Patent Publication Number: US-2023134221-A1

Title: Developing cartridge including first and second inclined surfaces, elastic member, and first protrusion

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 17/476,872, filed Sep. 16, 2021, which is a continuation of U.S. patent application Ser. No. 16/901,337, filed Jun. 15, 2020, now U.S. Pat. No. 11,126,139, which is a continuation of U.S. patent application Ser. No. 16/562,000, filed Sep. 5, 2019, now U.S. Pat. No. 10,719,051, which claims priority from Japanese Patent Application No. 2018-185275 filed Sep. 28, 2018. The entire contents of the aforementioned applications are incorporated herein by reference. 
    
    
     BACKGROUND ART 
     Technical Field 
     The present disclosure relates to a developing cartridge. 
     Background 
     An electro-photographic type image forming apparatus such as a laser printer and an LED printer is well known in the art. A developing cartridge is used for the image forming apparatus. The developing cartridge includes a developing roller for supplying toner. The conventional image forming apparatuses are described in the prior art. An image forming apparatus described in the prior art includes a drawer unit. The drawer unit includes a photosensitive drum. The developing cartridge is attachable to the drawer unit. When the developing cartridge is attached to the drawer unit, the developing roller contacts the photosensitive drum. 
     A developing cartridge disclosed in another prior art is attachable to a drum cartridge. The drum cartridge includes a photosensitive drum. When the developing cartridge is attached to the drum cartridge, the developing roller contacts the photosensitive drum. Then, the drum cartridge to which the developing cartridge has been attached is attached to a main casing of an image forming apparatus. 
     DESCRIPTION 
     Summary 
     The image forming apparatuses disclosed in the prior arts are switchable between a state in which the developing roller and the photosensitive drum are in contact with each other, and a state in which the developing roller and the photosensitive drum are separated from each other. In the prior arts, a component for moving the developing cartridge to separate the developing roller from the photosensitive drum is provided on both ends of the drawer unit or the drum cartridge, and both components for moving the developing cartridge are required to receive driving force from a main body of the image forming apparatus. 
     In view of the foregoing, it is an object of the present disclosure to provide a developing cartridge capable of moving relative to a photosensitive drum of the drawer by driving force acting on only one end of the developing cartridge, not by driving force acting on both ends of the developing cartridge. 
     In order to attain the above and other objects, the disclosure provides a developing cartridge including: a casing; a developing roller; a shaft; a first inclined surface; a second inclined surface; an elastic member; and a first protrusion. The casing is configured to accommodate developer therein. The developing roller is rotatable about a first axis extending in a first direction. The developing roller has an outer circumferential surface including one end portion and another end portion in a second direction. The one end portion is exposed to an outside of the casing. The another end portion is positioned inside the casing. The shaft extends along a second axis extending in the first direction. The shaft is movable in the first direction relative to the casing and the developing roller. The shaft is movable in the second direction together with the casing and the developing roller. The shaft has one end portion and another end portion in the first direction. The first inclined surface is positioned at the one end portion in the first direction of the shaft and is movable together with the shaft. The first inclined surface is inclined relative to the first direction such that a distance between the shaft and the first inclined surface in a radial direction of the shaft increases in a direction from the one end portion in the first direction of the shaft to the another end portion in the first direction of the shaft. The radial direction of the shaft is the second direction. The second inclined surface is positioned at the another end portion in the first direction of the shaft and is movable together with the shaft. The second inclined surface is inclined relative to the first direction such that a distance between the shaft and the second inclined surface in the radial direction of the shaft increases in the direction from the one end portion in the first direction of the shaft to the another end portion in the first direction of the shaft. The elastic member is configured to expand and contract in the first direction. The elastic member has one end and another end in the first direction. The one end in the first direction of the elastic member is connected to the second inclined surface. The another end in the first direction of the elastic member is connected to the casing. The first protrusion is positioned at the another end portion in the first direction of the shaft. The first protrusion is movable in the first direction together with the second inclined surface relative to the casing. The first protrusion is positioned closer to the developing roller than the second inclined surface is to the developing roller. The shaft is movable from a first position to a second position in response to the second inclined surface receiving a pressing force directed in a direction from the another end portion in the first direction of the shaft to the one end portion in the first direction of the shaft. 
