JP5320280B2 - Air conditioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control a supercooling degree of a refrigerant at an outlet of a supercooling heat exchanger, and to secure condensing capacity of the refrigerant in a heat source side heat exchanger, in an air conditioner equipped with a bypass refrigerant pipe and the supercooling heat exchanger, wherein the bypass refrigerant pipe branches a part of the refrigerant condensed in the heat source side heat exchanger and returns it to a suction side of a compression mechanism, and the supercooling heat exchanger cools the refrigerant condensed in the heat source side heat exchanger by the refrigerant flowing through the bypass refrigerant pipe. <P>SOLUTION: The air conditioner 1 is provided with the bypass refrigerant pipe 26 for branching a part of the refrigerant condensed in an outdoor heat exchanger 23 in cooling operation and returning it to the suction side of the compression mechanism 21, and the supercooling heat exchanger 25 for cooling the refrigerant condensed in the outdoor heat exchanger 23 by the refrigerant flowing through the bypass refrigerant pipe 26. The air conditioner can perform supercooling degree control for controlling apparatuses so that the supercooling degree of the refrigerant in the outlet of the outdoor heat exchanger 23 approaches a target supercooling degree when the high pressure in refrigeration cycle operation is equal to or more than a prescribed pressure. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an air conditioner, in particular, a bypass refrigerant pipe that branches a part of the refrigerant condensed in a heat source side heat exchanger and returns it to the suction side of the compression mechanism, and heat source side heat exchange by the refrigerant flowing through the bypass refrigerant pipe. It is related with the air conditioning apparatus which has a supercooling heat exchanger which cools the refrigerant condensed in the unit.

  Conventionally, as shown in Patent Document 1 (Japanese Patent Application Laid-Open No. 2005-345069), a bypass refrigerant pipe for branching a part of the refrigerant condensed in the heat source side heat exchanger and returning it to the suction side of the compressor, and this bypass There is an air conditioner having a supercooling heat exchanger that cools the refrigerant condensed in the heat source side heat exchanger by the refrigerant flowing through the refrigerant pipe. In this air conditioner, by controlling the bypass expansion valve provided in the bypass refrigerant pipe so that the superheat degree on the suction side of the compressor becomes constant at the target superheat degree, the refrigerant at the outlet of the supercooling heat exchanger is controlled. The degree of supercooling is ensured.

  When excessive refrigerant is generated in the refrigerant circuit in the configuration in which the bypass expansion valve provided in the bypass refrigerant pipe is controlled so that the superheat degree on the suction side of the compressor becomes constant at the target superheat degree as described above. Even so, it is not possible to aggressively treat the surplus refrigerant, and the condensing capacity of the heat source side heat exchanger tends to be reduced.

  For this reason, it is preferable to manage the supercooling degree of the refrigerant at the outlet of the supercooling heat exchanger and to secure the refrigerant condensing capacity in the heat source side heat exchanger.

  The problem of the present invention is that a part of the refrigerant condensed in the heat source side heat exchanger is branched and returned to the suction side of the compression mechanism, and condensed in the heat source side heat exchanger by the refrigerant flowing through the bypass refrigerant pipe. In an air conditioner having a supercooling heat exchanger that cools the refrigerant, the supercooling degree of the refrigerant at the outlet of the supercooling heat exchanger can be managed, and the refrigerant condensing capacity in the heat source side heat exchanger can be secured. Is to make it.

An air conditioner according to a first aspect of the present invention includes at least one heat source unit, at least one utilization unit, a liquid refrigerant communication tube, and a gas refrigerant communication tube. The heat source unit includes a compression mechanism that compresses the refrigerant, a heat source side heat exchanger that condenses the refrigerant compressed in the compression mechanism by exchanging heat with a cooling medium, and a part of the refrigerant that is condensed in the heat source side heat exchanger. A bypass refrigerant pipe that branches and returns to the suction side of the compression mechanism, a bypass expansion mechanism that is provided in the bypass refrigerant pipe and depressurizes the refrigerant flowing through the bypass refrigerant pipe, and a refrigerant that has condensed in the heat source side heat exchanger And a supercooling heat exchanger that cools by heat exchange with the decompressed refrigerant. The utilization unit has a utilization side heat exchanger that evaporates by heat exchange of the refrigerant cooled in the supercooling heat exchanger with the heating medium. The liquid refrigerant communication tube is connected to the heat source unit and the utilization unit, and is a refrigerant tube that sends the refrigerant cooled in the supercooling heat exchanger to the utilization side heat exchanger. The gas refrigerant communication pipe is connected to the heat source unit and the use unit, and is a refrigerant pipe that sends the refrigerant evaporated in the use side heat exchanger to the compression mechanism. Then, when the high pressure in the refrigeration cycle operation is equal to or higher than the predetermined pressure, the air conditioner has a supercooling degree when the refrigerant subcooling degree at the outlet of the heat source side heat exchanger is smaller than the target supercooling degree. By controlling the equipment constituting the heat source unit so that the degree of supercooling is larger than the target degree of supercooling, by controlling the equipment constituting the heat source unit so that the degree of supercooling is reduced, It is possible to control the degree of supercooling that controls the equipment that constitutes the heat source unit so that the degree of supercooling approaches the target degree of supercooling , and when the high pressure in the refrigeration cycle operation is less than the predetermined pressure, It is possible to perform superheat degree control for controlling devices constituting the heat source unit so that the superheat degree of the refrigerant at the outlet of the exchanger on the bypass refrigerant pipe side approaches the target superheat degree.

  A bypass refrigerant pipe that branches part of the refrigerant condensed in the heat source side heat exchanger and returns to the suction side of the compression mechanism, and supercooling that cools the refrigerant condensed in the heat source side heat exchanger by the refrigerant flowing through the bypass refrigerant pipe In the configuration having the heat exchanger, the change in the refrigerant condensing capacity in the heat source side heat exchanger mainly appears as a change in the degree of supercooling of the refrigerant at the outlet of the heat source side heat exchanger. For this reason, in order to ensure the refrigerant | coolant condensing capability in the heat source side heat exchanger, what is necessary is just to make the subcooling degree of the refrigerant | coolant in the exit of a heat source side heat exchanger appropriate. Moreover, when the refrigerant | coolant condensing capability in the heat source side heat exchanger falls by generation | occurrence | production of the excess refrigerant | coolant in a refrigerant circuit, there exists a tendency for the high voltage | pressure in a refrigerating cycle operation to rise.

  Therefore, in this air conditioner, when the high pressure in the refrigeration cycle operation is equal to or higher than a predetermined pressure, the device that configures the heat source unit so that the refrigerant subcooling degree at the outlet of the heat source side heat exchanger approaches the target subcooling degree When the high pressure in the refrigeration cycle operation is lower than the predetermined pressure, the superheat degree of the refrigerant at the outlet on the bypass refrigerant pipe side of the supercooling heat exchanger approaches the target superheat degree. The superheat degree control for controlling the equipment constituting the heat source unit is performed.

  Thereby, in this air conditioning apparatus, in the supercooling heat exchanger, the refrigerant at the outlet of the supercooling heat exchanger (i.e., cooling the refrigerant sent to the use side heat exchanger by the refrigerant flowing through the bypass refrigerant pipe (that is, In addition, it is possible to manage the degree of supercooling of the refrigerant (refrigerant sent from the supercooling heat exchanger to the use side heat exchanger) and to secure the refrigerant condensing capacity in the heat source side heat exchanger.

  An air conditioner according to a second aspect of the present invention is the air conditioner according to the first aspect, wherein there are a plurality of heat source units, connected in parallel via a liquid refrigerant communication tube and a gas refrigerant communication tube, Based on the degree of supercooling in the heat source unit, it is possible to perform the degree of supercooling degree variation prevention control for correcting the value of the target degree of supercooling.

  When a plurality of heat source units connected in parallel via the liquid refrigerant communication tube and the gas refrigerant communication tube are employed, supercooling degree control and supercooling degree-superheat degree establishment control are performed in each heat source unit. At this time, if the refrigerant drifts between the heat source units, the degree of supercooling between the heat source units, that is, the refrigerant condensing ability in the heat source side heat exchanger may vary.

  Therefore, in this air conditioner, the subcooling degree variation prevention control for correcting the value of the target supercooling degree based on the supercooling degree in the plurality of heat source units is performed.

  Thereby, in this air conditioning apparatus, the variation in the degree of supercooling between the heat source units can be reduced while performing the degree of supercooling in each heat source unit.

  An air conditioner according to a third aspect of the present invention is the air conditioner according to the second aspect, wherein the supercooling degree variation prevention control is obtained by subtracting the target supercooling degree from the supercooling degree among the plurality of heat source units. Correction is performed when the absolute value of the subcooling degree deviation is less than the predetermined deviation and there is a heat source unit that satisfies the correction execution condition that the degree of supercooling is less than the predetermined supercooling degree. Correct the target subcooling degree of the heat source unit that satisfies the condition so that it is larger than the current value, and the correction cancellation condition that the subcooling degree of all the heat source units is larger than the predetermined supercooling degree. When the condition is satisfied, the correction of the target supercooling degree is canceled.

  In this air conditioner, since the flow rate of the refrigerant flowing through the heat source unit that satisfies the correction execution condition is reduced and is easily distributed to other heat source units, the variation in the degree of supercooling between the heat source units can be reduced. Then, when the variation in the degree of subcooling between the heat source units is reduced and the degree of subcooling of all the heat source units satisfies the predetermined correction release condition, the correction of the target supercooling degree is released, so that The normal supercooling degree control can be restored.

  The air conditioner according to the fourth aspect of the present invention is the air conditioner according to any one of the first to third aspects, wherein the target supercooling degree is equivalent to the temperature of the cooling medium or equivalent to the temperature of the cooling medium. The state quantity is changed so as to become smaller as the temperature of the cooling medium increases.

  The condensing capacity in the heat source side heat exchanger changes depending on the temperature difference between the refrigerant and the cooling medium. Therefore, if the temperature of the cooling medium is different, the target subcooling value of the refrigerant at the outlet of the heat source side heat exchanger is also different. become.

  Therefore, in this air conditioner, the target supercooling degree is changed in accordance with the temperature of the cooling medium or the state quantity equivalent to the temperature of the cooling medium.

  Thereby, in this air conditioning apparatus, appropriate control can be performed in consideration of a change due to the temperature of the cooling medium of the condensing capacity in the heat source side heat exchanger.

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

  In the air conditioning apparatus according to the first aspect of the present invention, in the supercooling heat exchanger, the refrigerant sent to the use side heat exchanger is cooled by the refrigerant flowing through the bypass refrigerant pipe, and the outlet of the supercooling heat exchanger is cooled. In addition, the degree of supercooling of the refrigerant (that is, the refrigerant sent from the supercooling heat exchanger to the use side heat exchanger) can be managed, and the refrigerant condensing capacity in the heat source side heat exchanger can be secured.

  In the air conditioner according to the second aspect of the present invention, it is possible to reduce the variation in the degree of supercooling between the heat source units while performing the degree of supercooling control or the degree of supercooling-superheat degree establishment control in each heat source unit.

  In the air conditioner according to the third aspect of the present invention, the bypass expansion mechanism is controlled so that the flow rate of the refrigerant flowing through the bypass refrigerant pipe of the heat source unit satisfying the correction execution condition is reduced, and the heat source unit satisfying the correction execution condition is Since the flow rate of the flowing refrigerant decreases and is easily distributed to other heat source units, the variation in the degree of supercooling between the heat source units can be reduced. Then, when the variation in the degree of subcooling between the heat source units is reduced and the degree of subcooling of all the heat source units satisfies the predetermined correction release condition, the correction of the target supercooling degree is released, so that It is possible to return to normal supercooling degree control or supercooling degree-superheat degree establishment control.

  In the air conditioning apparatus according to the fourth aspect of the present invention, appropriate control can be performed in consideration of a change in the condensation capacity of the heat source side heat exchanger due to the temperature of the cooling medium.

