GB2558116A - Refrigeration cycle device - Google Patents

Abstract

A refrigeration cycle device in which a plurality of outdoor units each have a compressor, an outdoor heat exchanger, and expansion devices, and are connected to an indoor unit having an indoor heat exchanger by refrigerant pipes, thereby forming a plurality of refrigeration cycles. The refrigeration cycle device is equipped with a control device that controls the operation of the plurality of outdoor units. The control device has a drive control unit that performs multiple drive control to cause at least two outdoor units to operate according to the load when a demand signal is input.

Description

(56) Documents Cited:

JP 2014062668 A JP 2009144950 A

JP 2013224784 A JP 2000186844 A (86) International Application Data:

PCT/JP2015/083332 Ja 27.11.2015 (87) International Publication Data:

WO2017/090171 Ja 01.06.2017 (58) Field of Search:

INT CL F24F

Other: Jitsuyo Shinan Koho 1922-1996, Jitsuyo Shinan Toroku Koho 1996-2016, Kokai Jitsuyo Shinan Koho 1971-2016, Toroku Jitsuyo Shinan Koho 1994-2016 (71) Applicant(s):

Mitsubishi Electric Corporation (Incorporated in Japan)

7-3 Marunouchi 2-chome, Chiyodaku, Tokyo 100-8310, Japan (72) Inventor(s):

Hiromitsu Kikuchi (74) Agent and/or Address for Service:

Mewburn Ellis LLP

City Tower, 40 Basinghall Street, LONDON, Greater London, EC2V 5DE, United Kingdom (54) Title of the Invention: Refrigeration cycle device Abstract Title: Refrigeration cycle device (57) A refrigeration cycle device in which a plurality of outdoor units each have a compressor, an outdoor heat exchanger, and expansion devices, and are connected to an indoor unit having an indoor heat exchanger by refrigerant pipes, thereby forming a plurality of refrigeration cycles. The refrigeration cycle device is equipped with a control device that controls the operation of the plurality of outdoor units. The control device has a drive control unit that performs multiple drive control to cause at least two outdoor units to operate according to the load when a demand signal is input.

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HXΓ b

19b

5b‘

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40b I 4b I 5Π b I_

FIG. 1

Ό

Ρ3

2/11

FIG. 2

22a

CONTROLLER

INPUT

PROCESSING UNIT

-S.-FREQUENCY COMPUTING UNIT

23a —

DRIVE

CONTROL UNIT

THRESHOLD DETERMINING UNIT

24a

FIG. 3

3/11

FIG. 4

TOTAL FREQUENCY F (Hz) = F1 (Hz) + F2 (Hz)

FIG. 5

4/11

FIG. 6

D2

TOTAL FREQUENCY F (Hz) = F1 (Hz) + F2 (Hz)

5/11

FIG. 7

6/11

FIG. 8

400

7/11

FIG. 9

TOTAL FREQUENCY F (Hz) = F1 (Hz) + F2 (Hz) + F3 (Hz)

8/11

FIG. 10

TOTAL FREQUENCY F (Hz) = F1 (Hz) + F2 (Hz) + F3 (Hz)

9/11

FIG. 11

TOTAL FREQUENCY F (Hz) = F1 (Hz) + F2 (Hz) + F3 (Hz)

10/11

FIG. 12

500a

100b

11/11

FIG. 13

DESCRIPTION

Title of Invention

REFRIGERATION CYCLE APPARATUS

Technical Field [0001]

The present invention relates to a refrigeration cycle apparatus configured to perform capacity control on compressors.

Background Art [0002]

A refrigeration cycle apparatus provided with outdoor units including two compressors performs control in which one of the two compressors is started first, and the second compressor is started when a shortage in capacity occurs with an increase in load, for example (see Patent Literature 1, for example).

[0003]

Moreover, of refrigeration cycle apparatuses each including a plurality of outdoor units, an air-conditioning apparatus used in constant-temperature, constanthumidity or outside air processing uses, such as packaged air-conditioning apparatus for facilities, often use capacity control on the compressors. The capacity control on the compressors is achieved by determining the number of operating compressors and operating frequencies of the compressors depending on a demand control command value from outside the refrigeration cycle apparatus and a difference between a temperature at an inlet port of a compressor and a set temperature, for example.

Citation List

Patent Literature [0004]

Patent Literature 1: Japanese Unexamined Patent Application Publication No.

2006-266644

Summary of Invention

Technical Problem [0005]

However, the refrigeration cycle apparatus of Patent Literature 1 is configured to determine the number of operating compressors depending on the load, and only one compressor is continuously operated while the load is small. When such a state in which only one compressor is operated continues for a long time, the operating compressor enters an abnormal state of being overcharged with refrigerant, and the compressor may stop in some cases.

[0006]

Moreover, in the refrigeration cycle apparatus including the plurality of outdoor units, a state in which only one outdoor unit is operated occurs depending on the demand control command value and a variation in load. Such a refrigeration cycle apparatus is filled with an amount of refrigerant to be circulated through the plurality of outdoor units, and in the case of the packaged air-conditioning apparatus for facilities, the outdoor units are connected to an indoor unit on a one-to-one basis. Consequently, when only one outdoor unit is operated, the indoor unit and the outdoor units become unbalanced. Consequently, there is a problem in that, when the operation under such a state is continued for a long time, the refrigerant is unevenly distributed to the operating outdoor unit, and a malfunction due to the overcharge with the refrigerant eventually occurs to stop the outdoor unit.

[0007]

Moreover, also when an operating frequency of the compressor is increased with an oil recovery operation in the state in which only one outdoor unit is operated, the refrigerant dwelling in an existing pipe returns to the one operating outdoor unit. Consequently, there are problems in that the one operating outdoor unit enters the abnormal state of being overcharged with the refrigerant to stop the outdoor unit, and hence that a temperature and a humidity cannot be controlled any more.

[0008]

The present invention has been made to solve the above-mentioned problems, and therefore has an object to provide a refrigeration cycle apparatus including a plurality of outdoor units, with which a state in which only one outdoor unit is operated is reduced to prevent the one outdoor unit from being overcharged with refrigerant, and to prevent stoppage of the outdoor unit during operation for a long time.

Solution to Problem [0009]

According to one embodiment of the present invention, there is provided a refrigeration cycle apparatus, in which a plurality of outdoor units are connected to an indoor unit through a refrigerant pipe to form a plurality of refrigeration cycles, the plurality of outdoor units each including a compressor, an outdoor heat exchanger, and an expansion device, the indoor unit including an indoor heat exchanger, the refrigeration cycle apparatus including a controller configured to control operations of the plurality of outdoor units, the controller including a drive control unit configured to execute, when a demand signal is input, multiple drive control in which at least two of the plurality of outdoor units are operated depending on a load.

Advantageous Effects of Invention [0010]

According to one embodiment of the present invention, the controller is configured to execute, when the demand signal is input, the multiple drive control in which at least two outdoor units are driven, and hence the state in which only one outdoor unit is operated can be reduced. Consequently, the one outdoor unit can be prevented from being overcharged with the refrigerant, and the stoppage of the outdoor unit can be prevented during the operation for a long time.

Brief Description of Drawings [0011] [Fig. 1] Fig. 1 is an overall configuration diagram of a refrigeration cycle apparatus according to Embodiment 1 of the present invention.

[Fig. 2] Fig. 2 is a block diagram for illustrating functional configurations of 5 controllers included in the refrigeration cycle apparatus of Fig. 1.

[Fig. 3] Fig. 3 is a graph for showing multiple drive control in the refrigeration cycle apparatus of Fig. 1.

[Fig. 4] Fig. 4 is a graph for showing sequential drive control in the refrigeration cycle apparatus of Fig. 1.

[Fig. 5] Fig. 5 is a graph for showing an example of processing of switching from the sequential drive control to the multiple drive control in the refrigeration cycle apparatus of Fig. 1.

[Fig. 6] Fig. 6 is a graph for showing another example of the processing of switching from the sequential drive control to the multiple drive control in the refrigeration cycle apparatus of Fig. 1.

[Fig. 7] Fig. 7 is a flow chart for illustrating operation of the refrigeration cycle apparatus of Fig. 1.

[Fig. 8] Fig. 8 is an overall configuration diagram of a refrigeration cycle apparatus according to Embodiment 2 of the present invention.

[Fig. 9] Fig. 9 is a graph for showing multiple drive control in the refrigeration cycle apparatus of Fig. 8.

[Fig. 10] Fig. 10 is a graph for showing sequential drive control in the refrigeration cycle apparatus of Fig. 8.

[Fig. 11] Fig. 11 is a graph for showing an example of processing of switching from the sequential drive control to the multiple drive control in the refrigeration cycle apparatus of Fig. 8.

