JP2008064421A - Refrigerating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To switch and control an operation state to keep a compressing mechanism in a proper driving state, in a refrigerating device where a single-stage compressing operation and a two-stage compressing operation are switchable. <P>SOLUTION: This refrigerating device 1 comprises a refrigerant circuit 10 having a booster compressing mechanism 41 and a high stage-side compressing mechanism 11, and is switchable between the single-stage compressing operation where a refrigerant bypasses the booster compressing mechanism 41 and is compressed only by the high stage-side compressing mechanism 11, and the two-stage compressing operation where the refrigerant is compressed by the booster compressing mechanism 41 and the high stage-side compressing mechanism 11. In this refrigerating device 1, a switch control portion 101 of a controller 100 switches the operation state to perform the single-stage compressing operation when the difference between high and low pressures as pressure difference between high-pressure refrigerant and low-pressure refrigerant in the refrigerant circuit 10 is less than a prescribed first set pressure value P1, and to perform the two-stage compressing operation when the pressure difference between high and low pressures is more than the prescribed first set pressure value P1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

    The present invention relates to a refrigeration apparatus having a low-stage compression mechanism and a high-stage compression mechanism, and particularly relates to switching control between a single-stage compression operation and a two-stage compression operation.

    Conventionally, a refrigerating apparatus that includes a refrigerant circuit having a low-stage compression mechanism and a high-stage compression mechanism and compresses the refrigerant in two stages is known (for example, Patent Document 1).

    The refrigeration apparatus of Patent Document 1 is an air conditioner, and includes a first compressor that is a low-stage side compression mechanism, a second compressor that is a high-stage side compression mechanism, a four-way switching valve, an indoor heat exchanger, and an expansion valve. And an outdoor heat exchanger are connected in order, and a cooling operation and a heating operation can be switched. Further, the air conditioner includes both a cooling operation and a heating operation, a two-stage compression operation in which the refrigerant is compressed by the first and second compressors, and a single-stage operation in which the refrigerant is compressed only by the first compressor. It is configured to be switchable between.

Specifically, in the heating operation in the air conditioner, during the two-stage compression operation, the first compressor and the second compressor are connected in series, and the first compressor and the second compressor are sequentially compressed. The refrigerant dissipates heat in the indoor heat exchanger, condenses, expands in the expansion valve, evaporates in the outdoor heat exchanger, and is compressed again by both compressors. In the single-stage compression operation, the refrigerant compressed in the first compressor bypasses the second compressor, then dissipates and condenses in the indoor heat exchanger, expands in the expansion valve, and then in the outdoor heat exchanger. It evaporates and is compressed again by the first compressor. The air conditioner switches between the single-stage compression operation and the two-stage compression operation based on the outside air temperature and the load (difference between the room temperature and the set temperature), thereby improving the efficiency with the capacity required for air conditioning. I try to do good driving.
JP 2000-314566 A

    Incidentally, some compressors used in the refrigerant circuit of the refrigeration apparatus cannot maintain the driving state properly if the differential pressure between the discharge pressure and the suction pressure is smaller than a predetermined value. When such a compressor is used, when the two-stage compression operation is performed in a state where the high and low pressure differential between the high pressure refrigerant and the low pressure refrigerant in the refrigerant circuit is small, the high and low pressure difference in the refrigerant circuit is reduced to the low stage compression mechanism and the high stage side. Since the compressor cannot be appropriately distributed to the compression mechanism, the compressor constituting at least one of the compression mechanisms cannot maintain an appropriate driving state, and the reliability as the compressor is lowered. However, in the refrigeration apparatus of Patent Document 1, the single-stage compression operation and the two-stage compression operation are switched based on the outside air temperature and the load, and no consideration is given to the characteristics of each compressor.

    The present invention has been made in view of the above points, and an object of the present invention is to switch operation states in which a compression mechanism is maintained in an appropriate driving state in a refrigeration apparatus capable of switching between single-stage compression operation and two-stage compression operation. The purpose is to control.

    The first invention is a refrigerant circuit in which a low-stage compression mechanism (41), a high-stage compression mechanism (11), a condenser (13), an expansion mechanism (32), and an evaporator (31) are connected in order. 10), one of the low-stage compression mechanism (41) and the high-stage compression mechanism (11) is driven, the other compression mechanism is stopped, and the refrigerant is compressed into the one compression The single stage compression operation compressed by the mechanism, the low stage side compression mechanism (41), and the high stage side compression mechanism (11) are both driven, and the refrigerant is the low stage side compression mechanism (41) and the high stage. A refrigeration apparatus that can be switched to a two-stage compression operation compressed by a side compression mechanism (11) is intended. When the high / low differential pressure, which is the pressure difference between the high-pressure refrigerant and the low-pressure refrigerant in the refrigerant circuit (10), is smaller than a predetermined first set pressure value, the single-stage compression operation is performed, while the high / low differential pressure is A switching control means (101) for switching the operation state so as to perform the two-stage compression operation when the pressure is equal to or higher than the first set pressure value is provided.

    In the first aspect of the invention, the predetermined first set pressure value is necessary for maintaining both the low-stage and high-stage compression mechanisms (11, 41) in an appropriate driving state in the two-stage compression operation. In the two-stage compression operation, a high-low differential pressure equal to or higher than the first set pressure value is appropriately distributed to the low-stage compression mechanism (41) and the high-stage compression mechanism (11).

    In the first aspect of the invention, the switching control means (101) causes the two-stage compression operation when the high / low differential pressure of the refrigerant circuit (10) becomes equal to or higher than a predetermined first set pressure value during the single-stage compression operation. The operation state is switched so as to perform the operation in the middle, and when the differential pressure of the refrigerant circuit (10) becomes smaller than the predetermined first set pressure value during the two-stage compression operation, the operation is switched to the single-stage operation.

    In a second aspect based on the first aspect, at least one of the low-stage compression mechanism (41) and the high-stage compression mechanism (11) stores refrigeration oil in a high-pressure space in the dome. At the same time, it is composed of differential pressure oil supply type compressors (11a, 11b, 11c, 41a, 41b, 41c) for supplying refrigerating machine oil to the sliding portion in the dome by differential pressure.

    In the second aspect of the invention, the sliding portion is a sliding portion between the drive shaft of the compressor (11a, 11b, 11c, 41a, 41b, 41c) and the bearing, and is supplied with refrigerating machine oil as lubricating oil. This is the part. And the differential pressure oil supply type compressor (11a, 11b, 11c, 41a, 41b, 41c) is a refrigeration stored in the high pressure space when the differential pressure between the high pressure space and the low pressure space in the dome exceeds a predetermined value. Machine oil is supplied to the sliding part.

    Therefore, in the second aspect of the invention, the compressors (11a, 11b, 11c, 41a, 41b, 41c) are provided in order to properly supply oil in the dome of the compressors (11a, 11b, 11c, 41a, 41b, 41c). ) Discharge pressure and suction pressure must be maintained at predetermined values. Therefore, as the predetermined first set pressure value for switching from the single-stage compression operation to the two-stage compression operation, the high and low differential pressure of the refrigerant circuit (10) at which the compression mechanism (11, 41) can appropriately supply oil is set. To do.

    In a third aspect based on the first aspect, at least one of the low-stage compression mechanism (41) and the high-stage compression mechanism (11) is a scroll compressor (11a, 11b, 11c, 41a, 41b, 41c).

    In this third aspect of the invention, the scroll compressor (11a, 11b, 11c, 41a, 41b, 41c) has a fixed scroll and a movable scroll meshing with each other in a spiral wrap so that the movable scroll The revolving motion is performed while being pressed against the fixed scroll by the refrigerant, and the refrigerant in the compression chamber formed by the spiral wraps is compressed. For this reason, when the differential pressure between the high-pressure refrigerant and the low-pressure refrigerant in the dome becomes small, the pressure difference necessary for pressing the movable scroll cannot be secured, and the movable scroll rolls over.

    Therefore, in the third aspect of the invention, in order to prevent the movable scroll of the compressor (11a, 11b, 11c, 41a, 41b, 41c) from overturning, the compressor (11a, 11b, 11c, 41a, 41b, 41c) It is necessary to keep the discharge pressure and the suction pressure at predetermined values. Therefore, the differential pressure of the refrigerant circuit (10) at which the movable scroll of the compression mechanism (11, 41) does not roll over is set as the predetermined first set pressure value for switching from the single-stage compression operation to the two-stage compression operation.

    In a fourth aspect based on the third aspect, the low-stage compression mechanism (41) is composed of a scroll compressor (41a, 41b, 41c), and the discharge of the low-stage compression mechanism (41). Differential pressure control means (102) for controlling the differential pressure between the pressure and the suction pressure so as to become equal to or higher than a predetermined overturning limit pressure value that increases as the evaporation temperature of the refrigerant in the evaporator (31) increases. Yes.

