Abstract:
A developing cartridge may include a housing configured to hold toner. The cartridge may further include a developing roller including a developing roller shaft, a supply roller including a supply roller shaft, a developing electrode and a supply electrode. The developing electrode and supply electrode may be configured to guide an electrical contact of an image forming apparatus in one or more directions. In some examples, the developing electrode and supply electrode may have angled surfaces that extend toward one another.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation application of U.S. patent application Ser. No. 14/045,929, which was filed on Oct. 4, 2013, which is a continuation of U.S. patent application Ser. No. 12/976,830, which was filed on Dec. 22, 2010 and issued as U.S. Pat. No. 8,577,244 on Nov. 5, 2013, which claims priority from Japanese Patent Application No. 2009-294594 filed on Dec. 25, 2009, the entire subject matter of each of which are incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    Apparatuses and devices consistent with the invention relates to a developing cartridge that is detachably mounted to a main body of an image forming apparatus. 
       BACKGROUND 
       [0003]    In an image forming apparatus such as laser printers, there is known a developing cartridge that is detachably mounted to a main body of the apparatus. 
         [0004]    The developing cartridge includes a developing roller and a supply roller that supplies toner to the developing roller. When the developing cartridge is mounted to the main body, the developing roller contacts a photosensitive drum that is provided in the main body. When forming an image, a bias having the same value is supplied to the developing roller and the supply roller, for example. When an electrostatic latent image formed on the photosensitive drum is opposed to the developing roller in accordance with rotation of the photosensitive drum, toner is supplied to the electrostatic latent image from the developing roller by a potential difference between the developing roller and the photosensitive drum. Thereby, the electrostatic latent image is developed as a toner image. Then, the toner image is transferred to a sheet, so that an image is formed on the sheet. 
         [0005]    In order to improve an image quality, it is considered to individually set the bias that is supplied to the developing roller and the supply roller. In this case, it is required to provide electrodes individually to the developing roller and the supply roller and to configure them such that contact point members, which are provided to the main body in correspondence to the respective electrodes, contact the respective electrodes when the developing cartridge is mounted to the main body. 
         [0006]    There has been proposed a related art developing cartridge in which electrodes are respectively provided to a developing roller and a supply roller, and a first contact point member and a second contact point member, which are electrically connected to a rotation shaft of the developing roller and a rotation shaft of the supply roller, respectively, are provided in a cover member that covers end portions of the developing roller and the supply roller. The first contact point member and the second contact point member are respectively extended toward positions away from the developing roller and the supply roller. Each leading end of the first and second contact point members is bent into a substantially U shape and is exposed as a contact point part (electrode) through each of openings that are arranged at the cover member in an upper-lower direction. 
       SUMMARY 
       [0007]    However, the related-art developing cartridge does not consider making the developing cartridge (developing apparatus) thin. In the related-art developing cartridge, the cover member should have a predetermined thickness (dimension of a height direction) in order to arrange the respective contact point parts of the first and second contact point members. 
         [0008]    Illustrative aspects of the invention provide a developing cartridge which is made to be thin while individually providing electrodes to a developing roller and a supply roller. 
         [0009]    According to one illustrative aspect of the invention, there is provided a developing cartridge that can be detachably mounted to a main body of an image forming apparatus, the developing cartridge comprising: a housing including a developing chamber and a developer accommodating chamber that accommodates developer to be supplied to the developing chamber, wherein the developing chamber and the developer accommodating chamber are adjacent to each other; a developing roller, which is provided in the developing chamber, and which includes a developing roller shaft extending in a facing direction of both sidewalls of the housing; a supply roller, which is provided in the developing chamber, which includes a supply roller shaft extending in the facing direction of the both sidewalls of the housing, and which supplies the developer to the developing roller; a developing electrode, which is provided on an outer side of one sidewall of the housing, wherein the developing electrode is electrically connected to the developing roller shaft, and wherein the developing electrode includes a developing protrusion protruding in a direction parallel to the developing roller shaft at a position different from the developing roller shaft when seen from a side face; and a supply electrode, which is provided on the outer side of the one sidewall, wherein the supply electrode is electrically connected to the supply roller shaft, and wherein the supply electrode includes a supply protrusion protruding in a direction parallel to the supply roller shaft at a position different from the supply roller shaft when seen from the side face, and wherein the developing protrusion and the supply protrusion are arranged in an arrangement direction of the developing chamber and the developer accommodating chamber. 
         [0010]    According to another illustrative aspect of the invention, there is provided a developing cartridge that is detachably mounted to a main body of an image forming apparatus, the developing cartridge comprising: a housing; a developing roller, which is provided in the housing, and which includes a developing roller shaft extending in a direction orthogonal to opposing sidewalls of the housing; a supply roller, which is provided in the housing, which includes a supply roller shaft extending in the direction orthogonal to the opposing sidewalls of the housing, and which supplies the developer to the developing roller; a developing electrode, which is provided on an outer side of one sidewall of the housing, wherein the developing electrode is electrically connected to the developing roller shaft, and wherein the developing electrode includes a developing protrusion protruding in a direction parallel to the developing roller shaft at a position different from the developing roller shaft when seen from a side face; and a supply electrode, which is provided on the outer side of the one sidewall, wherein the supply electrode is electrically connected to the supply roller shaft, and wherein the supply electrode includes a supply protrusion protruding in a direction parallel to the supply roller shaft at a position different from the supply roller shaft when seen from the side face, wherein the main body comprises: a developing contact point member that contacts the developing protrusion; and a supply contact point member that contacts the supply protrusion when the developing cartridge is mounted to the main body, and wherein a contact position between the developing contact point member and the developing protrusion is offset from a contact position between the supply contact point member and the supply protrusion in an arrangement direction of the developing roller shaft and the supply roller shaft. 
