WO2018167961A1

WO2018167961A1 - Air conditioner

Info

Publication number: WO2018167961A1
Application number: PCT/JP2017/010999
Authority: WO
Inventors: 和典是永
Original assignee: 三菱電機株式会社
Priority date: 2017-03-17
Filing date: 2017-03-17
Publication date: 2018-09-20
Also published as: JPWO2018167961A1; JP6625265B2

Abstract

An air conditioner comprises: a refrigerant circuit in which a compressor, an outdoor heat exchanger, a plurality of expansion units, and a plurality of indoor heat exchangers are connected by piping and in which refrigerant flows; an outdoor unit that houses at least the compressor and the outdoor heat exchanger; a plurality of indoor units that respectively houses at least the plurality of indoor heat exchangers; and a control unit that has, as modes to control the operation of the plurality of expansion units, an overheating control mode to control each of the expansion units on the basis of the amount of overheating on the outlet side of the plurality of indoor heat exchangers during cooling operation and an overcooling control mode to control all of the expansion units on the basis of the amount of overcooling of the outdoor heat exchanger during cooling operation. The control unit has a determination means for determining whether an indoor unit from the plurality of indoor units is not suitable for overheating control mode, and a switching means for switching from the overheating control mode to the overcooling control mode when the determination means determines that an indoor unit is not suitable for overheating control mode.

Description

Air conditioner

The present invention relates to an air conditioner including a plurality of indoor units.

Conventionally, a multi-type air conditioner having a plurality of indoor units is known. The multi-type air conditioner includes an outdoor unit and an indoor unit connected to the outdoor unit by an extension pipe. The outdoor unit includes a compressor, a four-way valve that switches the refrigerant flow direction, an outdoor heat exchanger, an outdoor blower, a liquid side extension pipe connection valve, a gas side extension pipe connection valve, and a discharge that is on the high pressure side of the compressor. There are provided a pressure sensor arranged in the side pipe, an outdoor outlet side temperature sensor for detecting the temperature of the refrigerant flowing to the outlet side of the outdoor heat exchanger during the cooling operation, and an outdoor control device. The indoor unit includes a plurality of electronic expansion valves that depressurize the condensed refrigerant, a plurality of indoor heat exchangers, a plurality of indoor fans, and an indoor inlet that detects the temperature of the refrigerant flowing to the inlet side of the indoor heat exchanger during cooling operation A side temperature sensor, an indoor outlet side temperature sensor that detects the temperature of the refrigerant that flows to the outlet side of the indoor heat exchanger during cooling operation, and an indoor control device are provided. A refrigerant circuit is configured by connecting a compressor, a four-way valve, an outdoor heat exchanger, an electronic expansion valve, and an indoor heat exchanger by piping. The outdoor control device and the indoor control device operate the electronic expansion valve based on the pressure detected by the pressure sensor, the outdoor outlet side temperature sensor, the indoor inlet side temperature sensor, and the indoor outlet side temperature sensor. Control.

In addition, the indoor control device stores the indoor unit configuration or capability band, which is information unique to each indoor unit, and the indoor control device uses information on the indoor unit configuration or capability band, etc., using various communication means. To the outdoor control device. Thereby, the indoor unit and the outdoor unit can share information such as the indoor unit form or the capacity band. In the refrigerant circuit, during the cooling operation, the four-way valve is switched so that the discharge side piping of the compressor and the outdoor heat exchanger are connected, and the outdoor heat exchanger acts as a condenser to exchange the indoor heat. The vessel acts as an evaporator. During the cooling operation, the electronic expansion valve in each indoor unit causes the evaporator overheating derived from the difference between the indoor evaporation temperature detected by the indoor inlet side temperature sensor and the indoor outlet temperature detected by the indoor outlet side temperature sensor. The degree of opening is controlled such that the degree SH_e [deg] approaches the target superheat degree SHm_e [deg]. In general, SH_e increases as the opening of the electronic expansion valve decreases, and SH_e decreases as the opening of the electronic expansion valve increases.

In a multi-type air conditioner, multiple indoor units are connected. And there may be a gap between the indoor temperature and the set temperature of the place where each indoor unit is installed. In the case of a room where the room temperature and the set temperature are substantially equal, the cooling capacity may be small. On the other hand, in a room where there is a gap between the room temperature and the set temperature, it is necessary to increase the cooling capacity. That is, in a room where the room temperature and the set temperature are substantially equal, control is performed to suppress the cooling capacity by increasing the value of SHm_e and reducing the amount of refrigerant flowing by reducing the opening of the electronic expansion valve. desired. In addition to controlling the degree of opening of the electronic expansion valve using the degree of superheat of the evaporator, it is also known to control the degree of opening of the electronic expansion valve using the degree of supercooling of the condenser. The electronic expansion valve in each indoor unit has a supercooling degree SC_hex of the condenser derived from the difference between the high pressure side saturation temperature at which the high pressure detected by the pressure sensor is obtained and the temperature detected by the outdoor outlet side temperature sensor. The degree of opening is controlled so that [deg] approaches the target supercooling degree SCm_hex [deg], and is distributed according to the capacity band of each indoor unit.

In addition, when controlling the electronic expansion valve of each indoor unit during cooling operation using the degree of supercooling of the condenser, there is no individual control target value for each indoor unit. For this reason, in a room where the room temperature and the set temperature are substantially equal, it is difficult to control each room such as increasing the value of SHm_e. In addition, the outlet of the indoor heat exchanger may be wet, increasing the amount of refrigerant required, increasing the low-pressure pressure loss due to the dryness of the refrigerant sucked into the compressor, and liquid back to the compressor There are concerns. For this reason, in a multi-type air conditioner, control of an electronic expansion valve using the degree of superheat of the evaporator is often employed.

