Patent Publication Number: US-2004046855-A1

Title: Image forming apparatus

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention is related to an electro-photographic type 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] The above-described prior art is represented in FIG. 6. In this prior art, a recording medium which has been transported from a paper supply unit  200  by a transport roller  202  is traveled through a transport path  204  which is formed along a substantially vertical direction, and an image is formed on this recording medium by an image forming section  206 , and then, this recording medium on which the image has been formed is ejected to an ejection unit  210  which is formed at an upper portion of a main body  208  of the image forming apparatus. The image forming section  206  contains an image carrier  212  constructed of a photosensitive member, a charging apparatus  214  for charging this image carrier  212 , an optical writing apparatus  216 , a developing apparatus  218 , a transferring apparatus  200 , a cleaning apparatus  222 , and also a fixing apparatus  224 . The charging apparatus  214  charges this image carrier  212 . The optical writing apparatus  216  forms a latent image on the image carrier  214  charged by this charging apparatus  214 . The developing apparatus  218  develops the latent image of the image carrier  214  formed by this optical writing apparatus  216  so as to produce a visible toner image. The transferring apparatus  218  transfers the toner image of the image carrier  214  developed by this developing apparatus  218  onto the recording medium. The cleaning apparatus  222  is constituted by a blade for cleaning developer left on the image carrier  214 . The fixing apparatus  224  fixes the toner image which has been transferred onto the recording medium.  
       [0006] The optical writing apparatus  216  is constituted by a scanning type laser exposing apparatus, and is arranged on the side of the developing apparatus  218 . In this prior art, when reliability is taken into account, it is preferable to arrange the optical writing apparatus  216  along a horizontal direction. However, since this optical writing apparatus  216  is arranged along an oblique direction, such a device capable of reducing a width of this optical writing apparatus  216  along forward/backward directions (namely, right/left directions as viewed in FIG. 6) can be made.  
       [0007] However, in such a type of image forming apparatus that the recording medium is transported along the substantially vertical direction, dead spaces  226  and  228  are formed at both upper/lower portions of the optical writing apparatus  216  within the ejection unit  210  provided at the upper portion of this image forming apparatus. In other words, since the developing apparatus  218  is arranged at a position lower than a latent image writing position “P” where the latent image is written onto the image carrier  212  by the optical writing apparatus  216 , the optical writing apparatus  216  must be arranged above the developing apparatus  218 . As a result, the dead space  226  is formed between the ejection unit  210  and the optical writing apparatus  216 , and also, the dead space  228  is formed between the optical writing apparatus  216  and the paper supply unit  200 .  
       SUMMARY OF THE INVENTION  
       [0008] An object of the present invention is to provide an image forming apparatus capable of reducing a dead space, otherwise, by which even when such a dead space is formed, this dead space can be effectively utilized.  
       [0009] To achieve the above-described object, a first feature of the present invention is to provide an image forming apparatus comprising: an image forming apparatus main body in which an ejection unit is provided at an upper portion thereof; a recording medium storage section arranged along a substantially horizontal direction; a transport path for transporting a recording medium supplied from the recording medium storage section along a substantially vertical direction, and for ejecting the transported recording medium to the ejection unit of the image forming apparatus main body; an image carrier; an optical writing section for forming an electrostatic latent image on the image carrier; and developing section for developing the electrostatic latent image formed on the image carrier to produce a visible image; in which the developing section owns a developer storage space for storing thereinto developer; and a latent image writing position of the image carrier written by the optical writing apparatus is located lower than at least a portion of the developer storage space along the vertical direction. As a consequence, since the latent image writing position written by the optical writing apparatus is located at the lower position, the space defined between the optical writing apparatus and the recording medium storage section can be made smaller than that of the conventional image forming apparatus.  
