Abstract:
A recording apparatus includes a recording head which discharges an ink onto a recording medium to form an image thereon; a sub tank which is movable together with the recording head and which stores the ink to be supplied to the recording head; an ink supplement section which supplements the sub tank with the ink; and a controller which controls the ink supplement section. The controller controls the ink supplement section to supplement the sub tank with the ink when a residual-ink amount of the ink contained in the sub tank is not more than a threshold value, and the controller is capable of changing the threshold value. Therefore, the number of times of the ink supplement operation is reduced as much as possible by flexibly changing the threshold value depending on the situation while avoiding the discontinuity of the recording operation.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority from Japanese Patent Application No. 2006-356793, filed on Dec. 29, 2006, the disclosure of which is incorporated herein by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a recording apparatus for forming an image by discharging an ink onto a recording medium, and a recording method based on the use of the recording apparatus. In particular, the present invention relates to a recording apparatus of the type wherein a sub tank, which is movable together with a recording head, is supplemented with the ink at a predetermined timing, and a recording method based on the use of the recording apparatus. 
         [0004]    2. Description of the Related Art 
         [0005]    For example, the station supply system (also referred to as “on-demand system”) is known as one of the ink supply systems for the recording apparatus such as the ink-jet printer. As described, for example, in U.S. Pat. No. 6,447,084 (corresponding to Japanese Patent Application Laid-open No. 2000-334976), the recording apparatus based on this system is provided with a sub tank which is movable together with a recording head, and an ink supplement section which supplements the sub tank with the ink. The ink supplement section is operated at a predetermined timing to supplement the sub tank with the ink. 
         [0006]    In U.S. Pat. No. 6,447,084, in order to avoid such a situation that the recording operation is discontinued to supplement the ink during the recording operation on one sheet of the recording medium, the ink amount, which is minimally required for the completion of the recording on one sheet of the recording medium, is preset or defined as a threshold value. If it is judged that the ink residual amount in the sub tank is not more than the threshold value, the ink supplement is executed prior to the start of the recording. 
         [0007]    The images, which are to be formed by the recording apparatus, involve various image quality modes and various image types which require mutually different ink amounts to complete the recording for on one sheet of the recording medium. In the case of the recording apparatus disclosed in Japanese Patent Application Laid-open No. 2000-334976, if a low ink residual amount is preset as the basis of the threshold value to find out the timing for the ink supplement, for example, there is a possibility that the ink supplement may be required during the recording operation in the high image quality mode. Therefore, in order to appropriately avoid the discontinuity of the recording operation caused by the ink supplement, the threshold value is inevitably determined while assuming the recording of the image in which the largest amount of the ink is consumed, of those of the image quality modes and the image types. 
         [0008]    However, if the threshold value is determined as described above, when it is intended to execute the recording in which the ink consumption amount is actually relatively small and even when the ink residual amount has a margin to such an extent that it is unnecessary to supplement the ink, the ink supplement operation is executed in some cases. As a result, there is a possibility that the ink supplement operation may be frequently executed during the period in which the image is recorded on a plurality of sheets of the recording medium. The recording waiting time is prolonged, and a disagreeable impression arises in the user. Such a situation may commonly occur in the recording apparatus of such a type that the sub tank, which is movable together with the recording head, is supplemented with the ink, without being limited to only the station supply system. 
       SUMMARY OF THE INVENTION 
       [0009]    In view of the above, an object of the present invention is to provide a recording apparatus which makes it possible to reduce the recording waiting time by suppressing the frequent occurrence of the ink supplement operation while avoiding the discontinuity of the recording operation caused by the ink supplement. 
         [0010]    According to a first aspect of the present invention, there is provided a recording apparatus including: a recording head which discharges an ink onto a recording medium to form an image thereon; a sub tank which is movable together with the recording head and which stores the ink to be supplied to the recording head; an ink supplement section which supplements the sub tank with the ink; and a controller which controls the ink supplement section, wherein the controller controls the ink supplement section to supplement the sub tank with the ink when a residual-ink amount of the ink contained in the sub tank is not more than a threshold value, and the controller is capable of changing the threshold value. 
         [0011]    According to the first aspect of the present invention, the ink supplement is performed when the residual-ink amount of the ink contained in the sub tank is not more than the threshold value, and thus the recording operation is prevented from being discontinued, while the number of times of the ink supplement operation is reduced as much as possible by flexibly changing the threshold value depending on the situation. It is possible to reduce the recording waiting time which would be otherwise required due to the ink supplement. 
         [0012]    In the recording apparatus of the present invention, the controller may be capable of changing the threshold value based on an image type of the image to be formed on the recording medium. In this case, when the recording operation is performed for various image types in which the ink consumption amount differs, the ink supplement operation can be executed based on the threshold value according to the image type. It is possible to appropriately reduce the number of times of the ink supplement operation. 
         [0013]    In the recording apparatus of the present invention, the image type may include a text type for mainly recording letters and symbols, a paint graph type for performing record of an image including an area densely recorded with the ink without leaving any space, and a photograph type for recording a photograph image. In this case, when the recording operation is performed in accordance with at least the text type, the paint graph type, and the photograph type, the ink supplement operation can be executed based on the threshold value according to each of the image types. The text type herein means the image type in which letters and symbols are mainly recorded as described above, and the image is mainly composed of sentences and numerical expressions. The paint graph type corresponds to the image type to be adopted, for example, when a poster of an abstract picture or painting is recorded. The paint graph type means the image type in which all of the dots for forming the image have relatively high gradations (i.e., a relatively large amount of ink is required to form the dot). Further, the photograph type corresponds to the image type to be adopted when the photograph is recorded. The photograph type means the image type in which the gradations of the respective dots for forming the image have the difference in level (i.e., the concentration differs between the respective dots). 
         [0014]    In the recording apparatus of the present invention, the threshold value may be greater in an order of the paint graph type, the photograph type, and the text type. In this case, the threshold value can be preset or defined appropriately depending on each of the image types. 
         [0015]    In the recording apparatus of the present invention, the controller may be capable of changing the threshold value based on an image quality mode of the image to be formed on the recording medium. In this case, when the recording operation is performed in various image quality modes in which the ink consumption amount differs, the ink supplement operation can be executed based on the threshold value corresponding to the image quality mode. It is possible to appropriately reduce the number of times of the ink supplement operation. 
         [0016]    In the recording apparatus of the present invention, when a same image is recorded on a plurality of sheets of the recording medium respectively, the controller may determine, based on an ink amount used in recording on a first sheet among the plurality of sheets of the recording medium, a threshold value for recording on a second sheet of the recording medium and thereafter. In this case, when the same image is recorded on a plurality of sheets of the recording medium respectively, the threshold value can be defined more accurately when the recording is performed on the second sheet of the recording medium and thereafter. 