Here, when SH_e becomes excessive during the cooling operation, a part of the indoor heat exchanger may be in a dry state. When a part of the indoor heat exchanger is in a dry state, the air that has passed through the dry part is not cooled and becomes a high-temperature and high-humidity wind. On the other hand, the air that has passed through the portion that is not dry is cooled to become low-temperature and low-humidity wind. When the high-temperature, high-humidity wind and the low-temperature, low-humidity wind are mixed, the high-temperature, high-humidity air is cooled, and when it reaches the dew point temperature, it becomes dew and accumulates in the air path. As a result, there is a risk that a dew phenomenon occurs in which the accumulated dew pops out from the outlet of the indoor unit by the wind passing through the air passage.

Depending on various circumstances such as productivity, the indoor outlet side temperature sensor may be attached at a position slightly shifted to the intermediate side between the inlet and outlet of the indoor heat exchanger. In this case, when the opening degree of the electronic expansion valve is controlled by deriving SH_e based on the temperature detected by the indoor inlet side temperature sensor and the temperature detected by the indoor outlet side temperature sensor, the derived SH_e However, the value is smaller than the actual degree of superheat. That is, in the degree of superheat, a flaw occurs between the detected value and the actual value. If the control of the opening degree of the electronic expansion valve of each indoor unit is continued in an attempt to bring SH_e closer to the target superheat degree SHm_e with soot, the actual superheat degree becomes larger than the target superheat degree. Phenomenon such as dew erosion due to dry condition is likely to occur.

The optimum value of the degree of superheat on the indoor unit outlet side is about 1 to 5 [deg], and the target superheat degree SHm_e is generally set to about 2 to 4 [deg]. In order to avoid a dry state, when the indoor outlet side temperature sensor is attached at a position slightly shifted to the intermediate side between the inlet and outlet of the indoor heat exchanger, the value of the target superheat degree SHm_e of the indoor unit is set. Although it is necessary to make it small intentionally, it is not easy to know how small it is. Moreover, the indoor outlet side temperature sensor may be attached to a position where the degree of superheat cannot be detected at all. In this case, a simple specification change such as changing the target superheat degree cannot cope. In this case, it is necessary to change the installation position of the indoor outlet side temperature sensor to a position where the degree of superheat can be detected appropriately. That is, it involves a change in hardware specifications.

Here, Patent Document 1 discloses an air conditioner that stores in advance a target superheat degree of an evaporator according to the model of the indoor unit connected to the outdoor unit. Patent Document 1 thereby performs optimal control individually for each indoor unit.

JP 2001-263760 A

However, Patent Document 1 does not disclose where the indoor outlet side temperature sensor is provided in the indoor heat exchanger. In Patent Document 1, SH_e is derived based on the temperature detected by the indoor inlet side temperature sensor and the temperature detected by the indoor outlet side temperature sensor, and the opening degree of the electronic expansion valve is adjusted so that SH_e approaches SHm_e. Is controlled. Here, when the indoor outlet side temperature sensor is attached between the inlet and the outlet of the indoor heat exchanger, the derived SH_e has a value smaller than the actual degree of superheat. At this time, the indoor heat exchanger is in a dry state, and there is a possibility that a dew-off phenomenon occurs. In addition, the heat exchange performance may be reduced due to the deterioration of the refrigerant distribution rate inside the indoor heat exchanger.

In order to avoid this, it is conceivable to change the control of the electronic expansion valve corresponding to each indoor unit to control using the degree of supercooling of the condenser. The control of the electronic expansion valve using the degree of supercooling of the condenser is performed by controlling the degree of opening of the electronic expansion valve of each indoor unit so that the degree of supercooling SC_hex [deg] of the condenser approaches the target degree of supercooling SCm_hex [deg]. This is a control that determines the total value of these and distributes them according to the capacity of each indoor unit. However, compared with control using the degree of superheat of the evaporator, effects such as optimization of heat exchange capacity, reduction of the necessary refrigerant amount, avoidance of low pressure loss and avoidance of liquid back to the compressor cannot be obtained. Further, if the control based on the degree of superheat on the outlet side of the indoor heat exchanger is kept, it is necessary to change the arrangement of the indoor outlet side temperature sensor. In this case, since the position of the indoor outlet side temperature sensor set in consideration of productivity or the like is changed in the first place, the productivity is lowered as a result. Moreover, since it is necessary to change the position, a new development load increases. Thus, in the conventional technology, in the control based on the degree of supercooling, appropriate control cannot be performed for each indoor unit, and when there is an indoor unit that is inappropriate for control based on the degree of superheat, the indoor outlet This is accompanied by a change in the position of the side temperature sensor.

The present invention has been made to solve the above-described problems, and does not change the design even when there is an indoor unit in which control based on the degree of superheat is inappropriate while performing control based on the degree of superheat. An air conditioner is provided.

