Abstract:
An ink circulation system, an inkjet recording apparatus having the ink circulation system, and an ink circulating method thereof. The ink circulation system includes an ink tank including an ink outlet and an ink inlet, a head assembly including a head chip through which an ink is discharged, and a filter, a supply path which supplies the ink of the ink tank to the head assembly, a first feed line through which ink of the head assembly at the upstream of the filter is conveyed into the ink tank, a second feed line through which the ink of the head assembly at the downstream of the filter is conveyed to the ink tank, and a pump which is provided at the ink inlet of the ink tank to provide the first and the second feed lines with a negative pressure to circulate the ink.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 U.S.C. §119(a) from Korean Patent Application No. 10-2006-096173, filed Sep. 29, 2006, in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein in its entirety by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present general inventive concept relates to an ink circulation system and an inkjet recording apparatus. More particularly, the present inventive concept relates to an ink circulation system to perform ink circulation between an ink head, which discharges ink to form an image onto a recording medium, and an ink tank, and an inkjet recording apparatus using the same. 
         [0004]    2. Description of the Related Art 
         [0005]    An image forming apparatus such as an inkjet printer fires droplets of printing ink onto a printing medium such as a paper sheet or fabric to form an image in a desired color. 
         [0006]    A conventional inkjet printer generally includes an ink circulation system which allows the ink to circulate between an ink tank and an ink firing head assembly.  FIG. 1  illustrates a general ink circulation system. Referring to  FIG. 1 , an ink tank  10  (i.e., an ink cartridge) stores printing ink therein, and is connected to a pressure adjusting unit  11 . The pressure adjusting unit  11  is connected to a head assembly  12  which fires an ink onto a printing medium to form an image. A pump  14  is provided on an ink circulation path  13  between the head assembly  12  and the ink tank  10 . 
         [0007]    In the above construction, the pump  14  is driven and negative pressure is generated from the ink tank  10 . According to the negative pressure being produced at the ink circulation path  13 , ink of the pressure adjusting unit  11  is introduced into the head assembly  12 . The pressure adjusting unit  11  usually includes a filter which filters out impurities or bubbles of the fed ink. The ink from the pump  14  is recovered into the ink tank  10 . In the meantime, by the negative pressure, the bubbles at the head assembly  12  are moved to the pressure adjusting unit  11  and recovered into the ink tank  10 . The negative pressure is exerted by the pressure adjusting unit  11  in the standby mode, such that the ink does not gravitate through a head chip  12   a  of the head assembly  12 . 
         [0008]    In the general ink circulation system as explained above, due to a resistance of the filter housed inside the pressure adjusting unit  11 , it is difficult to recover the bubbles of the head assembly  12  back to the ink tank  10 , which causes inefficient ink circulation. As a result, an amount of ink charged in the head assembly  12  is unsatisfactory, thereby causing inefficient ink firing and image quality degradation. 
         [0009]    Also the ink circulation system as illustrated in  FIG. 1  is not capable of purging, which removes bubbles not only from the head assembly  12 , but also from the nozzles of the head chip  12   a.    
       SUMMARY OF THE INVENTION 
       [0010]    The present general inventive concept provides an ink circulation system, an inkjet recording apparatus and an ink circulation method, which provide smooth ink circulation between a head assembly and an ink tank, and are capable of removing bubbles efficiently. 
         [0011]    The present general inventive concept additionally provides an ink circulation system, an inkjet recording apparatus and an ink circulation method, to prime a head chip with ink after removing bubbles from the head assembly. 
         [0012]    Additional aspects and utilities of the present general inventive concept will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the general inventive concept. 
         [0013]    The foregoing and/or other aspects and utilities of the present general inventive concept are achieved by providing an ink circulation system, including an ink tank including an ink outlet and an ink inlet, a head assembly including a head chip through which an ink is discharged, and a filter, a supply path to supply the ink of the ink tank to the head assembly, a first feed line through which ink of the head assembly at the upstream of the filter is conveyed into the ink tank, a second feed line through which the ink of the head assembly at the downstream of the filter is conveyed to the ink tank, and a pump which is provided at the ink inlet of the ink tank, and which provides the first and the second feed lines with a negative pressure to circulate the ink. 
