KR101479458B1 - Refrigeration device - Google Patents

Abstract

The superheating degree of the refrigerating device, which is likely to be in a supercooled state at the front of the evaporator, is appropriately controlled. The indoor expansion valve 41 of the refrigerating device 10 is configured to cool the refrigerant flowing into the indoor heat exchanger 42 based on the target value of the low pressure target value and the degree of superheat on the outflow side of the indoor heat exchanger 42 And controls the expansion. The supercooled state of the refrigerant on the inflow side of the indoor heat exchanger (42) is detected by the indoor liquid temperature sensor (44) and the suction pressure sensor (33). The indoor control device 47 determines that the refrigerant on the inflow side of the indoor heat exchanger 42 is in the supercooled state based on the detection results of the indoor liquid temperature sensor 44 and the suction pressure sensor 33, The target value is changed from the first superheat degree target value Tsh1 to the second superheat degree target value Tsh2.

Description

REFRIGERATION DEVICE

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerating device, particularly a refrigerating device having a refrigerating circuit including an evaporator.

2. Description of the Related Art Conventionally, an air conditioner having a refrigerating circuit for circulating a refrigerant and a refrigerating device for transferring heat between an indoor heat exchanger and an outdoor heat exchanger of a refrigerating circuit is known. In such an air conditioner, as described in Patent Document 1 (Japanese Patent Laid-Open Publication No. 2004-271066), in order to perform appropriate heat exchange in the indoor heat exchanger and the outdoor heat exchanger, The degree of superheat control for controlling the degree of superheat is performed.

Japanese Patent Application Laid-Open No. 2004-271066

[0004] In recent years, there has been an increasing demand for energy saving in the air conditioner to suppress power consumption. For example, as one of countermeasures therefor, there is a case where the differential pressure between the high pressure and the low pressure in the refrigeration cycle is small. In such an air conditioner, when the operation of increasing the evaporation temperature when the refrigerant charge amount is large and the outside air temperature is low, the refrigerant may be supercooled in front of the indoor heat exchanger functioning as the evaporator. When the supercooling state occurs in the indoor heat exchanger, there arises a problem that it is impossible to control the superheat of the indoor heat exchanger.

An object of the present invention is to appropriately control the degree of superheat of a refrigerating device in which the refrigerant tends to be supercooled in the front of the evaporator.

A refrigerating device according to a first aspect of the present invention is a refrigerating device in which a refrigerating circuit in which a compressor, a radiator, and an evaporator are connected in order to circulate a refrigerant is provided. The refrigerating device is provided on an inflow side of the evaporator, An expansion mechanism for controlling the expansion of the refrigerant flowing into the evaporator based on at least one of a target value of the low pressure of the refrigerant circuit and a target value of superheat degree of the outlet side of the evaporator, A setting change for raising the high pressure target value, a setting change for lowering the low pressure target value, and a setting change for raising the target value for the superheat degree in the case where it is judged that the refrigerant on the inflow side of the evaporator is in a supercooled state based on the detection result of the detector And a control unit which can change the setting of at least one of the control unit and the control unit.

In the refrigeration system according to the first aspect, when it is determined that the refrigerant on the inflow side of the evaporator is in a supercooled state, at least one of setting change for increasing the high pressure target value, lowering the low pressure target value, The superheating degree of the evaporator can not be controlled. Therefore, it is possible to appropriately control the degree of superheat of the evaporator.

A refrigerating device according to a second aspect of the present invention is the refrigerating device according to the first aspect, wherein the evaporator is a utilization side heat exchanger, and the control part controls the supercooling degree of the refrigerant on the inflow side of the utilization side heat exchanger based on the detection result of the detector It is possible to perform at least one of a setting change for lowering the low pressure target value and a setting change for increasing the superheat degree target value.

In the refrigeration system according to the second aspect, when it is determined that the refrigerant on the inflow side of the utilization side heat exchanger is in the supercooled state, at least one of the setting change for lowering the low pressure target value and the setting change for increasing the superheat degree target value is performed, It is possible to sufficiently cope with the case where the refrigerant tends to be in a supercooled state in front of the utilization-side heat exchanger functioning as an evaporator because the amount of refrigerant is large.

A refrigeration apparatus according to a third aspect of the present invention is the refrigeration apparatus according to the second aspect, wherein the detector comprises a first detector for detecting the pressure saturation temperature on the inlet side of the utilization side heat exchanger, And a third detector for detecting the temperature of the refrigerant on the inflow side of the expansion mechanism, wherein the control unit controls the first detector and the second detector such that the detection results of the first detector and the second detector It is possible to determine whether or not the refrigerant on the inflow side of the utilization-side heat exchanger is in the supercooled state based on the comparison between the detection results of the first detector and the third detector.

In the refrigerating apparatus according to the third aspect, it is preferable that the determination of whether or not the refrigerant on the inflow side of the utilization side heat exchanger is in the supercooled state is performed by comparing the detection results of the first detector and the second detector, Therefore, even if the refrigerant on the inlet side of the utilization-side heat exchanger is supercooled, it is possible to accurately determine the supercooled state.

A refrigerating device according to a fourth aspect of the present invention is the refrigerating device according to the second aspect or the third aspect, wherein the third detector is a liquid pipe temperature sensor provided on the outflow side of the radiator, The temperature obtained by subtracting the correction value corresponding to the heat loss from the position to the expansion mechanism from the detection temperature of the liquid pipe temperature sensor is used as the temperature of the refrigerant on the inflow side of the expansion mechanism so that the refrigerant on the inflow side of the utilization side heat exchanger is supercooled Or not.

In the refrigeration apparatus according to the fourth aspect, a conventional heat source side liquid pipe temperature sensor can be used for judging whether or not the refrigerant on the inlet side of the utilization side heat exchanger is in a supercooled state.

A refrigerating device according to a fifth aspect of the present invention is the refrigerating device according to the second aspect or the third aspect, wherein the first detector is a suction pressure sensor for detecting the pressure on the suction side of the compressor, The pressure saturation temperature can be calculated from the detected pressure.

In the refrigeration apparatus according to the fifth aspect, since the control section can calculate the pressure saturation temperature from the pressure detected by the suction pressure sensor, a conventional suction pressure sensor can be used.

