Patent Publication Number: US-7588309-B2

Title: Image forming apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This Nonprovisional application claims priority under 35 U.S.C §119(a) on Patent Application No. 2005-052324 filed in Japan on Feb. 28, 2005, the entire contents of which are hereby incorporated by reference. 
   BACKGROUND 
   The present invention aims at providing an image forming apparatus capable of reliably applying cleaning liquid onto a conveyance belt. 
   In the prior art, image forming apparatuses are known in which ink is ejected from nozzles perforated in a recording head, toward a recording medium placed on a conveyance belt so that an image is formed on the recording medium. Image forming apparatuses of this type have a problem that, for example, when page-margin free printing is performed, ink can be adhered to the conveyance belt conveying the recording medium, and that the adhered ink can then be transferred to the recording medium. 
   In order to solve this problem, for example, Japanese Patent Application Laid-Open No. 2004-196505 discloses a technique that a tank for storing cleaning liquid is connected to an absorber via a tube so that the cleaning liquid is absorbed from the tank to the absorber via the tube. Then, when the absorber having absorbed the cleaning liquid contacts with the surface of the conveyance belt, the cleaning liquid is applied onto the conveyance belt, while the applied cleaning liquid is wiped away by a blade so that the ink adhered to the conveyance belt is removed. 
   SUMMARY 
   Nevertheless, in the technique disclosed in Japanese Patent Application Laid-Open No. 2004-196505 described above, air bubbles can enter from the tube into the cleaning liquid in the course that the cleaning liquid is supplied from the tank to the absorber. Then, for example, when the absorber is composed of a porous body such as sponge, the air bubbles having entered clog in the absorber, and then the cleaning liquid is not applied onto the conveyance belt in a portion where the air bubbles have clogged. This has caused a problem that the ink on the conveyance belt cannot be removed. 
   Therefore, in order to solve the above-mentioned problem, and it is an object to provide an image forming apparatus capable of reliably applying cleaning liquid onto a conveyance belt. 
   In order to achieve this object, an image forming apparatus according to the first aspect is an image forming apparatus comprising: a recording head having a nozzle surface provided with nozzles for ejecting ink; an endless conveyance belt for circulating around in order to convey a recording medium to a position that opposes the nozzle surface of said recording head; an absorber capable of coming into contact with said conveyance belt and absorbing cleaning liquid to be applied onto said conveyance belt; and a first storing unit for storing cleaning liquid to be supplied to said absorber, characterized by further comprising: a passage forming member connected to said absorber and said first storing unit, forming a passage for supplying, to said absorber, cleaning liquid stored in said first storing unit, and having an air discharging hole for discharging, to the outside, air bubbles contained in said cleaning liquid. 
   In the image forming apparatus according to the first aspect, the cleaning liquid stored in the first storing unit is absorbed by the absorber via the passage formed in the passage forming member, and then applied onto the conveyance belt when the absorber comes into contact with the conveyance belt. At that time, even when air bubbles enter into the cleaning liquid supplied to the absorber, the air bubbles are discharged to the outside through the air discharging hole. This suppresses the occurrence of a problem that air bubbles having entered into the cleaning liquid clog in the absorber so that the cleaning liquid is not sufficiently applied from the absorber onto the conveyance belt. Thus, an effect is achieved that the cleaning liquid is sufficiently applied onto the conveyance belt so that a blot on the conveyance belt is removed. 
   The above and further objects and features will more fully be apparent from the following detailed description with accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       FIG. 1  is a schematic diagram showing the internal configuration of an ink jet printer serving as an image forming apparatus; 
       FIG. 2A  is a sectional view of a holder and a sponge taken along line IIa-IIa of  FIG. 1 ; 
       FIG. 2B  is a plan view of a holder and a sponge viewed in the direction of an arrow IIb of  FIG. 2A ; 
       FIG. 3  is a schematic diagram showing the internal configuration of a printer incorporating a cleaning liquid supply unit according to a second embodiment; 
       FIG. 4A  is a sectional view of a holder and a sponge according to a second embodiment, corresponding to  FIG. 2A ; 
       FIG. 4B  is a plan view of a holder and a sponge according to a second embodiment, viewed in the direction of an arrow IVb of  FIG. 4A , corresponding to  FIG. 2B ; and 
       FIG. 5  is a sectional view showing the internal structure of an ink cartridge according to a second embodiment. 