An air conditioner according to the present invention includes a refrigerant circuit in which a compressor, an outdoor heat exchanger, a plurality of expansion units, and a plurality of indoor heat exchangers are connected by pipes and through which refrigerant flows, and at least the compressor and the outdoor heat exchanger. As a mode for controlling the operation of the outdoor unit to be accommodated, the plurality of indoor units respectively accommodating at least a plurality of indoor heat exchangers, and the plurality of expansion sections, the superheat degree on the outlet side of the plurality of indoor heat exchangers during cooling operation A control unit having a superheat control mode for controlling each expansion unit based on the above, and a supercooling control mode for controlling all the expansion units based on the degree of supercooling of the outdoor heat exchanger during cooling operation, The control unit determines that there is an indoor unit unsuitable for the overheat control mode by a determination unit that determines whether there is an indoor unit unsuitable for the overheat control mode among the plurality of indoor units. If A switching means for switching from overheating control mode to the subcooling control mode, the.

According to the present invention, when there is an indoor unit unsuitable for the superheat control mode, the superheat control mode is switched to the supercooling control mode. For this reason, when there is no indoor unit unsuitable for the superheat control mode, control is performed in the superheat control mode, and only when there is an indoor unit unsuitable for the superheat control mode, control is performed in the supercooling control mode. Therefore, the effect obtained in the overheat control mode is maintained as much as possible, and no design change is involved.

It is a circuit diagram which shows the air conditioner 100 which concerns on Embodiment 1 of this invention. It is a block diagram which shows the control part 30 of the air conditioner 100 which concerns on Embodiment 1 of this invention. It is a Mollier diagram which shows the superheat degree in Embodiment 1 of this invention. It is a Mollier diagram which shows the degree of supercooling in Embodiment 1 of this invention. It is sectional drawing of the indoor heat exchanger 11 in Embodiment 1 of this invention. It is sectional drawing of the indoor heat exchanger 11 in Embodiment 1 of this invention. It is a flowchart which shows operation | movement of the air conditioner 100 which concerns on Embodiment 1 of this invention. It is a circuit diagram which shows the air conditioner 200 which concerns on Embodiment 2 of this invention. It is a circuit diagram which shows the air conditioner 300 which concerns on Embodiment 3 of this invention. It is a circuit diagram which shows the air conditioner 400 which concerns on Embodiment 4 of this invention.

Embodiment 1 FIG.
Hereinafter, embodiments of an air conditioner according to the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing an air conditioner 100 according to Embodiment 1 of the present invention. The air conditioner 100 is demonstrated based on this FIG. As shown in FIG. 1, the air conditioner 100 includes, for example, one outdoor unit 7 and n indoor units 13-1 to 13-n. The outdoor unit 7 and the n indoor units 13- 1 to 13-n are connected by a liquid side extension pipe 8 and a gas side extension pipe 9, respectively.

The air conditioner 100 is a multi air conditioner that performs air conditioning using, for example, a refrigeration cycle. In the air conditioner 100, for example, all of the n indoor units 13-1 to 13-n perform a cooling operation mode, and all of the n indoor units 133-1 to 13-n perform a heating operation. A heating operation mode in which either one of the modes is selected. In addition, although the case where there is one outdoor unit 7 is illustrated, two or more outdoor units may be used. Moreover, although the case where there are n indoor units 13 is illustrated, two or more indoor units 13 may be used. The indoor units 13-1 to 13-n may be collectively referred to as the indoor unit 13.

(Outdoor unit 7, indoor unit 13)
The outdoor unit 7 is installed outdoors, and includes a compressor 1, a flow path switching device 2, an outdoor heat exchanger 3, an outdoor blower 4, a liquid side extension pipe connection valve 5, and a gas side extension pipe connection valve. 6, a discharge sensor, an outdoor outlet side temperature sensor 15, and an outdoor control device 16. The n indoor units 13-1 to 13-n include expansion units 10-1 to 10-n, indoor heat exchangers 11-1 to 11-n, indoor blowers 12-1 to 12-n, and indoor entrance sides, respectively. It has temperature sensors 18-1 to 18-n, indoor outlet side temperature sensors 19-1 to 19-n, and indoor control devices 17-1 to 17-n. Here, the compressor 1, the flow path switching device 2, the outdoor heat exchanger 3, the n expansion units 10-1 to 10-n, and the n indoor heat exchangers 11-1 to 11-n are connected by piping. Thus, a refrigerant circuit 50 through which the refrigerant flows is configured.

In some cases, the inflating portions 10-1 to 10-n are collectively referred to as the inflating portion 10. Also, the indoor heat exchangers 11-1 to 11-n may be collectively referred to as the indoor heat exchanger 11. Furthermore, the indoor fans 12-1 to 12-n may be collectively referred to as the indoor fan 12. Furthermore, the indoor inlet side temperature sensors 18-1 to 18-n may be collectively referred to as indoor inlet side temperature sensors 18. The indoor outlet side temperature sensors 19-1 to 19-n may be collectively referred to as an indoor outlet side temperature sensor 19. Furthermore, the indoor control devices 17-1 to 17-n may be collectively referred to as the indoor control device 17.

(Refrigerant circuit 50)
The compressor 1 is a device that sucks refrigerant in a low-temperature and low-pressure state, compresses the sucked refrigerant, and discharges it as a refrigerant in a high-temperature and high-pressure state. The flow path switching device 2 is a device that switches the direction in which the refrigerant flows in the refrigerant circuit 50, and is, for example, a four-way valve. The outdoor heat exchanger 3 is a device that exchanges heat between, for example, outdoor air and a refrigerant. The outdoor heat exchanger 3 acts as a condenser during the cooling operation, and acts as an evaporator during the heating operation. The outdoor blower 4 is a device that is provided in the vicinity of the outdoor heat exchanger 3 and sends outdoor air to the outdoor heat exchanger 3. The expansion unit 10 is a pressure reducing valve or an expansion valve that expands by depressurizing the refrigerant. The expansion part 10 is an electronic expansion valve whose opening degree is adjusted, for example. The indoor heat exchanger 11 is a device that exchanges heat between indoor air and a refrigerant, for example. The indoor heat exchanger 11 acts as an evaporator during cooling operation and acts as a condenser during heating operation. The indoor blower 12 is a device that is provided in the vicinity of the indoor heat exchanger 11 and sends indoor air to the indoor heat exchanger 11.