    Here, the predetermined rollover limit pressure value is less than the rollover limit pressure value in the scroll compressor (41a, 41b, 41c) of the low stage compression mechanism (41). Is the limit pressure value for preventing the movable scroll from overturning, and is expressed as a function of the evaporation temperature that increases as the evaporation temperature in the evaporator (31) increases. Therefore, in the fourth aspect of the invention, the differential pressure between the discharge pressure and the suction pressure of the low stage side compression mechanism (41) is set to be equal to or greater than the predetermined rollover limit pressure value.

    According to a fifth aspect, in the first aspect, the one compression mechanism (11) is configured to have a variable operating capacity, and the one compression mechanism (11) is switched when the single-stage compression operation is switched to the two-stage compression operation. By controlling the operating capacity of (11) from that in the single-stage compression operation, control is performed so that the differential pressure between the suction side and the discharge side of the other compression mechanism (41) is equal to or higher than a predetermined second set pressure value. Differential pressure control means (102) is provided.

    In the fifth aspect of the invention, the predetermined second set pressure value is a differential pressure necessary to keep the other compression mechanism (41) in an appropriate driving state. When switching from the single-stage compression operation to the two-stage compression operation, the other compression mechanism (41) that has been stopped is driven, so that the differential pressure control means (102) is operated by the one compression mechanism (102). The operation capacity of 11) is reduced from that in the single-stage compression operation, and the differential pressure between the suction side and the discharge side of the other compression mechanism (41) is controlled to be equal to or higher than a predetermined second set pressure value.

    According to the first aspect of the invention, in the refrigeration apparatus capable of switching between the single-stage compression operation and the two-stage compression operation, when the high / low differential pressure of the refrigerant circuit (10) is smaller than the first set pressure value, the single-stage compression operation is performed. Since the two-stage compression operation is performed when the high / low differential pressure is equal to or higher than the first set pressure value, if the first set pressure value is appropriately set in advance, the high / low differential pressure is equal to or higher than the first set pressure value. The pressure difference can be appropriately distributed between the low-stage compression mechanism (41) and the high-stage compression mechanism (11) to improve the reliability of each compression mechanism (11, 41).

    According to the second aspect of the invention, at least one of the low-stage compression mechanism (41) and the high-stage compression mechanism (11) is replaced with a differential pressure oil supply type compressor (11a, 11b, 11c, 41a, 41b, 41c), so that the high-low differential pressure of the first set pressure value is appropriately distributed between the low-stage compression mechanism (41) and the high-stage compression mechanism (11), The differential pressure in the dome of each compressor (11a, 11b, 11c, 41a, 41b, 41c) can be kept at the differential pressure required for refueling. Thereby, oil supply can be appropriately performed in each compressor (11a, 11b, 11c, 41a, 41b, 41c).

    According to the third aspect of the invention, at least one of the low-stage compression mechanism (41) and the high-stage compression mechanism (11) is a scroll compressor (11a, 11b, 11c, 41a, 41b, 41c), so that the differential pressure higher than the first set pressure value is appropriately distributed between the low-stage compression mechanism (41) and the high-stage compression mechanism (11). It is possible to prevent the movable scroll of the compressor (11a, 11b, 11c, 41a, 41b, 41c) from overturning.

    According to the fourth aspect of the invention, the pressure difference between the discharge pressure and the suction pressure of the low stage compression mechanism (41) constituted by the scroll type compressor (41a, 41b, 41c) Since the pressure exceeds the predetermined rollover limit pressure value that becomes higher as the evaporation temperature of the refrigerant in the vessel (31) becomes higher, the rollover of the movable scroll of the low stage side compression mechanism (41) can be reliably prevented.

    According to the fifth aspect of the present invention, the differential pressure between the discharge pressure and the suction pressure of the other compression mechanism (41) is set to a predetermined second setting when switching from the single-stage compression operation to the two-stage compression operation. Since the pressure value is set, the differential pressure of the other compression mechanism (41), which has started driving by switching the two-stage compression operation, can be appropriately maintained, so that the other compression mechanism (41) is stable. It can be driven in a state.

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

    As shown in FIG. 1, an embodiment of the present invention is a refrigeration apparatus (1) that cools an inside of a cabinet, and includes an outdoor unit (2), a cooling unit (3), a booster unit (4), a controller (100 ).

    The outdoor unit (2) is provided with an outdoor circuit (20), the cooling unit (3) is provided with a cooling circuit (30), and the booster unit (4) is provided with a booster circuit (40). The outdoor circuit (20) and the cooling circuit (30) are connected via a liquid communication pipe (21), and the cooling circuit (30) and the booster circuit (40) are connected to a first gas communication pipe (22). The booster circuit (40) and the outdoor circuit (20) are connected via a second gas communication pipe (23). The outdoor circuit (20), the cooling circuit (30), and the booster circuit (40) are connected in order to constitute the refrigerant circuit (10) of the vapor compression refrigeration cycle.

<Outdoor unit>
The outdoor circuit (20) includes a high-stage compression mechanism (11), an outdoor heat exchanger (13), a receiver (14), a refrigerant heat exchanger (50), a first expansion valve (57), and a second expansion. A valve (58) and a third expansion valve (59) are provided. The outdoor circuit (20) is provided with a four-way switching valve (12), a liquid side closing valve (53), and a gas side closing valve (54). In the outdoor circuit (20), one end of the liquid communication pipe (21) is connected to the liquid side stop valve (53), and one end of the second gas communication pipe (23) is connected to the gas side stop valve (54). ing.

    The high stage compression mechanism (11) is composed of three compressors (11a, 11b, 11c) connected in parallel to each other. Each of the three compressors (11a, 11b, and 11c) is configured by a high-pressure dome type scroll compressor, although illustration of a specific configuration is omitted. That is, each compressor (11a, 11b, 11c) stores the refrigerating machine oil in the high-pressure space in the dome, and supplies the refrigerating machine oil to the sliding portion of the drive shaft and the bearing by a differential pressure. It is composed of a compressor of the type. Further, in each compressor (11a, 11b, 11c), the fixed scroll and the movable scroll engage with each other in a spiral wrap, and the revolving motion is performed while the movable scroll is pressed to the fixed scroll side by the differential pressure in the dome. By carrying out, it is comprised so that the refrigerant | coolant in the compression chamber formed of a mutual spiral wrap may be compressed.

    The first compressor (11a) is configured such that electric power is supplied to a compressor motor (not shown) via an inverter and the output frequency of the inverter is changed to vary the operating capacity. The second compressor (11b) and the third compressor (11c) are configured to have a fixed operating capacity. In the high-stage compression mechanism (11), the first compressor (11a) of the three compressors (11a, 11b, 11c) is preferentially driven during the operation of the refrigeration apparatus (1). The second compressor (11b) and the third compressor (11c) are sequentially driven in accordance with the load in the storage. That is, as shown in FIG. 2A, the high-stage compression mechanism (11) is in the mode H0 when the operation of the refrigeration apparatus (1) is stopped, and from a small load state to a large load state during operation. The drive mode is configured to change between mode H1, mode H2, and mode H3 as it changes.

    A suction main pipe (55) is connected to the suction side of the high-stage compression mechanism (11). One end of the suction main pipe (55) is connected to the four-way switching valve (12), and the other end is branched into a third suction pipe (61c) and a suction connection pipe (56), and the third suction pipe (61c ) Is connected to the suction side of the third compressor (11c). The suction connection pipe (56) is branched into a first suction pipe (61a) and a second suction pipe (61b), and the first suction pipe (61a) is a suction side of the first compressor (11a). On the other hand, the second suction pipe (61b) is connected to the suction side of the second compressor (11b).

    A discharge main pipe (64) is connected to the discharge side of the high-stage compression mechanism (11). One end of the discharge main pipe (64) is connected to the four-way switching valve (12), while the other ends are the first discharge pipe (64a), the second discharge pipe (64b), and the third discharge pipe (64c). It is branched to. The first discharge pipe (64a) is on the discharge side of the first compressor (11a), the second discharge pipe (64b) is on the discharge side of the second compressor (11b), and the third discharge pipe (64c) Are connected to the discharge side of the third compressor (11c). Each discharge pipe (64a, 64b, 64c) has a check valve (CV-1, CV that allows only the refrigerant flow from each compressor (11a, 11b, 11c) to the four-way selector valve (12). -2, CV-3) are provided.