         [0017]    In the recording apparatus of the present invention, when the same image is recorded on the plurality of sheets of the recording medium respectively, the controller may control, before performing recording on the first sheet of the recording medium, the ink supplement section to supplement the sub tank with the ink until the residual-ink amount in the sub tank is maximized. In this case, even when the correct consumption amount of the ink required for the recording on a first sheet of the recording medium is not definite, there is a margin while the residual amount of the ink contained in the sub tank is previously maximized. Therefore, the ink is not exhausted during the recording operation on the first sheet of the recording medium. 
         [0018]    In the recording apparatus of the present invention, when the same image is recorded on a plurality of sheets of the recording medium respectively and when the residual-ink amount in the sub tank is not more than the threshold value before performing recording on a first sheet of the recording medium, the controller may control the ink supplement section to supplement the sub tank with the ink; and after completing the recording on the first sheet of the recording medium, the controller may calculate a second threshold value based on an ink-amount of the ink used for the recording of the first sheet; and may determine the second threshold value as a new threshold value for recording on a second sheet of the recording medium and thereafter. In this case, the second threshold value can be preset or defined highly accurately when the recording is performed on the second sheet of the recording medium and thereafter. Further, when the recording is initially performed on the first sheet of the recording medium, it is also possible to judge whether or not the ink supplement operation is required based on the first threshold value appropriate thereto. 
         [0019]    In the recording apparatus of the present invention, the controller may determine the threshold value depending on at least the image type. In this case, when the recording operation is performed for various image types in which the ink consumption amount differs, the ink supplement operation can be performed based on the threshold value corresponding to at least the image type, in the same manner as explained above. It is possible to appropriately reduce the number of times of the ink supplement operation. 
         [0020]    In the recording apparatus of the present invention, the threshold value may be greater than the value calculated as the second threshold value. In this case, it is possible to avoid the occurrence of the exhaustion of the ink during the recording on a first sheet of the recording medium. It is possible to reliably obtain the amount of the ink consumed by the recording on the first sheet of the recording medium. 
         [0021]    The recording apparatus of the present invention may further include a scanner which reads an image recorded on the recording medium, and when the image which is read by the scanner is to be recorded on the recording medium and when the sub tank is supplemented with the ink, the controller may control the ink supplement section to supplement the sub tank with the ink during a period in which the scanner reads the image. In this case, when the ink supplement is required upon the recording on the recording medium in the recording apparatus having so-called scanner, it is possible to complete the ink supplement during the reading (scanning) of the image performed by the scanner. Therefore, the ink supplement can be performed efficiently in a temporal viewpoint. 
         [0022]    The recording apparatus of the present invention may further comprise a scanner which reads an image recorded on a recording medium, and when the image which is read by the scanner is to be recorded on each of the plurality of sheets of the recording medium and when the sub tank is to be supplemented with the ink prior to the recording on the first sheet of the recording medium, the controller may control the ink supplement section to supplement the sub tank with the ink during a period in which the scanner reads the image. In this case, when the same scan image is recorded on a plurality of sheets of the recording medium respectively, the ink can be supplemented during the scanning prior to the recording on the first sheet of the recording medium. Therefore, it is possible to avoid the occurrence of the ink exhaustion during the recording on the first sheet of the recording medium. Further, it is also possible to perform the ink supplement efficiently during the scanning. 
         [0023]    In the recording apparatus of the present invention, the controller may control the ink supplement section to communicate the ink supplement section with the sub tank and then to recover the residual ink in the sub tank to the ink supplement section, and may cause the ink to be supplemented from the ink supplement section to the sub tank. In this case, it is possible to realize the prevention of the discontinuity of the recording operation caused by the ink supplement as described above and the suppression of the frequent occurrence of the ink supplement operation, even in the case of the recording apparatus based on the so-called station supply system as well. 
         [0024]    According to a second aspect of the present invention, there is provided a recording method for using a recording apparatus provided with a recording head which discharges an ink onto a recording medium to form an image, a sub tank which is movable together with the recording head and which stores the ink to be supplied to the recording head, and an ink supplement section which supplies the ink to the sub tank, the recording method comprising: receiving a recording instruction; determining a threshold value based on the recording instruction; detecting a residual-ink amount of the ink contained in the sub tank; recovering the ink contained in the sub tank to the ink supplement section when the residual-ink amount in the sub tank is not more than the threshold value; supplementing the sub tank with the ink from the ink supplement section until the residual-ink amount in the sub tank is greater than the threshold value; and recording the image by discharging the ink supplemented in the sub tank. 
         [0025]    According to the second aspect of the present invention, the discontinuity of the recording operation is avoided by performing the ink supplement when the residual amount of the ink contained in the sub tank is not more than the threshold value, while the number of times of the ink supplement operation is reduced as much as possible by determining the threshold value depending on the recording instruction. It is possible to reduce the recording waiting time which would be otherwise required due to the ink supplement. 
         [0026]    In the recording method of the present invention, the threshold value may be an amount of the ink required for recording on one sheet of the recording medium. 
         [0027]    In the recording method of the present invention, when the residual-ink amount in the sub tank is not more than the threshold value, then the ink contained in the sub tank may be recovered to the ink supplement section, and the sub tank may be thereafter supplemented with the ink from the ink supplement section to be fully filled with the ink. 
         [0028]    In the recording method of the present invention, when the residual-ink amount in the sub tank is greater than the threshold value, the image may be recorded based on the recording instruction. 
         [0029]    In the recording method of the present invention, the recording instruction may include an information that including a type of the image to be recorded is a text type for mainly recording letters and symbols, a paint graph type for performing a record of an image including an area densely recorded with the ink without leaving any space, or a photograph type for recording a photograph image; and the threshold value may be determined based on the information about the type of the image included in the recording instruction. 
         [0030]    In the recording method of the present invention, the recording instruction may further include another image-quality information about an image quality mode of the image to be recorded; and the threshold value may be determined based on the information about the image quality mode included in the recording instruction. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]      FIG. 1  shows a perspective view illustrating a structural appearance of a recording apparatus according to an embodiment of the present invention. 
           [0032]      FIG. 2  shows a schematic sectional view illustrating an arrangement of a printer provided for the recording apparatus shown in  FIG. 1 . 
           [0033]      FIG. 3  shows a plan view illustrating main components of the printer shown in  FIG. 2 , which depicts a state in which an image-recording unit is positioned at a predetermined position for performing the ink supplement. 
           [0034]      FIG. 4  shows a sectional view principally illustrating the arrangement of the image-recording unit and an ink supplement section, which depicts the arrangement as obtained by cutting a part of the printer shown in  FIG. 3  along a cutting line IV-IV. 
           [0035]      FIG. 5  shows a block diagram illustrating the function possessed by the recording apparatus shown in  FIG. 1 . 