         [0011]    According to still another illustrative aspect of the invention, there is provided a developing cartridge comprising: a housing comprising an upper wall, a bottom wall and a pair of opposing side walls connecting the upper wall and the bottom wall; a developing roller disposed between back end portions of the pair of opposing side walls, wherein the developing roller comprises a cylindrical developing roller main body and a developing roller shaft extending along a central axis of the developing roller main body, and wherein end portions of the developing roller shaft penetrate the side walls of the housing; a supply roller disposed between the opposing sidewalls of the housing at a position below and more toward a front side of the housing than the developing roller, wherein the supply roller comprises a cylindrical supply roller main body having a circumferential surface that contacts a circumferential surface of the developing roller main body, and wherein the supply roller also comprises a supply roller shaft that extends along a central axis of the supply roller main body and that penetrates the side walls of the housing; a developing electrode, which is electrically connected to the developing roller shaft, and which is disposed on an outer surface of one of the pair of opposing side walls of the housing at a position further toward the front side of the housing than a position where the developing roller shaft penetrates the one of the pair of opposing side walls, wherein the developing electrode comprises a developing protrusion, which is located at a position above and further toward the front side of the housing than the position where the developing roller shaft penetrates the one of the pair of side walls, wherein the developing protrusion protrudes from the one of the pair of side walls in a direction parallel to the developing roller shaft, and wherein the developing protrusion comprises: a parallel surface, which extends in a direction parallel to the front-back direction of the housing, a first inclined surface, which is inclined with respect to the parallel surface and which extends from a back most portion of the parallel surface; and a second inclined surface, which is inclined with respect to the parallel surface and which extends from a front most portion of the parallel surface; a supply electrode, which is electrically connected to the supply roller shaft, and which is disposed on the outer surface of the one of the pair of opposing side walls of the housing at a position further toward the front side of the housing than a position where the supply roller shaft penetrates the one of the pair of opposing side walls, wherein the supply electrode comprises a supply protrusion, which is located at a position above and further toward the front side of the housing than the position where the supply roller shaft penetrates the one of the pair of opposing side walls, wherein the supply protrusion protrudes from the one of the pair of side walls in a direction parallel to the supply roller shaft, and wherein the supply protrusion comprises: a parallel surface, which extends in a direction parallel to the front-back direction of the housing, a first inclined surface, which is inclined with respect to the parallel surface and which extends from a back most portion of the parallel surface, wherein the supply protrusion and the developing protrusion are arranged in sequence along the front to back direction of the housing. 
         [0012]    According to the illustrative aspects of the invention, the housing of the developing cartridge includes therein the developing chamber and the developer accommodating chamber, which are formed adjacent to each other. The developer accommodating chamber accommodates developer and the developer is supplied to the developing chamber. The developing chamber includes the developing roller and the supply roller. The developing roller includes the developing roller shaft that extends in a facing direction of both sidewalls of the housing. In addition, the supply roller includes the supply roller shaft that extends in the facing direction of both sidewalls of the housing. The developing electrode, which is electrically connected to the developing roller shaft, and the supply electrode, which is electrically connected to the supply roller shaft, are provided at an outer face of one sidewall of the housing. The developing protrusion of the developing electrode protrudes in a direction parallel to the developing roller shaft at a position different from the developing roller shaft, when seen from a side face. The supply protrusion of the supply electrode is protruded at a position different from the supply roller in a direction parallel to the supply roller shaft, when seen from the side face. The developing protrusion and the supply protrusion are arranged in an arrangement direction, which extends in a front-back direction of the developing cartridge of the developing chamber and the developer accommodating chamber. 
         [0013]    The developing protrusion is arranged at the position different from the developing roller shaft, and the supply protrusion is arranged at the position different from the supply roller shaft. Accordingly, it is possible to freely arrange the developing protrusion and the supply protrusion, irrespective of the arrangement of the developing roller shaft and the supply roller shaft. Therefore, it is possible to increase a degree of freedom of layouts of the developing protrusion and the supply protrusion. 
         [0014]    The developing protrusion and the supply protrusion are arranged in the arrangement direction of the developing chamber and the developer accommodating chamber. Accordingly, even when a size in a thickness direction of the developing cartridge orthogonal to the arrangement direction is small, it is possible to arrange the developing protrusion and the supply protrusion. In other words, it is possible to make the developing cartridge thin by arranging the developing protrusion and the supply protrusion in the arrangement direction of the developing chamber and the developer accommodating chamber. 
         [0015]    In addition, in order to feed power to the developing electrode through the developing protrusion, the main body includes the developing contact point member that is electrically connected to the developing protrusion. The developing protrusion is protruded in the direction parallel to the developing roller shaft. Accordingly, when connecting the developing contact point member to the developing protrusion, the developing contact point member does not scrape the sidewall of the developing cartridge. Hence, it is possible to prevent the sidewall of the developing cartridge and the developing contact point member from being worn. 
         [0016]    Further, in order to feed power to the supply electrode through the supply protrusion, the main body includes the supply contact point member that is electrically connected to the supply protrusion. The supply protrusion is protruded in the direction parallel to the supply roller shaft. Accordingly, when connecting the supply contact point member to the supply protrusion, the supply contact point does not scrape the sidewall of the developing cartridge. Hence, it is possible to prevent the sidewall of the developing cartridge and the supply contact point member from being worn. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is a side sectional view of a printer including a developing cartridge according to a first exemplary embodiment of the invention; 
           [0018]      FIG. 2  is a perspective view of the developing cartridge according to the first exemplary embodiment; 
           [0019]      FIG. 3  is a plan view of the developing cartridge according to the first exemplary embodiment; 
           [0020]      FIG. 4  is a right side sectional view of the developing cartridge according to the first exemplary embodiment; 
           [0021]      FIG. 5  is a sectional view of the developing cartridge according to the first exemplary embodiment taken along a line V-V of  FIG. 4 ; 
           [0022]      FIG. 6  is a perspective view of the developing cartridge according to the first exemplary embodiment, which shows a state in which a developing electrode and a supply electrode are removed; 
           [0023]      FIG. 7A  is a right side sectional view showing a state in which a process cartridge including the developing cartridge according to the first exemplary embodiment is being mounted to a body casing of the printer; 
           [0024]      FIG. 7B  is a right side sectional view of the process cartridge showing a next state of  FIG. 7A ; 
           [0025]      FIG. 7C  is another right side sectional view of the process cartridge showing a next state of  FIG. 7B ; 
           [0026]      FIG. 7D  is still another right side sectional view showing a state in which the process cartridge has been mounted to the body casing; and 
           [0027]      FIG. 7E  is still another right side sectional view showing a state in which the process cartridge is being detached from the body casing. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    Hereinafter, an exemplary embodiment of the invention will be described in detail with reference to the drawings. 
