Patent Publication Number: US-8523337-B2

Title: Image forming apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Rule 1.53(b) continuation of application Ser. No. 13/058,648, filed on Feb. 11, 2011 as a Section 371 national stage of International Application No. PCT/JP2009/064900 filed Aug. 20, 2009. 
    
    
     TECHNICAL FIELD 
     The present invention generally relates to liquid containers and image forming apparatuses. More specifically, the present invention relates to an image forming apparatus having a recording head configured to jet liquid drops and a liquid container used in the image forming apparatus. 
     BACKGROUND ART 
     As an image forming apparatus such as a printer, facsimile, copier, plotter, or a multifunctional peripheral including the printer, facsimile, copier, and the plotter, an inkjet recording apparatus is known. The inkjet recording apparatus is a liquid jet recording type image forming apparatus using a recording head configured to jet ink liquid drops. In this liquid jet recording type image forming apparatus, the ink liquid drops are jetted from the recording head onto a conveyed sheet so that image forming such as recording or printing is performed. 
     Hereinafter, the “image forming apparatus” means an apparatus configured to jet liquid onto a medium such as a paper, thread, fiber, leather, hides, metal, plastic, glass, wood, or ceramic so that images are formed. The image forming apparatus includes a mere liquid jetting apparatus. In addition, “image forming” means not only providing an image of characters, figures, or the like on the medium but also providing an image such as a pattern having no meaning on the medium. “Image forming” includes adherence of the liquid drops onto the medium. 
     Furthermore, “ink” is not limited to the recording liquid or the ink and any liquid that is a fluid when being jetted can be applied to the liquid such as fixing liquid. In addition, the “ink” includes a liquid whereby the image forming can be performed, such as a resist or DNA testing material. 
     In addition, “sheet” is not limited to a paper but includes an OHP sheet or leather. In other words, the sheet means a subject where the ink drops are adhered. The sheet includes a recorded medium, a recording medium, a recording paper, and a recording sheet. 
     As such an image forming apparatus (hereinafter “ink jet recording apparatus”), the following apparatuses have been known. In one apparatus, a sub-tank (buffer tank) configured to supply ink to a recording head is mounted on a carriage; a main ink cartridge (main tank) is provided at an apparatus main body; and the ink is supplied and supplemented from the main ink cartridge of the apparatus main body to the sub-tank. In another apparatus, an ink cartridge which is a liquid container exchangeable with a recording head is provided. 
     As described in Japanese Laid-Open Patent Application Publication No. 2003-1846 and Japanese Laid-Open Patent Application Publication No. 2003-89217, a sub-tank having an air opening valve configured to open an inside to the atmosphere has been suggested. In this suggested example, the air opening valve includes an opening part, a seal part, a spring mechanism, a pressing mechanism part, and a filter. The opening part corresponding to an air opening part is provided on an upper surface of the sub-tank. The seal part is configured to seal the opening part. The spring mechanism part presses the seal part to the opening part. The pressing mechanism part is configured to press the seal part into a sub-tank. The filter is provided outside the opening part. The air opening valve normally blocks an inside of the sub-tank from the atmosphere and is opened by the pressing mechanism part. The example where the filter is provided has been suggested in Japanese Laid-Open Patent Application Publication No. 2003-53985 and Japanese Patent 3087535. 
     However, in a case where the filter is simply provided at the air side opening of an air communicating path like the above-mentioned related art, foreign particles which cannot be caught by a filter member may enter the air opening path as they are so that of sealability of the valve member may be degraded. As a result of this, sealability of the liquid container may be degraded so that the air enters the container. Hence, it may not be possible to supply the ink stably. 
     DISCLOSURE OF THE INVENTION 
     Accordingly, embodiments of the present invention may provide a novel and useful liquid container and image forming apparatus solving one or more of the problems discussed above. 
     More specifically, the embodiments of the present invention may provide a liquid container whereby the probability of entry of foreign particles which cannot be caught by a filter member into an air opening path as they are is decreased so that degradation of sealability of a valve member is prevented, and an image forming apparatus having the liquid container. 
     One aspect of the present invention may be to provide an image forming apparatus, including a liquid jet head configured to eject a liquid droplet onto a recording medium; a container main body configured to receive liquid to be supplied to the liquid jet head from an liquid cartridge; an air opening mechanism configured to open and close an air opening path in the container main body, the air opening path being configured to open an inside of the container main body to the atmosphere, wherein the air opening mechanism includes a holding part including a valve body part configured to open and close the air opening path, and an opening member movably provided at the holding part, the opening member being configured to open and close the valve body part by pushed from an outside the container main body; wherein the opening member includes an air communicating path configured to be in communication with the atmosphere and forming a part of the air opening path; a filter member provided at an air side opening part of the air communicating path of the opening member, the filter member having an external surface coming in contact with the atmosphere; and an air room provided at an internal surface side of the filter member; and wherein an opening cross-sectional area of the air room in a direction perpendicular to an air flow-in direction is greater than an opening cross-sectional area of the air communicating path in a direction perpendicular to an air flow-in direction. 
     Another aspect of the present invention may be to provide an image forming apparatus, including a liquid jet head configured to eject a liquid droplet onto a recording medium; a container main body configured to receive liquid to be supplied to the liquid jet head from an liquid cartridge; and an air opening mechanism configured to open and close an air opening path in the container main body, the air opening path being configured to open an inside of the container main body to the atmosphere, wherein the air opening mechanism includes a holding part including a valve body part configured to open and close the air opening path, an opening member movably provided at the holding part, the opening member being configured to open and close the valve body part by pushed from an outside the container main body, an air communicating path formed between the holding part and the opening member so as to form a part of the air opening path, a filter holding member provided at an air side end part of the opening member, the filter holding member holding a filter member having an external surface coming in contact with the atmosphere, and an elastically deformable sealing member provided between the filter holding member and the holding part, the sealing member being configured to cover an external circumferential side of the opening member; and wherein the filter holding member includes an air room, to which an internal surface side of the filter member faces, and a small communicating path provided between the air room and the air communicating path, an opening cross-sectional area of the small communicating path in a direction perpendicular to an air flow-in direction being smaller than the opening cross-sectional area of the air room in a direction perpendicular to an air flow-in direction. 
