Patent Publication Number: US-2004052547-A1

Title: Image forming apparatus and process cartridge used in the same

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention is related to an electro-photographic type, or other types of image forming apparatus, and a process cartridge employed in this image forming apparatus.  
       [0003] 2. Description of the Related Art  
       [0004] As this sort of image forming apparatus, such an image forming apparatus is known in which while a recording medium is transported along a substantially vertical direction, an image is formed on this transported recording medium, and then, the recording medium on which the image has been formed is ejected to an ejection unit provided on an upper portion of a main body of this image forming apparatus as disclosed in JP-A-10-207160.  
       [0005] As previously explained, in such a type of image forming apparatus that the recording medium is transported along the vertical direction, a dead space may be readily formed at a lower portion of the ejection unit. In other words, for instance, in an electro-photographic type image forming apparatus, a developing apparatus is arranged under a vertical transport path, and also, a fixing apparatus is arranged above the vertical transport path, respectively. As a result, a lower portion of an ejection unit, which is extended from the fixing apparatus to a side direction while being inclined, may constitute a dead space.  
       SUMMARY OF THE INVENTION  
       [0006] An object of the present invention is to effectively utilize a space just under the inclination portion of the ejection unit, where the dead space may be easily produced.  
       [0007] To achieve an object, a first feature of the present invention is such an image forming apparatus includes an image forming section having a developer storage space into which developer is stored, and an ejection unit for ejecting therefrom a recording medium on which an image has been formed by the image forming section, in which the ejection unit owns an inclination portion which has a lower end and an upper end, while being obliquely formed, and at least a portion of the developer storage space of the image forming section is arranged in an area which is surrounded by the inclination portion, a horizontal plane extended from the lower end of the inclination portion, and a vertical plane extended from the upper end of the inclination portion. As a consequence, since the developer storage space is arranged in the area which is surrounded by the inclination portion, the horizontal plane extended from the lower end, and the vertical plane extended from the upper end, a lower portion of the inclination portion of the ejection unit can be utilized as the developer storage space.  
       [0008] A second feature of the present invention is such an image forming apparatus includes an image forming section having a developer storage space into which developer is stored, and an ejection unit for ejecting therefrom a recording medium on which an image is formed by the image forming section, in which the ejection unit owns an inclination portion which is obliquely formed, and at least a portion of a wall surface which surrounds the developer storage space along the inclination portion is formed. As a result, since the wall surface of the developer storage space is formed along the inclination portion, the lower portion of the inclination portion of the ejection unit can be similarly utilized as the developer storage space.  
       [0009] The image forming section is not limited only to an ink jet type image forming section, but also not to an electro-photographic type image forming section. However, the electro-photographic type image forming section is preferably employed. In the case of such an electro-photographic image forming system, the image forming section may be arranged by employing an image carrier on which is a latent image is formed; the developer storage space owns a first developer storage portion arranged at an upper portion thereof, and a second developer storage portion arranged at a lower portion thereof, while sandwiching therebetween a horizontal line which is extended from a latent image forming position of the image carrier along a horizontal direction; and the first developer storage portion is connected to the second developer storage portion. Preferably, a developer storage capacity of the first developer storage portion is larger than that of the second developer storage portion.  
       [0010] It should be noted that in the case of the electro-photographic type image forming system, the developer is a toner, or such a mixture made of a toner and a carrier. In the case of the ink jet type image forming system, the developer is ink, and then, a portion of an ink tank is arranged at the lower portion of the ejection unit.  
       [0011] Also, in the case of the electro-photographic type image forming system, the image carrier is a photosensitive member, and an optical writing apparatus for forming a latent image on the image carrier is employed. Furthermore, the optical writing apparatus is constituted by a laser exposing apparatus, and may be arranged at a position which is extended from the latent image forming position of the image carrier to the horizontal direction.  
