Abstract:
A developer container for an image forming apparatus includes a developer accommodating chamber, provided with an opening, for accommodating a developer to be supplied to the opening; a feeding member, provided in the developer accommodating chamber and having an elasticity, for feeding the developer by rotation thereof; a deforming portion, provided in the developer accommodating chamber and contactable to the feeding member, for deforming the feeding member against the elasticity with the rotation of the feeding member; and a restoration portion for permitting the feeding member deformed by the deformed portion to restore elastically, thereby to throw the developer toward the opening, wherein a boundary portion between the deformed portion the restoration portion is disposed below a lower end of the opening.

Description:
FIELD OF THE INVENTION AND RELATED ART 
       [0001]    The present invention relates to a developer container, a developing apparatus, and a process cartridge removably mountable in an electrophotographic image forming apparatus. 
         [0002]    Here, an “electrophotographic image forming apparatus (which hereafter may be referred to simply as “image forming apparatus”)” means an apparatus which forms an image on recording medium (sheet of recording medium) with the use of an electrophotographic image forming system. An “electrophotographic image forming apparatus” includes, for example, a copying machine, a printer (laser beam printer, LED printer, etc.), a facsimile machine, a wordprocessor, and a multifunction machine capable of performing two or more functions of the preceding image forming apparatus, etc. 
         [0003]    An image forming apparatus, such as a printer, which uses an electrophotographic image forming system (electrophotographic process), records an image by carrying out the following steps: First, its electrophotographic photosensitive member (which hereafter will be referred to as “photosensitive member”), which is an image bearing member, is uniformly charged. Then, an electrostatic latent image is formed on the peripheral surface of the photosensitive member by selectively exposing numerous points of the uniformly charged peripheral surface of the photosensitive member. Then, the electrostatic latent image formed on the peripheral surface of the photosensitive member is developed with the toner as developer, into a visible image, that is, an image formed of toner (which hereafter will be referred to simply as toner image). Then, the toner image formed on the peripheral surface of the photosensitive member is transferred onto a sheet of recording medium, such as recording paper, plastic sheet, etc. After the transfer of the toner image onto the sheet of recording medium, the toner image on the sheet of recording medium is fixed to the recording medium by applying heat and pressure to the toner image. 
         [0004]    An image forming apparatus, such as the above described one, generally requires to be replenished with developer, and also, requires maintenance for its various processing means. Thus, various ideas have been proposed for making easier the operation for replenishing an image forming apparatus developer, and also, making it easier to maintain the various processing means. One of the ideas is to integrally dispose a photosensitive member, a charging means, a developing means, a cleaning means, etc., in a cartridge which is removably mountable in the main assembly of an image forming apparatus. This idea has been put to practical use as a process cartridge, which is removably mountable in the main assembly of an image forming apparatus. The employment of an image formation system which uses a process cartridge makes it possible to provide an image forming apparatus superior in usability to an image forming apparatus which does not employ the image forming system based on a process cartridge. 
         [0005]    In recent years, a color image forming apparatus which forms a color image by using multiple developers different in color has come to be commonly used. One of the well-known color image forming apparatuses is an image forming apparatus of the so-called in-line type, that is, an image forming apparatus which employs multiple photosensitive members, the number of which corresponds to the number of monochromatic image forming operations carried out, per multicolor image, using multiple developers different in color, and in which the multiple photosensitive members are arranged side by side (juxtaposed) in a single row which is parallel to the direction in which the surface of the member of apparatus, onto which toner images are transferred, is moved. In some of the color image forming apparatuses of the in-line type, the multiple photosensitive members are juxtaposed in a straight row which is intersectional (perpendicular) to the vertical direction (direction of gravity); for example, they are juxtaposed in a straight row parallel to the horizontal direction. The in-line configuration is preferable in that the employment of the in-line configuration makes it easier to deal with the demand for the increase in the image formation speed, demand for a multifunction printer, etc., or the like. 
         [0006]    Among the image forming apparatuses of the in-line type, in which the multiple photosensitive members are arranged side by side (juxtaposed) in a straight row intersectional to the vertical direction, there are image forming apparatuses in which the multiple photosensitive members are disposed under an intermediary transfer member, that is, a member onto which toner images are temporarily transferred, or under the recording medium bearing member for conveying a sheet of recording medium, which is a final medium onto which toner images are transferred (U.S. Pat. No. 6,907,215). 
         [0007]    In the case of the image forming apparatuses in which the photosensitive members are disposed under the intermediary transfer member or recording medium bearing member, the fixing apparatus and developing apparatus, for example, can be positioned so that the intermediary transfer member or recording medium member is between the fixing apparatus and developing apparatus. Therefore, the image forming apparatuses in which the photosensitive members are under the intermediary transfer member or recording medium bearing member enjoy the benefit that the developing apparatus (or exposing apparatus) is unlikely to be affected by the heat from the fixing apparatus. 
         [0008]    In the case of some image forming apparatuses in which the photosensitive members are under the intermediary transfer member or recording medium bearing member as described above, it is necessary for developer to be supplied to the developing apparatus against gravity. 
         [0009]    That is, generally, a developing apparatus has a development chamber and a developer storage chamber. The development chamber is a chamber in which a member (developer bearing member) for supplying a photosensitive member with developer, a member (developer supplying member) for supplying a developer bearing member with developer, etc., are located. The developer storage chamber is a chamber in which the developer to be conveyed to the development chamber is stored. As described above, in the case of some image forming apparatus in which the photosensitive members are under the intermediary transfer member or recording medium bearing member, it is necessary for developer to be supplied to the development chamber from the developer storage chamber located at a lower level than the development chamber, that is, developer must be supplied against gravity. 
         [0010]    U.S. Pat. No. 6,507,215 discloses one of the means for conveying developer from the developer storage chamber to the development chamber located at a higher level than the developer storage chamber. According to this patent, a member (stirring member) for stirring the developer in the developer storage chamber is provided with a conveying member, which is pasted to the edge of the stirring member. The conveying member is formed of flexible sheet. In the case of the means recorded in U.S. Pat. No. 6,507,215, however, the developing apparatus is structured so that developer is conveyed into the developer storage chamber by the conveying member attached to the outward edge of the stirring member, in terms of the radius direction of the stirring member, while remaining held by the conveying member. Therefore, the developing apparatus disclosed in the abovementioned patent is difficult to be reduced in the size of its developer storage chamber. Further, its toner receiving (catching) member is below the supply roller  31 . Therefore, it is necessary to ensure that developer will not become packed in the gap between the toner receiving (catching) member and supply roller  31 . 
       SUMMARY OF THE INVENTION 
       [0011]    Thus, the primary object of the present invention is to provide a developer container, a developing apparatus, and a process cartridge, which are significantly simpler in structure and smaller than those in accordance with the prior art, and are capable of satisfactorily conveying developer therein against gravity, while being structured so that developer needs to be conveyed against gravity. 
         [0012]    Another object of the present invention is to provide a developing apparatus, and a process cartridge, which have a stirring portion capable of stirring developer, between the developer supplying roller and the partition wall located below the developer supplying roller, and supplying the stirred developer to the developer supplying roller. 
         [0013]    According to an aspect of the present invention, there is provided a developer container for an image forming apparatus comprising a developer accommodating chamber, provided with an opening, for accommodating a developer to be supplied to said opening; a feeding member, provided in said developer accommodating chamber and having an elasticity, for feeding the developer by rotation thereof; a deforming portion, provided in said developer accommodating chamber and contactable to said feeding member, for deforming said feeding member against the elasticity with the rotation of said feeding member; and a restoration portion for permitting said feeding member deformed by said deformed portion to restore elastically, thereby to throw the developer toward said opening, wherein a boundary portion between said deformed portion said restoration portion is disposed below a lower end of said opening; and a developing device including the container and a process cartridge including such a developing device 
         [0014]    According to another aspect of the present invention, there is provided a developing device for use with an image forming apparatus, comprising a rotatable developing roller for carrying a developer; a rotatable developer supplying roller for supplying the developer to said developing roller; a partition provided at a position lower than said developer supplying roller; a stirring portion, having an opening for the developer and provided between said developer supplying roller and said partition, for stirring the developer by swing motion including a movement of bring the opening closer to said developer supplying roller and a movement of the opening away from said developer supplying roller; and a process cartridge including the developing device. 
         [0015]    These and other objects, features, and advantages of the present invention will become more apparent upon consideration of the following description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a sectional view of the image forming apparatus in the first of the preferred embodiments of the present invention. 
           [0017]      FIG. 2  is a cross-sectional view of the process cartridge in the first preferred embodiment of the present invention. 
           [0018]      FIG. 3  is also a cross-sectional view of the process cartridge in the first preferred embodiment of the present invention. 
           [0019]      FIG. 4  is a schematic drawing of the toner conveying member of the process cartridge in the first preferred embodiment of the present invention, showing the structure of the toner conveying member. 
           [0020]      FIG. 5  is a cross-sectional view of a part of the process cartridge in the first embodiment of the present invention, showing how toner is being stirred in the development chamber. 
           [0021]      FIG. 6  is a front view of the stirring means of the process cartridge in the first preferred embodiment of the present invention. 
           [0022]      FIG. 7  is a cross-sectional view of the process cartridge in another (second) of the preferred embodiments of the present invention. 
           [0023]      FIG. 8  is a cross-sectional view of the process cartridge in the second embodiment of the present invention, showing how toner is being conveyed in the development chamber. 
           [0024]      FIG. 9  is a cross-sectional view of the process cartridge in yet another (third) of the preferred embodiments of the present invention. 
           [0025]      FIG. 10  is an enlarged perspective view of a part of the toner conveying member with which the process cartridge shown in  FIG. 9  is provided. 
           [0026]      FIG. 11  is a cross-sectional view of the process cartridge in yet another (fourth) of the preferred embodiments of the present invention. 
           [0027]      FIG. 12  is a cross-sectional view of a part of the process cartridge in the fifth of the preferred embodiments of the present invention. 
           [0028]      FIG. 13  is a cross-sectional view of a part of the process cartridge in yet another (sixth) of the preferred embodiments of the present invention. 
           [0029]      FIG. 14  is a side view of the stirring portion of the process cartridge in the seventh of the preferred embodiments of the present invention. 
           [0030]      FIG. 15  is an exploded perspective view of the stirring regulating portion of the process cartridge in the eighth of the preferred embodiments of the present invention. 
           [0031]      FIG. 16  is an exploded perspective view of a part of the process cartridge shown in  FIG. 15 , from which the stirring regulating portion has been removed. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0032]    Hereinafter, the developing containers, developing apparatuses, and process cartridges, which are in accordance with the present invention, will be described with reference to the appended drawings. 
       Embodiment 1 
     [Electrophotographic Image Forming Apparatus] 
       [0033]    First, the electrophotographic image forming apparatus (image forming apparatus) in the first preferred embodiment of the present invention will be described regarding its general structure.  FIG. 1  is a schematic sectional view of the image forming apparatus  100  in this embodiment. The image forming apparatus  100  in this embodiment is a full-color laser beam printer of the in-line type, and also, is of the intermediary transfer type. The image forming apparatus  100  is capable of forming a full-color image on a sheet of recording medium (recording paper, plastic sheet, fabric, or the like) according to pictorial information. Pictorial information is inputted into the main assembly of the image forming apparatus from a host device, such as an image reading apparatus connected to the main assembly, a personal computer connected to the main assembly so that information can be exchanged between the main assembly and computer, or the like apparatuses. 
         [0034]    The image forming apparatus  100  has multiple image forming portions, more specifically, the first, second, third, and fourth 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 first-fourth image forming portions SY, SM, SC, and SK are arranged side by side (juxtapose) in a straight row intersectional to the vertical direction. 
         [0035]    Incidentally, in this embodiment, the first-fourth image forming portions are virtually the same in structure and operation, although they are different in the color of the image they form. Therefore, unless they need to be differentiated, they will be described together without referring to the alphabetic referential symbols Y, M, C, and K which represent the colors of toner. 
