Abstract:
A air-conditioner and the refrigerant charging method of the air-conditioner are disclosed. When a refrigerant amount determining mode is requested to be performed, whether or not the refrigerant amount in the air-conditioner is proper is automatically determined and a shortage amount of refrigerant can be charged. Thus, a user can easily check whether or not the refrigerant charged in the air-conditioner is sufficient or insufficient, and if the refrigerant is not sufficient, the user can automatically charge the refrigerant without having to entirely remove the refrigerant from the air-conditioner, thus increasing the user convenience and reducing time and costs.

Description:
[0001]    This application claims the benefit of Korean Patent Application No. 10-2008-0026348, filed on Mar. 21, 2008, which is hereby incorporated by reference as if fully set forth herein. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to an air-conditioner and a method for charging a refrigerant of an air-conditioner, and more particularly, to an air-conditioner and a refrigerant charging method of an air-conditioner capable of automatically charging a refrigerant when the amount of refrigerant charged in the air-conditioner is not sufficient. 
         [0004]    2. Description of the Related Art 
         [0005]    As for a multi-air-conditioner, if a refrigerant flowing in the multi-air-conditioner is more than or less than a fixed quantity, a system performance is degraded, and worse, the multi-air-conditioner may be damaged. In the related art, a manometer (or a pressure gauge) is installed at a particular position of the air-conditioner to determine overs and shorts of the amount of refrigerant based on the pressure of the refrigerant detected by the monometer. However, only an expert or a technician of the air-conditioner is able to determine the overs and shorts of the refrigerant by using such method, so using of the method is inconvenient for general users. In addition, even the technician has no choice but to determine the overs and shorts of the refrigerant indirectly, lowering the reliability of the results of the determination of the overs and shorts of the refrigerant. Thus, in most cases, the refrigerant in the air-conditioner is wholly removed out, and then, the air-conditioner is charged with a new refrigerant. Such unnecessary re-charging of the air-conditioner with the new refrigerant takes much time and incurs much cost. In addition, the operation of the air-conditioner should be stopped for the process of re-charging the refrigerant, which causes user inconvenience. 
       SUMMARY OF THE INVENTION 
       [0006]    Thus, an object of the present invention is to provide an air-conditioner and a method for charging a refrigerant of the air-conditioner capable of automatically charging a refrigerant if the refrigerant charged in the air-conditioner is insufficient. 
         [0007]    To achieve the above object, there is provided a method for charging a refrigerant of an air-conditioner, including: receiving a request for performing a refrigerant amount determining mode to determine whether or not a refrigerant charged in the air-conditioner is proper; if it is determined that the refrigerant amount determining mode can be started while the air-conditioner is operated in a first operation mode, changing the air-conditioner to a second operation mode; determining whether or not the refrigerant charged in the air-conditioner is proper while the air-conditioner is operated in the second operation mode; and if the refrigerant charged in the air-conditioner is not sufficient, charging a certain amount of refrigerant to the air-conditioner. 
         [0008]    The first operation mode may be a mode for operating the air-conditioner in a blowing mode, and after the air-conditioner is operated in the blowing mode, if an indoor temperature and an outdoor temperature are within a pre-set temperature range, respectively, in a state that pre-set condition is met, it may be determined that the refrigerant amount determining mode can be started. In this case, the pre-set condition may be a condition that an operation time (time period or duration) of the blowing mode is a pre-set time or longer. 
         [0009]    The air-conditioner may be a multi-air-conditioner including a plurality of indoor units, and the second operation mode may be an all-room cooling operation mode in which the plurality of indoor units are operated for cooling. 
         [0010]    The method may further include: determining whether or not the air-conditioner is stable after the air-conditioner is changed to the second operation mode. In determining whether or not the air-conditioner is stable, if a plurality of operation variables of the air-conditioner are within pre-set ranges, it may be determined that the air-conditioner is stable. 
         [0011]    The air-conditioner may include an outdoor heat exchanger and an indoor heat exchanger that heat-exchange a refrigerant; and a liquid pipe (connection pipe) that connects the outdoor heat exchanger and the indoor heat exchanger, and whether or not the refrigerant charged in the air-conditioner is proper may be determined based on the temperature of the liquid pipe. The air-conditioner may further include a liquid pipe temperature sensor installed at the liquid pipe, and if the temperature of the liquid pipe detected by the liquid pipe temperature sensor is higher than a pre-set liquid pipe temperature, it may be determined that the refrigerant charged in the air-conditioner is insufficient. 
