Patent Abstract:
A developer supply container for an image forming apparatus includes a container shell; a developer accommodation bag contained in the container shell; a developer discharging path for discharging the developer from the bag an outside of the developer supply container; an air fluid communication path for fluid communication between inside and outside of the container shell; and a maintaining portion sealing the air fluid communication path to maintain a pressure inside the container shell in a negative pressure state, wherein the developer accommodation bag deforms to discharge the developer, by the maintaining portion opening the air fluid communication path to permit air to enter the container shell through the air fluid communication path.

Full Description:
FIELD OF THE INVENTION AND RELATED ART 
       [0001]    The present invention relates to an image forming apparatus, such as a laser beam printer, an LED printer, a copying machine, etc., which employs a developer supply container, which is removably installable in an image forming apparatus, to supply the image forming apparatus with developer. 
         [0002]    An electrophotographic image forming apparatus such as an electrophotographic printer uses developer made up of microscopic particles. Developer is consumed for image formation. Thus, as an electrophotographic image forming apparatus runs out of developer, it has to be replenished with developer with the use of a developer supply container. 
         [0003]    It has been widely known that a developer supply container is equipped with such a member as a screw which is for conveying the developer in the container while stirring the developer. 
         [0004]    In recent years, however, it has come to be desired to simplify a developing device in structure to reduce a developing device in cost, and/or make a developer supply container recyclable. 
         [0005]    There is disclosed in Japanese Laid-open Patent Application S60-232578, for example, a developer supply container which is substantially smaller in component count than any conventional developer supply container. According to this patent application, the developer storing portion of the developer supply container is formed of an elastic substance, being enabled to expand or contract so that the developer in the main section can be discharged with the utilization f the resiliency of the elastic substance. Structuring a developer supply container like the one disclosed in the abovementioned patent application makes it unnecessary to equip a developer supply container with a screw or the like member for conveying developer while stirring the developer. Therefore, it can reduce a developer supply container in component count. 
         [0006]    By the way, a developer supply container for an image forming apparatus is required to stir the developer therein, and discharge the developer as necessary to supply or replenish the image forming apparatus with developer. In the case of the image forming apparatus disclosed in the abovementioned patent application, its developer passage, through which the developer is discharged, is provided with a valve in order to control the discharging of the developer in the developer supply container by the resiliency of the elastic substance of which the developer supply container is made. Thus, the developer in the developer supply container can be discharged as necessary from the developer supply container while being stirred. 
         [0007]    In the case of the developer supply container disclosed in Japanese Laid-open Patent Application S60-232578, the abovementioned valve always remains under the pressure generated by the resiliency of the elastic substance in the direction to cause the developer supply container to discharge the developer therein. Therefore, the moment the valve begins to be opened, the pressurized air in the developer supply container begins to be released, and therefore, the developer begins to be discharged from the developer supply container by the released pressurized air. This creates a problem. That is, the developer begins to be discharged from the developer supply container before the valve is fully opened. Thus, the portion of the valve, which is still in the developer passage, increases the developer passage in the developer flow resistance preventing thereby the developer from being properly discharged from the developer supply container. 
         [0008]    As the developer flow is partially blocked by the portion of the developer discharge passage, which is higher in developer flow resistance, it occurs sometimes that the toner particles in the block portion of the developer flow developer agglomerates into larger particles, which reduce the developing device (image forming apparatus) in image quality. 
         [0009]    Further, in the case of a developer supply container structured to utilize temporary force, such as the resiliency of the elastic substance of which the developer storing portion of the developer supply container is made to discharge the developer in the developer storing portion, if the positive pressure in the developer storing portion is lost before the valve is fully opened, the pressure difference between the internal air pressure of the developer storing portion and the atmospheric pressure is sometimes lost before the developer in the developer storing portion is fully discharged. Therefore, the amount by which the developer in the developer supply container fails to be discharged is affected by the speed with which the valve is opened. Thus, it sometimes occurred that a substantial mount of developer in the developer supply container fail to be discharged from the container. 
       SUMMARY OF THE INVENTION 
       [0010]    The present invention is made in consideration of the above-described issues. Thus, the primary object of the present invention is to provide a developer supply container which is significantly less in the amount of developer flow resistance to which the developer in the developer supply container is subjected as the developer is discharged from the developer supply container, and also, to provide an image forming apparatus which is compatible with such a developer supply container. 
         [0011]    According to an aspect of the present invention, there is provided a developer supply container for use with an image forming apparatus, comprising a container shell; a developer accommodation bag accommodating a developer, said developer accommodation bag being contained in said container shell; a developer discharging path for discharging the developer accommodated in said developer accommodation bag to an outside of said developer supply container; an air fluid communication path for fluid communication between inside and outside of said container shell; and a maintaining portion sealing said air fluid communication path to maintain a pressure inside said container shell in a negative pressure state which is lower than a pressure outside said container shell, wherein said developer accommodation bag deforms to discharge the developer, by said maintaining portion opening said air fluid communication path to permit air to enter said container shell through said air fluid communication path. 
         [0012]    Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings). 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a schematic sectional view of a typical image forming apparatus to which the present invention is applicable. 
           [0014]      FIG. 2  is a schematic sectional view of a typical process cartridge which is removably installable in an image forming apparatus in accordance with the present invention, and is for describing the structure of the cartridge. 
           [0015]      FIG. 3  is a schematic sectional view of a typical toner cartridge which is removably installable in an image forming apparatus in accordance with the present invention. 
           [0016]      FIG. 4  is a schematic external perspective view of the toner cartridge in the first embodiment of the present invention. 
           [0017]      FIG. 5  is a schematic external perspective view of the image forming apparatus in the first embodiment, when the apparatus is ready for the replacement of the toner cartridges therein, or after the replacement of the toner cartridges in the apparatus. 
           [0018]      FIGS. 6(   a ) and  6 ( b ) are schematic sectional views of the toner cartridge, and the portion of the image forming apparatus, with which the toner cartridge is coupled, in the first embodiment, after the installation of the cartridge into the apparatus, and is for showing the state of the toner cartridge in the apparatus. 
           [0019]      FIG. 7  is a schematic sectional view of the toner cartridge in the second embodiment of the present invention, and is for showing the structure of the toner cartridge. 
           [0020]      FIG. 8  is a schematic sectional view of the third embodiment of the present invention, and is for showing the structure of the toner cartridge. 
           [0021]      FIG. 9  is a schematic perspective view of the toner cartridge shown in  FIG. 8 , and is for showing the structure of the toner cartridge. 
           [0022]      FIGS. 10(   a ) and  10 ( b ) are schematic sectional views of the toner cartridge in  FIG. 8 , and the portion of the image forming apparatus, with which the toner cartridge is coupled, and is for showing the state of the toner cartridge and the portion of the image forming apparatus, with which the toner cartridge is coupled, after the proper installation of the cartridge into the image forming apparatus. 
           [0023]      FIGS. 11(   a ) and  11 ( b ) are drawings for showing the mechanism for re-inflating the toner storage pouch of the toner cartridge in the image forming apparatus, and the operational modes in which the image forming apparatus is operated to re-inflate the toner storage pouch. 
           [0024]      FIGS. 12  ( a ) and  12  ( b ) are drawings for showing another mechanism for re-inflating the toner storage pouch of the toner cartridge in the image forming apparatus, and the operational modes in which the image forming apparatus is operated to re-inflate the toner storage pouch. 
           [0025]      FIGS. 13(   a ) and  13 ( b ) are drawings showing yet another mechanism for re-inflating the toner storage pouch of the toner cartridge in the image forming apparatus, and the operational modes in which the image forming apparatus is operated to re-inflate the toner storage pouch. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0026]    Hereinafter, some of the embodiments of the present invention are described in detail with reference with appended drawings. 
         [0027]    In the following description of the embodiments of the present invention, the terms such as “upward, downward, vertical and horizontal” indicate the directions when an image forming apparatus is in normal usage, that is, when a development unit or a process cartridge has been properly installed in an image forming apparatus, and is ready for image formation. 
       Embodiment 1 
     (General Structure of Image Forming Apparatus) 
       [0028]    To being with, referring to  FIGS. 1 and 2 , the image forming apparatus in this embodiment is described. 
         [0029]      FIG. 1  is a schematic sectional view of the image forming apparatus in this embodiment.  FIG. 2  is a process cartridge, which is installable in the image forming apparatus shown in  FIG. 1 . It shows the general structure of the process cartridge. 
         [0030]    The image forming apparatus  100  is a full-color laser printer of the so-called inline type, and also, of the so-called intermediary transfer type. The image forming apparatus  100  forms a full-color image on a sheet  12  of recording medium such as ordinary paper, plastic, fabric, etc., according to the information of an image to be formed. 
         [0031]    The information about an image to be formed is inputted into the main assembly  101  of the image forming apparatus  100  from an image reading apparatus which is in connection to the main assembly  101 , or a host device such as a personal computer which is in connection to the main assembly  101  so that electrical signals can be exchanged between the host device and the main assembly  101 . 
         [0032]    The image forming apparatus  100  has multiple image forming portions, more specifically, image forming portions SY, SM, SC and SK for forming yellow (Y), magenta (M), cyan (C) and black (K) images, respectively. In this embodiment, the image forming portions SY, SM, SC and SK are horizontally aligned in parallel (tandem). 
         [0033]    The image forming portions SY, SM, SC and SK are practically the same in structure and operation, although they are different in the color of the images they form. Thus, in the following description of the image forming apparatus, the suffixes Y, M, S and K which are for indicating color are not shown. That is, in terms of structural components, the four image forming portions are described together, unless they need to be differentiated. 
