Patent Publication Number: US-2007095083-A1

Title: Method and apparatus for removing partial overload in an air conditioner

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims priority under 35 U.S.C. §119 to Korean Patent Application No. 10-2005-0102165 filed on Oct. 28, 2005, the entirety of which is hereby incorporated by reference.  
     BACKGROUND OF THE INVENTION  
      This description relates to a method for removing partial overload in an air conditioner.  
      In general, an air conditioner withdraws hot air from a room and performs heat exchange at an evaporator in a refrigeration cycle thereof. Then, the air conditioner discharges cold air generated by the heat exchange into the room. The air conditioner repeats these processes to cool the room.  
      Typically, the refrigeration cycle includes a closed circuit having a compressor, a condenser, an expansion device and an evaporator.  
      The compressor compresses a gaseous refrigerant of low temperature and pressure and converts it into a gaseous refrigerant of high temperature and pressure. The gaseous refrigerant of high temperature and pressure converted by the compressor is condensed in the condenser and then converted into a liquid refrigerant of high temperature and pressure.  
      The liquid refrigerant of high temperature and pressure condensed in the condenser is expanded in the expansion device and then converted into a liquid refrigerant of low temperature and pressure. The liquid refrigerant of low temperature and pressure expanded in the expansion device is subjected to heat exchange with indoor air in the evaporator and then evaporated and converted into the gaseous refrigerant of low temperature and pressure.  
      The gaseous refrigerant of low temperature and pressure generated by the heat exchange in the evaporator is converted again into the gaseous refrigerant of high temperature and pressure in the compressor.  
      That is, the refrigeration cycle including a closed circuit consisting of the compressor, the condenser, the expansion device and the evaporator repeatedly performs the compression, condensation, expansion and evaporation of a refrigerant. The refrigeration cycle carries out the heat exchange of indoor air with the refrigerant in the evaporator to generate cold air and then discharges the generated cold air into the room so that the room can be cooled.  
      In the air conditioner in which such a refrigeration cycle is operated, components such as the compressor and the condenser, producing much noise and heat, are generally provided in an outdoor unit.  
      On the contrary, the expansion device and the evaporator that hardly produce noise and generate cold air are provided in an indoor unit. The indoor and outdoor units are connected to each other through a pipe.  
      Recently, in order to increase the cooling capacity of an air conditioner, a multi-type air conditioner has been popularized, in which an outdoor unit includes two or more compressors and a plurality of indoor units are connected to one outdoor unit so as to cool a plurality of rooms.  
      In a multi-type air conditioner having a plurality of indoor units, chances are a cooling load increases only in a room where a specific indoor unit is installed to come to an overload state, whereas cooling loads in other rooms where the other indoor units are installed do not increase only to maintain a constant level.  
      In such a case, if the air conditioner is operated at a room temperature detected in each of the indoor units, the cooling capacity of an indoor unit installed in a room with an increased cooling load is reduced while the cooling capacity of an indoor unit installed in a room with a constant cooling load is increased to cause the room to be excessively cooled so that a user may feel a chill.  
      In an air conditioner having a plurality of indoor units, therefore, it is necessary to correctly detect an indoor unit operated in an overload state due to an increased cooling load, and to increase the cooling capacity of only the indoor unit operated in the overload state so that a corresponding room can be quickly cooled  
     SUMMARY OF THE INVENTION  
      It is an object of the present invention to provide a method for removing a partial overload in an air conditioner, wherein a first indoor unit operating in an overload state due to an increased cooling load is correctly detected from a plurality of indoor units, and the cooling capacity of the detected indoor unit is increased so that the first indoor unit can be operated in a normal load state within a short period of time.  
      In the present invention for achieving the above object, a change in the temperature of indoor air in a room with each of a plurality of indoor units installed therein is used to detect a first indoor unit, which is operating in an overload state due to an increased cooling load, among the plurality of indoor units provided in a multi-type air conditioner.  