     According to another aspect, the disclosure provides a developing cartridge including: a casing; a developing roller; a shaft; and a first inclined surface. The casing is configured to accommodate developer therein. The developing roller is rotatable about a first axis extending in a first direction. The developing roller has an outer circumferential surface including one end portion and another end portion in a second direction. The one end portion is exposed to an outside of the casing. The another end portion is positioned inside the casing. The shaft extends along a second axis extending in the first direction. The shaft is movable in the first direction relative to the casing and the developing roller. The shaft is movable in the second direction together with the casing and the developing roller. The shaft has one end portion and another end portion in the first direction and has a peripheral surface. The first inclined surface is positioned at the one end portion in the first direction of the shaft and is movable together with the shaft. The first inclined surface is inclined relative to the first direction such that a distance between the shaft and the first inclined surface in a radial direction of the shaft increases in a direction from the one end portion in the first direction of the shaft to the another end portion in the first direction of the shaft. The radial direction of the shaft is the second direction. The first inclined surface is positioned at only a portion of the peripheral surface of the shaft. 
     According to still another aspect, the disclosure provides a developing cartridge including: a casing; a developing roller; a shaft; a first inclined surface; and a second inclined surface. The casing is configured to accommodate developer therein. The developing roller is rotatable about a first axis extending in a first direction. The developing roller has an outer circumferential surface including one end portion and another end portion in a second direction. The one end portion is exposed to an outside of the casing. The another end portion is positioned inside the casing. The shaft extends along a second axis extending in the first direction. The shaft is movable in the first direction relative to the casing and the developing roller. The shaft is movable in the second direction together with the casing and the developing roller. The shaft has one end portion and another end portion in the first direction and has a peripheral surface. The first inclined surface is positioned at the one end portion in the first direction of the shaft and is movable together with the shaft. The first inclined surface is inclined relative to the first direction such that a distance between the shaft and the first inclined surface in a radial direction of the shaft increases in a direction from the one end portion in the first direction of the shaft to the another end portion in the first direction of the shaft. The radial direction of the shaft is the second direction. The second inclined surface is positioned at the another end portion in the first direction of the shaft and is movable together with the shaft. The second inclined surface is inclined relative to the first direction such that a distance between the shaft and the second inclined surface in the radial direction of the shaft increases in the direction from the one end portion in the first direction of the shaft to the another end portion in the first direction of the shaft. The second inclined surface is positioned at only a portion of the peripheral surface of the shaft. 
     According to still another aspect, the disclosure provides a developing cartridge including: a developing cartridge including: a casing; a developing roller; a shaft; a first inclined surface; a second inclined surface; an elastic member; and a first protrusion. The casing is configured to accommodate developer therein. The developing roller is rotatable about a first axis extending in a first direction. The developing roller has an outer circumferential surface including one end portion and another end portion in a second direction. The one end portion is exposed to an outside of the casing. The another end portion is positioned inside the casing. The shaft extends along a second axis extending in the first direction. The shaft is movable in the first direction relative to the casing and the developing roller. The shaft is movable in the second direction together with the casing and the developing roller. The shaft has one end portion and another end portion in the first direction. The first inclined surface is positioned at the one end portion in the first direction of the shaft and is movable together with the shaft. The first inclined surface is inclined relative to the first direction such that the first inclined surface extends radially outward of the shaft in a direction from the one end portion in the first direction of the shaft to the another end portion in the first direction of the shaft. The second inclined surface is positioned at the another end portion in the first direction of the shaft and is movable together with the shaft. The second inclined surface is inclined relative to the first direction such that the second inclined surface extends radially outward of the shaft in the direction from the one end portion in the first direction of the shaft to the another end portion in the first direction of the shaft. The elastic member is configured to expand and contract in the first direction. The elastic member has one end and another end in the first direction. The one end in the first direction of the elastic member is connected to the second inclined surface. The another end in the first direction of the elastic member is connected to the casing. The first protrusion is positioned at the another end portion in the first direction of the shaft. The first protrusion is movable in the first direction together with the second inclined surface relative to the casing. The first protrusion is positioned closer to the developing roller than the second inclined surface is to the developing roller. The shaft is movable from a first position to a second position in response to the second inclined surface receiving a pressing force directed in a direction from the another end portion in the first direction of the shaft to the one end portion in the first direction of the shaft. 
