Abstract:
An image forming apparatus includes a main body having an opening, and image bearing member or an intermediate transfer unit, and an arrangement. The image bearing member or the intermediate transfer unit is configured to have a toner image formed thereon or transferred thereto. The image bearing member or the intermediate transfer unit is configured to be attached to or detached from the main body via the opening. The arrangement includes a positioning member configured to position the image bearing member or the intermediate transfer unit, wherein the arrangement is configured to adjust a position of the image bearing member of the intermediate transfer unit at a position where the opening is closed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a divisional of U.S. application Ser. No. 11/224,927, filed Sep. 14, 2005 now U.S. Pat. No. 7,164,874, which is a continuation of U.S. application Ser. No. 10/695,794, filed Oct. 30, 2003, now U.S. Pat. No. 6,970,665. This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2002-316709, filed Oct. 30, 2002. The entire contents of each of these documents are incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an image forming apparatus with a power-requiring unit that is detachable and requires power supply. 
   2. Description of the Related Art 
   Electronic copying machines, printers, facsimiles, and multifunction peripherals are the examples of image forming apparatuses. Such image forming apparatuses include a power-requiring unit and a power source, which supplies power to the power-requiring unit. The power-requiring unit is, for example, an electric charger, which charges an image bearing member. The power-requiring unit is attached inside a main body of the image forming apparatus in a detachable manner. 
   The power source is placed at the far inside of the main body along the direction of insertion or detachment (hereinafter, “insertion-detachment direction”) of the power-requiring unit. When the power-requiring unit is set inside the image forming apparatus at its appropriate position, a connector of the power-requiring unit makes an electric contact with a connector of the power source and an electric connection between the two is established. 
   The connectors of the power-requiring unit and the power source may be placed in the front, instead of far inside, along the insertion-detachment direction. However, in that case, a harness becomes necessary to establish an electric connect between the connectors of the power-requiring unit and the power source. However, when the harness is provided, when detaching the power-requiring unit, it is necessary to dismantle the harness first, attach the power-requiring unit, and then attach the harness again. Thus, the detachment of the power-requiring unit becomes cumbersome. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to solve at least the above in the conventional technology. 
   An image forming apparatus includes a main body having an opening; a power-requiring unit that can be attached to the main body by being inserted in an insertion direction via the opening, and that can be detached from the main body by being pulled out in a detachment direction via the opening, the power-requiring unit having a front side toward the insertion direction and an electrode arranged on the front side; and a power source that supplies power to the power-requiring unit, the power source having a front side and an electrode arranged on the front side; an arrangement that detachably fits almost into the opening and that includes an electric conductor, wherein the electric conductor makes electric contact with the electrodes of the power-requiring unit and the power source when the arrangement is fit, and the power-requiring unit can be attached or detached via the opening when arrangement is detached. 
   These and other objects, features and advantages of the present invention are specifically set forth in or will become apparent from the following detailed descriptions of the invention when read in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cross-section of an image forming apparatus according to an embodiment of the present invention; 
       FIG. 2  is a perspective view when a holder is opened; 
       FIG. 3  illustrates the positional relation between an image bearing unit, an intermediate transfer body, a power source, the holder, and a door; 
       FIG. 4  is an exploded perspective of the holder; 
       FIG. 5  is a perspective view of the positional relation between the holder at the closing position and a power source; 
       FIG. 6  illustrates a holding unit that maintains the holder at the opening position; and 
       FIG. 7  is a cross-sectional view of a locking unit that locks the holder at the closing position. 
   

   DETAILED DESCRIPTION 
   Exemplary embodiments of the present invention are explained next with reference to the accompanying drawings. 
     FIG. 1  is a vertical cross-section of an image forming apparatus according to an embodiment of the present invention. This image forming apparatus includes a main body  1  that houses first to fourth image bearing members  2 Y,  2 M,  2 C, and  2 BK, and an intermediate transfer body  3 . The image bearing members are drum-shaped and are photosensitive elements. The transfer body  3  is an endless belt and holds a toner image. The toner image is transferred to a recording medium. The intermediate transfer body  3  is suspended by supporting rollers  4 ,  5 , and  6 . These supporting rollers  4 ,  5 , and  6  rotatably drive the intermediate transfer body  3  in the direction of the arrow A. 