         [0036]    The image forming apparatus  100  in this embodiment has multiple image bearing members, more specifically, four electrophotographic photosensitive members  1  which are in the form of a drum (photosensitive drums  1 ). The multiple image bearing members are arranged side by side (juxtaposed) in parallel in a straight row intersectional to the vertical direction. The photosensitive drum  1  is rotationally driven in the direction (clockwise direction) indicated by an arrow mark A in the drawing, by an unshown driving means (driving force source). The image forming apparatus  100  is also provided with a charge roller  2  and a scanner unit  3  (exposing apparatus), which are in the adjacencies of the peripheral surface of the photosensitive drum  1 . The charge roller  2  is a charging means for uniformly charging the peripheral surface of the photosensitive drum  1 . The scanner unit  3  (exposing apparatus) is an exposing means for forming an electrostatic image (electrostatic latent image) on the peripheral surface of the photosensitive drum  1 , by projecting a beam of laser light, while modulating the beam with pictorial information. Also disposed in the adjacencies of the peripheral surface of the photosensitive drum  1  are a development unit  4  (developing apparatus) and a cleaning member  6 . The development unit  4  is a developing means for developing an electrostatic image into a visible image, that is, an image formed of toner. The cleaning member  6  is a cleaning means for removing the toner (transfer residual toner) remaining on the peripheral surface of the photosensitive drum  1  after the toner image transfer. The image forming apparatus  100  is also provided with an intermediary transfer belt  5 , which is an intermediary member onto which the toner image on the photosensitive drum  1  is temporarily transferred. The intermediary transfer belt  5  is disposed so that it opposes the four photosensitive drums  1 . In terms of the rotational direction of the photosensitive drum  1 , the area in which the photosensitive drum  1  is charged by the charge roller  2 , the area in which the photosensitive drum  1  is exposed by the scanner unit  3 , the area in which the electrostatic image is developed by the development unit  4 , the area in which the toner image is transferred from the intermediary transfer belt  5 , and the area in which the photosensitive drum  1  is cleaned by the cleaning member  6 , are located in the listed order. 
         [0037]    Incidentally, in this embodiment, the developer which the development unit  4  uses is nonmagnetic single component developer (toner). The development unit  4  develops an electrostatic image in reverse by placing the development roller (developer bearing member, which will be described later) in contact with the photosensitive drum  1 . That is, the development unit  4  in this embodiment adheres the toner, which is the same in polarity as the polarity (negative in this embodiment) to which the photosensitive drum  1  is charged, to the numerous points of the peripheral surface of the photosensitive drum  1 , which have reduced in the amount of electric charge by being exposed. As a result, the electrostatic image on the photosensitive drum  1  becomes visible; it is developed. 
         [0038]    Also in this embodiment, the photosensitive drum  1 , charge roller  2  as a processing means for processing the photosensitive drum  1 , developing apparatus  4 , and cleaning member  6 , are integrated in the form of a cartridge (process cartridge  7 ), which is removably mountable in the main assembly of the image forming apparatus  100  while being assisted by cartridge mounting means, such as cartridge mounting guides, cartridge positioning members, etc., with which the main assembly is provided. In this embodiment, the four process cartridges  7 , which the image forming apparatus requires for the image formation of a multicolor image and are different in the color of the toner they contain, are the same in shape. The four process cartridges  7  contain yellow (Y), magenta (M), cyan (C), and black (K) toners, respectively. Although this embodiment is described with reference to a process cartridge, the present invention is also compatible with an image forming apparatus structured so that the developing apparatus  4  is removably mountable in the main assembly of the image forming apparatus, independently from the other processing means. 
         [0039]    The intermediary transfer belt  5  as an intermediary transferring member is an endless belt. It is in contact with all of the four photosensitive drums  1 , and rotates (circularly moves) in the direction (counterclockwise direction) indicated by an arrow mark B in the drawing. It is stretched around multiple supporting members (driver roller  51 , auxiliary secondary transfer roller  52 , follower roller  53 ), being thereby supported by them. 
         [0040]    On the inward side of the loop which the intermediary transfer belt  5  forms, four primary transfer rollers  8 , as primary transferring means, are arranged in parallel so that they oppose the four photosensitive drums  1  one for one. The primary transfer roller  8  keeps the intermediary transfer belt  5  against the photosensitive drum  1 , forming thereby a primary transfer portion N 1  (primary transfer nip), which is the area of contact between the intermediary transfer belt  5  and peripheral surface of the photosensitive drum  1 . To the primary transfer roller  8 , bias which is opposite in polarity to the normal polarity to which toner is charged is applied from an unshown primary transfer bias power source (high voltage power source), which is the means for applying the primary transfer bias. As the primary transfer bias is applied to the primary transfer roller  8 , the toner image on the photosensitive drum  1  is transferred (primary transfer) onto the intermediary transfer belt  5 . 
         [0041]    On the outward side of the loop which the intermediary transfer belt  5  forms, a roller  9  (secondary transfer roller) for the secondary transfer, which is the means for transferring a toner image for the second time, is disposed so that it opposes an auxiliary secondary transfer roller  52 . The secondary transfer roller  9  presses the intermediary transfer belt  5  against the auxiliary secondary transfer roller  52 , forming thereby the transfer portion N 2  (transfer nip), which is the area of contact between the intermediary transfer belt  5  and secondary transfer roller  9 , and in which a toner image is transferred for the second time. To the secondary transfer roller  9 , bias which is opposite in polarity to the normal polarity to which toner is charged, is applied from an unshown secondary transfer bias power source (high voltage power source), which is the means for applying the secondary transfer bias. As the secondary transfer bias is applied to the secondary transfer roller  9 , the toner image on the intermediary transfer belt  5  is transferred (secondary transfer) onto a sheet of recording medium  12 . The transfer rollers  8  and  9 , which are the transfer rollers for the first and secondary transfers, respectively, are the same in structure. 
         [0042]    The image forming operation carried out by the image forming apparatus in this embodiment is as follows: First, the peripheral surface of the photosensitive drum  1  is uniformly charged by the charge roller  2 . Next, the charged peripheral surface of the photosensitive drum  1  is scanned (exposed) by the beam of laser light emitted by the scanner unit  3  while being modulated according to the pictorial information. As a result, an electrostatic image, which is accordance with the pictorial information, is formed on the photosensitive drum  1 . Then, the electrostatic image on the photosensitive drum  1  is developed by the development unit  4  into a visible image, that is, an image formed of toner (which hereafter will be referred to as toner image). The toner image on the photosensitive drum  1  is transferred (primary transfer) onto the intermediary transfer belt  5  by the function of the transfer roller  8 . 
         [0043]    For example, when the image forming apparatus is in the full-color image formation mode, the above described processes are sequentially carried out in the first-fourth image forming portions SY, SM, SC, and SK so that toner images different in color are sequentially transferred (primary transfer) in layers onto the intermediary transfer belt  5 . 
         [0044]    Thereafter, a recording medium  12  is conveyed to the secondary transfer portion N 2  in synchronism with the movement of the intermediary transfer belt  5 . The toner images on the intermediary transfer belt  5 , which are different in color, are transferred together (secondary transfer) onto the recording medium  12  by the function of the secondary transfer roller  9 , which is kept pressed against the intermediary transfer belt  5  with the presence of the recording medium  12  between the secondary transfer roller  9  and intermediary transfer belt  5 . 
         [0045]    After the transfer of the toner images onto the recording medium  12 , the recording medium  12  is conveyed to the fixing apparatus  10  as a fixing means. In the fixing apparatus  10 , the toner images are fixed to the recording medium  12  by the application of heat and pressure to the recording medium  12  and the toner images thereon. 
         [0046]    The residual toner remaining on the photosensitive drum  1  after the primary transfer step is removed by the cleaning member  6  and is recovered into a chamber for the removed toner (which will be described later). The residual toner remaining on the intermediary transfer belt  5  after the secondary transfer step is removed by a cleaning apparatus  11 , which is an apparatus for cleaning the intermediary transfer belt  5 . 
         [0047]    The image forming apparatus  100  is designed so that it can form a monochromatic or multicolor image, with the use of only one, or two or more, (not all of them) of the image forming portions. 
       [Process Cartridge] 
       [0048]    Next, the process cartridge  7  which is to be mounted in the image forming apparatus  100  will be described regarding its general structure.  FIG. 2  is a schematic sectional (cross-sectional) view of the process cartridge, at a plane perpendicular to the lengthwise direction (rotational axis direction) of the photosensitive drum  1 . The four process cartridges  7 , which the image forming apparatus  100  requires for image formation and are different in the color of the developer they contain, are practically identical in structure and operation, although they are different in the color of the developer they contain. 
         [0049]    The process cartridge  7  has a photosensitive member unit  13  having the photosensitive drum  1 , etc., and the development unit  4  having a development roller  17 , etc. 
         [0050]    The photosensitive member unit  13  has a cleaning means frame  14 , which is a frame for supporting various components of the photosensitive member unit  13 . The photosensitive drum  1  is rotatably supported by the cleaning means frame  14  with the interposition of unshown bearings. The photosensitive drum  1  is rotationally driven in the direction (clockwise direction) indicated by an arrow mark A in the drawing, by the driving force which it receives from an unshown motor as a photosensitive drum driving means (driving force source). 
         [0051]    The photosensitive member unit  13  also includes the charge roller  2  and cleaning member  6 , which are attached to the cleaning means frame  14  so that they remain in contact with the peripheral surface of the photosensitive drum  1 . The photosensitive member unit  13  is also provided with a chamber  14   a  for removed toner, which is for storing the transfer residual toner removed from the peripheral surface of the photosensitive drum  1  by the cleaning member  6 . The chamber  14   a  for removed toner is a part of the internal space of the cleaning means frame  14 . The photosensitive member unit  13  is structured so that the transfer residual toner removed from the peripheral surface of the photosensitive drum  1  by the cleaning member  6  falls into the chamber  14   a  for removed toner. 
         [0052]    Further, the cleaning means frame  14  holds charge roller bearings  2 , which are attached to the cleaning means frame  14  so that the axial line of the bearings  2  are parallel to the rotational axes of the charge roller  2  and photosensitive drum  1 . More specifically, the charge roller bearings  15  are disposed so that they can be moved in the direction indicated by an arrow mark C. The rotational shaft  2   a  of the charge roller  2  is rotatably held by the charge roller bearings  15 . Further, each charge roller bearing  15  is kept pressed toward the photosensitive drum  1  by a charge roller pressing spring  16  as a pressure generating means. 
         [0053]    As for the development unit  4 , it has a developing means frame  18 , which is a frame for supporting various components of the development unit  4 . The development unit  4  includes the development roller  17 , which is a developer bearing member and is rotated in contact with the peripheral surface of the photosensitive drum  1  in the direction (counterclockwise direction) indicated by an arrow mark D. That is, in this embodiment, the relationship, in terms of rotational direction, between the development roller  17  and photosensitive drum  1  is such that the direction in which the peripheral surface of the development roller  17  moves in the area of contact between the development roller  17  and photosensitive drum  1  is the same (upward in this embodiment) as the direction in which the peripheral surface of the photosensitive drum  1  moves in the area of contact between the development roller  17  and photosensitive drum  1 . The development roller  17  is rotatably supported by its lengthwise end portions (in terms of rotational axis direction), by the developing means frame  18 , with the interposition of lateral plates  19  ( 19 R and  19 L) which are attached to the right and left sides of the developing means frame  18 , respectively. Incidentally, in this embodiment, the development roller  17  is disposed in contact with the photosensitive drum  1 . However, the present invention is also compatible to a process cartridge (image forming apparatus) in which a preset amount of microscopic gap is kept between its photosensitive drum and development roller. 
         [0054]    The development unit  4  also includes a toner supply roller  20 , which is a developer supply roller and rotates in the direction (counterclockwise direction) indicated by an arrow mark E in the drawing. The toner supply roller  20  contacts the peripheral surface of the development roller  17 . In this embodiment, the toner supply roller  20  and development roller  17  are rotated so that the direction in which the peripheral surface of the toner supply roller  20  moves in the area of contact between the two rollers is opposite to the direction in which the peripheral surface of the development roller  17  moves in the area of contact between the two rollers. The toner supply roller  20  supplies the peripheral surface of the development roller  17  with toner, and also, strips away from the peripheral surface of the development roller  17 , the toner remaining on the peripheral surface of the development roller  17 , that is, the toner on the peripheral surface of the development roller  17 , which was not used for development. Further, the development unit  4  includes a development blade  21 , which is a member for regulating in thickness the toner layer formed on the peripheral surface of the development roller  17  by the toner supplied onto the peripheral surface of the thickness by the toner supply roller  20 . The development blade  21  makes contact with the peripheral surface of the development roller  17 . 
