JP2007232250A - Refrigerating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely achieve a cooling capacity in an use unit 60 without impairing operation efficiency in a refrigerating device 1 comprising a refrigerant circuit 4 constituted by connecting a heat source unit 10 and the use unit 60 by communication piping 2, 3. <P>SOLUTION: An opening control means 52 adjusting an opening of a use-side expansion valve 63 performs a discharge temperature lowering motion for expanding the opening of the use-side expansion valve 63 to lower a temperature of a discharged refrigerant of a compressor 14, when it is necessary to increase the cooling capacity of the use unit 60 in the state in which the increase of an operation capacity of the compressor 14 is limited. As a degree of superheat of the refrigerant sucked by the compressor 14 is reduced, the temperature of the discharged refrigerant of the compressor 14 is lowered, and the operation capacity of the compressor 14 can be increased. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a refrigeration apparatus including a refrigerant circuit in which a heat source unit and a utilization unit are connected by a communication pipe.

  Conventionally, a heat source unit and a use unit are provided with a refrigerant circuit configured to be connected by a communication pipe. In the refrigerant circuit, the heat exchanger of the heat source unit becomes a condenser and the heat exchanger of the use unit becomes an evaporator. A refrigeration apparatus that performs a cooling operation is known. In this type of refrigeration system, the opening degree of the expansion valve upstream of the evaporator is generally adjusted so that the refrigerant flowing out of the evaporator is overheated in order to prevent damage to the compressor due to so-called liquid back. The An example of this type of refrigeration apparatus is disclosed in Patent Document 1.

Specifically, FIG. 1 of Patent Document 1 shows an air conditioner in which three indoor units, which are utilization units, are connected in parallel to an outdoor unit, which is a heat source unit, through a communication pipe. The outdoor unit is provided with a compressor and an outdoor heat exchanger. Each indoor unit is provided with an indoor expansion valve and an indoor heat exchanger. In this refrigeration apparatus, the operating capacity of the compressor and the opening of the indoor expansion valve of each indoor unit are adjusted so that the internal temperature of each indoor unit becomes the set temperature.
JP 2004-340430 A

  By the way, in the conventional refrigeration apparatus, even if it is attempted to increase the cooling capacity of the utilization unit, the cooling capacity may not be increased if the temperature of the refrigerant discharged from the compressor is increased to a state close to an allowable value. is there. Specifically, in this type of refrigeration apparatus, a reference value is usually provided for the temperature of refrigerant discharged from the compressor in order to protect the compressor. This reference value is set to a value slightly smaller than the allowable value. When the operating capacity of the compressor is increased, the temperature of the refrigerant discharged from the compressor also rises. Therefore, in the state where the temperature of the refrigerant discharged from the compressor exceeds the reference value, it is limited to increase the operating capacity of the compressor. I try to do it. For this reason, when the temperature of the refrigerant discharged from the compressor is high, the operating capacity cannot be increased even though the operating capacity of the compressor has not reached the maximum operating capacity, and the cooling capacity of the utilization unit is reduced. It cannot be increased.

  In addition, when liquid injection is performed to send the liquid refrigerant to the compressor, the temperature of the refrigerant discharged from the compressor is lowered, so that the operating capacity of the compressor can be increased. However, in liquid injection, the amount of refrigerant supplied to the use unit is reduced by the amount of refrigerant supplied to the compressor. For this reason, the increase in the operating capacity of the compressor is not reflected as it is as the increase in the cooling capacity of the utilization unit, and there is a possibility that the operating efficiency is reduced.

  The present invention has been made in view of the above points, and the object of the present invention is to reduce operating efficiency in a refrigeration apparatus including a refrigerant circuit in which a heat source unit and a utilization unit are connected by a communication pipe. It is to reliably obtain the cooling capacity in the utilization unit without causing it.

  1st invention has the heat source unit (10) which has a compressor (14), the cooling heat exchanger (64) for cooling a target object, and the utilization side expansion valve (63) of variable opening degree. Refrigerant circuit (4) constructed by connecting use unit (60) with connecting pipe (2, 3), capacity control means (51) for adjusting the operating capacity of compressor (14), and the use A refrigeration apparatus (1) provided with opening degree control means (52) for adjusting the opening degree of the side expansion valve (63) is assumed.

  The refrigeration apparatus (1) includes discharge temperature detection means (38) for detecting the temperature of refrigerant discharged from the compressor (14), and the capacity control means (51) includes the discharge temperature detection means (38). ) Is configured to limit the increase of the operating capacity of the compressor (14) when the detected value exceeds the reference value, while the opening control means (52) includes the use unit (60). If the detected value of the discharge temperature detecting means (38) exceeds the reference value when an increase in the cooling capacity of the compressor is required, the use side is used to reduce the temperature of the refrigerant discharged from the compressor (14). A discharge temperature lowering operation is performed to increase the opening degree of the expansion valve (63).

  In the first invention, if the detected value of the discharge temperature detecting means (38) exceeds the reference value, the capacity control means (51) restricts the operating capacity of the compressor (14) from increasing. When the increase in the cooling capacity of the use unit (60) is necessary in the state where the increase in the operating capacity of the compressor (14) is restricted, the opening degree control means (52) is connected to the use side expansion valve (63 The discharge temperature lowering operation is performed to increase the opening degree. If the opening of the use side expansion valve (63) is enlarged, the refrigerant evaporating pressure in the cooling heat exchanger (64) becomes high and the refrigerant becomes difficult to evaporate. Therefore, the refrigerant flowing out of the cooling heat exchanger (64) Decreases in the degree of superheat or changes from an overheated state to a wet state. Furthermore, since the superheat degree of the refrigerant sucked by the compressor (14) also decreases or changes from a superheated state to a wet state, the temperature of the refrigerant discharged from the compressor (14) decreases. When the temperature of the refrigerant discharged from the compressor (14) decreases to a reference value or lower by the discharge temperature lowering operation of the opening degree control means (52), the operating capacity of the compressor (14) can be increased.

  According to a second aspect, in the first aspect, in the refrigerant circuit (4), a plurality of utilization units (60) are connected in parallel to the heat source unit (10) through connection pipes (2, 3). The opening degree control means (52) individually adjusts the opening degree of the usage side expansion valve (63) of the usage unit (60) and uses the cooling capacity increase in the discharge temperature lowering operation. Only the opening of the use side expansion valve (63) of the unit (60) is enlarged.

  In the second invention, the opening degree control means (52) of the use side expansion valve (63) of the use unit (60) that requires an increase in cooling capacity among the plurality of use units (60) in the discharge temperature lowering operation. Enlarge only the opening. Therefore, when the discharge temperature lowering operation is performed, the ratio of the refrigerant flowing into the usage unit (60) whose opening degree of the usage side expansion valve (63) is increased increases.

  According to a third aspect of the present invention, in the first or second aspect of the invention, the cooling heat exchanger (64) of the utilization unit (60) that requires an increase in cooling capacity in the discharge temperature lowering operation of the opening degree control means (52). The degree of opening of the utilization side expansion valve (63) of the utilization unit (60) is increased so that the refrigerant flowing out from the utilization unit (60) becomes wet.

  In the third invention, the opening temperature control means (52) reduces the discharge temperature so that the refrigerant flowing out from the cooling heat exchanger (64) of the utilization unit (60) requiring an increase in cooling capacity becomes wet. In operation, the opening of the use side expansion valve (63) of the use unit (60) is expanded. That is, the refrigerant flowing out from the cooling heat exchanger (64) of the utilization unit (60) is in a gas-liquid two-phase state in which a gas refrigerant and a liquid refrigerant are mixed.

