Patent Publication Number: US-11650518-B2

Title: Developing cartridge capable of reducing size of image forming apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 17/568,337, filed Jan. 4, 2022, which is a continuation of U.S. patent application Ser. No. 17/077,147, filed Oct. 22, 2020, which is a continuation of U.S. patent application Ser. No. 16/867,612, filed May 6, 2020, which is a continuation of U.S. patent application Ser. No. 16/593,623, filed Oct. 4, 2019, which is a continuation of U.S. patent application Ser. No. 16/361,519, filed Mar. 22, 2019, which is a continuation of U.S. patent application Ser. No. 16/031,011, filed Jul. 10, 2018, which is a continuation of U.S. patent application Ser. No. 15/280,614, filed Sep. 29, 2016, which claims priority from Japanese Patent Application No. 2015-254201 filed on Dec. 25, 2015. The contents of all prior applications are incorporated herein by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a developing cartridge. 
     BACKGROUND 
     Conventionally, a developing cartridge is capable of being attached to an image forming apparatus such as a laser printer is known. One conventional developing cartridge accommodates developer therein. The developing cartridge includes an electrode for receiving electric power from the image forming apparatus. The electrode can supply a developing roller with the received electric power from the image forming apparatus. The developing cartridge also includes a coupling. The coupling is configured to receive driving force from the image forming apparatus. The one conventional developing cartridge further includes a detection gear. The detection gear is a gear for transmit, to the image forming apparatus, information representing one or more of specifications of the developing cartridge or information representing as to whether the developing cartridge is a new developing cartridge or not. After the developing cartridge is attached to the image forming apparatus, the coupling receives the driving force from the image forming apparatus, and then, the detection gear can rotate. 
     Another conventional developing cartridge includes a storage medium (e.g., IC chip). The storage medium can store information representing, for example, a number of printing pages. The another developing cartridge includes a cartridge-side electrical contact portion provided at a contact portion of the detection gear. 
     SUMMARY 
     In the other conventional developing cartridge, the coupling, the detection gear and the IC chip are positioned at a first side surface of a casing of the developing cartridge, and the first side surface is positioned at one side of the casing. In this case, the first side surface becomes larger because a lot of components (e.g., the coupling, the detection gear and the IC chip) have to be positioned at the first side surface. That causes the developing cartridge to have a large size. Alternatively, the image forming apparatus also includes a driving unit configured to transmit the driving force to the coupling, an actuator configured to detect the detection gear, and an electrical contact portion configured to read information from the IC chip at an inner surface of the image forming apparatus and the inner surface faces the first side surface of the developing cartridge. Therefore, configurations of the inner surface facing the first side surface may be complex structures and that may cause the image forming apparatus to have a large size. 
     It is an object of the present disclosure to arrange the coupling, the detection gear and an electric contact surface of the storage medium (e.g., IC chip) in an appropriate manner at the developing cartridge in order that a size of the image forming apparatus becomes smaller. Other objects, features, and advantages will be apparent to persons of ordinary skill in the art from the following detailed description of the disclosure and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of a developing cartridge; 
         FIG.  2    is a perspective view of the developing cartridge; 
         FIG.  3    is a perspective view of the developing cartridge; 
         FIG.  4    is an exploded perspective view of an IC (Integrated Circuit) chip assembly; 
         FIG.  5    is a perspective view of the developing cartridge; 
         FIG.  6    is a perspective view of the developing cartridge; 
         FIG.  7    is a perspective view of a developing cartridge and a drum cartridge according to a modification; 
         FIG.  8    is a view for illustrating attachment of the drum cartridge to an image forming apparatus in a state where the developing cartridge is attached to the drum cartridge according to the modification. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     A preferred embodiment of the present invention will be described with reference to drawings. In the following embodiment, an extending direction of a rotation axis of a developing roller will be referred to as a “first direction” A direction perpendicular to the first direction will be referred to as a “second direction”. Specifically, the second direction is defined by a virtual line connecting an agitator shaft  21  of an agitator and a roller shaft  32  of a developing roller  30 . 
     1. Overall Structure of Developing Cartridge 
       FIGS.  1  to  5    are perspective views of a developing cartridge  1 .  FIG.  6    is a perspective view of positions of a plurality of gears relative to the developing cartridge  1 . The developing cartridge  1  is used for an electro-photographic type image forming apparatus (for example, a laser printer or a LED printer), and is a unit for supplying developer (toner, for example) to a photosensitive drum. As shown in  FIG.  1   , the developing cartridge  1  is attached to a drawer unit  90  of the image forming apparatus. 
     When the developing cartridge  1  is replaced, the drawer unit  90  is drawn out from a front surface of the image forming apparatus. The drawer unit  90  includes four cartridge holding portions  91 , and the developing cartridge  1  is attached to four cartridge holding portions  91 , respectively. Each of four cartridge holding portions  91  includes a photosensitive drum. 
     In the present embodiment, four developing cartridges  1  are attached to one drawer unit  90 . Each of the four developing cartridges  1  is configured to accommodate developer therein, and the color of the developer is different colors (cyan, magenta, yellow, and black, for example) among the four developing cartridges respectively. However, the number of developing cartridges  1  that can be attached to the drawer unit  90  may be 1 to 3 or be greater than or equal to 5. 