         [0055]    A toner storage chamber  18   a , as a developer storage chamber, which is a part of the internal space of the developing means frame  18 , stores nonmagnetic single component developer, that is, toner. There is a toner conveying member  22 , which is rotatably supported in the toner storage chamber  18   a , by the developing means frame  18 . As will be described later, the toner conveying member  22  stirs the toner in the toner storage chamber  18   a , and conveys the toner to the development chamber  18   b  in which the above described development roller  17  and toner supplying roller  20  are disposed. Incidentally, this embodiment of the present invention is also compatible with a toner cartridge (developer container), which is removably mountable in the apparatus main assembly and has only the toner storage chamber  18   a  and toner conveying member  22 . 
         [0056]    The development unit  4  is attached to the photosensitive member unit  13 , with the use of a pair of connective pins  23  ( 23 R and  23 L) which are put through the holes  19   a  ( 19 Ra and  19 La) of the lateral plates  19  ( 19 R and  19 L) of the development unit  4 , respectively, so that both units are pivotally movable relative to each other. When the image forming apparatus  100  is in an image forming operation, the development unit  4  is kept pressured by the compression springs  24 , as means for pressing the development unit, in the direction to rotate about the connective pins  23  in the direction (clockwise direction) indicated by an arrow mark F. Therefore, the development roller  17  is kept in contact with the photosensitive drum  1 . 
       [Structure of Toner Conveying Member] 
       [0057]    Next, the structure of the toner conveying member of the development unit  4  of the process cartridge  7  in this embodiment will be described in detail. 
         [0058]    Incidentally, in this specification, terms, such as “upward”, “downward”, “vertical”, and “horizontal”, which indicate the directions regarding the structure of the development unit  4  (developing apparatus) or process cartridge  7 , means the upward, downward, vertical, and horizontal direction of the entirety, or a given member (component), of the development unit  4  or process cartridge  7 , which is in the normal state of usage. That is, the normal state of usage of the development unit (developing apparatus) or process cartridge means the state in which they are in when they are in their proper positions in the main assembly of a properly positioned image forming apparatus and are ready for image formation. 
         [0059]      FIG. 3  is a schematic cross-sectional view of the process cartridge  7  in which toner is being conveyed. 
         [0060]    The development unit  4  has the development chamber  18   b  and toner storage chamber  18   a , as described above. There are the development roller  17 , toner supplying roller  20 , development blade  21 , etc., in the development chamber  18   b . The toner storage chamber  18   a  contains the toner to be supplied to the development chamber  18   b , and a toner conveying member  22  (sheet-like member) for conveying toner to the development chamber  18   b . The toner storage chamber  18   a  is under the development chamber  18   b . Therefore, the toner must be conveyed from the toner storage chamber  18   a  to the development chamber  18   b  against gravity. 
         [0061]    As described above, it has been difficult to come up with a toner conveying mechanism (means) which is small, simple in structure, and yet, capable of efficiently and satisfactorily conveying toner in a development unit structured so that toner must be conveyed against gravity. Failure in satisfactorily conveying toner to the development chamber  18   b , in which the development roller  17  and toner supplying roller  20  are located, results in the formation of an image which suffers from unwanted white spots (which are attributable to phenomenon that points on peripheral surface of photosensitive member, to which toner is to be adhered, fail to be supplied with toner), or the like defects. 
         [0062]    Thus, one of the objects of the present invention is to provide a toner (developer) conveying mechanism (means) which is simple, inexpensive, small, and yet, capable of efficiently and satisfactorily conveying toner in a development unit structured so that toner must be conveyed against gravity, in order to prevent the formation of a defective image, more specifically, an image suffering from unwanted white spots attributable to the unsatisfactory delivery of toner, or the like defects. 
         [0063]    As one of the means to achieve the above described object, the development unit  4  in this embodiment is structured as follows. That is, the development unit  4  has the development chamber  18   b  and toner storage chamber  18   a , which are parts of the internal space of the developing means frame  18 . The development chamber  18   b  has the development roller  17  and toner supplying roller  20 . The toner storage chamber  18   a  is under the development chamber  18   b . The toner storage chamber  18   a  stores the toner to be supplied to the development chamber  18   b . There is a partition wall  26  between the development chamber  18   b  and toner storage chamber  18   a . The partition wall  26  has a hole  18   c  as the toner passage. The hole  18   c  is positioned so that its position matches the top portion of the toner storage chamber  18   a . There is the toner conveying member  22  in the toner storage chamber  18   a . The toner conveying member  22 , which is elastic, is for supplying toner to the development chamber  18   b . It is rotatably supported. 
         [0064]    The toner storage chamber  18   a  is provided with a guiding portion  18   a   2 , which is the portion of the wall of the toner storage chamber  18 , which causes the toner conveying member  22  to resiliently bend (deform), and with which the toner conveying member  22  makes contact as it is rotated. The guiding portion  18   a   2  is located below the hole  18   c . As the toner conveying member  22  is rotated, it comes into contact with the guiding portion  18   a   2 , receiving therefore the reactive force from the guiding portion  18   a   2 . As a result, the toner conveying member  22  bends (deforms) against its resiliency. Further, as the toner conveying member  22  is rotated in contact with the guiding portion  18   a   2 , it conveys toner by holding the toner on its downstream surface, in terms of its rotational direction. Referring to  FIG. 3 , in this embodiment, the guiding portion  18   a   2  is the portion of the straight portion of the internal surface of the toner storage chamber  18   a , which is between the bottom end of the straight portion and the point p at which the toner conveying member  22  separates from the straight portion. Further, the toner storage chamber  18   a  has a toner conveying member recovery space (which hereafter may be referred to simply as recovery space), which corresponds to a portion  18   a   4  of the internal surface of the toner storage chamber  18   a . The portion  18   a   4  is on the immediately downstream side of the guiding portion  18   a   2  and on the immediately upstream side of the hole  18   c , in terms of the rotational direction of the toner conveying member  22 . The recovery space, which corresponds to the portion  18   a   4 , is the space in which there is no contact between the toner conveying member  22  and the internal surface of the toner storage chamber  18   a . In this embodiment, the portion  18   a   4  (which hereafter may be referred to as recovery portion  18   a   4 ), to which the recovery space corresponds, is the portion of the internal surface of the toner storage chamber  18   a , which is between the abovementioned point p and hole  18   c . Further, the recovery portion  18   a   4  is above the horizontal plane which includes the rotational axis of the toner conveying member  22 . In other words, the development unit  4  is structured so that the border line  18   a   3  is at the same level as the horizontal plane which includes the rotational center of the toner conveying member  22 , or above the horizontal plane. 
         [0065]    Therefore, as the sweeping edge moves past the downstream end of the guiding portion  18   a   2 , the sweeping edge portion (portion next to internal surface of toner storage chamber  18   a ) of the toner conveying member  22  separates from the internal surface of the toner storage chamber  18   a . As the toner conveying member  22  separates from the internal surface of the toner storage chamber  18   a , it recovers from its deformation attributable to its contact with the internal surface of the toner storage chamber  18   a , due to its own resiliency; the toner conveying member  22  changes its shape in a manner to restore its normal shape. This change in the shape of the toner conveying member  22  in a manner to restore its normal shape causes the toner on the downstream surface of the toner conveying member  22 , which is being conveyed by the toner conveying member  22 , to catapult against gravity toward the hole  18   c  (which is on downstream side of recovery portion  18   a   4 , in terms of rotational direction of toner conveying member  22 ). 
         [0066]    The point p corresponds to the border portion  18   a   3  (border line) between the guiding portion  18   a   2  and recovery portion  18   a   4 . Further, the development unit  4  is structured so that the border line  18   a   3  is at a lower level than the bottom edge  18   c   1  (that is, lowest point) of the hole  18   c . As soon as the toner conveying member  22  separates from the border line  18   a   3 , its resiliency causes it to rotate into the area in which it can contact the edge portion of the hole  18   c . Thus, the moment the toner conveying member  22  separates from the border line  18   a   3 , its resiliency causes it to bump into the edge portion of the hole  18   c , ensuring thereby that the toner catapults into the hole  18   c.    
         [0067]    Further, the development unit  4  is structured so that the border line  18   a   3  is at a level higher than the horizontal plane which includes the rotational center of the toner conveying member  22 . 
         [0068]    Therefore, the development unit  4  in this embodiment can efficiently and satisfactorily convey toner against gravity, while being small and simple in structure. Next, the development unit  4  in this embodiment will be described in more detail. 
         [0069]    The developing means frame  18  has the partition wall  26 , which separates the development chamber  18   b  from the toner storage chamber  18   a . In this embodiment, the partition wall  26  is made up of a first portion  26   a  and second portion  26   b . The first portion  26   a  is more tilted relative to the horizontal plane than the second portion  26   b , and is located on the lateral side (left side in drawing) of the toner supply roller  20 . The second portion  26   a  is less tilted relative to the horizontal plane than the first portion  26   a , and is below the toner supply roller  20 . Tilting the partition wall  26  relative to the horizontal plane improves the efficiency with which toner is conveyed in the development chamber  18   b . In particular, in this embodiment, the partition wall  26  is made up of the first and second portions  26   a  and  26   b , which are different in the angle relative to the horizontal plane, being therefore greater in the surface area facing the toner supply roller  20  than the partition wall ( 26 ) of a process cartridge in accordance with the prior art. Therefore, the development chamber  18   b  in this embodiment is greater in the amount of the toner in the adjacencies of the toner supply roller  20 , being therefore greater in the amount by which toner is supplied to the toner supply roller  20 , than a development chamber in accordance with the prior art. 
         [0070]    The first portion  26   a  of the partition wall  26 , which is on the opposite side of the toner supply roller  20  from the area of contact between the toner supply roller  20  and development roller  17 , is provided with the hole  18   c , through which the toner in the toner storage chamber  18   a  is conveyed into the development chamber  18   b . In this embodiment, the toner supply roller  20  rotates so that the portion of its peripheral surface, which is facing the hole  18   c , moves in the downward direction. That is, the rotation of the toner supply roller  20  is such that the toner supplied to the development chamber  18   b  through the hole  18   c  is captured by the portion of the peripheral surface of the toner supply roller  20 , which is downwardly moving along the partition wall  26 . Further, the development unit  4  is structured so that the bottom edge  18   c   1  of the hole  18   c  is at a level higher than the bottom end  20   b  of the toner supply roller  20 . Thus, the vertical position of the top surface of the body of toner in the development chamber  18   b  is dependent upon the vertical position of the bottom edge  18   c   1  of the hole  18   c . Therefore, the top surface of the body of toner in the development chamber  18   b  is at a level higher than the vertical position of the bottom end of the toner supply roller  20 . Therefore, the development unit  4  in this embodiment is greater in the size of the area of contact between the peripheral surface of the toner supply roller  20  and the body of toner in the development chamber  18   b , being therefore greater in the efficiency with which toner is supplied to the toner supply roller  20 , than a development unit in accordance with the prior art. 
         [0071]    The toner storage chamber  18   a  contains the toner conveying member  22 , that is, the toner conveying member for conveying toner into the development chamber  18   b , which is rotatably supported. More specifically, the toner conveying member  22  is rotatably supported in the toner storage chamber  18   a  by its lengthwise end portions (in terms of direction of its rotational axis), by the developing means frame  18  which includes the toner storage chamber  18   a . The toner conveying member  22  is rotationally driven in the direction (clockwise direction) indicated by an arrow mark G in the drawing, by an unshown driving means (driving force source). 
         [0072]    The toner conveying member  22  has a sheet portion  22   a  and a sheet supporting shaft  22   b  (rotational shaft). The sheet portion  22   a  is the portion which actually conveys toner, and is flexible. The shaft  22   b  is the portion to which the sheet portion  22   a  is attached, and through which the toner conveying member  22  receives rotational driving force. The shaft  22   b  extends in the direction roughly parallel to the lengthwise direction (direction parallel to their axial lines) of the photosensitive drum  1 , development sleeve  17 , and toner supply roller  20 , across the entire range of the toner storage chamber  18   a  in terms of the lengthwise direction of the toner storage chamber  18   a . The sheet portion  22   a  is made up of a single sheet (plate-like member) of a resinous substance, which extends in the lengthwise direction (direction parallel to axial line of shaft portion  22   b ) of the shaft portion  22   b  across roughly the entire range of the shaft portion  22   b . The sheet portion  22   a  is attached to the shaft portion  22   b  by one of its edges which are roughly parallel to the lengthwise direction of the shaft portion  22   b  (one of the edges perpendicular to the radius of its sweeping area, that is, perpendicular to its width direction). 
