Patent Publication Number: US-2012023981-A1

Title: Refrigerator and driving method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present disclosure relates to subject matter contained in priority Korean Application No. 10-2010-0073049, filed on Jul. 28, 2010, which is herein expressly incorporated by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This specification relates to a refrigerator and a method for driving the same, and particularly, to a refrigerator having a refrigeration cycle with a plurality of compressors and evaporators, and a method for driving the same. 
     2. Background of the Invention 
     In general, a refrigerator is an apparatus for keeping an inside of the refrigerator at low temperature using a refrigeration cycle having a compressor, a condenser, an expansion apparatus and an evaporator. The compressor of the refrigerator is lubricated using oil for protection from a mechanical friction, and the oil within the compressor is allowed to circulate a refrigeration cycle forming a closed loop together with high temperature and high pressure refrigerant gas discharged out of the compressor. 
     If such oil is aggregated (accumulated) in the condenser, the evaporator and pipes of the refrigeration cycle, the performance of the refrigeration cycle may be lowered. If the oil does not smoothly flow back into the compressor, the lack of oil within the compressor may be caused, resulting in a damage of the compressor. 
     The refrigeration cycle applied to the refrigerator may be classified, according to the number of compressors and evaporators, into an 1Eva-cycle having a single compressor and a single evaporator, a parallel 2Eva cycle in which a plurality of evaporators are connected in parallel to an inlet of a single compressor, a 1Comp 2Stage cycle in which a plurality of evaporators are connected to a single 2-stage compressor, a serial cycle having a plurality of evaporators connected to the single compressor in series, a bypass serial cycle in which a plurality of evaporators are selectively connected to a single compressor in series. 
     SUMMARY OF THE INVENTION 
     In the refrigerator having the related art refrigeration cycle, when one evaporator is connected to one compressor, a refrigerating chamber is overcooled and thereby power consumption is increased. When a plurality of evaporators are connected to one compressor in parallel or in series, the refrigerating chamber and the freezing chamber can be separately driven, which allows power consumption to be lowered to some degree. However, the power consumption is still increased as compared with required cooling capability and additionally the compressor should be configured as a two-stage compressor. 
     Therefore, an aspect of the detailed description is to provide a refrigerator capable of reducing power consumption with simultaneously driving a freezing chamber and a refrigerating chamber and being facilitated for fabrication. 
     To achieve these and other advantages and in accordance with the purpose of this specification, as embodied and broadly described herein, a refrigerator may include a plurality of compressors sequentially connected to perform a multi-stage compression for a refrigerant, a condenser connected to an outlet side of a secondary compressor of the plurality of compressors, the secondary compressor located at a downstream based on the flowing direction of the refrigerant, a first evaporator diverged from the condenser and connected to an inlet side of a primary compressor of the plurality of compressors, the primary compressor located at an upstream based upon the flowing direction of the refrigerant, a second evaporator diverged from the condenser together with the first evaporator and connected between an outlet side of the primary compressor and an inlet side of the secondary compressor, a refrigerant switching valve installed such that an inlet side of the first evaporator and an inlet side of the second evaporator are connected to an outlet side of the condenser in parallel and configured to control the flowing direction of the refrigerant toward the first evaporator or the second evaporator, a refrigerant amount detecting unit configured to detect an amount of refrigerant introduced into the first or second evaporator, and a refrigerant amount adjusting unit configured to adjust amounts of refrigerant flowing toward the first and second evaporators, respectively, according to the result detected by the refrigerant amount detecting unit. 
     In accordance with one exemplary embodiment, a driving method for a refrigerator may include detecting the number of vibration of each of primary and secondary compressors sequentially connected to each other, determining whether the flow of refrigerant is biased by comparing the detected number of vibration with a reference value set in a micom, and increasing a cooling capability of a compressor, to which it is determined more refrigerant flows. 
     In accordance with another exemplary embodiment, a driving method for a refrigerator may include detecting evaporation temperatures of first and second evaporators connected to a condenser in parallel, determining whether or not a flow of refrigerant is biased by comparing the detected evaporation temperatures with a reference temperature, and adjusting an open value of a refrigerant switching valve to reduce the amount of refrigerant introduced into an evaporator to which it is determined more refrigerant flows. 