The liquid side extension pipe connection valve 5 is a device provided in the vicinity of the liquid side extension pipe 8 that connects the outdoor unit 7 and the indoor unit 13. The liquid side extension pipe connection valve 5 allows or blocks the flow of refrigerant flowing from one of the outdoor unit 7 and the indoor unit 13 to the other. The gas side extension pipe connection valve 6 is a device provided in the vicinity of the gas side extension pipe 9 that connects the outdoor unit 7 and the indoor unit 13. The gas side extension pipe connection valve 6 allows or blocks the flow of the refrigerant flowing from one of the outdoor unit 7 and the indoor unit 13 to the other.

The pressure sensor 14 is a sensor that is provided in the discharge-side piping of the compressor 1 and detects the pressure Pd [kgf / cm ² G] of the high-temperature and high-pressure refrigerant that is compressed and discharged by the compressor 1. . The outdoor outlet side temperature sensor 15 is a sensor that detects the outdoor outlet side temperature Tcout [° C.] of the refrigerant flowing to the outlet side of the outdoor heat exchanger 3 during the cooling operation. The indoor inlet side temperature sensor 18 is a sensor that detects the indoor inlet side temperature Tein [° C.] of the refrigerant flowing to the inlet side of the indoor heat exchanger 11 during the cooling operation. Here, the indoor inlet side temperature of the refrigerant flowing to the inlet side of the indoor heat exchanger 11-n during the cooling operation of the indoor unit 13-n is referred to as Tein-n [° C.]. The indoor outlet side temperature sensor 19 is a sensor that detects the indoor outlet side temperature Teout [° C.] of the refrigerant flowing to the outlet side of the indoor heat exchanger 11 during the cooling operation. Here, the indoor outlet side temperature of the refrigerant flowing to the outlet side of the indoor heat exchanger 11-n during the cooling operation of the indoor unit 13-n is referred to as Teout-n [° C.].

(Control unit 30)
The outdoor control device 16 is provided in the outdoor unit 7 and receives information such as the pressure detected by the pressure sensor 14 and the temperature detected by the outdoor outlet side temperature sensor 15, and various kinds of information such as the compressor 1 and the expansion unit 10 are received. It is a device that controls the operation of the actuator. The indoor control device 17 receives information such as the temperature detected by the indoor inlet side temperature sensor 18 and the temperature detected by the indoor outlet side temperature sensor 19. The indoor control device 17 communicates with the outdoor control device 16 and shares each information. And the indoor control apparatus 17 adjusts the opening degree of the expansion | swelling part 10, the rotation speed of the indoor air blower 12, etc. FIG. The outdoor control device 16 and the indoor control device 17 constitute a control unit 30.

(Control unit 30, calculation means 31)
FIG. 2 is a block diagram showing the control unit 30 of the air conditioner 100 according to Embodiment 1 of the present invention. As illustrated in FIG. 2, the control unit 30 includes a calculation unit 31, a determination unit 32, and a switching unit 33. The calculation means 31 calculates the degree of superheat SH_e-1 to SH_e-n [of each indoor unit 13 based on the difference between the indoor inlet side temperatures Tein-1 to Tein-n and the indoor outlet side temperatures Teout-1 to Teout-n. deg] is calculated. The degree of superheat is also called superheat. Further, the calculation means 31 calculates the high pressure saturation temperature Ct [° C.] based on the saturation temperature corresponding to the pressure Pd [kgf / cm ² G], and the outdoor outlet side temperature Tcout [° C.] from the high pressure saturation temperature Ct [° C.]. ] Is subtracted to calculate the degree of supercooling SC_hex. The degree of supercooling is also called a subcool.

(Overheat control mode)
The control unit 30 has a superheat control mode and a supercooling control mode as modes for controlling the operations of the plurality of expansion units 10. The overheat control mode is a mode in which each expansion unit 10 is controlled based on the outlet side superheat degree of the plurality of indoor heat exchangers 11 during the cooling operation. The calculation means 31 calculates the degree of superheat SH_e-1 to SH_e-n [of each indoor unit 13 based on the difference between the indoor inlet side temperatures Tein-1 to Tein-n and the indoor outlet side temperatures Teout-1 to Teout-n. deg] is calculated. Then, the control unit 30 adjusts the corresponding expansion units 10-1 to 10-n so that the superheat degrees SH_e-1 to SH_en [deg] approach the target superheat degrees SHm_e-1 to SHm_en [deg]. Control the opening.

FIG. 3 is a Mollier diagram showing the degree of superheat in Embodiment 1 of the present invention. In FIG. 3, the horizontal axis represents specific enthalpy and the vertical axis represents pressure. As shown in FIG. 3, the control unit 30 controls the opening degree of the expansion units 10-1 to 10-n to control the degree of superheat. When the superheat degree SH_e-1 to SH_en is larger than the target superheat degree SHm_e-1 to SHm_en, the control unit 30 sets the target opening degree An = Anf + ΔS1n of the expansion unit 10 (Anf: opening of the expansion unit 10 at the current time). Degree, ΔS1n: correction opening degree by superheat degree control, ΔS1n of n = 1, 2,..., N) is set to a positive value.

