JP5535504B2 - Multi-type air conditioner - Google Patents

Description

  The present invention relates to a multi-type air conditioner in which a plurality of indoor units are connected in parallel to one outdoor unit.

  In air conditioners, humidity control during cooling operation detects the temperature and humidity of the indoor air, calculates the dew point, and adjusts the refrigerant evaporation temperature in the indoor heat exchanger to be above or below the dew point temperature of the indoor air Therefore, it is performed by controlling the rotation speed of the compressor and the rotation speed of the indoor fan. This prevents condensation in the indoor heat exchanger during the cooling operation, so that it does not become uncooled.

  In other words, the dew condensation prevention operation in the air conditioner calculates the dew point of indoor air, compares the dew point temperature with the temperature of the indoor heat exchanger, and if the dew point temperature is lower than the temperature of the indoor heat exchanger, Since no condensation occurs, the operation is continued as it is. On the other hand, when the dew point temperature is higher than the temperature of the indoor heat exchanger, condensation occurs, so the number of rotations of the indoor fan is increased so that the temperature of the indoor heat exchanger is higher than the dew point temperature. When the rotational speed of the blower is maximum, condensation is prevented by lowering the rotational speed of the compressor and making the temperature of the indoor heat exchanger higher than the dew point temperature (for example, see Patent Document 1).

JP-A-6-307705

  However, in a multi-type air conditioner in which a plurality of indoor units are connected, the evaporation temperature of the refrigerant is generally determined in accordance with the indoor unit having the lowest temperature among the plurality of indoor units. For this reason, even if one indoor unit is placed under high humidity conditions, when the other indoor units are operating, the rotation speed of the compressor is controlled so that the evaporation temperature of the refrigerant is maintained under high humidity conditions. It cannot be raised to match the indoor unit. As a result, condensation may occur in the heat exchanger of the indoor unit placed under high humidity conditions, resulting in non-cooling.

  The present invention has been made in view of such circumstances, and can prevent dew condensation in an indoor unit placed under a high humidity condition without affecting other indoor units and outdoor units. An object of the present invention is to provide a multi-type air conditioner that can be used.

In order to solve the above problems, the multi-type air conditioner of the present invention employs the following means.
That is, the multi-type air conditioner according to the present invention is the multi-type air conditioner in which a plurality of indoor units having an indoor heat exchanger and an indoor expansion valve are connected in parallel to the outdoor unit. In each of the indoor units , during the cooling operation, the condensation determining means for determining whether or not the indoor air condition is the dew condensation condition, and when the condensation determination means determines the dew condensation condition, the indoor expansion valve is controlled. And a dew condensation prevention means for preventing dew condensation by reducing the amount of refrigerant circulating to the indoor heat exchanger, and a controller for preventing dew condensation is provided for each indoor unit.

In the multi-type air conditioner, the evaporation temperature of the refrigerant is generally determined in accordance with the indoor unit having the lowest temperature among the plurality of indoor units. Therefore, even if a certain indoor unit is placed under a high humidity condition, the evaporation temperature of the refrigerant cannot be raised in accordance with the indoor unit placed under a high humidity condition while another indoor unit is in operation. As a result, condensation may occur in the heat exchanger of the indoor unit placed under high humidity conditions, resulting in non-cooling. According to the present invention, it is determined whether or not each indoor unit is in a dew condensation condition, and when it is determined as the dew condensation condition, the indoor expansion valve of the indoor unit is controlled to reduce the amount of refrigerant circulation to the indoor heat exchanger. Therefore, the amount of refrigerant circulating to the indoor unit is reduced via the indoor expansion valve of the indoor unit that has been determined to be the dew condensation condition, and the indoor capacity is reduced by appropriately reducing the cooling capacity. Condensation on the exchanger can be prevented. Therefore, in a multi-type air conditioner, even if a certain indoor unit is placed under a high humidity condition, it does not affect other indoor units and outdoor units, while preventing condensation of the indoor unit, The cooling operation can be continued so as not to be uncooled.

  Furthermore, the multi-type air conditioner of the present invention is the multi-type air conditioner described above, wherein when the condensation prevention means is determined to be a dew condensation condition, the indoor expansion valve is opened and closed intermittently at a set time interval. It is configured to operate.