     According to still another aspect, the disclosure provides a developing cartridge comprising: a casing; a developing roller; a shaft; and a first inclined surface. The casing is configured to accommodate developer therein. The developing roller is rotatable about a first axis extending in a first direction. The developing roller has an outer circumferential surface including one end portion and another end portion in a second direction. The one end portion is exposed to an outside of the casing. The another end portion is positioned inside the casing. The shaft extends along a second axis extending in the first direction. The shaft is movable in the first direction relative to the casing and the developing roller. The shaft is movable in the second direction together with the casing and the developing roller. The shaft has one end portion and another end portion in the first direction and has a peripheral surface. The first inclined surface is positioned at the one end portion in the first direction of the shaft and is movable together with the shaft. The first inclined surface is inclined relative to the first direction such that the first inclined surface extends radially outward of the shaft in a direction from the one end portion in the first direction of the shaft to the another end portion in the first direction of the shaft. The first inclined surface is positioned at only a portion of the peripheral surface of the shaft. 
     According to still another aspect, the disclosure provides a developing cartridge comprising: a casing; a developing roller; a shaft; a first inclined surface; and a second inclined surface. The casing is configured to accommodate developer therein. The developing roller is rotatable about a first axis extending in a first direction. The developing roller has an outer circumferential surface including one end portion and another end portion in a second direction. The one end portion is exposed to an outside of the casing. The another end portion is positioned inside the casing. The shaft extends along a second axis extending in the first direction. The shaft is movable in the first direction relative to the casing and the developing roller. The shaft is movable in the second direction together with the casing and the developing roller. The shaft has one end portion and another end portion in the first direction and has a peripheral surface. The first inclined surface is positioned at the one end portion in the first direction of the shaft and is movable together with the shaft. The first inclined surface is inclined relative to the first direction such that the first inclined surface extends radially outward of the shaft in a direction from the one end portion in the first direction of the shaft to the another end portion in the first direction of the shaft. The second inclined surface is positioned at the another end portion in the first direction of the shaft and is movable together with the shaft. The second inclined surface is inclined relative to the first direction such that the second inclined surface extends radially outward of the shaft in the direction from the one end portion in the first direction of the shaft to the another end portion in the first direction of the shaft. The second inclined surface is positioned at only a portion of the peripheral surface of the shaft. 
     According to still another aspect, the disclosure provides a developing cartridge including: a casing; a developing roller; a shaft; a first inclined surface; a second inclined surface; an elastic member; and a first protrusion. The casing is configured to accommodate developer therein. The developing roller is rotatable about a first axis extending in a first direction. The developing roller has an outer circumferential surface including one end portion and another end portion in a second direction. The one end portion is exposed to an outside of the casing. The another end portion is positioned inside the casing. The shaft extends along a second axis extending in the first direction. The shaft is movable in the first direction relative to the casing and the developing roller. The shaft is movable in the second direction together with the casing and the developing roller. The shaft has one end portion and another end portion in the first direction. The first inclined surface is positioned at the one end portion in the first direction of the shaft and is movable together with the shaft. The first inclined surface is inclined relative to the first direction such that a distance between the first inclined surface and the developing roller in the second direction increases in a direction away from the casing in the first direction. The second inclined surface is positioned at the another end portion in the first direction of the shaft and is movable together with the shaft. The second inclined surface is inclined relative to the first direction such that a distance between the second inclined surface and the developing roller in the second direction increases in a direction away from the casing in the first direction. The elastic member is configured to expand and contract in the first direction. The elastic member has one end and another end in the first direction. The one end in the first direction of the elastic member is connected to the second inclined surface. The another end in the first direction of the elastic member is connected to the casing. The first protrusion is positioned at the another end portion in the first direction of the shaft. The first protrusion is movable in the first direction together with the second inclined surface relative to the casing. The first protrusion is positioned closer to the developing roller than the second inclined surface is to the developing roller. The shaft is movable from a first position to a second position in response to the second inclined surface receiving a pressing force directed in a direction from the another end portion in the first direction of the shaft to the one end portion in the first direction of the shaft. 