In the refrigeration apparatus according to the first aspect, it is possible to avoid a situation in which the superheat of the evaporator can not be controlled so that the degree of superheat of the evaporator can be appropriately controlled, and the refrigerant in the supercooled state, It is possible to appropriately perform the control of the degree of superheat.

In the refrigeration system according to the second aspect, it is possible to avoid a situation in which it is impossible to control the superheat of the utilization-side heat exchanger, thereby appropriately controlling the degree of superheat of the utilization-side heat exchanger, It is possible to appropriately control the degree of superheat of the refrigerating device in which the refrigerant is likely to be in a supercooled state.

In the refrigeration apparatus according to the third aspect, the supercooled state can be accurately determined, and the superheating degree of the refrigerating apparatus in which the refrigerant is supercooled in front of the evaporator can be appropriately controlled.

In the refrigeration apparatus according to the fourth aspect, since the conventional heat source side liquid pipe temperature sensor can be used, an increase in cost can be suppressed.

In the refrigeration apparatus according to the fifth aspect, since a conventional suction pressure sensor can be used, an increase in cost can be suppressed.

1 is a view showing a refrigerant piping system of an air conditioner including a refrigerating apparatus according to one embodiment;
Fig. 2 is a block diagram showing a control system of the air conditioner of Fig. 1. Fig.
3 is a graph for explaining the operation of the refrigeration circuit.

(1) Overall configuration of air conditioner

1 shows a refrigerant piping system of an air conditioner including a refrigerating apparatus according to an embodiment of the present invention. The air conditioner 1 is a dispersion type air conditioner of a refrigerant piping system, and is a device used for cooling and heating each room in a building by performing a vapor compression refrigeration cycle operation. The air conditioner 1 includes an air conditioner outdoor unit 2 as a heat source unit and an air conditioner indoor unit 4 of a plurality of units (two air conditioner indoor units 4a and an air conditioner indoor unit 4b in FIG. 1) And a first refrigerant communication pipe (6) and a second refrigerant communication pipe (7) as refrigerant communication pipes for connecting the air conditioning outdoor unit (2) and the air conditioning indoor unit (4).

The refrigerating apparatus 10 of the air conditioner 1 is constituted by connecting the air conditioning outdoor unit 2, the air conditioning indoor unit 4 and the refrigerant communication pipes 6 and 7. Then, the refrigerating cycle is performed in which the refrigerant is sealed in the refrigerating device 10 and the refrigerant is compressed, cooled, reduced in pressure, heated and evaporated, and then compressed again as described later. As the refrigerant, for example, R410A, R407C, R22, R134a, carbon dioxide and the like are used.

(2) Detailed configuration of air conditioner

(2-1) Air conditioning indoor unit

The air conditioning indoor unit is installed in a ceiling of a room such as a building by embedding, hanging, or the like, or by wall hanging on the indoor wall surface. The air conditioning indoor unit 4 is connected to the air conditioning outdoor unit 2 through the refrigerant communication pipes 6 and 7 and constitutes a part of the refrigerating device 10. [

Next, the configuration of the air conditioning indoor unit 4 will be described. Although two air conditioning indoor units 4a and 4b are shown in FIG. 1 as the air conditioning indoor unit 4, since both of the air conditioning indoor units 4 have substantially the same configuration, the configuration of the air conditioning indoor unit 4a Only.

The air conditioning indoor unit (4a) has an indoor main refrigerant circuit (10a) constituting a part of the refrigerating device (10). The indoor main refrigerant circuit 10a mainly has an indoor expansion valve 41 as a pressure reduction unit and an indoor heat exchanger 42 as a utilization side heat exchanger.

The indoor expansion valve (41) is a mechanism for reducing the pressure of the refrigerant, and is an electric valve capable of adjusting the opening degree. One end of the indoor expansion valve (41) is connected to the first refrigerant communication pipe (6), and the other end thereof is connected to the indoor heat exchanger (42).

The indoor heat exchanger 42 is, for example, a cross-fin type fin-and-tube heat exchanger constituted by, for example, a heat transfer pipe and a plurality of fins. The indoor heat exchanger 42 functions as an evaporator of the refrigerant during cooling operation, Is a heat exchanger that functions as a refrigerant condenser and heats room air. One end of the indoor heat exchanger (42) is connected to the indoor expansion valve (41), and the other end is connected to the second refrigerant communication pipe (7).

The air conditioning indoor unit 4a is provided with an indoor fan 43 for sucking room air into the unit and supplying it again to the room, and performs heat exchange between the room air and the refrigerant flowing through the indoor heat exchanger 42. [ The indoor fan 43 is a fan capable of varying the amount of air to be supplied to the indoor heat exchanger 42 and is rotationally driven by an indoor fan motor 43a such as a DC fan motor. In the indoor fan (43), for example, a centrifugal fan or a multi-blade fan is driven by the indoor fan motor (43a) for blowing air to the indoor heat exchanger (42).

In the air conditioning indoor unit 4a, various sensors are provided. Specifically, the indoor liquid temperature sensor 44 and the indoor gas pipe temperature sensor 45, which are thermistors, are provided, and the temperature of the refrigerant is measured from the temperature of the refrigerant pipe close to the indoor heat exchanger 42. A room temperature sensor 46 is also provided, and the room temperature sensor 46 detects the temperature of the room air sucked into the air conditioning indoor unit 4 before heat exchange is performed. The air conditioning indoor unit 4a has an indoor control unit 47 for controlling the operation of each unit constituting the air conditioning indoor unit 4a. The indoor control device 47 has a microcomputer or a memory provided for controlling the air conditioning indoor unit 4a and is controlled by a remote controller (not shown) for individually operating the air conditioning indoor unit 4a, Or sends or receives a control signal or the like between the outdoor control devices 30 of the outdoor air conditioner 2 to be described later via the transmission line 8a.

(2-2) Outdoor Air Conditioning Unit

The outdoor air conditioning outdoor unit 2 is installed outside the building or the like and is connected to the air conditioning indoor units 4a and 4b via the first refrigerant communication pipe 6 and the second refrigerant communication pipe 7. [ The outdoor air conditioning outdoor unit (2) has an outdoor side main refrigerant circuit (10c) constituting a part of the refrigerating device (10) and a supercooling refrigerant flow path (61) branched from the refrigerating device (10).