     As shown in  FIGS.  2  to  5   , each developing cartridge  1  according to the present embodiment includes a casing  10 , an agitator  20 , a developing roller  30 , a first gear portion  40 , a second gear portion  50 , and an IC (Integrated Circuit) chip assembly  60 . 
     The casing  10  is a case configured to accommodate therein developer (toner, for example) for electro-photographic printing. The casing  10  includes a first outer surface  11  and a second outer surface  12 . The first outer surface  11  is an outer surface being positioned at one side of the casing  10  in the first direction. The second outer surface  12  is an outer surface being positioned at another side of the casing  10  in the first direction. The first outer surface  11  and the second outer surface  12  are separated from each other in the first direction. The first gear portion  40  and the IC chip assembly  60  are positioned at the first outer surface  11 . The second gear portion  50  is positioned at the second outer surface  12 . The casing  10  extends in the first direction between the first outer surface  11  and the second outer surface  12 . The developing chamber  13  for accommodating the developer is provided in the casing  10 . The first direction may be an extending direction of the casing  10 . The first direction may be an extending direction of the developing roller  30 . 
     The agitator  20  extends in the first direction. The agitator  20  includes an agitator shaft  21  and an agitation blade  22 . The agitator shaft  21  extends along the rotation axis  81  extending in the first direction. The agitator shaft  21  has a columnar shape extending in the first direction. The agitator shaft  21  is an example of a first shaft. The agitation blade  22  expands outward from the agitator shaft  21  in a radial direction. The agitation blade  22  is positioned inside a developing chamber  13  of the casing  10 . 
     As shown in  FIG.  4   , the agitator shaft  21  includes a first end portion  211  and a second end portion (not shown in the figures). The first end portion  211  is positioned at one end portion of the agitator shaft  21  in the first direction. The first end portion  211  penetrates through the first outer surface  11  of the casing  10 . A first agitator gear  44  described later is mounted to the first end portion  211 . More specifically, the first agitator gear  44  is mounted to the first end portion  211  so as to be incapable of rotating relative to the first end portion  211 . The first agitator  44  is positioned at the first outer surface  11 . 
     The second end portion is positioned at another end portion of the agitator shaft  21  in the first direction. The second end portion penetrates through the second outer surface  12  of the casing  10 . A second agitator gear  51  described later is mounted to the second end portion. More specifically, the second agitator gear  51  is mounted to the second end portion so as to be incapable of rotating relative to the second end portion. The second agitator  51  is positioned at the second outer surface  12 . 
     Accordingly, the agitator shaft  21  and the agitation blade  22  are rotatable with the first agitator gear  44  and the second agitator gear  51 . The developer which is accommodated in the developing chamber  13  is agitated by rotation of the agitation blade  22 . Instead of the agitation blade  22 , the agitator may include an agitation film. 
     The developing roller  30  is rotatable about a rotation axis  82  extending in the first direction. The developing roller  30  according to the present embodiment includes a roller body  31  and a roller shaft  32 . The roller body  31  is a cylinder-shaped member extending in the first direction. The roller body  31  is made of an elastic rubber, for example. The roller shaft  32  is a cylindrical member penetrating through the roller body  31  in the first direction. The roller shaft  32  is made of metal or conductive resin. The roller body  31  is fixed to the roller shaft  32  so as to be incapable of rotating relative to the roller shaft  32 . When the roller shaft  32  rotates, the roller body  31  rotates together with the roller shaft  32 . 
     The roller shaft  32  may not penetrate through the roller body  31  in the first direction. For example, each of a pair of roller shafts  32  may extend from each end of the roller body  31  in the first direction. 
     One end portion of the roller shaft  32  in the first direction is mounted to a developing gear  42  described later so as to be incapable of rotating relative to the developing gear  42 . Accordingly, the roller shaft  32  rotates with rotation of the developing gear  42  and the roller body  31  also rotates with the roller shaft  32 , when the developing gear  42  rotates 
     The second direction may be defined by a direction parallel to a virtual line connecting the agitator shaft  21  and the roller shaft  32  at the same position in the first direction. The roller shaft  32  is positioned at one side of the agitator shaft  21  in the second direction. The agitator shaft  21  is positioned at another side of the roller shaft  32  in the second direction. The second direction is perpendicular to the first direction. 
     The casing  10  has an opening  14 . The opening  14  communicates between the developing chamber  13  and an exterior of the developing chamber  13 . The opening  14  is positioned at one end portion of the casing in the second direction. The developing roller  30  is positioned at the opening  14 . That is, the developing roller  30  is positioned closer to one side of the casing  10  than to the center of the casing  10  in the second direction. 
     When the developing cartridge  1  receives a driving force, the developer is supplied from the developing chamber  13  in the casing  10  onto an outer peripheral surface of the developing roller  30  via a supply roller (omitted in the figure). At this time, the developer is tribocharged between the supply roller and the developing roller  30 . On the other hand, bias voltage is applied to the roller shaft  32  of the developing roller  30 . Accordingly, static electricity between the roller shaft  32  and the developer moves the developer toward the outer peripheral surface of the roller body  31 . 