   

   DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
   Preferred embodiments are described below with reference to the accompanying drawings.  FIG. 1  is a schematic diagram showing the internal configuration of an ink jet printer  1  (referred to as a “printer  1 ”, hereafter) serving as an image forming apparatus. The printer  1  is a color ink jet printer having a head unit  3 . The head unit  3  includes four recording heads  3   a - 3   d  corresponding to inks of four colors consisting of cyan, magenta, yellow, and black. 
   Each of the recording heads  3   a - 3   d  is formed in an approximate rectangular shape in a sectional view, and extends in the width direction perpendicular to the conveying direction of the recording medium. These recording heads are arranged and positioned closely to each other. Further, each of the recording heads  3   a - 3   d  has a head body  26  at its lower end. Each head body  26  extends in the width direction perpendicular to the conveying direction of the recording medium, and is arranged such that its bottom surface should oppose a conveyance belt  8 . In the bottom surface of the head body  26 , a large number of nozzles each having a minute diameter are provided in the longitudinal direction of the head body  26  across the entire width of a recording medium to be conveyed. That is, the printer  1  is a line type printer. The recording heads  3   a - 3   d  need be positioned at the above-mentioned position only in recording operation and flushing operation described later. In other occasions, the recording heads may be located at other positions. 
   In an ink jet method, in order to maintain or recover the performance of ink ejected from the nozzles, a flushing process is performed in which ink is ejected from the nozzles as a process other than the recording operation. The flushing process resolves clogging in the nozzles resulting from dried ink, and discharges air bubbles mixed in the ink. In the present embodiment, the flushing process is performed by ejecting ink from the nozzles onto the conveyance belt  8 . The ink ejected onto the conveyance belt in the flushing process is removed from the conveyance belt  8  when cleaning liquid is applied onto the conveyance belt  8  by a sponge  13  (absorber) described later, and then the adhered ink and the cleaning liquid are wiped away by a blade  16 . In addition to the flushing process, also in frameless recording, ink may be adhered to the conveyance belt  8 . Also in this case, the adhered ink can be removed by the same method described above. 
   Thus, the flushing process can be performed without the necessity that the head unit  3  should retract from above the conveyance belt  8 . Further, the flushing process can be performed without the necessity of providing a mechanism for moving the conveyance belt  8  (belt rollers  7   a  and  7   b  and the like) downward relative to the head body  26  in order that a maintenance unit for receiving ink ejected from the nozzles should be inserted between the bottom surface of the head body  26  and the conveyance belt  8 . This avoids the necessity of a large mechanism for moving the head unit  3  or the conveyance belt  8  as well as a space for their retraction, and hence permits size reduction in the main body of the apparatus. 
   The head body  26  is arranged in such a manner that a small gap is formed between its bottom surface and the conveyance surface of the conveyance belt  8 . Then, a recording medium conveyance path is formed in the gap portion. In this configuration, when a recording medium conveyed on the conveyance belt  8  sequentially passes immediately under the four head bodies  26 , ink drops of each color are ejected from the nozzles onto the upper surface, that is, the printing surface, of the recording medium. As a result, a desired color image is formed on the recording medium. 
   Further, in the recording medium conveyance path, a sheet feed tray  4  is provided on the upstream side of the head unit  3  (right side in  FIG. 1 ). The sheet feed tray  4  is constructed so as to accommodate a plurality sheets of recording media. A pair of feed rollers  6   a  and  6   b  are provided immediately on the downstream side of the sheet feed tray  4 . The recording media accommodated in the sheet feed tray  4  is nipped and conveyed by the feed rollers  6   a  and  6   b,  and then and transported from the right side to the left side in  FIG. 1 . 
   On the downstream side of the feed rollers  6   a  and  6   b , pressing members  10   a  and  10   b  composed of a pair of roller members are arranged each over or under the conveyance belt  8  positioned therebetween. The pressing members  10   a  and  10   b  press the recording medium against the conveyance surface of the conveyance belt  8  in order that the recording medium on the conveyance belt  8  should not be floated from the conveyance surface, and thereby cause the recording medium to reliably be stuck onto the conveyance surface. 