[Fig. 12] Fig. 12 is an overall configuration diagram of a refrigeration cycle apparatus according to Embodiment 3 of the present invention.

[Fig. 13] Fig. 13 is a flow chart for illustrating operation of the refrigeration cycle apparatus of Fig. 12.

Description of Embodiments [0012]

Embodiment 1

A case is exemplified below in which a refrigeration cycle apparatus according to Embodiment 1 of the present invention is an air-conditioning apparatus to describe a configuration and operation of the refrigeration cycle apparatus.

[0013] (Overall Configuration)

Fig. 1 is an overall configuration diagram of the refrigeration cycle apparatus according to Embodiment 1 of the present invention. As illustrated in Fig. 1, a refrigeration cycle apparatus 300 according to Embodiment 1 includes an outdoor unit 100a and an outdoor unit 100b, which are units on a heat source side, and an indoor unit 200, which is a unit on a use side. Hereinafter, the outdoor unit 100a and the outdoor unit 100b are also collectively referred to as outdoor units 100, or any one of the outdoor unit 100a and the outdoor unit 100b is also simply referred to as outdoor unit 100.

[0014]

Moreover, the refrigeration cycle apparatus 300 includes refrigerant pipes for connecting the outdoor unit 100a and the outdoor unit 100b to the indoor unit 200.

The refrigeration cycle apparatus 300 includes, as the above-mentioned refrigerant pipes, a liquid pipe 17a, a liquid pipe 17b, a liquid pipe 17c, a gas pipe 18a, a gas pipe 18b, and a gas pipe 18c through which refrigerant is circulated between the outdoor unit 100a and the indoor unit 200 and between the outdoor unit 100b and the indoor unit 200. Further, the refrigeration cycle apparatus 300 includes a liquid distributor 15 connecting the liquid pipe 17a, the liquid pipe 17b, and the liquid pipe 17c, and a gas distributor 16 connecting the gas pipe 18a, the gas pipe 18b, and the gas pipe 18c.

[0015]

The outdoor unit 100a includes a compressor 1a, a check valve 2a, a four-way valve 3a, an outdoor heat exchanger 4a, an outdoor fan 40a, a subcooling heat exchanger 5a, an expansion device 6a, an expansion device 7a, a liquid control valve 8a, a gas control valve 9a, an accumulator 10a, a controller 11a, and a storage unit 19a. The subcooling heat exchanger 5a includes a high-pressure-side passage 51a and a low-pressure-side passage 52a.

[0016]

The outdoor unit 100b includes a compressor 1b, a check valve 2b, a four-way valve 3b, an outdoor heat exchanger 4b, an outdoor fan 40b, a subcooling heat exchanger 5b, an expansion device 6b, an expansion device 7b, a liquid control valve 8b, a gas control valve 9b, an accumulator 10b, a controller 11b, and a storage unit 19b. The subcooling heat exchanger 5b includes a high-pressure-side passage 51 b and a low-pressure-side passage 52b.

[0017]

Hereinafter, the compressor 1a and the compressor 1b are also collectively referred to as compressors 1, or any one of the compressor 1a and the compressor 1 b is also simply referred to as compressor 1. Moreover, a state in which one compressor 1 is operated is referred to as one-compressor operating state, and a state in which two compressors 1 are operated is referred to as two-compressor operating state.

[0018]

The indoor unit 200 includes an expansion device 12, an indoor heat exchanger 13, and an indoor fan 13c.

[0019]

A refrigeration cycle formed between the outdoor unit 100a and the indoor unit 200 is described below.

Between the outdoor unit 100a and the indoor unit 200, the compressor 1a, the check valve 2a, the four-way valve 3a, the outdoor heat exchanger 4a, the subcooling heat exchanger 5a, the expansion device 7a, the expansion device 12, the indoor heat exchanger 13, the four-way valve 3a, and the accumulator 10a are connected in the stated order through the refrigerant pipes to form a refrigerant circuit. During a cooling operation, as illustrated in Fig. 1, the refrigerant circuit is formed by connecting the compressor 1a, the check valve 2a, the four-way valve 3a, the outdoor heat exchanger 4a, the subcooling heat exchanger 5a, the expansion device 7a, the expansion device 12, the indoor heat exchanger 13, the four-way valve 3a, the accumulator 10a, and again the compressor 1a in the stated order to form the refrigeration cycle.

[0020]

Moreover, the outdoor unit 100a includes a bypass pipe 14a connecting the refrigerant pipe connecting the subcooling heat exchanger 5a and the expansion device 7a and the refrigerant pipe connecting the four-way valve 3a and the accumulator 10a. The bypass pipe 14a branches off the refrigerant pipe connecting the subcooling heat exchanger 5a and the expansion device 7a to bypass the refrigerant to the refrigerant pipe connecting the four-way valve 3a and the accumulator 10a via the expansion device 6a and the subcooling heat exchanger 5a. [0021]

In the above-mentioned refrigerant circuit, the expansion device 7a and the expansion device 12 are connected via the liquid control valve 8a and the liquid distributor 15, and the liquid control valve 8a and the liquid distributor 15 are connected through the liquid pipe 17a. Moreover, the indoor heat exchanger 13 and the four-way valve 3a are connected via the gas distributor 16 and the gas control valve 9a, and the gas distributor 16 and the gas control valve 9a are connected through the gas pipe 18a.

[0022]

Next, a refrigeration cycle formed between the outdoor unit 100b and the indoor unit 200 is described.

Between the outdoor unit 100b and the indoor unit 200, the compressor 1b, the check valve 2b, the four-way valve 3b, the outdoor heat exchanger 4b, the subcooling heat exchanger 5b, the expansion device 7b, the expansion device 12, the indoor heat exchanger 13, the four-way valve 3b, and the accumulator 10b are connected in the stated order through the refrigerant pipes to form a refrigerant circuit. During a cooling operation, the refrigerant circuit is formed by connecting the compressor 1b, the check valve 2b, the four-way valve 3b, the outdoor heat exchanger 4b, the subcooling heat exchanger 5b, the expansion device 7b, the expansion device 12, the indoor heat exchanger 13, the four-way valve 3b, the accumulator 10b, and again the compressor 1b in the stated order to form the refrigeration cycle.

[0023]

Moreover, the outdoor unit 100b includes a bypass pipe 14b connecting the refrigerant pipe connecting the subcooling heat exchanger 5b and the expansion device 7b and the refrigerant pipe connecting the four-way valve 3b and the accumulator 10b. The bypass pipe 14b branches off the refrigerant pipe connecting the subcooling heat exchanger 5b and the expansion device 7b to bypass the refrigerant to the refrigerant pipe connecting the four-way valve 3b and the accumulator 10b via the expansion device 6b and the subcooling heat exchanger 5b. [0024]

In the above-mentioned refrigerant circuit, the expansion device 7b and the expansion device 12 are connected via the liquid control valve 8b and the liquid distributor 15, and the liquid control valve 8b and the liquid distributor 15 are connected through the liquid pipe 17b. Moreover, the indoor heat exchanger 13 and the four-way valve 3b are connected via the gas distributor 16 and the gas control valve 9b, and the gas distributor 16 and the gas control valve 9b are connected through the gas pipe 18b.

[0025]

Next, a detailed configuration of the outdoor unit 100a is described.

The compressor 1a is configured to suck and compress low-temperature and low-pressure gas refrigerant, and to discharge the compressed refrigerant as hightemperature and high-pressure refrigerant to the four-way valve 3a. Here, the outdoor unit 100a includes an inverter device (not shown) configured to control an operating frequency of the compressor 1 a. The inverter device is configured to adjust (suitably change) the operating frequency of the compressor 1a in accordance with a drive signal from the controller 11a, to thereby change a capacity of the compressor 1a. The check valve 2a is configured to prevent backflow of the refrigerant in a direction from the four-way valve 3a to the compressor 1a.