           [0036]      FIG. 6  shows a flow chart illustrating the operation of the recording apparatus in relation to the ink supplement process. 
           [0037]      FIG. 7  schematically shows the state change of the image-recording unit and an ink supplement section during the ink supplement process, wherein  FIG. 7A  shows a state in which a cartridge and a sub tank are communicated with each other before the ink supplement,  FIG. 7B  shows a state in which the ink is once recovered from the sub tank, and  FIG. 7C  shows a state in which the sub tank is supplemented with the ink. 
           [0038]      FIG. 8  shows a table illustrating the relationship between the image type, the image quality mode, and the threshold value (first threshold value) preset in the recording apparatus. 
           [0039]      FIGS. 9A and 9B  show a flow chart illustrating the process procedure for determining the threshold value to be performed by the controller. 
           [0040]      FIGS. 10A and 10B  show a flow chart illustrating the copy process procedure to be performed by the controller. 
           [0041]      FIG. 11  shows a flow chart illustrating the execution timing for the ink supplement process in the copy process for recording the scanned image on a plurality of sheets of recording paper. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0042]    An explanation will be specifically made below with reference to the drawings about a recording apparatus according to an embodiment of the present invention. 
         [0043]      FIG. 1  shows a perspective view illustrating a structural appearance of the recording apparatus  1  according to the embodiment of the present invention. In this embodiment, the so-called multifunction machine is depicted as the recording apparatus  1 . As shown in  FIG. 1 , the recording apparatus  1  is the multi function device provided with a printer  2  for recording the image in accordance with the ink-jet system at a lower portion of a box-shaped casing  1   a , and a scanner  3  at an upper portion of the casing  1   a . The recording apparatus  1  has the printer function, the scanner function, the copy function, and the facsimile function. 
         [0044]    The recording apparatus  1  is connected to an external information device such as a personal computer so that the image, which includes, for example, the text, the photograph, and the paint graph, is recorded on the recording paper as the recording medium based on the data transmitted from the computer or the like. When a digital camera or the like is connected to the recording apparatus  1 , the photograph is recorded on the recording paper on the basis of the data outputted from the digital camera or the like. Further, when various storage media such as memory cards are inserted, the image is recorded on the recording paper on the basis of the data recorded on the storage medium. 
         [0045]    As shown in  FIG. 1 , the recording apparatus  1  has an opening  4  which is disposed on the front surface (front side) of the printer  2  arranged at the lower portion. A paper feed tray  5  disposed on the lower side and a paper discharge tray  6  disposed on the upper side are provided in a two-stage form at the inside of the opening  4 . A plurality of sheets of the recording paper can be accommodated in the paper feed tray  5 . For example, a plurality of sheets of the recording paper, which have various sizes of not more than the A4 size, can be accommodated. 
         [0046]    A door  7  is provided openably/closably at a lower-right portion on the front surface of the printer  2 . A main tank-carrying section  8  (see  FIG. 3 ) is provided at the inside of the door  7 . Therefore, when the door  7  is opened, the main tank-carrying section  8  is exposed on the front surface side, and main tanks (ink cartridges)  9  (see  FIG. 3 ) can be attached/detached. Accommodating chambers, which correspond to the ink colors to be used, are provided for the main tank-carrying section  8 . In the case of this printer  2 , those used are color inks of five colors, i.e., cyan (C), magenta (M), yellow (Y), and photo black (PBk) as dye inks and black (Bk) as pigment ink. Therefore, the five accommodating chambers are comparted in the main tank-carrying section  8 . The main tanks  9 , which store the inks of the respective colors of cyan (C), magenta (M), yellow (Y), photo black (PBk), and black (Bk), are accommodated in the respective accommodating chambers. 
         [0047]    The scanner  3 , which is provided at the upper portion of the recording apparatus  1 , is a so-called flat bed scanner. That is, as shown in  FIG. 1 , a manuscript cover  10 , which is provided openably/closably as a top plate of the recording apparatus  1 , is provided on the upper surface of the recording apparatus  1 . For example, a platen glass on which the manuscript is placed and an image sensor which reads the image of the manuscript are arranged under the manuscript cover  10 . 
         [0048]    An operation panel  11 , which is used to operate the printer  2  and the scanner  3 , is provided at a front upper portion of the recording apparatus  1 . The operation panel  11  is composed of various operation buttons and a liquid crystal display. The recording apparatus  1  is operated on the basis of the instruction outputted from the operation panel  11  as a result of the operation of the operation panel  11  by a user. When the recording apparatus  1  is connected to the external computer, the recording apparatus  1  is operated on the basis of the instruction transmitted from the computer via a printer driver or a scanner driver. 
         [0049]    A slot  12  is provided at a front upper-left portion of the recording apparatus  1 . Various small-sized memory cards as storage media can be installed to the slot  12 . When the predetermined operation is performed on the operation panel  11 , the data, which is stored in the small-sized memory card installed to the slot  12 , is read. The read data can be displayed on the liquid crystal display of the operation panel  11  as well. Any image, which is selected on the basis of the display, can be recorded on the recording paper by the printer  2 . 
         [0050]      FIG. 2  shows a schematic sectional view illustrating an arrangement of the printer  2 . As shown in  FIG. 2 , the paper feed tray  5  is provided in the vicinity of the bottom of the recording apparatus  1 . A platen  18  is provided over the paper feed tray  5 . An image-recording unit  22 , which includes, for example, a recording head  20  and a sub tank  21  carried on a carriage  19  as described later on, is further provided over the platen  18 . A recording paper transport passage  23  is provided to extend from the deep side portion of the paper feed tray  5 . The recording paper transport passage  23  is composed of a curved path  24  which is directed upwardly from the deep side portion of the paper feed tray  5  and which is further curved toward the front surface side, and a straight path  25  which extends frontwardly from the terminal end of the curved path  24 . The recording paper transport passage  23  is constructed by an outer guide surface and an inner guide surface which are opposed to one another while providing a predetermined spacing distance at portions other than the portion at which the image-recording unit  22  is arranged. 
         [0051]    A paper feed roller  26 , which supplies the recording paper accommodated in the paper feed tray  5  to the recording paper transport passage  23 , is provided just over the paper feed tray  5 . A pair of transport rollers  29 , which are composed of a transport roller  27  and a pinch roller  28 , are provided in the vicinity of the downstream portion of the curved path  24  in the recording paper transport passage  23  so that the recording paper transport passage  23  is interposed by the both rollers  27 ,  28  from the upper and lower positions. Further, a pair of paper discharge rollers  32 , which are composed of a paper discharge roller  30  and a pinch roller  31 , are provided in the vicinity of the downstream portion of the straight path  25  in the recording paper transport passage  23  so that the recording paper transport passage  23  is interposed by the both rollers  30 ,  31  from the upper and lower positions. The recording head  20  and the platen  18  described above are provided so that the straight path  25  is interposed from the upper and lower positions between the pair of transport rollers  29  and the pair of paper discharge rollers  32 . 