       (1) Printer 
       [0029]    As shown in  FIG. 1 , a printer  1  (one example of an image forming apparatus) includes a body casing  2  (one example of a main body). 
         [0030]    A process cartridge  3  is provided at a center portion in the body casing  2 . The process cartridge  3  is detachably mounted to the body casing  2  via a front cover  4  that is provided at one sidewall of the body casing  2 . 
         [0031]    In the following descriptions, a side at which the front cover  4  is provided to the body casing  2  is referred to as the front side and a side opposite to the front side is referred to as the back side. In addition, the left and the right are assigned based on viewing the printer from the front side of the printer  1 . Additionally, regarding a developing cartridge  32 , which will be described later, the front, back, left and right are set based on the state in which the developing cartridge is mounted to the body casing  2 . 
         [0032]    The process cartridge  3  includes a drum cartridge  31  and a developing cartridge  32 . The developing cartridge  32  is detachably mounted to the drum cartridge  31 . 
         [0033]    The drum cartridge  31  is provided with a rotatable photosensitive drum  6 . The drum cartridge  31  includes a charger  7  and a transfer roller  9 . 
         [0034]    The photosensitive drum  6  is rotatable about an axis line extending in a direction perpendicular to a sheet face of  FIG. 1 . 
         [0035]    The charger  7  is a scorotron-type charger and is arranged to be opposite to a circumferential surface of the photosensitive drum  6  with a predetermined interval provided between the charger  7  and the photosensitive drum. 
         [0036]    The developing cartridge  32  includes a developing housing  10  (one example of the housing) that accommodates toner. In the developing housing  10 , a developing chamber  33  and a toner accommodating chamber  34  (one example of a developer accommodating chamber), which accommodates toner supplied to the developing chamber  33 , are provided adjacent to each other. 
         [0037]    A developing roller  11  and a supply roller  37  are held in the developing chamber  33  such that the developing roller  11  and the supply roller  37  are rotatable with respect to the developing chamber  33 . 
         [0038]    The developing roller  11  has a circumferential surface, a part of which is exposed from a back end portion of the developing housing  10 . In addition, the supply roller  37  has a circumferential surface that contacts a front side of the developing roller  11 . The developing cartridge  32  is mounted to the drum cartridge  31  so that the part of the developing roller  11  exposed from the developing housing  10  contacts a circumferential surface of the photosensitive drum  6 . 
         [0039]    An agitator  25  is kept in the toner accommodating chamber  34  such that the agitator  25  is rotatable with respect to the toner accommodating chamber  34 . Toner in the toner accommodating chamber  34  is supplied into the developing chamber  33  while being agitated by rotation of the agitator  25 . 
         [0040]    The transfer roller  9  is provided at a lower side of the photosensitive drum  6 . The transfer roller  9  is rotatable about an axis line parallel to a rotation axis line of the photosensitive drum  6  and is arranged so that a circumferential surface of the transfer roller  9  contacts the circumferential surface of the photosensitive drum  6 . 
         [0041]    In the body casing  2 , an exposure unit  5  that can emit laser and the like is arranged above the process cartridge  3 . 
         [0042]    When forming an image, the photosensitive drum  6  rotates at a constant speed in a clockwise direction in  FIG. 1 . In accordance with rotation of the photosensitive drum  6 , the circumferential surface of the photosensitive drum  6  is uniformly charged by electric discharge from the charger  7 . In the meantime, based on image data received from a personal computer (not shown) connected to the printer  1 , a laser beam is emitted from the exposure unit  5 . The laser beam passes between the charger  7  and the developing cartridge  32  and is irradiated on the circumferential surface of the photosensitive drum  6  that is positively charged to be uniform. Thereby, the circumferential surface of the photosensitive drum  6  is selectively exposed, and the electric charges are selectively removed from the exposed part, so that an electrostatic latent image is formed on the circumferential surface of the photosensitive drum  6 . When the electrostatic latent image is opposed to the developing roller  11  by rotation of the photosensitive drum  6 , toner is supplied to the electrostatic latent image from the developing roller  11 . Thereby, a toner image is formed on the circumferential surface of the photosensitive drum  6 . 
         [0043]    A sheet feeding cassette  12  that stores sheets P is arranged at a bottom part of the body casing  2 . A pickup roller  13  for sending the sheet from the sheet feeding tray  12  is provided above the sheet feeding cassette  12 . 
         [0044]    A conveyance path  14 , which has an S shape when seen from the side face, is formed in the body casing  2 . The conveyance path  14  reaches a sheet discharge tray  15  formed at an upper surface of the body casing  2  via a portion between the photosensitive drum  6  and the transfer roller  9  from the sheet feeding cassette  12 . A separation roller  16  and a separation pad  17 , which are arranged to be opposite to each other, a pair of feeder rollers  18 , a pair of register rollers  19  and a pair of sheet discharge rollers  20  are provided on the conveyance path  14 . 