It is a schematic block diagram of the air conditioning apparatus concerning 1st Embodiment of this invention and its modification. It is a control block diagram of the air harmony device concerning a 1st embodiment and its modification. It is a flowchart of control including the supercooling degree control concerning 1st Embodiment. It is a flowchart of control including the supercooling degree control-superheat degree establishment control concerning the modification 2 of 1st Embodiment. It is a flowchart of control including the supercooling degree-superheat degree-liquid pipe temperature establishment control and superheat degree-liquid pipe temperature establishment control concerning the modification 3 of 1st Embodiment. It is a flowchart of the supercooling degree control-superheat degree-liquid pipe temperature-superheat compression prevention-wet compression prevention establishment control and superheat degree--liquid pipe temperature-overheat compression prevention establishment control concerning the modification 4 of 1st Embodiment. It is a schematic block diagram of the air conditioning apparatus concerning 2nd Embodiment of this invention. It is a control block diagram of the air conditioning apparatus concerning 2nd Embodiment. It is a flowchart of the supercooling degree dispersion | variation prevention control concerning 2nd Embodiment.

  Hereinafter, embodiments of an air-conditioning apparatus according to the present invention will be described based on the drawings.

(First embodiment)
(1) Configuration of Air Conditioner FIG. 1 is a schematic configuration diagram of an air conditioner 1 according to the first embodiment of the present invention. The air conditioner 1 is an apparatus used for air conditioning in a room such as a building by performing a vapor compression refrigeration cycle operation. The air conditioner 1 mainly includes an outdoor unit 2 as one heat source unit, and indoor units 5a and 5b as a plurality of (two in this embodiment) usage units connected in parallel with each other, A liquid refrigerant communication pipe 6 and a gas refrigerant communication pipe 7 are provided to connect the outdoor unit 2 and the indoor units 5a and 5b. That is, the vapor compression refrigerant circuit 10 of the air conditioner 1 of the present embodiment is configured by connecting the outdoor unit 2, the indoor units 5 a and 5 b, the liquid refrigerant communication pipe 6 and the gas refrigerant communication pipe 7. It is configured.

<Indoor unit>
The indoor units 5a and 5b are installed by embedding or hanging in a ceiling of a room such as a building or by hanging on a wall surface of the room. The indoor units 5 a and 5 b are connected to the outdoor unit 2 via the liquid refrigerant communication tube 6 and the gas refrigerant communication tube 7 and constitute a part of the refrigerant circuit 10.

  Next, the configuration of the indoor units 5a and 5b will be described. Since the indoor unit 5a and the indoor unit 5b have the same configuration, only the configuration of the indoor unit 5a will be described here. The configuration of the indoor unit 5b is a subscript “ Subscript “b” is attached instead of “a”, and description of each part is omitted.

  The indoor unit 5a mainly has an indoor refrigerant circuit 10a (in the indoor unit 5b, the indoor refrigerant circuit 10b) that constitutes a part of the refrigerant circuit 10. The indoor refrigerant circuit 10a mainly includes an indoor expansion valve 51a as a use side expansion mechanism and an indoor heat exchanger 52a as a use side heat exchanger.

  In the present embodiment, the indoor expansion valve 51a is an electric expansion valve connected to the liquid side of the indoor heat exchanger 52a in order to adjust the flow rate or reduce the pressure of the refrigerant flowing in the indoor refrigerant circuit 10a.

  The indoor heat exchanger 52a functions as an evaporator that evaporates by heat-exchanging the refrigerant cooled in the supercooling heat exchanger 26 (described later) with indoor air as a heating medium during the cooling operation, and during the heating operation. The heat exchanger functions as a condenser that condenses the refrigerant compressed in the compressor 21 (described later) by heat exchange with indoor air or the like as a cooling medium.

  Moreover, the indoor unit 5a has the indoor side control part 53a which controls operation | movement of each part which comprises the indoor unit 5a. And the indoor side control part 53a has the microcomputer, memory, etc. which were provided in order to control the indoor unit 5a, and is with the remote control (not shown) for operating the indoor unit 5a separately. Control signals and the like can be exchanged between them, and control signals and the like can be exchanged with the outdoor unit 2 via the transmission line 8.

<Outdoor unit>
The outdoor unit 2 is installed outside a building or the like, and is connected to the indoor units 5a and 5b via the liquid refrigerant communication pipe 6 and the gas refrigerant communication pipe 7, and a refrigerant circuit is provided between the indoor units 5a and 5b. 10 is constituted.

  Next, the configuration of the outdoor unit 2 will be described. The outdoor unit 2 mainly has an outdoor refrigerant circuit 10 c that constitutes a part of the refrigerant circuit 10. The outdoor refrigerant circuit 10c mainly includes a compressor 21 as a compression mechanism, a four-way switching valve 22, an outdoor heat exchanger 23 as a heat source side heat exchanger, and an outdoor expansion valve 24 as a heat source side expansion mechanism. And a supercooling heat exchanger 25, a bypass refrigerant pipe 26, an accumulator 27, a liquid side closing valve 28, and a gas side closing valve 29.

  In the present embodiment, the compressor 21 is a positive displacement compressor provided to compress the refrigerant, and is driven by a compressor motor 30. In the present embodiment, the number of the compressors 21 is only one. However, the present invention is not limited to this, and two or more compressors may be connected in parallel according to the number of indoor units connected.

  The four-way switching valve 22 is a valve for switching the direction of the refrigerant flow in the refrigerant circuit 10. During the cooling operation, the outdoor heat exchanger 23 is used as a condenser for the refrigerant compressed in the compressor 21, and In order for the heat exchangers 52a and 52b to function as an evaporator for the refrigerant condensed in the outdoor heat exchanger 23, the discharge side of the compressor 21 and the gas side of the outdoor heat exchanger 23 are connected and the suction of the compressor 21 is performed. Side (specifically, the accumulator 27) and the gas refrigerant communication pipe 7 side are connected (see the solid line of the four-way switching valve 22 in FIG. 1), and the indoor heat exchangers 52a and 52b are connected to the compressor during heating operation. In order to allow the outdoor heat exchanger 23 to function as a refrigerant evaporator condensed in the indoor heat exchangers 52a and 52b, as a refrigerant condenser compressed in the It is possible to connect the refrigerant communication pipe 7 side and the suction side of the compressor 21 (specifically, the accumulator 27) and the gas side of the outdoor heat exchanger 23 (four-way switching in FIG. 1). (See broken line for valve 22).

  The outdoor heat exchanger 23 functions as a condenser that condenses the refrigerant compressed in the compressor 21 by heat exchange with outdoor air as a cooling medium during the cooling operation, and depressurizes the outdoor expansion valve 24 during the heating operation. It is a heat exchanger that functions as an evaporator that evaporates by exchanging heat with the outdoor air as a heating medium. The outdoor heat exchanger 23 has a gas side connected to the four-way switching valve 22 and a liquid side connected to the liquid refrigerant communication pipe 6 side (specifically, the outdoor expansion valve 24 and the check valve 25). And the outdoor air as a cooling medium or a heating medium is supplied to the outdoor heat exchanger 23 by the outdoor fan 32 as a ventilation fan. The outdoor fan 32 is a propeller fan or the like driven by an outdoor fan motor 33.

  In the present embodiment, the outdoor expansion valve 24 is an electric expansion valve connected to the liquid side of the outdoor heat exchanger 23 in order to adjust the pressure and flow rate of the refrigerant flowing in the outdoor refrigerant circuit 10c. In the present embodiment, the outdoor refrigerant circuit 10c is provided with a check valve 31 so as to bypass the outdoor expansion valve 24. The check valve 31 allows the refrigerant to flow from the outdoor heat exchanger 23 toward the subcooling heat exchanger 25, but allows the refrigerant to flow from the subcooling heat exchanger 25 toward the outdoor heat exchanger 23. It is an unacceptable valve.

  In this embodiment, the supercooling heat exchanger 25 is a heat exchanger that cools the refrigerant condensed in the outdoor heat exchanger 23 during the cooling operation. In this embodiment, the supercooling heat exchanger 25 is connected between the outdoor expansion valve 24 and the check valve 31 and the liquid side closing valve 28.

  The bypass refrigerant pipe 26 is a refrigerant pipe that branches a part of the refrigerant condensed in the outdoor heat exchanger 23 and returns it to the suction side of the compressor 21. In the present embodiment, the bypass refrigerant pipe 26 branches a part of the refrigerant condensed in the outdoor heat exchanger 23 during the cooling operation from a position between the outdoor expansion valve 24 and the check valve 31 and the supercooling heat exchanger 25. The inlet pipe 34 connected to the inlet of the bypass refrigerant pipe 26 side of the supercooling heat exchanger 25 and the outlet of the bypass refrigerant pipe 26 side of the supercooling heat exchanger 25 are returned to the suction side of the compressor 21. And an outlet pipe 35 connected to the suction side of the compressor 21 (more specifically, the upstream side of the accumulator 27). The outlet pipe 35 is provided with a bypass expansion valve 36 as a bypass expansion mechanism for decompressing the refrigerant flowing through the bypass refrigerant pipe 26. In the present embodiment, the bypass expansion valve 36 is an electric expansion valve. Thereby, the supercooling heat exchanger 25 cools the refrigerant condensed in the outdoor heat exchanger 23 during the cooling operation by exchanging heat with the refrigerant decompressed in the bypass expansion valve 36.

  The accumulator 27 is connected between the four-way switching valve 22 and the suction side of the compressor 21.

  The liquid side shut-off valve 28 and the gas side shut-off valve 29 are valves provided at connection ports with external devices and pipes (specifically, the liquid refrigerant communication pipe 6 and the gas refrigerant communication pipe 7). The liquid side closing valve 28 is connected to the supercooling heat exchanger 25. The gas side closing valve 29 is connected to the four-way switching valve 22.

  The outdoor unit 2 is provided with various sensors. Specifically, the outdoor unit 2 includes a suction pressure sensor 37 that detects the suction pressure Ps of the compressor 21, a discharge pressure sensor 38 that detects the discharge pressure Pd of the compressor 21, and a suction temperature Ts of the compressor 21. And a discharge temperature sensor 40 for detecting the discharge temperature Td of the compressor 21 are provided. In the present embodiment, the suction temperature sensor 39 is provided at a position between the accumulator 27 and the compressor 21. A liquid side temperature sensor 41 for detecting the refrigerant temperature Tco is provided on the liquid side of the outdoor heat exchanger 23 (that is, the outlet side during the cooling operation). A liquid pipe temperature sensor 42 for detecting the temperature of the refrigerant (hereinafter referred to as a liquid pipe temperature Tlp) is provided on the liquid side shut-off valve 28 side of the supercooling heat exchanger 25 (that is, the outlet side during cooling operation). ing. Further, the outlet pipe 35 of the bypass refrigerant pipe 26 is provided with a bypass temperature sensor 43 that detects the temperature Tsh of the refrigerant flowing through the outlet of the supercooling heat exchanger 25 on the bypass refrigerant pipe 26 side. The outdoor unit 2 is also provided with an outdoor temperature sensor 44 that detects the temperature Ta of the outdoor air supplied to the outdoor heat exchanger 23 by the outdoor fan 32. In the present embodiment, the suction temperature sensor 39, the discharge temperature sensor 40, the liquid side temperature sensor 41, the liquid pipe temperature sensor 42, the bypass temperature sensor 43, and the outdoor temperature sensor 44 are composed of thermistors. Further, the outdoor unit 2 includes an outdoor side control unit 45 that controls the operation of each unit constituting the outdoor unit 2. And the outdoor side control part 45 has the microcomputer, memory, etc. which were provided in order to control the outdoor unit 2, and transmits between the indoor side control parts 53a and 53b of indoor unit 5a, 5b. Control signals and the like can be exchanged via the line 8. That is, the indoor side control units 53a and 53b, the outdoor side control unit 45, and the transmission line 8 that connects the control units 45, 53a, and 53b constitute the control unit 9 that controls the operation of the entire air conditioner 1. Yes.