         [0052]    Therefore, the recording paper, which is accommodated in the paper feed tray  5 , is supplied to the recording paper transport passage  23  by the paper feed roller  26 . Subsequently, the recording paper is transported from the curved path  24  to the straight path  25  on the recording paper transport passage  23  by the pair of transport rollers  29 . When the recording paper arrives at the straight path  25 , the image is recorded thereon with the inks discharged from the recording head  20 . When the recording is completed, then the recording paper is discharged from the straight path  25  by the pair of paper discharge rollers  32 , and the recording paper is accommodated in the paper discharge tray  6  (see  FIG. 1 ). 
         [0053]    The recording apparatus  1  executes, for example, the ink supplement process for the sub tanks  21  and the maintenance process for the recording head  20  as described later on, in addition to the recording with the image on the recording paper. An ink supplement section  88  is provided in front of the image-recording unit  22  as described later on. 
         [0054]      FIG. 3  shows a plan view illustrating main components of the printer  2 , which depicts a state in which the image-recording unit  22  is positioned at a predetermined position to perform the ink supplement. As shown in  FIG. 3 , a pair of guide rails  38 ,  39 , each of which has a flat plate-shaped form having a long size in the left-right direction (direction perpendicular to the transport direction of the recording paper), are arranged over or above the straight path  25  (see  FIG. 2 ) of the recording paper transport passage  23 . The guide rails  38 ,  39  are provided so that the guide rail  38  is positioned at the back of the guide rail  39  while being separated by a predetermined distance in the front-back direction (transport direction of the recording paper). The guide rails  38 ,  39  are provided in the casing la of the recording apparatus  1  (see  FIG. 1 ), which constitute a part of a frame for supporting the respective constitutive components for constructing the printer  2 . The carriage  19 , which constitutes the image-recording unit  22 , is supported by the guide rails  38 ,  39  so that the carriage  19  is slidable reciprocatingly in the extending direction (left-right direction) of the guide rails  38 ,  39 . 
         [0055]    As shown in  FIG. 3 , a belt-driving mechanism  40  is arranged on the upper surface of the guide rail  39 . The belt-driving mechanism  40  includes an endless annular timing belt  44  which has teeth provided on the inner side and which is tensionally arranged between a driving pulley (not shown) and a driven pulley  43  provided in the vicinity of the both ends in the widthwise direction of the recording paper transport passage  23  respectively. A carriage motor  45  is connected to the shaft of the driving pulley  42 . The driving pulley is rotated by inputting the driving force from the carriage motor  45 . The timing belt  44  receives the rotation to perform the rounding motion between the driving pulley and the driven pulley  43 . 
         [0056]    The carriage  19  is secured to the timing belt  44  at the bottom thereof. Therefore, the carriage  19  makes the reciprocating motion in the left and right directions on the guide rails  38 ,  39  in accordance with the rounding motion of the timing belt  44 . The recording head  20  and the sub tanks  21  are carried on the carriage  19  (see  FIG. 2 ). Therefore, the recording head  20  makes the reciprocating motion in the main scanning direction (left-right direction) in accordance with the movement of the carriage  19 . 
         [0057]    As shown in  FIG. 3 , the position, which is disposed in the vicinity of the left ends of the guide rails  38 ,  39  as viewed in a plan view, is the ink supplement position  50 . The main tanks  9  are arranged at the ink supplement position  50  in a state of being installed to the main tank-carrying section  8 . When the carriage  19 , which is movable along the guide rails  38 ,  39 , is moved to the ink supplement position  50  (state shown in  FIG. 3 ), the ink supplement process is executed to perform the ink supplement from the main tanks  9  to the sub tanks  21  as described later on. The position, which is disposed in the vicinity of the right ends of the guide rails  38 ,  39  as viewed in a plan view, is the maintenance position  51 . A maintenance mechanism  55  is arranged at the maintenance position  51 . Therefore, when the carriage  19  is moved to the maintenance position  51  (state shown by the two-dot chain lines in  FIG. 3 ), then the recording head  20  is subjected to the purge process by the maintenance mechanism  55 , and the maintenance is executed for the ink flow passage. 
         [0058]    Next, an explanation will be made about the arrangement of the image-recording unit  22  and the main tank  9 .  FIG. 4  shows a sectional view mainly illustrating the arrangement of the image-recording unit  22  and the main tank  9 , which depicts the arrangement as obtained by cutting a part of the printer  2  shown in  FIG. 3  along a cutting line IV-IV. 
         [0059]    As shown in  FIG. 4 , the image-recording unit  22  is provided with, for example, the recording head  20  and the sub tanks  21  which are carried on the carriage  19  having the rectangular casing form. The recording head  20  is constructed by stacking a plurality of plates (not shown) which has the ink flow passages (not shown) formed therein. Openings, which are disposed on the downstream side of the ink flow passages, form nozzle holes. 
         [0060]    The sub tank  21  has a box-shaped form in which the dimension in the left-right direction is smaller than the dimension in the front-back direction. Five of the sub tanks  21  are prepared in total one by one for each of the colors. As shown in  FIG. 4 , the sub tank  21  has a sub-ink chamber  21 A having a predetermined volume, which has a first communication port  61  provided at a front side portion of the inner bottom, and a second communication port  62  provided at a back side portion of the inner bottom. The sub tank  21  is communicated with the upstream side opening of the ink flow passage possessed by the recording head  20  via the second communication port  62 . The ink contained in the sub-ink chamber  21 A can be supplied to the recording head  20 . 
         [0061]    A refill port valve  64 , which communicates the sub-ink chamber  21 A and the main ink chamber  9 A of the main tank  9  during the supplement with the ink, is provided in front of the sub-ink chamber  21 A. In particular, a refill chamber  63 , which communicates with the sub-ink chamber  21 A via the first communication port  61 , is provided in front of the first communication port  61 . A refill port  63 A, which communicates with the outside, is formed at a lower portion of the refill chamber  63 . The refill port valve  64  is accommodated in the refill chamber  63 . The refill port valve  64  includes a valve plug  64 A which is inserted into the refill port  63 A and which is movable upwardly and downwardly, a coil spring  64 B which urges the valve plug  64 A in the direction to close the refill port  63 A (in the downward direction as viewed in  FIG. 5 ), and a seal member  64 C. The refill port valve  64  closes the refill port  63 A by the urging force of the coil spring  64 B in a state in which no external force is exerted on the valve plug  64 A. On the other hand, when the external force is applied to move the valve plug  64 A upwardly (toward the inside of the refill chamber  63 ), the refill port  63 A is opened to communicate the outside and the sub-ink chamber  21 A. 