         [0014]    The head assembly may include a first reservoir which comprises an ink inlet and a first ink outlet, and a second reservoir which is partitioned from the first reservoir by the filter, and comprises a second ink outlet. 
         [0015]    The head chip may be connected to the second reservoir such that the ink of the second reservoir is fired through the head chip. 
         [0016]    The second reservoir may be arranged at a lower portion of the first reservoir. 
         [0017]    The first reservoir may include an ink guider which guides the ink in a manner such that a distance of ink conveyance between the ink inlet and the first ink outlet is extended. 
         [0018]    A valve unit may be further provided, which selectively transmits a pumping force of the pump to the first and the second feed lines. 
         [0019]    The valve unit may include 2-way valves connected to the first and the second feed lines, respectively, and accordingly to the pump. 
         [0020]    A sub filter may be installed on the second feed line, and the sub filter may have a lower resistance than the filter inside the head assembly. 
         [0021]    The pump may include a uni-directional rotational pump which generates a negative pressure to the first and the second feed lines. 
         [0022]    The pump may include a bi-directional rotational pump to selectively provide the second feed line with the negative pressure or a positive pressure according to the direction in which the pump is driven. 
         [0023]    The supply path may connect the ink outlet of the ink tank to the ink inlet of the first reservoir. 
         [0024]    The first feed line may connect the first ink outlet to the pump. 
         [0025]    The second feed line may connect the second ink outlet to the pump. 
         [0026]    The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing an inkjet recording apparatus, including a main body, an ink circulation system including an ink tank including an ink outlet and an ink inlet, a head assembly including a head chip through which an ink is discharged, and a filter, a supply path to supply the ink of the ink tank to the head assembly, a first feed line through which ink of the head assembly at the upstream of the filter is conveyed into the ink tank, a second feed line through which the ink of the head assembly at the downstream of the filter is conveyed to the ink tank, and a pump which is provided at the ink inlet of the ink tank, and which provides the first and the second feed lines with a negative pressure to circulate the ink, and a control unit to selectively control the pump such that the ink is forcibly circulated through the first or the second feed line. 
         [0027]    A valve unit may be further installed between the first feed line and the pump and between the second feed line and the pump, respectively, to be selectively opened or closed and thus to open one of the first and the second feed line according to the control of the control unit. 
         [0028]    The valve unit may include 2-way valves connected to the first and the second feed lines and the pump. 
         [0029]    The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing an ink circulating method, including providing a first circulation in which an ink is circulated between a head assembly housing a filter therein, and an ink tank, the ink being circulated at the upstream of the filter, and providing a second circulation in which bubbles are removed from the downstream of the filter by circulating the ink between the head assembly and the ink tank. 
         [0030]    The first circulation may include generating a negative pressure to a first feed line which connects the ink tank and the upstream of the filter of the head assembly, supplying the ink of the ink tank to the head assembly by the negative pressure, and moving the ink of the head assembly from the upstream of the filter to the ink tank by the negative pressure. 
         [0031]    The generating of the negative pressure may include rotating a rotational pump which is provided on the first feed line, while the first feed line is open. 
         [0032]    The second circulation may include generating a negative pressure to a second feed line which connects the downstream of the filter of the head assembly to the ink tank, supplying the ink of the ink tank to the head assembly by the negative pressure, moving the ink of the head assembly at the upstream of the filter to the downstream by the negative pressure, and recovering a fluid via the second feed line, the fluid including the ink and the bubble at the downstream of the filter. 
         [0033]    The generating of negative pressure to the second feed line may include blocking the first feed line and opening the second feed line, and generating a negative pressure by driving a pump which is connected between the first and the second feed lines. 