   A toner image is formed on each of the first to fourth image bearing members  2 Y,  2 M,  2 C, and  2 BK and all those toner images are transferred to the intermediate transfer body  3 . The structure of all the image bearing members  2 Y,  2 M,  2 C, and  2 BK is same, except that they form toner images of different colors. Hence, the structure and the operation of the first image bearing member  2 Y, which forms a yellow image, will be explained. 
   The image bearing member  2 Y is rotated in the clockwise direction. While the image bearing member  2 Y rotates, a charging device, which is a charging roller  7 Y, charges it to a predetermined polarity. An optical unit  8  emits an optically modulated laser beam L onto the image bearing member  2 Y to form an electrostatic latent image on the image bearing member  2 Y. A developing device  9 Y develops the electrostatic latent image with a yellow toner. The developing device  9 Y includes a container  10 Y that contains dry developer and a roller  11 Y. The roller  11 Y is rotatably held it and carries the developer to the image bearing member  2 Y. A developing bias-potential is applied to the roller  11 Y when developing the electrostatic latent image on the image bearing member  2 Y. 
   A transferring device, which is a transfer roller  12 Y, is placed opposite to the image bearing member  2 Y with the intermediate transfer body  3  sandwiched between the two. A transfer voltage is applied to the transfer roller  12 Y so that the yellow image is transferred on to the intermediate transfer body  3 . A cleaning device  13 Y removes, or cleans, the yellow toner remaining on the image bearing member  2 Y after the yellow image has been transferred. 
   A magenta image, a cyan image, and a black image, are formed on the second to fourth image bearing members  2 M,  2 C, and  2 BK, respectively, in the same manner. The magenta, cyan, and black images are sequentially transferred on to the yellow image on the intermediate transfer body  3  to thereby form a full-color image. Suffices M, C, and BK are attached to components in the second to fourth image bearing members  2 M,  2 C, and  2 BK. 
   A cassette  14  that houses a recording medium P, and a paper feed device  16  that includes a paper feed roller  15  are provided at the bottom of the main body  1 . The paper feed roller  15  forwards the recording medium P in the direction of the arrow B. Rollers  17  feed the recording medium P between the supporting roller  4  and a roller  18  at a predetermined timing. A predetermined voltage is then applied to the supporting roller  4  and accordingly the full-color image on the intermediate transfer body  3  is transferred on to the recording medium P. 
   The recorded medium P with the full-color image is then passed through a fixing device  19  where the full-color image is fixed on the recording medium P. The fixing device  19  includes a fixing roller  20  and a pressure roller  21 . The recorded medium P is sandwiched between the fixing roller  20  and the pressure roller  21 . The fixing roller  20  is hot, and the heat causes the full-color image on the recorded medium P to be fixed on the recording medium P. The recording medium P with the image printed on it is then ejected to the outside of the main body  1 . A cleaning device  24  removes, or cleans, the toner remaining on the intermediate transfer body  3 . 
   The image bearing member  2 Y, the charging roller  7 Y, the developing device  9 Y, and the cleaning device  13 Y constitute a first image bearing unit  23 Y. The second to fourth image bearing units  23 M,  23 C, and  23 BK have similar structure. 
   All the image bearing units  23 Y,  23 M,  23 C, and  23 BK are fixed in the main body  1  in a detachable manner along a direction that is normal to the paper on which  FIG. 1  is printed.  FIG. 2  is a perspective view of the image bearing units  23 Y,  23 M,  23 C, and  23 BK.  FIG. 2  illustrates a case when the image bearing units  23 Y,  23 M, and  23 C are fixed inside the main body  1  and the image bearing unit  23 BK is being detached by being pulled toward the direction represented by the arrow C. 
   Frames  25  and  26  (see  FIG. 2 ) hold together the intermediate transfer body  3 , the supporting rollers  4 ,  5 , and  6 , the transfer rollers  12 Y,  12 M,  12 C, and  12 BK, the cleaning device  24  to thereby form an intermediate transfer unit  27 . Although  FIG. 2  illustrates that the intermediate transfer unit  27  is outside of the main body  1 , it is fixed inside the main body  1  in a detachable manner by inserting it inside the main body  1  in the direction opposite to that of the arrow C. 