         [0034]    The image forming apparatus  100  has multiple image bearing members, more specifically, four photosensitive drums  1  which are aligned in parallel (tandem) in the direction perpendicular to the vertical direction. Each photosensitive drum  1  is rotationally driven by an unshown driving means in the direction indicated by an arrow mark A in  FIG. 2 . The image forming apparatus  100  has also a charge roller  2  and a scanner unit  3 , which are in the adjacencies of the peripheral surface of the photosensitive drum  1 . The charge roller  2  is for uniformly charging the peripheral surface of the photosensitive drum  1 . The scanner unit  3  is an exposing means. It forms an electrostatic latent image on the peripheral surface of the photosensitive drum  1 , by emitting a beam of laser light while modulating the beam of laser light according to the information of the image to be formed. 
         [0035]    The image forming apparatus  100  has also development unit  4  and a cleaning member  6 , which also are disposed in the adjacencies of the peripheral surface of the photosensitive drum  1 . The development unit  4  is a developing means for developing the electrostatic image into a toner image. The cleaning member  6  is for removing the transfer residual toner, that is, the toner remaining on the peripheral surface of the photosensitive drum  1  after the transfer of a toner image from the photosensitive drum  1 . Further, the image forming apparatus  100  has an intermediary transfer belt  5 , as an intermediary transferring member, which is for transferring the toner image on the photosensitive drum  1 , onto the sheet  12  of recording medium. The intermediary transfer belt  5  is positioned so that it directly faces the four photosensitive drums  1 . In terms of the rotational direction of the photosensitive drum  1 , the point at which the peripheral surface of the photosensitive drum  1  is charged by the charge roller  2 , is the point at which the peripheral surface of the photosensitive drum  1  is exposed, the point at which the electrostatic latent image on the peripheral surface of the photosensitive drum  1  is developed, the point at which the toner image is transferred onto the intermediary transfer belt  5 , and the point at which the peripheral surface of the photosensitive drum  1  is cleaned by the cleaning member  6 , are positioned in the listed order. 
         [0036]    The development unit  4  reversely develops the electrostatic latent image on the peripheral surface of the photosensitive drum  1 , by placing the development roller  17 , as a developer bearing member, in contact with the photosensitive drum  1 . That is, the development unit  4  develops the electrostatic image, by adhering toner charged to the same polarity (negative in this embodiment) as the photosensitive drum  1 , to the various points of the peripheral surface of the photosensitive drum  1 , which have just been made to attenuate in the amount of charge, by the exposure. 
         [0037]    The intermediary transfer belt  5  is an endless belt. It is placed in contact with the peripheral surface of the photosensitive drum  1 , and circularly moves in the direction indicated by an arrow mark B in  FIG. 1 . It is suspended, and kept tensioned, by multiple belt supporting members, more specifically, an idler roller  51 , a belt backing roller  52  (which opposes primary transfer roller), and a driver roller  53 . 
         [0038]    On the inward side of the loop (belt loop) which the intermediary transfer belt  5  forms, four primary transfer rollers  8  are disposed in parallel in such a manner that they oppose the photosensitive drums  1  one for one. Each primary transfer roller  8  forms a primary transfer portion N 1 , which is the area of contact between the intermediary transfer belt  5  and photosensitive drum  1 , by pressing the intermediary transfer belt  5  upon the peripheral surface of the photosensitive drum  1 . To the primary transfer roller  8 , bias which is opposite in polarity from the normal toner polarity is applied from a first transfer bias power source (unshown). Thus, the toner image on the photosensitive drum  1  is transferred (primary transfer) onto the intermediary transfer belt  5 . 
         [0039]    On the outward side of the loop which the intermediary transfer belt  5  forms, there is a secondary transfer roller  9 , which is positioned so that it opposes the belt backing roller  52 . The secondary transfer roller  9  forms a secondary transfer portion N 2 , that is, the area of contact between itself and intermediary transfer belt  5 , by being pressed against the belt backing roller  52 , with the presence of the intermediary transfer belt  5  between itself and belt backing roller  52 . To the secondary transfer roller  9 , bias which is opposite in polarity from the normal toner polarity is applied from an unshown secondary transfer bias power source. Thus, the toner image on the intermediary transfer belt  5  is transferred (secondary transfer) onto the sheet  12  of recording medium. 
       (General Operation of Image Forming Apparatus) 
       [0040]    When an image is formed by the image forming apparatus  100  in this embodiment, first, the peripheral surface of the photosensitive drum  1  is uniformly charged by the charge roller  2 . Then, the uniformly charged portion of the peripheral surface of the photosensitive drum  1  is scanned by (exposed to) the beam of laser light projected by the scanner unit  3  while being modulated according to the information of the image to be formed. Consequently, an electrostatic latent image which is in accordance with the information is effected on the peripheral surface of the photosensitive drum  1 . This electrostatic latent image on the peripheral surface of the photosensitive drum  1  is developed into a toner image, by the development unit  4 . 
         [0041]    Then, the toner image on the photosensitive drum  1  is transferred (primary transfer) onto the intermediary transfer belt  5  by the function of the primary transfer roller  8 . During the formation of a full-color image, the above-described process is carried out in the listed sequence in the image forming portions SY, SM, SC and SK. As a result, four monochromatic toner images, different in color, are transferred (primary transfer) in layers onto the intermediary transfer belt  5 . 
         [0042]    Meanwhile, the sheet  12  of recording medium is conveyed to the secondary transfer portion N 2  in synchronism with the circular movement of the intermediary transfer belt  5 , and is conveyed through the secondary transfer portion N 2 . While the sheet  12  of recording medium is conveyed through the secondary transfer portion N 2 , the four monochromatic toner images, different in color, on the intermediary transfer belt  5  are transferred together (secondary transfer) onto the sheet  12  of recording medium by the function of the secondary transfer roller  9 . 
         [0043]    After the toner image transfer onto the sheet P of recording medium, the sheet  12  is conveyed to a fixing device  10 , in which the sheet  12  and the toner images thereon are subjected to heat and pressure. Thus, the toner images become fixed to the sheet  12 . 
         [0044]    The primary transfer toner, that is, the toner remaining on the peripheral surface of the photosensitive drum  1  after the primary transfer, is removed and recovered by the cleaning member  6 . As for the secondary transfer residual toner, that is, the toner remaining on the intermediary transfer belt  5  after the secondary transfer, is removed by an intermediary transfer belt cleaning device  11 ; the intermediary transfer belt  5  is cleaned by the device  11 . 
       (Structure of Process Cartridge) 
       [0045]    Next, the process cartridge which is removably installable in the image forming apparatus  100  is described about its structure. 
         [0046]    Referring to  FIG. 2 , the photosensitive drum  1 , charge roller  2 , development unit  4 , and cleaning member  6  make up a process cartridge  7  by being integrally placed in a cartridge. The process cartridge  7  is removably installable in the main assembly  101  of the image forming apparatus  100 , by being guided by such means as a cartridge installation guide, a cartridge positioning member, etc., of the main assembly  101  of the image forming apparatus  100 . In this embodiment, the four process cartridges  7  which correspond to four primary colors, one for one, of which the multicolor image to be formed is made up, are the same in structure. The four process cartridges  7  contain yellow (Y), magenta (M), cyan (C) and black (K) toners, one for one. 
         [0047]    The process cartridge  7  is an integral combination of a photosensitive member unit  13  having the photosensitive drum  1 , and the development unit  4  having the development roller  17 , etc. 
         [0048]    The photosensitive drum unit  13  has a cleaning means frame  14  as a frame for supporting various components of the photosensitive drum unit  13 . That is, the cleaning means frame  14  supports the charge roller  2 , cleaning member  6 , etc., in addition to the photosensitive drum  1 . 
         [0049]    As for the development unit  4 , it has a developing means frame as a frame for supporting various components of the development unit  4 . The development unit  4  has the development roller  17  which rotates in the direction indicated by an arrow mark in  FIG. 2 , in contact with the photosensitive drum  1 . 
         [0050]    The development unit  4  has also a toner supply roller  20 , which rotates in the direction indicated by an arrow mark E in  FIG. 2 , virtually in contact with the peripheral surface of the development roller  17  to supply the development roller  17  with toner. 
         [0051]    The developing means frame  18  has a development blade  21  for regulating in thickness the toner layer on the peripheral surface of the development roller  17 . The development blade  21  is a piece of springy metallic plate. It is kept pressed upon the peripheral surface of the development roller  17  so that a preset amount of contact pressure is maintained between the development blade  21  and development roller  17 . Thus, a thin layer of toner is formed on the peripheral surface of the development roller  17 , and is supplied to the peripheral surface of the photosensitive drum  1 . 
         [0052]    Further, the developing means frame  18  has a toner storage chamber  18   a  for temporarily storing toner, and a development chamber  18   b  in which the development roller  17 , toner supply roller  29 , etc., are held. The toner storage chamber  18   a  is provided with a toner entrance  22 , through which the toner storage chamber  18   a  receives toner. 
         [0053]    The toner storage chamber  18   a  and development chamber  18   b  are in connection to each other through an opening  18   c  as a toner passage. Thus, the toner with which the toner storage chamber  18   a  is supplied is conveyed to the development chamber  18   b  by a stirring member  19  with which the toner storage chamber  18   a  is provided. 
         [0054]    In the development unit  4  structured as described above, as toner enters the toner storage chamber  18   a  through the toner entrance  22 , it is temporarily stored in the toner storage chamber  18   a . However, the development unit  4  may be structured so that toner directly enters the development chamber  18   b  through the toner entrance  22 . 
       (Structure of Toner Cartridge) 
       [0055]    Next, the toner cartridge (developer supply container) which supplies the development unit  4  with toner is described. 