         [0034]    The generating of the negative pressure to the first feed line may include blocking the second feed line and opening the first feed line, and generating a negative pressure by driving a pump which is connected between the first and the second feed lines. 
         [0035]    The second circulation may further include filtering the ink being recovered via the second feed line. 
         [0036]    Conducting a purging may be further provided, in which the ink of the ink tank is supplied to the downstream of the filter such that the ink is charged in the head chip. 
         [0037]    The conducting the purging may include blocking a first feed line which connects the upstream of the filter to the ink tank, opening a second feed line which connects the downstream of the filter to the ink tank, and generating a positive pressure to the second feed line such that the ink of the ink tank is fed to the downstream of the filter and fired through nozzles of the head chip. 
         [0038]    The generating of the positive pressure may include rotating a rotational pump installed on the second feed line in opposite direction where the positive pressure is generated. 
         [0039]    The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing an ink circulation system, including a head assembly having a filter, an ink tank to supply ink to the head assembly, and a control unit to provide a first circulation in which an ink is circulated between the head assembly, and the ink tank, the ink being circulated at an upstream of the filter, and a second circulation in which bubbles are removed from a downstream of the filter by circulating the ink between the head assembly and the ink tank. 
         [0040]    The head assembly may be divided by the filter into a first reservoir and a second reservoir, and the control unit may control the ink to circulate between the first reservoir and the ink tank in the first circulation and between the second reservoir and the ink tank in the second circulation. 
         [0041]    The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing an ink circulation system, including a head assembly having a filter to partition an inside space into a first reservoir and a second reservoir, an ink inlet to supply ink to the first reservoir, a first ink outlet to discharge the ink from the first reservoir, an ink guider disposed in the first reservoir between the ink inlet and the first ink outlet, a second ink outlet disposed in the second reservoir to supply and discharge the ink to and from the second reservoir, and a head chip disposed opposite on the head assembly to the filter with respect to the second reservoir to eject the ink. 
         [0042]    The ink circulation system may further include an ink tank having an ink outlet to be connected to the ink inlet of the head assembly, and an ink inlet to be connected to one of the first ink inlet of the first reservoir and the second inlet of the second reservoir, 
         [0043]    The ink circulation system may further include a pump to selectively generate a negative pressure and a positive pressure, and a valve to connect the pump to one of the first ink outlet and the second ink outlet to selectively apply the negative pressure and the positive pressure to one of the first ink outlet and the second ink outlet. 
         [0044]    The ink circulation system may further include a control unit to control the pump and the valve to selectively provide the negative pressure to at least one of the first ink outlet to selectively provide the positive pressure to the second ink outlet. 
         [0045]    The ink circulation system may further include an ink tank connectable to the head assembly to supply ink to the head assembly and receive the ink from the head assembly, and a valve disposed between the head assembly and the ink tank to provide a first circulation mode in which the ink is circulated between the head assembly and the ink tank, the ink being circulated at an upstream of the filter, a second circulation mode in which bubbles are removed from a downstream of the filter by circulating the ink between the head assembly and the ink tank, and a third circulation mode in which the bubbles at a plurality of nozzles are also removed, and the head chip is charged with the ink. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0046]    These and/or other aspects and utilities of the present general inventive concept will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
           [0047]      FIG. 1  illustrates a conventional ink circulation system; 
           [0048]      FIG. 2  illustrates an inkjet recording apparatus having an ink circulation system according to an embodiment of the present general inventive concept; 
           [0049]      FIG. 3  illustrates a first circulation of the ink circulation system of  FIG. 2 ; 
           [0050]      FIG. 4  illustrates a second circulation of the ink circulation system of  FIG. 2 ; and 
           [0051]      FIG. 5  illustrates a purging operation of the ink circulation system of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0052]    Reference will now be made in detail to the embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present general inventive concept by referring to the figures. 
