GB2560455A

GB2560455A - Air-conditioning device

Info

Publication number: GB2560455A
Application number: GB1806958.3A
Authority: GB
Inventors: Baba Yohei
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2016-01-07
Filing date: 2016-01-07
Publication date: 2018-09-12
Anticipated expiration: 2036-01-07
Also published as: WO2017119105A1; GB201806958D0; GB2560455B; JPWO2017119105A1

Abstract

An air-conditioning device whereby it is possible to take measures against leakage of a refrigerant without the need for an additional component. This air-conditioning device is equipped with: an outdoor unit which has an outdoor heat exchanger and a compressor; a relay which has a relay throttle device, a first opening-closing valve, and a second opening-closing valve; and indoor units which each have an indoor heat exchanger and perform cooling and heating operations. The air-conditioning device configures a refrigerant circuit which circulates a refrigerant therethrough. During a heating operation of the indoor units, the first opening-closing valve and the relay throttle device are brought into an open position, thereby circulating the refrigerant. During a cooling operation of the indoor units, the second opening-closing valve and the relay throttle device are brought into an open position, thereby circulating the refrigerant. When the refrigerant is leaking, the first opening-closing valve, the second opening-closing valve, and the relay throttle device are brought into a closed state, thereby sealing the refrigerant in the refrigerant circuit which is configured from the first opening-closing valve, the second opening-closing valve, the compressor, the outdoor heat exchanger, and the relay throttle device within the refrigerant circuit.

Description

(54) Title of the Invention: Air-conditioning device Abstract Title: Air-conditioning device (57) An air-conditioning device whereby it is possible to take measures against leakage of a refrigerant without the need for an additional component. This air-conditioning device is equipped with: an outdoor unit which has an outdoor heat exchanger and a compressor; a relay which has a relay throttle device, a first opening-closing valve, and a second opening-closing valve; and indoor units which each have an indoor heat exchanger and perform cooling and heating operations. The air-conditioning device configures a refrigerant circuit which circulates a refrigerant therethrough. During a heating operation of the indoor units, the first opening-closing valve and the relay throttle device are brought into an open position, thereby circulating the refrigerant. During a cooling operation of the indoor units, the second opening-closing valve and the relay throttle device are brought into an open position, thereby circulating the refrigerant. When the refrigerant is leaking, the first opening-closing valve, the second opening-closing valve, and the relay throttle device are brought into a closed state, thereby sealing the refrigerant in the refrigerant circuit which is configured from the first opening-closing valve, the second openingclosing valve, the compressor, the outdoor heat exchanger, and the relay throttle device within the refrigerant circuit.

203

1/6

FIG. 1

2/6

FIG. 2

203 55b

3/6

FIG. 3

100

4/6

FIG. 4

* OPERATION FREQUENCY Fa η OF COMPRESSOR 1

J VOLUME AKa OF OUTDOOR * HEAT EXCHANGER 2

LEV6a OF INDOOR THROTTLE DEVICE 6a

LEV6b OF INDOOR THROTTLE DEVICE 6b

5/6

FIG. 5

END

6/6

FIG. 6

S17

END

DESCRIPTION

Title of Invention

AIR-CONDITIONING APPARATUS

Technical Field [0001]

The present invention relates to an air-conditioning apparatus, and particularly to measures against refrigerant leakage.

Background Art [0002]

In an air-conditioning apparatus, refrigerant that conveys heat flows through pipes provided between an outdoor side unit and an indoor side unit, thereby generating a conditioned air. If a crack, for example, is generated in a pipe through which refrigerant flows, refrigerant may leak, and widespread refrigerant may influence the human body.

[0003]

The following method has been proposed as measures not to allow refrigerant to flow out of a refrigerant circuit in a case of refrigerant leakage: if refrigerant leakage is detected by an installed detecting device, refrigerant is collected by a heat source side unit, and an opening and closing valve installed in a connection pipe that connects the outdoor side unit and the indoor side unit to each other is closed.

[0004]

For example, Patent Literature 1 discloses an air-conditioning apparatus including first and second opening and closing valves in a refrigerant pipe that connects an indoor unit and an outdoor unit to each other. The first and second opening and closing valves provided in the outdoor unit are normally open, and are closed if a detecting device in the indoor unit or the outdoor unit detects refrigerant leakage, so that, in a case of refrigerant leakage, refrigerant is charged in the outdoor unit and is not allowed to flow out of a refrigerant circuit of the air-conditioning apparatus.

Citation List

Patent Literature [0005]

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2015-105808 Summary of Invention Technical Problem [0006]

However, in a case in which opening and closing valves as measures against refrigerant leakage, such as the first and second opening and closing valves in Patent Literature 1, are not attached to units, it is necessary to additionally purchase and install them. Accordingly, it inevitably takes time and effort to mount them and increases the cost, although they are used only in a case of refrigerant leakage.

[0007]

In addition, installation of opening and closing valves as measures against refrigerant leakage increases the number of components of the whole system of the air-conditioning apparatus, increasing the possibility for malfunction.

[0008]

The present invention has been made to solve the above problems, and an object of the present invention is to provide an air-conditioning apparatus that enables taking measures against refrigerant leakage without additional components.

