Abstract:
Disclosed herewith is an air conditioner with a pressure regulation device. The air conditioner controls the number of operated compressors according to load. The air conditioner includes a plurality of bypass conduits for guiding gaseous refrigerant from the outlet sides of compressors to the inlet sides of the compressors. A plurality of bypass valves are arranged on the bypass conduits for selectively opening and shutting the bypass conduits. A control unit controls the opening and closing of the bypass valves so as to control pressure in the inlet sides of one or more started compressors during the starting of the compressors. In addition, a method for controlling the air conditioner is disclosed.

Description:
CLAIM OF PRIORITY 
     This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from my application entitled AIR CONDITIONER HAVING PRESSURE CONTROLLING UNIT AND ITS CONTROL METHOD filed with the Korean Industrial Property Office on Dec. 18, 2000 and there duly assigned Ser. No. 2000-77926. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to air conditioner, and more particularly to an air conditioner with a pressure regulation device and method for controlling the same. 
     2. Description of the Prior Art 
     An air conditioner generates cool air using a refrigeration cycle, and supplies it into a room. 
     The refrigeration cycle employed in the air conditioner is comprised of a compressor, a condenser, a capillary tube and an evaporator. Gaseous refrigerant sucked into the compressor is compressed into high-temperature, high-pressure gaseous refrigerant by the operation of a motor within the compressor. The compressed gaseous refrigerant discharged from the compressor is condensed (liquefied) to high-pressure liquid refrigerant by heat exchange with outdoor air supplied by a condenser fan. The condensed refrigerant in the condenser is expanded while passing through the capillary tube. The expended refrigerant is evaporated by heat exchange with indoor air, by which process the refrigerant absorbs heat from the surroundings. 
     FIG. 1 is a schematic diagram showing the construction of the outdoor unit of a conventional air conditioner. 
     Referring to drawing, the conventional outdoor unit includes a first compressor  1   a  and a second compressor  1   b  that are operated at constant-speeds and connected in parallel. In order to separate oil from refrigerant discharged from the compressors  1   a  and  1   b,  a first oil separator  2   a  is connected to the outlet side of the first compressor  1   a  and a second oil separator  2   b  is connected to the outlet side of the second compressor  1   b.  The outlet sides of the first and second oil separators  2   a  and  2   b  are merged together and then connected to first and second condensers  6   a  and  6   b  through a four-way valve  5 . The first and second condensers  6   a  and  6   b  are connected to an indoor unit (not shown) through a liquid receiver  8 . A first condenser fan  7   a  is situated in the vicinity of the first condenser  6   a  and a second condenser fan  7   b  is situated in the vicinity of the second condenser  6   b.  The refrigerant-return side of the indoor unit is connected to the inlet sides of the first and second compressors  1   a  and  1   b  through an accumulator  9 . 
     A pressure-equalizing pipe  3  for equalizing the pressures of the refrigerant of the first and second compressors  1   a  and  1   b  and an oil-equalizing pipe  4  for equalizing the quantities of the oil of the first and second compressors  1   a  and  1   b  are each provided to connect the first and second compressors  1   a  and  1   b.    
     A conventional method for controlling the conventional outdoor unit of the conventional air conditioner is described hereunder. 
     FIG. 2 is a flow chart showing the operation of the conventional outdoor unit of the conventional air conditioner. 
     In the operation of the conventional outdoor unit, when an increase of the total capacity of the outdoor unit is required according to a capacity-increase command while one compressor is being operated and the other compressor is being stopped(S 10 ), the compressor being currently operated is stopped and made to wait for a predetermined time period (S 20 ) to reduce a pressure difference between the compressor being operated and the other compressor being stopped. When it is determined that the predetermined time period has elapsed (S 30 ), the two compressors are started at the same time (S 40 ). 
     In the conventional outdoor unit operated as described above, when one compressor is intended to be started while the other compressor is being operated, there is a great concern that the compressor will not start due to the large pressure difference between its inlet and outlet sides. 
     Accordingly, in this case, it is necessary to reduce the pressure difference between the inlet and outlet sides of the compressor intended to start. 
     As described above, when the total capacity of the air conditioner should be increased while one of two compressors is being operated, the compressor being operated should be stopped before the other compressor is operated. Accordingly, the cooling or heating operation of the air conditioner is stopped for the predetermined time period, so that there occurs a problem that the comfort of a user is decreased by the stoppage of air conditioning. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide an air conditioner with a pressure regulation device and method for controlling the same, which is capable of starting one or more additional compressors without hindrance when it is necessary to start the additional compressors according to an increase capacity thereof. 