         [0053]    Referring to  FIG. 2 , an inkjet recording apparatus according to an exemplary embodiment of the present general inventive concept may include a main body  100 , an ink circulation system, and a controlling unit  700 . 
         [0054]    The ink circulation system may include a head assembly  200 , an ink tank  300 , an ink supply path  410 , a first feed line  420 , a second feed line  430 , a pump  500  and a valve unit  600 . 
         [0055]    The head assembly  200  may include a first reservoir  210  and a second reservoir  220  which each hold charged ink, a filter  230  to partition the first reservoir  210  and the second reservoir  220 , and a head chip  240  having nozzles through which ink is fired. 
         [0056]    The first reservoir  210  may include an ink inlet  211  and a first ink outlet  212 . The ink inlet  211  may be connected to the ink tank  300  via the ink supply path  410 , and ink is introduced through the ink inlet  211 . The first ink outlet  212  may be provided downstream of the ink inlet  211  and upstream of the filter  230 . The first ink outlet  212  may be connected to the first feed line  420 . 
         [0057]    The first reservoir  210  may additionally include an ink guider  250  to guide the ink being introduced through the ink inlet  211  to circulate around the first reservoir  210  and head toward the first ink outlet  212 . The ink guider  250  may be disposed across the first reservoir  210  such that the ink being introduced through the ink inlet  211  circulates around the first reservoir  210  and moves toward the first ink outlet  212 . More specifically, the ink guider  250  may increase the distance of ink flow and guide the ink to spread the interior of the first reservoir  210  thoroughly. The ink guider  250  may be extended from a wall on which at least one of the ink inlet  211  and the first ink outlet  212  is disposed toward an opposite wall disposed opposite to the wall with respect to the first reservoir  210 . 
         [0058]    The second reservoir  220  may be a space provided downstream of the first reservoir  210 , that is, downstream of the filter  230 . The second reservoir  220  may be provided lower than the first reservoir  210 . The first reservoir  210  and the second reservoir  220  may desirably have the same space. The second reservoir  220  may include a second ink outlet  222 . The second ink outlet  222  may be provided downstream of the filter  230 , and may be connected to the second feed line  430 . 
         [0059]    The second reservoir  220  may house the head chip  240  in a fluid connection. The head chip  240  may be exposed to outside of the head assembly  200 , and may include nozzles through which ink is fired. Accordingly, an image is formed on a recording medium by the ink fired through the nozzles. 
         [0060]    The filter  230  may be interposed between the first reservoir  210  and the second reservoir  220  to filter impurities or ink clots from the ink being moved from the first reservoir  210  to the second reservoir  220 . The filter  230  also operates to block bubbles of the ink from entering into the second reservoir  220 . The filter  230  provides the ink with resistance when the ink moves from the first reservoir  210  to the second reservoir  220 . Accordingly, to prevent the ink of the first reservoir  210  from entering into the second reservoir  220 , the second reservoir  220  may have a negative pressure. 
         [0061]    The ink tank  300  may be removably attached to the main body  100  as a removable ink tank, or securely fixed as a fixed ink tank. The removable ink tank  300  may include a cartridge type ink tank, and the fixed ink tank  300  may include a separate refillable ink cartridge. 
         [0062]    The ink tank  300  may store ink to output a printing process, and may include an ink outlet  310  and an ink inlet  320 . The ink outlet  310  may be connected to the ink inlet  211  of the first reservoir  210  via the ink supply path  410 . The ink inlet  320  may be connected to a pump  500  via an ink introducing path  440 . Accordingly, ink may be introduced through the ink inlet  320  and may circulate between the head assembly  200  and the ink tank  300 . 
         [0063]    A fluid port  330  may be provided at the upper part of the ink tank  300  as an air outlet to allow air to enter or exit from the fluid port  330 . A valve may be provided to the fluid port  330 . 
         [0064]    An ink level sensor  340  may also be provided at the ink tank  300  to detect an amount of stored ink. The ink level sensor  340  may be connected to the controlling unit  700  to provide the controlling unit  700  with information regarding the amount of stored ink. 
         [0065]    One end of the ink supply path  410  may be connected to the ink outlet  310  of the ink tank  300 , while the other end may be connected to the ink inlet  211  of the first reservoir  210 . The ink may be supplied from the ink tank  300  to the first reservoir  210  via the ink supply path  410 , when the negative pressure is produced at the first feed line  420  or the second feed line  430 . 