         [0073]    The preferable material for the sheet portion  22   a  is a flexible sheet (film) formed of a resinous substance, such as polyester, polyphenylene sulfide or polycarbonate, for example. It is preferable that the thickness of the sheet portion  22   a  is in a range of 50 μm-250 μm. 
         [0074]    The distance L 1 , which is the distance from the rotational center of the toner conveying member  22  to the sweeping edge of the sheet portion  22   a , is greater than a distance L 2 , which is the distance in a straight line from the rotational center of the toner conveying member  22  to the internal surface  18   a   1  of the toner storage chamber  18   a . The abovementioned distance L 1  is equivalent to the maximum value of the radius of the sweeping area of the toner conveying member  22 , that is, the radius of the toner conveying member  22  when the sheet portion  22   a  is in the natural form, that is, when the sheet portion  22   a  is not in the deformed (bent) state. A distance L 2  is the maximum value of the distance in a straight line from the abovementioned rotational center to the portion  18   a   1  of the internal surface of the toner storage chamber  18   a , with which the sheet portion  22   a  comes into contact. Further, a distance L 1  is greater than a distance L 3 , which is the distance in a straight line from the abovementioned rotational center to the bottom edge  18   c   1  (that is, lowest point of hole  18   c ) of the hole  18   c . Therefore, it is ensured that toner is sent to the hole  18   c . A distance L 4 , which is the distance in a straight line from the abovementioned rotational center to the guiding portion  18   a   2 , is smaller than the length L 2 , which is the maximum value of the distance in a straight line from the abovementioned rotational center to the portion  18   a   1  of the internal surface of the toner storage chamber  18   a . That is, in this embodiment, the abovementioned distances L 1 , L 2 , L 3 , and L 3  satisfy the following relationship: 
         [0000]      L1&gt;L2  (1) 
         [0000]      L1&gt;L3  (2) 
         [0000]      L2&gt;L4  (3) 
         [0075]    With Inequity (1), that is, L 1 &gt;L 2 , given above being satisfied, as the toner conveying member  22  is rotated, the sheet portion  22   a  comes into contact with the portion  18   a   1  of the internal surface of the toner storage chamber  18   a , and is substantially bent by the portion  18   a   1 . Then, as the toner conveying member  22  is further rotated, the body of toner swept up by the sheet portion  22   a  is conveyed by the rotation of the toner conveying member  22 . That is, the body of toner, which is conveyed by the toner conveying member  22 , is the body of toner in a wedge-like area  27 , that is, the area surrounded by the hypothetical extension of the surface of the straight portion (portion which is not bent in curvature) of the sheet portion  22   a , the bent portion of the sheet portion  22   a , and the portion  18   a   1  of the internal surface of the toner storage chamber  18   a.    
         [0076]    Further, with Inequity (2), that is, L 2 &gt;L 4 , given above being satisfied, as the toner conveying member  22  is rotated further, the sheet portion  22   a  comes into contact with the guiding portion  18   a   2 , and is bent in curvature by the guiding portion  18   a   2 . Then, as the toner conveying member  22  is rotated further, the body of toner swept up by the sheet portion  22   a , that is, the body of toner on the downstream side of the sheet portion  22   a  in terms of the rotational direction of the toner conveying member  22 , is conveyed into the development chamber  18   b . That is, the body of toner, which is conveyed into the development chamber  18   b , is the body of toner in the area  27   a , that is, the wedge-shaped area surrounded by the dotted line (hypothetical line) which represents the surface of the straight portion (portion which has not bent in curvature) of the sheet portion  22   a , the surface of the sheet portion  22   a  which is bent in curvature due to its contact with the guiding portion  18   a   2 , and the dotted line (hypothetical line) which represents the locus of the sweeping edge of the sheet portion  22   a.    
         [0077]    The toner storage chamber  18   a  has the abovementioned toner conveying member recovery space, which corresponds to the portion  18   a   4  of the internal surface of the toner storage chamber  18   a , and in which the sweeping edge  22   a   1  of the sheet portion  22   a  does not contact. In terms of the rotational direction G of the toner conveying member  22 , the recovery portion  18   a   4  is on the downstream side of the guiding portion  18   a   2  and on the upstream side of the top end  18   c   2  of the hole  18   c . The recovery portion  18   a   4  is a part of the internal surface of the toner storage chamber  18   a , which the sheet portion  22   a  does not contact. Further, the development unit  4  is structured so that the recovery portion  18   a   4  is at a level higher than the above described border (point p) (or on downstream side of border (point p) in terms of the rotational direction G). Here, the intersection between a hypothetical circle, which represents the locus of the sweeping edge  22   a   1  of the sheet portion  22   a  which is in the natural state (state prior to deformation), and the internal surface of the toner storage chamber  18   a , which includes the guiding portion  18   a   2 , will be referred to as a point q. Further, the development unit  4  in this embodiment is structured so that the point p is at a level lower than the point q (or on upstream side of point q in terms of rotational direction G), for the following reason. That is, the sheet portion  22   a  is bent in curvature by the friction between the sheet portion  22   a  and internal surface of the toner storage chamber  18   a , and also, by the weight of toner. Therefore, the point at which the sheet portion  22   a  separates from the internal surface of the toner storage chamber  18   a  is on the upstream side of the point q, in terms of the rotational direction G. Further, the development unit  4  is structured so that the border (point p), that is, the top end of the guiding portion  18   a   2 , is at a level lower than the bottom edge  18   c   1  of the hole  18   c , and also, so that when the sheet portion  22   a  is in the recovery space, that is, the space corresponding to the portion  18   a   4  of the internal surface of the toner storage chamber  18   a , the sweeping edge  22   a   1  of the sheet portion  22   a  does not contact the internal surface of the toner storage chamber  18   a.    
         [0078]    As the toner conveying member  22  rotates, the sweeping edge  22   a   1  of its sheet portion  22   a  moves in the rotational direction G through the range corresponding to the guiding portion  18   a   2 . As soon as the toner conveying member  22  becomes free from the force which kept it deformed (bent in curvature). As the sheet portion  22   a  becomes free from the force which kept it deformed (bent in curvature), it snaps back into its natural shape due to its resiliency. As a result, the toner on the sheet portion  22   a  is catapulted in the direction indicated by an arrow mark H in  FIG. 3 , that is, toward the hole  18   c  of the partition wall  26 . 
         [0079]    Further, with the abovementioned Inequity (2), that is, L 1 &gt;L 3 , being satisfied, the movement of the sheet portion  22   a  relative to the hole  18   c  is as follows. That is, after the sheet portion  22   a  becomes free from the force which kept it deformed (bent in curvature), that is, after the sheet portion  22   a  restores its natural shape, the sheet portion  22   a  reaches the hole  18   c . The moment the sheet portion  22   a  reaches the hole  18   c , the sweeping edge  22   a   1  of the sheet portion  22   a  is at a level higher than the bottom edge  18   c   1  of the hole  18   c . Therefore, it is ensured that the moment the sheet portion  22   a  becomes free from the force which kept it deformed (bent in curvature), the body of toner having collected on the sweeping edge portion of the sheet portion  22   a  is conveyed to the development chamber  18   b . Therefore, the toner supplying roller  20  is supplied with a satisfactory amount of toner, making it possible to prevent the formation of a defective image, more specifically, an image suffering from unwanted white spots or the like attributable to the insufficiency in toner supply delivery. However, satisfying the abovementioned Inequity (2), that is, L 1 &gt;L 3 , is only one of the measures for efficiently conveying toner into the development chamber  18   b , and is not a requisite in the case of this embodiment in which the development unit  4  is structured so that toner is catapulted by the force generated by the resiliency of the sheet portion  22   a.    
         [0080]    Further, satisfying the abovementioned Inequity (3), that is, L 2 &gt;L 4 , increases the extent by which the sheet portion  22   a  is made to elastically deform (in curvature) when it moves through the range corresponding to the guiding portion  18   a   2 . Therefore, it causes the sheet portion  22   a  to catapult the toner better. 
         [0081]      FIG. 4  is a schematic drawing of the toner conveying member  22 , as seen from the direction indicated by an arrow mark V in  FIG. 3 , showing the structure of the toner conveying member  22 . It is preferable that a length M, that is, the length of the sheet portion  22   a , is greater than a length N, that is, the length of the hole  18   c.    
         [0082]    Incidentally, in this embodiment, the development unit  4  is structured so that when the sweeping edge portion of the toner conveying member  22  is in contact with the border  18   a   3 , the extension of the normal line (indicated by arrow mark J in  FIG. 3 ) to the sweeping edge, in the downstream direction, in terms of the rotational direction of the toner conveying member  22 , is on the opposite side of the vertical plane, which includes the sweeping edge, from the hole  18   c . The employment of this structural arrangement can increases the amount by which toner is retained on the toner conveying member  22  up to immediately before the toner is catapulted. Therefore, the employment of this structural arrangement makes it possible to more efficiently convey toner to the hole  18   c.    
         [0083]    As described above, practically, the toner conveying member  22  in this embodiment is made up of nothing but the sheet portion  22   a  and sheet portion supporting shaft  22   b . That is, it is very simple in structure. Therefore, it is less expensive than a conventional means, such as a screw, for conveying toner upward. 
         [0084]    Further, in this embodiment, the sheet portion  22   a  of the toner conveying member  22  is formed of an elastic sheet. Therefore, the toner is catapulted by the force generated by the resiliency of the sheet portion  22   a . Thus, the toner storage chamber  18   a  in this embodiment is significantly smaller than that of a cartridge in accordance with the prior art, which is structured so that toner is conveyed to the development chamber  18   b  by a stirring member or the like while remaining held by the stirring member. Incidentally, the smaller the toner storage chamber  18   a , the smaller the developing apparatus  4 , process cartridge  7 , and image forming apparatus  100  can be made. 
         [0085]    Also in this embodiment, the toner is satisfactorily conveyed against gravity. In other words, this embodiment makes it possible to realize an image forming apparatus structured so that the process cartridge  7  is directly below the intermediary transfer belt  5 . Therefore, this embodiment makes it possible to dispose the scanner unit  3 , for example, away from the fixing apparatus  10  in order to prevent the heat from the fixing apparatus  10  from affecting the scanner unit  3 , or to eliminate or reduce the space necessary for reducing the effects of the heat from the fixing apparatus  10  upon the scanner unit  3 . Therefore, this embodiment can reduce in size (height, for example) the image forming apparatus  100 . Further, this embodiment makes it possible to dispose the fixing apparatus above and away from the developing apparatus  4  and process cartridge  7 , with the presence of the intermediary transfer belt  5  between the fixing apparatus  10  and developing apparatus  4 , and between the fixing apparatus  10  and process cartridge  7 . Therefore, this embodiment of the present invention can reduce the effects of the heat from the fixing apparatus  10  upon the developing apparatus  4  and process cartridge  7 , or to eliminate or reduce the space necessary for reducing the effects of the heat from the fixing apparatus  10  upon the developing apparatus  4  and process cartridge  7 . Therefore, this embodiment can reduce in size (height, for example) the image forming apparatus  100 . 
       [Structure of Mechanism for Stirring Toner in Development Chamber] 
       [0086]    Next, the structure of the mechanism for stirring the toner in the development chamber  18   b  will be described.  FIGS. 5(   a )- 5 ( d ) are cross-sectional views of the development chamber  18   b , more specifically, the toner stirring member, and its adjacencies, in the development chamber  18   b , showing the structure of the mechanism for stirring the toner in the development chamber  18   b.    
         [0087]    Regarding the flow and circulation of the toner in the development chamber  18   b , the development unit  4  is provided with a developer stirring member, which is in the adjacencies of both the development roller  17  and the developer supply roller  20  which supplies the development roller  17  with toner. The placement of the stirring member in the abovementioned area of the development chamber  18   b  prevents the phenomenon called “toner packing”, that is, the phenomenon that toner is compacted to an unnecessarily high level of density. Therefore, not only is development roller  17  is continuously supplied with a proper amount of toner by the toner supply roller  20 , but also, the toner layer on the development roller  17  remains stable in thickness. 
         [0088]    An image forming apparatus can be improved in image quality by reliably providing the development roller  17  with a proper amount of toner by preventing toner from being compacted, by improving the toner circulation in the adjacencies of the peripheral surface of the development roller  17  and toner supply roller  20 . On the other hand, if the toner supply to the development roller  17  becomes unstable, the image forming apparatus sometimes forms a defective image, more specifically, an image suffering from nonuniformity or the like. 