         [0045]    The sheets P are fed from the sheet feeding cassette  12  one at a time while passing between the separation roller  16  and the separation pad  17 . Then, the sheet P is fed toward the register rollers  19  by the feeder rollers  18 . Then, the sheet P is registered by the register rollers  19  and is conveyed toward a portion between the photosensitive drum  6  and the transfer roller  9  by the register rollers  19 . 
         [0046]    The toner image formed on the circumferential surface of the photosensitive drum  6  is electrically attracted and transferred onto the sheet P by the transfer roller  9  when the toner image is opposed to the sheet P passing between the photosensitive drum  6  and the transfer roller  9  by the rotation of the photosensitive drum  6 . 
         [0047]    On the conveyance path  14 , a fixing unit  21  is provided at a downstream side of a conveyance direction of the sheet P from the transfer roller  9 . The sheet P, on which the toner image is transferred, is conveyed through the conveyance path  14  and passes through the fixing unit  21 . The fixing unit  21  fixes the toner image on the sheet P by heating and pressing so as to form an image on the sheet P. 
         [0048]    As operation modes, the printer  1  includes a one-sided mode for forming an image (toner image) on one side of the sheet P and a duplex mode for forming an image on one side of the sheet P and then forming an image on the other side of the sheet P. 
         [0049]    In the one-sided mode, the sheet P having an image formed on one side thereof is discharged to the sheet discharge tray  15  by the sheet discharge rollers  20 . 
         [0050]    As a structure for realizing the duplex mode, the body casing  2  is formed therein with a reverse conveyance path  22 . The reverse conveyance path  22  extends between the conveyance path  14  and the sheet feeding cassette  12  from the vicinity of the sheet discharge rollers  20  and is connected to a part between the feeder rollers  18  and the register rollers  19  on the conveyance path  14 . On the reverse conveyance path  22 , a pair of first reverse conveying rollers  23  and a pair of second reverse conveying rollers  24  are provided. 
         [0051]    In the duplex mode, the sheet P having an image formed on one side thereof is conveyed to the reverse conveyance path  22  rather than being discharged to the sheet discharge tray  15 . Then, the sheet P is conveyed through the reverse conveyance path  22  by the first reverse conveying rollers  23  and the second reverse conveying rollers  24  and two sides thereof are reversed, so that the other side of the sheet P, on which no image is formed, is sent to the conveyance path  14  with being opposed to the circumferential surface of the photosensitive drum  6 . Then, an image is formed on the other side of the sheet P, so that the images are formed on both sides of the sheet P. 
       (2) Developing Cartridge 
       [0052]    The developing housing  10  of the developing cartridge  32  has a box shape having an opened back side. 
         [0053]    As shown in  FIG. 3 , the developing housing  10  includes a pair of sidewalls  36 , which are opposed to each other in the left-right direction. As shown in  FIGS. 2 and 3 , an upper wall  38  and a bottom wall  39  are bridged between the sidewalls  36 . The upper wall  38  and the bottom wall  39  are connected at a front end portion of the developing housing  10 . The connected part includes a holding part  40 . The holding part  40  is extended toward the front-upper direction from the front end portion of the developing housing  10  and has a sectional U shape having an opened front side. 
         [0054]    The developing roller  11  and the supply roller  37  (refer to  FIG. 1 ) are rotatably held between the sidewalls  36 . 
         [0055]    (2-1) Developing Roller 
         [0056]    As shown in  FIGS. 2 and 3 , the developing roller  11  is arranged between back end portions of the sidewalls  36 . As shown in  FIG. 5 , the developing roller  11  includes a cylindrical developing roller main body  45  extending in the left-right direction and a developing roller shaft  46  extending along a central axis line of the developing roller main body  45 . 
         [0057]    Both end portions of the developing roller shaft  46  penetrate the sidewalls  36  of the housing  10 . 
         [0058]    (2-2) Supply Roller 
         [0059]    As shown in  FIG. 1 , the supply roller  37  is arranged at a position of the front-lower direction of the developing roller  11 . As shown in  FIG. 5 , the supply roller  37  includes a cylindrical supply roller main body  55  extending in the left-right direction and a supply roller shaft  56  extending along a central axis line of the supply roller main body  55 . 
         [0060]    A circumferential surface of the supply roller main body  55  contacts a circumferential surface of the developing roller main body  45  from a front-lower part of the developing roller main body. 
         [0061]    Both end portions of the supply roller shaft  56  penetrate the sidewalls  36  of the developing housing  10 . 
         [0062]    (2-3) Bearing Member 
         [0063]    As shown in  FIGS. 2 ,  4  and  6 , a right bearing member  47  (one example of a bearing member) is provided at an outer side of the right sidewall  36 . The right end portions of developing roller shaft  46  and the supply roller shaft  56  are supported by the right sidewall  36  via the right bearing member  47  so that they can be relatively rotated. In other words, the right bearing member  47  collectively holds the right end portion of the developing roller shaft  46  and the right end portion of the supply roller shaft  56 . 
         [0064]    As shown in  FIG. 6 , the right bearing member  47  has a substantially triangle shape, when seen from the side face. 
         [0065]    The right bearing member  47  is formed with a first shaft insertion penetration hole  63  at a position opposite to the developing roller shaft  46  in the left-right direction. The first shaft insertion penetration hole  63  has an inner diameter that is substantially the same as an outer diameter of the developing roller shaft  46 . The right end portion of the developing roller shaft  46  is inserted into the first shaft insertion penetration hole  63 , and a leading end of the developing roller shaft  46  protrudes further protruded than the right bearing member  47  in the outer (right) direction. 