   The conveyance belt  8  is an endless belt that circulates around in the shape of a loop, and is wound around two belt rollers  7   a  and  7   b  arranged each on the upstream side or the downstream side of the recording medium conveyance path relative to the head unit  3  positioned therebetween. The outer periphery surface, that is, the conveyance surface, of the conveyance belt  8  is subjected to silicon treatment. Thus, the recording medium conveyed by a pair of the feed rollers  6   a  and  6   b  is retained on the conveyance surface of the conveyance belt  8  by the sticking force thereof, while the recording medium is conveyed toward the downstream side (left side in  FIG. 1 ) in association with the rotation of one belt roller  7   a  in the counterclockwise direction. 
   The recording medium having been fed from the sheet feed tray  4  onto the conveyance belt  8  is conveyed by the conveyance belt  8 , thereby passes the opposite surface (bottom surface of the head body  26 ) of the head unit  3 , and then moves toward a paper discharge unit not shown. On the other hand, after having conveyed the recording medium, the conveyance belt  8  moves around the belt roller  7   a  on the downstream side of the recording medium conveyance path, and further moves (returns) under the belt rollers  7   a  and  7   b  toward the belt roller  7   b.    
   On the left side of the belt roller  7   a,  a cleaning liquid supply unit  5  is arranged. The cleaning liquid supply unit  5  applies cleaning liquid onto the conveyance belt  8 , and comprises mainly: a first storage tank  10  (first storing unit) for storing cleaning liquid; a tube  11  (passage forming member, first passage forming member) an end of which is connected to the first storage tank  10 ; a holder  12  (passage forming member, second passage forming member) connected to the other end of the tube  11 ; and a sponge  13  retained by the holder  12  and arranged so as to come into contact with the conveyance belt  8 . Here, the cleaning liquid may be composed of water, detergent, or the like. 
   In the cleaning liquid supply unit  5 , the first storage tank  10  is arranged above the sponge  13 . Thus, by virtue of water head difference, the cleaning liquid stored in the first storage tank  10  is transported through the passage (first passage) formed in the tube  11  and the passage (second passage) formed in the holder  12 , and then absorbed by the sponge  13 . 
   On the other hand, since the sponge  13  is arranged so as to come into contact with the conveyance belt  8 , the cleaning liquid absorbed by the sponge  13  is applied onto the conveyance belt  8 , and then wiped away together with the ink adhered to the conveyance belt  8 , by the blade  16  described later. Thus, in comparison with the case that the ink adhered to the conveyance belt  8  is wiped away simply by the blade  16 , the blot on the conveyance belt  8  is removed more satisfactorily. 
   It should be noted that a valve  15  is arranged between the first storage tank  10  and the holder  12  of the cleaning liquid supply unit  5 . Thus, for example, when a certain failure arises in the holder  12  or the sponge  13 , the valve  15  is closed so that the supply of cleaning liquid from the first storage tank  10  is shut off. This permits change or repair of the holder  12  and the sponge  13  without useless consumption of the cleaning liquid stored in the first storage tank  10 . 
   The holder  12  and the sponge  13  are described below in detail with reference to  FIGS. 2A and 2B .  FIG. 2A  is a sectional view of the holder  12  and the sponge  13  taken along line IIa-IIa of  FIG. 1 .  FIG. 2B  is a plan view of the holder  12  and the sponge  13  viewed in the direction of an arrow IIb of  FIG. 2A . 
   As shown in  FIGS. 2A and 2B , the holder  12  is formed in the shape of a hollow box, and comprises: an opening  12   a  formed in the surface opposing the conveyance belt  8 ; an internal space  12   b  that leads to the opening  12   a;  a supply port  12   c  formed in the surface opposite to the surface which leads to the internal space  12   b  and in which the opening  12   a  is formed; and air discharging holes  12   d  formed in the same surface as the surface which leads to the internal space  12   b  and in which the opening  12   a  is formed. 
   The opening  12   a  causes the sponge  13  to be exposed to the conveyance belt  8  side. The contact surface of the sponge  13  is arranged so as to be exposed through the opening  12   a  and thereby come into contact with the conveyance belt  8 . 
   The internal space  12   b  is a space for forming a part of the passage for supplying the cleaning liquid to the sponge  13 . A part of the sponge  13  is retained in the holder  12  so as to occupy a part of the internal space  12   b.  A space not occupied by the sponge  13  (passage formation space, second passage) in the internal space  12   b  serves as a part of the passage for supplying the cleaning liquid to the sponge  13 . The cleaning liquid stored in the passage formation space is supplied to the sponge  13 . 