     According to still another aspect, the disclosure provides a developing cartridge including: a casing; a developing roller; a shaft; and a first inclined surface. The casing is configured to accommodate developer therein. The developing roller is rotatable about a first axis extending in a first direction. The developing roller has an outer circumferential surface including one end portion and another end portion in a second direction. The one end portion is exposed to an outside of the casing. The another end portion is positioned inside the casing. The shaft extends along a second axis extending in the first direction. The shaft is movable in the first direction relative to the casing and the developing roller. The shaft is movable in the second direction together with the casing and the developing roller. The shaft has one end portion and another end portion in the first direction and has a peripheral surface. The first inclined surface is positioned at the one end portion in the first direction of the shaft and is movable together with the shaft. The first inclined surface is inclined relative to the first direction such that a distance between the first inclined surface and the developing roller in the second direction increases in a direction away from the casing in the first direction. The first inclined surface is positioned at only a portion of the peripheral surface of the shaft. 
     According to still another aspect, the disclosure provides a developing cartridge including: a casing; a developing roller; a shaft; a first inclined surface; and a second inclined surface. The casing is configured to accommodate developer therein. The developing roller is rotatable about a first axis extending in a first direction. The developing roller has an outer circumferential surface including one end portion and another end portion in a second direction. The one end portion is exposed to an outside of the casing. The another end portion is positioned inside the casing. The shaft extends along a second axis extending in the first direction. The shaft is movable in the first direction relative to the casing and the developing roller. The shaft is movable in the second direction together with the casing and the developing roller. The shaft has one end portion and another end portion in the first direction and has a peripheral surface. The first inclined surface is positioned at the one end portion in the first direction of the shaft and is movable together with the shaft. The first inclined surface is inclined relative to the first direction such that a distance between the first inclined surface and the developing roller in the second direction increases in a direction away from the casing in the first direction. The second inclined surface is positioned at the another end portion in the first direction of the shaft and is movable together with the shaft. The second inclined surface is inclined relative to the first direction such that a distance between the second inclined surface and the developing roller in the second direction increases in a direction away from the casing in the first direction. The second inclined surface is positioned at only a portion of the peripheral surface of the shaft. 
     According to still another aspect, the disclosure provides a developing cartridge for use with a drum cartridge including a photosensitive drum. The developing cartridge includes: a casing; a developing roller; a shaft; a first cam; a second cam; and an elastic member. The casing is configured to accommodate developer therein. The developing roller is rotatable about a first axis extending in a first direction. The developing roller has an outer circumferential surface including one end portion and another end portion in a second direction. The one end portion is exposed to an outside of the casing. The another end portion is positioned inside the casing. The shaft extends along a second axis extending in the first direction. The shaft is movable in the first direction relative to the casing and the developing roller. The shaft is movable in the second direction together with the casing and the developing roller. The shaft has one end portion and another end portion in the first direction. The first cam is positioned at the one end portion in the first direction of the shaft and is movable together with the shaft. The second cam is positioned at the another end portion in the first direction of the shaft and is movable together with the shaft. The second cam includes a first protrusion movable in the first direction relative to the casing. The first protrusion is positioned closer to the developing roller than the shaft is to the developing roller. The elastic member has one end and another end in the first direction. The one end in the first direction of the elastic member is connected to the second cam. The another end in the first direction of the elastic member is connected to the casing. The first cam and the second cam are configured to move the shaft and the casing in the second direction relative to the photosensitive drum in response to moving in the first direction together with the shaft. The shaft is movable from a first position to a second position in response to the second cam receiving a pressing force directed in a direction from the another end portion in the first direction of the shaft to the one end portion in the first direction of the shaft. 
     According to still another aspect, the disclosure provides a developing cartridge for use with a drum cartridge including a photosensitive drum. The developing cartridge includes: a casing; a developing roller; a shaft; and a first cam. The casing is configured to accommodate developer therein. The developing roller is rotatable about a first axis extending in a first direction. The developing roller has an outer circumferential surface including one end portion and another end portion in a second direction. The one end portion is exposed to an outside of the casing. The another end portion is positioned inside the casing. The shaft extends along a second axis extending in the first direction. The shaft is movable in the first direction relative to the casing and the developing roller. The shaft is movable in the second direction together with the casing and the developing roller. The shaft has one end portion and another end portion in the first direction and has a peripheral surface. The first cam is positioned at the one end portion in the first direction of the shaft and is movable together with the shaft. The first cam has a first inclined surface inclined relative to the first direction such that a distance between the shaft and the first inclined surface in a radial direction of the shaft increases in a direction from the one end portion in the first direction of the shaft to the another end portion in the first direction of the shaft. The first inclined surface is positioned at only a portion of the peripheral surface of the shaft. 