      To this end, in the present invention, a temperature sensor is provided in each of the plurality of indoor units to detect a change in the temperature of indoor air. Based on the detected change in the temperature of indoor air, the first indoor unit operating in the overload state is detected.  
      There may be a case where although the first indoor unit has an increased cooling load and thus is in the overload state, the overload state does not continue but is maintained temporarily.  
      Accordingly, the present invention comprises determining whether the overload state of the first indoor unit continues beyond a predetermined period of time. If the overload state of the first indoor unit continues beyond the predetermined period of time, it is finally determined that the indoor unit is in the overload state.  
      If it is finally determined that only the first indoor unit is in the overload state and a plurality of second indoor units are not in the overload state, the amount of the refrigerant introduced into the first indoor unit, which is in the overload state, is increased to increase the cooling capacity of the first indoor unit.  
      Here, the present invention employs an expansion device such as a linear expansion valve for controlling a flow rate of the refrigerant so as to control the amount of the refrigerant introduced into a specific indoor unit.  
      When the amount of the refrigerant introduced into the first indoor unit, which is in the overload state, is increased, the amount of a refrigerant introduced into each of the second indoor units having constant cooling loads is decreased. Thus, there may be a case where the cooling capacities of the second indoor units are lowered.  
      Therefore, in a case where a plurality of compressors are provided, the present invention determines the current operation states of the compressors. If it is determined that the compressors are not operating with maximum compression capacities, control is made to increase the amount of the refrigerant introduced into the first indoor unit and the compression capacities of the compressors.  
      Thus, according to the present invention, without lowering the cooling capacities of the second indoor units having constant cooling loads, only the amount of the refrigerant introduced into the first indoor unit, which is in the overload state, is increased to increase the cooling capacity of the first indoor unit, thereby rapidly cooling the room with the first indoor unit installed therein. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The present invention is further described in the detail description which follows, in reference to the noted plurality of drawings, by way of non-limiting examples of preferred embodiments of the present invention, in which like characters represent like elements throughout the several views of the drawings, and wherein:  
       FIG. 1  is a schematic view showing the configuration of a multi-type air conditioner to which a method for removing a partial overload according to the present invention is applied;  
       FIG. 2  is a control block diagram of the air conditioner to which the method for removing a partial overload according to the present invention is applied; and  
       FIG. 3  is a flowchart illustrating the method for removing a partial overload according to the present invention 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the present invention may be embodied in practice.  
       FIG. 1  is a schematic view showing the configuration of a multi-type air conditioner to which a method for removing a partial overload according to the present invention is applied. Here, reference numeral “ 100 ” designates an accumulator for supplying a gaseous refrigerant of low temperature and pressure, and reference numerals “ 110 ” and “ 120 ” designate first and second compressors, respectively, for converting the gaseous refrigerant of low temperature and pressure, which may be supplied by the accumulator ( 100 ), into a gaseous refrigerant of high temperature and pressure.  
      For example, the compression capacity of the first compressor ( 110 ) may be about 60% of the total compression capacity of a system and the compression capacity of the second compressor ( 120 ) may be about 40% of the total compression capacity.  
      Reference numerals “ 112 ” and “ 122 ” designate back-flow preventers or preventing means for preventing the gaseous refrigerant of high temperature and pressure, which may be obtained through by the first and second compressors ( 110 ,  120 ) compressing the gaseous refrigerant of low temperature and pressure, from flowing backward.  
      For example, check valves can be used as the back-flow preventer or preventing means ( 112 ,  122 ) to prevent the refrigerant from flowing backward. However, it should be appreciated that any suitable preventers may be employed in order to prevent the refrigerant from flowing backwards.  
      Reference numeral “ 130 ” designates a condenser. The condenser ( 130 ) condenses the gaseous refrigerant of high temperature and pressure, which may be obtained through the compression by the first and second compressors ( 110 ,  120 ), into a liquid refrigerant of high temperature and pressure.  
