Air conditioning device

Abstract

An air conditioner includes: a refrigerant circuit configured to perform a refrigeration cycle for executing a heating operation of heating a utilization-side space by compressing a refrigerant to a critical pressure or more; and a control device. A radiator includes a first radiator and a second radiator connected in parallel with each other. An expansion valve includes a first expansion valve and a second expansion valve. The first radiator and the first expansion valve form a first utilization unit. The second radiator and the second expansion valve form a second utilization unit. If the first utilization unit is in a stop mode, the control device controls the first expansion valve to switch a first state in which the first expansion valve is fully closed or opened to a minute opening degree and a second state in which the first expansion valve is more opened than in the first state.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an air conditioner.BACKGROUND ART

[0002] Various techniques related to air conditioners are disclosed as shown in Patent Document 1, for example. The air conditioner disclosed in Patent Document 1 includes a refrigerant circuit. The refrigerant circuit includes a compressor, a radiator, an expansion valve, and an evaporator, and performs a refrigeration cycle for executing a heating operation to heat an indoor space. The air conditioner disclosed in Patent Document 1 performs a supercritical operation of compressing a refrigerant to a critical pressure or more.CITATION LISTPATENT DOCUMENT

[0003] Patent Document 1: Japanese Unexamined Patent Publication No. 2021-055874SUMMARY OF THE INVENTIONTECHNICAL PROBLEM

[0004] In a multi-type air conditioner in which one heat source unit is connected with a plurality of utilization units, some of the plurality of utilization units are stopped in some cases. At this time, in general, the expansion valve of the stopped utilization unit is throttled while being slightly opened.

[0005] A multi-type air conditioner that performs a supercritical operation has the problem that when some of the plurality of utilization units are stopped according to the above method, the pressure of the refrigerant on the downstream side of the radiator of the utilization unit rises. At the same time, it is necessary to reduce accumulation of the liquid refrigerant in the radiator of the stopped utilization unit.

[0006] Due to these circumstances, it is difficult for the multi-type air conditioner that performs a supercritical operation to stop some of the plurality of utilization units.

[0007] An object of the present disclosure is to enable a multi-type air conditioner that performs a supercritical operation to stop some of a plurality of utilization units.SOLUTION TO THE PROBLEM

[0008] A first aspect of the present disclosure is directed to an air conditioner (1). The air conditioner (1) includes: a refrigerant circuit (6) including a compressor (20), a radiator (64), an expansion valve (63), and an evaporator (24), and configured to perform a refrigeration cycle for executing a heating operation of heating a utilization-side space (R) by compressing a refrigerant to a critical pressure (Pc) or more; and a control device (130) configured to control the refrigerant circuit (6), wherein the radiator (64) includes a first radiator (64A) and a second radiator (64B) connected in parallel with each other, the expansion valve (63) includes a first expansion valve (63A) associated with the first radiator (64A), and a second expansion valve (63B) associated with the second radiator (64B), the first radiator (64A) and the first expansion valve (63A) form a first utilization unit (60A), the second radiator (64B) and the second expansion valve (63B) form a second utilization unit (60B), and if the first utilization unit (60A) is in a stop mode (M1), the control device (130) controls the first expansion valve (63A) to switch a first state (J1) in which the first expansion valve (63A) is fully closed or opened to a minute opening degree and a second state (J2) in which the first expansion valve (63A) is more opened than in the first state (J1).

[0009] According to the first aspect, it is possible for the multi-type air conditioner (1) that performs the supercritical operation to stop the first utilization unit (60A) among the first utilization unit (60A) and the second utilization unit (60B).

[0010] A second aspect of the present disclosure is directed to the air conditioner (1) of the first aspect. The refrigerant circuit (6) includes a gas-liquid separator (25) connected to a downstream side of the radiator (64) and configured to separate the refrigerant into a gas refrigerant and a liquid refrigerant, and the control device (130) switches the first expansion valve (63A) from the second state (J2) to the first state (J1) based on a rise in a pressure (Pd) of the gas-liquid separator (25).

[0011] According to the second aspect, by switching the first expansion valve (63A) of the first utilization unit (60A) from the second state (J2) to the first state (J1) to throttle the first expansion valve (63A) of the first utilization unit (60A) when the pressure (Pd) of the gas-liquid separator (25) located downstream of the radiator (64) rises, it is possible to reduce a rise in the pressure (Pd) of the gas-liquid separator (25).

[0012] A third aspect of the present disclosure is directed to the air conditioner (1) of the second aspect. The control device (130) switches the first expansion valve (63A) from the second state (J2) to the first state (J1) if a difference between a temperature (TIA) of the refrigerant at an inlet (IA) of the first radiator (64A) and a temperature (TEA) of the refrigerant at an outlet (EA) of the first radiator (64A) is larger than a first value (Q1), or if the temperature (TEA) of the refrigerant at the outlet (EA) of the first radiator (64A) rises as time passes.

[0013] According to the third aspect, without measuring the pressure (Pd) of the gas-liquid separator (25) directly, it is possible to switch the first expansion valve (63A) of the first utilization unit (60A) from the second state (J2) to the first state (J1) at the time when the pressure (Pd) of the gas-liquid separator (25) rises.

[0014] A fourth aspect of the present disclosure is directed to the air conditioner (1) of the second aspect. The control device (130) switches the first expansion valve (63A) from the second state (J2) to the first state (J1) if a duration of the second state (J2) is longer than a second value (Q2).

[0015] According to the fourth aspect, without measuring the pressure (Pd) of the gas-liquid separator (25) directly, it is possible to switch the first expansion valve (63A) of the first utilization unit (60A) from the second state (J2) to the first state (J1) at the time when the pressure (Pd) of the gas-liquid separator (25) rises.

[0016] A fifth aspect of the present disclosure is directed to the air conditioner (1) of any one of the first to fourth aspects. The control device (130) switches the first expansion valve (63A) from the first state (J1) to the second state (J2) if the temperature (TIA) of the refrigerant at the inlet (IA) of the first radiator (64A) is lower than a temperature (Tc) of the refrigerant at a critical point (C), or if the difference between the temperature (TIA) of the refrigerant at the inlet (IA) of the first radiator (64A) and the temperature (TEA) of the refrigerant at the outlet (EA) of the first radiator (64A) is smaller than a third value (Q3), or if a difference between the temperature (TIA) of the refrigerant at the inlet (IA) of the first radiator (64A) and a temperature (TRA) of the utilization-side space (RA) of the first utilization unit (60A) is smaller than a fourth value (Q4), or if a duration of the first state (J1) is longer than a fifth value (Q5).

[0017] According to the fifth aspect, by switching the first expansion valve (63A) of the first utilization unit (60A) from the first state (J1) to the second state (J2) to open the first expansion valve (63A) of the first utilization unit (60A), it is possible reduce accumulation of the liquid refrigerant in the radiator (64A) of the first utilization unit (60A).

[0018] A sixth aspect of the present disclosure is directed to the air conditioner (1) of any one of the first to fifth aspects. The control device (130) sets an opening degree of the first expansion valve (63A) smaller than an opening degree of the second expansion valve (63B) if the first utilization unit (60A) is in the stop mode (M1) and the second utilization unit (60B) is in an operating mode (M2).

[0019] According to the sixth aspect, it is possible to stop the first utilization unit (60A) while the second utilization unit (60B) is in operation.

[0020] A seventh aspect of the present disclosure is directed to the air conditioner (1) of any one of the first to sixth aspects. The control device (130) starts up the heating operation while a fan (62A) of the first utilization unit (60A) is stopped, and the control device (130) activates the fan (62A) if the temperature (TEA) of the refrigerant at the outlet (EA) of the first radiator (64A) rises beyond the temperature (Tc) of the refrigerant at the critical point (C) after the heating operation starts up.

[0021] According to the seventh aspect, it is possible to reduce an excessive increase in the pressure generated by the compressor (20) immediately after the heating operation starts up.

[0022] An eighth aspect of the present disclosure is directed to the air conditioner (1) of the seventh aspect. The refrigerant circuit (6) includes: the gas-liquid separator (25) connected to the downstream side of the radiator (64) and configured to separate the refrigerant into a gas refrigerant and a liquid refrigerant; a venting passage (41) connecting a gas reservoir (25a) of the gas-liquid separator (25) with a suction side (20i) of the compressor (20); and an on-off valve (42) provided in the venting passage (41), and the control device (130) opens the on-off valve (42) when the heating operation starts up.

