JP7590660B2 - Heat source unit, heat source system, and refrigeration device - Google Patents

Description

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

Patent Document 1 discloses a refrigeration device equipped with a heat source unit and a user unit. This refrigeration device performs a refrigeration cycle by circulating a refrigerant between the heat source unit and the user unit.

JP 2021-55919 A

Lubricating oil (refrigeration oil) is stored in the compressor of the heat source unit. Some of the lubricating oil stored in the compressor is discharged from the compressor together with the compressed refrigerant and flows out of the heat source unit. Therefore, the heat source unit performs an oil recovery operation to return the lubricating oil that has flowed out of the heat source unit to the compressor.

An example of an oil recovery operation is to forcibly increase the rotation speed of the compressor. When the rotation speed of the compressor is increased, the flow rate of the refrigerant circulating between the heat source unit and the user unit increases, and the lubricating oil remaining outside the heat source unit is sucked into the compressor of the heat source unit together with the refrigerant.

When the compressor rotation speed is increased during oil recovery operation, the cooling capacity of the user unit increases. As a result, during oil recovery operation, the cooling capacity may become excessive for the cooling load, causing the user unit to go into a sleep state. If the user unit goes into a sleep state during oil recovery operation, the compressor must be stopped to interrupt the oil recovery operation.

As a result, in conventional refrigeration systems, the amount of lubricating oil recovered from outside the heat source unit to the compressor is reduced, and the amount of lubricating oil stored in the compressor becomes insufficient, which can lead to damage to the compressor due to poor lubrication.

The purpose of this disclosure is to ensure the amount of lubricating oil stored in the compressor of a heat source unit and to increase the reliability of the compressor.

The first aspect of the present disclosure is a heat source unit (10) that is connected to a utilization side unit (70) that cools an object and circulates a refrigerant between the utilization side unit (70) and performs a refrigeration cycle, and includes a compressor (21) and a controller (131) that controls the compressor (21). In this aspect, the controller (131) performs an adjustment operation to adjust the rotation speed of the compressor (21) based on the low pressure of the refrigeration cycle, a stop operation to stop the compressor (21) when a stop condition is established that the low pressure of the refrigeration cycle falls below a reference pressure, a standby operation to prohibit the start of the compressor (21) until a standby time has elapsed from the time when the compressor (21) is stopped by the stop operation, and an oil recovery operation to increase the rotation speed of the compressor (21) to a reference speed or higher in order to return the lubricating oil of the compressor (21) that has flowed out of the heat source unit (10) together with the refrigerant to the compressor (21). In this embodiment, the standby time when the stop condition is satisfied during the execution of the oil recovery operation and the compressor (21) is stopped is longer than the standby time when the stop condition is satisfied during the execution of the adjustment operation and the compressor (21) is stopped.

While the compressor (21) of the heat source unit (10) is stopped, the utilization side unit (70) does not cool the object. Therefore, the longer the time that the compressor (21) is stopped, the greater the cooling load on the utilization side unit (70) when the compressor (21) is next started, and therefore the rotation speed of the compressor (21) after the compressor (21) is next started will be higher.

In the first embodiment, the standby time when the stop condition is satisfied during the oil recovery operation and the compressor (21) is stopped is longer than the standby time when the stop condition is satisfied during the adjustment operation and the compressor (21) is stopped. Therefore, when the stop condition is satisfied during the adjustment operation and the compressor (21) is stopped, the cooling load of the user side unit (70) is larger when the compressor (21) is next started up, and the rotation speed of the compressor (21) after restart is higher than when the stop condition is satisfied during the oil recovery operation and the compressor (21) is stopped. As a result, the flow rate of the refrigerant circulating between the heat source unit (10) and the user side unit (70) is increased, and the amount of lubricating oil that returns to the heat source unit (10) together with the refrigerant from outside the heat source unit (10) is increased. Therefore, according to this embodiment, the amount of lubricating oil stored in the compressor (21) of the heat source unit (10) can be secured, and the reliability of the compressor (21) is improved.

In a second aspect of the present disclosure, in the first aspect, the controller (131) outputs a continuation signal to the utilization side unit (70) to cause the target object to continue cooling while the oil recovery operation is being performed.

In the second mode, when the controller (131) outputs a continuation signal, the utilization side unit (70) continues cooling the object while the oil recovery operation is being performed. This avoids interruption of the oil recovery operation caused by the utilization side unit (70) ceasing to cool the object, and increases the amount of lubricating oil that returns to the heat source unit (10) together with the refrigerant from outside the heat source unit (10) while the oil recovery operation is being performed.

A third aspect of the present disclosure is a heat source system (200) comprising the heat source unit (10) of the second aspect and a drive unit (150) that drives an electronic expansion valve (73) provided in the user unit (70). In this embodiment, the drive unit (150) includes a driver (151) having a pair of terminals (152), which adjusts the opening degree of the electronic expansion valve (73) when the pair of terminals (152) are in a conductive state, and which fully closes the electronic expansion valve (73) when the pair of terminals (152) are in a non-conductive state; a first relay (161) provided in an electric circuit (153) connecting the pair of terminals (152) to each other and which operates in response to an output signal from the user side unit (70); and a second relay (162) arranged in parallel with the first relay (161) in the electric circuit (153) and which operates in response to the continuous signal from the heat source unit (10).

In the third embodiment, the driver (151) of the drive unit (150) controls the opening of the electronic expansion valve (73) of the utilization side unit (70). The operation of the driver (151) changes depending on the state of the first relay (161) that operates in response to an output signal from the utilization side unit (70) and the state of the second relay (162) that operates in response to the above-mentioned continuous signal from the heat source unit (10).

A fourth aspect of the present disclosure is a refrigeration system including the heat source unit (10) of the first or second aspect described above, or the heat source system (200) of the third aspect described above, and a utilization side unit (70) connected to the heat source unit (10) for cooling an object.

In the fourth aspect, a heat source unit (10) of any one of the first to third aspects and a utilization side unit (70) are provided in a refrigeration device (1).