  As shown in FIG. 2, the control unit 9 is connected so as to receive detection signals of various sensors 37 to 44, and based on these detection signals and the like, various devices 21 (specifically, The compressor motors 30), 22, 24, and 32 (specifically, the outdoor fan motor 33), 36, 51a, and 51b are connected so as to be controlled. Here, FIG. 2 is a control block diagram of the air conditioner 1.

<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 an installation location such as a building. In the present embodiment, the liquid refrigerant communication tube 6 is connected to the outdoor unit 2 and the indoor units 5a and 5b, and during cooling operation, the refrigerant cooled in the supercooling heat exchanger 25 is transferred to the indoor heat exchangers 52a and 52b. It is a refrigerant pipe which sends the refrigerant condensed in indoor heat exchangers 52a and 52b to outdoor heat exchanger 23 at the time of heating operation. The gas refrigerant communication pipe 7 is connected to the outdoor unit 2 and the indoor units 5a and 5b. During the cooling operation, the refrigerant evaporated in the indoor heat exchangers 52a and 52b is sent to the compressor 21, and during the heating operation, the compressor 21 is a refrigerant pipe which sends the refrigerant compressed in 21 to indoor heat exchangers 52a and 52b.

  As described above, the indoor-side refrigerant circuits 10a and 10b, the outdoor-side refrigerant circuit 10c, and the refrigerant communication pipes 6 and 7 are connected, so that the outdoor heat exchanger as a heat source-side heat exchanger is used during cooling operation. A refrigerant refrigerant condensed in the outdoor heat exchanger 23 is cooled by a bypass refrigerant pipe 26 that branches a part of the refrigerant condensed in the refrigerant 23 and returns to the suction side of the compressor 21 as a compression mechanism. The refrigerant circuit 10 of the air conditioner 1 having the supercooling heat exchanger 25 is configured. And the air conditioning apparatus 1 of this embodiment controls each apparatus of the outdoor unit 2 and indoor unit 5a, 5b by the control part 9 comprised from the indoor side control parts 53a and 53b and the outdoor side control part 45. FIG. The cooling operation and the heating operation can be performed.

(2) Operation of Air Conditioner Next, the operation (heating operation and cooling operation) of the air conditioner 1 of the present embodiment will be described. In the following description, the outdoor heat exchanger 23 (during cooling operation) functioning as a heat source side heat exchanger functioning as a refrigerant condenser from the discharge of the compressor 21 as a compression mechanism or the indoor side as a utilization side heat exchanger. The representative value of the pressure of the refrigerant flowing until it reaches the outlet of the heat exchangers 52a and 52b (during heating operation) is “high pressure in the refrigeration cycle operation” (hereinafter, simply referred to as “high pressure”). From the outlet of the indoor expansion valves 51a and 51b as a mechanism to the intake of the compressor 21 via the indoor heat exchangers 52a and 52b functioning as refrigerant evaporators (during cooling operation) or the heat source side expansion mechanism The representative value of the pressure of the refrigerant flowing from the outlet of the outdoor expansion valve 24 to the intake of the compressor 21 via the outdoor heat exchanger 23 functioning as a refrigerant evaporator (during cooling operation) is “ Frozen rhino (In the following description, simply referred to as low pressure) low pressure in the Le operation to ".

<Heating operation>
During the heating operation, the four-way switching valve 22 is in the state indicated by the broken line in FIG. 1, that is, the discharge side of the compressor 21 is connected to the indoor heat exchangers 52a and 52b via the gas-side closing valve 29 and the gas refrigerant communication pipe 7. It is connected to the gas side, and the suction side of the compressor 21 is connected to the gas side of the outdoor heat exchanger 23. The degree of opening of the outdoor expansion valve 24 is controlled so that the refrigerant flowing into the outdoor heat exchanger 23 is reduced to a pressure at which the refrigerant can be evaporated in the outdoor heat exchanger 23 (that is, near low pressure). Moreover, the liquid side closing valve 28 and the gas side closing valve 29 are fully opened. The opening degree of each indoor expansion valve 51a, 51b is controlled according to the air conditioning load of the indoor units 5a, 5b as the utilization units. Further, the bypass expansion valve 36 as a bypass expansion mechanism is fully closed, so that heat exchange between refrigerants is not performed in the supercooling heat exchanger 25.

  When the compressor 21, the outdoor fan 32, and the like are activated in such a state of the refrigerant circuit 10, the low-pressure gas refrigerant is sucked into the compressor 21 and compressed to become a high-pressure gas refrigerant, and the four-way switching valve 22 is activated. Then, the gas is sent to the indoor units 5 a and 5 b via the gas-side closing valve 29 and the gas refrigerant communication pipe 7.

  After the high-pressure gas refrigerant sent to the indoor units 5a and 5b is condensed by exchanging heat with indoor air or the like as a cooling medium in the outdoor heat exchangers 52a and 52b. When passing through the indoor expansion valves 51a and 51b, the pressure is reduced according to the opening degree of the indoor expansion valves 51a and 51b.

  The refrigerant that has passed through the indoor expansion valves 51 a and 51 b is sent to the outdoor unit 2 as a heat source unit via the liquid refrigerant communication pipe 6. Then, the refrigerant sent to the outdoor unit 2 is sent to the outdoor expansion valve 24 via the liquid side closing valve 28 and the supercooling heat exchanger 25 and further decompressed, and then flows into the outdoor heat exchanger 23. . The low-pressure gas-liquid two-phase refrigerant that has flowed into the outdoor heat exchanger 23 exchanges heat with outdoor air as a heating medium supplied by the outdoor fan 32 to evaporate into a low-pressure gas refrigerant. It flows into the accumulator 27 via the path switching valve 22. Then, the low-pressure gas refrigerant flowing into the accumulator 27 is again sucked into the compressor 21. Thus, the heating operation as the refrigeration cycle operation in the air-conditioning apparatus 1 of the present embodiment is performed.

<Cooling operation>
During the cooling operation, the four-way switching valve 22 is in the state shown by the solid line in FIG. 1, that is, the discharge side of the compressor 21 is connected to the gas side of the outdoor heat exchanger 23 and the suction side of the compressor 21 is the gas side. The state is connected to the gas side of the indoor heat exchangers 52a and 52b via the closing valve 29 and the gas refrigerant communication pipe 7. The outdoor expansion valve 24 is fully opened or fully closed. The liquid side closing valve 28 and the gas side closing valve 29 are fully opened. The opening degree of each indoor expansion valve 51a, 51b is controlled according to the air conditioning load of the indoor units 5a, 5b. The degree of opening of the bypass expansion valve 36 is controlled so that in the subcooling heat exchanger 25, the refrigerant condensed in the outdoor heat exchanger 23 is cooled by exchanging heat with the refrigerant depressurized in the bypass expansion valve 36. It has become. The details of the control of the bypass expansion valve 36 in this embodiment will be described later.

  When the compressor 21, the outdoor fan 32, and the like are started in the state of the refrigerant circuit 10, the low-pressure gas refrigerant is sucked into the compressor 21 and compressed to become a high-pressure gas refrigerant. Thereafter, the high-pressure gas refrigerant is sent to the outdoor heat exchanger 23 via the four-way switching valve 22, exchanges heat with outdoor air as a cooling medium supplied by the outdoor fan 32, and condenses to high pressure. It becomes a liquid refrigerant. The high-pressure liquid refrigerant is mainly produced by the check valve 31 (that is, both the check valve 31 and the outdoor expansion valve 24 when the outdoor expansion valve 24 is fully opened, or the outdoor expansion valve 24). Passes through the check valve 31 only), flows into the supercooling heat exchanger 25, exchanges heat with the refrigerant flowing through the bypass refrigerant pipe 26, and is further cooled to overheat. It becomes cool. At this time, a part of the high-pressure liquid refrigerant condensed in the outdoor heat exchanger 23 is branched to the bypass refrigerant pipe 26, decompressed by the bypass expansion valve 36, and then returned to the suction side of the compressor 21. Here, a part of the refrigerant passing through the bypass expansion valve 36 evaporates by being depressurized to near low pressure. The refrigerant flowing from the outlet of the bypass expansion valve 36 of the bypass refrigerant pipe 26 toward the suction side of the compressor 21 passes through the supercooling heat exchanger 25 and is condensed in the outdoor heat exchanger 23. And heat exchange.

  The supercooled high-pressure liquid refrigerant is sent to the indoor units 5 a and 5 b via the liquid-side closing valve 28 and the liquid refrigerant communication pipe 6. The high-pressure liquid refrigerant sent to the indoor units 5a and 5b is depressurized to near low pressure by the indoor expansion valves 51a and 51b to become a low-pressure gas-liquid two-phase refrigerant and sent to the indoor heat exchangers 52a and 52b. In the indoor heat exchangers 52a and 52b, heat is exchanged with room air or the like as a heating medium to evaporate into a low-pressure gas refrigerant.

  The low-pressure gas refrigerant is sent to the outdoor unit 2 via the gas refrigerant communication pipe 7 and flows into the accumulator 27 via the gas-side closing valve 29 and the four-way switching valve 22. Then, the low-pressure gas refrigerant flowing into the accumulator 27 is again sucked into the compressor 21. In this way, the cooling operation as the refrigeration cycle operation in the air conditioner 1 of the present embodiment is performed.

  During the cooling operation, the bypass expansion valve 36 provided in the bypass refrigerant pipe 26 is controlled so that the superheat degree SH on the suction side of the compressor 21 becomes constant at the target superheat degree SHs, as in the conventional case. Then, even if surplus refrigerant is generated in the refrigerant circuit 10, it is not possible to positively treat surplus refrigerant, and the condensation capacity in the outdoor heat exchanger 23 varies. For this reason, it is preferable to manage the supercooling degree SC of the refrigerant at the outlet of the supercooling heat exchanger 25 and to secure the refrigerant condensing capacity in the outdoor heat exchanger 23.

  By the way, like the air conditioner 1 of the present embodiment, a bypass refrigerant pipe 26 that branches a part of the refrigerant condensed in the outdoor heat exchanger 23 during the cooling operation and returns the refrigerant to the suction side of the compressor 21, and the bypass refrigerant. In the configuration including the supercooling heat exchanger 25 that cools the refrigerant condensed in the outdoor heat exchanger 23 by the refrigerant flowing through the pipe 26, when excess refrigerant is generated in the refrigerant circuit 10, the refrigerant is discharged from the outlet of the outdoor heat exchanger 23. The degree of supercooling SC of the refrigerant will change. That is, the change in the refrigerant condensing capacity in the outdoor heat exchanger 23 that fluctuates due to the generation of excess refrigerant on the outlet side of the outdoor heat exchanger 23 is mainly due to the change in the degree of refrigerant subcooling SC at the outlet of the outdoor heat exchanger 23. Will appear as. For this reason, in order to ensure the refrigerant | coolant condensing capability in the outdoor heat exchanger 23, what is necessary is just to make the subcooling degree SC of the refrigerant | coolant in the exit of the outdoor heat exchanger 23 appropriate. Moreover, when the refrigerant | coolant condensing capability in the outdoor heat exchanger 23 falls by generation | occurrence | production of the excess refrigerant | coolant in the refrigerant circuit 10, there exists a tendency for the high voltage | pressure in a refrigerating cycle operation to rise.

  Therefore, in the air conditioning apparatus 1 of the present embodiment, as described later, when the high pressure Pd in the cooling operation is equal to or higher than the predetermined pressure Pds during the cooling operation, the outdoor heat exchanger 23 is controlled as the bypass expansion valve 36. The supercooling degree control for controlling the bypass expansion valve 36 which is one of the devices constituting the heat source unit 2 is adopted so that the supercooling degree SC of the refrigerant at the outlet of the refrigerant approaches the target supercooling degree SCs.