Further, when the superheat degree SH_e-1 to SH_en is smaller than the target superheat degree SHm_e-1 to SHm_en, the control unit 30 sets ΔS1n to a negative value. The control unit 30 determines that the degree of superheat SH_e−1 to SH_e−n is SHm_e−1 to SHm_e−n−a1 ≦ SH_e−1 to SH_e−n ≦ SHm_e−1 to SHm_e−n + a2 (a1: SH_e−1 to SH_e− n lower limit side stable temperature range [° C.], a2: upper limit side stable temperature range [° C.] of SH_e−1 to SH_e−n) and within the stable opening range, ΔS1n is set to zero, The opening degree of the expansion part 10 is maintained.

Thus, in the overheat control mode, the opening degree of the expansion unit 10 corresponding to the indoor unit 13 can be individually controlled for each indoor unit 13. Here, there may be a difference between the indoor temperature and the set temperature of the place where each indoor unit 13 is installed. In a room where the room temperature and the set temperature are substantially equal, the cooling capacity may be small. However, in a room where there is a gap between the room temperature and the set temperature, it is necessary to increase the cooling capacity. In other words, in a room where the room temperature and the set temperature are almost the same, the target superheat degree SHm_e is increased, the amount of refrigerant flowing is suppressed by reducing the opening of the electronic expansion valve, and the cooling capacity is suppressed. Control to do is desired. In that case, since the opening degree of the expansion part 10 corresponding to the indoor unit 13 can be individually controlled in the superheat control mode, it can be controlled to a degree of superheat suitable for each indoor unit 13. Therefore, optimal control can be performed in all the indoor units 13.

(Supercooling control mode)
The supercooling control mode is a mode in which all the expansion units 10 are controlled based on the degree of supercooling of the outdoor heat exchanger 3 during the cooling operation. The calculating means 31 calculates the high-pressure saturation temperature Ct [° C.] based on the saturation temperature corresponding to the pressure Pd [kgf / cm ² G]. The control unit 30 sets all the expansion units 10-1 to 10-n so that the degree of supercooling SC_hex obtained by subtracting the outdoor outlet side temperature Tcout [° C] from the high-pressure saturation temperature Ct [° C] approaches the target degree of supercooling SCm_hex. To control the opening degree.

FIG. 4 is a Mollier diagram showing the degree of supercooling in Embodiment 1 of the present invention. In FIG. 4, the horizontal axis represents specific enthalpy and the vertical axis represents pressure. As shown in FIG. 4, the control unit 30 controls the opening degree of all the expansion units 10 to control the degree of supercooling. When the degree of supercooling SC_hex is larger than the target degree of supercooling SCm_hex, the control unit 30 calculates the total target opening ΣA = ΣAf + ΔS2 of all the expansion units 10 (ΣAf: the total opening of the expansion unit 10 at the current time, ΔS2: ΔS2 of the correction opening degree by supercooling degree control) is set to a positive value. In addition, when the degree of supercooling SC_hex is smaller than the target degree of supercooling SCm_hex, the control unit 30 sets ΔS2 to a negative value.

The control unit 30 opens the supercooling degree SC_hex satisfying Scm_hex−b1 ≦ SC_hex ≦ Scm_hex + b2 (b1: SC_hex lower limit side stable temperature range [° C.], b2: SC_hex upper limit side stable temperature range [° C.]). When it is within the stable range, ΔS2 is set to zero and the opening degree of the expansion portion 10 is maintained. The opening degrees A1 to An of the indoor units 13-1 to 13-n are obtained from the equation: An = ΣA × Cn after ΣA is calculated. Here, Cn is an evaluation value determined by the capacity band of each indoor unit 13, stored in the indoor control device 17, and information is transmitted from the indoor control device 17 to the outdoor control device 16 at the time of calculation.

(Determination means 32)
As shown in FIG. 2, the determination unit 32 determines whether there is an indoor unit 13 that is inappropriate for the overheat control mode among the plurality of indoor units 13. Here, the indoor unit 13 adapted to the overheat control mode and the indoor unit 13 inappropriate for the overheat control mode will be described.

(Indoor unit 13 suitable for overheat control mode)
FIG. 5 is a cross-sectional view of the indoor heat exchanger 11 according to Embodiment 1 of the present invention. As shown in FIG. 5, the indoor heat exchanger 11 has an upper path 11a and a lower path 11b. The upper path 11a is provided above the indoor heat exchanger 11 in the path through which the refrigerant flows. During the cooling operation, the refrigerant flows in from the first inlet 41 of the upper path 11a and flows out of the first outlet 42. The lower path 11b is provided in the lower part of the indoor heat exchanger 11 among the paths through which the refrigerant flows. During the cooling operation, the refrigerant flows in from the second inlet 43 of the lower path 11b and flows out of the second outlet 44. Here, the indoor inlet side temperature sensor 18 is provided in the vicinity of the inlet in the cooling operation in the lower path 11b. The indoor outlet side temperature sensor 19 is provided in the lower path 11b in the vicinity of the outlet during the cooling operation.