  According to the present invention, the dew condensation preventing means is configured to open and close the indoor expansion valve intermittently at set time intervals when it is determined that the dew condensation condition is satisfied. By appropriately setting the time interval, it is possible to reduce the refrigerant circulation amount to the indoor unit determined to be the dew condensation condition and to appropriately reduce the cooling capacity. In other words, if the time for which the indoor expansion valve is opened is short and the time for which the indoor expansion valve is closed is too long, the cooling capacity is too low and the air is not cooled, and conversely, if the time for opening the indoor expansion valve is too long, Since the risk of condensation increases, by appropriately setting the opening / closing time interval of the expansion valve in consideration of the cooling capacity and condensation, the cooling capacity is moderately reduced and the indoor unit placed under high humidity conditions Condensation can be prevented. Therefore, it is possible to continue the cooling operation so as not to be uncooled while preventing condensation of the indoor unit.

  Furthermore, the multi-type air conditioner of the present invention is the multi-type air conditioner described above, wherein the indoor expansion valve stores a valve opening when the indoor expansion valve is closed during the opening / closing operation, and is opened from the closed state. When the state is set, the opening / closing operation is performed so as to return to the valve opening degree when the closed state is stored.

  According to the present invention, the valve opening when the indoor expansion valve is closed during the opening / closing operation is stored, and when the indoor expansion valve is changed from the closed state to the open state, the stored valve when the closed state is stored is stored. Since the opening / closing operation is performed so as to return to the opening, the valve opening when the indoor expansion valve is opened by the opening / closing operation can be set to an appropriate valve opening, thereby improving the cooling capacity and increasing the valve opening. It is possible to reduce the risk of liquid back generated by becoming too much. Therefore, the indoor unit can be stably operated even during the condensation prevention operation.

  Furthermore, the multi-type air conditioner of the present invention is the multi-type air conditioner according to any one of the above-described multi-type air conditioners, wherein when the indoor expansion valve is changed from a closed state to an open state during the opening / closing operation, the opening degree of the valve changes. The opening operation is performed so that the amount is gradually increased.

  According to the present invention, when the indoor expansion valve is opened from the closed state to the open state during the opening / closing operation, the indoor expansion valve is opened by the opening / closing operation. The valve opening speed when the valve is in the open state can be set to an appropriate speed to improve the cooling capacity, and the risk of liquid back caused by the valve opening speed becoming too fast can be reduced. Therefore, the indoor unit can be stably operated even during the condensation prevention operation.

  Furthermore, the multi-type air conditioner of the present invention is the multi-type air conditioner described above, wherein the dew condensation prevention means is near the midpoint of the refrigerant temperature near the entrance of the indoor heat exchanger when the dew condensation preventing means is determined to be dew condensation conditions. The opening of the indoor expansion valve is reduced so that the difference from the refrigerant temperature increases to a set temperature.

  According to the present invention, when the dew condensation preventing means is determined to be the dew condensation condition, the indoor expansion is performed so that the difference between the refrigerant temperature near the entrance of the indoor heat exchanger and the refrigerant temperature near the intermediate point is raised to the set temperature. Since the valve is configured to reduce the opening of the valve, the opening of the indoor expansion valve is adjusted so that the difference between the refrigerant temperature near the entrance of the indoor heat exchanger and the refrigerant temperature near the midpoint is raised to the set temperature. By narrowing down, the refrigerant circulation amount to the indoor unit determined to be the dew condensation condition can be decreased, and the cooling capacity can be appropriately reduced. In other words, the refrigerant flowing into the indoor heat exchanger is gasified near its midpoint, and the opening of the indoor expansion valve is reduced so that the temperature difference from the refrigerant near the entrance is raised to the set temperature. It is possible to prevent condensation on indoor units placed under high humidity conditions with a moderate drop in capacity. Therefore, it is possible to continue the cooling operation so as not to be uncooled while preventing condensation of the indoor unit.

  Furthermore, the multi-type air conditioner of the present invention is the above multi-type air conditioner, wherein when the dew condensation preventing means is determined to be dew condensation conditions, the air temperature blown out from the indoor unit is raised to a set temperature. Thus, the opening of the indoor expansion valve is configured to be reduced.