  According to a fourth invention, in any one of the first to third inventions, the utilization unit (60) is configured to detect an evaporation temperature detecting means (67) for detecting an evaporation temperature of the refrigerant in the cooling heat exchanger (64). The opening degree control means (52) includes a set temperature and an evaporation temperature for the object to be cooled for the use unit (60) whose opening degree of the use side expansion valve (63) is expanded by the discharge temperature lowering operation. When the difference from the detection value of the detection means (67) falls below a predetermined value, the opening degree of the use side expansion valve (63) of the use unit (60) is limited to a range equal to or less than the upper limit value set according to the operating state. Perform the opening limit operation.

  In 4th invention, about the utilization unit (60) which expanded the opening degree of the utilization side expansion valve (63) by the said discharge temperature fall operation | movement, the detected value of the preset temperature with respect to the target object to cool and an evaporation temperature detection means (67) The opening degree control means (52) performs the opening degree limiting operation when the difference between the two values falls below a predetermined value. In the opening restriction operation, the upper limit value of the opening is set for the use side expansion valve (63) of the use unit (60) in which the opening degree of the use side expansion valve (63) is expanded, and the use side expansion valve (63) Is limited to a range not exceeding the upper limit. Here, if the opening degree of the use side expansion valve (63) is increased, the amount of refrigerant flowing in the cooling heat exchanger (64) increases, so that the cooling capacity of the use unit (60) increases. However, as the opening degree of the use side expansion valve (63) increases, the refrigerant evaporation temperature in the cooling heat exchanger (64) increases, so the difference between the set temperature of the use unit (60) and the refrigerant evaporation temperature. Becomes smaller. For this reason, the cooling capacity of the usage unit (60) increases until the opening degree of the use side expansion valve (63) reaches a certain level, but if the opening degree increases further, the cooling capacity of the usage unit (60) decreases. Resulting in. In the fourth aspect of the invention, when the difference between the set temperature of the use unit (60) and the detected value of the evaporating temperature detecting means (67) falls below a predetermined value, the opening of the use side expansion valve (63) is less than the upper limit value. By limiting the range, the cooling capacity of the utilization unit (60) is prevented from being lowered.

  According to a fifth invention, in the fourth invention, when the detected value of the discharge temperature detecting means (38) exceeds a reference value in a state in which the opening control means (52) is performing the opening restricting operation. And a liquid injection control means (53) for performing a liquid injection operation for sending a liquid refrigerant to the compressor (14).

  In the fifth invention, since the detected value of the discharge temperature detecting means (38) exceeds the reference value in a state where the opening degree control means (52) is performing the opening degree limiting operation, the operating capacity of the compressor (14) The liquid injection operation for feeding the liquid refrigerant to the compressor (14) is performed when the increase in the pressure is restricted. When the liquid injection operation is performed, the temperature of the refrigerant discharged from the compressor (14) decreases. That is, in the fifth aspect of the invention, when the discharge temperature lowering operation cannot be performed by the opening degree limiting operation, the liquid injection operation is performed to lower the temperature of the refrigerant discharged from the compressor (14), and the compressor ( 14) It is possible to increase the operating capacity.

  In a sixth aspect based on any one of the first to fifth aspects, the compressor (14) is a high-pressure dome type scroll compressor.

  In the sixth invention, the compressor (14) of the heat source unit (10) is a high-pressure dome type scroll compressor. Here, in the low-pressure dome type compressor, the suction refrigerant flows into the dome in which the refrigerating machine oil is stored. When the wet refrigerant flows into the dome, the liquid refrigerant dissolves in the refrigerating machine oil and the viscosity of the refrigerating machine oil decreases, so that the compressor is in a poorly lubricated state. In the case of the high-pressure dome type, the compressed refrigerant flows into the dome, so that the amount of refrigerant dissolved in the refrigerating machine oil is not so large and the viscosity of the refrigerating machine oil is maintained in an appropriate state. In addition, the scroll compressor has a characteristic that it is more resistant to liquid compression than a compressor of another mechanism such as a rotary compressor. In other words, in the fifth aspect of the invention, a high-pressure dome type scroll compressor having high durability against the wet refrigerant is used as the compressor (14) of the heat source unit (10).

  In a seventh invention, R410A is used as the refrigerant circulating in the refrigerant circuit (4) in any one of the first to sixth inventions.

  In the seventh invention, R410A is used as the refrigerant circulating in the refrigerant circuit (4). Here, the refrigerant R410A has a characteristic that the temperature of the refrigerant discharged from the compressor (14) is higher than that of other refrigerants (for example, R22). That is, in the case of the refrigeration apparatus (1) using the refrigerant R410A, it is likely to be limited to increase the operation capacity of the compressor (14) during operation.

  In the present invention, when the operation capacity of the compressor (14) is limited to increase the cooling capacity of the utilization unit (60), the discharge temperature lowering operation is performed to reduce the compressor (14). The operating capacity of the compressor (14) can be increased by lowering the temperature of the discharged refrigerant. In other words, the operating unit (60) has not been able to increase the operating capacity of the compressor (14) without performing liquid injection in which the refrigerant supply amount to the usage unit (60) side is reduced. The operation capacity of the compressor (14) can be increased by performing the discharge temperature lowering operation that does not reduce the amount of refrigerant supplied to the) side. Therefore, if the operating capacity of the compressor (14) is increased after the temperature of the refrigerant discharged from the compressor (14) has dropped below the reference value, the use unit (60) side is increased according to the increased operating capacity. As the circulation amount of the refrigerant increases, the cooling capacity of the usage unit (60) increases, so that the cooling capacity of the usage unit (60) can be reliably obtained without lowering the operation efficiency.

  In the second invention, the cooling capacity needs to be increased by expanding only the opening of the usage side expansion valve (63) of the usage unit (60) that needs to be increased in the discharge temperature lowering operation. The ratio of the refrigerant flowing into the use unit (60) is increased. Therefore, if the operating capacity of the compressor (14) is increased after the temperature of the refrigerant discharged from the compressor (14) has dropped below the reference value, the refrigerant flow rate of the utilization unit (60) that requires an increase in cooling capacity Tends to increase. Therefore, the increase in the operating capacity of the compressor (14) can be suppressed as much as possible, and the usage unit (60) that increases the cooling capacity can be adjusted to a predetermined cooling capacity, so that the operating efficiency of the refrigeration system (1) can be reduced. Can be improved.

  In the third invention, the refrigerant flowing out from the cooling heat exchanger (64) of the utilization unit (60) is in a gas-liquid two-phase state in the discharge temperature lowering operation by the opening degree control means (52). Yes. Therefore, the range in which the gas-liquid two-phase refrigerant with higher heat transfer coefficient than the gas refrigerant circulates in the cooling heat exchanger (64) increases, so the amount of heat exchange in the cooling heat exchanger (64) increases. The cooling capacity of the unit (60) can be increased.

  In the fourth invention, when the difference between the set temperature of the utilization unit (60) and the detected value of the evaporating temperature detecting means (67) falls below a predetermined value, the opening control means (52) performs the opening limiting operation. This prevents the cooling capacity of the utilization unit (60) from being reduced. In other words, although the discharge temperature lowering operation is performed to increase the cooling capacity of the usage unit (60), the difference between the set temperature of the usage unit (60) and the evaporation temperature of the refrigerant becomes too small and the cooling capacity is reduced. It is trying not to decline. Therefore, the cooling capacity of the utilization unit (60) can be properly controlled.