[0026]

The four-way valve 3a is configured to switch a flow of the refrigerant between the cooling operation and a heating operation. The flow switching by the four-way valve 3a is performed with a drive signal from the controller 11a. More specifically, the controller 11a performs the flow switching by the four-way valve 3a such that, during the cooling operation, the high-temperature and high-pressure refrigerant discharged from the compressor 1a is directed to the outdoor heat exchanger 4a, and the low-temperature and low-pressure gas refrigerant that has flowed from the indoor unit 200 via the gas control valve 9a is directed to the accumulator 10a. Meanwhile, the controller 11a performs the flow switching by the four-way valve 3a such that, during the heating operation, the high-temperature and high-pressure refrigerant discharged from the compressor 1a is directed to the indoor heat exchanger 13 via the gas control valve 9a, and low-temperature and low-pressure gas refrigerant that has flowed out of the outdoor heat exchanger 4a is directed to the accumulator 10a. [0027]

The outdoor heat exchanger 4a is formed of a fin-and-tube heat exchanger, for example, and is configured to exchange heat between the refrigerant that flows in and outside air that is sent from the outdoor fan 40a. The outdoor fan 40a is provided next to the outdoor heat exchanger 4a to facilitate the heat exchange in the outdoor heat exchanger 4a. The outdoor heat exchanger 4a serves as a radiator during the cooling operation, and is configured to cause the high-temperature and high-pressure refrigerant that flows in from the compressor 1a to transfer heat to the outside air. Meanwhile, the outdoor heat exchanger 4a serves as an evaporator during the heating operation, and is configured to cause two-phase gas-liquid refrigerant that flows from the subcooling heat exchanger 5a to remove heat from the outside air and to be evaporated.

[0028]

The subcooling heat exchanger 5a is used during the cooling operation, and is configured to subcool the refrigerant. The subcooling heat exchanger 5a includes the high-pressure-side passage 51a, through which the high-pressure refrigerant that has rejected heat in the outdoor heat exchanger 4a flows, and the low-pressure-side passage 52a, through which the low-pressure refrigerant that has been adjusted in flow rate and pressure by the expansion device 6a flows. In other words, the subcooling heat exchanger 5a is configured to further transfer heat from the refrigerant that has rejected heat in the outdoor heat exchanger 4a, has branched from the refrigerant pipe between the subcooling heat exchanger 5a and the expansion device 7a, and then has been adjusted in flow rate and pressure by the expansion device 6a. The expansion device 6a is formed of an electronic expansion valve, for example, and is configured to be adjusted in opening degree with a drive signal from the controller 11a.

[0029]

The expansion device 7a is formed of an electronic expansion valve, for example, and is configured to adjust a flow rate of the refrigerant that passes through, to thereby expand the refrigerant and reduce a pressure of the refrigerant.

Moreover, to prevent the compressor 1a from being damaged by liquid backflow during the heating operation, the expansion device 7a is configured to be adjusted in opening degree with a drive signal from the controller 11 a. The accumulator 10a is configured to accumulate surplus refrigerant of the refrigerant that has flowed via the four-way valve 3a.

[0030]

As described above, the bypass pipe 14a is configured, during the cooling operation, to bypass the refrigerant that has branched off the refrigerant pipe on the high pressure side between the subcooling heat exchanger 5a and the expansion device 7a to the refrigerant pipe on the low pressure side between the four-way valve 3a and the accumulator 10a. In the course of the bypassing of the refrigerant by the bypass pipe 14a, the refrigerant that has branched off the refrigerant pipe between the subcooling heat exchanger 5a and the expansion device 7a is reduced in pressure by the expansion device 6a, and has heat removed by the refrigerant flowing through the high-pressure-side passage 51a in the subcooling heat exchanger 5a.

[0031]

The controller 11a is configured to control the overall operation of the outdoor unit 100a. Specifically, the controller 11a is configured to control the operating frequency of the compressor 1a, perform flow switching control of the four-way valve 3a, and adjust the opening degrees of the expansion device 6a and the expansion device 7a, for example.

[0032]

The controller 11a is configured to execute, when a demand signal is input, multiple drive control in which at least two outdoor units 100 are operated depending on a load. Moreover, the controller 11a is configured to execute, when no demand signal is input at startup, sequential drive control in which the number of outdoor units 100 to be operated is changed depending on the load. When the controller 11a is executing the multiple drive control, two or more outdoor units 100 are always operated, and a state in which only one outdoor unit 100 is operated does not occur. Meanwhile, when the controller 11a is executing the sequential drive control, the state in which only one outdoor unit 100 is operated occurs in some cases. Further, when the demand signal is input while the controller 11a is executing the sequential drive control, processing of switching from the sequential drive control to the multiple drive control is performed.

[0033]

The demand signal as used herein is a signal input from a demand control device provided outside the refrigeration cycle apparatus 300, for example. The demand control device is configured to monitor power used by a plurality of controlled apparatuses, which changes with time, and perform control such that a demand value for each demand period of an electric power supplier does not exceed a target energy. In other words, the demand signal is a demand control signal that is externally input to reduce a total power usage by the plurality of controlled apparatuses to a certain amount.

[0034]

The storage unit 19a stores programs for various kinds of control by the controller 11a. The storage unit 19a also stores a multiple initial value Am that is an operating frequency used in starting each of the compressor 1a and the compressor 1b when the demand signal is input at startup, and a sequential initial value As that is an operating frequency used in starting the compressor 1a or the compressor 1b when no demand signal is input at startup. The storage unit 19a further stores a decreasing threshold A1 that is a criterion for switching the refrigeration cycle apparatus from the two-compressor operating state to the one-compressor operating state, and an increasing threshold A2 that is a criterion for switching the refrigeration cycle apparatus from the one-compressor operating state to the two-compressor operating state. The decreasing threshold A1 and the increasing threshold A2 are set to values that are smaller than the maximum operating frequency providable by one compressor 1, and the decreasing threshold A1 and the increasing threshold A2 have a relationship of A1 < A2.

[0035]

Here, the multiple initial value Am (Hz), the sequential initial value As (Hz), the decreasing threshold A1 (Hz), and the increasing threshold A2 (Hz) can be set from a remote controller (not shown), for example, depending on an on-site usage environment. The multiple initial value Am is set to a range of 15 < Am < 30. The sequential initial value As is set to a range of 15 < As < 30. The multiple initial value Am and the sequential initial value As may be the same value or mutually different values. Moreover, the decreasing threshold A1 and the increasing threshold A2 are set to satisfy relationships of 15 < A1, A2 < 100, and A2- - A1 > 10.

[0036]

In Embodiment 1, the decreasing threshold A1 is set to an operating frequency at which power consumption in the one-compressor operating state and power consumption in the two-compressor operating state are equal to each other. In other words, the decreasing threshold A1 is set such that power consumption in the case where one compressor 1 is driven at the decreasing threshold A1 and power consumption in a case where two compressors 1 are each driven at half the decreasing threshold A1 are equal to each other. Then, when a total frequency F is less than the decreasing threshold A1, the power consumption in the case where two compressors 1 are each driven at half the total frequency F is larger than the power consumption in the case where one compressor 1 is driven at the total frequency F. Moreover, when the total frequency F is more than the decreasing threshold A1, the power consumption in the case where one compressor 1 is driven at the total frequency F is larger than the power consumption in the case where two compressors 1 are each driven at half the total frequency F.

[0037]

Here, a detailed configuration of the outdoor unit 100b is similar to that of the outdoor unit 100a described above, and hence a description of each constituent member of the outdoor unit 100b is omitted. In the outdoor unit 100a and the outdoor unit 100b, the constituent members that function similarly are denoted by reference signs obtained by adding suffixes a and b to the same number as illustrated in Fig. 1. It should be noted, however, that in Embodiment 1, the controller 11b is configured to control the overall operation of the outdoor unit 100b in accordance with various control signals transmitted from the controller 11a.

[0038]

Next, a detailed configuration of the indoor unit 200 is described.

The indoor heat exchanger 13 is formed of a fin-and-tube heat exchanger, for example, and is configured to exchange heat between the refrigerant that flows in and air in an air-conditioned space that is sent from the indoor fan 13c. The indoor fan 13c is provided next to the indoor heat exchanger 13 to facilitate the heat exchange in the indoor heat exchanger 13. More specifically, the indoor heat exchanger 13 serves as an evaporator during the cooling operation, and is configured to cause twophase gas-liquid refrigerant that has been reduced in pressure by the expansion device 12 to remove heat from the air in the air-conditioned space and to be evaporated. Meanwhile, the indoor heat exchanger 13 serves as a radiator during the heating operation, and is configured to cause the high-temperature and high13 pressure refrigerant that flows from the compressor 1a of the outdoor unit 100a and the compressor 1 b of the outdoor unit 100b to transfer heat to the air in the airconditioned space and to be condensed. The expansion device 12 is formed of an electronic expansion valve, for example, and is configured to adjust a flow rate of the refrigerant circulating through the indoor unit 200, to thereby expand the refrigerant and reduce the pressure of the refrigerant.

[0039]

The liquid control valve 8a and the gas control valve 9a are opened to allow the refrigerant to flow into and out of the outdoor unit 100a and the indoor unit 200, to thereby establish the refrigeration cycle between the outdoor unit 100a and the indoor unit 200. Similarly, the liquid control valve 8b and the gas control valve 9b are opened to allow the refrigerant to flow into and out of the outdoor unit 100b and the indoor unit 200, to thereby establish the refrigeration cycle between the outdoor unit 100b and the indoor unit 200.