   Further, the passage formation space is formed along the sponge  13  and over a region larger than the opening  12   a . Furthermore, the passage diameter of the passage formation space is larger than the air discharging hole  12   d.  Thus, a sufficient amount of cleaning liquid is supplied approximately uniformly over the entire sponge  13 . As a result, a sufficient amount of cleaning liquid is applied onto the conveyance belt  8 . 
   The supply port  12   c  is formed by a connection unit  14  protruding from the surface opposite to the surface in which the opening  12   a  is formed, and supplies the cleaning liquid to the internal space  12   b  via the tube  11 . The connection unit  14  is arranged in an approximate center part of the longitudinal direction of the internal space  12   b  in  FIG. 2A . An end of the tube  11  is inserted into the connection unit  14  so that communication is established between the passage formed in the tube  11  and the supply port  12   c.  Thus, the cleaning liquid supplied from the first storage tank  10  via the tube  11  is supplied to the internal space  12   b  via the supply port  12   c.    
   Each air discharging hole  12   d  is a hole for discharging, to the outside, air bubbles having entered into the cleaning liquid through the sponge  13  or the wall surface of the tube  11 . The air discharging hole  12   d  is formed at a position distant as much as possible from the connection portion between the tube  11  and the connection unit  14 . In other words, the air discharging hole  12   d  is formed approximately at each tip of the passage formed by the supply port  12   c  and the internal space  12   b.    
   Thus, the cleaning liquid supplied to the internal space  12   b  via the tube  11  and the supply port  12   c  flows toward both side ends where resistance is small (see arrows A in  FIG. 2A ). Accordingly, air bubbles having entered into the cleaning liquid are prevented from stagnating in the internal space  12   b,  and are pushed out and discharged smoothly along the flow of the cleaning liquid to the outside through the air discharging holes  12   d.    
   Further, the air discharging holes  12   d  have the hole size that allows the cleaning liquid to form a meniscus. Thus, the cleaning liquid is prevented from leaking through the air discharging holes  12   d.  Furthermore, the hole size of the air discharging holes  12   d  is larger than the pore size of the sponge  13 . Thus, the air bubbles are prevented from clogging in the pores of the sponge  13 , so that the air bubbles having entered into the cleaning liquid are smoothly discharged to the outside through the air discharging holes  12   d.    
   The sponge  13  is a porous body capable of absorbing the cleaning liquid, and is formed in the shape of an approximately rectangular parallelepiped. Further, the contact surface in contact with the conveyance belt  8  extends beyond the width of the conveyance belt  8 , and is formed in an arc shape in a sectional view as shown in  FIG. 1 . This allows the sponge  13  to contact closely with the conveyance belt  8  and thereby apply the cleaning liquid onto the conveyance belt  8  reliably. 
   The following description is given with returning to  FIG. 1 . A blade  16  is arranged between the belt roller  7   a  and the belt rollers  7   b  and on the downstream side of the conveying direction (downstream side of the movement direction) of the conveyance belt  8  relative to the sponge  13  included in the cleaning liquid supply unit  5 . The blade  16  is fabricated from resin having resistance against the ink and the cleaning liquid, and is arranged perpendicularly from below the conveyance belt  8  toward the conveyance belt  8 . Its tip is arranged at a position coming into contact with the outer periphery of the returning conveyance belt  8 . 
   Further, the blade  16  extends across the width of the conveyance belt  8 , and is formed in the shape of a spatula provided with a tip which is thinner than other portions. The tip side of the spatula is formed in a manner curved toward the downstream side of the conveying direction relative to the above-mentioned perpendicular arrangement direction, so as to contact closely with the conveyance belt  8 . Thus, a predetermined width of the tip of the spatula contacts closely with the conveyance belt  8 , so that the ink and the cleaning liquid wiped away are prevented from being transported to the downstream side of the conveying direction relative to the blade  16 . 
   On the left side of the blade  16 , an ink cartridge  17  is arranged for storing inks supplied to the recording heads  3   a - 3   d . The ink cartridge  17  is composed of four ink cartridges  17   a - 17   d  each for storing each of the inks of colors consisting of cyan, magenta, yellow, and black to be supplied to each of the four recording heads  3   a - 3   d.  Each of the ink cartridges  17   a - 17   d  is constructed in a manner attachable to and detachable from the printer  1 , and is connected to a pump (not shown) in a state mounted on the printer  1 . Then, the ink stored in each of the ink cartridges  17   a - 17   d  is supplied to each of the recording heads  3   a - 3   d  via a tube  18  connected to the pump (not shown). 
