JP2013087975A - Refrigeration apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To speedily and securely determine insufficient lubricating oil supply to any communication path for lubricating oil supply from an oil reservoir of a compressor to a fluid machine.SOLUTION: A refrigeration apparatus with communication paths (48, 48a, and 48b) for supplying lubricating oil in oil reservoir (27, 67) of compressors (20, 60) to fluid machines (30, 60) is provided with fluid temperature detection parts (56, 56a, and 56b) which detect the temperatures of fluids flowing in the communication paths (48, 48a, and 48b), refrigerant temperature detection parts (57, 57a, and 57b) which detect the temperatures of refrigerants compressed by compressing mechanisms (24, 64) of the compressors (20, 60), and a determination part (58) which determines insufficient lubricating oil supply from the oil reservoirs (27, 67) to the communication paths (48, 48a, and 48b) based upon temperature differences (ΔT) between the temperatures (Ta) of the fluids detected by the fluid temperature detection parts (56, 56a, and 56b) and temperatures (Tb) of the refrigerants detected by the refrigerant temperature detection parts (57, 57a, and 57b).

Description

  The present invention relates to a refrigeration apparatus in which a compressor is connected to a refrigerant circuit, and particularly relates to measures for lack of lubricating oil in a compressor.

  Conventionally, as disclosed in Patent Document 1, for example, a refrigeration apparatus including a refrigerant circuit in which a compressor and an expander (fluid machine) are connected and a refrigerant circulates to perform a refrigeration cycle is known. The compressor of Patent Document 1 is configured as a so-called high-pressure dome type in which a casing is filled with compressed refrigerant discharged from a compression mechanism. In this refrigeration apparatus, the lubricating oil stored in the oil reservoir of the compressor is supplied to the compression mechanism and lubricates the sliding portion of the compression mechanism.

  The lubricating oil in the oil reservoir is also supplied to the expander through an oil supply pipe (communication path) to lubricate the sliding portion of the expansion mechanism.

JP 2009-185720 A

  By the way, when the lubricating oil discharged together with the refrigerant from the compression mechanism adheres to the inner wall of a heat exchanger or the like and remains, the amount of the lubricating oil returned to the oil sump decreases. If so, the amount of lubricating oil supplied to the communication path becomes insufficient, and the refrigerant in the casing flows through the communication path, so that a sufficient amount of lubricating oil cannot be supplied to the fluid machine.

  On the other hand, in order to grasp whether or not the lubricating oil is sufficiently supplied to the communication path, it is conceivable to provide a temperature sensor in the communication path. Since the temperature of the lubricating oil in the oil reservoir is usually lower than that of the compressed refrigerant in the casing, when the lubricating oil supplied to the communication path is reduced and the refrigerant flows into the communication path, the temperature detected by the temperature sensor is Get higher. Based on this temperature change, it is possible to determine whether or not the lubricating oil is insufficiently supplied to the communication path.

  However, when the temperature change of the fluid (lubricating oil or refrigerant) flowing through the communication path as described above is observed, the type of fluid flowing through the communication path cannot be determined until the temperature change occurs. Therefore, it is not possible to quickly determine the lack of supply of lubricating oil to the communication path.

  Moreover, since the temperature of the lubricating oil in the oil reservoir depends on the temperature of the refrigerant, for example, when the temperature of the refrigerant increases when the lubricating oil flows through the communication path, the temperature of the lubricating oil also increases. In this case, there is a risk that it may be determined that a shortage of lubricating oil has occurred even though the lubricating oil continues to flow through the communication path.

  The present invention has been made in view of such a point, and its object is to promptly and reliably determine insufficient supply of lubricating oil to the communication passage for supplying lubricating oil from the oil reservoir of the compressor to the fluid machine. It is to be.

  A first invention is directed to a refrigeration apparatus, wherein a compressor (20, 60) and a fluid machine (30, 60) that compresses or expands a refrigerant are connected, and a refrigerant circuit that performs a refrigeration cycle by circulating the refrigerant (10), the compressor (20, 60) includes a casing (21, 61) and a refrigerant disposed in the casing (21, 61) and compresses the sucked refrigerant, and the casing (21, 61) A compression mechanism (24, 64) that discharges to the casing, a discharge pipe (26, 66) that causes the refrigerant discharged into the casing (21, 61) to flow out to a refrigerant circuit outside the casing (21, 61), and the casing And an oil sump (27, 67) formed at the bottom of (21, 61) for storing lubricating oil, and supplying the lubricating oil in the oil sump (27, 67) to the fluid machine (30, 60) Communication passage (48, 48a, 48b), a fluid temperature detector (56, 56a, 56b) for detecting the temperature of the fluid flowing through the communication passage (48, 48a, 48b), and the compression mechanism (24 ) The refrigerant temperature detector (57, 57a, 57b) that detects the temperature of the compressed refrigerant, the fluid temperature (Ta) detected by the fluid temperature detector (56, 56a, 56b), and the refrigerant temperature Lubrication from the oil reservoir (27) to the communication path (48, 48a, 48b) based on the temperature difference (ΔT) from the refrigerant temperature (Tb) detected by the detector (57, 57a, 57b) And a determination unit (58) for determining the shortage of oil supply.

  In the first invention, the lubricating oil in the oil sump (27, 67) is supplied to the fluid machine (30, 60) through the communication path (48, 48a, 48b). Thereby, the sliding part of the fluid machine (30, 60) is lubricated.

  When a sufficient amount of lubricating oil is stored in the oil reservoir (27, 67), the lubricating oil is supplied to the fluid machine (30, 60) through the communication path (48, 48a, 48b). However, if the amount of lubricating oil in the oil sump (27) decreases and the refrigerant in the casing (21, 61) flows through the communication passages (48, 48a, 48b), the fluid machine (30, 60) will be sufficient. The amount of lubricating oil is not supplied.

  On the other hand, in the first invention, the temperature (Ta) of the fluid flowing through the communication path (48, 48a, 48b) detected by the fluid temperature detector (56, 56a, 56b) and the refrigerant temperature detector ( 57, 57a, 57b) based on the temperature difference (ΔT) from the temperature (Tb) of the refrigerant compressed by the compression mechanism (24) from the oil sump (27, 67) to the communication path (48, 48a). , 48b) is judged as insufficient supply of lubricating oil.