       [0012] Further, the image forming section may be preferably provided with a process cartridge which includes an image carrier on which a latent image is formed, and a developing unit containing the developer storage, for developing the latent image of the image carrier so as to produce a visible image. This process cartridge may be dismounted and mounted from the upper portion of the apparatus main body by opening/closing the inclination portion. In order to easily detachably mount this process cartridge, a grip portion is provided on a portion of a wall surface which constitutes the developer storage space, and then, the process cartridge may be detachably mounted by handling this grip portion.  
       [0013] Also, a third feature of the present invention is such a process cartridge used in an image forming apparatus containing an ejection unit having an inclination portion which is obliquely formed in order to eject therefrom a recording medium includes a developer storage space for storing thereinto developer, in which at least a portion of the developer storage space is arranged in a space which is surrounded by the inclination portion, a horizontal plane extended from a lower end of the inclination portion, and also, a vertical plane extended from an upper end of the inclination portion.  
       [0014] In addition, a fourth feature of the present invention is such a process cartridge used in an image forming apparatus containing an ejection unit having an inclination portion which is obliquely formed in order to eject therefrom a recording medium includes a developer storage space for storing thereinto developer; in which at least a portion of a wall surface which surrounds the developer storage space is formed along the inclination portion.  
       [0015] It should also be understood that in the present invention, a process cartridge implies such a cartridge having an image carrier on which a latent image is formed, and the developing unit containing the developer storage space and for developing the latent image of the image carrier so as to produce the visible image, and which is freely detachably mounted with respect to the main body of the image forming apparatus. This process cartridge may contain such components as the cleaning apparatus and the charging apparatus. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0016]FIG. 1 is a sectional view for indicating an image forming apparatus according to an embodiment mode of the present invention.  
     [0017]FIG. 2 is a sectional view for representing a process cartridge employed in the image forming apparatus according to an embodiment mode of the present invention.  
     [0018]FIG. 3 is a side view for showing a supply path of developer in the process cartridge employed in the image forming apparatus according to the embodiment mode of the present invention.  
     [0019]FIG. 4 is a perspective view for indicating the process cartridge employed in the image forming apparatus according to the embodiment mode of the present invention.  
     [0020]FIG. 5 is an exploded perspective view for indicating an image carrier unit of the process cartridge employed in the image forming apparatus according to the embodiment mode of the present invention.  
     [0021]FIG. 6 is an exploded perspective view for representing a developing appliance unit of the process cartridge employed in the image forming apparatus according to the embodiment mode of the present invention.  
     [0022]FIG. 7 is a perspective view for showing the developing apparatus unit of the process cartridge employed in the image forming apparatus according to the embodiment mode of the present invention.  
     [0023]FIG. 8 is an exploded perspective view of the developing apparatus unit of the process cartridge employed in the image forming apparatus according to the embodiment mode of the present invention, as viewed from a rear surface of the developing appliance unit. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0024] Referring now to drawings, embodiment modes of the present invention will be described.  
     [0025]FIG. 1 schematically shows an image forming apparatus  10  according to an embodiment mode of the present invention. The image forming apparatus  10  contains a main body  12  of the image forming apparatus. An image forming section  14  is mounted on this image forming apparatus main body  12 . An ejection unit  16  (will be explained later) is provided at an upper portion of this image forming apparatus main body  12 , and also, for instance, two stages of paper supply units  18   a  and  18   b  are arranged at a lower portion of this image forming apparatus main body  12 . Furthermore, two stages of paper supply units  18   c  and  18   d  are arranged below the image forming apparatus main body  12 , while these paper supply units  18   c  and  18   d  are detachably mounted thereon as an optical paper supply unit.  
     [0026] Each of the paper supply units  18   a  to  18   d  owns a paper supply unit main body  20  and a paper supply cassette  22  into which paper is stored. The paper supply cassette  22  is slidably mounted with respect to the paper supply unit main body  20 , and is drawn out from this paper supply unit main body  20  along a front plane direction (namely, right direction of FIG. 1). Also, a paper supply roller  24  is arranged at an upper portion near an inner end of the paper supply cassette  22 , and both a retard roller  26  and a nudger roller  28  are arranged in front of this paper supply roller  24 . Furthermore, feed rollers  30  are provided with the optionally-provided paper supply units  18   c  and  18   d , and these feed rollers  30  may constitute a pair of feed rollers.  
