CN109196288B - Multi-connected air conditioner - Google Patents

Abstract

To prevent dew condensation from occurring on a rotor of an indoor fan when a multi-type air conditioner is operated in a low-capacity cooling mode. At least one of the indoor units (40, 50, 60) is configured to increase the flow rate of the indoor fan (43, 53, 63) while increasing the wet area by reducing the superheat area of the indoor heat exchanger (42, 52, 62) by increasing the opening degree of the indoor expansion valve (41,51, 61) when the indoor temperature is higher than a set temperature in a low-energy cooling operation in which the superheat area is increased as compared to a normal cooling operation.

Description

Multi-connected air conditioner

Technical Field

The present invention relates to a multi-type air conditioner, and more particularly to a multi-type air conditioner including a plurality of indoor units each including an indoor heat exchanger capable of exchanging heat between air and a refrigerant.

Background

In a conventional air conditioner, when the cooling load is small during the cooling operation, as described in patent document 1 (japanese patent application laid-open No. 59-122864), for example, the operation frequency of the compressor is lowered, and thus the operation matching the small cooling load may be performed. In the following description, an operation in which the cooling capacity is reduced in accordance with a small cooling load by reducing the operating frequency of the compressor and increasing the superheat region of the indoor heat exchanger of the indoor unit as compared to the normal cooling operation will be referred to as a low-capacity cooling operation. As described in patent document 1, when one outdoor unit is connected to one indoor unit, even when the indoor temperature of the indoor unit changes during low-capacity cooling operation, for example, the operating frequency of the compressor can be changed in accordance with the demand of the indoor unit, and the operation can be easily handled.

However, for example, in a multi-type air conditioner in which one outdoor unit is connected to a plurality of indoor units and the plurality of indoor units are operated in parallel, it is difficult to change the operating frequency of the compressor of the outdoor unit in accordance with the request of any indoor unit. Therefore, in any indoor unit of the multi-air conditioner, for example, when the indoor temperature changes or the set temperature is changed and the cooling capacity required by any indoor unit changes, it is conceivable to cope with the changed cooling load by changing the opening degree of the expansion valve of the indoor unit in which the required cooling capacity changes.

Disclosure of Invention

Problems to be solved by the invention

However, when the cooling capacity is to be improved by increasing the opening degree of the expansion valve during the low-capacity cooling operation in the multi-air-conditioning apparatus, condensation may occur on the rotor of the indoor fan due to mixing of the air passing through the superheated region and the humid region of the indoor heat exchanger.

The invention aims to prevent condensation on a rotor of an indoor fan when a multi-connected air conditioner performs low-energy cooling operation.

Means for solving the problems

A multiple air conditioner according to claim 1 of the present invention includes: an outdoor unit having a compressor for compressing a refrigerant circulating to perform a refrigeration cycle; and a plurality of indoor units each having a plurality of indoor heat exchangers and a plurality of pressure reducing mechanisms, and a plurality of indoor fans, wherein refrigerant discharged from the compressor circulates through the plurality of indoor heat exchangers, and air passing through the plurality of indoor heat exchangers passes through the plurality of indoor fans, and at least one of the plurality of indoor units is configured to increase an opening degree of the pressure reducing mechanism to reduce a superheated region of the indoor heat exchanger and expand a humid region, and to increase an air volume of the indoor fan, when an indoor temperature is higher than a set temperature in a low-energy cooling operation in which the superheated region is increased as compared with a normal cooling operation.

According to this multi-type air conditioner, the cooling capacity is improved by increasing the opening degree of the pressure reducing mechanism to expand the wet area of the indoor heat exchanger, and the temperature of the mixed air formed by mixing the air passing through the superheated area of the indoor heat exchanger and the air passing through the wet area is reduced when the wet area is expanded. Here, the opening degree of the pressure reducing mechanism is controlled so as to restrict the expansion of the humid region within the upper limit of the temperature range within which condensation does not occur in the device downstream of the indoor heat exchanger, so that the temperature of the mixed air does not drop too much below the dew point temperature of the mixed air to cause condensation in the device downstream of the indoor heat exchanger, and the required cooling capacity is ensured by increasing the air volume of the indoor fan for further improvement of the cooling capacity. Thus, when the multi-type air conditioner performs a low-capacity cooling operation, dew condensation in the device can be prevented from occurring downstream of the indoor heat exchanger while ensuring a required cooling capacity.

A multiple air conditioner according to claim 2 of the present invention is the multiple air conditioner according to claim 1, wherein the at least one indoor unit is configured to be able to reduce the cooling capacity by reducing the opening degree of the pressure reducing mechanism and/or reducing the air volume of the indoor fan when the indoor temperature is lower than the set temperature in the low-capacity cooling operation.

According to this multi-type air conditioner, when the room temperature is lower than the set temperature during the low-power cooling operation during cooling, the cooling capacity is reduced by reducing the opening degree of the pressure reducing mechanism and/or reducing the air volume of the indoor fan, and therefore the humidification area is reduced and/or the air volume is reduced from a state in which the expansion of the humidification area is limited to within the upper limit of the downstream of the indoor heat exchanger in which condensation does not occur in the device.

A multiple air conditioning apparatus according to claim 3 of the present invention is the multiple air conditioning apparatus according to claim 1 or 2, wherein at least one of the indoor units performs cooling by using mixed air that has passed through the humid region and the superheated region during low-power cooling operation, and determines that expansion of the humid region downstream of the indoor heat exchanger is limited to an upper limit at which condensation does not occur in the apparatus, using the temperature of the mixed air or the humidity of the mixed air.

According to this multi-type air conditioning apparatus, whether or not the expansion of the wet area downstream of the indoor heat exchanger is limited to the upper limit at which condensation does not occur in the apparatus can be easily determined using the temperature of the mixed air or the humidity of the mixed air.

A multiple air conditioner according to claim 4 of the present invention is the multiple air conditioner according to any one of claims 1 to 3, wherein at least one of the indoor units further includes an indoor heat exchanger temperature sensor in the indoor heat exchanger, and during the low-power cooling operation, it is determined that the expansion of the moisture region downstream of the indoor heat exchanger is limited to an upper limit at which condensation does not occur in the device using a detection result of the indoor heat exchanger temperature sensor.

According to this multi-type air conditioner, whether or not the expansion of the moisture region downstream of the indoor heat exchanger is limited to the upper limit at which condensation does not occur in the device can be easily determined using the detection result of the indoor heat exchanger temperature sensor.

A multiple air conditioner according to claim 5 of the present invention is the multiple air conditioner according to any one of claims 1 to 4, wherein the mode of the low-capacity cooling operation is switched to the normal cooling operation mode when at least one of the indoor units increases the air volume of the indoor fan to obtain a required cooling capacity and the expansion of the humid area cannot be limited to the upper limit where condensation does not occur in the indoor unit downstream of the indoor heat exchanger.

According to this multi-type air conditioning apparatus, the entire indoor heat exchanger can be set to the humid region by switching from the low-capacity cooling operation mode to the normal cooling operation mode, and therefore the air passing through the superheated region of the indoor heat exchanger can be eliminated.

ADVANTAGEOUS EFFECTS OF INVENTION

In the multi-type air conditioning apparatus according to claim 1 of the present invention, condensation can be prevented from occurring in the apparatus downstream of the indoor heat exchanger during low-power cooling operation.

In the multi-type air conditioning apparatus according to claim 2 of the present invention, the cooling capacity can be reduced while maintaining a state in which condensation does not occur in the apparatus downstream of the indoor heat exchanger.

In the multi-type air conditioning apparatus according to claim 3 or 4 of the present invention, the reliability of preventing condensation in the apparatus downstream of the indoor heat exchanger is improved.

In the multiple air conditioner according to claim 5 of the present invention, condensation can be prevented from occurring in the device downstream of the indoor heat exchanger while ensuring a required cooling capacity.

Drawings

Fig. 1 is a circuit diagram showing a schematic configuration of a multi-type air conditioner according to an embodiment of the present invention.

Fig. 2 is a cross-sectional view illustrating an example of a structure of an indoor unit of the multi-air conditioning apparatus of fig. 1.

Fig. 3 is a perspective view showing a structure around the indoor heat exchanger with a front panel or the like of the indoor unit of fig. 2 removed.

Fig. 4 is a conceptual diagram illustrating an indoor heat exchanger in a normal cooling operation of the multi-air conditioner.

Fig. 5 is a conceptual diagram illustrating an indoor heat exchanger of a multi-type air conditioner in a low-capacity cooling operation.

Fig. 6 is a graph for explaining the concept of control during low-capacity cooling operation.

Fig. 7 is a graph for explaining an example of control during the low-capacity cooling operation.

Fig. 8 is a graph for explaining another example of the control during the low-capacity cooling operation.

Fig. 9 is a circuit diagram showing a schematic configuration of an air conditioner according to modification 1C of the present invention.

Fig. 10 is a perspective view showing an external appearance of an outdoor unit according to modification 1C.

Detailed Description

(1) Integral structure of air conditioner

Fig. 1 is a schematic configuration diagram of a multi-type air conditioner according to an embodiment of the present invention. The multi-type air conditioning apparatus 10 is used for cooling and heating rooms of a building or the like by performing a vapor compression type refrigeration cycle operation. The multi-type air conditioning apparatus 10 includes: an outdoor unit 20 as a heat source unit; a plurality of (three in the present embodiment) indoor units 40,50,60 connected in parallel to the outdoor unit 20 as usage units; and a liquid refrigerant connection pipe 71 and a gas refrigerant connection pipe 72 as refrigerant connection pipes for connecting the outdoor unit 20 and the indoor units 40,50, 60.

The refrigerant circuit 11 of the multi-type air conditioning apparatus 10 is configured by connecting the outdoor unit 20, the indoor units 40,50, and 60, the liquid refrigerant connection pipe 71, and the gas refrigerant connection pipe 72. The refrigerant circuit 11 includes an indoor- side refrigerant circuit 11a, 11b, 11c and an outdoor-side refrigerant circuit 11 d. A refrigerant circulates in the refrigerant circuit 11.

The multi-type air conditioner 10 further includes an operation control device 80, and the operation control device 80 controls the operation of the entire multi-type air conditioner 10. The indoor side controllers 47,57,67 and the outdoor side controller 37 are connected by a transmission line 80a to constitute an operation controller 80. Then, the indoor- side control devices 47,57,67 of the indoor units 40,50,60 can exchange control signals and the like via the transmission line 80 a.