         [0089]    Thus, one of the primary objects of this embodiment is to improve a process cartridge  7  in the toner circulation in the adjacencies of the development roller  17 , etc., in order to prevent an image forming apparatus from forming an unsatisfactory image, more specifically, an image suffering from the nonuniformity attributable to unsatisfactory toner delivery. 
         [0090]    Thus, in this embodiment, the development unit  4  is structured as will be described next. That is, in this embodiment, the development unit  4  is provided with a stirring member  25 , which is in the development chamber  18   b . The stirring member  25  has a stirring portion  25   a  and a stirring portion supporting shaft  25   b  (axle). The stirring portion supporting shaft  25   b  is rotatably supported by the walls of the development chamber  18   b . The stirring portion  25   a  is rotatably supported by the stirring portion supporting shaft  25   b , and is made to oscillate by the rotation of the stirring member supporting shaft  25   b . In terms of the rotational direction of the toner supply roller  20 , the stirring portion supporting shaft  25   b  is on the downstream side of the stirring portion  25   a . This structural arrangement makes the downstream portion of the stirring portion  25   a  greater in movement than the upstream portion of the stirring portion  25   a , in terms of the rotational direction of the toner supply roller  20 . The stirring portion  25   a  is between the toner supply roller  20  and partition wall  26 . The stirring portion  25   a  is provided with a through hole  25   c  as a toner passage. The stirring portion  25   a  is made to oscillate in such a manner to alternately repeat a stroke in which the hole  25   c  moves toward the toner supply roller  20  and a stroke in which the hole  25   c  moves away from the toner supply roller  20 . In the stroke in which the hole  25   c  moves toward the toner supply roller  20 , the portion of the stirring portion  25   a , which is next to the hole  25   c , moves the toner toward the toner supply roller  20 , whereas in the stroke in which the hole  25   c  moves away from the toner supply roller  20 , the body of toner, which is under the hole  25   c , moves toward the toner supply roller  20  through the hole  25   c . In other words, as the stirring portion  25   a  having the hole  25   c  oscillates, not only can it satisfactorily stir the toner, but also, it can satisfactorily supply the toner supply roller  20  with the loosened toner. Further, the stirring portion  25   a  also moves back and forth in the direction parallel to a line tangential to the peripheral surface of the toner supply roller  20 . That is, the stirring portion  25   a  oscillates in the direction parallel to a line perpendicular to the radius direction of the developer supply roller  20 . In other words, the stirring portion  25   a  also oscillates in the direction parallel to the rotational direction of the developer supply roller  20  (direction intersectional to rotational axis). The oscillation of the stirring portion  25   a  in this direction enhances the stirring function of the stirring portion  25   a.    
         [0091]    After toner is conveyed into the development chamber  18   b , the toner is stored in a first area e and a second area f. The first area e is between the toner supply roller  20  and a first portion  26   a  of the partition wall  26 , and the second area f is surrounded by the toner supply roller  20 , second portion  26   b  of the partition wall  26 , and development blade  21 . That is, the first area e of the development chamber  18   b  is the portion of the development chamber  18   b , which is between the toner supply roller  20  and the portion of the partition wall  26 , which is below the hole  18   c  and on the lateral side (on left side in drawing) of toner supply roller  20 , whereas the second area f of the development chamber  18   b  is the area of the development chamber  18   b , which is surrounded by the toner supply roller  20 , the portion of the partition wall  26 , which is below the toner supply roller  20 , and a development blade  21 . The toner supply roller  20  supplies the development roller  17  with the toner stored in the first and second areas e and f. 
         [0092]    The abovementioned stirring portion  25   a  is in the second area f. The stirring portion  25   a  is a piece of slightly angled plate, which is roughly L-shaped in cross section, that is, as seen from the direction parallel to the lengthwise direction of the development roller  17  and toner supply roller  20 . That is, in this embodiment, the stirring portion  25   a  has a first flat portion  25   g  (first surface), a second flat portion  25   h  (second surface), and a bend  25   f . The first flat portion  25   g  (first surface) extends in parallel to the rotational axis of the toner supply roller  20 . The second flat portion  25   f  (second surface) holds a preset angle relative to the first flat portion  25   g , and also extends in parallel to the rotational axis of the toner supply roller  20 . In other words, the first and second flat portions  25   g  and  25   f  are intersectional to each other. The bend  25   f  is the portion between the first and second flat portion  25   g  and  25   f ; it is the joint (intersection) between the first and second flat portions  25   g  and  25   f . In this embodiment, the stirring portion  25   a  is bent so that its bend  25   f  points outward of the development chamber  18   b , in terms of the radius direction of the toner supply roller  20 . That is, the recess formed by the first and second flat portions  25   g  and  25   h  faces the toner supply roller  20 . The stirring portion  25   a  is formed of a resinous substance. 
         [0093]    The abovementioned stirring portion supporting shaft  25   b , which is in the form of a crankshaft, is rotatably supported in the second area f. Further, the stirring portion  25   a  is rotatably supported by the crankshaft  25   b  (stirring portion supporting shaft  25   b ). The crankshaft  25   b  is more or less parallel to the lengthwise direction of the development roller  17  and toner supply roller  20 , and extends from one lengthwise end of the development chamber  18   b  to the other. The crankshaft  25   b  is rotatably supported at its lengthwise end portions (end portions in terms of direction parallel to its rotational axis), by the developing means frame  18 , to which the development chamber  18   b  belongs. 
         [0094]    Incidentally, in this embodiment, the stirring portion  25   a  is formed of a resinous substance. However, the stirring portion  25   a  may be formed of a metallic substance. 
         [0095]    The stirring portion  25   a  is rotatably attached to the crankshaft  25   b , by its connective portions  25   a   1 , which corresponds to one of the edges of the stirring portion  25   a , in terms of the width direction of the stirring portion  25   a . That is, in this embodiment, the stirring portion supporting shaft  25   b  of the stirring member  25  is in the form of a crankshaft, and the stirring portion  25   a  is rotatably attached to the portion of the stirring supporting shaft  25   b , which is equivalent to the crankpin portion of a crankshaft, being thereby rotatably supported by the portion equivalent to the crankpin portion, that is, the portion offset from the axial line of the crankshaft  25   b . Referring to  FIG. 5(   a )- 5 ( d ), as the crankshaft  25   b  is rotationally driven by an unshown driving means (driving force source), the free edge portion  25   a   2  of the stirring portion  25   a , that is, the edge portion of the stirring portion  25   a , which is not in engagement with the crankshaft  25   b , shuttles in the direction indicated by an arrow mark I. That is, the stirring portion  25   a  reciprocally moves in the direction parallel to the line tangential to the peripheral surface of the toner supply roller  20 . 
         [0096]    Regarding the locus of the free edge portion  25   a   2  of the stirring portion  25   a , the stirring member  25  is disposed so that as the stirring portion  25   a  is reciprocally moved as described above, its free edge portion  25   a   2  enters the first area e, and comes into contact with the body of toner in the first area e. In this embodiment, the partition wall  26  is made up of the first and second portions  26   a  and  26   b , and the stirring portion  25   a  reciprocally moves in the space surrounded by the toner supply roller  20 , and the first and second portions  26   a  and  26   b  of the partition wall  26 , as described above. Therefore, it does not occur that after toner is supplied to the development chamber  18   b , it becomes less fluid by being compacted in the first area e. Therefore, toner is more efficiently supplied to the second area f and the toner supply roller  20  than in a process cartridge in the prior art. 
         [0097]    Incidentally, in this embodiment, the process cartridge  7  is structured so that the stirring portion  25   a  enters the first area e. However, this embodiment is not intended to limit the present invention in terms of the process cartridge structure. That is, as long as the process cartridge  7  is structured so that the problem that toner becomes compacted and remains compacted, can be prevented by improving the toner circulation in the development chamber  18   b  by causing the free edge portion  25   a   2  of the stirring portion  25   a  to reciprocally move, it is not mandatory for the application of the present invention, that the free edge portion  25   a   2  of the stirring portion  25   a  enters the first area e. 
         [0098]    Further, in this embodiment, not only does the stirring portion  25   a  reciprocally move in the above described direction, but also, it oscillates in the direction parallel to the radius direction of the toner supply roller  20 , that is, it alternately repeats the stroke in which the hole  25   c  moves toward the toner supply roller  20  and the stroke in which the hole  25   c  moves away from the toner supply roller  20 . Thus, not only does the stirring portion  25   a  prevent the toner in the second area f from being compacted, by stirring the toner, but also, pushes the toner toward the toner supply roller  20  (presses toner against toner supply roller  20 ). Next, the movement of the stirring portion  25   a  will be described referring to  FIG. 5 . When the stirring portion  25   a  is in the state shown in  FIG. 5(   a ), the tip portion of the free edge portion  25   a   2  (first pressing portion), presses the toner against the toner supply roller  20 . When the stirring portion  25   a  is in the state shown in  FIG. 5(   b ), the connective edge portion  25   a   1  (second pressing portion) of the stirring portion  25   a  presses the toner against the toner supply roller  20 . Further, when the stirring portion  25   a  is in the state shown in  FIG. 5(   d ), the tip portion (first pressing portion) of the free edge portion  25   a   2  again presses the toner against the toner supply roller  20 . That is, the toner is pressed against the toner supply roller  20  by various areas (in terms of the rotational direction of the toner supply roller  20 ) of the stirring portion  25   a . In other words, in this embodiment, the efficiency with which the toner supply roller  20  is supplied with toner is improved by the above described oscillation of the stirring portion  25   a.    
         [0099]    The effect of preventing the problem that toner becomes compacted in the first area e as described above, and the effect of improving the process cartridge  7  in the efficiency with which the toner supply roller  20  is supplied with toner as described above, can be achieved regardless of the rotational direction of the crankshaft  25   b . In this embodiment, the crankshaft  25   b  is rotated by an unshown driving means (driving force source) in the direction (clockwise direction) indicated by the arrow mark J to oscillate (reciprocally move) the stirring portion  25   a.    
         [0100]      FIG. 6  is a front view of the stirring member  25 . The stirring portion  25   a  in this embodiment, which is in the form of a piece of plate, is provided with multiple hole  25   c  (through hole), which face the toner supply roller  20 . Further, the stirring portion  25   a  oscillates; it alternately repeats the stroke in which the hole  25   c  moves toward the toner supply roller  20  and the stroke in which the hole  25   c  moves away from the toner supply roller  20 . Thus, with the provision of the holes  25   c , toner is allowed to escape through the holes  25   c , and therefore, toner is not compacted downward of the stirring portion  25   a  by the oscillatory movement of the stirring portion  25   a . Therefore, it is ensured that toner remains fluid so that the toner supply roller  20  is efficiently supplied with toner. Here, each of the holes  25   c  in the downstream row, in terms of the rotational direction of the toner supply roller  20 , will be referred to as a first hole  25   c   1 , and each of the holes  25   c  in the upstream row, will be referred to as a second hole  25   c   2 . The positional relationship between the first and second holes  25   c   1  and  25   c   2 , in terms of roughly the width direction of the stirring portion  25   a , is such that if the first and second holes  25   c   1  is projected upon the rotational axis of the toner supply roller  20 , they partially overlap with each other. This structural arrangement significantly reduces the nonuniformity in the stirring of toner in terms of the lengthwise direction of the toner supply roller  20 . Referring to  FIG. 6 , designated by an alphanumeric referential symbol  25   c   3  is one of the holes  25   c  which is in the same row as the row to which the second hole  25   c   2  belongs, and which is next to the hole  25   a   2 . Designated by a referential letter R is the area between the second and third holes  25   c   2  and  25   c   3 . If the area R and first hole  25   c   1  are projected upon the rotational axis of the toner supply roller  20 , the area R partially overlaps with the first hole  25   c   1 . Therefore, it is possible to prevent the formation of an image, which is nonuniform across the area corresponding to the area R. In this embodiment, the first holes  25   c   1  belong to the first portion  25   g , whereas the second and third holes  25   c   2  and  25   c   3  belong to the second portion  25   h . However, the process cartridge  7  may be designed so that these holes belong to the portions of the stirring portion  25   a , which are different from the portions to which they belong in this embodiment. That is, the process cartridge  7  may be designed so that the second portion  25   h  is provided with the first holes  25   c   1 , and the first portion  25   g  is provided with the second and third holes  25   c   2  and  25   c   3 . 