  Further, in the fifth invention, when the discharge temperature lowering operation cannot be performed in a state where the increase of the operation capacity of the compressor (14) is restricted, the liquid injection operation is performed to perform the compressor (14). It is possible to increase the operating capacity of the vehicle. Therefore, even if the operation capacity of the compressor (14) is restricted and the discharge temperature lowering operation cannot be performed, the cooling capacity in the usage unit (60) can be increased. The cooling capacity in (60) can be obtained more reliably.

  In the sixth aspect of the invention, the compressor (14) of the heat source unit (10) is a high-pressure dome type scroll compressor that has high durability against wet refrigerant. Here, if the opening degree of the use side expansion valve (63) is increased by the discharge temperature lowering operation, the superheat degree of the refrigerant sucked by the compressor (14) gradually decreases, and the refrigerant becomes a gas-liquid two-phase. The wetness of the water gradually decreases. And the burden to a compressor (14) becomes large, so that the opening degree of a utilization side expansion valve (63) is expanded. In the sixth aspect of the invention, since the high-pressure dome type scroll compressor having high durability against the wet refrigerant is used, the use side expansion valve (63) is opened more greatly than the compressors of other mechanisms. Can be expanded to a degree. Therefore, the cooling capacity in the utilization unit (60) can be obtained more reliably.

  In the seventh aspect of the invention, R410A that tends to be restricted from increasing the operating capacity of the compressor (14) is used as the refrigerant circulating in the refrigerant circuit (4). Therefore, especially in the case of the refrigeration apparatus (1) using the refrigerant R410A, the temperature of the refrigerant discharged from the compressor (14) can be lowered without reducing the amount of refrigerant flowing to the use unit (60). A discharge temperature lowering operation that can be performed is effective.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<Overall configuration of refrigeration equipment>
FIG. 1 is a schematic configuration diagram of a refrigeration apparatus (1) according to this embodiment. This refrigeration apparatus (1) is a multi-type low-temperature refrigeration apparatus including one external unit (10), a first internal unit (60a), and a second internal unit (60b). . The refrigeration apparatus (1) is configured to cool the inside of the refrigerated warehouse.

  The outside unit (10) is provided with an outside circuit (11). The first internal unit (60a) is provided with a first internal circuit (61a), and the second internal unit (60b) is provided with a second internal circuit (61b). In this refrigeration system (1), the internal circuit (61a, 61b) is connected in parallel with the liquid side communication pipe (2) and the gas side communication pipe (3) to the external circuit (11), A refrigerant circuit (4) for performing a vapor compression refrigeration cycle is configured. In the refrigeration apparatus (1), the refrigerant circuit (4) is filled with R410A as a refrigerant. In addition, the kind of refrigerant | coolant shown here is only an example.

  A first closing valve (12) and a second closing valve (13) are provided at the end of the external circuit (11), respectively. One end of the liquid side communication pipe (2) is connected to the first closing valve (12). The other end of the liquid side connecting pipe (2) is branched into two, one connected to the liquid side end of the first internal circuit (61a) and the other connected to the liquid in the second internal circuit (61b). Connected to the side edge. One end of the gas side communication pipe (3) is connected to the second closing valve (13). The other end of the gas side communication pipe (3) is branched into two, one connected to the gas side end of the first internal circuit (61a) and the other to the gas in the second internal circuit (61b). Connected to the side edge.

《Outside unit》
The external circuit (11) of the external unit (10) includes two compressors (14a, 14b), an external heat exchanger (15), a receiver (16), a supercooling heat exchanger (17), A first external expansion valve (18), a second external expansion valve (19), a four-way switching valve (20), and an oil separator (33) are provided. The two compressors (14a, 14b) are composed of a first compressor (14a) and a second compressor (14b) connected in parallel to each other.

  Both the first compressor (14a) and the second compressor (14b) are configured as a hermetic high-pressure dome type scroll compressor. Electric power is supplied to the first compressor (14a) via an inverter. The capacity of the first compressor (14a) can be changed by changing the rotation speed of the electric motor by changing the output frequency of the inverter. On the other hand, in the second compressor (14b), the electric motor is always operated at a constant rotational speed, and the capacity thereof cannot be changed.

  One end of the first discharge pipe (21a) is connected to the discharge side of the first compressor (14a), and one end of the second discharge pipe (21b) is connected to the discharge side of the second compressor (14b). Yes. The first discharge pipe (21a) is provided with a check valve (CV1), and the second discharge pipe (21b) is provided with a check valve (CV2). The other ends of these discharge pipes (21a, 21b) are connected to the first port (P1) of the four-way switching valve (20) via the discharge junction pipe (21). These check valves (CV1, CV2) are valves that allow only the flow of refrigerant from the compressors (14a, 14b) toward the discharge junction pipe (21).

  One end of a first suction pipe (22a) is connected to the suction side of the first compressor (14a), and one end of a second suction pipe (22b) is connected to the suction side of the second compressor (14b). Yes. The other ends of these suction pipes (22a, 22b) are connected to the second port (P2) of the four-way switching valve (20) via the suction junction pipe (22).

  The discharge junction pipe (21) is provided with an oil separator (33). The oil separator (33) is for separating the refrigerating machine oil from the refrigerant discharged from each compressor (14a, 14b). One end of an oil return pipe (34) is connected to the oil separator (33). The other end of the oil return pipe (34) is connected to a first oil return pipe (34a) connected to the first suction pipe (22a) and a second oil return pipe (34b) connected to the second suction pipe (22b). Branched. Each oil return pipe (34a, 34b) is provided with a solenoid valve (SV1, SV2).

  The external heat exchanger (15) is configured as a cross-fin type fin-and-tube heat exchanger. An external fan (23) is provided in the vicinity of the external heat exchanger (15). Although the external heat exchanger (15) is not illustrated, the heat transfer tubes are arranged in a plurality of paths, and the refrigerant pipes are branched and connected to the heat transfer tubes of the respective paths. And in this outside heat exchanger (15), heat exchange is performed between the outside air sent by the outside fan (23) and the refrigerant flowing through the heat transfer tube. One end of the external heat exchanger (15) is connected to the third port (P3) of the four-way selector valve (20). The other end of the external heat exchanger (15) is connected to the top of the receiver (16) via the first liquid pipe (24). The first liquid pipe (24) is provided with a check valve (CV3) that allows only the flow of refrigerant toward the receiver (16).

  The supercooling heat exchanger (17) includes a high-pressure channel (17a) and a low-pressure channel (17b), and exchanges heat between the refrigerants flowing through the channels (17a, 17b). This supercooling heat exchanger (17) is constituted by, for example, a plate heat exchanger.

  The inflow end of the high-pressure channel (17a) is connected to the bottom of the receiver (16) via a refrigerant pipe. The outflow end of the high-pressure channel (17a) is connected to the first closing valve (12) via the second liquid pipe (25). The second liquid pipe (25) is provided with a check valve (CV4) that allows only the flow of refrigerant toward the liquid side communication pipe (2).

  On the other hand, a first branch pipe (26) branched from the second liquid pipe (25) on the upstream side of the check valve (CV4) is connected to the inflow end of the low pressure side flow path (17b). The first branch pipe (26) is provided with a first external expansion valve (18). This 1st outside expansion valve (18) is comprised as an electronic expansion valve which can adjust an opening degree. In addition, one end of a gas injection pipe (30) is connected to the outflow end of the low-pressure channel (17b). The other end of the gas injection pipe (30) joins with the liquid injection pipe (31) branched from the first branch pipe (26) on the downstream side of the first external expansion valve (18) to suck and join the pipe (22) It is connected to the. The liquid injection pipe (31) is provided with a solenoid valve (SV3).

