Abstract:
A multi-unit air conditioner and a method for controlling the same are disclosed which are capable of preventing continuous introduction of a refrigerant into indoor units in an OFF state where the indoor units can be independently powered on or off, thereby preventing a degradation in the cooling and heating efficiencies. The air conditioner includes a plurality of indoor units each including a power controller adapted to independently power on or off an associated one of the indoor units, an outdoor unit connected with the indoor units, the outdoor unit including a microcomputer for controlling an operation of the outdoor unit, and enabling the outdoor unit to communicate with the indoor units, and a controller for determining whether each of the indoor units is in a normal operation state or in a non-operation state, and controlling an operation of a distributor in accordance with the result of the determination.

Description:
[0001]     This application claims the benefit of Korean Patent Application No. 10-2004-0105331, filed on Dec. 14, 2004, which is hereby incorporated by reference as if fully set forth herein.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to an air conditioner, and more particularly, to a multi-unit air conditioner and a method for controlling the same which are capable of preventing continuous introduction of a refrigerant into an indoor unit or indoor units in an OFF state, thereby preventing a degradation in the cooling and heating efficiencies of the air conditioner.  
         [0004]     2. Discussion of the Related Art  
         [0005]     Generally, air conditioners perform procedures of compressing, condensing, expanding and evaporating a refrigerant to cool and/or heat a confined space. Such air conditioners are classified into a cooling type wherein a refrigerant flows only in one direction through a refrigerant cycle, to supply cold air to a confined space, and a cooling and heating type wherein a refrigerant flows bi-directionally in a selective manner through a refrigerant cycle, to selectively supply cold air or hot air to a confined space.  
         [0006]     Also, such air conditioners are classified into a general type wherein one indoor unit is connected to one outdoor unit, and a multi-unit type wherein a plurality of indoor units are connected to one outdoor unit. For the multi-unit type, an air conditioner may be implemented which includes at least one outdoor unit.  
         [0007]     Multi-unit air conditioners are classified into a switching type wherein all indoor units operate in the same operating mode, that is, in cooling mode or heating mode alone, and a simultaneous type wherein a part of the indoor units operate in cooling mode, and the remaining indoor unit or indoor units operate in heating mode.  
         [0008]     In such a multi-unit air conditioner, a controller is provided at each of the indoor units and outdoor unit. Through communications between a microcomputer included in the controller of the outdoor unit and a microcomputer included in the controller of each indoor unit, the outdoor unit controls the indoor unit. Also, each indoor unit is electrically connected in parallel with the outdoor unit such that the outdoor unit and indoor units are simultaneously powered on or off. The outdoor unit also controls the power ON/OFF of each indoor unit.  
         [0009]     An electronic expansion valve is arranged in a refrigerant line extending to each indoor unit, in order to prevent the refrigerant from entering the indoor unit when the indoor unit does not operate. When the indoor unit operates, the electronic expansion valve allows introduction of the refrigerant into the indoor unit, and reduces the pressure of the refrigerant to expand the refrigerant to a low-temperature and low-pressure mist state.  
         [0010]     Meanwhile, if necessary, power controllers may be installed in the indoor units, respectively, in order to individually control the power ON/OFF of the indoor units. In this case, however, there may be a problem in that, when a fraction of the indoor units are powered off during operation of the air conditioner, the electronic expansion valves connected to the powered-off indoor units can be no longer controlled from an open state thereof.  
         [0011]     That is, when one indoor unit is powered off during operation of the air conditioner, the electronic expansion valve connected to the indoor unit can be no longer controlled from an open state thereof, so that the refrigerant is continuously introduced into the powered-off indoor unit. In this case, the performance of the other indoor units, which operate normally, is degraded, thereby causing a degradation in cooling and heating efficiencies. Furthermore, since no heat exchange is carried out in the powered-off indoor unit, the refrigerant, which does not perform heat exchange in the powered-off indoor unit, is introduced into a compressor. As a result, a degradation in the performance of the air conditioner occurs.  
       SUMMARY OF THE INVENTION  
       [0012]     Accordingly, the present invention is directed to a multi-unit air conditioner and a method for controlling the same that substantially obviate one or more problems due to limitations and disadvantages of the related art.  
         [0013]     An object of the present invention is to provide a multi-unit air conditioner system capable of recovering a refrigerant from powered-off one or ones of the indoor units included in the multi-unit air conditioner, and cutting off the refrigerant supplied to the powered-off indoor unit or units, thereby preventing a degradation in the performance of the air conditioner.  