[0023] According to the eighth aspect, by promoting the gas refrigerant flowing from the gas reservoir (25a) of the gas-liquid separator (25) to the suction side (20i) of the compressor (20) when the heating operation starts up, it is possible to accelerate a rise in the pressure generated by the compressor (20).BRIEF DESCRIPTION OF THE DRAWINGS

[0024] [FIG. 1] FIG. 1 is a piping system diagram of an air conditioner (1) according to a first embodiment. [FIG. 2] FIG. 2 is a piping system diagram of the vicinity of an air conditioning unit (60) according to the first embodiment. [FIG. 3] FIG. 3 is a block diagram showing the connection relationship between a controller (130) and peripheral devices according to the first embodiment. [FIG. 4] FIG. 4 is a graph showing the relationship between a specific enthalpy (h) and pressure (P) of a refrigerant according to the first embodiment. [FIG. 5] FIG. 5 is a piping system diagram according to the first embodiment where the first air conditioning unit (60A) is in the stop mode (M1) and the second air conditioning unit (60B) is in the operating mode (M2). [FIG. 6] FIG. 6 is a control flowchart of the first air conditioning unit (60A) according to the first embodiment. [FIG. 7] FIG. 7 is a piping system diagram according to the second embodiment where the first air conditioning unit (60A) is in the stop mode (M1) and the second air conditioning unit (60B) is in the operating mode (M2). DESCRIPTION OF EMBODIMENTS

[0025] Embodiments of the present disclosure will be described in detail below with reference to the drawings. The present disclosure is not limited to the embodiments below, and various changes can be made within the scope without departing from the technical concept of the present disclosure. Since each of the drawings is intended to illustrate the present disclosure conceptually, dimensions, ratios, or numbers may be exaggerated or simplified as necessary for ease of understanding.<First Embodiment>

[0026] An air conditioner (1) according to a first embodiment will be described. The air conditioner (1) performs a refrigeration cycle. The air conditioner (1) is also referred to as a refrigeration apparatus. The air conditioner (1) performs air conditioning of indoor air. The air conditioner (1) cools a target. The target referred to herein includes air present in facilities such as a refrigerator, a freezer, and a show case. Hereinafter, such facilities are each referred to as a refrigeration facility. The air conditioner (1) is a multi-type air conditioner in which one heat source unit (10) is connected with a plurality of utilization units (a first air conditioning unit (60A), a second air conditioning unit (60B), and a refrigeration facility unit (70)).(1) General Configuration

[0027] FIG. 1 is a piping system diagram of the air conditioner (1). As illustrated in FIG. 1, the air conditioner (1) includes the heat source unit (10) placed outside, the air conditioning unit (60) configured to perform air conditioning of an indoor space, and the refrigeration facility unit (70) configured to cool inside air. The air conditioning unit (60) includes the first air conditioning unit (60A) and the second air conditioning unit (60B) connected in parallel with each other.

[0028] The air conditioner (1) includes four connection pipes (2, 3, 4, 5) connecting the heat source unit (10), the air conditioning unit (60), and the refrigeration facility unit (70). In the air conditioner (1), the heat source unit (10), the air conditioning unit (60), and the refrigeration facility unit (70) are connected with each other by the connection pipes (2, 3, 4, 5) in order to form a refrigerant circuit (6). In other words, the air conditioner (1) has the refrigerant circuit (6).

[0029] The refrigerant circuit (6) is filled with a refrigerant. The refrigerant circuit (6) circulates the refrigerant to perform a refrigeration cycle. The refrigerant of this embodiment is carbon dioxide. The refrigerant circuit (6) performs a refrigeration cycle in which the refrigerant is compressed to a critical pressure or more.(1-1) Connection Pipes

[0030] The four connection pipes (2, 3, 4, 5) consist of a first liquid connection pipe (2), a first gas connection pipe (3), a second liquid connection pipe (4), and a second gas connection pipe (5). The first liquid connection pipe (2) and the first gas connection pipe (3) are associated with the air conditioning unit (60). The second liquid connection pipe (4) and the second gas connection pipe (5) are associated with the refrigeration facility unit (70).(2) Heat Source Unit

[0031] The heat source unit (10) includes a heat source circuit (11) and an outdoor fan (12). The heat source circuit (11) includes a compressor (20), an outdoor heat exchanger (24), and a gas-liquid separator (25). The heat source circuit (11) includes a first outdoor expansion valve (26) and a second outdoor expansion valve (27). The heat source circuit (11) further includes a subcooling heat exchanger (28) and an intercooler (29).

[0032] The heat source circuit (11) includes four shut-off valves (13, 14, 15, 16). The four shut-off valves (13,14,15,16) consist of a first gas shut-off valve (13), a first liquid shut-off valve (14), a second gas shut-off valve (15), and a second liquid shut-off valve (16).

[0033] The first gas shut-off valve (13) is connected with the first gas connection pipe (3). The first liquid shut-off valve (14) is connected with the first liquid connection pipe (2). The second gas shut-off valve (15) is connected with the second gas connection pipe (5). The second liquid shut-off valve (16) is connected with the second liquid connection pipe (4).

[0034] The heat source unit (10) includes a flow path switching mechanism (30). The piping system diagram of the refrigerant circuit (6) in FIG. 1 and the other drawings omits the detail of the flow path switching mechanism (30). The flow path switching mechanism (30) switches the flow path of a refrigerant in the refrigerant circuit (6).(2-1) Compressor

[0035] The compressor (20) compresses the refrigerant. The compressor (20) includes a first compressor (21), a second compressor (22), and a third compressor (23). The compressor (20) performs an operation for compressing a refrigerant in a single stage, and an operation for compressing a refrigerant in two stages.

[0036] The first compressor (21) is a refrigeration facility compressor associated with the refrigeration facility unit (70). The second compressor (22) is an air conditioning compressor associated with the air conditioning unit (60). The first compressor (21) and the second compressor (22) are low-stage compressors. The first compressor (21) and the second compressor (22) are connected in parallel.

[0037] The third compressor (23) is a high-stage compressor. The third compressor (23) is connected in series with the first compressor (21) or connected in series with the second compressor (22).

[0038] The first compressor (21), the second compressor (22), and the third compressor (23) are rotary compressors, each having a compression mechanism driven by a motor. The first compressor (21), the second compressor (22), and the third compressor (23) are variable displacement compressors. The number of rotations of each motor of the first compressor (21), the second compressor (22), and the third compressor (23) is adjusted by an inverter device. In other words, the operating capacities of the first compressor (21), the second compressor (22), and the third compressor (23) are adjustable.

[0039] The suction portion of the first compressor (21) is connected with a first suction pipe (21a). The discharge portion of the first compressor (21) is connected with a first discharge pipe (21b). The suction portion of the second compressor (22) is connected with a second suction pipe (22a). The discharge portion of the second compressor (22) is connected with a second discharge pipe (22b). The suction portion of the third compressor (23) is connected with a third suction pipe (23a). The discharge portion of the third compressor (23) is connected with a third discharge pipe (23b).(2-2) Intermediate Flow Path

[0040] The heat source circuit (11) includes an intermediate flow path (18). The intermediate flow path (18) connects each discharge portion of the first compressor (21) and the second compressor (22) with the suction portion of the third compressor (23). The intermediate flow path (18) includes the first discharge pipe (21b), the second discharge pipe (22b), and the third suction pipe (23a).(2-3) Outdoor Heat Exchanger and Outdoor Fan

[0041] The outdoor heat exchanger (24) is an example of an evaporator. The outdoor heat exchanger (24) is a fin-and-tube air heat exchanger. The outdoor fan (12) is disposed near the outdoor heat exchanger (24). The outdoor fan (12) transfers outdoor air. The outdoor heat exchanger exchanges heat between the refrigerant flowing therein and the outdoor air transferred by the outdoor fan (12).(2-4) Liquid-Side Flow Path

[0042] The heat source circuit (11) includes a liquid-side flow path (40). The liquid-side flow path (40) is provided between the liquid end of the outdoor heat exchanger (24) and the two liquid shut-off valves (14, 16). The liquid-side flow path (40) includes first to fifth pipes (40a, 40b, 40c, 40d, 40e).

[0043] One end of the first pipe (40a) is connected to the liquid end of the outdoor heat exchanger (24). The other end of the first pipe (40a) is connected to the top portion of the gas-liquid separator (25). One end of the second pipe (40b) is connected to the bottom portion of the gas-liquid separator (25). The other end of the second pipe (40b) is connected to the second liquid shut-off valve (16). One end of the third pipe (40c) is connected to the intermediate portion of the second pipe (40b). The other end of the third pipe (40c) is connected to the first liquid shut-off valve (14). One end of the fourth pipe (40d) is connected to part of the first pipe (40a) between the first outdoor expansion valve (26) and the gas-liquid separator (25). The other end of the fourth pipe (40d) is connected to the intermediate portion of the third pipe (40c). One end of the fifth pipe (40e) is connected to part of the first pipe (40a) between the outdoor heat exchanger (24) and the first outdoor expansion valve (26). The other end of the fifth pipe (40e) is connected to part of the second pipe (40b) between the gas-liquid separator (25) and the junction with the third pipe (40c).(2-5) Outdoor Expansion Valves

[0044] The first outdoor expansion valve (26) is provided in the first pipe (40a). The first outdoor expansion valve (26) is provided in part of the first pipe (40a) between the liquid end of the outdoor heat exchanger (24) and the junction with the fourth pipe (40d). The second outdoor expansion valve (27) is provided in the fifth pipe (40e). The opening degrees of the first outdoor expansion valve (26) and the second outdoor expansion valve (27) are adjustable. The first outdoor expansion valve (26) and the second outdoor expansion valve (27) are electronic expansion valves, the opening degrees of which are adjusted based on pulse signals.(2-6) Gas-Liquid Separator

[0045] The gas-liquid separator (25) is also referred to as a receiver. The gas-liquid separator (25) is a closed container that stores a refrigerant. The gas-liquid separator (25) separates the refrigerant into a gas refrigerant and a liquid refrigerant. A gas reservoir (25a) and a liquid reservoir (25b) are formed in the gas-liquid separator (25). The gas reservoir (25a) is formed near the top portion of the gas-liquid separator (25). The liquid reservoir (25b) is formed near the bottom portion of the gas-liquid separator (25).(2-7) Venting Pipe

[0046] The heat source circuit (11) includes a venting pipe (41). The venting pipe (41) is an example of a venting passage. One end of the venting pipe (41) is connected to the gas reservoir (25a) near the top portion of the gas-liquid separator (25). The other end of the venting pipe (41) is connected to the intermediate flow path (18). The venting pipe (41) sends the gas refrigerant in the gas-liquid separator (25) to the intermediate flow path (18). The venting pipe (41) allows the gas reservoir (25a) of the gas-liquid separator (25) to communicate with the suction side (20i) of the third compressor (23) as the high-stage compressor.