FIG. 1 is a piping diagram of a refrigeration system according to a first embodiment. FIG. 2 is a configuration diagram of the flow path switching mechanism. FIG. 3 is a block diagram showing the connections between the components of the refrigeration device and the control system. FIG. 4 is a block diagram showing the configuration of the drive unit. FIG. 5 is a piping diagram of a refrigeration system, showing the flow of refrigerant during cooling operation. FIG. 6 is a piping diagram of a refrigeration system, showing the flow of refrigerant during cooling operation. FIG. 7 is a piping diagram of a refrigeration system, showing the flow of refrigerant during cooling operation. FIG. 8 is a piping diagram of a refrigeration system, showing the flow of refrigerant during heating operation. FIG. 9 is a piping diagram of the refrigeration system, showing the flow of refrigerant in the first heating/cooling operation. FIG. 10 is a piping diagram of the refrigeration system, showing the flow of refrigerant in the second heating/cooling operation. FIG. 11 is a piping diagram of the refrigeration system, showing the flow of refrigerant in the third heating/cooling operation. FIG. 4 is a diagram showing the relationship between the operation frequency and the suction pressure of the first compressor used in control of the first compressor by the outdoor controller. FIG. 13 is a piping diagram of a refrigeration system according to the second embodiment.

Embodiments of the present disclosure are described in detail below with reference to the drawings.

First Embodiment
The refrigeration system (1) of the first 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, a showcase, etc. 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. One air conditioning unit (60) is illustrated in Fig. 1. The refrigeration system (1) may include two or more air conditioning units (60) connected in parallel. One cold-setting unit (70) is illustrated in Fig. 1. 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 subcooling 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 details of the flow path switching mechanism (30) will be described later.

(2-1) Compression Section The compression section (20) compresses the refrigerant and includes a first compressor (21), a second compressor (22), and a third compressor (23).

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. For example, the first compressor (21), the second compressor (22), and the third compressor (23) are hermetic scroll compressors. Lubricating oil is stored inside each of these compressors (21, 22, 23). In each compressor (21, 22, 23), the lubricating oil stored inside is supplied to sliding parts such as the compression mechanism and bearings to lubricate the sliding parts. In each compressor (21, 22, 23), a part of the lubricating oil supplied to the compression mechanism is discharged from the compressor (21, 22, 23) together with the compressed refrigerant.

The operating capacity of each of the first compressor (21), second compressor (22), and third compressor (23) is changeable. An inverter device (not shown) supplies alternating current to the motors of each of the first compressor (21), second compressor (22), and third compressor (23). When the output frequency of the inverter device is changed, the rotation speed of the motor of each of the compressors (21, 22, 23) changes, and as a result, the operating capacity of each of the compressors (21, 22, 23) changes. The output frequency of the inverter device is the operating frequency of the compressor.

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 degree is adjustable. The first outdoor expansion valve (26) and the second outdoor expansion valve (27) are electronic expansion valves equipped with a valve body and a stepping motor that drives the valve body.

(2-6) Gas-Liquid Separator The gas-liquid separator (25) is a sealed container that stores a 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 valve (42) is an expansion valve whose opening is adjustable. The gas vent valve (42) is an electronic expansion valve equipped with a valve body and a stepping motor that drives the valve body.

(2-8) Subcooling Heat Exchanger The subcooling heat exchanger (28) has a first flow path (28a) which is a high-pressure side flow path and a second flow path (28b) which is a low-pressure side 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) cools the refrigerant flowing in the first flow path (28a) by the refrigerant flowing in the second flow path (28b).

The second 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 second flow path (28b). The upstream flow path (44) is provided with an injection valve (46) which is a subcooling side pressure reducing valve. The injection valve (46) is an expansion valve whose opening degree is adjustable. The injection valve (46) is an electronic expansion valve equipped with a valve body and a stepping motor which drives the valve body.

One end of the downstream flow path (45) is connected to the outlet 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 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 installed indoors to perform air conditioning. 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 degree is adjustable. The indoor expansion valve (63) is an electronic expansion valve equipped with a valve body and a stepping motor that drives the valve body.

The indoor heat exchanger (64) is a fin-and-tube type air 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).

The air conditioning unit (60) includes an indoor temperature sensor (65). The indoor temperature sensor (65) is disposed upstream of the indoor heat exchanger (64) in the air flow path in the air conditioning unit (60) and measures the temperature of the air (indoor air) sucked into the air conditioning unit (60).

(4) Refrigeration Unit The refrigeration unit (70) is an example of a user-side unit that cools the interior of a refrigerator. A specific example of the refrigeration unit (70) is a refrigerated showcase. The refrigeration unit (70) has a refrigeration circuit (71) and a refrigeration fan (72). A second liquid connection pipe (4) is connected to a liquid end of the refrigeration circuit (71). A second gas connection pipe (5) is connected to a gas end of the refrigeration 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 equipped with a valve body and a stepping motor that drives the valve body.

The cold-air heat exchanger (74) is a fin-and-tube type air 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 cabinet. The cold-air heat exchanger (74) exchanges heat between the refrigerant flowing therethrough and the air inside the cabinet transported by the cold-air fan (72). The evaporation temperature of the cold-air heat exchanger (74) is lower than the evaporation temperature of the indoor heat exchanger (64).

The cold storage unit (70) is equipped with an internal temperature sensor (75). The internal temperature sensor (75) is disposed upstream of the cold storage heat exchanger (74) in the air flow path in the cold storage unit (70) and measures the temperature of the air (internal air) flowing toward the cold storage heat exchanger (74).

The cold-installed unit (70) includes an inlet refrigerant temperature sensor (76) and an outlet refrigerant temperature sensor (77). The inlet refrigerant temperature sensor (76) and the outlet refrigerant temperature sensor (77) are attached to the cold-installed circuit (71). The inlet refrigerant temperature sensor (76) is disposed between the cold-installed expansion valve (73) and the cold-installed heat exchanger (74) and measures the temperature of the refrigerant flowing into the cold-installed heat exchanger (74). The outlet refrigerant temperature sensor (77) is disposed near the gas side end of the cold-installed heat exchanger (74) and measures the temperature of the refrigerant flowing out of the cold-installed heat exchanger (74).

(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. 2, 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 switching flow path (31), a second switching flow path (32), a third switching flow path (33), and a fourth switching flow path (34). The first switching flow path (31) is provided with a first opening and closing mechanism (81), the second switching flow path (32) is provided with a second opening and closing mechanism (82), the third switching flow path (33) is provided with a third opening and closing mechanism (83), and the fourth switching flow path (34) is provided with a fourth opening and closing mechanism (84).