         [0012]    The method may further include: if the refrigerant charged in the air-conditioner is proper after the certain amount of refrigerant is charged in the air-conditioner, preventing the refrigerant from being introduced any further. 
         [0013]    The air-conditioner and the refrigerant charging method of the air-conditioner according to the present invention are advantageous in that when the refrigerant amount determining mode is requested to be performed, whether or not the refrigerant amount in the air-conditioner is proper is automatically determined and a shortage amount of refrigerant can be charged. Thus, a user can easily check whether or not the refrigerant charged in the air-conditioner is sufficient or insufficient, and if the refrigerant is not sufficient, the user can automatically charge the refrigerant without having to entirely remove the refrigerant from the air-conditioner, thus increasing the user convenience and reducing time and costs. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    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 embodiments of the invention and together with the description serve to explain the principles of the invention. 
           [0015]    In the drawings: 
           [0016]      FIG. 1  shows a configuration of a multi-air-conditioner applied for a refrigerator charging method of an air-conditioner according to an embodiment of the present invention. 
           [0017]      FIG. 2  illustrates a flow of a refrigerant when the air-conditioner is operated for cooling all the rooms. 
           [0018]      FIG. 3  illustrates a flow of a refrigerant when the air-conditioner is operated for heating all the rooms. 
           [0019]      FIG. 4  is a flow chart illustrating a control flow of the refrigerant charging method of the air-conditioner according to an embodiment of the present invention. 
           [0020]      FIG. 5  shows a configuration of an outdoor unit of the air-conditioner illustrated in  FIG. 1  and a refrigerant charging device. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0021]    Air-conditioners include a general air-conditioner that performs a cooling operation, a heater that performs a heating operation, a general heat pump type air-conditioner that performs both cooling and heating operations, and a multi-air-conditioner that cools/heats a plurality of indoor spaces. Hereinafter, the multi-air-conditioner will now be described in detail as an embodiment of the air-conditioner. 
         [0022]      FIG. 1  shows the configuration of a multi-air-conditioner (referred to as an ‘air-conditioner’, hereinafter)  100  applied for a refrigerator charging method of an air-conditioner according to an embodiment of the present invention. With reference to  FIG. 1 , the air-conditioner includes an outdoor unit (OU) and indoor units (IUs). The OU includes a compressor  110 , an outdoor heat exchanger  140 , an outdoor expansion valve  132 , a supercooler  180 , and a controller (not shown). Although the air-conditioner  100  is shown to have a single OU, but the present invention is not limited thereto and the air-conditioner  100  may include a plurality of OUs. 
         [0023]    The IUs include an indoor heat exchanger  120 , an indoor air blower  125 , and an indoor expansion valve  131 , respectively. The indoor heat exchanger  120  acts as an evaporator for a cooling operation and acts as a condenser for a heating operation. The outdoor heat exchanger  140  acts as a condenser for a cooling operation and acts as an evaporator for a heating operation. 
         [0024]    The compressor  110  compresses an introduced low temperature low pressure refrigerant into a high temperature high pressure refrigerant. The compressor  110  may have various structures, and an inverter type compressor may be employed. A flow sensor  191 , a discharge temperature sensor  171 , and a discharge pressure sensor  151  are installed at a discharge pipe  161  of the compressor  110 . A suction temperature sensor  175  and a suction pressure sensor  154  are installed at a suction pipe (or intake pipe)  162  of the compressor, and a frequency sensor  188  is installed to measure the frequency of the compressor  110 . The OU is shown to have one compressor  110 , but without being limited thereto, the present invention may include a plurality of compressors. An accumulator  187  s installed at the suction pipe  162  of the compressor  110  to prevent a liquid refrigerant from being introduced into the compressor  110 . 
         [0025]    A four-way valve  160 , a flow path switching valve for switching the cooling and heating, guides the refrigerant compressed by the compressor  110  to the outdoor heat exchanger  140  for the cooling operation and guides the compressed refrigerant to the indoor heat exchangers  120  for the heating operation. 