[0047] The venting pipe (41) is provided with a venting valve (42). The venting valve (42) is an example of an on-off valve. The venting valve (42) is an expansion valve of which the opening degree is adjustable. The venting valve (42) is an electronic expansion valve of which the opening degree is adjusted based on pulse signals. The venting valve (42) may be an electric valve, an electromagnetic on-off valve, or the like.(2-8) Subcooling Heat Exchanger

[0048] The subcooling heat exchanger (28) includes a first flow path (28a) as a high-pressure flow path and a second flow path (28b) as a low-pressure flow path. The subcooling heat exchanger (28) exchanges heat between the refrigerant in the first flow path (28a) and the refrigerant in the second flow path (28b). In other words, the subcooling heat exchanger (28) uses the refrigerant flowing in the second flow path (28b) in order to cool the refrigerant flowing in the first flow path (28a).

[0049] The second flow path (28b) forms part of an injection flow path (43). The injection flow path (43) includes an upstream flow path (44) and a downstream flow path (45).

[0050] One end of the upstream flow path (44) is connected to part of the third pipe (40c) that is upstream of the junction with the fourth pipe (40d). The other end of the upstream flow path (44) is connected to the inflow end of the second flow path (28b). The upstream flow path (44) is provided with an injection valve (46) as a subcooling decompression valve. The injection valve (46) is an expansion valve of which the opening degree is adjustable. The injection valve (46) is an electronic expansion valve of which the opening degree is adjusted based on pulse signals.

[0051] One end of the downstream flow path (45) is connected to the outflow end of the second flow path (28b). The other end of the downstream flow path (45) is connected to the intermediate flow path (18).(2-9) Intercooler

[0052] The intercooler (29) is provided in the intermediate flow path (18). The intercooler (29) is a fin-and-tube air heat exchanger. A cooling fan (29a) is disposed near the intercooler (29). The intercooler (29) exchanges heat between the refrigerant flowing therein and the outdoor air transferred by the cooling fan (29a).(2-10) Oil Separation Circuit

[0053] The heat source circuit (11) includes an oil separation circuit. The oil separation circuit includes an oil separator (50), a first oil return pipe (51), and a second oil return pipe (52).

[0054] The oil separator (50) is connected to the third discharge pipe (23b). The oil separator (50) separates oil from the refrigerant discharged from the compressor (20). The inflow ends of the first oil return pipe (51) and the second oil return pipe (52) communicate with the oil separator (50). The outflow end of the first oil return pipe (51) is connected to the intermediate flow path (18). The first oil return pipe (51) is provided with a first oil level control valve (53).

[0055] The outflow side of the second oil return pipe (52) is separated into a first branch pipe (52a) and a second branch pipe (52b). The first branch pipe (52a) is connected to an oil reservoir of the first compressor (21). The second branch pipe (52b) is connected to an oil reservoir of the second compressor (22). The first branch pipe (52a) is provided with a second oil level control valve (54). The second branch pipe (52b) is provided with a third oil level control valve (55).(2-11) Bypass Pipes

[0056] The heat source circuit (11) includes a first bypass pipe (56), a second bypass pipe (57), and a third bypass pipe (58). The first bypass pipe (56) is associated with the first compressor (21). The second bypass pipe (57) is associated with the second compressor (22). The third bypass pipe (58) is associated with the third compressor (23).

[0057] Specifically, the first bypass pipe (56) connects the first suction pipe (21a) and the first discharge pipe (21b) directly. The second bypass pipe (57) connects the second suction pipe (22a) and the second discharge pipe (22b) directly. The third bypass pipe (58) connects the third suction pipe (23a) and the third discharge pipe (23b) directly.(2-12) Check Valves

[0058] The heat source circuit (11) includes a plurality of check valves. The plurality of check valves include first to twelfth check valves (CV1 to CV12). The check valves (CV1 to CV12) allow the flow of a refrigerant in the direction of the arrow in FIG. 1 and disallow the flow of a refrigerant in the reverse direction.

[0059] The first check valve (CV1) and the second check valve (CV2) are provided in the flow path switching mechanism (30).

[0060] The third check valve (CV3) is provided in the third discharge pipe (23b). The fourth check valve (CV4) is provided in the first pipe (40a). The fifth check valve (CV5) is provided in the third pipe (40c). The sixth check valve (CV6) is provided in the fourth pipe (40d). The seventh check valve (CV7) is provided in the fifth pipe (40e). The eighth check valve (CV8) is provided in the first bypass pipe (56). The ninth check valve (CV9) is provided in the second bypass pipe (57). The tenth check valve (CV10) is provided in the third bypass pipe (58). The eleventh check valve (CV11) is provided in the first discharge pipe (21b). The twelfth check valve (CV12) is provided in the second discharge pipe (22b).(3) Air Conditioning Unit

[0061] FIG. 2 is a piping system diagram of the vicinity of the air conditioning unit (60). The air conditioning unit (60) is a utilization unit placed indoors. The air conditioning unit (60) includes an indoor circuit (61) and an indoor fan (62). The liquid end of the indoor circuit (61) is connected with the first liquid connection pipe (2). The gas end of the indoor circuit (61) is connected with the first gas connection pipe (3). The indoor fan (62) is an example of a fan.

[0062] As shown in FIG. 2, the indoor circuit (61) includes an indoor expansion valve (63) and an indoor heat exchanger (64) arranged sequentially from the liquid end to the gas end. The indoor expansion valve (63) is an example of an expansion valve. The indoor expansion valve (63) is an expansion valve of which the opening degree is adjustable. The indoor expansion valve (63) is an electronic expansion valve of which the opening degree is adjusted based on pulse signals.

[0063] The indoor heat exchanger (64) is a fin-and-tube air heat exchanger. The indoor heat exchanger (64) is an example of a radiator. The indoor fan (62) is disposed near the indoor heat exchanger (64). The indoor fan (62) transfers indoor air. The indoor heat exchanger (64) exchanges heat between the refrigerant flowing therein and the indoor air transferred by the indoor fan (62).

[0064] The air conditioning unit (60) includes the first air conditioning unit (60A) and the second air conditioning unit (60B) connected in parallel with each other. The air conditioning unit (60) is an example of a utilization unit. The first air conditioning unit (60A) is an example of a first utilization unit. The second air conditioning unit (60B) is an example of a second utilization unit. The indoor circuits (61) include a first indoor circuit (61A) and a second indoor circuit (61B) connected in parallel with each other. The first indoor circuit (61A) is associated with the first air conditioning unit (60A). The second indoor circuit (61B) is associated with the second air conditioning unit (60B).

[0065] The indoor heat exchanger (64) includes a first indoor heat exchanger (64A) and a second indoor heat exchanger (64B) connected in parallel with each other. The first indoor heat exchanger (64A) is an example of a first radiator. The second indoor heat exchanger (64B) is an example of a second radiator.

[0066] The indoor expansion valve (63) includes a first indoor expansion valve (63A) associated with the first indoor heat exchanger (64A), and a second indoor expansion valve (63B) associated with the second indoor heat exchanger (64B). The first indoor expansion valve (63A) is an example of a first expansion valve. The second indoor expansion valve (63B) is an example of a second expansion valve. The indoor fan (62) includes a first indoor fan (62A) associated with the first indoor heat exchanger (64A), and a second indoor fan (62B) associated with the second indoor heat exchanger (64B). The first indoor fan (62A) is an example of a first fan. The second indoor fan (62B) is an example of a second fan.(4) Refrigeration Facility Unit

[0067] The refrigeration facility unit (70) is a utilization unit that cools the internal space. The refrigeration facility unit (70) includes a refrigeration facility circuit (71) and a refrigeration facility fan (72). The liquid end of the refrigeration facility circuit (71) is connected with the second liquid connection pipe (4). The gas end of the refrigeration facility circuit (71) is connected with the second gas connection pipe (5).

[0068] The refrigeration facility circuit (71) includes a refrigeration facility expansion valve (73) and a refrigeration facility heat exchanger (74) arranged sequentially from the liquid end to the gas end. The refrigeration facility expansion valve (73) is an expansion valve of which the opening degree is adjustable. The refrigeration facility expansion valve (73) is an electronic expansion valve of which the opening degree is adjusted based on pulse signals.

[0069] The refrigeration facility heat exchanger (74) is a fin-and-tube air heat exchanger. The refrigeration facility fan (72) is disposed near the refrigeration facility heat exchanger (74). The refrigeration facility fan (72) transfers inside air. The refrigeration facility heat exchanger (74) exchanges heat between the refrigerant flowing therein and the inside air transferred by the refrigeration facility fan (72).(5) Flow Path Switching Mechanism

[0070] The flow path switching mechanism (30) is provided in the heat source circuit (11). The flow path switching mechanism (30) switches the flow path of the refrigerant circuit (6) in order to switch at least a first refrigeration cycle and a second refrigeration cycle. The first refrigeration cycle is a refrigeration cycle in which the outdoor heat exchanger (24) functions as a radiator, and the indoor heat exchanger (64) and the refrigeration facility heat exchanger (74) function as evaporators. The second refrigeration cycle is a refrigeration cycle in which the outdoor heat exchanger (24) functions as an evaporator, and the indoor heat exchanger (64) and the refrigeration facility heat exchanger (74) function as radiators.

