JP7481639B2 - Heat source unit and refrigeration device - Google Patents

Description

This disclosure relates to a heat source unit and a refrigeration device.

The refrigeration device of Patent Document 1 has a refrigerant circuit equipped with a flow path switching mechanism. As shown in FIG. 6 of the document, the flow path switching mechanism has four flow paths. Each of the four flow paths has multiple on-off valves arranged in parallel.

Patent Publication No. 6984046

As described in Patent Document 1, if multiple on-off valves are provided in each of the four flow paths, the structure of the flow path switching mechanism becomes complex.

The purpose of this disclosure is to simplify the flow path switching mechanism.

The first aspect is a heat source unit including a compression section (20), a flow path switching mechanism (30), and a heat source side heat exchanger (24), and configured to form a refrigerant circuit (6) by being connected to a first utilization side heat exchanger (64) and a second utilization side heat exchanger (74),
The compression section (20) includes a first compression element (21) and a second compression element (22) arranged in parallel with each other,
a suction portion of the first compression element (21) is connected to a gas end portion of the second utilization side heat exchanger (74);
The flow path switching mechanism (30)
a first port (P1) connected to a discharge portion of the first compression element (21) and a discharge portion of the second compression element (22);
a second port (P2) connected to a suction portion of the second compression element (22);
a third port (P3) connected to a gas end of the first utilization side heat exchanger (64);
a fourth port (P4) connected to a gas end of the heat source side heat exchanger (24);
a first flow path (31) communicating between the first port (P1) and the third port (P3);
a second flow path (32) communicating between the first port (P1) and the fourth port (P4);
a third flow path (33) communicating between the second port (P2) and the third port (P3);
a fourth flow path (34) communicating between the second port (P2) and the fourth port (P4), and configured to open and close each of the first flow path (31), the second flow path (32), the third flow path (33), and the fourth flow path (34),
two or more on-off valves (V) are provided in parallel in each of the first flow path (31) and the second flow path (32);
At least one of the third flow path (33) and the fourth flow path (34) is provided with an on-off valve (V).

In the first embodiment, at least one of the third flow path (33) and the fourth flow path (34) is provided with a single on-off valve. This simplifies the flow path switching mechanism (30).

The refrigerant discharged from both the first compression element (21) and the second compression element (22) flows through the first flow path (31) and the second flow path (32). In contrast, the refrigerant drawn into the first compression element (21) does not flow through the third flow path (33) and the fourth flow path (34), but the refrigerant drawn into the second compression element (22) flows through them. Therefore, the flow rate of the refrigerant flowing through the third flow path (33) and the fourth flow path (34) is smaller than the flow rate of the refrigerant flowing through the first flow path (31) and the second flow path (32). Therefore, even if the number of opening and closing valves (V) in the third flow path (33) and the fourth flow path (34) is one, it is possible to prevent the pressure loss in the third flow path (33) and the fourth flow path (34) from increasing significantly. Therefore, it is possible to prevent the efficiency of the refrigeration cycle from decreasing due to the pressure loss in the refrigerant circuit (6).

In the second aspect, in the first aspect, one on-off valve (V) is provided in the fourth flow path (34).

In the second embodiment, the number of on-off valves (V) in the fourth flow path (34) is one. In the refrigerant circuit (6), the refrigerant evaporated in the second utilization side heat exchanger (74) is sucked into the first compression element (21), and the refrigerant evaporated in the heat source side heat exchanger (24) is sucked into the second compression element (22). In this operation, the second utilization side heat exchanger (74) becomes a heat input source in addition to the heat source side heat exchanger (24), so that the flow rate of the refrigerant flowing through the heat source side heat exchanger (24) and further through the fourth flow path (34) is reduced. Therefore, even if the number of on-off valves (V) in the fourth flow path (34) is one, it is possible to suppress a large increase in the pressure loss in the fourth flow path (34).

In the third aspect, in the second aspect, two or more on-off valves (V) are provided in parallel in the third flow path (33).

In the third aspect, the number of on-off valves (V) provided in the third flow path (33) is two or more. In the refrigerant circuit (6), the refrigerant evaporated in the first utilization side heat exchanger (64) can be operated to be sucked into the second compression element (22) through the third flow path (33). Here, the cooling load of the first utilization side heat exchanger (64) varies according to the demand of the utilization side. Therefore, the flow rate of the refrigerant flowing through the third flow path (33) may also increase according to this demand. Therefore, by setting the number of on-off valves (V) in the third flow path (33) to two or more, it is possible to suppress an increase in the pressure loss in the third flow path (33) when the flow rate of the refrigerant in the third flow path (33) increases.

A fourth aspect is any one of the first to third aspects, in which a first check valve (CV1) is provided in the fourth flow path (34) to limit the flow of refrigerant from the second port (P2) to the fourth port (P4).

In the fourth aspect, a first check valve (CV1) is provided in the fourth flow path (34). In the refrigerant circuit (6), the refrigerant compressed in the compression section (20) is sent to the heat source side heat exchanger (24) through the second flow path (32), and the refrigerant evaporated in the first utilization side heat exchanger (64) is sucked into the second compression element (22) through the third flow path (33). In this operation, if the internal pressure of the heat source side heat exchanger (24) decreases, the refrigerant that has flowed out of the third flow path (33) may flow through the fourth flow path (34) from the second port (P2) to the fourth port (P4). In this case, the refrigerant flows through the opening and closing valve (V) of the fourth flow path (34) in the opposite direction to normal, so that the opening and closing valve (V) of the fourth flow path (34) may become clogged with debris or the valve body of the opening and closing valve (V) may break down. In response to this, the first check valve (CV1) restricts the flow of refrigerant from the second port (P2) to the fourth port (P4) in the fourth flow path (34), thereby preventing the refrigerant from flowing in the opposite direction to normal through the opening/closing valve (V) of the fourth flow path (34).

A fifth aspect is any one of the first to fourth aspects, in which a second check valve (CV2) is provided in the first flow path (31) to limit the flow of refrigerant from the third port (P3) to the first port (P1).

In the fifth aspect, a second check valve (CV2) is provided in the first flow path (31). In the refrigerant circuit (6), the refrigerant compressed in the compression section (20) is sent to the heat source side heat exchanger (24) through the second flow path (32), and the refrigerant evaporated in the first utilization side heat exchanger (64) is sucked into the second compression element (22) through the third flow path (33). In this operation, if the internal pressure of the heat source side heat exchanger (24) decreases, the refrigerant flowing through the third flow path (33) may flow through the first flow path (31) from the third port (P3) to the first port (P1). In this case, the refrigerant flows through the opening and closing valve (V) of the first flow path (31) in the opposite direction to normal, so that the opening and closing valve (V) of the first flow path (31) may become clogged with debris or the valve body of the opening and closing valve (V) may break down. In contrast, the second check valve (CV2) restricts the flow of refrigerant from the third port (P3) to the first port (P1) in the first flow path (31), thereby preventing the refrigerant from flowing in the opposite direction to normal through the opening/closing valve (V) of the first flow path (31).

A sixth aspect is any one of the first to fifth aspects, further comprising a control unit (100) that controls the refrigerant circuit (6) to perform a first refrigeration cycle in which the heat source side heat exchanger (24) is a radiator and the first utilization side heat exchanger (64) is an evaporator, and a second refrigeration cycle in which the first utilization side heat exchanger (64) is a radiator and the heat source side heat exchanger (24) is an evaporator, and the control unit (100) reduces the capacity of the compression unit (20) in conjunction with switching between the first refrigeration cycle and the second refrigeration cycle.

When switching between the first and second refrigeration cycles, the pressure of the high-pressure refrigerant acts abruptly on the piping that previously contained the low-pressure refrigerant, which may cause noise or breakage of the piping. In the sixth aspect, the capacity of the compression section (20) is reduced in conjunction with the switching between the first and second refrigeration cycles, so the pressure of the high-pressure refrigerant can be reduced. As a result, the shock acting on the piping, etc., due to the switching between these refrigeration cycles can be reduced.

The seventh aspect is a refrigeration device equipped with a heat source unit according to any one of the first to sixth aspects.