  As described above, the receiver (16) is arranged between the external heat exchanger (15) and the supercooling heat exchanger (17), and temporarily stores the high-pressure refrigerant condensed in the external heat exchanger (15). Can be stored. One end of a gas vent pipe (27) is connected to the top of the receiver (16). The gas vent pipe (27) is provided with a check valve (CV5), and the other end is connected to the second discharge pipe (21b). This check valve (CV5) is a valve that allows only the flow of refrigerant toward the second discharge pipe (21b).

  One end of the second branch pipe (28) is connected between the check valve (CV4) and the first closing valve (12) in the second liquid pipe (25). The other end of the second branch pipe (28) is connected between the check valve (CV3) and the receiver (16) in the first liquid pipe (24). The second branch pipe (28) is provided with a check valve (CV6) that allows only the flow of refrigerant toward the receiver (16).

  A third branch pipe (29) that bypasses the receiver (16) and the supercooling heat exchanger (17) is connected between the first liquid pipe (24) and the second liquid pipe (25). The third branch pipe (29) is connected between the external heat exchanger (15) and the check valve (CV3) in the first liquid pipe (24) and excessive in the second liquid pipe (25). It connects between the connection part of a cooling heat exchanger (17) and a 1st branch pipe (26). The third branch pipe (29) is provided with a second external expansion valve (19). The second external expansion valve (19) is configured as an electronic expansion valve whose opening degree can be adjusted.

  The four-way selector valve (20) has the first port (P1) for the discharge junction pipe (21), the second port (P2) for the suction junction pipe (22), and the third port (P3) for external heat exchange. The container (15) has a fourth port (P4) connected to the second closing valve (13). The four-way selector valve (20) is in a first state in which the first port (P1) and the third port (P3) communicate with each other and the second port (P2) and the fourth port (P4) communicate with each other (see FIG. 1 and a second state (FIG. 1) in which the first port (P1) and the fourth port (P4) communicate with each other and the second port (P2) and the third port (P3) communicate with each other. In a state indicated by a broken line in FIG.

  Various sensors and pressure switches are provided in the external circuit (11). Specifically, the suction junction pipe (22) is provided with a suction temperature sensor (35). A suction pressure sensor (36) is provided at the joining point of the first suction pipe (22a) and the second suction pipe (22b) (the downstream end of the suction joint pipe (22)). Each discharge pipe (21a, 21b) is provided with a high pressure switch (37a, 37b) and a discharge temperature sensor (38a, 38b) as discharge temperature detecting means. Each high pressure switch (37a, 37b) detects the discharge pressure, and urgently stops the refrigeration apparatus (1) as a protection device when the pressure is abnormally high. A discharge pressure sensor (43) is provided at the junction (the upstream end of the discharge junction pipe (21)) between the first discharge pipe (21a) and the second discharge pipe (21b). A liquid temperature sensor (45) is provided in the second liquid pipe (25) of the external heat exchanger (15). An outside temperature sensor (44) is provided in the vicinity of the outside fan (23).

<Inside unit>
The two internal units (60a, 60b) are similarly configured. Hereinafter, the first internal unit (60a) will be described, and description of the second internal unit (60b) will be omitted. In the first internal circuit (61a) of the first internal unit (60a), in order from the liquid side end to the gas side end, the drain pan heating pipe (62a), the internal expansion valve (63a), and the storage An internal heat exchanger (64a) is provided.

  The internal expansion valve (63a) is an electronic expansion valve whose opening degree can be adjusted, and constitutes a use side expansion valve. The internal heat exchanger (64a) is for cooling the object by exchanging heat with the refrigerant in the internal air, and is configured as a cross fin type fin-and-tube heat exchanger. . An internal fan (65a) is provided in the vicinity of the internal heat exchanger (64a). Although the internal heat exchanger (64a) is not illustrated, the heat transfer tubes are arranged in a plurality of paths, and the refrigerant pipes are branched and connected to the heat transfer tubes of the respective paths. And in this internal heat exchanger (64a), heat exchange is performed between the internal air sent by the internal fan (65a) and the refrigerant flowing through the heat transfer tube.

  A drain pan (66a) provided with a drain pan heating pipe (62a) is provided below the internal heat exchanger (64a). This drain pan (66a) collects frost and condensed water falling from the surface of the internal heat exchanger (64a). In the drain pan (66a), the ice block generated by freezing the collected frost and condensed water is melted using the heat of the refrigerant flowing through the drain pan heating pipe (62a).

  The first internal circuit (61a) is provided with three temperature sensors. Specifically, the heat transfer tube of the internal heat exchanger (64a) is provided with an evaporation temperature sensor (67a) as an evaporation temperature detecting means. A gas temperature sensor (68a) is provided in the vicinity of the gas side end of the first internal circuit (61a). In the vicinity of the internal fan (65a), an internal temperature sensor (69a) is provided.

<Configuration of control unit of refrigeration system>
This refrigeration system (1) is provided in the external unit (10) and includes a compressor (14a, 14b), a four-way switching valve (20), each external expansion valve (18, 19), and each solenoid valve ( External unit control unit (55) for controlling SV1 to SV3), internal expansion valves (63a, 63b) and internal fans (65a, 65b) provided in each internal unit (60a, 60b) And an in-compartment unit control section (56a, 56b). The outside unit control unit (55) and each inside unit control unit (56a, 56b) are connected by an electric line (not shown).

  The outside unit control section (55) includes a capacity control section (51) which is a capacity control means, and a liquid injection control section (53) which is a liquid injection control means. A capacity | capacitance control part (51) controls the operating capacity of a compressor (14a, 14b) so that the cooling capacity required for each unit (60a, 60b) can be obtained. Specifically, when the required operating capacity is equal to or less than the maximum operating capacity of the first compressor (14a), the capacity control unit (51) operates only the first compressor (14a) and operates the first compressor. Control the operating capacity of (14a). When the required operating capacity exceeds the maximum operating capacity of the first compressor (14a), the first compressor (14a) is operated by operating both the first compressor (14a) and the second compressor (14b). ) To control the operating capacity.

  Further, the capacity control unit (51) limits the increase in the operating capacity of the compressor (14a, 14b) when the detected value of the discharge temperature sensor (38a, 38b) exceeds a reference value (for example, 100 ° C.). It is configured as follows. The capacity control unit (51) also detects the degree of superheat of the refrigerant discharged from each compressor (14a, 14b) detected from the detected value of the discharge temperature sensor (38a, 38b) and the detected value of the discharge pressure sensor (43). However, the operation capacity of the compressors (14a, 14b) is controlled so as not to become a predetermined value (for example, 10 ° C.) or less. The reason for controlling the degree of superheat of the discharged refrigerant to be a predetermined value or more is to prevent the refrigerating machine oil in the dome of the compressor (14a, 14b) from being diluted by the compressed refrigerant.

  The liquid injection control unit (53) is configured to compress the compressor when the detected value of the discharge temperature sensor (38a, 38b) exceeds the reference value in a state where the opening degree control means (52), which will be described later, is performing the opening degree limiting operation. The liquid injection operation for sending the liquid refrigerant to (14a, 14b) is executed. The liquid injection control unit (53) executes the liquid injection operation by opening the electromagnetic valve (SV3) while appropriately adjusting the opening degree of the first external expansion valve (18).