      Reference numerals “ 140   a ”, “ 140   b ”, . . . designate a plurality of expansion devices. Each of the plurality of expansion devices ( 140   a ,  140   b , . . . ) expands the liquid refrigerant of high temperature and pressure, which has been condensed in the condenser ( 130 ), so that it can be converted into a liquid refrigerant of low temperature and pressure.  
      Reference numerals “ 150   a ”, “ 150   b ”, designate a plurality of evaporators installed in an outdoor unit.  
      Each of the evaporators ( 150   a ,  150   b , . . . ) perform heat exchange between the liquid refrigerant of lower temperature and pressure, which has been expanded in the expansion devices ( 140   a ,  140   b  . . . ), and indoor air to generate cold air and to covert the liquid refrigerant into a gaseous refrigerant of lower temperature and pressure.  
      In the air conditioner described above, in a case where the first compressor ( 110 ) or the second compressor ( 120 ) is operated, the gaseous refrigerant of lower temperature and pressure, which may be stored in the accumulator ( 100 ), is introduced into the first compressor ( 110 ) or the second compressor ( 120 ) where the refrigerant is compressed to be the gaseous refrigerant of high temperature and pressure.  
      Here, the accumulator ( 100 ) functions to prevent damage to the first and second compressors ( 110 ,  120 ) due to introduction of the liquid refrigerant of lower temperature and pressure into the compressors.  
      The gaseous refrigerant of high temperature and pressure, which has been compressed by the first and second compressors ( 110 ,  120 ), may be introduced into the condenser ( 130 ) through the back-flow preventing means ( 112 ,  122 ).  
      The condenser ( 130 ) condenses the gaseous refrigerant of high temperature and pressure so that the refrigerant can be converted into the liquid refrigerant of high temperature and pressure. This liquid refrigerant of high temperature and pressure may be expanded in each of the expansion devices ( 140   a ,  140   b  . . . ) and then converted into the liquid refrigerant of low temperature and pressure.  
      The liquid refrigerant of low temperature and pressure may be subjected to heat exchange with indoor air in each of the evaporators ( 150   a ,  150   b , . . . ) and then converted into the gaseous refrigerant of low temperature and pressure, and cold air generated by the heat exchange is discharged into a room so that the room can be cooled.  
      The gaseous refrigerant of low temperature and pressure, which has been evaporated in each of the evaporators ( 150   a ,  150   b , . . . ), may be collected in the accumulator ( 100 ), and the collected gaseous refrigerant of low temperature and pressure is compressed again by the first and second compressors ( 110 ,  120 ) and becomes the gaseous refrigerant of high temperature and pressure. This circulation of the refrigerant may be repeated.  
       FIG. 2  is a control block diagram of the air conditioner to which the method for removing a partial overload according to the present invention is applied. In  FIG. 2 , reference numeral “ 200 ” designates a user input unit through which a user&#39;s command such as an operation command or a control command for an air conditioner is input according to a user&#39;s manipulation. Reference numeral “ 210 ” designates a temperature detecting unit.  
      A temperature sensor (not shown) such as a thermostat may be provided at each of a plurality of indoor units, and the temperature detecting unit ( 210 ) detects the temperature of a room with each of the indoor units installed therein, using a detection signal of the temperature sensor. Further, temperature in an overload state to be detected by the temperature sensor may be a preset temperature. In this regard, the temperature sensor may detect the overload state when the temperature is above the preset temperature.  
      Reference numeral “ 220 ” designates a control unit. The control unit ( 220 ) controls the operation of the air conditioner according to a user&#39;s command input through the user input unit ( 200 ).  
      Further, the control unit ( 220 ) determines whether a corresponding indoor unit is in an overload state, based on the detection signal of the temperature detecting unit ( 210 ), and controls the operation of the air conditioner according to the determination on whether the indoor unit is in the overload state.  