The operation control device 80 is connected to receive detection signals of the suction pressure sensor 29, the discharge pressure sensor 30, the suction temperature sensor 31, the discharge temperature sensor 32, the outdoor temperature sensor 36, the liquid side temperature sensors 44, 54, 64, the gas side temperature sensors 45,55,65, and the like. The operation control device 80 is connected to the compressor 21, the four-way switching valve 22, the outdoor fan 28, the outdoor expansion valve 38, the indoor expansion valves 41,51,61, the indoor fans 43,53,63, and the like so as to control the outdoor unit 20 and the indoor units 40,50,60 based on detection signals thereof, and the like.

(2) Detailed structure

(2-1) outdoor unit 20

The outdoor unit 20 includes an outdoor-side refrigerant circuit 11d, and the outdoor-side refrigerant circuit 11d constitutes a part of the refrigerant circuit 11. The outdoor-side refrigerant circuit 11d is connected to the compressor 21, the four-way switching valve 22, the outdoor heat exchanger 23, the outdoor expansion valve 38, and the accumulator 24.

The compressor 21 is a compressor capable of varying its operating capacity, and is a positive displacement compressor driven by a motor 21m, and the rotational speed of the motor 21m is controlled by an inverter. The four-way switching valve 22 is a valve for switching the flow direction of the refrigerant.

During the cooling operation, the four-way switching valve 22 in fig. 1 is switched to the connection state indicated by the solid line. That is, by connecting the discharge side of the compressor 21 and the outdoor heat exchanger 23 by the four-way switching valve 22 and connecting the suction side of the compressor 21 (specifically, the accumulator 24) and the gas refrigerant connection pipe 72, the outdoor heat exchanger 23 functions as a radiator of the refrigerant compressed by the compressor 21 and the indoor heat exchange devices 42,52,62 function as evaporators of the refrigerant deprived of heat in the outdoor heat exchanger 23 during the cooling operation.

During the heating operation, the four-way switching valve 22 in fig. 1 is switched to a connection state indicated by a broken line. By connecting the discharge side of the compressor 21 and the gas refrigerant connection pipe 72 side by the four-way switching valve 22 and connecting the suction side of the compressor 21 and the outdoor heat exchanger 23, the indoor heat exchange devices 42,52,62 function as radiators for the refrigerant compressed by the compressor 21, and the outdoor heat exchanger 23 functions as an evaporator for the refrigerant deprived of heat in the indoor heat exchange devices 42,52, 62.

The outdoor heat exchanger 23 is, for example, a cross fin (cross fin) type finned tube (fin and tube) type heat exchanger, and is equipment for performing heat exchange between air and refrigerant to use the air as a heat source. The gas side of the outdoor heat exchanger 23 is connected to the four-way switching valve 22, and the liquid side of the outdoor heat exchanger 23 is connected to the outdoor expansion valve 38.

The outdoor expansion valve 38 is an electrically driven expansion valve that is disposed downstream of the outdoor heat exchanger 23 in the direction of flow of the refrigerant in the refrigerant circuit 11 during the cooling operation to adjust the pressure, flow rate, and the like of the refrigerant flowing through the outdoor side refrigerant circuit 11 d. The outdoor expansion valve 38 is connected to the liquid side of the outdoor heat exchanger 23.

The outdoor unit 20 includes an outdoor fan 28 as a blower fan, and the outdoor fan 28 sucks outdoor air into the unit, exchanges heat with refrigerant in the outdoor heat exchanger 23, and discharges the heat to the outside. The outdoor fan 28 is a fan capable of varying the volume of air supplied to the outdoor heat exchanger 23, and is, for example, a propeller fan driven by a motor 28m including a DC fan motor or the like.

For example, the outdoor unit 20 is provided with the following sensors and the like: a suction pressure sensor 29 that detects a suction pressure of the compressor 21 (i.e., a refrigerant pressure corresponding to the evaporation pressure Pe during the cooling operation); a discharge pressure sensor 30 that detects a discharge pressure of the compressor 21; a suction temperature sensor 31 that detects a suction temperature of the compressor 21; and a discharge temperature sensor 32 that detects the discharge temperature of the compressor 21. An outdoor temperature sensor 36 is provided at an outdoor air inlet of the outdoor unit 20, and the outdoor temperature sensor 36 detects the temperature of outdoor air flowing into the outdoor unit.

The outdoor unit 20 further includes an outdoor-side control device 37 for controlling operations of the respective units constituting the outdoor unit 20. The outdoor side control device 37 includes a microcomputer (not shown), a memory (not shown), an inverter circuit (not shown) for controlling the motor 21m, and the like, which are provided for controlling the outdoor unit 20.

The plurality of indoor units 40,50,60 are different in set temperature, set humidity, indoor temperature, indoor humidity, and the like, and it is difficult to adjust the capacity required for the outdoor unit 20 to be suitable for all the indoor units 40,50,60 because they are varied. Therefore, for example, the outdoor-side controller 37 controls the operating capacity of the compressor 21 and/or the air volume of the outdoor fan 28 in accordance with the request of some indoor units among the plurality of indoor units 40,50,60, such as the indoor unit with the highest request among the plurality of indoor units 40,50, 60. Therefore, in many of the indoor units 40,50, and 60, the operating capacity of the compressor 21 and/or the air volume of the outdoor fan 28 may be set higher than necessary.

(2-2) indoor Unit

(2-2-1) overview of indoor Unit

The indoor units 40,50, and 60 are installed in a room such as a conference room by being embedded in or suspended from an indoor ceiling of a building or the like, or by being hung on an indoor wall surface. The indoor units 40,50, and 60 may be disposed in the same room, or may be disposed in different rooms. Since the indoor unit 40 and the indoor units 50 and 60 have the same configuration, only the configuration of the indoor unit 40 will be described below. In the structure of the indoor units 50 and 60, No. 50 or No. 60 is assigned with a reference numeral instead of the reference numeral of the No. 40 segment showing each part of the indoor unit 40, and the description of each part of the indoor units 50 and 60 is omitted.

The indoor units 40,50, and 60 are connected to the outdoor unit 20 via a liquid refrigerant connection pipe 71 and a gas refrigerant connection pipe 72. For example, the outdoor unit 40 includes an indoor-side refrigerant circuit 11a (an indoor-side refrigerant circuit 11b in the indoor unit 50 and an indoor-side refrigerant circuit 11c in the indoor unit 60), and the indoor-side refrigerant circuit 11a constitutes a part of the refrigerant circuit 11. The indoor-side refrigerant circuit 11a includes an indoor expansion valve 41 and an indoor heat exchanger 42 as a pressure reducing mechanism. In the present embodiment, the indoor expansion valves 41,51,61 are provided as the pressure reducing mechanisms in the indoor units 40,50,60, respectively, but the present invention is not limited to this, and a plurality of pressure reducing mechanisms corresponding to the indoor units 40,50,60 may be provided in the outdoor unit 20, or a connection unit separate from the indoor units 40,50,60 or the outdoor unit 20 may be provided.

The indoor expansion valve 41 is an electrically operated expansion valve connected to the liquid side of the indoor heat exchanger 42 to adjust the flow rate of the refrigerant flowing through the indoor-side refrigerant circuit 11a, and can also shut off the passage of the refrigerant. The indoor expansion valve 41 is controlled by an indoor-side controller 47, and can adjust the refrigerant flow rate and reduce the pressure by changing the opening degree.

The indoor heat exchanger 42 is a heat exchanger for exchanging heat between air and refrigerant, and is, for example, a cross fin type finned tube (fin and tube) heat exchanger including a heat transfer tube and a plurality of fins. The indoor heat exchanger 42 functions as an evaporator of the refrigerant to cool the indoor air during the cooling operation, and functions as a radiator of the refrigerant to heat the indoor air during the heating operation.

The outdoor unit 40 has an indoor fan 43 as a blower fan, and the indoor fan 43 sucks indoor air into the unit, and supplies the heat-exchanged indoor air to the indoor space as supply air after exchanging heat with the refrigerant in the indoor heat exchanger 42. The indoor fan 43 is a fan capable of varying the air volume of the air supplied to the indoor heat exchanger 42 within a predetermined air volume range, and is, for example, a centrifugal fan or a sirocco fan driven by a motor 43m constituted by a DC fan motor or the like. In the indoor unit 40 shown in fig. 2, a cross-flow fan is used as the indoor fan 43.

Detailed structure of (2-2-2) indoor unit

Fig. 2 shows a cross section of the indoor unit 40. The indoor unit 40 shown in fig. 2 is a wall-mounted indoor unit. In fig. 2, an arrow Ar1 indicated by a two-dot chain line indicates a flow of the sucked indoor air, and an arrow Ar2 indicated by a one-dot chain line indicates a flow of the blown conditioned air. The indoor unit 40 includes a casing 411, an air cleaner 412, an indoor heat exchanger 42, an indoor fan 43, vertical blades 416, and horizontal blades 417 shown in fig. 2. Fig. 3 is a perspective view showing the configurations of the front side heat exchange unit 421 and the rear side heat exchange unit 422 of the indoor unit 40 shown in fig. 2 and their surroundings.

An opening of the casing 411, that is, a suction port 431 is present above the wall-mounted indoor unit 40 shown in fig. 2. The indoor air sucked from the suction port 431 enters the suction space S1. The space on the downstream side of the air filter 412 is also included in the suction space S1. An indoor temperature sensor 451 that measures the temperature of the intake air and an indoor humidity sensor 452 that measures the relative humidity of the intake air are provided in the intake space S1, for example. The temperature measured by the room temperature sensor 451 is the room temperature Tr1 and is also the intake temperature Ti.

Located downstream of the indoor heat exchanger 42 and upstream of the indoor fan 43 is an intermediate space S2. Further, located downstream of the indoor fan 43 is the outlet space S3. While the indoor air sucked from above the case 411 flows from the suction space S1 to the intermediate space S2, the temperature and humidity thereof are adjusted by the indoor heat exchanger 42 inside the case 411. The air in the intermediate space S2 is mixed when passing through the indoor fan 43 to become mixed air, and the mixed air passes through the outlet space S3 and is blown out as conditioned air from the lower outlet 432.