[0071] The flow path switching mechanism (30) includes a first port (P1), a second port (P2), a third port (P3), a fourth port (P4), a first switching flow path (31), a second switching flow path (32), a third switching flow path (33), and a fourth switching flow path (34). Each of the switching flow paths (31 to 34) is provided with an on-off mechanism (not shown). Each on-off mechanism includes an on-off valve and an expansion valve.

[0072] The first port (P1) is connected with the discharge portion of the third compressor (23). The second port (P2) is connected with the suction portion of the second compressor (22). The third port (P3) is connected with the gas end portion of the indoor heat exchanger (64). The fourth port (P4) is connected with the gas end portion of the outdoor heat exchanger (24).

[0073] The first switching flow path (31), the second switching flow path (32), the third switching flow path (33), and the fourth switching flow path (34) are connected in a bridge shape. The first switching flow path (31) allows the first port (P1) and the third port (P3) to communicate with each other. The second switching flow path (32) allows the first port (P1) and the fourth port (P4) to communicate with each other. The third switching flow path (33) allows the second port (P2) and the third port (P3) to communicate with each other. The fourth switching flow path (34) allows the second port (P2) and the fourth port (P4) to communicate with each other.

[0074] The fourth switching flow path (34) is provided with the first check valve (CV1). The first switching flow path (31) is provided with the second check valve (CV2). The first check valve (CV1) in the fourth switching flow path (34) allows the flow of a refrigerant from the fourth port (P4) to the second port (P2) and disallows the flow of a refrigerant from the second port (P2) to the fourth port (P4). The second check valve (CV2) in the first switching flow path (31) allows the flow of a refrigerant from the first port (P1) to the third port (P3) and disallows the flow of a refrigerant from the third port (P3) to the first port (P1).(6) Sensors

[0075] The air conditioner (1) includes a plurality of sensors. The plurality of sensors include a refrigerant pressure sensor that detects the pressure of a refrigerant; a refrigerant temperature sensor that detects the temperature of a refrigerant; and an air temperature sensor that detects the temperature of air.

[0076] The refrigerant pressure sensor includes a high-pressure sensor (101), an intermediate-pressure sensor (102), a first suction pressure sensor (103), a second suction pressure sensor (104), and a receiver pressure sensor (105). The high-pressure sensor (101) is provided in the third discharge pipe (23b). The high-pressure sensor (101) detects the pressure of a refrigerant on the discharge side of the compressor (20), in other words, the high pressure (Ph) of the refrigerant circuit (6).

[0077] The intermediate-pressure sensor (102) is provided in the third suction pipe (23a). The intermediate-pressure sensor (102) detects the pressure of a refrigerant between the low-stage compressor and the high-stage compressor, in other words, the intermediate pressure of the refrigerant circuit (6). The first suction pressure sensor (103) is provided in the first suction pipe (21a). The first suction pressure sensor (103) detects the pressure of a refrigerant on the suction side of the first compressor (21). The second suction pressure sensor (104) is provided in the second suction pipe (22a). The second suction pressure sensor (104) detects the pressure of a refrigerant on the suction side of the second compressor (22).

[0078] The receiver pressure sensor (105) is provided in the liquid-side flow path (40). Specifically, the receiver pressure sensor (105) is provided in the second pipe (40b). The receiver pressure sensor (105) detects the pressure (the receiver pressure (Pd) described later) corresponding to the internal pressure of the gas-liquid separator (25). The receiver pressure sensor (105) detects the pressure corresponding to the pressure of the refrigerant in the first flow path (28a). The receiver pressure sensor (105) may be a sensor that detects the pressure of a refrigerant in the gas-liquid separator (25).

[0079] The refrigerant temperature sensor includes a first discharge temperature sensor (111), a first suction temperature sensor (112), a second discharge temperature sensor (113), a second suction temperature sensor (114), a third discharge temperature sensor (115), a third suction temperature sensor (116), a liquid-side temperature sensor (117), an injection-side temperature sensor (118), an outdoor heat exchanger liquid-side temperature sensor (119), an outdoor heat exchanger gas-side temperature sensor (120), an indoor heat exchanger liquid-side temperature sensor (121), and an indoor heat exchanger gas-side temperature sensor (122).

[0080] The first discharge temperature sensor (111) is provided in the first discharge pipe (21b) and detects the temperature of the refrigerant discharged from the first compressor (21). The first suction temperature sensor (112) is provided in the first suction pipe (21a), and detects the temperature of the refrigerant sucked into the first compressor (21). The second discharge temperature sensor (113) is provided in the second discharge pipe (22b) and detects the temperature of the refrigerant discharged from the second compressor (22). The second suction temperature sensor (114) is provided in the second suction pipe (22a) and detects the temperature of the refrigerant sucked into the second compressor (22). The third discharge temperature sensor (115) is provided in the third discharge pipe (23b) and detects the temperature of the refrigerant discharged from the third compressor (23). The third suction temperature sensor (116) is provided in the third suction pipe (23a) and detects the temperature of the refrigerant sucked into the third compressor (23).

[0081] The liquid-side temperature sensor (117) is provided in the liquid-side flow path (40). Specifically, the liquid-side temperature sensor (117) is provided on the outflow side of the first flow path (28a) of the subcooling heat exchanger (28) in the liquid-side flow path (40). The liquid-side temperature sensor (117) detects the temperature of the refrigerant flowing out of the first flow path (28a).

[0082] The injection-side temperature sensor (118) is provided in the downstream flow path (45) of the injection flow path (43). In other words, the injection-side temperature sensor (118) is provided on the outflow side of the second flow path (28b) of the subcooling heat exchanger (28). The injection-side temperature sensor (118) detects the temperature of the refrigerant flowing out of the second flow path (28b).

[0083] The outdoor heat exchanger liquid-side temperature sensor (119) is provided in the heat transfer tube of the outdoor heat exchanger (24). The outdoor heat exchanger liquid-side temperature sensor (119) is provided on the liquid end portion of the outdoor heat exchanger (24). The outdoor heat exchanger liquid-side temperature sensor (119) detects the temperature of the refrigerant on the liquid end portion of the outdoor heat exchanger (24).

[0084] The outdoor heat exchanger gas-side temperature sensor (120) is provided in the heat transfer tube of the outdoor heat exchanger (24). The outdoor heat exchanger gas-side temperature sensor (120) is provided on the gas end portion of the outdoor heat exchanger (24). The outdoor heat exchanger gas-side temperature sensor (120) detects the temperature of the refrigerant on the gas end portion of the outdoor heat exchanger (24).

[0085] The indoor heat exchanger liquid-side temperature sensor (121) is provided in the heat transfer tube of the indoor heat exchanger (64). The indoor heat exchanger liquid-side temperature sensor (121) is provided on the liquid end portion of the indoor heat exchanger (64). The indoor heat exchanger liquid-side temperature sensor (121) detects the temperature of the refrigerant on the liquid end portion of the indoor heat exchanger (64). The indoor heat exchanger liquid-side temperature sensor (121) includes a first indoor heat exchanger liquid-side temperature sensor (121A) and a second indoor heat exchanger liquid-side temperature sensor (121B).

[0086] The first indoor heat exchanger liquid-side temperature sensor (121A) is associated with the first indoor heat exchanger (64A). The first indoor heat exchanger liquid-side temperature sensor (121A) is provided in the heat transfer tube of the first indoor heat exchanger (64A). The first indoor heat exchanger liquid-side temperature sensor (121A) is provided on the liquid end portion of the first indoor heat exchanger (64A). The first indoor heat exchanger liquid-side temperature sensor (121A) detects the temperature of the refrigerant on the liquid end portion of the first indoor heat exchanger (64A).

[0087] The second indoor heat exchanger liquid-side temperature sensor (121B) is associated with the second indoor heat exchanger (64B). The second indoor heat exchanger liquid-side temperature sensor (121B) is provided in the heat transfer tube of the second indoor heat exchanger (64B). The second indoor heat exchanger liquid-side temperature sensor (121B) is provided on the liquid end portion of the second indoor heat exchanger (64B). The second indoor heat exchanger liquid-side temperature sensor (121B) detects the temperature of the refrigerant on the liquid end portion of the second indoor heat exchanger (64B).

[0088] The indoor heat exchanger gas-side temperature sensor (122) is provided in the heat transfer tube of the indoor heat exchanger (64). The indoor heat exchanger gas-side temperature sensor (122) is provided on the gas end portion of the indoor heat exchanger (64). The indoor heat exchanger gas-side temperature sensor (122) detects the temperature of the refrigerant on the gas end portion of the indoor heat exchanger (64). The indoor heat exchanger gas-side temperature sensor (122) includes a first indoor heat exchanger gas-side temperature sensor (122A) and a second indoor heat exchanger gas-side temperature sensor (122B).

[0089] The first indoor heat exchanger gas-side temperature sensor (122A) is associated with the first indoor heat exchanger (64A). The first indoor heat exchanger gas-side temperature sensor (122A) is provided in the heat transfer tube of the first indoor heat exchanger (64A). The first indoor heat exchanger gas-side temperature sensor (122A) is provided on the gas end portion of the first indoor heat exchanger (64A). The first indoor heat exchanger gas-side temperature sensor (122A) detects the temperature of the refrigerant on the gas end portion of the first indoor heat exchanger (64A).