      Moreover, based on the detection signal of the temperature detecting unit ( 210 ), the control unit ( 220 ) detects a first indoor unit (e.g., at least one of a plurality of indoor units) of which a cooling load is in an overload state, and then controls the operation of the air conditioner to efficiently remove an overload condition of the first indoor unit.  
      Reference numeral “ 230 ” designates a compressor driving unit. The compressor driving unit ( 230 ) selectively drives the first compressor ( 110 ) or the second compressor ( 120 ), or simultaneously drives both the first compressor ( 110 ) and the second compressor ( 120 ) according to the control of the control unit ( 220 ).  
      Reference numeral “ 240 ” designates an expansion device driving unit. The expansion device driving unit ( 240 ) drives the expansion devices ( 140   a ,  140   b , . . . ) according to the control of the control unit ( 220 ), thereby adjusting the expansion amount of the refrigerant.  
      In the air conditioner having the above construction, if a command for operating the air conditioner is input through the user input unit ( 200 ) (manipulated by a user), the control unit ( 220 ) controls the compressor driving unit ( 230 ) according to the command for operating the air conditioner so that the first compressor ( 110 ) or the second compressor ( 120 ) can be driven, and also controls the expansion device driving unit ( 240 ) to adjust the opening/closing amounts of the expansion devices ( 140   a ,  140   b , . . . ), thereby performing a cooling operation of the air conditioner.  
      Furthermore, based on the detection signal of the temperature detecting unit ( 210 ), the control unit ( 220 ) determines whether there is an indoor unit, i.e., the first indoor unit, which is operating in an overload state, among the plurality of indoor units.  
      For example, assume that the first indoor unit with the evaporator ( 150   a ) installed therein is operating in an overload state.  
      If it is determined that the first indoor unit with the evaporator ( 150   a ) installed therein is operating in an overload state, the control unit ( 220 ) determines whether the overload state of the first indoor unit continues beyond a predetermined period of time (That is, if at least one indoor unit is in the overload state for a time period longer than a predetermined (or preset) period of time). If it is determined that the first indoor unit is operating in the overload state beyond the predetermined period of time, the control unit determines whether a plurality of second indoor units (e.g. at least another of the plurality of indoor units) is also operating in an overload state.  
      If it is determined that there is no first indoor unit operating in the overload state, that the first indoor unit is operating in the overload state but the overload state does not continue beyond the predetermined period of time, or that the plurality of second indoor units in addition to the first indoor unit are also operating in the overload state, the control unit ( 220 ) recognizes that a plurality of indoor units are operating in the overload state. Then, the control unit ( 220 ) controls the operation of the air conditioner according to the temperature of a room with each of the indoor units installed therein, which is detected by the temperature detecting unit ( 210 ), so that the air conditioner can operate in a normal state.  
      If it is determined that the first indoor unit is operating in the overload state beyond the predetermined period of time and the plurality of second indoor units are not operating in the overload state, the control unit ( 200 ) recognizes that only the first indoor unit is operating in the overload state and then determines the current operation states of the first and second compressors ( 110 ,  120 ).  
      In a full (100%) operating state where all the first and second compressors ( 110 ,  120 ) are operating currently, the control unit ( 200 ) controls the expansion device driving unit ( 240 ) to increase the amount of the refrigerant introduced through the expansion device ( 140   a ) into the evaporator ( 150   a ) of the first indoor unit that is in the overload state.  
      If only some of the first and second compressors ( 110 ,  120 ) operate, the control unit ( 200 ) controls the compressor driving unit ( 230 ) to increase a refrigerant compression capacity. That is, if only the second compressor ( 120 ) of which a refrigerant compression capacity may be about 40% of the total refrigerant compression capacity of a system is operating currently, the control unit ( 220 ) stops the operation of the second compressor ( 120 ) and drives the first compressor ( 110 ) of which a refrigerant compression capacity may be about 60% of the total refrigerant compression capacity of the system to increase a refrigerant compression capacity. If only the first compressor ( 110 ) of which a refrigerant compression capacity is about 60% of the total refrigerant compression capacity of the system is currently operating, the control unit ( 220 ) operates all the first and second compressors ( 110 ,  120 ) to increase a refrigerant compression capacity to 100%.  