         [0062]    Further, a pressure-adjusting section  70  is provided in front of the sub tank  21 . The pressure-adjusting section  70  has a negative pressure-adjusting chamber  71  which is communicated with the sub-ink chamber  21 A via a passage  65  having a small cross-sectional area and having a labyrinth structure formed on the upper surface of the upper wall of the sub tank  21 , and a positive pressure-adjusting chamber  72  which is positioned over or above the negative pressure-adjusting chamber  71 . Further, the pressure-adjusting section  70  has a negative pressure-adjusting valve  73  which communicates the outside and the sub-ink chamber  21 A via the negative pressure-adjusting chamber  71  during the purge, and a positive pressure-adjusting valve  74  which communicates the outside and the sub-ink chamber  21 A via the positive pressure-adjusting chamber  72  and the negative pressure-adjusting chamber  71 . 
         [0063]    On the other hand, the main tank  9  has a box-shaped form in which the dimension in the left-right direction is smaller than the dimension in the front-back direction as shown in  FIG. 3 . Five of the main tanks  9  are prepared in total one by one for each of the colors. As shown in  FIG. 4 , the main tank  9  has a main ink chamber  9 A having a predetermined volume. An ink supply port  80 , which is communicated with the main ink chamber  9 A, is provided in the vicinity of the bottom. A positive pressure-adjusting valve  81  and a pump  82  are provided at upper portions. 
         [0064]    The positive pressure-adjusting valve  81  has a valve plug  81 A, and a coil spring  81 B which urges the valve plug  81 A. The positive pressure-adjusting valve  81  maintains the internal pressure of the main ink chamber  9 A to be not more than a predetermined positive pressure value. That is, the communication is blocked between the main ink chamber  9 A and the outside in a state in which the internal pressure of the main ink chamber  9 A is not more than the predetermined positive pressure value, while the main ink chamber  9 A and the outside are communicated with each other when the internal pressure exceeds the predetermined positive pressure value. A push rod  81 C, which has a long dimension and which is rod-shaped, is provided to extend backwardly toward the pump  82  from the end surface of the valve plug  81 A possessed by the positive pressure-adjusting valve  81 . 
         [0065]    The pump  82  is provided to change the volume of the main ink chamber  9 A in order to supplement the sub-ink chamber  21 A with the ink and recover the ink from the sub-ink chamber  21 A as described later on. The pump  82  is provided with a cylinder  83 , a piston  84  which has a long dimension, which is rod-shaped, and which is accommodated in the cylinder  83 , and a pinion gear  85  which drives the piston  84 . In particular, the piston  84 , which constitutes the pump  82 , is provided with a rack gear  84 A which is formed at an upper portion thereof, and a piston crown  84 B which is provided at the forward end. 
         [0066]    The rack gear  84 A is meshed with the pinion gear  85 . The piston  84  makes the reciprocating movement in the front-back direction in the cylinder  83  in accordance with the rotary driving of the pinion gear  85 . During this process, the piston crown  84 B makes the reciprocating movement while making the sliding contact with the inner wall surface of the cylinder  83  in the air-tight manner. A hole having a small diameter is formed through the wall disposed on one side of the cylinder  83 . The push rod  81 C, which is possessed by the positive pressure-adjusting valve  81 , penetrates through the hole to extend to the interior of the cylinder  83 . Therefore, when the piston  84  is moved frontwardly, then the piston crown  84 B pushes and moves the valve plug  81 A frontwardly by the aid of the push rod  81 C, and the positive pressure-adjusting valve  81  is opened. 
         [0067]    A joint valve  87 , which is jointed to the refill port valve  64  provided for the sub tank  21 , is attached via a tube  86  arranged outside the main tank  9  to the ink supply port  80  provided in the vicinity of the bottom of the main tank  9 . The joint valve  87  includes, for example, a valve plug  87 A which is movable in the vertical direction, and a coil spring  87 B which urges the valve plug  87 A upwardly. The joint valve  87  is closed by the urging force of the coil spring  87 B when no external force is exerted on the valve plug  87 A. When the external force directed in the downward direction is exerted on the valve plug  87 A, and the valve plug  87 A is moved in the downward direction against the urging force of the coil spring  87 B, then the main ink chamber  9 A communicates with the outside via the tube  86  and the joint valve  87 . 
         [0068]    The joint valve  87  as described above is moved upwardly and downwardly by a lifting mechanism  104 . Therefore, when the joint valve  87  is moved upwardly by the lifting mechanism  104  when the image-recording unit  22  is positioned at the ink supplement position  50 , then the valve plug  87 A of the joint valve  87  and the valve plug  64 A of the refill port valve  64  are mutually pushed and moved, and the both valves  64 ,  87  are opened. As a result, the main ink chamber  9 A of the main tank  9  and the sub-ink chamber  21 A of the sub tank  21  communicate with each other via the valves  64 ,  87 . 
         [0069]    In this embodiment, the ink supplement section  88  includes, for example, the main tank  9  provided with, for example, the main ink chamber  9 A and the pump  82 , the tube  86 , the joint valve  87 , the lifting mechanism  104 , the pinion gear  85  meshed with the pump  82 , and the pinion gear-driving circuit  105  (see  FIG. 5 ) for driving the pinion gear  85  included in the arrangement described above. 
         [0070]      FIG. 5  shows a block diagram illustrating the function possessed by the recording apparatus  1  constructed as described above. As shown in  FIG. 5 , the recording apparatus  1  is provided with the controller  100 . The controller  100  includes, for example, unillustrated CPU (Central Processing Unit), RAM (Random-Access Memory), ROM (Read-Only Memory), and an input/output interface. The scanner  3 , the operation panel  11 , and the slot  12  (see  FIG. 1 ), which have been already explained, are connected to the controller  100 . Those further connected to the controller  100  include, for example, the transport mechanism-driving circuit  101 , the recording head-driving circuit  102 , the carriage-driving circuit  103 , the lifting mechanism  104 , and the pinion gear-driving circuit  105 . These components execute the operation as explained below on the basis of the instruction signal supplied from the controller  100 . 
         [0071]    The transport mechanism-driving circuit  101  drives the unillustrated motor to rotate the transport roller pair  29  and the paper discharge roller pair  32  (see  FIG. 2  as well) which are connected to the output shaft of the motor so that the recording paper is transported along the recording paper transport passage  23 . 
         [0072]    The recording head-driving circuit  102  makes the recording head  20  discharge the ink toward the recording paper at the timing and in the ink amount determined on the basis of the signal supplied from the controller  100 . The recording head-driving circuit  102  is capable of changing the image quality mode of the image to be recorded on the recording paper on the basis of the signal supplied from the controller  100 . The recording head-driving circuit  102  is capable of discharging the ink in accordance with one mode selected from the draft mode in which the low image quality is permitted, the fine mode in which the high image quality is required, and the normal mode in which the intermediate image quality between those of the both modes is required. The controller  100  calculates the cumulative value of the discharge amount of each of the inks on the basis of the instruction signal as described above outputted to the recording head-driving circuit  102  so that the residual amount of the ink contained in the sub tank  21  is calculated. The cumulative value of the ink discharge amount may be appropriately accumulated, for example, in RAM of the controller  100  for each of the ink colors. 