         [0056]      FIG. 3  is a sectional view of the toner cartridge, and  FIG. 4  is an external perspective view of the toner cartridge. 
         [0057]    The toner cartridge  15  has a toner storage pouch  41  (developer storage pouch), which has elasticity (resiliency) and is expandable (inflatable) to store toner  140 . It has also an external shell  40  which internally holds the toner storage pouch  41 . The external shell  40  functions as a frame for supporting the internal components of the toner cartridge  15  other than the toner storage pouch  41 , in addition to the toner storage pouch  40 . 
         [0058]    The external shell  40  is provided with a toner discharge nozzle  42  (developer discharge passage), an air passage  43 , and a cartridge installation guide  48 . The toner discharge nozzle  42  is in connection to the toner storage pouch  41 , in the external shell  40 . Thus, it is through the toner discharge nozzle that the toner  140  in the toner storage pouch  41  is discharged from the external shell  40 . The toner storage pouch  41  is supported by the external shell  40  by being in connection to the toner discharge nozzle  42 . 
         [0059]    The toner discharge nozzle  42  is a cylindrical tube, and protrudes from the external shell  40  in such a direction that its axial line is parallel to the direction in which the toner cartridge  15  is installed into the apparatus main assembly  101 . 
         [0060]    The air passage  43  connects an airtight chamber  44 , which is the space between the external shell  40  and toner storage pouch  41 , with the ambient air (atmospheric air). It allows air to move between the airtight chamber  44  and the outside of the external shell  40 . 
         [0061]    As for the material for the external shell  40 , it is desired to be such a substance that can provide the external shell  40  with such an amount of rigidity that can prevent the external shell  40  from being severely deformed by the change in the internal pressure of the external shell  40 . In this embodiment, polystyrene is used as the material for the external shell  40 . Also regarding the material for the external shell  40 , it may be practically any substance as long as it can enable the external shell  40  to withstand a certain amount of pressure. For example, it may be ABS, polyester, polyethylene, polypropylene, or the like resin. It may be also a metallic substance. 
         [0062]    As the material for the toner storage pouch  41 , various resins can be used. For example, polyamide, polyurethane, polyamide elastomer, polyester elastomer, polyurethane elastomer, polystyrene elastomer, fluorinated elastomer, silicone rubber, latex rubber, or the like elastomer, may be used. Further, the material for the toner storage pouch  41  may be a combination of two or more among the above listed substances. In particular, from the standpoint of providing the toner storage pouch  41  with a large amount of internal pressure for discharging the toner, it is desired that a substance which is substantially stretchable and great in resiliency is used as the material for the toner storage pouch  41 . In this embodiment, among the above listed substances, latex rubber was used as a preferable material for the toner storage pouch  41 , from the standpoint of stretchability and flexibility. 
         [0063]    In consideration of the amount of resistance which the toner discharge nozzle  42  generates against the toner flow as the toner  140  is discharged through the toner discharge passage  14 , the internal diameter of the toner discharge passage  41  is desired to be no less than 4 mm. In comparison, the air passage  43  is a passage through which only air moves into, or out of, the airtight chamber  44 . Therefore, the amount of resistance which the air passage  43  generates when air moves through the air passage  43  is does not matter. Therefore, the air passage  43  may be smaller in internal diameter than the toner discharge nozzle  42 . However, the internal diameter of the air passage  43  is desired to be no less than 2 mm. 
         [0064]    Concretely, in this embodiment, the toner discharge nozzle  42  and air passage  43  are 6 mm and 4 mm, respectively, in internal diameter. Setting the internal diameter of the air passage  43  to be smaller than that of the toner discharge nozzle  42  makes it possible to reduce the toner cartridge  15  and image forming apparatus  100  in size. 
         [0065]    According to the gist of the present invention, this embodiment is not intended to limit the present invention in scope in terms of the specification, in particular, dimension, of the toner cartridge  15 . 
         [0000]    (Filling of Toner Cartridge with Toner) 
         [0066]    Next, the procedure for filling the toner cartridge  15  with toner  140  is described. 
         [0067]    The toner storage pouch  41  for storing toner  140  is filled with a preset amount of toner  140 , and also, a certain amount of air. The toner storage pouch  41  is elastic. Thus, as air is injected into the toner storage pouch  41 , the toner storage pouch  41  expands (inflates) in the external shell  40 , causing thereby the air in the airtight chamber  44  to discharge out of the external shell  40  through the air passage  43 . 
         [0068]    After the filling of the toner storage pouch  41  with the preset amount of toner  140 , and the certain amount of air, the air passage  43  is airtightly sealed with a thin film seal  47  (means for keeping airtight chamber negative in internal pressure) for preventing air from entering into, or exiting from, the airtight chamber  44  through the air passage  43 . Thus, unless the thin film seal  47  is removed, it does not occur that the atmospheric air flows into the airtight chamber  44 , or the air in the airtight chamber  44  flows out of the external shell  40  (airtight chamber  44 ). 
         [0069]    In other words, it is after the air in the airtight chamber  44  is pushed out of the external shell  40  by the expansion (inflation) of the toner storage pouch  41  that the air passage  4  is blocked by the thin film seal  47  to prevent the atmospheric air from flowing into the interior (airtight chamber  44 ) of the external shell  40 . 
         [0070]    On the other hand, the toner storage pouch  41  tends to contract (deflate) because of its resiliency provided by the elasticity of the substance of which it is made. However, the ambient air is prevented by the thin film seal  47  from flowing into the airtight chamber  44 . Therefore, as the toner storage pouch  41  begins contract (deflate), the air in the airtight chamber  44  begins to be reduced in internal pressure. Thus, the air in the airtight chamber  44  begins to become low in pressure than the ambient air pressure (it becomes negative in pressure relative to atmospheric pressure). Consequently, the toner storage pouch  41  is made to remain expanded (inflated) in the external shell  40 , with the amount of the force which causes the toner storage pouch  41  filled with the ambient air, to contract, being equal to the amount of the force generated by the negative air pressure in the airtight chamber  44 . That is, the thin film seal  47  keeps the interior (airtight chamber  44 ) negative in pressure. 
         [0071]    Therefore, even when the interior of the toner storage pouch  41  is open to the atmospheric air through the toner discharge nozzle  42 , it is possible to prevent the toner  140  and air in the toner storage pouch  41  from being discharged out of the toner storage pouch  41  by the resiliency of the toner storage pouch  41 . 
         [0072]    Further, the toner discharge nozzle  42  is sealed with a seal  46  for the toner discharge nozzle  42 , during the manufacturing of the toner cartridge  15 , in order to prevent the toner  140  and air in the toner storage pouch  41  from being discharged while the toner cartridge  15  is shipped. 
         [0073]    After the toner storage pouch  41  in which a preset amount of toner  140 , and a certain amount of air, was present, was expended (inflated) in the external shell  40 , which is 250 cc in capacity, to a size of 200 cc, the air pressure in the airtight chamber  44  was roughly −10 kPa relative to the atmospheric pressure. That is, the airtight chamber  44  remained negative in air pressure relative to the atmospheric air. 
       (Installation of Toner Cartridge) 
       [0074]    Next, the procedure for installing the toner cartridge  15  into the image forming apparatus  100 , and the procedure for discharging the toner  140  in the toner storage pouch  41 , into the toner storage chamber  18   a  (supplying toner storage chamber with toner), are described. 
         [0075]      FIG. 5  is an external perspective view of the image forming apparatus  100  during the installation of the toner cartridge  15  into the image forming apparatus  100 . 
         [0076]    Referring to  FIG. 5 , as an operator opens the front door  70  of the image forming apparatus  100 , an opening  71  for installing the toner cartridge  15  appears. The main assembly  101  of the image forming apparatus  100  is provided with toner cartridge installation ribs  72 . Thus, the toner cartridge  15  is to be slid (inserted) into the main assembly  101 , with the installation ribs  72  being fitted in the installation guide  48  of the external shell  40 . 
         [0077]      FIG. 6  is a schematic sectional view of the toner cartridge  15 , and the portion of the image forming apparatus  100 , with which the toner cartridge  15  is in connection. More specifically,  FIG. 6(   a ) is a schematic sectional view of the toner cartridge  15 , and the portion of the image forming apparatus  10 , with which the toner cartridge  15  is in connection, right after the completion of the installation of the toner cartridge  15 .  FIG. 6(   b ) is practically the same as  FIG. 16(   a ), except that in  FIG. 6(   b ), the thin film seal  47  has just been peeled away. 
         [0078]    The first step for installing the toner cartridge  15  into the image forming apparatus  100  is to peel the toner discharge passage seal  46 . Then, the toner cartridge  15  is to be slid into the toner cartridge chamber of the apparatus main assembly  101 . As the toner cartridge  15  is inserted, the toner discharge nozzle  42  enters the toner discharge nozzle receptacle  80  (developer discharge passage connector) of the image forming apparatus  100 . 
         [0079]    The toner discharge nozzle  42  is in the form of a piece of cylindrical tube, and its axial line is parallel to the direction in which the toner cartridge  15  is inserted into the apparatus main assembly  101 . Further, the apparatus main assembly  101  is structured so that as the toner cartridge  15  is slid into the apparatus main assembly  101 , the toner discharge nozzle  42  becomes connected to the toner discharge nozzle receptacle  80  of the apparatus main assembly  101 . 
         [0080]    The toner discharge nozzle receptacle  80  is in connection to the toner entrance  22  of the toner storage chamber  18   a , enabling the toner storage chamber  18   a  to be supplied with toner  140  from the toner cartridge  15 . Further, the toner discharge nozzle receptacle  80  is provided with a seal  81 , which engages with the toner discharge nozzle  42  (toner discharge passage is inserted into seal  81 ) to prevent the toner  140  from scattering while the toner storage chamber  18   a  is supplied with the toner  140 . 