[0040]

The liquid distributor 15 has a function of merging the refrigerant that has passed the expansion device 7a of the outdoor unit 100a and the refrigerant that has passed the expansion device 7b of the outdoor unit 100b, and allowing the merged refrigerant to flow into the indoor unit 200 during the cooling operation. The liquid distributor 15 also has a function of bifurcating the refrigerant that has been reduced in pressure by the expansion device 12 of the indoor unit 200, and allowing the bifurcated refrigerant to flow into each of the outdoor unit 100a and the outdoor unit 100b during the heating operation.

[0041]

The gas distributor 16 has a function of bifurcating low-temperature and lowpressure gas refrigerant that has flowed out of the indoor heat exchanger 13 of the indoor unit 200, and allowing the bifurcated refrigerant to flow into each of the outdoor unit 100a and the outdoor unit 100b during the cooling operation. The gas distributor 16 also has a function of merging the refrigerant of the outdoor unit 100a and the refrigerant of the outdoor unit 100b, and allowing the merged refrigerant to flow into the indoor unit 200 during the heating operation.

[0042]

Fig. 2 is a block diagram for illustrating functional configurations of the controller 11a and the controller 11b included in the refrigeration cycle apparatus 300. With reference to Fig. 2, the functional configurations of the controller 11a and the controller 11b are described specifically.

[0043]

As illustrated in Fig. 2, the controller 11a includes an input processing unit 21a, a frequency computing unit 22a, a threshold determining unit 23a, and a drive control unit 24a. The controller 11 b includes a drive control unit 24b.

[0044]

The input processing unit 21a is configured to receive the demand signal and other signals as an input from the outside. The input processing unit 21a is also configured to output the input demand signal to the drive control unit 24a.

[0045]

The frequency computing unit 22a is configured to determine the total frequency F that is a total of the operating frequencies of the compressors depending on the load. Here, the refrigeration cycle apparatus 300 includes a temperature sensor (not shown) that is formed of a thermistor, for example, and is configured to measure a temperature of the air-conditioned space. The frequency computing unit 22a has a function of determining the load on the basis of a difference between the temperature of the air-conditioned space, which has been measured by the temperature sensor, and a target temperature. The frequency computing unit 22a is configured to output the determined total frequency F to the threshold determining unit 23a and the drive control unit 24a.

[0046]

The threshold determining unit 23a is configured to determine, in the onecompressor operating state during the sequential drive control, whether the total frequency F input from the frequency computing unit 22a has increased to the increasing threshold A2. Then, the threshold determining unit 23a is configured to output, when the total frequency F has increased to the increasing threshold A2, an increasing signal indicating the increasing threshold A2 to the drive control unit 24a. [0047]

Further, the threshold determining unit 23a is configured to determine, in the two-compressor operating state during the sequential drive control, whether the total frequency F input from the frequency computing unit 22a has decreased to the decreasing threshold A1. Then, the threshold determining unit 23a is configured to output, when the total frequency F has decreased to the decreasing threshold A1, an decreasing signal indicating the decreasing threshold A1 to the drive control unit 24a. [0048]

The drive control unit 24a is configured to execute the multiple drive control when the demand signal is input from the input processing unit 21a. More specifically, the drive control unit 24a is configured to drive the compressor 1a and the compressor 1b at the multiple initial value Am, and to execute the multiple drive control continuously when the demand signal is input from the input processing unit 21a at startup.

[0049]

Moreover, the drive control unit 24a is configured to perform, when the demand signal is input from the input processing unit 21a during the sequential drive control, processing of switching from the sequential drive control to the multiple drive control. In other words, the drive control unit 24a has a function of determining, when the demand signal is input during the operation under the sequential drive control, whether the refrigeration cycle apparatus is in the one-compressor operating state. Then, the drive control unit 24a is configured to receive the total frequency F as an input from the frequency computing unit 22a, and to drive each of the compressor 1a and the compressor 1 b at an operating frequency that is half the input total frequency F when the drive control unit 24a determines that the refrigeration cycle apparatus is in the one-compressor operating state.

[0050]

Further, the drive control unit 24a is configured to determine the number of operating compressors 1 when the increasing signal is input from the threshold determining unit 23a, and to drive the non-operating compressor 1 and switch the refrigeration cycle apparatus to the two-compressor operating state when the refrigeration cycle apparatus is in the one-compressor operating state. The drive control unit 24a is configured to stop driving of any one of the compressors 1 and switch the refrigeration cycle apparatus to the one-compressor operating state when a decreasing signal is input from the threshold determining unit 23a during the operation under the sequential drive control.

[0051]

The controller 11a and the controller 11b may be implemented by hardware, such as a circuit device configured to achieve the above-mentioned functions, or may be implemented by software executed on a DSP or other microcomputer, or a CPU or other arithmetic unit, for example. Moreover, the storage unit 19a and the storage unit 19b may be formed of a hard disk drive (HDD) or a flash memory, for example. [0052]

Next, with reference to Fig. 1 and Fig. 2, operation of the refrigeration cycle apparatus 300 according to Embodiment 1 is described. Here, the cooling operation in the refrigeration cycle formed between the outdoor unit 100a and the indoor unit 200 is described. Consequently, the four-way valve 3a is assumed to have been switched to a passage for the cooling operation by the controller 11a.

[0053]

The high-temperature and high-pressure refrigerant that has been compressed and discharged by the compressor 1a flows into the outdoor heat exchanger 4a via the check valve 2a and the four-way valve 3a. The high-temperature and highpressure refrigerant that has flowed into the outdoor heat exchanger 4a exchanges heat with, and transfers heat to the outside air that is sent by the outdoor fan 40a, and flows out of the outdoor heat exchanger 4a. The high-pressure refrigerant that has flowed out of the outdoor heat exchanger 4a flows into the high-pressure-side passage 51a of the subcooling heat exchanger 5a, and has heat removed and cooled by the refrigerant flowing through the low-pressure-side passage 52a of the subcooling heat exchanger 5a. Then, the refrigerant that has flowed out of the highpressure-side passage 51a of the subcooling heat exchanger 5a is bifurcated into the refrigerant that flows into the bypass pipe 14a, and the refrigerant that is directed to the expansion device 7a.

[0054]

Liquid refrigerant that is directed to the expansion device 7a flows out of the outdoor unit 100a via the expansion device 7a and the liquid control valve 8a. Twophase gas-liquid refrigerant that has flowed out of the outdoor unit 100a flows into the indoor unit 200 via the liquid pipe 17a, the liquid distributor 15, and the liquid pipe 17c. At this time, when the outdoor unit 100b is also operated, the refrigerant that has flowed out of the outdoor unit 100a is merged with the refrigerant that has flowed out of the outdoor unit 100b in the liquid distributor 15, and the merged refrigerant flows into the indoor unit 200 through the liquid pipe 17c.

[0055]

The refrigerant that has flowed into the indoor unit 200 is expanded and reduced in pressure by the expansion device 12 to flow into the indoor heat exchanger 13 as two-phase gas-liquid refrigerant. The two-phase gas-liquid refrigerant that has flowed into the indoor heat exchanger 13 exchanges heat with the air in the air-conditioned space to be evaporated, flows out of the indoor heat exchanger 13 as the low-temperature and low-pressure gas refrigerant, and flows out of the indoor unit 200 through the gas pipe 18c.

[0056]

The low-temperature and low-pressure gas refrigerant that has flowed out of the indoor unit 200 flows into the outdoor unit 100a via the gas distributor 16 and the gas pipe 18a. At this time, gas refrigerant that has flowed out of the indoor unit 200 is bifurcated into the refrigerant that is directed to the outdoor unit 100a, and the refrigerant that is directed to the outdoor unit 100b in the gas distributor 16.

[0057]

The gas refrigerant that has flowed into the outdoor unit 100a is merged, via the four-way valve 3a, with the refrigerant that has passed through the bypass pipe

14a, and the merged refrigerant flows into the accumulator 10a. The refrigerant that has flowed into the accumulator 10a is separated into the liquid refrigerant and the gas refrigerant, of which the gas refrigerant flows out of the accumulator 10a. The gas refrigerant that has flowed out of the accumulator 10a is sucked by the compressor 1a to be compressed again.