     Another aspect of the present invention may be to provide an image forming apparatus, including a liquid jet head configured to eject a liquid droplet onto a recording medium; a container main body configured to receive liquid to be supplied to the liquid jet head from an liquid cartridge; and an air opening mechanism configured to open and close an air opening path in the container main body, the air opening path being configured to open an inside of the container main body to the atmosphere; wherein the air opening mechanism includes a holding part including a valve body part configured to open and close the air opening path, an opening member movably provided at the holding part, and the opening member being configured to open and close the valve body part by pushed from an outside the container main body, an air communicating path formed between the holding part and the opening member so as to form a part of the air opening path, and a filter member held by the holding part having an external surface coming in contact with the atmosphere; and wherein the holding part includes an air room configured to face an internal surface side of the filter member, and a small communicating path provided between the air room and the air communicating path, and an opening cross-sectional area of the small communication path in a direction perpendicular to an air flow-in direction being smaller than an opening cross-sectional area of the air room in a direction perpendicular to an air flow-in direction. 
     According to the liquid container of the embodiments of the present invention, an air room is provided between the filter member and the air communicating path or the communicating path which communicates with the air communicating path. The air room has an opening cross-sectional area greater than that of the air communicating path or the communicating path. Accordingly, the foreign particles which cannot be caught by the filter member stay in the air room. Hence, it is possible to prevent the foreign particles from entering the valve member so that bad operations of the valve member can be prevented or the probability of the bad operations can be reduced. 
     According to the image forming apparatus of the embodiments of the present invention, since the image forming apparatus has the above-mentioned liquid container, it is possible to prevent the sealability of the liquid container from being decreased and prevent the air from unnecessarily entering. Hence, it is possible to perform stable ink supplying without wasting the ink. 
     Additional objects and advantages of the embodiments will be set forth in part in the description which follows, and in part will become obvious from the description, or may be learned by practice of the invention. The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side structural view of an ink jet recording apparatus as an image forming apparatus of embodiments of the present invention having a liquid container (sub-tank) of a first embodiment of the present invention; 
         FIG. 2  is a partial plan view of a mechanism part of the ink jet recording apparatus; 
         FIG. 3  is a perspective view of a liquid container of the ink jet recording apparatus; 
         FIG. 4  is a side view of a sub-tank main body (container main body) of the ink jet recording apparatus; 
         FIG. 5  is an exploded perspective view of the sub-tank main body; 
         FIG. 6  is a plan cross-sectional view of an air opening mechanism of the liquid container; 
         FIG. 7  is an expanded cross-sectional view of an air opening mechanism of a liquid container of a second embodiment of the present invention; 
         FIG. 8  is a cross-sectional view of a filer holding member of the air opening mechanism; 
         FIG. 9  is a perspective view of the filter holding member; 
         FIG. 10  is an expanded cross-sectional view of an air opening mechanism of a liquid container of a third embodiment of the present invention; 
         FIG. 11  is an expanded cross-sectional view of an air opening mechanism of a liquid container of a fourth embodiment of the present invention; 
         FIG. 12  is a perspective view of the air opening mechanism of the liquid container of the fourth embodiment of the present invention; 
         FIG. 13  is an expanded cross-sectional view of the air opening mechanism of the liquid container of the fifth embodiment of the present invention; 
         FIG. 14  is a perspective view of a valve member; 
         FIG. 15  is a cross-sectional view for explaining the entry of ink into the air opening mechanism of the sub-tank; 
         FIG. 16  is a cross-sectional view for explaining leakage of the ink from the air opening mechanism of the sub-tank; 
         FIG. 17  is a side view for explaining a structure for preventing flow of the ink leaking from the air opening mechanism of the sub-tank; 
         FIG. 18  is an expanded perspective view of the periphery of a part where the recording head is attached to the carriage; 
         FIG. 19  is a partially expanded perspective view of  FIG. 18 ; 
         FIG. 20  is an expanded cross-sectional view of an air opening mechanism of a liquid container of a sixth embodiment of the present invention; 
         FIG. 21  is a perspective view of a valve member of the sixth embodiment of the present invention; 
         FIG. 22  is a cross-sectional view of a valve member of the sixth embodiment of the present invention; 
         FIG. 23  is a partial expanded view of a part A shown in  FIG. 22 ; 
         FIG. 24  is a schematic view for explaining an air opening mechanism driving mechanism configured to drive the air opening mechanism; 
         FIG. 25  is a schematic view for explaining operations of the air opening mechanism driving mechanism; 
         FIG. 26  is a schematic view for explaining an air opening mechanism driving mechanism of a comparative example; and 
         FIG. 27  is a schematic view for explaining operations of the air opening mechanism driving mechanism of the comparative example. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     A description is given below, with reference to the  FIG. 1  through  FIG. 27  of embodiments of the present invention. 
     First, an example of an image forming apparatus having a liquid container of a first embodiment of the present invention is discussed with reference to  FIG. 1  and  FIG. 2 . Here,  FIG. 1  is a schematic drawing showing the side view of an image forming apparatus according to one embodiment.  FIG. 2  is a schematic drawing showing the plan view of a main portion of the image forming apparatus according to one embodiment. 
     The image forming apparatus of this embodiment is a serial type image forming apparatus and includes a main guide rod  31  and a sub-guide rod  32  which are supported at their lateral ends by side boards  21 A,  21 B. The main guide rod  31  and the sub-guide rod  32  slidably hold a carriage  33 . The carriage  33  is moved to scan by a main scanning motor (not shown in  FIG. 1  and  FIG. 2 ) via a timing belt in the direction of an arrow (main scanning direction of the carriage) shown in  FIG. 2 . 