     According to still another aspect, the disclosure provides a developing cartridge for use with a drum cartridge including a photosensitive drum. The developing cartridge includes: a casing; a developing roller; a shaft; a first cam; a second cam. The casing is configured to accommodate developer therein. The developing roller is rotatable about a first axis extending in a first direction. The developing roller has an outer circumferential surface including one end portion and another end portion in a second direction. The one end portion is exposed to an outside of the casing. The another end portion is positioned inside the casing. The shaft extends along a second axis extending in the first direction. The shaft is movable in the first direction relative to the casing and the developing roller. The shaft is movable in the second direction together with the casing and the developing roller. The shaft has one end portion and another end portion in the first direction and has a peripheral surface. The first cam is positioned at the one end portion in the first direction of the shaft and is movable together with the shaft. The second cam is positioned at the another end portion in the first direction of the shaft and is movable together with the shaft. The second cam has a second inclined surface inclined relative to the first direction such that a distance between the shaft and the second inclined surface in a radial direction of the shaft decreases in a direction from the another end portion in the first direction of the shaft to the one end portion in the first direction of the shaft. The second inclined surface is positioned at only a portion of the peripheral surface of the shaft. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The particular features and advantages of the embodiment(s) as well as other objects will become apparent from the following description taken in connection with the accompanying drawings, in which: 
         FIG.  1    is a schematic diagram of an image forming apparatus including a developing cartridge according to a first embodiment of the present disclosure; 
         FIG.  2    is a perspective view of the developing cartridge according to the first embodiment; 
         FIG.  3    is another perspective view of the developing cartridge according to the first embodiment; 
         FIG.  4    is a plan view of the developing cartridge according to the first embodiment as viewed in a first direction; 
         FIG.  5    is another plan view of the developing cartridge according to the first embodiment as viewed in the first direction; 
         FIG.  6    is an exploded perspective view of a separation member of the developing cartridge according to the first embodiment; 
         FIG.  7    is an exploded enlarged view of a shaft and a first cam of the separation member; 
         FIG.  8    is a view for description of movement of the separation member in the first direction relative to a casing and a developing roller of the developing cartridge according to the first embodiment; 
         FIG.  9    is another view for description of movement of the separation member in the first direction relative to the casing and the developing roller; 
         FIG.  10    is a plan view of the developing cartridge according to the first embodiment as viewed in the third direction; 
         FIG.  11    is a perspective view of a drawer to which the developing cartridge according to the first embodiment is detachably attached; 
         FIG.  12    is a plan view of the drawer as viewed in the third direction; 
         FIG.  13    is a perspective view of the drawer and the developing cartridges according to the first embodiment, and illustrating a state where the developing cartridges are attached to the drawer; 
         FIG.  14    is a plan view of the drawer and the developing cartridges according to the first embodiment as viewed in the third direction, and illustrating a state where the developing cartridges are attached to the drawer; 
         FIG.  15    is a plan view of the drawer and the developing cartridges according to the first embodiment as viewed in the first direction, and illustrating a state where the developing cartridges are attached to the drawer; 
         FIG.  16 A  is a view for description of separation movement of the developing cartridge according to the first embodiment performed by the separation member; 
         FIG.  16 B  is another view for description of separation movement of the developing cartridge according to the first embodiment performed by the separation member; 
         FIG.  17    is a perspective view of the developing cartridge according to the first embodiment and a photosensitive drum of the drawer in a contact state of the image forming apparatus; 
         FIG.  18    is a perspective view of the developing cartridge according to the first embodiment and the photosensitive drum in a separation state of the image forming apparatus; 
         FIG.  19    is a plan view of a developing cartridge according to a second embodiment of the present disclosure as viewed in the third direction; 
         FIG.  20 A  is a view for description of separation movement of the developing cartridge according to the second embodiment performed by the separation member; 
         FIG.  20 B  is another view for description of separation movement of the developing cartridge according to the second embodiment performed by the separation member; 
         FIG.  21    is a perspective view of a developing cartridge according to a third embodiment of the present disclosure; 
         FIG.  22    is a perspective view of the developing cartridge according to the third embodiment in which a portion of the developing cartridge is exploded; 
         FIG.  23    is a perspective view of a first cam of the developing cartridge according to the third embodiment; 
         FIG.  24    is a perspective view of a second cam of the developing cartridge according to the third embodiment; 
         FIG.  25    is a cross-sectional view illustrating a portion in the vicinity of the second cam of the developing cartridge according to the third embodiment; 
         FIG.  26    is a plan view of the developing cartridge and a drawer according to the third embodiment; 
         FIG.  27    is an exploded perspective view of a first guide roller and a bearing of the drawer according to the third embodiment; and 
         FIG.  28    is an exploded perspective view of a second guide roller and another bearing of the drawer according to the third embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     1. First Embodiment 
     Hereinafter, a first embodiment of the present disclosure will be described with reference to the accompanying drawings. 
