JP2008209036A - Refrigeration device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress electric power consumption when a compressor is stopped in a refrigeration device using refrigerating machine oil which is not immiscible with refrigerant and has a higher density than the refrigerant. <P>SOLUTION: An air conditioner 1 includes a compressor 21, a heat source-side heat exchanger 23, an expansion mechanism 24, and an utilization-side heat exchanger 41, and further comprises: a refrigerant circuit 10 in which refrigerating machine oil immiscible with refrigerant and having a higher density than the refrigerant is sealed; and a crankcase heater 9 for heating that portion of the compressor 21 which is near the oil level U. Before the compressor is stopped, the air conditioner 1 performs oil recovery operation for returning refrigerating machine oil distributed in the refrigerant circuit 10, and when the compressor is stopped, the air conditioner 1 activates the crankcase heater 9. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a refrigeration apparatus, and more particularly, to a refrigeration apparatus including a refrigerant circuit in which a refrigerating machine oil incompatible with a refrigerant is enclosed.

Conventionally, in a refrigeration apparatus having a vapor compression refrigerant circuit, refrigerating machine oil is enclosed together with a refrigerant in order to ensure lubrication in the compressor. And as a refrigerating machine oil enclosed with a refrigerant circuit with such a refrigerant | coolant, when a refrigerant | coolant is used as a HFC type | system | group refrigerant | coolant as shown, for example in patent document 1, a refrigerating machine oil with high compatibility with a HFC type | system | group refrigerant | coolant (Specifically, ester oil) may be used, or refrigeration oil (specifically, alkylbenzene) that is incompatible with the HFC refrigerant may be used.
JP-A-8-193759

  By the way, in such a refrigeration apparatus, when the operation of the entire refrigeration apparatus is stopped, or when operation of some devices including a compressor such as a thermo-off is stopped (hereinafter referred to as a compressor stop). In this state, the refrigerant accumulates with the refrigerating machine oil in the compressor due to a temperature drop in the compressor (hereinafter, this state is referred to as “refrigerant stagnation state”, and the refrigerant accumulated in the compressor due to the refrigerant stagnation state is referred to as “sleeping refrigerant”. May occur). When the compressor is started after such a refrigerant stagnation state occurs, the stagnation refrigerant is easily supplied to the sliding portion in the compressor and the refrigerator oil is hardly supplied to the sliding portion. Insufficient lubrication may cause damage to the compressor.

  For such a refrigerant stagnation state, a compressor is provided in a heater, and the heater is operated when the compressor is stopped to heat the refrigeration oil, evaporate the stagnation refrigerant, and the refrigeration oil is applied to the sliding portion. It is preferable to be supplied. In a refrigeration system using refrigeration oil that is highly compatible with the refrigerant, the stagnation refrigerant and the refrigeration oil are compatible in the compressor, and no matter what part of the refrigeration oil is heated, Since it can be evaporated, the place where the heater is provided may be basically any place where the refrigeration oil in the compressor is accumulated. However, in a refrigeration system using refrigeration oil that is incompatible with the HFC-based refrigerant, the refrigeration refrigerant and the refrigeration oil are separated into two layers in the compressor, and if the portion of the refrigeration refrigerant is not heated, it can be efficiently Since the sleeping refrigerant cannot be evaporated, it is desirable that the location where the heater is provided corresponds to the portion of the sleeping refrigerant separated from the refrigerating machine oil in the compressor. Here, in Patent Document 1, in a refrigeration apparatus using a refrigerating machine oil that is incompatible with an HFC-based refrigerant, when adopting a compressor in which a refrigerating machine oil and a stagnant refrigerant are stored in the lower part, the bottom of the compressor is locally A heater is provided so that it can be heated. In the case where the heater is arranged at the bottom of the compressor in this way, when using refrigerating machine oil (for example, alkylbenzene) that is incompatible with the HFC refrigerant and has a density lower than that of the refrigerant, the stagnation refrigerant is used as the refrigerating machine oil. Since it accumulates on the lower side, the stagnation refrigerant can be efficiently heated by the heater that locally heats the bottom of the compressor.

  On the other hand, from the viewpoint of environmental problems, the use of carbon dioxide or the like, which has a smaller environmental impact than HFC-based refrigerants, is being promoted as the refrigerant sealed in the refrigerant circuit. However, in a refrigeration apparatus having a heater that locally heats the bottom of the compressor as in Patent Document 1, if a refrigeration oil that is incompatible with carbon dioxide is used, the density of carbon dioxide is smaller than that of the refrigeration oil. Therefore, in the lower part of the compressor, the sleeping refrigerant accumulates in a state of floating above the refrigerating machine oil, so that the heater that locally heats the bottom of the compressor can efficiently heat the sleeping refrigerant. However, there is a problem that the power consumption when the compressor is stopped increases.

  The subject of this invention is suppressing the power consumption at the time of a compressor stop in the refrigerating device which uses refrigerating machine oil which is incompatible with a refrigerant | coolant and whose density is higher than a refrigerant | coolant.

  The refrigeration apparatus according to the first invention includes a compressor, a first heat exchanger, an expansion mechanism, and a second heat exchanger, and contains refrigeration oil that is incompatible with the refrigerant and has a higher density than the refrigerant. And a heater for heating the vicinity of the oil level of the compressor. And this refrigeration apparatus performs the oil collection | recovery operation which returns the refrigeration oil distributed to the refrigerant circuit to a compressor before a compressor stop, and operates a heater at the time of a compressor stop.

  Since this refrigeration apparatus includes a refrigerant circuit in which refrigerating machine oil that is incompatible with the refrigerant and has a higher density than the refrigerant is enclosed, a heater that heats the vicinity of the oil level of the compressor is provided. By operating the compressor when the compressor is stopped, it is possible to heat and evaporate the stagnation refrigerant that accumulates in the compressor while floating above the refrigerating machine oil. Heating of the stagnation refrigerant is more efficient than when a heater for heating is provided.