    The outdoor heat exchanger (13) is a cross fin type fin-and-tube heat exchanger that exchanges heat between refrigerant and outdoor air, and is configured as a condenser. . The outdoor heat exchanger (13) has one end connected to the four-way switching valve (12) and the other end connected to the top of the receiver (14) via the first liquid pipe (81). The first liquid pipe (81) is provided with a check valve (CV-4) that allows only the refrigerant to flow from the outdoor heat exchanger (13) to the receiver (14). One end of the second liquid pipe (82) is connected to the bottom of the receiver (14).

    The refrigerant heat exchanger (50) is a plate heat exchanger, and performs heat exchange between the refrigerant and the refrigerant. The first flow path (50a) and the second flow path (50b) It has. One end of the first flow path (50a) of the refrigerant heat exchanger (50) is connected to the other end of the second liquid pipe (82), and the other end is connected to one end of the third liquid pipe (83). ing. The other end of the third liquid pipe (83) is connected to one end of the liquid communication pipe (21) via the liquid side closing valve (53). The third liquid pipe (83) is provided with a check valve (CV-5) that allows only the refrigerant to flow from the other end of the first flow path (50a) to the liquid side shut-off valve (53). Yes.

    One end of a fourth liquid pipe (84) is connected to the third liquid pipe (83) on the upstream side of the check valve (CV-5), and the other end of the fourth liquid pipe (84) is The refrigerant heat exchanger (50) is connected to one end of the second flow path (50b). The fourth liquid pipe (84) is provided with a second expansion valve (58). The second expansion valve (58) is an electronic expansion valve whose opening degree is adjustable.

    The other end of the second flow path (50b) of the refrigerant heat exchanger (50) is connected to the suction main pipe (55) through a gas injection pipe (85). The gas injection pipe (85) is for injecting a gas refrigerant into the suction side of the first to third compressors (11a, 11b, 11c).

    In the third liquid pipe (83), one end of a fifth liquid pipe (88) is connected between the check valve (CV-5) and the liquid side shut-off valve (53). The other end of the fifth liquid pipe (88) is connected between the check valve (CV-4) and the receiver (14) in the first liquid pipe (81). Further, the fifth liquid pipe (88) is provided with a check valve (CV-6) that allows only the flow of the refrigerant from one end to the other end.

    One end of the sixth liquid pipe (89) is connected between one end of the fourth liquid pipe (84) and the second expansion valve (58), and the other end of the sixth liquid pipe (89) is The first liquid pipe (81) is connected between the outdoor heat exchanger (13) and the check valve (CV-4). The sixth liquid pipe (89) is provided with a first expansion valve (57). The first expansion valve (57) is an electronic expansion valve whose opening degree is adjustable.

    One end of a communication pipe (78) is connected between the check valve (CV-4) and the connection part of the fifth liquid pipe (88) in the first liquid pipe (81). The other end of (78) is connected to the discharge main pipe (64). The communication pipe (78) is provided with a check valve (CV-7) that allows only the refrigerant to flow from the first liquid pipe (81) to the discharge main pipe (64).

    The four-way switching valve (12) has a first port at the discharge main pipe (64), a second port at the suction main pipe (55), a third port at one end of the outdoor heat exchanger (13), and a fourth port. Are connected to the gas-side closing valve (54), respectively. The four-way switching valve (12) is in a first state in which the first port and the third port communicate with each other and the second port and the fourth port communicate with each other (state indicated by a solid line in FIG. 1). ) And a second state (state indicated by a broken line in FIG. 1) in which the first port and the fourth port communicate with each other and the second port and the third port communicate with each other. ing.

    The outdoor circuit (20) includes an oil separator (70), a first liquid injection passage (15), first to third oil equalizing pipes (72a, 72b, 72c), and first to first Three three oil recovery pipes (73a, 73b, 73c) are provided.

    The oil separator (70) is provided in the discharge main pipe (64) and separates refrigeration oil from refrigerant discharged from the compressors (11a, 11b, 11c). One end of an oil return pipe (71) is connected to the oil separator (70), and the other end of the oil return pipe (71) is connected to a connection portion of the gas injection pipe (85) in the suction main pipe (55). Connected downstream. The oil return pipe (71) is provided with a fourth solenoid valve (SV-4) that can be freely opened and closed. When the fourth solenoid valve (SV-4) is opened, the oil separator (70) is separated. Refrigerator oil is returned to the compressors (11a, 11b, 11c) via the suction main pipe (55).

    The first liquid injection passage (15) includes a first liquid injection main pipe (16) and first to fourth liquid injection branch pipes (16a, 16b, 16c, 16d). One end of the first liquid injection main pipe (16) is connected between one end of the fourth liquid pipe (84) and a connection portion of the sixth liquid pipe (89), and a shunt (26) is connected to the other end. Is provided. A third expansion valve (59) is provided in the middle of the first liquid injection main pipe (16). The third expansion valve (59) is an electronic expansion valve whose opening degree is adjustable.

    The first to fourth liquid injection branch pipes (16a, 16b, 16c, 16d) are branched from the flow divider (26) of the first liquid injection main pipe (16), and the first to third liquid injection branch pipes (16a, 16b, 16c, 16d) are branched. Each liquid injection branch pipe (16a, 16b, 16c) is in the middle of each of the first to third suction pipes (61a, 61b, 61c), and a fourth liquid injection branch pipe (16d) is an oil return pipe (71). The fourth solenoid valve (SV-4) is connected between the other end. Each of the first to fourth liquid injection branch pipes (16a, 16b, 16c, 16d) is provided with a capillary tube (17a, 17b, 17c, 17d) on the way.

    In the three oil leveling pipes (72a, 72b, 72c), the first oil leveling pipe (72a) is connected to the dome of the first compressor (11a) and the middle of the fourth liquid injection branch pipe (16d), A first solenoid valve (SV-1) is provided on the way. The second oil leveling pipe (72b) is connected to the dome of the second compressor (11b) and the middle of the first suction pipe (61a), and includes a second electromagnetic valve (SV-2). The third oil equalizing pipe (72c) is connected to the dome of the third compressor (11c) and the suction connecting pipe (56), and includes a third electromagnetic valve (SV-3). In the refrigeration apparatus (1), the refrigeration oil returned to the suction main pipe (55) by the oil return pipe (71) is supplied to the third compressor (11c), the second compressor (11b), and the first compressor ( It is configured to return in the order of 11a). Then, through the oil equalizing pipes (72a, 72b, 72c), the refrigerating machine oil of the third compressor (11c) is sequentially sent to the second compressor (11b) and the first compressor (11a). The surplus of the refrigerating machine oil of one compressor (11a) is sent to the oil return pipe (71) so that the compressors (11a, 11b, 11c) are oil-equalized with each other.

    In the three oil recovery pipes (73a, 73b, 73c), one end of the first oil recovery pipe (73a) is in the middle of the first suction pipe (61a) and one end of the second oil recovery pipe (73b) is One end of the third oil recovery pipe (73c) is connected to the middle of the third suction pipe (61c) in the middle of the second suction pipe (61b), while each oil recovery pipe (73a, 73b, 73c) The other ends of the two are joined together. The oil recovery pipe (73a, 73b, 73c) is connected to the compressor (11b, 11c) when a specific compressor (11b, 11c) is stopped according to the load during operation of the refrigeration system (1). The refrigeration oil staying in the suction pipes (61b, 61c) is sent to the suction pipes (61a, 61b) of the other compressors (11a, 11b) being driven.

    The outdoor circuit (20) is provided with various sensors and pressure switches. Specifically, a suction pressure sensor (135) and a suction temperature sensor (136) are provided in the suction main pipe (55), a discharge pressure sensor (137) is provided in the discharge main pipe (64), and each discharge temperature sensor (138, 139, 140) is provided in each discharge pipe (64a, 64b, 64c). A temperature sensor (141) is provided in the vicinity of the connection portion of the first flow path (50a) of the refrigerant heat exchanger (50) in the third liquid pipe (83). In addition, pressure switches (151, 152, 153, 154) are provided in the discharge pipes (64a, 64b, 64c) and pipes between the gas side shut-off valve (54) and the four-way switching valve (12). ing.

    The outdoor unit (2) is provided with an outdoor air temperature sensor (13a) and an outdoor fan (13f). Outdoor air is sent to the outdoor heat exchanger (13) by the outdoor fan (13f).

<Cooling unit>
The cooling circuit (30) includes a cooling heat exchanger (31), a drain pan heater (36), and a cooling expansion valve (32).

    The cooling heat exchanger (31) is a cross-fin type fin-and-tube heat exchanger that exchanges heat between the refrigerant and the air in the cabinet, and is configured as an evaporator. ing. One end of the cooling heat exchanger (31) is connected to one end of the drain pan heater (36) via the cooling expansion valve (32), and the other end is connected to one end of the first gas communication pipe (22). Yes.