         [0081]    In this embodiment, an oil seal was employed as the seal  81 . However, the seal  81  may be made of felt or sponge so that it is compressible by a preset amount. 
         [0082]    Next, referring to  FIG. 6(   b ), after the installation of the toner cartridge  15  into the image forming apparatus  100 , a user is to remove the thin film seal  47  which is blocking the air passage  43 . Prior to the removal of the thin film seal  47  for the air passage  43 , the air in the airtight chamber  44  of the toner cartridge  15  is negative in pressure relative to the ambient air. Thus, the toner storage pouch  41  remained expanded (inflated) by the negative air pressure of the airtight chamber  44 . 
         [0083]    Thus, the moment the thin film seal  47  is removed, the ambient air flows (is introduced) into the airtight chamber  44 , cancelling the negative air pressure of the airtight chamber  44 . As a result, the force which kept the toner storage pouch  41  expanded (inflated), in coordination with the negative air pressure in the airtight chamber  44 , is lost. Thus, the toner storage pouch  41 , which is an elastic component, is allowed to be contracted (deflated) by its own resiliency (allowed to deform by contracting). 
         [0084]    That is, the phenomenon that as the air passage  43  is unblocked by the removal of the thin film seal  47 , the airtight chamber  44  stops remaining negative in its internal air pressure, and therefore, the toner storage pouch  41 , which is an elastic component, is allowed to contract, can be utilized to discharge the toner  140  in the toner storage pouch  41 , along with the air in the toner storage pouch  41 , through the toner discharge nozzle  42 . As the toner  140  is discharged through the toner discharge nozzle  42 , it passes through the toner discharge nozzle receptacle  80 , and enters the toner storage chamber  18   a  through the toner entrance  22 . 
         [0085]    The above-described structure of the combination of the image forming apparatus  100  and toner cartridge  15  in this embodiment, and its operation and effects, can be summarized as follows. That is, the developer supply container (toner cartridge  15 ) is equipped with a negative pressure maintaining-cancelling means (thin film seal  47 , negative pressure maintenance portion), which is capable of utilizing the resiliency of the developer storage pouch  41  (toner storage pouch  41 ) made of an elastic substance, to keep the airtight chamber  44  (interior of external shell  40 ) negative in internal air pressure relative to the air pressure of the outside of the external shell  40 , or cancelling the negative pressure of the internal air of the airtight chamber  41 . 
         [0086]    Therefore, until the developer supply container is installed into the apparatus main assembly  101 , or in the like situation, the airtight chamber  44  is kept negative in its internal pressure to prevent the developer storage pouch  41  from contracting, in order to prevent the developer in the developer storage pouch  41  from being discharged from the pouch  41 . 
         [0087]    On the other hand, when it is necessary to release the toner in the toner storage pouch  41  to supply the apparatus main assembly  101  with developer after the installation of the toner cartridge  15  into the apparatus main assembly  101  of the image forming apparatus  100 , the airtight chamber  44  is relieved of the negative pressure, being thereby made equal in air pressure to the ambience. Thus, the developer in the developer storage pouch  41  is discharged into the toner storage chamber  18   a  of the apparatus main assembly  101  through the developer discharge passage (toner discharge nozzle  42 ) by the resiliency of the developer storage pouch  41 . 
         [0088]    As described above, the developer is discharged by the negative pressure maintaining-cancelling means, the operation for discharging the developer can be controlled while the developer discharge passage (developer discharge nozzle  42 ) is kept open. Therefore, it is possible to prevent the problem which a combination of an image forming apparatus and a developer supply cartridge (toner cartridge  15 ), which is in accordance with the prior art, suffers, more specifically, the problem that, because the operation to discharge the toner in the toner storage pouch is controlled by the opening and closing of the developer discharge passage (developer discharge nozzle  42 ), a part of the developer discharge passage is increased in developer (toner) flow resistance, and therefore, the developer discharge passage is sometimes clogged up by the developer. 
       Embodiment 2 
       [0089]    Next, the image forming apparatus in another embodiment of the present invention is described. 
         [0090]    The portions of the image forming apparatus in this embodiment, which are the same as, or similar to, the counterparts in the first embodiment are given the same referential codes as those given to the counterparts, and are not described, in order not to repeat the same description. This embodiment is different from the first embodiment only in that the toner cartridge  15   a  is different in structure from the toner cartridge  15  in the first embodiment. 
       (Structure of Toner Cartridge) 
       [0091]      FIG. 7  is a schematic sectional view of the toner cartridge  15   a  in this embodiment. It shows the structure of the toner cartridge  15   a.    
         [0092]    Referring to  FIG. 7 , the external shell  40  of the toner cartridge  15   a  is similar in structure as the toner cartridge  15  in the first embodiment, except that the external shell  40  of the toner cartridge  15   a  in this embodiment is provided with a one-way valve  45  for allowing the air in the airtight chamber  44  to be discharged out of the external shell  40 . More specifically, the one-way valve  45  is between the airtight chamber  44  and the outside of the toner cartridge  15   a . It allows the air in the airtight chamber  45  to flow out of the airtight chamber  44  into the ambience, but does not allow the ambient air to enter the airtight chamber  44 . In other words, it is only in one direction, that is, from within the external shell  40  to the outside of the external shell  41 , that the one-way valve  45  allows air to move through it. 
         [0093]    More specifically, this embodiment is different from the first embodiment in the order in which the thin film seal  45  for preventing the ambient air from flowing into the airtight chamber  44  through the air passage  43 , is attached to the external shell  40 . Next, how the toner cartridge  15   a  is assembled is described. 
         [0000]    (Filling of Toner Cartridge with Toner) 
         [0094]    First, the process for filling the toner cartridge  15   a  with toner  140  is described. In the case of the toner cartridge  15   a  in this embodiment, it is after the attachment of the thin film seal  47  to the external shell  40  that the toner storage pouch  41  is filled with the toner  140 . 
         [0095]    When the toner storage pouch  41  for storing toner  140  is filled with toner  140 , not only is it filled with a preset amount of toner  140  through the toner discharge nozzle  42 , but also, the ambient air is forced into the toner storage pouch  40  through the toner discharge nozzle  42 . Thus, as the toner  140  and air are filled into the storage pouch  41 , the toner storage pouch  41  expands in the external shell  40 , because the toner storage pouch  41  is elastic. Thus, the air in the airtight chamber  44  is compressed by the expansion of the toner storage pouch  41 . However, the external shell  40  is provided with the one-way valve  45 . Thus, a certain amount of the air in the airtight chamber  44  is discharged out of the external shell  40  (airtight chamber  44 ) through the one-way valve  45 . 
         [0096]    As described above, the toner cartridge  15   a  in this embodiment is provided with the one-way valve  45 . Therefore, the toner storage pouch  41  in the external shell  40  of the toner cartridge  15   a  is allowed to expand even after the attachment of the thin film seal  47  to the external shell  40  to block the air passage  43 . 
         [0097]    By the way, the one-way valve  45  allows the air in the airtight chamber  44  to be discharged out of the external shell  40 , but does not allow the ambient air of the external shell  40  to flow into the airtight chamber  44 . That is, the air in the airtight chamber  44  is forced out of the external shell  40  by the expansion of the toner storage pouch  41 . But, as long as the external shell  40  is kept airtight, the ambient air is not allowed to flow into the airtight chamber  44 . 
         [0098]    As the injection of air into the toner storage pouch  41  is stopped, the toner storage pouch  41  is made to contract by its resiliency attributable to its elasticity, like the toner storage pouch  41  in the first embodiment. However, the toner cartridge  15   a  in this embodiment is structured as described above. Therefore, it does not occur that as the toner storage pouch  41  contracts, the ambient air flows into the airtight chamber  44 . Therefore, the air in the airtight chamber  44  is reduced in pressure. Thus, the airtight chamber  44  becomes, and remains, negative in air pressure relative to the atmospheric pressure (external pressure). Consequently, the force attributable to the contraction of the toner storage pouch  41  expanded by the air injected into the toner storage pouch  41  along with toner  140 , becomes equal to the force generated by the negative pressure of the air in the airtight chamber  44 . Thus, the toner storage pouch  41  remains expanded in the external shell  40 . 
         [0099]    Therefore, even after the toner storage pouch  41  becomes open to the atmospheric air through the toner discharge nozzle  42 , it is possible to prevent the toner  140  in the toner storage pouch  41  from being discharged, along with the air in the toner storage pouch  41 , from the toner storage pouch  41 . 
         [0100]    Prior to the shipment of the toner cartridge  15   a , a toner discharge passage seal  46  is attached to the external shell  40  to block the toner discharge nozzle  42 , in order to prevent the toner  140  and air in the toner storage pouch  41  from being discharged during the shipment of the toner cartridge  15   a.    
         [0101]    In the first embodiment, it is after the filling of the toner storage pouch  41  with a preset amount of a combination of toner  140  and air that the thin film seal  47  (negative pressure maintaining seal) is attached to the external shell  40  to block the air passage  43  to prevent the ambient air from flowing into the airtight chamber  44  through the air passage  43 , or the air in the airtight chamber  44  from flowing out of the airtight chamber  44  through the air passage  43 , in order to make, and keep, the air in the airtight chamber  44  negative in pressure. 
         [0102]    In comparison, in this embodiment, the external shell  40  is provided with the one-way valve  45 , which does not allow the ambient air to flow into the airtight chamber  44 . Thus, as the toner storage pouch  41  is made to contract by its resiliency attributable to its elasticity after the discharging of the air in the airtight chamber  44  through the one-way valve  45 , the airtight chamber  44  becomes negative in air pressure. 