FIG. 1 is a piping diagram of a refrigeration system according to an embodiment of the present invention. FIG. 2 is a block diagram showing the connection relationship between the controller and its peripheral devices. FIG. 3 is a diagram showing the configuration of the flow path switching mechanism. FIG. 4 is a piping diagram of a refrigeration system, showing the flow of refrigerant during cooling operation. FIG. 5 is a piping diagram of a refrigeration system, showing the flow of refrigerant during cooling operation (defrost operation). FIG. 6 is a piping diagram of a refrigeration system, showing the flow of refrigerant during cooling operation (defrost operation). FIG. 7 is a piping diagram of a refrigeration system, showing the flow of refrigerant during heating operation. FIG. 8 is a piping diagram of the refrigeration system, showing the flow of refrigerant in the first heating/cooling operation. FIG. 9 is a piping diagram of the refrigeration system, showing the flow of refrigerant in the second heating/cooling operation. FIG. 10 is a piping diagram of the refrigeration system, showing the flow of refrigerant in the third heating/cooling operation. FIG. 11 is a flow chart showing a control operation accompanying the switching between the first refrigeration cycle and the second refrigeration cycle. FIG. 12 is a flowchart showing the first control of the flow path switching mechanism. FIG. 13 is a flowchart showing the second control of the flow path switching mechanism. FIG. 14 is a configuration diagram of a flow path switching mechanism according to another embodiment.

Embodiments of the present disclosure will be described in detail below with reference to the drawings. Note that the present disclosure is not limited to the embodiments shown below, and various modifications are possible without departing from the technical spirit of the present disclosure. Each drawing is intended to conceptually explain the present disclosure, and therefore dimensions, ratios, or numbers may be exaggerated or simplified as necessary for ease of understanding.

<<Embodiment>>
The refrigeration system (1) according to the embodiment simultaneously cools an object to be cooled and conditions the air inside a room. The object to be cooled here includes the air inside equipment such as a refrigerator, a freezer, and a showcase. Hereinafter, such equipment will be referred to as a refrigeration facility.

(1) Overall Configuration As shown in FIG. 1, the refrigeration system (1) includes a heat source unit (10) installed outside a room, an air conditioning unit (60) that conditions the air inside the room, and a cold-setting unit (70) that cools the air inside the room. As shown in FIG. 2, the refrigeration system (1) includes a controller (100) that controls a refrigerant circuit (6). FIG. 1 illustrates one air conditioning unit (60). The refrigeration system (1) may include two or more air conditioning units (60) connected in parallel. FIG. 1 illustrates one cold-setting unit (70). The refrigeration system (1) may include two or more cold-setting units (70) connected in parallel.

The refrigeration system (1) includes four interconnecting pipes (2, 3, 4, 5) that connect the heat source unit (10), the air conditioning unit (60), and the cooling unit (70). In the refrigeration system (1), the heat source unit (10), the air conditioning unit (60), and the cooling unit (70) are connected by these interconnecting pipes (2, 3, 4, 5) to form a refrigerant circuit (6).

The refrigerant circuit (6) contains a filled refrigerant. The refrigerant circuit (6) circulates the refrigerant to perform a refrigeration cycle. In this embodiment, the refrigerant is carbon dioxide. The refrigerant circuit (6) performs a refrigeration cycle in which the refrigerant reaches or exceeds its critical pressure. The refrigerant may be a natural refrigerant other than carbon dioxide.

(1-1) Connecting pipes The four connecting pipes (2, 3, 4, 5) consist of the first liquid connecting pipe (2), the first gas connecting pipe (3), the second liquid connecting pipe (4), and the second gas connecting pipe (5). The first liquid connecting pipe (2) and the first gas connecting pipe (3) correspond to the air conditioning unit (60). The second liquid connecting pipe (4) and the second gas connecting pipe (5) correspond to the cooling unit (70).

(2) Heat Source Unit The heat source unit (10) has a heat source circuit (11) and an outdoor fan (12). The heat source circuit (11) has a compression section (20), an outdoor heat exchanger (24), and a gas-liquid separator (25). The heat source circuit (11) has a first outdoor expansion valve (26) and a second outdoor expansion valve (27). The heat source circuit (11) further has a cooling heat exchanger (28) and an intercooler (29).

The heat source circuit (11) has four shutoff valves (13, 14, 15, 16). The four shutoff valves are a first gas shutoff valve (13), a first liquid shutoff valve (14), a second gas shutoff valve (15), and a second liquid shutoff valve (16).

The first gas stop valve (13) is connected to the first gas connection pipe (3). The first liquid stop valve (14) is connected to the first liquid connection pipe (2). The second gas stop valve (15) is connected to the second gas connection pipe (5). The second liquid stop valve (16) is connected to the second liquid connection pipe (4).

The heat source unit (10) has a flow path switching mechanism (30). In the piping diagram of the refrigerant circuit in FIG. 1 and the like, the details of the flow path switching mechanism (30) are omitted. The flow path switching mechanism (30) switches the flow path of the refrigerant in the refrigerant circuit (6). The flow path switching mechanism (30) will be described in detail later.

(2-1) Compression Section The compression section (20) compresses the refrigerant. The compression section (20) has a first compressor (21), a second compressor (22), and a third compressor (23). The compression section (20) performs an operation in which the refrigerant is compressed in a single stage and an operation in which the refrigerant is compressed in two stages.

The first compressor (21) is a cold-conditioning compressor corresponding to the cold-conditioning unit (70). The first compressor (21) is an example of a first compression element. The second compressor (22) is an air-conditioning compressor corresponding to the air-conditioning unit (60). The second compressor (22) is an example of a second compression element. 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.

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

The first compressor (21), the second compressor (22), and the third compressor (23) are rotary compressors whose compression mechanisms are driven by a motor. The first compressor (21), the second compressor (22), and the third compressor (23) are of a variable capacity type. The rotation speed of the 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 first compressor (21), the second compressor (22), and the third compressor (23) are configured so that their operating capacities are adjustable.

The first compressor (21) is connected to a first suction pipe (21a) and a first discharge pipe (21b). The second compressor (22) is connected to a second suction pipe (22a) and a second discharge pipe (22b). The third compressor (23) is connected to a third suction pipe (23a) and a third discharge pipe (23b).

(2-2) Intermediate Flow Passage The heat source circuit (11) includes an intermediate flow passage (18). The intermediate flow passage (18) connects the discharge portions of the first compressor (21) and the second compressor (22) to the suction portion of the third compressor (23). The intermediate flow passage (18) includes a first discharge pipe (21b), a second discharge pipe (22b), and a third suction pipe (23a).

(2-3) Outdoor Heat Exchanger and Outdoor Fan The outdoor heat exchanger (24) is an example of a heat source side heat exchanger. The outdoor heat exchanger (24) is a fin-and-tube type air heat exchanger. The outdoor fan (12) is disposed near the outdoor heat exchanger (24). The outdoor fan (12) transports outdoor air. The outdoor heat exchanger exchanges heat between the refrigerant flowing therethrough and the outdoor air transported by the outdoor fan (12).

(2-4) Liquid Side Flow Path The heat source circuit (11) includes a liquid side flow path (40). The liquid side flow path (40) is provided between the liquid side end of the outdoor heat exchanger (24) and the two liquid stop valves (14, 16). The liquid side flow path (40) includes first to fifth pipes (40a, 40b, 40c, 40d, 40e).

One end of the first pipe (40a) is connected to the liquid side end of the outdoor heat exchanger (24). The other end of the first pipe (40a) is connected to the top of the gas-liquid separator (25). One end of the second pipe (40b) is connected to the bottom of the gas-liquid separator (25). The other end of the second pipe (40b) is connected to the second liquid shutoff valve (16). One end of the third pipe (40c) is connected to the middle of the second pipe (40b). The other end of the third pipe (40c) is connected to the first liquid shutoff valve (14). One end of the fourth pipe (40d) is connected to 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 middle of the third pipe (40c). One end of the fifth pipe (40e) is connected to 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 the second pipe (40b) between the gas-liquid separator (25) and the junction of the third pipe (40c).

(2-5) Outdoor Expansion Valve The first outdoor expansion valve (26) is provided in the first pipe (40a). The first outdoor expansion valve (26) is provided in the first pipe (40a) between the liquid side end of the outdoor heat exchanger (24) and the connection portion of the fourth pipe (40d). The second outdoor expansion valve (27) is provided in the fifth pipe (40e). The first outdoor expansion valve (26) and the second outdoor expansion valve (27) are expansion valves whose opening degrees are adjustable. The first outdoor expansion valve (26) and the second outdoor expansion valve (27) are electronic expansion valves whose opening degrees are adjusted based on a pulse signal.

(2-6) Gas-Liquid Separator The gas-liquid separator (25) is a sealed container that stores refrigerant. The gas-liquid separator (25) separates the refrigerant into a gas refrigerant and a liquid refrigerant. A gas layer and a liquid layer are formed inside the gas-liquid separator (25). The gas layer is formed on the top side of the gas-liquid separator (25). The liquid layer is formed on the bottom side of the gas-liquid separator (25).