Solution to Problem [0009]

An air-conditioning apparatus according to an embodiment of the present invention includes an outdoor unit including an outdoor heat exchanger and a compressor; a relay device including a relay-device expansion device, a first opening and closing valve, and a second opening and closing valve; and an indoor unit including an indoor heat exchanger and configured to perform a cooling operation and a heating operation. The outdoor heat exchanger, the compressor, the relay-device expansion device, the first opening and closing valve, the second opening and closing valve, and the indoor heat exchanger form a refrigerant circuit in which refrigerant is circulated. While the indoor unit is performing the heating operation, the first opening and closing valve and the relay-device expansion device are in an open state, and the refrigerant is circulated in the outdoor heat exchanger, the compressor, the first opening and closing valve, the indoor heat exchanger, and the relay-device expansion device in this order. While the indoor unit is performing the cooling operation, the second opening and closing valve and the relay-device expansion device are in an open state, and the refrigerant is circulated in the compressor, the outdoor heat exchanger, the relay-device expansion device, the indoor heat exchanger, and the second opening and closing valve in this order. In a case of refrigerant leakage, the first opening and closing valve, the second opening and closing valve, and the relay-device expansion device are in a closed state, and the refrigerant is charged in a refrigerant circuit included in the refrigerant circuit and formed of the first opening and closing valve, the second opening and closing valve, the compressor, the outdoor heat exchanger, and the relay-device expansion device. Advantageous Effects of Invention [0010]

According to the air-conditioning apparatus according to an embodiment of the present invention, by setting the relay-device expansion device and the opening and closing valves to a closed state in this order, the relay-device expansion device controlling the flow of refrigerant between the outdoor unit and each indoor unit, the refrigerant is charged between the outdoor unit and the relay device. Thus, refrigerant leakage into an indoor space can be prevented.

Brief Description of Drawings [0011] [Fig. 1] Fig. 1 illustrates a configuration of an air-conditioning apparatus according to an embodiment.

[Fig. 2] Fig. 2 illustrates the flow of refrigerant in a refrigerant circuit during a cooling only operation.

[Fig. 3] Fig. 3 illustrates the flow of refrigerant in a refrigerant circuit during a heating only operation.

[Fig. 4] Fig. 4 illustrates a relationship between control-related devices in the air-conditioning apparatus illustrated in Fig. 1.

[Fig. 5] Fig. 5 is a flowchart of a process for determining an opening degree of an indoor expansion device of an indoor unit.

[Fig. 6] Fig. 6 is a flowchart of a process performed by an outdoor side control device in a case of refrigerant leakage.

Description of Embodiments [0012]

Embodiment.

An air-conditioning apparatus according to the embodiment includes a plurality of indoor units that perform a cooling operation and a heating operation and performs a cooling only operation, a heating only operation, and a cooling and heating mixed operation. Fig. 1 illustrates a configuration of an air-conditioning apparatus 100 according to the embodiment. As illustrated in Fig. 1, the air-conditioning apparatus 100 includes an outdoor unit 51, a plurality of indoor units 52a and 52b, and a relay device 53 between the outdoor unit 51 and each of the indoor units 52a and 52b.

The outdoor unit 51 and the relay device 53 are connected to each other via a first liquid pipe 104 and a first gas pipe 103 through which refrigerant flows. The relay device 53 and the indoor units 52a and 52b are connected to one another via second liquid pipes 105a and 105b and second gas pipes 106a and 106b. In the airconditioning apparatus 100, for example, each of the indoor units 52a and 52b can independently perform a cooling operation or a heating operation. In the following description, an operation mode in which a cooling operation and a heating operation are mixed will be referred to as a cooling and heating mixed operation mode.

[0013] [Outdoor Unit 51]

The outdoor unit 51 includes a compressor 1, a four-way valve 3, an outdoor heat exchanger 2, an accumulator 4, and a refrigerant flow control unit 54. The compressor 1 suctions and compresses refrigerant and discharges the compressed refrigerant. As the compressor 1, for example, it is possible to use an inverter circuit or another circuit that can change the amount of refrigerant to be discharged per unit time by controlling a capacity. A first pressure sensor 31 that detects pressure is provided on the discharge side of the compressor 1, and a second pressure sensor 32 that detects pressure is provided on the suction side of the compressor 1.

Pressures Pd and Ps detected by the first pressure sensor 31 and the second pressure sensor 32, respectively, are sent to an outdoor side control device 201.

The outdoor side control device 201 serves as a controller that generally controls the entire air-conditioning apparatus.

[0014]

The outdoor heat exchanger 2 allows refrigerant to flow therethrough and allows heat exchange between the refrigerant and an outdoor air. The outdoor heat exchanger 2 serves as an evaporator to evaporate and vaporize refrigerant during a heating operation. In addition, the outdoor heat exchanger 2 serves as a condenser to condense and liquefy refrigerant during a cooling operation. The four-way valve 3 is a valve for switching the flow of refrigerant, and the switching changes operations among a cooling operation, a heating operation, and the like. The accumulator 4 accumulates an extra liquid refrigerant. The refrigerant flow control unit 54 allows the refrigerant to flow only in one direction.

[0015] [Refrigerant Flow Control Unit 54]

The refrigerant flow control unit 54 includes connection pipes 130, 131, 132, and 133 that are connected at connection portions a, b, c, and d, and check valves 7a, 7b, 7c, and 7d that allow the refrigerant to flow in one direction. The refrigerant flow control unit 54 is one of components of the outdoor unit 51. The connection pipe 130 connects the connection portion c and the connection portion a to each other, the connection pipe 131 connects the connection portion d and the connection portion b to each other, the connection pipe 132 connects the connection portion c and the connection portion d to each other, and the connection pipe 133 connects the connection portion a and the connection portion b to each other. The first gas pipe 103 to be connected to the relay device 53 is connected to a high-pressure pipe 102 to be connected to the compressor 1 via the connection pipe 132, and a low-pressure pipe 101 to be connected to the compressor 1 is connected to the first liquid pipe 104 to be connected to the relay device 53 via the connection pipe 133.

