JP5272717B2 - Refrigeration equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently defrost a utilization side heat exchanger of each utilization side circuit in a refrigerating apparatus including a plurality of utilization side circuits to perform a two-stage compression refrigerating cycle. <P>SOLUTION: The refrigerating apparatus is constituted to carry out individual defrosting operation of supplying a part of a discharge refrigerant of a high stage side compressor 31 to the utilization side heat exchanger 51 for defrosting after a simultaneous defrosting operation and at the same time, performing refrigerant discharge operation of supplying the refrigerant accumulated in the utilization side circuit corresponding to the other utilization side heat exchanger, to the utilization side heat exchanger to be defrosted. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a refrigeration apparatus that includes a plurality of use side circuits and performs a two-stage compression refrigeration cycle, and particularly relates to measures for improving the defrosting ability of a use side heat exchanger.

  DESCRIPTION OF RELATED ART Conventionally, the refrigerating apparatus which performs cooling of interiors, such as a refrigerator and a freezer, and indoor air conditioning is known. As this type of refrigeration apparatus, there is a refrigeration apparatus that includes a plurality of use side circuits and performs a two-stage compression refrigeration cycle.

  Patent Document 1 discloses this type of refrigeration apparatus. In this refrigeration apparatus, a plurality of utilization side circuits are connected in parallel to a heat source side circuit to constitute a refrigerant circuit. The heat source side circuit is provided with a high stage compressor and a heat source side heat exchanger, and the plurality of usage side circuits are each provided with a usage side heat exchanger and a low stage side compressor.

  During the cooling operation of the refrigeration apparatus, a so-called two-stage compression refrigeration cycle is performed in the refrigerant circuit. Specifically, the refrigerant compressed and discharged by the high stage side compressor is condensed by the heat source side heat exchanger and then sent to each use side circuit. In each use side circuit, the refrigerant flows through each use side heat exchanger after being depressurized by the use side expansion valve. As a result, in each use side heat exchanger, the refrigerant absorbs heat from, for example, air in the warehouse and evaporates, and the interior is cooled. The refrigerant evaporated in each use side heat exchanger is compressed by each low stage compressor, then sent to the heat source side circuit and sucked into the high stage compressor.

Further, in the refrigeration apparatus of Patent Document 1, an operation (simultaneous defrost operation) is performed in which a high-stage compressor is operated, so-called reverse cycle defrost is performed, and a plurality of usage-side heat exchangers are simultaneously defrosted. Specifically, the refrigerant discharged from the high stage compressor is sent to a plurality of use side heat exchangers and condensed in each use side heat exchanger. Thereby, a utilization side heat exchanger is heated from the inside with a refrigerant | coolant, and the frost adhering to the surface melt | dissolves. The refrigerant used for defrosting each use side heat exchanger is decompressed by the expansion valve, condensed by the heat source side heat exchanger, and sucked into the high stage compressor.
JP 2007-187431 A

  In the simultaneous defrost operation described above, the refrigerant is condensed in the plurality of usage-side heat exchangers to be in a liquid state. For this reason, the refrigerant | coolant which became the liquid state may accumulate in the inside of the utilization side heat exchanger of each utilization side circuit, and other liquid lines. If the simultaneous defrost operation is continuously performed while liquid refrigerant is accumulated in the use side circuit in this way, the amount of refrigerant sent to each use side heat exchanger becomes insufficient, and each use side heat exchanger has Defrosting capacity may be reduced. As a result, there arises a problem that the time required for defrosting each usage-side heat exchanger is prolonged, and the power consumption required for defrosting each usage-side heat exchanger is increased.

  The present invention has been made in view of the above points, and an object of the present invention is to efficiently use the utilization side heat exchanger of each utilization side circuit in a refrigeration apparatus including a plurality of utilization side circuits and performing a two-stage compression refrigeration cycle. It is to be able to defrost well.

The first invention includes a heat source side circuit (30) having a high stage side compressor (31) and a heat source side heat exchanger (32), and a low stage side compressor (71, 91) and a use side heat exchange respectively. And a plurality of utilization side circuits (50, 70, 60, 90) connected in parallel to the heat source side circuit (30) having a condenser (51, 61), and the high stage compressor (31) And a cooling operation for operating the low-stage compressor (71, 91) and performing a two-stage compression refrigeration cycle for evaporating the refrigerant in the use-side heat exchanger (51, 61), and the high-stage compressor (31 A refrigerant apparatus that performs switching between simultaneous defrosting operation in which the discharged refrigerant of) is sent to the plurality of use side heat exchangers (51, 61) to simultaneously defrost the plurality of use side heat exchangers (51, 61). After the simultaneous defrosting operation, the refrigerant discharged from the high-stage compressor (31) is sent to some of the usage-side heat exchangers (51, 61) for defrosting, and at the same time, other usage-side heat exchange Vessel (51,61 Can execute is configured to separate defrosting operation for performing refrigerant discharge operation to send the refrigerant accumulated in the utilization side circuit (50,70,60,90) corresponding defrosted utilization side heat exchanger (51, 61) to The plurality of use side circuits (50, 70, 60, 90) have one end branched from the liquid line through which the liquid refrigerant flows and the other end connected to the suction side of the low stage compressor (71, 91). A suction passage (80, 100) and a first opening / closing mechanism (79c, SV2, 99c, SV4) for opening and closing the suction passage (80, 100) are provided, respectively. In the circuit (50, 70, 60, 90), the first opening / closing mechanism (79c, SV2, 99c, SV4) is opened and the low-stage compressor (71, 91) is operated.
The liquid lines of the plurality of use side circuits (50, 70, 60, 90) are respectively provided with refrigerant containers (72, 92) in which liquid refrigerant is temporarily stored, and the suction flow paths (80, 100) The inflow end is connected to the outflow side of the liquid refrigerant in the refrigerant container (71, 91) .

  In the refrigeration apparatus according to the first aspect of the invention, the refrigerant discharged from the high stage compressor (31) is sent to the plurality of usage side heat exchangers (51, 61), so that the plurality of usage side heat exchangers ( 51, 61) is simultaneously defrosted to defrost at the same time. In this simultaneous defrost operation, the refrigerant is condensed in the use side heat exchangers (51, 61), respectively, so that the refrigerant in the liquid state may be accumulated in each use side circuit (50, 70, 60, 90). . Therefore, after the simultaneous defrost operation, the following individual defrost operation is executed.

  In the individual defrost operation, a part of the use side heat exchangers (51, 61) among the plurality of use side heat exchangers (51, 61) is a target for defrosting. That is, the refrigerant discharged from the high stage compressor (31) is sent to a part of the use side heat exchangers (51, 61) to be defrosted. At the same time, the refrigerant discharge operation is performed in the use side circuits (50, 70, 60, 90) corresponding to the other use side heat exchangers (51, 61) that are not to be defrosted. That is, in this refrigerant discharge operation, the refrigerant that has accumulated in the use side circuit (50, 70, 60, 90) by the simultaneous defrost operation is used as the use side heat exchanger (51, 61) to be defrosted. ). Thereby, the accumulation of the refrigerant in the use side circuit (50, 70, 60, 90) can be eliminated, and the amount of the refrigerant sent to the use side heat exchanger (51, 61) to be defrosted Can be secured sufficiently.

In the individual defrosting operation of the first invention, the first opening / closing mechanism (79c, SV2, 99c, SV4) of the utilization side circuit (50, 70, 60, 90) during the refrigerant discharge operation is opened, and the low stage compressor (71,91) is operated. When the low-stage compressor (71, 91) is operated, the refrigerant that has accumulated in the liquid line of the user-side circuit (50, 70, 60, 90) passes through the suction flow path (80, 100). It is sucked into the compressor (71, 91) and compressed. The refrigerant discharged from the low stage compressor (71, 91) is sent to the use side heat exchanger (51, 61) to be defrosted. Thereby, the heat | fever provided to the refrigerant | coolant in the low stage side compressor (71,91) is utilized for the defrost of the utilization side heat exchanger (51,61) used as the defrost object.

In the first invention, the refrigerant containers (71, 91) are respectively provided in the liquid lines of the plurality of use side circuits (50, 70, 60, 90). Therefore, for example, liquid refrigerant can be stored in the refrigerant container (71, 91) during the cooling operation, and the circulation amount of the refrigerant can be adjusted. On the other hand, when the refrigerant container (71, 91) is provided in the liquid line of the use side circuit (50, 70, 60, 90) in this way, each simultaneous use side circuit (50, 70, 60, 90) in the simultaneous defrost operation. There is a risk that a large amount of liquid refrigerant will accumulate in the refrigerant containers (71, 91).

  However, the suction flow path (80, 100) of the present invention has an inflow end connected to the outflow side of the refrigerant container (71, 91). For this reason, when the refrigerant discharge operation is performed in the use side circuit (50, 70, 60, 90), the refrigerant accumulated in the refrigerant container (71, 91) passes through the suction flow path (80, 100) and the low stage compressor (71, 91). 91). Therefore, the accumulation of the liquid refrigerant in the refrigerant container (71, 91) can be eliminated.

According to a second invention, in the first invention, the suction flow path (80, 100) is provided with an expansion valve (79c, 99c), and the use side circuit (50, 70, 60, 90) Provided are internal heat exchangers (73, 93) for exchanging heat between the refrigerant decompressed by the expansion valves (79c, 99c) of the suction flow path (80, 100) and the refrigerant flowing out of the refrigerant container (71, 91). It is characterized by being.