(2-2-1) Outdoor side main refrigerant circuit

The outdoor side main refrigerant circuit 10c mainly includes a compressor 21, a switching mechanism 22, an outdoor heat exchanger 23, an outdoor first expansion valve 25, a liquid gas heat exchanger 27, A liquid-side closing valve 28a, a gas-side closing valve 28b, and an accumulator 29. The liquid- This outdoor side main refrigerant circuit 10c mainly includes a compressor 21, a switching mechanism 22, an outdoor heat exchanger 23 as a heat source side heat exchanger, and an outdoor side heat exchanger 23 as a second cut- A first expansion valve 25, a liquid-gas heat exchanger 27 as a temperature regulating mechanism, a liquid-side shut-off valve 28a as a first shut-off mechanism, and a gas-side shut-off valve 28b.

The compressor (21) is a hermetic compressor driven by a compressor motor (21a). The number of revolutions of the compressor motor 21a is controlled by, for example, an inverter, and the compressor 21 is configured to be able to vary the operation capacity.

The switching mechanism 22 is a mechanism for switching the flow direction of the refrigerant. The outdoor heat exchanger 23 functions as a radiator of the refrigerant compressed by the compressor 21 and the indoor heat exchanger 42 functions as an evaporator of the refrigerant cooled in the outdoor heat exchanger 23 . Therefore, the switching mechanism 22 connects the refrigerant pipe on the discharge side of the compressor 21 and one end of the outdoor heat exchanger 23, and also connects the compressor suction side pipe 29a (including the accumulator 29) Side closing valve 28b (refer to the solid line of the switching mechanism 22 in Fig. 1). The switching mechanism 22 functions as a radiator of the refrigerant compressed by the compressor 21 while the indoor heat exchanger 42 functions as a radiator of the refrigerant compressed by the compressor 21. In the indoor heat exchanger 42, And functions as an evaporator of the cooled refrigerant. Therefore, the switching mechanism 22 connects the refrigerant pipe on the discharge side of the compressor 21 and the gas side close valve 28b, and connects the compressor suction side pipe 29a and the one end of the outdoor heat exchanger 23 (See the broken line of the switching mechanism 22 in Fig. 1). The switching mechanism 22 is, for example, a four-way switching valve.

The outdoor heat exchanger 23 is a cross-fin type fin-and-tube heat exchanger having a heat transfer pipe and a plurality of fins, one end of which is connected to the switching mechanism 22 and the other end thereof is connected to the outdoor first expansion valve 25 .

The air conditioner outdoor unit (2) has an outdoor fan (26) for sucking outdoor air into the unit and discharging it again to the outside. The outdoor fan (26) performs heat exchange between the outdoor air and the refrigerant flowing through the outdoor heat exchanger (23).

The outdoor first expansion valve (25) is a mechanism for reducing the pressure of the refrigerant in the refrigerating device (10) and is a motor-operated valve capable of adjusting the opening degree. The outdoor first expansion valve 25 controls the flow of the refrigerant in the refrigerating device 10 when the cooling operation is performed in order to control the pressure and the flow rate of the refrigerant flowing in the outdoor side main refrigerant circuit 10c, Gas heat exchanger 27, and can block the passage of the refrigerant. [0051] As shown in Fig. One end of the outdoor first expansion valve 25 is connected to the outdoor heat exchanger 23 and the other end thereof is connected to the liquid side close valve 28a through the liquid gas heat exchanger 27 and the indoor heat exchanger 42 Of the liquid crystal display device.

The air conditioning outdoor unit (2) has an outdoor fan (26) as a blowing fan for sucking outdoor air into the unit and performing heat exchange with the refrigerant in the outdoor heat exchanger (23) and then discharging the outdoor air to the outside. The outdoor fan 26 is a fan capable of varying the amount of air to be supplied to the outdoor heat exchanger 23, and is, for example, a propeller fan driven by a motor 26a such as a DC fan motor.

The liquid-gas heat exchanger (27) is connected between the outdoor first expansion valve (25) and the liquid side close valve (28a). The liquid-gas heat exchanger 27 is a piping heat exchanger having a double-pipe structure in which a refrigerant pipe through which condensed refrigerant flows in a heat source-side heat exchanger is brought into contact with a branch pipe 64 to be described later. The liquid-gas heat exchanger 27 exchanges the refrigerating apparatus 10 with the refrigerant flowing from the outdoor heat exchanger 23 toward the air conditioning indoor unit 4 and the supercooling refrigerant passage 61 from the outdoor second expansion valve 62 to the compressor And heat exchange is performed between refrigerants flowing to the suction side pipe 29a. Thereby, the liquid-gas heat exchanger 27 further cools the refrigerant condensed in the outdoor heat exchanger 23 during the cooling operation by this heat exchange, thereby increasing the supercooling degree of the refrigerant directed toward the air conditioning indoor unit 4 do.

The accumulator 29 is disposed in the compressor suction side piping 29a between the switching mechanism 22 and the compressor 21. [

(2-2-2) Subcooling refrigerant passage

The subcooling refrigerant flow path 61 is connected to the refrigerant pipe 19a directed to the compressor suction side piping 29a between the switching mechanism 22 and the accumulator 29 via the liquid gas heat exchanger 27 from the outdoor second expansion valve 62, . The outdoor second expansion valve (62) is a mechanism for reducing the refrigerant in the supercooling refrigerant passage (61), and is a motorized valve capable of adjusting the opening degree. The outdoor second expansion valve 62 is provided in the supercooling refrigerant passage 61 and is branched from the pipe connected to the liquid side close valve 28a from the outdoor first expansion valve 25 in the supercooling refrigerant passage 61 Gas heat exchanger 27 as shown in Fig.

The liquid-gas heat exchanger (27) is provided with a branch pipe (64) as a cooling source. The portion excluding the supercooling refrigerant passage (61) from the refrigerating apparatus (10) is the main refrigerant circuit. The subcooling refrigerant passage 61 is connected to the main refrigerant circuit so as to return the refrigerant branched between the liquid gas heat exchanger 27 and the outdoor first expansion valve 25 to the suction side of the compressor 21. The refrigerant branched into the supercooling refrigerant passage (61) is introduced into the liquid-gas heat exchanger (27) after being reduced in pressure. The refrigerant branched into the supercooling refrigerant passage 61 is subjected to heat exchange with the refrigerant sent from the outdoor heat exchanger 23 through the first refrigerant communication pipe 6 to the indoor expansion valve 41, As shown in Fig.