     [0027] A transport path  32  corresponds to a paper path defined from the feed roller  30  of the lowermost paper supply unit  18   d  up to an ejection port  34 . While this transport path  32  is located in the vicinity of a rear surface (namely, left side surface viewed in FIG. 1) of the image forming apparatus main body  12 , this transport path  32  owns such a portion which is formed along the substantially vertical direction from the feed roller  30  of the lowermost paper supply unit  18   d  up to a fixing apparatus  36  (will be discussed later) . Both a transfer apparatus  42  (will be explained later) and an image carrier  44  (will be explained later) are arranged on an upper stream side of the fixing apparatus  36  of this transport path  32 . Furthermore, a register roller  38  is arranged on an upper stream side of both the transfer apparatus  42  and the image carrier  44 . In addition, an ejection roller  40  is arranged in the vicinity of an ejection port  34  of the transport path  32 .  
     [0028] As a result, the recording mediums which are fed out from the paper supply cassettes  22  of the paper supply units  18   a  to l 8   d  by the paper supply roller  24  are smoothly separated by the retard roller  26  and the nudge roller  28  to be conducted to the transport path  32 , and then, are temporarily stopped by the register roller  38 . After proper timing is controlled, a developed image is transferred to the recording medium while the recording medium is penetrated between the transfer apparatus  42  and the image carrier  44  (will be explained later), and this transferred developed image is fixed on the fixing apparatus  36 , and then, the recording medium on which the fixed image has been formed is ejected from the ejection port  34  to the ejection unit  16  by the ejection roller  40 ,  
     [0029] It should be noted that when a double-surface printing mode is carried out, this recording medium is returned to an inversion path  48 . In other words, a front path portion of the transport path  30  as to the ejection roller  40  is separated into two paths, a switching craw  46  is provided at this separated path portion, and the inversion path  48  is formed from this separated path portion up to the register roller  38 . While transport rollers  50   a  to  50   c  are provided in this inversion path  48 , in the case of the double-surface printing mode, the switching claw  46  is switched to such a side that the inverted at a time instant when a front edge portion of a recording medium is engaged with the ejection roller  40 , so that this recording medium is conducted to the inversion path  48 , and then, is penetrated through the register roller  38 , the transfer apparatus  42 , the image carrier  44 , and the fixing apparatus  36  so as to be ejected from the ejection port  34  to the ejection unit  16 .  
     [0030] The ejection unit  16  owns an inclination portion  52  which is freely pivotable with respect to the image forming apparatus main body  12 . This inclination portion  52  is inclined in such a manner that an ejection port portion thereof is low and is gradually heightened toward a front surface direction (namely, right direction viewed in FIG. 1). This ejection port portion is used as a lower end of the inclination portion  52  and a tip portion which is heightened is used as an upper end thereof. This inclination portion  52  is supported with respect to the image forming apparatus main body  12  in such a manner that this inclination portion  52  is freely pivotable, while the lower end thereof is located at a center. As indicated by a two-dot/dash line in FIG. 1, when this inclination portion  52  is rotated toward the upper direction so as to be opened, an opening unit  54  is formed, and a process cartridge (will be explained later)  64  can be detachably mounted via this opening unit  54 .  