(2-2-3) case 411 and air Filter 412

The casing 411 forms the outer contour and the frame of the indoor unit 40. The rear guide 433 and the stabilizer 434 of the housing 411 form an outlet space S3 as an outlet flow path connected to the outlet 432. The air filter 412 is disposed between the suction port 431 and the indoor heat exchanger 42. The indoor air passes through the air filter 412 to thereby remove dust before passing through the indoor heat exchanger 42. Accordingly, the air filter 412 is mounted on the case 411 to surround the indoor heat exchanger 42. Since the temperature and humidity of the air do not change before and after the air filter 412, the space before and after the air filter 412 is treated as the suction space S1 in the same manner. Therefore, the indoor temperature sensor 451 and the indoor humidity sensor 452 may be provided either upstream or downstream of the air filter 412.

(2-2-4) indoor Heat exchanger 42

The indoor heat exchanger 42 is constituted by a front-side heat exchange portion 421 and a rear-side heat exchange portion 422. The indoor heat exchanger 42 includes a plurality of fins 481 and a plurality of heat transfer pipes 482. Each fin 481 is formed of a thin metal plate, and is arranged parallel to the adjacent fins 481 and perpendicular to the longitudinal direction of the indoor unit 40. Therefore, the air passing through the indoor heat exchanger 42 passes between the fins 481 adjacent to each other. The plurality of heat transfer pipes 482 are each a pipe made of metal, and are such components as: the penetration fin 481 extends in the longitudinal direction of the indoor unit 40, and exchanges heat between the refrigerant flowing inside and the air passing through the gap between the fin 481 and the heat transfer pipe 482. The refrigerant and the air exchange heat with each other through the plurality of fins 481 and the plurality of heat transfer tubes 482. Moisture in the indoor air is condensed and adheres to the fins 481 and the heat transfer tubes 482, whereby dehumidification by the indoor heat exchanger 42 is possible. The front-side heat exchange portion 421 includes an upper front-side heat exchange portion 426 and a lower front-side heat exchange portion 427, wherein the upper front-side heat exchange portion 426 is inclined toward the front-side lower side, and the lower front-side heat exchange portion 427 is inclined toward the rear-side lower side from a lower end portion of the upper front-side heat exchange portion 426. The rear side heat exchange portion 422 is inclined downward toward the rear side.

In this embodiment, for simplicity of explanation, a case where the heat transfer tubes 482 of the indoor heat exchanger 42 are arranged in a row will be described. However, the arrangement of the heat transfer tubes 482 of the indoor heat exchanger 42 to which the present invention is applicable is not limited to one row, and may be two or more rows. Further, the following case is assumed: during the cooling operation, the refrigerant enters from the heat transfer pipe 483 at the lowest stage of the lower front side heat exchange portion 427, and the refrigerant flows out from the heat transfer pipe 484 at the lowest stage of the rear side heat exchange portion 422. The heat transfer tubes 482 of each stage are connected to the heat transfer tubes 482 of another stage, but the heat transfer tubes 482 of different stages are connected to each other by, for example, U-shaped tubes 485 shown in fig. 3. In the indoor heat exchanger 42, the refrigerant flows in sequence to the adjacent heat transfer tubes 482.

(2-2-5) indoor Fan 43

The indoor fan 43 is positioned between the front-side heat exchange portion 421 and the rear-side heat exchange portion 422 and the blow-out port 432. The indoor fan 43 includes a cylindrical fan rotor 43a extending long in the longitudinal direction of the indoor unit 40, and a motor 43m for rotating the fan rotor 43 a. The fan rotor 43a is constituted by a plurality of fan blades arranged along the circumference, and, in fig. 2, the fan rotor 43a rotates clockwise about the center point O. The air flows from the front side heat exchange portion 421 and the rear side heat exchange portion 422 toward the air outlet 432 by rotating about the center point O. The flow of air toward the air outlet 432 passes through the fan rotor 43 a. Therefore, when the fan rotor 43a reaches a temperature lower than the dew point temperature of the air-fuel mixture (conditioned air), dew condensation occurs. In other words, at this time, the fan rotor dew condensation occurs downstream of the indoor heat exchanger 42. The rotation of the indoor fan 43 is controlled by the indoor-side controller 47, and the air volume can be changed in accordance with a command from the indoor-side controller 47.

(2-2-6) vertical blades 416 and horizontal blades 417

The vertical blades 416 are disposed in the outlet flow path as the outlet space S3. The vertical vane 416 is rotated by a stepping motor (not shown) to adjust the air flow direction in the longitudinal direction of the indoor unit 40. The horizontal blade 417 is disposed along the air outlet 432, and is rotated by a stepping motor (not shown) to adjust the air direction in the vertical direction. The vertical blade 416 and the horizontal blade 417 also cause dew condensation when the temperature is lower than the dew-point temperature of the air-fuel mixture. Such condensation also corresponds to condensation on the fan rotor that occurs downstream of the indoor heat exchanger 42.

(2-2-7) indoor side control device 47 and various sensors

The indoor-side control device 47 is housed in an electrical component box (not shown) provided inside the housing 411. The indoor-side controller 47 controls the indoor unit 40 based on, for example, instructions stored in a memory (not shown) and instructions from a remote controller (not shown).

In the indoor unit 40, various sensors are provided in addition to the indoor temperature sensor 451 and the indoor humidity sensor 452, but the description of the sensors that are not important for the description is omitted here. A liquid-side temperature sensor 44 is provided on the liquid side of the indoor heat exchanger 42, and the liquid-side temperature sensor 44 detects the temperature of the refrigerant (the refrigerant temperature corresponding to the evaporation temperature Te during the cooling operation). A gas side temperature sensor 45 that detects the temperature of the refrigerant is provided on the gas side of the indoor heat exchanger 42. The outlet space S3 is provided with an outlet temperature sensor 453, and the outlet temperature sensor 453 measures the air temperature (the temperature of the mixed air) of the outlet space S3. Further, an outlet humidity sensor 454 is provided in the outlet space S3, and the outlet humidity sensor 454 measures the air humidity (humidity of the mixed air) in the outlet space S3. The liquid side temperature sensor 44, the gas side temperature sensor 45, the indoor temperature sensor 451, and the outlet temperature sensor 453 may use thermistors, for example.

(3) Operation of air conditioner

In the multi-type air conditioner 10, during the cooling operation and the heating operation, the user performs the indoor temperature control of the indoor units 40,50,60 using the input device such as the remote controller, and the indoor temperature control is performed so that the indoor temperatures Tr1, Tr2, Tr3 approach the set temperatures Ts1, Ts2, Ts3 set independently for the indoor units 40,50, 60. In this indoor temperature control, when the indoor fans 43,53,63 are set to the air volume automatic mode, the air volume of the indoor fan 43 and the opening degree of the indoor expansion valve 41 are adjusted so that the indoor temperature Tr1 converges at the set temperature Ts1, the air volume of the indoor fan 53 and the opening degree of the indoor expansion valve 51 are adjusted so that the indoor temperature Tr2 converges at the set temperature Ts2, and the air volume of the indoor fan 63 and the opening degree of the indoor expansion valve 61 are adjusted so that the indoor temperature Tr3 converges at the set temperature Ts 3. In the low-capacity cooling operation mode, the air volumes of the indoor fans 43,53,63 are automatically adjusted by the operation control device 80.

The low-capacity cooling operation is important for the present invention, and the heating operation may be configured as in the related art, and therefore, the following description will be directed to the cooling operation. The multi-type air conditioning apparatus 10 is configured to be able to perform a cooling operation in a low-capacity cooling operation mode in addition to the normal refrigerant operation mode during the cooling operation. The normal cooling operation mode is a mode in which the normal cooling operation is performed, and the low-capacity cooling operation mode is a mode in which the low-capacity cooling operation is performed. The low-capacity cooling operation is a cooling operation in which the superheat region of the indoor heat exchanger 42 is increased as compared to the normal cooling operation, and cooling is performed using mixed air in which air having passed through the superheat region and air having passed through the moisture region are mixed.

(3-1) Cooling operation

During the cooling operation, the four-way switching valve 22 is in a state indicated by the solid line in fig. 1, that is, in a state in which 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 gas sides of the indoor heat exchangers 42,52,62 via the gas refrigerant connection pipe 72. In this case, during the cooling operation, the outdoor expansion valve 38 is in the fully open state. The opening degree of the indoor expansion valve 41 is adjusted such that the degree of superheat SH1 of the refrigerant at the outlet of the indoor heat exchanger 42 (i.e., the gas side of the indoor heat exchanger 42) becomes the target degree of superheat SHt1, the opening degree of the indoor expansion valve 51 is adjusted such that the degree of superheat SH2 of the refrigerant at the outlet of the indoor heat exchanger 52 (i.e., the gas side of the indoor heat exchanger 52) becomes constant at the target degree of superheat SHt2, and the opening degree of the indoor expansion valve 61 is adjusted such that the degree of superheat SH3 of the refrigerant at the outlet of the indoor heat exchanger 62 (i.e., the gas side of the indoor heat exchanger 62) becomes the target degree of superheat SHt 3.

The target degrees of superheat SHt1, SHt2, and SHt3 are set to optimum temperature values within a predetermined degree of superheat range so that the indoor temperatures Tr1, Tr2, and Tr3 converge to the set temperatures Ts1, Ts2, and Ts 3. The degrees of superheat SH1, SH2, SH3 of the refrigerant at the outlets of the respective indoor heat exchangers 42,52,62 are detected separately by, for example, subtracting the refrigerant temperature values (corresponding to the evaporation temperature Te) detected by the respective liquid- side temperature sensors 44, 54, 64 from the refrigerant temperature values detected by the respective gas- side temperature sensors 45,55, 65. However, the degrees of superheat SH1, SH2, SH3 of the refrigerant at the outlets of the respective indoor heat exchangers 42,52,62 are not limited to detection by the above-described method.

When the compressor 21, the outdoor fan 28, and the indoor fans 43,53, and 63 are operated in the state of the refrigerant circuit 11, low-pressure gas refrigerant is sucked into the compressor 21 and compressed into high-pressure gas refrigerant. Then, the high-pressure gas refrigerant is sent to the outdoor heat exchanger 23 via the four-way switching valve 22, exchanges heat with the outdoor air supplied by the outdoor fan 28, radiates heat, and becomes a high-pressure liquid refrigerant. Then, the high-pressure liquid refrigerant is sent to the indoor units 40,50, and 60 through the liquid refrigerant connection pipe 71.