     &lt;1.1. Configuration of Image Forming Apparatus&gt; 
       FIG.  1    is a schematic diagram of an image forming apparatus  100 . The image forming apparatus  100  is an electro-photographic type printer. For example, the image forming apparatus  100  may be a laser printer or an LED printer. 
     The image forming apparatus  100  includes four developing cartridges  1 , a drawer  2 , a main frame  101 , and a controller  102 . 
     The developing cartridges  1  are attachable to the drawer  2 . That is, the developing cartridges  1  are for use with the drawer  2 . The drawer  2  is a drum cartridge to which the four developing cartridges  1  are attachable, and includes four slots  2 A. The four developing cartridges  1  are attachable to the corresponding slots  2 A. The developing cartridges  1  are attachable to the main frame  101  in a state where the developing cartridges  1  are attached to the corresponding slots  2 A. That is, the drawer  2  is detachably attachable to the main frame  101  in a state where the developing cartridges  1  are attached to the corresponding slots  2 A. The four developing cartridges  1  accommodate developers (such as toner) of colors different from each other (such as cyan, magenta, yellow, and black). The plurality of developing cartridges  1 , however, may accommodate developers of the same color. The number of the developing cartridges  1  attachable to the drawer  2  may be one, two, or three, or five or more. 
     The image forming apparatus  100  is configured to form images on printing papers using the developers supplied from the four developing cartridges  1 . 
     Each of the four developing cartridges  1  includes an IC chip  51 . The IC chip  51  is a storage medium from which information is readable and to which information is writable. The storage medium may be a flash ROM or an EEPROM, for example. When the developing cartridges  1  attached to the slots  2 A of the drawer  2  are attached to the main frame  101 , the IC chips  51  of the developing cartridges  1  and the controller  102  are electrically connected to each other. The controller  102  is configured of, for example, a circuit board. The controller  102  includes a processor such as a CPU, and various memories. The controller  102  is configured to execute various types of processing in the image forming apparatus  100  by operating the processor in accordance with programs. 
     &lt;1.2. Developing Cartridge&gt; 
       FIGS.  2  and  3    are perspective views of the developing cartridge  1 .  FIGS.  4  and  5    are plan views of the developing cartridge  1  as viewed in a first direction. 
     In the following description, a direction in which a rotational axis (i.e., a first axis) of a developing roller  30  extends will be referred to as “first direction”. The first direction also denotes a direction in which a rotational axis (a drum axis) of a photosensitive drum  21  (described later) of the drawer  2  extends. Here, an outer circumferential surface of the developing roller  30  includes one end portion exposed to the outside of a casing  10 , and another end portion positioned inside the casing  10 . A direction in which the one end portion of the circumferential surface of the developing roller  30  and the other end portion of the circumferential surface are arrayed will be referred to as “second direction”. The second direction also denotes a direction crossing the circumferential surface of the developing roller  30  which is exposed to the outside of the casing  10  of the developing cartridge  1 . The second direction may denote a direction which the outer circumferential surface of the developing roller  30  is separated from and/or approaches an outer circumferential surface the photosensitive drum  21  (described later). The first direction and the second direction cross each other. Preferably, the first direction and the second direction are perpendicular to each other. 
     The developing cartridge  1  includes the casing  10  configured to accommodate developer therein. The casing  10  has a first outer surface  11  and a second outer surface  12  those are separated from each other in the first direction. The casing  10  extends in the first direction between the first outer surface  11  and the second outer surface  12 . That is, the first outer surface  11  is one end of the casing  10  in the first direction, and the second outer surface  12  is another end of the casing  10  in the first direction. 