[0090] The second indoor heat exchanger gas-side temperature sensor (122B) is associated with the second indoor heat exchanger (64B). The second indoor heat exchanger gas-side temperature sensor (122B) is provided in the heat transfer tube of the second indoor heat exchanger (64B). The second indoor heat exchanger gas-side temperature sensor (122B) is provided on the gas end portion of the second indoor heat exchanger (64B). The second indoor heat exchanger gas-side temperature sensor (122B) detects the temperature of the refrigerant on the gas end portion of the second indoor heat exchanger (64B).

[0091] The air temperature sensor includes an outdoor air temperature sensor (123) and an indoor temperature sensor (124). The outdoor air temperature sensor (123) detects the temperature of outdoor air.

[0092] The indoor temperature sensor (124) detects the indoor temperature of the room in which the air conditioning unit (60) (the indoor heat exchanger (64)) is placed. The indoor temperature sensor (124) includes a first indoor temperature sensor (124A) and a second indoor temperature sensor (124B).

[0093] The first indoor temperature sensor (124A) detects the indoor temperature of the room in which the first air conditioning unit (60A) (the first indoor heat exchanger (64A)) is placed. The second indoor temperature sensor (124B) detects the indoor temperature of the room in which the second air conditioning unit (60B) (the second indoor heat exchanger (64B)) is placed.(7) Controller

[0094] FIG. 3 is a block diagram showing the connection relationship between a controller (130) as a control device and peripheral devices. The air conditioner (1) includes the controller (130). The controller (130) is an example of a control device. The controller (130) controls the refrigerant circuit (6). The controller (130) includes a microcomputer mounted on a control board and a memory device (specifically, a semiconductor memory) that stores software for operating the microcomputer.

[0095] As illustrated in FIG. 3, the controller (130) includes an outdoor controller (131), an indoor controller (132), and a refrigeration facility controller (133). As illustrated in FIG. 1, the outdoor controller (131) is provided in the heat source unit (10). The indoor controller (132) is provided in the air conditioning unit (60). The refrigeration facility controller (133) is provided in the refrigeration facility unit (70). The outdoor controller (131) can exchange communications with the indoor controller (132) and the refrigeration facility controller (133).

[0096] The indoor controller (132) includes a first indoor controller (132A) and a second indoor controller (132B) connected in parallel with each other. The first indoor controller (132A) is associated with the first air conditioning unit (60A). The second indoor controller (132B) is associated with the second air conditioning unit (60B).

[0097] The controller (130) receives control commands from the user and detection signals from the sensors. The controller (130) controls each device of the air conditioner (1). Specifically, the controller (130) controls ON / OFF of the first compressor (21), the second compressor (22), and the third compressor (23). The controller (130) adjusts the capacity (strictly, the number of rotations of each motor) of the first compressor (21), the second compressor (22), and the third compressor (23). The controller (130) controls ON / OFF of each fan. The controller (130) adjusts the opening degree of each expansion valve. The controller (130) switches opening and closing of each valve.(8) Heating Operation(8-1) Operation of Air Conditioner for Heating

[0098] The operation of the air conditioner (1) will be described. The operation of the air conditioner (1) includes a refrigeration facility operation, a cooling operation, a cooling and refrigeration facility operation, a heating operation, a heating and refrigeration facility operation, and a defrosting operation. In this example, only the heating operation will be described. In the heating operation, the refrigeration facility unit (70) is stopped, and the air conditioning unit (60) heats the indoor space. The flow of the refrigerant in the heating operation is shown by the bold line in FIG. 1.

[0099] As shown in FIG. 1, in the heating operation, the controller (130) controls the on-off valves in the switching flow paths (31 to 34) in order to close the second switching flow path (32) and the third switching flow path (33) and to open the first switching flow path (31) and the fourth switching flow path (34).

[0100] The controller (130) stops the first compressor (21), and operates the second compressor (22) and the third compressor (23). The controller (130) opens the second outdoor expansion valve (27) and the injection valve (46) at predetermined opening degrees, and closes the first outdoor expansion valve (26). The controller (130) closes the refrigeration facility expansion valve (73) and opens the indoor expansion valve (63). The controller (130) operates the outdoor fan (12) and the indoor fan (62), and stops the refrigeration facility fan (72).

[0101] In the heating operation, the refrigeration cycle is performed in which the indoor heat exchanger (64) functions as a radiator, the outdoor heat exchanger (24) functions as an evaporator, and the function of the refrigeration facility heat exchanger (74) is substantially stopped.

[0102] Specifically, the refrigerant compressed by the second compressor (22) is cooled in the intercooler (29), and then is sucked into the third compressor (23). The refrigerant compressed by the third compressor (23) is sent to the air conditioning unit (60).

[0103] The refrigerant sent to the air conditioning unit (60) dissipates heat in the indoor heat exchanger (64). As a result, the indoor air is heated. The refrigerant having dissipated heat in the indoor heat exchanger (64) flows into the gas-liquid separator (25). In the gas-liquid separator (25), the refrigerant is separated into a gas refrigerant and a liquid refrigerant.

[0104] The liquid refrigerant separated in the gas-liquid separator (25) is cooled in the subcooling heat exchanger (28) by the refrigerant flowing through the injection flow path (43). The refrigerant in the injection flow path (43) is sent to the intermediate flow path (18).

[0105] The refrigerant having been cooled by the subcooling heat exchanger (28) is decompressed by the second outdoor expansion valve (27) and then evaporates in the outdoor heat exchanger (24). The refrigerant having evaporated in the outdoor heat exchanger (24) is sucked into and compressed again in the second compressor (22).(8-2) Components of Air Conditioner for Heating

[0106] In the heating operation, the refrigerant circuit (6) includes the second compressor (22) of the compressor (20), the third compressor (23) of the compressor (20), the indoor heat exchanger (64) as a radiator, the indoor expansion valve (63) as an expansion valve, and the outdoor heat exchanger (24) as an evaporator.

[0107] The air conditioning unit (60) as the utilization unit includes the first air conditioning unit (60A) as the first utilization unit, and the second air conditioning unit (60B) as the second utilization unit. The first air conditioning unit (60A) and the second air conditioning unit (60B) are connected in parallel with each other.

[0108] The indoor heat exchanger (64) as a radiator includes the first indoor heat exchanger (64A) as the first radiator, and the second indoor heat exchanger (64B) as the second radiator. The first indoor heat exchanger (64A) and the second indoor heat exchanger (64B) are connected in parallel with each other.

[0109] The indoor expansion valve (63) as an expansion valve includes the first indoor expansion valve (63A) as the first expansion valve associated with the first indoor heat exchanger (64A), and the second indoor expansion valve (63B) as the second expansion valve associated with the second indoor heat exchanger (64B). The first indoor expansion valve (63A) and the second indoor expansion valve (63B) are connected in parallel with each other.

[0110] The indoor fan (62) as a fan includes the first indoor fan (62A) as the first fan associated with the first indoor heat exchanger (64A), and the second indoor fan (62B) as the second fan associated with the second indoor heat exchanger (64B). The first indoor fan (62A) and the second indoor fan (62B) are connected in parallel with each other.

[0111] The indoor heat exchanger (64) as a radiator, the indoor expansion valve (63) as an expansion valve, and the indoor fans (62) as a fan compose the air conditioning unit (60) as a utilization unit.

[0112] The first indoor heat exchanger (64A) as the first radiator, the first indoor expansion valve (63A) as the first expansion valve, and the first indoor fan (62A) as the first fan compose the first air conditioning unit (60A) as the first utilization unit.

[0113] The second indoor heat exchanger (64B) as the second radiator, the second indoor expansion valve (63B) as the second expansion valve, and the second indoor fan (62B) as the second fan compose the second air conditioning unit (60B) as the second utilization unit.

[0114] The refrigerant circuit (6) includes the gas-liquid separator (25), the venting pipe (41) as a venting passage, and the venting valve (42) as an on-off valve.

[0115] In the heating operation, the gas-liquid separator (25) is connected with the downstream side of the indoor heat exchanger (64). The gas-liquid separator (25) separates the refrigerant into a gas refrigerant and a liquid refrigerant. The gas reservoir (25a) and the liquid reservoir (25b) are formed in the gas-liquid separator (25). The gas reservoir (25a) is disposed on the top portion of the gas-liquid separator (25), and stores the gas refrigerant. The liquid reservoir (25b) is disposed on the bottom portion of the gas-liquid separator (25), and stores the liquid refrigerant.

[0116] One end of the venting pipe (41) is connected to the gas reservoir (25a) of the gas-liquid separator (25). The other end of the venting pipe (41) is connected to the intermediate flow path (18). The intermediate flow path (18) is connected to the third suction pipe (23a) that is placed on the suction side (20i) of the third compressor (23) of the compressor (20).

[0117] The venting pipe (41) connects the gas reservoir (25a) of the gas-liquid separator (25) with the third suction pipe (23a) that is placed on the suction side (20i) of the third compressor (23) of the compressor (20) via the intermediate flow path (18). The venting valve (42) is provided in the venting pipe (41).

[0118] The high-pressure sensor (101) detects the high pressure in the refrigerant circuit (6). The high pressure of the refrigerant circuit (6) is also the pressure of the refrigerant on the discharge side of the third compressor (23).

[0119] The indoor heat exchanger liquid-side temperature sensor (121) detects the temperature of the refrigerant on the liquid end portion of the indoor heat exchanger (64). In the heating operation, the indoor heat exchanger liquid-side temperature sensor (121) detects the outlet refrigerant temperature (TE) as the temperature of the refrigerant at the outlet (E) of the indoor heat exchanger (64). The indoor heat exchanger liquid-side temperature sensor (121) includes the first indoor heat exchanger liquid-side temperature sensor (121A) and the second indoor heat exchanger liquid-side temperature sensor (121B).