Thus, since the indoor outlet side temperature sensor 19 is provided in the vicinity of the outlet of the indoor heat exchanger 11 during the cooling operation, the indoor outlet side temperature Tout [° C.] detected by the indoor outlet side temperature sensor 19. Is close to the actual temperature flowing out of the indoor heat exchanger 11 during the cooling operation. For this reason, the value of the superheat degree calculated based on the indoor outlet side temperature is close to the actual value of the superheat degree. Therefore, the indoor unit 13 having the indoor heat exchanger 11 shown in FIG. 5 is adapted to the overheat control mode.

(Indoor unit 13 not suitable for overheat control mode)
FIG. 6 is a cross-sectional view of the indoor heat exchanger 11 according to Embodiment 1 of the present invention. As shown in FIG. 6, the indoor heat exchanger 11 has an upper path 11a and a lower path 11b. The upper path 11a is provided in the upper part of the heat exchanger among the paths through which the refrigerant flows. During the cooling operation, the refrigerant flows in from the first inlet 41 of the upper path 11a and flows out of the first outlet 42. The lower path 11b is provided in the lower part of the heat exchanger among the paths through which the refrigerant flows. During the cooling operation, the refrigerant flows in from the second inlet 43 of the lower path 11b and flows out of the second outlet 44. Here, the indoor inlet side temperature sensor 18 is provided in the vicinity of the inlet in the cooling operation in the lower path 11b. In addition, the indoor outlet side temperature sensor 19 is provided not in the vicinity of the outlet during the cooling operation but in the middle between the inlet and the outlet in the lower path 11b.

Thus, since the indoor outlet side temperature sensor 19 is provided in the middle of the indoor heat exchanger 11 during the cooling operation, the indoor outlet side temperature Teout [° C.] detected by the indoor outlet side temperature sensor 19 is: The value is lower than the actual temperature flowing out of the indoor heat exchanger 11 during the cooling operation. For this reason, the value of the superheat degree calculated based on the indoor outlet side temperature is lower than the actual superheat degree. Therefore, when the control unit 30 attempts to bring the degree of superheat close to the target degree of superheat, the opening degree of the expansion unit 10 may be excessively reduced, and the degree of superheat may become excessively high. For this reason, the indoor unit 13 having the indoor heat exchanger 11 shown in FIG. 6 may be unsuitable for the overheat control mode.

Here, the indoor control device 17 stores information on whether or not its own indoor unit 13 is inappropriate for the overheat control mode. The outdoor control device 16 always transmits and receives information to and from the indoor control device 17 when energized, and immediately recognizes when the indoor unit 13 unsuitable for the overheat control mode is going to perform a cooling operation.

As shown in FIG. 2, the switching means 33 switches from the superheat control mode to the supercooling control mode when the judging means 32 determines that there is an indoor unit 13 unsuitable for the superheat control mode. The supercooling control mode is performed only when there is an indoor unit 13 that is not suitable for the superheat control mode.

(Operation mode, cooling operation)
Next, the operation mode of the air conditioner 100 will be described with reference to FIG. First, the cooling operation will be described. In the cooling operation, the refrigerant sucked into the compressor 1 is compressed by the compressor 1 and discharged in a high-temperature and high-pressure gas state. The high-temperature and high-pressure gaseous refrigerant discharged from the compressor 1 passes through the flow path switching device 2 and flows into the outdoor heat exchanger 3 that acts as a condenser. Heat exchanges with the outdoor air sent by the liquefaction and condensates. The condensed refrigerant in the liquid state flows into each indoor unit 13.

In each indoor unit 13, the refrigerant flows into each expansion section 10, and is expanded and depressurized in the expansion section 10 to become a low-temperature low-pressure gas-liquid two-phase refrigerant. Then, the gas-liquid two-phase refrigerant flows into the indoor heat exchanger 11 acting as an evaporator, and in the indoor heat exchanger 11, heat is exchanged with indoor air sent by the indoor blower 12 to evaporate gas. At this time, the room air is cooled, and the room is cooled. The evaporated refrigerant in a low-temperature and low-pressure gas state passes through the flow path switching device 2 and is sucked into the compressor 1.

(Operation mode, heating operation)
Next, the heating operation will be described. In the heating operation, the refrigerant sucked into the compressor 1 is compressed by the compressor 1 and discharged in a high-temperature and high-pressure gas state. The high-temperature and high-pressure gaseous refrigerant discharged from the compressor 1 passes through the flow path switching device 2 and flows into each indoor unit 13. The refrigerant flows into each indoor heat exchanger 11 acting as a condenser, and in the indoor heat exchanger 11, heat is exchanged with indoor air sent by the indoor blower 12 to condense and liquefy. At this time, indoor air is warmed and heating is performed indoors.

The condensed liquid refrigerant flows into the expansion unit 10 and is expanded and depressurized in the expansion unit 10 to become a low-temperature low-pressure gas-liquid two-phase refrigerant. The refrigerant in the gas-liquid two-phase state flows into the outdoor heat exchanger 3 acting as an evaporator, and in the outdoor heat exchanger 3, heat is exchanged with outdoor air sent by the outdoor blower 4 to evaporate gas. The evaporated refrigerant in a low-temperature and low-pressure gas state passes through the flow path switching device 2 and is sucked into the compressor 1.

(Operation of control unit 30)
FIG. 7 is a flowchart showing the operation of the air conditioner 100 according to Embodiment 1 of the present invention. Next, the operation of the control unit 30 will be described. When a command for starting the cooling operation is transmitted from the indoor unit 13 and the operation of the compressor 1 is started, the control unit 30 controls all the expansion units 10 to the initial opening degree (step ST1). The initial opening is set according to the capacity band of the indoor unit 13 and the conditions of the outside air temperature. And it is judged whether fixed time t1 passes (step ST2). Step ST2 is repeated until the fixed time t1 elapses (No in step ST2). When the fixed time t1 elapses (Yes in step ST2), it is assumed that the operation is stable immediately after the start-up, and the process shifts to the overheat control mode (step ST3).