    The cooling expansion valve (32) is an electronic expansion valve whose opening degree can be adjusted, and is configured as an expansion mechanism. The cooling heat exchanger (31) is provided with a first refrigerant temperature sensor (33) for measuring the evaporation temperature of the refrigerant in the heat transfer tube, while the other end of the cooling heat exchanger (31) A second refrigerant temperature sensor (34) is provided. The cooling expansion valve (32) is configured such that the temperature measured by the second refrigerant temperature sensor (34) is higher by a predetermined temperature (for example, 5 ° C.) than the refrigerant evaporation temperature measured by the first refrigerant temperature sensor (33). The so-called superheat control is performed in which the opening degree is adjusted.

    The drain pan heater (36) is disposed on the drain pan of the cooling heat exchanger (31) (not shown) to heat the drain pan and prevent frost formation and ice formation. The other end of the drain pan heater (36) is connected to the other end of the liquid communication pipe (21).

    The cooling unit (3) is provided with an internal temperature sensor (35f) and an internal fan (35a). To the cooling heat exchanger (31), the internal air is sent by the internal fan (35a).

<Booster unit>
The booster circuit (40) includes a booster compression mechanism (41) that is a low-stage side compression mechanism, a fourth expansion valve (38), and a fifth expansion valve (39).

    The booster compression mechanism (41) includes first to third booster compressors (41a, 41b, 41c) connected in parallel to each other. Each of the booster compressors (41a, 41b, 41c) is configured by a high-pressure dome type scroll compressor, like the compressors (11a, 11b, 11c) on the higher stage side. That is, each booster compressor (41a, 41b, 41c) is a differential pressure oil supply type compressor, and in the dome, a compression operation is performed by performing a revolving motion by pressing the movable scroll against the fixed scroll. .

    The first booster compressor (41a) is configured such that electric power is supplied to a compressor motor (not shown) via an inverter, and the output frequency of the inverter is changed to vary the operating capacity. On the other hand, the second booster compressor (41b) and the third booster compressor (41c) have a fixed operating capacity. The booster compression mechanism (41) is driven only when the refrigeration apparatus (1) performs the two-stage compression operation as described later, and is stopped during the single-stage compression operation. In addition, during the two-stage compression operation of the refrigeration system (1), the first booster compressor (41a) among the three booster compressors (41a, 41b, 41c) is driven preferentially, and the load in the warehouse Accordingly, the second booster compressor (41b) and the third booster compressor (41c) are sequentially driven in this order. That is, as shown in FIG. 2B, the booster compression mechanism (41) is in the mode L0 when the operation of the refrigeration apparatus (1) is stopped, and changes from a small load state to a large load state during operation. Accordingly, the drive mode is changed between mode L1, mode L2, and mode L3.

    A booster suction main pipe (42) is connected to the suction side of the booster compression mechanism (41). The suction main pipe (42) has one end connected to the other end of the first gas communication pipe (22) and the other end branched to a third booster suction pipe (44c) and a booster suction connection pipe (43). The other end of the third booster suction pipe (44c) is connected to the suction side of the third booster compressor (41c). The booster suction connection pipe (43) is branched into a first booster suction pipe (44a) and a second booster suction pipe (44b), and the first booster suction pipe (44a) is connected to the first booster compressor (44). The second booster suction pipe (44b) is connected to the suction side of the second booster compressor (41b) while being connected to the suction side of 41a).

    A booster discharge main pipe (45) is connected to the discharge side of the booster compression mechanism (41). One end of the booster discharge main pipe (45) is connected to one end of the second gas communication pipe (23) via the closing valve (51), while the other end is connected to the first booster discharge pipe (45a) and the second It is branched into a booster discharge pipe (45b) and a third booster discharge pipe (45c). The first booster discharge pipe (45a) is connected to the discharge side of the first booster compressor (41a), and the second booster discharge pipe (45b) is connected to the discharge side of the second booster compressor (41b). The third booster discharge pipe (45c) is connected to the discharge side of the third booster compressor (41c). Each booster discharge pipe (45a, 45b, 45c) has a check valve (CV-8, which allows only the refrigerant flow from each of the booster compressors (41a, 41b, 41c) to the booster discharge main pipe (45). CV-9 and CV-10) are provided respectively.

    The booster circuit (40) includes an oil separator (46), two second and third liquid injection passages (27, 29), an oil feed pipe (76), a fourth and a fifth two. An oil equalizing pipe (74a, 74b) and fourth to sixth oil recovery pipes (75a, 75b, 75c) are provided.

    The oil separator (46) is provided in the booster discharge main pipe (45), and separates the refrigerating machine oil from the refrigerant discharged from the first to third booster compressors (41a, 41b, 41c). Is. One end of a first bypass pipe (47) is connected to the oil separator (46), and the other end of the first bypass pipe (47) is connected to the booster suction main pipe (42). The first bypass pipe (47) has a fifth solenoid valve (SV-5), and the refrigerant discharged from the high-stage compression mechanism (11) is booster-compressed during the defrosting operation of the refrigeration apparatus (1). This is for bypassing the mechanism (41). Also, one end of the oil return pipe (48) is connected between the fifth solenoid valve (SV-5) and one end of the first bypass pipe (47), and the other end of the oil return pipe (48) It is connected in the middle of the booster suction main pipe (42). The oil return pipe (48) is provided with a sixth solenoid valve (SV-6) that can be freely opened and closed. When the sixth solenoid valve (SV-6) is opened, the oil separator (46) is refrigerated. Machine oil is returned to each booster compressor (41a, 41b, 41c) via the booster suction main pipe (42).

    The second liquid injection passage (27) includes a second liquid injection main pipe (28) and fifth to seventh liquid injection branch pipes (28a, 28b, 28c). In the second liquid injection passage (27), one end of the second liquid injection main pipe (28) is connected in the middle of the liquid communication pipe (21), and the other end of the second liquid injection main pipe (28) is the first. The fifth to seventh liquid injection branch pipes (28a, 28b, 28c) are branched, and the fifth to seventh liquid injection branch pipes (28a, 28b, 28c) are connected to the first to third boosters. The suction pipes (41a, 41b, 41c) are connected respectively.

    The second liquid injection main pipe (28) is provided with a fourth expansion valve (38), and each of the fifth to seventh liquid injection branch pipes (28a, 28b, 28c) has a capillary in the middle thereof. Tubes (37a, 37b, 37c) are provided. One end of the third liquid injection passage (29) is connected between one end of the second liquid injection main pipe (28) and the fourth expansion valve (38), and the other end is oil of the booster discharge main pipe (45). It is connected between the separator (46) and the closing valve (51). A fifth expansion valve (39) is provided in the third liquid injection passage (29). Each of the fourth and fifth expansion valves (38, 39) is an electronic expansion valve whose opening degree is adjustable.

    The oil feed pipe (76) is connected to the dome of the first booster compressor (41a) and the middle of the booster discharge main pipe (45), and is non-returnable with the seventh solenoid valve (SV-7) that can be opened and closed halfway. And a valve (CV-11). In the two oil leveling pipes (74a, 74b), the fourth oil leveling pipe (74a) is connected to the dome of the second booster compressor (41b) and the middle of the first booster suction pipe (44a). Is equipped with an eighth solenoid valve (SV-8). The fifth oil equalizing pipe (74b) is connected to the dome of the third booster compressor (41c) and the middle of the booster suction connecting pipe (43), and includes a ninth electromagnetic valve (SV-9).

    In the refrigeration apparatus (1), the refrigeration oil returned to the booster suction main pipe (42) by the oil return pipe (48) is supplied to the third booster compressor (41c), the second booster compressor (41b), the first The booster compressor (41a) is configured so as to return in order. The refrigerating machine oil of the third booster compressor (41c) is supplied to the second booster compressor (41b) and the first booster compressor (41a) through the fourth and fifth oil equalizing pipes (74a, 74b). The surplus of the refrigeration oil in the first booster compressor (41a) is sent to each compressor (11a, 11b, 11c) in the outdoor circuit (20) through the oil feed pipe (76). Yes.

    The three oil recovery pipes (75a, 75b, 75c) have one end of the fourth oil recovery pipe (75a) in the middle of the first booster suction pipe (44a) and one end of the fifth oil recovery pipe (75b) being the second. One end of the sixth oil recovery pipe (75c) is connected to the middle of the third booster suction pipe (44c) in the middle of the booster suction pipe (44b), while each oil recovery pipe (75a, 75b, 75c) The other ends are joined together. The oil recovery pipe (75a, 75b, 75c) is connected to the booster compressor (41b, 41c) when a specific booster compressor (41b, 41c) is stopped according to the load during operation of the refrigeration apparatus (1). ) Is sucked into the booster suction pipes (44a, 44b) of the other booster compressors (41a, 41b) that are driven.