In the second invention, an internal heat exchanger (73, 93) is provided in each use side circuit (50, 70, 60, 90). Thus, during the cooling operation, heat exchange can be performed between the refrigerant that has passed through the expansion valves (79c, 99c) of the suction flow path (80, 100) and the refrigerant that has flowed out of the refrigerant container (71, 91). In this case, the degree of supercooling of the refrigerant that flows out of the refrigerant container (71, 91) and is sent to the use side heat exchanger (51, 61) during the cooling operation increases, and the use side heat exchanger (51, 61) 61) Cooling capacity is improved. Further, the refrigerant flowing through the suction flow path (80, 100) can be vaporized by the internal heat exchanger (73, 93) to be in a gas state. Therefore, the gas refrigerant can be sent to the suction side of the low stage compressor (71, 91).

  Further, in the use side circuit (50, 70, 60, 90) during the refrigerant discharge operation, the refrigerant sucked into the suction flow path (80, 100) and decompressed by the expansion valve (79c, 99c), and the refrigerant container (71, The refrigerant that has flowed out 91) can be heat-exchanged by the internal heat exchanger (73, 93). Thereby, the liquid refrigerant which flows through the suction flow path (80, 100) can be evaporated by the internal heat exchanger (73, 93) to be in a gas state. Therefore, the gas refrigerant can be sent to the suction side of the low stage compressor (71, 91).

In a third aspect based on the second aspect , the outflow side of the suction flow path (80, 100) is connected to an intermediate port (71a, 91a) in the middle of the compression stroke of the low stage compressor (71, 91). It is characterized by being.

In the third invention, the outflow side of the suction flow path (80, 100) is connected to the intermediate port (71a, 91a) in the middle of the compression stroke of the low stage compressor (71, 91). Therefore, during the cooling operation or the refrigerant discharge operation, the refrigerant that has flowed out of the suction flow path (80, 100) is sucked in the middle of the compression stroke of the low-stage compressor (71, 91).

According to a fourth aspect of the present invention, in the second aspect of the present invention, during the individual defrost operation, an internal heat exchanger (73) is provided in the suction flow path (80, 100) of the use side circuit (50, 70, 60, 90) during the refrigerant discharge operation. , 93) is provided with superheat degree detection means (133, 134, 138, 139) for detecting the superheat degree of the refrigerant that has flowed out, and the refrigerant discharge operation is terminated when the superheat degree detected by the superheat degree detection means (133, 134, 138, 139) falls below a predetermined value. It is characterized by that.

In the fourth invention, during the individual defrost operation, the superheat degree detection means (133, 134, 138, 139) is connected to the internal heat exchanger (80, 100) in the suction flow path (80, 100) of the use side circuit (50, 70, 60, 90) during the refrigerant discharge operation. 73,93) is detected. Here, if the liquid refrigerant in the use side circuit (50, 70, 60, 90) is almost discharged and almost no refrigerant flows through the suction flow path (80, 100), the degree of superheat of the above refrigerant Becomes smaller. Therefore, in the present invention, the refrigerant discharge operation is terminated when the degree of superheat of the refrigerant in the suction flow path (80, 100) becomes a predetermined value or less.

The fifth invention includes a heat source side circuit (30) having a high stage side compressor (31) and a heat source side heat exchanger (32), and a low stage side compressor (71, 91) and a use side heat exchange respectively. A plurality of use side circuits (50, 70, 60, 90) connected in parallel to the heat source side circuit (30) having a heater (51, 61),
A cooling operation in which the high-stage compressor (31) and the low-stage compressor (71, 91) are operated to perform a two-stage compression refrigeration cycle in which the refrigerant is evaporated in the use-side heat exchanger (51, 61); Simultaneous defrosting of the refrigerant discharged from the high-stage compressor (31) to the plurality of usage-side heat exchangers (51, 61) to simultaneously defrost the plurality of usage-side heat exchangers (51, 61) Targeting a refrigeration system that switches between operation and operation, after the simultaneous defrost operation, the refrigerant discharged from the high- stage compressor (31) is sent to some use-side heat exchangers (51, 61) for defrosting At the same time, the refrigerant accumulated in the use side circuit (50, 70, 60, 90) corresponding to the other use side heat exchanger (51, 61) is transferred to the use side heat exchanger (51, 61) to be defrosted. is configured to be able to execute individual defrosting operation for performing refrigerant discharge operation to send, to each liquid line of the plurality of utilization side circuits (50,70,60,90) is interest for detecting the pressure of refrigerant Side pressure detection means (145, 146) is provided, and the liquid line of the heat source side circuit (30) is provided with heat source side pressure detection means (144) for detecting the pressure of the refrigerant. During the simultaneous defrost operation, When the difference between the refrigerant pressure detected by the heat source side pressure detection means (144) and the refrigerant pressure detected by the use side pressure detection means (145, 146) becomes a predetermined value or more, the use side pressure detection means (145, 146) The individual defrost operation is performed such that the refrigerant discharge operation is performed in the corresponding use side circuit (50, 70, 60, 90).

In the fifth invention, during the simultaneous defrost operation, the heat source side pressure detecting means (144) detects the pressure of the refrigerant in the liquid line of the heat source side circuit (30), and each use side pressure detecting means (145, 146) The refrigerant pressure in the liquid line of the user side circuit (50, 70, 60, 90) is detected. Here, for example, when refrigerant accumulates in the liquid line of the use side circuit (50, 70, 60, 90) during the simultaneous defrost operation, the detected pressure (for example, P2) in this liquid line is changed to the liquid in the heat source side circuit (30). It is relatively smaller than the detected pressure of the line (for example, P1). Therefore, in the present invention, the difference ΔP (P1−P2) between the detected pressure of the liquid line of the heat source side circuit (30) and the detected pressure of the liquid line of the use side circuit (50, 70, 60, 90) is a predetermined value. If it becomes above, it will determine with the use side circuit (50,70,60,90) from which pressure P2 was detected having accumulated liquid refrigerant, and refrigerant discharge operation will be carried out by this use side circuit (50,70,60,90) The individual defrost operation is executed so that

  In the present invention, after the simultaneous defrost operation, the refrigerant accumulated in the use side circuit (50, 70, 60, 90) is sent to the use side circuit (50, 70, 60, 90) to be defrosted. Defrost operation is possible. For this reason, sufficient refrigerant | coolant can be sent to the utilization side heat exchanger (51,61) used as a defrost object, eliminating the liquid pool in a utilization side circuit (50,70,60,90) rapidly. . Therefore, a plurality of use side heat exchangers (51, 61) can be efficiently defrosted. As a result, it is possible to shorten the defrosting time or improve the energy saving performance of the defrost operation.

In the first invention, in the refrigerant discharge operation during the individual defrost operation, the refrigerant accumulated in the liquid line of the use side circuit (50, 70, 60, 90) is compressed through the suction flow path (80, 100) on the low stage side. The refrigerant discharged from the low-stage compressor (71, 91) is sent to the use side heat exchanger (51, 61) to be defrosted. For this reason, the heat | fever provided to the refrigerant | coolant from the low stage side compressor (71,91) can be utilized for the defrost of a utilization side heat exchanger (51,61), and the efficiency of a defrost is further improved.

According to the first aspect of the present invention, the refrigerant accumulated in the refrigerant container (71, 91) during the simultaneous defrost operation is promptly passed from the use side circuit (50, 70, 60, 90) via the suction flow path (80, 100). Can be discharged.

According to the second aspect of the invention, the suction flow path (80, 100) for discharging the liquid refrigerant during the individual defrost operation also serves as a so-called injection flow path for supercooling the refrigerant during the cooling operation. Therefore, the refrigerant circuit can be simplified. In the cooling operation, the liquid refrigerant can be supercooled by the internal heat exchanger (73, 93) and then sent to the use side heat exchanger (51, 61), improving the cooling capacity during the cooling operation. . Further, during the individual defrosting operation, the liquid refrigerant flowing through the suction flow path (80, 100) can be evaporated by the internal heat exchanger (73, 93). Therefore, it is possible to avoid the liquid refrigerant from being sucked into the low-stage compressor (71, 91) from the suction flow path (80, 100), and so-called liquid compression in the low-stage compressor (71, 91) can be avoided. .

In the third invention, the refrigerant evaporated in the internal heat exchanger (73, 93) during the cooling operation is sent to the intermediate port (71a, 91a) of the low stage compressor (71, 91). The so-called economizer cycle can improve energy saving.

In the fourth aspect of the invention, the degree of superheat of the refrigerant that has flowed out of the internal heat exchanger (73, 93) is detected in the suction flow path (80, 100) during the refrigerant discharge operation, and the refrigerant is discharged when the degree of superheat falls below a predetermined value. The operation has been terminated. Therefore, it can be avoided that the refrigerant discharge operation is continuously executed even though the refrigerant is not accumulated in the use side circuit (50, 70, 60, 90), and the next operation can be performed promptly.

According to the fifth invention, by using the difference between the detected pressure of the liquid line of the heat source side circuit (30) and the detected pressure of the liquid line of the use side circuit (50, 70, 60, 90), a plurality of uses Of the side circuits (50, 70, 60, 90), it can be specified in which use side circuit (50, 70, 60, 90) the liquid refrigerant is accumulated. Therefore, the refrigerant discharge operation can be quickly performed by the specified use side circuit (50, 70, 60, 90), and the liquid pool of the refrigerant can be surely eliminated.