[0016]

The check valve 7a is provided in the connection pipe 132 and allows the refrigerant to flow in a direction from the connection portion c to the connection portion d. The check valve 7b is provided in the connection pipe 133 and allows the refrigerant to flow in a direction from the connection portion a to the connection portion b. The check valve 7c is provided in the connection pipe 131 and allows the refrigerant to flow in a direction from the connection portion d to the connection portion b. The check valve 7d is provided in the connection pipe 130 and allows the refrigerant to flow in a direction from the connection portion c to the connection portion a.

[0017] [Indoor Units 52a and 52b]

The indoor units 52a and 52b include indoor heat exchangers 5a and 5b and indoor expansion devices 6a and 6b. The indoor heat exchangers 5a and 5b allow refrigerant that has passed through the relay device 53 to flow therethrough and allow heat exchange between the refrigerant and an air that is to be air-conditioned. The indoor heat exchangers 5a and 5b serve as condensers to condense and liquefy refrigerant during a heating operation. The second liquid pipes 105a and 105b connected to the indoor expansion devices 6a and 6b, respectively, are connected to each other at an indoor trident portion 55a. In addition, the indoor heat exchangers 5a and 5b serve as evaporators to evaporate and vaporize refrigerant during a cooling operation. The indoor expansion devices 6a and 6b serve as pressure reducing valves and expansion valves to reduce the pressure of refrigerant and expand the refrigerant. Each of the indoor expansion devices 6a and 6b may be any device by which the pressure of refrigerant can be controlled in accordance with an air conditioning load and may be, for example, a flow rate control unit such as an electronic expansion valve. In the indoor units 52a and 52b, first temperature sensors 33a and 33b, second temperature sensors 34a and 34b, and leakage detecting devices 41a and 41 b are provided. The first temperature sensors 33a and 33b and the second temperature sensors 34a and 34b detect the temperature of refrigerant to flow into or out of the indoor heat exchangers 5a and 5b. The leakage detecting devices 41a and 41b measure the density of refrigerant and determine whether the density is lower than or equal to a fixed density. The first temperature sensors 33a and 33b, the second temperature sensors 34a and 34b, and the leakage detecting devices 41a and 41b send detected signals to indoor side control devices 202a and 202b.

[0018] [Relay Device 53]

The relay device 53 includes a gas-liquid separator 8, first opening and closing valves 9a and 9b, second opening and closing valves 10a and 10b, a first expansion device 11, a second expansion device 12, a first heat exchanger 13, and a second heat exchanger 14. Note that the first expansion device 11 is an example of a relaydevice expansion device according to an embodiment of the present invention. The components of the relay device 53 are controlled by a relay-device control device 203 and connected via a bypass pipe 110, a relay-device liquid pipe 111, and a relaydevice gas pipe 112. The relay device 53 is connected to the outdoor unit 51 via the first liquid pipe 104 and the first gas pipe 103 and is connected to both the indoor units 52a and 52b via the second liquid pipes 105a and 105b and the second gas pipes 106a and 106b. The relay device 53 controls the flow of refrigerant between the outdoor unit 51 and each of the indoor units 52a and 52b, and the indoor units 52a and 52b perform a cooling and heating mixed operation.

[0019]

The gas-liquid separator 8 separates refrigerant into a liquid refrigerant and a gas refrigerant and is connected to the first liquid pipe 104, the relay-device liquid pipe 111, and the relay-device gas pipe 112. The first liquid pipe 104 connects the outdoor unit 51 and the gas-liquid separator 8 to each other, the relay-device liquid pipe 111 connects the gas-liquid separator 8 and a relay-device trident portion 55b to each other, and the relay-device gas pipe 112 connects the gas-liquid separator 8 and each of the first opening and closing valves 9a and 9b to each other.

[0020]

Each of the first opening and closing valve 9a and the second opening and closing valve 10a is connected to a branch of the second gas pipe 106a, and each of the first opening and closing valve 9b and the second opening and closing valve 10b is connected to a branch of the second gas pipe 106b. By opening and closing of the first opening and closing valves 9a and 9b, the flow of the gas refrigerant in the relay-device gas pipe 112 is stopped, or the gas refrigerant is allowed to flow out of the relay device 53. While the indoor units 52a and 52b connected via the second gas pipes 106a and 106b are performing heating operations, the first opening and closing valves 9a and 9b are in an open state. The second opening and closing valves 10a and 10b stop the flow of the gas refrigerant in the second gas pipes 106a and 106b of the indoor units 52a and 52b, or allow the gas refrigerant to flow into the relay device 53. While the indoor units 52a and 52b connected via the second gas pipes 106a and 106b are performing cooling operations, the second opening and closing valves 10a and 10b are in an open state.

[0021]

The first heat exchanger 13 allows the liquid refrigerant separated by the gasliquid separator 8 and a liquid refrigerant that has flowed through the second heat exchanger 14 to flow therethrough and allow heat exchange between the liquid refrigerants. The first expansion device 11 reduces the pressure of the liquid refrigerant that has passed through the first heat exchanger 13 and allows the liquid refrigerant to flow into the second heat exchanger 14. The second heat exchanger 14 allows a refrigerant that has been pressure-reduced by the first expansion device 11 and a liquid refrigerant that has been pressure-reduced by the second expansion device 12 to pass therethrough and allows heat exchange between the refrigerants. The first heat exchanger 13, the first expansion device 11, and the second heat exchanger 14 are provided between the gas-liquid separator 8 and the relay-device trident portion 55b and connected to one another via the relay-device liquid pipe 111.

The bypass pipe 110 connects the relay-device trident portion 55b and the first gas pipe 103 to each other with the second expansion device 12, the second heat exchanger 14, and the first heat exchanger 13 provided therebetween, collects and returns the liquid refrigerant to the outdoor unit 51. As each of the first expansion device 11 and the second expansion device 12, for example, a flow rate control unit by which the flow rate can be accurately controlled by changing its opening degree, such as an electronic expansion valve, may be used.