         [0026]    The indoor heat exchangers  120  are disposed in the respective indoor spaces. In order to measure the temperature of the indoor spaces, indoor temperature sensors  176  are installed. The indoor expansion valves  131  are units for throttling the introduced refrigerant when the cooling operation is performed. The indoor expansion valves  131  are installed at indoor inlet pipes  163  of the IUs. Various types of indoor expansion vales  131  may be used, and an electronic expansion valve may be used for user convenience. Indoor inlet pipe temperature sensors  173  are installed at the indoor inlet pipes  163 . Specifically, the indoor inlet pipe temperature sensors  173  are installed between the indoor heat exchangers  120  and the indoor expansion valves  131 , respectively. In addition, indoor outlet pipe temperature sensors  172  and indoor pressure sensors  152  are installed at the indoor outlet pipes  164 . 
         [0027]    The outdoor heat exchanger  140  is disposed in an outer space. An outdoor temperature sensor  177  is installed to measure the temperature of an outdoor space. A liquid pipe temperature sensor  174  is installed at a liquid pipe  165  that connects the outdoor expansion valve  132  and the IUs. The outdoor expansion valve  132 , which throttles the refrigerant introduced when the heating operation is performed, is installed at the liquid pipe  165 . A first bypass pipe  167  for allowing the refrigerant to bypass the outdoor expansion valve  132  is installed at an inlet pipe  166  connecting the liquid pipe  165  and the outdoor heat exchanger  140 , and a check valve  133  is installed at the first bypass pipe  167 . The check valve  133  allows the refrigerant to flow from the outdoor heat exchanger to the IUs when the cooling operation is performed, and prevents the refrigerant from flowing when the heating operation is performed. An outdoor pressure sensor  153  is installed at the inlet pipe  166 . 
         [0028]    The supercooler  180  includes a supercooling heat exchanger  184 , a second bypass pipe  181 , a supercooling expansion valve  182 , and a discharge pipe  185 . The supercooling heat exchanger  184  is installed at the inlet pipe  166 . During the cooling operation, the second bypass pipe  181  bypasses the refrigerant discharged from the supercooling heat exchanger  184  to allow the refrigerant to be introduced into the supercooling heat exchanger  184 . The supercooling expansion valve  182  is disposed at the second bypass pipe  181 , throttles the liquid refrigerant introduced into the second bypass pipe  181  to lower the pressure and temperature of the refrigerant, so as for the refrigerant to be introduced into the supercooling heat exchanger  184 . Accordingly, during the cooling operation, the high temperature condensed refrigerant which has passed through the outdoor heat exchanger  140  is supercooled by being heat-exchanged with the low temperature refrigerant which has been introduced through the second bypass pipe  181 , and then flow to the IUs. The bypass refrigerant is heat-exchanged at the supercooling heat exchanger  184  and then introduced into the accumulator  187  through the discharge pipe  185 . A bypass flowmeter  183  is installed at the second bypass pipe  181  to measure the amount of flow bypassed through the second bypass pipe  181 . 
         [0029]      FIG. 2  shows a flow of the refrigerant when the air-conditioner  100  performs an all-room cooling operation. With reference to  FIG. 2 , the high temperature high pressure gaseous refrigerant discharged from the compressor  110  is introduced into the outdoor heat exchanger  140  via the four-way valve  160 , and then condensed in the outdoor heat exchanger. The outdoor expansion valve  132  is completely open. The indoor expansion valves  131  of the IUs are open at an opening degree which has been set for refrigerant throttling. Thus, the refrigerant discharged from the outdoor heat exchanger  140  is first introduced into the supercooler  180  through the outdoor expansion valve  132  and the check valve  133 . The discharged refrigerant is supercooled by the supercooler  180  and then introduced into the IUs. 
         [0030]    The refrigerant introduced into the IUs is throttled at the indoor expansion valve  131  and then evaporated at the indoor heat exchanger  120 . The evaporated refrigerant is introduced into the suction pipe  162  of the compressor  110  through the four-way valve  160  and the accumulator  187 . At this time, the indoor air blowers  125  are operated. 