  Each of the internal unit control units (56a, 56b) includes an opening degree control unit (52a, 52b). These opening degree control units (52a, 52b) constitute opening degree control means. Each opening degree control part (52a, 52b) adjusts the opening degree of the internal expansion valve (63a, 63b), respectively. Each opening control unit (52a, 52b) uses the detected value of the discharge temperature sensor (38a, 38b) as a reference when it is necessary to increase the cooling capacity of the internal unit (60a, 60b) in which it is installed. If the value exceeds the value, the discharge temperature lowering operation is performed to increase the opening degree of the internal expansion valves (63a, 63b). Further, each opening degree control unit (52a, 52b) sets a difference between a set temperature in the storage and a detected value of the evaporation temperature sensor (67a, 67b) to a predetermined value (for example, 8 ° C.) during wetness control described later. If it falls below, the opening degree limiting operation for limiting the opening degree of the internal expansion valves (63a, 63b) to a range equal to or less than the upper limit value set according to the operating state is performed. Details of the discharge temperature lowering operation and the opening degree limiting operation will be described later.

-Operation of refrigeration equipment-
Below, the operation | movement operation | movement of the freezing apparatus (1) of this embodiment is demonstrated. In this refrigeration system (1), the cooling operation and the defrost operation can be performed, and the switching between the cooling operation and the defrost operation can be performed by switching the four-way switching valve (20) by the external unit control unit (55). Done.

<Cooling operation>
During the cooling operation, the four-way selector valve (20) is set to the first state. Further, the opening degree of the first external expansion valve (18) is adjusted as appropriate, while the second external expansion valve (19) is fully closed. In the internal circuit (61), the opening degree of the internal expansion valve (63) is appropriately adjusted. Each solenoid valve (SV1 to SV3) is opened and closed according to the operating state. When the compressors (14a, 14b) are operated in this state, in the refrigerant circuit (4), the external heat exchanger (15) becomes a condenser and each internal heat exchanger (64) becomes an evaporator. A vapor compression refrigeration cycle is performed. In the refrigerant circuit (4), the refrigerant circulates in the direction indicated by the solid arrow in FIG.

  Specifically, when the compressor (14a, 14b) is operated, the compressor (14a, 14b) sucks the low-pressure gas refrigerant, compresses it to a predetermined pressure, and discharges it. The high-pressure gas refrigerant discharged from the compressor (14a, 14b) flows into the oil separator (33) of the discharge junction pipe (21) through the discharge pipes (21a, 21b). In the oil separator (33), the refrigeration oil is separated from the flowing refrigerant. The separated refrigerating machine oil is stored at the bottom of the oil separator (33). The refrigerating machine oil at the bottom of the oil separator (33) passes from the oil return pipe (34) through the suction pipe (22a, 22b) when the outside unit control section (55) opens the solenoid valve (SV1, SV2). Then, it is sucked into the compressor (14a, 14b).

  The refrigerant flowing out from the oil separator (33) flows into the external heat exchanger (15) through the four-way switching valve (20). In the external heat exchanger (15), the refrigerant flowing in is condensed by exchanging heat with external air. Then, the condensed refrigerant flows into the receiver (16) through the first liquid pipe (24). In the receiver (16), the flowing liquid refrigerant is temporarily stored.

  The refrigerant that has flowed out of the receiver (16) passes through the high-pressure channel (17a) of the supercooling heat exchanger (17) and flows into the second liquid pipe (25). In the second liquid pipe (25), a part of the refrigerant flows into the first branch pipe (26) and is decompressed by the first external expansion valve (18). The remaining refrigerant flows into the liquid side connecting pipe (2).

  The refrigerant decompressed by the first external expansion valve (18) is used for gas injection into the compressors (14a, 14b) if the solenoid valve (SV3) of the liquid injection pipe (31) is closed. If (SV3) is open, it is used for liquid injection into each compressor (14a, 14b). When performing gas injection, the refrigerant heading to each indoor circuit (61a, 61b) can be supercooled in the supercooling heat exchanger (17). When performing liquid injection, the temperature of the refrigerant discharged from the compressor (14a, 14b) can be lowered.

  Specifically, when the solenoid valve (SV3) of the liquid injection pipe (31) is in the closed state, the refrigerant depressurized by the first external expansion valve (18) is the low-pressure side flow of the supercooling heat exchanger (17). Circulates the road (17b). At that time, in the supercooling heat exchanger (17), heat exchange is performed between the high-pressure refrigerant flowing in the high-pressure side passage (17a) and the low-pressure refrigerant flowing in the low-pressure side passage (17b). As a result, the refrigerant flowing through the high-pressure channel (17a) is supercooled, while the refrigerant flowing through the low-pressure channel (17b) evaporates. The gas refrigerant evaporated in the low pressure side flow path (17b) is sucked into the compressor (14a, 14b) from the gas injection pipe (30) through the suction junction pipe (22).

  On the other hand, when the solenoid valve (SV3) is in the open state, the liquid refrigerant (strictly gas-liquid two-phase refrigerant) depressurized by the first external expansion valve (18) is transferred from the low-pressure channel (17b). A large amount flows into the liquid injection pipe (31) with little pressure loss. Then, it is sucked into the compressors (14a, 14b) through the suction junction pipe (22). The amount of gas refrigerant or liquid refrigerant sent through the gas injection pipe (30) or the liquid injection pipe (31) to the compressor (14a, 14b), that is, the injection amount is the first external expansion valve (18). It is adjusted by the opening degree.

  The refrigerant flowing into the liquid side communication pipe (2) is distributed to each internal circuit (61a, 61b). The refrigerant that has flowed into the internal circuit (61a, 61b) flows through the drain pan heating pipe (62a, 62b). In the drain pan (66a, 66b), the ice mass produced by the freezing of frost and condensed water that has fallen from the surface of the internal heat exchanger (64a, 64b) by the refrigerant flowing in the drain pan heating pipe (62a, 62b) is melted. Is done. At that time, the refrigerant flowing through the drain pan heating pipes (62a, 62b) is cooled by the frost and ice blocks and then supercooled.

  The refrigerant that has flowed out of the drain pan heating pipes (62a, 62b) passes through the internal expansion valves (63a, 63b), is decompressed, and then flows into the internal heat exchangers (64a, 64b). In the internal heat exchanger (64a, 64b), the refrigerant that has flowed in exchanges heat with the internal air and evaporates. As a result, the air in the refrigerator warehouse is cooled.

  The refrigerant evaporated in each internal heat exchanger (64a, 64b) flows into the gas side connecting pipe (3) and then flows into the external circuit (11). The refrigerant that has flowed into the external circuit (11) flows through the four-way switching valve (20) into the suction junction pipe (22) and is sucked into the compressors (14a, 14b).

<Defrost operation>
In the refrigeration apparatus (1), when the internal heat exchanger (64a, 64b) is frosted during the refrigeration operation, the defrost operation is performed to remove the frost. During the defrost operation, defrosting of the internal heat exchangers (64a, 64b) is performed simultaneously.

  In the external circuit (11) during the defrost operation, the four-way selector valve (20) is set to the second state. Moreover, while the 1st external expansion valve (18) will be in a fully closed state, the opening degree of a 2nd external expansion valve (19) is adjusted suitably. In the internal circuit (61a, 61b), the internal expansion valve (63a, 63b) is fully opened. And if a compressor (14a, 14b) is drive | operated in this state, in a refrigerant circuit (4), an external heat exchanger (15) will become an evaporator and each internal heat exchanger (64) will become a condenser. A vapor compression refrigeration cycle is performed. In the refrigerant circuit (4), the refrigerant circulates in the direction indicated by the dashed arrow in FIG.