More specifically, the supercooling refrigerant passage 61 has a branch pipe 64, a confluent pipe 65, and an outdoor second expansion valve 62. The branch pipe 64 is connected so that a part of the refrigerant sent from the outdoor first expansion valve 25 to the indoor expansion valve 41 is branched from the position between the outdoor heat exchanger 23 and the liquid gas heat exchanger 27 have. The confluent pipe 65 is connected to the suction side of the compressor 21 so as to return to the suction side of the compressor 21 from the outlet on the side of the supercooling refrigerant passage of the liquid gas heat exchanger 27. The outdoor second expansion valve (62) is composed of a motor-operated expansion valve and functions as a communicating pipe expansion mechanism for regulating the flow rate of the refrigerant flowing through the supercooling refrigerant passage (61). Thus, the refrigerant sent from the outdoor heat exchanger 23 to the indoor expansion valve 41 is supplied to the supercooling refrigerant passage 61 (see FIG. 6) after being reduced in pressure by the outdoor second expansion valve 62 in the liquid gas heat exchanger 27 The refrigerant is cooled by the refrigerant flowing through the evaporator. That is, the liquid-gas heat exchanger 27 is subjected to capacity control by adjusting the opening degree of the outdoor second expansion valve 62.

The supercooling refrigerant passage 61 is provided in a portion between the liquid side close valve 28a and the outdoor first expansion valve 25 in the refrigerating apparatus 10 and a portion on the suction side of the compressor 21, As shown in Fig.

The liquid-side shutoff valve 28a and the gas-side shutoff valve 28b are valves provided at connection ports to external equipment and piping (specifically, the first refrigerant communication pipe 6 and the second refrigerant communication pipe 7). The liquid side close valve 28a is connected to the liquid gas heat exchanger 27 and the gas side close valve 28b is connected to the switching mechanism 22 so as to block the passage of the refrigerant.

(2-2-3) Outdoor controller and various sensors

The outdoor air conditioning outdoor unit (2) has an outdoor control device (30) for controlling the operation of each part constituting the air conditioning outdoor unit (2). The outdoor control device 30 has a microcomputer installed to control the air conditioner outdoor unit 2 and an inverter circuit for controlling the memory and the motor 26a. The indoor unit 4a and the indoor unit 4b Control signals can be exchanged between the control devices 47 via the transmission line 8a. That is to say, the air conditioning control device 8 that controls the operation of the entire air conditioner 1 is constructed by the transmission line 8a connecting between the indoor control device 47, the outdoor control device 30 and the indoor control device 47 ).

Various kinds of sensors are installed in the air conditioner outdoor unit 2. The refrigerant pipe on the discharge side of the compressor (21) is provided with a discharge pressure sensor (31) for detecting the compressor discharge pressure and a discharge temperature sensor (32) for detecting the discharge temperature of the compressor. The compressor suction side pipe 29a is provided with a suction temperature sensor 34 for detecting the temperature of the gas refrigerant sucked into the compressor 21 and a suction pressure sensor 33 for detecting the suction pressure of the compressor. The outdoor control device 30 is configured to control the operation capacity of the compressor 21. The outdoor control device 30 is configured to control the operation of the compressor 21 during the heating operation and the target value of the suction pressure of the compressor 21 during the cooling operation, Pressure target value which is the discharge pressure target value of the discharge pressure of the fluid. During the cooling operation, the operating capacity of the compressor (21) is controlled so that the suction pressure sensor (33) is set to the low pressure target value, and in the heating operation, the discharge pressure sensor The operation capacity is controlled.

The liquid pipe temperature sensor 35 for detecting the temperature of the refrigerant (that is, the liquid pipe temperature) is provided at the outlet of the liquid-gas heat exchanger 27 on the side of the main refrigerant circuit. An outdoor temperature sensor 36 for detecting the temperature of the outdoor air (that is, the outdoor temperature) flowing into the inside of the outdoor air conditioning unit 2 is provided on the side of the outdoor air intake port. The supercooling of the liquid gas heat exchanger 27 is performed in the merging pipe 65 of the supercooling refrigerant passage 61 from the liquid gas heat exchanger 27 to the low pressure refrigerant pipe between the switching mechanism 22 and the accumulator 29, A bypass temperature sensor 63 for detecting the temperature of the refrigerant flowing through the outlet on the refrigerant flow path side for the refrigerant is provided. The discharge temperature sensor 32, the suction temperature sensor 34, the liquid pipe temperature sensor 35, the outdoor temperature sensor 36 and the bypass temperature sensor 63 are made of a thermistor.

(2-3) Refrigerant communication line

The refrigerant communication tubes 6 and 7 are refrigerant piping that is locally installed when installing the air conditioner outdoor unit 2 and the air conditioner indoor unit 4 at the installation site. The first refrigerant communication pipe 6 is connected to the air conditioning outdoor unit 2 and the air conditioning indoor units 4a and 4b so that the liquid refrigerant having a large degree of supercooling in the liquid gas heat exchanger 27 is supplied to the indoor expansion valve And sends the condensed liquid refrigerant in the indoor heat exchanger 42 to the outdoor heat exchanger 23 of the air conditioner outdoor unit 2 during the heating operation. The second refrigerant communication pipe 7 is connected to the air conditioning outdoor unit 2 and the air conditioning indoor units 4a and 4b so that the gas refrigerant evaporated in the indoor heat exchanger 42 is supplied to the air conditioning outdoor unit 2 And sends the compressed gas refrigerant in the compressor 21 to the indoor heat exchanger 42 in the air conditioning indoor units 4a and 4b at the time of heating operation.

(2-4) Air conditioning control device

Fig. 2 shows a control block diagram of the air conditioner 1. As shown in Fig. The air conditioner control device 8 as control means for controlling various operations of the air conditioner 1 includes an outdoor control device 30 and an indoor control device 47 connected via a transmission line 8a, ). The air conditioner control device 8 receives detection signals from the various sensors 31 to 36 and 44 to 46 and 63 and controls the various devices 21, 22, 25, 26, 41, 43 and 62 based on these detection signals, .