  According to the present invention, the dew condensation preventing means is configured to throttle the opening of the indoor expansion valve so that the air temperature blown out from the indoor unit is raised to the set temperature when it is determined as the dew condensation condition. Therefore, by reducing the opening of the indoor expansion valve so that the temperature of the air blown from the indoor unit rises to the set temperature, the amount of refrigerant circulating to the indoor unit determined to be the dew condensation condition is reduced, and the cooling capacity is moderately adjusted. Can be dropped. In other words, by reducing the opening of the indoor expansion valve so that the temperature of the air cooled from the indoor heat exchanger and blown out from the indoor unit is raised to the set temperature, the cooling capacity is moderately reduced and the high humidity condition is maintained. Condensation of the indoor unit placed can be prevented. Therefore, it is possible to continue the cooling operation so as not to be uncooled while preventing condensation of the indoor unit.

  According to the present invention, the amount of refrigerant circulating to the indoor unit is reduced through the indoor expansion valve of the indoor unit determined to be the dew condensation condition, and the condensation to the indoor heat exchanger is prevented by appropriately reducing the cooling capacity. Therefore, in a multi-type air conditioner, even if a certain indoor unit is placed under high humidity conditions, it prevents condensation of the indoor unit without affecting other indoor units or outdoor units. However, the cooling operation can be continued so as not to be uncooled.

It is a refrigerant circuit figure of the multi type air harmony machine concerning a 1st embodiment of the present invention. It is a dew condensation prevention control flowchart of the indoor unit of the multi-type air conditioner shown in FIG. It is operation | movement explanatory drawing at the time of the dew condensation prevention control of the indoor unit shown in FIG. It is a dew condensation prevention control flowchart of the indoor unit of the multi-type air conditioner concerning a 2nd embodiment of the present invention. It is a dew condensation prevention control flowchart of the indoor unit of the multi-type air conditioner concerning a 3rd embodiment of the present invention.

Embodiments according to the present invention will be described below with reference to the drawings.
[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1 to 3.
FIG. 1 shows a refrigerant circuit diagram of a multi-type air conditioner according to the present embodiment. The multi-type air conditioner 1 includes one outdoor unit 2, a gas side pipe 4 and a liquid side pipe 5 led out from the outdoor unit 2, and a branching device 6 between the gas side pipe 4 and the liquid side pipe 5. And a plurality of indoor units 7A and 7B connected in parallel.

  The outdoor unit 2 heats an inverter-driven compressor 21 that compresses refrigerant, an oil separator 22 that separates refrigeration oil from refrigerant gas, a four-way switching valve 23 that switches a refrigerant circulation direction, and refrigerant and outside air. An outdoor heat exchanger 24 to be exchanged, a supercooling coil 25 configured integrally with the outdoor heat exchanger 24, an outdoor electric expansion valve (EEVH) 26 for heating, a receiver 27 for storing liquid refrigerant, A supercooling heat exchanger 28 that supercools the liquid refrigerant, a supercooling electric expansion valve (EEVSC) 29 that controls the amount of refrigerant diverted to the supercooling heat exchanger 28, and a refrigerant sucked into the compressor 21 An accumulator 30 that separates the liquid component from the gas and causes the compressor 21 to suck only the gas component, a gas-side operation valve 31, and a liquid-side operation valve 32 are provided.

  The respective devices on the outdoor unit 2 side are connected in a known manner via refrigerant pipes such as a discharge pipe 33A, a gas pipe 33B, a liquid pipe 33C, a gas pipe 33D, a suction pipe 33E, and a subcooling branch pipe 33F. The outdoor refrigerant circuit 34 is configured. The outdoor unit 2 is provided with an outdoor fan 35 that blows outside air to the outdoor heat exchanger 24.

  Further, between the oil separator 22 and the suction pipe 33E of the compressor 21, a refrigerating machine oil separated from the discharged refrigerant gas in the oil separator 22 is returned to the compressor 21 side by a predetermined amount. A parallel circuit of a first oil return circuit 37 having a fixed throttle (throttle) 36 and a second oil return circuit 40 having a fixed throttle (throttle) 39 such as an electromagnetic valve 38 and a capillary tube is connected.