     [0031] The image forming section  14  is made of, for instance, an electro-photographic type image forming unit. This image forming section  14  is arranged by the image carrier  44  constructed of a photosensitive material, a charging apparatus  56 , an optical writing apparatus  58 , a developing apparatus  60 , a transfer apparatus  42 , a cleaning apparatus  62 , and a fixing apparatus  36 . The charging apparatus  56  is constituted by, for example, a charge roller capable of uniformly charging the image carrier  44 . The optical writing apparatus  58  writes a latent image in an optical manner on the image carrier  44  charged by the charging apparatus  56 . The developing apparatus  60  develops the latent image of the image carrier  44 , which has been formed by the optical writing apparatus  58 , by way of developer so as to produce a visible image. The transfer apparatus  42  is constituted by, for example, a transfer roller which transfers the developed image by the developing apparatus  60  to paper. The cleaning apparatus  62  is constituted by, for instance, a blade which cleans the developer left on the image carrier  44 . The fixing apparatus  36  is arranged by both a pressure-applying roller and a heating roller, by which the developed image which has been transferred onto the paper by the transfer apparatus  42  is fixed on this paper. The optical writing apparatus  58  is constructed of, for example, a scanning type laser exposing apparatus, and is arranged in parallel to the paper supply units  18   a  to  18   d , and is located in the vicinity of a front surface of the image forming apparatus main body  12 . As will be explained later, the optical writing apparatus  58  exposes the image carrier  44  by scanning light beams across the inner space of the developing apparatus  60 . This exposing position of the image carrier  44  may constitute a latent image writing position “P.” It should be noted that in this embodiment mode, the scanning type laser exposing apparatus has been employed as the optical writing apparatus  58 . Alternatively, an LED (Light Emitting Diode), a surface emitting laser, and the like may be employed.  
     [0032] The process cartridge  64  is arranged by employing the image carrier  44 , the charging apparatus  54 , the developing apparatus  60 , and the cleaning apparatus  62  in an integral body. This process cartridge  64  is arranged just under the inclination portion  52  of the ejection unit  16 , and as previously explained, is detachably mounted via the opening portion  54  which is formed when the inclination portion  52  is opened.  
     [0033] This process cartridge  64  is detachably separated into an image carrier unit  66  and a developing apparatus unit  68 . In the image carrier unit  66 , the image carrier  44 , the charging apparatus  54 , and the cleaning apparatus  62  are arranged. In the developing apparatus unit  68 , the developing apparatus  60  is arranged. The developing apparatus unit  68  owns a developer storage space  70  which stores thereinto, for example, developer. An upper portion of this developer storage unit  70  belongs to such an area “A” which is surrounded by the inclination portion  52 , a horizontal plane extended from the lower end of the inclination portion  52 , and also, a vertical plane extended from the upper end of this inclination portion  52  as indicated by a two-dot/dash line in FIG. 1. Also, an upper wall plane  72  which constitutes the developer storage space  70  is formed in such a manner that this upper wall plane  72  is located in parallel to the inclination portion  52  and along this inclination portion  52 . Also, a plurality of ribs  74  are formed on a lower surface of the inclination portion  52  in such a way that these plural ribs  74  are positioned in parallel to each other along the inclination direction of the inclination portion  52 . Since these ribs  74  are formed, a flow path  76  is formed between the inclination portion  52  and the process cartridge  64 . This flow path  76  is employed so as to penetrate air therethrough, and this flow path  76  may disperse heat produced from the fixing apparatus  36 . Furthermore, a grip portion  78  is formed on the upper portion of the developer storage space  70 . This grip portion  78  is formed in such a manner that wall surfaces of both sides of the upper portion of the developer storage space  70  are entered into the inside thereof. When the process cartridge  64  is detachably mounted, this process cartridge  64  can be readily detachably mounted by gripping this grip portion  78 .  
     [0034] In FIG. 2 to FIG. 8, a detailed construction of the process cartridge  64  is indicated. As explained above, the process cartridge  64  is arranged by the image carrier unit  66  and the developing apparatus unit  68 , and this image carrier unit  66  is coupled to the developing apparatus unit  68  via coupling pins  80   a  and  80   b  in such a manner that this image carrier unit  66  is freely pivotable with respect to the developing apparatus unit  68 . Also, both the image carrier unit  66  and the developing apparatus  68  are energized with each other by a tension spring  82  and a depression spring  84 , and a developing roller  86  is depressed against the image carrier  44 .  