(3) Operation of the air conditioner

Next, the basic operation of the air conditioner 1 according to the present embodiment will be described. In addition, control in various operations to be described below is performed by the air conditioning control device 8. [

(3-1) Cooling operation

In an air conditioner that operates at a low differential pressure in which the difference between the high pressure and the low pressure in the refrigeration cycle is small, for example, when the operation for increasing the evaporation temperature is performed when the refrigerant charge amount is large and the outside air temperature is low, There is a case where the refrigerant is supercooled in front of the heat exchanger (42). In the following description, the operation when the subcooling state is not performed in front of the indoor heat exchanger 42 is referred to as a normal cooling operation, and the operation when the subcooling state is set is referred to as an abnormal cooling operation, Described separately.

(3-1-1) Cooling operation in normal operation

1, that is, when 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 connected to the suction side of the compressor 21, Is connected to the gas side of the indoor heat exchanger (42) through the gas side shutoff valve (28b) and the second refrigerant communication pipe (7). During the cooling operation, the outdoor first expansion valve (25) is in a fully opened state, and the liquid side close valve (28a) and the gas side close valve (28b) are in the open state.

Each indoor expansion valve 41 is controlled such that the superheat degree of the refrigerant at the outlet of the indoor heat exchanger 42 (that is, the gas side of the indoor heat exchanger 42) is constant at the first superheat degree target value Tsh1 The opening is also adjusted. For example, in Fig. 3, the point C of the pressure P1 is the inflow side of the indoor expansion valve 41, and the point B of the pressure P2 is the outflow side of the indoor expansion valve 41. Fig. The degree of superheat of the refrigerant at the outlet of each indoor heat exchanger 42 is controlled by the indoor control device 47 from the refrigerant temperature Th1 detected by the indoor gas pipe temperature sensor 45 to the indoor liquid temperature sensor 44 By subtracting the refrigerant temperature Th2 detected by the refrigerant temperature Th2.

The reason why the subcooling state is not provided in front of the indoor heat exchanger 42 is that the indoor unit liquid pipe pressure saturation temperature Tein is lower than the refrigerant temperature Th2 detected by the indoor liquid pipe temperature sensor 44 (Tein ≤ Th2). This indoor unit liquid pipe pressure saturation temperature Tein is obtained, for example, by converting the suction pressure LP of the compressor 21 detected by the suction pressure sensor 33 into the saturation temperature corresponding to the evaporation temperature Te.

The outdoor second expansion valve 62 is also controlled so that the superheat degree of the refrigerant at the outlet of the liquid gas heat exchanger 27 on the side of the subcooling refrigerant flow path becomes the target value of the superheat degree (hereinafter, ). The superheat degree of the refrigerant at the outlet of the liquid-gas heat exchanger 27 on the side of the supercooling refrigerant passage is set so that the suction pressure of the compressor 21 detected by the suction pressure sensor 33 reaches the saturation temperature corresponding to the evaporation temperature And is subtracted from the refrigerant temperature detected by the bypass temperature sensor 63 to subtract the saturation temperature of the refrigerant.

When the compressor 21, the outdoor fan 26 and the indoor fan 43 are operated in the state of the refrigerating device 10, the low-pressure gas refrigerant is sucked into the compressor 21 and compressed to be a high-pressure gas refrigerant . Thereafter, the high-pressure gas refrigerant is sent to the outdoor heat exchanger 23 via the switching mechanism 22, and is subjected to heat exchange with the outdoor air supplied by the outdoor fan 26 and is condensed to become a high-pressure liquid refrigerant. After passing through the outdoor first expansion valve 25, the high-pressure liquid refrigerant flows into the liquid-gas heat exchanger 27, performs heat exchange with the refrigerant flowing in the supercooling refrigerant passage 61, State. At this time, a part of the high-pressure liquid refrigerant condensed in the outdoor heat exchanger 23 is branched into the supercooling refrigerant passage 61, is decompressed by the outdoor second expansion valve 62, and then flows to the suction side of the compressor 21 Is returned. Here, the refrigerant passing through the outdoor second expansion valve 62 is decompressed to the vicinity of the suction of the compressor 21, so that a part of the refrigerant evaporates. The refrigerant flowing from the outlet of the outdoor second expansion valve (62) of the supercooling refrigerant passage (61) toward the suction side of the compressor (21) passes through the liquid gas heat exchanger (27) And performs heat exchange with the high-pressure liquid refrigerant sent from the heat exchanger (23) to the air conditioning indoor unit (4).

Then, the high-pressure liquid refrigerant in the supercooled state is sent to the air conditioning indoor unit 4 via the liquid side shut-off valve 28a and the first refrigerant communication pipe 6. [

The high-pressure liquid refrigerant sent to the air conditioning indoor unit 4 is depressurized by the indoor expansion valve 41 to the vicinity of the suction pressure of the compressor 21 to become a low-pressure gas-liquid two-phase refrigerant and is supplied to the indoor heat exchanger 42 Exchanges heat with room air in the indoor heat exchanger (42) and evaporates to become a low-pressure gas refrigerant.

This low-pressure gas refrigerant is sent to the air conditioner outdoor unit 2 via the second refrigerant communication pipe 7 and is supplied to the compressor 21 again via the gas-side closing valve 28b and the switching mechanism 22 Inhaled. As described above, the air conditioner 1 is configured such that the outdoor heat exchanger 23 is used as a condenser for the refrigerant compressed in the compressor 21, and the indoor heat exchanger 42 is condensed in the outdoor heat exchanger 23 The first refrigerant communication pipe 6 and the indoor expansion valve 41 to perform the cooling operation to function as the evaporator of the refrigerant.

(3-1-2) Cooling operation in abnormal condition

The reason for switching from the normal cooling operation to the abnormal cooling operation is when it is determined in the indoor control device 47 that the front of the indoor heat exchanger 42 is in a supercooled state. The indoor control device 47 determines that the front of the indoor heat exchanger 42 is supercooled when the indoor liquid pressure saturation temperature Tein is higher than the refrigerant temperature Th2 detected by the indoor liquid temperature sensor 44 (Tein> Th2) State.