[0058]

Meanwhile, as described above, of the refrigerant that has flowed out of the high-pressure-side passage 51a of the subcooling heat exchanger 5a, the refrigerant that has flowed into the bypass pipe 14a is expanded and reduced in pressure by the expansion device 6a, and flows into the low-pressure-side passage 52a of the subcooling heat exchanger 5a as low-temperature and low-pressure two-phase gasliquid refrigerant. The two-phase gas-liquid refrigerant that has flowed into the lowpressure-side passage 52a of the subcooling heat exchanger 5a is heated by the refrigerant flowing through the high-pressure-side passage 51a, and flows out of the low-pressure-side passage 52a. As described above, the refrigerant that has flowed out of the low-pressure-side passage 52a of the subcooling heat exchanger 5a is merged with the gas refrigerant that has passed through the four-way valve 3a, and the merged refrigerant flows into the accumulator 10a.

[0059]

When the outdoor unit 100a is operated at the same time as the outdoor unit 100b, the refrigeration cycle is formed also between the outdoor unit 100b and the indoor unit 200. A cooling operation in the refrigeration cycle is similar to the cooling operation in the refrigeration cycle formed between the outdoor unit 100a and the indoor unit 200.

[0060]

In the case of the heating operation, the refrigerant flows in a direction opposite to that in the cooling operation, but the controller 11a executes the multiple drive control and the sequential drive control similarly as in the cooling operation. During the heating operation, the four-way valve 3a is switched to a passage for the heating operation, which is indicated by the broken line in Fig. 1, by the controller 11a.

[0061]

Fig. 3 is a graph for showing the multiple drive control in the refrigeration cycle apparatus 300. Fig. 4 is a graph for showing the sequential drive control in the refrigeration cycle apparatus 300. Fig. 5 is a graph for showing an example of the processing of switching from the sequential drive control to the multiple drive control in the refrigeration cycle apparatus 300. Fig. 6 is a graph for showing another example of the processing of switching from the sequential drive control to the multiple drive control in the refrigeration cycle apparatus. With reference to Fig. 3 to Fig. 6, capacity control on the compressors 1 is described specifically. In Fig. 3 to Fig. 6, the vertical axes indicate a frequency F1 that is an operating frequency at which the compressor 1a is driven and a frequency F2 that is an operating frequency at which the compressor 1b is driven, and the horizontal axis indicates the total frequency F that is a total of the frequency F1 and the frequency F2.

[0062]

When the demand signal is input from the outside at startup or during operation, the refrigeration cycle apparatus 300 executes the multiple drive control in which at least two compressors 1 are operated depending on the load. Meanwhile, when no demand signal is input at startup, the refrigeration cycle apparatus 300 executes the sequential drive control in which the number of operating compressors 1 and the operating frequencies of the compressors 1 are changed depending on the load until the demand signal is input. Then, when the demand signal is input while the sequential drive control is executed, the refrigeration cycle apparatus 300 stops the sequential drive control, and starts the multiple drive control.

With reference to Fig. 3 to Fig. 6, the multiple drive control, the sequential drive control, and the processing of switching control between the multiple drive control and the sequential drive control are described below.

[0063] (Multiple Drive Control)

As shown in Fig. 3, when the demand signal is input at startup, the input processing unit 21a outputs the demand signal to the drive control unit 24a. When the demand signal is input from the input processing unit 21a at startup, the drive control unit 24a drives the compressor 1a and the compressor 1b each at the multiple initial value Am.

[0064]

At and after startup, the drive control unit 24a acquires the total frequency F corresponding to the load from the frequency computing unit 22a, and adjusts the operating frequency of each of the compressor 1 a and the compressor 1 b on the basis of the acquired total frequency F. More specifically, when the demand signal is input at startup, the drive control unit 24a transmits a drive command signal containing information on the multiple initial value Am to the drive control unit 24b of the controller 11 b, and drives the compressor 1 a at the multiple initial value Am. The drive control unit 24b drives the compressor 1b at the multiple initial value Am in accordance with the drive command signal transmitted from the drive control unit 24a. [0065]

Moreover, every time the load varies, the drive control unit 24a acquires the total frequency F from the frequency computing unit 22a, and transmits a drive command signal containing information on the acquired total frequency F to the controller 11b. At this time, the drive control unit 24a drives the compressor 1 a at the operating frequency that is half the total frequency F. The drive control unit 24b drives the compressor 1 b at the operating frequency that is half the total frequency F in accordance with the drive command signal transmitted from the drive control unit 24a.

[0066]

In other words, when the demand signal is input at startup, the refrigeration cycle apparatus 300 drives the compressor 1a and the compressor 1b at the multiple initial value Am at startup, and then equally divides the total frequency F, which is determined depending on the load, between the compressor 1a and the compressor 1b.

[0067] (Sequential Drive Control)

As shown in Fig. 4, when the total frequency F reaches the increasing threshold A2, the threshold determining unit 23a outputs the increasing signal to the drive control unit 24a. When the increasing signal is received as an input from the threshold determining unit 23a, the drive control unit 24a transmits a drive command signal containing information on the increasing threshold A2 to the drive control unit 24b, and drives the compressor 1a at an operating frequency that is half the increasing threshold A2. Then, the drive control unit 24b drives the compressor 1 b at the operating frequency that is half the increasing threshold A2 in accordance with the drive command signal output from the drive control unit 24a.

[0068]

Subsequently, unless the total frequency F falls to the decreasing threshold A1, the drive control unit 24a continues the two-compressor operating state while increasing or decreasing the operating frequency of each of the compressor 1a and the compressor 1b depending on the load.

[0069]

Moreover, when the total frequency F falls to the decreasing threshold A1, the threshold determining unit 23a outputs the decreasing signal to the drive control unit 24a. When the decreasing signal is received as an input from the threshold determining unit 23a, the drive control unit 24a outputs a stop command signal to the drive control unit 24b, and drives the compressor 1a at the decreasing threshold A1. Then, the drive control unit 24b stops driving the compressor 1b in accordance with the stop command signal output from the drive control unit 24a.

[0070] (Processing of Switching Control)

When the demand signal is input during the sequential drive control, as shown in Fig. 4 and Fig. 5, the drive control unit 24a executes the processing of switching from the sequential drive control to the multiple drive control even if the total frequency F is an operating frequency D1 that is smaller than the decreasing threshold A1, for example. In other words, when the demand signal is input at the operating frequency D1, the drive control unit 24a transmits a drive command signal containing information on the operating frequency D1 to the drive control unit 24b, and drives the compressor 1a at an operating frequency that is half the operating frequency D1. Then, the drive control unit 24b drives the compressor 1 b at the operating frequency that is half the operating frequency D1 in accordance with the drive command signal transmitted from the drive control unit 24a.

[0071]

Further, when the demand signal is input during the sequential drive control, as shown in Fig. 4 and Fig. 6, the drive control unit 24a executes the processing of switching from the sequential drive control to the multiple drive control even if the total frequency F is an operating frequency D2 that is larger than the decreasing threshold A1 and smaller than the increasing threshold A2, for example. In other words, when the demand signal is input at the operating frequency D2, the drive control unit 24a transmits a drive command signal containing information on the operating frequency D2 to the drive control unit 24b, and drives the compressor 1a at an operating frequency that is half the operating frequency D2. Then, the drive control unit 24b drives the compressor 1 b at the operating frequency that is half the operating frequency D2 in accordance with the drive command signal transmitted from the drive control unit 24a.

[0072]

In other words, when the demand signal is input in the one-compressor operating state, the refrigeration cycle apparatus 300 according to Embodiment 1 is configured to switch to the two-compressor operating state, to thereby start the multiple drive control, even if the total frequency F is an operating frequency that is smaller than the increasing threshold A2.

[0073]

Fig. 7 is a flow chart for illustrating operation of the refrigeration cycle apparatus 300. With reference to Fig. 7, compressor capacity control by the controller 11 a and the controller 11 b is described.

[0074]

First, the drive control unit 24a determines whether the demand signal is input at startup (Fig. 7: Step S101). When the demand signal is input (Fig. 7: Step S101, YES), the drive control unit 24a executes the multiple drive control. In other words, the drive control unit 24a drives two compressors 1 simultaneously at the multiple initial value Am (Fig. 7: Step S102). Then, at and after startup, the drive control unit 24a executes the multiple drive control continuously until the power is turned off (Fig. 7: Step S103).

[0075]

Meanwhile, when no demand signal is input (Fig. 7: Step S101, NO), the drive control unit 24a executes the sequential drive control (Fig. 7: Step S104).

[0076]

Incidentally, even if no demand signal is input at startup, the demand signal may be input during the operation. Consequently, the drive control unit 24a determines whether the demand signal is input also during the operation (Fig. 7: Step S105). When no demand signal is input (Fig. 7: Step S105, NO), the processing returns to Step S104, and the drive control unit 24a continues the sequential drive control until the demand signal is input.