         [0073]    The carriage-driving circuit  103  is connected to the carriage motor  45 . The carriage  19  is moved in the left-right direction by driving and rotating the carriage motor  45 . The lifting mechanism  104  is driven on the basis of the signal supplied from the controller  100  to move the joint valve  87  upwardly and downwardly. The pinion gear-driving circuit  105  drives the unillustrated motor to rotate the pinion gear  85  connected to the output shaft of the motor so that the pump  82  is driven to change the volume of the main ink chamber  9 A. 
         [0074]    Further, the controller  100  is connected to the personal computer (PC, hereinafter abbreviated as “computer”)  106  as the external information device. The controller  100  outputs the instruction signal on the basis of the signal supplied from the computer  106  or the operation panel  11 . 
         [0075]    Next, an explanation will be made about the operation of the recording apparatus  1  as described above. 
         [0076]    At first, an explanation will be made about the ink supplement process for performing the ink supplement from the main tank  9  to the sub tank  21 . When the residual amount of the ink contained in the sub-ink chamber  21 A of the sub tank  21  is decreased to be not more than the predetermined threshold value, the recording apparatus  1  executes the ink supplement process by driving the ink supplement section  88  by the aid of the controller  100 . The recording apparatus  1  according to this embodiment adopts the station supply system. When the process is executed, the series of operation, which will be explained in detail below, is performed such that the residual ink is once recovered from the sub tank  21  to the main tank  9 , and then the ink supplement is performed from the main tank  9  to the sub tank  21 . 
         [0077]      FIG. 6  shows a flow chart illustrating the operation of the recording apparatus  1  in relation to the ink supplement process.  FIG. 7  schematically shows the state change of the image-recording unit  22  and the ink supplement section  88  during the ink supplement process, wherein  FIG. 7A  shows a state in which the main tank  9  and the sub tank  21  are communicated with each other before the ink supplement,  FIG. 7B  shows a state in which the ink is once recovered from the sub tank  21 , and  FIG. 7C  shows a state in which the sub tank  21  is supplemented with the ink. The state, in which the main tank  9  and the sub tank  21  are not communicated with each other before the ink supplement, is shown in  FIG. 4  having been already referred to. 
         [0078]    As shown in  FIG. 6 , the recording apparatus  1  performs the recording of the image on the recording paper (Step S 1 ). When the recording is completed for one sheet of the paper (Step S 2 ), it is judged whether or not the residual amount of the ink contained in the sub tank  21  is not more than the predetermined threshold value (this judging process will be described later on) (Step S 3 ). If the ink residual amount has a value which exceeds the threshold value (Step S 3 : NO), the routine returns to Step S 1  to perform the recording on the next recording paper. If it is judged that the ink residual amount is not more than the threshold value (Step S 3 : YES), the carriage motor  45  (see  FIG. 5 ) is driven to position the carriage  19  at the ink supplement position  50  (Step S 4 ). In this situation, the main tank  9  and the sub tank  21  are in the positional relationship shown in  FIG. 4 . Subsequently, the ink supplement section  88  is driven to joint the main tank  9  and the sub tank  21 . That is, the lifting mechanism  104  is driven to move the joint valve  87  upwardly, and the sub-ink chamber  21 A and the main ink chamber  9 A are communicated with each other via the joint valve  87  and the refill port valve  64  as shown in  FIG. 7A  (Step S 5 ). 
         [0079]    When the both ink chambers  9 A,  21 A are communicated with each other, then the pinion gear  85  is rotated to move the piston  84  backwardly, and the negative pressure is provided in the main ink chamber  9 A. Accordingly, as shown in  FIG. 7B , the residual ink contained in the sub-ink chamber  21 A is once recovered to the main ink chamber  9 A (Step S 6 ). After the completion of the recovery process, the pinion gear  85  is reversely rotated to move the piston  84  frontwardly so that the positive pressure is provided in the main ink chamber  9 A. Accordingly, as shown in  FIG. 7C , the ink supplement is performed from the main ink chamber  9 A to the sub-ink chamber  21 A (Step S 7 ). When the supplement with the ink is completed by rotating the pinion gear  85  by a predetermined angle (number of revolutions), then the routine returns to Step S 1  to restart the recording on the next recording paper. 
         [0080]    In this way, in the ink supplement process of the recording apparatus  1  according to this embodiment, the vacant volume in the sub-ink chamber  21 A is always substantially constant upon the supplement with the ink from the main ink chamber  9 A, because the residual ink contained in the sub-ink chamber  21 A is once recovered. Therefore, the ink supplement can be performed accurately to arrive at the maximum volume of the sub-ink chamber  21 A without providing any sensor for detecting the ink amount for the sub tank  21 . 
         [0081]    In the case of the recording apparatus  1  according to the embodiment of the present invention, the threshold value, which relates to the ink residual amount referred to in the judgment in Step S 3  shown in  FIG. 6  described above, is changeable. The threshold value is appropriately established on the basis of the image type and the image quality mode.  FIG. 8  shows a table illustrating the relationship between the image type, the image quality mode, and the threshold value (first threshold value) preset in the recording apparatus  1 .  FIGS. 9A and 9B  show a flow chart illustrating the process procedure for determining the threshold value to be performed by the controller  100 . 
         [0082]    As shown in  FIG. 8 , the three types are defined or preset as the image types in ROM of the controller  100 . There are the text type in which letters and symbols are mainly recorded, the paint graph type for performing a record of an image including an area densely recorded with the ink without any space, the photograph type for recording the photograph image. The three types of the image quality modes are defined or preset as well. As having been already explained, there are the draft mode in which the low image quality is permitted, the fine mode in which the high image quality is required, and the normal mode in which the intermediate image quality between those of the both modes is required. In this case, x of Th(xn) shown in  FIG. 8  represents the image quality mode, wherein x=a represents the draft mode, x=b represents the normal mode, and x=c represents the fine mode. On the other hand, n of Th(xn) represents the image type, wherein n=1 represents the text type, n=2 represents the paint graph type, and n=3 represents the photograph type. Th(xn) means the ink amount required, for example, when the recording is performed with the designated image type and the designated image quality mode on one sheet of the recording paper having the A4 size. In the text type, the threshold values of Th(a 1 ) and Th(b 1 ) (Th(a 1 )&lt;Th(b 1 )) are preset in this order for the draft mode and the normal mode. In the paint graph type, the threshold values are preset for all of the image quality modes, wherein the threshold values of Th(a 2 ), Th(b 2 ), and Th(c 2 ) (Th(a 2 )&lt;Th(b 2 )&lt;Th(c 2 )) are preset in this order for the draft mode, the normal mode, and the fine mode. In the photograph type, the threshold values of Th(b 3 ) and Th(c 3 ) (Th(b 3 )&lt;Th(c 3 )) are preset in this order for the normal mode and the fine mode. The setting shown in the table of  FIG. 8  may be made for every color of the ink and/or every size of the recording paper. Alternatively, the setting may be made as a calculating formula or expression without being limited to the table form. 