     The developing cartridge  1  further includes a layer thickness regulation blade which is omitted in the figure. The layer thickness regulation blade regulates a thin layer of the developer supplied onto the outer peripheral surface of the roller body  31  so that the thickness of the developer becomes constant. Then, the developer on the outer peripheral surface of the roller body  31  is supplied to the photosensitive drum of the drawer unit  90 . At this time, the developer moves from the roller body  31  to the photosensitive drum on the basis of an electrostatic latent image formed on the outer peripheral surface of the photosensitive drum. Accordingly, the electrostatic latent image is visualized on the outer peripheral surface of the photosensitive drum. 
     The first gear portion  40  is positioned at one end portion in the first direction of the casing  10 . That is, the first gear portion  40  is positioned at the first outer surface  11 .  FIG.  4    is a perspective view of the developing cartridge  1  in a state in which the first gear portion  40  is disassembled. As shown in  FIG.  4   , the first gear portion  40  includes a coupling  41 , a developing gear  42 , an idle gear  43 , a first agitator gear  44 , and a first cover  45 . As shown in  FIG.  4   , the coupling  41 , the developing gear  42 , the idle gear  43  and the first agitator gear are positioned at the first outer surface  11 . A plurality of gear teeth of each gear are not illustrated in  FIG.  4   . 
     The coupling  41  is a gear for initially receiving the driving force applied from the image forming apparatus. The coupling  41  is rotatable about a rotation axis  83  extending in the first direction. The rotational axis  83  which is a rotational center of the coupling  41  is one example of a first axis. The coupling  41  includes a coupling portion  411  and a coupling gear  412 . The coupling portion  411  and the coupling gear  412  are integral with each other and made of a resin, for example. 
     The coupling portion  411  has a coupling hole  413  recessed in the first direction. The coupling hole  413  is an example of a recessed portion configured to receive driving force from the image forming apparatus. Instead of the coupling hole  413 , the coupling portion  411  may have a concave portion which is configured to receive driving force from the image forming apparatus. The coupling gear  412  includes a plurality of gear teeth. The gear teeth are provided on the entire outer peripheral surface of the coupling gear  412  at equal intervals. 
     When the drawer unit  90  to which the developing cartridge  1  is attached is accommodated in the image forming apparatus, a drive shaft of the image forming apparatus is inserted into the coupling hole  413  of the coupling portion  411 . With this configuration, the drive shaft and the coupling portion  411  are connected so as to be incapable of rotating relative to each other. Accordingly, the coupling portion  411  rotates when the drive shaft rotates, and the coupling gear  412  rotates together with the coupling portion  411 . 
     The developing gear  42  is a gear for rotating the developing roller  30 . The developing gear  42  is rotatable about a rotation axis extending in the first direction. The developing gear  42  includes a plurality of gear teeth. The gear teeth are provided on the entire outer peripheral surface of the developing gear  42  at equal intervals. At least a portion of the plurality of gear teeth of the coupling gear  412  meshes with at least a portion of the plurality of gear teeth of the developing gear  42 . Further, the developing gear  42  is mounted to the end portion of the roller shaft  32  in the first direction so as to be incapable of rotating relative to the roller shaft  32 . With this construction, when the coupling gear  412  rotates, the developing gear  42  rotates with the coupling gear  412  and the developing roller  30  also rotates with the developing gear  42 . 
     The idle gear  43  is a gear for transmitting rotational driving force of the coupling gear  412  to the first agitator gear  44 . The idle gear  43  is an example of a first idle gear. The idle gear  43  is rotatable about a rotation axis  84  extending in the first direction. As shown in  FIG.  6   , the idle gear  43  includes a large diameter gear portion  431  and a small diameter gear portion  432 . The large diameter gear portion  431  and the small diameter gear portion  432  are arranged in the first direction. The small diameter gear portion  432  is positioned at another side of the large diameter gear portion  431  in the first direction. That is, the small diameter gear portion  432  is positioned between the large diameter gear portion  431  and the first outer surface  11  of the casing  10 . In other words, the large diameter gear portion  431  is farther away from the first outer surface  11  than the small diameter gear portion  432  is. A diameter of the small diameter gear portion  432  is smaller than a diameter of the large diameter gear portion  431 . In other words, a diameter of an addendum circle of the small diameter gear portion  432  is smaller than a diameter of an addendum circle of the large diameter gear portion  431 . The large diameter gear portion  431  and the small diameter gear portion  432  are integral with each other and are made of a resin. 
     The large diameter gear portion  431  includes a plurality of gear teeth, and the plurality of gear teeth are provided on the entire outer peripheral surface of the large diameter gear portion  431  at equal intervals. The small diameter gear portion  432  includes a plurality of gear teeth, and the plurality of gear teeth are provided on the entire outer peripheral surface of the small diameter gear portion  432  at equal intervals. The number of gear teeth of the small diameter gear portion  432  is less than the number of gear teeth of the large diameter gear portion  431 . At least a portion of the plurality of gear teeth of the coupling gear  412  meshes with at least a portion of the plurality of gear teeth of the large diameter gear portion  431 . Further, at least a portion of the plurality of gear teeth of the small diameter gear portion  432  meshes with at least a portion of the plurality of gear teeth of the first agitator gear  44 . When the coupling gear  412  rotates, the large diameter gear portion  431  rotates together with the coupling gear  412  and the small diameter gear portion  432  rotates together with the large diameter gear portion  431 . Also, the first agitator gear  44  rotates with the rotation of the small diameter gear portion  432 . 