  When the amount of lubricating oil in the oil sump (27) is large and the lubricating oil flows through the communication passages (48, 48a, 48b), the fluid temperature detectors (56, 56a, 56b) detect the temperature of the lubricating oil. In general, the temperature of the lubricating oil in the oil sump (27, 67) is lower than the temperature (Tb) of the refrigerant detected by the refrigerant temperature detector (57, 57a, 57b). ) Is relatively large. On the other hand, when the amount of lubricating oil in the oil sump (27, 67) is small and the refrigerant flows through the communication path (48, 48a, 48b), the temperature of the refrigerant is detected by the fluid temperature detection unit (56, 56a, 56b). . The temperature of the refrigerant is substantially equal to the temperature of the refrigerant compressed by the compression mechanism (24, 64) (that is, the temperature (Tb) of the refrigerant detected by the refrigerant temperature detection unit (57, 57a, 57b)). Therefore, the temperature difference (ΔT) is relatively small. The determination unit (58) determines that the amount of lubricating oil supplied to the communication passages (48, 48a, 48b) is insufficient based on the magnitude of the temperature difference (ΔT).

  In a second aspect based on the first aspect, the determination unit (58) includes the temperature (Ta) of the fluid detected by the fluid temperature detection unit (56, 56a, 56b) and the refrigerant temperature detection unit ( When the temperature difference (ΔT) with respect to the refrigerant temperature (Tb) detected at 57, 57a, 57b) is equal to or less than a predetermined value (ΔTs) or 0, the oil reservoir (27) is connected to the communication path (48, 48a, It is characterized in that it is judged that the supply of lubricating oil to 48b) is insufficient.

  In the second invention, the determination unit (58) determines whether the lubricating oil supplied to the communication passages (48, 48a, 48b) when the temperature difference (ΔT) exceeds a predetermined value (ΔTs) or is not zero. Determine that the amount is sufficient. On the other hand, when the temperature difference (ΔT) is less than or equal to the predetermined value (ΔTs) or 0, the determination unit (58) has an insufficient amount of lubricating oil supplied to the communication passages (48, 48a, 48b). judge.

  According to a third invention, in the first or second invention, the fluid machine is configured by an expander (30) for expanding a refrigerant.

  In the third invention, the lubricating oil in the oil sump (27, 67) is supplied to the expander (30) through the communication path (48, 48b). The lubricating oil supplied to the expander (30) lubricates the sliding part of the expander (30).

  According to a fourth aspect of the present invention, in the first or second aspect, the fluid machine sucks and compresses the refrigerant compressed by the compressor (20) on the low stage side, and compresses the high stage side compressor (60). It is characterized by comprising.

  In the fourth invention, the lubricating oil in the oil sump (27) is supplied to the high-stage compressor (60) through the communication passage (48a). The lubricating oil supplied to the high stage compressor (60) lubricates the sliding portion of the high stage compressor (60).

  According to the first invention, the temperature (Ta) detected by the fluid temperature detector (56, 56a, 56b) and the temperature (Tb) detected by the refrigerant temperature detector (57, 57a, 57b) Insufficient supply of lubricating oil to the communication path (48, 48a, 48b) is judged based on the difference (ΔT), so insufficient supply of lubricating oil to the communication path is based on the temperature change of the fluid in the communication path Compared to the case of determining the above, the above determination can be performed in a short time.

  Further, according to the first invention, when the temperature of the compressed refrigerant suddenly changes as the operating condition changes, the temperature of the lubricating oil flowing through the communication passages (48, 48a, 48b) also changes in the same manner. For this reason, the temperature difference between Ta and Tb, that is, ΔT does not substantially change. Therefore, in the first invention, it is possible to avoid erroneous determination due to a rapid temperature change of the refrigerant, and to reliably determine the shortage of supply of lubricating oil to the communication passages (48, 48a, 48b). Therefore, the reliability of the refrigeration apparatus can be ensured by performing an appropriate measure for the refrigeration apparatus based on this reliable determination result.

  According to the second invention, the temperature difference (ΔT) between the temperatures (Ta, Tb) detected by the two temperature detectors (56, 56a, 56b, 57, 57a, 57b) is a predetermined value (ΔTs ) When it becomes below or 0, it is determined that the supply of lubricating oil to the communication passages (48, 48a, 48b) is insufficient. Therefore, it can be determined quickly and reliably that the lubricating oil supplied to the communication passages (48, 48a, 48b) is insufficient.

  Further, according to the third invention, it is possible to reliably determine the shortage of the lubricating oil supplied to the expander (30). The reliability of the expander (30) can be ensured by performing an appropriate process for the refrigeration apparatus based on this reliable determination result.

  Further, according to the fourth aspect of the invention, it is possible to reliably determine the shortage of lubricating oil supplied to the high stage compressor (60). The reliability of the high-stage compressor (60) can be ensured by performing an appropriate process for the refrigeration system based on this reliable determination result.

FIG. 1 is a refrigerant circuit diagram of the air conditioner according to the first embodiment. FIG. 2 is a block diagram illustrating a configuration of the determination unit. FIG. 3 is a refrigerant circuit diagram of the air conditioner according to the second embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following embodiments are essentially preferable examples, and are not intended to limit the scope of the present invention, its application, or its use.

Embodiment 1 of the Invention
A first embodiment of the present invention will be described. As shown in FIG. 1, this Embodiment 1 is an air conditioner (1) comprised by the freezing apparatus which concerns on this invention. The air conditioner (1) performs a vapor compression refrigeration cycle by circulating a refrigerant in a refrigerant circuit (10), and performs switching between a cooling operation and a heating operation. The air conditioner (1) has a so-called multi-type configuration including one outdoor unit (5) and a plurality (three in the example of FIG. 1) of indoor units (2, 3, 4).