         [0014]     Another object of the present invention is to provide a multi-unit air conditioner system capable of achieving an enhancement in cooling and heating performance.  
         [0015]     Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.  
         [0016]     To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a multi-unit air conditioner comprising: a plurality of indoor units each comprising a power controller adapted to independently power on or off an associated one of the indoor units; an outdoor unit connected with the indoor units, the outdoor unit comprising a microcomputer for controlling an operation of the outdoor unit, and enabling the outdoor unit to communicate with the indoor units; and at least one controller for determining whether each of the indoor units is in a normal operation state or in a non-operation state, and controlling an operation of a distributor in accordance with the result of the determination.  
         [0017]     The at least one controller may be installed in at least one of the outdoor unit and the distributor, respectively.  
         [0018]     The distributor may comprise at least one first intermittent valve arranged in a refrigerant line through which a refrigerant is introduced into the indoor units, and at least one second intermittent valve arranged in a refrigerant line through which the refrigerant from the indoor units is discharged into the outdoor unit.  
         [0019]     Each of the first and second intermittent valves may be a solenoid valve controlled by the controller or by the microcomputer of the outdoor unit. The at least one first intermittent valve may comprise a plurality of first intermittent valves respectively arranged in branch refrigerant lines, through each of which the refrigerant is introduced into an associated one of the indoor units. The at least one second intermittent valve may comprise a plurality of second intermittent valves respectively arranged in branch refrigerant lines, through each of which the refrigerant from an associated one of the indoor units is discharged into the outdoor unit.  
         [0020]     In another aspect of the present invention, a multi-unit air conditioner comprises: a plurality of indoor units; an outdoor unit connected with the indoor units, the outdoor unit comprising a microcomputer for controlling an operation of the outdoor unit, and enabling the outdoor unit to communicate with the indoor units; an electronic expansion valve arranged in a refrigerant line through which a refrigerant from the outdoor unit is introduced into the indoor units; first intermittent valves arranged in a refrigerant line through which the refrigerant is introduced into the indoor units; second intermittent valves arranged in a refrigerant line through which the refrigerant from the indoor units is discharged into the outdoor unit; and at least one controller for determining whether each of the indoor units is in a normal operation state or in a non-operation state, and controlling an operation of a distributor in accordance with the result of the determination, the at least one controller being arranged in at least one of the outdoor unit and a distributor, respectively.  
         [0021]     The electronic expansion valve may comprise sub electronic expansion valves respectively arranged in branch refrigerant lines, through each of which the refrigerant is introduced into an associated one of the indoor units, and a main electronic expansion valve arranged in the refrigerant line, through which the refrigerant is introduced into the indoor units, and which is branched into the branch refrigerant lines.  
         [0022]     In particular, each of the first intermittent valves may be arranged between an associated one of the sub electronic expansion valves and the indoor unit associated with the associated sub electronic expansion valve. The electronic expansion valve and the first and second intermittent valves may be controlled by the microcomputer of the outdoor unit. Each of the first and second intermittent valves may be a solenoid valve controlled by the microcomputer of the outdoor unit or by the controller.  
         [0023]     In another aspect of the present invention, a method for controlling a multi-unit air conditioner including an outdoor unit and a plurality of indoor units, comprising the steps of: checking a communication state established between the outdoor unit and each of the indoor units; determining whether or not there is a powered-off one of the indoor units under a condition in which a communication state is established between the outdoor unit and each of the indoor units; recovering a refrigerant from the powered-off indoor unit; and cutting off the refrigerant supplied to the powered-off indoor unit.  
         [0024]     The determining step may comprise the step of determining one of the indoor units, which does not provide a response to the outdoor unit for a predetermined response time, as the powered-off indoor unit. The predetermined response time may be 5 minutes.  
         [0025]     The refrigerant recovering step may comprise the steps of closing a first intermittent valve arranged in an inlet refrigerant line of the powered-off indoor unit, and operating the powered-off indoor unit for a predetermined time, thereby recovering the refrigerant from the powered-off indoor unit.  
         [0026]     The refrigerant cutting-off step may comprise the steps of closing first and second intermittent valves respectively arranged in inlet and outlet refrigerant lines of the powered-off indoor unit.  
         [0027]     The method may further comprise the step of executing a normal operation of the air conditioner after execution of the refrigerant cutting-off step.  