  The gas side pipe 4 and the liquid side pipe 5 are refrigerant pipes connected to the gas side operation valve 31 and the liquid side operation valve 32 of the outdoor unit 2, and are connected to the outdoor unit 2 and to it during installation on site. The length is set according to the distance between the indoor units 7A and 7B. An appropriate number of branching devices 6 are provided in the middle of the gas side piping 4 and the liquid side piping 5, and an appropriate number of indoor units 7 </ b> A and 7 </ b> B are connected via the branching devices 6. Thereby, one sealed refrigeration cycle 3 is configured.

  The indoor units 7A and 7B are configured so that the indoor air is passed through the indoor heat exchanger 71 that exchanges heat between the refrigerant and room air for indoor air conditioning, the indoor electric expansion valve (EEVC) 72 for cooling, and the indoor heat exchanger 71. The indoor fan 73 is circulated, and is connected to the branching device 6 through the branch gas pipe 4A and the branch liquid pipe 5A on the indoor side.

In the multi-type air conditioner 1 described above, the cooling operation is performed as follows.
The high-temperature and high-pressure refrigerant gas compressed by the compressor 21 is discharged to the discharge pipe 33A, and the oil separator 22 separates the refrigerating machine oil contained in the refrigerant. Thereafter, the refrigerant gas is circulated to the gas pipe 32B side by the four-way switching valve 23, and heat is exchanged with the outside air blown by the outdoor fan 35 in the outdoor heat exchanger 24 to be condensed and liquefied. The liquid refrigerant is further cooled by the supercooling coil 25, passes through the outdoor electric expansion valve 26, and is temporarily stored in the receiver 27.

  The liquid refrigerant whose circulation amount is adjusted by the receiver 27 is partly divided into the subcooling branch pipe 33F in the process of being circulated through the supercooling heat exchanger 28 via the liquid pipe 33C, and the supercooling electric expansion is performed. Heat is exchanged with the refrigerant adiabatically expanded by the valve (EEVSC) 29 to give a degree of supercooling. This liquid refrigerant is led out from the outdoor unit 2 to the liquid side pipe 5 via the liquid side operation valve 32, and the liquid refrigerant led out to the liquid side pipe 5 is further branched into the indoor units 7A and 7B by the branching device 6. The flow is diverted to the liquid pipes 5A and 5B.

  The liquid refrigerant divided into the branch liquid pipes 5A and 5B flows into the indoor units 7A and 7B, is adiabatically expanded by the indoor electric expansion valve (EEVC) 72, becomes a gas-liquid two-phase flow, and the indoor heat exchanger 71. Is flowed into. In the indoor heat exchanger 71, the indoor air circulated by the indoor fan 73 and the refrigerant are heat-exchanged, and the indoor air is cooled and provided for indoor cooling. On the other hand, the refrigerant is gasified, reaches the branching device 6 through the branch gas pipes 4A and 4B, and merges with the refrigerant gas from the other indoor units in the gas side pipe 4.

  The refrigerant gas merged in the gas side pipe 4 returns to the outdoor unit 2 again, reaches the suction pipe 33E through the gas side operation valve 31, the gas pipe 33D, and the four-way switching valve 23, and merges with the refrigerant gas from the branch pipe 33F. Then, it is introduced into the accumulator 30. In the accumulator 30, the liquid component contained in the refrigerant gas is separated, and only the gas component is sucked into the compressor 21. This refrigerant is compressed again in the compressor 21, and the cooling operation is performed by repeating the above cycle.

On the other hand, the heating operation is performed as follows.
The high-temperature and high-pressure refrigerant gas compressed by the compressor 21 is discharged to the discharge pipe 33A, and after the refrigerating machine oil contained in the refrigerant is separated by the oil separator 22, the four-way switching valve 23 causes the gas pipe 33D side. It is circulated in. The refrigerant is led out from the outdoor unit 2 through the gas side operation valve 31 and the gas side pipe 4, and is further introduced into the indoor units 7A and 7B through the branching unit 6 and the branch gas pipes 4A and 4B on the indoor side.