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

  The refrigeration apparatus (10) of this embodiment cools the inside of a freezer or a refrigerator. As shown in FIG. 1, the refrigeration apparatus (10) includes an outdoor unit (13), a first refrigeration showcase (15), a second refrigeration showcase (16), a first booster unit (17), and a second booster. Unit (19) is provided. The outdoor unit (13) is installed outdoors, and each refrigeration showcase (15, 16) and each booster unit (17, 19) are installed in a store such as a convenience store.

  The outdoor unit (13) has an outdoor circuit (30), the first refrigeration showcase (15) has a first refrigeration circuit (50), and the second refrigeration showcase (16) has a second refrigeration circuit (60). However, the first booster unit (17) is provided with a first booster circuit (70), and the second booster unit (19) is provided with a second booster circuit (90). The outdoor circuit (30) constitutes a heat source side circuit. Moreover, the 1st freezing circuit (50) and the 1st booster circuit (70) are connected in series, and comprise the 1st utilization side circuit. The 2nd freezing circuit (60) and the 2nd booster circuit (90) are connected in series, and constitute the 2nd use side circuit. In the refrigeration apparatus (10), the refrigerant circuit (11) is configured by connecting the first usage side circuit and the second usage side circuit in parallel to the heat source side circuit. In the refrigerant circuit (11), a vapor compression refrigeration cycle is performed by circulating the filled refrigerant.

  A first closing valve (21) and a second closing valve (22) are provided at the end of the outdoor circuit (30), and a third closing valve (23 is provided at the end of the first booster circuit (70). ) And a fourth closing valve (24), and a fifth closing valve (25) and a sixth closing valve (26) are provided at the end of the second booster circuit (90). One end of a gas communication pipe (27) is connected to the first closing valve (21). The other end of the gas communication pipe (27) is bifurcated. One end is connected to the third closing valve (23) and the other end is connected to the fifth closing valve (25). Yes. One end of a liquid communication pipe (28) is connected to the second closing valve (22). The other end of the liquid communication pipe (28) is bifurcated. One end is connected to the fourth closing valve (24) and the other end is connected to the sixth closing valve (26). Yes.

《Outdoor unit》
The outdoor circuit (30) of the outdoor unit (13) includes a high-stage compressor (31), an outdoor heat exchanger (32), a first receiver (33), a first internal heat exchanger (34), and an outdoor expansion. A valve (35) and a four-way switching valve (36) are provided. The high-stage compressor (31) is a hermetic high-pressure dome type scroll compressor. The high stage compressor (31) constitutes a variable capacity compressor to which electric power is supplied via an inverter. That is, in the high stage compressor (31), the rotational speed of the compressor motor is variable by changing the output frequency of the inverter. In the present embodiment, one high-stage compressor (31) is provided in the outdoor circuit (30), but a plurality of these may be provided.

  One end of a discharge pipe (37) is connected to the discharge side of the high stage compressor (31). The other end of the discharge pipe (37) is connected to the four-way switching valve (36). The discharge pipe (37) of the high stage compressor (31) is provided with an oil separator (not shown) for separating oil from the discharged refrigerant. The oil separated by the oil separator is returned to the high stage compressor (31) through a predetermined oil return circuit (not shown). One end of a suction pipe (38) is connected to the suction side of the high stage compressor (31). The other end of the suction pipe (38) is connected to the four-way switching valve (36).

  The outdoor heat exchanger (32) is a cross-fin type fin-and-tube heat exchanger and constitutes a heat source side heat exchanger. An outdoor fan (39) is provided in the vicinity of the outdoor heat exchanger (32). In the outdoor heat exchanger (32), heat is exchanged between the outdoor air blown by the outdoor fan (39) and the refrigerant. One end of the outdoor heat exchanger (32) is connected to the four-way switching valve (36) via a pipe. The other end of the outdoor heat exchanger (32) is connected to the top of the first receiver (33) via the first liquid pipe (40).

  The 1st receiver (33) is comprised by the airtight refrigerant container which stores the liquid refrigerant of the liquid line of a refrigerant circuit (11) temporarily. A liquid reservoir for storing the liquid refrigerant is formed in the bottom of the first receiver (33). The inflow end of the second liquid pipe (41) is connected to the bottom of the first receiver (33).

  A 1st internal heat exchanger (34) has a 1st heat exchanger tube (34a) and a 2nd heat exchanger tube (34b), and heat-exchanges the refrigerant | coolants which flow through both heat exchanger tubes (34a, 34b). . The first internal heat exchanger (34) is constituted by, for example, a plate heat exchanger. In the first internal heat exchanger (34), the second liquid pipe (41) is connected to the inflow end of the first heat transfer pipe (34a), and the third liquid pipe (42 is connected to the outflow end of the first heat transfer pipe (34a). ) Is connected at one end. The other end of the third liquid pipe (42) is connected to the second closing valve (22).

  In the first internal heat exchanger (34), one end of the first introduction branch pipe (43) is connected to the inflow end of the second heat transfer pipe (34b). The other end of the first introduction branch pipe (43) is connected to the third liquid pipe (42). The first introduction branch pipe (43) is provided with a first motor operated valve (43a). The first motor operated valve (43a) is a flow rate control valve whose opening degree is adjustable. In the first internal heat exchanger (34), one end of the first injection pipe (44) is connected to the outflow end of the second heat transfer pipe (34b). The other end of the first injection pipe (44) is connected to the intermediate port (31a) of the high stage compressor (31). The intermediate port (31a) faces an intermediate pressure point (during compression) between the suction side (low pressure side) and the discharge side (high pressure side) in the compression chamber of the high stage compressor (31). The first injection pipe (44) is provided with an openable / closable solenoid valve (SV1).

  One end of the first branch pipe (45) is connected to the third liquid pipe (42). The other end of the first branch pipe (45) is connected to the first liquid pipe (40). The first branch pipe (45) is provided with an outdoor expansion valve (35). The outdoor expansion valve (35) is an electronic expansion valve whose opening degree is adjustable. One end of the second branch pipe (46) is connected to the third liquid pipe (42). The other end of the second branch pipe (46) is connected to the first liquid pipe (40).

  The four-way switching valve (36) includes first to fourth ports as described above. In the four-way selector valve (36), the first port is connected to the discharge pipe (37) of the high stage compressor (31), and the second port is connected to the suction pipe (38) of the high stage compressor (31). The third port is connected to the outdoor heat exchanger (32), and the fourth port is connected to the first closing valve (21). In the four-way switching valve (36), the first port and the third port communicate with each other and the second port and the fourth port communicate with each other (first state indicated by a solid line in FIG. 1), The port can be switched to a state in which the second port communicates and the third port communicates with the fourth port (second state indicated by a broken line in FIG. 1).

  The outdoor circuit (30) is provided with a plurality of check valves. Specifically, in the outdoor circuit (30), a check valve (CV1) is provided in the discharge pipe (37) of the high-stage compressor (31), and a check valve (CV2) is provided in the first liquid pipe (40). The third liquid pipe (42) is provided with a check valve (CV3), and the second branch pipe (46) is provided with a check valve (CV4). These check valves (CV1 to CV4) allow the flow of refrigerant in the direction of the arrow attached to FIG. 1 and prohibit the flow of refrigerant in the opposite direction.

《First frozen showcase》
The first refrigeration circuit (50) of the first refrigeration showcase (15) is provided with a first cooling heat exchanger (51), a first internal expansion valve (52), and a first drain pan heater (53). ing.

  The first cooling heat exchanger (51) is a cross fin type fin-and-tube heat exchanger, and constitutes a use side heat exchanger. A first internal fan (54) is provided in the vicinity of the first cooling heat exchanger (51). In the first cooling heat exchanger (51), heat exchange is performed between the air blown by the first internal fan (54) and the refrigerant. The first internal expansion valve (52) is an electronic expansion valve whose opening degree is adjustable.

  The first drain pan heater (53) is a heating heat exchanger for melting ice blocks and the like peeled off from the first cooling heat exchanger (51). The first drain pan heater (53) is disposed, for example, inside the drain pan of the first cooling heat exchanger (51). In addition, the first drain pan heater (53) is connected to the outflow end of the first internal bypass pipe (55) that bypasses the first internal expansion valve (52). A check valve (CV5) is provided in the first internal bypass pipe (55).

《Second frozen showcase》
The second refrigeration circuit (60) of the second refrigeration showcase (16) has the same configuration as the first refrigeration circuit (50) described above. That is, the second refrigeration circuit (60) of the second refrigeration showcase (16) includes a second cooling heat exchanger (61), a second internal expansion valve (62), and a second drain pan heater (63). Is provided. A second internal fan (64) is provided in the vicinity of the second cooling heat exchanger (61), and a second internal bypass pipe (65) is connected to the second drain pan heater (63). The second internal bypass pipe (65) is provided with a check valve (CV6). The configuration of each device is the same as the configuration of each device in the first refrigeration showcase.

《First booster unit》
The first booster circuit (70) of the first booster unit (17) is provided with a first low-stage compressor (71), a second receiver (72), and a second internal heat exchanger (73). Yes.