         [0028]     It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0029]     The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings:  
         [0030]      FIG. 1  is a schematic view illustrating a configuration of a multi-unit air conditioner according to an embodiment of the present invention;  
         [0031]      FIG. 2  is a block diagram illustrating an example of a communication controlling apparatus in the multi-unit air conditioner according the embodiment of the present invention; and  
         [0032]      FIG. 3  is a flow chart illustrating a method for controlling indoor units of a multi-unit air conditioner in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0033]     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.  
         [0034]      FIG. 1  is a schematic view illustrating a configuration of a multi-unit air conditioner according to an embodiment of the present invention.  
         [0035]     As shown in  FIG. 1 , the multi-unit air conditioner (hereinafter, simply referred to as an “air conditioner”) includes an outdoor unit  40  installed outdoors, and a plurality of indoor units, that is, an indoor unit  10  for a room A, an indoor unit  20  for a room B, and an indoor unit  30  for a room C, installed indoors. The indoor units  10 ,  20 , and  30  are connected to the outdoor unit  40  so that they operate as a single system.  
         [0036]     As shown in  FIG. 2 , the outdoor unit  40  includes a compressor  41  for compressing a refrigerant to a high-temperature and high-pressure gas state, and an outdoor heat exchanger  43  for condensing the refrigerant gas, compressed to a high-temperature and high-pressure state in the compressor  41 , into a low-temperature and high-pressure liquid state. The outdoor unit  40  also includes a 4-way valve  42 , a main electronic expansion valve  45 , and room-A, B, and C electronic expansion valves  11 ,  21 , and  31  (hereinafter, simply referred to as “sub electronic expansion valves”).  
         [0037]     An outdoor fan  44  is arranged at one side of the outdoor heat exchanger  43 . The outdoor fan  44  sucks outdoor air, and blows the sucked air toward the outdoor heat exchanger  43 , in order to enable the outdoor heat exchanger  43  to perform effective heat exchange.  
         [0038]     The 4-way valve  42  changes the flow path of the refrigerant gas compressed to a high-temperature and high-pressure state in the compressor  41  in accordance with the operation mode (cooling mode or heating mode) of the air conditioner.  
         [0039]     The main electronic expansion valve  45  controls the temperature of the refrigerant discharged from the outdoor heat exchanger  43  to control the over-heating degree in the cooling mode and the over-cooling degree in the heating mode.  
         [0040]     Each of the sub electronic expansion valves  11 ,  21 , and  31  is opened or closed under control of a controller (not shown) in order to enable the associated indoor unit  10 ,  20  or  30  to selectively perform an air conditioning operation for the associated room in accordance with the operation condition of the associated indoor unit  10 ,  20  or  30 . That is, the sub electronic expansion valves  11 ,  21 , or  31  distribute the refrigerant supplied through the main electronic expansion valve  45 , and selectively cut off the refrigerant supplied to the indoor units  10 ,  20 , and  30 , respectively. In particular, each of the sub electronic expansion valves  11 ,  21 , and  31  receives the low-temperature and high-pressure refrigerant liquid cooled and condensed in the outdoor unit  43 , and reduces the pressure of the received refrigerant to expand the refrigerant to an easily-evaporable low-temperature and low-pressure mist state.  
         [0041]     The indoor units  10 ,  20 , and  30  include respective indoor heat exchangers  12 ,  22 , and  32  for evaporating the low-temperature and low-pressure misty refrigerant emerging from respective sub electronic expansion valves  11 ,  21 , and  31 , thereby changing the refrigerant to a low-temperature and low-pressure pure gas state. The indoor units  10 ,  20 , and  30  also include indoor fans  13 ,  23 , and  33  for circulating indoor air to enable the indoor heat exchangers  12 ,  22 , and  32  to effectively perform heat exchange, respectively.  
         [0042]     First intermittent valves  55   a  are arranged in first refrigerant lines, through each of which the refrigerant from the outdoor unit  40  is introduced into an associated one of the indoor units  10 ,  20 , and  30 , in order to cut off the refrigerant introduced into the indoor unit  10 ,  20 , and  30 , respectively. Second intermittent valves  55   b  are arranged in second refrigerant lines, through each of which the refrigerant from an associated one of the indoor units  10 ,  20 , and  30  is discharged into the outdoor unit  40 , in order to cut off the refrigerant discharged from the indoor units  10 ,  20 , and  30 , respectively. The first intermittent valves  55   a  and second intermittent valves  55   b  constitute a distributor  50 , together with a microcomputer (not shown) adapted to control the intermittent valves  55   a  and  55   b . It is preferred that each of the first and second intermittent valves  55   a  and  55   b  be a solenoid valve.  