     The casing  10  includes a container  10 A and a lid  10 B. The container  10 A is configured to accommodate developer therein, and has an opening (not illustrated). The lid  10 B covers the opening (not illustrated) of the container  10 A. The container  10 A and the lid  10 B are disposed at a position between the first outer surface  11  and the second outer surface  12  in the first direction. 
     The casing  10  also extends in a predetermined direction. Hereinafter, the predetermined direction in which the casing  10  extends will be referred to as “third direction”. The third direction crosses the first direction. Preferably, the third direction is perpendicular to the first direction. The third direction may denote a direction which the developing cartridges  1  are inserted into and/or extracted from the corresponding slots  2 A (see  FIG.  1   ) of the drawer  2 . The casing  10  has an opening  10 C. The opening  10 C is positioned at one end portion of the casing  10  in the third direction. The container  10 A and an outside of the casing  10  are in communication with each other through the opening  10 C. 
     The developing cartridge  1  further includes an agitator  20 . The agitator  20  is rotatable about an axis (i.e., a third axis) extending in the first direction. The agitator  20  is a member configured to agitate the developer accommodated in the container  10 A. The agitator  20  includes a shaft extending in the first direction, and an agitation blade extending radially outward from the shaft. Upon rotation of the shaft, the developer accommodated in the container  10 A is agitated by the agitation blade. 
     The developing cartridge  1  further includes the developing roller  30 . The developing roller  30  is spaced apart from the agitator  20  in the second direction. Further, the agitator  20  is positioned closer to the developing roller  30  than a shaft  61  (described later) is to the developing roller  30  in the second direction. The developing roller  30  is positioned at the opening  10 C, which is positioned at the one end portion of the casing  10  in the third direction. The developing roller  30  is a roller supported by the casing  10  so as to be rotatable about the first axis extending in the first direction. 
     The developing roller  30  includes a developing roller body  31  and a developing roller shaft  32 . The developing roller body  31  has a hollow cylindrical shape extending in the first direction. The developing roller body  31  is made of a material having elasticity, such as rubber. The developing roller shaft  32  has a columnar shape extending through the developing roller body  31  in the first direction. The developing roller shaft  32  is made of metal or a resin having electrical conductivity. The developing roller body  31  is fixed to the developing roller shaft  32  so as not to rotate relative to the developing roller shaft  32 . With this configuration, the developing roller body  31  is rotatable together with the developing roller shaft  32 . The developing roller  30  (i.e., the developing roller body  31 ) is at least partially exposed to the outside of the casing  10 . That is, at least a part of an outer circumferential surface of the developing roller  30  is exposed to the outside of the casing  10 . More specifically, the one end portion of an outer circumferential surface of the developing roller body  31  in the second direction is exposed to the outside of the casing  10  through the opening  10 C. The other end portion of the outer circumferential surface of the developing roller body  31  in the second direction is positioned inside the casing  10 . That is, the other end portion of the outer circumferential surface of the developing roller body  31  in the second direction is not exposed to the outside of the casing  10 . 
     The developing cartridge  1  further includes a developing electrode  33 . The developing electrode  33  is positioned at one end of the developing roller shaft  32  in the first direction. Here, the developing roller shaft  32  to which the developing electrode  33  is provided is rotatably attached to a bearing (not illustrated) of the casing  10 . The bearing may be integrally formed at the casing  10 , or may be separately formed from the casing  10 . The developing electrode  33  is positioned at the first outer surface  11 . The developing electrode  33  is electrically connected to the developing roller shaft  32  of the developing roller  30 . The developing electrode  33  is an electrode for applying a developing bias to the developing roller  30 . The developing electrode  33  is positioned closer to the developing roller  30  than the shaft  61  and a first cam  62  of a separation member  60  (described later) are to the developing roller  30  in the second direction. 
     A developing roller gear (not illustrated) is coupled to another end portion of the developing roller shaft  32  in the first direction. The developing roller gear is positioned at the second outer surface  12 . The developing roller shaft  32  is fixed to the developing roller gear so as not to rotate relative to the developing roller gear. When the developing roller gear rotates, the developing roller shaft  32  also rotates, thereby causing rotation of the developing roller body  31  together with the developing roller shaft  32 . 