   Next, a second embodiment concerning the above-mentioned cleaning liquid supply unit  5  is described below with reference to  FIG. 3 .  FIG. 3  is a schematic diagram showing the internal configuration of a printer  100  incorporating a cleaning liquid supply unit  9  of the second embodiment. Here, like configuration components to those described above are designated by like numerals, and hence their description is omitted. 
   The cleaning liquid supply unit  9  of the second embodiment comprises a first storage tank  10 , a tube  11 , a holder  12 , and a sponge  13  which are the same as those of the cleaning liquid supply unit  5  of the first embodiment. The cleaning liquid supply unit  9  further comprises: a pump  19  arranged in the middle of the tube  11  connected to the first storage tank  10 ; a second storage tank  20  (first adjusting means, second storing unit) arranged between the tube  11  and the holder  12  and storing the cleaning liquid; a fluctuation plate  21  connected to the second storage tank  20 ; a coil spring  22  (first adjusting means, pressing member) for pressing the fluctuation plate  21 ; and a displacement sensor  23  (detecting means) for detecting the displacement of the fluctuation plate  21 . 
   The pump  19  (second adjusting means) forcibly supplies the cleaning liquid stored in the first storage tank  10  to the second storage tank  20 . More specifically, the pump  19  supplies a predetermined amount of cleaning liquid to the second storage tank  20  in accordance with the detection result of the displacement sensor  23  described later. In the cleaning liquid supply unit  9  of the second embodiment, the first storage tank  10  is arranged below the downstream portion in contrast to the case of the cleaning liquid supply unit  5  of the first embodiment. Thus, the cleaning liquid stored in the first storage tank  10  is forcibly supplied to the downstream side by the pump  19 . When the pump  19  is provided as described here, the degree of freedom with respect to the position of arrangement of the first storage tank  10  is improved in comparison with the first embodiment. 
   The second storage tank  20  is constructed in the shape of a bag fabricated by sealing the edges of two flexible sheet bodies with each other, and is arranged horizontally such that its broader surface should align approximately at the same level as the sponge  13 . The fluctuation plate  21  is connected to the upper surface of the second storage tank  20 . In its opposite surface, the coil spring  22  is connected for biasing the fluctuation plate  21  toward the second storing unit. 
   Then, when the cleaning liquid absorbed in the sponge  13  is consumed, the fluctuation plate  21  is displaced downward by the pressing force of the coil spring  22  so that the cleaning liquid stored in the second storage tank  20  is forcibly supplied to the sponge  13 . 
   Further, the displacement of the fluctuation plate  21  is monitored by the displacement sensor  23 , so that when the fluctuation plate  21  is displaced downward as described above, the pump  19  is driven in accordance with the detection result of the displacement sensor  23  such that the amount of the cleaning liquid in the second storage tank  20  should be recovered by a predetermined amount of cleaning liquid. Then, a predetermined amount of cleaning liquid is supplied to the second storage tank  20  so that the fluctuation plate  21  is pushed up again. Since the displacement of the fluctuation plate  21  is monitored by the displacement sensor  23 , the pump  19  is stopped when the fluctuation plate  21  is pushed up to a predetermined position. 
   When the cleaning liquid supply unit  9  is constructed as described here, the supply pressure is prevented from changing depending on the amount of the cleaning liquid stored in the first storage tank  10  as in the above-mentioned cleaning liquid supply unit  5  of the first embodiment where the cleaning liquid has been supplied to the sponge  13  simply by virtue of the water head difference. Accordingly, a necessary and sufficient amount of cleaning liquid can be supplied to the sponge  13  at a predetermined pressure. That is, the cleaning liquid can stably be supplied to the sponge  13 . 
   Next, the second embodiment concerning the above-mentioned holder  12  is described below with reference to  FIGS. 4A and 4B .  FIG. 4A  is a sectional view of a holder  25  and a sponge  13  according to the second embodiment, corresponding to  FIG. 2A .  FIG. 4B  is a plan view of the holder  25  and the sponge  13  of the second embodiment, viewed in the direction of an arrow IVb of  FIG. 4A , corresponding to  FIG. 2B . Here, like configuration components to those described above are designated by like numerals, and hence their description is omitted. 
   In the above-mentioned holder  12  of the first embodiment, the supply port  12   c  has been arranged in the approximate center part of the internal space  12   b  such that the cleaning liquid should flow through the internal space  12   b  in a bifurcated manner (see arrows A in  FIG. 2A ), while the air discharging holes  12   d  have been formed at both side ends. 