(2-7) Gas Venting Pipe The heat source circuit (11) has a gas venting pipe (41). One end of the gas venting pipe (41) is connected to the top of the gas-liquid separator (25). The other end of the gas venting pipe (41) is connected to the intermediate flow path (18). The gas venting pipe (41) sends gas refrigerant in the gas-liquid separator (25) to the intermediate flow path (18).

The gas vent pipe (41) is provided with a gas vent valve (42). The gas vent pipe (41) is an expansion valve whose opening is adjustable. The gas vent valve (42) is an electronic expansion valve whose opening is adjusted based on a pulse signal.

(2-8) Cooling Heat Exchanger The cooling heat exchanger (28) has a high-pressure side flow path (28a) and a low-pressure side flow path (28b). The cooling heat exchanger (28) exchanges heat between the refrigerant in the high-pressure side flow path (28a) and the refrigerant in the low-pressure side flow path (28b). In other words, the cooling heat exchanger (28) cools the refrigerant flowing through the high-pressure side flow path (28a) by the refrigerant flowing through the low-pressure side flow path (28b).

The low-pressure side flow path (28b) constitutes a part of the injection flow path (43). The injection flow path (43) includes an upstream flow path (44) and a downstream flow path (45).

One end of the upstream flow path (44) is connected to the third pipe (40c) upstream of the connection portion of the fourth pipe (40d). The other end of the upstream flow path (44) is connected to the inlet end of the low-pressure side flow path (28b). An injection valve (46) is provided in the upstream flow path (44). The injection valve (46) is an expansion valve whose opening is adjustable. The injection valve (46) is an electronic expansion valve whose opening is adjusted based on a pulse signal.

One end of the downstream flow path (45) is connected to the outlet end of the low-pressure side flow path (28b). The other end of the downstream flow path (45) is connected to the intermediate flow path (18).

(2-9) Intercooler The intercooler (29) is provided in the intermediate flow path (18). The intercooler (29) is a fin-and-tube type air heat exchanger. A cooling fan (29a) is disposed in the vicinity of the intercooler (29). The intercooler (29) exchanges heat between the refrigerant flowing therethrough and the outdoor air transported by the cooling fan (29a).

(2-10) Oil Separation Circuit The heat source circuit (11) includes an oil separation circuit. The oil separation circuit has an oil separator (50), a first oil return pipe (51), and a second oil return pipe (52).

The oil separator (50) is connected to the third discharge pipe (23b). The oil separator (50) separates oil from the refrigerant discharged from the compression section (20). The inlet ends of the first oil return pipe (51) and the second oil return pipe (52) communicate with the oil separator (50). The outlet 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 amount control valve (53).

The outlet 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 the oil reservoir of the first compressor (21). The second branch pipe (52b) is connected to the oil reservoir of the second compressor (22). The first branch pipe (52a) is provided with a second oil amount control valve (54). The second branch pipe (52b) is provided with a third oil amount control valve (55).

(2-11) Bypass Pipe The heat source circuit (11) has a first bypass pipe (56), a second bypass pipe (57), and a third bypass pipe (58). The first bypass pipe (56) corresponds to the first compressor (21). The second bypass pipe (57) corresponds to the second compressor (22). The third bypass pipe (58) corresponds to the third compressor (23).

Specifically, the first bypass pipe (56) directly connects the first suction pipe (21a) and the first discharge pipe (21b). The second bypass pipe (57) directly connects the second suction pipe (22a) and the second discharge pipe (22b). The third bypass pipe (58) directly connects the third suction pipe (23a) and the third discharge pipe (23b).

(2-12) Check Valve The heat source circuit (11) has a plurality of check valves. The plurality of check valves includes first to twelfth check valves (CV1 to CV12). These check valves (CV1 to CV12) allow the flow of refrigerant in the direction of the arrow in FIG. 1 and prohibit the flow of refrigerant in the opposite direction.

The first check valve (CV1) and the second check valve (CV2) are provided in the flow path switching mechanism (30), the details of which will be described later.

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 The air conditioning unit (60) is a first utilization unit installed indoors. The air conditioning unit (60) has an indoor circuit (61) and an indoor fan (62). A first liquid connection pipe (2) is connected to a liquid side end of the indoor circuit (61). A first gas connection pipe (3) is connected to a gas side end of the indoor circuit (61).

The indoor circuit (61) has, in order from the liquid side end to the gas side end, an indoor expansion valve (63) and an indoor heat exchanger (64). The indoor expansion valve (63) is an expansion valve whose opening is adjustable. The indoor expansion valve (63) is an electronic expansion valve whose opening is adjusted based on a pulse signal.

The indoor heat exchanger (64) is a fin-and-tube type air heat exchanger. The indoor heat exchanger (64) is an example of a first utilization side heat exchanger. The indoor fan (62) is disposed near the indoor heat exchanger (64). The indoor fan (62) transports indoor air. The indoor heat exchanger (64) exchanges heat between the refrigerant flowing therethrough and the indoor air transported by the indoor fan (62).

(4) Chilling Unit The chilling unit (70) is a second utilization unit that cools the interior of the refrigerator. The chilling unit (70) has a chilling circuit (71) and a chilling fan (72). A second liquid connection pipe (4) is connected to a liquid side end of the chilling circuit (71). A second gas connection pipe (5) is connected to a gas side end of the chilling circuit (71).

The cold-setting circuit (71) has, in order from the liquid side end to the gas side end, a cold-setting expansion valve (73) and a cold-setting heat exchanger (74). The cold-setting expansion valve (73) is an expansion valve whose opening is adjustable. The cold-setting expansion valve (73) is an electronic expansion valve whose opening is adjusted based on a pulse signal.

The cold-air heat exchanger (74) is a fin-and-tube type air heat exchanger. The cold-air heat exchanger (74) is an example of a second user-side heat exchanger. The cold-air fan (72) is disposed near the cold-air heat exchanger (74). The cold-air fan (72) transports the air inside the storage unit. The cold-air heat exchanger (74) exchanges heat between the refrigerant flowing therethrough and the air inside the storage unit transported by the cold-air fan (72).

The evaporation temperature of the cold heat exchanger (74) is lower than the evaporation temperature of the indoor heat exchanger (64).

(5) Flow path switching mechanism The flow path switching mechanism (30) is provided in the heat source circuit (11). As shown in Fig. 1 and Fig. 3, the flow path switching mechanism (30) has a first port (P1), a second port (P2), a third port (P3), a fourth port (P4), a first flow path (31), a second flow path (32), a third flow path (33), and a fourth flow path (34). A first opening and closing mechanism (81) is provided in the first flow path (31), a second opening and closing mechanism (82) is provided in the second flow path (32), a third opening and closing mechanism (83) is provided in the third flow path (33), and a fourth opening and closing mechanism (84) is provided in the fourth flow path (34).

(5-1) Port The first port (P1) is connected to the discharge portion of the first compressor (21) and the discharge portion of the second compressor (22). The discharge portion of the first compressor (21) is connected to the first port (P1) via a first discharge line (L1). The first discharge line (L1) is a flow path having one end connected to the discharge portion of the first compressor (21) and the other end connected to the first port (P1). In other words, the first discharge line (L1) is a flow path extending from the discharge portion of the first compressor (21) to the first port (P1).

The discharge portion of the second compressor (22) is connected to the first port (P1) via the second discharge line (L2). The second discharge line (L2) is a flow path having one end connected to the discharge portion of the second compressor (22) and the other end connected to the first port (P1). In other words, the second discharge line (L2) is a flow path extending from the discharge portion of the second compressor (22) to the first port (P1).

The second port (P2) is connected to the suction portion of the second compressor (22). The second port (P2) is not connected to the suction portion of the first compressor (21). The second port (P2) is connected to the suction portion of the second compressor (22) via the suction line (L3). The suction line (L3) is a flow path having one end connected to the suction portion of the second compressor (22) and the other end connected to the second port (P2). In other words, the suction line (L3) is a flow path extending from the suction portion of the second compressor (22) to the second port (P2).

The third port (P3) is connected to the gas end of the indoor heat exchanger (64). The third port (P3) is connected to the gas end of the indoor heat exchanger (64) via the first gas line (L4). The first gas line (L4) is a flow path having one end connected to the indoor heat exchanger (64) and the other end connected to the third port (P3). In other words, the first gas line (L4) is a flow path extending from the gas end of the indoor heat exchanger (64) to the third port (P3).

The fourth port (P4) is connected to the gas end of the outdoor heat exchanger (24). The fourth port (P4) is connected to the gas end of the outdoor heat exchanger (24) via a second gas line (L5). One end of the second gas line (L5) is connected to the gas end of the outdoor heat exchanger (24) and the other end is connected to the fourth port (P4). The second gas line (L5) is a flow path extending from the gas end of the outdoor heat exchanger (24) to the fourth port (P4).