The refrigerant circuit (10) is filled with carbon dioxide (CO ₂ ) as a refrigerant. The refrigerant circuit (10) includes three indoor circuits (11, 12, 13) that are use side circuits and one outdoor circuit (14) that is a heat source side circuit. The three indoor circuits (11, 12, 13) are connected to the outdoor circuit (14) via the first communication pipe (15) and the second communication pipe (16).

  The indoor circuit (11, 12, 13) is housed in each indoor unit (2, 3, 4). Each indoor circuit (11, 12, 13) includes an indoor heat exchanger (2a, 3a, 4a) which is a use side heat exchanger and an indoor expansion valve (2b, 3b) which is a use side expansion valve and whose opening is variable. 4b) are connected in series. Although not shown, each indoor unit (2, 3, 4) is provided with an indoor fan.

  Each indoor heat exchanger (2a, 3a, 4a) is configured by a so-called cross fin type fin-and-tube heat exchanger. Room air is supplied to each indoor heat exchanger (2a, 3a, 4a) by an indoor fan (not shown). In each indoor heat exchanger (2a, 3a, 4a), heat exchange is performed between the supplied indoor air and the refrigerant flowing through the indoor heat exchanger (2a, 3a, 4a). Each indoor expansion valve (2b, 3b, 4b) is constituted by an electronic expansion valve.

  The outdoor circuit (14) is housed in the outdoor unit (5). The outdoor circuit (14) includes a compressor (20), an expander (30) as a fluid machine, a gas-liquid separator (51), an outdoor heat exchanger (44), and an internal heat that is a cooling heat exchanger. An exchanger (45), a four-way switching valve (42), and a bridge circuit (41) are provided. Although not shown, the outdoor unit (5) is provided with an outdoor fan.

  The compressor (20) includes a hermetic compressor casing (21), an electric motor (22) disposed in the compressor casing (21), and a compression mechanism (24) driven by the electric motor (22). And. The compressor (20) of the first embodiment is configured as a so-called high-pressure dome type in which the compressor casing (21) is filled with a high-pressure refrigerant compressed by the compression mechanism (24).

  The compressor casing (21) is a vertically long and cylindrical sealed container. The upper part of the compressor casing (21) has a discharge pipe (26) for discharging the refrigerant compressed by the compression mechanism (24), and the lower part of the compressor casing (21) is for sucking the refrigerant. The suction pipes (25) are respectively inserted and fixed. An oil sump (27) for storing lubricating oil is formed at the bottom of the compressor casing (21). The lower part of the suction pipe (25) and the compression mechanism (24) is immersed in the lubricating oil in the oil sump (27). Since the lubricating oil in the oil sump (27) is cooled by the low-pressure refrigerant flowing through the suction pipe (25), the temperature is lower than that of the high-pressure refrigerant in the compressor casing (21).

  The electric motor (22) includes a stator (22a) and a rotor (22b). The stator (22a) is formed in a substantially cylindrical shape, and is fitted into the upper portion of the compressor casing (21). The rotor (22b) is formed in a columnar shape, and is inserted through the inner periphery of the stator (22a) via a predetermined gap (air gap). A drive shaft (23) is inserted and fixed in the center of the rotor (22b).

  The drive shaft (23) is formed to extend in the vertical direction from the rotor (22b) to the oil sump (27). The drive shaft (23) is provided with an oil supply passage (23a) for supplying the lubricating oil in the oil reservoir (27) to the sliding portion of the compression mechanism (24). Further, a centrifugal pump (23b) for pumping up the lubricating oil is formed at the lower end of the drive shaft (23). When the drive shaft (23) is rotated by driving the electric motor (22), the lubricating oil is pumped upward by the centrifugal pump (23b) and supplied to the sliding portion of the compression mechanism (24) through the oil supply passage (23a). .

  The compression mechanism (24) is a rotary type compression mechanism. The compression mechanism (24) is disposed in a lower part of the compressor casing (21). The compression mechanism (24) includes a cylinder and a piston. The compression mechanism (24) compresses the refrigerant sucked from the suction pipe (25) by the rotation of the piston, and discharges the compressed high-pressure refrigerant upward in the compressor casing (21). This high-pressure refrigerant is discharged to the refrigerant circuit (10) through the discharge pipe (26).

  The expander (30) includes a hermetic expander casing (31). An expansion mechanism (34), a generator (32), and an output shaft (33) are accommodated in the expander casing (31). The expansion mechanism (34) constitutes a so-called rotary positive displacement fluid machine. In the expander casing (31), the generator (32) is disposed above the expansion mechanism (34). The output shaft (33) extends in the vertical direction and connects the expansion mechanism (34) and the generator (32).

  The expander casing (31) is provided with an inflow pipe (35) and an outflow pipe (36). Both the inflow pipe (35) and the outflow pipe (36) penetrate the vicinity of the lower part of the trunk of the expander casing (31). The end of the inflow pipe (35) is connected to the expansion mechanism (34). The outflow pipe (36) has a start end connected to the expansion mechanism (34). Inside the expansion mechanism (34), the refrigerant flowing in through the inflow pipe (35) expands while rotating a piston (not shown). As a result, the generator (32) is driven to rotate. That is, the power generated by the expansion of the refrigerant is used for power generation. The refrigerant circuit (10) is provided with a bypass pipe (38) connected to the inflow side and the outflow side of the expander (30). The bypass pipe (38) is provided with a bypass valve (29) for adjusting the flow rate of the refrigerant flowing through the bypass pipe (38). An oil return channel (55) is connected to the bottom of the expander casing (31). The outflow end of the oil return channel (55) is connected to the compressor (20) side of the gas injection pipe (37).

  A communication pipe (48) is connected to the compressor (20) and the expander (30). The communication pipe (48) constitutes a communication path for supplying lubricating oil in the oil sump (27) of the compressor (20) to the expander (30). The inflow end of the communication pipe (48) passes through the bottom of the compressor casing (21) and opens to the oil sump (27). On the other hand, the outflow end of the communication pipe (48) is connected to the sliding portion of the bearing portion in the expansion mechanism (34).