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

As shown in FIG. 2, the first switching flow path (31) has two or more first branch paths (31a) that are parallel to each other. In this example, the first switching flow path (31) has seven first branch paths (31a). In this example, the second switching flow path (32) has two or more second branch paths (32a) that are parallel to each other. The second switching flow path (32) has seven second branch paths (32a). The third switching flow path (33) has third branch paths (33a) that are parallel to each other. In this example, the third switching flow path (33) has four third branch paths (33a). The fourth switching 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 switching flow path (31). In this example, seven first opening/closing valves (V1) are provided in the first switching 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 switching flow path (32). In this example, seven second opening/closing valves (V2) are provided in the second switching 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 solenoid opening/closing valve (94). There is one second expansion valve (93), and six second solenoid 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 switching flow path (32). In this example, four third opening/closing valves (V3) are provided in the third switching 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 switching flow path (34) is provided with a fourth opening/closing valve (V4). 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 3.

(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 switching flow path (34). A second check valve (CV2) is provided in the first switching 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 switching 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 switching 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 switching flow path (34) closer to the second port (P2) than the on-off 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 switching 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 switching 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 switching 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 switching flow path (31) closer to the third port (P3) than the opening/closing valve (V).

(6) Sensor As shown in Fig. 1, the heat source unit (10) has a plurality of sensors. The plurality of sensors includes a refrigerant pressure sensor that detects the pressure of the refrigerant, a refrigerant temperature sensor that detects the temperature of the refrigerant, and an air temperature sensor that detects the temperature of the air.

The refrigerant pressure sensors include a high-pressure pressure sensor (101), an intermediate pressure sensor (102), a first suction pressure sensor (103), a second suction pressure sensor (104), and a liquid-side pressure sensor (105). The high-pressure pressure sensor (101) is provided in the third discharge pipe (23b). The high-pressure pressure sensor (101) detects the pressure of the refrigerant on the discharge side of the compression section (20), in other words, the high-pressure pressure of the refrigerant circuit (6). The intermediate pressure sensor (102) is provided in the third suction pipe (23a). The intermediate pressure sensor (102) detects the pressure of the 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 the 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 the refrigerant on the suction side of the second compressor (22).

The liquid side pressure sensor (105) is provided in the liquid side flow path (40). Specifically, the liquid side pressure sensor (105) is provided in the second pipe (40b). The liquid side pressure sensor (105) detects a pressure equivalent to the internal pressure of the gas-liquid separator (25). The liquid side pressure sensor (105) detects a pressure equivalent to the pressure of the refrigerant in the first flow path (28a).

The refrigerant temperature sensors include a first discharge temperature sensor (111), a first intake temperature sensor (112), a second discharge temperature sensor (113), a second intake temperature sensor (114), a third discharge temperature sensor (115), a third intake temperature sensor (116), a liquid side temperature sensor (117), an injection side temperature sensor (118), and a heat source side temperature sensor (119). 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 intake temperature sensor (112) is provided in the first intake 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 intake temperature sensor (114) is provided in the second intake pipe (22a) and detects the temperature of the refrigerant drawn 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 intake temperature sensor (116) is provided in the third intake pipe (23a) and detects the temperature of the refrigerant drawn into the third compressor (23).

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 outlet side of the first flow path (28a) of the subcooling heat exchanger (28) in the liquid side flow path (40). More specifically, the liquid side temperature sensor (117) is provided in the liquid side flow path (40) between the outlet end of the first flow path (28a) and the inlet end of the injection flow path (43). The liquid side temperature sensor (117) detects the temperature of the refrigerant that has flowed out of the first flow path (28a).

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 that has flowed out of the second flow path (28b).

The heat source side temperature sensor (119) is provided on the heat transfer tube of the outdoor heat exchanger (24). The heat source side temperature sensor (119) is provided on the liquid side end of the outdoor heat exchanger (24). The heat source side temperature sensor (119) detects the temperature of the refrigerant at the liquid side end of the outdoor heat exchanger (24).

The air temperature sensor includes an outside air temperature sensor (121). The outside air temperature sensor (121) detects the temperature of the outside air.

(7) Control System As shown in Fig. 3, the refrigeration apparatus (1) includes an outdoor controller (131), an indoor controller (132), a cold-conditioning controller (133), and a drive unit (150). The outdoor controller (131), the indoor controller (132), the cold-conditioning controller (133), and the drive unit (150) constitute a control system (130) that controls the components of the refrigeration apparatus. The drive unit (150), together with the heat source unit (10), constitutes a heat source system (200).

As shown 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 cold setting controller (133) is provided in the cold setting unit (70). The drive unit (150) is provided near the cold setting unit (70).

As shown in FIG. 3, each of the outdoor controller (131), the indoor controller (132), and the cold controller (133) includes a microcomputer mounted on a control board and a memory device (specifically, a semiconductor memory) that stores software for operating the microcomputer.

The outdoor controller (131) can communicate with the indoor controller (132). Signals, data, and the like are transmitted and received between the outdoor controller (131) and the indoor controller (132). On the other hand, the outdoor controller (131) does not communicate with the cold unit controller (133). No signals, data, and the like are transmitted and received between the outdoor controller (131) and the cold unit controller (133).

(7-1) Outdoor Controller Measurement values of each sensor provided in the heat source unit (10) are input to the outdoor controller (131). The outdoor controller (131) controls devices provided in the heat source unit (10). For example, the outdoor controller (131) adjusts the operating capacities of the first compressor (21), the second compressor (22), and the third compressor (23). The outdoor controller (131) also adjusts the openings of the expansion valves (26, 27, 63). The outdoor controller (131) also controls the valves constituting the flow path switching mechanism (30) to switch the state of the flow path switching mechanism (30).

The outdoor controller (131) outputs an enable signal and a continue signal to the drive unit (150). The enable signal is a signal that enables the operation of the cooling unit (70). The continue signal is a signal that causes the operation of the cooling unit (70) to continue.

(7-2) Indoor Controller The indoor controller (132) receives a measurement value of the indoor temperature sensor (65). The indoor controller (132) controls devices provided in the air conditioning unit (60). For example, the outdoor controller (131) adjusts the rotation speed of the indoor fan (62) and the opening of the indoor expansion valve (63).

(7-3) Chilling Unit Controller The chilling unit controller (133) receives measurement values from the inside temperature sensor (75), the inlet refrigerant temperature sensor (76), and the outlet refrigerant temperature sensor (77). The chilling unit controller (133) controls devices provided in the chilling unit (70). For example, the chilling unit controller (133) adjusts the rotation speed of the chilling unit fan (72).

The cold-setting controller (133) outputs a command signal and a request signal to the drive unit (150). The command signal is a signal that instructs the cold-setting expansion valve (73) to adjust the opening degree. The request signal is a signal that requests the cold-setting unit (70) to cool the air inside the storage compartment.