         [0066]    In addition, the right bearing member  47  is formed with two boss insertion penetration holes  61 . The boss insertion penetration holes  61  are formed at front-upper and back-lower positions from the first shaft insertion penetration hole  63 , respectively. The right sidewall  36  is formed with two protruding bosses  62  at positions corresponding to the boss insertion penetration holes  61 . The two bosses  62  of the right sidewall  36  are inserted into the respective boss insertion penetration holes  61  of the right bearing member  47 , so that the right bearing member  47  is mounted to the right sidewall  36  with being positioned relative to the right sidewall  36 . 
         [0067]    In addition, the right bearing member  47  is formed with a second shaft insertion penetration hole  64  at a position opposite to the supply roller shaft  56  in the left-right direction. The second shaft insertion penetration hole  64  has a substantially angular shaped hole having a size greater than an outer diameter of the supply roller shaft  56 . A front side part of the second shaft insertion penetration hole  64  is bent in such a way that it protrudes in a diametrically outer direction of the supply roller shaft  56 . The right end portion of the supply roller shaft  56  is inserted into the second shaft insertion penetration hole  64 , and a leading end of the supply roller shaft  56  protrudes further protruded than the right bearing member  47  in the outer (right) direction. A gap is formed between an inner surface of the second shaft insertion penetration hole  64  and the supply roller shaft  56 . 
         [0068]    As shown in  FIG. 5 , left bearing members  49 ,  58  are provided at an outer side of the left sidewall  36 . 
         [0069]    A left end portion of the developing roller shaft  46  is supported by the left sidewall  36  via the left bearing member  49  so that the left end portion of the developing roller shaft  46  can be relatively rotated. 
         [0070]    A left end portion of the supply roller shaft  56  is supported by the left sidewall  36  via the left bearing member  58  so that the left end portion of the supply roller shaft  56  can be relatively rotated. 
         [0071]    (2-4) Gear Unit 
         [0072]    As shown in  FIG. 3 , a gear cover  42  is mounted to the left end portion of the developing cartridge. 
         [0073]    As shown in  FIG. 5 , the left end portion of the developing roller shaft  46  is protrudes leftward from the gear cover  42 , and a cylindrical collar member  41  is attached to the protruding portion. In addition, the left end portion of the supply roller shaft  56  is arranged between the gear cover  42  and the left sidewall  36 . 
         [0074]    A developing roller gear  50  is attached to the developing roller shaft  46  between the gear cover  42  and the left sidewall  36  so that the developing roller gear  50  cannot be relatively rotated. A driving force for driving the developing roller  11  is input to the developing roller gear  50  with the developing cartridge  32  (process cartridge  3 ) being mounted in the body casing  2 . 
         [0075]    A supply roller gear  59  is attached to the supply roller shaft  56  between the gear cover  42  and the left sidewall  36  so that the supply roller gear  59  cannot be relatively rotated. A driving force for driving the supply roller  37  is input to the supply roller gear  59  with the developing cartridge  32  (process cartridge  3 ) being mounted in the body casing  2 . 
       (3) Structure for Feeding Power to Developing Roller and Supply Roller 
       [0076]    As shown in  FIG. 4 , a developing electrode  48  and a supply electrode  57  are provided at an outer side of the right sidewall  36 . 
         [0077]    (3-1) Developing Electrode 
         [0078]    The developing electrode  48  is made of a conductive resin. As shown in  FIG. 4 , the developing electrode  48  integrally includes a developing connection part  70 , a developing protrusion  71  and a developing coupling part  72 . 
         [0079]    The developing connection part  70  has a cylindrical shape. As shown in  FIG. 5 , a protruded portion of the developing roller shaft  46 , which protrudes rightward from the right bearing member  47 , is inserted in the developing connection part  70 . Thereby, the developing electrode  48  contacts the circumferential surface of the developing roller shaft  46 , so that the developing electrode  48  and the developing roller shaft  46  are electrically connected. 
         [0080]    As shown in  FIG. 4 , the developing protrusion  71  has a plate shape that protrudes further than the developing connection part  70  in the left direction at the back-upper position with respect to the developing connection part  70 . 
         [0081]    Specifically, a parallel surface  85 , a first inclined surface  86  and a second inclined surface  87  (examples of inclined surfaces) are formed on an upper surface of the developing protrusion  71 . The parallel surface  85  extends in the front-back direction. The first inclined surface  86  continues from a back end portion of the parallel surface  85 . The second inclined surface  87  continues from a front end portion of the parallel surface  85 . 
         [0082]    The parallel surface  85  extends in the front-back direction at a position above the developing roller shaft  46 , when seen from a side face. 
         [0083]    The first inclined surface  86  continues toward the back end portion of the parallel surface  85  and forms a bent surface that is gently bent and downward extended. 
         [0084]    The second inclined surface  87  continues toward the front end portion of the parallel surface  85  and forms a plane that is extended with a constant gradient in the front-lower direction. 
         [0085]    In addition, as indicated by the dotted line in  FIG. 3 , a developing-side contact position  91  (one example of a contact position), to which a developing contact point member  90  (which will be described later) contacts when the developing cartridge  32  is mounted in the body casing  2 , is set to the parallel surface  85 . 
         [0086]    As shown in  FIG. 4 , the developing coupling part  72  has a plate shape extending in the substantially front-back direction and couples the developing connection part  70  and the developing protrusion  71 . In addition, the developing coupling part  72  is formed with a screw hole (not shown). A screw  73  is engaged with the right sidewall  36  through the screw hole, so that the developing electrode  48  is fixed to the developing housing  10  of the developing cartridge  32 . 
         [0087]    When the process cartridge  3 , in which the developing cartridge  32  is mounted to the drum cartridge  31 , is mounted in the body casing  2 , a main body-side developing electrode (not shown) provided in the body casing  2  connects to the developing protrusion  71 . When a developing bias is input to the developing protrusion  71  from the main body-side developing electrode, the developing bias is applied to the developing roller shaft  46  through the developing coupling part  72  and the developing connection part  70 . 