         [0043]     Meanwhile, the microcomputer may also be arranged in the distributor  50 , in addition to the outdoor unit  40 .  
         [0044]     When the indoor units  10 ,  20 , and  30  operate in cooling mode in the air conditioner having the above-described configuration, the 4-way valve  42  is in an OFF state. In this case, accordingly, a refrigerant cycle is established in which the refrigerant flows along the path as indicated by solid-line arrows in  FIG. 2 .  
         [0045]     This will be described in more detail. First, the high-temperature and high-pressure refrigerant gas discharged from the compressor  41  of the outdoor unit  40  is introduced into the outdoor heat exchanger  43  through the 4-way valve  42 . The introduced refrigerant heat-exchanges with air, blown to the outdoor heat exchanger  43  by the outdoor fan  44 , in the outdoor heat exchanger  43 . That is, the compressed high-temperature and high-pressure refrigerant gas is forcibly cooled and condensed to a low-temperature and high-pressure liquid state.  
         [0046]     The low-temperature and high-pressure refrigerant liquid discharged from the outdoor heat exchanger  43  is introduced into the sub electronic expansion valves  11 ,  21 , and  31  via the main electronic expansion valve  45 . As a result, the refrigerant is expanded to an easily-evaporable low-temperature and low-pressure mist state. The refrigerant is then introduced into the indoor heat exchangers  12 ,  22 , and  32  of the indoor units  10 ,  20 , and  30 . In each of the indoor heat exchangers  12 ,  22 , and  32 , the pressure-reduced low-temperature and low-pressure misty refrigerant absorbs heat from air, blown to the associated indoor heat exchanger  12 ,  22 , or  32  by the associated indoor fan  13 ,  23 , or  33 , while being evaporated, thereby cooling the air. The cooled air is discharged to the rooms to reduce the temperatures of the rooms. Thus, the air conditioner operates in cooling mode.  
         [0047]     The low-temperature and low-pressure refrigerant gas evaporated in the indoor heat exchangers  12 ,  22 , and  32  is introduced again into the compressor  41 , and is then changed to a high-temperature and high-pressure refrigerant gas state. Thus, the above-described refrigerant cycle is repeated.  
         [0048]     The main electronic expansion valve  45  performs an over-heating degree control operation in accordance with the operation conditions of the indoor units  10 ,  20 , and  30 . Each of the sub electronic expansion valves  11 ,  21 , and  31  distributes the refrigerant to the associated indoor unit  10 ,  20 , or  30  when the associated indoor unit  10 ,  20 , or  30  operates, and cuts off the refrigerant distributed to the associated indoor unit  10 ,  20 , or  30  when the associated indoor unit  10 ,  20 , or  30  does not operate.  
         [0049]     Meanwhile, when the indoor units  10 ,  20 , and  30  operate in heating mode, the 4-way valve  42  is in an ON state. In this case, accordingly, a refrigerant cycle is established in which the refrigerant flows along the path as indicated by dotted-line arrows in  FIG. 2 .  
         [0050]     In this case, first, the high-temperature and high-pressure refrigerant gas discharged from the compressor  41  of the outdoor unit  40  is introduced into the indoor heat exchangers  12 ,  22 , and  32  of the indoor units  10 ,  20 , and  30  through the 4-way valve  42 . Accordingly, the indoor heat exchangers  12 ,  22 , and  32  operate in heating mode. That is, each indoor heat exchanger  12 ,  22 , or  32  heat exchanges with air blown by the associated indoor fan  13 ,  23 , or  33 , thereby releasing heat to the air, and thus, heating the air. The heated air is discharged to the associated room. At this time, the refrigerant is cooled to an ambient-temperature and high-pressure liquid state.  
         [0051]     The refrigerant liquefied in each of the indoor heat exchangers  12 ,  22 , and  32  is introduced into the associated sub electronic expansion valve  11 ,  21 , or  31 , and is then pressure-reduced to expand to an easily-evaporable low-temperature and low-pressure mist state. The refrigerant is subsequently introduced into the outdoor heat exchanger  43  via the main electronic expansion valve  45 .  
