Abstract:
A multi type air conditioner comprises: an outdoor unit including an outdoor heat exchanger heat-exchanged with the outdoor air, a compressor compressing a refrigerant, and a first four-way valve and a second four-way valve switching a refrigerant flow path; indoor units performing at least one of cooling operation and heating operation; and a distributor including a low pressure pipe connected between the first four-way valve and each of the indoor units, a high pressure pipe connected between the second four-way valve and each of the indoor units, and a refrigerant pipe connected between the outer heat-exchanger and each of the indoor units. Accordingly, flow resistance of a refrigerant is reduced in heating operation, thereby improving heating performance and heating efficiency, and the amount of refrigerant accumulated within a high pressure pipe is minimized in cooling operation, thereby improving cooling performance and cooling efficiency.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a multi type air conditioner and its control method, and more particularly, to a multi type air conditioner and its control method capable of improving heating operation efficiency by minimizing the flow resistance of a refrigerant when all operating indoor units are in a heating operation mode and of improving cooling efficiency by preventing an accumulation of a liquefied refrigerant in a high pressure pipe when all operating indoor units are in a cooling operation mode. 
   2. Description of the Conventional Art 
   In general, a multi type air conditioner includes several indoor units such that some perform heating and others perform cooling. 
     FIG. 1  is a construction view of the multi type air conditioner in accordance with the conventional art. 
   The multi type air conditioner in accordance with the conventional art includes an outdoor unit  102  heat-exchanged with the outdoor air, a plurality of indoor units  104  heat-exchanged with the indoor air and performing cooling and heating operation, and a distributor  106  disposed between the outdoor unit  102  and the indoor units  104  and properly distributing a refrigerant of the outdoor unit  102  to the indoor units  104 . 
   The outdoor unit  102  includes a plurality of outdoor heat exchangers  108  heat-exchanged with the outdoor air, a four-way valve  110  switching the flow of a refrigerant in a forward or reverse direction, an outdoor expansion valve  122  disposed at a refrigerant pipe  120  connected between the outdoor heat exchanger  108  and the indoor unit  104 , for changing a refrigerant to a low-temperature low-pressure refrigerant, a plurality of compressors  130  compressing the refrigerant to a high-temperature high-pressure refrigerant, and an accumulator  132  connected to an intake side of the compressors  130 , dividing a refrigerant into a gas and a liquid and supplying a gaseous refrigerant to the compressor. 
   A blower fan  134  for blowing the outdoor air for heat exchange to the outdoor heat exchangers  108  is installed at one side of the outdoor heat exchanger  108 , and a bypass flow path  126  provided with the check valve  124  is installed at the refrigerant pipe  120  where the outdoor expansion valve  122  is installed. 
   The indoor unit  104  includes a plurality of indoor heat exchangers  112  heat-exchanged with the indoor air, and an indoor expansion valve  114  installed at one side of the indoor heat exchanger  112 . 
   The distributor  106  includes a high pressure pipe  140  connected to a discharge side of the compressors  130 , first distribution pipes  144  diverged from the high pressure pipe to each indoor unit  104 , a low pressure pipe  142  connected to an intake side of the compressors  130 , second distribution pipes  146  diverged from the low pressure pipe  142  to the plurality of indoor units  104 , first two-way valves  150  respectively installed at the first distribution pipes  144  and opening and closing the first distribution pipes  144 , and second two-way valves  152  respectively installed at the second distribution pipes  146  and opening and closing the second distribution pipes  146 . 
   Third distribution pipes  148  are diverged from the refrigerant pipe  120  connected to the outdoor heat exchanger  108  and are connected to the indoor heat exchanger  112 . 
   Here, a large-diameter pipe having the biggest diameter is used as the low pressure pipe  142 , and a middle-diameter pipe having a diameter smaller than that of the low pressure pipe  142  is used as the high pressure pipe  140 , and a small-diameter pipe having a diameter smaller than that of the high pressure pipe  140  is used as the refrigerant pipe  120 . 
   The operation of the air conditioner constructed in the aforementioned manner in accordance with the conventional art will now be described. As shown in  FIG. 1 , if all of operating indoor units  104  are operated for heating, the four-way valve  110  is controlled to connect the outdoor heat exchanger  108  with the intake side of the compressors  130 , the first two-way valves  150  are all turned ON to open the high pressure pipe  140 , and the second two-way valves are turned OFF to close the low pressure pipe  142 . 