  The first low-stage compressor (71) is a hermetic and high-pressure dome type scroll compressor. The low stage compressor (71) constitutes a variable capacity compressor to which electric power is supplied via an inverter. That is, in the first low-stage compressor (71), the rotation speed of the compressor motor is variable by changing the output frequency of the inverter. In the present embodiment, one first low-stage compressor (71) is provided in the first booster circuit (70), but a plurality of these may be provided.

  One end of a discharge pipe (74) is connected to the discharge side of the first low-stage compressor (71). The other end of the discharge pipe (74) is connected to the third closing valve (23). One end of a suction pipe (75) is connected to the suction side of the first low-stage compressor (71). The other end of the suction pipe (75) is connected to the first refrigeration circuit (50).

  The second receiver (72) constitutes a sealed refrigerant container that temporarily stores the liquid refrigerant in the refrigerant circuit (11). The outflow end of the fourth liquid pipe (76) is connected to the top of the second receiver (72). The inflow end of the fourth liquid pipe (76) is connected to the fourth closing valve (24). A liquid reservoir for storing the liquid refrigerant is formed in the bottom of the second receiver (72). The inflow end of the fifth liquid pipe (77) is connected to the bottom of the second receiver (72).

  The second internal heat exchanger (73) has a first heat transfer tube (73a) and a second heat transfer tube (73b), and exchanges heat between the refrigerants flowing through the heat transfer tubes (73a, 73b). . In the second internal heat exchanger (73), the fifth liquid pipe (77) is connected to the inflow end of the first heat transfer pipe (73a) and the sixth liquid pipe (78 is connected to the outflow end of the first heat transfer pipe (73a). ) Is connected at one end. The other end of the sixth liquid pipe (78) is connected to the first refrigeration circuit (50).

  In the second internal heat exchanger (73), one end of the second introduction branch pipe (79a) is connected to the inflow end of the second heat transfer pipe (73b). The other end of the second introduction branch pipe (79a) is connected to the fifth liquid pipe (77). The second induction branch pipe (79a) is provided with a second motor operated valve (79c). The second motor operated valve (79c) constitutes an expansion valve whose opening degree is adjustable. In the second internal heat exchanger (73), one end of the second injection pipe (79b) is connected to the outflow end of the second heat transfer pipe (73b). The other end of the second injection pipe (79b) is connected to the intermediate port (71a) of the first low stage compressor (71). The intermediate port (71a) faces the intermediate pressure point (during compression) between the suction side (low pressure side) and the discharge side (high pressure side) in the compression chamber of the first low stage compressor (71). Yes. The second injection pipe (79b) is provided with an openable / closable solenoid valve (SV2). As described above, the second introduction branch pipe (79a), the second heat transfer pipe (73b) of the second internal heat exchanger (73), and the second injection pipe (79b) are connected to each other. One suction flow path (80) is configured. The second motor operated valve (79) and the solenoid valve (SV2) constitute a first opening / closing mechanism that opens and closes the first suction passage (80).

  One end of a third branch pipe (81) is connected to the sixth liquid pipe (78). The other end of the third branch pipe (81) is connected to the fourth liquid pipe (76). One end of the fourth branch pipe (82) is connected to the sixth liquid pipe (78). The other end of the fourth branch pipe (82) is connected to the fourth liquid pipe (76). The first booster circuit (70) is provided with first and second bypass pipes (83, 84) that connect the discharge pipe (74) and the suction pipe (75) of the first low-stage compressor (71). ing. The first bypass pipe (83) is provided with an openable / closable solenoid valve (SV3).

  The first booster circuit (70) is provided with a plurality of check valves. Specifically, in the first booster circuit (70), a check valve (CV7) is provided in the discharge pipe (74) of the first low-stage compressor (71), and a check valve is provided in the fourth liquid pipe (76). (CV8) has a check valve (CV9) in the sixth liquid pipe (78), a check valve (CV10) in the third branch pipe (81), and a check valve (CV11 in the fourth branch pipe (82)). However, a check valve (CV12) is provided in the second bypass pipe (84). These check valves (CV7 to CV12) allow the flow of refrigerant in the direction of the arrow attached to FIG. 1 and prohibit the flow of refrigerant in the opposite direction.

《Second booster unit》
The second booster circuit (90) of the second booster unit (19) has the same configuration as the first booster circuit (70). That is, the second booster circuit (90) is provided with a second low-stage compressor (91), a third receiver (92) as a refrigerant container, and a third internal heat exchanger (93). The discharge pipe (94) of the low-stage compressor (91) is connected to the fifth closing valve (25), and the suction pipe (95) of the second low-stage compressor (91) is the second refrigeration circuit (60). Connected.

  The second refrigeration circuit (60) includes a seventh liquid pipe (96), an eighth liquid pipe (97), a ninth liquid pipe (98), a third introduction branch pipe (99a), a third injection pipe ( 99b), a fifth branch pipe (101), a sixth branch pipe (102), a third bypass pipe (103), and a fourth bypass pipe (104).

  The third introduction branch pipe (99a) is provided with a third electric valve (99c) as an expansion valve, the third injection pipe (99b) is provided with an electromagnetic valve (SV4), and a third bypass pipe ( 103) is provided with a solenoid valve (SV5). By connecting the third introduction branch pipe (99a), the second heat transfer pipe (93b) of the third internal heat exchanger (93), and the third injection pipe (99b), the second suction flow path (100) Is configured. Moreover, said 3rd motor operated valve (99c) and electromagnetic valve (SV4) comprise the 1st opening / closing mechanism which opens and closes the 1st suction flow path (80).

  In addition, a check valve (CV13) is provided in the discharge pipe (94) of the second low-stage compressor (91), a check valve (CV14) is provided in the seventh liquid pipe (96), and a ninth liquid pipe (98). Check valve (CV15), check valve (CV16) on the fifth branch pipe (101), check valve (CV17) on the sixth branch pipe (102), reverse check on the fourth bypass pipe (104) A stop valve (CV18) is provided. These check valves (CV13 to CV18) allow the flow of the refrigerant in the direction of the arrow attached to FIG. 1 and prohibit the flow of the refrigerant in the opposite direction.

<Sensor>
Various sensors are provided in the refrigeration apparatus (10). In the outdoor unit (13), the discharge pipe (37) is provided with a first discharge temperature sensor (120) and a first discharge pressure sensor (121), and the suction pipe (38) is provided with a first suction temperature sensor (122). A first suction pressure sensor (123) is provided. In the outdoor unit (13), the first refrigerant temperature sensor (124) is provided in the first introduction branch pipe (43), and the second refrigerant temperature sensor (125) is provided in the first injection pipe (44). Yes.

  In the 1st freezing showcase (15), the 3rd refrigerant temperature sensor (126) is provided in refrigerant piping connected with the end of the 1st cooling heat exchanger (51), and the heat exchanger tube of the 1st cooling heat exchanger (51) Is provided with a fourth refrigerant temperature sensor (127). In the second refrigeration showcase (16), the fifth refrigerant temperature sensor (128) is provided in the refrigerant pipe connected to one end of the second cooling heat exchanger (61), and the heat transfer tube of the second cooling heat exchanger (61). Is provided with a sixth refrigerant temperature sensor (129).

  In the first booster unit (17), the discharge pipe (74) is provided with a second discharge temperature sensor (130) and a second discharge pressure sensor (131), and the suction pipe (75) is provided with a second suction pressure sensor (132). ) Is provided. In the first booster unit (17), a seventh refrigerant temperature sensor (133) is provided in the second introduction branch pipe (79a), and an eighth refrigerant temperature sensor (134) is provided in the second injection pipe (79b). It has been.

  In the second booster unit (19), the discharge pipe (94) is provided with a third discharge temperature sensor (135) and a third discharge pressure sensor (136), and the suction pipe (95) is provided with a third suction pressure sensor (137). ) Is provided. In the second booster unit (19), a ninth refrigerant temperature sensor (138) is provided in the third introduction branch pipe (99a), and a tenth refrigerant temperature sensor (139) is provided in the third injection pipe (99b). It has been.

  Each temperature sensor mentioned above detects the temperature of the refrigerant | coolant of a corresponding location, and each pressure sensor mentioned above is comprised so that the pressure of the refrigerant | coolant of a corresponding location may be detected. An outdoor temperature sensor (140) for detecting the temperature of outdoor air is provided in the vicinity of the outdoor fan (39), and a first refrigeration showcase (15) is provided in the vicinity of the second indoor fan (64). A first internal temperature sensor (141) for detecting the temperature of the internal air of the second refrigerator is provided, and in the vicinity of the second internal fan (64), the temperature of the internal air of the second freezer showcase (16) is set. A second internal temperature sensor (142) for detection is provided.

"controller"
The refrigeration apparatus (10) of the present embodiment is provided with a controller (150) as a control unit. The controller (150) is configured to be able to input detection signals from the various sensors described above. The controller (150) includes the indoor unit (13), the first refrigeration showcase (15), the second refrigeration showcase (16), the first booster unit (17), and the second booster unit (19). The control means for controlling each of the element devices is configured (details will be described later).

-Driving action-
Below, the operation | movement operation | movement of the freezing apparatus (10) of embodiment is demonstrated. The refrigeration system (10) includes a cooling operation for cooling the interior of the plurality of refrigeration showcases (15, 16) and a defrosting of the cooling heat exchanger (51, 61) in each refrigeration showcase (15, 16). It is configured to switch between the defrost operation and the defrost operation.