<Control including supercooling degree control>
In the present embodiment, the refrigerant supercooling degree SC at the outlet of the outdoor heat exchanger 23 during the cooling operation is the saturation temperature value corresponding to the condensation temperature Tc, which is the discharge pressure Pd of the compressor 21 detected by the discharge pressure sensor 38. And is obtained by subtracting the refrigerant temperature Tco on the outlet side of the outdoor heat exchanger 23 during the cooling operation detected by the liquid side temperature sensor 41 from the condensation temperature Tc (that is, SC = Tc−Tco). . Although not adopted in the present embodiment, when a temperature sensor for detecting the temperature of the refrigerant in the outdoor heat exchanger 23 is provided, the temperature of the refrigerant detected by the temperature sensor is set as the condensation temperature Tc, In the case where a pressure sensor for detecting the pressure of the refrigerant in the heat exchanger 23 is provided, the supercooling degree SC is obtained by converting the refrigerant pressure detected by the pressure sensor into a saturation temperature value corresponding to the condensation temperature Tc. It may be.

  Further, in the present embodiment, the degree of superheat SH of the refrigerant at the outlet on the bypass refrigerant pipe 26 side of the supercooling heat exchanger 25 corresponds to the suction pressure Ps of the compressor 21 detected by the suction pressure sensor 37 corresponding to the evaporation temperature Te. It is obtained by subtracting the evaporation temperature Te from the refrigerant temperature Tsh detected by the bypass temperature sensor 43 (ie, SH = Tsh−Te). Although not adopted in this modification, a temperature sensor is provided at the inlet of the bypass refrigerant pipe 26 side of the supercooling heat exchanger 25, and the temperature of the refrigerant detected by this temperature sensor is set as the evaporation temperature Te. When a pressure sensor for detecting the refrigerant pressure in the supercooling heat exchanger 25 is provided, the refrigerant pressure detected by the pressure sensor is converted into a saturation temperature value corresponding to the evaporation temperature Te to obtain the superheat degree SH. You may do it.

  And control including the supercooling degree control concerning this embodiment is performed according to the flowchart shown in FIG.

  First, in step S1, the target supercooling degree SCs and the target superheat degree SHs are set, and the supercooling degree SC and the superheat degree SH are acquired.

  Next, in step S2, it is determined whether the high pressure Pd is equal to or higher than a predetermined pressure Pds.

  If it is determined in step S2 that the high pressure Pd is equal to or higher than the predetermined pressure, the process proceeds to the supercooling degree control process in step S3. In this supercooling degree control, the bypass expansion valve 36 is controlled so that this supercooling degree SC approaches the target supercooling degree SCs. Specifically, when the degree of supercooling SC is smaller than the target degree of supercooling SCs, the bypass expansion valve 36 is controlled in a direction in which the opening degree of the bypass expansion valve 36 becomes smaller, so that the inside of the outdoor heat exchanger 23 is increased. When the amount of liquid refrigerant accumulated in the refrigerant is increased so that the refrigerant subcooling degree SC at the outlet of the outdoor heat exchanger 23 approaches the target subcooling degree SCs, the supercooling degree SC is larger than the target subcooling degree SCs. In other words, by controlling the bypass expansion valve 36 in the direction in which the opening degree of the bypass expansion valve 36 increases, the amount of liquid refrigerant that accumulates in the outdoor heat exchanger 23 is reduced, and at the outlet of the outdoor heat exchanger 23. The supercooling degree SC of the refrigerant is brought close to the target supercooling degree SCs. If it is determined in step S2 that the high pressure Pd is not equal to or higher than the predetermined pressure Pds (that is, the high pressure Pd is less than the predetermined pressure), the process proceeds to the superheat degree control process in step S4. In this superheat degree control, the bypass expansion valve 36 is controlled so that the superheat degree SH approaches the target superheat degree SHs. Specifically, when the superheat degree SH is smaller than the target superheat degree SHs, the bypass expansion valve 36 is controlled in a direction in which the opening degree of the bypass expansion valve 36 is reduced, so that the refrigerant flowing through the bypass refrigerant pipe 26 is controlled. The degree of superheat at the outlet on the bypass refrigerant pipe 26 side of the supercooling heat exchanger 25 is set so that the flow rate is reduced and the temperature of the refrigerant at the outlet on the bypass refrigerant pipe 26 side of the supercooling heat exchanger 25 is increased. By making SH close to the target superheat degree SHs, and when the superheat degree SH is larger than the target superheat degree SHs, the bypass expansion valve 36 is controlled in the direction in which the opening degree of the bypass expansion valve 36 is increased, thereby bypass refrigerant. The supercooling is performed by increasing the flow rate of the refrigerant flowing through the pipe 26 so that the temperature of the refrigerant at the outlet on the bypass refrigerant pipe 26 side of the supercooling heat exchanger 25 is lowered. The degree of superheating SH at the outlet of the bypass refrigerant pipe 26 side of the exchanger 25 to be close to the target degree of superheat SHs.

  And after the process of step S3, S4 is performed, it returns to the process of step S1 again, and the determination in step S2 and the supercooling degree control in step S3 or the superheat degree control in step S4 are performed repeatedly.

  Thus, in the air conditioning apparatus 1 of the present embodiment, when the high pressure Pd is equal to or higher than the predetermined pressure Pds in step S2, the degree of supercooling is controlled in step S3, and in step S2, the high pressure Pd is set to the predetermined pressure. When it is less than Pds, the degree of superheat control in step S4 is performed, so in the supercooling heat exchanger 25, the refrigerant sent to the indoor heat exchangers 51a and 51b by the refrigerant flowing through the bypass refrigerant pipe 26. While controlling the supercooling degree SC of the refrigerant at the outlet of the supercooling heat exchanger 25 (that is, the refrigerant sent from the supercooling heat exchanger 25 to the indoor heat exchangers 51a and 51b), The refrigerant condensing capacity in the heat exchanger 23 can be ensured.

(3) Modification 1
In the air conditioner 1 of the above-described embodiment, the condensation capacity in the outdoor heat exchanger 23 as the heat source side heat exchanger changes depending on the temperature difference between the refrigerant and the outdoor air as the cooling medium. If they are different, the value of the target supercooling degree SCs of the refrigerant at the outlet of the outdoor heat exchanger 23 is also different.

  Therefore, in the air conditioner 1 of this modification, the target supercooling degree SCs is changed according to the temperature of the outdoor air. Specifically, the target supercooling degree SCs is changed so as to decrease as the outdoor air temperature Ta detected by the outdoor temperature sensor 44 increases. Although not adopted in this modification, a sensor other than the outdoor temperature sensor 44 such as a temperature detected by a temperature sensor provided for protection of a control board constituting the outdoor control unit 45 or the like. If the state quantity equivalent to the temperature of the outdoor air as the cooling medium can be used, the target supercooling degree SCs may be changed in accordance with such a state quantity.

  Thereby, in the air conditioning apparatus 1 of this modification, appropriate control can be performed in consideration of the change of the condensation capacity in the outdoor heat exchanger 23 due to the temperature of the outdoor air.

(4) Modification 2
In the case where the high pressure Pd is equal to or higher than the predetermined pressure Pds as in the air conditioner 1 of the above-described embodiment and modification 1, when only the supercooling degree control is employed, the bypass of the supercooling heat exchanger 25 is performed. Since the degree of superheat SH of the refrigerant at the outlet on the refrigerant pipe 26 side becomes a matter of course, the refrigerant at the outlet on the bypass refrigerant pipe 26 side of the supercooling heat exchanger 25 becomes wet (that is, the degree of superheat SH is zero). Or the refrigerant at the outlet of the supercooling heat exchanger 25 on the bypass refrigerant pipe 26 side may be excessively heated.

  Therefore, in the air conditioner 1 of the present modification, the bypass refrigerant pipe 26 of the supercooling heat exchanger 25 is used not only when the high pressure Pd is equal to or lower than the predetermined pressure Pds but also when the high pressure Pd is equal to or higher than the predetermined pressure Pds. The superheat degree control for controlling the bypass expansion valve 36 as a bypass expansion mechanism can be performed so that the superheat degree SH of the refrigerant at the outlet on the side approaches the target superheat degree SHs, and the target supercool degree SCs is subtracted from the supercool degree SC. The degree of supercooling-superheating that performs either the supercooling degree control or the superheat degree control based on the superheat degree deviation ΔSH obtained by subtracting the target superheat degree SHs from the supercooling degree deviation ΔSC and superheat degree SH obtained by Degree establishment control is performed.

  And control including the supercooling degree-superheat degree establishment control concerning this modification is performed according to the flowchart shown in FIG.

  First, in step S11, the target supercooling degree SCs and the target superheat degree SHs are set, and the supercooling degree SC and the superheat degree SH are acquired. Here, the target degree of supercooling SCs may be changed according to the temperature of the outdoor air as the cooling medium or the state quantity equivalent to the temperature of the outdoor air, as in the first modification.

  Next, in step S12, it is determined whether the high pressure Pd is equal to or higher than a predetermined pressure Pds.

  If it is determined in step S12 that the high pressure Pd is equal to or higher than the predetermined pressure, the process proceeds to the supercooling degree-superheat degree establishment control process in steps S13 to S15. In step S12, the high pressure Pd is set to the predetermined pressure. When it is determined that the pressure is not equal to or greater than Pds (that is, the high pressure Pd is less than the predetermined pressure), the process proceeds to the superheat degree control process of step S16, and the bypass is performed so that the superheat degree SH approaches the target superheat degree SHs. The expansion valve 36 is controlled. The superheat degree control process in step S16 is the same as the control step S4 including the supercooling degree control in the above-described embodiment, and thus detailed description thereof is omitted here.

  Next, in step S13, the supercooling degree deviation ΔSC is calculated from the supercooling degree SC and the target supercooling degree SCs, the superheating degree deviation ΔSH is calculated from the superheating degree SH and the target superheating degree SHs, and the supercooling degree deviation ΔSC is calculated. Is determined to be larger than the superheat degree deviation ΔSH. This determination is made based on the idea that the supercooling degree deviation ΔSC and the superheating degree deviation ΔSH should be compared and the side with the larger deviation should be preferentially controlled.

  In step S13, when it is determined that the supercooling degree deviation ΔSC is larger than the superheating degree deviation ΔSH, the process proceeds to the supercooling degree control process in step S3, and the supercooling is performed as in the above-described embodiment. The bypass expansion valve 36 is controlled so that the degree SC approaches the target supercooling degree SCs. If it is determined in step S13 that the supercooling degree deviation ΔSC is not larger than the superheating degree deviation ΔSH, the process proceeds to the superheat degree control process in step S15, and the superheat degree SH is set to the target superheat degree SHs. The bypass expansion valve 36 is controlled so as to approach. The superheat degree control process in step S16 is the same as the control step S4 including the supercooling degree control in the above-described embodiment, and thus detailed description thereof is omitted here.

  And after the process of step S14, S15 is performed, it returns to the process of step S11 again, the determination in step S12, the superheat degree control in step S16, the determination in step S13, and the supercooling degree control in step S14 Or the superheat degree control in step S15 is performed repeatedly.

  As described above, in the air conditioner 1 of this modification, when it is determined that the high pressure Pd is equal to or higher than the predetermined pressure, the supercooling degree is not simply controlled, but the supercooling is performed in steps S13 to S15. The degree of deviation ΔSC is compared with the degree of superheat deviation ΔSH so that the control with the larger deviation is preferentially performed. Therefore, the refrigerant supercooling degree SC and the supercooling heat exchanger at the outlet of the outdoor heat exchanger 23 are controlled. For any of the refrigerant superheat degrees SH at the outlet of the 25 bypass refrigerant pipes 26 side, it can be avoided that the deviation from the respective target values SCs and SHs becomes large.

  Thereby, in the air conditioner 1 of this modification, even when it is determined that the high pressure Pd is equal to or higher than the predetermined pressure, the supercooling heat exchanger 25 is bypassed by properly using the supercooling degree control and the superheat degree control. The superheat degree SH of the refrigerant at the outlet on the refrigerant pipe 26 side approaches the target superheat degree SHs, and the supercool degree SC of the refrigerant at the outlet of the outdoor heat exchanger 23 approaches the target supercool degree SCs. it can.