   In such a state, when the compressors  130  are operated, a refrigerant compressed by the compressors  130  flows along the high pressure pipe  140  having a middle diameter and is distributed to each indoor unit  104  by the first distribution pipe  144 . The refrigerant supplied to each of the indoor units  104  is heat-exchanged with the indoor air to perform heating while passing through the indoor heat exchanger  112 , and the refrigerant discharged from the indoor heat exchanger  112  flows along the refrigerant pipe  120  and is decompressed and expanded while passing through the outdoor expansion valve  122 . Then, the refrigerant is introduced into the outdoor heat exchanger  108 , is heat-exchanged with the outdoor air therein, and then is introduced to the compressors  130  via the four-way valve  110 . 
   However, the air conditioner in accordance with the conventional art has the following problems. 
   If all of the operating indoor units are operated for heating, flow resistance occurs while a refrigerant passes through the high pressure pipe having a middle diameter because the refrigerant compressed in the compressors are supplied to each indoor unit through the high pressure pipe, which causes deterioration of the heating capacity and heating efficiency. 
   As shown in  FIG. 2 , if all of the operating indoor units  104  are operated for cooling, the first two-way valves  150  are turned OFF, and the second two-way valves  152  are turned ON. If the compressors  130  are driven in such a state, a refrigerant compressed by the compressors  130  are condensed while passing through the outdoor heat exchanger  108  and is supplied to each indoor unit  104  through the refrigerant pipe  120  and each third distribution pipe  148 . The refrigerant supplied to the indoor unit  104  is decompressed and expanded while passing through the indoor expansion valve  114 , and then, the refrigerant is supplied to the indoor heat exchanger  112 . Having passed through the indoor heat exchanger  112 , the refrigerant is heat-exchanged with the indoor air and performs cooling. The refrigerant having passed through the indoor heat exchanger  112  is introduced to the compressors  130  through the second distribution pipe  146  and the low pressure pipe  142  which are opened as the second two-way valves  152  are turned ON. 
   As mentioned above, because the first two-way valves  150  is turned OFF and thus, the high pressure pipe  140  is closed when all of the operating indoor unit  104  are operated for cooling, a portion of a high-temperature high-pressure refrigerant compressed in the compressors  130  fills in the high pressure pipe  140 . Accordingly, condensation of the refrigerant occurs within the high pressure pipe  140 , and thus a liquefied refrigerant is accumulated in the high pressure pipe  140 , which causes a shortage of a circulating refrigerant and deterioration of cooling performance. 
   Particularly, if the high pressure pipe  140  becomes long because of a long distance between the outdoor unit  104  and the distributor  106 , quite a large amount of liquefied refrigerant is accumulated within the high pressure pipe  140 , which worsens the shortage of a circulating refrigerant and causes damage to the compressors  130  for lack of oil. 
   BRIEF DESCRIPTION OF THE INVENTION 
   Therefore, an object of the present invention is to provide a multi type air conditioner capable of improving heating performance and heating efficiency by reducing flow resistance of a refrigerant in heating operation and of improving cooling performance and cooling efficiency by minimizing the amount of refrigerant accumulated within a high pressure pipe in cooling operation. 
   To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a multi type air conditioner comprising: an outdoor unit including an outdoor heat exchanger heat-exchanging with the outdoor air, a plurality of compressors compressing a refrigerant, and a first four-way valve and a second four-way valve switching a refrigerant flow path; indoor units performing at least one of cooling operation and heating operation; and a distributor including a low pressure pipe connected between the first four-way valve and each of the indoor units, a high pressure pipe connected between the second four-way valve and each of the indoor units, and a refrigerant pipe connected between the outer heat-exchanger and each of the indoor units. 
   The first four-way valve is connected to a discharge side and an intake side of the compressors, a low pressure pipe and an outdoor heat exchanger, and the second four-way valve is connected to the discharge side and the intake side of the compressors and the high pressure pipe, so as to selectively switch the refrigerant flow path. 
   A control unit controlling the first four-way valve and the second four-way valve according to an operation mode of the indoor units and turning ON/OFF the first two-way valve and the second two-way valve, is further included. 
   To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a control method of a multi type air conditioner comprising: determining an operation mode of each of indoor unit according to a signal applied from the indoor units; and controlling a first four-way valve and a second four-way valve when the operation mode of each of the indoor units is determined, and also turning ON/OFF first two-way valves and second two-way valves. 
   When all of the indoor units are operated for heating, the first four-way valve and the second four-way valve are controlled such that a refrigerant discharged from a compressors are supplied to the indoor units through a low pressure pipe and a high pressure pipe. 