  The high-temperature and high-pressure refrigerant gas introduced into the indoor units A and 7B is heat-exchanged with the indoor air circulated by the indoor fan 73 in the indoor heat exchanger 71, and the indoor air is heated and used for indoor heating. The liquid refrigerant condensed and liquefied in the indoor heat exchanger 71 reaches the branching device 6 through the indoor electric expansion valve (EEVC) 72 and the branch liquid pipes 5A and 5B, and is merged with the refrigerant from other indoor units. It returns to the outdoor unit 2 through the liquid side pipe 5. During heating, in the indoor units 7A and 7B, the opening degree of the indoor electric expansion valve (EEVC) 72 is set so that the degree of supercooling of the refrigerant at the outlet of the indoor heat exchanger 71 functioning as a condenser becomes a constant value. It is controlled.

  The refrigerant that has returned to the outdoor unit 2 reaches the supercooling heat exchanger 28 via the liquid side operation valve 32 and the liquid pipe 33C, and is given supercooling as in the case of cooling, and then flows into the receiver 27. Once stored, the amount of circulation is adjusted. This liquid refrigerant is supplied to the outdoor electric expansion valve (EEVH) 26 through the liquid pipe 33C, and is adiabatically expanded there, and then flows into the outdoor heat exchanger 24 through the supercooling coil 25.

  In the outdoor heat exchanger 24, heat is exchanged between the outside air blown from the outdoor fan 35 and the refrigerant, and the refrigerant absorbs heat from the outside air and is evaporated and gasified. This refrigerant is merged with the refrigerant from the subcooling branch pipe 33F from the outdoor heat exchanger 24 via the gas pipe 33B, the four-way switching valve 23, and the suction pipe 33E, and is introduced into the accumulator 30. In the accumulator 30, the liquid component contained in the refrigerant gas is separated and only the gas component is sucked into the compressor 21. This refrigerant is compressed again by the compressor 21, and the heating operation is performed by repeating the above cycle.

  In a multi-type air conditioner, a plurality of indoor units 7A and 7B are usually installed at different locations, and different types of indoor units may be installed depending on the installation location. For this reason, when a certain indoor unit among a plurality of indoor units 7A and 7B is placed in a high humidity condition during the cooling operation described above, the indoor heat exchanger 71 is a type of indoor unit that is susceptible to condensation. Condensation may occur and may result in non-cooling. In order to prevent such dew condensation, each indoor unit 7A, 7B is provided with a control unit 80 for preventing dew condensation as follows.

  As shown in FIG. 1, the control unit 80 includes a humidity sensor 81 that detects the humidity of the indoor air sucked into the indoor units 7A and 7B, a temperature sensor 82 that detects the intake air temperature, and a blowout from the indoor units 7A and 7B. Detection of a temperature sensor 83 for detecting the temperature of the air to be performed, a temperature sensor 84 for detecting the refrigerant temperature near the entrance of the indoor heat exchanger 71, and a temperature sensor 85 for detecting the refrigerant temperature near the midpoint of the indoor heat exchanger 71 A value is entered. The control unit 80 and the sensors 81 to 85 provided on the indoor unit 7B side are not shown.

  During the cooling operation, the control unit 80 determines whether or not the indoor air condition is a dew condensation condition based on the difference between the detected value of the humidity sensor 81 or the detected value of the intake air temperature sensor 82 and the detected value of the blown air temperature sensor 83. Dew condensation determining means 86 for determining, and when the indoor air condition is determined to be a dew condensation condition by the dew condensation determining means 86, the indoor expansion valve 72 is controlled to reduce the refrigerant circulation amount to the indoor heat exchanger 71, Condensation preventing means 87 for preventing condensation is provided, and the indoor units 7A and 7B are configured to be able to prevent condensation individually.

  Further, as shown in FIG. 2, the control unit 80 determines, in step S <b> 1, based on the temperature difference between the detected humidity of the humidity sensor 81 or the detected temperature of the intake air temperature sensor 82 and the detected temperature of the blown air temperature sensor 83. When the indoor air condition is determined by the dew condensation determination means 86 to determine whether the indoor air condition is the dew condensation condition or not, it is determined that the indoor unit 7A or 7B is under the dew condensation condition. Thus, the control for reducing the refrigerant circulation amount is started for the indoor unit 7A or 7B.