(5) Modification 3
In the case where it is determined that the high pressure Pd is equal to or higher than the predetermined pressure as in the above-described embodiment and the air conditioners 1 of the first and second modifications, only the supercooling degree control or the supercooling degree-superheat degree establishment control is performed. When it is determined that the high pressure Pd is not equal to or higher than the predetermined pressure, when only the superheat control is employed, the refrigerant at the outlet of the supercooling heat exchanger 25 (that is, from the supercooling heat exchanger 25). Since the temperature Tlp of the refrigerant sent to the indoor heat exchangers 52a and 52b becomes an event, the liquid pipe temperature Tlp at the outlet of the supercooling heat exchanger 25 may be excessively low.

  Therefore, in the air conditioner 1 of the present modification, the bypass expansion valve 36 as a bypass expansion mechanism is controlled so that the liquid pipe temperature Tlp at the outlet of the supercooling heat exchanger 25 does not decrease to a predetermined minimum liquid pipe temperature Tlpm. When the liquid pipe temperature control can be performed and used together with the supercooling degree control, the supercooling degree deviation ΔSC obtained by subtracting the target supercooling degree SCs from the supercooling degree SC and the outlet of the supercooling heat exchanger 25. The subcooling degree-liquid pipe temperature establishment control for performing either the supercooling degree control or the liquid pipe temperature control based on the liquid pipe temperature deviation ΔTlp obtained by subtracting the minimum liquid pipe temperature Tlpm from the liquid pipe temperature Tlp in FIG. In the case where it is performed or used together with the supercooling degree-superheat degree establishment control, the supercooling obtained by subtracting the target supercooling degree SCs from the supercooling degree SC. The liquid pipe obtained by subtracting the minimum liquid pipe temperature Tlpm from the superheat degree deviation ΔSH obtained by subtracting the target superheat degree SHs from the degree deviation ΔSC and superheat degree SH and the liquid pipe temperature Tlp at the outlet of the supercooling heat exchanger 25. When performing supercooling degree-superheat degree-liquid pipe temperature establishment control for performing any of supercooling degree control, superheat degree control, and liquid pipe temperature control based on the temperature deviation ΔTlp, or in combination with superheat degree control Includes a superheat degree deviation ΔSH obtained by subtracting the target superheat degree SHs from the superheat degree SH and a liquid pipe temperature obtained by subtracting the minimum liquid pipe temperature Tlpm from the liquid pipe temperature Tlp at the outlet of the supercooling heat exchanger 25. Based on the deviation ΔTlp, superheat degree-liquid pipe temperature establishment control for performing either superheat degree control or liquid pipe temperature control is performed.

  In this modification, the liquid pipe temperature Tlp at the outlet of the supercooling heat exchanger 25 is detected by the liquid pipe temperature sensor 42. Further, the degree of supercooling SC and the degree of superheating SH can be obtained in the same manner as in the above-described embodiment and Modification 2.

  For example, the control including the supercooling degree-superheat degree-liquid pipe temperature establishment control and the superheat degree-liquid pipe temperature establishment control according to the present modification is performed according to the flowchart shown in FIG.

  First, in step S21, the target supercooling degree SCs, the target superheat degree SHs, and the minimum liquid pipe temperature Tlpm are set, and the supercooling degree SC, the superheat degree SH, and the liquid pipe temperature Tlp are acquired. Here, the target degree of supercooling SCs may be changed according to the temperature of the outdoor air as the cooling medium or the state quantity equivalent to the temperature of the outdoor air, as in the first modification.

  Next, in step S22, it is determined whether the high pressure Pd is equal to or higher than the predetermined pressure Pds.

  If it is determined in step S22 that the high pressure Pd is equal to or higher than the predetermined pressure, the process proceeds to the supercooling degree-superheat degree-liquid pipe temperature establishment control process in steps S23 to S25. When it is determined that Pd is not equal to or higher than the predetermined pressure Pds (that is, the high pressure Pd is lower than the predetermined pressure), the process proceeds to the superheat degree-liquid pipe temperature establishment control process in steps S26 to S28.

  Next, in step S23, the supercooling degree deviation ΔSC is calculated from the supercooling degree SC and the target supercooling degree SCs, the superheating degree deviation ΔSH is calculated from the superheating degree SH and the target superheating degree SHs, and the liquid pipe temperature Tlp and the lowest The liquid pipe temperature deviation ΔTlp is calculated from the liquid pipe temperature Tlpm to determine whether the liquid pipe temperature deviation ΔTlp is smaller than the larger one of the supercooling degree deviation ΔSC and the superheat degree deviation ΔSH. This determination is made even when the supercooling degree deviation ΔSC or the superheating degree deviation ΔSH occurs, but when the liquid pipe temperature deviation ΔTlp is very small, the liquid at the outlet of the supercooling heat exchanger 25 This is based on the idea that the tube temperature Tlp should be controlled so as not to decrease to the minimum liquid tube temperature Tlpm.

  If it is determined in step S23 that the liquid pipe temperature deviation ΔTlp is smaller than either the supercooling degree deviation ΔSC or the superheat degree deviation ΔSH, the process proceeds to the liquid pipe temperature control process in step S24. Thus, the bypass expansion valve 36 is controlled so that the liquid pipe temperature Tlp at the outlet of the supercooling heat exchanger 25 does not drop to the lowest liquid pipe temperature Tlpm. Specifically, by controlling the bypass expansion valve 36 in a direction in which the opening degree of the bypass expansion valve 36 is reduced, the flow rate of the refrigerant flowing through the bypass refrigerant pipe 26 is reduced, so that the supercooling heat exchanger 25 The liquid pipe temperature Tlp at the outlet is not lowered below the minimum liquid pipe temperature Tlpm. If it is determined in step S23 that the liquid pipe temperature deviation ΔTlp is not smaller than the larger one of the supercooling degree deviation ΔSC and the superheating degree deviation ΔSH, the supercooling degree-superheat degree establishment control in step S25 is performed. The bypass expansion valve 36 is controlled so that the superheat degree SH approaches the target superheat degree SHs so that the supercool degree SC approaches the target supercool degree SCs. Specifically, the same processing as Steps S13 to S15 in Modification 2 is performed.

  On the other hand, in step S26, the superheat degree deviation ΔSH is calculated from the superheat degree SH and the target superheat degree SHs, the liquid pipe temperature deviation ΔTlp is calculated from the liquid pipe temperature Tlp and the minimum liquid pipe temperature Tlpm, and the liquid pipe temperature deviation ΔTlp. Is determined to be smaller than the superheat degree deviation ΔSH. This determination is made even when the superheat degree deviation ΔSH occurs, but when the liquid pipe temperature deviation ΔTlp is very small, the liquid pipe temperature Tlp at the outlet of the supercooling heat exchanger 25 is the lowest liquid. This is based on the idea that the temperature should be controlled so as not to decrease to the tube temperature Tlpm.

  In step S26, when it is determined that the liquid pipe temperature deviation ΔTlp is smaller than the superheat degree deviation ΔSH, the process proceeds to the liquid pipe temperature control process in step S27, and at the outlet of the supercooling heat exchanger 25. The bypass expansion valve 36 is controlled so that the liquid pipe temperature Tlp does not fall to the minimum liquid pipe temperature Tlpm. The liquid pipe temperature control process in step S27 is the same as that in step S24 described above, and a detailed description thereof is omitted here. When it is determined in step S26 that the liquid pipe temperature deviation ΔTlp is not smaller than the superheat degree deviation ΔSH, the process proceeds to the superheat degree control process in step S28, and the superheat degree SH is changed to the target superheat degree SHs. The bypass expansion valve 36 is controlled so as to approach. Since the superheat degree control process in step S28 is the same as step S4 in the above-described embodiment and step S16 in the above-described modified example 2, detailed description thereof is omitted here.

  And after the process of step S23-S28 is performed, it returns to the process of step S21 again, the determination in step S22, and the supercooling degree-superheat degree-liquid pipe temperature establishment control or step in step S23-S25 or step The superheat degree-liquid pipe temperature establishment control in S26 to S28 is repeatedly performed.

  As described above, in the air conditioner 1 of the present modification, when it is determined that the high pressure Pd is equal to or higher than the predetermined pressure, in step S23, the supercooling degree deviation ΔSC or the superheat degree deviation ΔSH occurs. Even if the liquid pipe temperature deviation ΔTlp is very small (here, the liquid pipe temperature deviation ΔTlp is smaller than the larger one of the supercooling degree deviation ΔSC and the superheat degree deviation ΔSH), When the liquid pipe temperature is controlled so that the liquid pipe temperature Tlp at the outlet of the supercooling heat exchanger 25 does not become too low, and the liquid pipe temperature deviation ΔTlp is not very small (here, the liquid pipe temperature deviation) When ΔTlp is not smaller than the larger one of the supercooling degree deviation ΔSC and the superheating degree deviation ΔSH), in step S25, the supercooling degree-superheat degree establishment control is performed, and the high pressure If it is determined that d is not equal to or higher than the predetermined pressure, even if the superheat degree deviation ΔSH has occurred in step S26, the liquid pipe temperature deviation ΔTlp is very small (here, the liquid temperature When the pipe temperature deviation ΔTlp is smaller than the superheat degree deviation ΔSH), the liquid pipe temperature control is performed so that the liquid pipe temperature Tlp at the outlet of the supercooling heat exchanger 25 does not become too low. When ΔTlp is not very small (here, when the liquid pipe temperature deviation ΔTlp is not smaller than the superheat degree deviation ΔSH), the superheat control is performed in step S28. The liquid pipe temperature Tlp at the outlet of the exchanger 25 can be prevented from becoming too low.

  When it is determined that the high pressure Pd is equal to or higher than the predetermined pressure, as described above, the liquid tube temperature control is not used in combination with the supercooling degree-superheat degree establishment control, but the liquid pipe temperature control is performed. When used together with the control, the comparison between the liquid pipe temperature deviation ΔTlp and the superheat degree deviation ΔSH is omitted in step S23, and in step S25, the supercooling degree control is adopted instead of the supercooling degree-superheat degree establishment control. Thus, the degree of supercooling-liquid pipe temperature establishment control can be performed.

  Thereby, in the air conditioning apparatus 1 of this modification, when it is determined that the high pressure Pd is equal to or higher than the predetermined pressure, the liquid pipe temperature control and the supercooling degree control are selectively used, and the supercooling heat exchanger 25 While preventing the liquid pipe temperature Tlp at the outlet from becoming excessively low, the supercooling degree SC of the refrigerant at the outlet of the outdoor heat exchanger 23 can be made closer to the target supercooling degree SCs. By bypassing the temperature control and the supercooling degree-superheat degree establishment control, the liquid refrigerant temperature Tlp at the outlet of the supercooling heat exchanger 25 is not excessively lowered, and the bypass refrigerant pipe of the supercooling heat exchanger 25 is used. While the superheat degree SH of the refrigerant at the outlet on the 26th side approaches the target superheat degree SHs, the subcool degree SC of the refrigerant at the outlet of the outdoor heat exchanger 23 approaches the target supercool degree SCs. In addition, when it is determined that the high pressure Pd is not equal to or higher than the predetermined pressure, the liquid pipe temperature Tlp at the outlet of the supercooling heat exchanger 25 is excessively low by properly using the liquid pipe temperature control and the superheat degree control. While avoiding the state, the superheat degree SH of the refrigerant at the outlet on the bypass refrigerant pipe 26 side of the supercooling heat exchanger 25 can be made to approach the target superheat degree SHs.

(6) Modification 4
In the air conditioner 1 of the above-described embodiment and Modifications 1 to 3, overheat compression in which the discharge temperature Td of the compressor 21 as the compression mechanism becomes very high, and the saturation temperature at which the discharge temperature Td corresponds to the discharge pressure Pd. There is a possibility that wet compression that decreases to near may occur, and it is necessary to protect the compressor 21 from such overheat compression or wet compression. And a part of the refrigerant | coolant condensed in the outdoor heat exchanger 23 as a heat source side heat exchanger like the air conditioning apparatus 1 of the above-mentioned embodiment and the modifications 1-3 is branched, and it is made into the suction side of the compressor 21. In the configuration having the bypass refrigerant pipe 26 to be returned and the supercooling heat exchanger 25 that cools the refrigerant condensed in the outdoor heat exchanger 23 by the refrigerant flowing through the bypass refrigerant pipe 26, the flow rate of the refrigerant flowing through the bypass refrigerant pipe 26 is By controlling, it is possible to adjust the temperature of the refrigerant sucked into the compressor 21.