      After the refrigerant compression capacity is increased by controlling the operations of the first and second compressors ( 110 ,  120 ), the control unit ( 220 ) controls the expansion device driving unit ( 240 ) to increase the amount of the refrigerant introduced into the evaporator ( 150   a ) of the first indoor unit through the expansion device ( 140   a ).  
      In this state, the control unit ( 220 ) determines whether the overload state of the first indoor unit is removed, on the basis of the temperature of the room with the first indoor unit installed therein, which is detected by the temperature detecting unit ( 210 ). If it is determined that the overload state of the first indoor unit has not yet been removed, the control unit repeatedly performs the process of determining whether the overload state of the first indoor unit has been removed, while increasing the amount of the refrigerant introduced into the first evaporator ( 150   a ).  
      If it is determined that the overload state of the first indoor unit has been removed, the control unit ( 220 ) stops the operation of the air conditioner in a partial overload state, and then controls the operation of the air conditioner according to the temperatures of the rooms with the indoor units installed therein, which are detected by the temperature detecting units ( 210 ), so that the air conditioner can operate in a normal state.  
       FIG. 3  is a flowchart illustrating a method for removing a partial overload according to the present invention. Referring to  FIG. 3 , when a command for operating the air conditioner is input, e.g., through the user input unit ( 200 ) (which may be manipulated by a user (S 300 )), the control unit ( 220 ) starts the operation of the air conditioner (S 302 ). That is, the control unit ( 220 ) controls the compressor driving unit ( 230 ) according to the command for operating the air conditioner so as to drive the first compressor ( 110 ) or the second compressor ( 120 ), and controls the expansion device driving unit ( 240 ) to adjust the opening/closing amounts of the expansion devices ( 140   a ,  140   b , . . . ), thereby performing a cooling operation of the air conditioner.  
      Further, on the basis of an output signal of the temperature detecting unit ( 210 ), the control unit ( 220 ) recognizes the temperature of a room with each of the indoor units installed therein (s 304 ), and determines whether there is a first indoor unit operating in an overload state, on the basis of the recognized room temperature (S 306 ).  
      If it is determined that a first indoor unit is operating in an overload state, the control unit ( 220 ) determines whether the first indoor unit has been operating in the overload state beyond a predetermined period of time (S 308 ).  
      If it is determined that the overload state continues beyond the predetermined period of time, the control unit ( 200 ) determines whether the plurality of second indoor units are also overloaded (S 310 ). That is, the control unit ( 220 ) determines whether the other indoor units in addition to the first indoor unit are also overloaded.  
      If it is determined that there is no first indoor unit operating in the overload state, that the overload state of the first indoor unit does not continue beyond the predetermined period of time, or that the plurality of second indoor units in addition to the first indoor unit are also operating in the overload state, the control unit ( 220 ) recognizes that the air conditioner is operating in the overload state as a whole. Then, the control unit ( 220 ) controls the operation of the air conditioner according to the temperature of a room with each of the indoor units installed therein, which is detected by the temperature detecting unit ( 210 ), so that the air conditioner can operate in a normal state (S 324 ).  
      If it is determined that the first indoor unit is operating in the overload state beyond the predetermined period of time and the plurality of second indoor units are not operating in the overload state, the control unit ( 200 ) recognizes that the air conditioner is operating in a partial overload state (S 312 ).  