[0022]

Next, operations of the air-conditioning apparatus 100 will be described. The air-conditioning apparatus 100 performs a cooling only operation, a heating only operation, and a cooling and heating mixed operation. Among these operations, the cooling and heating mixed operation can have two operation modes: a heating main operation in which a heating load is high; and a cooling main operation in which a cooling load is high. Accordingly, the air-conditioning apparatus 100 can have four operation modes.

[0023]

Fig. 2 illustrates the flow of refrigerant in a refrigerant circuit during a cooling only operation. The arrows in Fig. 2 each represent the direction of the refrigerant. During a cooling only operation, the indoor units 52a and 52b both perform cooling operations, the first opening and closing valves 9a and 9b of the relay device 53 are in a closed state, and the second opening and closing valves 10a and 10b are in an open state. As illustrated in Fig. 2, the refrigerant is compressed by the compressor 1 to become a high-temperature, high-pressure gas refrigerant and is discharged, and the refrigerant flows into the outdoor heat exchanger 2 through the four-way valve 3. The refrigerant is condensed and liquefied through heat exchange with an outdoor air in the outdoor heat exchanger 2, and flows out of the outdoor heat exchanger 2 into the refrigerant flow control unit 54 through the low-pressure pipe 101. In the refrigerant flow control unit 54, the refrigerant is stopped by the check valve 7d so as not to flow into the connection pipe 130 and passes through the check valve 7b of the connection pipe 133. The refrigerant then flows out of the refrigerant flow control unit 54 and flows into the relay device 53 out of the outdoor unit 51.

[0024]

The refrigerant is separated into a liquid refrigerant and a gas refrigerant by the gas-liquid separator 8 of the relay device 53. During a cooling only operation, since all the refrigerant is a liquid refrigerant, all the refrigerant flows into the relay-device liquid pipe 111, and no refrigerant flows into the relay-device gas pipe 112. While the refrigerant flows through the relay-device liquid pipe 111, the degree of supercooling is increased by the first heat exchanger 13, and the pressure is decreased to an intermediate pressure by the first expansion device 11. The degree of supercooling is further increased by the second heat exchanger 14, and then the refrigerant arrives at the relay-device trident portion 55b.

[0025]

The refrigerant is distributed at the relay-device trident portion 55b, a part thereof flowing into the bypass pipe 110, the remaining part flowing out of the relay device 53. The refrigerant flowing into the bypass pipe 110 is pressure-reduced to a low pressure by the second expansion device 12, flows through the second heat exchanger 14 and the first heat exchanger 13 in this order, and is evaporated by heat exchange to become a gas refrigerant to merge into the first gas pipe 103. At this time, the refrigerant in the bypass pipe 110 increases the degree of supercooling of the refrigerant flowing through the relay-device liquid pipe 111 by heat exchange. [0026]

The refrigerant that has been distributed at the relay-device trident portion 55b and flowed out of the relay device 53 flows through the second liquid pipes 105a and 105b into each of the indoor units 52a and 52b. After the pressure of the refrigerant is reduced by the indoor expansion devices 6a and 6b of the indoor units 52a and 52b, the refrigerant then performs heat exchange in the indoor heat exchangers 5a and 5b with an air in an air-conditioned space. The refrigerant cools the air in the airconditioned space and is also evaporated and vaporized to become a gas refrigerant, and the gas refrigerant flows out of the indoor heat exchangers 5a and 5b. Thus, the air-conditioned space is cooled.

[0027]

The refrigerant flows from the indoor heat exchangers 5a and 5b through second gas pipes 106a and 106b, flows out of the indoor units 52a and 52b into the relay device 53 again, and passes through the second opening and closing valves 10a and 10b in an open state. The refrigerant merges, in the first gas pipe 103, with the refrigerant that has flowed through the bypass pipe 110, and flows out of the relay device 53 into the outdoor unit 51.

[0028]

In the outdoor unit 51, the refrigerant passes through the check valve 7a provided in the connection pipe 132 of the refrigerant flow control unit 54 and is sucked into the compressor 1 through the accumulator 4. Thus, the refrigerant is circulated in the refrigerant circuit.

[0029]

Fig. 3 illustrates the flow of refrigerant in a refrigerant circuit during a heating only operation. During the heating only operation, both the indoor units 52a and 52b perform heating operations together. As illustrated in Fig. 3, the refrigerant is compressed by the compressor 1 to become a high-temperature, high-pressure gas refrigerant and is discharged, and the refrigerant flows into the refrigerant flow control unit 54 through the four-way valve 3 to arrive at the connection portion d. The refrigerant cannot flow from the connection portion d into the connection pipe 132 by the check valve 7a. The refrigerant flows into the connection pipe 131 and passes through the check valve 7c and then passes through the connection portion b to flow out of the outdoor unit 51.

[0030]

The refrigerant that has flowed out of the outdoor unit 51 passes through the first liquid pipe 104 to flow into the relay device 53. The refrigerant is then separated into a gas refrigerant and a liquid refrigerant by the gas-liquid separator 8 of the relay device 53. During a heating only operation, all the refrigerant is a gas refrigerant, and no refrigerant flows into the relay-device liquid pipe 111. The refrigerant that has passed through the gas-liquid separator 8 arrives at the first opening and closing valves 9a and 9b and passes through the first opening and closing valves 9a and 9b both in an open state to flow out of the relay device 53.