The first discharge line (L1), the second discharge line (L2), the suction line (L3), the first gas line (L4), and the second gas line (L5) refer to the flow path including the piping and the component equipment connected to the piping.

(5-2) Flow Channels As shown in FIG. 1, the first flow channel (31), the second flow channel (32), the third flow channel (33), and the fourth flow channel (34) are connected in a bridge shape. The first flow channel (31) communicates between the first port (P1) and the third port (P3). The second flow channel (32) communicates between the first port (P1) and the fourth port (P4). The third flow channel (33) communicates between the second port (P2) and the third port (P3). The fourth flow channel (34) communicates between the second port (P2) and the fourth port (P4). The first flow channel (31) and the second flow channel (32) are high-pressure side flow channels on which a high pressure acts. In other words, the first flow channel (31) and the second flow channel (32) are discharge side flow channels on which the discharge pressure of the compression section (20) acts. The third flow path (33) and the fourth flow path (34) are low-pressure side flow paths on which low pressure acts. The third flow path (33) and the fourth flow path (34) are suction side flow paths on which the suction pressure of the compression section (20) acts.

As shown in FIG. 3, the first flow path (31) has two or more first branch paths (31a) that are parallel to each other. In this example, the first flow path (31) has seven first branch paths (31a). In this example, the second flow path (32) has two or more second branch paths (32a) that are parallel to each other. The second flow path (32) has seven second branch paths (32a). The third flow path (33) has third branch paths (33a) that are parallel to each other. In this example, the third flow path (33) has four third branch paths (33a). The fourth flow path (34) is formed by one flow path.

(5-3) Opening/Closing Mechanism The first opening/closing mechanism (81) has a plurality of first opening/closing valves (V1). Two or more first opening/closing valves (V1) are provided in parallel in the first flow path (31). In the present example, seven first opening/closing valves (V1) are provided in the first flow path (31). One first opening/closing valve (V1) is provided in each of the first branch flow paths (31a). The plurality of first opening/closing valves (V1) include a first expansion valve (91) and a first solenoid opening/closing valve (92). The number of the first expansion valve (91) is one, and the number of the first solenoid opening/closing valves (92) is six. The first expansion valve (91) is an electronic expansion valve whose opening degree is variable.

The second opening/closing mechanism (82) has a plurality of second opening/closing valves (V2). Two or more second opening/closing valves (V2) are provided in parallel in the second flow path (32). In this example, seven second opening/closing valves (V2) are provided in the second flow path (32). One second opening/closing valve (V2) is provided in each of the second branch flow paths (32a). The plurality of second opening/closing valves (V2) include a second expansion valve (93) and a second electromagnetic opening/closing valve (94). There is one second expansion valve (93), and six second electromagnetic opening/closing valves (94). The second expansion valve (93) is an electronic expansion valve whose opening degree is variable.

The third opening/closing mechanism (83) has a plurality of third opening/closing valves (V3). Two or more third opening/closing valves (V3) are provided in parallel in the second flow path (32). In this example, four third opening/closing valves (V3) are provided in the third flow path (33). One third opening/closing valve (V3) is provided in each of the third branch flow paths (33a). These third opening/closing valves (V3) are electromagnetic opening/closing valves.

The fourth opening/closing mechanism (84) has one fourth opening/closing valve (V4). The fourth opening/closing valve (V4) is provided in the fourth flow path (34). The fourth opening/closing valve (V4) is an electromagnetic opening/closing valve.

The first on-off valve (V1), the second on-off valve (V2), the third on-off valve (V3), and the fourth on-off valve (V4) may be simply referred to as on-off valves (V) as shown in Figure 2.

The number N1 of the on-off valves (V) in the first flow path (31) is two or more. The number N2 of the on-off valves (V) in the second flow path (32) is two or more. The number N3 of the on-off valves (V) in the third flow path (33) is two or more. The number N4 of the on-off valves (V) in the fourth flow path (34) is one. N1 is greater than N3 and N4. N1 and N2 are the same. N2 is greater than N3 and N4. N3 is greater than N4.

(5-5) Check Valve The flow path switching mechanism (30) has check valves (CV1, CV2). Specifically, a first check valve (CV1) is provided in the fourth flow path (34). A second check valve (CV2) is provided in the first flow path (31).

The first check valve (CV1) restricts the flow of refrigerant from the second port (P2) to the fourth port (P4) in the fourth flow path (34). Strictly speaking, the first check valve (CV1) allows the flow of refrigerant from the fourth port (P4) to the second port (P2) in the fourth flow path (34) and prohibits the flow of refrigerant from the second port (P2) to the fourth port (P4). The first check valve (CV1) is provided in the fourth flow path (34) closer to the second port (P2) than the opening/closing valve (V).

The second check valve (CV2) restricts the flow of refrigerant from the third port (P3) to the first port (P1) in the first flow path (31). Strictly speaking, the second check valve (CV2) allows the flow of refrigerant from the first port (P1) to the third port (P3) in the first flow path (31) and prohibits the flow of refrigerant from the third port (P3) to the first port (P1). The second check valve (CV2) is provided in the main flow path (31b) in the first flow path (31). The main flow path (31b) is a flow path to which the ends of the multiple first branch flow paths (31a) are connected. The second check valve (CV2) is provided in the first flow path (31) closer to the third port (P3) than the opening/closing valve (V).

(6) Sensors The refrigeration system (1) has a plurality of sensors (not shown). The plurality of sensors includes a refrigerant pressure sensor that detects the pressure of the refrigerant, and a refrigerant temperature sensor that detects the temperature of the refrigerant. The refrigerant pressure sensors include sensors that detect, for example, the high pressure, low pressure, and intermediate pressure of the refrigerant circuit, the suction pressure of each compressor (21, 22, 23), the discharge pressure of each compressor (21, 22, 23), the internal pressure of the gas-liquid separator (25), and the like. The refrigerant temperature sensors include sensors that detect, for example, the temperature of the suction refrigerant of each compressor (21, 22, 23), the temperature of the discharge refrigerant of each compressor (21, 22, 23), and the temperature of the refrigerant of each heat exchanger (24, 64, 74).

The multiple sensors include air temperature sensors that detect the temperature of the outdoor air, the temperature of the indoor air, and the temperature of the air inside the refrigerated storage unit.

(7) Controller The controller (100) includes a microcomputer mounted on a control board and a memory device (specifically, a semiconductor memory) for storing software for operating the microcomputer.

As shown in FIG. 2, the controller (100) has an outdoor controller (101), an indoor controller (102), and a cold-conditioning controller (103). As shown in FIG. 1, the outdoor controller (101) is provided in the heat source unit (10). The indoor controller (102) is provided in the air conditioning unit (60). The cold-conditioning controller (103) is provided in the cold-conditioning unit (70). The outdoor controller (101) can communicate with the indoor controller (102) and the cold-conditioning controller (103).

The controller (100) receives control commands and detection signals from the sensors. The controller (100) controls the devices of the refrigeration system (1). Specifically, the controller (100) controls ON/OFF of the first compressor (21), the second compressor (22), and the third compressor (23). The controller (100) adjusts the capacity (strictly speaking, the motor rotation speed) of the first compressor (21), the second compressor (22), and the third compressor (23). The controller (100) controls ON/OFF of the fans (12, 62, 72). The controller (100) adjusts the opening degree of each expansion valve (26, 27, 63). The controller (100) switches the open/closed state of each valve (42, 43). The controller (100) switches the open/closed state of each on-off valve (V) and adjusts the opening degree of each on-off valve (V).

(8) Operation Operation of the refrigeration system (1) will be described. The operation of the refrigeration system (1) includes cooling operation, cooling operation, cooling and cooling operation, heating operation, heating and cooling operation, and defrost operation. The heating and cooling operation includes a first heating and cooling operation, a second heating and cooling operation, and a third heating and cooling operation.

In cooling operation, the cooling unit (70) cools the air inside the cabinet, and the air conditioning unit (60) is stopped. In cooling operation, the cooling unit (70) is stopped, and the air conditioning unit (60) cools the room. In cooling-cooling operation, the cooling unit (70) cools the air inside the cabinet, and the air conditioning unit (60) cools the room. In heating operation, the cooling unit (70) is stopped, and the air conditioning unit (60) heats the room. In heating-cooling operation, the cooling unit (70) cools the air inside the cabinet, and the air conditioning unit (60) heats the room. In defrost operation, frost adhering to the outdoor heat exchanger (24) is melted.