   The main body  1  includes a front board  28 , a rear board  29 , and an outer cover  30  ( FIG. 1 ).  FIG. 3  illustrates the positional relation between the main body  1 , the image bearing units  23 Y,  23 M,  23 C, and  23 BK, and the intermediate transfer unit  27 . The outer cover  30  has a door  31 . When the door  31  is opened by pulling along the direction of the arrow D, the image bearing units  23 Y,  23 M,  23 C, and  23 BK and the intermediate transfer unit  27  are accessible for attachment/detachment via an opening  32  (see  FIG. 2 ) in the front board  28 . A residual toner container for collecting once used toner is supported by the door  31 . The residual toner collected by cleaning devices  13 Y,  13 M,  13 C, and  13 BK and the cleaning device  24  transported into the residual toner container  34 . After opening the holder  33  by pulling it along the direction of the arrow E, the image bearing units  23 Y,  23 M,  23 C, and  23 BK can be accessed for attachment/detachment. 
   Power-requiring units are provided inside the main body  1  in a detachable manner. The charging rollers  7 Y,  7 M,  7 C, and  7 BK, the transfer rollers  12 Y,  12 M,  12 C, and  12 BK, rollers  11 Y,  11 M,  11 C, and  11 BK, and the supporting roller  4 , etc, constitute the power-requiring units. 
   A power source  35  supplies power to all of or desired one of the power-requiring units. The power source  35  is, for example, a high-voltage supplying board. In order to avoid complications in the drawing, it is assumed here that the power source  35  supplies power to only the transfer roller  12 C and the supporting roller  4 . The power source  35  has electrodes  35 A,  35 B,  35 C,  35 D,  35 E, and  35 F (see  FIG. 2 ). The charging rollers  7 Y,  7 M,  7 C, and  7 BK have electrodes  36 A,  36 B,  36 C, and  36 D, respectively. The transfer roller  12 C has an electrode  36 E, and the supporting roller  4  has an electrode  36 F. Thus, all these electrodes are placed in the front, and not far inside, of the main body  1 . The holder  33  electrically connects the electrodes of the power source  35  to those of the charging rollers, the transfer rollers, and the supporting roller. As shown in  FIG. 4 , the holder  33  holds first to sixth conductors, namely,  39 A,  39 B,  39 C,  39 D,  39 E, and  39 F. The electrodes  36 A to  36 F are electrically connected to the electrodes  35 A to  35 D, respectively, via each conductor  39 A to  39 F. These conductors are, for example, metallic wires. An opening  80  (see  FIG. 2 ,  3 ) is provided in a portion of the front board  28  opposite to the electrodes  35 A to  35 D of the power source  35 . 
   The holder  33  is supported by the front board  28  such that the holder  33  can turn and open-close along the direction of the arrows E and F (see  FIG. 2 ,  3 ).  FIG. 3  illustrates a case when the holder  33  is fixed in its appropriate position, while  FIG. 2  illustrates a case when the holder  33  is detached, or opened. The holder  33  and the main body  1  have a mechanism so that the holder  33  can be fit or detached to the main body easily. 
     FIG. 4  is an exploded perspective of the holder  33 . The holder  33  includes plural insulation plates. For example, as illustrated in  FIG. 4 , the holder  33  includes a front plate  40 , a rear plate  41 , a first intermediate plate  42 , and a second intermediate plate  43 . These plates are fixed to each other with screws (not shown). The conductors  39 A to  39 F are sandwiched between two successive insulation plates. The first to fourth conductors  39 A to  39 D are sandwiched between the first intermediate plate  42  and the second intermediate plate  43 , while the fifth and sixth conductors  39 E and  39 F are sandwiched between the front plate  40  and the first intermediate plate  42 . A hinge pin  60  supports free turn and open-close movement of the holder  33  in the main body  1 . 