         [0088]    (3-2) Supply Electrode 
         [0089]    The supply electrode  57  is made of conductive resin. As shown in  FIG. 4 , the supply electrode  57  integrally includes a supply connection part  75 , a supply protrusion  76  and a supply coupling part  77 . 
         [0090]    The supply connection part  75  has a substantially cylindrical shape having a sealed right end. The supply connection part  75  is fitted to a gap between a protruded portion of the supply roller shaft  56 , which protrudes rightward from the right bearing member  47 , and the second shaft insertion penetration hole  64  formed at the right bearing member  47 . Thereby, the right end portion of the supply roller shaft  56  is inserted into the cylindrical supply connection part  75 , and the supply electrode  57  is fixed to the right bearing member  47 . Thus, the supply electrode  57  contacts the circumferential surface of the supply roller shaft  56 , so that the supply electrode  57  and the supply roller shaft  56  are electrically connected. 
         [0091]    The supply protrusion  76  has a plate shape that protrudes further than the supply connection part  75  in the left direction at the back-upper position from the supply connection part  75 . In addition, the supply protrusion  76  is arranged at the front of the developing protrusion  71  of the developing electrode  48 . In other words, the developing protrusion  71  and the supply protrusion  76  are arranged in the front-back direction. 
         [0092]    Specifically, an upper surface of the supply protrusion  76  includes a parallel surface  88  extending in the front-back direction and a third inclined surface  89  (one example of an inclined surface) continuing to a back end portion of the parallel surface  88 . 
         [0093]    The parallel surface  88  is extended in the front-back direction at a position slightly above the parallel surface  85  formed at the developing protrusion  71 , when seen from the side face. 
         [0094]    The third inclined surface  89  is continued from the back end portion of the parallel surface  88  and forms a plane that extends with a constant gradient in the back-lower direction. 
         [0095]    In addition, as indicated by the dotted line in  FIG. 3 , a supply-side contact position  93  (one example of a contact position) to which a supply contact point member  92  (which will be described later) is contacted when the developing cartridge  32  is mounted in the body casing  2 , is set to the parallel surface  88 . The supply-side contact position  93  is provided at a position further left than the developing-side contact position  91 . In other words, the developing-side contact position  91  and the supply-side contact position  93  are not aligned in the axis direction (left-right direction) of the developing roller  11 . 
         [0096]    As shown in  FIG. 4 , the supply coupling part  77  has a plate shape extending from the back-lower side to the front-upper side and couples the supply connection part  75  and the supply protrusion  76 . A screw hole (not shown) is formed in the supply coupling part  77 . A screw  80  is engaged with the right sidewall  36  through the screw hole, so that the supply electrode  57  is fixed to the developing housing  10  of the developing cartridge  32 . 
         [0097]    When the process cartridge  3 , in which the developing cartridge  32  is mounted to the drum cartridge  31 , is mounted in the body casing  2 , a main body-side supply electrode (not shown) provided in the body casing  2  is connected to the supply protrusion  76 . When a supply bias is input to the supply protrusion  76  from the main body-side supply electrode, the supply bias is applied to the supply roller shaft  56  through the supply coupling part  77  and a contact part  79  of the supply connection part  75 . 
       (4) Structure in Body Casing 
       [0098]    In  FIGS. 7A to 7E , the drum cartridge  31  and the body casing  2  are not shown so as more easily understand the drawings. 
         [0099]    A developing contact point member  90  and a supply contact point member  92  are formed in the body casing  2  (refer to  FIG. 1 ). 
         [0100]    The developing contact point member  90  is formed by bending a metal wire, for example, and integrally includes an engage part  95  and an elastic part  96 . 
         [0101]    The engage part  95  is formed by winding the wire into a vortex spring shape many times. A protrusion (not shown) provided in the body casing  2  is inserted into a center of the vortex of the engage part  95 , so that the developing contact point member  90  is engaged in the body casing  2 . 
         [0102]    The elastic part  96  extends in the back-lower direction from the engage part  95 . The elastic part  96  is bent at a center portion thereof and extends in the back-upper direction, so that the elastic part has a V shape when seen from the side face. A peak portion (bent portion)  96 A of the elastic part  96  is slightly circular and is gently bent. 
         [0103]    A back end portion of the elastic part  96  is further bent and is then extended backward. 
         [0104]    The supply contact point member  92  is arranged at the front of the developing contact point member  90  and has the substantially same shape as the developing contact point member  90 . In other words, the supply contact point member  92  integrally includes an engage part  97  having a vortex spring shape and an elastic part  98  having a substantially V shape when seen from a side face. A peak portion (bent portion)  98 A of the elastic part  98  is slightly circular and is gently bent. 
       (5) Operation of Attaching and Detaching Process Cartridge to and from Body Casing 
       [0105]    As shown in  FIG. 1 , in the printer  1 , the process cartridge  3 , in which the developing cartridge  32  is mounted to the drum cartridge  31 , is detachably mounted to the body casing  2 . 
         [0106]    Incidentally, since the drum cartridge  31  is not shown in  FIGS. 7A to 7E , an operation of attaching and detaching the process cartridge  3  to and from the body casing  2  will be described using the developing cartridge  32 . 
         [0107]    (5-1) Operation of Mounting Process Cartridge to Body Casing 
         [0108]    When mounting the process cartridge  3  to the body casing  2 , the front cover  4  shown in  FIG. 1  is first opened. Then, the developing cartridge  3  is moved backward through an opening formed at the front side of the body casing  2 . At this time, the photosensitive drum  6  of the process cartridge  3  is arranged at a downstream side (back side) of a mounting direction of the developing unit  3  to the body casing  2 . 
         [0109]    During the mounting of the process cartridge  3 , as shown in  FIG. 7A , the developing contact point member  90  and the supply contact point member  92  are opposed to the process cartridge  3  from the back side. 