(7-4) Drive Unit As shown in FIG. 4, the drive unit (150) includes a driver (151), a first relay (161), a second relay (162), and a third relay (163).

The driver (151) outputs a pulse signal to the stepping motor of the cold-setting expansion valve (73). When the driver (151) receives a command signal output by the cold-setting controller (133), it outputs a pulse signal including a predetermined number of pulses. When the stepping motor of the cold-setting expansion valve (73) rotates in response to the pulse signal output by the driver, the valve body moves, and the opening of the cold-setting expansion valve (73) changes.

The driver (151) has a pair of signal terminals (152). The driver (151) is configured to output a pulse signal based on a command signal to the cold-set expansion valve (73) when the pair of signal terminals (152) are in a conductive state. The driver (151) is also configured to output a pulse signal to the cold-set expansion valve (73) to fully close the cold-set expansion valve (73) when the pair of signal terminals (152) are in a non-conductive state.

A connection circuit (153) is connected to each signal terminal (152) of the driver (151). One end of the connection circuit (153) is connected to one of the pair of signal terminals (152), and the other end of the connection circuit (153) is connected to the other of the pair of signal terminals (152). The connection circuit (153) is an electric circuit that connects the pair of signal terminals (152) to each other.

The first relay (161), the second relay (162), and the third relay (163) are provided in the connection circuit (153). In the connection circuit (153), the first relay (161) and the second relay (162) are connected in parallel. Also, in the connection circuit (153), the third relay (163) is connected in series with the first relay (161) and the second relay (162).

The first relay (161), the second relay (162), and the third relay (163) each switch between a conductive state (short-circuit state) and a non-conductive state (open state). When at least one of the first relay (161) and the second relay (162) is in a conductive state and the third relay (163) is in a conductive state, the pair of signal terminals (152) of the driver (151) are in a mutually conductive state. On the other hand, when both the first relay (161) and the second relay (162) are in a non-conductive state or when the third relay (163) is in a non-conductive state, the pair of signal terminals (152) of the driver (151) are in a mutually non-conductive state.

The first relay (161) operates based on a request signal output by the cold setting controller (133). The first relay (161) is in a conductive state when a request signal is input, and is in a non-conductive state when a request signal is not input.

The second relay (162) operates based on a continuation signal output by the outdoor controller (131). The second relay (162) is in a conductive state when a continuation signal is input, and is in a non-conductive state when a continuation signal is not input.

The third relay (163) operates based on an enable signal output by the outdoor controller (131). The third relay (163) is in a conductive state when an enable signal is input, and is in a non-conductive state when an enable signal is not input.

(8) Operation Operation of the refrigeration system (1) will be described. The operations of the refrigeration system (1) include cooling operation, cooling operation, cooling and cooling operation, heating operation, and heating and cooling 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 each of these operations, refrigerant circulates in the refrigerant circuit (6) to perform a refrigeration cycle.

An overview of each operation will be explained with reference to Figures 5 to 11. In the figures, the flow of the refrigerant is indicated by dashed arrows, and the flow path through which the refrigerant flows is shown in thick lines. In the figures, heat exchangers that function as radiators are hatched, and heat exchangers that function as evaporators are dotted.

5, the heat source unit (10) and the cooling unit (70) operate, and the air conditioning unit (60) is shut down. In the heat source unit (10), the first compressor (21) and the third compressor (23) operate, and the second compressor (22) is shut down.

During cooling operation, the outdoor heat exchanger (24) functions as a radiator, the indoor heat exchanger (64) is inactive, and the cooling heat exchanger (74) functions as an evaporator.

The refrigerant supplied from the heat source unit (10) to the cold-setting unit (70) is reduced in pressure as it passes through the cold-setting expansion valve (73), absorbs heat from the air inside the cabinet in the cold-setting heat exchanger (74) and evaporates, and is then sucked into the first compressor (21). The cold-setting unit (70) blows the cooled air into the cabinet space. The third compressor (23) sucks in and compresses the refrigerant discharged by the first compressor (21).

6, the heat source unit (10) and the air conditioning unit (60) operate, and the cooling unit (70) is shut down. In the heat source unit (10), the second compressor (22) and the third compressor (23) operate, and the first compressor (21) is shut down.

During cooling operation, the outdoor heat exchanger (24) functions as a radiator, the indoor heat exchanger (64) functions as an evaporator, and the cooling heat exchanger (74) is shut down.

The refrigerant supplied from the heat source unit (10) to the air conditioning unit (60) is reduced in pressure as it passes through the indoor expansion valve (63), absorbs heat from the indoor air in the indoor heat exchanger (64) and evaporates, and is then sucked into the second compressor (22). The air conditioning unit (60) blows the cooled air into the interior space. The third compressor (23) sucks in and compresses the refrigerant discharged by the second compressor (22).

7, the heat source unit (10), the cooling unit (70), and the air conditioning unit (60) are operated. In the heat source unit (10), the first compressor (21), the second compressor (22), and the third compressor (23) are operated.

In the cooling operation, the outdoor heat exchanger (24) functions as a radiator, and the indoor heat exchanger (64) and the cooling heat exchanger (74) function as evaporators.

In the cooling operation, as in the cooling operation, the refrigerant evaporated in the cooling heat exchanger (74) is sucked into the first compressor (21), and the cooling unit (70) blows the cooled air into the interior space. As in the cooling operation, the refrigerant evaporated in the indoor heat exchanger (64) is sucked into the second compressor (22), and the air conditioning unit (60) blows the cooled air into the interior space. The third compressor (23) sucks in the refrigerant discharged from the first compressor (21) and the refrigerant discharged from the second compressor (22), and compresses the sucked refrigerant.

8, the heat source unit (10) and the air conditioning unit (60) operate, and the cooling unit (70) is shut down. In the heat source unit (10), the second compressor (22) and the third compressor (23) operate, and the first compressor (21) is shut down.

During heating operation, the indoor heat exchanger (64) functions as a radiator, the outdoor heat exchanger (24) functions as an evaporator, and the cooling heat exchanger (74) is shut down.

The refrigerant supplied from the heat source unit (10) to the air conditioning unit (60) releases heat to the indoor air in the indoor heat exchanger (64), is reduced in pressure as it passes through the second outdoor expansion valve (27), absorbs heat from the outdoor air in the outdoor heat exchanger (24) and evaporates, and is then sucked into the second compressor (22). The air conditioning unit (60) blows the heated air into the interior space. The third compressor (23) sucks in and compresses the refrigerant discharged by the second compressor (22).