     The first agitator gear  44  is a gear for rotating the agitator  20  in the developing chamber  13 . The first agitator gear  44  is rotatable about a rotation axis  81  extending in the first direction. The first agitator gear  44  includes a plurality of gear teeth, and the plurality of gear teeth are provided on the entire outer peripheral surface of the first agitator gear  44  at equal intervals. As described above, the at least a portion of the plurality of gear teeth of the small diameter gear portion  432  meshes with the at least a portion of the plurality of gear teeth of the first agitator gear  44 . Further, the first agitator gear  44  is mounted to one end portion of the agitator shaft  21  in the first direction so as to be incapable of rotating relative to the agitator shaft  21 . With the configuration, when the rotational driving force is transmitted from the coupling  41  to the first agitator gear  44  via the idle gear  43 , the first agitator gear  44  rotates and the agitator  20  rotates together with the first agitator gear  44 . That is, the agitator  20  including the agitator shaft  21  rotates together with the coupling  41 . 
     In the developing cartridge  1  of this embodiment, the idle gear  43  is positioned between the coupling gear  412  and the first agitator gear  44 , however, the idle gear  43  may be omitted. That is, the coupling gear  412  may directly mesh with the first agitator gear  44 . 
     The first cover  45  is positioned at one side of the casing in the first direction. More specifically, the first cover is positioned at the first outer surface. The first cover  45  is fixed to the first outer surface  11  of the casing  10  by screws, for example. The coupling gear  412 , the developing gear  42 , the idle gear  43 , and the first agitator gear  44  are accommodated in a space between the first outer surface  11  and the first cover  45 . The coupling hole  413  of the coupling portion  411  is exposed to an outside of the first cover  45 . The first cover  45  according to the present embodiment also serves as a holder cover for holding the holder  62  of the IC chip assembly  60  described later. A structure of the first cover  45  as the holder cover will be described later in detail. 
     The second gear portion  50  is positioned at the other side of the casing  10  in the first direction. In other words, the second gear portion  50  is positioned at the second outer surface  12 .  FIG.  5    is a perspective view of the developing cartridge  1  in which the second gear portion  50  is exploded. As illustrated in  FIG.  5   , the second gear portion  50  includes a second agitator gear  51 , a detection gear  52 , an electrically conductive member  53 , and a second cover  54 . Note that, in  FIG.  5   , gear teeth are not illustrated in the second agitator gear  51  and the detection gear  52 . 
     The second agitator gear  51  is for transmitting rotational driving force of the agitator shaft  21  to the detection gear  52 . The second agitator gear  51  is rotatable about a rotation axis  81  extending in the first direction. The second agitator gear  51  includes a plurality of gear teeth, and the plurality of gear teeth are provided on the entire outer peripheral surface of the second agitator gear  51  at equal intervals. At least a portion of the plurality of gear teeth of the second agitator gear  51  meshes with at least a portion of a plurality of gear teeth of the detection gear  52 . The second agitator gear  51  is mounted to the first end portion of the agitator shaft  21  in the first direction so as to be incapable of rotating relative to the agitator shaft  21 . With this configuration, the second agitator gear  51  rotates with rotation of the agitator shaft  21 . 
     The detection gear  52  is a gear for providing information on the developing cartridge  1  for the image forming apparatus. The information on the developing cartridge  1  includes, for example, information as to whether the developing cartridge  1  is a new (unused) cartridge or a used cartridge. The information on the developing cartridge  1  also includes, for example, a product specification of the developing cartridge  1 . The product specification of the developing cartridge  1  includes, for example, the number of sheets that can be printed with the developer accommodated in the developing cartridge  1  (i.e. sheet-yield number). 
     The detection gear  52  is rotatable about a rotation axis  85  extending in the first direction. The rotational axis  85  which is a rotational center of the detection gear  52  is an example of a second axis. The detection gear  52  includes a plurality of gear teeth  521 . The gear teeth  521  are provided on a portion of an outer peripheral surface of the detection gear  52 . That is, the detection gear  52  is a tooth-less gear, that is, the plurality of gear teeth  521  are provided on one portion of an outer peripheral surface of the detection gear  52 . The other portion of the outer peripheral surface of the detection gear  52  does not include a gear tooth. 
     When the developing cartridge  1  is in an unused state, at least a portion of the plurality of gear teeth of the detection gear  52  can mesh with at least a portion of the plurality of gear teeth of the second agitator gear  51 . In this case, the detection gear  52  rotates together with the agitator  20  including agitator shaft  21 . For this reason, the detection gear  52  rotates based on the driving force transmitted via the coupling  41  receives driving force, the coupling  41 , the idle gear  43 , the first agitator gear  44 , the agitator  20  and the second agitator gear  51 . That is the detection gear  52  is rotatable with the coupling  41 . 
     When the image forming apparatus starts to operate, the developing cartridge  1  is attached to the drawer unit  90  and the drawer unit is inserted into the inside of the image forming apparatus and accommodated in the inside of the image forming apparatus. When the drawer unit  90  to which an unused developing cartridge  1  is attached is attached in the image forming apparatus, the coupling  41  receives driving force and then, the detection gear  52  can rotate by meshing with the second agitator gear  51 . When the detection gear  52  rotates at a predetermined angle, the detection gear  52  is disengaged from the second agitator gear  51 , rotation of the detection gear  52  is stopped. 