     The carriage  33  carries a liquid ejecting head including ejecting heads  34   a  and  34   b  which eject ink liquids of yellow (Y), cyan (C), magenta (M), and black (K). Plural nozzles are arranged in rows, and the rows of the nozzles are disposed a sub-scanning direction, which is orthogonal to the main scanning direction of the carriage. The ink liquid ejecting direction is downward. 
     The ejecting heads  34   a  and  34   b  each include two rows of nozzles. The ejecting head  34   a  ejects black (K) ink liquid from nozzles arranged in one row, and cyan (C) ink liquid from nozzles arranged in a second row. The ejecting head  34   b  ejects magenta (M) ink liquid from nozzles arranged in one row, and yellow (Y) ink liquid from nozzles arranged in a second row. 
     Sub-tanks  35   a ,  35   b , which hold in reserve the four color ink liquids corresponding to the ink liquids ejected from the ejecting heads  34   a  and  34   b , are mounted on the carriage  33 . The ink liquids are delivered from ink cartridges  10 Y,  10 M,  10 C, and  10 K to the sub-tanks  35   a  and  35   b  by a pump unit  24  via delivering lines  36 . The ink cartridges  10 Y,  10 M,  10 C, and  10 K are detachably attached to a cartridge mounting portion  4 . 
     The image forming apparatus of the present embodiment includes a crescent-shaped roller (sheet feeding roller)  43  and a dividing pad  44  which is biased toward the roller  43 . Sheets  42  are loaded on a sheet loading portion (pressing plate)  41 , which is composed of a pressure plate of a sheet feeding tray  2 . The roller  43  and the dividing pad  44  are disposed as a sheet feeding portion that feeds the sheets  42  one by one from the sheet loading portion  41 . 
     The image forming apparatus of this embodiment includes a guide portion  45  which guides the sheet  42 , a counter roller  46 , a guide portion  47 , a holding portion  48  which includes a press roller  49 , and a feeding belt  51  which holds the sheet  42  by electrostatic attraction and feeds the sheet  42  relative to the position of the ejecting heads  34   a  and  34   b . The feeding belt  51  is disposed as a feeding portion. 
     The feeding belt  51  is a looped belt, which is placed in tension about a feeding roller  52  and a tension roller  53 , and rotates in a belt conveyance direction (sub-scanning direction), i.e. clockwise direction in  FIG. 1 . The image forming apparatus of this embodiment includes a charged roller (charging part)  56  which is electrostatically charged and charges the feeding belt  51 . The charged roller  56  contacts the surface of the feeding belt  51 , and is rotated by the feeding belt  51 . The feeding belt  51  is rotated in the sub-scanning direction shown in  FIG. 2  by the feeding roller  52 , which is rotated by a sub-scanning motor (not shown in  FIG. 2 ). 
     The image forming apparatus of this embodiment includes, as a sheet discharge part, a separating tooth  61 , which separates the sheet  42  from the feeding belt  51 , a large sheet discharge roller  62 , a small sheet discharge roller  63 , and a tray  3  disposed underneath the large sheet discharge roller  62 . 
     The image forming apparatus of this embodiment includes a reversing unit  71  which is detachably attached to a main body  1 . The reversing unit  71  receives the sheet  42  which is fed by reverse rotation of the feeding belt  51 , and then reverses and feeds the sheet  42  between the feeding belt  51  and the counter roller  46 . The reversing unit  71  includes a manual sheet feed tray  72  on its top surface. 
     Further, the image forming apparatus of the present embodiment includes a maintaining recovering mechanism  81  that maintains the performance of the ejecting heads  34   a  and  34   b  by a restoring process. The maintaining recovering mechanism  81  is disposed in a non-recording area located at one end of the main scanning direction of the carriage  33 . The maintaining recovering mechanism  81  includes caps  82 A,  82 B which cap the nozzle surfaces of the ejecting heads  34   a ,  34   b  respectively, a wiper blade (a wiper member)  83  which wipes the nozzle surfaces, a liquid receiving pan  84  which receives a liquid that does not contribute to the recording and is ejected from the ejecting heads  34   a ,  34   b  in order to remove attached thickened recording liquid, and a carriage lock  87  which locks the carriage  33 . A waste liquid tank  100  is disposed under the maintaining recovering mechanism  81  and holds waste liquid generated by maintaining/recovering operations. The waste liquid tank  100  is replaceable relative to the main body  1 . 
     Referring again to  FIG. 2 , the image forming apparatus of this embodiment includes an idle-ejected liquid receiving pan  88  which is disposed in a non-recording area located at the other end of the main scanning direction of the carriage  33 . The liquid receiving pan  88  receives an idle-ejected liquid that does not contribute to the recording and is ejected from the ejecting heads  34   a ,  34   b  in order to remove attached thickened recording liquid. The liquid receiving pan  88  includes an opening  89  provided along the row of the nozzles of the ejecting head  34   a  (or  34   b ). 
     The image forming apparatus as described above feeds the sheets  42  one by one from the sheet feeding tray  2 , and guides the sheet  42  upward along the guide portion  45 . The sheet  42  is fed in between the belt  51  and the counter roller  46 , guided by the guide portion  47 , and is then pressed to the feeding belt  51  by the press roller  49  so as to turn round approximately 90 degrees from the guide portion  45 . 
     The image forming apparatus applies an alternating voltage of plus voltage and minus voltage to the charged roller  56  while the sheet  42  is guided along the feeding belt  51 . Thus, the alternating charge distribution of plus charges and minus charges of predetermined length is applied to the feeding belt  51  in the sub-scanning direction, i.e. the rotational direction of the feeding belt  51 . When the sheet  42  is fed by the feeding belt  51  with the alternating charge distribution, the sheet  42  is held electrostatically to the feeding belt  51  and fed in the sub-scanning direction by the rotation of the feeding belt  51 . 