The first heating/cooling operation is an operation in which the heat absorbed by the refrigerant in the outdoor heat exchanger (24) and the cooling heat exchanger (74) is used for heating. The second heating/cooling operation is an operation in which the outdoor heat exchanger (24) is not functioning, and the heat absorbed by the refrigerant in the cooling heat exchanger (74) is used for heating. The third heating/cooling operation is an operation in which the heat of the refrigerant is released from the outdoor heat exchanger (24).

The outline of each operation will be explained with reference to Figures 4 to 10. In the figures, the flow of the refrigerant is indicated by dashed arrows, and the flow path through which the refrigerant flows is made thick. In the figures, the heat exchangers that function as radiators are hatched, and the heat exchangers that function as evaporators are dotted.

(8-1) Cooling Operation In the cooling operation shown in FIG. 4, the controller (100) closes the first on-off valve (V1), the third on-off valve (V3), and the fourth on-off valve (V4), and opens the second on-off valve (V2). The controller (100) stops the second compressor (22) and operates the first compressor (21) and the third compressor (23). The controller (100) opens the first outdoor expansion valve (26) and the injection valve (46) to a predetermined opening degree, and closes the second outdoor expansion valve (27). The controller (100) closes the indoor expansion valve (63) and adjusts the opening degree of the cold-setting expansion valve (73). The controller (100) operates the outdoor fan (12) and the cold-setting fan (72), and stops the indoor fan (62).

In the cooling operation, the outdoor heat exchanger (24) functions as a radiator, the indoor heat exchanger (64) essentially stops functioning, and the cooling heat exchanger (74) functions as an evaporator, resulting in a refrigeration cycle.

Specifically, the refrigerant compressed by the first compressor (21) is cooled in the intercooler (29) and then sucked into the third compressor (23). The refrigerant compressed to or above the critical pressure by the third compressor (23) dissipates heat in the outdoor heat exchanger (24) and then passes through the first outdoor expansion valve (26). The first outdoor expansion valve (26) reduces the pressure of the refrigerant to a pressure lower than the critical pressure.

The subcritical refrigerant flows into the gas-liquid separator (25). The gas-liquid separator (25) separates the refrigerant into gas refrigerant and liquid refrigerant.

The liquid refrigerant separated in the gas-liquid separator (25) is cooled in the cooling 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).

The refrigerant cooled by the cooling heat exchanger (28) is sent to the cold storage unit (70). The refrigerant sent to the cold storage unit (70) is decompressed by the cold storage expansion valve (73) and then evaporates in the cold storage heat exchanger (74). As a result, the air inside the storage unit is cooled. The refrigerant evaporated in the cold storage heat exchanger (74) is sucked into the first compressor (21) and compressed again.

(8-2) Cooling Operation In the cooling operation shown in FIG. 5, the controller (100) closes the first on-off valve (V1) and the fourth on-off valve (V4) and opens the second on-off valve (V2) and the third on-off valve (V3). The controller (100) stops the first compressor (21) and operates the second compressor (22) and the third compressor (23). The controller (100) opens the first outdoor expansion valve (26) and the injection valve (46) to a predetermined opening degree and closes the second outdoor expansion valve (27). The controller (100) closes the cold-setting expansion valve (73) and adjusts the opening degree of the indoor expansion valve (63). The controller (100) operates the outdoor fan (12) and the indoor fan (62) and stops the cold-setting fan (72).

During cooling operation, a refrigeration cycle is performed in which the outdoor heat exchanger (24) functions as a radiator, the indoor heat exchanger (64) functions as an evaporator, and the function of the cooling heat exchanger (74) is essentially stopped.

Specifically, the refrigerant compressed by the second compressor (22) is cooled in the intercooler (29) and then sucked into the third compressor (23). The refrigerant compressed to or above the critical pressure by the third compressor (23) dissipates heat in the outdoor heat exchanger (24) and then passes through the first outdoor expansion valve (26). The first outdoor expansion valve (26) reduces the pressure of the refrigerant to a pressure lower than the critical pressure.

The subcritical refrigerant flows into the gas-liquid separator (25). The gas-liquid separator (25) separates the refrigerant into gas refrigerant and liquid refrigerant.

The liquid refrigerant separated in the gas-liquid separator (25) is cooled in the cooling 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).

The refrigerant cooled by the cooling heat exchanger (28) is sent to the air conditioning unit (60). The refrigerant sent to the air conditioning unit (60) is depressurized by the indoor expansion valve (63) and then evaporates in the indoor heat exchanger (64). As a result, the air in the room is cooled. The refrigerant evaporated in the indoor heat exchanger (64) is sucked into the second compressor (22) and compressed again.

(8-3) Cooling/Cooling-Set Operation In the cooling/cooling-set operation shown in FIG. 6, the controller (100) closes the first on-off valve (V1) and the fourth on-off valve (V4) and opens the second on-off valve (V2) and the third on-off valve (V3). The controller (100) operates the first compressor (21), the second compressor (22), and the third compressor (23). The controller (100) opens the first outdoor expansion valve (26) and the injection valve (46) to a predetermined opening degree and closes the second outdoor expansion valve (27). The controller (100) adjusts the opening degree of the cold-set expansion valve (73) and the indoor expansion valve (63). The controller (100) operates the outdoor fan (12), the indoor fan (62), and the cold-set fan (72).

In the cooling operation, a refrigeration cycle is performed in which the outdoor heat exchanger (24) functions as a radiator, and the indoor heat exchanger (64) and the cooling heat exchanger (74) function as evaporators.

Specifically, the refrigerant compressed by the first compressor (21) and the second compressor (22) is cooled in the intercooler (29) and then sucked into the third compressor (23). The refrigerant compressed to or above the critical pressure by the third compressor (23) dissipates heat in the outdoor heat exchanger (24) and then passes through the first outdoor expansion valve (26). The first outdoor expansion valve (26) reduces the pressure of the refrigerant to a pressure lower than the critical pressure.

The subcritical refrigerant flows into the gas-liquid separator (25). The gas-liquid separator (25) separates the refrigerant into gas refrigerant and liquid refrigerant.

The liquid refrigerant separated in the gas-liquid separator (25) is cooled in the cooling 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).

The refrigerant cooled by the cooling heat exchanger (28) is sent to the air conditioning unit (60) and the cold installation unit (70). The refrigerant sent to the air conditioning unit (60) is decompressed by the indoor expansion valve (63) and then evaporates in the indoor heat exchanger (64). As a result, the air in the room is cooled. The refrigerant evaporated in the indoor heat exchanger (64) is sucked into the first compressor (21) and compressed again.

The refrigerant sent to the cold storage unit (70) is decompressed by the cold storage expansion valve (73) and then evaporates in the cold storage heat exchanger (74). As a result, the air inside the cabinet is cooled. The refrigerant evaporated in the cold storage heat exchanger (74) is sucked into the second compressor (22) and compressed again.

(8-4) Heating Operation In the heating operation shown in FIG. 7, the controller (100) closes the second on-off valve (V2) and the third on-off valve (V3) and opens the first on-off valve (V1) and the fourth on-off valve (V4). The controller (100) stops the first compressor (21) and operates the second compressor (22) and the third compressor (23). The controller (100) opens the second outdoor expansion valve (27) and the injection valve (46) to a predetermined opening degree and closes the first outdoor expansion valve (26). The controller (100) closes the cold-setting expansion valve (73) and adjusts the opening degree of the indoor expansion valve (63). The controller (100) operates the outdoor fan (12) and the indoor fan (62) and stops the cold-setting fan (72).

During heating operation, the indoor heat exchanger (64) functions as a radiator, the outdoor heat exchanger (24) functions as an evaporator, and a refrigeration cycle is performed in which the function of the cooling heat exchanger (74) is essentially stopped.

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

The refrigerant sent to the air conditioning unit (60) dissipates heat in the indoor heat exchanger (64). As a result, the air in the room is heated. The refrigerant that has dissipated heat in the indoor heat exchanger (64) flows into the gas-liquid separator (25). The gas-liquid separator (25) separates the refrigerant into gas refrigerant and liquid refrigerant.

The liquid refrigerant separated in the gas-liquid separator (25) is cooled in the cooling 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).

The refrigerant cooled by the cooling heat exchanger (28) is decompressed by the second outdoor expansion valve (27) and then evaporates in the outdoor heat exchanger (24). The refrigerant evaporated in the outdoor heat exchanger (24) is sucked into the second compressor (22) and compressed again.