  Therefore, in this modification, the supercooling degree control, superheat degree control, supercooling degree—liquid pipe temperature establishment control, superheat degree—liquid pipe temperature establishment control, supercooling degree— In addition to the superheat degree establishment control or the supercooling degree-superheat degree-liquid pipe temperature establishment control, the bypass expansion valve 36 as a bypass expansion mechanism so that the discharge temperature Td of the compressor 21 does not become higher than the predetermined maximum discharge temperature Tdm. And / or bypass so that the discharge superheat degree SHd obtained by subtracting the saturation temperature corresponding to the discharge pressure Pd from the discharge temperature Td of the compressor 21 does not fall below the predetermined minimum discharge superheat degree SHdm. Wet compression prevention control for controlling the expansion valve 36 is performed.

  In this modification, the discharge temperature Td and the discharge pressure Pd of the compressor 21 are detected by the discharge temperature sensor 40 and the discharge pressure sensor 38, respectively. Further, the discharge superheat degree SHd of the refrigerant in the discharge of the compressor 21 is obtained by converting the discharge pressure Pd of the compressor 21 detected by the discharge pressure sensor 38 into a saturation temperature value corresponding to the condensation temperature Tc, and by the discharge temperature sensor 40. It is obtained by subtracting this Tc from the detected discharge temperature Td (ie, SHd = Td−Tc). Furthermore, the degree of supercooling SC, the degree of superheating SH, and the liquid pipe temperature Tlp can be obtained in the same manner as in the above-described embodiment and Modifications 2 and 3.

  And here, when the high pressure Pd in the cooling operation is equal to or higher than the predetermined pressure Pds, the supercooling degree-superheat degree-liquid pipe temperature establishment control is taken as an example of the control including the supercooling degree control. Degree-superheat degree-liquid pipe temperature-superheat compression prevention-wet compression prevention establishment control is performed, and when the high pressure Pd in the cooling operation is less than the predetermined pressure Pds, supercooling degree control centering on superheat degree control is included. An example of performing superheat degree-liquid pipe temperature-overheat compression prevention establishment control as an example of control without superheat degree-liquid pipe temperature establishment control will be described with reference to the flowchart shown in FIG.

  First, in step S31, the target supercooling degree SCs, the target superheat degree SHs, the minimum liquid pipe temperature Tlpm, the maximum discharge temperature Tdm, and the minimum discharge superheat degree SHdm are set, and the supercooling degree SC, the superheat degree SH, and the liquid pipe temperature are set. Tlp, discharge temperature Td, and discharge superheat degree SHd are acquired. Here, the target degree of supercooling SCs may be changed according to the temperature of the outdoor air as the cooling medium or the state quantity equivalent to the temperature of the outdoor air, as in the first modification.

  Next, in step S32, it is determined whether the high pressure Pd is equal to or higher than a predetermined pressure Pds.

  If it is determined in step S32 that the high pressure Pd is equal to or higher than the predetermined pressure, the supercooling degree-superheat degree-liquid pipe temperature-overheat compression prevention-wet compression prevention establishment control processing in steps S33 to S37 is performed. In step S32, when it is determined that the high pressure Pd is not equal to or higher than the predetermined pressure Pds (that is, the high pressure Pd is less than the predetermined pressure), the degree of superheat-liquid pipe temperature-overheat compression prevention in steps S38 to S40. The process proceeds to establishment control processing.

  Next, in step S33, the supercooling degree deviation ΔSC is calculated from the supercooling degree SC and the target supercooling degree SCs, the superheating degree deviation ΔSH is calculated from the superheating degree SH and the target superheating degree SHs, and the liquid pipe temperature Tlp and the lowest The liquid pipe temperature deviation ΔTlp is calculated from the liquid pipe temperature Tlpm, the discharge temperature deviation ΔTd is calculated by subtracting the discharge temperature Td from the maximum discharge temperature Tdm, and the discharge superheat is calculated by subtracting the minimum discharge superheat degree SHdm from the discharge superheat degree SHd. The degree deviation ΔSHd is calculated, and first, the liquid pipe temperature deviation ΔTlp is compared with the supercooling degree deviation ΔSC or the superheat degree deviation ΔSH, whichever is larger, and the smaller is determined by this determination. Is compared with the discharge temperature deviation ΔTd to determine which is larger, and further, this determination It is determined whether the discharge superheat error ΔSHd is less than the determined deviation with. A series of these determinations is performed even when the supercooling degree deviation ΔSC and the superheat degree deviation ΔSH are generated or when the liquid pipe temperature deviation ΔTlp is very small, the discharge superheat degree deviation ΔSHd is very small. In such a case, wet compression may occur in the compressor 21, and this is performed based on the idea that the compressor 21 should be protected from such wet compression.

  When it is determined in step S33 that the discharge superheat degree deviation ΔSHd is small, the process proceeds to the wet compression prevention control process in step S34, and the refrigerant discharge superheat degree SHd in the discharge of the compressor 21 is the lowest discharge. The bypass expansion valve 36 is controlled so as not to decrease to the degree of superheat SHdm. Specifically, by controlling the bypass expansion valve 36 in a direction in which the opening degree of the bypass expansion valve 36 is reduced, the flow rate of the refrigerant flowing through the bypass refrigerant pipe 26 is reduced, so that the supercooling heat exchanger 25 The refrigerant discharge superheat degree SHd at the discharge of the compressor 21 is set to the lowest discharge superheat degree SHdm so that the refrigerant temperature at the outlet on the bypass refrigerant pipe 26 side is increased and the suction temperature Ts of the compressor 21 is increased. To prevent it from dropping. If it is determined in step S33 that the discharge superheat degree deviation ΔSHd is not small, the process proceeds to step S35.

  Next, in step S35, first, the liquid pipe temperature deviation ΔTlp is compared with the supercooling degree deviation ΔSC and the superheating degree deviation ΔSH to determine which is smaller, and the smaller is determined by this determination. And the discharge temperature deviation ΔTd are compared to determine which is larger. In these series of determinations, the discharge temperature deviation ΔTd becomes very large even when the supercooling degree deviation ΔSC and the superheat degree deviation ΔSH are generated or the liquid pipe temperature deviation ΔTlp is very small. In such a case, there is a possibility that overheat compression may occur in the compressor 21, and this is performed based on the idea that the compressor 21 should be protected from such overheat compression.

  If it is determined in step S35 that the discharge temperature deviation ΔTd is large, the process proceeds to the overheat compression prevention control process in step S36 so that the discharge temperature Td of the compressor 21 does not increase to the maximum discharge temperature Tdm. The bypass expansion valve 36 is controlled at the same time. Specifically, by controlling the bypass expansion valve 36 in the direction in which the opening of the bypass expansion valve 36 is increased, the flow rate of the refrigerant flowing through the bypass refrigerant pipe 26 is increased, so that the supercooling heat exchanger 25 The refrigerant temperature at the outlet on the bypass refrigerant pipe 26 side is lowered so that the suction temperature Ts of the compressor 21 is lowered so that the discharge temperature Td of the compressor 21 does not become higher than the maximum discharge temperature Tdm. To do. If it is determined in step S35 that the discharge temperature deviation ΔTd is not large, the process proceeds to the process of subcooling degree-superheat degree-liquid pipe temperature establishment control in step S26, and the supercooling heat exchanger 25 While preventing the liquid pipe temperature Tlp at the outlet from becoming excessively low, the degree of superheat SH of the refrigerant at the outlet on the bypass refrigerant pipe 26 side of the supercooling heat exchanger 25 is made close to the target superheat degree SHs, while the outdoor heat The bypass expansion valve 36 is controlled such that the refrigerant supercooling degree SC at the outlet of the exchanger 23 approaches the target supercooling degree SCs. Specifically, the same processing as Steps S23 to S25 in Modification 3 is performed.

  On the other hand, in step S38, the superheat degree deviation ΔSH is calculated from the superheat degree SH and the target superheat degree SHs, the liquid pipe temperature deviation ΔTlp is calculated from the liquid pipe temperature Tlp and the minimum liquid pipe temperature Tlpm, and the discharge is performed from the maximum discharge temperature Tdm. The discharge temperature deviation ΔTd is calculated by subtracting the temperature Td, and first, the liquid pipe temperature deviation ΔTlp is compared with the superheat degree deviation ΔSH to determine which is smaller, and this determination determines that the temperature is small. It is determined whether the discharge temperature deviation ΔTd is larger than the deviation. In a series of these determinations, the discharge temperature deviation ΔTd becomes very large even when the superheat degree deviation ΔSH occurs or the liquid pipe temperature deviation ΔTlp is very small, as in step S35. If it is, there is a possibility that overheat compression may occur in the compressor 21, and this is performed based on the idea that the compressor 21 should be protected from such overheat compression.

  If it is determined in step S38 that the discharge temperature deviation ΔTd is large, the process proceeds to the overheat compression prevention control process in step S39 so that the discharge temperature Td of the compressor 21 does not increase to the maximum discharge temperature Tdm. The bypass expansion valve 36 is controlled at the same time. Specifically, the same processing as in step S36 described above is performed. If it is determined in step S38 that the discharge temperature deviation ΔTd is not large, the process proceeds to the superheat degree-liquid pipe temperature establishment control process in step S40, and the liquid pipe at the outlet of the supercooling heat exchanger 25 is transferred. The bypass expansion valve 36 is controlled so that the superheat degree SH of the refrigerant at the outlet of the supercooling heat exchanger 25 on the bypass refrigerant pipe 26 side approaches the target superheat degree SHs while preventing the temperature Tlp from becoming too low. . Specifically, the same processing as Steps S26 to S28 in Modification 3 is performed.

  And after the process of step S34, S36, S37, S39, S40 is performed, it returns to the process of step S31 again, the determination in step S32, S33, S35, S38, and the wet compression prevention control in step S34 The superheat compression prevention control in step S36, the supercooling degree-superheat degree-liquid pipe temperature establishment control in step S37, the superheat compression prevention control in step S9, or the superheat degree-liquid pipe temperature establishment control in step S40 are repeatedly performed.

  As described above, in the air conditioner 1 of the present modified example, when the high pressure Pd is equal to or higher than the predetermined pressure Pds, the supercooling degree deviation ΔSC and the superheat degree deviation ΔSH are generated in steps S33 and S34, or the liquid Even when the pipe temperature deviation ΔTlp is very small, the discharge superheat degree deviation ΔSHd is very small (here, the discharge superheat degree deviation ΔSHd is small in the series of determinations in step S33). ) Performs wet compression prevention control so that the refrigerant discharge superheat degree SHd in the discharge of the compressor 21 does not decrease to the minimum discharge superheat degree SHdm. In steps S35 and S36, the supercooling degree deviation ΔSC and the superheat degree deviation ΔSH are performed. Even when the liquid pipe temperature deviation ΔTlp is very small, the discharge temperature deviation ΔTd is very large. If the discharge temperature deviation ΔTd is large in the series of determinations in step S35, overheat compression prevention control is performed so that the discharge temperature Td of the compressor 21 does not rise to the maximum discharge temperature Tdm. When the discharge temperature deviation ΔTd is not very large (here, when the discharge temperature deviation ΔTd is small in the series of determinations in step S35), in step S37, the degree of supercooling-superheat-liquid pipe temperature is established. Since the control is performed, the outlet of the outdoor heat exchanger 23 is protected while the compressor 21 is protected and the liquid pipe temperature Tlp at the outlet of the supercooling heat exchanger 25 is not excessively lowered. The refrigerant supercooling degree SC and the refrigerant superheating degree SH at the outlet of the supercooling heat exchanger 25 on the bypass refrigerant pipe 26 side However, it is possible to avoid a state where the deviation from the target values SCs and SHs is large, and when the high pressure Pd is not equal to or higher than the predetermined pressure Pds, a superheat degree deviation ΔSH occurs in steps S38 and S39. Even when the liquid pipe temperature deviation ΔTlp is very small, the discharge temperature deviation ΔTd is very large (here, the discharge temperature deviation ΔTd in the series of determinations in step S38). If the discharge temperature deviation ΔTd is not very large (here, in step S38), the overheat compression prevention control is performed so that the discharge temperature Td of the compressor 21 does not rise to the maximum discharge temperature Tdm. In a series of determinations, when the discharge temperature deviation ΔTd is small), in step S40, the superheat-liquid pipe temperature establishment control Since the compressor 21 is protected and the liquid pipe temperature Tlp at the outlet of the supercooling heat exchanger 25 is not excessively lowered, the bypass of the supercooling heat exchanger 25 is performed. It can be avoided that the degree of superheat SH of the refrigerant at the outlet on the refrigerant pipe 26 side has a large deviation from the target value SHs.