《Cooling operation》
In the cooling operation shown in FIG. 2, the four-way selector valve (36) is set to the first state. In addition, the outdoor expansion valve (35) is fully closed, and the first motor-operated valve (43a), the second motor-operated valve (79c), the third motor-operated valve (99c), the first indoor expansion valve (52), and the first The opening degree of the two-chamber expansion valve (62) is adjusted as appropriate. In addition, the solenoid valves (SV1, SV2, SV4) are opened, and the remaining solenoid valves (SV3, SV5) are closed.

  In the cooling operation, the outdoor fan (39), the first internal fan (54), and the second internal fan (64) are operated, and the high stage compressor (31) and the first low stage compressor are operated. (71) and the second low-stage compressor (91) are also operated. As a result, in the refrigerant circuit (11), the outdoor heat exchanger (32) becomes a condenser, and each cooling heat exchanger (51, 61) becomes an evaporator, and the low-stage compressor (71, 91) and A two-stage compression refrigeration cycle is performed in which the refrigerant is compressed by both the high-stage compressor (31).

  Specifically, the refrigerant discharged from the high-stage compressor (31) passes through the discharge pipe (37) and the four-way switching valve (36) and flows through the outdoor heat exchanger (32). In the outdoor heat exchanger (32), the refrigerant dissipates heat to the outdoor air and condenses. The refrigerant condensed in the outdoor heat exchanger (32) passes through the first receiver (33), then passes through the first heat transfer pipe (34a) of the first internal heat exchanger (34), and passes through the third liquid pipe. To (42). A part of the refrigerant flowing through the third liquid pipe (42) is diverted to the first introduction branch pipe (43) and is decompressed by the first motor operated valve (43a). The refrigerant decompressed by the first motor operated valve (43a) flows through the second heat transfer tube (34b) of the first internal heat exchanger (34). In the first internal heat exchanger (34), the high-pressure refrigerant flowing through the first heat transfer tube (34a) and the intermediate-pressure refrigerant flowing through the second heat transfer tube (34b) exchange heat. As a result, the refrigerant in the first heat transfer tube (34a) absorbs heat from the refrigerant flowing through the second heat transfer tube (34b) and evaporates. In this manner, in the first internal heat exchanger (34), the refrigerant flowing through the first heat transfer tube (34a) is supercooled. The refrigerant that has flowed out of the second heat transfer pipe (34b) is sucked into the compression chamber in the middle of the compression stroke through the intermediate port (31a) of the high-stage compressor (31). The refrigerant supercooled in the first internal heat exchanger (34) flows out from the outdoor circuit (30) to the liquid communication pipe (28) and is divided into a plurality of booster circuits (70, 90).

  The refrigerant flowing into the first booster circuit (70) passes through the second receiver (72), then passes through the first heat transfer pipe (73a) of the second internal heat exchanger (73), and reaches the sixth liquid pipe. To (78). A part of the refrigerant flowing through the sixth liquid pipe (78) is diverted to the second introduction branch pipe (79a) and is decompressed by the second motor operated valve (79c). The refrigerant decompressed by the second motor operated valve (79c) flows through the second heat transfer tube (73b) of the second internal heat exchanger (73). In the second internal heat exchanger (73), the high-pressure refrigerant flowing through the first heat transfer tube (73a) and the intermediate-pressure refrigerant flowing through the second heat transfer tube (73b) exchange heat. As a result, the refrigerant in the first heat transfer tube (73a) absorbs heat from the refrigerant flowing through the second heat transfer tube (73b) and evaporates. In this way, in the second internal heat exchanger (73), the refrigerant flowing through the first heat transfer tube (73a) is further subcooled. The refrigerant that has flowed out of the second heat transfer tube (73b) is sucked into the compression chamber in the middle of the compression stroke through the intermediate port (71a) of the first low-stage compressor (71).

  The refrigerant supercooled in the second internal heat exchanger (73) flows into the first refrigeration circuit (50) and passes through the first drain pan heater (53). The heat of the refrigerant flowing through the first drain pan heater (53) is used to melt the ice blocks and the like that have fallen off from the first cooling heat exchanger (51). The refrigerant further cooled by the first drain pan heater (53) is depressurized by the first internal expansion valve (52) and then flows through the first cooling heat exchanger (51). In the first cooling heat exchanger (51), the refrigerant absorbs heat from the internal air of the first refrigeration showcase (15) and evaporates. The refrigerant evaporated in the first cooling heat exchanger (51) is sent again to the first booster circuit (70) and compressed by the first low-stage compressor (71). The refrigerant discharged from the first low stage compressor (71) flows out to the gas communication pipe (27).

  The refrigerant flowing into the second booster circuit (90) passes through the third receiver (92), then passes through the first heat transfer pipe (93a) of the third internal heat exchanger (93), and enters the ninth liquid pipe. To (98). A part of the refrigerant flowing through the ninth liquid pipe (98) is diverted to the third introduction branch pipe (99a) and is decompressed by the third motor operated valve (99c). The refrigerant decompressed by the third motor operated valve (99c) flows through the second heat transfer tube (93b) of the third internal heat exchanger (93). In the third internal heat exchanger (93), the high-pressure refrigerant flowing through the first heat transfer tube (93a) and the intermediate-pressure refrigerant flowing through the second heat transfer tube (93b) exchange heat. As a result, the refrigerant in the first heat transfer tube (93a) absorbs heat from the refrigerant flowing through the second heat transfer tube (93b) and evaporates. In this way, in the third internal heat exchanger (93), the refrigerant flowing through the first heat transfer tube (93a) is further subcooled. The refrigerant that has flowed out of the second heat transfer tube (93b) is sucked into the compression chamber in the middle of the compression stroke through the intermediate port (91a) of the second low-stage compressor (91).

  The refrigerant supercooled in the third internal heat exchanger (93) flows into the second refrigeration circuit (60) and passes through the second drain pan heater (63). The heat of the refrigerant flowing through the second drain pan heater (63) is used to melt the ice blocks and the like peeled off from the second cooling heat exchanger (61). The refrigerant further cooled by the second drain pan heater (63) is depressurized by the second internal expansion valve (62) and then flows through the second cooling heat exchanger (61). In the second cooling heat exchanger (61), the refrigerant absorbs heat from the internal air of the second refrigeration showcase (16) and evaporates. The refrigerant evaporated in the second cooling heat exchanger (61) is sent again to the second booster circuit (90) and compressed by the second low-stage compressor (91). The refrigerant discharged from the second lower stage compressor (91) flows out to the gas communication pipe (27).

  The refrigerant merged in the gas communication pipe (27) is sent again to the outdoor circuit (30), passes through the four-way switching valve (36), and then sucked into the high stage compressor (31) and compressed.

《Defrost operation》
The defrosting operation of the refrigeration apparatus (10) includes a simultaneous defrosting operation for simultaneously defrosting the plurality of cooling heat exchangers (51, 61) and a part of the cooling heat of the plurality of cooling heat exchangers (51, 61). It is roughly divided into individual defrost operation for defrosting the exchanger. The individual defrost operation includes a first individual defrost operation for defrosting the first cooling heat exchanger (51) and a second individual defrost operation for defrosting the second cooling heat exchanger (61). .

  In the refrigeration apparatus (10), when a predetermined time elapses after the above cooling operation is started, the cooling operation is shifted to the defrost operation. In addition to this, for example, from the cooling operation to the defrost operation using the temperature in the refrigerator of each freezer showcase (15, 16), the amount of frost formation of each cooling heat exchanger (51, 61), etc. You may make it determine transfer.

<Simultaneous defrost operation>
As shown in FIG. 3, when there is a request for defrost operation, first, simultaneous defrost operation is started (step S1). In the simultaneous defrost operation, both the first cooling heat exchanger (51) and the second cooling heat exchanger (61) are to be defrosted. As shown in FIG. 4, in the simultaneous defrost operation, the four-way switching valve (36) is set to the second state. Also, the first internal expansion valve (52), the second internal expansion valve (62), the first electric valve (43a), the second electric valve (79c), and the third electric valve (99c) are fully closed. Thus, the opening degree of the outdoor expansion valve (35) is adjusted as appropriate. In addition, the solenoid valves (SV1, SV2, SV4) are closed, and the remaining solenoid valves (SV3, SV5) are opened.

  In the simultaneous defrost operation, the outdoor fan (39), the first internal fan (54), the second internal fan (64), and the high stage compressor (31) are operated, and the first low stage compression is performed. The machine (71) and the second low-stage compressor (91) are stopped. As a result, in the refrigerant circuit (11), the first cooling heat exchanger (51) and the second cooling heat exchanger (61) serve as condensers, and the outdoor heat exchanger (32) serves as an evaporator. So-called reverse cycle defrost is performed in which the refrigerant is compressed by the side compressor (31).