         [0103]    It takes a certain length of time for the adhesive used to attach the thin film seal  47  to the external shell  40  to block the air passage  43 , to cure enough to prevent air from flowing into, or out of, the airtight chamber  44  through the air passage  43 . Therefore, in the case of a toner cartridge structured like the one in the first embodiment, it was necessary for the toner cartridge to be left alone while the toner storage pouch  41  is kept high in internal pressure. 
         [0104]    In the case of the toner cartridge  15   a  in this embodiment, the external shell  40  is provided with the one-way valve  45 . Therefore, this embodiment is shorter than the first embodiment in the length of time it take to make the airtight chamber  44  negative in internal air pressure. In other words, providing a toner cartridge with the one-way valve  45  can improve the manufacturing of the toner cartridge in productivity. 
         [0105]    The installation of the toner cartridge  15   a  in this embodiment into the image forming apparatus  100 , and the discharging of toner  140  from the toner cartridge  15   a  into the toner storage chamber  18   a  to replenish with the toner storage chamber  18   a , are the same as the installation of the toner cartridge  15  in the first embodiment into the image forming apparatus  100 , and the discharging of toner  140  into the toner storage chamber  18   a  in the first embodiment. 
       Embodiment 3 
       [0106]    Next, the image forming apparatus in another embodiment of the present invention is described. 
         [0107]    The portions of the image forming apparatus in this embodiment, which are the same as, or similar to, the counterparts in the first embodiment are given the same referential codes as those given to the counterparts, and are not described in order not to repeat the same description. This embodiment is different from the first embodiment in that the toner cartridge  15   b  is different in structure from the toner cartridge  15  in the first embodiment. 
       (Structure of Toner Cartridge) 
       [0108]      FIG. 8  is a schematic sectional view of the toner cartridge  15   b  in this embodiment. It shows the structure of the toner cartridge  15   b .  FIG. 9  is a schematic sectional view of the toner cartridge  15   b  in this embodiment. It shows the structure of the toner cartridge  15   b.    
         [0109]    Referring to  FIGS. 8 and 9 , the toner cartridge  15   b  in this embodiment is provided with an air suction nozzle  43   a , which is on the same side as the toner discharge nozzle  42 . The air suction nozzle  43   a  is the same in shape as the toner discharge nozzle  42 . That is, it is in the shape of a cylindrical tube, and protrudes from the external shell  40 , in the same direction as the direction in which the toner cartridge  15   b  is inserted into the apparatus main assembly  101 . 
       (Installation of Toner Cartridge) 
       [0110]      FIG. 10  is a schematic sectional view of the toner cartridge  15   b , and the portion of the image forming apparatus  100   a , with which the toner cartridge  15   b  is in connection. More specifically,  FIG. 10(   a ) is a schematic sectional view of the toner cartridge  15   b , and the portion of the image forming apparatus  10 , with which the toner cartridge  15  is in connection, right after the insertion of the installation of the toner cartridge  15   b  halfway into the apparatus main assembly  101 .  FIG. 10(   b ) is practically the same as  FIG. 10(   a ), except that in  FIG. 10(   b ), the toner cartridge  15   b  is all the way in the image forming apparatus  100   a.    
         [0111]    The image forming apparatus  100   a  into which the toner cartridge  15   b  is slid is provided with an air suction nozzle receptacle  90 , with which the air suction nozzle  43   a  is coupled. 
         [0112]    As the toner cartridge  15   b  is slid into the image forming apparatus  100   a , the toner discharge nozzle  42  begins to enter the toner discharge nozzle receptacle  80  of the image forming apparatus  100   a , at a first point, shown in  FIG. 10   a ), during the sliding of the toner cartridge  15   b  into the image forming apparatus  100   a.    
         [0113]    The toner discharge nozzle receptacle  80  is in connection to the toner entrance  22  with which the toner storage chamber  18   a  is provided as is the toner discharge nozzle receptacle  80  in the first embodiment. Thus, the toner  140  in the toner cartridge  15   b  can be supplied to the toner storage chamber  18   a . Further, the toner discharge nozzle receptacle  80  is provided with a receptacle seal  81  which airtightly fits around the toner discharge nozzle  42  to prevent toner  140  from being scattered while the toner  140  is supplied into the toner storage chamber  18   a . It is at the first position that the toner discharge nozzle  42  begins to fit into the receptacle seal  81 . 
         [0114]    Then, the toner cartridge  15   b  is inserted further into the apparatus main assembly  100   a  until it reaches the position (second position) shown in  FIG. 10(   b ). During this movement of the toner cartridge  15   b , the air suction nozzle  43  enters the air suction nozzle receptacle  90  with which the image forming apparatus  100   a  is provided. 
         [0115]    The air suction nozzle  43   a  is in the form of a cylindrical tube. It axial line is parallel to the direction in which the toner cartridge  15   b  is inserted into the apparatus main assembly  101 . Therefore, as the toner cartridge  15   b  is slid into the apparatus main assembly  101 , the air suction nozzle  43   a  becomes connected to the air suction nozzle receptacle  90  of the apparatus main assembly  101 . 
         [0116]    The air suction nozzle receptacle  90  is provided with a seal breaking cylindrical member  91  for breaking the thin film seal  47   a  (negative pressure maintaining portion) with which the air suction nozzle  43   a  remains sealed. The central hollow of the seal breaking cylindrical member  91  is in connection to the internal space of the image forming apparatus  100   a , the air pressure of which is the same as the atmospheric pressure. 
         [0117]    As described before, the air suction nozzle  43   a  has been kept sealed by the thin film seal  47   a  in order to prevent the ambient air from entering into the airtight chamber  44 , or the air in the airtight chamber  44  from being discharged from the airtight chamber  44 . However, while the toner cartridge  15   b  is inserted to the second position from the first position, the thin film seal  47   a  for the air suction nozzle  43   a  comes into contact with the seal breaking member  91 , and is broken by the seal breaking member  91 . 
         [0118]    Until the thin film seal  47   a  for the air suction nozzle  43   a  is broken, the airtight chamber  44  of the toner cartridge  15   b  remains negative in air pressure relative to the atmospheric pressure. That is, the toner storage pouch  41  is kept expanded by the negative air pressure of the airtight chamber  44 . 
         [0119]    However, the moment the thin film seal  47   a  is broken by the seal breaking member  91 , the atmospheric air flows into the airtight chamber  44  through the cylindrical hollow of the seal breaking member  91  and the air suction nozzle  43   a , making the internal air pressure of the airtight chamber  44  the same as the atmospheric pressure. Thus, the force generated by the negative internal air pressure of the airtight chamber  44  in the direction to keep the toner storage pouch  41  expanded is lost. Therefore, the toner storage pouch  41  is made to contract by its resiliency attributable to its elasticity. 
         [0120]    Thus, the moment the airtight chamber  44  is made to lose its negative internal air pressure, it becomes possible to utilize the contraction of the toner storage pouch  41 , which is an elastic member, to discharge the toner  140  in the toner storage pouch  41 , along with the air in the toner storage pouch  41 , through the toner discharge nozzle  42 . As the toner  140  is discharged through the toner discharge nozzle  42 , it travels through the toner discharge nozzle receptacle  80 , and then, is supplied to the toner storage chamber  18   a  through the toner entrance  22 . 
         [0121]    In this embodiment, the toner cartridge  15   a  is structured so that the toner discharge nozzle  42  and air suction nozzle  43   a  protrude from the same side of the external shell  40 . Thus, as the toner cartridge  15   b  is slid into the image forming apparatus  101   a , the toner cartridge  15   b  is readied at the first position for discharging the toner  140  in the toner storage pouch  41 , and then, the airtight chamber  44  is made to lose its negative internal air pressure at the second position to enable the toner cartridge  15   a  to discharge the toner  140 . 
         [0122]    That is, as the toner cartridge  15   b  is inserted into the image forming apparatus  100   a , first, the toner passage is fully open, and then, the toner  140  begins to be discharged. Therefore, it does not occur that the toner  140  begins to be discharged before the toner passage is fully opened as in the case of a conventional toner cartridge. In other words, the toner cartridge  15   b  in this embodiment is substantially smaller in the amount of developer (toner) flow resistance which toner encounter as it flows through the toner passage of the toner cartridge when the toner is discharged from the toner cartridge, than any toner cartridge in accordance with the prior art. 
         [0123]    Further, in the case of the toner cartridge  15   b  in this embodiment, its airtight chamber  44  is made to lose its negative internal air pressure with a preset timing while it is slid into the image forming apparatus  100   a . Thus, it is unlikely for the toner cartridge  15   b  to be erroneously installed. That is, in the case of the toner cartridge  15  in the first embodiment, it is structured so that a user has to peel away the thin film seal  47  to make the airtight chamber  44  to lose its negative pressure in order to allow the toner storage pouch  41  to contract. Thus, it has to be after the insertion of the toner cartridge  15  into the image forming apparatus  100  that the thin film seal  47  is to be peed away. 
         [0124]    In comparison, the toner cartridge  15   a  and image forming apparatus  100   a  in this embodiment are structured so that the thin film seal  47   a  (negative pressure maintaining means (portion)) is automatically broken with a preset timing during the insertion of the toner cartridge  15   a  into the image forming apparatus  100   a . Thus, this embodiment can prevent the erroneous toner cartridge installation attributable to a user. 