   When all of the indoor units are operated for cooling, the first four-way valve and the second four-way valve are controlled such that a refrigerant discharged from the indoor units is introduced to the compressors through the low pressure pipe and the high pressure pipe. 
   The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 

   
     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 unit of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. 
     In the drawings: 
       FIG. 1  is a construction view of a multi type air conditioner in accordance with the conventional art; 
       FIG. 2  is a construction view that illustrates an operational state of the multi type air conditioner in accordance with the conventional art; 
       FIG. 3  is a construction view of a multi type air conditioner in accordance with the present invention; 
       FIG. 4  is a block diagram that illustrates a control unit of the multi type air conditioner in accordance with the present invention; and 
       FIGS. 5 to 7  are construction views that illustrate an operational states of the multi type air conditioner in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
   A plurality of embodiments of a multi type air conditioner in accordance with the present invention will now be described, and the most preferred embodiment will now be described. 
     FIG. 3  is a construction view of a multi type air conditioner in accordance with the present invention. 
   The multi type air conditioner in accordance with the present invention includes an outdoor unit  10  disposed outdoors and heat-exchanged with the outdoor air, a plurality of indoor units  20  disposed indoors and performing cooling and heating for a room, and a distributor  30  installed between the outdoor unit  10  and the indoor units  20  and distributing a refrigerant discharged from the outdoor unit  10  to each of the indoor units  20 . 
   The outdoor unit  10  includes a plurality of outdoor heat exchangers  12  heat- exchanged with the outdoor air, a plurality of compressors  14  compressing a refrigerant, a first four-way valve  16  and a second four-way valve  18  connected to a discharge side and an intake side of the compressors  14  and the outdoor heat exchanger  12  and switching the flow of a refrigerant, an outdoor expansion valve  22  disposed at a refrigerant pipe  32  connected between the outdoor heat exchanger  12  and the indoor units  20  and decompressing and expanding a refrigerant, and an accumulator  24  connected to intake sides of the compressors  14 , dividing a refrigerant into a gas and a liquid and supplying a gaseous refrigerant to the compressors  14 . 
   A blower fan  26  for blowing the outdoor air for heat exchange to the outdoor heat exchanger  12  is installed at one side of the outdoor heat exchangers  12 , and a bypass flow path  36  provided with a check valve  34  is installed at the refrigerant pipe  32  where the outdoor expansion valve  22  is installed. 
   The indoor units each include a heat exchanger  38  heat-exchanging with the indoor air, and an indoor expansion valve  40  installed at one side of the outdoor heat exchanger  38 . 
   The distributor  30  includes a low pressure pipe  50  connected to the first four-way valve  16  and connected to each of the indoor units by first distribution pipes  42 , a high pressure pipe  52  connected to the second four-way valve  18  and connected to each of the indoor units  20  by second distribution pipes  44 , and a refrigerant pipe  32  connected to the outdoor heat exchanger  12  and connected to each of the indoor units  20  by third distribution pipes  46 . 
   The low pressure pipe  50  is a pipe having a large diameter, the high pressure pipe  52  is a pipe having a diameter smaller than that of the low pressure pipe  50 , and the refrigerant pipe  32  is a pipe having a diameter smaller than that of the high pressure pipe  52 . 
   Here, as an example of the diameters of the pipes, if the diameter of the low pressure pipe  50  is 9/8 inches, preferably, the high pressure pipe  52  is formed to have a diameter of about ⅞˜1 inch, and the refrigerant pip  32  is formed to have a diameter of about ½ inch. 
   A first two-way valve  54  is installed at each of the first distribution pipes  42  so as to open and close the first distribution pipes  42 , and a second two way valve  56  is installed at each of the second distribution pipes  44  so as to open and close the second distribution pipes  44 . 
   The first four-way valve  16  switches a refrigerant flow path by being respectively connected to the outdoor heat exchanger  12 , the discharge side and the intake side of the compressors  14  and the low pressure pipe  50 , and the second four-way valve  18  switches a refrigerant flow path by being respectively connected to the discharge side and the intake side of the compressors  14  and the high pressure pipe  52 . 
   As shown in  FIG. 4 , the air conditioner further includes a control unit  60  respectively controlling the first four-way valve  16 , the second four-way valve  18 , the first two-way valve  54  and the second two-way valve  56  according to an operation mode. 