[0077]

Meanwhile, when the demand signal is input during the operation (Fig. 7: Step S105, YES), the drive control unit 24a determines the number of operating compressors 1. In other words, the drive control unit 24a determines whether the current operating state is the one-compressor operating state or the two-compressor operating state (Fig. 7: Step S106).

[0078]

When only one compressor 1 is operated (Fig. 7: Step S106, YES), the drive control unit 24a acquires the total frequency F from the frequency computing unit 22a, and transmits the drive command signal to the drive control unit 24b. Then, the drive control unit 24a drives the compressor 1a at the operating frequency that is half the total frequency F, and the drive control unit 24b drives the compressor 1 b at the operating frequency that is half the total frequency F (Fig. 7: Step S107).

Subsequently, the controller 11a executes the multiple drive control continuously until the power is turned off (Fig. 7: Step S103). Meanwhile, when two compressors 1 are operated (Fig. 7: Step S106, NO), the drive control unit 24a returns to Step S104. [0079]

As described above, in the refrigeration cycle apparatus 300, when the demand signal is input, the controller 11a executes the multiple drive control in which at least two outdoor units 100 are operated, with the result that the one-compressor operating state can be reduced. Consequently, one outdoor unit 100 can be prevented from being overcharged with the refrigerant, and stoppage of the outdoor unit 100 can be prevented during operation for a long time.

[0080]

In other words, the refrigerant accumulated in the accumulator 10a of the outdoor unit 100a is sucked by the compressor 1a to be compressed and discharged. Moreover, the refrigerant accumulated in the accumulator 10b of the outdoor unit 100b is also sucked by the compressor 1 b to be compressed and discharged. In other words, in the refrigeration cycle apparatus 300, the refrigerant is not excessively and unevenly distributed to any of the outdoor unit 100a and the outdoor unit 100b, with the result that a disadvantage of overcharging one outdoor unit 100 with the refrigerant and stopping the outdoor unit 100 can be avoided. Consequently, in the refrigeration cycle apparatus 300, the temperature and the humidity can be controlled accurately.

[0081]

In the above description, there has been exemplified the case in which the compressor 1a is driven in the one-compressor operating state. However, the present invention is not limited to this example, and only the compressor 1b may be operated in the one-compressor operating state. Here, the compressor 1a and the compressor 1 b may have the same capacity or mutually different capacities. When the compressor 1a and the compressor 1b have the different capacities, the controller 11a preferably selects the one with the larger capacity as the compressor 1 to be driven in the one-compressor operating state.

[0082]

Moreover, the controller 11a may be configured not to perform the sequential drive control, but to execute only the multiple drive control. In addition, in the above description, there has been exemplified the case in which the controller 11a transmits the drive command signal containing the information on the total frequency F to the controller 11b, but the present invention is not limited to this example. For example, the controller 11a may transmit a drive command signal containing information on the operating frequency that is half the total frequency F to the controller 11b, and the controller 11b may operate the compressor 1b at the operating frequency transmitted by the controller 11a.

[0083]

Embodiment 2

Fig. 8 is an overall configuration diagram of a refrigeration cycle apparatus according to Embodiment 2 of the present invention. Fig. 9 is a graph for showing multiple drive control in the refrigeration cycle apparatus of Fig. 8. Fig. 10 is a graph for showing sequential drive control in the refrigeration cycle apparatus of Fig. 8.

Fig. 11 is a graph for showing an example of processing of switching from the sequential drive control to the multiple drive control in the refrigeration cycle apparatus of Fig. 8. With reference to Fig. 8 to Fig. 11, a configuration and operation of the refrigeration cycle apparatus according to Embodiment 2 are described. Constituent members similar to those of the refrigeration cycle apparatus 300 according to Embodiment 1 described above are denoted by the same reference signs, and a description of the constituent members is omitted.

[0084]

In Fig. 9 to Fig. 11, the vertical axes indicate a frequency F1 that is an operating frequency at which a compressor 1a is driven, a frequency F2 that is an operating frequency at which a compressor 1 b is driven, and a frequency F3 that is an operating frequency at which a compressor 1c is driven, and the horizontal axis indicates a total frequency F that is a total of the frequency F1, the frequency F2, the frequency F2. Further, hereinafter, the compressor 1 a to the compressor 1 c are also collectively referred to as compressors 1, or any one of the compressor 1a to the compressor 1c is also simply referred to as compressor 1. Moreover, a state in which one compressor 1 is operated is referred to as one-compressor operating state, a state in which two compressors 1 are operated is referred to as twocompressor operating state, and a state in which three compressors 1 are operated is referred to as three-compressor operating state. In addition, the outdoor units 100a to 100c are also collectively referred to as outdoor units 100, or any one of the outdoor units 100a to 100c is also simply referred to as outdoor unit 100.

[0085]

As illustrated in Fig. 8, a refrigeration cycle apparatus 400 according to Embodiment 2 includes an outdoor unit 100a, an outdoor unit 100b, an outdoor unit 100c, and an indoor unit 200. In Fig. 8, the compressor 1a and a controller 11a are illustrated as constituent members of the outdoor unit 100a, and the compressor 1b and a controller 11b are illustrated as constituent members of the outdoor unit 100b. Moreover, the outdoor unit 100c is configured similarly to the outdoor unit 100b of Fig. 1, but in Fig. 8, the compressor 1c and a controller 11c, which is configured similarly to the controller 11b, are illustrated as constituent members of the outdoor unit 100c. Moreover, the refrigeration cycle apparatus 400 includes a liquid distributor 150 connecting liquid pipes as refrigerant pipes, and a gas distributor 160 connecting gas pipes as refrigerant pipes. In other words, in the refrigeration cycle apparatus 400, each of the three outdoor units is connected to the indoor unit through the refrigerant pipes to form three refrigeration cycles.

[0086]

Moreover, in Embodiment 2, the three compressors 1 have a relationship that the compressor 1a has the largest capacity, the compressor 1b has the second largest capacity, and the compressor 1c has the smallest capacity (compressor 1a > compressor 1b > compressor 1c). Further, the three compressors 1 each have an address. Consequently, the controller 11a can identify the compressor 1a, the compressor 1b, and the compressor 1c, and drive the compressors 1 in decreasing order of the capacities.

[0087]

Moreover, the storage unit 19a stores a decreasing threshold A3 that is a criterion for switching from the three-compressor operating state to the twocompressor operating state, and an increasing threshold A4 that is a criterion for switching from the two-compressor operating state to the three-compressor operating state. The decreasing threshold A3 and the increasing threshold A4 have a relationship of 'A3 < A4. Here, the decreasing threshold A3 (Hz) and the increasing threshold A4 (Hz) can be set, similarly to the multiple initial value Am, the sequential initial value As, the decreasing threshold A1, and the increasing threshold A2, from a remote controller (not shown), for example, depending on an on-site usage environment.

[0088]

With reference to Fig. 9 to Fig. 11, the multiple drive control, the sequential drive control, and the processing of switching control between the multiple drive control and the sequential drive control are described below.

[0089] (Multiple Drive Control)

As shown in Fig. 9, when a demand signal is input at startup, the controller 11a drives the compressor 1a, the compressor 1b, and the compressor 1c each at the sequential initial value As. Hereinafter, the compressor 1a, the compressor 1b, and the compressor 1c are also referred to as three compressors 1, any two of the compressor 1a, the compressor 1b, and the compressor 1c are also referred to as two compressors 1, and any one of the compressor 1a, the compressor 1b, and the compressor 1c is also referred to as one compressor 1. Moreover, at and after startup, the controller 11a adjusts the number of operating compressors of the three compressors 1 and the operating frequency of each of the three compressors 1 depending on the load.

[0090]

More specifically, when the demand signal is input at startup, the controller 11a transmits a drive command signal containing information on the multiple initial value Am to the controller 11b and the controller 11c, and drives the compressor 1a at the multiple initial value Am. Moreover, everytime the load varies, the controller 11a determines the total frequency F corresponding to the load, and transmits a drive command signal containing information on the determined total frequency F to the controller 11 b and the controller 11c. At this time, the controller 11 a drives the compressor 1a at an operating frequency that is half the total frequency F.

[0091]

The controller 11b drives the compressor 1b at the multiple initial value Am or the operating frequency that is half the total frequency F in accordance with the drive command signal transmitted from the controller 11a. The controller 11c drives the compressor 1b at the multiple initial value Am or the operating frequency that is half the total frequency F in accordance with the drive command signal transmitted from the controller 11a.

[0092]

When the total frequency F has increased to the increasing threshold A4, the controller 11a transmits a drive command signal containing information on the increasing threshold A4 to the controller 11b and the controller 11c, and drives the compressor 1a at an operating frequency that is half the increasing threshold A4.