         [0066]    One end of the first feed line  420  may be connected to the first ink outlet  212  of the first reservoir  210 , while the other end may be connected to the pump  500 . A valve unit  600  may be installed on the path between the other end of the first feed line  420  and the pump  500 . The first feed line  420  may feed the ink of the first reservoir  210  directly to the ink tank  300 . Because there is no significant fluid resistance, ink of the first reservoir  210  can be fast fed to the ink tank  300  via the first feed line  420 . Ink in the ink tank  300  may be added to the first reservoir  210  when the ink of the first reservoir  210  has stayed in a non-use state for a long period of time, and the first feed line  420  is used to feed the ink from the first reservoir  210  to the ink tank  300 . Any bubbles remaining in the first reservoir  210  may be returned to the ink tank  300  via the first feed line  420 . The recovered bubbles may be subsequently discharged through the fluid port  330 . 
         [0067]    The second feed line  430  connects the second reservoir  220 , that is, a downstream portion of the filter  230 , to the ink tank  300 . More specifically, a first end of the second feed line  430  is connected to the second ink outlet  222  of the second reservoir  220 , a second other end is connected to the pump  500 . A valve unit  600  may be provided between the second reservoir  220  and the pump  500 . The ink downstream of the filter  230  may thus be recovered to the ink tank  300  via the second feed line  430 . Accordingly, bubbles can be introduced to the ink tank  300  via the second feed line  430  if bubbles are stuck in the second reservoir  220  due to the filter  230 . The second ink outlet  222  may be formed on the wall on which at least one of the ink inlet  211  and the first ink outlet  212 . 
         [0068]    The ink in the ink tank  300  may be supplied directly to the second reservoir  220  through the second feed line  430  without bypassing the first reservoir  210 , according to the direction of a pump driving status and an operational status of the valve unit  600 . By supplying the ink of the ink tank  300  directly to the second reservoir  220 , a purging operation is enabled in which bubbles remaining in the second reservoir  220  and the nozzles of the head chip  240  are removed and the head chip  240  is primed with ink. Here, the ink contained in the first reservoir  210  may not be fed to the ink tank  300 . 
         [0069]    A sub filter  431  may be installed on the second feed line  430 . The sub filter  431  filters the ink which is fed from the ink tank  300  to the second reservoir  220  via the second feed line  430  to perform the purging operation. The sub filter  431  may have a lower fluid resistance than the filter  430  inside the head assembly  200 . Therefore, the ink from the ink tank  300  may pass through the sub filter  431  into the second reservoir  220 , but will not pass through the filter  430  which has a greater resistance than the sub filter  431  and flow back to the first reservoir  210 . Because the ink is discharged through the head chip  240  without having a backflow, the purging operation is possible. 
         [0070]    The pump  500  may be rotatable in a bi-directional manner. Accordingly, the pump  500  may produce negative pressure at the head assembly  200  by being rotated in a direction A 1 , and may produce positive pressure by being rotated in a direction A 2 . If the negative pressure is generated, the ink of the ink tank  300  is introduced into the head assembly  200  via the supply path  410 , and the ink of the head assembly  200  re-enters the ink tank  300  via the first feed line  420  and the second feed line  430 . If the positive pressure is generated, the ink of the ink tank  300  is fed to the second reservoir  220  via the second feed line  430  by an operation of the valve unit  600 . One end of the pump  500  may be connected to the ink inlet  320  of the ink tank  300 , and the other end may be connected to the first feed line  420  and the second feed line  430  via the valve  600 . 
         [0071]    The valve unit  600  may include two-way valves  610  and  620  which are connected to the first feed line  420  and the second feed line  430 , respectively. Accordingly, one two-way valve  610  may open or close the first feed line  420 , and the other two-way valve  620  may open or close the second feed line  430 . 
         [0072]    The pump  500  and the valve unit  600  are independently controlled by the control unit  700 . 
         [0073]    The operation and effect of an inkjet recording apparatus constructed as explained above according to exemplary aspects of the present general inventive concept will be explained in greater detail below. 
         [0074]    Ink circulation may be conducted mainly in three circulation modes as listed below, excluding the circulation modes during a power off state. 
         [0000]    
       