     When the developing cartridge  1  is in the unused state, the detection gear is in a first position representing that the developing cartridge  1  is in the unused state. When the detection gear  52  is in the first position, at least a portion of the plurality of gear teeth of the detection gear  52  can mesh with at least a portion of the plurality of gear teeth of the second agitator gear  51 . When the developing cartridge  1  starts to work in the image forming apparatus, the detection gear  52  rotates from the first position and a second position. Therefore, the detection gear  52  is in the second position representing that the developing cartridge  1  is an used state, after the developing cartridge  1  starts to work. When the detection gear  52  is in the second position, the detection gear  52  does not mesh with the second agitator gear  51 . Thus, the detection gear  52  can change between the unused state and the used state and then, the detection gear  52  cannot rotate. 
     Further, the detection gear  52  may be configured of a movable gear that can move in the first direction. The movable gear may not be limited to a partially toothless gear. In other words, the movable gear includes a plurality of gear teeth, and the plurality of gear teeth are provided on an outer peripheral surface of the movable gear along the circumference of the movable gear. In this case, the movable gear moves in the first direction in accordance with rotation of the movable gear, thereby the movable gear is disengaged from the second agitator gear  51 . The movable gear may be moved in the first direction away from the second outer surface  12  or toward the second outer surface  12 . 
     When the drawer unit  90  to which a used developing cartridge  1  is attached is attached in the image forming apparatus, the detection gear  52  cannot rotate because the detection gear  52  is disengaged from the second agitator gear  51 . 
     A gear may be provided between the second agitator gear  51  and the detection gear  52 . For example, the second gear portion  50  may further include a second idle gear meshing with both the second agitator gear  51  and the detection gear  52 . The second idle gear is positioned at the second outer surface  12 . In this case, rotational driving force of the second agitator gear  51  may be transmitted to the detection gear  52  via the second idle gear. 
     The electrically conductive member  53  is electrically conductive. The electrically conductive member  53  is an example of an electrode. The electrically conductive member  53  is formed of a material such as electrically conductive metal or electrically conductive resin. The electrically conductive member  53  is positioned at the second outer surface  12  of the casing  10 . The electrically conductive member  53  includes a gear shaft  531  protruding in the first direction. The gear shaft  531  is positioned at the second outer surface  12 . The gear shaft  531  extends in the first direction from the second outer surface  12  along the rotational axis  85 . The rotational axis  85  is an example of a second axis. The gear shaft  531  is an example of a second shaft. The detection gear  52  rotates about the gear shaft  531  in a state where the detection gear  52  is supported by the gear shaft  531 . The electrically conductive member  53  further includes a bearing portion  532 . The bearing portion  532  is in contact with the roller shaft  32  of the developing roller  30 . A portion of the electrically conductive member  53  may be in contact with the roller shaft  32 . Alternatively, the roller shaft  32  may be in contact with the electrically conductive member  53  in a state where the roller shaft  32  is inserted into the electrically conductive member  53 . 
     The drawer unit  90  includes an electrically conductive lever (not illustrated) that is in contact with the gear shaft  531  in a state where the developing cartridge  1  is attached to the drawer unit  90 . Instead of the drawer unit  90 , the image forming apparatus may include the electrically conductive lever. When the lever contacts the gear shaft  531 , electrical connection between the lever, and the electrically conductive member  53  is established and electrical connection between the electrically conductive member  53  and the roller shaft  32  is also established. When the image forming apparatus is in operation, electric power is supplied to the roller shaft  32  through the lever, and the roller shaft  32  can keep a prescribed bias voltage. That is, the electrically conductive member  53  including the gear shaft  531  has a function of the electrode supplying the roller shaft  32  with the bias voltage (electric power). 
     The second cover  54  is positioned at the other side of the casing  20  in the first direction. More specifically, the second cover  54  is positioned at the second outer surface  12 . The second cover  54  is fixed to the second outer surface  12  of the casing  10  by a screw, for example. At least a portion of one or more of the second agitator gear  51  and the detection gear  52 , and the electrically conductive member  53  are accommodated in a space between the second outer surface  12  and the second cover  54 . Therefore, the second cover  54  covers at least a portion of the detection gear  52 . The second cover  54  has an opening  541 . A portion of the detection gear  52  and a portion of the gear shaft  531  are exposed to the outside through the opening  541 . The electrically conductive lever of the drawer unit  90  contacts the detection gear  52  and the gear shaft  531  through the opening  541 . 
     As illustrated in  FIG.  5   , the detection gear  52  includes a detecting protrusion  522 . The detection gear  52  covers a portion of an outer peripheral surface of the gear shaft  531 . The protrusion  522  is positioned at another side the plurality of gear teeth  521  in the first direction. The detecting protrusion  522  protrudes in the first direction. The detecting protrusion  522  has a circular arc shape extending along a portion of an addendum circle of the detection gear about the rotation axis of the detection gear  52 . Note that the detecting protrusion  522  covers a portion of an outer peripheral surface of the gear shaft  531 . The detecting protrusion  522  is rotatable with the detection gear  52 . 