  However, in this refrigeration apparatus, a refrigeration cycle operation is performed in which the refrigerant circulates in the refrigerant circuit including the compressor, the first heat exchanger, the expansion mechanism, and the second heat exchanger. When this is done, the refrigerating machine oil accumulated in the compressor gradually comes out of the compressor accompanying the refrigerant circulating in the refrigerant circuit. Therefore, the first and second refrigerating cycle operations before the compressor stop are performed. It will be distributed in parts other than the compressor such as a refrigerant pipe connecting various devices such as a heat exchanger and various devices, and the oil level height of the compressor will change. For this reason, even if a heater that heats the vicinity of a predetermined oil level is provided, the oil level of the compressor changes due to the refrigeration cycle operation in which the refrigerant circulates in the refrigerant circuit. It becomes impossible to heat the vicinity of the oil level. In such a case, the heating efficiency of the stagnation refrigerant is lowered according to the change in the oil level height, thereby increasing the power consumption when the compressor is stopped.

  Therefore, in this refrigeration system, the oil level height of the compressor when the compressor is stopped is set to a predetermined oil level as much as possible by performing an oil recovery operation for returning the refrigeration oil distributed in the refrigerant circuit to the compressor before the compressor is stopped. By keeping the surface level constant, the stagnation refrigerant is efficiently heated and evaporated by a heater that heats the vicinity of a predetermined oil level. Thereby, the power consumption at the time of a compressor stop can be suppressed.

  The refrigeration apparatus according to a second aspect of the present invention is the refrigeration apparatus according to the first aspect of the present invention, wherein the heater is disposed so as to overlap the oil level of the compressor when the compressor is viewed from the side.

  A refrigeration apparatus according to a third aspect of the present invention is a compressor in which a compression element that compresses refrigerant and a motor that drives the compression element are housed in a casing, a first heat exchanger, an expansion mechanism, and a second heat exchanger. And a refrigerant circuit in which refrigeration oil that is incompatible with the refrigerant and has a higher density than the refrigerant is enclosed. The refrigeration apparatus performs an oil recovery operation to return the refrigeration oil distributed in the refrigerant circuit to the compressor before the compressor is stopped, and the compression is performed in a state where the motor stator and the oil level of the compressor substantially coincide with each other. Energize the motor so that it does not rotate when the machine stops.

  This refrigeration apparatus includes a refrigerant circuit in which refrigeration oil that is incompatible with the refrigerant and has a density higher than that of the refrigerant is enclosed, so that the motor stator and the oil level height of the compressor are substantially matched. By energizing the motor so that the motor does not rotate when the compressor is stopped, it is possible to heat and evaporate the stagnation refrigerant accumulated in the compressor while floating above the refrigerating machine oil. The heating of the stagnation refrigerant becomes more efficient than the conventional case where a heater for locally heating the bottom of the compressor is provided.

  However, in this refrigeration apparatus, a refrigeration cycle operation is performed in which the refrigerant circulates in the refrigerant circuit including the compressor, the first heat exchanger, the expansion mechanism, and the second heat exchanger. When this is done, the refrigerating machine oil accumulated in the compressor gradually comes out of the compressor accompanying the refrigerant circulating in the refrigerant circuit. Therefore, the first and second refrigerating cycle operations before the compressor stop are performed. It will be distributed in parts other than the compressor such as a refrigerant pipe connecting various devices such as a heat exchanger and various devices, and the oil level height of the compressor will change. For this reason, even if the position of the stator of the motor and the predetermined oil level are substantially matched, the oil level of the compressor changes due to the refrigeration cycle operation in which the refrigerant circulates in the refrigerant circuit. This makes it impossible to heat the vicinity of the oil level of the compressor. In such a case, the heating efficiency of the stagnation refrigerant is lowered according to the change in the oil level height, thereby increasing the power consumption when the compressor is stopped.

  Therefore, in this refrigeration system, the oil level height of the compressor when the compressor is stopped is set to a predetermined oil level as much as possible by performing an oil recovery operation for returning the refrigeration oil distributed in the refrigerant circuit to the compressor before the compressor is stopped. By keeping the surface level constant, the stagnation refrigerant is efficiently heated and evaporated in the vicinity of a predetermined oil level by the motor stator. Thereby, the power consumption at the time of a compressor stop can be suppressed.

  The refrigeration apparatus according to a fourth aspect of the present invention is the refrigeration apparatus according to the third aspect of the present invention, wherein the lower part of the stator of the motor reaches the oil level of the compressor.

  The refrigeration apparatus according to a fifth aspect of the present invention is the refrigeration apparatus according to any one of the first to fourth aspects of the invention, wherein the oil recovery operation is performed by changing the rotational speed of the compressor.

  In this refrigeration apparatus, in the oil recovery operation, for example, the compressor is operated at a rotational speed higher than the rotational speed of the compressor immediately before the oil recovery operation, or the compressor is operated at the maximum rotational speed. Since the flow rate of the refrigerant circulating in the refrigerant circuit is increased as much as possible by changing the rotation speed of the compressor, the refrigeration oil distributed in the refrigerant circuit can be reliably returned to the compressor.

  A refrigeration apparatus according to a sixth invention is the refrigeration apparatus according to any one of the first to fifth inventions, wherein the refrigerant circuit is in the order of the compressor, the first heat exchanger, the expansion mechanism, and the second heat exchanger. A switching mechanism capable of switching between a first circulation state in which the refrigerant is circulated and a second circulation state in which the refrigerant is circulated in the order of the compressor, the second heat exchanger, the expansion mechanism, and the first heat exchanger; It is out. The oil recovery operation is performed by switching to the other of the first and second circulation states before stopping the compressor in one of the first and second circulation states.

  In this refrigeration apparatus, when the refrigeration cycle operation is performed in the first circulation state, a large amount of refrigeration oil is distributed in a portion of the refrigerant circuit between the compressor and the first heat exchanger that functions as a refrigerant cooler. When the refrigeration cycle operation is performed in the second circulation state, a large amount of refrigeration oil is distributed in a portion of the refrigerant circuit between the compressor and the second heat exchanger that functions as a refrigerant cooler. .