Then, the information stored as to whether or not the own indoor unit 13 is unsuitable for the overheat control mode is read from the indoor control device 17 by the determination means 32, and whether there is an unsuitable indoor unit 13 for the overheat control mode. It is determined whether or not (step ST4). When it is determined that there is no indoor unit 13 that is not suitable for the overheat control mode (No in step ST4), it is determined whether or not SHm_e−1 to na−a1 ≦ SH_e−1 to n ≦ SHm_e−1 to n + a2 is satisfied. (Step ST5). When SHm_e−1 to n−a1 ≦ SH_e−1 to n ≦ SHm_e−1 to n + a2 is not satisfied (No in step ST5), the degree of superheat is controlled using an equation of An = Anf + ΔS1n (step ST6).

Then, it is determined whether or not the operation command for the indoor unit 13 is continued (step ST7). When the operation command for the indoor unit 13 is continued (Yes in step ST7), the process returns to step ST4 after a predetermined time t2 has elapsed (step ST8). In step ST7, when the operation command for the indoor unit 13 is not continued (No in step ST7), the control is terminated. Here, in step ST5, when SHm_e-1 to n-a1≤SH_e-1 to n≤SHm_e-1 to n + a2 are satisfied (Yes in step ST5), the process proceeds to step ST7.

On the other hand, when it is determined in step ST4 that there is an indoor unit 13 unsuitable for the overheat control mode (Yes in step ST4), it is determined whether or not Scm_hex−b1 ≦ SC_hex ≦ Scm_hex + b2 is satisfied (step ST9). When Scm_hex−b1 ≦ SC_hex ≦ Scm_hex + b2 is not satisfied (No in step ST9), the degree of supercooling is controlled using the formula of ΣA = ΣAf + ΔS2 and the formula of An = ΣA × Cn (step ST10 and step ST11).

Then, it is determined whether or not the operation command for the indoor unit 13 is continued (step ST12). When the operation command for the indoor unit 13 is continued (Yes in step ST12), the process returns to step ST4 after a predetermined time t3 has elapsed (step ST13). In step ST12, when the operation command for the indoor unit 13 is not continued (No in step ST12), the control is terminated. Here, in step ST9, when Scm_hex−b1 ≦ SC_hex ≦ Scm_hex + b2 is satisfied (Yes in step ST9), the process proceeds to step ST12.

According to the first embodiment, when there is an indoor unit 13 unsuitable for the superheat control mode, the superheat control mode is switched to the supercooling control mode. For this reason, when the indoor unit 13 unsuitable for the overheat control mode does not exist, the indoor unit 13 is controlled in the overheat control mode, and is controlled in the supercooling control mode only when the indoor unit 13 unsuitable for the overheat control mode exists. Therefore, the effect obtained in the overheat control mode is maintained as much as possible, and no design change is involved.

Here, the effect obtained in the overheat control mode is that the opening degree of the expansion unit 10 corresponding to the indoor unit 13 can be individually controlled as described above, and the degree of superheat suitable for each indoor unit 13 is controlled. It can be done. In order to change to the supercooling mode even when the indoor outlet side temperature sensor 19 is attached at a position slightly shifted to the intermediate side between the inlet and outlet of the indoor heat exchanger 11 due to various circumstances such as productivity. There is no need to make design changes.

The air conditioner 100 further includes an indoor outlet side temperature sensor 19 that detects the temperature of the refrigerant flowing on the outlet side of the indoor heat exchanger 11 during the cooling operation, and the indoor unit 13 that is not suitable for the overheat control mode The outlet side temperature sensor 19 is the indoor unit 13 provided in the middle of the inlet and outlet of the indoor heat exchanger 11. As described above, even if there is an indoor unit 13 that is inappropriate for the overheat control mode, the effect obtained in the overheat control mode is maintained as much as possible, and the design is not changed.

Embodiment 2. FIG.
FIG. 8 is a circuit diagram showing an air conditioner 200 according to Embodiment 2 of the present invention. The second embodiment is different from the first embodiment in that the air conditioner 200 includes a storage kit 20. In the second embodiment, the same parts as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. The description will focus on differences from the first embodiment.

As shown in FIG. 8, the storage kit 20 includes a plurality of expansion units 10 and an expansion control device 21. That is, the expansion unit 10 is not provided inside the indoor unit 13. The expansion part 10 of the storage kit 20 is connected to the indoor unit 13 by the indoor unit liquid side extension pipes 23-1 to 23-n, respectively. The expansion control device 21 can communicate with the outdoor control device 16 and the indoor control device 17 to share the operation status of various actuators, information from sensors, and the like. Even if the expansion unit 10 is stored not in the indoor unit 13 but in the storage kit 20 as in the second embodiment, the superheat control mode and the supercooling control mode are the same as in the first embodiment. Is implemented. Therefore, the same effects as those of the first embodiment are obtained.

Embodiment 3 FIG.
FIG. 9 is a circuit diagram showing an air conditioner 300 according to Embodiment 3 of the present invention. The third embodiment is different from the first embodiment in that a plurality of expansion units 10 are provided in the outdoor unit 7. In the third embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. The description will focus on differences from the first embodiment.