(8-5) First heating/cooling operation The first heating/cooling operation shown in Fig. 9 is performed when the heating load of the air conditioning unit (60) is high. In the first heating/cooling operation, the heat source unit (10), the cooling unit (70), and the air conditioning unit (60) operate. In the heat source unit (10), the first compressor (21), the second compressor (22), and the third compressor (23) operate.

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

In the first heating/cooling operation, as in the heating operation, the refrigerant supplied from the heat source unit (10) to the air conditioning unit (60) dissipates heat to the indoor air in the indoor heat exchanger (64), and the refrigerant evaporated in the outdoor heat exchanger (24) is sucked into the second compressor (22). The air conditioning unit (60) blows out the heated air into the interior space.

In the first heating/cooling operation, similarly to the cooling operation, the refrigerant evaporated in the cooling heat exchanger (74) is sucked into the first compressor (21), and the cooling unit (70) blows the cooled air into the interior space. The third compressor (23) sucks in the refrigerant discharged from the first compressor (21) and the refrigerant discharged from the second compressor (22), and compresses the sucked refrigerant.

(8-6) Second heating/cooling operation The second heating/cooling operation shown in Fig. 10 is performed when the heating load of the air conditioning unit (60) is neither excessively high nor low. In the second heating/cooling operation, the heat source unit (10), the cooling unit (70), and the air conditioning unit (60) operate. In the heat source unit (10), the first compressor (21) and the third compressor (23) operate, and the second compressor (22) is stopped.

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

The refrigerant supplied from the heat source unit (10) to the air conditioning unit (60) dissipates heat to the indoor air in the indoor heat exchanger (64). The air conditioning unit (60) blows the heated air into the interior space. The refrigerant flowing out of the air conditioning unit (60) returns to the heat source unit (10) and is then supplied to the cooling unit (70).

The refrigerant supplied from the heat source unit (10) to the cold setting unit (70) evaporates in the cold setting heat exchanger (74) as in the cold setting operation, and is then sucked into the first compressor (21). The cold setting unit (70) blows the cooled air into the interior space. The third compressor (23) sucks in and compresses the refrigerant discharged by the first compressor (21).

(8-7) Third heating/cooling operation The third heating/cooling operation shown in Fig. 11 is performed when the heating load of the air conditioning unit (60) is low. In the second heating/cooling operation, the heat source unit (10), the cooling unit (70), and the air conditioning unit (60) operate. In the heat source unit (10), the first compressor (21) and the third compressor (23) operate, and the second compressor (22) is stopped.

In the third heating/cooling operation, the indoor heat exchanger (64) and the outdoor heat exchanger (24) function as radiators, and the cooling heat exchanger (74) functions as an evaporator.

The refrigerant supplied from the heat source unit (10) to the air conditioning unit (60) dissipates heat to the indoor air in the indoor heat exchanger (64). The air conditioning unit (60) blows the heated air into the interior space. The refrigerant flowing out of the air conditioning unit (60) returns to the heat source unit (10).

The refrigerant that has dissipated heat in the outdoor heat exchanger (24) is supplied to the cooling unit (70) together with the refrigerant that has returned from the air conditioning unit (60) to the heat source unit (10).

The refrigerant supplied from the heat source unit (10) to the cold setting unit (70) evaporates in the cold setting heat exchanger (74) as in the cold setting operation, and is then sucked into the first compressor (21). The cold setting unit (70) blows the cooled air into the interior space. The third compressor (23) sucks in and compresses the refrigerant discharged by the first compressor (21).

(9) Operation of the Cold Service Controller The operation of the cold service controller (133) for outputting a command signal and a request signal will be described.

(9-1) Command Signal The cold-service controller (133) outputs a command signal so that the degree of superheat SH of the refrigerant flowing out of the cold-service heat exchanger (74) falls within a target range of the degree of superheat (for example, a range of 5° C.±1° C.). The command signal is a signal that instructs adjustment of the opening degree of the cold-service expansion valve (73).

The cold-setting controller (133) calculates the difference between the measurement value of the outlet refrigerant temperature sensor (77) and the measurement value of the inlet refrigerant temperature sensor (76), and sets the calculated value as the superheat degree SH of the refrigerant flowing out from the cold-setting heat exchanger (74). If the calculated superheat degree SH exceeds the target range, the cold-setting controller (133) outputs a command signal to the driver (151) of the drive unit (150) to increase the opening degree of the cold-setting expansion valve (73). If the calculated superheat degree SH falls below the target range, the cold-setting controller (133) outputs a command signal to the driver (151) of the drive unit (150) to decrease the opening degree of the cold-setting expansion valve (73). If the calculated superheat degree SH is within the target range, the cold-setting controller (133) does not output a command signal. Therefore, in this case, the opening degree of the cold-setting expansion valve (73) is maintained.

(9-2) Demand Signal The cold section controller (133) outputs a demand signal based on a measurement value of the inside temperature sensor (75). The demand signal is a signal for the cold section unit (70) to request cooling of the inside air.

The cold storage controller (133) executes or stops outputting a request signal so that the measurement value of the internal temperature sensor (75) falls within the target range of the internal temperature (e.g., within the range of the set temperature ±0.5°C).

The cold setting controller (133) outputs a request signal when the measurement value of the internal temperature sensor (75) is higher than the upper limit of the target range. The cold setting controller (133) continues to output the request signal until the measurement value of the internal temperature sensor (75) decreases and reaches the lower limit of the target range. When the measurement value of the internal temperature sensor (75) falls below the lower limit of the target range, the cold setting controller (133) stops outputting the request signal. The cold setting controller (133) continues to stop outputting the request signal until the measurement value of the internal temperature sensor (75) increases and reaches the upper limit of the target range.

(10) Operation of the Outdoor Controller As described above, the outdoor controller (131) controls the first compressor (21), the second compressor (22), and the third compressor (23).

The outdoor controller (131) adjusts the operating capacity (rotation speed) of the second compressor (22) based on the pressure of the refrigerant sucked into the second compressor (22) (specifically, the measurement value of the second suction pressure sensor (104)) and other factors. The outdoor controller (131) adjusts the operating capacity (rotation speed) of the third compressor (23) based on the pressure of the refrigerant sucked into the third compressor (23) (specifically, the measurement value of the intermediate pressure sensor (102)) and other factors.