  Specifically, the reduction control of the refrigerant circulation amount is performed by intermittently opening and closing the indoor expansion valve 72 of the indoor unit 7A or 7B at a set time interval, as shown in step S3. Thus, by appropriately setting the time interval of the indoor expansion valve 72 that is intermittently opened and closed at set time intervals, the refrigerant circulation amount to the indoor unit 7A or 7B determined as the dew condensation condition is reduced, It becomes possible to reduce the cooling capacity appropriately.

  That is, when it is determined that the humidity is high and there is a possibility of condensation, the indoor expansion valve 7 is closed to stop the circulation of the refrigerant to the indoor heat exchanger 71, and the temperature of the indoor heat exchanger 71 gradually increases. By repeating the operation of recirculating the refrigerant with the indoor expansion valve 7 in the open state at the rising stage, the cooling capacity can be appropriately reduced. In this case, if the time during which the indoor expansion valve 72 is opened is short and the time during which the indoor expansion valve 72 is closed is too long, the cooling capacity is too low, resulting in non-cooling, and conversely, the time during which the indoor expansion valve 72 is opened is long. If it is too high, the risk of condensation increases. Therefore, by setting the opening / closing time interval of the indoor expansion valve 72 in consideration of the cooling capacity and condensation, for example, the opening time is set to 10 minutes and the closing time is set to 3 minutes. As in step S4, the indoor unit 7A, 7B is prevented from dew condensation, and the cooling operation can be continued so as not to be uncooled.

  The dew condensation prevention operation according to the above is continued in step S4 until the cooling operation is stopped or the humidity of the room air is lowered and escaped from the dew condensation condition, and the cooling operation is stopped or the humidity of the room air is decreased. When it is lowered, it is stopped by step S5.

  Further, the indoor expansion valve 72 stores the valve opening when it is closed when the controller 80 is opened and closed as described above, and is stored when it is opened again from the closed state. It returns to the valve opening when it is in the closed state. Further, when the indoor expansion valve 72 is operated from the closed state to the open state during the above opening / closing operation, the amount of change in the opening of the valve is gradually increased.

With the configuration described above, according to the present embodiment, the following operational effects can be obtained.
In the multi-type air conditioner, since a plurality of indoor units 7A and 7B are installed at different locations, the indoor units 7A and 7B are operated under different conditions. When a certain indoor unit among the plurality of indoor units 7A and 7B is placed in a high humidity condition during cooling operation, condensation may occur in the indoor heat exchanger 71 of the indoor unit 7A or 7B. However, in the multi-type air conditioner, it is necessary to prevent the cooling operation of the other indoor units 7A and 7B from being affected. Therefore, it is possible to increase the evaporation temperature of the refrigerant by controlling the rotation speed of the compressor. Can not.

  However, in this embodiment, the control unit 80 is provided in each indoor unit 7A, 7B, and the difference between the detected value of the humidity sensor 81 or the detected value of the intake air temperature sensor 82 and the detected value of the blown air temperature sensor 83 is determined. Based on the above, it is determined whether or not the indoor air condition is the dew condensation condition by the dew condensation determination means 86, and when it is determined as the dew condensation condition, the indoor expansion valve 72 of the indoor unit 7A or 7B is controlled by the condensation prevention means 87. Thus, the amount of refrigerant circulating to the indoor heat exchanger 71 is reduced, and the cooling capacity is appropriately reduced to prevent condensation.

  That is, when the dew condensation condition is determined, the indoor expansion valve 72 of the indoor unit 7A or 7B is intermittently opened at a time interval set by the dew condensation prevention means 87, for example, 10 minutes open as described above, and 3 minutes closed. It can be opened and closed. For this reason, the amount of refrigerant circulating to the indoor unit 7A or 7B determined to be the dew condensation condition can be reduced, whereby the cooling capacity can be appropriately reduced and the dew condensation to the indoor heat exchanger 71 can be prevented. . Therefore, in the multi-type air conditioner 1, the cooling operation is continued so as not to be uncooled while preventing condensation of the indoor unit 7A or 7B without affecting other indoor units or outdoor units. be able to.