The controller 11 b drives the compressor 1 b at the operating frequency that is half the increasing threshold A4 in accordance with the drive command signal transmitted from the controller 11 a. The controller 11 c drives the compressor 1 c at the operating frequency that is half the increasing threshold A4 in accordance with the drive command signal transmitted from the controller 11a.

[0093]

Subsequently, unless the total frequency F falls to the decreasing threshold A3, the controller 11a continues the three-compressor operating state while increasing or decreasing the operating frequency of each of the three compressors 1 depending on the load. Meanwhile, when the total frequency F falls to the decreasing threshold A3 in the three-compressor operating state, the controller 11a transmits a drive command signal containing information on the decreasing threshold A3 to the controller 11b, and transmits a stop command signal to the controller 11c. At this time, the controller 11a drives the compressor 1a at an operating frequency that is half the decreasing threshold A3. Moreover, the controller 11 b drives the compressor 1 b at the operating frequency that is half the decreasing threshold A3 in accordance with the drive command signal transmitted from the controller 11a. The controller 11c stops driving the compressor 1c in accordance with the stop command signal output from the drive control unit 24a.

[0094]

In other words, when the demand signal is input at startup, the refrigeration cycle apparatus 400 drives two compressors 1 each at the multiple initial value Am at startup. Moreover, when the total frequency F has increased to the increasing threshold A4 in the two-compressor operating state, the refrigeration cycle apparatus 400 switches to the three-compressor operating state. Meanwhile, when the total frequency F falls to the decreasing threshold A3 in the three-compressor operating state, the refrigeration cycle apparatus 400 switches to the two-compressor operating state. In the two-compressor operating state, the total frequency F that is determined depending on the load, is evenly divided between the two compressors 1, and in the three-compressor operating state, the total frequency F that is determined depending on the load, is evenly divided among three compressors 1.

[0095] (Sequential Drive Control)

As shown in Fig. 10, when no demand signal is input at startup, the controller 11a drives one compressor 1 at the sequential initial value As. When the total frequency F reaches the increasing threshold A2, the controller 11a transmits a drive command signal containing information on the increasing threshold A2 to the controller 11b, and drives the compressor 1a at an operating frequency that is half the increasing threshold A2. The controller 11 b drives the compressor 1 b at the operating frequency that is half the increasing threshold A2 in accordance with the drive command signal transmitted from the controller 11a.

[0096]

Subsequently, as long as the total frequency F is in a range that is larger than the decreasing threshold A1 and is smaller than the increasing threshold A4, the controller 11 a and the controller 11 b continue the two-compressor operating state while increasing or decreasing the operating frequency of each of two compressors 1 depending on the load. Meanwhile, when the total frequency F falls to the decreasing threshold A1 in the two-compressor operating state, the controller 11a transmits a drive stop signal to the controller 11b, and drives the compressor 1a at the decreasing threshold A1. Then, the controller 11 b stops the compressor 1 b in accordance with the drive stop signal transmitted from the controller 11a.

[0097]

Moreover, as shown in Fig. 10, the controller 11a executes processing of switching between the two-compressor operating state and the three-compressor operating state as in the case of the multiple drive control.

[0098] (Processing of Switching Control)

When the demand signal is input during the sequential drive control, the controller 11a executes the processing of switching from the sequential drive control to the multiple drive control even if the total frequency F is smaller than the increasing threshold A2. In other words, as shown in Fig. 11, even if the total frequency F is an operating frequency D3 that is smaller than the increasing threshold A2, the controller 11a executes the processing of switching from the sequential drive control to the multiple drive control when the demand signal is input. More specifically, when the demand signal is input at the operating frequency D3, for example, the controller 11a transmits a drive command signal containing information on the operating frequency D3 to the controller 11b, and drives the compressor 1a at an operating frequency that is half the operating frequency D3. Then, the controller 11 b drives the compressor 1 b at the operating frequency that is half the operating frequency D3 in accordance with the drive command signal transmitted from the controller 11a.

[0099]

As described above, in the refrigeration cycle apparatus 400 of Embodiment 2, when the demand signal is input, the controller 11a executes the multiple drive control in which at least two outdoor units 100 are driven depending on the load, and hence the one-compressor operating state can be reduced. Consequently, one outdoor unit 100 can be prevented from being overcharged with the refrigerant, and stoppage of the outdoor unit 100 can be prevented during operation for a long time. Consequently, in the refrigeration cycle apparatus 400, a temperature and a humidity can be controlled accurately.

[0100]

Moreover, when three compressors 1 are driven at the multiple initial value Am at startup, there is a possibility of excess capacity, but with the refrigeration cycle apparatus 400, the number of compressors 1 to be driven simultaneously at the multiple initial value Am is set to two, with the result that the situation of excess capacity can be avoided. The three compressors 1 may have the same capacity, or only any two of the three compressors 1 may have the same capacity.

[0101]

Embodiment 3

Fig. 12 is an overall configuration diagram of a refrigeration cycle apparatus according to Embodiment 3 of the present invention. With reference to Fig. 12, an overall configuration of the refrigeration cycle apparatus according to Embodiment 3 is described. Constituent members similar to those of the refrigeration cycle apparatus 300 according to Embodiment 1 described above are denoted by the same reference signs, and a description of the constituent members is omitted. In other words, differences from Embodiment 1 are mainly described.

[0102]

In the refrigeration cycle apparatus 300 of Embodiment 1, as described above, the one-compressor operating state can be reduced, with the result that the one outdoor unit 100 can be prevented from being overcharged with the refrigerant, and abnormal stoppage of the outdoor unit 100 can be prevented. However, there is a possibility of the excess capacity, and of an increased frequency of thermo-off states in the two-compressor operating state.

To address these problems, a refrigeration cycle apparatus 500 according to

Embodiment 3 adopts a configuration of reducing the increase in frequency of thermo-off states.

[0103]

As illustrated in Fig. 12, the refrigeration cycle apparatus 500 includes an outdoor unit 500a, an outdoor unit 100b, and an indoor unit 200. The outdoor unit 500a includes a controller 511 a, and the controller 511 a includes, in addition to the input processing unit 21a, the frequency computing unit 22a, and the threshold determining unit 23a, a drive control unit 524a and an airflow control unit 525a. Moreover, the storage unit 19a stores a reduction amount table that is table information in which the total frequency F and a reduction amount of an air sending amount of the indoor fan 13c are associated with each other.

[0104]

The drive control unit 524a is configured to function similarly to the drive control unit 24a in Embodiment 1. Moreover, the drive control unit 524a is configured to output, when the total frequency F input from the frequency computing unit 22a falls below the decreasing threshold A1, an airflow reduction command containing the total frequency F to the airflow control unit 525a. Then, the airflow control unit 525a is configured to reduce, when the total frequency F that is less than the decreasing threshold A1 is input from the drive control unit 524a, the air sending amount of the indoor fan 13c by an amount corresponding to the total frequency F.

[0105]

In other words, the airflow control unit 525a is configured to reduce, when the total frequency F determined by the frequency computing unit 22a falls below the decreasing threshold A1, which is set to a value smaller than an operating frequency providable by one compressor 1, during multiple drive control by the drive control unit 524a, the air sending amount of the indoor fan 13c by the amount corresponding to the total frequency F.

[0106]

In Embodiment 3, the airflow control unit 525a is configured to determine the reduction amount of the air sending amount of the indoor fan 13c that corresponds to the total frequency F determined by the frequency computing unit 22a according to the reduction amount table in the storage unit 19a, and to reduce the air sending amount of the indoor fan 13c by the determined reduction amount.

[0107]

More specifically, the indoor unit 200 includes a fan inverter device (not shown) configured to control a rotational frequency of the indoor fan 13c, for example. The airflow control unit 525a reads reduction airflow information indicating the reduction amount of the air sending amount of the indoor fan 13c from the reduction amount table, and transmits a drive control signal containing the read reduction airflow information to the fan inverter device. The reduction amount table in the storage unit 19a stores, as the reduction airflow information, the reduction amount of the rotational frequency of the indoor fan 13c, for example. The fan inverter device reduces the rotational frequency of the indoor fan 13c in accordance with the drive control signal transmitted from the airflow control unit 525a.

[0108]

In the above description, there has been exemplified the case in which, when the total frequency F input from the frequency computing unit 22a falls below the decreasing threshold A1, the drive control unit 524a outputs the total frequency F to the airflow control unit 525a. However, the present invention is not limited to this example, and the airflow control unit 525a may directly acquire the total frequency F from the frequency computing unit 22a, and determine whether the total frequency F has fallen below the decreasing threshold A1.