[0120] The first indoor heat exchanger liquid-side temperature sensor (121A) detects the temperature of the refrigerant on the liquid end portion of the first indoor heat exchanger (64A). In the heating operation, the first indoor heat exchanger liquid-side temperature sensor (121A) detects the first outlet refrigerant temperature (TEA) as the temperature of the refrigerant at the first outlet (EA) of the first indoor heat exchanger (64A). The first outlet refrigerant temperature (TEA) is associated with the first indoor heat exchanger (64A). The second indoor heat exchanger liquid-side temperature sensor (121B) detects the temperature of the refrigerant on the liquid end portion of the second indoor heat exchanger (64B). In the heating operation, the second indoor heat exchanger liquid-side temperature sensor (121B) detects the second outlet refrigerant temperature (TEB) as the temperature of the refrigerant at the second outlet (EB) of the second indoor heat exchanger (64B). The second outlet refrigerant temperature (TEB) is associated with the second indoor heat exchanger (64B).

[0121] The indoor heat exchanger gas-side temperature sensor (122) detects the temperature of the refrigerant on the gas end portion of the indoor heat exchanger (64). In the heating operation, the indoor heat exchanger gas-side temperature sensor (122) detects the inlet refrigerant temperature (TI) as the temperature of the refrigerant at the inlet (I) of the indoor heat exchanger (64). The indoor heat exchanger gas-side temperature sensor (122) includes the first indoor heat exchanger gas-side temperature sensor (122A) and the second indoor heat exchanger gas-side temperature sensor (122B).

[0122] The first indoor heat exchanger gas-side temperature sensor (122A) detects the temperature of the refrigerant on the gas end portion of the first indoor heat exchanger (64A). In the heating operation, the first indoor heat exchanger gas-side temperature sensor (122A) detects the first inlet refrigerant temperature (TIA) as the temperature of the refrigerant at the first inlet (IA) of the first indoor heat exchanger (64A). The first inlet refrigerant temperature (TIA) is associated with the first indoor heat exchanger (64A). The second indoor heat exchanger gas-side temperature sensor (122B) detects the temperature of the refrigerant on the gas end portion of the second indoor heat exchanger (64B). In the heating operation, the second indoor heat exchanger gas-side temperature sensor (122B) detects the second inlet refrigerant temperature (TIB) as the temperature of the refrigerant at the second inlet (IB) of the second indoor heat exchanger (64B). The second inlet refrigerant temperature (TIB) is associated with the second indoor heat exchanger (64B).

[0123] The indoor temperature sensor (124) detects the indoor temperature (TR) of the indoor space (RA) as a utilization-side space in which the air conditioning unit (60) (the indoor heat exchanger (64)) is placed. The indoor space (R) is an example of a utilization-side space. The indoor space (R) is associated with the air conditioning unit (60).

[0124] The indoor space (R) includes the first indoor space (RA) as the first utilization-side space and the second indoor space (RB) as the second utilization-side space. The first indoor space (RA) is an example of the first utilization-side space. The first indoor space (RA) is associated with the first air conditioning unit (60A). The second indoor space (RB) is an example of the second utilization-side space. The second indoor space (RB) is associated with the second air conditioning unit (60B).

[0125] The indoor temperature sensor (124) includes a first indoor temperature sensor (124A) and a second indoor temperature sensor (124B). The first indoor temperature sensor (124A) detects the first indoor temperature (TRA) in the first indoor space (RA) in which the first air conditioning unit (60A) (the first indoor heat exchanger (64A)) is placed. The first indoor temperature (TRA) is associated with the first indoor heat exchanger (64A). The second indoor temperature sensor (124B) detects the second indoor temperature (TRB) in the second indoor space (RB) in which the second air conditioning unit (60B) (the second indoor heat exchanger (64B)) is placed. The second indoor temperature (TRB) is associated with the second indoor heat exchanger (64B).

[0126] The receiver pressure sensor (105) detects a receiver pressure (Pd) as a pressure of the gas-liquid separator (25).(9) Supercritical Operation

[0127] FIG. 4 is a graph showing the relationship between the specific enthalpy (h) and the pressure (P) of a refrigerant. FIG. 4 is also referred to as a P-h diagram. The refrigerant circulating in the refrigerant circuit (6) is carbon dioxide. The critical pressure (Pc) of carbon dioxide as a refrigerant at the critical point (C) is lower than those of other natural refrigerants, and specifically, is 7.38 [MPa] in absolute pressure. The critical temperature (Tc) of carbon dioxide as a refrigerant at the critical point (C) is 31.1 [°C]. The critical specific enthalpy (hc) of carbon dioxide as a refrigerant at the critical point (C) is about 330 [kJ / kg]. The critical pressure (Pc), the critical temperature (Tc), and the critical specific enthalpy (hc) are associated with each other.

[0128] The refrigerant circuit (6) performs the refrigeration cycle for executing the heating operation of heating the indoor space (R) as the utilization-side space by compressing the refrigerant to the critical pressure (Pc) or more.

[0129] The refrigerant circuit (6) performs supercritical operation. The high pressure (Ph) of the refrigerant circuit (6) becomes the critical pressure (Pc) or more.

[0130] If the refrigerant is compressed to the critical pressure (Pc) or more, in other words, if the high pressure (Ph) of the refrigerant circuit (6) becomes the critical pressure (Pc) or more, the condensing temperature of the refrigerant does not exist in the area of the critical pressure (Pc) or more, and thus it is difficult to control the temperature of the refrigerant.

[0131] If the specific enthalpy (h) of the refrigerant is smaller, the ratio of liquid in the refrigerant is higher and the ratio of gas in the refrigerant is lower. If the specific enthalpy (h) of the refrigerant is larger, the ratio of liquid in the refrigerant is lower and the ratio of gas in the refrigerant is higher.

[0132] As shown in FIG. 4, the outlet specific enthalpy (he) of the refrigerant at the outlet (E) of the indoor heat exchanger (64) is smaller than the critical specific enthalpy (hc) of the refrigerant at the critical point (C). At the outlet (E) of the indoor heat exchanger (64), the ratio of liquid in the refrigerant is larger and the ratio of gas in the refrigerant is smaller than at the critical point (C).(10) Stop Mode

[0133] The controller (130) executes a stop mode (M1) and an operating mode (M2) for the first air conditioning unit (60A) and the second air conditioning unit (60B). Specifically, the stop mode (M1) is a thermo-off mode. In this example, the first air conditioning unit (60A) is in the stop mode (M1) and the second air conditioning unit (60B) is in the operating mode (M2). FIG. 5 is a piping system diagram where the first air conditioning unit (60A) is in the stop mode (M1) and the second air conditioning unit (60B) is in the operating mode (M2).

[0134] The thickness of the solid line in FIG. 5 indicates the flow rate, in other words, the opening degree of the first indoor expansion valve (63A) and the opening degree of the second indoor expansion valve (63B). The upper part of FIG. 5 shows the first state (J1) described later, and the lower part of FIG. 5 shows the second state (J2) described later.

[0135] The controller (130) sets the opening degree of the first indoor expansion valve (63A) smaller than the opening degree of the second indoor expansion valve (63B) if the first air conditioning unit (60A) is in the stop mode (M1) and the second air conditioning unit (60B) is in the operating mode (M2). The opening degree of the second indoor expansion valve (63B) in the operating mode (M2) is the fully opened degree (100%), for example. The opening degree of the first indoor expansion valve (63A) in the stop mode (M1) will be described later.

[0136] If the first air conditioning unit (60A) is in the stop mode (M1), the controller (130) controls the first indoor expansion valve (63A) to switch the first state (J1) and the second state (J2). In the first state (J1), the first indoor expansion valve (63A) is fully closed (0%). In the second state (J2), the first indoor expansion valve (63A) is more opened than in the first state (J1). However, the opening degree of the first indoor expansion valve (63A) in the second state (J2) is larger than the opening degree of the second indoor expansion valve (63B) in the operating mode (M2). The opening degree of the first indoor expansion valve (63A) in the second state (J2) is about several percent, for example.

[0137] In the operating mode (M2), the second indoor fan (62B) is operated. In the stop mode (M1), the first indoor fan (62A) is stopped, or operated under lower load than in the operating mode (M2).

[0138] If the first indoor expansion valve (63A) is in the first state (J1) (fully closed), the liquid refrigerant accumulates in the first indoor heat exchanger (64A), and thus the first indoor expansion valve (63A) is in the second state (J2) when the stop mode (M1) starts.

[0139] On the other hand, if the first indoor expansion valve (63A) is in the second state (J2), the receiver pressure (Pd) of the gas-liquid separator (25) rises. The receiver pressure (Pd) of the gas-liquid separator (25) rises in the second state (J2) because the air conditioner (1) performs the supercritical operation.

[0140] Thus, the controller (130) switches the first indoor expansion valve (63A) from the second state (J2) to the first state (J1) based on the rise in the receiver pressure (Pd) as the pressure of the gas-liquid separator (25). As will be described later, the rise in the receiver pressure (Pd) of the gas-liquid separator (25) may be measured directly by the receiver pressure sensor (105) or may be determined indirectly by another means.