     The image forming apparatus causes the carriage  33  to scan, and activates the ejecting heads  34   a  and  34   b  in response to an image signal. Thus, the sheet  42  is recorded one line at a time by the ink liquid ejected from the ejecting heads  34   a  and  34   b . The image forming apparatus ends recording of the sheet  42  and ejects the sheet  42  to the ejecting tray  3  when the image forming apparatus receives a recording completion signal or a signal indicating that the rear end of the sheet  42  reaches the recording area. 
     The image forming apparatus moves the carriage  33  to a home position at which the ejecting heads  34   a  and  34   b  oppose the maintaining recovering mechanism  81  when the image forming apparatus maintains and recovers the nozzles of the ejecting heads  34   a ,  34   b . The image forming apparatus suctions the ink liquid in the ejecting heads  34   a  and  34   b  with the caps  82  capping the nozzle surfaces of the ejecting heads  34   a  and  34   b , and idle-ejects the liquid which does not contribute to the recording in order to maintain the ejecting heads  34   a  and  34   b . Thus, the image forming apparatus can provide image forming with stable ejecting. 
     Next, a liquid container (sub-tank) of the first embodiment of the present invention is discussed with reference to  FIG. 3  through  FIG. 5 . Here,  FIG. 3  is a perspective view of a head part.  FIG. 4  is a side view of the head part.  FIG. 5  is an exploded perspective view of the sub-tank main body. 
     The head part includes a single recording head  34 , a sub-tank  35 , and a filter unit  101 . The sub-tank  35  is configured to supply different color inks to the single recording head  34  and two nozzle rows. The filter unit  101  is provided between the sub-tank  35  and the recording head  34 . Flexible cables  102 A and  102 B are lead out from the recording head  34 . The flexible cables  102 A and  102 B are configured to transfer signals for driving an actuator part of the recording head  34 . 
     In the sub-tank  35 , two ink receiving parts  201 A, as liquid receiving parts, are formed one at each side of a container main body (tank main body  202 ). Film members  211  (flexible film members) having flexibility are attached over the openings of the ink receiving parts  201 A by adhering or melting the film members  211  so that a sealing state is achieved. In addition, inside the ink receiving part  201 A, a spring  212  as an elastic member configured to bias the film member  211  outward is provided between the tank main body  202  and the film member  211 . The film member  211  and the spring  212  form a negative pressure generating mechanism. In addition, negative pressure detecting levers  213 A/ 213 B are oscillateably provided at the tank main body  202  so as to deform based on deformation of the corresponding film members  211 . 
     Air opening paths  203  are formed at an upper part of the tank main body  202  so as to open the ink receiving parts  201 A to the atmosphere. Air opening mechanisms  204 A,  204 B are provided at the upper part of the tank main body  202  so as to open and close the corresponding air opening paths  203 . 
     Ink supply opening parts  207  are formed in the tank main body  202  so as to supply the inks to the corresponding ink receiving parts  201 . The delivering lines  36  are connected to the ink supply opening parts  207  by a connecting member  208 . In addition, two detecting electrodes  216  are provided in the upper part of the container main body  202  so as to detect the ink situated in each of the ink receiving parts  201 A. 
     In a bottom surface of the tank main body  202 , supply openings  217 A,  217 B are formed at edge parts of the ink receiving parts  201 A so as to individually supply the ink from the ink receiving parts  201 A to the filter unit  101 . In addition, expanding parts  218 A,  218 B are provided one in each of the ink receiving parts  201 A so as to be expanded into the other receiving part  201 A, so that the supply openings  217 A,  217 B is situated in the center parts. 
     Next, an air opening mechanism  204  in the sub-tank  35  is discussed with reference to  FIG. 6 . Here,  FIG. 6(   a ) is a plan cross-sectional view of the air opening mechanism part and  FIG. 6(   b ) is a partial view showing another example. 
     The air opening mechanisms  204 A and  204 B are in communication with the corresponding air opening paths  203  at an upper side part of the tank main body  202 . Hollow holder attaching parts  221  forming air opening paths  220  communicating inside and outside of the tank main body  202  with each other are provided in a body with the air opening mechanism  204 . Cylindrical shaped holders  222  are attached to the holder attaching parts  221 . 
     Furthermore, a seat member (seat)  223  is sandwiched and held by an outside end surface of the holder attaching part  221  and an inside step part of the holder  222 . Balls  224  are received inside the air opening paths  220 , as valves pressed and biased in a direction where the seat members are pushed by coil springs  225  as pressing parts. The seat  223 , the ball  224 , and the coil spring  225  form a valve body part (valve mechanism) configured to open and close the air opening path  220 . The holding part which holds this valve body part includes the holder  222  and the holder attaching part  221 .  FIG. 6  shows where the air opening mechanism  204 A opens the corresponding air opening path  220  and the air opening mechanism  204 B closes the corresponding air opening path  220 . 
     In the holder  222  forming a holding part which holds the valve body part, an opening member  241  is movably provided. The opening member  241  is configured to open and close the atmosphere opening path  220  by pressing the valve  224  of the valve body part from the outside. At the time of atmosphere opening, the opening member  241  is pressed from the outside (the main body  1  side) by a pressing member  401 . 
     The air communicating path  242  is formed inside the opening member  241 . The air communicating path  242  is in communication with the atmosphere and forms a part of the air opening path  220 . In addition, as shown in  FIG. 6(   a ), horizontal holes  242   a  are provided in the opening member  241  so as to be in communication with the air opening paths  242 . The air opening path  220  and the air communicating path  242  inside the opening member  241  are in communication with each other via the horizontal hole  242   a  and an air room  244   b . In a case where the air communicating path  242  is formed only in an axial direction as shown in  FIG. 6(   b ), an air path as a concavoconvex surface may be formed at a part where the opening member  241  and the ball  224  come in contact with each other, so that the air communicating path  242  may not be sealed completely by the ball  224 . 