  Therefore, in this refrigeration apparatus, in the oil recovery operation before stopping the compressor in the first circulation state, the first heat exchanger is caused to function as a refrigerant heater by switching from the first circulation state to the second circulation state. In the first circulation state, refrigeration oil distributed in a portion of the refrigerant circuit between the compressor and the first heat exchanger functioning as a refrigerant cooler flows toward the compressor, and the second circulation In the oil recovery operation before stopping the compressor in the state, the second heat exchanger is made to function as a refrigerant heater by switching from the second circulation state to the first circulation state, and in the refrigerant circuit in the second circulation state, Since the refrigeration oil distributed in the portion between the compressor and the second heat exchanger functioning as a refrigerant cooler flows toward the compressor, the refrigeration oil distributed in the refrigerant circuit is reliably It can be returned to the compressor.

  As described above, according to the present invention, the following effects can be obtained.

  In the first to fourth inventions, the heating of the stagnation refrigerant is more efficient than the conventional case where a heater for locally heating the bottom of the compressor is provided, and the power consumption when the compressor is stopped is reduced. Can be suppressed.

  In 5th or 6th invention, the refrigeration oil distributed to the refrigerant circuit can be reliably returned to a compressor.

  Hereinafter, an embodiment of a refrigeration apparatus according to the present invention will be described based on the drawings.

(1) Configuration of refrigeration apparatus <Overall configuration of air conditioner>
FIG. 1 is a schematic configuration diagram of an air conditioner 1 according to an embodiment of the refrigeration apparatus of the present invention. In this embodiment, the air conditioning apparatus 1 is an apparatus used for indoor air conditioning, and mainly includes a heat source unit 2, a utilization unit 4, a refrigerant communication pipe 6 that connects the heat source unit 2 and the utilization unit 4, 7 is a so-called separate type air conditioner. And the refrigerant circuit 10 of the air conditioning apparatus 1 of this embodiment is comprised by connecting the heat-source unit 2 and the utilization unit 4 via the refrigerant | coolant communication pipes 6 and 7. FIG. And in the refrigerant circuit 10, carbon dioxide is enclosed as a refrigerant. For this reason, in the air conditioning apparatus 1 of the present embodiment, the refrigeration cycle operation is performed by compressing carbon dioxide as a refrigerant until the critical pressure or higher.

<Usage unit>
The utilization unit 4 is connected to the heat source unit 2 via the first refrigerant communication pipe 6 and the second refrigerant communication pipe 7 and constitutes a part of the refrigerant circuit 10.

  Next, the configuration of the usage unit 4 will be described.

  The usage unit 4 mainly has a usage-side refrigerant circuit 10 b that constitutes a part of the refrigerant circuit 10. This use side refrigerant circuit 10b mainly has a use side heat exchanger 41 as a second heat exchanger.

  In the present embodiment, the use-side heat exchanger 41 is a heat exchanger that functions as a refrigerant heater during cooling and functions as a refrigerant cooler during heating. The use side heat exchanger 41 has one end connected to the second refrigerant communication pipe 7 and the other end connected to the first refrigerant communication pipe 6.

  In the present embodiment, the usage unit 4 includes an indoor fan 42 for supplying indoor air after sucking indoor air into the unit and exchanging heat, and flows through the indoor air and usage-side heat exchanger 41. It is possible to exchange heat with the refrigerant. The indoor fan 42 is rotationally driven by a fan motor 42a.

  In addition, the usage unit 4 includes a usage-side control unit 43 that controls the operation of each unit constituting the usage unit 4. The use side control unit 43 includes a microcomputer, a memory, and the like provided to control the use unit 4, and controls signals with the heat source side control unit 28 (described later) of the heat source unit 2. Etc. can be exchanged.

<Heat source unit>
The heat source unit 2 is connected to the utilization unit 4 via the first refrigerant communication pipe 6 and the second refrigerant communication pipe 7, and constitutes a refrigerant circuit 10 between the utilization units 4.

  Next, the configuration of the heat source unit 2 will be described. The heat source unit 2 mainly has a heat source side refrigerant circuit 10 a that constitutes a part of the refrigerant circuit 10. The heat source side refrigerant circuit 10a mainly includes a compressor 21, a switching mechanism 22, a heat source side heat exchanger 23 as a first heat exchanger, an expansion mechanism 24, and closing valves 25 and 26. Yes.

  The compressor 21 is a compressor for compressing a low-pressure gas refrigerant until the pressure becomes equal to or higher than a critical pressure. Here, in the present embodiment, the number of the compressors 21 is one, but is not limited thereto, and two or more compressors may be connected in parallel.

  Next, the internal structure of the compressor 21 will be described with reference to FIGS. Here, FIG. 2 is a schematic longitudinal sectional view of the compressor 21. FIG. 3 is a schematic cross-sectional view of the compressor 21 and corresponds to the AA cross-section of FIG.

  In this embodiment, the compressor 21 is a hermetic compressor in which a casing 61, which is a vertical cylindrical container, includes a compression element 62 and a compressor motor 63 as a motor for driving the compression element 62. .

  The casing 61 has a substantially cylindrical body plate 61a, an upper end plate 61b welded and fixed to the upper end of the body plate 61a, and a lower end plate 61c welded and fixed to the lower end of the body plate 61a. In the casing 61, a compression element 62 is mainly disposed at the lower portion, and a compressor motor 63 is disposed above the compression element 62. The compression element 62 and the compressor motor 63 are connected by a crankshaft 64 that is disposed so as to extend in the vertical direction in the casing 61. In the present embodiment, the lower part of the casing 61 stores refrigerating machine oil necessary for lubricating the compressor 21 (particularly, the compression element 62). In this embodiment, the refrigerating machine oil has a high viscosity characteristic in order to ensure lubrication in the compressor 21 in consideration of the high pressure of the refrigerating cycle by using carbon dioxide as a refrigerant. Alkylene glycol (hereinafter referred to as PAG) is used. This PAG is incompatible with carbon dioxide as a refrigerant and has a density higher than that of carbon dioxide under use conditions of the air conditioner 1. For this reason, in the refrigerant circuit 10 of the air conditioner 1, refrigeration oil that is incompatible with the refrigerant and has a higher density than the refrigerant is enclosed together with the refrigerant.