     When the developing cartridge in the unused state is attached to the image forming apparatus, a portion of the gear shaft  531  is exposed to the outside through the opening  541 . That is, the lever of the drawer unit  90  is in contact with the gear shaft  531 . When the image forming apparatus is in operation and the coupling  41  receives driving force, the detection gear  52  rotates. Then, the detecting protrusion  522  pass through between the lever and the gear shaft  531  according to the rotation of the detection gear  52 . The lever is not in contact with the gear shaft  531 , when the detecting protrusion  522  is positioned between the lever and the gear shaft  531 . After the detection gear  42  further rotates, the detecting protrusion  522  pass through between the lever and the gear shaft  531  and the lever is in contact with the gear shaft  531 . When the detection gear  52  rotates at a predetermined angle, the detection gear  52  is disengaged from the second agitator gear  51 , rotation of the detection gear  52  is stopped. Therefore, the contact state between the lever and the gear shaft  531  is maintained. 
     Hence, when the detection gear  52  rotates after a new developing cartridge  1  is attached in the drawer unit  90 , the contact state between the lever and the gear shaft  531  changes according to the shape of the detection gear  52 . More specifically, the contact state between the lever and the gear shaft  531  changes according to the shape of the detecting protrusion  522  because the detecting protrusion  522  pass through between the lever and the gear shaft according to the rotation of the detection gear  52 . Alternatively, the contact state between the lever and the gear shaft  531  changes according to the number of the detecting protrusions  522  which are provided with the detection gear  52  because one or more of detecting protrusions  522  pass through between the lever and the gear shaft according to the rotation of the detection gear  52 . The image forming apparatus recognizes the change in the contact state between the lever and the gear shaft  531  to identify whether the attached developing cartridge  1  is new or used and/or the product specification of the mounted developing cartridge  1 . That is, the detection gear  52  has a shape representing information regarding a specification of the developing cartridge. For example the specification of the developing cartridge may represent a color of the developer accommodated in the developing cartridge. The detection gear  52  may have a shape representing other information representing a color of the developer accommodated in the developing cartridge. 
     However, the method for detecting the information on the developing cartridge  1  using the detection gear  52  is not limited to detection of electrical conduction. For example, movement of the lever may be optically detected. Further, the detecting protrusion  522  may be formed to have different circumferential position and length from those in the present embodiment. Further, the detection gear  52  may have a plurality of detecting protrusions  522 . The shape of the detection gear  52  may vary according to the product specification of the developing cartridge  1  such as the number of printable sheets. More specifically, the number of the detecting protrusions  522  may be differentiated among a plural type of the developing cartridges, and the product specification regarding each of the developing cartridges may be identified based on the number of the detecting protrusions  522 . When each of the plural type of the developing cartridges includes the number of the detecting protrusions  522 , circumferential intervals between the plurality of detecting protrusions  522  may be differentiated among the plural type of the developing cartridges. In the above-described case, a circumferential length of each detecting protrusion  522  and/or a radial length of each detecting protrusion  522  may be differentiated based on the product specification regarding each of the developing cartridges. In this way, variations in the number of the detecting protrusions  522  and/or circumferential positions of each of the detecting protrusion  522  enables the image forming apparatus to identify the product specification regarding each of the developing cartridges. 
     The detection gear  52  may be configured of plural components. For example, the detecting protrusion  522  and the detection gear  52  may be different components. Further, the detection gear  52  may include a detection gear body and a supplemental member that shifts its position relative to the detection gear body in accordance with rotation of the detection gear body. In this case, the supplemental member changes between a first position in which the supplemental member is in contact with the lever and a second position in which the supplemental member is not in contact with the lever in accordance with shifting the position of the supplemental member relative to the detection gear body. As a result, the supplemental member may change the position of the lever. 
     Further, the detection gear  52  may include a cam, and the cam may contact the detecting protrusion  522 . In this case, the cam rotates together with rotation of the detection gear  52 , and the rotating cam contacts the detecting protrusion  522 . This causes the detecting protrusion  522  to move relative to the detection gear  52 . The detecting protrusion  522  may be rotatably attached to a shaft provided at the second outer surface  12  or the second cover  54 . Alternatively, the detecting protrusion  522  may have a shaft, and the shaft of the detecting protrusion  522  may be inserted into a hole formed in the second outer surface  12  or the second cover  54  so that the detecting protrusion  522  is rotatably supported by the second outer surface  12  or the second cover  54 . 
     Further, in the present embodiment, the gear shaft  531  extends in the first direction from the second outer surface  12 . However, the gear shaft  531  does not need to be in direct contact with the second outer surface  12 . For example, the casing  10  may have a through-hole penetrating the second outer surface  12  and a cap attached or fitted with the through-hole, and a gear shaft may extend from the cap in the first direction. In this case, the cap includes the gear shaft protruding in the first direction toward the detection gear  52 , and the detection gear  52  rotates about the gear shaft  531  in a state where the detection gear is supported by the gear shaft  531 . 
     2. IC Chip Assembly 
     The IC chip assembly  60  is positioned at the one side of the casing in the first direction. The IC chip assembly  60  is positioned at the first outer surface  11  of the casing  10 .  FIG.  6    is an exploded perspective view of the IC chip assembly  60 .  FIG.  7    is a cross-sectional view of the IC chip assembly  60  taken along a plane perpendicular to the first direction. As shown in  FIGS.  2  through  7   , the IC chip assembly  60  includes an IC (Integrated Circuit) chip  61  as a storage medium and a holder  62  for holding the IC chip  61 . The holder  62  is held to the first cover  45  at one end of the casing  10  in the first direction. The IC chip  61  stores various information on the developing cartridge  1 . 