         
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                 Pump (500) 
                 Valve 1 (620) 
                 Valve 2 (610) 
               
               
                   
                   
               
             
             
               
                   
                 1 
                 Negative pressure 
                 Close 
                 Open 
               
               
                   
                 2 
                 Negative pressure 
                 Open 
                 Close 
               
               
                   
                 3 
                 Positive pressure 
                 Open 
                 Close 
               
               
                   
                 4 
                 Off 
                 Close 
                 Open 
               
               
                   
                 5 
                 Off 
                 Close 
                 Open 
               
               
                   
                   
               
             
          
         
       
     
         [0075]    Referring to  FIGS. 2 and 3 , in a first circulation mode, the pump  500  is driven in the direction A 1 . The first valve  620  is closed and the second valve  610  is open. As a result, a negative pressure is generated by the pump  500  and is applied to the first feed line  420 . Due to the negative pressure exerted to the first feed line  420 , the ink upstream of the filter  430 , that is, the ink of the first reservoir  210  is passed via the first feed line  420 , the valve  600  and the pump  500 , and enters the ink tank  300 . The ink of the ink tank  300  is supplied into the first reservoir  210  via the supply path  410 . Because the flow of ink to the ink tank  300  does not meet any resistance of the filter  430 , a smooth flow of ink may occur. Additionally, because negative pressure is not exerted to the second reservoir  220  and the head chip  240 , the ink may circulate without breaking a meniscus of each of the nozzles. The first circulation mode is utilized when the ink within the head assembly  200  has not been used for a long period of time, and thus, the ink of the ink tank  300  may mix with the ink of the first reservoir  210 , and move the ink to prevent ink hardening or uneven ink density. The first circulation mode is also useful when the bubbles of the first reservoir  210  increase due to long use. Accordingly, the bubbles of the first reservoir  210  may be forcibly moved to the ink tank  300 . 
         [0076]    Referring to  FIGS. 2 and 4 , in a second circulation mode, the pump  500  is driven in the direction A 1  to generate negative pressure. The first valve  620  is open and the second valve  610  is closed. As a result, a negative pressure is exerted to the second reservoir  220  via the second feed line  430 . According to the negative pressure, the ink of the second reservoir  220  may be passed via the second feed line  430 , the valve  600 , and the pump  500 , and recovered into the ink tank  300 . Because the first valve  610  is closed, negative pressure exerted through the first feed line  420  to the first reservoir  210  is not so big, but a small portion of the negative pressure is applied through the filter  430 . 
         [0077]    As the ink of the second reservoir  220  is moved into the ink tank  300 , a considerable amount of bubbles stuck in the filter  230  at the second reservoir  220  may re-enter the ink tank  300 . Also, when the negative pressure exerted to the second reservoir  220 , the ink of the first reservoir  210  is moved to the second reservoir  220  via the filter  230 , and the ink of the ink tank  300  is supplied to the first reservoir  210  via the supply path  410 . In the second circulation mode, the bubbles generated by the printing operation which remain in the second reservoir  220  can re-enter the ink tank  300  to be removed from the second reservoir  220 . As a result, efficient ink firing may be enabled in the following printing operation, such that image degradation can be prevented. The sub filter  431  on the second feed line  430  may have a lower fluid resistance than the filter  230  such that the ink is moved along the second feed line  430  due to the negative pressure, along with the bubbles. At this time, the bubbles of the recovered ink may pass through the sub filter  431  and re-enter the ink tank  300 . 
         [0078]    The purging operation as mentioned above with reference to  FIG. 2  will be explained in greater detail below, with reference to  FIG. 5 . The pump  500  is driven in the direction A 2  to perform the purging operation. The second valve  610  is closed, and the first valve  620  is open. As a result, the pump  500  is driven in the direction A 2  to generate positive pressure, and the generated positive pressure is exerted to the ink tank  300 . Accordingly, the ink of the ink tank  300  is passed through the pump  500 , the valve unit  600  and the sub filter  431 , and is fed into the second reservoir  220 . The ink of the second reservoir  220  is discharged out through the nozzles of the head chip  240 . Because the sub filter  431  has a lower resistance than the filter  230 , the ink is passed through the sub filter  431  by the positive pressure, but does not flow into the first reservoir  210  through the filter  230  while the ink is discharged through the head chip  240 . Along with the ink discharged through the head chip  240 , the bubbles at the nozzles are also removed, and the head chip  240  is charged with the ink. After the ink is discharged through the head chip  240 , meniscus can be recovered by an appropriate recovery operation such as wiping or spitting. 
         [0079]    When the pump  500  is stopped, the first valve  620  may be closed and the second valve  610  may be opened in the printing operation. Then by appropriately controlling the head chip  240 , the ink may be fired to form an image. 
         [0080]    The pump  500  may stop when the power is off. Accordingly, the first value  620  and the second valve  610  are closed. 
         [0081]    An ink circulation system and an inkjet recording apparatus according to a plurality of exemplary embodiments of the present general inventive concept have been outlined. According to the exemplary embodiments of the present general inventive concept, the head assembly  200  is divided into a first reservoir  210  and a second reservoir  220  by a filter  230 , and ink circulation is appropriately controlled between a first circulation mode in which the ink is replaced with new ink, and a second circulation mode in which negative pressure is produced at the second reservoir  220  and ink is circulated to remove bubbles accumulated at the filter  230 . 
         [0082]    Accordingly, a smooth ink circulation is enabled with a small driving load in the first circulation mode, while efficient removal of bubbles from the filter  230  is enabled in the second circulation mode. 
         [0083]    Additionally, positive pressure may be generated in the paths associated with the second circulation mode, such that the ink of the ink tank  300  is supplied to the second reservoir  220 , a head chip  240  is charged with the ink, and the bubbles are removed. As a result, the optimum condition to perform a printing operation is provided. 
         [0084]    Although a few embodiments of the present general inventive concept have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the general inventive concept, the scope of which is defined in the appended claims and their equivalents.