     In accordance with another exemplary embodiment, a driving method for a refrigerator may include detecting an open time of a refrigerant switching valve with respect to each of first and second evaporators, the refrigerant switching valve installed to allow the first and second evaporators to be connected to a condenser in parallel, determining whether a flow of refrigerant is biased by comparing the detected open time with a reference open time, and adjusting the open time of the refrigerant switching valve to reduce the amount of refrigerant introduced into an evaporator to which more refrigerant flows. 
     In accordance with another exemplary embodiment, a driving method for a refrigerator having a freezing chamber refrigeration cycle comprising a plurality of compressors sequentially connected to each other, and a refrigerating chamber refrigeration cycle comprising a compressor located at a downstream of the plurality of compressors, the method may be configured such that one of the number of vibration, evaporation temperatures or a flow of refrigerant is measured with respect to the freezing chamber refrigeration cycle and the refrigerating chamber refrigeration cycle, to control the amount of refrigerant flowing between the freezing chamber refrigeration cycle and the refrigerating chamber refrigeration cycle. 
     Further scope of applicability of the present application will become more apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from the detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments and together with the description serve to explain the principles of the invention. 
       In the drawings: 
         FIG. 1  is a perspective view schematically showing a refrigerator in accordance with the present disclosure; 
         FIG. 2  is a block diagram showing one exemplary embodiment of a refrigeration cycle according to  FIG. 1 ; 
         FIGS. 3 and 4  are a block diagram and a flowchart each showing a driving method for a refrigerator using a vibration sensor in the refrigerator of  FIG. 1 ; 
         FIGS. 5 and 6  are a block diagram and a flowchart each showing a driving method for a refrigerator using a temperature sensor in the refrigerator of  FIG. 1 ; and 
         FIGS. 7 and 8  are a block diagram and a flowchart each showing a driving method for a refrigerator using a timer in the refrigerator of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Description will now be given in detail of a refrigerator according to the exemplary embodiments, with reference to the accompanying drawings. For the sake of brief description with reference to the drawings, the same or equivalent components will be provided with the same reference numbers, and description thereof will not be repeated. 
       FIG. 1  is a perspective view schematically showing a refrigerator in accordance with the present disclosure, and  FIG. 2  is a block diagram showing one exemplary embodiment of a refrigeration cycle according to  FIG. 1 . 
     As shown in  FIGS. 1 and 2 , a refrigerator may include a refrigerator main body  1  having a freezing chamber and a refrigerating chamber, and a freezing chamber door  2  and a refrigerating chamber door  3  for opening or closing the freezing chamber and the refrigerating chamber of the refrigerator main body  1 , respectively. 
     A lower side of the refrigerator main body  1  may be shown having a machine chamber, in which a refrigeration cycle for generating cold air is disposed. The refrigeration cycle may be implemented in various configurations according to a type of refrigerator. The refrigeration cycle according to this exemplary embodiment may include a plurality of compressors and a plurality of evaporators and be divided into a freezing chamber refrigeration cycle and a refrigerating chamber refrigeration cycle. The freezing chamber refrigeration cycle may be a closed loop cycle formed by connecting a primary compressor  11 , a secondary compressor  12 , a condenser  13  and a first evaporator  14 , while the refrigerating chamber side refrigeration cycle may be a closed loop cycle formed by connecting the secondary compressor  12 , the condenser  13  and a second evaporator  15 . 
     The plurality of compressors  11  and  12  and the condenser  13  may be installed in the machine chamber. The plurality of compressors  11  and  12  may be connected to each other in series. Namely, an outlet of the primary compressor  11  may be connected to an inlet of the secondary compressor  12  such that a refrigerant, which underwent a primary (one-stage) compression in the primary compressor  11 , then experiences a secondary (two-stage) compression in the secondary compressor  12 . An outlet of the secondary compressor  12  may be connected to an inlet of the condenser  13 . The primary and secondary compressors  11  and  12  may be designed to have the same capacity. For a typical refrigerator, a refrigerating chamber driving mode is run more frequently, so it may also be possible that the secondary compressor  12 , operatively in association with the refrigerating chamber driving mode, is designed to have a capacity twice larger than that of the primary compressor  11 . 
     The plurality of evaporators  14  and  15  configuring a part of the refrigeration cycle may be connected to each other in parallel by a first branch pipe L 1  and a second branch pipe L 2  diverged near the outlet of the condenser  13 . A refrigerant switching valve  16  for control of a flowing direction of a refrigerant may be installed at the diverged point between the first and second branch pipes L 1  and L 2 . A first expansion apparatus  17  and a second expansion apparatus  18  each for expanding a refrigerant may be installed in the middle of the branch pipes L 1  and L 2 , respectively, namely, near inlets of both evaporators  14  and  15 . 