(8-5) First heating/cooling operation The first heating/cooling operation shown in FIG. 8 is performed when the heating load of the air conditioning unit (60) is high. In the first heating/cooling operation, the controller (100) closes the second on-off valve (V2) and the third on-off valve (V3) and opens the first on-off valve (V1) and the fourth on-off valve (V4). The controller (100) operates the first compressor (21), the second compressor (22), and the third compressor (23). The controller (100) opens the second outdoor expansion valve (27) and the injection valve (46) to a predetermined opening degree and closes the first outdoor expansion valve (26). The controller (100) adjusts the opening degree of the indoor expansion valve (63) and the cooling-set expansion valve (73). The controller (100) operates the outdoor fan (12), the indoor fan (62), and the cooling-set fan (72).

In the first heating/cooling operation, a refrigeration cycle is performed in which the indoor heat exchanger (64) functions as a radiator, and the outdoor heat exchanger (24) and the cooling heat exchanger (74) function as evaporators.

Specifically, the refrigerant compressed by the first compressor (21) and the second compressor (22) is cooled in the intercooler (29) and then sucked into the third compressor (23). The refrigerant compressed by the third compressor (23) is sent to the air conditioning unit (60).

The refrigerant sent to the air conditioning unit (60) dissipates heat in the indoor heat exchanger (64). As a result, the air in the room is heated. The refrigerant that has dissipated heat in the indoor heat exchanger (64) flows into the gas-liquid separator (25). The gas-liquid separator (25) separates the refrigerant into gas refrigerant and liquid refrigerant.

The liquid refrigerant separated in the gas-liquid separator (25) is cooled in the cooling 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).

A portion of the refrigerant cooled by the cooling heat exchanger (28) is decompressed by the second outdoor expansion valve (27) and then evaporates in the outdoor heat exchanger (24). The refrigerant evaporated in the outdoor heat exchanger (24) is sucked into the first compressor (21) and compressed again.

The remainder of the refrigerant cooled by the cooling heat exchanger (28) is sent to the cold storage unit (70). The refrigerant sent to the cold storage unit (70) is depressurized by the cold storage expansion valve (73) and then evaporates in the cold storage heat exchanger (74). As a result, the air inside the storage unit is cooled. The refrigerant evaporated in the cold storage heat exchanger (74) is sucked into the second compressor (22) and compressed again.

(8-6) Second heating/cooling operation The second heating/cooling operation shown in FIG. 9 is executed when the heating load of the air conditioning unit (60) is neither excessively high nor low. In the second heating/cooling operation, the controller (100) closes the second on-off valve (V2), the third on-off valve (V3), and the fourth on-off valve (V4), and opens the first on-off valve (V1). The controller (100) operates the first compressor (21) and the third compressor (23), and stops the second compressor (22). The controller (100) opens the injection valve (46) at a predetermined opening degree, and closes the first outdoor expansion valve (26) and the second outdoor expansion valve (27). The controller (100) adjusts the opening degree of the indoor expansion valve (63) and the cooling expansion valve (73). The controller (100) stops the outdoor fan (12) and operates the indoor fan (62) and the cooling fan (72).

In the second heating/cooling operation, the indoor heat exchanger (64) functions as a radiator, the outdoor heat exchanger (24) is essentially stopped, and a refrigeration cycle is performed in which the cooling heat exchanger (74) functions as an evaporator.

Specifically, the refrigerant compressed by the first compressor (21) is cooled in the intercooler (29) and then sucked into the third compressor (23). The refrigerant compressed by the third compressor (23) is sent to the air conditioning unit (60).

The refrigerant sent to the air conditioning unit (60) dissipates heat in the indoor heat exchanger (64). As a result, the air in the room is heated. The refrigerant that has dissipated heat in the indoor heat exchanger (64) flows into the gas-liquid separator (25). The gas-liquid separator (25) separates the refrigerant into gas refrigerant and liquid refrigerant.

The liquid refrigerant separated in the gas-liquid separator (25) is cooled in the cooling 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).

The refrigerant cooled by the cooling heat exchanger (28) is decompressed by the cold expansion valve (73) and then evaporates in the cold heat exchanger (74). As a result, the air inside the storage unit is cooled. The refrigerant evaporated in the cold heat exchanger (74) is sucked into the first compressor (21) and compressed again.

(8-7) Third heating/cooling operation The third heating/cooling operation shown in FIG. 10 is performed when the heating load of the air conditioning unit (60) is low. In the second heating/cooling operation, the controller (100) closes the third on-off valve (V3) and the fourth on-off valve (V4) and opens the first on-off valve (V1) and the second on-off valve (V2). The controller (100) operates the first compressor (21) and the third compressor (23) and stops the second compressor (22). The controller (100) opens the injection valve (46) and the first outdoor expansion valve (26) to a predetermined opening degree and closes the second outdoor expansion valve (27). The controller (100) adjusts the opening degree of the indoor expansion valve (63) and the cooling-use expansion valve (73). The controller (100) operates the outdoor fan (12), the indoor fan (62), and the cooling-use fan (72).

In the third heating/cooling operation, a refrigeration cycle is performed in which the indoor heat exchanger (64) and the outdoor heat exchanger (24) function as radiators and the cooling heat exchanger (74) functions as an evaporator.

Specifically, the refrigerant compressed by the first compressor (21) is cooled in the intermediate cooler (29) and then sucked into the third compressor (23). A portion of the refrigerant compressed by the third compressor (23) is sent to the air conditioning unit (60). The refrigerant sent to the air conditioning unit (60) dissipates heat in the indoor heat exchanger (64). As a result, the air in the room is heated. The refrigerant that dissipates heat in the indoor heat exchanger (64) flows into the gas-liquid separator (25). The remaining portion of the refrigerant compressed by the third compressor (23) dissipates heat in the outdoor heat exchanger (24) and then flows into the gas-liquid separator (25). The gas-liquid separator (25) separates the refrigerant into gas refrigerant and liquid refrigerant.

The liquid refrigerant separated in the gas-liquid separator (25) is cooled in the cooling 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).

The refrigerant cooled by the cooling heat exchanger (28) is decompressed by the cold expansion valve (73) and then evaporates in the cold heat exchanger (74). As a result, the air inside the storage unit is cooled. The refrigerant evaporated in the cold heat exchanger (74) is sucked into the first compressor (21) and compressed again.

(8-8) Defrost Operation The defrost operation is performed in winter or the like to melt the frost that has formed on the outdoor heat exchanger (24). For example, during heating/cooling operation, the controller (100) performs the defrost operation when a condition indicating that frost has formed on the outdoor heat exchanger (24) is met. The basic operation of the defrost operation is the same as that of the cooling operation shown in FIG. 5 and the cooling/cooling operation shown in FIG. 6. In the outdoor heat exchanger (24), the high-pressure refrigerant dissipates heat to the outside, melting the frost on the surface of the outdoor heat exchanger (24).

(9) Other Control Operations The controller (100) performs the following controls during the above-mentioned operation.

(9-1) Control Linked to Switching Between the First Refrigeration Cycle and the Second Refrigeration Cycle The controller (100) controls the refrigerant circuit (6) to perform a first refrigeration cycle in which the outdoor heat exchanger (24) serves as a radiator and the indoor heat exchanger (64) serves as an evaporator, and a second refrigeration cycle in which the indoor heat exchanger (64) serves as a radiator and the outdoor heat exchanger (24) serves as an evaporator. The first refrigeration cycle includes a refrigeration cycle executed in the above-mentioned cooling operation, cooling and cooling operation, defrost operation, and the like. The second refrigeration cycle includes a refrigeration cycle executed in the above-mentioned heating operation and first heating and cooling operation, and the like. For example, in the first refrigeration cycle, a low-pressure refrigerant is present in the first gas line (L4). When switching from this state to the second refrigeration cycle, the high pressure of the compression section (20) acts abruptly on the first gas line (L4) that had been in a low-pressure atmosphere. As a result, noise may be generated in the first gas line (L4) and the piping may be broken. Similarly, when the second refrigeration cycle is switched to the first refrigeration cycle, noise may occur in the second gas line (L5) or the piping may be broken. In particular, in this embodiment, the refrigerant is carbon dioxide, and the refrigeration cycle is performed in which the refrigerant pressure is equal to or higher than the critical pressure, so the high pressure is extremely high. Therefore, this problem becomes more pronounced.

The controller (100) therefore performs the following control to prevent the high pressure from acting abruptly on the piping when switching between the first and second refrigeration cycles. The following describes an example of switching between the second refrigeration cycle during the first heating/cooling operation and the first refrigeration cycle during the defrost operation.

In step S11, the second refrigeration cycle of the first heating/cooling operation is executed. When a command to execute the first refrigeration cycle is input to the controller (100) in step S12, the process proceeds to step S13. In step S13, the controller (100) reduces the capacity of the compression section (20). Here, "reducing the capacity of the compression section (20)" means not only reducing the rotation speed of the motor of at least one of the first compressor (21), second compressor (22), and third compressor (23), but also stopping some of these compressors (21, 22, 23).