The state in which the indoor unit liquid pipe pressure saturation temperature Tein is higher than the refrigerant temperature Th2 detected by the indoor liquid pipe temperature sensor 44 is a state in which the refrigeration cycle is operating as shown in Fig. 3, the enthalpy hB of the refrigerant at point B after expansion by the indoor expansion valve 41 is lower than the enthalpy hA at the point A where the saturated liquid line L1 crosses the evaporation pressure P2. In this state, since the refrigerant flowing into the indoor heat exchanger 42 has a supercooling degree, if the superheat degree is controlled based on the temperature difference between before and after the indoor heat exchanger 42, the actual superheat degree is erroneously detected. As a result, even if the refrigerant at the outlet of the indoor heat exchanger 42 is mistaken as an overheated state despite the two-phase state and the opening degree of the indoor expansion valve 41 is slightly adjusted, the refrigerant temperature in the two- The control may be disabled.

Accordingly, when it is determined that Tein > Th2, the indoor controller 47 switches the target value of the superheat degree of the refrigerant from the first superheat degree target value Tsh1 to the second superheat degree target value Tsh2, 41 is controlled. Here, the second superheat degree target value Tsh2 is greater than the first superheat degree target value Tsh1 (Tsh2> Tsh1).

The degree of supercooling at the entrance of the indoor heat exchanger 42 that can be generated is evaluated and the second superheating degree target value Tsh2 set at a temperature higher than the first superheating degree target value Tsh1 is changed to the superheating degree control The refrigerant at the outlet of the indoor heat exchanger 42 at the time of performing the operation can be surely made to be the superheated refrigerant, and deterioration of the controllability can be prevented.

However, if the target value of the superheat degree is changed to the second superheat degree target value Tsh2 and operated, the efficiency is lowered. Therefore, when the first superheating degree can be returned to the target value Tsh1, the indoor control device 47 returns the target value of the superheat degree to the first superheat degree target value Tsh1. Specifically, for example, the indoor control device 47 determines whether the indoor liquid pressure saturation temperature Tein is lower than the refrigerant temperature Th2 detected by the indoor liquid temperature sensor 44 by a preset temperature? 3 DEG C)], the target value of the superheat degree is changed from the second superheat degree target value Tsh2 to the first superheat degree target value Tsh1. That is, the target value of the superheat degree is switched when the condition of Tein < Th2 -? Is satisfied. This temperature β is a margin for hunting prevention.

(3-2) Heating operation

1, that is, the discharge side of the compressor 21 is connected to the indoor heat exchanger (not shown) through the gas-side shut-off valve 28b and the second refrigerant communication pipe 7, 42, and the suction side of the compressor 21 is connected to the gas side of the outdoor heat exchanger 23. The outdoor first expansion valve 25 is regulated to be opened to reduce the pressure of the refrigerant flowing into the outdoor heat exchanger 23 to a pressure capable of evaporating the refrigerant in the outdoor heat exchanger 23 (i.e., evaporation pressure). The liquid-side shutoff valve 28a and the gas-side shutoff valve 28b are in an open state. The opening degree of the indoor expansion valve 41 is adjusted such that the supercooling degree of the refrigerant at the outlet of the indoor heat exchanger 42 becomes constant at the target value of the supercooling degree. The degree of supercooling of the refrigerant at the outlet of the indoor heat exchanger 42 is calculated by converting the discharge pressure of the compressor 21 detected by the discharge pressure sensor 31 to the saturation temperature corresponding to the condensation temperature, Is detected by subtracting the refrigerant temperature detected by the indoor liquid pipe temperature sensor (44).

When the compressor 21, the outdoor fan 26 and the indoor fan 43 are operated in the state of the refrigeration apparatus 10, the low-pressure gas refrigerant is sucked and compressed by the compressor 21 to become a high-pressure gas refrigerant The switching mechanism 22, the gas-side shutoff valve 28b and the second refrigerant communication pipe 7 to the air conditioning indoor unit 4. [

The high-pressure gas refrigerant sent to the air conditioning indoor unit 4 undergoes heat exchange with the room air in the indoor heat exchanger 42 to be condensed to become a high-pressure liquid refrigerant. Thereafter, when the indoor refrigerant passes through the indoor expansion valve 41, And is reduced in accordance with the valve opening degree of the expansion valve (41).

The refrigerant that has passed through the indoor expansion valve 41 is sent to the air conditioner outdoor unit 2 via the first refrigerant communication pipe 6 and is supplied to the liquid side close valve 28a, the liquid gas heat exchanger 27, Is further decompressed via the expansion valve (25), and then flows into the outdoor heat exchanger (23). The low-pressure gas-liquid two-phase refrigerant introduced into the outdoor heat exchanger 23 is heat-exchanged with the outdoor air supplied by the outdoor fan 26 and evaporates to become a low-pressure gas refrigerant. The switching mechanism 22 And then sucked into the compressor 21 again.

The above-described operation control is performed by the air conditioning control device 8 (the indoor control device 47 and the outdoor control device 30 and the transmission line 8a connecting between them) for performing the normal operation including the cooling operation and the heating operation, Lt; / RTI &gt;

(4) Characteristics of refrigeration system

(4-1) In the refrigeration apparatus 10 according to the present embodiment, the compressor 21, the outdoor heat exchanger 23 (radiator), and the indoor heat exchanger 42 (evaporator) are connected in order Side main refrigerant circuit 10a and the outdoor side main refrigerant circuit 10c (refrigerating circuit) in which the refrigerant circulates are formed. The indoor expansion valve 41 (expansion mechanism) provided on the inflow side of the indoor heat exchanger 42 is introduced into the indoor heat exchanger 42 based on the target value of superheat on the outflow side of the indoor heat exchanger 42 Thereby controlling expansion of the refrigerant. The supercooled state of the refrigerant on the inflow side of the indoor heat exchanger (42) is detected by the indoor liquid temperature sensor (44) and the suction pressure sensor (33) (detector). When the indoor control device 47 determines that the refrigerant on the inflow side of the indoor heat exchanger 42 is in the supercooled state based on the detection results of the indoor liquid pipe temperature sensor 44 and the suction pressure sensor 33, And the setting of increasing the superheat degree target value from the first superheat degree target value Tsh1 to the second superheat degree target value Tsh2 is performed.