         [0125]    Concretely, in this embodiment, the toner discharge nozzle  42  and air suction nozzle  43   a  are 6 mm and 4 mm in internal diameter. In consideration of the developer (toner) flow resistance which the toner encounter as it is discharged from the toner cartridge  15   b , the toner discharge nozzle  42  is desired to be no less than 4 mm in internal diameter. In comparison, the air suction nozzle  43   a  is for air to flow into, or out of, the airtight chamber  44 . Therefore, the developer (toner) flow resistance of the air suction nozzle  43   a  has little effect upon the performance of the toner cartridge  15   b . Therefore, the air suction nozzle  43   a  may be made smaller in internal diameter than the toner discharge nozzle  42 . However, it is desired to be no less than 2 mm in internal diameter. 
         [0126]    Further, making the air suction nozzle  43   a  smaller in diameter than the toner discharge nozzle  42  can makes it possible to reduce the toner cartridge  15   b  and image forming apparatus  100   a  in size, and also, to prevent the installation error. 
         [0127]    Further, in this embodiment, the discharging of the toner  140  from the toner storage pouch  41  is controlled by a portion other than the toner discharge nozzle  42 , through which the toner  140  flows when the toner  140  is discharged from the toner storage pouch  41 . Therefore, the toner cartridge  15   b  in this embodiment is smaller in the developer (toner) flow resistance which the toner  140  encounters as it is discharged from the toner storage pouch  41 , than the toner cartridge  15  in the first embodiment. That is, it can prevent the problem that when the toner  140  is discharged, the portion of the toner passage, which has not been fully opened, increases in developer (toner) flow resistance, and therefore, the toner flow is partially dammed up (blocked) by the partially open portion of the toner passage, causing a certain amount of toner  140  to agglomerate into larger particles or the like. 
         [0128]    Further, it is after the toner passage becomes fully opened that the toner  140  is discharged. In addition, the discharging of the toner  140  is triggered by the beginning of the air flow (which is less affected by developer (toner) flow resistance of air passage) into the airtight chamber  44 . Therefore, the pressure can be effectively released from the toner storage pouch  41  even though the image forming apparatus  100   a  is structured so that only temporary force, that is, the resiliency of elastic substance, is utilized to discharge the toner  140 . Therefore, the toner cartridge  15   b  in this embodiment is less variable in the amount by which the toner  140  fails to be discharged from the toner storage pouch  41 . 
       Embodiment 4 
       [0129]    Next, the image forming apparatus in another embodiment of the present invention is described. 
         [0130]    The portions of the image forming apparatus in this embodiment, which are the same as, or similar to, the counterparts in the first embodiment are given the same referential codes as those given to the counterparts, and are not described in order not to repeat the same description. 
       (Structure of Toner Cartridge) 
       [0131]      FIG. 11  is a drawing which shows the structure and operational modes of the image forming apparatus in this embodiment. More specifically,  FIG. 11(   a ) is a schematic sectional view of the toner cartridge, and the portion of the image forming apparatus, with which the toner cartridge is coupled, and  FIG. 11(   b ) shows the operational modes of the image forming apparatus. 
         [0132]    The image forming apparatus in this embodiment, shown in  FIG. 11(   a ), is similar in basic structure to that in the third embodiment. It is different from the image forming apparatus in the third embodiment only in the following features. 
         [0133]    That is, the image forming apparatus  100   b  in this embodiment is a toner discharge passage valve  82  (first opening-closing mechanism), which is in the middle of the toner entry passage  120  (developer entry passage), which is between the toner entrance  22  of the toner storage chamber  18   a , and the toner discharge nozzle receptacle  80 . Thus, the movement of airflow into, or out of, the toner storage pouch  41  through the toner discharge nozzle  42  can be controlled by the toner discharge passage vale  82 . Further, an air injection passage  83  is provided between the toner discharge nozzle receptacle  80  and toner discharge passage valve  82 . Further, the image forming apparatus  100   b  is provided with an air pump  73 . Therefore, it is possible to inject air into the toner storage pouch  41  through the air injection passage  83  and toner discharge nozzle  42 , with the use of the pump  73 . 
         [0134]    Further, the image forming apparatus  100   b  is provided with an air suction nozzle receptacle  90  which couples with the air suction nozzle  43   a  of the toner cartridge  15   b  when the toner cartridge  15   b  is inserted into the image forming apparatus  100   a . The air suction nozzle receptacle  90  is provided with an air seal  92  for keeping airtight the joint between the air suction nozzle receptacle  90  and air suction nozzle  43   a . Further, the air passage  130  which connects the air suction nozzle receptacle  90  and the apparatus main assembly  101   b  is provided with an air passage valve  93  (second mechanism for opening or closing air passage), which is for controlling the air movement into, or out of, the airtight chamber  44  (external shell  40 ). 
         [0135]    The air suction nozzle receptacle  90  is provided with a seal breaking cylindrical member  91 , like the seal breaking cylindrical member  91  in the third embodiment, which is for breaking the thin film seal  47   a  for the air suction nozzle  43   a . In the third embodiment, the hollow of the seal breaking member  91  is directly in connection to the atmospheric air in the apparatus main assembly  101   a . This embodiment is different from the third embodiment in that the air passage valve  91  in this embodiment is in connection to the atmospheric air through the air passage valve  93 . 
       (Operation for Re-Expanding (Inflating) Toner Storage Pouch) 
       [0136]    The toner storage pouch  41  is elastic. Thus, as air is injected into the toner storage pouch  41 , it expands (elastically deform). When the toner cartridge  15   b  is shipped out of its manufacturing facility, the toner storage pouch  41  contains a preset amount of toner  140  and air, and therefore, remains expanded (inflated) in the external shell  40 . It is possible, however, that as a substantially length of time elapses between when the toner cartridge  15   a  was shipped out and when it is used for the first time, the air in the toner storage pouch  41  will escape from the toner storage pouch  41 . The following is the description of the operation to be carried out to re-expand (re-inflate) the toner storage pouch  41  in a case where the air in the toner storage pouch  41  will have escaped. 
         [0137]    The toner discharge passage valve  82  and air passage valve  93  can be opened or closed, and are controlled in the modes shown in  FIG. 11(   b ). 
         [0138]    The first mode is the initial mode in which both the toner discharge passage valve  82  and air passage valve  93  are kept closed. In the next mode, or the second mode, the toner discharge passage valve  82  is kept closed, whereas air passage valve  93  is kept opened. Further, the pump  73  is activated to being to inject (send) air into the toner entry passage  120 . As air is injected into the toner entry passage  120  by the pump  73 , it is sent into the toner storage pouch  41  through the toner discharge nozzle  42 , because the toner discharge passage valve  82  is closed. 
         [0139]    As air is injected into the toner storage pouch  41 , the toner storage pouch  41  begins to expand (inflate) in the external shell  40 . The air passage valve  93  is open. Therefore, the air in the airtight chamber  44  is discharged out of the external shell  40  through the air suction nozzle  43   a , by the expansion of the toner storage pouch  41 . 
         [0140]    Also in the second mode, as air is sent into the toner storage pouch  41 , the toner  140  in the toner storage pouch  41  is loosened by the air flow, being made to higher in fluidity. 
         [0141]    After the injection of a preset amount of air into the toner storage pouch  41  in the second mode, the operation is switched to the third mode, in which the toner discharge passage valve  82  is kept closed, and the air passage valve  93 , which was kept open in the second mode, is opened. That is, the airflow into, or out of, the toner storage pouch  41  through the air suction nozzle  43   a  is blocked in order not to allow ambient air to flow into, or out of, the airtight chamber  44  (internal space of external shell  40 ) from outside the external shell  40 . After the operation is switched to the third mode, the driving of the pump  73  is stopped to stop injecting air into the toner storage pouch  41 . 
         [0142]    Next, in the fourth mode, the air passage valve  93  is kept closed, and the toner discharge passage valve  82 , which was kept closed in the second mode, is opened. Thus, the toner storage pouch  41  begins to be made to contract by its resiliency attributable to its elasticity. However, the air passage valve  93  is closed, and therefore, the atmospheric air is not allowed to flow into the airtight chamber  44 . Thus, as the toner storage pouch  41  begins to contract, the airtight chamber  44  is reduced in its internal air pressure. Consequently, the internal air pressure of the airtight chamber  44  becomes lower than the atmospheric pressure; it becomes negative relative to the atmospheric pressure. 
         [0143]    Thus, the toner storage pouch  41  can remain expanded in the external shell  40 , in such a state that the force generated by the resiliency of the expanded toner storage pouch  41  in the direction to contract the toner storage pouch  41 , is equal to the negative internal air pressure of the airtight chamber  41 . 
         [0144]    Therefore, even when the internal space of the toner storage pouch  41  is in connection to the atmospheric air through the toner discharge nozzle  42  which is in connection to the toner storage pouch  41 , it is possible to prevent the toner  140  and air in the toner storage pouch  41  from being discharged from the toner storage pouch  41 . As described above, in the fourth embodiment, the toner discharge passage valve  82  is fully opened to prepare for the discharging of the toner  140  from the toner storage pouch  41 . 
         [0145]    Lastly, in the fifth mode, the toner discharge passage valve  82  is kept open, and the air passage valve  93 , which was kept closed in the third mode, is opened. Thus, the atmospheric air flows into the airtight chamber  44  through the air suction nozzle  43   a , making the airtight chamber  41  not negative in internal pressure. Consequently, the force generated by the negative air pressure in the internal space of the airtight chamber  44  in the direction to keep the toner storage pouch  41  expanded is lost. Thus, the toner storage pouch  41  is made to contract by its resiliency attributable to its elasticity (deforms in a manner to reduce in size). 
         [0146]    That is, the toner  140  in the toner storage pouch  41  can be discharged along with the air in the toner storage pouch  41 , through the toner discharge nozzle  42  by the unitization of the phenomenon that the moment the airtight chamber  44  is made to begin losing its negative internal air pressure, the toner storage pouch  41  begins to contract. 