     In order to accomplish the above object, the present invention provides an air conditioner with pressure regulation device, the air conditioner controlling the number of operated compressors according to load, comprising: a bypass conduit for guiding gaseous refrigerant from the outlet side of compressor to the inlet side of the compressor; a bypass valve arranged on the bypass conduit for selectively opening and shutting the bypass conduit; and a control unit for controlling the opening and closing of the bypass valve so as to assist of the compressor in stop. 
     In addition, the present invention provides a method for controlling an air conditioner, the air conditioner being comprised of a bypass conduit for guiding gaseous refrigerant from the outlet side of compressor to the inlet side of the compressor; a bypass valve arranged on the bypass conduit for selectively opening and shutting the bypass conduit; and a control unit for controlling the opening and closing of the bypass valve so as to assist of the compressor in stop, a plurality of compressors operated according to load, a plurality of bypass conduits for guiding gaseous refrigerant from the outlet sides of the compressors to the inlet sides of the compressors, and a pressure regulation unit consisting of a first valve disposed between the inlet side of the compressor and a refrigerant conduit connected to the return side of the indoor unit of the air conditioner, a capillary tube connected in parallel with the first valve and a second valve connected in serial with the capillary tube to be selectively opened and closed, comprising the steps of: opening the bypass valves for one or more compressors to be started, and closing all the valves of the pressure regulation units for one or more compressors to be started; starting the compressors and reducing the pressure difference between the interior and exterior of each of the compressors stage by stage by controlling the opening of the pressure regulation units; and shutting the bypass conduits and normally driving the compressors. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein: 
     FIG. 1 is a schematic diagram showing the construction of the outdoor unit of a conventional air conditioner; 
     FIG. 2 is a flow chart showing the operation of the conventional outdoor unit of the conventional air conditioner; 
     FIG. 3 is a schematic diagram showing the construction of the outdoor unit of an air conditioner with a pressure regulation device in accordance with the present invention; 
     FIG. 4 is a block diagram showing the control of the air conditioner of the present invention; and 
     FIG. 5 is a flowchart showing the operation of the air conditioner of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 3 is a schematic diagram showing the construction of the outdoor unit of an air conditioner with a pressure regulation device in accordance with the present invention. 
     With reference to this drawing, the outdoor unit of the present invention includes a plurality of constant-speed compressors. In this embodiment, the constant-speed compressors are comprised of a first compressor  11  and a second compressor  12  that are connected in parallel. An pressure-equalizing pipe  13  for equalizing the pressures of the refrigerant of the first and second compressors  11  and  12  and an oil-equalizing pipe  14  for equalizing the quantities of the oil of the first and second compressors  11  and  12  are each provided to connect the first and second compressors  11  and  12  to each other. 
     In order to separate oil from refrigerant discharged from the compressors  11  and  12 , a first oil separator  21  is connected to the outlet side of the first compressor  11  and a second oil separator  22  is connected to the outlet side of the second compressor  12 . 
     A first bypass conduit  31  is arranged to guide refrigerant from the outlet side of the first oil separator  21  to the inlet side of the first compressor  11 , and a first bypass valve  32  is disposed on the first bypass conduit  31  to selectively open and shut the first bypass conduit  31 . A second bypass conduit  33  is arranged to guide refrigerant from the outlet side of the second oil separator  22  to the inlet side of the second compressor  12 , and a second bypass valve  34  is disposed on the second bypass conduit  33  to selectively open and shut the second bypass conduit  33 . 
     Meanwhile, the outlet sides of the first and second oil separators  21  and  22  are merged together and then connected to first and second condensers  51  and  61  through a four-way valve  40 . The condensers  51  and  61  are connected to an indoor unit (not shown) through a liquid receiver  70 . A first condenser fan  52  is situated in the vicinity of the first condenser  51  and a second condenser fan  62  is situated in the vicinity of the second condenser  61 . The refrigerant return side of the indoor unit is connected to an accumulator  80 , and the outlet side conduit  81  of the accumulator  80  is branched into a first refrigerant conduit  82  connected to the inlet side of the first compressor  11  and a second refrigerant conduit  83  connected to the inlet side of the second compressor  12 . 
     A first pressure regulation unit  90  is arranged on the first refrigerant conduit  82 , and a second pressure regulation unit  100  is arranged on the second refrigerant conduit  83 . The first and second pressure regulation units  90  and  100  serve to regulate the suction pressures of started compressors stage by stage, together with the first and second bypass valves  32  and  34 . 
     Each of the first and second pressure regulation units  90  and  100  includes a first valve  91  or  101  arranged on the first or second refrigerant conduit  82  or  83  connected to the inlet side of the first or second compressor  11  or  12 , a capillary tube  93  or  103  connected in parallel with the first valve  91  or  101 , and a second valve  92  or  102  connected in serial with the capillary tube  93  or  103  for adjusting the opening of the inlet side of the compressor  11  or  12 . 