      Then, the control unit ( 220 ) determines whether the air conditioner is operating in a full operating state where all the first and second compressors ( 110 ,  120 ) are operating (S 314 ) That is, the control unit ( 220 ) determines whether all of the first compressor ( 110 ) of which a refrigerant compression capacity is 60% of the total refrigerant compression capacity of the system and the second compressor ( 120 ) of which a refrigerant compression capacity is 40% of the total refrigerant compression capacity of the system are operating in a state where the compressor driving unit ( 230 ) is controlled.  
      If it is determined that the air conditioner is operating in the full (100%) operating state where all the first and second compressors ( 110 ,  120 ) are operating currently, the control unit ( 200 ) increases the amount of the refrigerant to be introduced into the evaporator ( 150   a ) of the first indoor unit (S 316 ). That is, the control unit ( 200 ) controls the expansion device driving unit ( 240 ) to increase the amount of the refrigerant introduced through the expansion device ( 140   a ) into the evaporator ( 150   a ), thereby enhancing the cooling capacity of the first indoor unit.  
      If it is determined that only some of the first and second compressors ( 110 ,  120 ) are operating, the control unit ( 200 ) controls the compressor driving unit ( 230 ) to increase a refrigerant compression capacity (S 318 ).  
      That is, if only the second compressor ( 120 ) of which the refrigerant compression capacity is, e.g., about 40% of the total refrigerant compression capacity of the system is operating currently, the control unit ( 220 ) stops the operation of the second compressor ( 120 ) and drives the first compressor ( 110 ) of which the refrigerant compression capacity is 60% of the total refrigerant compression capacity of the system to increase a refrigerant compression capacity. On the contrary, if only the first compressor ( 110 ) of which the refrigerant compression capacity is, e.g., about 60% of the total refrigerant compression capacity of the system is operating currently, the control unit ( 220 ) operates all the first and second compressors ( 110 ,  120 ) to increase a refrigerant compression capacity to 100%.  
      After a refrigerant compression capacity is increased by controlling the operations of the first and second compressors ( 110 ,  120 ), the control unit ( 220 ) controls the expansion device driving unit ( 240 ) to increase the amount of the refrigerant introduced into the evaporator ( 150   a ) of the first indoor unit through the expansion device ( 140   a ) (S 320 ).  
      In this state, the control unit ( 220 ) determines whether the overload state of the first indoor unit has been removed, on the basis of the detection signal of the temperature detecting unit ( 210 ) (S 322 ).  
      If it is determined that the overload state of the first indoor unit has not yet been removed, the control unit ( 220 ) returns to step S 314  to repeatedly perform the processes of increasing the amount of the refrigerant introduced into the first evaporator ( 150   a ) and determining whether the overload state of the first indoor unit has been removed.  
      If it is determined in step S 322  that the overload state of the first indoor unit has been removed, the control unit ( 220 ) stops the operation of the air conditioner in a partial overload state and then controls the air conditioner according to the temperature of a room with each of the indoor units installed therein, which is detected by the temperature detecting unit ( 210 ), so that the air conditioner is operating in a normal state (S 324 ).  
      According to the present invention, the temperature of indoor air may be detected by, e.g., the temperature sensor installed in each of indoor units, and a first indoor unit operating in an overload state due to an increased cooling load may be detected based on the detected temperature of indoor air. Then, the cooling capacity of the first indoor unit that is detected may be increased by increasing the amount of a refrigerant introduced into an evaporator of the first indoor unit, thereby removing the overload state of the first indoor unit.  
      If a plurality of compressors are provided, the amount of the refrigerant introduced into the evaporator of the first indoor unit may be increased so that the refrigerant compression capacities of the compressors is, e.g., increased simultaneously. Accordingly, without lowering the cooling capacities of second indoor units of which cooling loads are constantly maintained, a room with the first indoor unit installed therein can be cooled rapidly by increasing only the amount of the refrigerant to be introduced into the first indoor unit having an increased cooling load, and thus, the overload state can be removed.  
      It is further noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to a preferred embodiment, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular means, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.