         [0147]    After the discharging of the toner  140  in the toner storage pouch  41 , the operation is switched to the initial mode, or the first mode, to prepare the toner cartridge  15   b  for the next toner discharging operation. 
         [0148]    As described above, in this embodiment, the apparatus main assembly  101  is provided with a mechanism for re-injecting air into the toner storage pouch  41 . Thus, even the air injected into the toner storage pouch  41  happens to escape from the toner storage pouch  41 , it is possible to discharge the toner  140  from the toner cartridge  15   b.    
         [0149]    Incidentally, in this embodiment of the present invention, the toner passage through which the toner  140  is discharged from the toner storage pouch  41  is provided with the toner discharge passage valve  82 . However, the process of discharging toner  140  is started in the fifth mode after the toner discharge passage valve  82  is fully opened in the fourth mode. Thus, it does not occur that the toner  140  begins to be discharged before the toner passage becomes fully open, as in the case of the toner cartridge in accordance with the prior art. Therefore, the toner cartridge  15   b  in this embodiment is substantially smaller in the amount of the developer (toner) flow resistance of its toner passage. Thus, it can prevent the problem that the portion of the toner passage, which is not fully open, increases the toner passage in developer (toner) flow resistance, partially dams up (blocks) the toner flow, and causes the toner particles to agglomerate into large particles or the like. 
       Embodiment 5 
       [0150]    Next, the image forming apparatus in another embodiment of the present invention is described. 
         [0151]    The portions of the image forming apparatus in this embodiment, which are the same as, or similar to, the counterparts in the first embodiment are given the same referential codes as those given to the counterparts, and are not described in order not to repeat the same description. 
       (Structure of Toner Cartridge) 
       [0152]      FIG. 12  is a drawing which shows the structure and operational modes of the image forming apparatus in this embodiment. More specifically,  FIG. 12(   a ) is a schematic sectional view of the toner cartridge, and the portion of the image forming apparatus, with which the toner cartridge is coupled, and  FIG. 12(   b ) shows the operational modes of the image forming apparatus. 
         [0153]    The image forming apparatus in this embodiment, shown in  FIG. 12(   a ), is similar in basic structure to that in the fourth embodiment. It is different from the image forming apparatus in the fourth embodiment only in the following features. 
         [0154]    The toner cartridge  15   c  in this embodiment has a one-way valve  45  for discharging the air in the airtight chamber  44  out of the external shell  40 . 
         [0155]    The toner cartridge  15   c  in this embodiment has the one-way valve  45 . Therefore, it is different from the toner cartridge  15   b  in the fourth embodiment in the second and third modes in which air is re-injected into the toner storage pouch  41 . 
       (Operation for Re-Expanding (Re-Inflating) Toner Storage Pouch) 
       [0156]    Next, the operation to re-expanding (re-inflating) the toner storage pouch  41  in this embodiment is described. 
         [0157]    Referring to  FIG. 12(   b ), the apparatus main assembly  101   c  in this embodiment can be operated in one of the first to fifth modes in order to control the toner discharge passage valve  82  and air passage valve  93 , and pump  73 . 
         [0158]    In the first mode, or the initial mode, both the toner discharge passage valve  82  and air passage valve  93  are kept closed. 
         [0159]    Next, in the second mode, the pump  73  begins to be driven to inject air, with the toner discharge passage valve  82  and air passage valve  93  being kept closed. In the fourth embodiment, the toner discharge passage valve  82  is kept closed, and the air passage valve  93 , which was kept closed in the first mode, is opened. In comparison, in this embodiment, in the second mode, both the toner discharge passage valve  82  and air passage valve  93  are kept closed. 
         [0160]    Since the toner discharge passage valve  82  is kept closed, the air injected by the pump  73  is sent into the toner storage pouch  41  through the air injection passage  83  and toner discharge passage  41 . 
         [0161]    As air begins to be injected into the toner storage pouch  41 , the toner storage pouch  41  begins to be inflated in the external shell  40 , where by the air in the airtight chamber  44  begins to be compressed by the inflation of the toner storage pouch  41 . However, the external shell  40  is provided with the one-way valve  45 . Thus, as the air in the airtight chamber  44  begins to be compressed, it is allowed to be escape from the airtight chamber  44 , into the outside of the external shell  40 . In other words, in this embodiment, in the second mode, the air passage valve  93  is kept closed, the air in the airtight chamber  44  is discharged from the airtight chamber  44 , out into the outside of the external shell  40 , through the one-way valve  45 . 
         [0162]    In the second mode, as air is sent into the toner storage pouch  41 , the toner  140  in the toner storage pouch  41  is loosened by the airflow, becoming therefore higher in fluidity, as in the case of the fourth embodiment. 
         [0163]    After the injection of a preset amount of air into the toner storage pouch  41  in the second mode, the operation is switched to the third mode, in which both the toner discharge passage valve  82  and air passage valve  93  are kept closed as in the second mode, and then, the air injection into the toner storage pouch  41  is stopped by stopping the driving of the pump  73 . 
         [0164]    The one-way valve  45  allows the air in the airtight chamber  44  to be discharged out of the external shell  40 , but, does not allow the ambient air of the external shell  40  to flow into the airtight chamber  44 . That is, the air in the airtight chamber  44  is pushed out of the external shell  40  by the expansion of the toner storage pouch  41 , but the atmospheric air is not allowed to flow into the airtight chamber  44  as long as it is ensured that the external shell  40  is kept airtight. 
         [0165]    As the air injection into the toner storage pouch  41  is stopped as in the case of the fourth embodiment, the resiliency of the toner storage pouch  41  attributable to the elasticity of the toner storage pouch  41  begins to make the toner storage pouch  41  to contract. The image forming apparatus in this embodiment, however, is structured as described above. Therefore, even after the toner storage pouch  41  began to contract, no air flows into the airtight chamber  44 . Thus, the air in the airtight chamber  44  is reduced in pressure. Therefore, the airtight chamber  44  becomes negative in internal air pressure relative to the atmospheric pressure. Consequently, the resiliency of the toner storage pouch  41 , which works in the direction to make the toner storage pouch  41  to contract, balances with the negative internal air of the airtight chamber  44 , allowing thereby the toner storage pouch  41  to remain inflated in the external shell  40 . 
         [0166]    Thus, even when the internal space of the toner storage pouch  41  is open to the atmospheric air through the toner discharge nozzle  42  which is in contraction to the internal space of the toner storage pouch  41 , it is possible to prevent the toner  140  in the toner storage pouch  41  from being discharged along with the air in the toner storage pouch  41 . 
         [0167]    Next, in the fourth mode, the air passage valve  93  is kept closed and the toner discharge passage valve  82 , which was kept closed in the third mode, is opened. As soon as the toner discharge passage valve  82  is opened, the toner storage pouch  41  begins to contract because of its resiliency attributable to its elasticity. However, the image forming apparatus in this embodiment is structured as described above. Thus, even after the toner storage pouch  41  begins to contract, the atmospheric air does not flow into the airtight chamber  44 , because the air passage valve  93  is kept closed. Therefore, the air in the airtight chamber  44  is reduced in pressure, becoming negative in pressure relative to the atmospheric pressure (ambient air pressure). 
         [0168]    Thus, the toner storage pouch  41  is allowed to remain inflated in the external shell  40 , with the force which works in the direction to make the toner storage pouch  41  remain inflated by the air injected into the toner storage pouch  41 , becoming equal to the negative pressure of the air in the airtight chamber  44 . 
         [0169]    Also in the fifth embodiment, the toner discharge passage valve  82  is kept opened, and the air passage valve  93 , which was kept closed in the fourth mode, is also opened. Thus, the atmospheric air flows into the airtight chamber  44  through the air suction nozzle  43   a , making thereby the airtight chamber  44  not negative in pressure. As a result, the force which was generated by the negative air pressure in the airtight chamber  44  and kept the toner storage pouch  41  inflated is lost, and therefore, the toner storage pouch  41  is made to contracts by its resiliency attributable to the elastic substance of which it is made of. 
         [0170]    That is, the phenomenon that as soon as the airtight chamber  44  is made to lose its negative internal air pressure, the toner storage pouch  41 , which is an elastic member, is made to contact by its resiliency, can be utilized to discharge the toner  140  in the toner storage pouch  41 , along with the air in the air in the toner storage pouch  41 , through the toner discharge nozzle  42 . 
         [0171]    After the discharging of the toner  140  in the toner storage pouch  41  in the fifth mode, the operation is switched to the first mode, in which the image forming apparatus is kept in the initial state, in order to prepare the image forming apparatus for the next toner discharge. 
       Embodiment 6 
       [0172]    Next, the image forming apparatus in another embodiment of the present invention is described. 
         [0173]    The portions of the image forming apparatus in this embodiment, which are the same as, or similar to, the counterparts in the first embodiment are given the same referential codes as those given to the counterparts, and are not described in order not to repeat the same description. 
       (Structure of Toner Cartridge) 
       [0174]      FIG. 13  is a drawing which shows the structure and operational modes of the image forming apparatus in this embodiment. More specifically,  FIG. 13(   a ) is a schematic sectional view of the toner cartridge, and the portion of the image forming apparatus, with which the toner cartridge is coupled, and  FIG. 13(   b ) shows the operational modes of the image forming apparatus. 
         [0175]    Basically, the image forming apparatus in this embodiment, shown in  FIG. 13(   a ), is similar in basic structure to that in the fourth embodiment. It is different from the image forming apparatus in the fourth embodiment only in the following features. 
         [0176]    In this embodiment, an air suction passage  83   a  which is in connection to the pump  73   a  is between the air suction nozzle receptacle  90  and air passage valve  93 . Thus, the atmospheric air can be suctioned into the airtight chamber  44  by the pump  73   a  through the air suction passage  83   a  and air suction nozzle  43   a . The toner cartridge in this embodiment is the same as the toner cartridge  15   b  in the fourth embodiment. 