[0141] The controller (130) switches the first indoor expansion valve (63A) from the second state (J2) to the first state (J1) if the difference between the first inlet refrigerant temperature (TIA) of the refrigerant at the inlet (IA) of the first indoor heat exchanger (64A) and the first outlet refrigerant temperature (TEA) of the refrigerant at the first outlet (EA) of the first indoor heat exchanger (64A) is larger than the first value (Q1). That difference is obtained by subtracting the first outlet refrigerant temperature (TEA) from the first inlet refrigerant temperature (TIA). The first value (Q1) is about several degrees Celsius, for example.

[0142] Or, the controller (130) switches the first indoor expansion valve (63A) from the second state (J2) to the first state (J1) if the first outlet refrigerant temperature (TEA) of the refrigerant at the first outlet (EA) of the first indoor heat exchanger (64A) rises as time passes. A possible example of this case is that the first outlet refrigerant temperature (TEA) rises by about several degrees Celsius as the time of about several seconds to several minutes passes.

[0143] Alternatively, the controller (130) switches the first indoor expansion valve (63A) from the second state (J2) to the first state (J1) if the duration of the second state (J2) is longer than the second value (Q2). The second value (Q2) is about several seconds to several minutes, for example.

[0144] Alternatively, the controller (130) may switch the first indoor expansion valve (63A) from the second state (J2) to the first state (J1) if the receiver pressure (Pd) of the gas-liquid separator (25) measured by the receiver pressure sensor (105) rises beyond the threshold or if the receiver pressure (Pd) of the gas-liquid separator (25) measured by the receiver pressure sensor (105) rises as time passes (for example, if the pressure rises by about several pascals as the time of about several seconds to several minutes passes).

[0145] The controller (130) switches the first indoor expansion valve (63A) from the first state (J1) to the second state (J2) if the liquid refrigerant accumulates in the first indoor heat exchanger (64A).

[0146] Specifically, the controller (130) switches the first indoor expansion valve (63A) from the first state (J1) to the second state (J2) if the first inlet refrigerant temperature (TIA) of the refrigerant at the inlet (IA) of the first indoor heat exchanger (64A) is lower than the critical temperature (Tc) of the refrigerant at the critical point (C).

[0147] Or, the controller (130) switches the first indoor expansion valve (63A) from the first state (J1) to the second state (J2) if the difference between the first inlet refrigerant temperature (TIA) of the refrigerant at the inlet (IA) of the first indoor heat exchanger (64A) and the first outlet refrigerant temperature (TEA) of the refrigerant at the first outlet (EA) of the first indoor heat exchanger (64A) is smaller than the third value (Q3). That difference is obtained by subtracting the first outlet refrigerant temperature (TEA) from the first inlet refrigerant temperature (TIA). The third value (Q3) is about several degrees Celsius, for example.

[0148] Or, the controller (130) switches the first indoor expansion valve (63A) from the first state (J1) to the second state (J2) if the difference between the first inlet refrigerant temperature (TIA) of the refrigerant at the inlet (IA) of the first indoor heat exchanger (64A) and the first indoor temperature (TRA) of the first indoor space (RA) (the first utilization-side space) of the first air conditioning unit (60A) (the first utilization unit) is smaller than the fourth value (Q4). That difference is obtained by subtracting the first indoor temperature (TRA) from the first inlet refrigerant temperature (TIA). The fourth value (Q4) is about several degrees Celsius, for example.

[0149] Or, the controller (130) switches the first indoor expansion valve (63A) from the first state (J1) to the second state (J2) if the duration of the first state (J1) is longer than a fifth value (Q5). The fifth value (Q5) is about several seconds to several minutes, for example.(11) Start-up of Heating Operation

[0150] The start-up of the heating operation of the air conditioner (1) will be described. Only the description of the start-up of the heating operation of the first air conditioning unit (60A) will be presented, and the description of the start-up of the heating operation of the second air conditioning unit (60B) will be omitted.

[0151] The controller (130) executes a start-up mode (M3) for the first air conditioning unit (60A). In the start-up mode (M3), the controller (130) starts up the heating operation while the first indoor fan (62A) of the first air conditioning unit (60A) is stopped. In the start-up mode (M3), the controller (130) activates the first indoor fan (62A) if the first outlet refrigerant temperature (TEA) of the refrigerant at the first outlet (EA) of the first indoor heat exchanger (64A) becomes larger than the critical temperature (Tc) of the refrigerant at the critical point (C) after the heating operation starts up.

[0152] In the start-up mode (M3), the controller (130) opens the venting valve (42) of the venting pipe (41) when the heating operation starts up. "Opening the venting valve (42)" includes not only newly opening the venting valve (42) of which the opening degree is zero but also further increasing the opening degree of the venting valve (42) that has been opened.

[0153] The same applies to the start-up of the second air conditioning unit (60B).(12) Control Flow

[0154] FIG. 6 is a control flowchart of the first air conditioning unit (60A). The process begins from the start, and in the first step (S1), the first air conditioning unit (60A) starts the start-up mode (M3) in response to a heating operation start command from the user to the controller (130).

[0155] In the second step (S2), the controller (130) starts up the heating operation while the first indoor fan (62A) of the first air conditioning unit (60A) is stopped. Specifically, the controller (130) operates the second compressor (22) and the third compressor (23). The controller (130) opens the first indoor expansion valve (63A). At this time, the first indoor expansion valve (63A) is fully opened (100%), for example. At this time, the first indoor fan (62A) remains stopped. At this time, the venting valve (42) of the venting pipe (41) remains closed.

[0156] In the third step (S3), the controller (130) determines whether the first outlet refrigerant temperature (TEA) of the refrigerant at the first outlet (EA) of the first indoor heat exchanger (64A) is higher than the critical temperature (Tc) of the refrigerant at the critical point (C). If it is determined that the first outlet refrigerant temperature (TEA) is higher than the critical temperature (Tc), the process proceeds to the fourth step (S4). Otherwise, the process returns to the second step (S2).

[0157] In the fourth step (S4), the controller (130) opens the venting valve (42) of the venting pipe (41).

[0158] In the fifth step (S5), the first air conditioning unit (60A) switches to the operating mode (M2).

[0159] In the sixth step (S6), the first air conditioning unit (60A) starts the stop mode (M1) (the thermo-off mode) in response to a stop command (a thermo-off command) from the user to the controller (130).

[0160] In the seventh step (S7), the first indoor expansion valve (63A) is switched to the second state (J2). Specifically, the opening degree of the first indoor expansion valve (63A) is reduced to about several percent, for example.

[0161] In the eighth step (S8), the controller (130) determines a rise in the receiver pressure (Pd) of the gas-liquid separator (25). Specifically, the controller (130) determines whether any of the following conditions is satisfied: the difference between the first inlet refrigerant temperature (TIA) and the first outlet refrigerant temperature (TEA) is larger than the first value (Q1); or the first outlet refrigerant temperature (TEA) rises as time passes; or the duration of the second state (J2) is longer than the second value (Q2).

[0162] Alternatively, the controller (130) may determine whether any of the following conditions is satisfied: the receiver pressure (Pd) of the gas-liquid separator (25) rises beyond the threshold; or the receiver pressure (Pd) of the gas-liquid separator (25) rises as time passes.

[0163] If any of the above conditions is satisfied, the process proceeds to the ninth step (S9). If none of the above conditions is satisfied, the process returns to the seventh step (S7).

[0164] In the ninth step (S9), the first indoor expansion valve (63A) is switched to the first state (J1). Specifically, the opening degree of the first indoor expansion valve (63A) is the fully closed degree (0%).

[0165] In the tenth step (S10), the controller (130) determines whether the liquid refrigerant accumulates in the first indoor heat exchanger (64A).

[0166] Specifically, the controller (130) determines whether any of the following conditions is satisfied: the first inlet refrigerant temperature (TIA) is lower than the critical temperature (Tc); or the difference between the first inlet refrigerant temperature (TIA) and the first outlet refrigerant temperature (TEA) is smaller than the third value (Q3); or the difference between the first inlet refrigerant temperature (TIA) and the first indoor temperature (TRA) is smaller than the fourth value (Q4); or the duration of the first state (J1) is longer than the fifth value (Q5).

[0167] If any of the above conditions is satisfied, the process returns to the seventh step (S7). If none of the above conditions is satisfied, the process proceeds to the eleventh step (S11).

[0168] In the eleventh step (S11), whether an operation stop command from the user is present is determined. If the operation stop command is present, the process proceeds to the twelfth step (S12). If no operation stop command is present, the process returns to the seventh step (S7).

[0169] In the twelfth step (S12), the controller (130) stops the operation of the first air conditioning unit (60A). Then, the process ends.

[0170] In the stop mode (M1), the seventh step (S7) (the second state (J2)) and the ninth step (S9) (the first state (J1)) are repeated.

[0171] The controller (130) may return to the fifth step (S5), based on an operating mode switch command from the user.

[0172] The controller (130) may automatically execute each operation regardless of each command from the user.(Advantages)

[0173] According to this embodiment, it is possible for the multi-type air conditioner (1) that performs the supercritical operation to stop the first air conditioning unit (60A) among the first air conditioning unit (60A) and the second air conditioning unit (60B).

[0174] By switching the first indoor expansion valve (63A) of the first air conditioning unit (60A) from the second state (J2) to the first state (J1) to throttle the first indoor expansion valve (63A) of the first air conditioning unit (60A), it is possible to reduce a rise in the pressure of the refrigerant at the downstream side of the indoor heat exchanger (64) of the air conditioning unit (60). In particular, it is possible to reduce a rise in the receiver pressure (Pd) of the gas-liquid separator (25) located downstream of the indoor heat exchanger (64) of the air conditioning unit (60).