The high-pressure liquid refrigerant sent to the indoor units 40,50, and 60 is decompressed by the indoor expansion valves 41,51, and 61 to a pressure close to the suction pressure of the compressor 21, and becomes a low-pressure gas-liquid two-phase refrigerant, which is sent to the indoor heat exchangers 42,52, and 62, exchanges heat with the indoor air in the indoor heat exchangers 42,52, and 62, and evaporates, and becomes a low-pressure gas refrigerant.

The low-pressure gas refrigerant is sent to the outdoor unit 20 through the gas refrigerant connection pipe 72, and flows into the accumulator 24 through the four-way switching valve 22. Then, the low-pressure gas refrigerant flowing into the accumulator 24 is again sucked into the compressor 21. As described above, the multi-type air conditioner 10 can perform the cooling operation as follows: the outdoor heat exchanger 23 is caused to function as a radiator of the refrigerant compressed by the compressor 21, and the indoor heat exchangers 42,52,62 are caused to function as evaporators of the refrigerant that is condensed in the outdoor heat exchanger 23 and then sent through the liquid-refrigerant connection pipe 71 and the indoor expansion valves 41,51, 61. In the multi-type air conditioning apparatus 10, since there is no mechanism for adjusting the pressure of the refrigerant on the gas side of the indoor heat exchangers 42,52,62 in the indoor units 40,50,60, the evaporation pressure Pe in all the indoor heat exchangers 42,52,62 is the common pressure.

(3-2) Normal Cooling operation and Low-Power Cooling operation

In the normal cooling operation, as shown in fig. 4, substantially all of the indoor heat exchanger 42 is a wet area 491 (hatched area). In contrast, in the low-capacity cooling operation, as shown in fig. 5, the lowermost heat transfer tube 483 of the lower front side heat exchange portion 427 closest to the refrigerant inlet to the next 4 th-stage heat transfer tube 486 of the upper front side heat exchange portion 426 form a wet region 491 (hatched region). However, the heat transfer pipe 484 from the 5 th-stage heat transfer pipe 487 below the upper front-side heat exchange portion 426 to the lowermost stage of the rear-side heat exchange portion 422 is a superheated region 492 (a region not hatched). In the following description, the superheated region 492 is also referred to as a dry region. In the normal cooling operation, the entire region is generally the wet region 491 in order to obtain a high cooling capacity, but due to the relationship with the superheat control, a portion near the outlet of the indoor heat exchanger 42 may become a superheated region (dry region).

The gas-liquid two-phase refrigerant flows through the humidifying region 491, and the gas refrigerant flows through the superheated region 492. Therefore, heat exchange between the refrigerant and the air hardly occurs in the overheating area 492, and the temperature of the air passing through the overheating area 492 is substantially the same as the temperature of the air before passing.

When the low-capacity cooling operation mode is selected, the operation control device 80 adjusts the opening degree of the indoor expansion valve 41 and the air volume of the indoor fan 43, and performs the low-capacity cooling operation in the state shown in fig. 5. In the low-capacity cooling operation, dew condensation is likely to occur in the devices downstream of the indoor heat exchanger 42, as compared with the normal cooling operation in which dew condensation water is removed in the indoor heat exchanger 42. Therefore, control for avoiding dew condensation in the device of the multi-type air conditioning device 10, particularly in the indoor unit 40 during the low-energy cooling operation will be described below.

(3-3) control in Low-energy Cooling operation

(3-3-1) overview of control during Low-energy Cooling operation

The plurality of arrows shown in fig. 5 conceptually show the intake air Ar6, the mixed air Ar7, the humid region passing air Ar8, and the superheated region passing air Ar9, respectively. In the low-capacity cooling operation, when the indoor temperature Tr1 is higher than the set temperature Ts1, the operation controller 80 controls to increase the opening degree of the indoor expansion valve 41 to reduce the superheated region 492 and expand the humid region 491. Here, the value of the room temperature Tr1 is the value of the intake temperature Ti of the intake air Ar6, and is measured by the room temperature sensor 451 and sent to the operation control device 80.

Since the humid region 491 having a higher heat exchange capacity than the superheated region 492 expands and the temperature of the mixed air Ar7 decreases, the indoor unit 40 can be operated by increasing the opening degree of the indoor expansion valve 41, and the indoor temperature Tr1 can be brought close to the set temperature Ts 1. However, when the wet area 491 is excessively enlarged during the low-capacity cooling operation, dew condensation occurs on the fan rotor 43a of the indoor fan 43.

Here, a case where condensation occurs on the fan rotor 43a when the wet area 491 is excessively enlarged will be described with reference to the air line map calculation table shown in fig. 6. In fig. 6, RH100, RH90, RH80, and RH70 are curves showing relative humidities of 100% RH, 90% RH, 80% RH, and 70% RH, respectively. Assuming that the intake temperature of the intake air Ar6 is 27 ℃ and the relative humidity is about 85% RH, the point P1 in fig. 6 corresponds to the state of the intake air Ar 6. Assuming that the evaporation temperature of the indoor heat exchanger 42 is 7 ℃, a point P2 at which the dry bulb temperature of 7 ℃ and the curve RH100 (saturation line) intersect is obtained. The point P3 is defined as the intersection of the straight line LN20 connecting the point P1 and the point P2 and the curved line RH 100. If the state of the mixed air Ar7 is within the range D1 from the point P1 to the point P3, dew condensation does not occur, but if the state of the mixed air Ar7 is within the range D2 from the point P2 to the point P3, dew condensation occurs. The size of the wet area 491 at the point P3 is the upper limit of the occurrence of condensation. In order to control the humidity to not exceed the upper limit, the size of the humid area 491 is determined by a method or the like described later. Then, the opening degree of the indoor expansion valve 41 and the air volume of the indoor fan 43 are adjusted so that the determined size of the humid area 491 (occupancy of the humid area 491) does not exceed the size of the humid area 491 at the point P3. If the occupancy of the humid region 491 during low-capacity cooling operation approaches the occupancy of the humid region 491 at the point P3, the air volume of the indoor fan 43 is increased to improve the cooling capacity, and control is performed without opening the opening degree of the indoor expansion valve 41.

Hereinafter, control for avoiding dew condensation on the fan rotor by determining the size of the humid region 491 by measuring the temperature or humidity of the mixed air Ar7 is shown in (3-4), and control for avoiding dew condensation on the fan rotor by determining the size of the humid region 491 by using the detection results of the two or more indoor heat exchanger temperature sensors 455 is shown in (3-5).

In the low-capacity cooling operation, when the indoor temperature Tr1 is lower than the set temperature Ts1, the opening degree of the indoor expansion valve 41 is decreased and/or the air volume of the indoor fan 43 is decreased to reduce the cooling capacity. In the control for coping with the case where the indoor temperature Tr1 is lower than the set temperature Ts1, the state is changed to a state in which condensation on the fan rotor is more unlikely to occur, and therefore, the determination of the size of the wet area 491 may be omitted.

(3-4) avoidance control in Low-Power Cooling operation

(3-4-1) overview of control for avoiding dew condensation on Fan rotor

The plurality of arrows shown in fig. 5 conceptually show the intake air Ar6, the mixed air Ar7, the humid region passing air Ar8, and the superheated region passing air Ar9, respectively. During the low-power cooling operation, the operation control device 80 determines the size of the humid region 491 using the temperature of the mixed air Ar7, and controls the temperature of the mixed air Ar7 so as to exceed the dew-point temperature of the mixed air Ar7, thereby preventing the occurrence of dew condensation on the fan rotor downstream of the indoor heat exchanger 42. More specifically, the size of the humid area 491 is determined using the intake temperature and the intake humidity (relative humidity) of the intake air Ar6, the temperature of the mixed air Ar7, and the evaporation temperature, and control is performed according to the determination result of the size of the humid area 491. The size of the wet region 491 (the area of the wet region 491) is determined by, for example, (the area of the wet region 491) ÷ ((the area of the wet region 491) + (the area of the overheated region 492)) × 100 (the occupancy of the wet region 491). That is, the size of the wet area 491 can be determined by calculating the occupancy of the wet area 491. Control by the operation control device to prevent the occurrence of condensation on the fan rotor downstream of the indoor heat exchanger 42 by calculating the occupancy of the humid region 491 will be described in detail below.

(3-4-2) calculation in control for avoiding dew condensation of Fan rotor

In the following description, the inhalation temperature of the inhalation air Ar6 is represented as Ti ℃, and the inhalation humidity of the inhalation air Ar6 is represented as Hi% RH. The temperature of the mixed air Ar7 is expressed as Tm DEG, and the absolute humidity of the mixed air Ar7 is expressed as Xmkg/kgDA. The air temperature of the wet area passing air Ar8 is represented as Tw, and the absolute humidity of the wet area passing air Ar8 is represented as Xmkg/kgDA. The air temperature of the superheat region through air Ar9 is denoted as Td deg.c and the absolute humidity of the superheat region through air Ar9 is denoted as Xdmkg/kgDA. However, it may be assumed that the superheat region is represented by the air temperature Td ° of the air Ar9 being equal to the suction temperature Ti ° using Ti instead of Td. Even if so replaced, the accuracy hardly changes, and by so replacing, a temperature sensor for measuring the air temperature Td ° c of the superheated region passing air Ar9 can be omitted.

The operation control device 80 stores information on the bypass factor BF of the indoor heat exchanger 42 in, for example, an internal memory. The bypass factor BF is obtained in advance by experiments or simulations, and the obtained value is input to the operation control device 80. The operation control device 80 is configured to be able to read and acquire a required bypass factor BF from, for example, an internal memory when performing control to avoid dew condensation on the fan rotor during low-power cooling operation.

As described above, the intake temperature Ti of the intake air Ar6 is detected by the indoor temperature sensor 451. The operation control device 80 obtains the value of the intake temperature Ti detected by the indoor temperature sensor 451 from the indoor temperature sensor 451.

The evaporation temperature Te ° c of the indoor heat exchanger 42 is detected by the liquid-side temperature sensor 44. The operation control device 80 acquires the value of the evaporation temperature Te detected by the liquid-side temperature sensor 44 from the liquid-side temperature sensor 44.

The temperature Tm ° c of the mixed air Ar7 is detected by the blowout temperature sensor 453. The operation control device 80 obtains the value of the temperature Tm of the mixed air Ar7 detected by the blowout temperature sensor 453 from the liquid-side temperature sensor 44.