       [0010] Although a laser apparatus and/or an LED (Light Emitting Diode) may be employed as the optical writing apparatus, a scanning type laser exposing apparatus is employed. This scanning type laser exposing apparatus maybe arranged along a substantially horizontal direction, so that the space defined between the optical writing apparatus and the recording medium storage section arranged along the substantially horizontal direction maybe made smaller. As the optical system of the scanning type laser exposing apparatus, there are both an over-field type optical system and an under-field type optical system. In this over-field type optical system, a width of a luminous flux entered into a rotary polygon along a main scanning direction is made wider than a plane width of this rotary polygon. In the under-field type optical system, a width of a luminous flux entered into a rotary polygon along a main scanning direction is made narrower than a plane width of this rotary polygon. In such a case that a plurality of machine sorts of image forming apparatus are wanted to be manufactured in which printing speeds thereof and maximum paper sizes thereof are changed, while image forming apparatus main bodies and the like are commonly utilized, the over-field type optical system is employed when either a high printing speed or a larger maximum paper size is realized, whereas the under-field type optical system is employed when either a low printing speed or a smaller maximum paper size is realized. Generally speaking, since an optical path of an over-field type optical system is long and complex, a larger installation space is required, as compared with that of an under-field type optical system. To the contrary, in such a case that the optical writing apparatus is arranged along the substantially horizontal direction, a lower space of an ejection unit is extended. As a result, if this lower space is made coincident with the storage capacity of the over-field type, then both the over-field type optical system and the under-field type optical system can be properly utilized while the dead space is suppressed to a minimum dead space.  
       [0011] Also, the optical writing apparatus may be preferably arranged on the front surface side of the image forming apparatus main body.  
       [0012] Also, a control board for controlling drives of the respective components of the image forming apparatus, a network interface board used to constitute a network, or a developer storage vessel for storing thereinto developer is arranged in another space defined between the ejection unit and the optical writing apparatus, sot that this space can be effectively utilized.  
       [0013] As explained above, in order that the developer storage space is formed at the position higher than the latent image writing position written by the optical writing apparatus, the developer storage space is subdivided into a first developer storage portion arranged at an upper portion thereof, and a second developer storage portion arranged at a lower portion thereof, and also, a window portion is formed between these first and second developer storage portions. As a result, an optical scanning path from the optical writing apparatus can be constituted by this window portion. Also, when such a construction is made that at least a portion of the optical writing apparatus is arranged to be overlapped with respect to the developer storage space along a direction in parallel to an optical axis of incident light to the image carrier, since the incident light optical axial direction of the image forming apparatus can be made short, the better construction of the image forming apparatus can be realized. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0014]FIG. 1 is a sectional view for indicating an image forming apparatus according to a first embodiment mode of the present invention.  
     [0015]FIG. 2 is a sectional view for representing a process cartridge employed in the image forming apparatus according to the first embodiment mode of the present invention.  
     [0016]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 first embodiment mode of the present invention.  
     [0017]FIG. 4 is a side view for indicating a portion of an image forming apparatus according to a second embodiment mode of the present invention.  
     [0018]FIG. 5 is a sectional view for indicating a portion of an image forming apparatus according to a third embodiment mode of the present invention.  
     [0019]FIG. 6 is a sectional view for showing the conventional image forming apparatus. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0020] Referring now to drawings, embodiment modes of the present invention will be described.  
     [0021]FIG. 1 schematically shows an image forming apparatus  10  according to a first 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 optional paper supply unit.  
     [0022] 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.  
     [0023] 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 transferring 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 transferring 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 .  
     [0024] As a result, the recording mediums which are fed out from the paper supply cassettes  22  of the paper supply units  18   a  to  18   d  are smoothly separated by the retard roller  26  and the nudger 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 developer image is transferred to the recording medium while the recording medium is penetrated between the transferring apparatus  42  and the image carrier  44  (will be explained later), and this transferred developer 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 .  
     [0025] 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 inversion path  48  is opened. Then, the ejection roller  40  is 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 .  
     [0026] The ejection unit  16  owns an inclination unit  52  which is freely pivotable with respect to the image forming apparatus main body  12 . This inclination unit  52  is inclined in such a manner that an ejection port portion 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 unit  52  and a tip portion which is heightened is used as an upper end thereof. This inclination unit  52  is supported with respect to the image forming apparatus main body  12  in such a manner that this inclination unit  52  is freely pivotable, while the lower end thereof is located at a center. When this inclination unit  52  is rotated toward the upper direction so as to be opened, an open unit  54  is formed, and a process cartridge (will be explained later)  64  can be detachably mounted via this opening unit  54 .  