  Specifically, the refrigerant discharged from the high-stage compressor (31) is divided into the first booster circuit (70) and the second booster circuit (90) via the gas communication pipe (27). In the first booster circuit (70), the refrigerant is sent to the first refrigeration circuit (50) through the first bypass pipe (83). The refrigerant sent to the first refrigeration circuit (50) flows through the first cooling heat exchanger (51). In the first cooling heat exchanger (51), the inside of the heat transfer tube is heated by the refrigerant, whereby the frost on the surface of the first cooling heat exchanger (51) is melted. The refrigerant condensed in the first cooling heat exchanger (51) passes through the first internal bypass pipe (55) and the first drain pan heater (53), and is sent again to the first booster circuit (70). The refrigerant sent to the first booster circuit (70) passes through the second receiver (72) and the second internal heat exchanger (73), and then passes through the third branch pipe (81) to the liquid communication pipe ( To 28).

  In the second booster circuit (90), the refrigerant is sent to the second refrigeration circuit (60) through the third bypass pipe (103). The refrigerant sent to the second refrigeration circuit (60) flows through the second cooling heat exchanger (61). In the second cooling heat exchanger (61), the inside of the heat transfer tube is heated by the refrigerant, whereby the frost on the surface of the second cooling heat exchanger (61) is melted. The refrigerant condensed in the second cooling heat exchanger (61) passes through the second internal bypass pipe (65) and the second drain pan heater (63) and is sent again to the second booster circuit (90). The refrigerant sent to the second booster circuit (90) passes through the third receiver (92) and the third internal heat exchanger (93), and then passes through the fifth branch pipe (101) to the liquid communication pipe ( To 28).

  The refrigerant combined in the liquid communication pipe (28) is sent to the outdoor circuit (30), passes through the first receiver (33) and the first internal heat exchanger (34), and flows through the first branch pipe (45). . The refrigerant flowing through the first branch pipe (45) is depressurized by the outdoor expansion valve (35) and then flows through the outdoor heat exchanger (32). In the outdoor heat exchanger (32), the refrigerant absorbs heat from the outdoor air and evaporates. The refrigerant evaporated in the outdoor heat exchanger (32) is sucked into the high stage compressor (31) and compressed again.

<Individual defrost operation>
In the simultaneous defrost operation, the refrigerant discharged from the high stage compressor (31) is sent to both the first cooling heat exchanger (51) and the second cooling heat exchanger (61). For this reason, in the simultaneous defrost operation, the refrigerant is supplied to both the first usage side circuit (50, 70) and the second usage side circuit (60, 90). Here, in the simultaneous defrost operation, the refrigerant condenses in each cooling heat exchanger (51, 61), so that the refrigerant is stored in a liquid state in these use side circuits (50, 70, 60, 90). May end up. In particular, in this embodiment, since each booster circuit (70, 90) is provided with a receiver (72, 92), a large amount of liquid refrigerant accumulates in each receiver (72, 92) in the simultaneous defrost operation. Sometimes. In such a case, even if the high stage compressor (31) is operated, the liquid refrigerant in the receiver (72, 92) cannot be sufficiently sucked into the outdoor circuit (30), and the refrigerant circulation There is a risk that the amount will be insufficient. As described above, when the circulation amount of the refrigerant at the time of the simultaneous defrost operation is insufficient, it becomes impossible to supply sufficient refrigerant to each cooling heat exchanger (51, 61), and the efficiency of the defrost operation is reduced. Resulting in. Therefore, in this embodiment, after the simultaneous defrost operation, the individual defrost operation is performed in which the cooling heat exchanger (51, 61) is defrosted while collecting the refrigerant accumulated in the receiver (72, 92) or the like. Yes.

<First individual defrost operation>
As shown in FIG. 3, the first individual defrost operation is executed when a predetermined time (for example, 5 minutes) elapses after the simultaneous defrost operation is started (step S2). In the first individual defrost operation, the first cooling heat exchanger (51) is a defrost target, but the second cooling heat exchanger (61) is not a defrost target. In the first individual defrosting operation, a refrigerant discharge operation is performed in which the refrigerant accumulated in the second booster circuit (90) is sent to the first booster circuit (70) side.

  Specifically, in the first individual defrost operation, the four-way switching valve (36) is set to the second state. The first internal expansion valve (52), the second internal expansion valve (62), the first electric valve (43a), and the second electric valve (79c) are fully closed, and the third electric valve (99c) And the opening degree of an outdoor expansion valve (35) is adjusted suitably. Here, the opening degree of the third electric valve (99c) is so-called SH control so that the degree of superheat of the refrigerant flowing out of the second heat transfer pipe (93b) of the third internal heat exchanger (93) becomes a predetermined value. Is done. In addition, the solenoid valves (SV1, SV2, SV5) are closed, and the remaining solenoid valves (SV3, SV4) are opened.

  In the first individual defrost operation, the outdoor fan (39), the first internal fan (54), the high stage compressor (31), and the second low stage compressor (91) are operated, and the first The low-stage compressor (71) and the second internal fan (64) are stopped. As a result, in the refrigerant circuit (11), the first cooling heat exchanger (51) becomes a condenser, the outdoor heat exchanger (32) becomes an evaporator, and the refrigerant is compressed by the high-stage compressor (31). A so-called reverse cycle defrost is performed. In the refrigerant circuit (11), the refrigerant compressed by the second low-stage compressor (91) is also used for defrosting the first cooling heat exchanger (51).

  Specifically, the refrigerant discharged from the high-stage compressor (31) is sent to the first refrigeration circuit (50) via the first booster circuit (70), and the first defrost operation is performed in the same manner as in the first defrost operation. Used for defrosting the cooling heat exchanger (51). On the other hand, in the second booster circuit (90), when the second low-stage compressor (91) is operated, the liquid refrigerant accumulated in the third receiver (92) and the like passes through the eighth liquid pipe (97). It flows through the 1st heat exchanger tube (93a) of the 3rd internal heat exchanger (93) via. This refrigerant is diverted from the ninth liquid pipe (98), is diverted to the third introduction branch pipe (99a), and is decompressed when passing through the third motor-operated valve (99c). The refrigerant decompressed by the third motor operated valve (99c) flows through the second heat transfer pipe (93b) of the third internal heat exchanger (93), absorbs heat from the refrigerant flowing through the first heat transfer pipe (93a), and evaporates. . The refrigerant evaporated in the second heat transfer pipe (93b) flows into the intermediate port (91a) of the second low-stage compressor (91) via the third injection pipe (99b).

  The refrigerant compressed by the second low stage compressor (91) is sent to the gas communication pipe (27) via the discharge pipe (94). This refrigerant merges with the refrigerant that has flowed out of the outdoor circuit (30) into the gas communication pipe (27), and is sent to the first refrigeration circuit (50) via the first booster circuit (70).

  By the first individual defrost operation as described above, the accumulation of liquid refrigerant in the second booster circuit (90) is eliminated. Moreover, since the heat | fever provided to the discharge refrigerant | coolant of a 2nd low stage side compressor (91) is utilized for the defrost of a 1st cooling heat exchanger (51), the efficiency of a defrost improves.

  The first individual defrost operation ends when a predetermined condition is satisfied (step S4 in FIG. 3). In the present embodiment, the end of the first individual defrost operation is determined based on the degree of superheat of the refrigerant flowing out to the third injection pipe (99b) of the second booster circuit (90). Here, the degree of superheat is obtained from the difference between the refrigerant temperature detected by the ninth refrigerant temperature sensor (138) and the refrigerant temperature detected by the tenth refrigerant temperature sensor (139). That is, the ninth refrigerant temperature sensor (138) and the tenth refrigerant temperature sensor (139) detect the degree of superheat of the refrigerant on the outflow side of the third internal heat exchanger (93) in the second suction flow path (100). The superheat degree detection means is constituted.

  If the degree of superheat of the refrigerant flowing out to the third injection pipe (99b) is smaller than a predetermined value (for example, 5 degrees) and the third motor-operated valve (99c) is fully open, the third internal heat exchanger (93) It can be considered that the liquid refrigerant hardly flows through the first heat transfer tube (93a) and the second heat transfer tube (93b). Therefore, when this condition is satisfied, the second low-stage compressor (91) is stopped to end the first individual defrost operation.

<Second individual defrost operation>
When the first individual defrost operation ends, the second individual defrost operation is executed (step S5 in FIG. 3). In the second individual defrost operation, the second cooling heat exchanger (61) is a defrost target, but the first cooling heat exchanger (51) is not a defrost target. In the second individual defrost operation, a refrigerant discharge operation is performed in which the refrigerant accumulated in the first booster circuit (70) is sent to the second booster circuit (90) side.

  Specifically, in the second individual defrost operation, the four-way switching valve (36) is set to the second state. The first internal expansion valve (52), the second internal expansion valve (62), the first electric valve (43a), and the third electric valve (99c) are fully closed, and the second electric valve (79c) And the opening degree of an outdoor expansion valve (35) is adjusted suitably. Here, the opening degree of the second motor operated valve (79c) is so-called SH control so that the degree of superheat of the refrigerant flowing out of the second heat transfer pipe (73b) of the second internal heat exchanger (73) becomes a predetermined value. Is done. In addition, the solenoid valves (SV1, SV3, SV4) are closed, and the remaining solenoid valves (SV2, SV5) are opened.

  In the second individual defrost operation, the outdoor fan (39), the second internal fan (64), the high stage compressor (31), and the first low stage compressor (71) are operated, and the second The low-stage compressor (91) and the first internal fan (54) are stopped. As a result, in the refrigerant circuit (11), the second cooling heat exchanger (61) serves as a condenser, the outdoor heat exchanger (32) serves as an evaporator, and the refrigerant is compressed by the high stage compressor (31). A so-called reverse cycle defrost is performed. In the refrigerant circuit (11), the refrigerant compressed by the first low-stage compressor (71) is also used for defrosting the second cooling heat exchanger (61).