         [0083]    The amount of use of the ink is increased in an order of “text type&lt;photograph type&lt;paint graph type” in the same image quality mode. Therefore, with reference to  FIG. 8  as well, there is given Th(b 1 )&lt;Th(b 3 )&lt;Th(b 2 ) when the comparison is made for the threshold values between the respective image types in the normal mode. As for the various combinations of the image types and the image quality modes, the amount of consumption of the ink is the largest in the image recording in the fine mode of the paint graph type. Therefore, the threshold value Th(c 2 ) in this case has the largest value. 
         [0084]    When the controller  100  receives the recording instruction in accordance with the signal fed from the computer  106  or the signal based on the operation of the operation panel  11  by the user, the controller  100  judges whether or not the type of the image to be recorded next is the text on the basis of the recording instruction as shown in  FIG. 9A  (Step S 10 ). If it is judged that the image type is the text (Step S 10 : YES), it is judged whether the image quality mode is either the draft or the normal (Step S 11 ). If the image quality mode is the draft as a result of the judgment, Th(a 1 ) is obtained as the threshold value Th (Step S 12 ). If the image quality mode is the normal, Th(b 1 ) is obtained as the threshold value Th (Step S 13 ). The threshold value-determining process comes to an end. 
         [0085]    If it is judged in Step S 10  that the image type is not the text (Step S 10 : NO), it is judged whether or not the image type is the paint graph (Step S 14 ). If it is judged that the image type is the paint graph (Step S 14 : YES), it is judged whether the image quality mode is any one of the draft, the normal, and the fine (Step S 15 ). If the image quality mode is the draft as a result of the judgment, Th(a 2 ) is obtained as the threshold value Th (Step S 16 ). If the image quality mode is the normal, Th(b 2 ) is obtained as the threshold value Th (Step S 17 ). If the image quality mode is the fine, Th(c 2 ) is obtained as the threshold value Th (Step S 18 ). The threshold value-determining process comes to an end. 
         [0086]    If it is judged in Step S 14  that the image type is not the paint graph (Step S 14 : NO), then it is definitely decided that the image type is the remaining photograph type, and it is judged whether the image quality mode is either the normal or the fine (Step S 19 ). If the image quality mode is the normal as a result of the judgment, Th(b 3 ) is obtained as the threshold value Th (Step S 20 ). If the image quality mode is the fine, Th(c 3 ) is obtained as the threshold value Th (Step S 21 ). The threshold value-determining process comes to an end. 
         [0087]    As described above, the recording apparatus  1  appropriately determines the threshold value in relation to the ink residual amount based on the type and the image quality mode of the image to be recorded next. As explained with reference to  FIG. 6 , the determined threshold value and the ink residual amount are compared with each other to judge whether or not the ink supplement process for the sub tank  21  is executed (see Step S 3  shown in  FIG. 6 ). Therefore, it is possible to reduce the number of operations of the ink supplement by suppressing the execution of the ink supplement in the state in which the surplus ink is present, while avoiding the exhaustion of the ink during the recording operation on one sheet of the recording paper. 
         [0088]    When the copy process, in which a same image is recorded on a plurality of sheets, is executed, the recording apparatus  1  can determine the threshold value (second threshold value) as the judgment basis to judge whether or not the ink supplement process (see  FIG. 6 ) is executed prior to the recording on the second sheet and the thereafter, based on the ink amount used in the recording on the first sheet of the recording paper. An explanation will be made below about the operation in the copy process. 
         [0089]      FIGS. 10A and 10B  show a flow chart illustrating the copy process procedure. As shown in  FIG. 10A , when the controller  100  receives the instruction to execute the copy process in accordance with the signal fed from the computer  106  or the signal based on the operation of the operation panel  11  by the user (Step S 30 ), the controller  100  determines the threshold value (first threshold value) prior to the recording on the first sheet of the recording paper (Step S 31 ). In this case, the threshold value is determined in accordance with the procedure explained with reference to  FIGS. 9A and 9B . It is judged whether or not the ink residual amount of the sub tank  21  is not more than the threshold value (Step S 32 ). If the ink residual amount is not more than the threshold value, then the ink supplement is performed (Step S 33 ), and then the recording is performed on the first sheet of the recording paper (Step S 34 ). If the ink residual amount is more than the threshold value, the recording is performed on the first sheet of the recording paper (Step S 34 ) without performing the ink supplement. The amount of use of the ink Vp, which is used for the recording on the first sheet of the recording paper, is calculated and obtained (Step S 35 ). 
         [0090]    Subsequently, the residual amount of the ink Vr of the sub tank  21  is obtained based on the amount of use of the ink Vp (Step S 36 ), and it is judged whether or not the recording is completed on the total number of the sheets of the recording paper (Step S 37 ). If it is judged that the recording is completed (Step S 37 : YES), it is judged whether or not the ink residual amount Vr is not more than the predetermined threshold value Thx (Step S 38 ). If it is judged that the ink residual amount Vr is not more than the threshold value Thx (Step S 38 : YES), then the ink supplement process as shown in Steps S 4  to S 7  in  FIG. 6  is executed (Step S 39 ), and the copy process is completed. If it is judged that the ink residual amount Vr is more than the threshold value Thx (Step S 38 : NO), the copy process is completed without performing the ink supplement process. In the judgment in Step S 38 , it is unclear in this situation what kind of the recording is to be performed next. Therefore, for example, the amount of use of the ink, which is to be used when the recording is performed in the fine mode on the entire surface of one sheet of the recording paper, can be regarded as the threshold value Thx. Alternatively, it is also allowable to adopt, as the threshold value Thx, any one of the threshold values Th(a 1 ), Th(b 1 ), Th(a 2 ), Th(b 2 ), Th(c 2 ), Th(b 3 ), and Th(c 3 ) shown in  FIG. 8 . 
         [0091]    On the other hand, if it is judged in Step S 37  that the recording is uncompleted for the total number of the sheets (Step S 37 : NO), the amount of use of the ink Vp used for the recording on the first sheet of the recording paper is set as the threshold value (second threshold value) Th as the basis for judging whether or not the ink supplement is required (Step S 40 ). When the first threshold value and the second threshold value are compared with each other, a relationship of “first threshold value&gt;second threshold value” is given. 