<Cooling capacity control>
In the refrigeration apparatus (1), the set temperature in the storage is set for each of the storage units (60a, 60b). During the cooling operation, the cooling capacity of each internal unit (60a, 60b) is adjusted so that the detected value of the internal temperature sensor (69a, 69b) of each internal unit (60a, 60b) approaches the set temperature. Yes. The cooling capacity of each internal unit (60a, 60b) is adjusted by adjusting the operating capacity of the compressor (14a, 14b) by the external unit control unit (55) and by the opening control unit (52a, 52b). This is done by adjusting the opening of the internal expansion valves (63a, 63b).

  The cooling operation is started when the external unit control unit (55) starts the compressors (14a, 14b). When the cooling operation is started, the capacity control unit (51) controls the operation capacity of the compressors (14a, 14b) based on the cooling capacity required for each internal unit (60a, 60b), and opens it. The degree control unit (52a, 52b) performs overheat control on each internal unit (60a, 60b). In the overheat control, for example, the difference between the detected value of the gas temperature sensor (68) and the detected value of the evaporation temperature sensor (67) so that the refrigerant flowing out of the internal heat exchangers (64a, 64b) is overheated. Each opening degree control part (52a, 52b) adjusts the opening degree of the in-chamber expansion valve (63a, 63b) so that the degree of superheat detected from the above becomes a target value (for example, 5 ° C.). The opening degree of the internal expansion valves (63a, 63b) is adjusted by feedback control based on the degree of superheat detected from, for example, the gas temperature sensor (68) and the evaporation temperature sensor (67). In addition, the cooling capacity of each internal unit (60a, 60b) is also adjusted by the amount of supercooling of the refrigerant in the supercooling heat exchanger (17). The amount of supercooling of the refrigerant in the supercooling heat exchanger (17) is adjusted by the outside unit control unit (55) controlling the opening degree of the first outside expansion valve (18).

  During the overheat control, the capacity control unit (51) determines the increase or decrease in the cooling capacity for each of the in-compartment units (60a, 60b) at a predetermined time interval (for example, every 10 seconds). The capacity control unit (51) determines that the cooling capacity of the first in-compartment unit (60a) needs to be increased, for example, when the following equation 1 is satisfied for the first in-compartment unit (60a). If the condition of Expression 2 is satisfied, it is determined that there is no possibility that the temperature of the refrigerant discharged from the compressor (14a, 14b) exceeds the allowable value (for example, 115 ° C), and the compressor (14a, 14b) is operated. Increase capacity. The same applies to the case where the condition of the following expression 1 is satisfied for the second internal unit (60b).

Formula 1: Tset-1 <Tr
Formula 2: Td ≦ 100
In the above formulas 1 and 2, Tset is the set temperature of the internal unit (60a, 60b), Tr is the detection value of the internal temperature sensor (69a, 69b), and Td is the detection of the discharge gas temperature sensor (38a, 38b) Each of the higher values is shown.

  When the operating capacity of the compressors (14a, 14b) increases in order to increase the cooling capacity of the first internal unit (60a), the amount of refrigerant circulating in the refrigerant circuit (4) increases. Each opening degree control unit (52a) is configured so that the degree of superheat detected from the gas temperature sensor (68) and the evaporation temperature sensor (67) becomes the target value even after the operating capacity of the compressor (14a, 14b) is increased. The opening degree of each expansion valve (63a, 63b) is controlled.

  In addition, when both the condition of the following formula 3 and the condition of the formula 4 are satisfied for the first internal unit (60a), and the conditions of the formula 5 and the formula 6 are both satisfied, the first internal unit (60a) The opening degree control unit (52a) performs the discharge temperature lowering operation to increase the opening degree of the internal expansion valve (63a). At that time, the opening degree control unit (52a) sets the opening degree of the internal expansion valve (63a) so that the refrigerant flowing out of the internal heat exchanger (64a) becomes wet. In this embodiment, the discharge temperature lowering operation is performed only for the first internal unit (60a) that requires an increase in cooling capacity. That is, only the opening degree of the in-compartment expansion valve (63a) of the first in-compartment unit (60a) that requires an increase in cooling capacity is expanded.

Formula 3: Tset-1 <Tr <Tset + 5
Formula 4: Tset <5
Formula 5: Td> 100
Formula 6: Ta> 25
In the above formula 6, Ta represents the detection value of the outside temperature sensor (44). Specifically, when Expression 3 is established, the capacity control unit (51) determines that the cooling capacity of the first internal unit (60a) needs to be increased. When Expression 4 is established, the capacity control unit (51) is more likely to raise the temperature of the refrigerant discharged from the compressor (14a, 14b) as the set temperature in the warehouse is lower. Judge that the temperature may exceed the allowable value. If Formula 5 is materialized, a capacity | capacitance control part (51) will judge that the operating capacity of a compressor (14a, 14b) cannot be increased. When the condition of Equation 6 is satisfied, the capacity control section (51) is more likely to raise the temperature of the refrigerant discharged from the compressor (14a, 14b) as the outside air temperature is higher. Judge that the temperature may exceed the allowable value. In other words, when the capacity control unit (51) determines that the cooling capacity of the first internal unit (60a) needs to be increased, but the operating capacity of the compressors (14a, 14b) cannot be increased, it is opened. The degree control unit (52a) performs the discharge temperature lowering operation.

  Note that the cooling capacity needs to be increased also when Tr ≧ Tset + 5. In this case, the internal expansion valve (63a) is opened so that the refrigerant flowing out of the internal heat exchanger (64a) becomes wet. Since the opening degree control may not be stable, the discharge temperature lowering operation is not performed. The case where Tr ≧ Tset + 5 is mainly assumed to be a transitional state such as after the start of the refrigeration apparatus (1) or after switching from the defrost operation to the cooling operation.

  When the opening of the internal expansion valve (63a) is increased by the discharge temperature lowering operation, the refrigerant flowing out of the internal heat exchanger (64a) changes from the overheated state to the wet state, and the compressors (14a, 14b) The refrigerant to be sucked becomes superheated or becomes wet. Therefore, the temperature of the refrigerant discharged from the compressor (14a, 14b) decreases. When the detection value of the discharge gas temperature sensor (38a, 38b) becomes 100 ° C. or less, the operating capacity of the compressor (14a, 14b) can be increased, and the capacity control unit (51) Increase the operating capacity of 14a, 14b). Thereby, since the refrigerant | coolant circulation amount of the internal heat exchanger (64a) increases, the cooling capacity of the 1st internal unit (60a) increases. Since the refrigerant flowing out of the internal heat exchanger (64a) is in a wet state, the internal heat exchanger (64a) is a gas-liquid two-phase refrigerant having a higher heat transfer coefficient than the gas refrigerant. The range of distribution is expanded. Accordingly, the amount of heat exchange in the internal heat exchanger (64a) increases, and this also increases the cooling capacity of the internal unit (60a).

  When the discharge temperature lowering operation is performed in the overheat control, the opening degree control unit (52a) opens the opening degree of the internal expansion valve (63a) so that the refrigerant flowing out of the internal heat exchanger (64a) becomes wet. Wet control is performed for the first internal unit (60a). In the wetness control, the refrigeration apparatus (1) is controlled based on the flowchart shown in FIG.