     A filter member  243  is provided at an air side opening part of the air communicating path  242  of the opening member  241 . The filter member  243  has an external surface coming in contact with the atmosphere. An air room  244  is provided at an internal surface side of the filter member  243 . The air room  244  has an opening cross-sectional area in a direction perpendicular to an air flow-in direction. The opening cross-sectional area of the air room  244  is greater than an opening cross-sectional area of the air communicating path  242 . 
     As the filter member  243 , for example, a metal filter mesh, a compressed sintered filter made of metal fibers, an electroformed metal filter, a foam filter having a porous structure, or the like can be used. In addition, as the filter member  243 , a filter having a capillary effect where the air can pass but liquid does not pass in a case of a pressure less than a designated pressure, may be used. 
     An elastically deformable sealing member  245  is provided between the opening member  241  and the holder  222 . The sealing member  245  is configured to cover an external circumferential side of the opening member  241 . The sealing member  245  blocks a gap formed between the opening member  241  and the holder  222  from the atmosphere. The sealing member  245  is configured to deform based on a moving action of the opening member  241 . 
     Thus, the air room  244  is provided at the internal surface side of the filter member  243 . The air room  244  has the opening cross-sectional area in the direction perpendicular to the air flow-in direction. The opening cross-sectional area of the air room  244  is greater than the opening cross-sectional area of the air communicating path  242 . Hence, at the time of the air introduction from the outside, after the air is introduced and diffused in the air room  244 , the air is introduced to the air communicating path  242  whose inside is narrow. Therefore, even if a large foreign particle which should be filtered by the filter member  243  passed the filter member  243 , the foreign particle may stay in the space (the air room  244 ). Accordingly, the probability of a foreign particle entering further inside via the air communicating path  242  and the foreign particle being sandwiched at the valve body part (between the seat  223  and the valve  224 ) so that sealability of the valve body part may be degraded, may be decreased. As a result of this, it is possible to prevent the sealability of the sub-tank being degraded and the air entering the sub-tank unnecessarily so that the ink cannot be supplied stably. 
     In this case, as shown in  FIG. 6(   b ), one more air room in front of the valve, namely the air room  244   b  in the sealing member  245  is provided. The volume of the air room  244   b  can be made greater than that of the air room  244 . Therefore, even if a large foreign particle which should be filtered by the filter member  243  passes the filter member  243 , the probability of the foreign particle entering further inside via the air communicating path  242  and the foreign particle being sandwiched at the valve body part (between the seat  223  and the valve  224 ) so that sealability of the valve body part may be degraded, may be decreased. 
     Next, a liquid container of a second embodiment of the present invention is discussed with reference to  FIG. 7  through  FIG. 9 .  FIG. 7  is an expanded cross-sectional view of an air opening mechanism of the liquid container of the second embodiment of the present invention.  FIG. 8  is a cross-sectional view of a filer holding member of the air opening mechanism.  FIG. 9  is a perspective view of the filer holding member. In  FIG. 7  through  FIG. 9 , parts that are the same as the parts shown in  FIG. 1  through  FIG. 8  of the first embodiment of the present invention are given the same reference numerals, and their explanation is omitted. 
     In this example, the opening member  241  is movably provided in the holder  222 . The holder  222  is attached to the holder attaching parts  221 . A rear end of the holder  222  is engaged with an engaging part of the container main body  202 . The opening member  241  is configured to open and close the ball  224  forming a valve body part from the outside. The air communicating path  242  forming a part of the air opening path  220  is formed between the holder  222  and the opening member  241 . 
     A filter holding member  250  is provided at the air side head end part of the opening member  241  by press-fitting. The filter member  243  is held at the filter holding member  250 . The filter member  243  has an external surface coming in contact with the atmosphere. The air room  244  and a communicating path  246  are provided in the filter holding member  250 . An internal surface side of the filter member  243  faces the air room  244 . The communicating path  246  is provided between the air room  244  and the air communicating path  242 . The communicating path  246  has an opening cross-sectional area in a direction perpendicular to an air flow-in direction, smaller than that of the air room  244 . Although the filter member  243  is fixed by thermal adhesion in this example, the filter member  243  may be adhered by ultrasonic adhesion. 
     A sealing member  251  having a bellows configuration is provided between the filter holding member  250  and the holder  222  forming the holding member. The sealing member  251  can be elastically deformed. The sealing member  251  is configured to cover the external circumferential side of the opening member  241 . The sealing member  251  may be made of, for example, a thin rubber material, an elastomer resin material, or the like. In addition, the filter holding member  250  and the sealing member  251  may be formed in a body. When the filter holding member  250  and the sealing member  251  are formed in a body, for example, a dual molding method by insert or outsert molding can be used. The filter adhesion may be performed before or after unified molding. The sealing member  251  may be formed by the unified molding using the same material as that of the filter holding member  250 . In this case, the filter member  243  is made by insert molding. 
     Thus, in this embodiment as well as the first embodiment, the air room  244  is provided at the internal surface side of the filter member  243 . The air room  244  and the air communicating path  242  are in communication with each other by the communicating path  246  having the opening cross-sectional area in the direction perpendicular to the air flow-in direction smaller than that of the air room  244 . Hence, at the time of the air introduction from the outside, after the air is introduced and diffused in the air room  244 , the air is introduced to the air communicating path  242  whose inside is narrow. Therefore, even if a large foreign particle which should be filtered by the filter member  243  passes the filter member  243 , the foreign particle may stay in the space (the air room  244 ). Accordingly, the probability of a foreign particle entering further inside via the air communicating path  242  and the foreign particle being sandwiched at the valve body part (between the seat  223  and the ball  224 ) so that sealability of the valve body part may be degraded, may be decreased. As a result of this, it is possible to prevent the sealability of the sub-tank being degraded and the air entering the sub-tank  35  unnecessarily so that the ink cannot be supplied stably. 