    Further, the booster circuit (40) is provided with a second bypass pipe (49) for connecting the booster suction main pipe (42) and the booster discharge main pipe (45). The second bypass pipe (49) bypasses the booster compression mechanism (41) and sends the refrigerant flowing through the booster suction main pipe (42) to the booster discharge main pipe (45) when the booster compression mechanism (41) is stopped. A check valve (CV-12) that allows only the flow of refrigerant from the booster suction main pipe (42) to the booster discharge main pipe (45) is provided.

    The booster circuit (40) is provided with various sensors and pressure switches. Specifically, a booster suction pressure sensor (142) and a booster suction temperature sensor (143) are provided in the booster suction main pipe (42), and a booster discharge pressure sensor (144) and a booster discharge main temperature sensor (145) are provided in the booster discharge main pipe. (45), each booster discharge sub temperature sensor (148, 149, 150) and each pressure switch (155, 156, 157) are provided in each booster discharge pipe (45a, 45b, 45c).

<controller>
The controller (100) performs switching and opening adjustment of various valves provided in the refrigerant circuit (10), as well as compressors (11a, 11b, 11c, 41a, 41b, 41c) and fans (13f). , 35f) to control the operation of the refrigeration apparatus (1). The controller (100) includes a switching control unit (101) and a differential pressure control unit (102) as a feature of the present invention.

    The switching control unit (101) performs the single-stage compression operation when the height differential pressure, which is the pressure difference between the high pressure refrigerant and the low pressure refrigerant, is smaller than a predetermined first set pressure value (P1). When the pressure is equal to or higher than a predetermined first set pressure value (P1), the operation state is switched so as to perform the above-described two-stage compression operation, and is configured as a switching control means.

    The differential pressure control unit (102) controls the differential pressure between the discharge pressure and the suction pressure of the booster compression mechanism (41) to be equal to or higher than a predetermined second set pressure value (P2). It is comprised by the differential pressure control means. Specifically, the second set pressure value (P2) is the larger one of the predetermined rollover limit pressure value indicated by line A in FIG. 5 and the predetermined oil supply limit pressure value indicated by line B, as will be described later. This is a differential pressure necessary to keep the booster compression mechanism (41) in an appropriate driving state. The differential pressure control unit (102) reduces the operating capacity of the high-stage compression mechanism (11) from the single-stage compression operation when switching from the single-stage compression operation to the two-stage compression operation. Control is performed so that the differential pressure between the suction side and the discharge side of the compression mechanism (41) is equal to or higher than the predetermined second set pressure value (P2).

-Driving action-
Next, the operation | movement operation | movement of the freezing apparatus (1) of this embodiment is demonstrated based on FIGS. The refrigeration apparatus (1) performs a cooling operation for cooling the interior and a defrosting operation for removing frost formation on the cooling heat exchanger (31).

<Cooling operation>
In the cooling operation of the refrigeration apparatus (1), a cooling operation is performed to keep the interior at the set temperature Ts appropriately set by the user. In the cooling operation, when the pressure difference between the high pressure refrigerant and the low pressure refrigerant in the refrigerant circuit (10) is smaller than a predetermined first set pressure value (P1), a single-stage compression operation is performed, and the above height difference If the pressure is greater than or equal to a predetermined first set pressure value (P1), a two-stage compression operation is performed. Specifically, immediately after the start of the cooling operation or immediately after returning from the defrosting operation to the cooling operation, the high / low differential pressure is small, so the single-stage compression operation is first performed, and then the high / low differential pressure is set to a predetermined first setting. When the pressure value (P1) or more is reached, the control is switched to the two-stage compression operation by the control of the switching control unit (101). Thereafter, the two-stage compression operation is performed until the high-low differential pressure becomes smaller than the predetermined first set pressure value (P1). Is done.

(Single-stage compression operation)
In the single-stage compression operation, as shown in FIG. 3, the four-way switching valve (12) of the outdoor circuit (20) is set to the first state, and the first, fourth and fifth expansion valves (57, 38) are set. , 39) is set to the fully closed state. In this state, in the high-stage compression mechanism (11), for example, the first and second compressors (11a, 11b) are driven, and the compressors (41a, 41b, 41c) of the booster compression mechanism (41) are driven. ) Is stopped, and the refrigerant circulates in the direction indicated by the arrow in FIG. That is, the drive mode of the compression mechanism (11, 41) shown in FIG. 2 is H2-L0. Each fan (13f, 35f) is driven. The opening degree of the cooling expansion valve (32) and the second and third expansion valves (58, 59) are adjusted as appropriate. In the outdoor circuit (20), the first, second, and fourth solenoid valves (SV-1, 2, 4) are intermittently controlled to be opened and closed appropriately, while the third solenoid valve (SV-3) is always open. In the booster circuit (40), the fifth to ninth solenoid valves (SV-5, 6, 7, 8, 9) are set to the normally closed state.

    In the outdoor circuit (20), the refrigerant discharged from the first and second compressors (11a, 11b) flows from the discharge pipes (64a, 64b) to the discharge main pipe (64), and the four-way switching valve (12 ) Through the outdoor heat exchanger (13). In the outdoor heat exchanger (13), the refrigerant dissipates heat to the outdoor air and is condensed and liquefied. The liquefied refrigerant flows through the first liquid pipe (81), passes through the receiver (14), flows through the second liquid pipe (82), and flows into the first flow path (50a) of the refrigerant heat exchanger (50). To do. The liquid refrigerant that has flowed through the first flow path (50a) flows through the third liquid pipe (83) and is introduced into the cooling circuit (30) through the liquid communication pipe (21). Further, when the refrigerant flows through the third liquid pipe (83), a part of the refrigerant branches into the fourth liquid pipe (84).

    A part of the refrigerant flowing through the fourth liquid pipe (84) is decompressed by the second expansion valve (58) and flows into the second flow path (50b) of the refrigerant heat exchanger (50). The liquid refrigerant flowing through the channel (50a) exchanges heat and evaporates, and the liquid refrigerant flowing through the first channel (50a) is cooled to a predetermined temperature. The refrigerant evaporated in the second flow path (50b) is supplied to the suction main pipe (55) through the gas injection pipe (85). Further, the remaining part of the refrigerant that has flowed through the fourth liquid pipe (84) is adjusted in flow rate through the third expansion valve (59) whose opening degree is adjusted, and is passed through the first liquid injection passage (15). Supplied to the suction side of the high stage compression mechanism (11).

    The liquid refrigerant introduced into the cooling circuit (30) flows through the drain pan heater (36) to prevent the drain pan from frosting and melts the frost that has fallen from the cooling heat exchanger (31) to the drain pan. The liquid refrigerant flowing out of the drain pan heater (36) is decompressed and expanded when flowing through the cooling expansion valve (32), and flows through the cooling heat exchanger (31). In the cooling heat exchanger (31), the refrigerant absorbs heat from the air in the cabinet and evaporates at the evaporation temperature Te. Thereby, in the cooling unit (3), the air cooled by the cooling heat exchanger (31) is supplied into the warehouse, and the interior is cooled to the temperature Tr. The gas refrigerant evaporated in the cooling heat exchanger (31) flows through the first gas communication pipe (22) and is introduced into the booster circuit (40).

    The gas refrigerant introduced into the booster circuit (40) flows through the booster suction main pipe (42), the entire amount flows through the second bypass pipe (49), bypasses the booster compression mechanism (41), and the booster discharge main pipe (45 ) And the second gas communication pipe (23) and introduced into the outdoor circuit (20).

    The refrigerant introduced into the outdoor circuit (20) flows through the suction main pipe (55) through the four-way switching valve (12). The refrigerant that has flowed through the suction main pipe (55) flows through the suction connection pipe (56) and branches into the first suction pipe (61a) and the second suction pipe (61b), and the first and second compressors ( 11a, 11b) is inhaled and compressed.

<Switching operation from single-stage compression operation to two-stage compression operation>
When the differential pressure becomes equal to or higher than a predetermined first set pressure value (P1) during the single-stage compression operation, the single-stage compression operation is switched to the two-stage compression operation under the control of the switching control unit (101). This switching control will be described based on the flowchart of FIG.

    First, as shown in FIG. 4, when the switching control is started, it is determined in step ST1 whether the set temperature Ts in the cabinet set by the user is equal to or higher than −5 ° C. or lower than −5 ° C. The And if it is -5 degreeC or more, it will move to step ST2, and if it is less than -5 degreeC, it will move to step ST5. That is, usually, the set temperature Ts in the warehouse is often set and used in a refrigeration temperature range of 0 to 10 ° C. or a refrigeration temperature range of −20 or less. Not often used. In general, if the set temperature Ts is in the refrigeration temperature range, sufficient cooling can be performed even in the single-stage compression operation. If the set temperature Ts is in the refrigeration temperature range, the two-stage compression operation is performed because the cooling load is large. Is called. Therefore, the set temperature Ts is determined at a boundary of −5 ° C., which is not normally set, and, as will be described later, only a single-stage compression operation is performed at −5 ° C. or higher (refrigerated temperature range) unless there is a rapid pull-down setting. Do.