  The compression element 62 is a compression element constituting a swing compressor. In the present embodiment, the compression element 62 mainly includes a crankshaft 64, a front head 65, an element main body 66, and a rear head 67. Here, the element main body 66 is disposed so as to be sandwiched between the front head 65 and the rear head 67 and mainly includes a piston 70, a bush 71, and a cylinder 72. In the present embodiment, the front head 65, the cylinder 72, and the rear head 67 are fastened and integrated by a plurality of bolts (not shown). In the present embodiment, the compression element constituting the swing compressor is selected as the compression element 62 because the friction loss and the power loss are relatively small compared to other types of positive displacement compression elements. is there. The cylinder 72 has a cylinder hole 72a, a suction hole 72b, a discharge path 72c, and a blade accommodation hole 72d. The cylinder hole 72 a is a cylindrical hole that penetrates along the rotation axis O. The suction hole 72b penetrates from the outer peripheral surface 72e to the cylinder hole 72a. The discharge path 72c is formed by cutting out a part on the inner peripheral side of the cylindrical portion forming the cylinder hole 72a. The blade accommodation hole 72 d is a hole for accommodating a blade portion 70 b (described later) of the piston 70, and penetrates along the plate thickness direction of the cylinder 72. The portion of the blade accommodation hole 72d on the rotation axis O side accommodates the bush 71 and slides with the bush 71. An eccentric shaft portion 64a of the crankshaft 64 and a roller 70a (described later) of the piston 70 are accommodated in the cylinder hole 72a of the cylinder 72, and a blade portion 70b and a bush 71 of the piston 70 are accommodated in the blade accommodation hole 72d. Is contained between the front head 65 and the rear head 67 so that the discharge path 72c faces the front head 65 side. Thus, a cylinder chamber 76 is formed in the compression element 62, and the cylinder chamber 76 is partitioned into a suction chamber 76a communicating with the suction hole 72b by the piston 70 and a discharge chamber 76b communicating with the discharge passage 72c. It will be. The piston 70 includes a cylindrical roller 70a and a blade 70b that is formed integrally with the roller 70a and protrudes radially outward of the roller 70a. The roller 70 a is inserted into the cylinder hole 72 a of the cylinder 72 while being fitted to the first eccentric shaft portion 64 a of the crankshaft 64. Accordingly, when the crankshaft 64 rotates, the roller 70a performs a revolving motion around the rotation axis O of the crankshaft 64. The blade 70b is accommodated in the blade accommodation hole 72d. As a result, the blade 70b swings and moves forward and backward along the longitudinal direction with respect to the bush 71 and the blade accommodation hole 72d. The bush 71 is a pair of substantially semi-cylindrical members, and is accommodated in the blade accommodation hole 72d so as to sandwich the blade 70b of the piston 70. The front head 65 is a member that covers the discharge path 72 c side of the cylinder 72 and is fitted in the casing 61. A bearing portion 65a is formed on the front head 65, and a crankshaft 64 is inserted into the bearing portion 65a. Further, the front head 65 is formed with an opening (not shown) for guiding the gas refrigerant flowing through the discharge passage 72c formed in the cylinder 72 to a discharge pipe 85 (described later). And this opening is obstruct | occluded or open | released by the discharge valve (not shown) for preventing the back flow of a gas refrigerant. The rear head 67 is a member that covers the discharge path 72 c side of the cylinder 72 and is fitted to the casing 61. A bearing portion 67a is formed in the rear head 67, and a crankshaft 64 is inserted into the bearing portion 67a. The crankshaft 64 is provided with the above-described eccentric shaft portion 64a at the lower portion thereof, and the upper portion where the eccentric shaft portion 64a is not provided is fixed to a rotor 80 (described later) of the compressor motor 63.

  In this embodiment, the compressor motor 63 is a DC motor, and mainly includes an annular stator 79 fixed to the inner surface of the casing 61, and a rotor that is rotatably accommodated with a slight gap inside the stator 79. 80. A copper wire is wound around the stator 79, and coil ends 79a are formed above and below. A crankshaft 64 is fixed at the center of the rotor 80 along the rotation axis O. The copper wire wound around the stator 79 of the compressor motor 63 is connected to a terminal 86 provided on the casing 61 and supplied with power. In the present embodiment, the compressor motor 63 can change its rotational speed (frequency) by an inverter device (not shown).

  In the present embodiment, the oil level of the refrigerating machine oil is near the upper part of the compression element 62 (more specifically, when the total amount of refrigerating machine oil sealed in the refrigerant circuit 10 is present in the compressor 21) It is set so as to reach the vicinity of the lower surface of the front head 65 (this set oil level height is referred to as oil level height U), and each part of the compression element 62 is lubricated by the refrigerating machine oil. It has become. In the present embodiment, the casing 61 is provided with a crankcase heater 9 as a heater for heating the vicinity of the oil surface height U of the refrigeration oil. The crankcase heater 9 is an annular one disposed so as to surround the outer peripheral portion of the casing 61 (specifically, the body plate 61a). The crankcase heater 9 is disposed so as to overlap the oil level of the compressor 21 when the compressor 21 is viewed from the side. More specifically, the crankcase heater 9 is disposed such that its upper end is positioned above the oil level height U and its lower end coincides with the oil level height U. Further, the height from the upper end to the lower end of the crankcase heater 9 has a height corresponding to the amount of the sleeping refrigerant described later.

  The casing 61 is provided with a suction pipe 81 so as to penetrate the body plate 61a. The suction pipe 81 communicates with the suction hole 72 b of the cylinder 72. Further, the casing 61 is provided with a discharge pipe 85 so as to penetrate the upper end plate 61b.

  The switching mechanism 22 is a mechanism for switching the direction of refrigerant flow in the refrigerant circuit 10 when switching between cooling and heating operations. The switching mechanism 22 includes a compressor 21, a heat source side heat exchanger 23, an expansion mechanism 24, and The cooling switching state (see the solid line of the switching mechanism 22 in FIG. 1) as the first circulation state in which the refrigerant is circulated in the order of the usage side heat exchanger 41, the compressor 21, the usage side heat exchanger 41, the expansion mechanism 24, And it is possible to switch the heating switching state (refer to the broken line of switching mechanism 22 of Drawing 1) as the 2nd circulation state which circulates a refrigerant in order of heat source side heat exchanger 23. In the present embodiment, the switching mechanism 22 is a four-way switching valve connected to the suction side of the compressor 21, the discharge side of the compressor 21, the heat source side heat exchanger 23, and the second closing valve 26. The switching mechanism 22 is not limited to the four-way switching valve, and is configured to have a function of switching the refrigerant flow direction as described above, for example, by combining a plurality of electromagnetic valves. There may be.