  The gas-liquid separator (51) is a vertically long and cylindrical sealed container. The gas-liquid separator (51) has one end of the gas injection pipe (37) at the top, one end of the liquid pipe (49) at the bottom, and one end of the expander side outflow pipe (39) at the side. Are connected to each other. The other end of the gas injection pipe (37) is connected to the suction side of the compressor (20). The other end of the liquid pipe (49) is connected to the bridge circuit (41). The other end of the expander side outflow pipe (39) is connected to the outflow pipe (36) of the expander (30). The gas injection pipe (37) is provided with a gas vent valve (52). The gas vent valve (52) is constituted by, for example, an electronic expansion valve.

  The outdoor heat exchanger (44) is a so-called cross fin type fin-and-tube heat exchanger. Outdoor air is supplied to the outdoor heat exchanger (44) by an outdoor fan (not shown). In the outdoor heat exchanger (44), heat is exchanged between the supplied outdoor air and the refrigerant flowing through the outdoor heat exchanger (44). In the outdoor circuit (14), one end of the outdoor heat exchanger (44) is connected to the third port of the four-way switching valve (42), and the other end is connected to the bridge circuit (41).

  The internal heat exchanger (45) includes a first flow path (46) and a second flow path (47) disposed adjacent to each other, and the refrigerant in the first flow path (46) and the second flow path (47). ) To exchange heat with the refrigerant. In the outdoor circuit (14), the first flow path (46) constitutes a part of the gas injection pipe (37), and the second flow path (47) constitutes a part of the liquid pipe (49). In the internal heat exchanger (45), heat is exchanged between the refrigerant in the first flow path (46) and the refrigerant in the second flow path (47).

  The bridge circuit (41) is formed by connecting three check valves (CV-1 to CV-3) and one outdoor expansion valve (43) in a bridge shape. Each check valve (CV-1 to CV-3) allows the refrigerant to flow in the direction of the arrow in FIG. 1 and prohibits the reverse flow. In this bridge circuit (41), the inflow side of the first check valve (CV-1) and one end side of the outdoor expansion valve (43) are connected to the other end of the outdoor heat exchanger (44), and the second check valve The inflow side of (CV-2) and the other end side of the outdoor expansion valve (43) are connected to the liquid pipe (49). In addition, the bridge circuit (41) is configured such that the outflow side of the second check valve (CV-2) and the inflow side of the third check valve (CV-3) are connected to the first closing valve (17), The outflow side of the stop valve (CV-3) and the outflow side of the first check valve (CV-1) are connected to the inflow side of the expander (30).

  In the outdoor circuit (14), the first port of the four-way switching valve (42) is connected to the suction side of the compressor (20). The second port is connected to the second closing valve (18). The third port is connected to one end of the outdoor heat exchanger (44). The fourth port is connected to the discharge side of the compressor (20). The four-way switching valve (42) includes a state in which the first port communicates with the second port and the third port communicates with the fourth port (state indicated by a solid line in FIG. 1), The port is configured to be switched to a state where the second port communicates with the third port and the second port communicates with the fourth port (a state indicated by a broken line in FIG. 1).

  One end of the first communication pipe (15) is connected to the first closing valve (17). Further, the first communication pipe (15) is branched into three at the other end side, and is connected to the end portion on the indoor expansion valve (2b, 3b, 4b) side in each indoor circuit (11, 12, 13). ing. One end of the second communication pipe (16) is connected to the second closing valve (18). In addition, the second connecting pipe (16) is branched into three at the other end, and is connected to the end on the indoor heat exchanger (2a, 3a, 4a) side in each indoor circuit (11, 12, 13) Has been.

  The air conditioner (1) includes a fluid temperature detection unit (56) and a refrigerant temperature detection unit (57). The fluid temperature detector (56) is for detecting the temperature of the fluid (lubricating oil or high-pressure refrigerant) flowing through the communication pipe (48). The fluid temperature detector (56) is provided in the vicinity of the compressor (20) in the communication pipe (48). The refrigerant temperature detector (57) is for detecting the temperature of the refrigerant compressed by the compression mechanism (24). The refrigerant temperature detector (57) is provided in the discharge pipe (26) of the compressor (20). The temperatures (Ta, Tb) detected by the temperature detection units (56, 57) are transmitted to the determination unit (58).

  The air conditioner (1) includes a controller (70). As shown in FIG. 2, the controller (70) includes a determination unit (58) and a control unit (59).

  The determination unit (58) uses the temperatures (Ta, Tb) transmitted from the temperature detection units (56, 57) to sufficiently supply the lubricating oil from the oil reservoir (27) to the communication pipe (48). To determine whether it is missing. The determination unit (58) includes a calculation unit (58a), a storage unit (58b), and a comparison determination unit (58c).

  In the calculation unit (58a), the temperature difference (ΔT) of the temperatures (Ta, Tb) transmitted from the temperature detection units (56, 57) is calculated. The storage unit (58b) stores a set temperature difference (ΔTs). This set temperature difference (ΔTs) is a value determined in advance by experiments or the like. The set temperature difference (ΔTs) is detected by the temperature (Ta) detected by the fluid temperature detector (56) and the refrigerant temperature detector (57) when high-pressure refrigerant is flowing through the communication pipe (48). It is determined based on the temperature difference from the temperature (Tb). In the first embodiment, a value slightly higher than 0 degrees is set as the set temperature difference (ΔTs).

  In the comparison determination unit (58c), the temperature difference (ΔT) calculated by the calculation unit (58a) is compared with the set temperature difference (ΔTs) stored in the storage unit (58b). When the temperature difference (ΔT) exceeds the set temperature difference (ΔTs), the comparison / determination unit (58c) determines that the amount of lubricating oil supplied to the communication pipe (48) is sufficient. On the other hand, when the temperature difference (ΔT) becomes equal to or less than the set temperature difference (ΔTs), the comparison / determination unit (58c) determines that the supply amount of the lubricating oil to the communication pipe (48) is insufficient, and the control unit ( 59), the signal S is transmitted.

  When the control unit (59) receives the signal S from the comparison / determination unit (58c), the rotational speed of the electric motor (22) of the compressor (20), the indoor expansion valves (2b, 3b, 4b), and the outdoor expansion valves (43) is configured to control the opening degree.