         [0101]    According to this embodiment, the stirring portion  25   a  is reciprocally moved so that the free edge portion of the stirring portion  25   a  enters the first area e and reciprocally moves in the first area e. Therefore, the toner in the first area e is stirred by the free edge portion  25   a , being thereby prevented from becoming compacted. Therefore, it does not occur that toner reduces in fluidity in the area e. Also according to this embodiment, it is possible to improve a process cartridge  7  in terms of the efficiency with which toner is supplied to the second area f and toner supply roller  20 . Therefore, it is possible to ensure that the toner is reliably supplied by a proper amount from the toner supply roller  20  to the development roller  17  to prevent the formation of an unsatisfactory image, that is, an image suffering from the nonuniformity attributable to unsatisfactory toner delivery to the toner supply roller  20 . 
         [0102]    As described above, according to this embodiment, the elastic toner conveying member  22  becomes separated from the internal surface of the toner storage chamber  18   a  after the toner conveying member  22  moves past the area of the toner storage chamber  18   a , which corresponds to the guiding portion  18   a   2  of the toner storage chamber  18   a . More specifically, as soon as the toner conveying member  22  becomes separated from the internal surface of the toner storage chamber  18   a , the toner on the toner conveying member  22  is conveyed (catapulted) into the development chamber  18   b , which is right above the toner storage chamber  18   a . Further, according to this embodiment, the process cartridge  7  is structured so that toner is conveyed upward. Therefore, it is possible to realize an image forming apparatus structured so that the process cartridge  7  is mountable directly below the intermediary transfer belt  5 , for example. With the placement of the process cartridge  7  directly below the intermediary transfer belt  5 , it is possible to place the fixing apparatus  10  away from the scanner unit  3 , developing apparatus, and/or the process cartridge  7 , as described above, making it thereby possible to prevent them (scanner unit  3 , developing apparatus  4  and/or process cartridge  7 ) from being affected by the heat from the fixing apparatus  10 , or to eliminate or reduce the space necessary for reducing the effects of the heat from the fixing apparatus  10  upon the scanner unit  3 , developing apparatus  4 , and/or process cartridge  7 . Therefore, it is possible to reduce in size an image forming apparatus ( 100 ); it is possible to reduce an image forming apparatus ( 100 ) in height, for example. 
         [0103]    According to this embodiment, the toner conveying member  22  is elastic. Therefore, it is catapulted by the force generated by the resiliency (elasticity) of the toner conveying member  22 . Thus, the employment of the toner conveying member  22  in this embodiment makes it possible to reduce in size the toner storage chamber  18   a , compared to the toner storage chamber ( 18   a ) of a process cartridge employing a stirring member or the like structured so that toner is conveyed to the development chamber  18   b  while remaining held by the stirring member or the like. Moreover, practically, only the elastic toner conveying member is required to convey toner. Therefore, it is possible to realize a toner conveying mechanism which is small in component count, simple in structure, and inexpensive. 
         [0104]    Thus, even if an image forming apparatus (process cassette) needs to be structured to convey toner against gravity, it is possible to provide an image forming apparatus which is simple in structure, low in cost, and small in size, and yet, does not form an unsatisfactory image, more specifically, an image suffering from unwanted white spots or the like attributable to unsatisfactory toner delivery. 
         [0105]    Further, the stirring portion  25   a , which is oscillatory, is disposed between the toner supply roller  20  in the development chamber  18   b , and the partition wall  26  which separates the development chamber  18   b  from the toner storage chamber  18   a . Therefore, after toner is supplied to the development chamber  18   b , it is ensure that the toner is stirred so that it is efficiently supplied to the toner supply roller  20 . Therefore, it is ensured that toner is reliably supplied by a proper amount from the toner supply roller  20  to the development roller  17 . Therefore, it is possible to prevent the formation of an unsatisfactory image, more specifically, an image suffering from the nonuniformity attributable to the unsatisfactory toner delivery. 
       Embodiment 2 
       [0106]    Next, another (second) preferred embodiment of the present invention will be described. The developing apparatus, process cartridge, and image forming apparatus, in this embodiment, are the same in basic structure as those in the first preferred embodiment. Therefore, the components, or the like, of the image forming apparatus in this embodiment, which are the same in function and structure as the counterparts in the first embodiment will be given the same referential symbols as those given to the counterparts in the first embodiment, and will not be described in detail. This embodiment is different from the first embodiment in that the guiding portion  18   a   2  in this embodiment is shaped so that a portion of the guiding portion  18   a   2  protrudes inward of the toner storage chamber  18   a , as seen from the direction perpendicular to the lengthwise direction of the process cartridge  7 . 
         [0107]      FIG. 7  is a cross-sectional view of the process cartridge  7  in this embodiment. In this embodiment, the guiding portion  18   a   2  of the toner storage chamber  18   a  is on the upstream side of the hole  18   c  of the partition wall  26 , in terms of the rotation direction G of the toner conveying member  22 . Here, the guiding portion  18   a   2 , which is a portion of the wall of the toner storage chamber  18   a , functions as the portion which causes the sheet portion  22   a  to deform against its own resiliency as the toner conveying member  22  rotates. The shape of the guiding portion  18   a   2  is such that as the toner conveying member  22  is rotated in the direction indicated by the arrow mark G, the distance between the guiding portion  18   a   2  and the rotational axis of the toner conveying member  22  gradually reduces. Further, the toner storage chamber  18   a  is provided with a recovery space, which corresponds to a recovery portion  18   a   4  of the wall of the toner storage chamber  18   a , with which the sweeping edge  22   a   1  of the free edge portion of the sheet portion  22   a  does not make contact. In terms of the rotational direction G of the toner conveying member  22 , the recovery portion  18   a   4  is on the downstream side of the guiding portion  18   a   2 , and on the upstream side of the hole  18   c . More specifically, the recovery portion  18   a   4  is a part of the internal surface of the wall of the toner storage chamber  18   a . Also in terms of the rotational direction G of the toner conveying member  22 , the recovery portion  18   a   4  is on the downstream side of the downstream end (which hereafter will be referred to as “border line”) of the guiding portion  18   a   2 . Further, the recovery portion  18   a   4  is created by forming the internal surface wall of the toner storage chamber  18   a  so that a step-like portion  18   a   5  is provided between the guiding portion  18   a   2  and recovery portion  18   a   4 . Further, the recovery portion  18   a   4  is shaped so that in terms of the rotational direction G of the toner conveying member  22 , the distance between the recovery portion  18   a   4  and the rotational axis of the toner conveying member  22  gradually increases. Here, the step-like portion  18   a   5  is slanted so that its angle is greater than the angle of repose of toner so that as toner comes into contact with the step-like portion  18   a   5 , it slides downward. Further, when the sheet portion  22   a  of the toner conveying member  22  is in the abovementioned recovery space, the sweeping edge  22   a   1  of the free end portion of the sheet portion  22   a  does not make contact with the internal surface of the wall of the toner storage chamber  18   a.    
         [0108]    After the rotation of the toner conveying member  22  causes the sweeping edge  22   a   1  of the free end portion of the sheet portion  22   a  to move past the border line  18   a   3  (border line), there is no contact between the sheet portion  22   a  and the internal surface (recovery portion  18   a   4 ) of the wall of the toner storage chamber  18   a . Thus, as soon as the sweeping edge  22   a   1  moves past the border line  18   a   3 , the sheet portion  22   a  is allowed to restore its natural shape. Since the sheet portion  22   a  is formed of an elastic substance (highly resilient substance), it instantly restores its natural shape, that is, the shape prior to its deformation, as soon as it is allowed to restore its natural shape. As a result, the toner on the sheet portion  22   a  (toner on toner conveying member  22 ) is catapulted by the force generated by the resiliency of the sheet portion  22   a  toward the hole  18   c  (direction indicated by arrow mark H in  FIG. 7 ). Incidentally, also in this embodiment, the border line  18   a   3  is at a lower level than the bottom edge  18   c   1  of the hole  18   c.    
         [0109]    Next, the toner behavior which occurs when the border line  18   a   3  coincides with the horizontal line which coincides with the rotational axis of the toner conveying member  22 , and the toner behavior which occurs when the border line  18   a   3  is above the abovementioned horizontal line, will be described.  FIG. 8  is a cross-sectional view of the process cartridge  7 , showing the change which the change in the position of the border line  18   a   3  causes to the manner in which toner is conveyed. 
         [0110]      FIG. 8(   a ) corresponds to the case in which the border line  18   a   3  (point at which sweeping edge  22   a   1  of sheet portion  22   a  leaves guiding portion  18   a   2 , that is, point at which sheet portion  22   a  is freed from guiding portion  18   a   2 ) coincides with the horizontal line which coincides with the rotational axis of the toner conveying member  22 . In this case, the amount by which toner slides off the sheet portion  22   a  is small. Therefore, the amount by which toner collects on the free end portion of the sheet portion  22   a  is larger. On the other hand, the distance from the border line  18   a   3  to the hole  18   c  is greater. Thus, adjustment has to make to satisfactorily convey (catapult) toner into the development chamber  18   b . For example, toner can be satisfactorily conveyed into the development chamber  18   b  by increasing in thickness the sheet portion  22   a  to increase the amount of force generated by the resiliency of the sheet portion  22   a  when the sheet portion  22   a  is freed from the guiding portion  18   a   2  (sheet deforming portion), provided that the sheet portion  22   a  is not changed in material. If it is preferred to change in material the sheet portion  22   a , toner can be conveyed into the development chamber  18   b  by using a substance which is relatively high in rigidity, as the material for the sheet portion  22   a , just as satisfactorily as by changing in thickness the sheet portion  22   a  as described above. 
         [0111]      FIGS. 8(   b ) and  8 ( c ) correspond to the cases in which the border line  18   a   3  is above the horizontal line which coincides with the rotational axis of the toner conveying member  22 . In the case of the structural arrangement shown in  FIG. 8(   c ), the border line  18   a   3  is farther above the horizontal line than in the case shown in  FIG. 8(   b ). That is, in the case of the structural arrangements shown in  FIGS. 8(   b ) and  8 ( c ), the border line  18   a   3  is closer to the hole  18   c  of the partition wall  26  than in the case of the structural arrangement shown in  FIG. 8(   a ). In these cases, the amount by which toner slides downward on the sheet portion  22   a  is greater, being therefore smaller in the amount by which toner collects on the free end portion of the sheet portion  22   a , than that in the case shown in  FIG. 8(   a ). In these cases, therefore, adjustment has to be made to satisfactorily convey (catapult) toner into the development chamber  18   b . For example, toner can be satisfactorily conveyed into the development chamber  18   b  by reducing in thickness the sheet portion  22   a  to make the sheet portion  22   a  bend more so that toner collects on the free end portion of the sheet portion  22   a  by a greater amount, provided that the sheet portion  22   a  is not changed in material. If it is preferred to change in material the sheet portion  22   a , the amount by which toner collects on the free end portion of the sheet portion  22   a  can be increased by using a substance which is relatively low in rigidity, as the material for the sheet portion  22   a . If a substance which is relatively low in rigidity is used as the material for the sheet portion  22   a , the sheet portion  22   a  is smaller in resiliency. However, the distance from the border line  18   a   3  to the hole  18   c  of the partition wall  26  is shorter. Therefore, toner can be conveyed to the development chamber  18   b , just as satisfactorily as by changing in thickness the sheet portion  22   a  as described above. 
         [0112]    The earnest studies made in consideration of the above described subjects revealed the following. That is, in order to convey toner into the development chamber  18   b  by a satisfactory amount to prevent the problem that an unsatisfactory image, that is, an image suffering from the unwanted white spots or the like which are attributable to the unsatisfactory toner delivery, it is desired that the position of the guiding portion  18   a   2  is set as follows. 
         [0113]    That is, the position of the border line  18   a   3  is desired to at the same level as the horizontal plane which includes the rotational axis of the toner conveying member  22 , or to be above this horizontal plane. 