  The heat source side heat exchanger 23 functions as a refrigerant cooler during cooling, and functions as a refrigerant heater during heating. The heat source side heat exchanger 23 has one end connected to the switching mechanism 22 and the other end connected to the expansion mechanism 24.

  The expansion mechanism 24 is a mechanism for decompressing the refrigerant, and is an electric expansion valve in the present embodiment. One end of the expansion mechanism 24 is connected to the other end of the heat source side heat exchanger 23, and the other end is connected to the first closing valve 25.

  In this embodiment, the heat source unit 2 includes an outdoor fan 27 for sucking outdoor air into the unit, exchanging heat, and then discharging the air to the outside, and flows through the outdoor air and the heat source side heat exchanger 23. It is possible to exchange heat with the refrigerant. The outdoor fan 27 is rotationally driven by a fan motor 27a. Note that the heat source of the heat source side heat exchanger 23 is not limited to outdoor air, and may be another heat medium such as water.

  The shut-off valves 25 and 26 are valves connected to external devices and pipes (specifically, the refrigerant communication pipes 6 and 7). The first closing valve 25 is connected to the expansion mechanism 24. The second closing valve 26 is connected to the switching mechanism 22.

  The heat source unit 2 is provided with various sensors. Specifically, a suction pressure sensor 31 that detects the compressor suction pressure Ps is provided on the suction side of the compressor 21. A suction temperature sensor 32 for detecting the compressor suction temperature Ts is provided on the suction side of the compressor 21, and a discharge temperature sensor 33 for detecting the compressor discharge temperature Td is provided on the discharge side of the compressor 21. Is provided. In the present embodiment, the suction temperature sensor 32 and the discharge temperature sensor 33 are composed of thermistors. Further, the heat source unit 2 includes a heat source side control unit 28 that controls the operation of each unit constituting the heat source unit 2. The heat source side control unit 28 includes a microcomputer, a memory, and the like provided for controlling the heat source unit 2, and communicates with the usage side control unit 43 of the usage unit 4 via the transmission line 8 a. The control signals can be exchanged. That is, the use side control unit 43 and the heat source side control unit 28 constitute a control unit 8 as an operation control unit that performs operation control of the air conditioner 1. As shown in FIG. 4, the control unit 8 is connected so that various devices and valves 21, 22, 24, 27, 42 can be controlled. Here, FIG. 4 is a control block diagram of the air-conditioning apparatus 1 according to the present embodiment.

<Refrigerant communication pipe>
The refrigerant communication pipes 6 and 7 are refrigerant pipes that are constructed on site when the air conditioner 1 is installed at the installation location.

  As described above, the heat source side refrigerant circuit 10a, the use side refrigerant circuit 10b, and the refrigerant communication pipes 6 and 7 are connected, so that the compressor 21, the heat source side heat exchanger 23 as the first heat exchanger, the expansion A refrigerating machine oil (here, PAG) that includes the mechanism 24 and a use side heat exchanger 41 as a second heat exchanger and is incompatible with the refrigerant (here, carbon dioxide) and has a density higher than that of the refrigerant. The refrigerant circuit 10 in which is enclosed is configured. And the air conditioning apparatus 1 of this embodiment controls each apparatus of the heat source unit 2 and the utilization unit 4 by the control part 8 comprised from the utilization side control part 43, the heat source side control part 28, and the transmission line 8a. Can be done.

(2) Operation of refrigeration system <Overall operation>
First, the operation during cooling will be described with reference to FIGS.

  During cooling, the switching mechanism 22 is in a cooling switching state indicated by a solid line in FIG. 1, that is, the discharge side of the compressor 21 is connected to the heat source side heat exchanger 23, and the suction side of the compressor 21 is the second closing valve 26. It is in a connected state. The opening degree of the expansion mechanism 24 is adjusted. Moreover, the closing valves 25 and 26 are opened.

  When the compressor 21, the outdoor fan 27, and the indoor fan 42 are started in the state of the refrigerant circuit 10, the low-pressure refrigerant is sucked into the compressor 21 and compressed to a pressure exceeding the critical pressure to become a high-pressure refrigerant. Thereafter, the high-pressure refrigerant is sent to the heat source side heat exchanger 23 functioning as a refrigerant cooler via the switching mechanism 22, and is cooled by exchanging heat with outdoor air supplied by the outdoor fan 27. The The high-pressure refrigerant cooled in the heat source side heat exchanger 23 is decompressed by the expansion mechanism 24 to become a low-pressure gas-liquid two-phase refrigerant, and passes through the first closing valve 25 and the first refrigerant communication pipe 6. To the usage unit 4. The low-pressure gas-liquid two-phase refrigerant sent to the utilization unit 4 evaporates when heated by exchanging heat with room air in the utilization-side heat exchanger 41 functioning as a refrigerant heater. It becomes a low-pressure refrigerant. Then, the low-pressure refrigerant heated in the use side heat exchanger 41 is sent to the heat source unit 2 via the second refrigerant communication pipe 7, and again via the second closing valve 26 and the switching mechanism 22. Then, it is sucked into the compressor 21. In this way, cooling is performed.

  Next, the operation | movement at the time of heating is demonstrated using FIGS.

  During heating, the switching mechanism 22 is in a heating switching state indicated by a broken line in FIG. 1, that is, the discharge side of the compressor 21 is connected to the second closing valve 26, and the suction side of the compressor 21 is the heat source side heat exchanger 23. It is in a connected state. The opening degree of the expansion mechanism 24 is adjusted. Moreover, the closing valves 25 and 26 are opened.