-Driving action-
In the air conditioner (1) of the first embodiment, the cooling operation and the heating operation are selectively performed. When the determination unit (58) determines that the lubricating oil supplied from the oil sump (27) to the communication pipe (48) is insufficient during the cooling operation and the heating operation, the operation is switched to the oil return operation. It is done.

  Note that a start-up operation is performed at the start of both the cooling operation and the heating operation. In this starting operation, the rotational speed of the electric motor (22) of the compressor (20) is increased stepwise. During the start-up operation, the temperature of the refrigerant in the compressor casing (21) is not stable, so that the temperatures (Ta, Tb) detected by the temperature detectors (56, 57) become unstable. Accordingly, during the start-up operation, the determination by the determination unit (58) is not performed.

《Cooling operation》
The operation during the cooling operation of the air conditioner (1) will be described.

  During the cooling operation, the four-way switching valve (42) is switched to the state shown by the solid line in FIG. 1, and the opening degree of each indoor expansion valve (2b, 3b, 4b) is individually adjusted. The outdoor expansion valve (43) is set to a fully closed state, and the opening degree of the bypass valve (29) and the gas vent valve (52) is adjusted as appropriate.

  When the compressor (20) is driven in this state, the refrigerant circulates in the refrigerant circuit (10) to perform a refrigeration cycle. At that time, the outdoor heat exchanger (44) functions as a radiator, and the indoor heat exchangers (2a, 3a, 4a) function as an evaporator.

  Specifically, high-pressure refrigerant that has been compressed to a pressure higher than the critical pressure is discharged from the compressor (20). The high-pressure refrigerant passes through the four-way switching valve (42) and is sent to the outdoor heat exchanger (44). The high-pressure refrigerant flowing through the outdoor heat exchanger (44) exchanges heat with the outdoor air and radiates heat to the outdoor air.

  The refrigerant radiated by the outdoor heat exchanger (44) flows into the expander (30) through the bridge circuit (41). In the expander (30), the refrigerant expands and is depressurized. The decompressed refrigerant flows into the gas-liquid separator (51) and is separated into liquid refrigerant and gas refrigerant. The saturated liquid refrigerant in the gas-liquid separator (51) flows out from the bottom and flows into the first flow path (46) of the internal heat exchanger (45). On the other hand, the saturated gas refrigerant in the gas-liquid separator (51) is decompressed by the gas vent valve (52) and then flows into the second flow path (47) of the internal heat exchanger (45).

  In the internal heat exchanger (45), heat exchange is performed between the refrigerant in the first flow path (46) and the refrigerant in the second flow path (47). The refrigerant in the first channel (46) is cooled by the refrigerant in the second channel (47).

  The liquid refrigerant that has passed through the first flow path (46) is distributed to the indoor circuits (11, 12, 13) through the bridge circuit (41) and the first communication pipe (15). The liquid refrigerant is decompressed by the indoor control valves (2b, 3b, 4b) and then flows into the indoor heat exchangers (2a, 3a, 4a). In each indoor heat exchanger (2a, 3a, 4a), heat is exchanged between the refrigerant and room air. By this heat exchange, the refrigerant absorbs heat from the room air and evaporates, while the room air is cooled and supplied to the room. The refrigerant evaporated in each indoor heat exchanger (2a, 3a, 4a) joins in the second connecting pipe (16) and flows into the outdoor circuit (14). The refrigerant that has flowed into the outdoor circuit (14) joins the refrigerant that has flowed out of the second flow path (47), and is sucked into the compressor (20). The refrigerant sucked into the compressor (20) is compressed again and discharged.

《Heating operation》
The operation during the heating operation of the air conditioner (1) will be described.

  During the heating operation, the four-way switching valve (42) is switched to the state shown by the broken line in FIG. 1, and the opening degree of each indoor expansion valve (2b, 3b, 4b) is individually adjusted. Further, the opening degree of the bypass valve (29), the outdoor expansion valve (43), and the gas vent valve (52) is appropriately adjusted.

  When the compressor (20) is driven in this state, the refrigerant circulates in the refrigerant circuit (10) to perform a refrigeration cycle. At that time, the indoor heat exchanger (2a, 3a, 4a) functions as a radiator, and the outdoor heat exchanger (44) functions as an evaporator.

  Specifically, the compressor (20) discharges high-pressure refrigerant that has been compressed to a pressure higher than the critical pressure. The high-pressure refrigerant passes through the four-way switching valve (42), flows into the second connecting pipe (16), and is distributed to the indoor circuits (11, 12, 13). In that case, the refrigerant | coolant of the quantity according to the opening degree of the indoor expansion valve (2b, 3b, 4b) is supplied with respect to each indoor circuit (11,12,13).

  The high-pressure refrigerant distributed to the indoor circuits (11, 12, 13) is introduced into the indoor heat exchangers (2a, 3a, 4a) to exchange heat with room air. By this heat exchange, the high-pressure refrigerant radiates heat to the room air, and the room air is heated. The refrigerant radiated by the indoor heat exchangers (2a, 3a, 4a) flows into the first connecting pipe (15), joins, and is then sent back to the outdoor circuit (14). On the other hand, the indoor air heated in the indoor heat exchanger (2a, 3a, 4a) is supplied indoors.

  The refrigerant flowing into the outdoor circuit (14) from the first communication pipe (15) passes through the bridge circuit (41) and flows into the expander (30). In the expander (30), the refrigerant expands and is depressurized. The decompressed refrigerant flows into the gas-liquid separator (51) and is separated into liquid refrigerant and gas refrigerant. The liquid refrigerant in the gas-liquid separator (51) flows out from the bottom, flows through the outdoor expansion valve (43) of the bridge circuit (41), is decompressed, and then flows into the outdoor heat exchanger (44). The refrigerant exchanges heat with the outdoor air, whereby the refrigerant absorbs heat from the outdoor air and evaporates. The refrigerant evaporated in the outdoor heat exchanger (44) is sucked into the compressor (20), compressed again, and discharged.