     The refrigerant switching valve  16  may be implemented as a 3-way valve. For example, the refrigerant switching valve  16  may have a structure that the outlet of the condenser selectively communicates with one of the evaporators or simultaneously communicates with both the evaporators. 
     The refrigerator having the configuration may have the following operational effects. 
     That is, the refrigerant switching valve  16  may control the refrigerant to flow toward the first evaporator or the second evaporator according to a driving mode of the refrigerator, thereby implementing a simultaneous driving mode for simultaneously driving the refrigerating chamber and the freezing chamber, a freezing chamber driving mode for driving only the freezing chamber, or a refrigerating chamber driving mode for driving only the refrigerating chamber. 
     For example, in the simultaneous driving mode of the refrigerator, the refrigerant switching valve  16  is all open such that a refrigerant can circulate the freezing chamber refrigeration cycle and the refrigerating chamber refrigeration cycle. That is, a refrigerant flowed through the condenser  13  may flow by being distributed into the first evaporator  14  and the second evaporator  15 . Simultaneously, the primary compressor  11  and the secondary compressor  12  start to be driven. 
     Accordingly, a refrigerant, which is sucked into the primary compressor  11  via the first evaporator  14 , experiences a primary compression in the primary compressor  11 . The primarily compressed refrigerant, which is discharged out of the primary compressor  11 , is introduced into the secondary compressor  12 . Here, a refrigerant, which flows through the second evaporator  15 , is mixed with the primarily compressed refrigerant discharged out of the primary compressor  11 , thereby being introduced into the secondary compressor  12 . 
     The primarily compressed refrigerant and the refrigerant flowed through the second evaporator  15  are compressed in the secondary compressor  12  and discharged. The refrigerant discharged out of the secondary compressor  12  flows into the condenser  13  to be condensed. The condensed refrigerant in the condenser  13  is re-distributed toward the first evaporator  14  and the second evaporator  15  by means of the refrigerant switching valve  16  for circulation. Such series of processes are repeated. 
     On the other hand, when the refrigerator is in the freezing chamber driving mode, the refrigerant switching valve  16  blocks the direction toward the second evaporator  15  as the refrigerating chamber refrigeration cycle, and opens only the direction toward the first evaporator  14  as the freezing chamber refrigeration cycle, such that a refrigerant flowed through the condenser  13  can move only toward the first evaporator  14 . However, the primary compressor  11  and the secondary compressor  12  are driven simultaneously. Accordingly, the refrigerant flowed through the first evaporator  14  can circulate with being secondarily compressed sequentially via the primary and secondary compressors  11  and  12 . 
     When the refrigerator is in the refrigerating chamber driving mode, on the other hand, the refrigerant switching valve  16  blocks the direction toward the first evaporator  14  as the freezing chamber refrigeration cycle and opens the direction toward the second evaporator  15  as the refrigerating chamber refrigeration cycle. Also, only the secondary compressor  12  starts to be driven with the primary compressor  11  stopped. 
     Accordingly, a refrigerant flowed through the condenser  13  flows only toward the second evaporator  15  to be introduced into the secondary compressor  12 . The refrigerant, which is discharged after being compressed in the secondary compressor  12 , flows into the condenser  13  to be condensed. Such series of processes are repeated. 
     Consequently, the refrigerator can be driven with the refrigeration cycles, which are independently run in correspondence with the load of the freezing chamber or the refrigerating chamber, which allows reduction of unnecessary power consumption of the refrigerator, thereby remarkably improving efficiency of the refrigerator. 
     However, with the configuration of the refrigerator, as the plurality of refrigeration cycles are connected to one pipe, a refrigerant may be biased to any one side according to loads of the freezing chamber and the refrigerating chamber when the refrigerator is driven in the simultaneous driving mode or the freezing chamber driving mode. However, when preventing this, the temperature of the refrigerator may not reach a target temperature, accordingly, an operating factor is increased to make the refrigerator consecutively driven, which may further increase power consumption. 
       FIGS. 3 to 8  are block diagrams each showing a micom, which is capable of preventing a refrigerant from being biased toward one evaporator in the refrigerator, and flowcharts showing a driving method for the refrigerator using the micom. 