  When the compressor 21, the outdoor fan 27, and the indoor fan 42 are started in the state of the refrigerant circuit 10, the low-pressure refrigerant is sucked into the compressor 21 and compressed to a pressure exceeding the critical pressure to become a high-pressure refrigerant. Thereafter, the high-pressure refrigerant is sent to the utilization unit 4 via the switching mechanism 22, the second closing valve 26 and the second refrigerant communication pipe 7. The high-pressure refrigerant sent to the utilization unit 4 is cooled by exchanging heat with room air in the utilization-side heat exchanger 41 functioning as a refrigerant cooler, and then passes through the first refrigerant communication tube 6. Then, it is sent to the heat source unit 2. The high-pressure refrigerant sent to the heat source unit 2 is decompressed by the expansion mechanism 24 to become a low-pressure gas-liquid two-phase refrigerant, and flows into the heat source side heat exchanger 23 that functions as a refrigerant heater. The low-pressure gas-liquid two-phase refrigerant that has flowed into the heat source side heat exchanger 23 is heated by exchanging heat with the outdoor air supplied by the outdoor fan 27 to become a low-pressure refrigerant. The air is sucked into the compressor 21 again via the switching mechanism 22. In this way, heating is performed.

  Here, the operation of the compressor 21 during the above-described cooling and heating will be described in detail.

  First, in the compressor 21, since the piston 70 (more specifically, the roller 70 a) of the compression element 62 revolves in the cylinder chamber 76 by the compressor motor 63, the suction is performed via the suction pipe 81. The low-pressure gas refrigerant that has flowed into the cylinder chamber 76 from the hole 72b is compressed by the roller 70a. The high-pressure gas refrigerant compressed by the roller 70 a of the compression element 62 passes from the opening (not shown) of the front head 65 to the space inside the casing 61 outside the compression element 62 via the discharge path 72 c of the cylinder 72. Further, the high-pressure gas refrigerant is discharged from the discharge pipe 85 to the outside of the casing 61. At this time, in the present embodiment, the refrigeration cycle is increased in pressure by using carbon dioxide as a refrigerant, such as an increase in sliding load or seizure in a sliding portion such as between the piston 70 and the bush 71. Problems tend to occur. However, in the present embodiment, since a highly viscous PAG is used as the refrigeration oil, if a sufficient amount of the refrigeration oil is supplied to the compression element 62, the piston 70 (more specifically, the blade 70b) is used. ) And the bush 71 can be satisfactorily lubricated, and problems such as an increase in sliding load and seizure of the sliding portion can be suppressed.

  However, when the operation of the entire air conditioner 1 is stopped or when the operation of some devices including the compressor 21 such as the thermo-off is stopped (hereinafter, referred to as when the compressor is stopped), the compressor 21 is started and the above-described cooling and heating operations are performed, a state in which the refrigerant accumulates together with the refrigeration oil in the compressor 21 due to a temperature drop in the compressor 21 when the compressor is stopped (hereinafter, referred to as “cooling”). This state may be referred to as “refrigerant stagnation state”, and the refrigerant accumulated in the compressor 21 due to the refrigerant stagnation state may be referred to as “sleeping refrigerant”). When the above-described cooling or heating operation is performed after such a refrigerant stagnation state occurs, the stagnation refrigerant is easily supplied to the sliding portion such as the compression element 62 in the compressor 21, and the sliding portion Since it becomes difficult to supply the refrigerating machine oil, poor lubrication of the sliding portion occurs, and the compressor 21 may be damaged. In this embodiment, since the refrigeration oil is incompatible with the refrigerant and has a higher density than the refrigerant, the stagnation refrigerant floats above the oil surface of the refrigeration oil in the lower part of the compressor 21. Will accumulate.

  On the other hand, in this embodiment, the crankcase heater 9 for heating the vicinity of the oil level height U of the compressor 21 is provided, and the crankcase heater 9 is operated when the compressor is stopped, so that the upper side of the refrigerating machine oil. It is possible to heat and evaporate the stagnation refrigerant accumulated in the compressor 21 in a floating state. Thereby, the heating of the stagnation refrigerant becomes more efficient than the case of providing a heater that locally heats the bottom of the compressor as in the prior art.

  However, in the air conditioner 1, when the refrigeration cycle operation in which the refrigerant circulates in the refrigerant circuit 10, such as the above-described cooling and heating operations, is performed and the refrigeration cycle operation is performed for a long time, the compressor Since the refrigerating machine oil accumulated in the 21 gradually comes out of the compressor 21 along with the refrigerant circulating in the refrigerant circuit 10, the heat source side heat exchanger 23 and the refrigerating cycle operation before the compressor is stopped are performed. It will be distributed in parts other than the compressor such as various devices such as the use-side heat exchanger 41 and refrigerant tubes connecting the various devices such as the refrigerant communication pipes 6 and 7. Will change. For this reason, even if the crankcase heater 9 that heats the vicinity of the oil level height U is provided, the oil level height of the compressor 21 changes due to the refrigeration cycle operation in which the refrigerant circulates in the refrigerant circuit 10. The crankcase heater 9 cannot heat the vicinity of the oil level height U of the compressor 21. In such a case, the heating efficiency of the stagnation refrigerant is reduced according to the change in the oil level height U, thereby increasing the power consumption when the compressor is stopped.

  Therefore, in the air conditioning apparatus 1 of the present embodiment, the above problem is solved by performing the refrigerant stagnation prevention operation including the heating operation by the crankcase heater 9 when the compressor is stopped. Hereinafter, the refrigerant stagnation prevention operation will be described with reference to FIGS.

<Refrigerant sleep prevention operation>
FIG. 5 is a flowchart of the refrigerant stagnation prevention operation of the present embodiment.

  First, in step S1, compression such as whether or not a command to stop the operation of the entire air conditioner 1 has been issued, whether or not to enter a control operation to stop the operation of some devices including the compressor 21, such as a thermo-off, etc. It is determined whether or not a process involving stopping of the machine 21 is performed. And when performing the process accompanied by the stop of the compressor 21, it transfers to the process of step S2 before moving to step S3 which is the process accompanied by the stop of the compressor 21 (that is, before the compressor is stopped). .