     Furthermore, the air room  244   b  in communication with the air room  244  can be provided inside the sealing member  251 . The volume of the air room  244   b  can be made greater than that of the air room  244 . Therefore, even if a large foreign particle which should be filtered by the filter member  243  passes the filter member  243 , the probability of the foreign particle entering further inside via the air communicating path  242  and the foreign particle being sandwiched at the valve body part (between the seat  223  and the valve  224 ) so that sealability of the valve body part may be degraded, may be decreased. 
     According to the structure in this embodiment, it is possible to make configurations of components themselves simple and to easily clean the components before assembling. If the components are not well cleaned, foreign particles may be adhered to the components. The foreign particles may move and be sandwiched by the valve body part so that sealability may be degraded. Hence, by improving the cleanability, it is possible to further improve maintaining the sealability. 
     Next, a liquid container of a third embodiment of the present invention is discussed with reference to  FIG. 10 .  FIG. 10  is an expanded cross-sectional view of an air opening mechanism of the liquid container of the third embodiment of the present invention. 
     Here, an elastically deformable sealing member  251  having a drum-shaped configuration is provided between the filter holding member  250  and the holder  222  forming the holding part so as to cover the external circumferential side of the opening member  241 . An inside of the sealing member  251  is used as the air room  244   b  having a large volume and communicating with the air room  244 . The action and the effect of this embodiment is the same as the second embodiment. 
     Next, a liquid container of a fourth embodiment of the present invention is discussed with reference to  FIG. 11  and  FIG. 12 .  FIG. 11  is an expanded cross-sectional view of an air opening mechanism of the liquid container of the fourth embodiment of the present invention.  FIG. 12  is an exploded perspective view of the air opening mechanism of the liquid container of the fourth embodiment of the present invention. In  FIG. 11  through  FIG. 12 , parts that are the same as the parts shown in  FIG. 1  through  FIG. 8  of the first embodiment of the present invention are given the same reference numerals, and their explanation is omitted. 
     Here, a packing as the seat member  223  is provided inside the holder  222  attached to the holder attaching part  221 . The seat member  223  and a valve body part  262  form a valve part. The valve part and an opening member part  263  are formed in a body so that a valve member  261  is formed. The opening member part  263  is configured to open the valve part with the seat member  223  by being pressed from the outside. The valve member  261  is movably provided. The air communicating path  242  forming a part of the air opening path  220  is formed between the holder  222  and a groove  262   a  of the opening member part  263  of the valve member  261 . 
     Here, the valve body part  262  of the valve member  261  is pressed to the seat  223  by a force of the spring  225  so that air blocking is performed. 
     A filter member  243  having an external surface coming in contact with the atmosphere is held by the holder  222  as the holding part. An air room  244  and a communicating path  246  are provided in the holder  222 . An internal surface side of the filter member  243  faces the air room  244 . The communicating path  246  is provided between the air room  244  and the air communicating path  242  and has an opening cross-sectional area in a direction perpendicular to an air flow-in direction. The opening cross-sectional area of the communicating path  246  is smaller than an opening cross-sectional area of the air room  244 . The communicating path  246  faces the air communicating path  242  in a direction perpendicular to a moving direction of the opening member  263 . The air room  244  has an opening part where the filter member  243  is provided. The opening part is provided in a vertical downward direction. 
     A cap member  265  as an elastically deformable sealing member is provided at the holder  222 . The cap member  265  is configured to cover the opening member part  263  of the valve member  261 . 
     As shown in  FIG. 12 , the holder  222  is a single member configured to receive two valve members  261  corresponding to two air opening mechanisms  204 A and  204 B. The holder  222  is sealed by the cap member  265  common to each of the air communicating paths  242  (air opening path  220 ). In addition, a seal member  266  is sandwiched between the holder  222  and the holder attaching part  221 . Engaging parts  222   a  engaged with the holder attaching part  221  are provided in the holder  222 . 
     Thus, in this embodiment as well as the first embodiment, the air room  244  is provided at the internal surface side of the filter member  243 . The air room  244  and the air communicating path  242  are in communication with each other by the communicating path  246  having the opening cross-sectional area in the direction perpendicular to the air flow-in direction smaller than that of the air room  244 . Hence, at the time of the air introduction from the outside, after the air is introduced and diffused in the air room  244 , the air is introduced to the air communicating path  242  whose inside is narrow. Therefore, even if a large foreign particle which should be filtered by the filter member  243  passes the filter member  243 , the foreign particle may stay in the space (the air room  244 ). Accordingly, the probability of the foreign particle entering further inside via the air communicating path  242  and the foreign particle being sandwiched at the valve body part (between the seat member  223  and the valve body part  262 ) so that sealability of the valve body part  262  may be degraded, may be decreased. As a result of this, it is possible to prevent the sealability of the sub-tank being degraded and the air entering the sub-tank  35  unnecessarily so that the ink cannot be supplied stably. 
     Next, a liquid container of a fifth embodiment of the present invention is discussed with reference to  FIG. 13  and  FIG. 14 .  FIG. 13  is an expanded cross-sectional view of the air opening mechanism  204  of the liquid container of the fifth embodiment of the present invention.  FIG. 14  is a perspective view of a valve member  261 . 
     In this embodiment as well as the fourth embodiment, a packing as the seat member  223  is provided inside the holder  222  attached to the holder attaching part  221 . The seat member  223  and a valve body part  262  form a valve part. The valve part and an opening member part  263  are formed in a body so that the valve member  261  is formed. The opening member part  263  is configured to open the valve part with the seat member  223  by being pressed from the outside. The valve member  261  is movably provided. The air communicating path  242  forming a part of the air opening path  220  is formed between the holder  222  and a groove  263   a  of the opening member part  263  of the valve member  261 . 
     Here, the valve body part  262  of the valve member  261  is pressed to the seat member  223  by a force of the coil spring  225  so that air blocking is performed. 