  Further, when the indoor expansion valve 72 is opened and closed as described above, the valve opening degree when the indoor expansion valve 72 is closed is stored, and when the indoor expansion valve 72 is changed from the closed state to the open state, the stored closed state is stored. As shown in R1 in FIG. 3, the valve opening when the indoor expansion valve 72 is opened by the opening / closing operation is set to an appropriate valve opening, and the cooling capacity is increased. In addition to being able to improve, it is possible to reduce the risk of liquid back that occurs when the valve opening becomes too large. Therefore, the indoor unit 7A or 7B can be stably operated even during the condensation prevention operation.

  Further, when the indoor expansion valve 72 is opened and closed, when the indoor expansion valve 72 is changed from the closed state to the open state, the amount of change in the opening of the valve is gradually increased. In addition, the valve opening speed when the indoor expansion valve 72 is opened by the opening / closing operation can be set to an appropriate speed, the cooling capacity can be improved, and the risk of liquid back generated when the valve opening speed becomes too high. Can be reduced. Therefore, the indoor unit 7A or 7B can be stably operated even during the condensation prevention operation.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG.
In the present embodiment, the difference between the refrigerant temperature near the entrance of the indoor heat exchanger 71 and the refrigerant temperature near the intermediate point is raised to the set temperature during the dew condensation prevention operation compared to the first embodiment described above. The difference is that the opening of the indoor expansion valve 72 is reduced. Since other points are the same as those in the first embodiment, description thereof will be omitted.
In this embodiment, as shown in FIG. 4, it is determined in step S11 whether or not the indoor air condition is a dew condensation condition, and if it is determined that the indoor unit 7A or 7B is under the dew condensation condition. Then, the process proceeds to step S12, and the control for reducing the refrigerant circulation amount for the indoor unit 7A or 7B is started.

  As shown in step S <b> 13, the refrigerant circulation amount decrease control is performed between the refrigerant temperature near the entrance of the indoor heat exchanger 71 detected by the temperature sensor 84 and the indoor heat exchanger 71 detected by the temperature sensor 85. This is performed by reducing the opening of the indoor expansion valve 72 so that the temperature difference from the refrigerant temperature near the point is raised to a set temperature (for example, 3 deg). In this way, the condensation condition is determined by reducing the opening of the indoor expansion valve 72 so that the difference between the refrigerant temperature near the entrance of the indoor heat exchanger 71 and the refrigerant temperature near the midpoint is raised to the set temperature. It is possible to reduce the refrigerant circulation amount to the indoor unit 7A or 7B that has been made and to appropriately reduce the cooling capacity. Steps S14 and S15 are the same as steps S4 and S5 of the first embodiment.

  Thus, according to the present embodiment, when it is determined by the condensation prevention means 86 that the indoor unit 7A or 7B is under the dew condensation condition, the entrance of the indoor heat exchanger 71 of the indoor unit 7A or 7B. Since the opening of the indoor expansion valve 72 is narrowed so that the difference between the refrigerant temperature in the vicinity and the refrigerant temperature in the vicinity of the intermediate point is raised to the set temperature, the indoor unit 7A or 7B determined as the dew condensation condition Therefore, the cooling capacity can be reduced appropriately. That is, the degree of opening of the indoor expansion valve 72 is such that the refrigerant that has flowed into the indoor heat exchanger 71 is gasified near its midpoint and the temperature difference from the refrigerant near the entrance is increased to 3 deg as described above. By narrowing down, it is possible to prevent condensation on the indoor unit 7A or 7B placed under a high humidity condition by appropriately reducing the cooling capacity. Therefore, according to the present embodiment, as in the first embodiment, the cooling operation can be continued so as to prevent the indoor unit 7A or 7B from condensing and not to be uncooled.

[Third Embodiment]
Next, a third embodiment of the present invention will be described with reference to FIG.
This embodiment is different from the first and second embodiments described above in that the degree of opening of the indoor expansion valve 72 is such that the temperature of the air blown from the indoor unit 7A or 7B is raised to the set temperature during the dew condensation prevention operation. The point that is trying to narrow down. Since other points are the same as those in the first and second embodiments, description thereof will be omitted.
In this embodiment, as shown in FIG. 5, it is determined in step S21 whether or not the indoor air condition is a dew condensation condition, and it is determined that the indoor unit 7A or 7B is under the dew condensation condition. Then, the process proceeds to step S22, and the control for reducing the refrigerant circulation amount for the indoor unit 7A or 7B is started.