The operation control device 80 calculates the value of the air temperature Tw passing through the humid region 491 using the following expression (1). The operation control device 80 can obtain the value of the air temperature Tw passing through the humid region 491 by the calculation of the equation (1).

Tw＝(Ti-Te)×BF+Te···(1)。

The operation control device 80 calculates the occupancy ratio Rw% of the wet area 491 by using the following expression (2). The operation control device 80 can obtain the value of the occupancy rate Rw of the wet area 491 by using the calculation of the equation (2).

Rw＝(Tm-Ti)/(Tw-Ti)···(2)。

The operation control device 80 uses the occupancy rate Rw of the humid region 491 and performs control such that the temperature Tm of the mixed air Ar7 does not fall below the dew-point temperature Tp of the mixed air Ar7, using the result obtained by the calculation described later, thereby preventing the occurrence of condensation on the fan rotor downstream of the indoor heat exchanger 42. That is, during the low-power cooling operation, the operation control device 80 determines the size of the humid region 491 using the temperature Tm of the mixed air Ar7, and controls so that the temperature Tm of the mixed air Ar7 exceeds the dew-point temperature Tp of the mixed air Ar7, thereby preventing the occurrence of condensation on the fan rotor downstream of the indoor heat exchanger 42.

Next, a method of obtaining a relationship between the temperature Tm of the mixed air Ar7 and the dew point temperature Tp of the mixed air Ar7 using the occupancy rate Rw of the humid region 491 will be described.

The suction humidity Hi of the suction air Ar6 is detected by the indoor humidity sensor 452. The operation control device 80 obtains the value of the intake humidity Hi detected by the indoor humidity sensor 452 from the indoor humidity sensor 452.

When the function of the absolute humidity obtained by using the dry-bulb temperature and the relative humidity as parameters is expressed as fx, the operation control device 80 calculates the absolute humidity Xd of the air passing through the overheated region 492 using the following equation (3). The operation control device 80 can obtain the value of the absolute humidity Xd by using the calculation of the equation (3). The function fx is obtained by approximating an air line map calculation table by a calculation formula, for example.

Xd＝fx(Ti，Hi)···(3)。

The operation control device 80 calculates the absolute humidity Xw of the air passing through the humid area 491 using the following equation (4). The operation control device 80 can obtain the value of the occupancy rate Rw of the wet area 491 by using the calculation of the equation (4).

Xw＝(Xd-fx(Te，100))×BF+fx(Te，100)···(4)。

The operation control device 80 calculates the absolute humidity Xm of the mixed air Ar7 using the following equation (5). The operation control device 80 can obtain the value of the absolute humidity Xm of the mixed air Ar7 by the calculation of the equation (5).

Xm＝Rw×Xw+(1-Rw)×Xd···(5)。

When the function of finding the dew point temperature using the dry-bulb temperature and the relative humidity as parameters is represented by fp, the operation control device 80 calculates the value of the dew point temperature Tp of the mixed air Ar7 using the following equation (6). The function fp is obtained by approximating an air line map calculation table by a calculation formula, for example. The operation control device 80 can obtain the value of the dew point temperature Tp of the mixed air Ar7 by the calculation of the equation (6).

Tp＝fp(Tm，Xm)···(6)。

The operation control device 80 performs the following control: the temperature Tm of the mixed air Ar7 is set to be not lower than the dew point temperature Tp of the mixed air Ar7 determined by the expression (6), so that the fan rotor condensation does not occur downstream of the indoor heat exchanger 42.

(3-4-3) device control for avoiding dew condensation of fan rotor in low-power cooling operation

The device control for avoiding dew condensation on the fan rotor during low-energy cooling operation is performed using the calculation results calculated from the size of the wet region (occupancy of the wet region) obtained using the above equations (1) to (6). For example, the operation control device 80 controls the indoor expansion valve 41 and/or the indoor fan 43 by comparing the temperature Tm of the mixed air Ar7 (the temperature detected by the blowout temperature sensor 453) with the dew-point temperature Tp of the mixed air Ar7 obtained by using the above equations (1) to (6).

Fig. 7 shows the limit lines of the evaporation temperature, the intake temperature, and the fan rotor dew condensation with respect to the temperature of the air-fuel mixture obtained from the intake temperature. The graph shown in fig. 7 is a graph obtained by plotting the relationships obtained by using the above equations (1) to (6). The limit lines LN1, LN2, LN3, LN4 are limit lines at the inhalation humidity Hi of 85% RH, 80% RH, 70% RH, and 60% RH, respectively. If the temperature Tm of the mixed air Ar7 is higher than these limit lines LN1 to LN4, dew condensation does not occur. Conversely, if the temperature Tm of the mixed air Ar7 is lower than these limit lines, dew condensation occurs.

Using fig. 7, it can be seen that: for example, if the evaporation temperature Te is about 7 ℃ and the intake humidity Hi is 80% RH, the fan rotor can be prevented from dewing by making the temperature Tm of the mixed air Ar7 higher than about 17 ℃. In other words, the limit lines LN1 to LN4 represent the dew-point temperatures Tp of the mixed air Ar7 under the respective conditions.

Under the above-described conditions that the evaporation temperature Te is about 7 ℃, the intake humidity Hi is 80% RH, and the dew point temperature Tp of the mixed air Ar7 is about 17 ℃, the operation control device 80 operates the indoor unit 40, and operates the indoor unit 40 at the operation point OP1 in fig. 7. In such a case, there is no fear that dew condensation of the fan rotor occurs. In such a case, if the temperature Tm of the mixed air Ar7 at the operating point OP1 of the indoor unit 40 is higher than 17 ℃, control for continuing the original operation is possible, but in order to reliably avoid dew condensation on the fan rotor, it is conceivable that even if the temperature Tm of the mixed air at the operating point OP1 of the indoor unit 40 is higher than 17 ℃, the operating condition is changed to an operating point at which dew condensation on the fan rotor is more difficult to occur, so that the temperature Tm of the mixed air is not lower than the dew point temperature Tp due to a sudden change in the environment or the setting conditions.

Further, for example, when the evaporation temperature Te is about 7 ℃ and the intake humidity Hi is not changed at 80% RH under the above-described conditions, the operation controller 80 may be configured to control to decrease the opening degree of the indoor expansion valve 41 as the pressure reducing mechanism and increase the air volume of the indoor fan 43 when the temperature difference between the temperature Tm of the mixed air Ar7 and the limit line LN2 (dew point temperature Tp) is lower than the 1 st threshold value. For example, if the value of the 1 st threshold is 7 ℃, when the temperature Tm of the mixed air Ar7 at the operation point OP1 becomes 23 ℃, the operation control device 80 determines (Tm-Tp) <7 ℃, thereby performing control to reduce the opening degree of the indoor expansion valve 41 and increase the air volume of the indoor fan 43. When the operation control device 80 controls to decrease the opening degree of the indoor expansion valve 41, the refrigerant circulation amount decreases and the superheated region 492 of the indoor heat exchanger 42 becomes large, so that it is possible to prevent the temperature Tm of the mixed air from decreasing, and to suppress the occurrence of dew condensation on the fan rotor. The decrease in the cooling capacity due to the decrease in the refrigerant circulation amount can be compensated for by increasing the air volume of the indoor fan 43.

For example, if the evaporation temperature Te is about 7 ℃ and the intake humidity Hi is not changed at 80% RH under the above conditions, the operation controller 80 may be configured to control the air volume of the indoor fan 43 to be increased when the temperature difference between the temperature Tm of the mixed air Ar7 and the limit line LN2 (dew point temperature Tp) is lower than the 2 nd threshold value. For example, if the value of the 2 nd threshold is 8 ℃, when the temperature Tm of the mixed air Ar7 at the operation point OP1 becomes 24 ℃, the operation control device 80 determines (Tm-Tp) <8 ℃, and performs control so as to increase the air volume of the indoor fan 43. When the operation control device 80 controls the air volume of the indoor fan 43 to increase, the air volume increases, the cooling capacity increases, and the air volume changes in a direction in which the superheated region 492 of the indoor heat exchanger 42 increases, so that the temperature Tm of the mixed air Ar7 can be prevented from decreasing, and the occurrence of condensation on the fan rotor can be suppressed.

Further, for example, when the evaporation temperature Te is about 7 ℃ and the intake humidity Hi is not changed at 80% RH under the above-described conditions, the operation controller 80 may be configured to perform control for switching from the low-energy cooling operation mode to the normal cooling operation mode when the temperature difference between the temperature Tm of the mixed air Ar7 and the limit line LN2 (dew point temperature Tp) is lower than the 3 rd threshold value. For example, if the value of the 3 rd threshold is 0.5 ℃, when the temperature Tm of the mixed air Ar7 at the operating point OP1 becomes 17 ℃, the operation control device 80 determines (Tm-Tp) <0.5 ℃, and performs control so as to switch from the low-energy cooling operation mode to the normal cooling operation mode. When the operation control device 80 controls the mode to be switched from the low-capacity cooling operation mode to the normal cooling operation mode, the state shown in fig. 5 is changed to the state shown in fig. 4, and the entire indoor heat exchanger 42 can be substantially brought into the humid region 491, so that the air passing through the superheated region 492 of the indoor heat exchanger 42 can be eliminated, and therefore, the fan rotor can be prevented from condensation while ensuring the required cooling capacity.

(3-4-4)

The graph shown in fig. 8 is a graph obtained by plotting the relationships obtained by using the above equations (1) to (6). The limit lines LN11, LN12, LN13, LN14 are limit lines at the inhalation humidity Hi of 85% RH, 80% RH, 70% RH, and 60% RH, respectively. If the occupancy Rw of the wet area 491 is smaller than the limit lines LN11 to LN14, condensation does not occur. Conversely, if the occupancy Rw of the wet area 491 is larger than the limit lines LN11 to LN14, dew condensation occurs.

Using fig. 8, it can be seen that: for example, if the evaporation temperature Te is about 7 ℃ and the suction humidity Hi is 80% RH, the fan rotor can be prevented from dew condensation by setting the occupancy Rw of the wet region 491 to less than about 50%.