  Specifically, the refrigerant discharged from the high-stage compressor (31) is sent to the second refrigeration circuit (60) via the second booster circuit (90), and the second refrigerant is discharged in the same manner as in the simultaneous defrost operation. Used for defrosting the cooling heat exchanger (61). On the other hand, in the first booster circuit (70), when the first low-stage compressor (71) is operated, the liquid refrigerant accumulated in the second receiver (72) and the like passes through the fifth liquid pipe (77). It flows through the 1st heat exchanger tube (73a) of the 2nd internal heat exchanger (73) via. This refrigerant is diverted from the sixth liquid pipe (78), is diverted to the second introduction branch pipe (79a), and is decompressed when passing through the second motor-operated valve (79c). The refrigerant decompressed by the second motor operated valve (79c) flows through the second heat transfer pipe (73b) of the second internal heat exchanger (73), absorbs heat from the refrigerant flowing through the first heat transfer pipe (73a), and evaporates. . The refrigerant evaporated in the second heat transfer pipe (73b) flows into the intermediate port (71a) of the first low-stage compressor (71) via the second injection pipe (79b).

  The refrigerant compressed by the first low-stage compressor (71) is sent to the gas communication pipe (27) via the discharge pipe (74). This refrigerant merges with the refrigerant that has flowed out of the outdoor circuit (30) into the gas communication pipe (27), and is sent to the second refrigeration circuit (60) via the second booster circuit (90).

  The second individual defrosting operation as described above eliminates the accumulation of liquid refrigerant in the first booster circuit (70). Moreover, since the heat | fever provided to the discharge refrigerant | coolant of a 1st low stage side compressor (71) is utilized for the defrost of a 2nd cooling heat exchanger (61), the efficiency of a defrost improves.

  The second individual defrost operation ends when a predetermined condition is satisfied (step S6 in FIG. 3). In the present embodiment, the end of the second individual defrost operation is determined based on the degree of superheat of the refrigerant flowing out to the second injection pipe (79b) of the first booster circuit (70). Here, the degree of superheat is obtained from the difference between the refrigerant temperature detected by the seventh refrigerant temperature sensor (133) and the refrigerant temperature detected by the eighth refrigerant temperature sensor (134). That is, the seventh refrigerant temperature sensor (133) and the eighth refrigerant temperature sensor (134) detect the degree of superheat of the refrigerant on the outflow side of the second internal heat exchanger (73) in the first suction flow path (80). The superheat degree detection means is constituted. Specifically, when the degree of superheat of the refrigerant flowing out to the second injection pipe (79b) is smaller than a predetermined value (for example, 5 degrees) and the second motor operated valve (79c) is fully opened, the second internal heat exchange is performed. It can be considered that the liquid refrigerant hardly flows through the first heat transfer tube (73a) and the second heat transfer tube (73b) of the heater (73). Therefore, when this condition is satisfied, the first low-stage compressor (71) is stopped to end the second individual defrost operation.

  When the second individual defrost operation ends, the process returns to step S1 in FIG. 3 and the simultaneous defrost operation is performed again. In addition, you may make it transfer to step S3 after step S6, and to transfer to a 1st separate defrost driving | operation again. Moreover, the above defrost operation is complete | finished when predetermined time passes after the start of a defrost operation, and transfers to cooling operation again. In addition to this, for example, by using the temperature in the refrigerator of each refrigeration showcase (15, 16), the amount of frost formation of each cooling heat exchanger (51, 61), etc., the defrost operation is changed to the cooling operation. You may make it determine transfer.

-Effect of the embodiment-
In the above embodiment, the individual defrost operation is performed after the simultaneous defrost operation. For this reason, the liquid refrigerant collected in the booster circuit (70, 90) during the simultaneous defrost operation can be sent to the cooling heat exchanger (51, 61) to be defrosted. Thereby, the cooling heat exchanger (51, 61) to be defrosted can be efficiently defrosted while eliminating the accumulation of liquid refrigerant in the booster circuit (70, 90) and ensuring the circulation amount of the refrigerant.

  In the individual defrost operation, the liquid refrigerant accumulated in the booster circuit (70, 90) is sucked into the low stage compressor (71, 91) and the refrigerant compressed by the low stage compressor (71, 91) is used. It is sent to the cooling heat exchanger (51, 61) to be defrosted. For this reason, the heat | fever provided to the refrigerant | coolant with the low stage side compressor (71,91) can be utilized for a cooling heat exchanger (51,61).

  In addition, since the inflow end of the suction flow path (79, 80, 99, 100) for sucking liquid refrigerant during the refrigerant discharge operation is connected to the outflow side of the receiver (72, 92), it accumulates in the receiver (72, 92). The liquid refrigerant that has been collected can be reliably sucked into the low-stage compressor (71, 91).

  Further, the suction flow path (79, 80, 99, 100) for performing the refrigerant discharge operation also serves as a gas injection flow path during the cooling operation. For this reason, simplification of a refrigerant circuit (11) can be achieved. Further, since the internal heat exchanger (73, 93) is provided in the suction flow path (79, 80, 99, 100), the refrigerant flowing through the suction flow path (79, 80, 99, 100) during the refrigerant discharge operation is transferred to the internal heat exchanger ( 73, 93). Therefore, it is possible to prevent the liquid refrigerant from being sucked into the low-stage compressor (71, 91), and so-called liquid compression in the low-stage compressor (71, 91) can be prevented.

  Further, during the refrigerant discharge operation, the internal expansion valves (52, 62) of the corresponding use side circuit (50, 70, 60, 90) are fully closed. For this reason, even if the low-stage compressor (71, 91) is operated, the liquid refrigerant accumulated on the booster circuit (70, 90) side is compressed via the cooling heat exchanger (51, 61). It can avoid flowing to the suction side (low pressure side) of the machine (71, 91). Therefore, it is possible to avoid the refrigerant on the booster circuit (70, 90) side from accumulating in the cooling heat exchanger (51, 61) with the refrigerant discharging operation.

  In the above embodiment, the individual defrost operation is performed so that the use side circuits (50, 70, 60, 90) for executing the refrigerant discharge operation are sequentially changed when a predetermined time has elapsed after the simultaneous defrost operation is started. I do it regularly. Therefore, the accumulation of liquid refrigerant can be reliably eliminated in the plurality of use side circuits (50, 70, 60, 90).

  In the above embodiment, in the booster circuit (70, 90) during the refrigerant discharge operation, the superheat degree of the refrigerant on the outflow side of the supercooling heat exchanger (51, 61) in the suction flow path (80, 100) is a predetermined value. The refrigerant discharge operation is terminated when the following occurs. Therefore, the execution time of the refrigerant discharge operation can be minimized, and the efficiency of the defrost operation can be further improved.

<< Other Embodiments >>
In the said embodiment, it can also be set as the following structures.

  In the above embodiment, the individual defrost operation is executed when a predetermined time has elapsed from the simultaneous defrost operation. However, during simultaneous defrosting operation, liquid refrigerant accumulation in the booster circuit (70, 90) is provided with refrigerant accumulation detection means, and the booster circuit (70 , 90), the individual defrosting operation may be performed so as to perform the above-described refrigerant discharge operation.

  Specifically, for example, in the refrigeration apparatus (10) shown in FIG. 7, the first internal pressure sensor (144) is connected to the first receiver (33) of the outdoor circuit (30), and the second receiver of the first booster circuit (70). The second internal pressure sensor (145) is provided at (72), and the third internal pressure sensor (146) is provided at the third receiver (92) of the second booster circuit (90). Each internal pressure sensor (144, 145, 146) is configured to detect the pressure of the refrigerant inside the corresponding receiver (33, 72, 92). And the 1st internal pressure sensor (144) comprises the heat source side pressure detection means which detects the pressure of the refrigerant | coolant of the liquid line of an outdoor circuit (30). The second internal pressure sensor (145) constitutes a first use side pressure detecting means for detecting the pressure of the refrigerant in the liquid line of the first use side circuit (50, 70). Moreover, the 3rd internal pressure sensor (146) comprises the 2nd utilization side pressure detection means which detects the pressure of the refrigerant | coolant of the liquid line of a 2nd utilization side circuit (60,90).

  In the refrigeration apparatus (10) of the example shown in FIG. 7, by comparing the internal pressure of each receiver (33, 72, 92) detected by each internal pressure sensor (144, 145, 146) at the time of simultaneous defrost operation, A migration decision is made. Specifically, during the above-described simultaneous defrost operation, the controller (150) has a difference ΔP1 (P1−P2) between the detected pressure P1 of the first internal pressure sensor (144) and the detected pressure P2 of the second internal pressure sensor (145). ) Is calculated. At the same time, the controller (150) calculates a difference ΔP2 (P1−P3) between the detected pressure P1 of the first internal pressure sensor (144) and the detected pressure P3 of the third internal pressure sensor (146).

  Here, for example, when liquid refrigerant is accumulated in the first booster circuit (70), the internal pressure of the second receiver (72) on the side where the liquid refrigerant is accumulated tends to be lower than the internal pressure of the first receiver (33). Therefore, ΔP1 is increased. Therefore, the controller (150) performs the second individual defrosting operation so that the refrigerant discharge operation is performed by the first booster circuit (70) when ΔP1 becomes a predetermined value or more (for example, 0 or more).