The outdoor controller (131) performs the following operations to control the first compressor (21): adjustment operation, stop operation, standby operation, and oil recovery operation.

(10-1) Adjustment Operation The adjustment operation of the outdoor controller (131) is an operation for adjusting the operating capacity of the first compressor (21) based on the measurement value LP of the first suction pressure sensor (103). The measurement value of the first suction pressure sensor (103) indicates the pressure of the refrigerant sucked into the first compressor (21). Therefore, the measurement value of the first suction pressure sensor (103) is the low pressure of the refrigeration cycle performed by circulating the refrigerant between the heat source unit (10) and the cooling unit (70).

The adjustment operation of the outdoor controller (131) is explained with reference to Figure 12.

The target line shown by a solid line indicates the target value of the measured value LP of the first suction pressure sensor (103). When the operating frequency of the first compressor (21) is Hz1 or less, the target value of the measured value LP is LP2. When the operating frequency of the first compressor (21) is Hz2 or more, the target value of the measured value LP is LP1. When the operating frequency of the first compressor (21) is between Hz1 and Hz2, the target value of the measured value LP decreases in proportion to the operating frequency of the first compressor (21).

The dashed line located above the target line is the upper limit line. The upper limit line indicates the upper limit of the target range of the measurement value LP of the first suction pressure sensor (103). The upper limit line is higher than the target line by a predetermined value (e.g., 0.15 MPa).

The dashed line located below the target line is the lower limit line. The lower limit line indicates the lower limit of the target range of the measurement value LP of the first suction pressure sensor (103). The lower limit line is lower than the target line by a predetermined value (e.g., 0.15 MPa).

The area below the lower line is the decline area. The area above the upper line is the rise area. The area between the lower and upper lines is the holding area.

During the adjustment operation, the outdoor controller (131) acquires the measurement value LP of the first suction pressure sensor (103) and the operating frequency Hz of the first compressor (21).

When the acquired measured value LP and the point represented by the operating frequency Hz are in the decreasing region in FIG. 12, the outdoor controller (131) reduces the operating frequency of the first compressor (21). When the operating frequency of the first compressor (21) is reduced, the flow rate of the refrigerant sucked by the first compressor (21) from the cooling unit (70) decreases, and the measured value LP of the first suction pressure sensor (103) increases.

When the acquired measured value LP and the point represented by the operating frequency Hz are in the increasing region in FIG. 12, the outdoor controller (131) increases the operating frequency of the first compressor (21). When the operating frequency of the first compressor (21) increases, the flow rate of the refrigerant sucked by the first compressor (21) from the cooling unit (70) increases, and the measured value LP of the first suction pressure sensor (103) decreases.

When the point represented by the acquired measurement value LP and the operating frequency Hz is within the holding region in FIG. 12, the outdoor controller (131) does not change the operating frequency of the first compressor (21).

The holding region in FIG. 12 is provided to reduce the frequency of changes in the operating frequency Hz of the first compressor (21). The wider the width of the holding region (the difference between the upper limit line and the lower limit line), the less frequently the operating frequency Hz of the first compressor (21) is changed.

(10-2) Shutdown Operation The shutdown operation of the outdoor controller (131) is an operation for stopping the first compressor (21) when a predetermined shutdown condition is satisfied. The shutdown condition is that “the measured value LP of the first suction pressure sensor (103) falls below a reference pressure (e.g., 1.0 MPa).”

As described above, the outdoor controller (131) does not communicate with the cold storage controller (133). Therefore, the outdoor controller (131) cannot obtain information regarding the operating state of the cold storage unit (70).

On the other hand, when the cold-setting unit (70) is in a stopped state and the cold-setting expansion valve (73) is fully closed, the pressure of the refrigerant sucked into the first compressor (21) decreases. Therefore, when the measured value LP of the first suction pressure sensor (103) falls below the reference pressure, it can be determined that the cold-setting unit (70) is in a stopped state.

When the above-mentioned stop condition is met, the outdoor controller (131) determines that it is not necessary to continue operating the first compressor (21), and stops the first compressor (21).

(10-3) Standby Operation The standby operation of the outdoor controller is an operation for prohibiting the start-up of the first compressor (21) until a standby time has elapsed from the time the first compressor (21) is stopped.

If the first compressor (21) is started and stopped frequently, the first compressor (21) may be damaged. Therefore, in order to prevent damage to the first compressor (21) caused by frequent starting and stopping, the outdoor controller (131) performs a standby operation when the first compressor (21) stops.

When the stop condition is met during the adjustment operation and the first compressor (21) stops, the outdoor controller (131) sets the standby time to a first time (e.g., one minute) and performs standby operation. On the other hand, when the stop condition is met during the oil recovery operation described below and the first compressor (21) stops, the outdoor controller (131) sets the standby time to a second time (e.g., three minutes) and performs standby operation. The second time is longer than the first time. It is desirable that the second time be greater than or equal to three minutes and less than or equal to five minutes.

Here, while the first compressor (21) is stopped, the cooling unit (70) does not cool the inside air. Therefore, the longer the standby time, the greater the increase in the temperature of the inside air. Therefore, in this embodiment, the second time is set to a time that does not cause an excessive increase in the temperature of the inside air.

(10-4) Oil Recovery Operation The oil recovery operation of the outdoor controller (131) is an operation of increasing the rotational speed of the first compressor (21) to a reference speed or higher in order to return the lubricating oil of the first compressor (21), which has flowed out from the heat source unit (10) together with the refrigerant, to the first compressor (21).

When a predetermined oil recovery condition is met, the outdoor controller (131) performs an oil recovery operation. One example of an oil recovery condition is that the operating frequency of the first compressor (21) remains relatively low (e.g., 20 Hz or less) for a predetermined period of time (e.g., 20 minutes).

In the oil recovery operation, the outdoor controller (131) increases the operating frequency of the first compressor (21) to a reference frequency (e.g., 40 Hz) or higher that corresponds to the reference speed. When the operating frequency of the first compressor (21) is increased to a frequency higher than the reference frequency, the rotation speed of the first compressor (21) becomes higher than the reference speed.

When the rotation speed of the first compressor (21) becomes relatively high, the flow rate of the refrigerant sucked by the first compressor (21) from the cooling unit (70) becomes relatively high. Therefore, the amount of lubricating oil returning to the heat source unit (10) together with the refrigerant from outside the heat source unit (10) increases. The lubricating oil that flows into the heat source unit (10) together with the refrigerant is sucked into the first compressor (21) together with the refrigerant. As a result, the amount of lubricating oil stored in the first compressor (21) increases.