  In Step 1 (ST1), whether or not the cooling capacity of the first internal unit (60a) needs to be increased, and if the cooling capacity needs to be increased, the operating capacity of the compressor (14a, 14b) is increased. It is determined whether or not it is possible. The capacity control unit (51) needs to increase the cooling capacity of the first in-compartment unit (60a) when all the conditions of the above formula 3, formula 4, formula 5, and formula 6 are satisfied, but the compressor (14a , 14b), it is determined that the operating capacity cannot be increased, and the process proceeds to step 2 (ST2). Otherwise, the process proceeds to step 6 (ST6).

  In Step 2 (ST2), the opening degree control unit (52a) executes the discharge temperature lowering operation to increase the opening degree of the internal expansion valve (63a) by a preset expansion amount. You may change the expansion amount of an opening according to a driving | running state. When the opening degree of the internal expansion valve (63a) is increased, the temperature of the refrigerant discharged from the compressor (14a, 14b) decreases. When the detection value of the discharge gas temperature sensor (38a, 38b) becomes 100 ° C. or less, the operating capacity of the compressor (14a, 14b) can be increased, and the capacity control unit (51) Increase the operating capacity of 14a, 14b). When step 2 (ST2) ends, the process proceeds to step 3 (ST3).

  In step 3 (ST3), it is determined whether or not the opening control unit (52a) performs the opening limiting operation. The opening control unit (52a) shifts to step 4 (ST4) when the condition of the following expression 7 is satisfied, performs the opening limiting operation, and otherwise shifts to step 1 (ST1). . In Equation 7, Te represents the detected value of the evaporation temperature sensor (67a). When the temperature difference (ΔT) between the set temperature in the chamber and the detected value of the evaporation temperature sensor (67a) becomes smaller than a predetermined value (for example, X = 8 ° C.), the execution of the opening degree limiting operation is determined.

Formula 7: ΔT = Tset−Te <X
In step 4 (ST4), the opening degree control unit (52a) performs the opening degree limiting operation. Specifically, if the opening degree of the internal expansion valve (63a) is increased, the amount of refrigerant flowing in the internal heat exchanger (64a) increases, so the cooling capacity of the first internal unit (60a) increases. . However, as the opening of the internal expansion valve (63a) increases, the evaporation temperature of the refrigerant in the internal heat exchanger (64a) increases, so the set temperature of the first internal unit (60a) and the evaporation of the refrigerant The difference with temperature becomes smaller. For this reason, the cooling capacity of the first internal unit (60a) increases until the opening degree of the internal expansion valve (63a) reaches a certain level, but if the opening degree increases further, the first internal unit (60a) Instead, the cooling capacity will decrease. In this embodiment, when the opening degree control unit (52a) has a temperature difference (ΔT) between the set temperature of the first internal unit (60a) and the detected value of the evaporation temperature sensor (67a) below a predetermined value, The upper limit of the opening degree at which the cooling capacity of the single unit (60a) is not reduced is estimated, and the opening degree is set as the upper limit value. Then, the opening degree control unit (52a) limits the opening degree of the internal expansion valve (63a) to a range equal to or lower than the upper limit value. For example, the opening degree control unit (52a) sets the opening degree when the condition of Expression 4 is satisfied as the upper limit value. In addition, you may set the opening degree of predetermined time before the time of the conditions of Formula 4 as an upper limit. When step 4 (ST4) ends, the process proceeds to step 5 (ST5).

  In step 5 (ST5), the liquid injection control unit (53) performs a liquid injection operation in order to reduce the temperature of the refrigerant discharged from the first compressor (14a). In the liquid injection operation, the electromagnetic valve (SV3) of the liquid injection pipe (31) is set to an open state, and liquid injection is performed. In this embodiment, the upper limit value of the opening of the internal expansion valve (63a) is set and the discharge temperature lowering operation is performed in a state where the increase in the operating capacity of the compressor (14a, 14b) is restricted. When this is not possible, a liquid injection operation is performed so that the operating capacity of the compressor (14) can be increased. When step 5 (ST5) ends, the process proceeds to step 1 (ST1).

  In step 6 (ST6), it is determined whether or not to return from wetness control to overheat control. The opening degree control unit (52a) is any one of the four conditions of the conditions of Expression 8 and Expression 9 for the first in-compartment unit (60a) and the conditions of Expression 10 and Expression 11 of the outside-unit (10). If any one of them is established, the wet control is returned to the superheat control, and otherwise the wet control is continued. When wetting control is continued, the process proceeds to step 1 (ST1). When returning to the superheat control, the opening degree control unit (52a) adjusts the opening degree of the internal expansion valve (63a) so that the refrigerant flowing out of the internal heat exchanger (64a) is overheated. .

Formula 8: Tr <Tset-2 and Tr> Tset + 6
Formula 9: Tset> 5
Formula 10: Td <90
Formula 11: Ta <24
-Effect of the embodiment-
In this embodiment, when it is limited to increase the operating capacity of the compressor (14) even if it is intended to increase the cooling capacity of the in-compartment unit (60), the compressor ( The operating capacity of the compressor (14) can be increased by lowering the temperature of the discharged refrigerant in 14). In other words, the internal unit has not been able to increase the operating capacity of the compressor (14) without performing liquid injection that reduces the amount of refrigerant supplied to the internal unit (60). It is possible to increase the operating capacity of the compressor (14) by performing the discharge temperature lowering operation that does not reduce the amount of refrigerant supplied to the (60) side. Therefore, if the operating capacity of the compressor (14) is increased after the temperature of the refrigerant discharged from the compressor (14) has dropped below the reference value, the internal unit (60) side is increased according to the increased operating capacity. As the refrigerant flow rate increases, the cooling capacity of the in-compartment unit (60) increases, so that the cooling capacity in the in-compartment unit (60) can be reliably obtained without lowering the operation efficiency.

  Further, in this embodiment, only the opening of the internal expansion valve (63) of the internal unit (60) that requires an increase in cooling capacity is expanded in the discharge temperature lowering operation, so that the cooling capacity needs to be increased. The ratio of the refrigerant flowing into the storage unit (60) is increased. Therefore, if the operating capacity of the compressor (14) is increased after the temperature of the refrigerant discharged from the compressor (14) has dropped below the reference value, the distribution of the refrigerant in the internal unit (60) that requires an increase in cooling capacity The amount tends to increase. Therefore, the increase in the operating capacity of the compressor (14) can be suppressed as much as possible, and the internal unit (60) that increases the cooling capacity can be adjusted to the predetermined cooling capacity, so that the operating efficiency of the refrigeration system (1) Can be improved.

  In the present embodiment, the refrigerant flowing out of the internal heat exchanger (64) of the internal unit (60) is in a gas-liquid two-phase state in the discharge temperature lowering operation by the opening degree control unit (52). ing. Accordingly, since the range in which the gas-liquid two-phase refrigerant having a higher heat transfer coefficient than the gas refrigerant flows in the internal heat exchanger (64), the amount of heat exchange in the internal heat exchanger (64) increases. The cooling capacity of the internal unit (60) can be increased.

  Note that the refrigeration apparatus (1) of the present embodiment is of a multi-type, and it is individually determined whether or not the wetness control is performed for each in-compartment unit (60a, 60b). Therefore, even if the wet refrigerant flows out from one of the internal units (60a, 60b), the overheated refrigerant often flows out from the other internal unit (60a, 60b). The refrigerant in the state is mixed with the refrigerant in the overheated state and sucked into the compressor (14a, 14b). Further, even when the refrigerant flowing out of the internal units (60a, 60b) is in a wet state, the dryness may increase until the refrigerant reaches the suction side of the compressor (14a, 14b), resulting in an overheated state. Therefore, there is almost no risk of liquid back in the compressors (14a, 14b). In addition, when the number of units (60) in a store | warehouse | chamber is larger, the possibility of a liquid back | bag will further decrease.