         [0031]      FIG. 3  shows the flow of the refrigerant when the air-conditioner  100  performs all-room heating operation. With reference to  FIG. 3 , the high temperature high pressure gaseous refrigerant discharged from the compressor  110  is introduced into the IUs through the four-way valve  160 . The indoor expansion valves  131  of the IUs are completely open. In addition, the supercooling expansion valve  192  is closed. Accordingly, the refrigerant introduced from the IUs is throttled at the outdoor expansion valve  132  and then evaporated from the outdoor heat exchanger  140 . The evaporated refrigerant is introduced into the suction pipe  162  of the compressor  110  through the four-way valve  160  and the accumulator  187 . At this time, the indoor air blowers  125  are operated. 
         [0032]      FIG. 4  is a flow chart illustrating a control flow of the refrigerant charging method of the air-conditioner according to an embodiment of the present invention. With reference to  FIG. 4 , first, a required for performing of a refrigerant amount determining mode to determine whether or not the refrigerant charged in the air-conditioner  100  is proper is received from a user (S 100 ). The controller (not shown) is installed in the OU, and the user requests performing of the refrigerant amount determining mode by using an input device (not shown). 
         [0033]    Upon receiving the request for performing the refrigerant amount determining mode, the air-conditioner  100  is operated in a first operation mode (S 200 ). Here, the first operation mode is a mode in which the air-conditioner  100  is operated in a blowing mode. The air-conditioner, specifically, the IUs, is/are operated in the blowing mode to thereby wholly ventilate the indoor and outdoor spaces and accurately obtain indoor and outdoor temperature values in measuring indoor and outdoor temperatures (to be described). 
         [0034]    When the OU and all the IUs are operated in the blowing mode, namely, in the first operation mode (S 200 ), the indoor expansion valves  131  and the outdoor expansion valves  132  are closed, so the refrigerant cannot be introduced into the IUs but the indoor air blowers  125  are operated. 
         [0035]    After the air-conditioner  100  is operated in the blowing mode, it is determined whether or not a pre-set condition is met (S 300 ). Here, the pre-set condition refers to whether or not the operation time of the blowing mode is greater than or equal to a pre-set time. As mentioned above, in order to enhance reliability in wholly ventilating the indoor and outdoor spaces and measuring the indoor and outdoor temperatures, the operation time of the blowing mode is preferably set to be longer than the pre-set time. 
         [0036]    After the air-conditioner  100  is operated in the blowing mode for longer than the pre-set time, indoor and outdoor temperatures are received from the indoor temperature sensors  176  and the outdoor temperature sensors  177  (S 400 ). If the indoor and outdoor temperatures are within pre-set temperature ranges, it is determined that the refrigerant amount determining mode can be started (S 500 ). If the indoor temperature is lower than a temperature at which cooling operation can be performed by using the air-conditioner  100  or if the outdoor temperature is higher than a temperature at which the air-conditioner  100  can be operated, operation itself of the air-conditioner is not possible. Thus, it is required to determine whether or not the air-conditioner  100  can be operated by comparing the indoor and the outdoor temperatures with the pre-set temperature ranges. In this case, it may be determined that the refrigerant amount determining mode can be started only when all the outdoor and indoor temperatures as received satisfy the pre-set temperature ranges. Also, it may be determined that the refrigerant amount determining mode can be started only when a portion (or a number) of outdoor and indoor temperatures, among outdoor and indoor temperatures of the places where the plurality of IUs are installed, satisfies the pre-set temperature range. 
         [0037]    When it is determined that the refrigerant amount determining mode can be started (S 500 ), the operation mode of the air-conditioner  100  is changed to a second operation mode (S 600 ). Here, the second operation mode may refer to an all-room cooling operation mode in which the plurality of IUs are operated for a cooling operation. Alternatively, the IUs may be changed for the all-room heating operation and operated. 