[0109]

Fig. 13 is a flow chart for illustrating operation of the refrigeration cycle apparatus 500. With reference to Fig. 13, compressor capacity control by the controller 511 a and the controller 11 b and airflow control by the airflow control unit 525a are described.

[0110]

Steps S102 to S107 are similar to details of the operation described with reference to Fig. 7 in Embodiment 1, and hence a description of the steps is omitted.

[0111]

The drive control unit 524a determines, during the two-compressor operating state, whether the total frequency F input from the frequency computing unit 22a has fallen below the decreasing threshold A1 (Fig. 13: Step S201). When the total frequency F is the decreasing threshold A1 or more (Fig. 13: Step S201, NO), the drive control unit 524a continues the control of driving two compressors 1 at operating frequencies corresponding to the load until the total frequency F falls below the decreasing threshold A1.

[0112]

Meanwhile, when the total frequency F falls below the decreasing threshold A1 (Fig. 13: Step S201, YES), the drive control unit 524a determines the excess capacity. Consequently, the drive control unit 524a outputs, when the total frequency F has fallen below the decreasing threshold A1, the airflow reduction command containing the total frequency F to the airflow control unit 525a while continuing the two-compressor operating state. The airflow control unit 525a, on the basis of the total frequency F that is less than the decreasing threshold A1 and input from the drive control unit 524a according to the reduction amount table, determines the reduction amount of the air sending amount of the indoor fan 13c (Fig. 13: Step S202), and reduces the air sending amount of the indoor fan 13c in accordance with the determined reduction amount (Fig. 13: Step S203).

[0113]

Subsequently, the controller 511a repeatedly executes a series of processing of Steps S201 to S203 to execute the multiple drive control and the airflow control of the indoor fan 13c. Even if the air sending amount of the indoor fan 13c falls to the lowest flow rate, the controller 511a continues the two-compressor operating state. [0114]

In the above description, the decreasing threshold A1 has been adopted as the criterion used when the controller 511 a performs the airflow control of the indoor fan 13c. However, the present invention is not limited to this configuration, and as the criterion for starting the airflow control of the indoor fan 13c, a threshold that is different from the decreasing threshold A1 may be set separately on the basis of on an operating capacity of each of the compressors 1, for example.

[0115]

The refrigeration cycle apparatus 500 adopts the above-mentioned control specification such that the disadvantage of abnormal stoppage of the outdoor unit 100 during the capacity control on the compressors 1 can be prevented, and the frequency of thermo-off states due to the excess capacity can be reduced, with the result that the control on a temperature and a humidity can be improved.

[0116]

Each of Embodiments described above is a specific exemplary example of the refrigeration cycle apparatus, and a technical scope of the present invention is not limited to these modes. For example, in Fig. 1, Fig. 8, and Fig. 12, there has been exemplified the case where each of the refrigeration cycle apparatus 300, 400, and 500 is an air-conditioning apparatus. However, the present invention is not limited to this example, and each of the refrigeration cycle apparatus 300, 400, and 500 functions as described above to achieve similar effects also when each of the refrigeration cycle apparatus 300, 400, and 500 is a heat pump type water heater, a floor heating system, or a refrigerator, for example.

[0117]

Moreover, when the input of the demand signal stops during the multiple drive control, the controller 11a and the controller 511a may perform the processing of switching control from the multiple drive control to the sequential drive control.

[0118]

In addition, the refrigeration cycle apparatus 300 may include, instead of the controller 11a and the controller 11b, one controller configured to similarly function as the controller 11a and the controller 11b. Similarly, the refrigeration cycle apparatus 400 may include one controller configured to similarly function as the controller 11a, the controller 11b, and the controller 11c, and the refrigeration cycle apparatus 500 may include one controller configured to similarly function as the controller 511a and the controller 11b.

[0119]

Further, in each of Embodiments described above, there has been exemplified the case where the number of outdoor units 100 included in the refrigeration cycle apparatus 300, 400, or 500 is two or three. However, the present invention is not limited to this example, and the refrigeration cycle apparatus 300, 400, or 500 may include four or more outdoor units 100. Then, when the demand signal is input at startup and when the multiple drive control is started, the refrigeration cycle apparatus 300, 400, or 500 including the four or more outdoor units 100 may be configured to operate two outdoor units 100. With this configuration, the excess capacity can be prevented at startup. When the demand signal is input at startup, the refrigeration cycle apparatus 300, 400, or 500 including the four or more outdoor units 100 may be configured to operate the number of outdoor units 100 that is smaller than the total number of outdoor units and is three or more to start the multiple drive control.

[0120]

Moreover, in each of Embodiments described above, there has been exemplified the case where, when the demand signal is input, the controller 11a executes the processing of switching from the sequential drive control to the multiple drive control, but the present invention is not limited to this example. For example, the refrigeration cycle apparatus 300, 400, or 500 may include an operation unit configured to receive a switching operation for issuing an instruction to switch from the sequential drive control to the multiple drive control, and when a user performs the switching operation via the operation unit, the controller 11a may execute the processing of switching from the sequential drive control to the multiple drive control. [0121]

In addition, in each of Embodiments described above, there has been described the configuration in which the total frequency F is equally divided among a plurality of compressors 1. However, the present invention is not limited to this example, and for example, the total frequency F may be allocated to the compressors 1 in a proportion corresponding to the capacities of the plurality of compressors 1.

Reference Signs List [0122]

1, 1a, 1b, 1c compressor 2a, 2b checkvalve 3a, 3b four-way valve 4a, 4b outdoor heat exchanger 5a subcooling heat exchanger5b subcooling heat exchanger 6a, 6b, 7a, 7b, 12 expansion device 8a, 8b liquid control valve9a, 9b gas control valve 10a, 10b accumulator 11a, 11b, 11c, 511a controller 13 indoor heat exchanger 13c indoor fan 14a, 14b bypass pipe 15,150 liquid distributor 16,160 gas distributor 17a, 17b, 17c liquid pipe 18a, 18b, 18c gas pipe 19a, 19b storage unit 21a input processing unit

22a frequency computing unit 23a threshold determining unit 24a,

24b, 524a drive control unit 40a, 40b outdoor fan 51a, 51b high-pressureside passage 52a, 52b low-pressure-side passage 100, 100a, 100b, 100c, 500a outdoor unit 200 indoor unit 300, 400, 500 refrigeration cycle apparatus 525a airflow control unitAm multiple initial valueAs sequential initial value

Claims (6)

1. CLAIMS [Claim 1]

   A refrigeration cycle apparatus, in which a plurality of outdoor units are connected to an indoor unit through a refrigerant pipe to form a plurality of refrigeration cycles, the plurality of outdoor units each including a compressor, an outdoor heat exchanger, and an expansion device, the indoor unit including an indoor heat exchanger, the refrigeration cycle apparatus comprising a controller configured to control operations of the plurality of outdoor units, the controller including a drive control unit configured to execute, when a demand signal is input, multiple drive control in which at least two of the plurality of outdoor units are operated depending on a load.
2. [Claim 2]

   The refrigeration cycle apparatus of claim 1, wherein the drive control unit is configured to operate two of the plurality of outdoor units when the demand signal is input at startup and the multiple drive control is started.
3. [Claim 3]

   The refrigeration cycle apparatus of claim 1 or 2, wherein the drive control unit is configured to start the multiple drive control when the demand signal is input in a case where one of the plurality of outdoor units is operated.
4. [Claim 4]

   The refrigeration cycle apparatus of any one of claims 1 to 3, wherein the indoor unit includes an indoor fan provided next to the indoor heat exchanger and is configured to send air to the indoor heat exchanger, and wherein the controller includes a frequency computing unit configured to determine, depending on the load, a total frequency that is a total of operating frequencies of the compressors, and an airflow control unit configured to reduce, when the total frequency determined by the frequency computing unit falls below a threshold that is set to a value smaller than an operating frequency providable by one of the compressors during the multiple drive control, an air sending amount of the indoor fan by an amount corresponding to the total frequency.
5. [Claim 5]

   The refrigeration cycle apparatus of claim 4, wherein the threshold is set so that power consumption in a case where one of the compressors is driven at the threshold is equal to power consumption in a case where two of the compressors are

   10 each driven at half the threshold.
6. [Claim 6]

   The refrigeration cycle apparatus of claim 4 or 5, further comprising a storage unit storing table information in which the total frequency is associated with a

   15 reduction amount of the air sending amount of the indoor fan, wherein the airflow control unit is configured to determine, when the air sending amount of the indoor fan is to be reduced, the reduction amount of the air sending amount of the indoor fan corresponding to the total frequency determined by the frequency computing unit according to the table information.