[0175] By switching the first indoor expansion valve (63A) of the first air conditioning unit (60A) from the first state (J1) to the second state (J2) to open the first indoor expansion valve (63A) of the first air conditioning unit (60A), it is possible reduce accumulation of the liquid refrigerant in the first indoor heat exchanger (64A) of the first air conditioning unit (60A).

[0176] By switching the first indoor expansion valve (63A) of the first air conditioning unit (60A) from the second state (J2) to the first state (J1) to throttle the first indoor expansion valve (63A) of the first air conditioning unit (60A) when the receiver pressure (Pd) of the gas-liquid separator (25) located downstream of the indoor heat exchanger (64) of the air conditioning unit (60) rises, it is possible to reduce a rise in the receiver pressure (Pd) of the gas-liquid separator (25).

[0177] Without measuring the receiver pressure (Pd) of the gas-liquid separator (25) directly, it is possible to switch the first indoor expansion valve (63A) of the first air conditioning unit (60A) from the second state (J2) to the first state (J1) at the time when the receiver pressure (Pd) of the gas-liquid separator (25) rises.

[0178] It is possible to stop the first air conditioning unit (60A) while the second air conditioning unit (60B) is in operation.

[0179] In the first air conditioning unit (60A), the first indoor fan (62A) is not activated until the first outlet refrigerant temperature (TEA) at the first outlet (EA) of the first indoor heat exchanger (64A) rises beyond the critical temperature (Tc) of the refrigerant at the critical point (C). Accordingly, it is possible to reduce an excessive increase in the high pressure (Ph) generated by the compressor (20) immediately after the heating operation starts up.

[0180] By promoting the gas refrigerant flowing from the gas reservoir (25a) of the gas-liquid separator (25) to the suction side (20i) of the compressor (20) when the heating operation starts up, it is possible to accelerate a rise in the high pressure (Ph) generated by the compressor (20).

[0181] Employment of carbon dioxide as a refrigerant is advantageous in terms of protection of the environment.<Second Embodiment>

[0182] An air conditioner (1) according to a second embodiment will be described. In the following description, the same components as those of the above embodiment are denoted by the same reference numerals, and their detailed descriptions are omitted. FIG. 7 is a piping system diagram according to the second embodiment where the first air conditioning unit (60A) is in the stop mode (M1) and the second air conditioning unit (60B) is in the operating mode (M2).

[0183] In the first state (J1), the first indoor expansion valve (63A) is not fully closed but opened to a minute opening degree. However, the minute opening degree of the first indoor expansion valve (63A) in the first state (J1) is smaller than the opening degree of the first indoor expansion valve (63A) in the second state (J2). In other words, the opening degree of the first indoor expansion valve (63A) in the second state (J2) is larger than the minute opening degree of the first indoor expansion valve (63A) in the first state (J1). In the second state (J2), the first indoor expansion valve (63A) is more opened than in the first state (J1). The minute opening degree of the first indoor expansion valve (63A) in the first state (J1) is several percent or less, for example.

[0184] The other configurations are similar to those of the first embodiment. This embodiment provides the same advantages as those of the first embodiment.<Other Embodiments>

[0185] The compressor may be a single compressor (for a single-stage operation).

[0186] The number of the indoor heat exchanger (64) as a radiator may be three or more.

[0187] The air conditioner (1) may be configured without the refrigeration facility unit (70).

[0188] The refrigerant is not necessarily carbon dioxide.

[0189] The refrigeration facility unit (70) may be employed as the whole or part of the first utilization unit and the second utilization unit.

[0190] While the embodiments and variations thereof have been described above, it will be understood that various changes in form and details may be made without departing from the spirit and scope of the claims. The elements according to the embodiments, the variations thereof, and the other embodiments may be combined and replaced with each other.

[0191] The expressions of "first," "second," "third," . . . described above are used to distinguish the terms to which these expressions are given, and do not limit the number and order of the terms.DESCRIPTION OF REFERENCE CHARACTERS

[0192] 1Air Conditioner 6Refrigerant Circuit 20Compressor 20iSuction Side 24Outdoor Heat Exchanger (Evaporator) 25Gas-Liquid Separator 25aGas Reservoir 41Venting Pipe (Venting Passage) 42Venting Valve (On-off Valve) 60AFirst Air Conditioning Unit (First Utilization Unit) 60BSecond Air Conditioning Unit (Second Utilization Unit) 62AFirst Indoor Fan (Fan) 63Indoor Expansion Valve (Expansion Valve) 63AFirst Indoor Expansion Valve (First Expansion Valve) 63BSecond Indoor Expansion Valve (Second Expansion Valve) 64Indoor Heat Exchanger (Radiator) 64AFirst Indoor Heat Exchanger (First Radiator) 64BSecond Indoor Heat Exchanger (Second Radiator) 130Control Device CCritical Point PcCritical Pressure TcCritical Temperature (Temperature) RIndoor Space (Utilization-Side Space) RAFirst Indoor Space (Utilization-Side Space) PdReceiver Pressure (Pressure) IAFirst Inlet (Inlet) TIAFirst Inlet Refrigerant Temperature (Temperature) EAFirst Outlet (Outlet) TEAFirst Outlet Refrigerant Temperature (Temperature) Q1First Value Q2Second Value Q3Third Value Q4Fourth Value Q5Fifth Value M1Stop Mode M2Operating Mode J1First State J2Second State

Claims

1. An air conditioner comprising: a refrigerant circuit (6) including a compressor (20), a radiator (64), an expansion valve (63), and an evaporator (24), and configured to perform a refrigeration cycle for executing a heating operation of heating a utilization-side space (R) by compressing a refrigerant to a critical pressure (Pc) or more; and a control device (130) configured to control the refrigerant circuit (6), wherein the radiator (64) includes a first radiator (64A) and a second radiator (64B) connected in parallel with each other, the expansion valve (63) includes a first expansion valve (63A) associated with the first radiator (64A), and a second expansion valve (63B) associated with the second radiator (64B), the first radiator (64A) and the first expansion valve (63A) form a first utilization unit (60A), the second radiator (64B) and the second expansion valve (63B) form a second utilization unit (60B), and if the first utilization unit (60A) is in a stop mode (M1), the control device (130) controls the first expansion valve (63A) to switch a first state (J1) in which the first expansion valve (63A) is fully closed or opened to a minute opening degree and a second state (J2) in which the first expansion valve (63A) is more opened than in the first state (J1).

2. The air conditioner of claim 1, wherein the refrigerant circuit (6) includes a gas-liquid separator (25) connected to a downstream side of the radiator (64) and configured to separate the refrigerant into a gas refrigerant and a liquid refrigerant, and the control device (130) switches the first expansion valve (63A) from the second state (J2) to the first state (J1) based on a rise in a pressure (Pd) of the gas-liquid separator (25).

3. The air conditioner of claim 2, wherein the control device (130) switches the first expansion valve (63A) from the second state (J2) to the first state (J1) if a difference between a temperature (TIA) of the refrigerant at an inlet (IA) of the first radiator (64A) and a temperature (TEA) of the refrigerant at an outlet (EA) of the first radiator (64A) is larger than a first value (Q1), or if the temperature (TEA) of the refrigerant at the outlet (EA) of the first radiator (64A) rises as time passes.

4. The air conditioner of claim 2, wherein the control device (130) switches the first expansion valve (63A) from the second state (J2) to the first state (J1) if a duration of the second state (J2) is longer than a second value (Q2).

5. The air conditioner of any one of claims 1 to 4, wherein the control device (130) switches the first expansion valve (63A) from the first state (J1) to the second state (J2) if the temperature (TIA) of the refrigerant at the inlet (IA) of the first radiator (64A) is lower than a temperature (Tc) of the refrigerant at a critical point (C), or if the difference between the temperature (TIA) of the refrigerant at the inlet (IA) of the first radiator (64A) and the temperature (TEA) of the refrigerant at the outlet (EA) of the first radiator (64A) is smaller than a third value (Q3), or if a difference between the temperature (TIA) of the refrigerant at the inlet (IA) of the first radiator (64A) and a temperature (TRA) of the utilization-side space (RA) of the first utilization unit (60A) is smaller than a fourth value (Q4), or if a duration of the first state (J1) is longer than a fifth value (Q5).

6. The air conditioner of any one of claims 1 to 5, wherein the control device (130) sets an opening degree of the first expansion valve (63A) smaller than an opening degree of the second expansion valve (63B) if the first utilization unit (60A) is in the stop mode (M1) and the second utilization unit (60B) is in an operating mode (M2).

7. The air conditioner of any one of claims 1 to 6, wherein the control device (130) starts up the heating operation while a fan (62A) of the first utilization unit (60A) is stopped, and the control device (130) activates the fan (62A) if the temperature (TEA) of the refrigerant at the outlet (EA) of the first radiator (64A) rises beyond the temperature (Tc) of the refrigerant at the critical point (C) after the heating operation starts up.

8. The air conditioner of claim 7, wherein the refrigerant circuit (6) includes: the gas-liquid separator (25) connected to the downstream side of the radiator (64) and configured to separate the refrigerant into a gas refrigerant and a liquid refrigerant; a venting passage (41) connecting a gas reservoir (25a) of the gas-liquid separator (25) with a suction side (20i) of the compressor (20); and an on-off valve (42) provided in the venting passage (41), and the control device (130) opens the on-off valve (42) when the heating operation starts up.

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