   In the holder  25  (passage forming member, second passage forming member) of the second embodiment, as shown in  FIGS. 4A and 4B , the supply port  25   c  is arranged at an end of the internal space  25   b,  while the air discharging hole  25   d  is formed at the opposite end of the supply port  25   c  which is a position distant as much as possible from the supply port  25   c  (in other words, approximately at a tip position of the passage). 
   Also in the case that the holder  25  is constructed as described here, as described above, the cleaning liquid supplied to the internal space  25   b  via the tube  11  and the supply port  25   c  flows toward the other side end where resistance is small (see an arrow B in  FIG. 4A ). Accordingly, air bubbles having entered into the cleaning liquid are prevented from stagnating in the internal space  25   b,  and are pushed out and discharged smoothly along the flow of the cleaning liquid to the outside through the air discharging hole  25   d.    
   Next, the second embodiment concerning the above-mentioned ink cartridges  17   a - 17   d  is described below with reference to  FIG. 5 .  FIG. 5  is a sectional view showing the internal structure of an ink cartridge  30  (ink tank) of the second embodiment. The ink cartridges  17   a - 17   d  described above stores solely the ink to be supplied to the recording heads  3   a - 3   d.  In contrast, the ink cartridge  30  of the second embodiment is constructed so as to store also the cleaning liquid in addition to the ink. 
   Specifically, the ink cartridge  30  is formed approximately in the shape of a hollow box. Its inside is partitioned into two spaces by a partition wall  31 . Then, one space stores the cleaning liquid, while the other space stores the ink. Further, in a side wall of each space, a cap  32  or  33  made of rubber is fitted by pressing. 
   When the ink cartridge  30  is mounted on the printer  1 , each of needles  34  and  37  connected to each of pumps  35  and  38  is pierced through each of the caps  32  and  33 , so that the cleaning liquid stored in the ink cartridge  30  is supplied to the sponge  13  via the needle  34 , the pump  35 , and the tube  11 . On the other hand, the ink stored in the ink cartridge  30  is supplied to each of the recording heads  3   a - 3   d  via the needle  37 , the pump  38 , and the tube  18 . According to the ink cartridge  30 , the cleaning liquid can be changed at the same time as the change of the ink cartridge  30 . Thus, time and effort associated with the change is reduced in comparison with the case that the ink and the cleaning liquid are changed separately. 
   Although the configuration has been described and illustrated on the basis of the embodiments, it can be readily understood that it is not limited to the above-mentioned embodiments, and numerous modifications and variations can be devised without departing from the scope. 
   For example, a pump may be provided in place of the valve  15  of the cleaning liquid supply unit  5  of the first embodiment described above, while a sub-tank capable of storing the cleaning liquid may be arranged between the pump and the holder  12  at a position above the sponge  13 , and while a sensor is arranged for detecting the amount of the cleaning liquid in the sub-tank. In this case, the pump is driven in accordance with the change in the amount of the cleaning liquid in the sub-tank detected by the sensor, so that a predetermined amount of cleaning liquid should be supplied to the sub-tank. Also in this alternative configuration, the cleaning liquid can stably be supplied to the sponge  13  in comparison with the case that the cleaning liquid is directly supplied from the first storage tank  10  to the sponge  13 . 
   Further, the above-mentioned embodiments have been described for the case that one or two air discharging holes  12   d  or  25   d  have been provided. However, the number of the air discharging holes is not limited to one or two, and may be three or more as long as air bubbles can be discharged. 
   Further, the ink cartridge  30  of the second embodiment has been described for the case that the inside of the ink cartridge  30  is partitioned up and down, so that the cleaning liquid is stored in the upper part while the ink is stored in the lower part. However, the cartridge may be partitioned into right and left parts. Further, the space for storing the cleaning liquid and the space for storing the ink may have different sizes with each other, depending on the consumption rate of the cleaning liquid and the consumption rate of the ink. Furthermore, the pumps  35  and  38  may have different performance. Such approaches reduce the amount of the cleaning liquid and the ink discarded uselessly. 
   As this description may be embodied in several forms without departing from the spirit of essential characteristics thereof, the present embodiment is therefore illustrative and not restrictive, since the scope is defined by the appended claims rather than by the description preceding them, and all changes that fall within metes and bounds of the claims, or equivalence of such metes and bounds thereof are therefore intended to be embraced by the claims.