     [0035] It should also be understood that a memory  88  for storing thereinto a total print number and the like is provided on a side surface of the process cartridge  64  (namely, side surface of one, or both image carrier unit  66  and developing apparatus unit  68 ).  
     [0036] The image carrier unit  66  owns a main body  90  of the image carrier unit  66 , and both the image carrier  44  and the charging apparatus  56  are supported by this image carrier unit main body  90  in such a manner that both the image carrier  44  and the charging apparatus  56  are rotatably supported by this image carrier unit main body  90  via bearing  92   a  and  93   b  used for the image carrier  44 , and bearings  94   a  and  94   b  used for the charging apparatus  56 , respectively. The bearing  94   a  and bearing  94   b  for the charging apparatus  56  own another function of a power supply portion. Also, for example, two fingers  96   a  and  96   b  are supported by the image carrier unit main body  90  in such a manner that these fingers  96   a  and  96   b  are freely pivotable with respect to this image carrier unit main body  90 . Since tip portions of these fingers  96   a  and  96   b  are depressed by a spring for the fingers  96   a  and  96   b  on the surface of the image carrier  44 , a recording medium which will wrap the image carrier  44  is stripped by these tip portions. Also, a developer collecting space  98  is formed the cleaning apparatus (cleaning blade)  62  within the image carrier unit main body  90 , and thus, developer which has been scratched/dropped by the cleaning apparatus  62  is collected into this developer collecting space  98 . A paddle  100  is rotatably provided in this developer collecting space  98 . This paddle  100  is supported via a gear  102  for the paddle  100  by the image carrier unit main body  90 , and transports the developer which has been collected by being rotated to an inner side of the developer collecting space  98 . Also, a shutter  104  is provided at the upper portion of the image carrier unit main body  90  in such a manner that this shutter  104  can be freely opened/closed. This shutter  104  is supported via a shaft  106  for the shutter  104  with respect to the image carrier unit main body  90  in a freely movable manner. This shutter  104  closes an opening portion of the image carrier  44  before the process cartridge  64  is mounted, and is opened in order that the image carrier  44  is come out to the front in the case that the process cartridge  64  is mounted.  
     [0037] The developing apparatus unit  68  contains a main body  112  of the developing apparatus unit  68  which is constituted by jointing a front housing  108  to a rear housing  110 . An inner space of this developing apparatus unit main body  112  is segmented into the developer collecting space  70  and a developing unit  114  in which. the developing roller  86  is arranged. The developer collecting space  70  is separated into a first developer storage portion  116   a  and a second developer storage portion  116   b  via a partition wall  118 , while a horizontal line extended from the latent image writing position “P” is defined as a boundary. This horizontal line corresponds to a scanning optical path originated from the optical writing apparatus  58 . The first developer collecting portion  116   a  is located at an upper portion of the developer storage portion  116   b  is located at a lower portion thereof. A developer storage capacity of the first developer storage unit  116   a  is made larger than a developer storage capacity of the second developer storage unit  11   b.    