Under the above-described conditions that the evaporation temperature Te is about 7 ℃, the suction humidity Hi is 80% RH, and the limit occupancy Rmw of the wet area 491 where condensation occurs is about 50%, the operation control device 80 operates the indoor unit 40, and operates the indoor unit 40 at the operation point OP2 in fig. 8. In such a case, there is no fear that dew condensation of the fan rotor occurs. In such a case, if the occupancy Rw of the wet region 491 at the operating point OP2 of the indoor unit 40 is less than 50%, the control for continuing the original operation is possible, but in order to reliably avoid the dew condensation on the fan rotor, it is conceivable that the operating condition is changed to an operating point at which the dew condensation on the fan rotor is more difficult to occur even if the occupancy Rw of the operating point OP2 of the indoor unit 40 is less than 50%.

For example, if the evaporation temperature Te is about 7 ℃ and the intake humidity Hi is not changed at 80% RH under the above-described conditions, the operation controller 80 may be configured to control the opening degree of the indoor expansion valve 41 as the pressure reducing means to be decreased and the air volume of the indoor fan 43 to be increased when the difference between the occupancy rate Rw of the humid region 491 and the limit line LN12 is lower than the 4 th threshold value. For example, if the 4 th threshold value is set to 15%, when the occupancy Rw of the humid region 491 at the operation point OP2 becomes 40%, the operation control device 80 determines (Rmw-Rw) < 15, and performs control to decrease the opening degree of the indoor expansion valve 41 and increase the air volume of the indoor fan 43. The decrease in the cooling capacity due to the decrease in the refrigerant circulation amount can be compensated for by increasing the air volume of the indoor fan 43.

Further, for example, when the evaporation temperature Te is about 7 ℃ and the intake humidity Hi is not changed at 80% RH under the above-described conditions, the operation controller 80 may be configured to perform control to increase the air volume of the indoor fan 43 when the difference between the occupancy Rw of the humid region 491 and the limit line LN12 is less than the 5 th threshold value. For example, if the value of the 5 th threshold is 25%, the operation control device 80 determines (Rmw-Rw) < 25% when the occupancy Rw of the humid region 491 at the operation point OP2 becomes 30%, and performs control to increase the air volume of the indoor fan 43.

Further, for example, when the evaporation temperature Te is about 7 ℃ and the intake humidity Hi is not changed at 80% RH under the above-described conditions, the operation control device 80 may be configured to perform control for switching from the low-capacity cooling operation mode to the normal cooling operation mode when the difference between the occupancy rate Rw of the humid region 491 and the limit line LN12 is less than the 6 th threshold value. For example, if the value of the 6 th threshold is 1%, when the occupancy rate Rw of the humid region 491 at the operation point OP2 becomes 50%, the operation control device 80 determines (Rmw-Rm) < 1% and performs control for switching from the low-capacity cooling operation mode to the normal cooling operation mode.

(3-4-5)

In the above control, the following control performed by the operation control device 80 is explained: in the low-capacity cooling operation in which the superheated region 492 of the indoor heat exchanger 42 is increased as compared with the normal cooling operation, control for avoiding dew condensation of the fan rotor as described with reference to fig. 7, for example, is performed using the intake temperature Ti, the intake humidity Hi, the temperature Tm of the mixed air Ar7, and the evaporation temperature Te, and the temperature Tm of the mixed air Ar7 is made to exceed the dew-point temperature Tp of the mixed air so that dew condensation of the fan rotor does not occur downstream of the indoor heat exchanger 42. However, the operation control device 80 may perform the following control: the control for avoiding the dew condensation of the fan rotor is performed using the intake temperature Ti, the intake humidity Hi, the humidity of the mixed air Ar7, and the evaporation temperature Te instead of the intake temperature Ti, the intake humidity Hi, the temperature Tm of the mixed air Ar7, and the evaporation temperature Te, and the humidity of the mixed air Ar7 is made to exceed the saturation humidity of the mixed air, so that the dew condensation of the fan rotor does not occur downstream of the indoor heat exchanger 42. Therefore, for example, as shown in fig. 2, the outlet air humidity sensor 454 may be provided in the outlet air space S3.

(3-5) control for avoiding dew condensation on fan rotor during low-power cooling operation

(3-5-1) overview of control for avoiding dew condensation on Fan rotor

During the low-capacity cooling operation, the operation control device 80 determines the size of the humid region 491 using the detection results of the two or more indoor heat exchanger temperature sensors 455, and controls the temperature of the mixed air Ar7 shown in fig. 5 to exceed the dew-point temperature of the mixed air Ar7, thereby preventing the occurrence of condensation on the fan rotor downstream of the indoor heat exchanger 42. More specifically, the size of the humid area 491 is determined using the intake temperature, the intake humidity (relative humidity), and the evaporation temperature of the intake air Ar6, and the detection results of the two or more indoor heat exchanger temperature sensors 455, and control is performed based on the determination result of the size of the humid area 491.

(3-5-2) calculation in the operation control device 80

The operation control device 80 inputs the temperature of the installed U-shaped tube 485 from the plurality of indoor heat exchanger temperature sensors 455. The temperature of the U-shaped tubes 485 is the temperature of the refrigerant flowing in the U-shaped tubes 485. The temperature of the heat transfer tubes 482 in the wet region 491 is substantially the evaporation temperature Te which is the temperature of the gas-liquid two-phase refrigerant. In contrast, the heat transfer pipe 482 of the superheating region 492 has a temperature higher than the evaporation temperature Te. For example, if there are 10 heat transfer pipes 482 and if there are 11 indoor heat exchanger temperature sensors 455, the indoor heat exchanger temperature sensors 455 may be disposed before and after the heat transfer pipes 482. For example, in any of the heat transfer pipes 482, if a difference in level equal to or greater than a predetermined threshold value occurs in the temperature detected by the two indoor heat exchanger temperature sensors 455 before and after the difference, it may be determined that the moist region 491 has been reached up to the heat transfer pipe 482. For example, if the evaporation temperature Te is detected by the indoor heat exchanger temperature sensor 455 on the side close to the outlet of the 10 th-stage heat transfer pipe 482 at the outlet of the indoor heat exchanger 42, the operation control device 80 determines that the occupancy Rw of the wet area 491 is 100%. For example, if a difference in temperature between the two indoor heat exchanger temperature sensors 455 at the two ends of the 6 th-stage heat transfer pipe 482 is equal to or greater than a predetermined threshold value, the operation control device 80 may determine that the region up to the 6 th-stage heat transfer pipe 482 is the superheated region 492 and obtain a value at which the occupancy rate Rw of the humid region 491 is 50%.

The indoor heat exchanger temperature sensors 455 may be arranged uniformly or may be arranged in a concentrated manner. For example, since the indoor heat exchanger 42 in fig. 2 has 8 heat transfer tubes 482 in the upper front side heat exchanger 426, the indoor heat exchanger temperature sensors 455 may be disposed in front of and behind the 8 heat transfer tubes 482 in the upper front side heat exchanger 426. With such a configuration, it is possible to determine in detail whether the occupancy Rw is around 50% with a small number of sensors.

The operation control device 80 is configured to be able to acquire the air temperature Tw of the humid region 491, the absolute humidity xwgk/kgDA of the air passing through the humid region 491, and the absolute humidity Xdkg/kgDA of the air passing through the superheated region 492. For example, the operation control device 80 can acquire the values of the air temperature Tw passing through the humid region 491, the absolute humidity Xw of the air passing through the humid region 491, and the absolute humidity Xd of the air passing through the superheated region 492 by performing the calculation of the following equations (14), (15), and (16).

The operation control device 80 obtains the temperature Tm of the mixed air Ar7 from the following equation (11) using the occupancy Rw of the humid region 491 obtained from the detection result of the indoor heat exchanger temperature sensor 455, the obtained temperature Tm of the mixed air Ar7, the absolute humidity Xw of the air passing through the humid region 491, and the absolute humidity Xd of the air passing through the superheated region 492.

Tm＝Rw×Tw+(1-Rw)×Ti···(11)。

The absolute humidity Xm of the mixed air Ar7 is obtained from the following expression (12).

Xm＝Rw×Xw+(1-Rw)×Xd···(12)。

Then, the dew point temperature Tp of the mixed air is obtained from the following expression (13) using the values of the temperature Tm and absolute humidity Xm of the mixed air Ar7 obtained from expressions (11) and (12). Wherein fp is a function of dew point temperature using dry bulb temperature and absolute humidity as parameters. The function fp is obtained by approximating an air line map calculation table by a calculation formula, for example.

Tp＝fp(Tm，Xm)···(13)。

The operation control device 80 performs the following control: using the result obtained from equation (13), the temperature Tm of the mixed air Ar7 is not lower than the dew-point temperature Tp of the mixed air Ar7, so that no dew condensation of the fan rotor occurs downstream of the indoor heat exchanger 42.

Next, one embodiment in which the operation control device 80 obtains the values of the temperature Tm of the mixed air Ar7, the absolute humidity Xw of the air passing through the humid region 491, and the absolute humidity Xd of the air passing through the superheated region 492 will be described. As described above, the operation control device 80 is configured to read and acquire the required bypass factor BF from, for example, the internal memory, acquire the value of the intake temperature Ti detected by the indoor temperature sensor 451 from the indoor temperature sensor 451, acquire the value of the intake humidity Hi detected by the indoor humidity sensor 452 from the indoor humidity sensor 452, and acquire the value of the evaporation temperature Te detected by the liquid side temperature sensor 44 from the liquid side temperature sensor 44.

The operation control device 80 obtains the air temperature Tw passing through the wet area 491 according to the following expression (14).

Tw＝(Ti-Te)×BF+Te···(14)。

The operation control device 80 obtains the absolute humidity Xd of the air passing through the superheated region 492 according to the following expression (15). Where fx is a function of absolute humidity using dry bulb temperature and relative humidity as parameters.

Xd＝fx(Ti，Hi)···(15)。

The absolute humidity Xd of the air passing through the superheated region 492, which is obtained from the equation (15), is used to obtain the absolute humidity Xw of the air passing through the humid region from the equation (16) below.

Xw＝(Xd-fx(Te，100))×BF+fx(Te，100)···(16)。

The operation control device 80 can obtain the values of the temperature Tm of the mixed air Ar7, the absolute humidity Xw of the air passing through the humid region 491, and the absolute humidity Xd of the air passing through the superheated region 492 by performing the calculations of the above equations (14), (15), and (16).