         [0114]    To elaborate, it is desired that an angle θ 1 , which is the angle formed by the horizontal line which coincides with the rotational axis of the toner conveying member  22  and the straight line connecting the rotational axis of the toner conveying member  22  and border line  18   a   3 , is in the following range: 
         [0000]      0°≦θ1≦70°  (4) 
         [0115]    Further, it is desired that an angle θ 2 , which is the angle formed by the vertical straight line which coincides with the border line  18   a   3  and the surface (tangential line) of the guiding portion  18   a   2  is in the following range: 
         [0000]      15°≦θ2≦60°  (5) 
         [0116]    Further, the wall of the toner storage chamber  18   a  is shaped so that it does not occur that the sweeping edge  22   a   1  of the free end portion of the sheet portion  22   a  makes contact with the internal surface of the wall of the toner storage chamber  18   a  after the sheet portion  22   a  is allowed to restore its natural shape. Further, it is desired that an angle θ 3 , which is the angle formed by the hypothetical extension of the surface (tangential to bent portion of sheet portion  22   a ) and the straight line which coincides with the step-like portion  18   a   5 , which is between the guiding portion  18   a   2  and recovery portion  18   a   4 , is within the following range: 
         [0000]      0°≦θ3≦90°  (6) 
         [0117]    Also in this embodiment, the relationship among the distances L 1 , L 2 , L 3 , and L 4 , which was described regarding the first embodiments, is applicable. 
         [0118]    As described above, this embodiment can provide the same effects as those obtained by the first embodiment. Further, in this embodiment, the process cartridge  7  is structured so that the distance between the guiding portion  18   a   2  and the rotational axis of the toner conveying member  22  is smallest at the border line  18   a   3 , and also, so that the distance between the guiding portion  18   a   2  and the rotational axis of the toner conveying member  22  gradually reduces as the toner conveying member  22  rotates in the direction indicated by the arrow mark G. That is, the closer to the border line  18   a   3 , the smaller the distance between the guiding portion  18   a   2  and the rotational axis of the toner conveying member  22 . Therefore, as the sheet portion  22   a  moves through the area of the toner storage chamber  18   a , which corresponds to the guiding portion  18   a   2 , the sheet portion  22   a  gradually increases in deformation. Then, as soon as the sheet portion  22  moves past the border line  18   a   3 , it is allowed to instantly restore its natural shape. Therefore, this embodiment is greater in the amount by which toner is supplied to the development chamber  18   b  than the first embodiment. 
         [0119]    Incidentally, also in this embodiment, by the time when the sweeping edge of the toner conveying member  22  separates from the border line  18   a   3 , the toner conveying member  22  will have rotated into the position in which its sweeping edge portion is placed in contact with the adjacencies of the hole  18   c  by its resiliency (elasticity). 
         [0120]    Further, also in this embodiment, the maximum value of the radius of the sweeping area of the toner conveying member  22  is greater than the distance between the rotational axis of the toner conveying member  22  and the bottom edge  18   c   1  of the hole  18   c . Therefore, it is ensured that the toner in the toner storage chamber  18   a  is reliably supplied by a satisfactory amount to the development chamber  18   b  through the hole  18   c.    
         [0121]    Further, also in this embodiment, the process cartridge  7  is structured so that when the sweeping edge portion of the toner conveying member  22  is in contact with the border line  18   a   3 , the normal line to the abovementioned locus of the sweeping edge of the toner conveying member  22  at the sweeping edge, which extends downstream in terms of the rotational direction of the toner conveying member  22 , is on the opposite side of the vertical line which extends upward from the sweeping edge of the toner conveying member  22 , from the hole  18   c . Therefore, the amount by which toner is held on the toner conveying member  22  immediately before the catapulting of toner is significantly greater than that in the first embodiment. Therefore, toner can be more efficiently supplied to the development chamber  18   b  through the hole  18   c.    
       Embodiment 3 
       [0122]    Next, another (third) preferred embodiment of the present invention will be described. The developing apparatus, process cartridge, and image forming apparatus, in this embodiment, are the same in basic structure as those in the first and second preferred embodiments. Therefore, the components, or the like, of the image forming apparatus in this embodiment, which are the same in function and structure as the counterparts in the first and second embodiments will be given the same referential symbols as those given to the counterparts in the first and second embodiments, and will not be described in detail. This embodiment is different from the first and second embodiments in that a toner conveying member  28  in this embodiment, which is provided in the toner storage chamber  18   a  in this embodiment, is different in structure from the toner conveying members  22  in the first and second embodiments. 
         [0123]      FIG. 9  is a cross-sectional view of the process cartridge  7  in this embodiment.  FIG. 10  is an enlarged perspective view of a part of the toner conveying member  28  in this embodiment. 
         [0124]    In this embodiment, the toner conveying member  28  has (a) rotational shaft  28   a , (b) stationary wing  28   b , and (c) rotational wing  28   c . The stationary wing  28   b  is an integral part of the rotational shaft  28   a . The rotational wing  28   c  is rotatable relative to the stationary wing only in the opposite direction from the rotational direction G of the toner conveying member  28 . In this embodiment, the toner conveying member  28  is also provided with (d) elastic member  28   d . The elastic member  28  is fitted around the portion of the rotational wing  28   c , which connects the stationary wing  28   b  and rotational wing  28   c . It is wound so that the rotational wing  28   c  is kept pressured in the same direction as the rotational direction G of the toner conveying member  28 . In particular, in this embodiment, the elastic member  28   d  is a tortional coil spring  28   d  (fitted around a shaft  28   c   1 , which is an integral part of the rotational wing  28   c ). The shaft  28   c   1  is fitted in the hole of the connective portion  28   b   1  of the stationary wing  28   b , being thereby rotatably supported by the stationary wing  28   b.    
         [0125]    As the toner conveying member  22  is rotated in the direction indicated by the arrow mark G, the rotational wing  28   c  comes into contact with the portion  18   a   1  of the internal surface of the wall of the toner storage chamber  18   a , and is rotated in the opposite direction from the rotational direction G of the toner conveying member  28 . While the rotational wing  28   c  is in contact with the portion  18   a   1  of the toner storage chamber  18   a , it conveys toner while remaining in the position into which it has been moved by the portion  18   a   1 . As the toner conveying member  28  is rotated further, the sweeping edge of the free edge portion of the rotational wing  28   c  is moved past the border line  18   a   3 . As soon as the sweeping edge is moved past the border line  18   a   3 , the rotatable wing  28   b  is rotated by the force generated by the resiliency of the tortional coil spring  28   d  in the same direction as the rotational direction G of the toner conveying member  28 . As a result, the rotation stopper surface  28   b   2  of the stationary wing  28   b , which is the surface of the stationary wing  28   b  on the rotatable wing side, comes into contact with the rotation stopper surface  28   c   2 , which is the surface of the rotational wing  28   c  on the stationary wing side. That is, in this embodiment, the toner conveying member  28  has the first and the second portions  28   b  and  28   c . The second portion  28   c  is rotatably connected to the first portion  28   b . It is located farther from the rotational axis of the toner conveying member  28  than the first portion  28   b . Also in this embodiment, the toner conveying member  28  is provided with the elastic member  28   d , which keeps the second portion  28   c  pressured so that the second portion  28   c  rotates in the same direction as the rotational direction of the toner conveying member  28 . Further, as the toner conveying member  28  is rotated, it changes in shape. More specifically, as the toner conveying member  28  is rotated, its second portion  28   c  is rotated by the guiding portion  18   a   2  against the force generated by the resiliency of the elastic member  28   d.    
         [0126]    As described above, as the rotational wing  28   c  rotates in the same direction as the rotational direction G of the toner conveying member  28 , the toner which is being conveyed by the rotational wing  28   c , is catapulted by the rotational wing  28   c . In other words, the toner conveying member  28  in this embodiment plays the same role as those of the toner conveying members  22  in the first and second embodiments. 
         [0127]    The relationship among the distances L 1 , L 2 , L 3 , and L 4 , which was described regarding the first embodiments, also applies to this embodiment. Incidentally, in this embodiment, the distance L 1  is equivalent to the radius (maximum value) of the sweeping area of the toner conveying member  28  when the rotational stopper surface  28   b   2  of the stationary wing  28   b  is in contact with the rotation stopper surface  28   c   2  of the rotational wing  28   c . Further, also in this embodiment, the same ranges as those described regarding the second embodiment is applicable to the angles θ 1 , θ 2 , and θ 3  in this embodiment. 
         [0128]    In particular, in this embodiment, the radius of the sweeping area of the toner conveying member  28  when the rotation stopper surfaces  28   b   2  and  28   c   2  are in contact with each other is desired to be greater than the distance from the rotational axis of the toner conveying member  28  to the bottom edge  18   c   1  of the hole  18   c , as the radius of the sweeping area of the toner conveying member  22  is desired to be greater than the distance from the rotational axis of the toner conveying member  22  to the bottom edge  18   c   1  of the hole  18   c , in the first embodiment. Further, also in this embodiment, it is desired, as in the second embodiment, that the position of the guiding portion  18   a   2  is set so that the angle θ 1  is in the range expressed by the formula: 0°≦θ1≦70°. 
         [0129]    As described above, this embodiment can provide the same effects as those provided by the first and second embodiments. However, in this embodiment, the force for upwardly conveying toner is generated by the resiliency of the tortional coil spring  28   d , and therefore, toner can be more reliably supplied by a satisfactory amount into the development chamber  18   b  regardless of the amount of toner in the toner storage chamber  18   a.    
       Embodiment 4 
       [0130]    Next, another (fourth) preferred embodiment of the present invention will be described. The developing apparatus, process cartridge, and image forming apparatus, in this embodiment, are the same in basic structure as those in the first and second preferred embodiments. Therefore, the components, or the like, of the image forming apparatus in this embodiment, which are the same in function and structure as the counterparts in the first and second embodiments will be given the same referential symbols as those given to the counterparts in the first and second embodiments, and will not be described in detail. This embodiment is different, in the position of the hole  18   c  relative to the toner supply roller  20 , from the first and second embodiments. 
         [0131]      FIG. 11  is a cross-sectional view of the process cartridge  7  in this embodiment. In this embodiment, the bottom edge of the hole  18   c  with which the partition wall  26  between the toner storage chamber  18   a  and development chamber  18   b  is provided, is above the horizontal plane which includes the top c (highest point) of the toner supply roller  20 . 
         [0132]    Incidentally, for the purpose of simplifying the description of this embodiment, the stirring member  25  in the development chamber  18   b , which was described regarding the first embodiment, is not shown in  FIG. 11 . However, also in this embodiment, a stirring member similar to the stirring members  25  in the first and second embodiments may be provided in the development chamber  18   b.    
         [0133]    In particular, also in this embodiment, it is desired, as in the second embodiment, that the position of the guiding portion  18   a   2  is set so that the angle θ 1  is in the range expressed by the formula: 0°≦θ1≦70°. 
         [0134]    In this embodiment, the direction in which toner is catapulted can be adjusted by adjusting the position of the guiding portion  18   a   2  and/or the thickness of the sheet portion  22   a . Therefore, even if the process cartridge  7  is structured so that the hole  18   c  is above the horizontal plane which includes the highest point c of the toner supply roller  20 , the following adjustment can be made to satisfactorily convey toner into the development chamber  18   b . That is, in this case, all that is necessary is to adjust the amount by which toner is conveyed is to make such an adjustment as positioning the guiding portion  18   a   2  above the horizontal plane which coincides with the rotational axis of the toner conveying member  22 , and increasing in thickness the sheet portion  22   a.    
         [0135]    As described above, this embodiment also can provide the same effects as those provided by the first and second embodiments. In this embodiment, however, the entirety of the peripheral surface of the toner supply roller  20  is covered with the toner conveyed into the development chamber  18   b  by the toner conveying member  22 . Therefore, toner is more easily supplied from the toner supply roller  20  to the development roller  17  than in the first and second embodiments. 
       Embodiment 5 
       [0136]    Next, another (fifth) preferred embodiment of the present invention will be described. The developing apparatus, process cartridge, and image forming apparatus, in this embodiment, are the same in basic structure as those in the first and second preferred embodiments. Therefore, the components, or the like, of the image forming apparatus in this embodiment, which are the same in function and structure as the counterparts in the first and second embodiments will be given the same referential symbols as those given to the counterparts in the first and second embodiments, and will not be described in detail. This embodiment is different from the first and second embodiments, in the structure of the partition wall  26  which separates the development chamber  18   b  from the toner storage chamber  18   a.    
         [0137]      FIG. 12  is a cross-sectional view of a part of the process cartridge  7  in this embodiment. In this embodiment, the process cartridge  7  is structured so that the partition wall  26 , which separates the development chamber  18   b  from the toner storage chamber  18   a , is a single flat piece of wall and angled relative to the horizontal plane. 