<Lubricating operation of compressor and expander>
When the electric motor (22) of the compressor (20) is driven, the lubricating oil stored in the oil sump (27) of the compressor (20) is pumped upward by the centrifugal pump (23b) and passes through the oil supply passage (23a). Supplied to the sliding part of the compression mechanism (24). Thereby, the sliding part of a compression mechanism (24) is lubricated. The lubricating oil that has lubricated the sliding portion is returned to the oil reservoir (27) as it is, or flows out to the refrigerant circuit (10) together with the refrigerant compressed by the compression mechanism (24). The lubricating oil circulates through the refrigerant circuit (10) and then returns to the compressor (20) again.

  On the other hand, the lubricating oil in the oil sump (27) of the compressor (20) uses the differential pressure generated between the compressor (20) and the expander (30) to expand the expander ( 30) to be supplied. The lubricating oil supplied to the expansion mechanism (34) lubricates the sliding portion of the expansion mechanism (34) and then flows out to the refrigerant circuit (10) together with the expanded refrigerant. This lubricating oil is circulated through the refrigerant circuit (10) and then returned to the compressor (20), or passes through the sliding portion of the bearing portion of the expander (30) and passes through the bottom of the expander (30). And is returned from the bottom to the compressor (20) through the oil return channel (55).

  Here, when the amount of lubricating oil in the oil reservoir (27) is sufficiently large and the oil level of the lubricating oil is above the inflow end of the communication pipe (48), the lubricating oil passes through the communication pipe (48). Supplied to the expander (30).

  However, when the amount of lubricating oil returned to the oil sump (27) decreases and the oil level of the lubricating oil is below the inflow end of the communication pipe (48), the high-pressure refrigerant in the compressor casing (21) communicates. It will flow through the pipe (48), and the amount of lubricating oil supplied to the expansion mechanism (34) will be insufficient.

  On the other hand, in the first embodiment, the determination unit (58) determines whether the supply of lubricating oil to the communication pipe (48) is insufficient. The air conditioner (1) performs an oil return operation for returning the lubricating oil accumulated in the refrigerant circuit (10) to the oil reservoir (27) based on the determination result.

<Operation of judgment unit>
The determination unit (58) determines whether the amount of lubricating oil supplied to the communication pipe (48) is insufficient.

  First, in the calculation unit (58a) of the determination unit (58), the temperature difference between the temperature (Ta) detected by the fluid temperature detection unit (56) and the temperature (Tb) detected by the refrigerant temperature detection unit (57). (ΔT) is calculated, and then the temperature difference (ΔT) is compared with the set temperature difference (ΔTs) stored in the storage unit (58b) by the comparison determination unit (58c).

  Since the temperature of the lubricating oil in the oil sump (27) is lower than that of the high-pressure refrigerant in the casing (21), when the lubricating oil is flowing through the communication pipe (48), the temperature difference (ΔT) is less than 0 degrees. It becomes higher than the set temperature difference (ΔTs) set to a slightly higher value. On the other hand, when the high-pressure refrigerant is flowing through the communication pipe (48), Ta and Tb have almost the same value, so the temperature difference (ΔT) is substantially zero. Therefore, the temperature difference (ΔT) is equal to or less than the set temperature difference (ΔTs).

  When the value of the temperature difference (ΔT) is higher than the set temperature difference (ΔTs), the comparison determination unit (58c) determines that the lubricating oil is sufficiently supplied to the communication pipe (48). On the other hand, when the value of ΔT becomes equal to or less than the set temperature difference (ΔTs), the comparison determination unit (58c) determines that the amount of lubricating oil supplied to the communication pipe (48) is insufficient, and the control unit (59 ) Signal S.

<Oil return operation>
When the control unit (59) receives the signal S from the determination unit (58), the air conditioner (1) performs an oil return operation for returning the lubricating oil accumulated in the refrigerant pipe to the oil reservoir (27). Control the refrigerant circuit (10).

  When the control unit (59) receives the signal S during the cooling operation, the control unit (59) causes the refrigerant flowing from the indoor heat exchangers (2a, 3a, 4a) to the compressor (20) to be wet refrigerant. The opening of each indoor expansion valve (2b, 3b, 4b) is adjusted so that If it carries out like this, each indoor heat exchanger (2a, 3a, 4a) and the lubricating oil which remain | survives downstream can be sent to a compressor (20) with a refrigerant | coolant. This increases the amount of lubricating oil in the oil sump (27).

  When the control unit (59) receives the signal S during the heating operation, the control unit (59) switches the four-way switching valve (42) from the broken line state to the solid line state in FIG. The opening degree of each indoor expansion valve (2b, 3b, 4b) is adjusted so that the refrigerant flowing from the compressor (2a, 3a, 4a) toward the compressor (20) becomes a wet refrigerant. As a result, the lubricating oil remaining in each indoor heat exchanger (2a, 3a, 4a), etc. can be sent together with the refrigerant to the compressor (20) as in the case of the oil return operation during the cooling operation. The amount of lubricating oil (27) increases.

  As a result of the oil return operation as described above, when the lubricating oil in the oil sump (27) increases and a sufficient amount of lubricating oil is supplied to the communication pipe (48) again, the control unit (59) Adjusts the opening of each indoor expansion valve (2b, 3b, 4b) so that the air conditioner (1) performs normal cooling operation or normal heating operation.

-Effect of Embodiment 1-
As described above, in the air conditioner (1) according to the first embodiment, the fluid temperature detection unit (56) detects the lack of lubricating oil supply from the oil reservoir (27) to the communication pipe (48). The determination is based on the temperature difference (ΔT) between the temperature (Ta) and the refrigerant temperature (Tb) detected by the refrigerant temperature detector (57). If it carries out like this, the said determination can be performed in a short time compared with the case where the insufficient supply of the lubricating oil to this communication pipe is determined based on the temperature change of the fluid of a communication pipe.

  Moreover, in the air conditioner (1) of Embodiment 1, when the temperature of the compressed refrigerant | coolant changes rapidly with the change of an operating condition, the temperature of the lubricating oil which flows through a communicating pipe (48) changes similarly. For this reason, the temperature difference between Ta and Tb, that is, ΔT does not substantially change. Therefore, in the first invention, it is possible to avoid an erroneous determination due to a sudden temperature change of the refrigerant, and to reliably determine the insufficient supply of lubricating oil to the communication pipe (48).