(10-5) Permission Signal and Continue Signal The outdoor controller (131) outputs a permission signal and a continue signal to the drive unit (150).

The permission signal is a signal that permits the operation of the cooling unit (70). The outdoor controller (131) outputs the permission signal when the standby operation is not being performed, and stops outputting the permission signal when the standby operation is being performed. Since the first compressor (21) is stopped during the standby operation, the outdoor controller (131) prohibits the operation of the cooling unit (70) by stopping output of the permission signal.

The continuation signal is a signal that causes the operation of the cooling unit (70) to continue. The outdoor controller (131) outputs the continuation signal while the oil recovery operation is being performed, and stops outputting the continuation signal when the oil recovery operation is not being performed. If the cooling unit (70) goes into a paused state during the oil recovery operation, the oil recovery operation will be interrupted. Therefore, the outdoor controller (131) outputs the continuation signal while the oil recovery operation is being performed, causing the cooling unit (70) to continue cooling the air inside the storage unit.

(11) Operation of the Drive Unit The operation of the drive unit (150) for driving the cold-set expansion valve (73) will be described with reference to FIG.

(11-1) Operation of the Driver The driver (151) operates differently depending on whether the pair of signal terminals (152) is in a conductive state or a non-conductive state.

When the pair of signal terminals (152) are in a mutually conductive state (conductive state), the driver (151) outputs a pulse signal based on the command signal to the cold-set expansion valve (73). Specifically, the driver (151) outputs a pulse signal to the stepping motor of the cold-set expansion valve (73) to increase or decrease the opening degree of the cold-set expansion valve (73) based on the command signal.

When the pair of signal terminals (152) are not electrically connected to each other (non-conductive state), the driver (151) outputs a pulse signal to the cold-set expansion valve (73) to fully close the cold-set expansion valve (73). Specifically, the driver (151) outputs a pulse signal to the stepping motor of the cold-set expansion valve (73) to reduce the opening of the cold-set expansion valve (73) to the fully closed state.

(11-2) Control of the cold-conditioning expansion valve The third relay (163) operates based on an enable signal output by the outdoor controller (131). The outdoor controller (131) outputs an enable signal when the outdoor controller (131) is not performing a standby operation. Therefore, when the first compressor (21) is in a state in which it can operate, the outdoor controller (131) outputs an enable signal, and the third relay (163) becomes conductive.

When the third relay (163) is in a conductive state, if at least one of the first relay (161) and the second relay (162) is in a conductive state, a pair of signal terminals (152) of the driver (151) are in a conductive state with each other, and as a result, the opening degree of the cold-setting expansion valve (73) is adjusted.

The cold-setting controller (133) outputs a request signal when the cold-setting unit (70) needs to cool the air inside the container. When the request signal is input to the first relay (161), the first relay (161) enters a conductive state. When the first relay (161) and the third relay (163) enter a conductive state, a pair of signal terminals (152) of the driver (151) enter a conductive state, and as a result, the opening degree of the cold-setting expansion valve (73) is adjusted. When the cold-setting expansion valve (73) is open, refrigerant circulates between the heat source unit (10) and the cold-setting unit (70), and the air inside the container is cooled in the cold-setting heat exchanger (74).

When there is no need to cool the air inside the refrigerator in the refrigerator unit (70), the refrigerator controller (133) does not output a request signal. Therefore, the first relay (161) is in a non-conductive state. At this time, if the second relay (162) is in a non-conductive state, the pair of signal terminals (152) of the driver (151) are in a non-conductive state with each other, and as a result, the refrigerator expansion valve (73) is in a fully closed state.

When the cold-setting expansion valve (73) is fully closed, the air inside the container is not cooled in the cold-setting heat exchanger (74), and the cold-setting unit (70) is in a stopped state. When the cold-setting expansion valve (73) is fully closed, the pressure of the refrigerant sucked into the first compressor (21) decreases. When the pressure of the refrigerant sucked into the first compressor (21) decreases and the stop condition is met, the outdoor controller (131) performs a stop operation to stop the first compressor (21).

In this way, when the second relay (162) is in a non-conductive state and the third relay (163) is in a conductive state, when the first relay (161) is in a conductive state, the cooling unit (70) enters an operating state in which it cools the air inside the storage compartment, and when the first relay (161) is in a non-conductive state, the cooling unit (70) enters a paused state in which it does not cool the air inside the storage compartment.

The outdoor controller (131) outputs a continuation signal while the oil recovery operation is being performed. When the outdoor controller (131) outputs a continuation signal, the second relay (162) enters a conductive state. When the second relay (162) enters a conductive state, if the third relay (163) is in a conductive state, even if the first relay (161) is in a non-conductive state, the pair of signal terminals (152) of the driver (151) enter a conductive state with each other, and as a result, the opening of the cold-set expansion valve (73) is adjusted.

In this way, while the outdoor controller (131) is performing the oil recovery operation, even if the cold-setting controller (133) is not outputting a request signal, the opening of the cold-setting expansion valve (73) is adjusted, and the refrigerant continues to pass through the cold-setting heat exchanger (74). Therefore, even if the cold-setting controller (133) stops outputting a request signal, the outdoor controller (131) continues to circulate the refrigerant between the heat source unit (10) and the cold-setting unit (70) through the oil recovery operation, and the lubricating oil that has flowed out of the heat source unit (10) is recovered together with the refrigerant into the first compressor (21).

As described above, while the outdoor controller (131) is performing the oil recovery operation, the opening adjustment of the cold-setting expansion valve (73) continues even when the cold-setting controller (133) is not outputting a request signal. In this state, since there is no need to cool the air inside the refrigerator in the cold-setting unit (70), the opening of the cold-setting expansion valve (73) becomes smaller.

If the opening of the cold-setting expansion valve (73) continues to be very small, the pressure of the refrigerant sucked into the first compressor (21) may decrease, and the stop condition may be satisfied. If the stop condition is satisfied, the outdoor controller (131) performs a stop operation to stop the first compressor (21). After stopping the first compressor (21) by the stop operation, the outdoor controller (131) performs a standby operation.

(12) Features of the present embodiment The features of the present embodiment will be described.

(12-1) First Feature When a stop condition is satisfied while the outdoor controller (131) is performing an oil recovery operation and the oil recovery operation is interrupted, there is a possibility that a sufficient amount of lubricating oil has not been recovered from outside the heat source unit (10) to the first compressor (21).