(3-5-3) device control for avoiding dew condensation of fan rotor in low-power cooling operation

Fig. 7 shows the limit lines of the evaporation temperature, the intake temperature, and the fan rotor dew condensation with respect to the temperature of the air-fuel mixture obtained from the intake temperature. The graph shown in fig. 7 is a graph obtained by plotting the relationships obtained by using the above equations (11) to (16). Since the graph of fig. 7 is a graph obtained by plotting the relationships obtained by the above equations (1) to (6), the device control for avoiding the condensation of the fan rotor during the low energy cooling operation can be performed using the relationships obtained by the above equations (11) to (16) as in the section of "(3-4-3) for avoiding the condensation of the fan rotor during the low energy cooling operation" described above using the relationships obtained by the above equations (1) to (6).

(3-5-4)

The graph shown in fig. 8 is a graph obtained by plotting the relationships obtained by using the above equations (11) to (16). Since the graph of fig. 8 is a graph obtained by plotting the relationships obtained by the above equations (1) to (6), the device control for avoiding the condensation of the fan rotor during the low energy cooling operation can be performed using the relationships obtained by the above equations (11) to (16) as in the section of "(3-4-4) for the device control for avoiding the condensation of the fan rotor during the low energy cooling operation" described above using the relationships obtained by the above equations (1) to (6).

(4) Feature(s)

(4-1)

As described above, in the multi-type air conditioning apparatus 10, the cooling capacity is improved by increasing the opening degree of the indoor expansion valve 41 (an example of the pressure reducing mechanism) to expand the humid region 491 of the indoor heat exchanger 42, and when the humid region 491 is expanded, the temperature of the mixed air formed by mixing the air passing through the superheated region 492 of the indoor heat exchanger 42 and the air passing through the humid region 491 is reduced. Here, the opening degree of the indoor expansion valve 41 is controlled so as to restrict the expansion of the humid region 491 within the upper limit at which condensation does not occur on the fan rotor 43a, so that the temperature Tm of the mixed air Ar7 does not excessively decrease to the dew point temperature Tp of the mixed air Ar7 or less to cause condensation on the fan rotor 43a, and the air volume of the indoor fan 43 is increased to further improve the cooling capacity, thereby ensuring the required cooling capacity. As a result, when the multi-type air conditioning apparatus 10 performs the low-capacity cooling operation, it is possible to prevent condensation from occurring on the fan rotor 43a of the indoor fan 43 while ensuring the required cooling capacity.

(4-2)

In the low-capacity cooling operation during cooling, when the indoor temperature Tr1 is lower than the set temperature Ts1, the opening degree of the indoor expansion valve 41 is decreased and/or the air volume of the indoor fan 43 is decreased, thereby reducing the cooling capacity. Since the expansion of the humid area 491 is limited to the upper limit that does not cause dew condensation on the fan rotor 43a of the indoor fan 43, the humid area 491 is reduced and/or the air volume is reduced, the cooling capacity can be reduced while maintaining no dew condensation on the fan rotor 43 a. In this case, since the operation control device 80 does not perform control for avoiding dew condensation on the fan rotor, an increase in the load on the operation control device 80 can be suppressed.

(4-3)

If the indoor unit 40 is provided with the outlet temperature sensor 453 or the outlet humidity sensor 454 that measures the temperature Tm of the mixed air Ar7 or the humidity of the mixed air Ar7, the occupancy Rw of the humid region 491 can be determined using the temperature Tm of the mixed air Ar7 or the humidity of the mixed air Ar 7. As a result, it is possible to easily determine whether or not the expansion of the humid region 491 is limited to the upper limit that does not cause dew condensation on the fan rotor 43a, using the temperature Tm of the mixed air Ar7 or the humidity of the mixed air Ar7, thereby improving the reliability of the prevention of dew condensation of the fan rotor 43 a.

(4-4)

If two or more indoor heat exchanger temperature sensors 455 are provided in the indoor heat exchanger 42, the occupancy rate Rw of the humid area 491 can be determined using the detection result of the indoor heat exchanger temperature sensors 455. As a result, it is possible to easily determine whether or not the expansion of the humid area 491 is limited to the upper limit that does not cause dew condensation on the fan rotor 43a, using the detection results of the two or more indoor heat exchanger temperature sensors 455, and to improve the reliability of the fan rotor 43a in preventing dew condensation.

(4-5)

When the expansion of the humid region cannot be limited to the upper limit that condensation does not occur on the rotor even if the air volume of the indoor fan 43 is increased in order to obtain the required cooling capacity, the entire indoor heat exchanger 42 can be substantially brought into the humid region by switching from the low-capacity cooling operation mode to the normal cooling operation mode. As a result, the air passing through the superheated region 492 of the indoor heat exchanger 42 can be eliminated, and condensation of the fan rotor 43a can be prevented while ensuring a required cooling capacity.

(4-6)

From one aspect, the multi-type air conditioner 10 may be a device including: an outdoor unit (20), wherein the outdoor unit (20) has a compressor (21), and the compressor (21) compresses a refrigerant that circulates to perform a refrigeration cycle; and a plurality of indoor units (40, 50, 60), the plurality of indoor units (40, 50, 60) having a plurality of indoor heat exchangers (42, 52, 62) and a plurality of pressure reducing mechanisms (41,51,61,41a, 51a, 61a), and having a plurality of indoor fans (43, 53, 63), wherein refrigerant discharged from the compressor circulates in the plurality of indoor heat exchangers (42, 52, 62), air passing through the plurality of indoor heat exchangers passes through the plurality of indoor fans (43, 53, 63), at least one of the plurality of indoor units is configured to expand a humid region by reducing the superheated region of the indoor heat exchanger by increasing an opening degree of the pressure reducing mechanism when an indoor temperature is higher than a set temperature in a low-capacity cooling operation in which the superheated region is increased as compared to a normal cooling operation, on the other hand, increasing the air volume of the indoor fan can limit the expansion of the humid area to an upper limit where condensation does not occur in the device downstream of the indoor heat exchanger.

(5) Modification example

(5-1) modification 1A

In the above embodiment, the control for avoiding the condensation of the fan rotor has been described for the indoor unit 40, but the operation control device 80 may be configured to perform the control for avoiding the condensation of the fan rotor in the indoor units 50 and 60 in the same manner as in the indoor unit 40. In this case, the indoor expansion valves 51 and 61 function as decompression mechanisms of the indoor units 50 and 60. The indoor fans 53 and 63 include fan rotors through which the same air-fuel mixture as the fan rotor 43a of the indoor fan 43 passes.

(5-2) modification 1B

In the above-described embodiment, the example in which the indoor unit 40 is provided with the outlet air temperature sensor 453, the outlet air humidity sensor 454, and the two or more indoor heat exchanger temperature sensors 455 has been described, but since the size of the humid area can be determined by providing any one of the sensors, any one of the outlet air temperature sensor 453, the outlet air humidity sensor 454, and the two or more indoor heat exchanger temperature sensors 455 may be provided.

(5-3) modification 1C

In the above embodiment, the indoor expansion valves 41,51,61, the liquid side temperature sensors 44, 54, 64, and the gas side temperature sensors 45,55,65 are respectively attached to the indoor units 40,50,60 as the multi-air-conditioning apparatus 10, but these components may be provided in the outdoor unit 20 as shown in fig. 9 and 10. The expansion valves 41a, 51a, and 61a are provided in the outdoor unit 20, but function as decompression mechanisms for the refrigerant flowing through the indoor heat exchangers 42,52, and 62, respectively.

(5-3-1) outdoor unit 20

As described above, the outdoor unit 20 shown in fig. 9 and 10 is different from the outdoor unit 20 shown in fig. 1 in that the outdoor unit 20 includes the expansion valves 41a, 51a, 61a, the liquid side temperatures 44, 54, 64, and the gas side temperature sensors 45,55, 65. The outdoor unit 20 shown in fig. 9 and 10 is the same as the outdoor unit 20 shown in fig. 1 with respect to the connection among the other compressors 21, the four-way switching valve 22, the outdoor heat exchanger 23, and the accumulator 24.

In the outdoor unit 20 shown in fig. 9 and 10, the liquid side of the outdoor heat exchanger 23 is connected to one end of the liquid pipe 271 in the outdoor unit 20. Here, the other end of the liquid pipe 271 is branched into three, and the ends of the branching destinations are connected to one ends of the expansion valves 41a, 51a, 61a, respectively. The other ends of the expansion valves 41a, 51a, and 61a are connected to three liquid-side connection ports 222 provided in the outdoor unit 20. Liquid- side temperature sensors 44, 54, 64 are respectively installed between the other ends of these expansion valves 41a, 51a, 61a and the three liquid-side connection ports 222. The three liquid-side connection ports 222 are connected to the liquid sides of the indoor heat exchangers 42,52,62 of the indoor units 40,50,60, respectively.

The outdoor unit 20 shown in fig. 9 and 10 includes three gas-side connection ports 221, and the three gas-side connection ports 221 are connected to the gas sides of the indoor heat exchangers 42,52, and 62 of the indoor units 40,50, and 60, respectively. The three gas-side connection ports 221 are connected to three other ends of the three-branched gas pipes 272, respectively. The refrigerant flowing through the three other ends flows through one end of the gas pipe 272. One end of the gas pipe 272 is connected to the four-way switching valve 22. One end of the gas pipe 272 is connected to the accumulator 24 during the cooling operation, and one end of the gas pipe 272 is connected to the discharge side of the compressor 21 during the heating operation. In order to detect the temperature of the refrigerant flowing through the three other ends of the gas pipe 272, gas- side temperature sensors 45,55,65 are attached to the three other ends, respectively.

(5-3-2) indoor unit 40,50,60

The indoor units 40,50, and 60 shown in fig. 9 have the same configurations as the indoor units 40,50, and 60 shown in fig. 1 except for the expansion valves 41a, 51a, and 61a, the liquid side temperature sensors 44, 54, and 64, and the gas side temperature sensors 45,55, and 65, and therefore, the descriptions thereof are omitted.

(5-3-3) operation of the multiple air conditioner 10

In the outdoor unit 20 shown in fig. 9 and 10, the opening degrees of the expansion valves 41a, 51a, and 61a are controlled by the outdoor-side controller 37. Temperature values detected by the liquid side temperature sensors 44, 54, 64 and the gas side temperature sensors 45,55,65 are acquired by the outdoor side control device 37.