  As shown in step S23, the refrigerant circulation amount reduction control is performed by opening the indoor expansion valve 72 so that the air temperature blown from the indoor unit 7A or 7B detected by the temperature sensor 83 is raised to the set temperature. It is done by narrowing down the degree. As described above, the refrigerant circulation to the indoor unit 7A or 7B determined to be the dew condensation condition by reducing the opening of the indoor expansion valve 72 so that the temperature of the air blown from the indoor unit 7A or 7B is raised to the set temperature. It is possible to reduce the amount and appropriately reduce the cooling capacity. Steps S24 and S25 are the same as steps S4 and S5 of the first embodiment.

  Thus, according to the present embodiment, when the dew condensation preventing means 86 determines that the indoor unit 7A or 7B is under the dew condensation condition, the air temperature blown from the indoor unit 7A or 7B is set. Since the opening of the indoor expansion valve 72 is reduced so that the temperature is raised, the amount of refrigerant circulating to the indoor unit 7A or 7B determined to be the dew condensation condition can be reduced, and the cooling capacity can be lowered appropriately. it can. That is, the cooling capacity is appropriately reduced by reducing the opening of the indoor expansion valve 72 so that the temperature of the air cooled by the indoor heat exchanger 71 and blown from the indoor unit 7A or 7B is raised to the set temperature. Condensation of the indoor unit 7A or 7B placed under high humidity conditions can be prevented. Therefore, according to the present embodiment, as in the first and second embodiments, the cooling operation can be continued so as to prevent the indoor unit 7A or 7B from condensing and not to be uncooled.

  In addition, this invention is not limited to the invention concerning the said embodiment, In the range which does not deviate from the summary, it can change suitably. For example, the setting values and the like exemplified in the above-described embodiments are merely examples, and it goes without saying that the setting values are not limited to these setting values.

DESCRIPTION OF SYMBOLS 1 Multi-type air conditioner 2 Outdoor unit 7A, 7B Indoor unit 71 Indoor heat exchanger 72 Indoor expansion valve 80 Control part 81 Humidity sensor 82, 83, 84, 85 Temperature sensor 86 Condensation determination means 87 Condensation prevention means

Claims (6)

In the multi-type air conditioner in which a plurality of indoor units having an indoor heat exchanger and an indoor expansion valve are connected in parallel to the outdoor unit,
Each of the plurality of indoor units includes a condensation determination unit that determines whether the indoor air condition is a dew condensation condition during cooling operation, and the indoor expansion valve when the dew condensation determination unit determines the dew condensation condition. And a condensation prevention means for preventing condensation by controlling and reducing the amount of refrigerant circulating to the indoor heat exchanger, and a controller for preventing condensation is provided for each indoor unit. Multi-type air conditioner.   2. The multi type according to claim 1, wherein the dew condensation preventing unit is configured to open and close the indoor expansion valve intermittently at a set time interval when it is determined that the dew condensation condition is satisfied. Air conditioner.   The indoor expansion valve stores a valve opening when the indoor expansion valve is closed during the opening and closing operation, and stores the valve opening when the closed state is stored when the indoor expansion valve is opened from the closed state. The multi-type air conditioner according to claim 2, wherein the multi-type air conditioner is opened and closed so as to be returned.   The said indoor expansion valve is opened so that when the opening / closing operation is changed from the closed state to the opened state, the amount of change in the opening of the valve is gradually increased. Multi-type air conditioner.   The dew condensation preventing means opens the indoor expansion valve so that the difference between the refrigerant temperature near the entrance of the indoor heat exchanger and the refrigerant temperature near the intermediate point is raised to a set temperature when it is determined that the dew condensation condition is satisfied. The multi-type air conditioner according to claim 1, wherein the multi-type air conditioner is configured to reduce the degree.   The dew condensation prevention means is configured to restrict the opening of the indoor expansion valve so that the air temperature blown out from the indoor unit is raised to a set temperature when it is determined that the dew condensation condition is satisfied. The multi-type air conditioner according to claim 1.

Images