    In step ST2, it is determined whether or not rapid pull-down is set. This rapid pull-down is an operation mode in which the interior temperature Tr is rapidly cooled when the interior temperature Tr is significantly higher than the set temperature Ts, such as at the start-up or after opening or closing the cooling door, and this operation is performed by user input. Whether or not to perform the mode is set. If rapid pull-down is not set, the process proceeds to return. If rapid pull-down is set, the process proceeds to step ST2. That is, when the set temperature Ts is −5 ° C. or higher and the rapid pull-down is not set, the switching to the two-stage compression operation is not performed and only the single-stage compression operation is performed.

    In step ST3, it is determined whether or not the difference between the actual internal temperature Tr and the set temperature Ts is 1 ° C. or less. When the difference between the actual internal temperature Tr and the set temperature Ts is greater than 1 ° C. and the internal cooling is insufficient, the process proceeds to return, and the difference between the actual internal temperature Tr and the set temperature Ts is If the interior is sufficiently cooled at 1 ° C. or lower, the process proceeds to step ST4. That is, in this step ST4, even if the two-stage compression operation is performed in a state where the interior is not sufficiently cooled, the interior cannot be efficiently cooled, and wasteful power is consumed by the compression mechanism (11, 41). Therefore, when the inside of the refrigerator is not sufficiently cooled, it is not switched to the two-stage compression operation.

    In step ST4, it is determined whether or not the evaporation temperature Te is −8 ° C. or lower and whether or not the internal temperature Tr is −3 ° C. or lower. That is, it is determined whether the evaporation temperature Te is sufficiently low or the inside temperature Tr is sufficiently low. If none of these conditions is satisfied, the process proceeds to return, and if both are satisfied, the process proceeds to step ST5.

    In step ST5, it is determined whether the high / low differential pressure, which is the pressure difference between the high-pressure refrigerant and the low-pressure refrigerant in the refrigerant circuit (10), is equal to or higher than a predetermined first set pressure value (P1). The pressure of the high-pressure refrigerant is measured by the discharge pressure sensor (137), and the pressure of the low-pressure refrigerant is measured by the booster suction pressure sensor (142).

    The predetermined first set pressure value (P1) is a differential pressure necessary to keep both the booster and the high-stage compression mechanisms (11, 41) in an appropriate driving state in the two-stage compression operation. Here, the setting of the predetermined first set pressure value (P1) will be described with reference to FIG. A line A in FIG. 5 shows a predetermined overturning limit pressure value of the booster compression mechanism (41) with respect to the evaporation temperature Te during the two-stage compression operation, and a line B shows a predetermined oil supply limit pressure value of the booster compression mechanism (41). Is shown. The predetermined rollover limit pressure value is the movable scroll when the differential pressure between the discharge pressure and the suction pressure is less than the rollover limit pressure value in each booster compressor (41a, 41b, 41c) of the booster compression mechanism (41). Is the limit pressure value that prevents the movable scroll from overturning, and as shown by the line A, the evaporation temperature Te increases as the evaporation temperature Te in the cooling heat exchanger (31) increases. Expressed as a function. Further, the predetermined oil supply limit pressure value is a pressure value necessary for supplying oil to the sliding portion by the differential pressure in the dome of each booster compressor (41a, 41b, 41c). So that it is a constant value.

    In other words, during the operation of the booster compression mechanism (41), the discharge pressure of the booster compression mechanism (41) is such that the rollover of the movable scroll does not occur and oil supply to the sliding portion in the dome can be performed. And the suction pressure must be maintained above the larger of these pressure values. In this embodiment, as shown in FIG. 5, the overturning limit pressure value is larger than the oil supply limit pressure value over the entire evaporation temperature Te, so that the booster compression mechanism (41) is maintained in an appropriate driving state. The predetermined second set pressure value (P2) is set to the same pressure value as the rollover limit pressure value indicated by the line A. The first set pressure value (P1) is set to a value obtained by adding the second set pressure value (P2) to the differential pressure for properly maintaining the driving state of the high-stage compression mechanism (11). .

    If it is determined in step ST5 that the differential pressure in the refrigerant circuit (10) is equal to or higher than the first set pressure value (P1), the process proceeds to step ST6, where the differential pressure in the refrigerant circuit (10) is set to the first setting. If it is less than the pressure value (P1), return to return. That is, when the two-stage compression operation is performed in a state where the height difference pressure of the refrigerant circuit (10) is less than the first set pressure value (P1), the height difference pressure less than the first set pressure value (P1) is increased to the booster compression mechanism. (41) and the high-stage compression mechanism (11) cannot be properly distributed, so the driving state of each compression mechanism (41, 11) cannot be maintained properly, so switching to the two-stage compression operation is not possible. Like that. When the high / low differential pressure of the refrigerant circuit (10) becomes equal to or higher than the first set pressure value (P1), the high / low differential pressure is appropriately distributed to the booster compression mechanism (41) and the high-stage compression mechanism (11). Therefore, it moves to step ST6 and switches to a two-stage compression operation.

    In step ST6, the switching control unit (101) of the controller (100) switches the operation state of the refrigeration apparatus (1) from the single-stage compression operation to the two-stage compression operation. At this time, the differential pressure control unit (102) controls the differential pressure between the discharge pressure and the suction pressure of the booster compression mechanism (41) to be equal to or higher than the predetermined second set pressure value (P2). Specifically, at the time of this switching, the differential pressure control unit (102) determines that the combination of drive modes of the high stage compression mechanism (11) and the booster compression mechanism (41) shown in FIG. 2 is H1-L0, H2- Control is performed so that either L0 or H3-L0 becomes H1-L1, and the operating capacity of the first compressor (11a) is set to the minimum.

    That is, in the operation of the single-stage compression operation described above, the operation in which the first and second compressors (11a, 11b) of the high-stage compression mechanism (11) are driven is described as an example. In operation, only the first compressor (11a) of the high-stage compression mechanism (11) is driven, or all the first to third compressors (11a, 11b, 11c) are driven. Even in this case, when switching to the two-stage compression operation, the high-stage compression mechanism (11) operates only the first compressor (11a) with the minimum operation capacity.

    As described above, when the switching control unit (101) is equal to or higher than the predetermined first set pressure value (P1), the single-stage compression operation is switched to the two-stage compression operation. It is appropriately distributed to the compressor (41a) and the first compressor (11a), and the driving state of each compressor (11a, 41a) is maintained appropriately. Further, since the differential pressure control unit (102) maintains the differential pressure between the discharge pressure and the suction pressure of the booster compression mechanism (41) at the predetermined second set pressure value (P2) or more, the booster compression mechanism (41 ) Of the movable scroll can be prevented, and the sliding portion in the dome can be properly lubricated. The differential pressure control unit (102) always controls the differential pressure between the discharge pressure and the suction pressure of the booster compression mechanism (41) to the second set pressure value (P2) during the two-stage compression operation. To do.

(Operation of two-stage compression operation)
As described above, immediately after the switching of the two-stage compression operation, the compression mechanism (11, 41) is operated in the driving mode of H1-L1. That is, as shown in FIG. 6, only the first compressor (11a) is driven in the high-stage compression mechanism (11), and only the first booster compressor (41a) is driven in the booster compression mechanism (41). To do.

    Specifically, the four-way selector valve (12) of the outdoor circuit (20) is set to the first state, and the first expansion valve (57) is set to the fully closed state. In this state, the first compressor (11a) of the high-stage compression mechanism (11) is driven, the first booster compressor (41a) of the booster compression mechanism (41) is driven, and the refrigerant is indicated by an arrow in FIG. Cycle in the direction shown. Each fan (13f, 35f) is driven. The opening degree of the cooling expansion valve (32) and the second to fifth expansion valves (58, 59, 38, 39) are adjusted as appropriate. In the outdoor circuit (20), the first and fourth solenoid valves (SV-1, 4) are intermittently controlled to be opened and closed appropriately, and the second and third solenoid valves (SV-2, 3). Is set to a normally closed state, while in the booster circuit (40), the sixth and seventh solenoid valves (SV-6, 7) are intermittently controlled to be appropriately opened and closed, and the fifth, eighth and ninth are controlled. Each solenoid valve (SV-5, 8, 9) is normally closed.