         [0110]    When the process cartridge  3  is moved further backward, the elastic part  98  of the supply contact point member  92  contacts the developing protrusion  71  of the developing electrode  48  from the back side, as shown in  FIG. 7B . Specifically, the peak portion  98 A of the elastic part  98  contacts the first inclined surface  86  of the developing protrusion  71 . Then, the elastic part  98  of the supply contact point member  92  is put on the first inclined surface  86  while being deformed at the engage part  97 , which serves as a support point, and is then guided toward the parallel surface  85 . 
         [0111]    After that, when the process cartridge  3  is moved backward, the elastic part  98  of the supply contact point member  92  moves away from the parallel surface  85 . Then, as shown in  FIG. 7C , the elastic part  98  of the supply contact point member  92  contacts the supply protrusion  76  of the supply electrode  57  from the back side thereof. Specifically, the peak portion  98 A of the elastic part  98  contacts the third inclined surface  89  of the supply protrusion  76 . Then, the elastic part  98  of the supply contact point member  92  is put on the third inclined surface  86  while being deformed at the engage part  97 , which serves as a support point, and is then guided toward the parallel surface  88 . 
         [0112]    When the process cartridge  3  is further moved backward, the peak portion  98 A of the elastic part  98  of the supply contact point member  92  is put on the parallel surface  88  of the supply protrusion  76 . At this time, the peak portion  98 A contacts the supply-side contact position  93  indicated by the dotted line in  FIG. 3 . In addition, the peak portion  96 A of the elastic part  96  of the developing contact point member  90  contacts the first inclined surface  86  of the developing protrusion  71  from the back side thereof and the elastic part  96  is put on the first inclined surface  86  while being deformed at the engage part  95 , which serves as a support point. Then, the peak portion  96 A of the elastic part  96  is guided along the first inclined surface  86 , so that the peak portion  96 A is put on the parallel surface  85 . At this time, the peak portion  96 A contacts the developing-side contact position  91  indicated by the dotted line in  FIG. 3 . Thereby, the mounting of the process cartridge  3  to the body casing  2  is completed. 
         [0113]    (5-2) Operation of Detaching Process Cartridge from Body Casing 
         [0114]    The detachment of the process cartridge  3  from the body casing  2  is made by pulling out the process cartridge  3  toward the front. 
         [0115]    Specifically, when the process cartridge  3  is retreated forward from the state shown in  FIG. 7D , the peak portion  96 A of the developing contact point member  90  is moved backward on the parallel surface  85  of the developing protrusion  71  and is guided along the first inclined surface  86 . Then, the peak portion  96 A is spaced from the developing electrode  48 . Further, the peak portion  98 A of the supply contact point member  92  is moved backward on the parallel surface  88  of the supply protrusion  76  and is guided along the third inclined surface  89 . Then, the peak portion  98 A is spaced from the supply electrode  57 . 
         [0116]    After that, when the process cartridge  3  is further moved forward, the peak portion  98 A of the supply contact point member  92  contacts the second inclined surface  87  of the developing protrusion  71  from the front side thereof, as shown in  FIG. 7E . 
         [0117]    Then, as the process cartridge  3  is moved forward, the peak portion  98 A is moved backward on the second inclined surface  87  while the elastic part  98  is elastically deformed at the engage part  97 , which serves as a support point. After being put on the parallel surface  85 , the peak portion  98 A is moved backward on the parallel surface  85  and is guided along the first inclined surface  86 . Then, the peak portion  98 A is spaced from the developing electrode  48 . Thereby, the supply contact point member  92  is spaced from the developing electrode  48 . 
         [0118]    After that, when the process cartridge  3  is pulled out from the body casing  2 , the detachment of the process cartridge  3  from the body casing  2  is completed. 
         [0119]    As described above, the developing chamber  33  and the toner accommodating chamber  34  are formed adjacent to each other in the developing housing  10  of the developing cartridge  32 . The toner is accommodated in the toner accommodating chamber  34  and is supplied to the developing chamber  33 . The developing roller  11  and the supply roller  37  are provided to the developing chamber  33 . The developing roller  11  includes the developing roller shaft  46  extending in the facing direction of both sidewalls of the developing housing  10 . In addition, the supply roller  37  includes the supply roller shaft  56  extending in the facing direction of both sidewalls of the developing housing  10 . In other words, the developing roller shaft  46  extends in the direction orthogonal to opposing sidewalls of the developing housing  10 , and the supply roller shaft  56  extends in the direction orthogonal to opposing sidewalls of the developing housing  10 . The developing electrode  48  and the supply electrode  57  are provided at the outer side of the right sidewall  36  of the developing housing  10 . Further, the developing electrode  48  is electrically connected to the developing roller shaft  46 , and the supply electrode  57  is electrically connected to the supply roller shaft  56 . The developing protrusion  71  of the developing electrode  48  protrudes in a direction parallel to the developing roller shaft  46  at a position different from the developing roller shaft  46 , when seen from the side face. In addition, the supply protrusion  76  of the supply electrode  57  protrudes in a direction parallel to the supply roller  37  (supply roller shaft  56 ) at a position different from the supply roller shaft  56 , when seen from the side face. The developing protrusion  71  and the supply protrusion  76  are arranged in the arrangement direction (front-back direction) of the developing chamber  33  and the toner accommodating chamber  34 . 
         [0120]    Since the developing protrusion  71  is arranged at the position different from the developing roller shaft  46  and the supply protrusion  76  is arranged at the position different from the supply roller shaft  56 , it is possible to freely arrange the developing protrusion  71  and the supply protrusion  76 , irrespective of the arrangement of the developing roller shaft  46  and the supply roller shaft  56 . Accordingly, it is possible to increase a degree of freedom of layouts of the developing protrusion  71  and the supply protrusion  76 . 