         [0052]     In the outdoor heat exchanger  43 , the low-temperature and low-pressure misty refrigerant heat-exchanges with air blown by the outdoor fan  44 , so that the refrigerant is cooled to a low-temperature and low-pressure gas state. Thus, the above-described refrigerant cycle is repeated.  
         [0053]     The main electronic expansion valve  45  performs an over-cooling degree control operation in accordance with the operation conditions of the indoor units  10 ,  20 , and  30 . Each of the sub electronic expansion valves  11 ,  21 , and  31  distributes the refrigerant to the associated indoor unit  10 ,  20 , or  30  when the associated indoor unit  10 ,  20 , or  30  operates, and cuts off the refrigerant distributed to the associated indoor unit  10 ,  20 , or  30  when the associated indoor unit  10 ,  20 , or  30  does not operate.  
         [0054]      FIG. 2  is a block diagram illustrating an example of a communication controlling apparatus in the multi-unit air conditioner according the illustrated embodiment of the present invention.  
         [0055]     The operation of the air conditioner is controlled through control signal communications between an outdoor unit controller  46  constituted by a microcomputer installed in the outdoor unit  40  and room-A, B, and C controllers  15 ,  25 , and  35  respectively constituted by microcomputers installed in the indoor units  10 ,  20 , and  30 .  
         [0056]     That is, when an operation key on an operating panel installed in the room-A indoor unit  10  is pressed, the room-A controller  15  receives an operation signal, and performs a control operation for drivers (for example, an indoor fan driver, a blowing direction driver, an indoor temperature sensor, an indoor conduit temperature sensor, and the like) required in the room-A indoor unit  10 , in accordance with the operation signal. The room-A controller  15  also outputs a communication control signal to the outdoor unit controller  46 , so as to enable the outdoor unit controller  46  to perform a control operation for the compressor  41 , 4-way valve  42 , outdoor fan  44 , main electronic expansion valve  45 , and the like.  
         [0057]     The control operations carried out by the room-B and C indoor units  20  and  30  are identical to the above-described control operation carried out by the room-A indoor unit  10 .  
         [0058]     Meanwhile, the indoor units  10 ,  20 , and  30  are electrically connected with the outdoor unit  40  in parallel such that the indoor units  10 ,  20 , and  30 , and the outdoor unit  40  are simultaneously powered on or off. If necessary, each of the indoor units  10 ,  20 , and  30  may includes a power ON/OFF device adapted to independently power on or off the associated indoor unit  10 ,  20 , or  30 .  
         [0059]     Hereinafter, a method for controlling the indoor units of the multi-unit air conditioner having the above-described configuration in accordance with an embodiment of the present invention will be described with reference to  FIG. 3 .  
         [0060]     The control method according to the illustrated embodiment of the present invention includes the steps of (S 1 ) establishing a communication path between the outdoor unit  40  and each of the indoor units  10 ,  20 , and  30 , (S 2 ) determining whether or not there is a powered-off one of the indoor units  10 ,  20 , and  30 , (S 5 ), if a powered-off indoor unit is present, recovering a refrigerant from the powered-off indoor unit, and (S 6 ) cutting off the refrigerant supplied to the powered-off indoor unit after completion of the refrigerant recovery.  
         [0061]     At the determination step S 2 , the indoor unit or indoor units, which do not provide a response to the outdoor unit  40  for a predetermined response time (for example, 5 minutes), are determined to be in a powered-off state.  
         [0062]     After execution of the determination step S 2 , the first intermittent valve  55   a  of the powered-off indoor unit or each of the powered-off indoor units is closed (S 4 ). Subsequently, a refrigerant recovery operation is executed for a predetermined time (for example, 3 minutes). On the other hand, the powered-on indoor unit or indoor units are continuously normally operated (S 7 ).  
         [0063]     After the refrigerant is completely recovered from the powered-off indoor unit or indoor units (S 5 ), the first intermittent valve  55   a  and second intermittent valve  55   b  associated with the powered-off indoor unit or each of the powered-off indoor units are closed (S 6 ), so as to cut off refrigerant flows respectively introduced into and discharged from the associated indoor unit.  
         [0064]     Since the introduction and discharge of the refrigerant into and from the powered-off indoor unit or indoor units are prevented, the remaining indoor unit or indoor units, which are in operation, can operate normally without any influence by the powered-off indoor unit or indoor units.  
         [0065]     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.