       (Operation to Re-Expand (Re-Inflate) Toner Storage Pouch) 
       [0177]    Next, the operation to re-expand (re-inflate) the toner storage pouch  41  in this embodiment is described. 
         [0178]    Referring to  FIG. 13(   b ), the image forming apparatus  100   d  in this embodiment is provided with the first to fourth operational modes in which the toner discharge passage valve  82  and air passage valve  93 , and pump  73   a  are controlled. 
         [0179]    In the first mode, the image forming apparatus  100   d  are kept in the initial state, in which both the toner discharge passage valve  82  and air passage valve  93  are kept closed. 
         [0180]    In the second mode, the air passage valve  93  is kept closed, whereas the toner discharge passage valve  82  is kept opened. 
         [0181]    Also in the second mode, the pump  73   a  begins to be driven suction the air in the airtight chamber  44  out of the external shell  40 , into the ambience through the air suction passage  83   a  and air suction nozzle  43   a . Thus, the airtight chamber  44  is made to be negative in internal air pressure by the suctioning of the air in the airtight chamber  44  by the pump  73   a.    
         [0182]    As the airtight chamber  44  becomes negative in internal air pressure, the toner storage pouch  41  begins to inflate so that the force generated by the negative pressure of the internal air of the airtight chamber  44  becomes equal to the force generated by the elasticity of the toner storage pouch  41 . In this mode, the toner discharge passage valve  82  is kept open. Therefore, the atmospheric air flows into the toner storage pouch  41  through the toner discharge nozzle  42 , allowing thereby the toner storage pouch  41  to expand (inflate). 
         [0183]    After a preset amount of air is suctioned out of the airtight chamber  44  in the second mode, the operation is switched to the third mode, in which the driving of the pump  73   a  is stopped to stop suctioning air out of the airtight chamber  44 , while the air passage valve  93  is kept closed, and the toner discharge passage valve  82  is kept open. 
         [0184]    Thus, the resiliency of the toner storage chamber  44  attributable to the elasticity of the toner storage pouch  41  begins to make the toner storage pouch  44  to contract. However, the air passage valve  93  of the image forming apparatus  100   d  in this embodiment structured as described above is kept closed. Thus, even the toner storage pouch  41  begins to contract, no air flows into the airtight chamber  44 . Thus, the air in the airtight chamber  44  is reduced in pressure. Thus, the air in the airtight chamber  44  remains negative in pressure relative to the atmospheric pressure (ambient air pressure). As a result, the toner storage pouch  41  remains expanded (inflated) in the external shell  40 , with the force which is generated by the resiliency of the inflated toner storage pouch  41 , and works in the direction to make the inflated toner storage pouch  40  contracts, becoming equal to the negative air pressure in the toner storage pouch  41 . 
         [0185]    Therefore, even when the toner discharge passage valve  82  is kept open, and therefore, the internal space of the toner storage pouch  41  is open to the atmospheric air through the toner discharge nozzle  42  which is in connection to the internal space of the toner storage pouch  41 , it is possible to prevent the toner  140  in the toner storage pouch  41  from being discharged, along with the air in the toner storage pouch  41 . As described above, in the third mode, the toner discharge passage valve  82  is fully opened to prepare the image forming apparatus  100   d  and toner cartridge  15   c , to discharge the toner  140  out of the toner storage pouch  41 . 
         [0186]    Lastly, in the fourth mode, the toner discharge passage valve  82  is kept open, and the air passage valve  93 , which was kept closed in the third mode, is opened. Thus, the atmospheric air flows into the airtight chamber  44  through the air suction nozzle  43   a , making thereby the air in the airtight chamber  44  loses its negative pressure. Therefore, the force which is attributable to the negative air pressure in the airtight chamber  44  and kept expanded (inflated) the toner storage pouch  41  is lost. Consequently, the resiliency of the toner storage pouch  41  which is an elastic member causes the toner storage pouch  41  to contract. In other words, it is possible to discharge the toner  140  in the toner storage pouch  41 , along with the air in the toner storage pouch  41 , by utilizing the phenomenon that the moment the air in the airtight chamber  44  loses its negative pressure, the toner storage pouch  41  contracts because of its resiliency. 
         [0187]    After the discharging of the toner  140  in the toner storage pouch  41  by a present amount in the fourth mode, the operation is switched back to the first mode to prepare the image forming apparatus  100   d  for the next toner discharge. 
       Superiority of Present Invention to Prior Art 
       [0188]    Next, the superiority of the present invention to the prior art is described. In the prior art, in order to control the operation to discharge the developer in a developer supply container with the utilization of the resiliency of the elastic member of the developer supply container, the developer passage through which the developer is discharged is provided with a valve. 
         [0189]    That is, the developer in the developer supply container is prevented by the valve from being discharged from the container. However, the developer pouch is always under the pressure which is attributable to the resiliency of the elastic substance of which the developer pouch is made. This pressure continuously works in the direction to discharge the developer in the developer supply container out of the container. Therefore, as soon as the valve, which has been preventing the developer in the developer supply container from being discharged, begins to be opened, the pressure is released, and therefore, the developer in the developer supply container begins to be discharged. 
         [0190]    This creates the following problem. That is, the developer begins to be discharged from the developer supply container before the valve is fully opened. Thus, the partially open portion of the valve increases the outward developer passage of the developer supply container in developer (toner) flow resistance. As the outward developer flow is impeded by the partially open portion of the valve, it is sometimes partially dammed up (blocked). Thus, some toner particles in the developer flow agglomerate into large particles of toner, which sometimes reduces an image forming apparatus in image quality. 
         [0191]    Further, in the case of a toner cartridge in accordance with the prior art, which is structured to utilize temporary force, such as the force generated by the resiliency of the elastic substance of which the developer storage pouch of the toner cartridge is made, to discharge the developer from the developer storage pouch, it is possible the pressure for discharging the developer will be lost before the valve is fully opened. If the pressure for discharging the developer is lost before the valve is fully opened, the pressure difference for discharging the developer is sometimes lost before the developer is discharged from the developer container by a preset amount. Thus, the amount by which the developer in the developer supply container fails to be discharged is affected by the speed with which the valve is opened. That is, in some cases, the amount by which the developer in the developer supply container fails to be discharged became substantial. 
         [0192]    In comparison, in the case of a toner cartridge in accordance with the present invention, in order to prevent the expanded (inflated) elastic toner storage pouch  41  from contracting (deflating), the air in the internal space (airtight chamber  44 ) of the external shell  40  is kept negative in air pressure. Further, when it is necessary to discharge the toner  140  in the toner storage pouch  41 , the atmospheric air is allowed to flow into the airtight chamber  44  through the air suction nozzle  43   a  to make the air in the airtight chamber  44  lose its negative pressure. 
         [0193]    That is, it is in the portion of the image forming apparatus and/or toner cartridge other than the toner discharge nozzle  42 , which is the passage through which the toner  140  flows when it is discharged from the toner storage pouch  41 , that the mechanism for controlling the discharging of the toner  140  in the toner storage pouch  41  is positioned. Therefore, the toner cartridge in accordance with the present invention is significantly smaller than any toner cartridge in accordance with the prior art, in the amount of the developer (toner) flow resistance which the toner  140  encounters in the toner passage while it is discharged from the toner storage pouch  41 . 
         [0194]    Further, in the preceding embodiments of the present invention, it does not occur that the toner  140  begins to be discharged before the toner passage is fully opened as in the case of a toner cartridge in accordance with the prior art. This alone can make the toner cartridges in the preceding embodiments significantly smaller in developer (toner) resistance than any toner cartridge in accordance with the prior art. 
         [0195]    In addition, the preceding embodiments of the present invention can prevent the problem which the prior art suffers, more specifically, the problem that the portion of the toner passage, which is yet to be fully opened, temporarily increases the toner passage in developer (toner) flow resistance, which is likely to results in the formation of large particles of toner. Further, not only can the present invention ensure that it is only after the toner passage becomes fully open that the toner  140  can be discharged, but also, that the discharging of the toner  140  is triggered by the beginning of the airflow (which is less affected by the resistance of its passage than the developer (toner)) into the airtight chamber  44 . Therefore, even thought the image forming apparatus and toner cartridge in accordance with the present invention are structured to utilize the temporary force, such as the force generated by the resiliency of the elastic substance of which the toner storage pouch  41  is made, to discharge the toner  140  in the toner storage pouch  41 , they can effectively release the force attributable to the elastic substance. Thus, a toner cartridge in accordance with the present invention is unlikely to vary in the amount by which the toner  140  therein fails to be discharged. 
         [0196]    Further, in the case of the prior art, the pressure for discharging the toner  140  and air in the toner storage pouch  41  is always present. Therefore, toner is likely to be scattered when the toner storage pouch  41  is refilled with air. 
         [0197]    In comparison, in the case of the present invention, in order to keep expanded (inflated) the expanded (inflated) elastic toner storage pouch  41 , the air in the airtight chamber  44  in the external shell  41  is made negative in air pressure. Therefore, the toner  140  is not discharged until the air in the airtight chamber  44  is made to lose its negative pressure. Therefore, even when the toner storage pouch  41  is refilled with air, the force for discharging the toner  140  can be kept under control. Therefore, the toner  140  can be prevented from scattering even when the toner storage pouch  41  is refilled with air. 
         [0198]    While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
         [0199]    This application claims priority from Japanese Patent Application No. 122650/2013 filed Jun. 11, 2013, which is hereby incorporated by reference.

Technology Classification (CPC): 6