   Namely, the control unit  60  switches a refrigerant flow path upon applying an electric signal to the first four-way valve  16  and the second four-way valve  18  according to an operation mode of the indoor unit  20 , and turns ON/OFF the first valve  54  and the second valve  56  to thereby open and close the first distribution pipes  42  and the second distribution pipes  44 . 
   The operation of the air conditioner constructed in the aforementioned manner in accordance with the present invention will now be described. 
   First, if the number of indoor units  20  performing heating operation is greater than the number of indoor units performing cooling operation, as shown in  FIG. 3 , the control unit  60  turns ON the first two-way valve  54  installed at the first distribution pipe  42  connected to the indoor unit  20  performing the heating operation and turns OFF the second two-way valve  56  according to a signal applied from the indoor units  20 , thereby opening the low pressure pipe  50  and closing the high pressure pipe  44 . Also, the control unit  60  turns OFF the first two-way valve  54  installed at the first distribution pipe  44  connected to the indoor unit  20  performing the cooling operation and turns ON the second two-way valve  56 . 
   The control unit  60  controls the first four-way valve  16  to connect the discharge side of the compressors  14  with the low pressure pipe  50  and to connect the intake side of the compressors  14  with the outdoor heat exchanger  12 . Also, the control unit  60  controls the second two-way valve  18  to connect the high pressure pipe  52  with the intake side of the compressors  14 . 
   If the compressors  14  is driven in such a state, a refrigerant compressed in the compressors  14  is supplied to the indoor unit  20 , which performs heating operation, through the low pressure pipe  50 , and is heat-exchanged with the indoor air to perform the heating operation while passing through the indoor heat exchanger  38 . A portion of a refrigerant discharged from the indoor heat exchanger  38  is introduced to the indoor unit  20  performing cooling, and the remaining refrigerant flows to the outdoor unit  10  through the refrigerant pipe  32 . The refrigerant flowing to the outdoor unit  10  is decompressed and expanded while passing through the outdoor expansion valve  22 , and is heat-exchanged with the outdoor air while passing through the outdoor heat exchanger  12 . Then, the refrigerant is supplied to the compressors  14  via the first four-way valve  16 . 
   Also, the refrigerant introduced to the indoor unit  20  performing the cooling operation is decompressed and expanded while passing through the indoor expansion valve  40 , and then is supplied to the indoor heat exchanger  38  to perform the cooling operation by being heat-exchanged with the indoor air. The refrigerant discharged from the indoor heat exchanger  38  flows along the high pressure pipe  52  and is received in the compressors  14  via the second four-way valve  18 . 
   If all of the indoor units  20  are operated for heating only, as shown in  FIG. 5 , the control unit  60  turns ON all of the first two-way valves  54  installed at the first distribution pipes  42  connected to the indoor units  20  and all of the second valves  56  installed at the second distribution pipes  44 , thereby opening all of the high pressure pipes  52  and the low pressure pipes  50 . 
   Also, the control unit  60  controls the first four-way valve  16  to thereby connect the discharge side of the compressors  14  with the low pressure pipe  50  and to connect the outdoor heat exchanger  12  with the intake side of the compressors  14 . Also, the control unit  60  controls the second four-way valve  18  to thereby connect the discharge side of the compressors  14  with the high pressure pipe  52 . 
   If the compressors  14  are driven in such a state, the refrigerant compressed in the compressors  14  are supplied to each indoor unit  20  through the low pressure pipe  50  and the high pressure pipe  52 , and the refrigerant supplied to the indoor unit  20  is heat-exchanged with the indoor air to perform the heating operation while passing through the indoor heat exchanger  38 . Namely, when all of the indoor units  20  are operated in the heating operation mode, the flow resistance of a refrigerant can be prevented because the refrigerant compressed in the compressors  14  flows to the indoor units  20  through the low pressure pipe  50  having a large diameter and the high pressure pipe  52  having a middle diameter. 
   The refrigerant discharged from the indoor heat exchanger  38  flows to the outdoor unit  10  along the refrigerant pipe  32 . The refrigerant having flowed to the outdoor unit  10  is decompressed and expanded while passing through the outdoor expansion valve  22 . Then, the refrigerant is introduced to the outdoor heat exchanger  12 , is heat-exchanged with the outdoor air, and then is introduced to the compressors  14  via the first four-way valve  16  to be compressed. 
   If all of the indoor units  20  are operated for cooling only, as shown in  FIG. 6 , the control unit  60  turns ON the first valves  54  and the second valves  56  according to a signal transferred from the indoor units  20  to thereby open the low pressure pipe  50  and the high pressure pipe  52 . 