         [0092]    It is judged whether or not the ink residual amount Vr obtained in Step S 36  is not more than the threshold value Th (=Vp) (Step S 41 ). If it is judged that the ink residual amount Vr is not more than the threshold value Th (=Vp) as a result of the judgment (Step S 41 : YES), then the ink supplement process described in Steps S 4  to S 7  shown in  FIG. 6  is executed (Step S 42 ), and then the recording is executed on the second sheet of the recording paper (Step S 43 ). If it is judged that the ink residual amount Vr is greater than the threshold value Th (=Vp) (Step S 41 : NO), the recording is executed on the second sheet of the recording paper without performing the ink supplement process (Step S 43 ). Further, the processes in Step S 36  and the followings are repeated again. 
         [0093]    As described above, the recording apparatus  1  determines the threshold value Th to be used as the judgment basis to judge whether or not the ink supplement process is executed when the recording is performed on the second sheet of the recording paper, based on the amount of use of the ink Vp in the recording on the first sheet of the recording paper. Therefore, the threshold value can be preset more accurately. It is possible to reduce the number of operations of the ink supplement, while suppressing the execution of the ink supplement in the state in which the surplus ink is present. 
         [0094]    In the process procedure explained with reference to  FIGS. 10A and 10B , the threshold value is determined in accordance with the procedure shown in  FIGS. 10A and 10B  prior to the recording on the first sheet of the recording paper, and it is judged whether or not the ink supplement process is required based on the threshold value (Steps S 31  to S 33 ). However, there is no limitation thereto. For example, the ink supplement process may be uniformly executed so that the ink residual amount in the sub tank  21  is maximized prior to the recording on the first sheet of the recording paper. When it is estimated that a predetermined amount of the ink remains in the sub tank  21  after the ink recovery operation during the ink supplement process, the second threshold value Th is strictly the value obtained by adding Vp to the amount of estimation. 
         [0095]    The explanation has been made with reference to  FIGS. 10A and 10B  about the process procedure to be adopted when the image, which is the same as the image to be recorded on the first sheet of the recording paper, is also recorded on the second sheet of the recording paper and the thereafter. However, in the case of the copy process in which a plurality of sets of a series of document recorded on a plurality of sheets of the recording paper are prepared, the following procedure is appropriately adopted. 
         [0096]    That is, the processes of Steps S 31  to S 35  are executed on the respective sheets of the recording paper until the recording is completed on all of the sheets of the recording paper of the first set. Accordingly, it is judged whether or not the ink supplement is required prior to the recording on the respective sheets of the recording paper, and the amounts of use of the ink in the recording on the respective sheets of the recording paper are individually obtained. In the processes in Step S 36  and the followings, when the recording is performed on the sheets of the recording paper of the second set, the threshold values for the respective sheets of the recording paper are individually determined based on the amounts of use of the ink corresponding to the respective sheets of the recording paper of the first set having been already obtained. It is judged whether or not the ink supplement process is required prior to the recording for each of the sheets of the recording paper based on the threshold values. 
         [0097]    According to the process as described above is executed, it is possible to make the judgment whether or not the ink supplement process is required prior to the recording on the respective sheets of the recording paper based on the threshold values obtained at the higher accuracy, even in the case of the copy process in which a plurality of sets of a series of document recorded on a plurality of sheets of the recording paper are prepared. 
         [0098]    As shown in  FIG. 1 , the recording apparatus  1  according to the embodiment of the present invention is provided with the scanner  3 . Therefore, the image scanned by the scanner  3  can be recorded on the recording paper, and it is also possible to execute the copy process in which the image is recorded on a plurality of sheets of the recording paper. Also in this case, the threshold value-determining process shown in  FIGS. 9A and 9B  is performed prior to the recording on the recording paper. If necessary, the ink supplement process shown in Steps S 4  to S 7  in  FIG. 6  is executed. 
         [0099]      FIG. 11  shows a flow chart illustrating the execution timing for the ink supplement process in the copy process for recording the scanned image on a plurality of sheets of the recording paper. As shown in  FIG. 11 , when the controller  100  receives the instruction to execute the scan on the basis of the signal fed from the computer  106  or the signal from the operation panel  11  in accordance with the operation by the user (Step S 50 ), then after the start of the scan (Step S 51 ), the threshold value is determined in accordance with the procedure explained with reference to  FIGS. 9A and 9B  (Step S 52 ), and it is judged whether or not the ink supplement process is required based on the threshold value (Step S 53 ). If it is judged that the ink supplement process is required (Step S 53 : YES), the ink supplement process is executed (Step S 54 ) in accordance with the procedure explained in Steps S 4  to S 7  shown in  FIG. 6 . After that, the routine waits until the completion of the scan (Step S 55 ). 
         [0100]    Usually, a relatively long period of time is required until the image, which is recorded on one sheet of the recording paper, is completely scanned. Therefore, the processes of Steps S 52  to S 54  are completed during the scan. Accordingly, if the ink supplement process of Step S 54  is completed and if it is judged in Step S 53  that the ink supplement process is unnecessary (Step S 53 : NO), then the routine waits until the completion of the scan (Step S 55 ). When the scan is completed (Step S 56 ), the processes of Step S 34  and the followings are executed as shown in  FIGS. 10A and 10B  to record the image on a plurality of sheets of the recording paper (Step S 57 ). When the scanned image is recorded on only one sheet of the recording paper, then the scanned image may be recorded on one sheet of the recording paper after the scan is completed in the procedure shown in  FIG. 11  (Step S 56 ), and the series of the processes may be completed. 
         [0101]    When the ink supplement process is executed prior to the recording on the first sheet of the recording paper at the timing as described above, since the ink supplement process required can be completed during the scan which takes a relatively long period of time, it is efficient. 
         [0102]    As having been already explained, according to the recording apparatus  1  as described above, it is possible to reduce the recording waiting time by suppressing the frequent occurrence of the ink supplement operation, while avoiding the discontinuity of the recording operation which would be otherwise caused by the ink supplement. Further, for example, when the recording is performed on the first sheet of the recording paper, the threshold value is determined based on the image type and the image quality mode, and the actual ink amount, which is necessary for the recording, is not calculated. Therefore, it is possible to suppress the increase in the cost which would be otherwise caused by the large capacity of the internal memory. Further, it is possible to realize the reduction of the recording waiting time owing to the reduction of the calculation time. 
         [0103]    The present invention has been explained above on the basis of the embodiment in which the present invention is applied to the recording apparatus based on the station supply system. However, the present invention is not limited thereto. The present invention is applicable to any recording apparatus of the type wherein the sub tank, which is movable together with the recording head, is supplemented with the ink at a predetermined timing, for example, even in the case of the recording apparatus based on the so-called tube system (recording apparatus of the type in which the main tank and the sub tank are always connected to one another via the tube).