  It should be noted that the wet compression prevention control and the superheat compression prevention control are not used together with the supercooling degree-superheat degree-liquid tube temperature establishment control, but the wet compression prevention control and the superheat compression prevention control are established. When used together with the control, the comparison between the liquid pipe temperature deviation ΔTlp, the supercooling degree deviation ΔSC, and the superheat degree deviation ΔSH is omitted in steps S33 and S35, and the supercooling degree—superheat degree—liquid pipe in step S37. By adopting supercooling degree-superheat degree establishment control instead of temperature establishment control, supercooling degree-superheat degree-overheat compression prevention-wet compression prevention establishment control can be performed. In addition, the above-described wet compression prevention control and overheat compression prevention control are not used in combination with the supercooling degree-superheat degree-liquid pipe temperature establishment control, but the wet compression prevention control and overheat compression prevention control are used with the supercooling degree-liquid pipe temperature. When used together with the establishment control, the comparison between the liquid pipe temperature deviation ΔTlp and the superheat degree deviation ΔSH is omitted in steps S33 and S35, and the supercooling degree−superheat degree−liquid pipe temperature establishment control is replaced in step S37. By adopting the supercooling degree-liquid pipe temperature establishment control, the supercooling degree-liquid pipe temperature-overheat compression prevention-wet compression prevention establishment control can be performed. In addition, the above-described wet compression prevention control and overheat compression prevention control are not used together with the supercooling degree-superheat degree-liquid tube temperature establishment control, but the wet compression prevention control and overheat compression prevention control are used together with the supercooling degree control. In this case, in steps S33 and S35, the comparison between the liquid pipe temperature deviation ΔTlp, the supercooling degree deviation ΔSC, and the superheat degree deviation ΔSH is omitted, and in step S37, the supercooling degree-superheat degree-liquid pipe temperature establishment control is performed. Instead, supercooling degree-overheat compression prevention-wet compression prevention establishment control can be performed by employing supercooling degree control. Further, when the superheat compression prevention control is used in combination with the superheat degree control instead of the superheat compression-liquid pipe temperature establishment control described above, the liquid pipe temperature deviation ΔTlp and the superheat in step S38. The comparison with the degree deviation ΔSH is omitted, and the superheat degree-superheat compression prevention establishment control can be performed by adopting the superheat degree control instead of the superheat degree-liquid pipe temperature establishment control in step S40. Furthermore, instead of both wet compression prevention control and overheat compression prevention control, only one of wet compression prevention control and overheat compression prevention control may be employed as necessary. For example, when only wet compression prevention control is employed, steps S35 and S36 and steps S38 and S39 are omitted, and when only overheat compression prevention control is employed, steps S33 and S34 may be omitted.

  Thereby, in the air conditioning apparatus 1 of this modification, when it is determined that the high pressure Pd is equal to or higher than the predetermined pressure, the overheat compression prevention control, the wet compression prevention control, and the supercooling degree control are selectively used, and the compressor 21, the supercooling degree SC of the refrigerant at the outlet of the outdoor heat exchanger 23 can be made closer to the target supercooling degree SCs, and overheat compression prevention control, wet compression prevention control, and supercooling can be performed. The superheat degree SH of the refrigerant at the outlet on the bypass refrigerant pipe 26 side of the supercooling heat exchanger 25 is made to approach the target superheat degree SHs while properly protecting the compressor 21 by using the degree-superheat degree establishment control. The supercooling degree SC of the refrigerant at the outlet of the outdoor heat exchanger 23 can be made closer to the target supercooling degree SCs, and the overheat compression prevention control and the wet compression prevention control and the supercooling degree-superheating degree-liquid By bypassing the supercooling heat exchanger 25, the compressor 21 is protected by properly using the temperature establishment control, and the liquid pipe temperature Tlp at the outlet of the supercooling heat exchanger 25 is not excessively lowered. The superheat degree SH of the refrigerant at the outlet on the refrigerant pipe 26 side approaches the target superheat degree SHs, and the supercool degree SC of the refrigerant at the outlet of the outdoor heat exchanger 23 approaches the target supercool degree SCs. Further, when it is determined that the high pressure Pd is not equal to or higher than the predetermined pressure, the bypass refrigerant of the supercooling heat exchanger 25 is used while protecting the compressor 21 by properly using the superheat compression prevention control and the superheat degree control. It can be avoided that the degree of deviation of the superheat degree SH of the refrigerant at the outlet on the pipe 26 side from the target value SHs is large.

(Second Embodiment)
(1) Configuration of Air Conditioner FIG. 7 is a schematic configuration diagram of an air conditioner 101 according to the second embodiment of the present invention. The air conditioning apparatus 101 is an apparatus used for air conditioning in a room such as a building by performing a vapor compression refrigeration cycle operation, as in the air conditioning apparatus 1 of the first embodiment. The air conditioner 1 includes only one outdoor unit (that is, the outdoor unit 2) as a heat source unit, whereas a plurality of units connected in parallel via the liquid refrigerant communication pipe 106 and the gas refrigerant communication pipe 107 are provided. In that the outdoor unit (here, two outdoor units 2a and 2b) is provided. That is, the refrigerant circuit 110 of the air conditioning apparatus 101 of the present embodiment is configured by connecting the outdoor units 2a and 2b, the indoor units 5a and 5b, and the refrigerant communication pipes 106 and 107.

  In addition, since the structure of the indoor units 5a and 5b which comprise the air conditioning apparatus 101 of this embodiment is the same as that of the indoor units 5a and 5b of 1st Embodiment, description is abbreviate | omitted here. Also, since the configuration of the outdoor units 2a and 2b is the same as that of the outdoor unit 2 of the first embodiment, the reference numerals of the outdoor refrigerant circuits are “10d” or “10e”, and are attached to the reference numerals indicating the other parts. The letter “a” or “b” is attached, and the description is omitted here. Further, as shown in FIG. 8, the control unit 109 of the air conditioner 101 of the present embodiment is connected so as to receive detection signals of various sensors 37a to 44a, 37b to 44b, and these Various devices 21a, 21b (specifically, compressor motors 30a, 30b), 22a, 22b, 24a, 24b, 32a, 32b (specifically, outdoor fan motors 33a, 33b) based on the detection signals and the like, It is connected so that 36a, 36b, 51a, 51b etc. can be controlled. Here, FIG. 8 is a control block diagram of the air conditioner 101.

(2) Operation of Air Conditioner The operation (heating operation and cooling operation) of the air conditioner 101 of the present embodiment is basically the same as that of the two outdoor units 2a and 2b except that the two outdoor units 2a and 2b are operated. It is the same as that of the air conditioning apparatus 1 of 1 embodiment and its modification.

  However, when the outdoor units 2a and 2b as a plurality of heat source units connected in parallel via the liquid refrigerant communication pipe 106 and the gas refrigerant communication pipe 107 like the air conditioner 101 of the present embodiment are employed, In each of the outdoor units 2a and 2b, control including the supercooling degree control in the first embodiment and its modification (that is, supercooling degree control, supercooling degree-wet compression prevention establishment control, supercooling degree-overheat compression prevention establishment control). Degree of supercooling-superheat compression prevention-wet compression prevention establishment control, supercooling degree-superheat degree establishment control, supercooling degree-superheat degree-wet compression prevention establishment control, supercooling degree-superheat degree-overheat compression prevention establishment control, Supercooling degree-Superheat degree-Superheat compression prevention-Wet compression prevention establishment control, Supercooling degree-Superheat degree-Liquid pipe temperature establishment control, Supercooling degree-Superheat-Liquid pipe temperature-Wet compression prevention establishment control, Supercooling degree -Degree of superheat Liquid pipe temperature-superheat compression prevention establishment control, supercooling degree-superheat degree-liquid pipe temperature-overheat compression prevention-wet compression prevention establishment control) are performed. At this time, the refrigerant drift between the outdoor units 2a, 2b If it occurs, there is a possibility that the degree of supercooling SC between the outdoor units 2a and 2b, that is, the refrigerant condensing capacity in the outdoor heat exchangers 23a and 23b as heat source side heat exchangers may vary. In addition, regarding the control including the supercooling degree control, the supercooling in the first embodiment and its modifications is provided except that the reference numerals indicating the respective parts of the outdoor unit do not include the suffixes “a” and “b”. Since this is the same as the control including the degree control, the description is omitted here.

  Therefore, in this embodiment, in each of the outdoor units 2a and 2b, the control including the supercooling degree control in the first embodiment and the modification thereof (that is, the supercooling degree control, the supercooling degree-wet compression prevention establishment control, Supercooling degree-Superheat compression prevention establishment control, Supercooling degree-Superheat compression prevention-Wet compression prevention establishment control, Supercooling degree-Superheat degree establishment control, Supercooling degree-Superheat degree-Wet compression prevention establishment control, Supercooling degree- Superheat degree-Superheat compression prevention establishment control, Supercooling degree-Superheat degree-Superheat compression prevention-Wet compression prevention establishment control, Supercooling degree-Superheat degree-Liquid pipe temperature establishment control, Supercooling degree-Superheat degree-Liquid pipe temperature- Wet compression prevention establishment control, supercooling degree-superheat degree-liquid pipe temperature-overheat compression prevention establishment control, supercooling degree-superheat degree-liquid pipe temperature-overheat compression prevention prevention control-wet compression prevention establishment control), outdoor unit To supercooling degree SC in 2a and 2b Zui and is to perform the subcooling degree variation prevention control for correcting the value of the target degree of supercooling SCs.

  Here, when the high pressure Pd in the cooling operation is equal to or higher than the predetermined pressure Pds, the supercooling degree-superheat degree-liquid pipe temperature establishment control supercooling degree-superheat degree-liquid as control including the supercooling degree control. When the pipe temperature-superheat compression prevention-wet compression prevention establishment control is performed, and the high pressure Pd in the cooling operation is less than the predetermined pressure Pds, the control not including the supercooling degree control centering on the superheating degree control is performed. As an example (refer to Modification 4 of the first embodiment), an example of performing the supercooling degree variation prevention control while performing this control will be described according to the flowchart shown in FIG.

  First, in step S41, whether or not the target supercooling degree SCs should be corrected is determined by whether or not the outdoor units 2a and 2b satisfy a predetermined correction execution condition. This correction execution condition satisfies the first condition that there is an outdoor unit in which the absolute value of the supercooling degree deviation ΔSC obtained from the supercooling degree SC and the target supercooling degree SCs is equal to or smaller than the predetermined deviation ΔSCs1; The second condition is that there is an outdoor unit in which the degree of supercooling SC is equal to or lower than the predetermined degree of supercooling SC1. Here, the first condition is to determine whether or not there is an outdoor unit in which the supercooling degree SC is close to the target supercooling degree SCs. In this embodiment, the supercooling degree SC is In order to add to the determination whether the target supercooling degree SCs around the compressor of the outdoor unit in the state close to the target supercooling degree SCs is correct, the suction of the compressors 21a and 21b The pressure difference obtained by converting the pressure Ps into a saturation temperature value corresponding to the evaporation temperature Te and subtracting the evaporation temperature Te from the suction temperature Ts of the compressors 21a and 21b is equal to or less than a predetermined temperature difference, and the compression It is also determined whether or not the discharge temperature Td of the machines 21a and 21b is below a predetermined temperature. Further, the second condition is to determine whether or not there is an outdoor unit in which the degree of supercooling SC is a very small value. Thus, the determination in step S41 is whether or not there is an outdoor unit in which the degree of supercooling SC is close to the target degree of supercooling SCs among a plurality of (here, two) outdoor units 2a and 2b. In addition, it is determined whether or not there is an outdoor unit in which the degree of supercooling SC is a very small value.