         [0138]    The partition wall  26  in this embodiment is also provided with the hole  18   c  through which toner is conveyed from the toner storage chamber  18   a  into the development chamber  18   b , as are the partition walls  26  in the first and second embodiments. The bottom edge  18   c   1  of the hole  18   c  is above the horizontal plane which coincides with the lowest point b of the toner supply roller  20 . Further, in the second area f of the development chamber  18   b , which is surrounded by the toner supply roller  20 , partition wall  26 , and development blade  21 , the stirring member  25  is located. To describe in more detail, the second area f is the area surrounded by the toner supply roller  20 , the portion of the partition wall  26 , which is below the toner supply roller  20 , and development blade  21 . 
         [0139]    Regarding the locus of the free edge portion  25   a   2  of the stirring portion  25   a , the stirring member  25  is positioned so that as the stirring portion  25   a  is reciprocally moved, the free edge portion  25   a   2  of the stirring portion  25   a  enters the first area e of the development chamber  18   b  and contacts the toner therein. The first area e is the area between the toner supply roller  20 , and the portion of the partition wall  26 , which is below the horizontal plane which coincides with the bottom edge of the hole  18   c  and on the lateral side (left side in drawings) of the toner supply roller  20 . Therefore, it is possible to prevent the problem that as toner is supplied to the development chamber  18   b , it reduces in fluidity by becoming compacted in the first area e and its adjacencies. Therefore, toner can be more efficiently supplied to the second area f and the toner supply roller  20 . 
       Embodiment 6 
       [0140]    Next, another (sixth) preferred embodiment of the present invention will be described. The developing apparatus, process cartridge, and image forming apparatus, in this embodiment, are the same in basic structure as those in the first and second preferred embodiments. Therefore, the components, or the like, of the image forming apparatus in this embodiment, which are the same in function and structure as the counterparts in the first and second embodiments will be given the same referential symbols as those given to the counterparts in the first and second embodiments, and will not be described in detail. This embodiment is different from the first and second embodiments, in the structure of the partition wall  26  which separates the development chamber  18   b  from the toner storage chamber  18   a.    
         [0141]      FIG. 13  is a cross-sectional view of a part of the process cartridge  7  in this embodiment. In this embodiment, the partition wall  26  which separates the development chamber  18   b  from the toner storage chamber  18   a  has a curved portion  26   c , the curvature of which is such that the distance between the curved portion  26   c  and the peripheral surface of the toner supply roller  20  is uniform. That is, in this embodiment, a part of the partition wall  26  is curved in a manner to conform to the curvature of the peripheral surface of the toner supply roller  20 . In other words, in this embodiment, the portion of the partition wall  26 , which corresponds to the angled connective portion between the first and second portions  26   a  and  26   b  of the partition wall  26  in the first embodiment, is curved. 
         [0142]    The hole  18   c  for conveying toner from the toner storage chamber  18   a  to the development chamber  18   b  is positioned higher than the curved portion  26   c  of the partition wall  26 . Further, the bottom edge  18   c   1  of the hole  18   c  is positioned higher than the lowest point b of the toner supply roller  20 . Further, in the second area f of the development chamber  18   b , which is surrounded by the toner supply roller  20 , partition wall  26 , and development blade  21 , the stirring member  25  is located. To describe in more detail, the second area f is the area surrounded by the toner supply roller  20 , the portion of the partition wall  26 , which is below the toner supply roller  20 , and the blade  21 . 
         [0143]    Regarding the locus of the sweeping edge  25   a   2  of the stirring portion  25   a , the stirring member  25  is disposed so that as the stirring portion  25   a  is reciprocally moved, the sweeping edge  25   a   2  enters the first area e of the development chamber  18   b , and contacts the toner therein. The first area e is the area between the toner supply roller  20 , and the curved portion  26   c  of the partition wall  26 , which is below the horizontal plane which coincides with the bottom edge of the hole  18   c . Therefore, it is possible to prevent the problem that as toner is supplied to the development chamber  18   b , it reduces in fluidity by becoming compacted in the first area e and its adjacencies. Therefore, toner can be more efficiently supplied to the second area f and the toner supply roller  20 . 
         [0144]    As described above, the structural arrangement for the process cartridge  7  in this embodiment can also make it possible to stir the toner in the development chamber  18   b  as effectively as those described regarding the first and second embodiments. 
       Embodiment 7 
       [0145]    Next, another (seventh) preferred embodiment of the present invention will be described. The developing apparatus, process cartridge, and image forming apparatus, in this embodiment, are the same in basic structure as those in the first and second preferred embodiments. Therefore, the components, or the like, of the image forming apparatus in this embodiment, which are the same in function and structure as the counterparts in the first and second embodiments will be given the same referential symbols as those given to the counterparts in the first and second embodiments, and will not be described in detail. This embodiment is different from the first and second embodiments, in the structure of the stirring member  25  in the development chamber  18   b.    
         [0146]      FIG. 14  is a side view of the stirring member  25  in this embodiment. In this embodiment, the stirring portion  25   a  is provided with multiple ribs  25   d  (projections), which project from the surface (downwardly facing surface) of the stirring portion  25   a  which is in the bottom portion of the development chamber  18   b . That is, in this embodiment, the downwardly facing surface of the stirring portion  25   a  is provided with multiple ribs  25   d . More specifically, in order to ensure that the toner in development chamber  18   b  is stirred across the entirety of the development chamber  18   bc  in terms of the lengthwise direction of the development chamber  18   bc , the downwardly facing surface of the stirring portion  25   a  is provided with multiple ribs  25   d  which extend across the entirety of the development chamber  18   bc  in terms of the lengthwise direction of the development chamber  18   bc , or multiple shorter ribs  25   d  which extend also in the lengthwise direction of the stirring portion  25   a  and are arranged in multiple rows, which are parallel to the lengthwise direction of the stirring portion  25   a  (parallel to axial line of crankshaft  25   b ), so that they overlap in terms of the width direction of the stirring portion  25   a.    
         [0147]    Therefore, even if toner becomes compacted on the downwardly facing surface side of the stirring portion  25   a , in the second area f, for example, of the development chamber  18   b , the reciprocal movement of the stirring portion  25   a  can cause the ribs  25   d  to satisfactorily loosen the compacted toner. 
         [0148]    As described above, the structural arrangement for the process cartridge  7  in this embodiment can also make it possible to stir the toner in the development chamber  18   b  as effectively as those described regarding the first and second embodiments. In particular, in this embodiment, the provision of the ribs  25   d  on the downwardly facing surface of the stirring portion  25   a  makes it possible to more satisfactorily loosen the toner in the development chamber  18   b . Therefore, this embodiment can better prevent the problem that toner reduces in fluidity by becoming compacted, and therefore, can more efficiently supply toner to the toner supply roller  20 . Therefore, this embodiment can more effectively stabilize the amount by which toner is supplied from the toner supply roller  20  to the development roller  17 , and therefore, can more effectively prevent the formation of an unsatisfactory image, more specifically, an image suffering from the nonuniformity attributable to the unsatisfactory toner delivery. 
       Embodiment 8 
       [0149]    Next, another (eighth) preferred embodiment of the present invention will be described. The developing apparatus, process cartridge, and image forming apparatus, in this embodiment, are the same in basic structure as those in the first and second preferred embodiments. Therefore, the components, or the like, of the image forming apparatus in this embodiment, which are the same in function and structure as the counterparts in the first and second embodiments will be given the same referential symbols as those given to the counterparts in the first and second embodiments, and will not be described in detail. This embodiment is different from the first and second embodiments, in the structure of the stirring member  25  in the development chamber  18   b.    
         [0150]      FIGS. 15 and 16  are exploded perspective views of a part of the process cartridge  7  in this embodiment, and show the structural arrangement, in this embodiment, for controlling the vertical movement of the stirring portion  25   a.    
         [0151]    The stirring portion  25   a  is connected to the crankshaft  25   b , the end portions of which are in the grooves  18   d  of the developing means frame  18 . Thus, the crankshaft  25   b  is supported at its lengthwise end portions, by the developing means frame  18 . A crankshaft bushing  30  is used as the member for keeping the crankshaft  25   b  pressed downward. That is, the crankshaft  25   b  is attached to the developing means frame  18  by moving each of the lengthwise end portions of the crankshaft  25   b  into the bottom of the corresponding groove  18   d  from the top side (in drawing) of the groove  18   d . The shaft pressing portion  30   b  of the crankshaft bushing  30  prevents the lengthwise end portion of the crankshaft  25   b  from moving toward the top side of the groove  18   d.    
         [0152]    The crankshaft bushing  30  is provided with a portion  30   a  for regulating the stirring portion  25   a . The stirring member regulating portion  30   a  regulates the vertical movement of the portion  25   e  (portion to be regulated) of the stirring portion  25   a . In this embodiment, the portion  25   e  projects from the lengthwise end of the stirring portion  25   a  (which is plate-like member), in the lengthwise direction of the stirring portion  25   a . That is, in this embodiment, the process cartridge  7  is structured so that the crankshaft bushing  30  is utilized as the means (member) for regulating the stirring portion  25   a  in terms of its locus, in order to prevent the stirring portion  25   a  from moving upward. 
         [0153]    Therefore, even if toner becomes compacted on the downwardly facing surface side of the stirring portion  25   a , the stirring portion  25   a  is not lifted by the body of compacted toner, being therefore prevented from reciprocally sliding on top of the body of compacted toner. Therefore, it is ensured that the stirring portion  25   a  enters the body of compacted toner. 
         [0154]    As described above, the structural arrangement for the process cartridge  7  in this embodiment can also make it possible to stir the toner in the development chamber  18   b  as effectively as those described regarding the first and second embodiments. In particular, in this embodiment, the stirring portion regulating portion  30   a  for regulating the vertical movement of the stirring portion  25   a  is provided. Therefore, it is further ensured that the toner in the development chamber  18   b  is effectively stirred to prevent the problem that toner reduces in fluidity by becoming compacted. Therefore, this embodiment can more satisfactorily supply the toner supply roller  20  with toner to ensure that the toner is continuously supplied a satisfactory amount from the toner supply roller  20  to the development roller  17 . Therefore, this embodiment can make it possible to more effectively prevent the formation of an unsatisfactory image, more specifically, an image suffering from the nonuniformity attributable to the unsatisfactory toner delivery. 
         [0155]    In the above, the present invention was described with reference to the concrete embodiments of the present invention. However, these embodiments are not intended to limit the present invention in applicability. That is, the preceding embodiments were described with reference to the developing apparatus (development unit), which is a part of the process cartridge removably mountable in the main assembly of an image forming apparatus. However, the application of the present invention is not limited to a developing apparatus such as those in the preceding embodiments. That is, the present invention is also applicable to a developing apparatus, which is an nonremovable part of an image forming apparatus, or a development cartridge, that is, a cartridge in which only a developing apparatus is disposed, which is removably mountable in the main assembly of an image forming apparatus. 
         [0156]    Also, the preceding embodiments were described with reference to the image forming apparatus of the intermediary transfer type, that is, an image forming apparatus employing an intermediary transfer member. However, the preceding embodiments were not intended to limit the present invention in applicability. As has been known to the people who work in the field of image formation, there are image forming apparatuses which employ an endless conveyer belt as a member for holding and conveying recording medium. In the case of these image forming apparatuses, after the formation of a toner image on a photosensitive member, the toner image is directly transferred onto a sheet of recording medium borne by the recording medium holding member. In some image forming apparatuses of the abovementioned direct transfer type, which employs a conveyer belt instead of an intermediary transfer belt, such as those in the preceding embodiments, image forming portions in which a process cartridge is removably mountable are disposed under the conveyer belt. In some of these image forming apparatuses, it is necessary to convey toner against gravity in the developing apparatus. In the case of these image forming apparatuses, the present invention is very effectively applicable. 
         [0157]    According to the embodiments of the present invention described above, it is possible to provide a developer conveying mechanism which is small, simple in structure, and yet, capable of satisfactorily conveying developer against gravity. Further, it is possible to stir developer, in the area between the developer supply roller, and the partition wall located below the developer supply roller, and then, supply the stirred developer to the developer supply roller. 
         [0158]    Incidentally, it is optional to combine two or more of the preceding embodiments described above, and the combination can provide the same effects as those obtainable by the preceding embodiments. 
         [0159]    While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth, and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claims. 
         [0160]    This application claims priority from Japanese Patent Applications Nos. 333897/2006 and 278173/2007 filed Dec. 11, 2006 and Oct. 25, 2007, respectively which are hereby incorporated by reference.