   The conductors  39 A to  39 D have ends  44 A to  44 D on one side thereof. These ends  44 A to  44 D pass through holes  45 A to  45 D, respectively, provided in the second intermediate plate  43  and holes  46 A to  46 D, respectively, provided in the rear plate  41 , and then appear outside the holder  33  (see  FIG. 2 ). When the holder  33  is at fixed, the ends  44 A to  44 D respectively make contact with the electrodes  36 A to  36 D. 
   The fifth and sixth conductors  39 E and  39  have ends  44 E and  44 F, respectively. These ends  44 E and  44 F pass through holes  47 E and  47 F, respectively, provided in the first intermediate plate  42 , holes  45 E and  45 F, respectively, provided in the second intermediate plate  43 , and holes  46 E and  46 F, respectively, provided in the rear plate  41 , and then appear outside the holder  33  (see  FIG. 2 ). When the holder  33  is fixed, the end  44 E makes contact with the electrode  36 E of the transfer roller  12 C and the end  44 F makes contact with the electrode  36 F of the supporting roller  4 . The electrodes  36 A to  36 D may be fabricated, for instance, from plate blades that make contact with the rollers  7 Y,  7 M,  7 C, and  7 BK,  12 C, and  4 , or plate blades that make contact with bearings which support free turning movement of these rollers, etc. It is also possible to convert a portion of the rollers  7 Y,  7 M,  7 C, and  7 BK,  12 C, and  4  into power-requiring units by applying a direct contact between the ends of the conductors  39 A to  39 F and the rollers  7 Y,  7 M,  7 C, and  7 BK,  12 C, and  4 . 
   The first to fourth conductors  39 A to  39 D have ends  48 A to  48 D, respectively. These ends  48 A to  48 D pass through holes  49 A to  49 D, respectively, provided in the second intermediate plate  43  and holes  50 A to  50 D, respectively, provided in the rear plate  41 . The fifth and sixth conductors  39 E and  39 F have ends  48 E and  48 F, respectively. These ends  4 SE and  48 F pass through holes  51 E and  51 F, respectively, provided in the first intennediate plate  42 , holes  49 E and  49 F, respectively, provided in the second intermediate plate  43 , and holes  50 E and  50 F, respectively, provided in the rear plate  41 . The ends  48 A to  48 F then appear outside the holder  33  (see  FIG. 2 ). When the holder  33  is fixed, the ends  48 A to  48 F make contact with the electrodes  35 A to  35 F, respectively, of the power source  35  (see  FIG. 5 ). In this way, when the holder  33  is fixed, the ends  44 A to  44 F of the conductors  39 A to  39 F make contact with the electrodes  36 A to  36 D, respectively, of the power-requiring units, while the ends  44 A to  44 F of the conductors  39 A to  39 F make contact with the electrodes  35 A to  35 F, respectively, of the power source  35 . Thus, it is possible to apply a respective predetermined voltage to the charging rollers, the transfer rollers, and the supporting rollers. 
   When detaching the image bearing units  23 Y,  23 M,  23 C, and  23 BK and the intermediate transfer unit  27  from the main body  1 , the door  31  is opened, the holder  33  is opened, and the image bearing units  23 Y,  23 M,  23 C, and  23 BK and the intermediate transfer unit  27  are detached. When the holder  33  is opened, the ends  44 A to  44 F and  48 A to  48 F of the conductors  39 A to  39 F part away from the respective electrodes. 
   As described above, although a harness is not provided, the electrodes of the power source and the electrodes of the power-requiring units are located in the front along the insertion-detachment direction. As a result, insertion or detachment of parts can be performed easily. 
   Although, in the holder  33 , the conductors  39 A to  39 F are located close to each other, as the holder  33  is made of insulation plates, short-circuit between the conductors can be prevented. Because the conductors are located close to each other, it is possible to miniaturize the holder  33 . 