     [0027] 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 transferring 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 transferring apparatus  42  is constituted by, for example, a transfer roller which transfers the developer 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 developer image which has been transferred onto the paper by the transferring 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 above-described paper supply units  18   a  to  18   d , and is located in the vicinity of a front surface of the image forming apparatus menu 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”. This exposing position “P” is located lower than an upper portion of a developer storage space (will be explained later)  70  along the vertical direction.  
     [0028] The optical writing apparatus  58  is arranged in a space “A” within the image forming apparatus main body  12 , while this space “A” is surrounded by the ejection unit  16 , the uppermost paper supply unit  18   a , the process cartridge  64 , and the front surface portion of the image forming apparatus main body  12 . In this first embodiment mode, the optical writing apparatus  58  owns an under-field type optical system in which a width of a luminous flux entered into a rotary polygon along the main scanning direction is made narrower than a plane width of the rotary polygon. Since this optical writing apparatus  58  owns the under-field type optical system, a width of this optical writing apparatus  58  along the vertical direction is made narrower, and the under-field type optical system is arranged at a lower portion of the space “A” for arranging the optical writing apparatus  58 . It should also be noted that this space “A” is set under such a condition that another optical writing apparatus  59  (denoted by two dot/dash line in FIG. 1) having an over-field type optical system may be accepted. In this over-field type optical system, a width of a luminous flux entered into a rotary polygon is made wider than a plane width of this rotary polygon. Thus, the above-described optical writing apparatus  58  may be replaced by this optical writing apparatus  59 . Since this another optical writing apparatus  59  is mounted and the presently-used drive system is substituted by another drive system, the presently-used image forming apparatus may be changed into either a high-speed type image forming apparatus or such an image forming apparatus having a larger maximum paper size than that of the presently-used image forming apparatus  10 , while other components thereof are commonly used.  
     [0029] As explained in this first embodiment mode, when either the optical writing apparatus  58  or the optical writing apparatus  59  is arranged along the substantially horizontal direction, the rotary polygon may be rotated by being maintained along the substantially horizontal direction, so that reliability thereof with respect to the rotation of the rotary polygon may be improved.  
     [0030] It should also be noted that a door is provided on the front surface portion of the image forming apparatus main body  12 , and then, since this door is opened/closed, the replacement of the optical writing apparatus  58  may be readily carried out.  
     [0031] The process cartridge  64  is arranged by employing the image carrier  44 , the charging apparatus  54 , the developing apparatus  58 , and the cleaning apparatus  60  in an integral body. This process cartridge  64  is arranged just under the inclination unit  52  of the ejection unit  16 , and as previously explained, is detachably mounted via the open portion  54  which is formed when the inclination unit  52  is opened.  
     [0032] 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  60  are arranged. In the developing apparatus unit  68 , the developing apparatus  58  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 which is surrounded by the inclination unit  52 , a horizontal plane extended from the lower end of the inclination unit  52 , and also, a vertical plane extended from the upper end of this inclination unit  52 . 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 unit  52  and along this inclination unit  52 . Also, a plurality of ribs  74  are formed on a lower surface of the inclination unit  52  in such a way that these plural ribs  74  are positioned in parallel to each other along the inclination direction of the inclination unit  52 . Since these ribs  74  are formed, a flow path  76  is formed between the inclination unit  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 unit  78  is formed on the upper portion of the developer storage space  70 . This grip unit  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 unit  78 .  
     [0033] In FIG. 2 and FIG. 3, a detailed construction of the above-described 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 a coupling pin (not shown) 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 spring (not shown), and a developing roller  86  is depressed against the image carrier  44 .  
     [0034] 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. Both a bearing  94   a  and another bearing  94   b  for the charging apparatus  56  own another function of a power supply portion. Also, for example, two fingers  96  are supported by the image carrier unit main body  90  in such a manner that these fingers  96  are freely pivotable. Since tip portions of these fingers  96  are depressed 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 above 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 by the image carrier unit main body  98 , 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.  
     [0035] 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 above-described 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 collecting space  70 , whereas the second developer storage portion  116   b  is located at a lower portion thereof.  
     [0036] As indicated in FIG. 3, the partition wall  118  forms a window portion  120  having, for example, a rectangular shape, which is located in parallel to an incident optical axis from the optical writing apparatus  58  to the image carrier  44 . 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 , 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 directions 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 .  