     As shown in  FIG.  5   , the IC chip  61  includes an electric contact surface  611 . The electric contact surface  611  is made of electrically conductive metal. The electric contact surface  611  is positioned at one side of the casing  10  in the first direction. The electric contact surface is positioned at the first outer surface. 
     The drawer unit  90  includes an electric connector. The electric connector is made of metal, for example. The electric connector of the drawer unit  90  contacts the electric contact surface  611  when the developing cartridge  1  is attached to the drawer unit  90 . At this time, the image forming apparatus can perform at least one of reading information from the IC chip  61  and writing information in the IC chip  61 . 
     In this developing cartridge  1 , both the IC chip  61  and the electric contact surface  611  of the IC chip  61  are positioned at the one side of the casing in the first direction. 
     At least a portion of the holder  62  is covered by the first cover  45 . The holder  62  includes a boss  621   a , a boss  621   b , and a boss  621   c . Each of the boss  621   a  and boss  621   b  extends in the first direction toward the first cover  45  from a surface of the holder  62  opposite to a surface thereof facing the casing  10 . The boss  621   a  and boss  621   b  are aligned in the second direction. The boss  621   c  extends in the first direction toward the casing  10  from the surface of the holder  62  facing the casing  10 . As shown in  FIGS.  2  and  4   , the first cover  45  has a through-hole  451   a  and a through-hole  451   b . The through-hole  451   a  and through-hole  451   b  penetrate the first cover  45  in the first direction, respectively. The through-hole  451   a  and through-hole  451   b  are aligned in the second direction. On the other hand, the casing  10  includes a recessed portion  15 . The recessed portion  15  is recessed in the first direction on the first outer surface  11  of the casing  10 . 
     The boss  621   a  is inserted into the through-hole  451   a . The boss  621   b  is inserted into the through-hole  451   b . The boss  621   c  is inserted into the recessed portion  15 . The through-hole  451   a  has a dimension (inner dimension) larger than a dimension (outside dimension) of the boss  621   a . The through-hole  451   b  has a dimension (inner dimension) larger than a dimension (outside dimension) of the boss  621   b . Further, the recessed portion  15  has a dimension (inner dimension) larger than a dimension (outer dimension) of the boss  621   c . Hence, the holder  62  can move with the bosses  621   a ,  621   b  and  621   c  in direction perpendicular to the first direction relative to the casing  10  and the first cover  45 . The holder  62  moves between the first cover  45  and the first outer surface  11   
     Alternatively, the holder  62  may include a single boss, or three or more bosses. Likewise, the first cover  45  may have a single through-hole, or three or more through-holes. The bosses  621   a ,  621   b  and  621   c  may have a circular columnar shape or a rectangular columnar shape, respectively. 
     Or, instead of the through-holes  451   a  and  451   b , the first cover  45  may include one or more of recesses to have the bosses  621   a  and/or  621   b  inserted thereinto. 
     A projected area of the developing cartridge  1  in the first direction should be smaller in order to down size of the image forming apparatus. That is the first outer surface  11  should be smaller in order to down size of the image forming apparatus. That is the second outer surface  12  also should be smaller in order to down size of the image forming apparatus. On the other hand, it is difficult to arrange the coupling  41 , the electric contact surface  611  and the detection gear  52  at one side of the casing  10  in the first direction in a state where at least a portion of the coupling  41 , the electric contact surface  611  and the detection gear  52  are overlapping in the first direction, because the coupling  41 , each of the electric contact surface  611  and the detection gear is a component for interacting with the image forming apparatus. 
     As shown in the  FIG.  6   , in the developing cartridge  1 , the detection gear  52  is positioned at the other side of the casing  10  in the first direction, and the coupling  41  and the electric contact surface  611  of the IC chip  61  are also positioned at the one side of the casing  10  in the first direction. Therefore, the first outer surface  11  and the second outer surface  12  become smaller because the coupling  41  and the electric contact surface  611  are positioned at the first outer surface  11  and the detection gear  52  is positioned at the second outer surface  12  which is different from the first outer surface  11 . 
     In this embodiment, the coupling  41  is positioned at one side of the agitator shaft  21  in the second direction, and the coupling  41  is positioned at the one side of the casing in the first direction. The detection gear  52  is positioned at the one side of the agitator shaft  21  in the second direction and the detection gear is positioned at the other side of the casing in the first direction. Therefore, the coupling  41  and the detection gear are positioned at the same side of the agitator shaft  21  in the second direction. For this reason, a length of the developing cartridge in the second direction can be shortened. Accordingly, the developing cartridge  1  can be downsized in the second direction. The image forming apparatus can also be downsized in the second direction. 
     Specifically, in this embodiment, the detection gear  52  and the electrically conductive member  53  should be the same outer surface (either the first outer surface  11  or the second outer surface  12 ) of the casing  10 , because the detection gear  52  is supported by the electrically conductive member  53 . On the other hand, the electrically conductive member  53  (an example of the electrode) receives high electrical voltage (electrical power). For this reason, IC chip  61  is affected by, for example, high-frequency noise, if a distance between the electrically conductive member  53  and the electric contact surface  611  of the IC chip  61  is too short or a distance between the electrically conductive member  53  and the IC chip  61  is too short. 