   The image forming apparatus according to the present embodiment comprises the image bearing members  2 Y,  2 M,  2 C, and  2 BK in which the toner images are formed, and these image bearing members  2 Y,  2 M,  2 C, and  2 BK are the components of the respective image bearing units  23 Y,  23 M,  23 C, and  23 BK. By attaching the image bearing units to the main body  1  or removing the image bearing units from the main body  1 , the image bearing members can be attached or removed. In this way, the image bearing members are attached in the main body  1  in a detachable manner. By opening the holder  33 , the image bearing members can be attached to or removed from the main body  1 . As shown in  FIG. 2 , in the rear plate  41  of the holder  33 , index holes  53 Y,  53 M,  53 C, and  53 K are provided where bearings  52 Y,  52 M,  52 C, and  52 K, which are placed in the front along the direction in which the image bearing members  2 Y,  2 M,  2 C, and  2 BK are detached, undergo interdigitation. When the holder  33  is fixed, the bearings  52 Y,  52 M,  52 C, and  52 K of the image bearing members  2 Y,  2 M,  2 C, and  2 BK undergo interdigitation with the index holes  53 Y,  53 M,  53 C, and  53 K, respectively, and each image bearing member is set to a predetermined position. In this way, by keeping the holder  33  at the closing position, the position of the image bearing members attached in the main body  1  can be set. 
   The image forming apparatus according to the present embodiment includes the intermediate transfer unit  27  that comprises the intermediate transfer body  3  on which the toner images formed on the image bearing members are transferred. The intermediate transfer unit  27  is attached in the main body  1  in a detachable manner. By keeping the holder  33  at the opening position as shown in  FIG. 2 , the intermediate transfer unit  27  can be attached to or removed from the main body  1 . In the rear plate  41  of the holder  33 , index holes  56  and  57  are provided. When the holder  33  is fixed, a bearing  54  (see  FIG. 2 ) of the supporting roller  5 , which is a component of the intermediate transfer unit  27 , and an index pin  55 , which is provided as a protrusion in the frame  25  that is a component of the intermediate transfer unit  27 , undergo interdigitation with index holes  56  and  57 , respectively, and the position of the intermediate transfer unit  27  is set. In this way, by keeping the holder  33  at the closing position, the position of the intermediate transfer unit  27  attached inside the main body  1  can be set. 
   As the position of the image bearing members and the intermediate transfer unit can be set by means of the holder  33 , there is no need to provide another component exclusively to set the position. Hence, the structure of the image forming apparatus can be simplified. 
   The ends  44 A to  44 F of the conductors  39 A to  39 F and making contact with the electrodes  36 A to  36 D of the power-requiring units, and the ends  48 A to  48 F of the conductors  39 A to  39 F and making contact with the electrodes  35 A to  35 F of the power source  35  are fabricated from a compression coil spring. The structure is such that when the holder  33  is fixed, according to the elasticity, the ends  44 A to  44 F of the conductors  39 A to  39 F are pressed upon and pressure-welded to the electrodes  36 A to  36 D of the electrodes, while the ends  48 A to  48 F of the conductors  39 A to  39 F are pressed against the electrodes  35 A to  35 F of the power source  35 . Consequently, the ends of the conductors make firm contact with the power-requiring units and the ends of the conductors make definite contact with the electrodes, and the defect due to bad contact can be prevented. 
   The image bearing units  23 Y,  23 M,  23 C, and  23 BK include the image bearing members  2 Y,  2 M,  2 C, and  2 BK, respectively, and the power-requiring units. As shown in  FIG. 2 , a coupling component  58 BK is fixed at the back along the direction in which the image bearing member  2 BK is detached. A partner coupling component  59 BK is rotatably supported by the rear board  29  of the main body  1  and is rotate-driven by means of a not shown driving motor supported by the rear board  29 . When the image bearing member  23 BK is set inside the main body  1 , the coupling component  58 BK and the partner coupling component  29 BK get coupled, the rotation movement of the driving motor is transmitted to the image bearing member  2 BK via the coupling component  58 BK and the partner coupling component  29 BK, and the image bearing member  2 BK is rotate-driven. At the same time, this rotation movement is transmitted to the charging roller  7 BK or the roller  11 BK via a transmission component, etc., and the charging roller  7 BK and the roller  11 BK are rotate-driven. 