In the multi-type air conditioner 10 shown in fig. 1, the operation control device 80 acquires the temperature values detected by the liquid side temperature sensors 44, 54, 64 and the gas side temperature sensors 45,55,65 via the indoor side control devices 47,57,67 and controls the expansion valves 41a, 51a, 61a via the indoor side control devices 47,57,67, whereas in the multi-type air conditioner 10 shown in fig. 9, the operation control device 80 acquires the temperature values detected by the liquid side temperature sensors 44, 54, 64 and the gas side temperature sensors 45,55,65 via the outdoor side control device 37 and controls the expansion valves 41a, 51a, 61a via the indoor side control device 37. However, the operation control device 80 acquires the temperature values detected by the liquid side temperature sensors 44, 54, 64 and the gas side temperature sensors 45,55,65, and controls the expansion valves 41a, 51a, 61a via the devices, and the multi-type air conditioner 10 shown in fig. 1 is the same as the multi-type air conditioner 10 shown in fig. 9, and the multi-type air conditioner 10 shown in fig. 9 can perform the same control as the above-described embodiment as the multi-type air conditioner 10 shown in fig. 1.

In addition, although the outdoor expansion valve 38 is omitted in the multi-type air conditioning apparatus 10 shown in fig. 9, since the operation of setting the outdoor expansion valve 38 in the fully open state does not contribute to the cooling operation in the multi-type air conditioning apparatus 10 shown in fig. 1, the multi-type air conditioning apparatus 10 shown in fig. 9 can perform the operation other than the operation of the outdoor expansion valve 38 in the cooling operation in the same manner as the multi-type air conditioning apparatus 10 shown in fig. 1.

(5-4) modification 1D

In the above-described embodiment, the case where the size of the humid area is determined using any one of the outlet air temperature sensor 453, the outlet air humidity sensor 454, and the indoor heat exchanger temperature sensor 455 provided in the indoor unit 40 has been described, but these may be used in combination for the purpose of improving accuracy.

(5-5) modification 1E

In the above embodiment, the dew condensation in the fan rotor 43a of the indoor fan 43 has been described as an example of the dew condensation in the device downstream of the indoor heat exchanger 42, but the dew condensation in the device is not limited to the dew condensation in the fan rotor 43 a. For example, dew condensation may occur on the vertical blade 416 and/or the horizontal blade 417 downstream of the indoor heat exchanger 42, and the dew condensation may occur in the device.

(5-6) modification 1F

In the above-described embodiment, the occupancy rate Rw of the humid region 491, in which the upper limit of dew condensation in the device does not occur downstream of the indoor heat exchanger 42 of the indoor unit 40 is calculated by using two or more indoor heat exchanger temperature sensors 455, has been described. However, the expansion of the humid region 491 may be limited to the upper limit that condensation does not occur in the device downstream of the indoor heat exchanger 42 by using one indoor heat exchanger temperature sensor 455. For example, when the occupancy of the humid region 491 where dew condensation does not occur in the device downstream of the indoor heat exchanger 42 is specified within a predetermined operating range of a specific indoor unit 40, the indoor heat exchanger temperature sensor 455 is disposed at a position where the occupancy of the humid region 491 where dew condensation does not occur in the device can be determined, and the indoor heat exchanger temperature sensor 455 at that position is caused to detect the temperature of the overheated region 492 during the low-capacity cooling operation. With this configuration, during the low-power cooling operation, the expansion of the humid region 491 can be limited to the upper limit that condensation does not occur in the device downstream of the indoor heat exchanger 42. Such control can be performed not only in the indoor unit 40 but also in the indoor units 50 and 60 in the same manner.

Description of the reference symbols

10: an air conditioning device;

20: an outdoor unit;

21: a compressor;

40,50, 50: an indoor unit;

41,51, 61: an indoor expansion valve (an example of a decompression mechanism);

41a, 51a, 61 a: an expansion valve (an example of a decompression mechanism);

42,52, 62: an indoor heat exchanger;

43,53, 63: an indoor fan;

80: an operation control device.

Prior art documents

Patent document 1: japanese laid-open patent publication No. 59-122864

Claims (8)

1. A multi-connected air conditioner is provided with:

an outdoor unit (20), wherein the outdoor unit (20) has a compressor (21), and the compressor (21) compresses a refrigerant that circulates to perform a refrigeration cycle; and

a plurality of indoor units (40, 50, 60), the plurality of indoor units (40, 50, 60) having a plurality of indoor heat exchangers (42, 52, 62) and a plurality of decompression mechanisms (41,51,61,41a, 51a, 61a), and having a plurality of indoor fans (43, 53, 63), wherein refrigerant discharged from the compressor circulates in the plurality of indoor heat exchangers (42, 52, 62), and air passing through the plurality of indoor heat exchangers passes through the plurality of indoor fans (43, 53, 63),

at least one of the indoor units is configured to increase the flow rate of the indoor fan while increasing the flow rate of the indoor fan, when the indoor temperature is higher than a set temperature in a low-energy cooling operation in which the flow rate of the indoor fan is increased,

at least one of the plurality of indoor units is configured to perform cooling by using mixed air having passed through the humid area and the superheated area during the low-energy cooling operation in which the superheated area is increased as compared to the normal cooling operation, and is configured to increase the opening degree of the pressure reducing mechanism to reduce the superheated area of the indoor heat exchanger and expand the humid area when the indoor temperature is higher than a set temperature during the low-energy cooling operation, and to increase the air volume of the indoor fan to restrict expansion of the humid area downstream of the indoor heat exchanger to a range in which dew condensation in the apparatus does not occur.

2. A multi-connected air conditioning unit as set forth in claim 1,

the at least one indoor unit uses the temperature of the mixed air or the humidity of the mixed air to determine that the expansion of the humid area downstream of the indoor heat exchanger has been limited to an upper limit within which dew condensation within the device does not occur.

3. A multi-connected air conditioning device as set forth in claim 1 or 2,

the at least one indoor unit further includes an indoor heat exchanger temperature sensor (455) in the indoor heat exchanger, and determines that the expansion of the wet area downstream of the indoor heat exchanger is limited to an upper limit at which dew condensation does not occur in the device, using a detection result of the indoor heat exchanger temperature sensor during the low-power cooling operation.

4. A multi-connected air conditioning device as set forth in claim 1 or 2,

the at least one indoor unit switches from the low-capacity cooling operation mode to the normal cooling operation mode when the air volume of the indoor fan is increased to obtain a required cooling capacity and the expansion of the wet area cannot be limited to an upper limit where dew condensation does not occur in the indoor unit downstream of the indoor heat exchanger.

5. A multi-connected air conditioning unit as set forth in claim 1,

the at least one indoor unit is configured to be able to reduce cooling capacity by reducing the opening degree of the pressure reducing mechanism and/or reducing the air volume of the indoor fan when the indoor temperature is lower than a set temperature in the low-power cooling operation.

6. A multi-connected air conditioner is provided with:

an outdoor unit (20), wherein the outdoor unit (20) has a compressor (21), and the compressor (21) compresses a refrigerant that circulates to perform a refrigeration cycle; and

a plurality of indoor units (40, 50, 60), the plurality of indoor units (40, 50, 60) having a plurality of indoor heat exchangers (42, 52, 62) and a plurality of decompression mechanisms (41,51,61,41a, 51a, 61a), and having a plurality of indoor fans (43, 53, 63), wherein refrigerant discharged from the compressor circulates in the plurality of indoor heat exchangers (42, 52, 62), and air passing through the plurality of indoor heat exchangers passes through the plurality of indoor fans (43, 53, 63),

at least one of the indoor units is configured to increase the flow rate of the indoor fan while increasing the flow rate of the indoor fan, when the indoor temperature is higher than a set temperature in a low-energy cooling operation in which the flow rate of the indoor fan is increased,

the at least one indoor unit performs cooling using mixed air that has passed through the wet area and the superheated area during the low-capacity cooling operation, and uses the temperature of the mixed air or the humidity of the mixed air to determine that the expansion of the wet area downstream of the indoor heat exchanger is limited to an upper limit that does not cause dew condensation in the apparatus.

7. A multi-connected air conditioner is provided with:

an outdoor unit (20), wherein the outdoor unit (20) has a compressor (21), and the compressor (21) compresses a refrigerant that circulates to perform a refrigeration cycle; and

a plurality of indoor units (40, 50, 60), the plurality of indoor units (40, 50, 60) having a plurality of indoor heat exchangers (42, 52, 62) and a plurality of decompression mechanisms (41,51,61,41a, 51a, 61a), and having a plurality of indoor fans (43, 53, 63), wherein refrigerant discharged from the compressor circulates in the plurality of indoor heat exchangers (42, 52, 62), and air passing through the plurality of indoor heat exchangers passes through the plurality of indoor fans (43, 53, 63),

at least one of the indoor units is configured to increase the flow rate of the indoor fan while increasing the flow rate of the indoor fan, when the indoor temperature is higher than a set temperature in a low-energy cooling operation in which the flow rate of the indoor fan is increased,

the at least one indoor unit further includes an indoor heat exchanger temperature sensor (455) in the indoor heat exchanger, and determines that the expansion of the wet area downstream of the indoor heat exchanger is limited to an upper limit at which dew condensation does not occur in the device, using a detection result of the indoor heat exchanger temperature sensor during the low-power cooling operation.

8. A multi-connected air conditioner is provided with:

an outdoor unit (20), wherein the outdoor unit (20) has a compressor (21), and the compressor (21) compresses a refrigerant that circulates to perform a refrigeration cycle; and

a plurality of indoor units (40, 50, 60), the plurality of indoor units (40, 50, 60) having a plurality of indoor heat exchangers (42, 52, 62) and a plurality of decompression mechanisms (41,51,61,41a, 51a, 61a), and having a plurality of indoor fans (43, 53, 63), wherein refrigerant discharged from the compressor circulates in the plurality of indoor heat exchangers (42, 52, 62), and air passing through the plurality of indoor heat exchangers passes through the plurality of indoor fans (43, 53, 63),

at least one of the indoor units is configured to increase the flow rate of the indoor fan while increasing the flow rate of the indoor fan, when the indoor temperature is higher than a set temperature in a low-energy cooling operation in which the flow rate of the indoor fan is increased,

the at least one indoor unit switches from the low-capacity cooling operation mode to the normal cooling operation mode when the air volume of the indoor fan is increased to obtain a required cooling capacity and the expansion of the wet area cannot be limited to an upper limit where dew condensation does not occur in the indoor unit downstream of the indoor heat exchanger.

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