     In this case, the capillary tube  93  or  103  and the second valve  92  or  102  directly connected to the capillary tube  93  or  103  can be displaced by a motorized valve the degree of opening of which can be adjusted. The entire pressure regulation unit  90  or  100  can be displaced by a motorized valve, too. 
     Also, the entire pressure regulation unit  90  or  100  can be displaced by a first valve arranged on the refrigerant conduit connected to the inlet side of the compressor, an additional refrigerant conduit  84  or  85  connected in parallel with the first valve  91  or  101 , the diameter of which is smaller than refrigerant conduit, and a second valve  92  or  102  arranged on the additional refrigerant conduit  84  or  85 . 
     FIG. 4 is a block diagram showing the control of the air conditioner of the present invention. 
     With reference to this drawing, the air conditioner of the present invention includes a plurality of indoor units  200 . Each of the indoor units  200  includes input means  210  for receiving commands from users, a temperature sensor  220  for sensing indoor temperatures, and an indoor unit controller  230  for transmitting information input through the input means  210  to an outdoor unit controller (will be described). In this case, the input means  210  may include a remote controller. 
     The air conditioner of the present invention further includes the outdoor unit controller  310  for determining the amount of load using information transmitted from the indoor units  200 , a valve drive  320  for regulating the opening of the first and second bypass valves  32  and  34  and the first and second pressure regulation units  90  and  100 , a fan drive  330  for driving the first and second condenser fans  52  and  62 , a four-way valve drive  340  for switching the fluid passages of the four-way valve  40 , and first and second compressor drives  350  and  360  for driving the first and second compressors  11  and  12 , respectively. 
     The air conditioner of the present invention is characterized in that there can be prevented the failure of the start of one or more additional compressors due to the pressure difference between the interior and exterior of the additional compressors while one or more compressors are operated. This will be described in detail with reference to FIG.  5 . 
     FIG. 5 is a flowchart showing the operation of the air conditioner with a pressure regulation device in accordance with the present invention. 
     With reference to FIG. 5, when a capacity-increase command is input to drive an additional compressor (S 110 ) so as to increase the capacity of the air conditioner, the outdoor controller  310  opens the second bypass valve  34  for the second compressor  12  being currently stopped, by controlling the valve drive  320  (S 120 ). The outdoor controller  310  shuts all the valves of the second pressure regulation unit  100  (S 130 ). As a result, the outlet and inlet sides of the second compressor  12  being stopped are connected to each other through the second bypass conduit  33 , so that high-pressure gaseous refrigerant flows from the first compressor  11  to the inlet side of the second compressor  12 , thereby first reducing the pressure difference between the interior and exterior of the second compressor  12 . 
     After the second compressor  12  is started, the outdoor unit controller  310  determines if a predetermined time period has elapsed (S 150 ). The predetermined time period, for example, may be three minutes, and is a time period during which the pressure difference between the interior and exterior of the second compressor  12  is decreased sufficiently in order not to hinder the compressor from starting. 
     If it is determined that the predetermined time period has elapsed in STEP S 150 , the outdoor unit controller  310  opens the second valve  102  of the second pressure regulation unit  100  (S 160 ). In this case, the pressure in the inlet side of the second compressor  12  is greater than the pressure in the inlet side of the capillary tube  103 , so the pressure in the inlet side of the second compressor  12  is transmitted to the inlet side of the capillary tube  103  through the capillary tube  103 . Accordingly, the pressure in the inlet side of the second compressor  12  is reduced, while the pressure in the inlet side of the capillary tube  103  is increased. 
     The outdoor unit controller  310  opens the first valve  101  of the second pressure regulation unit  100  (S 170 ), shuts the second valve  102  of the second pressure regulation unit  100  (S 180 ), and shuts the second bypass valve  34  (S 190 ). Accordingly, the pressure in the inlet side of the second compressor  12  is reduced by one stage and the pressure of gaseous refrigerant returned from the indoor unit is increased by one stage, so both pressures are equalized. 
     The starting of the second compressor  12  is completed by reducing the pressure difference between the inlet side and outlet side of the second compressor  12  stage by stage. When the starting of the second compressor  12  is completed, the outdoor controller  310  normally drives the second compressor  12  by controlling the second compressor drive  360  (S 200 ). 
     The above-described procedure can be applied to the case, in which the first compressor  11  is started while the second compressor  12  is operated and the first compressor  11  is stopped. 
     As described above, the air conditioner with a pressure regulation device and method for controlling the same of the present invention is capable of safely starting one or more additional compressors without stopping one or more compressors in operation when the former compressors are started during the operation of the latter compressors, thereby maintaining comfortable air conditioning without stoppage. 
     Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.