As shown in FIG. 9, a plurality of expansion portions 10 are provided in the outdoor unit 7 at a position downstream of the liquid side extension pipe connection valve 5 during the cooling operation. That is, the expansion unit 10 is not provided inside the indoor unit 13. Further, the gas side extension pipe 9 is branched into n inside the outdoor unit 7 and connected to the indoor unit 13. Even if the expansion unit 10 is stored not in the indoor unit 13 but in the outdoor unit 7 as in the third embodiment, the superheat control mode and the supercooling control mode are the same as in the first embodiment. Is implemented. Therefore, the same effects as those of the first embodiment are obtained.

Embodiment 4 FIG.
FIG. 10 is a circuit diagram showing an air conditioner 400 according to Embodiment 4 of the present invention. The fourth embodiment is different from the first embodiment in that the air conditioner 100 includes an outdoor intermediate temperature sensor 22. In the fourth embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. The description will focus on differences from the first embodiment.

As shown in FIG. 10, the outdoor intermediate temperature sensor 22 is a sensor that is provided in the intermediate portion of the outdoor heat exchanger 3 and detects the outdoor intermediate temperature of the refrigerant flowing in the intermediate portion of the outdoor heat exchanger 3. The air conditioner 400 does not have the pressure sensor 14. The calculation means 31 directly calculates the high-pressure saturation temperature Ct [° C.] based on the outdoor intermediate temperature detected by the outdoor intermediate temperature sensor 22. In this case, since the high-pressure saturation temperature can be directly calculated without calculating the saturation temperature from the pressure, the processing speed of the control unit 30 can be improved.

1 compressor, 2 flow switching device, 3 outdoor heat exchanger, 4 outdoor fan, 5 liquid side extension pipe connection valve, 6 gas side extension pipe connection valve, 7 outdoor unit, 8, 8-1, 8- 2,8-n liquid side extension pipe, 9, 9-1, 9-2, 9-n gas side extension pipe, 10, 10-1, 10-2, 10-n expansion part, 11, 11-1, 11-2, 11-n indoor heat exchanger, 11a upper path, 11b lower path, 12, 12-1, 12-2, 12-n indoor blower, 13, 13-1, 13-2, 13-n indoor Machine, 14 pressure sensor, 15 outdoor outlet temperature sensor, 16 outdoor control device, 17, 17-1, 17-2, 17-n indoor control device, 18, 18-1, 18-2, 18-n indoor entrance Side temperature sensor 19, 19-1, 19-2, 19-n Indoor outlet Temperature sensor, 20 containment kit, 21 expansion control device, 22 outdoor intermediate temperature sensor, 23, 23-1, 23-2, 23-n indoor unit liquid side extension piping, 50 refrigerant circuit, 30 control unit, 31 calculation means, 32 determination means, 33 switching means, 41 first inlet, 42 first outlet, 43 second inlet, 44 second outlet, 100, 200, 300, 400 air conditioner.

Claims

A refrigerant circuit in which a compressor, an outdoor heat exchanger, a plurality of expansion sections, and a plurality of indoor heat exchangers are connected by piping, and a refrigerant flows;
An outdoor unit that houses at least the compressor and the outdoor heat exchanger;
A plurality of indoor units respectively accommodating at least a plurality of the indoor heat exchangers;
As a mode for controlling the operation of the plurality of expansion units, an overheat control mode for controlling each expansion unit based on the outlet side superheat degree of the plurality of indoor heat exchangers during cooling operation, and the outdoor heat during cooling operation A supercooling control mode for controlling all the expansion portions based on the degree of supercooling of the exchanger, and a control unit,
The controller is
Determining means for determining whether or not there is an indoor unit unsuitable for the overheat control mode among the plurality of indoor units;
An air conditioner, comprising: switching means for switching from the superheat control mode to the supercooling control mode when it is determined by the determination means that there is an indoor unit unsuitable for the superheat control mode.
An indoor outlet side temperature sensor for detecting the indoor outlet side temperature of the refrigerant flowing to the outlet side of the indoor heat exchanger during cooling operation;
Indoor units that are not suitable for the overheat control mode are:
The indoor outlet side temperature sensor is an indoor unit provided between an inlet and an outlet of the indoor heat exchanger;
The controller is
The air conditioner according to claim 1, wherein information on whether or not the indoor unit is inappropriate for the overheat control mode is stored.
The air conditioner according to claim 1, further comprising a storage kit that stores a plurality of the inflating portions.
The air conditioner according to claim 1 or 2, wherein the plurality of expansion portions are accommodated in the outdoor unit.
A pressure sensor for detecting the pressure of the refrigerant flowing on the discharge side of the compressor;
An outdoor outlet side temperature sensor that detects an outdoor outlet side temperature of the refrigerant flowing to the outlet side of the outdoor heat exchanger during cooling operation, and
The controller is
The air according to any one of claims 1 to 4, further comprising calculation means for calculating the degree of supercooling based on a pressure detected by the pressure sensor and a temperature detected by the outdoor outlet side temperature sensor. Harmony machine.
An intermediate temperature sensor for detecting an outdoor intermediate temperature of the refrigerant flowing in the intermediate part of the outdoor heat exchanger;
An outdoor outlet side temperature sensor that detects an outdoor outlet side temperature of the refrigerant flowing to the outlet side of the outdoor heat exchanger during cooling operation, and
The controller is
The calculation unit for calculating the degree of supercooling based on an outdoor intermediate temperature detected by the intermediate temperature sensor and a temperature detected by the outdoor outlet side temperature sensor. The air conditioner described.