         [0038]    After the air-conditioner  100  is changed to the all-room cooling operation mode, the second operation mode, before determining whether or not the refrigerant charged in the air-conditioner  100  is proper, first operation variables of the air-conditioner  100  are detected and analyzed (S 700 ) to determine whether or not the air-conditioner  100  is in a stable state (S 800 ). In detail, when the all-room cooling operation is performed, the first operation variables are detected (S 700 ) to determine whether or not the air-conditioner  100  is in a stable state (S 800 ). The first operation variables include an all-room cooling operation time, an operation frequency of the compressor  110 , the difference between a target low pressure and a current low pressure, and the difference between a condensation temperature and the liquid pipe temperature. The stable state is determined depending on whether or not the first operation variables satisfy stabilization conditions. Namely, the all-room cooling operation time should be longer than a pre-set time, a variation value of the frequency of the compressor  110  should be smaller than a pre-set value during a pre-set time, the difference between the target low pressure and the current low pressure should be maintained below a pre-set value during a pre-set time, and the difference between the condensation temperature and the liquid pipe temperature should be larger than a pre-set value. 
         [0039]    Here, the operation frequency of the compressor  110  is detected from information received from the frequency sensor  188 . The current low pressure is a current evaporation pressure which is detected from an average pressure detected by the indoor pressure sensors  152 . The condensation temperature is calculated as a saturation temperature corresponding to the pressure detected by the outdoor pressure sensor  153 , and the liquid pipe temperature is detected from information detected by the liquid pipe temperature sensor  174 . If the first operation variables do not satisfy the stabilization conditions during the pre-set time, whether or not the stabilization conditions are met can be detected again by setting and adjusting the number of target overheating degree of indoor units. However, in the present invention, the stabilization determining is not limited to the stabilization conditions with respect to the first operation variables, and whether or not the air-conditioner  100  is stable can be determined in consideration of various other operation variables. 
         [0040]    When the air-conditioner  100  is determined to be stable, whether or not the amount of the refrigerant charged in the air-conditioner  100  is proper (S 900 , S 1000 ). Because the air-conditioner  100  is first stabilized and then whether or not the amount of charged refrigerant is proper is automatically performed, so the amount of the charged refrigerant can be accurately determined. 
         [0041]    In the embodiment of the present invention, whether or not the amount of refrigerant charged in the air-conditioner  100  is determined based on the temperature of the liquid pipe  165  of the air-conditioner. In detail, with reference to FIGS. I to  3 , the liquid pipe temperature sensor  174  is installed at the liquid pipe  165  that connects the outdoor expansion valve  132  and the IUs. After the liquid pipe temperature is detected by the liquid pipe temperature sensor  174  (S 900 ), if the detected liquid pipe temperature is higher than a pre-set liquid pipe temperature, it is determined that the refrigerant charged in the air-conditioner  100  is not sufficient (S 1000 ). 
         [0042]    When the amount of refrigerant is insufficient during the cooling operation, the supercooling degree is reduced due to the shortage of the amount of condensed refrigerant, increasing the opening degree of the supercooling expansion valve  182 . Accordingly, the amount of refrigerant introduced into the IUs is reduced, a discharge temperature of the compressor  110  is increased, and a discharge overheating degree is increased. The temperature of all the pipes between the IUs and the OU goes up due to the increase in the discharge overheating degree, and accordingly, the temperature of the liquid pipe  165  also goes up. Thus, the controller (not shown) compares the liquid pipe temperature detected by the measurement-facilitated liquid pipe temperature sensor  174  installed at the liquid pipe  165  and a pre-set liquid pipe temperature to determine whether or not the charged refrigerant is excessive or insufficient. 
         [0043]    Meanwhile, if the liquid pipe temperature detected by the liquid pipe temperature sensor  174  is lower than or the same as the pre-set liquid pipe temperature, the controller determines that the refrigerant charged in the air-conditioner  100  is proper and terminates the refrigerant amount determining and charging process. 
         [0044]    Here, the shortage amount of refrigerant according to the difference between the detected liquid pipe temperature and the pre-set liquid pipe temperature may be made into a table through experimentation and stored in a database (not shown). The controller (not shown) may calculate the shortage amount of refrigerant according to the difference between the liquid pipe temperature and the pre-set liquid pipe temperature detected from the table, and charge the refrigerant as much as the shortage amount in the air-conditioner  100 . 
         [0045]    Whether or not the charged refrigerant is proper may be visually displayed (S 1100 ). The controller (not shown) may display whether or not the refrigerant has been properly charged by using the table stored in the database. By visually displaying whether or not the charged refrigerant is proper and the shortage amount of refrigerant to the user, the user can visually check the shortage amount of the charged refrigerant and manually charge the refrigerant to the air-conditioner  100  or automatically charge the shortage amount of the refrigerant based on the refrigerant charging method according to the present invention. 