  Next, in step S <b> 2, an oil recovery operation is performed in which the refrigeration oil distributed in the refrigerant circuit 10 is returned to the compressor 21 by cooling and heating operations. Thereby, the oil level height of the compressor 21 when the compressor is stopped is set to the oil level height U as much as possible (here, the oil in the case where the whole amount of the refrigerating machine oil enclosed in the refrigerant circuit 10 is present in the compressor 21). Keep the surface height constant. In the present embodiment, the oil recovery operation is performed by changing the rotation speed (frequency) of the compressor 21. More specifically, in the oil recovery operation, the rotational speed of the compressor motor 63 is varied by an inverter device (not shown), and is higher than the rotational speed of the compressor 21 immediately before the oil recovery operation (ie, step S1). As the compressor 21 is operated at the rotational speed or the compressor 21 is operated at the maximum rotational speed, the flow rate of the refrigerant circulating in the refrigerant circuit 10 is increased as much as possible and distributed to the refrigerant circuit 10. The refrigerating machine oil is returned to the compressor 21. Further, as the degree of opening control of the expansion mechanism 24, the degree of superheat SH at the outlet of the heat exchanger functioning as a refrigerant heater (that is, the use side heat exchanger 41 during cooling and the heat source side heat exchanger 23 during heating). In the embodiment, the value obtained by dividing the compressor suction pressure Ps detected by the suction pressure sensor 31 into the saturation temperature from the compressor suction temperature Ts detected by the suction temperature sensor 32 is constant at a predetermined value. In such a case, by reducing the predetermined value, the low-pressure refrigerant flowing through the path from the heat exchanger functioning as a refrigerant heater to returning to the compressor 21 is moistened. Thus, the operation of returning the refrigeration oil accumulated in the path to the compressor 21 may be promoted.

  And after performing this oil collection | recovery driving | operation and returning the refrigeration oil distributed to the refrigerant circuit 10 to the compressor 21, it transfers to step S3 and performs the process accompanied by the stop of the compressor 21. FIG. Then, the temperature drop in the compressor 21 starts, and this causes a refrigerant stagnation state, and above the oil level of the refrigerating machine oil in the compressor 21 (that is, above the oil level height U in FIG. 2). The sleeping refrigerant accumulates in the floating state.

  Therefore, in order to evaporate the stagnation refrigerant, when the temperature in the compressor 21 is lowered to a predetermined temperature or less, the crankcase heater 9 is operated to heat the stagnation refrigerant. In the present embodiment, the compressor discharge temperature Td detected by the discharge temperature sensor 33 for determining whether or not the temperature in the compressor 21 has decreased to a predetermined temperature or lower falls to a threshold value (for example, 70 ° C.) or lower. The crankcase heater 9 is stopped until the compressor discharge temperature Td becomes lower than the threshold value (step S5), and the compressor discharge temperature Td becomes lower than the threshold value. The crankcase heater 9 is operated to heat the stagnation refrigerant (step S6). Here, the crankcase heater 9 can heat the vicinity of the oil surface height U of the refrigeration oil by being disposed so as to overlap the oil surface of the compressor 21 when the compressor 21 is viewed from the side. Therefore, the sleeping refrigerant can be efficiently heated and evaporated. In particular, in the present embodiment, the crankcase heater 9 is arranged so that the upper end thereof is located above the oil level height U and the lower end thereof coincides with the oil level height U. Since the height from the upper end to the lower end of the crankcase heater 9 has a height corresponding to the amount of the sleeping refrigerant, only the sleeping refrigerant accumulated in the state of floating above the refrigerating machine oil is heated. Therefore, the power consumption when the compressor is stopped can be greatly reduced. In addition, about the determination whether the temperature in the compressor 21 in step S4 fell below to predetermined temperature, as above-mentioned, it is not limited to what uses the compressor discharge temperature Td, The inside of the compressor 21 is determined. A temperature sensor for detecting the temperature may be provided and used, and any state value corresponding to the temperature in the compressor 21 other than the compressor discharge temperature Td can be used.

(3) Modification 1
In the above-described embodiment, the crankcase heater 9 is provided so as to heat the vicinity of the oil level height U of the compressor 21 in order to heat the stagnant refrigerant when the compressor is stopped (see FIG. 2). Without being limited thereto, as shown in FIG. 6, the stator 79 of the compressor motor 63 and the oil level height U of the compressor 21 are substantially matched (more specifically, the stator 79 The coil end 79a, which is the lower part, has reached the oil level height U of the compressor 21), and energization is performed so that the compressor motor 63 does not rotate when the compressor is stopped. A refrigerant stagnation preventing operation for heating the vicinity of the oil level U of the compressor 21 may be performed by generating heat.

  Specifically, in this modification, as shown in FIG. 7, in addition to steps S <b> 1 to S <b> 4 in the above-described embodiment, in place of steps S <b> 5 and S <b> 6 in the above-described embodiment, The refrigerant stagnation prevention operation including step S15 which is a non-energization process and step S16 which is an energization process to the compressor motor 63 is performed. In the present embodiment, the energization of the compressor motor 63 in step S16 applies a low voltage that does not cause the compressor motor 63 to rotate. At this time, in order to increase the amount of heat generated, it is desirable to increase the frequency as much as possible by an inverter device (not shown).

  Thereby, also in this modification, the same effect as the above-mentioned embodiment can be acquired.

(4) Modification 2
In the above-described embodiment and Modification 1, in the oil recovery operation in the refrigerant stagnation prevention operation, the flow direction of the refrigerant in the refrigerant circuit 10 remains the same, and the flow rate of the refrigerant circulating in the refrigerant circuit 10 is increased as much as possible. By doing so, the refrigeration oil distributed in the refrigerant circuit 10 is returned to the compressor 21.

  However, when the switching mechanism 22 is in the cooling switching state, when the refrigeration cycle operation (that is, cooling) is performed (that is, when cooling is performed), the refrigerant functions in the refrigerant circuit 10 as the compressor 21 and the refrigerant cooler. When a large amount of refrigeration oil is distributed between the heat source side heat exchanger 23 and the switching mechanism 22 is in the heating switching state, when the refrigeration cycle operation (ie, heating) is performed, the refrigerant circuit 10 Among them, a lot of refrigerating machine oil is distributed in a portion between the compressor 21 and the use side heat exchanger 41 functioning as a refrigerant cooler.