  In step S41, when it is determined that there is an outdoor unit satisfying the correction execution condition among the plurality of (here, two) outdoor units 2a and 2b, the target subcooling degree SCs in step S42 is set. The process proceeds to the correction process, and the target supercooling degree SCs of the outdoor unit that satisfies the first condition of the correction execution condition is corrected so as to be larger than the current value. Then, the bypass expansion valve as the bypass expansion mechanism is controlled so that the flow rate of the refrigerant flowing through the bypass refrigerant pipe of the outdoor unit that satisfies the first condition of the correction execution condition is reduced, and the outdoor condition that satisfies the first condition of the correction execution condition is satisfied. Since the flow rate of the refrigerant flowing through the unit is reduced and is easily distributed to other outdoor units, the variation in the degree of supercooling SC between the outdoor units 2a and 2b can be reduced.

  Next, in step S43, whether or not the correction of the target supercooling degree SCs should be canceled is determined by whether or not the supercooling degrees SC of all the outdoor units 2a and 2b satisfy a predetermined correction cancellation condition. This correction cancellation condition is that the supercooling degree SC of all of the plurality of (here, two) outdoor units 2a and 2b is larger than the predetermined supercooling degree SC2. Here, the predetermined supercooling degree SC2 is set to a value larger than the predetermined supercooling degree SC1 in the second condition of the correction execution condition. As described above, the determination in step S43 determines whether or not the supercooling degree of the outdoor unit whose supercooling degree SC has become a very small value has been increased by correcting the target supercooling degree SCs in step S42. Judgment.

  If it is determined in step S43 that the supercooling degrees SC of all of the plurality of (here, two) outdoor units 2a and 2b satisfy the correction cancellation condition, the target supercooling is performed in step S44. The correction of the target supercooling degree SCs of the outdoor unit in which the degree SCs has been corrected is canceled, and the normal supercooling degree-superheat degree-liquid pipe temperature is quickly (ie, the state where the target supercooling degree SCs is not corrected). It is possible to return to establishment control supercooling degree-superheat degree-liquid pipe temperature-overheat compression prevention-wet compression prevention establishment control.

  In addition, the control including the supercooling degree control is not the supercooling degree-superheating degree-liquid pipe temperature establishment control described above, but the supercooling degree, not the supercooling degree-superheat degree-liquid pipe temperature-overheat compression prevention-wet compression prevention establishment control. Degree control, supercooling degree-wet compression prevention establishment control, supercooling degree-superheat compression prevention establishment control, supercooling degree-superheat compression prevention-wet compression prevention establishment control, supercooling degree-superheat degree establishment control, supercooling degree- Superheat degree-Wet compression prevention establishment control, Supercooling degree-Superheat degree-Superheat compression prevention establishment control, Supercooling degree-Superheat degree-Superheat compression prevention-Wet compression prevention establishment control, Supercooling degree-Superheat degree-Liquid pipe temperature establishment Control, supercooling degree-superheat degree-liquid pipe temperature-wet compression prevention establishment control, supercooling degree-superheat degree-liquid pipe temperature-overheat compression prevention establishment control may be used. In this embodiment, the control including the superheat degree control when the high pressure Pd is less than the predetermined pressure Pds includes not only the superheat degree control but also the superheat compression prevention control and the liquid pipe temperature control. Either or both may not be included. Furthermore, in the present embodiment, control is used that selectively uses control including supercooling degree control and control not including supercooling degree control centering on superheat degree control depending on the high pressure Pd. Only control including the above may be performed.

(Other embodiments)
As mentioned above, although embodiment of this invention and its modification were demonstrated based on drawing, specific structure is not restricted to these embodiment and its modification, It changes in the range which does not deviate from the summary of invention. Is possible.

<A>
In the above-described embodiment and its modification, the example in which the present invention is applied to the air conditioners 1 and 101 capable of switching between cooling and heating has been described. However, the present invention is not limited to this, and other air conditioning such as an air conditioner dedicated to cooling. The present invention may be applied to an apparatus.

<B>
In the above-described embodiment and its modification, a plurality of indoor units (that is, indoor units 5a and 5b) are provided as usage units. However, the present invention is not limited to this, and even if there is only one indoor unit. Good.

<C>
In the above-described embodiment and its modification, the check valves 31, 31a, 31b that bypass the outdoor expansion valves 24, 24a, 24b are provided, but the present invention is not limited to this, and no check valve is provided. May be. In this case, the outdoor expansion valves 24, 24a, and 24b may be opened during cooling operation.

<D>
In the above-described embodiment and the modification thereof, bypass expansion valves 36, 36a as bypass expansion mechanisms are used as devices constituting the outdoor units 2, 2a, 2b as heat source units used when performing supercooling degree control. 36b is used, but is not limited to this, for example, outdoor expansion valves 24, 24a, 24b connected to the downstream side of the outdoor heat exchangers 23, 23a, 23b as heat source side heat exchangers in the cooling operation. Alternatively, other devices that constitute the outdoor units 2, 2a, and 2b may be used, such as performed by the outdoor fans 32, 32a, and 32b. Here, when the degree of supercooling is controlled by the outdoor expansion valves 24, 24a, 24b, the openings of the outdoor heat exchangers 23, 23a, 23b are reduced by reducing the openings of the outdoor expansion valves 24, 24a, 24b. By increasing the degree of refrigerant subcooling SC and increasing the opening of the outdoor expansion valves 24, 24a, 24b, the refrigerant subcooling degree SC at the outlets of the outdoor heat exchangers 23, 23a, 23b can be reduced. . When the degree of supercooling is controlled by the outdoor fans 32, 32a, 32b, the refrigerant is supercooled at the outlets of the outdoor heat exchangers 23, 23a, 23b by increasing the air volume of the outdoor fans 32, 32a, 32b. The degree of supercooling SC of the refrigerant at the outlets of the outdoor heat exchangers 23, 23a, 23b can be reduced by increasing the degree SC and reducing the air volume of the outdoor fans 32, 32a, 32b.

<E>
In the above-described embodiment and its modifications, outdoor air is used as a cooling medium for the outdoor heat exchangers 23, 23a, and 23b as heat source side heat exchangers, but is not limited thereto, and water or brine is used. May be used.

<F>
In the above-described embodiment and its modification, the bypass refrigerant pipes 26, 26a, and 26b are branched from positions upstream of the supercooling heat exchangers 25, 25a, and 25b during the cooling operation. You may branch from the downstream position of the supercooling heat exchangers 25, 25a, and 25b.

<G>
In the second embodiment described above, two outdoor units (that is, the outdoor units 2a and 2b) are provided as heat source units. However, the present invention is not limited to this, and three or more outdoor units may be provided. Good. Even in this case, it is determined whether or not three or more outdoor units satisfy the correction execution condition and the target supercooling degree SCs is corrected. Thereafter, when the correction cancellation condition is satisfied, the target supercooling degree SCs is satisfied. By canceling this correction, it is possible to perform the same supercooling degree variation prevention control as in the case of two outdoor units.

  The present invention includes a bypass refrigerant pipe that branches a part of the refrigerant condensed in the heat source side heat exchanger and returns the refrigerant to the suction side of the compression mechanism, and refrigerant condensed in the heat source side heat exchanger by the refrigerant flowing through the bypass refrigerant pipe. The present invention is widely applicable to an air conditioner having a supercooling heat exchanger for cooling.

1, 101 Air conditioner 2, 2a, 2b Outdoor unit (heat source unit)
5a, 5b Indoor unit (Usage unit)
6, 106 Liquid refrigerant communication tube 7, 107 Gas refrigerant communication tube 21, 21a, 21b Compressor (compression mechanism)
23, 23a, 23b Outdoor heat exchanger (heat source side heat exchanger)
25, 25a, 25b Supercooling heat exchanger 26, 26a, 26b Bypass refrigerant pipe 36, 36a, 36b Bypass expansion valve (bypass expansion mechanism)
52, 52a, 52b Indoor heat exchanger (use side heat exchanger)

JP 2005-345069 A

Claims (4)

A compression mechanism (21, 21a, 21b) for compressing the refrigerant; a heat source side heat exchanger (23, 23a, 23b) for condensing the refrigerant compressed in the compression mechanism by exchanging heat with a cooling medium; and the heat source A bypass refrigerant pipe (26, 26a, 26b) for branching a part of the refrigerant condensed in the side heat exchanger and returning it to the suction side of the compression mechanism, and provided in the bypass refrigerant pipe and flowing through the bypass refrigerant pipe A bypass expansion mechanism (36, 36a, 36b) that decompresses the refrigerant, and a supercooling heat exchanger that cools the refrigerant condensed in the heat source side heat exchanger by exchanging heat with the refrigerant decompressed in the bypass expansion mechanism ( 25, 25a, 25b) at least one heat source unit (2, 2a, 2b);
At least one utilization unit (5a, 5b) having utilization side heat exchangers (52a, 52b) for evaporating the refrigerant cooled in the supercooling heat exchanger by heat exchange with a heating medium;
A liquid refrigerant communication pipe (6, 106) connected to the heat source unit and the utilization unit, and sending the refrigerant cooled in the supercooling heat exchanger to the utilization side heat exchanger;
Gas refrigerant communication pipes (7, 107) that are connected to the heat source unit and the utilization unit and send refrigerant evaporated in the utilization side heat exchanger to the compression mechanism,
When the high pressure in the refrigeration cycle operation is equal to or higher than a predetermined pressure, and the supercooling degree of the refrigerant at the outlet of the heat source side heat exchanger is smaller than the target supercooling degree, the supercooling degree is increased. By controlling the equipment constituting the heat source unit, and when the degree of supercooling is larger than the target degree of supercooling, by controlling the equipment constituting the heat source unit so that the degree of supercooling is reduced, When it is possible to perform a supercooling degree control for controlling the devices constituting the heat source unit so that the supercooling degree approaches the target supercooling degree, and when the high pressure in the refrigeration cycle operation is less than a predetermined pressure, Superheat degree control for controlling devices constituting the heat source unit such that the superheat degree of the refrigerant at the outlet of the bypass refrigerant pipe side of the supercooling heat exchanger approaches the target superheat degree It is possible to carry out,
Air conditioner (1, 101). There are a plurality of the heat source units (2a, 2b), which are connected in parallel via the liquid refrigerant communication pipe (106) and the gas refrigerant communication pipe (107).
Based on the degree of supercooling in the plurality of heat source units, it is possible to perform subcooling degree variation prevention control for correcting the value of the target supercooling degree.
The air conditioner (101) according to claim 1.   In the supercooling degree variation prevention control, an absolute value of a supercooling degree deviation obtained by subtracting the target supercooling degree from the supercooling degree among the plurality of heat source units (2a, 2b) is less than a predetermined deviation. And when there is a heat source unit that satisfies the correction execution condition that the degree of supercooling is equal to or less than a predetermined subcooling degree, the target subcooling degree of the heat source unit that satisfies the correction execution condition is determined. The target subcooling degree is corrected when the correction value satisfies a correction cancellation condition that the supercooling degree of all of the plurality of heat source units is larger than a predetermined supercooling degree. The air conditioner (101) according to claim 2, which cancels the correction.   The target degree of subcooling is changed so as to decrease as the temperature of the cooling medium increases or the state quantity equivalent to the temperature of the cooling medium changes in the same way as the temperature of the cooling medium increases. The air conditioning apparatus (1, 101) according to any one of claims 1 to 3.

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