   As the end  44 D on one side of the fourth conductor  39 D and making contact with the power-requiring unit  36 D is fabricated from a compression coil spring, the end  44 D increases the pressure on the coupling component  58 BK on the image bearing unit  23 BK with respect to the partner coupling component  59 BK of a driving device, which drives the image bearing unit  23 BK. Consequently, both the coupling components  58 BK and  59 BK get coupled and the image bearing member  2 BK and the roller  11 BK rotate stably, and a high quality image can be formed in the image bearing member  2 BK. An identical structure is applied to the image bearing units  23 Y to  23 C that include the image bearing members  2 Y to  2 C, respectively. 
   Similarly, a coupling component  61  is fixed in the supporting roller  4  of the intermediate transfer unit  27  shown in  FIG. 1 . When the intermediate transfer unit  27  is attached in the main body  1 , the coupling component gets coupled with a partner coupling component of a not shown driving device, and the supporting roller  4  is rotate-driven via these coupling components. In this case also, the end  44 F on one side of the conductor  39 F and fabricated from a compression coil spring increases the pressure on the coupling component  61  on the intermediate transfer unit  27  with respect to the partner coupling component on the driving device, which drives the intermediate transfer unit  27 . Consequently, both the coupling components get coupled and the intermediate transfer body  3  can rotate evenly. 
   As shown in  FIG. 5 , when the ends  44 A to  44 F and  48 A to  48 F of the conductors are fabricated from a compression coil spring, it is desirable to provide a cylindrical unit (not shown) integrated along with the holder  33 . It is also better to provide the cylindrical unit  62  in the first intermediate plate  42  and the second intermediate plate  43  and concentric to the holes  51 E,  51 F,  47 E,  47 F,  49 A to  49 F, and  45 A to  45 F. 
     FIG. 5  is a view of the relative positional relation between the power source  35  and the holder  33  when the holder  33  is fixed. As shown in  FIG. 5  and  FIG. 1 , the power source  35  is attached in the main body  1  along the direction of arrows G and H, and can be removed from the main body  1 . The structure is such that the power source  35  may be replaced with another component. When the holder  33  is fixed and. consequently the ends  48 A to  48 F of the conductors  39 A to  39 F make contact with the electrodes  35 A to  35 F of the power source  35 , if the power source  35  is detached along the direction of arrow G, a large frictional force is generated between the ends  48 A to  48 F and the electrodes  35 A to  35 F that may cause dents on the ends  48 A to  48 F and the electrodes  35 A to  35 F. 
   A stopper  63  is provided as a protrusion in the holder  33 . Hence, when the holder  33  is fixed, the power source  35  collides with the stopper  63  and thus cannot be detached along with the direction of arrow G. When the holder  33  is opened, the stopper  63  is removed from the power source  35  and then the power source can also be attached or removed. The stopper  63  illustrates an example of a power source removal-prohibiting unit that, when the holder  33  is fixed, prohibits the removal of the power source from the main body. 
   As shown in  FIG. 2  and  FIG. 3 , the residual toner container  34  is provided at a position in front than the holder  33  at the closing position and along the direction in which the power-requiring units are detached. The residual toner container  34  according to the present embodiment is supported at the inner surface of the door  31  and can be attached to or removed from the door  31 . Toner drain pipes  64 Y,  64 M,  64 C, and  64 BK and  65  are connected to the cleaning devices  13 Y,  13 M,  13 C, and  13 BK and  24 , respectively, shown in  FIG. 1 . When the door  31  and the holder  33  are closed, the toner drain pipes  64 Y,  64 M,  64 C, and  64 BK and  65  pass through holes  66 A to  66 E, respectively, provided in the holder  33 , and enter into toner inlet holes  67 A to  67 E, respectively, provided in the residual toner container  34 . The residual toner after transfer collected in the cleaning apparatuses  13 Y,  13 M,  13 C, and  13 BK and  24  is sent to the residual toner container  34  via the respective toner drain pipes  64 Y,  64 M,  64 C, and  64 BK and  65  and collected in the residual toner container  34 . When the door  31  and the holder  33  are opened, the toner inlet holes  67 A to  67 E of the residual toner container  34  are removed from the respective toner drain pipes  64 Y,  64 M,  64 C, and  64 BK and  65 . When the residual toner container  34  gets full with the toner, it is replaced with a new empty residual toner container. 