         [0121]    The developing protrusion  71  and the supply protrusion  76  are arranged in the arrangement direction (front-back direction) of the developing chamber  33  and the toner accommodating chamber  34 . Accordingly, even when a size in the thickness direction (upper-lower direction) of the developing cartridge  32  orthogonal to the arrangement direction is small, it is possible to arrange the developing protrusion  71  and the supply protrusion  76 . In other words, it is possible to make the developing cartridge  32  thin by arranging the developing protrusion  71  and the supply protrusion  76  in the arrangement direction. 
         [0122]    In addition, in order to feed power to the developing electrode  48  through the developing protrusion  71 , the body casing  2  is provided with the developing contact point member  90 , which is electrically connected to the developing protrusion  71 . The developing protrusion  71  protrudes in the direction parallel to the developing roller shaft  46 . Accordingly, when connecting the developing contact point member  90  to the developing protrusion  71 , the developing contact point member  90  does not scrape the sidewall  36  of the developing cartridge  32 . Hence, it is possible to prevent the sidewall  36  of the developing cartridge  32  and the developing contact point member  90  from being worn. 
         [0123]    Furthermore, in order to feed power to the supply electrode  57  through the supply protrusion  76 , the body casing  2  is provided with the supply contact point member  92 , which is electrically connected to the supply protrusion  76 . The supply protrusion  76  protrudes in the direction parallel to the supply roller shaft  56 . Accordingly, when connecting the supply contact point member  92  to the supply protrusion  76 , the supply contact point member  92  does not scrape the sidewall  36  of the developing cartridge  32 . Hence, it is possible to prevent the sidewall  36  of the developing cartridge  32  and the supply contact point member  92  from being worn. 
         [0124]    In addition, the right bearing member  47  is attached to the right sidewall  36 . The developing roller shaft  46  and the supply roller shaft  56  are rotatably held by the right bearing member  47 . Thereby, the developing roller  11  is supported through the developing roller shaft  46  and the supply roller  37  is supported through the supply roller shaft  56  with one right bearing member  47 . Accordingly, it is possible to improve the relative positioning precision of the developing roller  11  and the supply roller  37 . 
         [0125]    Additionally, the developing electrode  48  contacts the circumferential surface of the developing roller shaft  46 . Thereby, even when the developing roller shaft  46  is rotated, it is possible to always contact the developing electrode  48  to the circumferential surface of the developing roller shaft  46 . Accordingly, it is possible to stably feed the power from the developing electrode  48  to the developing roller shaft  46 . 
         [0126]    In addition, the supply electrode  57  contacts the circumferential surface of the supply roller shaft  56 . Thereby, even when the supply roller shaft  56  is rotated, it is possible to always contact the supply electrode  57  to the circumferential surface of the supply roller shaft  56 . Accordingly, it is possible to stably feed the power to the supply roller shaft  56  from the supply electrode  57 . 
         [0127]    Further, the developing contact point member  90  contacts the developing protrusion  71  with the developing cartridge  32  being mounted to the body casing  2 . In addition, the supply contact point member  92  contacts the supply protrusion  76  with the developing cartridge  32  being mounted to the body casing  2 . The contact position (developing-side contact position  91 ) between the developing contact point member  90  and the developing protrusion  71  is offset from the contact position (supply-side contact position  93 ) between the developing contact point member  92  and the supply protrusion  76  are in the left-right direction. 
         [0128]    Thereby, with the developing cartridge  32  being mounted to the body casing  2 , it is possible to supply the developing bias to the developing electrode  48  from the developing contact point member  90  through the developing protrusion  71  and to supply the supply bias to the supply electrode  57  from the supply contact point member  92  through the supply protrusion  76 . 
         [0129]    In addition, since the developing cartridge  32  is attached and detached to and from the body casing  2  along the front-back direction, the supply contact point member  92 , which is connected to the supply protrusion  76 , scrapes the developing protrusion  71  that is arranged at the downstream side (back side) of the mounting direction. Thus, the developing protrusion  71  is worn due to the scraping against the supply contact point member  92 . However, since the developing-side contact position  91  and the supply-side contact position  93  are not aligned in the left-right direction, it is possible to prevent the developing-side contact position  91  from being worn. 
         [0130]    In addition, the developing contact point member  90  contacts the developing protrusion  71  from the back side. The developing protrusion  71  includes the first inclined surface  86  at the back side of the developing protrusion from the parallel surface  85 . Therefore, it is possible to favorably guide the developing contact point member  90  to the parallel surface  85  by the first inclined surface  86 . 
         [0131]    Additionally, since the developing protrusion  71  is arranged further toward the back side than the supply protrusion  76 , the supply contact point member  92  contacts the developing protrusion  71  from the front side when the developing cartridge  32  is detached from the body casing  2 . The developing protrusion  71  includes the second inclined surface  87  at the front side regarding the parallel surface  85 . Therefore, it is possible to guide the supply contact point member  92  to the back side by the second inclined surface  87 . 
         [0132]    Further, since the supply protrusion  76  is arranged further toward the front side than the developing protrusion  71 , the supply contact point member  92  contacts the supply protrusion  76  from the developing protrusion  71  side (back side). The supply protrusion  76  includes the third inclined surface  89  at the developing protrusion  76  side from the parallel surface  88 . Therefore, it is possible to favorably guide the supply contact point member  92  to the parallel surface  88  by the third inclined surface  89 . 
       (6) Modified Exemplary Embodiment 
       [0133]    An exemplary embodiment of the invention has been described above. However, the invention can be implemented according to other exemplary embodiments. 
         [0134]    For example, in the above-described exemplary embodiment, a white-black printer has been described as an example of the image forming apparatus. However, a color printer may be adopted as an example of the image forming apparatus. In this case, the invention can be applied to a developing cartridge that is detachably mounted to the color printer.