     Referring to  FIGS. 3 and 4 , vibration sensors  21  may be installed at the primary compressor  11  and the secondary compressor  12 , respectively. A micom  30  may be electrically connected to the vibration sensors  21  so as to vary a cooling capability of one of the compressors according to the number of vibration of each of the primary and secondary compressors  11  and  12 , detected by the vibration sensors  21 . 
     The vibration sensor  21  may be installed on an inner surface or an outer surface of a hermetic case (reference numeral not given) of each compressor  11 ,  12 . 
     The micom  30  may include an input part  31  for receiving the number of vibration of each of the primary compressor  11  and the secondary compressor  12 , a determination part  32  connected to the input part  31  for comparing the number of vibration of each compressor  11 ,  12  with a reference value to determine to which evaporator the flow of the refrigerant is biased (inclined, more refrigerant flows), and an instruction part  33  connected to the determination part  32  to instruct an increase in a cooling capability of a compressor connected to the corresponding evaporator to which the flow of the refrigerant is biased. 
     Hereinafter, a driving method for the refrigerator will be described with reference to  FIG. 3 . 
     First, the vibration sensor  21  provided at the primary compressor  11  may detect the number of vibration of the primary compressor  11  so as to input to the input part  31  of the micom  30 . 
     The determination part  32  may then compare the detected number of vibration with a reference number of vibration (i.e. reference value) to determine whether the flow of the refrigerant is biased toward the first evaporator  14  (namely, whether or not a uniform distribution of the refrigerant is needed). 
     If it is determined the refrigerant is biased toward the first evaporator  14 , the cooling capability of the primary compressor  11  may be increased so as to mostly circulate the refrigerant biased toward the first evaporator  14 . Accordingly, the amount of refrigerant discharged out of the first evaporator  14  may be increased while the amount of refrigerant discharged out of the second evaporator  15  may be relatively decreased. Hence, the refrigerants at both the evaporators  14 ,  15  may be added and reduced with each other to be balanced. 
     However, if it is determined that the flow of the refrigerant is not biased toward the first evaporator  14 , the vibration sensor  21  provided at the secondary compressor  12  may be used to determine whether or not the flow of the refrigerant is biased toward the second evaporator  15 . If it is determined the flow of refrigerant is biased toward the second evaporator  15 , the cooling capability of the second evaporator  15  may be increased to mostly circulate the refrigerant biased toward the second evaporator  15 . Accordingly, the amount of refrigerant discharged out of the second evaporator  15  may be increased while the amount of refrigerant discharged out of the first evaporator  14  may be relatively decreased. Hence, the refrigerants at both the evaporators  14 ,  15  may be added and reduced with each other so as to be balanced. 
     In the meantime, the driving method for the refrigerator shown in  FIGS. 5 and 6  may be configured to balance the amount of refrigerant by adjusting an open value of a refrigerant switching valve. That is, temperature sensors  22  may be installed at the first and second evaporators  14  and  15 , respectively, to detect an evaporation temperature of the first evaporator  14  (i.e., a temperature difference between the inlet and the outlet of the first evaporator) and an evaporation temperature of the second evaporator (i.e., a temperature difference between the inlet and the outlet of the second evaporator). The refrigerant switching valve  16  and the temperature sensors  22  may be electrically connected to the micom  30 , respectively, to control an open value of the refrigerant switching valve  16  according to each evaporation temperature detected by the temperature sensors  22 . 
     The temperature sensors  22  may be installed at both inlet and outlet of the first evaporator  14  to detect a temperature difference therebetween, and also at both inlet and outlet of the second evaporator  15  to detect a temperature difference therebetween. 
     The micom  30  may include an input part  31  electrically connected to the temperature sensors  22  to receive the respective evaporation temperatures of the first and second evaporators  14  and  15 , a determination part  32  connected to the input part  31  to compare the received evaporation temperature of each evaporator  14 ,  15  with a reference temperature to determine to which evaporator the flow of the refrigerant is biased, and an instruction part  33  connected to the determination part  32  to instruct an opening or closing of the refrigerant switching valve  16 . 
     In accordance with the driving method for the refrigerator, first, the temperature sensors  22  located at the inlet and outlet of the first evaporator  14  detect the evaporation temperatures (i.e., temperature difference) of the first evaporator  14  and input the detected evaporation temperatures to the input part  31  of the micom  30 . 
