention, and is a configuration diagram of a refrigeration cycle of a multi-air conditioner.

FIG. 5 is a diagram illustrating an example of an embodiment of the present invention, and is a configuration diagram of a refrigeration cycle of a multi-air conditioner.

FIG. 6 is a diagram showing another example of the embodiment of the present invention;
FIG. 3 is a diagram illustrating a connection method between a bypass circuit and an accumulator.

FIG. 7 is a diagram showing another example of the embodiment of the present invention;
FIG. 3 is a diagram illustrating a connection method between a bypass circuit and an accumulator.

FIG. 8 is a diagram showing another example of the embodiment of the present invention;
It is a refrigeration cycle block diagram of a multi air conditioner.

FIG. 9 is a diagram showing another example of the embodiment of the present invention;
It is a refrigeration cycle block diagram of a multi air conditioner.

FIG. 10 is a diagram illustrating another example of the embodiment of the present invention, and is a diagram illustrating a method of connecting a bypass circuit and an accumulator.

FIG. 11 is a configuration diagram of a refrigeration cycle of a conventional multi-air conditioner.

[Explanation of symbols]

1a, 1b Outdoor unit, 2a, 2b Compressor, 3a, 3b
Four-way valve, 4a, 4b outdoor heat exchanger, 5a, 5b accumulator, 6 common gas pipe, 7 indoor unit, 8 indoor heat exchanger, 9 expansion valve, 10 common liquid pipe, 11
Connection point between the liquid pipe coming out of the outdoor unit and the common liquid pipe, 12
Connection point between the gas pipe exiting from the outdoor unit and the common gas pipe, 14 check valve, 15 solenoid valve, 16 bypass circuit, 17 flow control valve, 18 control device, 19 bypass circuit, 20 solenoid valve, 21 heat exchanger .

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yoshio Ueno 2-6-2 Otemachi, Chiyoda-ku, Tokyo Inside Mitsubishi Electric Engineering Co., Ltd. (72) Tomohiko Kawanishi 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation (72) Inventor Fumio Matsuoka 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation (56) References JP-A-7-269974 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F25B 13/00

Claims (15)

(57) [Claims] 1. A plurality of outdoor units having a compressor, an outdoor heat exchanger, and an accumulator; a plurality of indoor units having an indoor heat exchanger and a decompression device; and a common connecting the outdoor unit and the indoor unit. A gas pipe, a common liquid pipe connecting the outdoor unit and the indoor unit, and, when the operation capacity of the indoor unit is small during a heating operation, the operation is stopped and the communication between the gas pipe and the liquid pipe is cut off. And a bypass circuit for supplying the liquid refrigerant in the accumulator of the outdoor unit to the outdoor heat exchanger of the other outdoor unit during operation. Air conditioner. 2. The outdoor unit according to claim 1, wherein the bypass circuit is provided between the accumulator of the outdoor unit whose operation is stopped and a liquid pipe of another outdoor unit which is operating. Multi air conditioner. 3. The outdoor unit according to claim 1, wherein the bypass circuit is provided between the accumulator of the outdoor unit whose operation is stopped and a liquid pipe of the outdoor unit communicating with the common liquid pipe. 2. The multi-air conditioner according to 1. 4. A bypass circuit for flowing high-pressure gas from a high-pressure side communicating with the common gas pipe of the outdoor unit whose operation is stopped to the accumulator of the outdoor unit. Item 8. The multi-air conditioner according to Item 1. 5. The multi-air conditioner according to claim 1, wherein one end of the bypass circuit is connected to a bottom of the accumulator of the outdoor unit that is not operating. 6. The multi-air system according to claim 1, wherein one end of said bypass circuit is inserted from a top or a side of said accumulator of said outdoor unit during operation stop to reach a bottom of said accumulator. Harmony equipment. 7. The apparatus according to claim 1, further comprising: a flow control valve provided in the bypass circuit for controlling a flow rate of the refrigerant in the bypass circuit; and a control device for controlling the flow control valve. Multi air conditioner. 8. The multi-air conditioner according to claim 7, wherein the control device controls the flow control valve to be opened at the same time when the heating operation is started. 9. The multi-air conditioner according to claim 7, wherein the control device controls to open the flow control valve after a lapse of a predetermined time after the start of the heating operation. 10. The control device according to claim 1, wherein after the heating operation is started,
The multi-air conditioner according to claim 7, wherein the flow control valve is controlled to be opened when the low pressure of the refrigeration cycle of the air conditioner becomes equal to or lower than a predetermined value. 11. The controller according to claim 1, wherein the controller controls the opening degree of the flow control valve so that the liquid refrigerant completely evaporates in the outdoor heat exchanger of the other outdoor unit in operation and the liquid evaporates in the outdoor heat exchanger. 11. The multi-air conditioner according to claim 8, wherein the refrigerant is controlled to an appropriate constant value that does not decrease. 12. The control device controls the opening degree of the flow control valve so that the degree of superheat of the refrigerant at the outlet of the outdoor heat exchanger of the other outdoor unit during operation becomes a constant value. The multi-air conditioner according to claim 8 or claim 9 or claim 10. 13. The control device according to claim 8, wherein, after opening the flow control valve, the control device controls the flow control valve to close after a certain period of time necessary for starting the heating operation. The multi-air conditioner according to claim 9 or 10. 14. The bypass circuit is used as a liquid bypass circuit that suppresses a rise in high pressure by returning high pressure fluid to a low pressure side when a high pressure in the refrigeration cycle rises transiently during cooling operation. The multi air conditioner according to claim 3. 15. A heat exchanger for exchanging heat with the high-pressure liquid of the two-phase refrigerant after restricting the bypassed liquid refrigerant by the flow control valve in the bypass circuit. The multi-air conditioner as described.