The setting change for raising the target value of the superheat degree is performed when the refrigerant on the inflow side of the indoor heat exchanger 42 is judged as being in the supercooled state so that the situation that the superheat degree of the indoor heat exchanger 42 can not be controlled can be avoided So that the degree of superheat of the indoor heat exchanger 42 can be appropriately controlled. Therefore, the superheating degree of the refrigerating apparatus (10), which is likely to be in a supercooled state at the front of the indoor heat exchanger (42), can be appropriately controlled. In particular, since the amount of refrigerant is large, it is possible to sufficiently cope with the case where the refrigerant is likely to be supercooled in front of the indoor heat exchanger 42 (utilization side heat exchanger) functioning as an evaporator.

(4-2) The suction pressure sensor 33 is a first detector for detecting the pressure saturation temperature of the inlet side of the indoor heat exchanger 42 (use side heat exchanger), and the indoor liquid temperature sensor 44 is a first detector And a second detector for detecting the temperature of the refrigerant on the inflow side of the heater (42). The indoor control device 47 (control section) determines whether the indoor liquid pressure saturation temperature Tein is larger than the refrigerant temperature Th2 detected by the indoor liquid temperature sensor 44 (comparison of detection results of the first detector and the second detector) And determines whether or not the refrigerant on the inflow side of the indoor heat exchanger (42) is in a supercooled state. Therefore, even if the refrigerant on the inflow side of the indoor heat exchanger 42 is supercooled, the supercooled state can be accurately determined.

As described above, the conventional indoor liquid temperature sensor 44 can be used for the second detector for determining whether or not the refrigerant on the inflow side of the indoor heat exchanger 42 (utilization side heat exchanger) is in the supercooled state , It is possible to suppress an increase in cost. Likewise, since the conventional suction pressure sensor 33 can be used for the first detector for judging whether or not the refrigerant on the inflow side of the indoor heat exchanger 42 is in a supercooled state, an increase in cost can be suppressed .

(5) Modifications

(5-1) Modification Example A

The refrigerating device 10 of the above embodiment explains a case where the indoor control device 47 increases the target value of superheat degree when it is determined that the indoor heat exchanger 42 (evaporator) is in the supercooled state during the cooling operation However, when it is determined that the indoor control device 47 is in the supercooled state, the setting may be changed so that the outdoor control device 30 lowers the low-pressure target value. In the case of the refrigerating device 10, the low pressure target value is the indoor unit liquid pipe pressure saturation temperature Tein. In such a case, the air conditioning control apparatus 8 becomes a control section. The air conditioning control device 8 determines the low pressure target value from the first low pressure target value PL1 to the second low pressure lower than the first low pressure target value PL2 from the detection result of the indoor liquid temperature sensor 44 and the suction pressure sensor 33, To the target value PL2. That is, PL1 > PL2.

When the low pressure target value is changed to the second low pressure target value PL2 which is lower than the first low pressure target value PL1, the target value of the superheat degree does not change, so that the pressure drop in the indoor expansion valve 41 becomes large, Pressure is reduced. Thereby, the state of the refrigerant at the time point B1 when the refrigerant passes through the indoor expansion valve 41 is lowered to, for example, P3 as shown in Fig. 3, and the refrigerant is discharged to the downstream side of the indoor expansion valve 41 (The inlet side of the evaporator 42) is changed to the gas-liquid two-phase state, and control by the degree of superheat can be performed.

Is set to the second low-pressure target value (L2), the indoor controller (47) operates, for example, as the low-pressure target upper limit value and the indoor unit liquid pipe pressure saturation temperature Tein target value is equal to the indoor unit liquid pipe temperature Th2. If the low pressure Tein is lowered in relation to the load factor or the like under such a condition, the control automatically shifts from the above-described determination condition to the normal control. That is, the indoor control device 47 detects that the indoor liquid pressure saturation temperature Tein is equal to or lower than the temperature Th2 detected by the indoor liquid temperature sensor 44 (Tein? Th2), and based on the detection result, And changes from the second low-pressure target value PL2 to the first low-pressure target value PL1.

(5-2) Variation B

In the refrigeration apparatus 10 of the above embodiment, when the indoor unit liquid pipe pressure saturation temperature Tein is higher than the refrigerant temperature Th2 detected by the indoor liquid temperature sensor 44 (Tein> Th2), the indoor heat exchanger 42 are in a supercooled state, it is also possible to judge using the outdoor air liquid pipe inlet temperature T1. The outdoor liquid pipe inlet temperature T1 is a temperature detected by, for example, the liquid pipe temperature sensor 35 (third detector). The indoor control unit 47 determines that the inflow side of the indoor heat exchanger 42 is undercooling when the condition of Tein > T1- alpha is satisfied, taking into account heat loss. The indoor control device 47 determines whether the superheat degree target value is to be changed from the first superheat degree target value Tsh1 to the second superheat degree target value Tsh2 or the low pressure target value is set to be the first And changes from the low-pressure target value PL1 to the second low-pressure target value PL2. Is a value relating to heat loss and is a value derived from an experiment or the like and is, for example, about 3 캜.

The switching of the superheat degree target value and the switching of the low pressure target value performed by the indoor control device 47 when it is judged that the inflow side of the indoor heat exchanger 42 is a supercooling degree is the same as the above embodiment or the modification B.

The determination as to whether or not the inflow side of the indoor heat exchanger 42 changes from a supercooled state to a non-supercooled state to return the superheat degree target value or the low pressure target value to the original state is also determined by using the outdoor air liquid inlet temperature T1 Is done. That is, at the time when it is detected that the condition of Tein? T1 -? -? Is satisfied, the target value of the heat temperature is changed from the second superheat degree target value Tsh2 to the first superheat degree target value Tsh1, And changes the target value from the second low-pressure target value PL2 to the first low-pressure target value PL1.

In the third detector for judging whether or not the refrigerant on the inflow side of the indoor heat exchanger 42 (the utilization side heat exchanger) is in the supercooled state, the conventional liquid temperature sensor 35 Sensor) can be used, so that an increase in cost can be suppressed. Likewise, since the conventional suction pressure sensor 33 can be used for the first detector for judging whether or not the refrigerant on the inflow side of the indoor heat exchanger 42 is in a supercooled state, an increase in cost can be suppressed .