[0031]

The refrigerant that has been flowed out of the relay device 53 flows into each of the indoor units 52a and 52b. The refrigerant then performs heat exchange in the indoor heat exchangers 5a and 5b with an air in an air-conditioned space and is condensed and liquefied while heat is transferred to the air in the air-conditioned space. Thus, the air-conditioned space is heated. The refrigerant passes through the indoor heat exchangers 5a and 5b and pressure-reduced by the indoor expansion devices 6a and 6b to become an intermediate-pressure liquid refrigerant, and then flows out of the indoor units 52a and 52b.

[0032]

The refrigerant that has flowed out of the indoor units 52a and 52b flows through the second liquid pipes 105a and 105b to flow into the relay device 53, passes through the relay-device trident portion 55b to merge into the first gas pipe 103 from the bypass pipe 110, and flows out of the relay device 53. The refrigerant flows through the first gas pipe 103 to arrive at the connection portion c of the refrigerant flow control unit 54. The refrigerant cannot flow through the connection pipe 132 in a high-pressure state at the connection portion c, and passes through the check valve 7d of the connection pipe 130 to flow through the low-pressure pipe 101. The refrigerant is evaporated by heat exchange with an outdoor air while passing through the outdoor heat exchanger 2 from the low-pressure pipe 101, and is sucked into the compressor 1 through the four-way valve 3 and the accumulator 4. Thus, the refrigerant is circulated in the refrigerant circuit.

[0033]

Next, a cooling and heating mixed operation in which the indoor unit 52a performs a heating operation and the indoor unit 52b performs a cooling operation will be described. In this case, in the relay device 53, the first opening and closing valve 9a and the second opening and closing valvelOb are in an open state, and the first opening and closing valve 9b and the second opening and closing valvelOa are in a closed state.

[0034]

First, the flow of refrigerant in a case of a cooling main operation in which a cooling load is higher than a heating load will be described. The refrigerant is compressed by the compressor 1 and performs heat exchange in the outdoor heat exchanger 2 to be condensed and liquefied. As a result, a two-phase gas-liquid refrigerant flows out of the outdoor heat exchanger 2. The amount of refrigerant that is condensed and liquefied in the outdoor heat exchanger 2, that is, the ratio between the gas refrigerant and the liquid refrigerant, is determined in accordance with the ratio between the cooling load and the heating load. Once the refrigerant has flowed out of the outdoor heat exchanger 2, the refrigerant flows through the low-pressure pipe 101 and passes through the check valve 7b of the refrigerant flow control unit 54 to flow out of the outdoor unit 51, and flows through the first liquid pipe 104 to flow into the relay device 53.

[0035]

The refrigerant that has flowed into the relay device 53 is separated into a liquid refrigerant and a gas refrigerant by the gas-liquid separator 8. The liquid refrigerant flows into the relay-device liquid pipe 111, and the gas refrigerant flows into the relay-device gas pipe 112.

[0036]

While the liquid refrigerant that flows into the relay-device liquid pipe 111 passes through the first heat exchanger 13, the first expansion device 11, and the second heat exchanger 14, the degree of supercooling is increased, and then the refrigerant arrives at the relay-device trident portion 55b. The refrigerant is distributed at the relay-device trident portion 55b, a part thereof flowing into the bypass pipe 110, the remaining part flowing out of the relay device 53. While the refrigerant that has flowed into the bypass pipe 110 from the relay-device trident portion 55b passes through the second expansion device 12, the second heat exchanger 14, and the first heat exchanger 13, the refrigerant receives heat from heat exchange to be evaporated and vaporized, and then the refrigerant arrives at the first gas pipe 103.

[0037]

The gas refrigerant that has been separated by the gas-liquid separator 8 and flowed into the relay-device gas pipe 112 arrives at the first opening and closing valves 9a and 9b, and passes through the first opening and closing valve 9a in an open state to flow out of the relay device 53 into the indoor unit 52a through the second gas pipe 106a. The refrigerant passes through the indoor heat exchanger 5a of the indoor unit 52a and is condensed and liquefied while heat is transferred to the air in the air-conditioned space by heat exchange. Thus, the air-conditioned space is heated. The refrigerant that has passed through the indoor heat exchanger 5a is pressure-reduced by the indoor expansion device 6a to become an intermediate-pressure liquid refrigerant. The liquid refrigerant flows out of the indoor unit 52a and passes through the second liquid pipe 105a to arrive at the indoor trident portion 55a.

[0038]

At the indoor trident portion 55a, the refrigerant flowing through the second liquid pipe 105a connected to the indoor unit 52a and the refrigerant that has been distributed at the relay-device trident portion 55b and flowed out of the relay device 53 merge with each other and flow through the second liquid pipe 105b. The refrigerant from the second liquid pipe 105b is pressure-reduced by the indoor expansion device 6b in the indoor unit 52b and flows into the indoor heat exchanger 5b. The refrigerant is evaporated and vaporized in the indoor heat exchanger 5b by heat exchange with an air in an air-conditioned space to become a gas refrigerant, and the gas refrigerant flows out of the indoor heat exchanger 5b. Thus, the air-conditioned space is cooled. The refrigerant that has passed through the indoor heat exchanger 5b passes through the second opening and closing valve 10b in an open state to arrive at the first gas pipe 103.

[0039]

The refrigerant that has passed through the second opening and closing valve 10b merges with the refrigerant that has flowed through the bypass pipe 110 to arrive at the first gas pipe 103 in the same manner, and flows through the first gas pipe 103 to flow into the refrigerant flow control unit 54 of the outdoor unit 51. The refrigerant passes through the check valve 7a provided in the connection pipe 132 in the refrigerant flow control unit 54 to be sucked into the compressor 1 through the fourway valve 3 and the accumulator 4. Thus, the refrigerant is circulated in the refrigerant circuit.