Therefore, in this embodiment, when a stop condition is met while the oil recovery operation is being performed, the outdoor controller (131) extends the standby time from the first time to the second time and performs the standby operation.

While the first compressor (21) is stopped due to the standby operation of the outdoor controller (131), the cooling unit (70) is in a standby state in which it does not cool the air inside the storage unit. While the cooling unit (70) is at rest, the temperature of the air inside the storage unit gradually rises. Therefore, the longer the standby time, the greater the cooling load of the cooling unit (70) at the end of the standby time.

The greater the cooling load of the cooling unit (70), the higher the rotation speed of the first compressor (21) after the first compressor (21) is next started. The higher the rotation speed of the first compressor (21), the greater the flow rate of the refrigerant circulating between the heat source unit (10) and the cooling unit (70).

Therefore, when the outdoor controller (131) extends the standby time from the first hour to the second hour and performs the standby operation, the rotation speed of the first compressor (21) after the standby time has elapsed and the first compressor (21) is started becomes higher and the flow rate of the refrigerant circulating between the heat source unit (10) and the cooling unit (70) becomes larger than when the standby operation is performed with the standby time set to the first hour. As a result, the amount of lubricating oil sucked into the first compressor (21) together with the refrigerant from outside the heat source unit (10) increases, and the amount of lubricating oil stored in the first compressor (21) is secured.

Therefore, according to this embodiment, the amount of lubricating oil stored in the first compressor (21) of the heat source unit (10) can be secured, and the reliability of the first compressor (21) can be improved.

(12-2) Second Feature In the refrigeration system (1) of this embodiment, when the outdoor controller (131) outputs a continuation signal, the opening degree of the cold-set expansion valve (73) is continuously adjusted during the oil recovery operation, and the refrigerant continues to pass through the cold-set heat exchanger (74). This makes it possible to prevent interruption of the oil recovery operation caused by the cold-set expansion valve (73) being fully closed when the cold-set unit (70) is in a dormant state, and to increase the amount of lubricating oil that returns to the first compressor (21) together with the refrigerant from outside the heat source unit (10) during the oil recovery operation.

Second Embodiment
The refrigeration system (1) of the second embodiment is a modified version of the refrigeration system (1) of the first embodiment. Here, the refrigeration system (1) of the second embodiment will be described, mainly focusing on the differences from the refrigeration system (1) of the first embodiment.

As shown in FIG. 13, the refrigeration system (1) of this embodiment does not include an air conditioning unit (60). In the refrigeration system (1) of this embodiment, the refrigerant circuit (6) is configured by connecting the heat source unit (10) and the cooling unit (70) with a pair of connecting pipes (4, 5). In the heat source circuit (11) of this embodiment, the second compressor (22), the flow path switching mechanism (30), and the third pipe (40c), fourth pipe (40d), and fifth pipe (40e) of the liquid side flow path (40) are omitted.

The outdoor controller (131) of this embodiment performs an adjustment operation, a stop operation, a standby operation, and an oil recovery operation on the first compressor (21) in the same manner as the outdoor controller (131) of the first embodiment. Also, the outdoor controller (131) of this embodiment, like the outdoor controller (131) of the first embodiment, sets the standby time in the standby operation to a first time when the stop condition is satisfied during the adjustment operation and the first compressor (21) is stopped, and sets the standby time in the standby operation to a second time longer than the first time when the stop condition is satisfied during the oil recovery operation and the first compressor (21) is stopped.

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, the elements of the above embodiments, modifications, and other embodiments may be combined or substituted as appropriate. Furthermore, the descriptions "first," "second," "third," etc. in the specification and claims 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, heat source systems, and refrigeration devices.

1 Refrigeration equipment
10 Heat source unit
21 First compressor (compressor)
70 Refrigeration unit (user unit)
73 Refrigeration expansion valve (electronic expansion valve)
131 Outdoor controller (controller)
150 Drive Unit
151 Drivers
152 Signal terminal (terminal)
153 Connecting circuit (electrical circuit)
161 First relay
162 Second relay
200 Heat Source System

Claims (3)

A heat source unit (10) is connected to a utilization side unit (70) having a heat exchanger (74) for cooling an object and an expansion valve (73), and performs a refrigeration cycle by circulating a refrigerant between the utilization side unit (70),
The compressor (21) and a controller (131) for controlling the compressor (21),
The controller (131)
an adjusting operation for adjusting the rotation speed of the compressor (21) based on the low pressure of the refrigeration cycle;
a stopping operation for stopping the compressor (21) when a stopping condition is satisfied, that is, the low pressure of the refrigeration cycle falls below a reference pressure;
a standby operation for prohibiting start-up of the compressor (21) until a standby time has elapsed from the time when the compressor (21) is stopped by the stopping operation; and
an oil recovery operation is performed to increase the rotation speed of the compressor (21) to a reference speed or higher in order to return lubricating oil for the compressor (21) that has flowed out from the heat source unit (10) together with the refrigerant to the compressor (21);
the standby time when the stop condition is satisfied during the oil recovery operation and the compressor (21) is stopped is longer than the standby time when the stop condition is satisfied during the adjustment operation and the compressor (21) is stopped,
The controller (131) outputs a continuation signal to the utilization side unit (70) during the oil recovery operation to cause the utilization side unit (70) to continue cooling the object,
By outputting the continuation signal from the controller (131) , even in a state in which the utilization side unit (70) is not outputting a request signal to be output when an object needs to be cooled, the utilization side unit (70) is maintained in a state in which the expansion valve (73) is open and refrigerant continues to pass through the heat exchanger (74).
Heat source unit. A heat source unit (10) according to claim 1;
a drive unit (150) that drives an electronic expansion valve (73) provided in the utilization side unit (70),
The drive unit (150)
a driver (151) having a pair of terminals (152), adjusting an opening degree of the electronic expansion valve (73) when the pair of terminals (152) are in a mutually conductive state, and fully closing the electronic expansion valve (73) when the pair of terminals (152) are in a mutually non-conductive state;
a first relay (161) provided in an electric circuit (153) connecting the pair of terminals (152) to each other and operated in response to an output signal from the utilization side unit (70);
a second relay (162) that is arranged in parallel with the first relay (161) in the electric circuit (153) and operates in response to the continuous signal from the heat source unit (10). A heat source unit (10) according to claim 1 or a heat source system (200) according to claim 2;
The refrigeration system comprises a utilization side unit (70) connected to the heat source unit (10) for cooling an object.