  For example, when the liquid refrigerant is accumulated in the second booster circuit (90), the internal pressure of the third receiver (92) on the side where the liquid refrigerant is accumulated tends to be higher than the internal pressure of the first receiver (33). Therefore, ΔP2 increases. Therefore, the controller (150) performs the first individual defrost operation so that the refrigerant discharge operation is performed by the second booster circuit (90) when ΔP2 is equal to or greater than a predetermined value (eg, 0 or more).

  As described above, in the example of FIG. 7, in the simultaneous defrost operation, based on the difference in the detected pressure between the liquid line of the booster circuit (70, 90) and the liquid line of the outdoor circuit (30), the booster circuit (70 , 90) is detected, and the individual defrosting operation is performed so that the refrigerant discharge operation is performed in the booster circuit (70, 90) in which the accumulation of the liquid refrigerant is detected. Therefore, it is possible to avoid the transition from the simultaneous defrost operation to the individual defrost operation even though the liquid refrigerant is not accumulated in the booster circuit (70, 90), and the defrost efficiency can be improved.

  The means for detecting the accumulation of liquid refrigerant in the booster circuit (70, 90) is not limited to the above example. Examples of other means include those that directly detect the amount of liquid refrigerant accumulated in the second receiver (72) and the third receiver (92), for example.

  In the refrigeration apparatus of the above embodiment, the refrigerant circuit (11) is configured by connecting the two utilization side circuits (50, 70, 60, 90) in parallel to the heat source side circuit (30). The use side circuit may be connected to the heat source side circuit. Also in this case, the individual defrosting operation can be performed while changing the use side heat exchanger to be defrosted so that the refrigerant discharge operation is sequentially performed in each use side circuit.

  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 that includes a plurality of usage-side circuits and performs a two-stage compression refrigeration cycle.

FIG. 1 is a piping system diagram illustrating a schematic configuration of a refrigeration apparatus according to an embodiment. FIG. 2 is a piping system diagram illustrating a schematic configuration of the refrigeration apparatus according to the embodiment, and illustrates the flow of the refrigerant during the cooling operation. FIG. 3 is a schematic control flowchart during defrost operation. FIG. 4 is a piping system diagram illustrating a schematic configuration of the refrigeration apparatus according to the embodiment, and illustrates the flow of the refrigerant during the simultaneous defrost operation. FIG. 5 is a piping system diagram illustrating a schematic configuration of the refrigeration apparatus according to the embodiment, and illustrates the flow of the refrigerant during the first individual defrost operation. FIG. 6 is a piping system diagram illustrating a schematic configuration of the refrigeration apparatus according to the embodiment, and illustrates the flow of the refrigerant during the second individual defrost operation. FIG. 7 is a piping system diagram illustrating a schematic configuration of a refrigeration apparatus according to another embodiment.

30 Outdoor circuit (heat source side circuit)
31 High stage compressor
32 Outdoor heat exchanger (heat source side heat exchanger)
50 First refrigeration circuit (use side circuit)
51 1st cooling heat exchanger (use side heat exchanger)
52 1st chamber expansion valve (expansion valve, second opening / closing mechanism)
60 Second refrigeration circuit (use side circuit)
61 Second cooling heat exchanger (use side heat exchanger)
62 Second internal expansion valve (expansion valve, second opening / closing mechanism)
70 First booster circuit (use side circuit)
71 First low-stage compressor (low-stage compressor)
71a Intermediate port
72 Second receiver (refrigerant container)
73 1st internal heat exchanger (internal heat exchanger)
79a Second introduction branch pipe (suction flow path)
79b Second injection pipe (suction channel)
79c Second motor operated valve (expansion valve, first opening / closing mechanism)
80 1st suction flow path
90 Second booster circuit (use side circuit)
91 Second low-stage compressor (low-stage compressor)
91a Intermediate port
92 Third receiver (refrigerant container)
93 Second internal heat exchanger (internal heat exchanger)
99a Third introduction branch pipe (suction flow path)
99b 3rd injection pipe (suction channel)
99c 3rd electric valve (expansion valve, 1st opening / closing mechanism)
100 Second suction flow path
SV2 solenoid valve (first opening / closing mechanism)
SV4 solenoid valve (first opening / closing mechanism)

Claims (5)

A heat source side circuit (30) having a high stage side compressor (31) and a heat source side heat exchanger (32), and a low stage side compressor (71, 91) and a use side heat exchanger (51, 61), respectively. A plurality of use side circuits (50, 70, 60, 90) connected in parallel to the heat source side circuit (30),
A cooling operation in which the high-stage compressor (31) and the low-stage compressor (71, 91) are operated to perform a two-stage compression refrigeration cycle in which the refrigerant is evaporated in the use-side heat exchanger (51, 61); Simultaneous defrosting of the refrigerant discharged from the high-stage compressor (31) to the plurality of usage-side heat exchangers (51, 61) to simultaneously defrost the plurality of usage-side heat exchangers (51, 61) A refrigeration system that switches between operation and
After the simultaneous defrosting operation, the refrigerant discharged from the high stage compressor (31) is sent to some of the use side heat exchangers (51, 61) to be defrosted, and at the same time, another use side heat exchanger (51 , 61) Can perform individual defrost operation to perform refrigerant discharge operation to send refrigerant accumulated in the use side circuit (50, 70, 60, 90) to the use side heat exchanger (51, 61) to be defrosted Composed of
In the plurality of use side circuits (50, 70, 60, 90), one end is branched from the liquid line through which the liquid refrigerant flows, and the other end is connected to the suction side of the low stage compressor (71, 91) A flow path (80, 100) and a first opening / closing mechanism (79c, SV2, 99c, SV4) for opening and closing the suction flow path (80, 100), respectively,
During the individual defrost operation, the first opening / closing mechanism (79c, SV2, 99c, SV4) is opened and the low stage compressor (71) is used in the use side circuit (50, 70, 60, 90) during the refrigerant discharge operation. , 91) is driven,
The liquid lines of the plurality of use side circuits (50, 70, 60, 90) are respectively provided with refrigerant containers (72, 92) in which liquid refrigerant is temporarily stored,
The refrigerating apparatus, wherein an inflow end of the suction flow path (80, 100) is connected to a liquid refrigerant outflow side of the refrigerant container (71, 91) . In claim 1 ,
The suction flow path (80, 100) is provided with an expansion valve (79c, 99c),
The utilization side circuit (50, 70, 60, 90) includes a refrigerant that has passed through the expansion valve (79c, 99c) of the suction flow path (80, 100), and a refrigerant that has flowed out of the refrigerant container (71, 91). An internal heat exchanger (73, 93) for exchanging heat is provided, respectively. In claim 2 ,
The refrigeration apparatus characterized in that the outflow side of the suction flow path (80, 100) is connected to an intermediate port (71a, 91a) in the middle of the compression stroke of the low stage compressor (71, 91). In claim 2 ,
During the individual defrost operation, the degree of superheat of the refrigerant that has flowed out of the internal heat exchanger (73,93) is detected in the suction flow path (80,100) of the user side circuit (50,70,60,90) during the refrigerant discharge operation. Comprising superheating degree detecting means (133,134,138,139)
A refrigerating apparatus characterized in that the refrigerant discharge operation is terminated when the degree of superheat detected by the superheat degree detection means (133, 134, 138, 139) becomes a predetermined value or less. A heat source side circuit (30) having a high stage side compressor (31) and a heat source side heat exchanger (32), and a low stage side compressor (71, 91) and a use side heat exchanger (51, 61), respectively. A plurality of use side circuits (50, 70, 60, 90) connected in parallel to the heat source side circuit (30),
A cooling operation in which the high-stage compressor (31) and the low-stage compressor (71, 91) are operated to perform a two-stage compression refrigeration cycle in which the refrigerant is evaporated in the use-side heat exchanger (51, 61); Simultaneous defrosting of the refrigerant discharged from the high-stage compressor (31) to the plurality of usage-side heat exchangers (51, 61) to simultaneously defrost the plurality of usage-side heat exchangers (51, 61) A refrigeration system that switches between operation and
After the simultaneous defrosting operation, the refrigerant discharged from the high stage compressor (31) is sent to some of the use side heat exchangers (51, 61) to be defrosted, and at the same time, another use side heat exchanger (51 , 61) Can perform individual defrost operation to perform refrigerant discharge operation to send refrigerant accumulated in the use side circuit (50, 70, 60, 90) to the use side heat exchanger (51, 61) to be defrosted Composed of
The liquid line of the heat source side circuit (30) is provided with heat source side pressure detecting means (144) for detecting the pressure of the refrigerant,
Each liquid line of the plurality of usage side circuits (50, 70, 60, 90) is provided with usage side pressure detection means (145, 146) for detecting the pressure of the refrigerant,
During the simultaneous defrosting operation, if the difference between the refrigerant pressure detected by the heat source side pressure detection means (144) and the refrigerant pressure detected by the usage side pressure detection means (145, 146) becomes a predetermined value or more, the usage side The refrigeration apparatus, wherein the individual defrosting operation is performed so that the refrigerant discharge operation is performed in the use side circuit (50, 70, 60, 90) corresponding to the pressure detection means (145, 146).

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