         [0046]    If the refrigerant charged in the air-conditioner  100  is insufficient, a certain amount of refrigerant is charged to the air-conditioner  100  (S 1200 ). 
         [0047]    At this time, the certain amount of refrigerant refers to a pre-set amount of refrigerant, namely, a fixed quantity, and after the fixed quantity of refrigerant is charged, it may be determined whether or not the amount of charged refrigerant is proper. Alternatively, as stated above, the controller (not shown) may calculate the shortage amount of refrigerant according to the difference between the liquid pipe temperature detected from the table and the pre-set liquid pipe temperature and charge the refrigerant as much as the shortage amount to the air-conditioner. Whether or not the amount of charged refrigerant is proper may be determined by comparing the liquid pipe temperature detected by the liquid pipe temperature sensor  174  and the pre-set liquid pipe temperature. 
         [0048]    If the amount of refrigerant charged in the air-conditioner  100  is determined to be proper (S 1300 ), the refrigerant introduced into the air-conditioner  100  is cut off (S 1400 ). The process of cutting off the introduction of the refrigerant will now be described in detail. 
         [0049]    First, the four-way valve  160  is switched to cut off the introduction of the refrigerant and the operation of the compressor  110  is terminated. The four-way valve  160  is a flow path switching valve for switching (changing) cooling and heating operations. By switching the four-way valve  160  and terminating the operation of the compressor  110 , the all-room cooling operations of the IUs can be stopped. In this case, when the four-way valve  160  is switched while the refrigerant is being charged, an equilibrium pressure is temporarily formed between the pipe with the high pressure refrigerant and the pipe with the low pressure refrigerant in the air-conditioner  100 , restraining additional charging of the refrigerant. Thus, further introduction of the refrigerant can be cut off by switching the four-way valve  160  and terminating the operation of the compressor  110 . 
         [0050]      FIG. 5  shows a configuration of the outdoor unit of the air-conditioner  100  illustrated in  FIG. 1  and a refrigerant charging device. In order to cut off introduction of the refrigerant, a refrigerant charging device  300  that introduces the refrigerant into the air-conditioner  100  may be used. 
         [0051]    With reference to  FIG. 5 , in order to charge the refrigerant to the air-conditioner  100 , the refrigerant storage in a refrigerant storage unit  310  is supplied to the OU of the air-conditioner  100  by using the refrigerant charging device  300 . 
         [0052]    The refrigerant charging device  300  according to an embodiment of the present invention includes a pipe assembly  350 . The pipe assembly  350  includes a first coupling pipe  330 , a second coupling pipe  340 , and a flow controller  351 . Here, the refrigerant charging device  300  is coupled with the air-conditioner  100 . The refrigerant charging device  300  may be fixedly coupled to be integrated with the OU of the air-conditioner  100  or detachably attached. 
         [0053]    With reference to  FIG. 1 , the first coupling pipe  330  is coupled with the suction pipe  162  of the compressor  110  among the liquid pipes connected to a refrigerant circuit of the air-conditioner  100 . The first coupling pipe  330  and the suction pipe  162  can be coupled via a first coupling hose  331  that connects one end of the first coupling pipe  330  and that of the suction pipe  162 . Here, the first coupling hose  331  may be omitted, and the suction pipe  162  and the first coupling pipe  330  may be directly coupled. 
         [0054]    The suction pipe  162  is provided at the entrance, namely, at a suction stage, of the compressor  110 . Accordingly, the refrigerant introduced into the OU through the suction pipe  162  is introduced into the suction stage of the compressor  110 , so as to have a high temperature and high pressure. However, the present invention is not limited thereto and the suction pipe  162  may be connected with any portion of the refrigerant circuit where the refrigerant flows within the air-conditioner  100  to supply the refrigerant to the OU. 
         [0055]    A manifold gauge  360  may be installed at the first coupling hose  331 . The manifold gauge  360  may indicate the pressure of the refrigerant, and without being limited thereto, the manifold gauge  360  may also indicate even a pressure-to-temperature of the refrigerant to indicate the temperature of the refrigerant over the pressure of the refrigerant. In charging the refrigerant, the manifold gauge  360  is connected to the air-conditioner  100  through various hoses or the like, and then, the refrigerant is charged until a certain operation pressure is reached. 