   The control unit  60  controls the first four-way valve  16  to connect the discharge side of the compressors  14  with the outdoor heat exchanger  12  and to connect the low pressure pipe  50  with the intake side of the compressors  14 . Also, the control unit  60  controls the second four-way valve  18  to connect the high pressure pipe  52  with the intake side of the compressors  14 . 
   If the compressors  14  are driven in such a state, the refrigerant compressed in the compressors  14  are heat-exchanged with the outdoor air while passing through the outdoor heat exchanger  12 , flows along the refrigerant pipe  32 , and is supplied to each indoor unit  20  by the third distribution pipe  46 . Then, the refrigerant supplied to the indoor unit  20  is decompressed and expanded while passing through the indoor expansion valves  40 , and is heat-exchanged with the indoor air to perform the cooling operation while passing through the indoor heat exchanger  38 . A portion of a refrigerant discharged from the indoor heat exchangers  38  flows along the low pressure pipe  50  and is introduced to the compressors  14  via the first four-way valve  16 , and the remaining portion of the refrigerant flows along the high pressure pipe  52  and is introduced to the compressors  14  via the second four-way valve  18 . 
   As mentioned above, because the refrigerant flows along the high pressure pipe  52  when all of the indoor units  20  are operated for cooling only, an accumulation of a refrigerant within the high pressure pipe  52  is prevented, thereby preventing a shortage of a refrigerant and thusly improving cooling performance and cooling efficiency. 
   If the number of indoor units  20  operated for cooling is greater than the number of indoor units  20  operated for heating, as shown in  FIG. 7 , the control units  60  turns OFF the first two-way valve  54  connected to the indoor units  20  being operated for cooling and turns ON the second valve  56  according to a signal transferred from the indoor unit  20 . Also, the control units  60  turns ON the first two-way valve  54  connected to the indoor unit  20  operated for heating and turns OFF the second two-way valve  56 . 
   Also, the control unit  60  controls the first four-way valve  16  to connect the discharge side of the compressors  14  with the outdoor heat exchanger  12  and connect the low pressure pipe  50  with the intake side of the compressors  14 . Also, the control unit controls the second four-way valve  18  to connect the discharge side of the compressors  14  with the high pressure pipe  52 . 
   If the compressors  14  are driven in such a state, a portion of a refrigerant compressed in the compressors  14  are introduced to the outdoor heat exchanger  12  via the first four-way valve  16 , and the remaining refrigerant flows along the high pressure pipe  52  via the second four-way valve  18  to be supplied to the indoor unit  20  operated for heating. 
   The refrigerant introduced to the outdoor heat exchanger  12  is heat-exchanged with the outdoor air, flows along the refrigerant pipe  32  and is supplied, to each indoor unit  20  operated for cooling by the third distribution pipe  46 . Then, the refrigerant supplied to the indoor unit  20  is decompressed and expanded while passing through the indoor expansion valve  40 , and is heat-exchanged with the indoor air while passing through the indoor heat exchanger  38 , thereby performing the cooling operation. The refrigerant discharged from the indoor heat exchanger  38  flows along the low pressure pipe  50  and is introduced to the compressors  14  via the first four-way valve  16 . 
   The refrigerant introduced to the indoor unit  20  operated for heating is heat exchanged with the indoor air while passing through the indoor heat exchanger  38 , thereby performing the heating operation. Then, the refrigerant is supplied along the refrigerant pipe  32  to the indoor units  20  operated for cooling. 
   In the multi type air conditioner constructed in the aforementioned manner according to the present invention, because the outdoor unit includes the first four-way valve and the second four-way valve, when all of the indoor units are in a heating operation mode, a refrigerant compressed in the compressors are supplied to the indoor units through the low pressure pipe having a large diameter and the high pressure pipe having a middle diameter. Accordingly, flow resistance of the refrigerant is prevented, and the heating performance and the heating efficiency can be improved. 
   Also, because the outdoor unit includes the first four-way valve and the second four-valve, when all of the indoor units are operated in a cooling operation mode, the refrigerant discharged from the indoor unit flows to the outdoor unit through the high pressure pipe and the low pressure pipe. Accordingly, the refrigerant is prevented from staying in the high pressure pipe, thereby improving the cooling performance and the cooling efficiency. 
   As the present invention may be embodied in several forms without departing from the spirit or essential 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 spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalence of such metes and bounds are therefore intended to be embraced by the appended claims.