[0040]

Second, the flow of refrigerant in a case of a heating main operation in which a heating load is higher than a cooling load will be described. The refrigerant is compressed by the compressor 1 and is discharged, and the refrigerant passes through the four-way valve 3 to arrive at the connection portion d of the refrigerant flow control unit 54. Since the refrigerant cannot flow from the connection portion d into the connection pipe 132 by the check valve 7a, the refrigerant passes through the check valve 7c provided in the connection pipe 131 and flows out of the outdoor unit 51 through the first liquid pipe 104 to flow into the relay device 53.

[0041]

The refrigerant that has flowed into the relay device 53 flows into the relaydevice gas pipe 112 through the gas-liquid separator 8. At this time, since the heating main operation is being performed, there is no liquid refrigerant that is separated by the gas-liquid separator 8, and no refrigerant flows through the relaydevice liquid pipe 111. The refrigerant flows through the relay-device gas pipe 112 to arrive at the first opening and closing valves 9a and 9b, and passes through the first opening and closing valve 9a in an open state to flow out of the relay device 53 into the indoor unit 52a through the second gas pipe 106a. The refrigerant passes through the indoor heat exchanger 5a of the indoor unit 52a and is condensed and liquefied while heat is transferred to the air in an air-conditioned space by heat exchange. Thus, the air-conditioned space is heated. The refrigerant that has passed through the indoor heat exchanger 5a is pressure-reduced by the indoor expansion device 6a to become an intermediate-pressure liquid refrigerant. The liquid refrigerant flows out of the indoor unit 52a into the second liquid pipe 105a to arrive at the indoor trident portion 55a.

[0042]

The refrigerant is distributed at the indoor trident portion 55a, and a part thereof flows into the relay device 53 to flow through the bypass pipe 110. The remaining part of the distributed refrigerant flows into the indoor unit 52b through the second liquid pipe 105b, is pressure-reduced by the indoor expansion device 6b of the indoor unit 52b, and performs heat exchange in the indoor heat exchanger 5b with an air in an air-conditioned space. Thus, the refrigerant flowing through the indoor heat exchanger 5b is evaporated and vaporized, and the air-conditioned space is cooled. The refrigerant then flows through the second gas pipe106b from the indoor heat exchanger 5b and passes through the second opening and closing valve 10b in an open state.

[0043]

The refrigerant that has passed through the second opening and closing valve 10b merges with the refrigerant that has flowed through the bypass pipe 110 and flows out of the relay device 53 through the first gas pipe 103 into the outdoor unit 51. In the refrigerant flow control unit 54 of the outdoor unit 51, the refrigerant passes through the check valve 7d provided in the connection pipe 130 and flows into the outdoor heat exchanger 2 through the low-pressure pipe 101. The refrigerant is evaporated and forms drops by heat exchange in the outdoor heat exchanger 2 to be sucked into the compressor 1 through the four-way valve 3 and the accumulator 4. Thus, the refrigerant is circulated in the refrigerant circuit.

[0044]

Fig. 4 illustrates a relationship between control-related devices in the airconditioning apparatus 100 illustrated in Fig. 1. As illustrated in Fig. 4, the outdoor side control device 201 is electrically connected to each of the indoor side control devices 202a and 202b and the relay-device control device 203. The outdoor side control device 201 includes a function as a main control device that generally controls the air-conditioning apparatus 100. The outdoor side control device 201 further includes a timer (not illustrated) for measuring time. On the basis of information transmitted from the indoor side control devices 202a and 202b and the relay-device control device 203, the outdoor side control device 201 determines instructions for the indoor side control devices 202a and 202b and the relay-device control device 203 and transmits the instructions to them. The outdoor side control device 201 acquires pressures Pd and Ps detected by the first pressure sensor 31 and the second pressure sensor 32 provided in the outdoor unit 51 and controls an operating frequency Fa of the compressor 1 and a volume AKa of the outdoor heat exchanger 2. [0045]

The indoor side control devices 202a and 202b detect temperatures T33a,

T33b, T34a, and T34b by using the first temperature sensors 33a and 33b and the second temperature sensors 34a and 34b and transmit the temperatures T33a, T33b, T34a, and T34b to the outdoor side control device 201. In addition, the indoor side control devices 202a and 202b detect the presence or absence of refrigerant leakage by using the leakage detecting devices 41a and 41b and transmit the presence or absence to the outdoor side control device 201. Furthermore, on the basis of the temperatures T33a, T33b, T34a, and T34b, the indoor side control devices 202a and 202b calculate opening degrees LEV6a and LEV6b of the indoor expansion devices 6a and 6b and transmit the opening degrees LEV6a and LEV6b to the indoor expansion devices 6a and 6b.

[0046]

In response to an instruction from the outdoor side control device 201, the relay-device control device 203 transmits opening degrees LEV11 and LEV12 to the first expansion device 11 and the second expansion device 12 and instructs the first opening and closing valves 9a and 9b and the second opening and closing valves 10a and 10b to be open or closed.

[0047]

Fig. 5 is a flowchart of a process for determining the opening degree LEV6a of the indoor expansion device 6a of the indoor unit 52a. The opening degree LEV6a of the indoor expansion devices 6a and 6b is controlled by a controller that generally controls the entire air-conditioning apparatus, and is controlled by the outdoor side control device 201 in this example. As illustrated in Fig. 5, upon start of an operation of the indoor unit 52a, the outdoor side control device 201 acquires an initial value LEV6i of the opening degree LEV6a of the indoor expansion device 6a and starts measuring time by using the timer. In step S1, it is determined whether a predetermined time tm has elapsed. If it is determined that the predetermined time tm has elapsed, the process proceeds to step S2 in which the timer is reset to zero, and then the process proceeds to step S3. In step S3, the outdoor side control device 201 acquires the temperatures T33a and T34a detected by the first temperature sensor 33a and the second temperature sensor 34a. The temperature T33a and the temperature T34a represent the saturation temperature of the refrigerant and the temperature of the refrigerant, respectively. In step S4, the indoor side control device 202a calculates a difference SH between the temperature T33a and the temperature T34a.