         [0056]    In case of charging the shortage amount of refrigerant manually, the pressure is not uniformly maintained when the refrigerant is charged to the air-conditioner and the manifold gauge  360  varies slightly up and down while the air-conditioner  100  is being operated. Because accurate measurement can be performed after the refrigerant is stabilized to a degree (namely, uniform pressure), the pressure of the refrigerant is adjusted to a certain value, and then, after a certain time lapsed, the refrigerant is charged while checking the manifold gauge  360 . 
         [0057]    A connection pipe  311  is connected with the refrigerant storage unit  310 , through which the refrigerant is introduced from the refrigerant storage unit  310 , and the second coupling pipe  340  is connected with the connection pipe  311 . The second coupling pipe  340  and the connection pipe  311  can be couple through a second coupling hose  341  that connects one end of the second coupling pipe  340  and that of the connection pipe  311 . 
         [0058]    With reference to  FIG. 5 , the flow controller  351  of the pipe assembly  350  connects the first coupling pipe  330  and the second coupling pipe  340 , and limits the flow of refrigerant introduced into the OU of the air-conditioner  100 . The flow speed of the refrigerant introduced into the air-conditioner  100  may be lowered by the flow controller  351 . As the flow speed of the refrigerant introduced into the air-conditioner  100  is gradually lowered by the flow controller  351 , the introduction of the refrigerant may be eventually cut off. 
         [0059]    Namely, when the refrigerant by the shortage amount is supplied to the OU, the flow controller  351  prevents the refrigerant from being introduced while the shortage amount of the refrigerant is calculated at the initial stage, and if a large amount of flow of the refrigerant is introduced into the OU, there is a high possibility that the refrigerant exceeding the shortage amount is introduced into the OU, so the flow controller  351  limits the flow of the refrigerant such that the refrigerant introduced from the refrigerant storage unit  310  cannot be rapidly introduced into the OU. Thereafter, the flow of refrigerant is gradually reduced, and then, the introduction of the refrigerant is eventually cut off. 
         [0060]    In order to limit the flow of the refrigerant introduced into the OU, the flow controller  351  may be a pipe with an inner diameter smaller than the first and second coupling pipes  330  and  340 , and particularly, it may be a capillary tube. Here, the refrigerant charging device  300  may further include a cutoff valve  370  to cut off the refrigerant introduced into the air-conditioner  100  from the refrigerant storage unit  310 . 
         [0061]    The flow controller  351  may be a control valve for controlling the flow of the refrigerant by adjusting an opening degree. If the opening degree of the control valve is smaller than a certain level, the flow controller  351  may perform the function of a capillary tube as shown in  FIG. 5 . In addition, by completely closing or opening the control valve, it can also perform the function of the cutoff valve  370  as shown in  FIG. 5 . 
         [0062]    With reference to  FIG. 5 , the refrigerant charging device  300  may further include a check valve  345  installed at the first coupling pipe  330  or the second coupling pipe  340  and preventing the refrigerant from flowing back to the refrigerant storage unit  310  from the air-conditioner  100 . Namely, if the pressure of the refrigerant flowing to the OU from the refrigerant storage unit  310  is lowered, the refrigerant flowing in the pipes of the pipe assembly  350  might flow backward. Thus, in order to prevent the refrigerant from flowing backward, the check valve  340  is installed at the first coupling pipe  330  or the second coupling pipe  340 , to thereby stably charge the refrigerant. 
         [0063]    When the shortage amount of refrigerant is charged from the refrigerant storage unit  310  to the refrigerant circuit, the OU of the air-conditioner  100  can close the cutoff valve  370 . The cutoff valve  370  may be provided at any portion of the refrigerant charging device  300 . After the sufficient amount of refrigerant is introduced for charging, the refrigerant flowing in the pipe assembly  350  may be additionally introduced into the refrigerant circuit. Thus, only the required amount of refrigerant can be charged by closing the cutoff valve  370 . 
         [0064]    The preferred embodiments of the present invention have been described with reference to the accompanying drawings, and it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope of the invention. Thus, it is intended that any future modifications of the embodiments of the present invention will come within the scope of the appended claims and their equivalents.