  Therefore, in the present modification, in the oil recovery operation before the compressor stops in the cooling switching state, the heat source side heat exchanger 23 is caused to function as a refrigerant heater by switching from the cooling switching state to the heating switching state. In the switching state, the refrigeration oil distributed in the portion of the refrigerant circuit 10 between the compressor 21 and the heat source side heat exchanger 23 functioning as a refrigerant cooler flows toward the compressor 21, and heating switching In the oil recovery operation before the compressor is stopped in the state, the use side heat exchanger 41 is caused to function as a refrigerant heater by switching from the heating switching state to the cooling switching state, and the refrigerant circuit 10 is compressed in the heating switching state. The refrigeration oil distributed in a portion between the machine 21 and the use side heat exchanger 41 functioning as a refrigerant cooler flows toward the compressor 21. There.

  Thereby, in this modification, the refrigerating machine oil distributed to the refrigerant circuit 10 can be reliably returned to the compressor. In particular, in the so-called separate type air conditioner in which the heat source unit 2 is provided with the compressor 21 as in the air conditioner 1, the second refrigerant communicates between the use side heat exchanger 41 and the compressor 21. Since the pipe 7 is interposed and there is a high possibility that a large amount of refrigerating machine oil is distributed in this portion, it is effective when performing the process of stopping the compressor 21 from the heating switching state.

(5) Other Embodiments Although the embodiments of the present invention and the modifications thereof have been described with reference to the drawings, the specific configuration is not limited to these embodiments and the modifications thereof, and Changes can be made without departing from the scope of the invention.

<A>
In the above-described embodiment and its modification, the example in which the present invention is applied to an air conditioner in which one use unit is connected to one heat source unit has been described. The present invention can be applied even to an air conditioner in which a heat source unit and various utilization units are connected. Further, the present invention is not limited to an air conditioner, and may be applied to any refrigeration apparatus provided with a refrigerant circuit that performs vapor compression refrigeration cycle operation.

<B>
In the above-described embodiment and modification, a combination of using carbon dioxide as the refrigerant and using PAG as the refrigerating machine oil is taken as an example, but the present invention is not limited to this, and is incompatible with the refrigerant. In addition, the present invention can be applied if refrigeration oil having a density higher than that of the refrigerant is used.

<C>
In the second modification described above, the so-called separate type air conditioner in which the heat source unit is provided with the compressor has been described as being effective when performing the process of stopping the compressor 21 from the heating switching state. In a so-called remote condenser type air conditioner in which a compressor is provided in the use unit, a refrigerant communication pipe is interposed between the heat source side heat exchanger and the compressor, and a large amount of refrigerating machine oil is distributed in this part. This is effective when performing the process of stopping the compressor from the cooling switching state.

  By using the present invention, in a refrigeration apparatus that uses refrigeration oil that is incompatible with the refrigerant and has a density higher than that of the refrigerant, power consumption when the compressor is stopped can be suppressed.

It is a schematic block diagram of the air conditioning apparatus concerning one Embodiment of the freezing apparatus of this invention. It is a schematic longitudinal cross-sectional view of a compressor. FIG. 3 is a schematic cross-sectional view of the compressor, corresponding to the AA cross-section of FIG. 2. It is a control block diagram of an air conditioning apparatus. It is a flowchart of a refrigerant | coolant stagnation prevention operation | movement. It is a schematic longitudinal cross-sectional view of the compressor in the modification 1. 10 is a flowchart of a refrigerant stagnation prevention operation in Modification 1.

Explanation of symbols

1 Air conditioning equipment (refrigeration equipment)
9 Crankcase heater (heater)
DESCRIPTION OF SYMBOLS 10 Refrigerant circuit 21 Compressor 22 Switching mechanism 23 Heat source side heat exchanger (1st heat exchanger)
24 Expansion mechanism 41 User-side heat exchanger (second heat exchanger)
61 Casing 62 Compression element 63 Compressor motor (motor)
79 Stator U Oil level height

Claims (6)

It includes a compressor (21), a first heat exchanger (23), an expansion mechanism (24), and a second heat exchanger (41), and is incompatible with the refrigerant and has a higher density than the refrigerant. A refrigerant circuit (10) in which refrigeration oil is enclosed;
A heater (9) for heating the vicinity of the oil level (U) of the compressor,
Before stopping the compressor, perform an oil recovery operation to return the refrigeration oil distributed in the refrigerant circuit to the compressor,
Operating the heater when the compressor stops,
Refrigeration equipment (1).   The refrigerating apparatus (1) according to claim 1, wherein the heater (9) is disposed so as to overlap an oil level of the compressor when the compressor (21) is viewed from the side. The compressor (21), the first heat exchanger (23), and the expansion mechanism (24) in which the compression element (62) for compressing the refrigerant and the motor (63) for driving the compression element are housed in the casing (61). ), And a second heat exchanger (41), and includes a refrigerant circuit (10) in which refrigeration oil that is incompatible with the refrigerant and has a higher density than the refrigerant is enclosed,
Before stopping the compressor, perform an oil recovery operation to return the refrigeration oil distributed in the refrigerant circuit to the compressor,
In a state where the stator (79) of the motor and the oil level height (U) of the compressor substantially coincide with each other, energization is performed so that the motor does not rotate when the compressor is stopped.
Refrigeration equipment (1).   The refrigeration apparatus (1) according to claim 3, wherein a lower part of the stator (79) of the motor (63) reaches the oil level (U) of the compressor (21).   The refrigeration apparatus (1) according to any one of claims 1 to 4, wherein the oil recovery operation is performed by changing a rotation speed of the compressor (21). The refrigerant circuit (10) circulates refrigerant in the order of the compressor (21), the first heat exchanger (23), the expansion mechanism (24), and the second heat exchanger (41). A switching mechanism (22) capable of switching between a circulation state and a second circulation state in which refrigerant is circulated in the order of the compressor, the second heat exchanger, the expansion mechanism, and the first heat exchanger; Including
6. The oil recovery operation according to claim 1, wherein the oil recovery operation is performed by switching to the other of the first and second circulation states before the compressor stops in one of the first and second circulation states. Refrigeration equipment (1).

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