In step S14, the controller (100) executes a first control of the flow path switching mechanism (30) (details of which will be described later). In step S15, a first refrigeration cycle of the defrost operation is executed. In the first refrigeration cycle, the high pressure of the refrigerant discharged from the compression section (20) acts on the second gas line (L5). However, in step S13, by reducing the capacity of the compression section (20) before the first refrigeration cycle, the high pressure can be reduced before switching to the second refrigeration cycle. This makes it possible to prevent the high pressure from acting abruptly on the second gas line (L5), and to prevent noise and piping from breaking on the second gas line (L5) side.

When the first refrigeration cycle is started, in step S16, the controller (100) increases the capacity of the compression section (20). Here, "increasing the capacity of the compression section (20)" means not only increasing the rotation speed of at least one of the motors of the first compressor (21), the second compressor (22), and the third compressor (23), but also operating the stopped compressors (21, 22, 23).

In step S16, when a command to execute the second refrigeration cycle is input to the controller (100), the process proceeds to step S18. In step S18, the controller (100) reduces the capacity of the compression section (20).

In step S19, the controller (100) executes a second control of the flow path switching mechanism (30) (details will be described later). In step S20, the second refrigeration cycle of the first heating/cooling operation is resumed. In the second refrigeration cycle, the high pressure of the refrigerant discharged from the compression section (20) acts on the first gas line (L4). However, in step S18, the capacity of the compression section (20) is reduced before the second refrigeration cycle, so that the high pressure can be reduced before switching to the second refrigeration cycle. This makes it possible to prevent the high pressure from acting abruptly on the first gas line (L4), and to prevent noise and piping from breaking on the first gas line (L4) side.

Although the above description has exemplified switching between the first heating/cooling operation and the defrost operation, the controller (100) may also reduce the capacity of the compression section (20) in conjunction with switching between the first refrigeration cycle and the second refrigeration cycle of other operations. The controller (100) may reduce the capacity of the compression section (20) not only before or immediately before switching between these refrigeration cycles, but also simultaneously with the switching.

(9-2) First Control of Flow Path Switching Mechanism The first control of the flow path switching mechanism in step S14 of Fig. 11 will be described in detail. When switching from the second refrigeration cycle to the first refrigeration cycle, the controller (100) executes the first control shown in Fig. 12.

In the first heating/cooling operation, all of the first on-off valves (V1) and fourth on-off valves (V4) are open, and all of the second on-off valves (V2) and all of the third on-off valves (V3) are closed. When the first control is executed from this state, in step S31, the controller (100) gradually increases the opening of the second expansion valve (93) shown in FIG. 3. Accordingly, the pressure in the second gas line (L5) gradually increases.

When the second expansion valve (93) is fully opened in step S32, the process proceeds to step S33. In step S33, the controller (100) opens one second solenoid valve (94). If all the second solenoid valves (V2) are not open in step S34, the process returns to step S33, and the controller (100) opens the next second solenoid valve (94). There is a predetermined time interval between the opening of one second solenoid valve (94) and the opening of the next second solenoid valve (94). In this way, the pressure in the second gas line (L5) increases gradually as the multiple second solenoid valves (V2) are opened one by one.

When all the second on-off valves (V2) are open in step S34, in step S35, the controller (100) closes the first on-off valve (V1) and the fourth on-off valve (V4) and opens the third on-off valve (V3).

As described above, in the first control, the on-off valve (V) is controlled so that the pressure in the second gas line (L5) increases gradually. This makes it possible to suppress noise generation and pipe breakage in the second gas line (L5).

(9-3) Second Control of Flow Path Switching Mechanism The second control of the flow path switching mechanism in step S18 of Fig. 11 will be described in detail below. When switching from the first refrigeration cycle to the second refrigeration cycle, the controller (100) executes the second control shown in Fig. 13.

In the defrost operation, all the second on-off valves (V2) and all the third on-off valves (V3) are open, and all the first on-off valves (V1) and the fourth on-off valve (V4) are closed. When the second control is executed from this state, in step S41, the controller (100) gradually increases the opening of the first expansion valve (91) shown in FIG. 3. Accordingly, the pressure in the first gas line (L4) gradually increases.

When the first expansion valve (91) is fully opened in step S42, the process proceeds to step S43. In step S43, the controller (100) opens one first solenoid valve (92). If, in step S44, all of the first solenoid valves (V1) are not open, the process returns to step S43, and the controller (100) opens the next first solenoid valve (92). There is a predetermined time interval between the opening of one first solenoid valve (92) and the opening of the next first solenoid valve (92). In this way, the first solenoid valves (92) are opened one by one in a stepwise manner, so that the pressure in the first gas line (L4) increases gradually.

When all of the first on-off valves (V1) are open in step S44, the controller (100) closes the second on-off valve (V2) and the third on-off valve (V3) and opens the fourth on-off valve (V4) in step S45.

As described above, in the second control, the on-off valve (V) is controlled so that the pressure in the first gas line (L4) increases gradually. This makes it possible to suppress noise generation and pipe breakage in the first gas line (L4).

(9-4) Third Control of Flow Channel Switching Mechanism When switching from the second heating/cooling operation to the third heating/cooling operation, the controller (100) performs a third control of the flow channel switching mechanism (30).

In the second heating/cooling operation, all the first on-off valves (V1) are open, and all the second on-off valves (V2), all the third on-off valves (V3), and the fourth on-off valve (V4) are closed. The third control is the same as steps S31 to S33 of the first control described above. The controller (100) gradually increases the opening of the second expansion valve (93) until it is fully open. Thereafter, the controller (100) opens the second solenoid on-off valves (94), i.e., the second on-off valves (V2), one by one, until all the second on-off valves (V2) are open. This allows the pressure in the second gas line (L5) to be gradually increased, thereby suppressing noise generation and pipe breakage in the second gas line (L5).

(10) Characteristics and Effects of the Flow Path Switching Mechanism (10-1) Simplification of the Flow Path Switching Mechanism In the flow path switching mechanism (30), only one on-off valve (V) is provided in the fourth flow path (34). This makes it possible to simplify the flow path switching mechanism (30).

(10-2) Effect of Suppressing Pressure Loss In the first heating/cooling operation shown in FIG. 8, for example, the entire amount of refrigerant compressed in the compression section (20) flows through the first flow path (31). In the cooling/cooling operation shown in FIG. 6, for example, the entire amount of refrigerant compressed in the compression section (20) flows through the second flow path (32). In contrast, in the first heating/cooling operation shown in FIG. 8, for example, only the refrigerant sucked into the second compressor (22) flows through the fourth flow path (34). Therefore, the flow rate of the refrigerant flowing through the fourth flow path (34) is smaller than the flow rates of the refrigerant flowing through the first flow path (31) and the second flow path (32). Therefore, even if the number of opening/closing valves (V) in the fourth flow path (34) is one, a large increase in pressure loss in the fourth flow path (34) can be suppressed.

Because low-pressure refrigerant flows through the fourth flow path (34), the density of the refrigerant is lower than that of the first flow path (31) and the second flow path (32). Therefore, even if the number of opening/closing valves (V) in the fourth flow path (34) is one, a large increase in pressure loss in the fourth flow path (34) can be suppressed.

In the first heating/cooling operation shown in FIG. 8, not only the outdoor heat exchanger (24) but also the cooling heat exchanger (74) serves as an evaporator. Therefore, the flow rate of the refrigerant flowing through the fourth flow path (34) is smaller than in an operation in which only the outdoor heat exchanger (24) serves as an evaporator. Therefore, even if the number of opening/closing valves (V) in the fourth flow path (34) is one, a large increase in pressure loss in the fourth flow path (34) can be suppressed.

For example, in the cooling operation shown in FIG. 6, only the refrigerant sucked into the second compressor (22) flows through the third flow path (33). Therefore, the flow rate of the refrigerant flowing through the third flow path (33) is less than the flow rates of the refrigerant flowing through the first flow path (31) and the second flow path (32). Therefore, even if the number N3 of the on-off valves (V) of the third flow path (33) is made smaller than the number N1 of the on-off valves (V) of the first flow path (31) and the number N2 of the on-off valves (V) of the second flow path (32), a large increase in pressure loss in the third flow path (33) can be suppressed.

On the other hand, in the cooling operation, the controller (100) increases the capacity of the second compressor (22) due to an increase in the cooling load of the indoor heat exchanger (64). This may increase the flow rate of the refrigerant flowing through the third flow path (33). In response to this, by providing two or more (four in this example) on-off valves (V) in parallel in the third flow path (33), it is possible to prevent the pressure loss in the third flow path (33) from becoming excessively large under conditions of a large cooling load.