     [0038] As shown in FIG. 3, the partition wall  118  constitutes a window portion  120  having, for example, a rectangular shape, which forms the optical scanning path defined from the optical writing apparatus  58 . Also, this partition wall  118  constitutes developer paths  122   a  and  122   b  in connection with the developing apparatus unit main body  112  on both sides of this window portion  120 . Both the developer paths  122   a  and  122   b  cause the first developer storage portion  116   a  to be communicated with the second developer storage portion  116   b . In the first developer storage portion  116   a , as previously explained, an upper portion of this first developer storage portion  116   b  is arranged within the area “A”, and also, a first stirring/transporting member  124  is rotatably arranged. This first stirring/transporting member  124  is constituted by such a wire member which is formed in a helical shape along different winding directions to each other. The first stirring/transporting member  124  supplies the developer stored in the first developer storage port  116   a  to the developer paths  122   a  and  122   b . A second stirring/transporting member  126  is rotatably arranged at a lower position -of the first stirring/transporting member  124  within the second developer storage unit  116   b . This second stirring/transporting member  126  is constituted by a screw shaft formed along different direction from edge portions thereof (viewed along axial direction) toward a center portion thereof. Since the developer is uniformly dispersed by the second stirring/transporting member  124 , the developer supplied from the developer paths  122   a  and  122   b  formed on the both sides may be transported along the center direction. As a consequence, as indicated by an arrow of FIG. 3, the developer which has been stored in the first developer storage unit  116   a  is transported to the both sides of the first stirring/transporting member  124  by this first stirring/transporting member  124 , and then, is dropped via the developer paths  122 a and  122   b  to the second developer storage unit  116   b , and thereafter is uniformly dispersed by rotating the second stirring/transporting member  124 , so that the dispersed developer is transported to the side of the developing roller  86 .  
     [0039] Furthermore, both a third stirring/transporting member  128  and a fourth stirring/transporting member  130  are arranged in the second developer storage portion  116   b . The third stirring/transporting member  128  transports the developer transported by the second stirring/transporting member  126  to the fourth stirring/transporting member  130 . This fourth stirring/transporting member  130  is arranged at an output port of the second developing member storage portion  116   b . The fourth stirring/transporting member  130  transports the developer which has been transported by the third stirring/transporting member  128  to the developing roller  86 , and also, mixes this new developer with the deteriorated developer which has been scratched/dripped from the developing roller  86 .  
     [0040] As is well known in the field, the developing roller  86  is constructed in such a manner that a sleeve is wound on a magnet roller, and tracking caps  132   a  and  132   b  are provided on both sides of the magnet roller. These tracking caps  132   a  and  132   b  are made in contact to the image carrier  44 , and as explained in the above description, a developing gap may be secured by depressing these tracking caps  132   a  and  132   b  against the image carrier  44  by both the tension spring  82  and the depression spring  84 . A layer thickness restricting member  134  made of, for instance, a resin is made in contact with the developing roller  86 . A thickness of a developer layer adhered on the surface of the developing roller  86  is restricted by this layer thickness restricting member  134 . Also, a side surface of this developing roller  86  is sealed by a developing portion sealing member  136 .  
     [0041] It should also be noted that reference numerals  138   a  and  138   b  indicate developer caps which are detachably mounted on the developing apparatus unit main body  112 . Since these developer caps  138   a  and  138   b  are pulled out, the developer is supplied to either the first developer storage unit  116   a , or the second developer storage unit  116   b.    
     [0042] In the drive system of the process cartridge  64 , drive force is transferred from the side of the image carrier  44 , and then, is transferred via a developing roller gear  140 , a gear  142  for the respective first to fourth stirring/transporting members, and an idle gear  144  to the developing roller  86  and also to the respective first to fourth stirring/transporting members  124  to  130 . A stirring/transporting member sealing member  146  is inserted into a bearing portion of the stirring/transporting member gear  146 . Furthermore, a gear cover  148  is provided on the side surface of the developing apparatus unit main body  112 , while this gear cover  148  covers the gear  142  for the respective stirring/transporting members and the idle gear  144 .  
     [0043] Next, operations of the image forming apparatus according to the embodiment mode will now be described.  
     [0044] While the image carrier  44  is uniformly charged by the charging apparatus  56 , light emitted from the optical writing apparatus  58  is irradiated onto this charged image carrier  44  in response to an image signal, and then, a latent image is formed at the latent image forming position “P” thereof. The light emitted from the optical writing apparatus  58  passes through the process cartridge  64  via the window portion  120  of the process cartridge  64 . The latent image which has been formed on the image carrier  44  by this optical writing apparatus  58  is developed by the developer of the developing apparatus  60  so as to produce a visible image.  