   As the residual toner container  34  is placed close to the holder  33 , the components to be maintained by the serviceman, etc., are concentrated in a single area and the maintenance job can be carried out easily. 
   As shown in  FIG. 3 , the door  31  of the main body  1  is provided at a position in front than the holder  33  at the closing position and along the direction in which the power-requiring unit is detached. However, the structure is such that when the door  31  is opened, a sensor (not shown) detects opening of the door  31  and based on the detection signals, the feed to the power-requiring units is prohibited. As a result, when the holder  33  is opened and the ends of the conductors part away from the electrodes, the defect caused due to the discharging can be prevented. When the holder  33  is closed again and then the door  31  is closed, electricity is provided to the power-requiring units from the power source  35  via each conductor. 
   A holding unit may be arranged to hold the holder  33  opened. This arrangement will make the attaching and removing of the image bearing units or the intermediate transfer unit further easier.  FIG. 6  illustrates an example of the holding unit. The holding unit includes a plate blade  68 , the rear anchor part of which is fixed to the front board  28  of the main body  1 , and a coupling surface  60  provided in the holder  33 . When the holder  33  is opened, the plate blade  68  is pressure-welded to the coupling surface  69  of the holder  33  and thus the holder  33  is maintained at the opening position. Apart from this structure, a nail may be provided in the holder  33  and a coupling hole equivalent to the shape of the nail may be provided in the front board  28 . Consequently, when the holder is opened, it can be held by coupling the nail and the coupling hole. 
   A locking unit may be provided that locks the holder  33  when the holder  33  fixed.  FIG. 7  illustrates an example of the locking unit. The locking unit includes a locking component  72  that is rotatably supported by the holder  33 . Biasing of the locking component  72  in anticlockwise direction in  FIG. 7  is carried out by means of a helical coil spring  70 . When the holder  33  is closed, a nail  73  of the locking component  72  is coupled with the edge of a locking hole  74  provided in the front board  28  and the holder  33  is locked at the closing position. At the time of opening the holder  33 , a handle  75  of the locking component  72  is grabbed and rotated in the direction of the arrow, and the nail  73  is removed from the edge of the locking hole  74 . Instead of the locking unit as described above, a locking unit can be used that includes a screw, which fixes the holder  33  to the front board  28  such that the holder  33  can be attached to or removed from the front board  28 . Another locking unit can be used that includes a protrusion provided in the holder  33  and a sleeve provided in the front board  28 . When the holder is closed, the protrusion undergoes interdigitation with the sleeve and the frictional force generated in the protrusion and the sleeve locks the holder  33  at the closing position. 
   In  FIG. 6  and  FIG. 7 , the first intermediate plate  42  and the second intermediate plate  43  of the holder  33  are not shown. 
   When the locking component  72  is provided, if the color of the locking component  72  is different than that of the front board  28  of the holder  33 , the locking component  72  becomes distinctly visible. Thus, the user or the serviceman can easily locate the locking component  72  and the operations can be carried out comfortably. Hence, the color of a locking component is kept different than that of a holder. 
   As shown in  FIG. 4 , a mark M that shows the direction of rotation of the locking component  72  is either imprinted or a sticker that has the mark M on it is attached on the front side of the front plate  40  of the holder  33 , so that the user operation becomes easier. Imprinting on the front plate  40  an explanation of the procedure of replacing the holder  33  or attaching a sticker with such an explanation can also improve the user-friendliness. The explanation could be a message such as ‘Please open this particular part while replacing this particular component’, etc. 
   Similarly, the other rollers such as the transfer rollers  12 Y,  12 M, and  12 BK or the rollers  11 Y to  11 BK, etc., can also be electrically connected to the electrodes of the power-requiring units and the electrodes of the power source via the conductors supported by the holder. 
   According to the present invention, the electrodes of the power source as well as the electrodes of the power-requiring units are placed in the front along the direction in which the power-requiring units are detached. Moreover, the electrodes are electrically connected with corresponding ones using a holder. Thus, attachment or removal of the parts into or from the image forming apparatus can be performed easily. 
   Although the invention has been described with respect to a specific embodiment for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art which fairly fall within the basic teaching herein set forth.