     The determination part  32  compares the evaporation temperatures of the first evaporator  14  with a reference temperature to determine whether the flow of the refrigerant is biased toward the first evaporator  14  (i.e., whether a uniform distribution of refrigerant (refrigerant balancing) is needed). 
     If it is determined the flow of the refrigerant is biased toward the first evaporator  14 , the refrigerant switching valve  16  is kept open in the direction toward the refrigerating chamber, namely, toward the second evaporator  15 , and varies an open level in the direction toward the freezing chamber, namely, toward the first evaporator  14  so as to control the amount of refrigerant flowing toward the first evaporator  14 , thereby balancing the flow of refrigerant (the amount of refrigerant). 
     On the other hand, if it is determined the flow of the refrigerant is not biased toward the first evaporator  14 , whether the flow of the refrigerant is biased toward the second evaporator  15  is determined by the temperature sensors  22  located at the inlet and outlet of the second evaporator  15 . If it is determined that the flow of the refrigerant is biased toward the second evaporator  15 , the refrigerant switching valve  16  is kept open toward the first evaporator  14 , and varies the open level toward the second evaporator  15  so as to control the amount of refrigerant flowing toward the second evaporator  15 , thereby balancing the flow of refrigerant (the amount of refrigerant). 
     In the meantime, to which of the first and second evaporators the refrigerant is biased may also be determined by detecting an open time of the refrigerant switching valve, which will be described as follows with reference to  FIGS. 7 and 8 . 
     That is, the micom  30  may further include a timer  23  electrically connected to the refrigerant switching valve  16  to detect an open time of the refrigerant switching valve  16 . For example, the micom  30  may include an input part  31  electrically connected to the timer  23  to receive the detected open time of the refrigerant switching valve  16 , a determination part  32  connected to the input part  31  to compare the received open time of the refrigerant switching valve  16  with a reference open time (reference value) so as to determine or predict to which evaporator the flow of refrigerant is biased (more refrigerant flows), and an instruction part  33  connected to the determination part  32  to instruct the controlling of the open time of the refrigerant switching valve  16 . 
     According to the driving method for the refrigerator, the balancing of the amount or flow of refrigerant can be achieved by detecting the open time of the refrigerant switching valve  16 , comparing the detected open time with the reference value to determine or predict the biasing of the flow of the refrigerant, and controlling the open time of the refrigerant switching valve  16  such that less refrigerant is introduced into the passage toward the side determined as the flow of refrigerant is biased. 
     Here, the determination of the open time of the refrigerant switching valve  16  may be performed in the order of determining whether the open time in the direction toward the first evaporator  14  exceeds a preset open time, and determining whether the open time in the direction toward the second evaporator  15  exceeds the preset open time when determined the open time in the direction toward the first evaporator  14  did not exceed the preset open time. 
     The uniform distribution (balancing) of refrigerant is similar to the second exemplary embodiment, so detailed description thereof will be omitted. In this case, the use of the timer  23  allows the open time to be periodically adjusted after a predetermined time, accordingly, the control process can be more simplified. 
     In accordance with the refrigerator and the driving method thereof, the refrigerant can be uniformly distributed toward first and second evaporators by several methods, such as changing a cooling capability of a compressor according to a detected number of vibration of the compressor, detecting evaporation temperatures of each evaporator to control a refrigerant switching valve for controlling the flowing direction of refrigerant, or detecting an open time of the refrigerant switching valve to control the open time of the refrigerant switching valve. Consequently, the refrigerator can be driven with refrigeration cycles, which are independently run in correspondence with the load of the freezing chamber or the refrigerating chamber, resulting in reduction of unnecessary power consumption of the refrigerator. 
     Meanwhile, although not shown, an open value or open time of the refrigerant switching valve can be adjusted by detecting the number of vibration of the compressor, and also the capability of the compressor can be controlled by detecting the evaporation temperatures of the evaporators or the open time of the refrigerant switching valve. The thusly-expected operational effects are like/similar to the foregoing exemplary embodiments, so detailed description thereof will be omitted. 
     The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present disclosure. The present teachings can be readily applied to other types of apparatuses. This description is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. The features, structures, methods, and other characteristics of the exemplary embodiments described herein may be combined in various ways to obtain additional and/or alternative exemplary embodiments. 
     As the present features may be embodied in several forms without departing from the characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalents of such metes and bounds are therefore intended to be embraced by the appended claims.