     A filter member  243  having an external surface coming in contact with the atmosphere is held by the holder  222  as the holding part. An air room  244  and a communicating path  246  are provided at the holder  222 . An internal surface side of the filter member  243  faces the air room  244 . The communicating path  246  is provided between the air room  244  and the air communicating path  242  and has an opening cross-sectional area in a direction perpendicular to an air flow-in direction. The opening cross-sectional area of the communicating path  246  is smaller than an opening cross-sectional area of the air room  244 . 
     A cap member  265  as an elastically deformable sealing member is provided at the holder  222 . The cap member  265  is configured to cover the opening member part  263  of the valve member  261 . 
     In this embodiment, the communicating path  246  is provided in a direction along a moving direction of the opening member part  263  (valve member  261 ) relative to the air communicating path  242 . The communicating path  246  is in communication with the air communicating path  242  via the space (air opening)  267  formed between the holder  222  and the cap member  265  as the sealing member. The air room  244  has an opening part where the filter member  243  is provided. The opening part is provided in a vertical downward direction. 
     Thus, by providing the communicating path  246  which connects the air communicating path  242  and the air room  244  to each other in the direction along the moving direction of the opening member  263 , it is possible to securely prevent dust from entering from the air room  244  to the air communicating path  242 . 
     In the fourth embodiment and the fifth embodiment, by the air communicating path  242  and the air room  244 , connected to the atmosphere, being in communication with each other via the communicating path  246 , even if the ink leaks into the air opening mechanism  204 , it is possible to reduce the flow-out of the ink to the outside. In addition, since the opening part where the filter member  243  is provided is provided in a vertical downward direction in the air room  244  communicating with the outside via the filter member  243 , it is possible to drop the ink downward in the vertical direction even if the ink enters inside the air room  244 . Hence, it is possible to prevent the leaking ink from easily entering other parts. 
     Supply operations of moving the ink to the sub-tank  35  are performed while the ink liquid surface height is detected by the detecting electrodes  216 . However, there may be a case where the ink liquid surface height cannot be detected by the detecting electrodes  216 , namely a case where the ink which is being used does not have an expected resistance value. In this case, if excessive ink is supplied to the sub-tank  35 , the ink may enter the air opening mechanism  204  from the inside of the sub-tank  35 . 
     Here, as shown in  FIG. 15 , when then valve member  261  of the air opening mechanism  204  is closed, the entered ink stays at the internal side held by the seat member  223  and does not further flow. However, in this state when the valve member  261  is pushed, as shown in  FIG. 16 , for supplying the ink to the sub-tank  35 , the seat member  223  and the valve body part  262  are separated so that, as indicated by an arrow in  FIG. 16 , ink  300  flows into the a space  267  via the groove  263   a  of the valve member  261 . In addition, the ink flows from the space  267  to the air room  244  via the communicating path  246  so as to drop downward in the vertical direction via the filter member  243 . 
     Because of this, the ink  300  leaking from the air opening mechanism  204  of the sub-tank  35  is not scattered and can be gathered in a narrow area. It is possible to easily specify a portion where the ink further leaking is stored. Hence, it is possible to easily prevent the leaking ink from entering the board side of the driver IC provided at the flexible cables (FPC)  102 A,  102 B. 
     Next, a structure for preventing the ink leaking from the air opening mechanism  204  of the sub-tank  35  is discussed with reference to  FIG. 17  through  FIG. 19 .  FIG. 17  is a side view where the recording head  34  in a body with the sub-tank  35  is mounted on the carriage  33 .  FIG. 18  is an expanded perspective view of the periphery of a part where the recording (ejecting) head  34  is mounted on the carriage  33 .  FIG. 19  is a partially expanded perspective view of  FIG. 18 . 
     An adjusting member  81  for attaching the recording head  34  to the carriage  33  is provided at the recording head  34 . The adjusting member  81  and the carriage  33  are connected to each other by, for example, a UV adhesive so that recording head  34  is attached to the carriage  33 . 
     Here, the ink  300  dropping from the air opening mechanism  204  of the sub-tank  35  drops on the adjusting member  81 . In order to prevent the dropped ink  300  from entering inside the carriage  33 , a rib  82  having a block configuration is provided inside the carriage  33 . With this structure, the dropped ink  300  does not enter the FPC  102 A,  102 B of the recording head  34 . In addition, a piercing hole  83  is provided in the vicinity of a portion where the ink in the carriage  33  drops. The leaking ink  300  flows out from the piercing hole  83  to the outside. 
     A rib  81   a  is provided at the adjusting member  81  in order to prevent the leaked ink  300  from entering the recording head  34  side. 
     By providing a part configured to detect the ink at the portion where the leaked ink  300  drops, it is possible to detect that the ink liquid surface detection of the sub-tank  35  does not effectively function and detect an abnormality of the sub-tank  35 . In other words, by the ink flowing out and entering the air opening mechanism  204  of the sub-tank  35 , it is possible to give notice to the user of the abnormality that ink is overflowing and the necessity of repairing. 
     Next, a sixth embodiment of the present invention is discussed with reference to  FIG. 20  through  FIG. 23 .  FIG. 20  is an expanded cross-sectional view of an air opening mechanism  204  of a liquid container of the sixth embodiment of the present invention.  FIG. 21  is a perspective view of a valve member of the sixth embodiment of the present invention.  FIG. 22  is a cross-sectional view of a valve member of the sixth embodiment of the present invention.  FIG. 23  is a partial expanded view of a part A shown in  FIG. 22 . 
     In this embodiment, a valve member  271  is used instead of the valve member  261  of the fifth embodiment. The valve member  271 , as shown in  FIG. 21  through  FIG. 23 , is formed by double molding a valve pin  273  including a seat holding part  272  and a groove  273   a  in an external circumferential surface axial direction corresponding to the opening member and a seat  274  made of elastomer. 
     In this case, by moving of the valve member  271 , a gap is formed between the seat  274  and the step part of the holder  222  so that the air opening path  220  is opened. When the seat  274  comes in contact with the step part of the holder  222 , the air opening path  220  is blocked. 
     With this structure, it is possible to reduce the number of the components. 