    In the outdoor circuit (20), the refrigerant discharged from the first compressor (11a) flows from the first discharge pipe (64a) to the discharge main pipe (64), passes through the four-way switching valve (12), and the outdoor heat exchanger. Flow through (13). In the outdoor heat exchanger (13), the refrigerant dissipates heat to the outdoor air to condense and liquefy, and the first liquid pipe (81), the receiver (14), the second liquid pipe (82), and the refrigerant heat exchanger (50) It flows through the first flow path (50a), the third liquid pipe (83) and the liquid communication pipe (21) and is introduced into the cooling circuit (30). In addition, a part of the refrigerant flowing through the third liquid pipe (83) branches to the fourth liquid pipe (84), and a part thereof is connected to the second flow path (50b) of the refrigerant heat exchanger (50). It is supplied to the suction main pipe (55) through the gas injection pipe (85), and the remaining part is supplied to the suction side of the high-stage compression mechanism (11) through the first liquid injection passage (15). .

    The liquid refrigerant introduced into the cooling circuit (30) flows through the drain pan heater (36), expands at the cooling expansion valve (32), and flows through the cooling heat exchanger (31). In the cooling heat exchanger (31), the refrigerant absorbs heat from the air in the warehouse and evaporates at the evaporation temperature Te, whereby the interior is cooled to the temperature Tr. The gas refrigerant evaporated in the cooling heat exchanger (31) flows through the first gas communication pipe (22) and is introduced into the booster circuit (40).

    The gas refrigerant introduced into the booster circuit (40) flows through the booster suction main pipe (42), through the booster suction connection pipe (43), through the first booster suction pipe (44a), and to the first booster compressor ( 41a) is inhaled and compressed. The refrigerant discharged from the first booster compressor (41a) flows through the first booster discharge pipe (45a) through the booster discharge main pipe (45), through the second gas communication pipe (23), and into the outdoor circuit (20). To be introduced. A part of the refrigerant flowing through the liquid communication pipe (21) flows into the second liquid injection main pipe (28). Then, a part of the refrigerant flowing into the second liquid injection main pipe (28) passes through the fourth expansion valve (38) whose opening is adjusted, and through the second liquid injection passage (27), the booster compression mechanism ( 41) is supplied to the suction side, passes through the fifth expansion valve (39) whose opening is adjusted, and is supplied to the discharge side of the booster compression mechanism (41) through the third liquid injection passage (29).

    The refrigerant introduced into the outdoor circuit (20) flows through the suction main pipe (55) through the four-way switching valve (12). The refrigerant flowing through the suction main pipe (55) flows through the first suction pipe (61a) via the suction connection pipe (56), and is sucked into the first compressor (11a, 11b) and compressed.

    In the two-stage compression operation, when the cooling load in the warehouse increases, the second compressor (11b) and the third compressor (11c) of the high-stage compression mechanism (11) are sequentially driven as shown in FIG. The second booster compressor (41b) and the third booster compressor (41c) of the booster compression mechanism (41) are sequentially driven. That is, in the state of FIG. 7, the compression mechanism (11, 41) is operated in the drive mode of H3-L3.

    Specifically, the four-way switching valve (12) of the outdoor circuit (20) is set to the first state, the first expansion valve (57) is set to the fully closed state, and the first stage of the high stage side compression mechanism (11) is set. The first to third compressors (11a, 11b, 11c) are driven, and the first to third booster compressors (41a, 41b, 41c) of the booster compression mechanism (41) are driven. Circulate in the direction indicated by the arrow 7. Each fan (13f, 35f) is driven. The opening degree of the cooling expansion valve (32) and the second to fifth expansion valves (58, 59, 38, 39) are adjusted as appropriate. In the outdoor circuit (20), the first to fourth solenoid valves (SV-1, 2, 3, 4) are intermittently controlled to be opened and closed appropriately, while in the booster circuit (40), the fifth electromagnetic valve is controlled. The valve (SV-5) is set to a normally closed state, and the sixth to ninth solenoid valves (SV-6, 7, 8, 9) are intermittently controlled appropriately.

    In the outdoor circuit (20), the refrigerant discharged from the first to third compressors (11a, 11b, 11c) flows from the discharge pipes (64a, 64b, 64c) to the discharge main pipe (64), and passes through the four paths. It flows in the outdoor heat exchanger (13) through the switching valve (12). In the outdoor heat exchanger (13), the refrigerant dissipates heat to the outdoor air to condense and liquefy, and the first liquid pipe (81), the receiver (14), the second liquid pipe (82), and the refrigerant heat exchanger (50) It flows through the first flow path (50a), the third liquid pipe (83) and the liquid communication pipe (21) and is introduced into the cooling circuit. In addition, a part of the refrigerant flowing through the third liquid pipe (83) branches to the fourth liquid pipe (84), and a part thereof is connected to the second flow path (50b) of the refrigerant heat exchanger (50). It is supplied to the suction main pipe (55) through the gas injection pipe (85), and the remaining part is supplied to the suction side of the high-stage compression mechanism (11) through the first liquid injection passage (15). .

    The liquid refrigerant introduced into the cooling circuit (30) flows through the drain pan heater (36), expands at the cooling expansion valve (32), and flows through the cooling heat exchanger (31). In the cooling heat exchanger (31), the refrigerant absorbs heat from the air in the warehouse and evaporates at the evaporation temperature Te, whereby the interior is cooled to the temperature Tr. The gas refrigerant evaporated in the cooling heat exchanger (31) flows through the first gas communication pipe (22) and is introduced into the booster circuit (40).

    The gas refrigerant introduced into the booster circuit (40) flows through the booster suction main pipe (42), branches into a third booster suction pipe (44c) and a booster suction connection pipe (43), and the third booster suction pipe ( The refrigerant flowing through 44c) is sucked into the third booster compressor (41c) and compressed. On the other hand, the refrigerant flowing through the booster suction connection pipe (43) branches into a first booster suction pipe (44a) and a second booster suction pipe (44b), and the first and second booster compressors (41a, 41b) is inhaled and compressed. Refrigerant discharged from each compressor (41a, 41b, 41c) of the booster compression mechanism (41) flows through each booster discharge pipe (45a, 45b, 45c), joins in the booster discharge main pipe (45), and is supplied with the second gas. It flows through the connecting pipe (23) and is introduced into the outdoor circuit (20). In addition, a part of the refrigerant flowing through the liquid communication pipe (21) described above is disposed on the suction side of the booster compression mechanism (41) via the second liquid injection passage (27) and the third liquid injection passage (29). Each is supplied to the discharge side.

    The refrigerant introduced into the outdoor circuit (20) flows through the suction main pipe (55) through the four-way switching valve (12). The refrigerant flowing through the suction main pipe (55) branches into the third suction pipe (61c) and the suction connection pipe (56), and the refrigerant flowing through the third suction pipe (61c) is transferred to the third compressor (11c). ) Is inhaled and compressed. On the other hand, the refrigerant flowing through the suction connection pipe (56) branches to the first suction pipe (61a) and the second suction pipe (61b), and is sucked into the first and second compressors (11a, 11b). And compressed.

    Then, during the two-stage compression operation, when the pressure difference in the refrigerant circuit (10) becomes lower than the predetermined first set pressure value (P1) due to, for example, a decrease in the condensation temperature accompanying a decrease in the outside air temperature, the switching is performed. The control unit (101) switches the operation state from the two-stage compression operation to the single-stage compression operation.

<Defrosting operation>
The refrigeration apparatus (1) is configured to temporarily stop the cooling operation and perform a defrosting operation as shown in FIG.

    Specifically, the four-way selector valve (12) is set to the second state. Further, the opening degree of the first expansion valve (57) of the outdoor circuit (20) is appropriately adjusted, while the second to fifth expansion valves (58, 59, 38, 39) are fully closed, and the cooling circuit The (30) cooling expansion valve (32) is fully opened, and the fifth solenoid valve (SV-5) is opened. In this state, in the high stage compression mechanism (11), the first and second compressors (11a, 11b) are driven and the third compressor (11c) is stopped, while the booster compression mechanism ( In 41), each booster compressor (41a, 41b, 41c) is stopped. Thereby, as shown by the arrow in FIG. 8, reverse cycle defrost is performed in which the refrigerant circulates in the opposite direction to that during the cooling operation. In the outdoor circuit (20), the first, second, and fourth solenoid valves (SV-1, 2, 4) are intermittently controlled appropriately and the third solenoid valve (SV-3) is always open. On the other hand, in the booster circuit (40), the sixth to ninth solenoid valves (SV-6, 7, 8, 9) are normally set to the closed state in the booster circuit (40).