[0048]

In step S5, the outdoor side control device 201 calculates a difference ASH between the temperature difference SH and a target temperature difference SHm. In step S6, the indoor side control device 202a calculates a correction value ALEV6a of the opening degree of the indoor expansion device 6a. For example, a coefficient k2 may be calculated in advance through testing or the like, and the correction value ALEV6a may be obtained by multiplying the coefficient k2 by the difference ASH. In step S7, the outdoor side control device 201 adds the correction value ALEV6a to the current opening degree LEV6a of the indoor expansion device 6a and sets the resulting value as a new opening degree LEV6a of the indoor expansion device 6a. [0049]

In step S8, the outdoor side control device 201 determines whether the operation is to end. If it is determined that the operation is to end, the process ends. For example, the process may end by fully closing the indoor expansion device 6a.

If it is determined that the operation is not to end, the process returns to step S1, and the process from step S1 to S8 is repeated for each predetermined period of time. [0050]

Fig. 6 is a flowchart of a process performed by the outdoor side control device 201 in a case of refrigerant leakage. As illustrated in Fig. 6, upon start of an operation of the indoor unit 52a, the outdoor side control device 201 starts measuring time by using the timer. In step S11, the outdoor side control device 201 determines whether a predetermined time tm2 has elapsed. If it is determined that the predetermined time tm2 has elapsed, in step S12, the timer is reset to zero, and then the process proceeds to step S13. In step S13, the outdoor side control device 201 determines whether refrigerant leakage has been detected by a leakage detecting device 41a. The leakage detecting device 41a may be provided in, for example, a space in which the indoor unit 52a is provided. If it is determined in step S13 that refrigerant leakage has been detected, the process proceeds to step S14. If it is determined in step S13 that refrigerant leakage has not been detected, the process returns to step S11.

[0051]

In step S14, the outdoor side control device 201 issues an instruction for starting a cooling only operation and proceeds to step S15. In step S15, the outdoor side control device 201 sets the opening degrees of the first expansion device 11 and the second expansion device 12 in the relay device 53 to a fully closed state. In step S16, the outdoor side control device 201 determines whether the pressure Ps detected by the second pressure sensor 32 in the outdoor unit 51 is lower than or equal to a pressure a. The pressure a is a value that is determined in advance through testing or the like and is an example of a reference value in the present invention. If it is determined that the pressure Ps is lower than or equal to the pressure a, the outdoor side control device 201 proceeds to step S17 and closes the second opening and closing valves 10a and 10b in the relay device 53. Thus, all of the first opening and closing valves 9a and 9b and the second opening and closing valves 10a and 10b are set to a closed state, the first opening and closing valves 9a and 9b being in a closed state by the cooling only operation. Subsequently, in step S18, the outdoor side control device 201 stops the operation of the compressor, thereby ending the control in the case of refrigerant leakage.

[0052]

In the above manner, the air-conditioning apparatus 100 performs a normal operation by using the first opening and closing valves 9a and 9b, the second opening and closing valves 10a and 10b, the first expansion device 11, and the second expansion device 12. Upon detection of refrigerant leakage, a cooling operation is started by the indoor units 52a and 52b, and also the first expansion device 11 and the second expansion device 12 are set to a closed state, and refrigerant in the indoor units 52a and 52b is collected. After that, the first opening and closing valves 9a and 9b and the second opening and closing valves 10a and 10b are set to a closed state, and the flow of refrigerant is completely stopped. As a result, the refrigerant is collected inside pipes that connect the first opening and closing valves 9a and 9b, the second opening and closing valves 10a and 10b, the compressor 1, the outdoor heat exchanger 2, the first expansion device 11, and the second expansion device 12 to one another and is charged therein.

[0053]

In this manner, even if an opening and closing valve for refrigerant leakage is not provided, by controlling the first opening and closing valves 9a and 9b, the second opening and closing valves 10a and 10b, the first expansion device 11, and the second expansion device 12, the flow of refrigerant from the indoor units 52a and 52b can be prevented. In addition, it is unnecessary to additionally prepare an opening and closing valve, to purchase an opening and closing valve, and to mount an additional opening and closing valve. Thus, the number of components is decreased, and a system with low possibility for malfunction and with high reliability can be obtained.

[0054]

Since the collected refrigerant is charged within the refrigerant circuit in the outdoor unit 51 and the refrigerant circuit in the relay device 53, a larger amount of refrigerant can be charged than in a case in which, for example, an opening and closing valve for refrigerant leakage is installed in the outdoor unit 51. Furthermore, by setting the pipe volume of the refrigerant circuits in the outdoor unit 51 and the relay device 53 to be larger than the volume of refrigerant in the whole system, all the refrigerant can be charged.

[0055]

According to the air-conditioning apparatus according to the above-described embodiment of the present invention, the expansion devices that are in an open state during cooling and heating operations and the first opening and closing valves and the second opening and closing valves that are open and closed by the cooling and heating operations can be set to a fully closed state in a case of refrigerant leakage. Thus, it is unnecessary to individually provide an opening and closing valve to prevent damage due to refrigerant leakage by stopping the flow of refrigerant and to stop the flow of refrigerant in a case of refrigerant leakage.

[0056]

According to the air-conditioning apparatus according to an embodiment of the present invention, since the refrigerant is discharged from the indoor units 52a and 52b in a state in which the refrigerant does not flow from the relay device 53 into the indoor units 52a and 52b, refrigerant leakage from the indoor units 52a and 52b can be prevented.