Since a low-pressure refrigerant flows through the third flow path (33), the density of the refrigerant is lower than that of the first flow path (31) and the second flow path (32). Therefore, by making the number N3 of the on-off valves (V) in the third flow path (33) smaller than the number N1 of the on-off valves (V) in the first flow path (31) and the number N2 of the on-off valves (V) in the second flow path (32), it is possible to prevent a large increase in pressure loss in the third flow path (33).

(10-3) Restriction of Backflow by Check Valve At the start of the defrosting operation shown in FIG. 5 or FIG. 6, for example, under a condition where the outdoor air temperature is low, the internal pressure of the outdoor heat exchanger (24) may become low. In this case, the refrigerant that has flowed out of the third flow path (33) may flow from the second port (P2) to the fourth port (P4). If the refrigerant flows in the fourth flow path (34) in a direction opposite to the normal direction, the fourth on-off valve (V4) may become clogged with debris or the fourth on-off valve (V4) may become broken. In response to this, the fourth flow path (34) is provided with the first check valve (CV1) that restricts the flow of the refrigerant from the second port (P2) to the fourth port (P4). This makes it possible to prevent the refrigerant from flowing in the fourth flow path (34) in a direction opposite to the normal direction, thereby avoiding the above-mentioned problems.

In addition, when the internal pressure of the outdoor heat exchanger (24) becomes low, for example, at the start of the defrost operation shown in FIG. 5 or FIG. 6, the refrigerant flowing into the third flow path (33) may flow from the third port (P3) to the first port (P1). If the refrigerant flows in the first flow path (31) in the opposite direction to the normal direction, the first on-off valve (V1) may become clogged with debris or may break down. To address this, the first flow path (31) is provided with a second check valve (CV2) that limits the flow of refrigerant from the third port (P3) to the first port (P1). This makes it possible to prevent the refrigerant from flowing in the opposite direction to the normal direction through the first flow path (31), thereby avoiding the above-mentioned problems.

(10-4) Suppression of Chattering Noise Since the fourth flow path (34) is a low-pressure flow path, the pressure difference between the inlet and outlet sides of the on-off valve (V) is small. The on-off valve (V) is configured to hold the position of its valve disc by this pressure difference. For this reason, if multiple on-off valves are provided in the fourth flow path (34), chattering noise caused by the movement of the valve discs of the on-off valves is likely to become noise. In contrast, since the fourth flow path (34) has only one on-off valve (V), it is possible to suppress the chattering noise from becoming noise.

Similarly, since the third flow path (33) is a low-pressure flow path, chattering noise is likely to become noise. However, since the number N3 of the on-off valves (V) in the third flow path (33) is smaller than the number N1 of the on-off valves (V) in the first flow path (31) and the number N2 of the on-off valves (V) in the second flow path (32), chattering noise can be prevented from becoming noise.

(10-5) Prevention of sealing of refrigerant The first solenoid on-off valve (92) and the second solenoid on-off valve (94) are configured to close the valve body when de-energized. Therefore, if all the first on-off valves (V1) are solenoid on-off valves, the first flow path (31) is completely closed at the time of shipment of the refrigeration system (1). Similarly, if all the second on-off valves (V2) are solenoid on-off valves, the second flow path (32) is completely closed at the time of shipment of the refrigeration system (1). If the refrigerant is sealed on the discharge side of the compression section (20) in this way, there is a possibility that the pipe will burst when the volume of the refrigerant increases due to heat.

In response to this, a first expansion valve (91) is provided in the first flow path (31), and a second expansion valve (93) is provided in the second flow path (32). Therefore, when the refrigeration system (1) is shipped, the first expansion valve (91) and the second expansion valve (93) are opened to a predetermined degree, thereby preventing the refrigerant from being sealed on the discharge side of the compression section (20).

(11) Other embodiments As shown in FIG. 14, the number of on-off valves (V) in the third flow path (33) may be one. The third flow path (33) is formed of one flow path, and a third on-off valve (V3) is provided in the third flow path (33). The third on-off valve (V3) is an electromagnetic on-off valve, but may be an expansion valve. This can simplify the flow path switching mechanism (30). As described above, the third flow path (33) has a low refrigerant flow rate and a low refrigerant density. Therefore, even if the number of on-off valves (V) in the third flow path (33) is one, it is possible to suppress a large increase in pressure loss in the third flow path (33).

As shown in FIG. 14, a check valve (thirteenth check valve (CV13)) may be provided in the third flow path (33). The thirteenth check valve (CV13) restricts the flow of refrigerant from the second port (P2) to the third port (P3) in the third flow path (33).

All the on-off valves (V) in the first flow path (31) may be electromagnetic on-off valves, or all the on-off valves (V) in the second flow path (32) may be electromagnetic on-off valves. The on-off valves (V) in the third flow path (33) and the fourth flow path (34) may be expansion valves.

The first compression element and the second compression element may be configured with multiple compressors connected in series. The first compression element and the second compression element may be compressors having multiple compression mechanisms.

The first user-side heat exchanger (64) may be a heat exchanger that heats or cools water, brine, or the like. The first user-side heat exchanger (64) may be used as a heat source for a water heater.

Although the embodiments and modifications have been described above, it will be understood that various modifications of form and details are possible without departing from the spirit and scope of the claims. Furthermore, elements of the above embodiments, modifications, and other embodiments may be combined or substituted as appropriate.

The descriptions "first," "second," "third," etc. mentioned above are used to distinguish the words to which these descriptions are attached, and do not limit the number or order of the words.

As described above, the present disclosure is useful for heat source units and refrigeration devices.

1 Refrigeration equipment
6 Refrigerant circuit
10 Heat source unit
20 Compression section
21 First compressor (first compression element)
22 Second compressor (second compression element)
24 Outdoor heat exchanger (heat source side heat exchanger)
30 Flow path switching mechanism
31 First flow path
32 Second Flow Path
33 Third Stream
34 4th Stream
64 Indoor heat exchanger (first user side heat exchanger)
74 Refrigeration heat exchanger (second user side heat exchanger)
100 Controller (control unit)
CV1 First check valve
CV2 Second check valve
P1 First port
P2 Second port
P3 Third port
P4 4th port
V On-off valve

Claims (5)

A heat source unit comprising a compression section (20), a flow path switching mechanism (30), and a heat source side heat exchanger (24), and configured to form a refrigerant circuit (6) by being connected to a first utilization side heat exchanger (64) and a second utilization side heat exchanger (74),
The compression section (20) includes a first compression element (21) and a second compression element (22) arranged in parallel with each other,
a suction portion of the first compression element (21) is connected to a gas end portion of the second utilization side heat exchanger (74);
The flow path switching mechanism (30)
a first port (P1) connected to a discharge portion of the first compression element (21) and a discharge portion of the second compression element (22);
a second port (P2) connected to a suction portion of the second compression element (22);
a third port (P3) connected to a gas end of the first utilization side heat exchanger (64);
a fourth port (P4) connected to a gas end of the heat source side heat exchanger (24);
a first flow path (31) communicating between the first port (P1) and the third port (P3);
a second flow path (32) communicating between the first port (P1) and the fourth port (P4);
a third flow path (33) communicating between the second port (P2) and the third port (P3);
a fourth flow path (34) communicating between the second port (P2) and the fourth port (P4), and configured to open and close each of the first flow path (31), the second flow path (32), the third flow path (33), and the fourth flow path (34),
two or more on-off valves (V) are provided in parallel in each of the first flow path (31) and the second flow path (32);
At least one of the third flow path (33) and the fourth flow path (34) is provided with an on-off valve (V) ;
The fourth flow path (34) is provided with one on-off valve (V),
Two or more on-off valves (V) are provided in parallel in the third flow path (33).
Heat source unit. The heat source unit according to claim 1, wherein a first check valve (CV1) that restricts a flow of the refrigerant from the second port (P2) to the fourth port (P4) is provided in the fourth flow path (34). The heat source unit according to claim 1, wherein a second check valve (CV2) is provided in the first flow path (31) to limit a flow of the refrigerant from the third port (P3) to the first port (P1). a control unit (100) that controls the refrigerant circuit (6) to perform a first refrigeration cycle in which the heat source side heat exchanger (24) serves as a radiator and the first utilization side heat exchanger (64) serves as an evaporator, and a second refrigeration cycle in which the first utilization side heat exchanger (64) serves as a radiator and the heat source side heat exchanger (24) serves as an evaporator,
The heat source unit according to claim 1 , wherein the control section (100) reduces the capacity of the compression section (20) in conjunction with switching between the first refrigeration cycle and the second refrigeration cycle. A refrigeration device comprising the heat source unit according to claim 1 .