     [0045] While the developer has been stored in both the first developer storage portion  116   a  and the second developer storage portion  116   b , the developer stored in the first developer storage portion  116   a  is transported to both sides by rotating the first stirring/transporting member  124 , and then both the developer located on the both sides is transported via the two developer paths  122   a  and  122   b  to the second developer storage unit  116 . Furthermore, the developer of the second developer storage portion  116   b  is uniformly dispersed by rotating the second stirring/transporting member  126 , and then, the uniformly dispersed developer is transported to the developing unit  114  by the third stirring/transporting member  128  and the fourth stirring/transporting member  130 . In this developing unit  114 , the transported developer is adhered onto the developing roller  86 , the layer thickness of the adhered developer is restricted by the layer thickness restricting member  134 , the thickness restricted developer is transported up to a developing position located opposite to the image carrier  44 , and then, an image made of the developer is formed in correspondence with the latent image of the image carrier  44 .  
     [0046] On the other hand, one of the paper supply units  18   a  to  18   d  is selected in response to a size signal and the like, recording mediums stored in one of these paper supply cassettes  22  are fed out by the paper supply roller  24 , and these recording mediums are smoothly separated by the retard roller  26  and the nudger roller  28  so as to conduct a recording medium to the transport path  32 . Then, this conducted recording medium is temporarily stopped by the register roller  38 , and thereafter, this recording medium is conducted between the transfer apparatus  42  and the image carrier  44  at proper timing.  
     [0047] When the recording medium is conducted between the transfer apparatus  42  and the image carrier  44  in this manner, the developer on the image carrier  44  is transferred to the recording medium by the transfer apparatus  42 . This recording medium to which the developer has been transferred is penetrated through the fixing apparatus  36 , and then is ejected from the ejection port  34  to the ejection unit  16 .  
     [0048] The recording medium is penetrated through the transport path  32 , and then is ejected to the ejection unit  16 , and thus a so-called “C-path” is constituted, while this transport path  32  is formed along the substantially vertical direction from the paper supply units  18   a  to  18   d  arranged along the horizontal direction. In this embodiment mode, since the process cartridge  64  is stored within the C-path, the layout of this image forming apparatus can be made compact. However, if the developer storage space connected to the developing unit  114  is arranged lower than the latent image writing position “P” in the normal design manner, such a dead space is produced under the ejection portion  16 . More specifically, in the case that a storage capacity of the developer is increased, since the space located lower than the latent image writing position “P” must be increased, a larger dead space is produced.  
     [0049] However, in this embodiment mode, the window portion  120  which constitutes the scanning optical path from the optical writing apparatus  58  is formed in the process cartridge  64 , and the developer paths  122   a  and  123   b  are formed on both sides of this window portion  120 , and also the first developer storage portion  116   a  can be arranged above the scanning optical path. Further, a portion of the first developer storage unit  116   a  is located within the area “A” which is surrounded by the inclination portion  52 , the horizontal plane extended from the lower end of the inclination portion  52 , and also the vertical plane extended from the upper end of the inclination portion  52 . As a result, the lower portion of the ejection unit  16  can be effectively utilized as the developer storage portion.  
     [0050] In the embodiment modes, the one-component developing system is employed. The present invention is not limited to this one-component developing system, but may be applied to a two-component developing system. Also, in the embodiment mode, the developed image is directly transferred from the image carrier to the recording medium. However, the present invention is not limited to this transfer operation, but may be applied to another embodiment in which an intermediate transfer member may be interposed between the image carrier and the recording medium. Furthermore, in the embodiment modes, the black/white image forming apparatus has been described. Apparently, the present invention may be applied to a color image forming apparatus. In this case, for instance, assuming now that four developing apparatus are employed, if a developer storage space of at least one developing apparatus is arranged under the ejection unit, then the dead space problem may be sufficiently solved.  
     [0051] As previously described, in accordance with the present invention, since the lower portion of the ejection unit is used as the developer storage space, this lower portion where the dead space is readily produced can be effectively utilized. As a consequence, the compact image forming apparatus can be provided.