    In the outdoor circuit (20), the refrigerant discharged from the first and second compressors (11a, 11b) flows from the discharge pipes (64a, 64b) to the discharge main pipe (64), and the four-way switching valve (12 ) Through the second gas communication pipe (23) and introduced into the booster circuit (40).

    In the booster circuit (40), the refrigerant flows in order through the booster discharge main pipe (45), the first bypass pipe (47), and the booster suction main pipe (42), and then flows through the first gas communication pipe (22) to form the cooling circuit (30 ).

    In the cooling circuit (30), the refrigerant sequentially flows through the cooling heat exchanger (31) and the drain pan heater (36), dissipates heat to the frost attached to the cooling heat exchanger (31) and the drain pan, and is condensed and liquefied. Thereby, defrosting of a cooling heat exchanger (31) is performed. Then, the refrigerant flows through the liquid communication pipe (21) and is introduced into the outdoor circuit (20).

    In the outdoor circuit (20), the refrigerant sequentially flows through the fifth liquid pipe (88), the receiver (14), the first flow path (50a) of the refrigerant heat exchanger (50), and the fourth liquid pipe (84). Through the sixth liquid pipe (89). When the refrigerant flows through the sixth liquid pipe (89), the refrigerant expands in the first expansion valve (57), condenses in the outdoor heat exchanger (13), and passes through the four-way switching valve (12). The air is sucked into each second compressor (11a, 11b).

    When this defrosting operation is completed and the cooling operation is started again, first, the above-described single-stage compression operation shown in FIG. 2 is performed and switched to the two-stage compression operation based on the flowchart shown in FIG. .

-Effect of the embodiment-
In the refrigeration system (1), when the high / low differential pressure of the refrigerant circuit (10) is smaller than the first set pressure value (P1), single-stage compression operation is performed, and the high / low differential pressure is equal to or higher than the first set pressure value (P1). Since the two-stage compression operation is performed, the first set pressure value (P1) is appropriately set in advance so that the two-stage compression operation can be performed at a level higher than the first set pressure value (P1). The pressure difference can be appropriately distributed between the booster compression mechanism (41) and the high-stage compression mechanism (11) to improve the reliability of each compression mechanism (11, 41).

    The compressors (11a, 11b, 11c, 41a, 41b, 41c) of the booster compression mechanism (41) and the high-stage compression mechanism (11) are high-pressure dome type scroll compression mechanisms, and thus have been described above. Thus, the differential pressure between the discharge pressure and the suction pressure of each compressor (11a, 11b, 11c, 41a, 41b, 41c) is switched by switching to the two-stage compression operation based on the high / low differential pressure of the refrigerant circuit (10). It is possible to appropriately maintain oil and perform appropriate oil supply and to prevent the movable scroll from overturning. That is, the effect by the switching control of the present invention can be exhibited more remarkably.

    Further, the differential pressure control unit (102) sets the differential pressure between the discharge pressure and the suction pressure of the booster compression mechanism (41) to a second setting which is the larger one of the capsize limit pressure value and the oil supply limit pressure value. Since the pressure value (P2) is set to be greater than or equal to the pressure value (P2), in each compressor (41a, 41b, 41c) of the booster compression mechanism (41), the overturning of the movable scroll can be reliably prevented, and the sliding in the dome can be prevented. Oiling to the moving part can be performed reliably. Further, the differential pressure control unit (102) reduces the operating capacity of the high-stage compression mechanism (11) and discharges the booster compression mechanism (41) when switching from the single-stage compression operation to the two-stage compression operation. Since the differential pressure between the pressure and the suction pressure is set to the second set pressure value (P2) or more, the booster compression mechanism (41) can be brought into an appropriate driving state from the start of switching to the two-compression operation.

<< Other Embodiments >>
About the said embodiment, it is good also as the following structures.

    In the refrigeration apparatus (1) of the above embodiment, each compression mechanism (11, 41) is configured by connecting three compressors in parallel. For example, each compression mechanism (11, 41) is configured as one unit. You may make it comprise with a compressor. Moreover, although the refrigeration apparatus (1) of the said embodiment has one cooling heat exchanger (31), the structure by which a some cooling heat exchanger (31) is connected in parallel may be sufficient.

    Moreover, although the refrigeration apparatus (1) of the said embodiment was a refrigeration apparatus which cools the inside of a store | warehouse | chamber, a refrigeration apparatus (1) may be an air conditioning apparatus which performs indoor air conditioning, and also air-conditioning driving | operation May be a switchable air conditioner.

    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 switching control between a single-stage compression operation and a two-stage compression operation in a refrigeration apparatus having a low-stage compression mechanism and a high-stage compression mechanism and performing a refrigeration cycle. .

It is a piping system diagram of the refrigerant circuit of the refrigerating device concerning an embodiment. It is a table | surface which shows the drive mode of the high stage side compression mechanism and booster compression mechanism which concern on embodiment. It is a piping system diagram which shows the flow of the refrigerant | coolant in the single stage compression operation of the refrigeration apparatus which concerns on embodiment. It is a flowchart which shows the switching operation | movement from the single stage compression operation of the refrigeration apparatus which concerns on embodiment to a two stage compression operation. It is a figure which shows the relationship between the evaporation temperature of a cooling heat exchanger, and each 1st and 2nd setting pressure value. It is a piping system diagram which shows the flow of the refrigerant | coolant immediately after switching from the single stage compression operation of the refrigeration apparatus which concerns on embodiment to a two-stage compression operation. It is a piping system diagram which shows the flow of the refrigerant | coolant in the state with the large cooling load in the two-stage compression operation of the refrigeration apparatus which concerns on embodiment. It is a piping system diagram which shows the flow of the refrigerant | coolant during the defrost driving | operation of the freezing apparatus which concerns on embodiment.

Explanation of symbols

1 Refrigeration equipment
10 Refrigerant circuit
11 High-stage compression mechanism (one compression mechanism)
11a First compressor (compressor)
11b Second compressor (compressor)
11c 3rd compressor (compressor)
13 Outdoor heat exchanger (condenser)
31 Cooling heat exchanger (evaporator)
32 Cooling expansion valve (expansion mechanism)
41 Booster compression mechanism (low-stage compression mechanism, other compression mechanism)
41a First booster compressor (compressor)
41b Second booster compressor (compressor)
41c 3rd booster compressor (compressor)
101 Switching control unit (switching control means)
102 Differential pressure control unit (Differential pressure control means)

Claims (5)

A refrigerant circuit (10) in which a low-stage compression mechanism (41), a high-stage compression mechanism (11), a condenser (13), an expansion mechanism (32), and an evaporator (31) are sequentially connected;
One of the low-stage compression mechanism (41) and the high-stage compression mechanism (11) is driven, the other compression mechanism (41) is stopped, and the refrigerant is The single-stage compression operation compressed by the compression mechanism (11), the low-stage compression mechanism (41), and the high-stage compression mechanism (11) are both driven, and the refrigerant is the low-stage compression mechanism (41). And a refrigeration apparatus switchable to a two-stage compression operation compressed by the high-stage compression mechanism (11),
When the differential pressure difference between the high-pressure refrigerant and the low-pressure refrigerant in the refrigerant circuit (10) is smaller than a predetermined first set pressure value, the single-stage compression operation is performed, while the high / low differential pressure is equal to or higher than a predetermined first set pressure value. A refrigeration apparatus comprising switching control means (101) for switching the operating state so as to perform the two-stage compression operation. In claim 1,
At least one of the low-stage compression mechanism (41) and the high-stage compression mechanism (11) stores the refrigeration oil in the high-pressure space in the dome and supplies the refrigeration oil to the sliding portion in the dome. A refrigeration apparatus comprising a differential pressure oil supply type compressor (11a, 11b, 11c, 41a, 41b, 41c) that supplies oil by differential pressure. In claim 1,
At least one of the low-stage compression mechanism (41) and the high-stage compression mechanism (11) is composed of a scroll compressor (11a, 11b, 11c, 41a, 41b, 41c). A refrigeration apparatus characterized by. In claim 3,
The low-stage compression mechanism (41) is composed of scroll type compressors (41a, 41b, 41c),
The differential pressure between the discharge pressure and the suction pressure of the low-stage compression mechanism (41) is controlled to be equal to or higher than a predetermined rollover limit pressure value that increases as the refrigerant evaporation temperature in the evaporator (31) increases. A refrigeration apparatus comprising differential pressure control means (102) for performing In claim 1,
The one compression mechanism (11) is configured to have a variable operating capacity,
When switching from the single-stage compression operation to the two-stage compression operation, the operating capacity of the one compression mechanism (11) is reduced from that during the single-stage compression operation, and the suction side of the other compression mechanism (41) A refrigeration apparatus comprising differential pressure control means (102) for controlling the differential pressure on the discharge side to be equal to or higher than a predetermined second set pressure value.

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