     In this embodiment, in the developing cartridge  1 , the detection gear  52  and the electrically conductive member  53  are positioned at the second outer surface  12  which is positioned at opposite side of the first outer surface  11  in the first direction, and one or more of the electric surface  611  and the IC chip  61  is positioned at the first outer surface  11 . Accordingly, an electrical interference between the between the electrically conductive member  53  and the electric contact surface  611  can be reduced. Alternatively, an electrical interference between the between the electrically conductive member  53  and the IC chip  61  can be reduced. For example, the high-frequency noise on the IC chip  61  can be reduced based on charging the high electrical voltage (electrical power) to the electrically conductive member  53 . 
     In this embodiment, a whole of the IC chip  61  including the electric contact surface  611  is positioned at the first outer surface  11  which is opposite side of the second outer surface  12  in the first direction, the detection gear  52  and the electrically conductive member  53  are positioned at the second outer surface  12 . At least the electric contact surface  6111  may be positioned at the first outer surface  11  and the IC chip  61  is positioned at a different position from the first outer surface (e.g., another surface of the casing  10 ). An electrical interference between the between the electrically conductive member  53  and the electric contact surface  611  can be reduced, if at least the electric contact surface  6111  may be positioned at the first outer surface  11  and the IC chip  61  is positioned at a different position from the first outer surface (e.g., another surface of the casing  10 ). Alternatively, an electrical interference between the between the electrically conductive member  53  and the IC chip  61  can be reduced. For example, the high-frequency noise on the IC chip  61  can be reduced based on charging the high electrical voltage (electrical power) to the electrically conductive member  53 . 
     3. Modifications 
     While the description has been made in detail with reference to the specific embodiment thereof, it would be apparent to those skilled in the art that various changes and modifications may be made therein. In the following description, differences between the above embodiment and the modifications are mainly explained. 
       FIG.  7    is a perspective view showing a developing cartridge  1 A and a drum cartridge  70 A of a modification. The developing cartridge  1 A shown in  FIG.  7    includes a casing  10 A, a developing roller  30 A, a coupling  41 A a detection gear  52 A, and an IC chip  61 A. In the embodiment shown in  FIG.  7   , the developing cartridge  1 A is attached to the drum cartridge  70 A instead of the drawer unit. The drum cartridge  70 A includes one developing cartridge holding portion  71 A holding the developing cartridge  1 A. The developing cartridge holding portion  71 A includes a photosensitive drum  72 A. When the developing cartridge  1 A is attached to the drum cartridge  70 A, the developing roller  30 A of the developing cartridge  1 A is in contact with the photosensitive drum  72 A. 
       FIG.  8    is a view showing how to attach the drum cartridge  70 A to an image forming apparatus  100 A in a state where the developing cartridge  1 A is attached to the drum cartridge  70 A. As shown in  FIG.  8   , the drum cartridge  70 A is attached to a drum cartridge holding portion  101 A provided in the image forming apparatus  100 A in a state where the developing cartridge  1 A is attached to the drum cartridge  70 A. 
     In the above manner, a similar structure to that of the developing cartridge  1  according to the above embodiment can be applied to the developing cartridge  1 A to be attached to the drum cartridge  70 A. Specifically, as shown in  FIG.  7   , in the developing cartridge  1 A, the coupling  41 A and an electric contact surface  611 A of the IC chip  61 A are positioned at the one side of the casing  10 A in the first direction, and the detection gear  52 A is also positioned at the other side of the casing  10 A in the first direction. Therefore, the one outer surface and the other outer surface separated from the one outer surface in the first direction become smaller because the coupling  41 A and the electric contact surface  611 A are positioned at the one outer surface and the detection gear  52 A is positioned at the other outer surface which is different from the one outer surface. Accordingly, the developing cartridge  1 A can be downsized. The image forming apparatus  100 A can also be downsized. 
     In this embodiment, the gear shaft  531  (an example of the second shaft) extends in the first direction from the second outer surface  12 . The gear shaft  531  may not directly contact with the second outer surface  12 . For example, the casing  10  may have a through-hole penetrating the second outer surface  12  and a cap being attached to the through-hole. The gear shaft may extend from the cap in the first direction. 
     In this case the cap may include the gear shaft protruding in the first direction toward the detection gear  52 . The detection gear  52  may be rotatable about the gear shaft in a state where the detection gear  53  is supported by the gear shaft. 
     According to the above-described embodiments, the plural gears provided within each of the first gear portion and the second gear portion are engaged with one another through meshing engagement of the gear teeth. However, the plural gears provided within each of the first gear portion and the second gear portion may be engaged with one another through a frictional force. For example, instead of the plural gear teeth, frictional members, such as rubber members, may be provided to the outer circumferences of two gears that engage with each other. 
     The developing cartridge  1  in this embodiment is attached to the drawer unit of the image forming apparatus. The developing cartridge may be attached to another image forming apparatus which does not include the drawer unit. 
     Shapes of the details in the developing cartridge may differ from those shown in the drawings attached to this application. The respective components employed in the above-described embodiment and modifications can be selectively combined together within an appropriate range so that no inconsistency will arise.