     Next, an air opening mechanism driving mechanism  400  configured to move the opening member of the air opening mechanism  204  is discussed with reference to  FIG. 24 .  FIG. 24  is a schematic view for explaining the air opening mechanism driving mechanism  400  configured to drive the air opening mechanism  204 . It should be noted that, although the structure of the air opening mechanism  204  is discussed in the sixth embodiment, there is no limitation of the structure of the air opening mechanism  204 . 
     In the air opening driving mechanism  400 , a pressing member  401  is movably held at the carriage  33 . The pressing member  401  is configured to press the opening member part  263  of the valve member  261  of the air opening mechanism  204 . Here, two pressing members  401  are provided in a body corresponding to two air opening mechanisms  204 A,  204 B of a single sub-tank  35 . The pressing member  401  is held in a non-pressing position by a spring member (not shown). 
     On the other hand, a solenoid  402  is provided at an apparatus main body side. An end part of a first lever  405  is oscillateably engaged with a plunger  403  of the solenoid  402  by a pin member  406 . Another end part of the first lever  405  is pivotally supported at a spindle  404 . In addition, an end part of a second lever  407  is oscillateably and pivotally supported at the spindle  404 . Another end part of the second lever  407  can come in contact with the pressing member  401 . A spring member  408  is provided between the first lever  405  and the second lever  407 . The spring member  408  is configured to hold the first lever  405  and the second lever  407  with a designated positional relationship. 
     In the air opening driving mechanism  400  having the above-mentioned structure, when the air opening mechanism  204  is not opened, as shown in  FIG. 25(   a ), the second lever  407  does not come in contact with the pressing member  401 . In this state, by driving the solenoid  402  so that the plunger  403  is pulled in a direction indicated by an arrow A, the first lever  405  is oscillated in a direction indicated by an arrow B and the first lever  405  is oscillated. As a result of this, as shown in  FIG. 25(   b ), the second lever  407  pushes the pressing member  401  due to the first lever  405  so that the engaging part  401   a  of the pressing member  401  comes in contact with the carriage  33 . 
     At this time, as shown in  FIG. 25(   c ), the amount of oscillation of the first lever  405  is fixed by the engaging part  403   a  of the plunger  403  of the solenoid  402  coming in contact with the solenoid  402 . Here, in a case where an excessive load is generated when the pressing member  401  comes in contact with the carriage  33  so that a force indicated by an arrow C is applied to the second lever  407 , the excessive load is offset by a biasing force of the spring member  408 . A force at the time when the pressing member  401  comes in contact is held fixed. 
     Thus, the pressing member  401  can come in contact with the carriage  33  by dividing the lever member provided between the solenoid  402  and the pressing member  401  into the first lever  405  and the second lever  407  and providing the spring member between the first lever  405  and the second lever  407 . As a result of this, a gap between the components can be made zero, a necessary pushing amount can be reduced, and the difference of opening capabilities of two air opening mechanisms  204 A,  204 B of a single sub-tank  35  can be made zero so that reliability of the air opening capabilities can be improved. Furthermore, operations loss of the solenoid can be reduced. 
       FIG. 26  is a schematic view for explaining an air opening mechanism driving mechanism of a comparative example. 
     In an air opening driving mechanism  600  of the comparative example, an end part of a lever  605  is engaged with the plunger  603  of the solenoid  602 . The lever  605  is oscillateably and pivotally supported at a spindle  604 . The pressing member  601  is pressed by another end of the lever  605 . 
     In a structure of the comparative example, as shown in  FIG. 27 , in order to prevent the excessive load from being applied to the lever  605 , the carriage  33 , and the head  34  (sub-tank  35 ) at the time of air opening, it is necessary to provide a gap  610 . The gap  610  is formed by considering unevenness of components in the carriage  33  and the lever  605  when the pressing member  601  is in the pressing position (air opening position). 
     In other words, when the excessive load is applied to the lever  605 , the lever  605  is deformed. In addition, when the excessive load is applied to the carriage  33  and the head  34  via the sub-tank  35 , the jetting position of the ink is changed. In this case, if rigidity is increased in order to prevent deformation of the lever  605 , the plunger  603  of the solenoid  602  stops with a gap so that the air opening operations force is reduced. In addition, since it is necessary to make a design where a sealing force of the air opening mechanism is decreased corresponding to the reduced operations force, sealability of the sub-tank  35  is decreased so that degradation of the ink is induced. Furthermore, if plural sub-tanks  35  are opened to the atmosphere as shown in  FIG. 27(   b ), since the gap  610  is provided, the pressing member  601  may be inclined so that a portion where the air opening is available and a position where the air opening is not available may be generated left and right. As a result of this, it may be necessary to increase the gap including unevenness of the components and a pushing amount in a direction where the opening amount is small. This may cause the need for maximization of the apparatus. 
     On the other hand, in the air opening driving mechanism  400  discussed above, the excessive load is offset by the spring member. Therefore, when the pressing member  401  is in a pressing position, the gap with the carriage  33  is made zero so that it is possible to make the pressing member  401  come in contact with the carriage  33 . As a result of this, the necessary pushing amount is reduced. In addition, the difference of opening capabilities of two air opening mechanisms of a single sub-tank  35  can be made zero so that the reliability of the air opening capabilities can be improved. Furthermore, operations loss of the solenoid can be reduced. 
     The image forming apparatuses of the embodiments of the present invention are not limited to have a printer single function but may have multiple functions such as a printer/facsimile/copier. Accordingly, the liquid container of the embodiment of the present invention may be applied such an image forming apparatus. 
     All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority or inferiority of the invention. Although the embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention. 
     This patent application is based upon and claims the benefit of priority of Japanese Patent Application No. 2008-225246 filed on Sep. 2, 2008, Japanese Patent Application No. 2009-47125 filed on Feb. 27, 2009, and Japanese Patent Application No. 2009-72823 filed on Mar. 24, 2009, the entire contents of which are incorporated herein by reference.