  In the air conditioner (1) of the first embodiment, during the cooling operation or the heating operation, the oil return is performed based on the determination of insufficient supply of the lubricating oil that is determined in a relatively short time and reliably as described above. I am driving. If it carries out like this, since the supply shortage of the lubricating oil to the sliding part of an expander (30) is suppressed lasting for a long time, the reliability of an expander (30) is securable.

<< Embodiment 2 of the Invention >>
As shown in FIG. 3, the air conditioner (1) of the second embodiment is configured such that the refrigerant is compressed by two compressors (a low-stage compressor (20) and a high-stage compressor (60)). Has been.

  The configuration of the low-stage compressor (20) in the second embodiment is substantially the same as the configuration of the compressor in the first embodiment. However, unlike the compressor of the first embodiment, the low-stage compressor (20) is configured to compress the refrigerant compressed by the compression mechanism (24) to an intermediate pressure. Thereby, the inside of the compressor casing (21) of the low stage side compressor (20) is filled with the intermediate pressure refrigerant.

  The high stage side compressor (60) constitutes a fluid machine that sucks and compresses the refrigerant compressed by the low stage side compressor (20). The high stage side compressor (60) includes a sealed high stage side casing (61), a high stage side motor (62) disposed in the high stage side casing (61), and the high stage side motor ( 62) and a high-stage compression mechanism (64) driven by the motor. A discharge pipe (66) for discharging the refrigerant compressed by the high stage side compression mechanism (64) is provided at the upper part of the high stage side casing (61), and a low part is provided at the lower part of the high stage side casing (61). The suction pipes (65) for sucking the refrigerant from the stage side compressor (20) are respectively inserted and fixed. Further, the oil supply passage (63a) and the centrifugal pump (63b) are also formed in the drive shaft (63) of the high-stage compressor (60) as in the case of the first embodiment. When the high-stage electric motor (62) is driven, the lubricating oil pumped up by the centrifugal pump (63b) is supplied to the sliding portion of the high-stage compression mechanism (64) through the oil supply passage (63a).

  An intermediate pressure pipe (53) is connected between the discharge pipe (26) of the low-stage compressor (20) and the suction pipe (65) of the high-stage compressor (60). The intermediate pressure pipe (53) is provided with an intermediate cooler (54).

  By driving the high stage electric motor (62), the intermediate pressure refrigerant from the low stage compressor (20) is drawn into the high stage compression mechanism (64) through the intermediate pressure pipe (53). This refrigerant is compressed by the high-stage compression mechanism (64) to become a high-pressure refrigerant. The high-pressure refrigerant is discharged to the refrigerant circuit (10) through the discharge pipe (66) of the high-stage casing (61).

  The air conditioner (1) of the second embodiment includes two communication pipes (a first communication pipe (48a) and a second communication pipe (48b)). The first communication pipe (48a) has an inflow end that passes through the bottom of the compressor casing (21) and opens to the oil sump (27), and an outflow end of the intermediate communication pipe (53) in the intermediate pressure pipe (53). And a part between the high stage compressor (60). The second communication pipe (48b) has an inflow end that passes through the bottom of the high-stage casing (61) and opens to the oil sump (67), while an outflow end is a sliding portion of the bearing portion in the expansion mechanism (34). It is connected to the.

  In addition, the air conditioner (1) of the second embodiment includes two fluid temperature detectors (first fluid temperature detector (56a) and second fluid temperature detector (56b)) and two refrigerant temperature detectors (first 1 refrigerant temperature detector (57a) and second refrigerant temperature detector (57b)). The first fluid temperature detector (56a) is provided in the vicinity of the low-stage compressor (20) in the first communication pipe (48a). The second fluid temperature detector (56b) is provided in the vicinity of the high-stage compressor (60) in the second communication pipe (48b). The first refrigerant temperature detector (57a) is provided in the discharge pipe (26) of the low stage compressor (20). The second refrigerant temperature detector (57b) is provided in the discharge pipe (66) of the high stage compressor (60).

<Lubrication operation of low-stage compressor and high-stage compressor>
When the motor (22) of the low stage compressor (20) is driven, the lubricating oil stored in the oil sump (27) of the low stage compressor (20) is pumped upward by the centrifugal pump (23b), It is supplied to the sliding part of the compression mechanism (24) through the oil supply passage (23a). Thereby, the sliding part of the compression mechanism (24) of the low stage side compressor (20) is lubricated. The lubricating oil that has lubricated the sliding portion is returned to the oil reservoir (27) as it is, or flows out to the intermediate pressure pipe (53) together with the refrigerant compressed by the compression mechanism (24). The lubricating oil circulates through the refrigerant circuit (10) and then returns to the low-stage compressor (20) again. The lubricating oil in the oil sump (27) of the low-stage compressor (20) is sucked into the suction side of the high-stage compression mechanism (64) through the first communication pipe (48a), and the high-stage compression Lubricate the sliding part of the mechanism (64).

  On the other hand, in the high-stage compressor (60), when the electric motor (22) of the high-stage compressor (60) is driven, the lubricating oil in the oil sump (67) is compressed through the oil supply passage (63a). Supplied to the sliding part of the mechanism (64) and lubricates the sliding part. The lubricating oil that has lubricated the sliding part is returned to the oil reservoir (67) as it is, or flows out to the refrigerant circuit (10) together with the refrigerant compressed by the high-stage compression mechanism (64). The lubricating oil circulates in the refrigerant circuit (10) and then returns to the high-stage compressor (60) again via the low-stage compressor (20). The lubricating oil in the oil sump (67) of the high stage compressor (60) is supplied to the sliding portion of the bearing portion of the expander (30) through the second communication pipe (48b). Lubricate.

  The determination unit (58) of the air conditioner (1) of the second embodiment communicates the first communication from the oil sump (27) of the low stage compressor (20) during the cooling operation or heating operation of the air conditioner (1). It is determined whether or not the supply of lubricating oil to the pipe (48a) is insufficient, and a signal S is transmitted to the control section (59). When the control unit (59) receives the signal S, the opening degree of each indoor expansion valve (2b, 3b, 4b) is set so that the air conditioner (1) performs the oil return operation as in the case of the first embodiment. adjust. As a result of the oil return operation, the amount of lubricating oil in the oil sump (27) of the low-stage compressor (20) increases, and a sufficient amount of lubricating oil is again supplied to the first communication pipe (48a). Then, a control part (59) controls the opening degree of each indoor expansion valve (2b, 3b, 4b) so that an air conditioner (1) performs normal cooling operation or heating operation.