  Further, in this embodiment, when the difference between the set temperature of the internal unit (60) and the detected value of the evaporation temperature sensor (67) falls below a predetermined value, the opening control unit (52) performs the opening limiting operation. Therefore, the cooling capacity of the internal unit (60) is prevented from being lowered. In other words, the discharge temperature lowering operation is performed to increase the cooling capacity of the internal unit (60), but the difference between the set temperature of the internal unit (60) and the evaporation temperature of the refrigerant becomes too small to cool the unit. The ability is not reduced. Therefore, the cooling capacity of the internal unit (60) can be properly controlled.

  Further, in the present embodiment, when the discharge temperature lowering operation cannot be performed in a state where the increase in the operation capacity of the compressor (14) is restricted, the liquid injection operation is performed to perform the operation of the compressor (14). The operating capacity can be increased. Therefore, even when the operation capacity of the compressor (14) is limited and the discharge temperature lowering operation cannot be performed, it is possible to increase the cooling capacity of the internal unit (60). The cooling capacity in the inner unit (60) can be obtained more reliably.

  Further, in the present embodiment, the compressor (14) of the external unit (10) is constituted by a high-pressure dome type scroll compressor having high durability against the wet refrigerant. Here, if the opening degree of the internal expansion valve (63) is increased by the discharge temperature lowering operation, the superheat degree of the refrigerant sucked by the compressor (14) gradually decreases, and the refrigerant becomes a gas-liquid two-phase. The wetness of the water gradually decreases. And the burden to a compressor (14) becomes large, so that the opening degree of a chamber expansion valve (63) is expanded. In this embodiment, since the high-pressure dome type scroll compressor having high durability against the refrigerant in the wet state is used, the opening of the internal expansion valve (63) is made larger than the compressor of other mechanisms. Can be expanded to. Therefore, the cooling capacity in the internal unit (60) can be obtained more reliably.

  Moreover, in this embodiment, R410A which is easy to restrict | limit increasing the operating capacity of a compressor (14) is used as a refrigerant | coolant circulated in a refrigerant circuit (4). Therefore, especially in the case of the refrigeration apparatus (1) using the refrigerant R410A, the temperature of the refrigerant discharged from the compressor (14) is lowered without reducing the amount of refrigerant flowing to the internal unit (60) side. The operation of lowering the discharge temperature is effective.

(Other embodiments)
The present invention may be configured as follows with respect to the above embodiment.

  In this embodiment, the determination as to whether or not to perform the discharge temperature lowering operation may be performed using only Equation 3 and Equation 5. In addition, the determination as to whether or not to return from the wet control to the overheat control may be performed using only Expression 8 and Expression 10.

  In the present embodiment, when the discharge temperature lowering operation is performed in the overheat control, the process shifts to the wetness control. However, it is not necessary to shift to the wetness control by one discharge temperature lowering operation. That is, the opening degree control unit (52) gradually decreases the target value of the degree of superheat of the refrigerant flowing out from the internal heat exchangers (64a, 64b) every time the discharge temperature lowering operation is performed. Transition to wetness control.

  Moreover, about this embodiment, the unit (60) in a store | warehouse | chamber may be three or more, and may be one.

  Moreover, about this embodiment, you may apply the compressor (for example, rotary compressor) of another mechanism as a compressor (14) of an external unit (10).

  In addition, the above embodiment is an essentially preferable illustration, Comprising: It does not intend restrict | limiting the range of this invention, its application thing, or its use.

  As described above, the present invention is useful for a refrigeration apparatus including a refrigerant circuit in which a heat source unit and a utilization unit are connected by a communication pipe.

It is a schematic block diagram of the freezing apparatus concerning embodiment of this invention. It is a flowchart which shows the flow of operation | movement during the wetness control in the freezing apparatus concerning embodiment of this invention.

Explanation of symbols

1 Refrigeration equipment
2 Liquid side communication piping (Communication piping)
3 Gas side communication piping (connection piping)
4 Refrigerant circuit
10 External unit (heat source unit)
14 Compressor
38 Discharge temperature sensor (Discharge temperature detection means)
51 Capacity control unit (capacity control means)
52 Opening control unit (opening control means)
53 Liquid injection control unit (Liquid injection control means)
60 Inside unit (Usage unit)
63 Internal expansion valve (use side expansion valve)
64 Internal heat exchanger (cooling heat exchanger)
67 Evaporation temperature sensor (evaporation temperature detection means)

Claims (7)

A heat source unit (10) having a compressor (14), a cooling heat exchanger (64) for cooling an object, and a utilization unit (60) having a variable-opening utilization side expansion valve (63) A refrigerant circuit (4) that is connected by connecting pipes (2,3),
Capacity control means (51) for adjusting the operating capacity of the compressor (14);
A refrigeration apparatus comprising opening degree control means (52) for adjusting the opening degree of the use side expansion valve (63),
A discharge temperature detection means (38) for detecting the temperature of the discharge refrigerant of the compressor (14);
While the capacity control means (51) is configured to limit the increase of the operating capacity of the compressor (14) in a state where the detection value of the discharge temperature detection means (38) exceeds a reference value,
If the detected value of the discharge temperature detecting means (38) exceeds the reference value when the cooling capacity of the utilization unit (60) needs to be increased, the opening degree control means (52) (14) A refrigeration apparatus configured to perform a discharge temperature lowering operation to increase an opening degree of the use side expansion valve (63) in order to reduce the temperature of the discharged refrigerant. In claim 1,
In the refrigerant circuit (4), a plurality of utilization units (60) are connected in parallel with the heat source unit (10) through communication pipes (2, 3),
The opening degree control means (52) individually adjusts the opening degree of the usage side expansion valve (63) of the usage unit (60), and the usage unit (cooling capacity needs to be increased in the discharge temperature lowering operation) 60) The refrigeration apparatus characterized by expanding only the opening degree of the use side expansion valve (63). In claim 1 or 2,
In the discharge temperature lowering operation of the opening degree control means (52), the usage unit (60) is arranged such that the refrigerant flowing out of the cooling heat exchanger (64) of the usage unit (60) requiring an increase in cooling capacity becomes wet. 60) The refrigeration apparatus characterized in that the opening degree of the use side expansion valve (63) is enlarged. In any one of Claims 1 thru | or 3,
The utilization unit (60) includes an evaporation temperature detection means (67) for detecting the evaporation temperature of the refrigerant in the cooling heat exchanger (64),
The opening degree control means (52) includes a set temperature and an evaporation temperature detecting means (67 When the difference between the detected value and the detected value is less than a predetermined value, the opening limit of the use unit (60) is limited to a range equal to or less than the upper limit set according to the operating state. A refrigeration apparatus characterized by performing an operation. In claim 4,
Liquid that sends liquid refrigerant to the compressor (14) when the detected value of the discharge temperature detecting means (38) exceeds a reference value in a state in which the opening control means (52) is performing the opening restriction operation. A refrigeration apparatus comprising liquid injection control means (53) for performing an injection operation. In any one of claims 1 to 5,
The compressor (14) is a high-pressure dome type scroll compressor. In any one of Claims 1 thru | or 6,
R410A is used for the refrigerant | coolant circulated in the said refrigerant circuit (4), The freezing apparatus characterized by the above-mentioned.

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