     [0037] 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 .  
     [0038] 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 .  
     [0039] As previously explained, the latent image writing position “P” of the image carrier  44  is located at the position lower than the first developer storage portion  116   a . Also, since the optical writing apparatus  58  is substantially horizontally arranged, the upper portion of the optical writing apparatus  58  is arranged in such a manner that this upper portion is overlapped with respect to the first developer storage portion  116   a  in the direction parallel to the optical axis of the light entered into the image carrier  44 .  
     [0040] Next, operations of the above-described image forming apparatus according to this first embodiment mode will now be explained.  
     [0041] 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  108  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.  
     [0042] 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   b . 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 .  
     [0043] 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 feeding 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 transferring apparatus  42  and the image carrier  44  at proper timing.  
     [0044] When the recording medium is conducted between the transferring 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 transferring 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 .  
     [0045] 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 between the paper supply unit  18   a  and the optical writing apparatus  58 . 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.  
     [0046] However, in this first 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 also, the developer paths  122   a  and  123   b  are formed on both sides of this window portion  120 , so that the first developer storage portion  116   a  can be arranged above the scanning optical path. As a result, the position of the optical writing apparatus  58  can be lowered, and also, the space defined between the paper supply unit  18   a  and the optical writing apparatus  58  can be made small. In this case, although the space is produced between the ejection unit  16  and the optical writing apparatus  58 , another optical writing apparatus  58  may be arranged in this space, so that a plurality of machine sorts of image forming apparatus may be manufactured while the main bodies of the image forming apparatus and the like are commonly used.  
     [0047]FIG. 4 indicates an image forming apparatus according to a second embodiment mode of the present invention. In this second embodiment mode, both a control board  136  and a network interface board  138  are stored in a space “A”. A control circuit for controlling a drive system of the power supply units  18   a  to  18   d , and also a drive system of the image forming section  14  is mounted on this control board  136 . A circuit such as a router is mounted on the network interface board  138 , and this circuit is used to connect the image forming apparatus via this network interface board  138  to a LAN (Local Area Network) and the Internet. This network interface board  138  owns a connector  140 , and this connector  140  is arranged at a front surface portion of the image forming apparatus main body  12 . As a consequence, since both the control board  136  and the network interface board  138  are arranged on the front surface of the image forming apparatus main body  12 , users may easily access the boards, so that the maintenance characteristic thereof may be improved. Moreover, since the connector  140  for the network cable is arranged on the front surface of the image forming apparatus, the installation characteristic may be improved, and also the network cable may be readily connected.  
     [0048] It should be understood that both the control board  136  and the network interface board  138  are arranged in the space A in this second embodiment mode. Alternatively, any one of the control board  136  and the network interface board  138  may be arranged in the space A. Also, both the control board  136  and the network interface board  138  may be collectively mounted on a single board.  
     [0049]FIG. 5 indicates an image forming apparatus according to a third embodiment mode of the present invention. In this third embodiment mode, a developer storage vessel  142  is arranged in a space “A”. While developer is stored in this developer storage vessel  142 , the developer storage vessel  142  is connected to the above-described first developer storage unit  116   a , so that the developer can be supplied to the first developer storage portion  116   a . In other words, this developer storage vessel  142  constitutes a third developer storage portion, and this developer storage vessel  142  is arranged in the case that a storage capacity of the developer is wanted to be increased. As previously described, since the space “A” is utilized as the developer storage portion, the storage capacity of the developer may be simply increased without changing other structural elements.  
     [0050] It should also be understood that the developer storage vessel  142  is constructed as a separate member with respect to the process cartridge  64  in this third embodiment mode. Alternatively, as another embodiment mode, the developer storage vessel  42  may be constituted by employing the process cartridge  64  in an integral form. Also, not only the developer storage vessel  142 , but also the above-described control board and network interface board may be jointly stored in the space “A”.  
     [0051] As previously described, in accordance with the present invention, since the latent image writing position is set to be lower than at least a portion of the developer storage space, the space defined between the optical writing apparatus and the paper supply unit can be made narrow, and also the production of the dead space can be suppressed. Also, the control board, the interface board, the developer storage vessel, and the like are arranged between the ejection unit and the optical writing apparatus, so that the space can be effectively utilized.