  In addition, the determination unit (58) of the air conditioner (1) of the second embodiment is configured to start from the oil sump (67) of the high stage compressor (60) during the cooling operation or the heating operation of the air conditioner (1). It is determined whether the lubricating oil is insufficiently supplied to the two communication pipes (48b), and a signal S is transmitted to the control unit (59). When receiving the signal S, the control unit (59) controls the electric motor (62) so that the rotation speed of the piston of the high-stage compression mechanism (64) is reduced. As a result, the amount of lubricating oil in the oil sump (67) of the high stage compressor (60) increases. As a result, when a sufficient amount of lubricating oil is again supplied to the second communication pipe (48b), the control unit (59) causes the air conditioner (1) to perform normal cooling operation or heating operation. Control the high stage compressor (60).

-Effect of Embodiment 2-
As described above, even in the air conditioner (1) according to the second embodiment, communication is performed using the temperature difference (ΔT) of the detected temperatures (Ta, Tb) at the temperature detection units (56a, 56b, 57a, 57b). Since the shortage of the lubricating oil supplied to the pipes (48a, 48b) is determined, the shortage of the lubricating oil supplied to the communication pipes (48a, 48b) is relatively short as in the case of the first embodiment. Judgment can be made with time and certainty.

  In the air conditioner (1) according to the second embodiment, the amount of the lubricating oil supplied to the sliding portion of the high stage compressor (60) can be suppressed from being insufficient for a long time. The reliability of the high stage compressor (60) can be secured. In addition, since there is no need to add an excessive amount of lubricating oil to the system, the amount of lubricating oil in the compressor (20, 60) increases and the work of the compressor (20, 60) becomes excessive. Can be avoided. As a result, the performance of the system can be made appropriate.

-Other embodiments-
In the above embodiment, the set temperature difference (ΔTs) to be compared with the temperature difference (ΔT) calculated by the determination unit (58) is set to a value slightly higher than 0 ° C., but is not limited to this. You may set to ° C. In this case, the determination unit (58) determines that the supply of the lubricating oil to the communication pipes (48, 48a, 48b) is insufficient when the temperature difference (ΔT) reaches 0 ° C.

  In the above embodiment, the temperature difference (ΔT) calculated by the determination unit (58) is compared with the set temperature difference (ΔTs). However, the present invention is not limited to this. For example, the temperature difference (ΔT) is calculated. By comparing the corrected value with the set temperature difference (ΔTs) as necessary, it may be determined whether the lubricating oil is insufficiently supplied to the communication pipes (48, 48a, 48b).

  As described above, the present invention is useful for a refrigeration apparatus in which a compressor is connected to a refrigerant circuit.

10 Refrigerant circuit 20 Compressor, low stage compressor (compressor)
21 Compressor casing (casing)
24 compression mechanism 26 discharge pipe 27 oil sump 30 expander (fluid machine)
48 communication pipe (communication passage)
48a First communication pipe (communication path)
48b Second communication pipe (communication path)
56 Fluid temperature detector 56a First fluid temperature detector (fluid temperature detector)
56b Second fluid temperature detector (fluid temperature detector)
57 Refrigerant temperature detector 57a First refrigerant temperature detector (refrigerant temperature detector)
57b Second refrigerant temperature detector (refrigerant temperature detector)
58 Judgment unit 60 High stage compressor (compressor, fluid machine)
61 High-stage casing (casing)
64 High-stage compression mechanism (compression mechanism)
66 Discharge pipe 67 Oil sump

Claims (4)

A compressor (20, 60) and a fluid machine (30, 60) that compresses or expands the refrigerant, and includes a refrigerant circuit (10) that circulates the refrigerant to perform a refrigeration cycle;
The compressor (20, 60) includes a casing (21, 61) and a compression mechanism (in the casing (21, 61)) that compresses the sucked refrigerant and discharges the refrigerant into the casing (21, 61). 24, 64), a discharge pipe (26, 66) for allowing the refrigerant discharged into the casing (21, 61) to flow out into the refrigerant circuit outside the casing (21, 61), and the casing (21, 61) An oil sump (27,67) formed at the bottom and storing lubricating oil;
A communication passage (48, 48a, 48b) for supplying lubricating oil in the oil reservoir (27, 67) to the fluid machine (30, 60);
A fluid temperature detector (56, 56a, 56b) for detecting the temperature of the fluid flowing through the communication path (48, 48a, 48b);
A refrigerant temperature detector (57, 57a, 57b) for detecting the temperature of the refrigerant compressed by the compression mechanism (24);
Temperature difference between the fluid temperature (Ta) detected by the fluid temperature detector (56,56a, 56b) and the refrigerant temperature (Tb) detected by the refrigerant temperature detector (57,57a, 57b) A refrigeration apparatus comprising: a determination unit (58) that determines, based on (ΔT), insufficient supply of lubricating oil from the oil reservoir (27) to the communication path (48, 48a, 48b). In claim 1,
The determination unit (58) includes the fluid temperature (Ta) detected by the fluid temperature detection unit (56, 56a, 56b) and the refrigerant temperature detected by the refrigerant temperature detection unit (57, 57a, 57b). When the temperature difference (ΔT) from the temperature (Tb) is equal to or less than a predetermined value (ΔTs) or 0, it is determined that the supply of lubricating oil from the oil reservoir (27) to the communication path (48) is insufficient. A refrigeration apparatus characterized by that. In claim 1 or 2,
The said fluid machine is comprised with the expander (30) which expands a refrigerant | coolant, The freezing apparatus characterized by the above-mentioned. In claim 1 or 2,
The refrigeration apparatus, wherein the fluid machine includes a high-stage compressor (60) that sucks and compresses the refrigerant compressed by the compressor (20) on the low-stage side.

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