[0057]

According to the air-conditioning apparatus according to an embodiment of the present invention, since the first opening and closing valves and the second opening and closing valves are set to a closed state after it has been determined that the refrigerant is collected in the outdoor unit 51 and the relay device 53, refrigerant leakage from the indoor units 52a and 52b can be prevented.

[0058]

According to the air-conditioning apparatus according to an embodiment of the present invention, since the operation of the compressor 1 is stopped after the refrigerant circuit has been blocked, refrigerant leakage can be reliably stopped.

[0059]

According to the air-conditioning apparatus according to an embodiment of the present invention, since the refrigerant is charged in the refrigerant circuits in the outdoor unit 51 and the relay device 53, a larger volume of refrigerant can be stored in the outdoor unit 51 and the relay device 53 than in a case in which, for example, an opening and closing valve is provided in the outdoor unit 51.

[0060]

According to the air-conditioning apparatus according to an embodiment of the present invention, refrigerant leakage is detected by the leakage detecting device. [0061]

According to the air-conditioning apparatus according to an embodiment of the present invention, the entire operation of the air-conditioning apparatus 100 is generally controlled by the outdoor side control device 201 of the outdoor unit 51. Reference Signs List [0062] compressor, 2 outdoor heat exchanger, 3 four-way valve, 4 accumulator, 5a indoor heat exchanger, 5b indoor heat exchanger, 6a indoor expansion device, 6b indoor expansion device, 7a, 7b, 7c, 7d check valve, 8 gas-liquid separator, 9a, 9b first opening and closing valve, 10a, 10b second opening and closing valve, 11 first expansion device, 12 second expansion device, 13 first heat exchanger, 14 second heat exchanger, 31 first pressure sensor, 32 second pressure sensor, 33a, 33b first temperature sensor, 34a, 34b second temperature sensor, 41a, 41b leakage detecting device, 51 outdoor unit, 52a, 52b indoor unit, 53 relay device, 54 refrigerant flow control unit, 55a indoor trident portion, 55b relay-device trident portion, 100 air-conditioning apparatus, 101 low-pressure pipe, 102 highpressure pipe, 103 first gas pipe, 104 first liquid pipe, 105a, 105b second liquid pipe, 106a, 106b second gas pipe, 110 bypass pipe, 111 relay-device liquid pipe, 112 relay-device gas pipe, 130,131,132,133 connection pipe,

201 outdoor side control device, 202a, 202b indoor side control device, 203 relay-device control device.

Claims

CLAIMS [Claim 1]

An air-conditioning apparatus comprising:

an outdoor unit including an outdoor heat exchanger and a compressor; a relay device including a relay-device expansion device, a first opening and closing valve, and a second opening and closing valve; and an indoor unit including an indoor heat exchanger and configured to perform a cooling operation and a heating operation, wherein the outdoor heat exchanger, the compressor, the relay-device expansion device, the first opening and closing valve, the second opening and closing valve, and the indoor heat exchanger form a refrigerant circuit in which refrigerant is circulated, wherein, while the indoor unit is performing the heating operation, the first opening and closing valve and the relay-device expansion device are in an open state, and the refrigerant is circulated in the outdoor heat exchanger, the compressor, the first opening and closing valve, the indoor heat exchanger, and the relay-device expansion device in this order, wherein, while the indoor unit is performing the cooling operation, the second opening and closing valve and the relay-device expansion device are in an open state, and the refrigerant is circulated in the compressor, the outdoor heat exchanger, the relay-device expansion device, the indoor heat exchanger, and the second opening and closing valve in this order, and wherein, in a case of refrigerant leakage, the first opening and closing valve, the second opening and closing valve, and the relay-device expansion device are in a closed state, and the refrigerant is charged in a refrigerant circuit included in the refrigerant circuit and formed of the first opening and closing valve, the second opening and closing valve, the compressor, the outdoor heat exchanger, and the relay-device expansion device.
[Claim 2]

The air-conditioning apparatus of claim 1, wherein, in a case of refrigerant leakage, the first opening and closing valve and the second opening and closing valve are configured to be set to a closed state after the relay-device expansion device is set to a closed state.
[Claim 3]

The air-conditioning apparatus of claim 1 or 2, wherein, in a case of refrigerant leakage, the first opening and closing valve and the second opening and closing valve are configured to be set to a closed state when pressure in a suction side of the compressor becomes not higher than a reference value.
[Claim 4]

The air-conditioning apparatus of any one of claims 1 to 3, wherein the compressor is configured to stop an operation when the first opening and closing valve and the second opening and closing valve are set to a closed state.
[Claim 5]

The air-conditioning apparatus of any one of claims 1 to 4, wherein the relay device is provided at a position where a pipe volume of a refrigerant circuit formed of the outdoor unit and the relay device is larger than a volume of all refrigerant to be collected.
[Claim 6]

The air-conditioning apparatus of any one of claims 1 to 5, further comprising a leakage detecting device configured to detect leakage of the refrigerant.
[Claim 7]

The air-conditioning apparatus of any one of claims 1 to 6, wherein the outdoor unit includes an outdoor control device configured to control operations of the outdoor unit, the relay device, and the indoor unit, and wherein the outdoor control device is configured to perform a step for starting the cooling operation of the indoor unit in a case of refrigerant leakage, after the cooling operation is started, a step for setting the relay-device expansion device to a closed state, after the step for setting the relay-device expansion device to a closed state, a step for setting the first opening and closing valve and the second opening

5 and closing valve to a closed state, and after the step for setting the first opening and closing valve and the second opening and closing valve to a closed state, a step for stopping an operation of the compressor.