(5-3) Variation C

In the above embodiment and Modification A, the case where the indoor heat exchanger 42 functions as an evaporator during the cooling operation has been described. However, in the heating operation, the refrigerant on the inflow side of the outdoor heat exchanger 23 The present invention can be applied even in a case where it is easy to become a supercooled state.

Whether or not the supercooled state is occurring on the inflow side of the outdoor heat exchanger 23 can be determined by detecting whether or not the condition of Tein > T1- alpha is satisfied by using the low pressure Tein and the outdoor liquid pipe inlet temperature T1 The control device 30 can judge it.

When the supercooling state is judged to have occurred at the inflow side of the outdoor heat exchanger 23, the high-pressure target value is changed from the first high-pressure target value HP1 to the second high- Value (HP2). In this case, the second high-pressure target value HP2 is set higher than the first high-pressure target value HP1 (HP2> HP1).

Then, similarly to the above-described embodiment and Modifications A and B, when it is detected that the condition of Tein? T1-?? Is satisfied, the high-pressure target value is returned to the normal state. That is, when it is determined that the supercooled state has been eliminated on the inflow side of the outdoor heat exchanger 23, the high pressure target value is changed from the second high pressure target value HP2 to the first high pressure target value HP1.

(5-4) Variation example D

In the above embodiment, two air-conditioning indoor units 4a and 4b are connected as a configuration of the air-conditioning indoor unit 4. However, one or three air-conditioning indoor units may be connected. Further, when a plurality of air conditioning indoor units are connected, air conditioning indoor units of different configurations may be connected.

(5-5) Variation E

In the above embodiment, the case where the target superheat degree value is changed to the second superheat degree target value Tsh2 which is set to a temperature higher than the first superheat degree target value Tsh1 has been described. However, it is also possible to set a plurality of different superheat degree target values as the second superheat degree target value. For example, a third superheating degree target value Tsh3 higher than the second superheat degree target value Tsh2 is provided, and when the supercooling degree Tsc satisfies the condition of 0 <Tsc? Tsc1, the second superheat degree target value (Tsh2) is used, and when the supercooling degree Tsc satisfies the condition of Tsc1 < Tsc, the third superheat degree target value Tsh3 may be used. Further, a relational expression of the second superheating degree target value Tsh2 and the supercooling degree Tsc is prepared in advance, the supercooling degree at the inlet of the indoor heat exchanger 42 is evaluated, and the second superheating degree target The value Tsh2 may be changed to a temperature higher than the first superheating degree target value Tsh1. Further, the relational expression of the second superheat degree target value Tsh2 and the supercooling degree Tsc may be appropriately determined through, for example, experimentation or trial run performed beforehand.

10: Freezer
21: Compressor
23: outdoor heat exchanger
30: outdoor control device
32: Discharge temperature sensor
33: Suction pressure sensor
41: indoor expansion valve
42: Indoor heat exchanger
44: indoor liquid temperature sensor
47: indoor control device

Claims (8)

A refrigerating device (10) having a refrigerant circuit in which a compressor (21), a radiator (23, 42) and an evaporator (42, 23)
The expansion of the refrigerant flowing into the evaporator based on at least one of a target value of high pressure of the refrigerant circuit, a low pressure target value of the refrigerant circuit, and a target value of superheat degree of the outlet side of the evaporator, provided on the inflow side of the evaporator, An expansion mechanism (41) for controlling,
A detector (29, 44, 35, 31) for detecting the supercooled state of the refrigerant on the inflow side of the evaporator,
Pressure setting means for changing a setting for increasing the high-pressure target value, a setting for lowering the low-pressure target value, and a setting for increasing the superheating degree target value, when the refrigerant on the inflow side of the evaporator is determined to be in the supercooled state, (47, 30, 8) capable of changing at least one predetermined setting of the change,
. The method according to claim 1,
And the control unit returns the predetermined setting change to the original state when the supercooled state is resolved after the predetermined setting change. 3. The method of claim 2,
The control unit may prevent the hunting from occurring between the value when it is determined that the supercooled state has been changed in the case of performing the predetermined setting change and the value when it is determined that the supercooled state has deviated from the supercooled state in the case of returning the predetermined setting change to the original state Freezing device that provides a margin for. 4. The method according to any one of claims 1 to 3,
The evaporator is a utilization-side heat exchanger (42)
The control unit (47), when it is determined on the basis of the detection result of the detector that the refrigerant on the inflow side of the utilization side heat exchanger is in the supercooled state, changes the setting for lowering the low pressure target value And the setting change can be performed at least one of them. 5. The method of claim 4,
The detector includes a first detector (33) for detecting the pressure saturation temperature on the inlet side of the utilization side heat exchanger, a second detector (44) for detecting the temperature of the refrigerant on the inlet side of the utilization side heat exchanger, Or a third detector (35) for detecting the temperature of the refrigerant on the inflow side of the first detector (33) and the expansion mechanism,
Wherein the control unit determines whether the refrigerant on the inlet side of the utilization-side heat exchanger is under supercooled state based on a comparison between the detection results of the first detector and the second detector or a comparison between the detection results of the first detector and the third detector Is capable of determining whether or not the refrigerant is in the refrigerating cycle. 6. The method of claim 5,
The third detector is a liquid pipe temperature sensor (35) provided on the outflow side of the radiator,
The control unit uses a temperature obtained by subtracting a correction value corresponding to heat loss from the installation position of the liquid pipe temperature sensor to the expansion mechanism from the detection temperature of the liquid pipe temperature sensor as the temperature of the refrigerant on the inflow side of the expansion mechanism Side heat exchanger, so that it is possible to determine whether or not the refrigerant on the inlet side of the utilization-side heat exchanger is in a supercooled state. 6. The method of claim 5,
The first detector is a suction pressure sensor (33) for detecting the pressure on the suction side of the compressor,
Wherein the control unit is capable of calculating the pressure saturation temperature from a pressure detected by the suction pressure sensor. The method according to claim 6,
The first detector is a suction pressure sensor (33) for detecting the pressure on the suction side of the compressor,
Wherein the control unit is capable of calculating the pressure saturation temperature from a pressure detected by the suction pressure sensor.

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