     Incidentally, the developing roller shaft  32  may not extend through the developing roller body  31  in the first direction. For example, each of a pair of developing roller shafts  32  may extend in the first direction from each end portion of the developing roller body  31  in the first direction. 
     The developing cartridge  1  further includes a supply roller (not illustrated). The supply roller is disposed inside the container  10 A at a position between the developing roller  30  and the agitator  20 . The supply roller is rotatable about a rotational axis extending in the first direction. When the developing cartridge  1  receives a driving force, the developer is supplied from the container  10 A of the casing  10  to the outer circumferential surface of the developing roller  30  (i.e., an outer circumferential surface of the developing roller body  31 ) through the supply roller. At this time, the developer is triboelectric charged between the supply roller and the developing roller  30 . In the meantime, a developing bias is applied to the developing roller shaft  32  of the developing roller  30 . Accordingly, the developer is attracted to the outer circumferential surface of the developing roller body  31  by the electrostatic force generated between the developing roller shaft  32  and the developer. 
     The developing cartridge  1  further includes a layer-thickness regulation blade (not illustrated). The layer-thickness regulation blade regulates a thickness of a layer of the developer supplied onto the outer circumferential surface of the developing roller body  31  so that the thickness of the layer of the developer is formed to a constant thickness. The developer on the outer circumferential surface of the developing roller body  31  is then supplied to the photosensitive drum  21  (described later, see  FIG.  11   ) of the drawer  2 . At this time, the developer is transferred from the developing roller body  31  to the photosensitive drum  21 , in accordance with an electrostatic latent image formed on the outer circumferential surface of the photosensitive drum  21 . Accordingly, the electrostatic latent image formed on the outer circumferential surface of the photosensitive drum  21  becomes a visible image. 
     As illustrated in  FIGS.  3  and  4   , the developing cartridge  1  further includes a gear portion  40 . The gear portion  40  is positioned at the second outer surface  12  of the casing  10 . The gear portion  40  includes a coupling  41  and the developing roller gear (not illustrated). 
     The coupling  41  is a gear which receives the driving force applied from the main frame  101  of the image forming apparatus  100 . The coupling  41  is rotatable about a rotational axis extending in the first direction. The coupling  41  is positioned closer to the developing roller  30  than the shaft  61 , the first cam  62 , and a second cam  63  of the separation member  60  (described later) are to the developing roller  30  in the second direction. The coupling  41  has a coupling hole  411  recessed in the first direction. When the developing cartridge  1  attached to the slot  2 A of the drawer  2  is attached to the main frame  101  of the image forming apparatus  100 , a drive shaft (not illustrated) of the image forming apparatus  100  is inserted into the coupling hole  411 . Thus, the drive shaft and the coupling  41  are coupled with each other so that relative rotation between the drive shaft and the coupling  41  is prevented. Accordingly, when the drive shaft rotates, the coupling  41  also rotates. Further, as the coupling  41  rotates, a supply shaft connected to the supply roller (not illustrated) and the developing roller gear rotate. By this rotation, the supply roller rotates together with the supply shaft, and the developing roller  30  rotates together with the developing roller gear. The rotation of the coupling  41  also causes rotation of the agitator  20  through another gear (not illustrated). 
     The image forming apparatus  100  has a contact state and a separation state. In the contact state of the image forming apparatus  100 , the developing roller  30  and the photosensitive drum  21  of the drawer  2  are in contact with each other in a state where the developing cartridge  1  is attached to the slot  2 A of the drawer  2 . In the separation state of the image forming apparatus  100 , the developing roller  30  and the photosensitive drum  21  of the drawer  2  are separated from each other. At the time of attachment of the developing cartridge  1  to the slot  2 A of the drawer  2 , the image forming apparatus  100  is in the contact state. 
     The developing cartridge  1  further includes the separation member  60 . The separation member  60  is a member for switching a state of the image forming apparatus  100  between the contact state and the separation state. In the present embodiment, when the image forming apparatus  100  is switched from the contact state to the separation state, the developing roller  30  moves away from the photosensitive drum  21  in the second direction which is a separation direction of the developing roller  30  from the photosensitive drum  21 . 
     The separation member  60  is disposed at the lid  10 B. The separation member  60  is movable in the first direction relative to the casing  10  and the developing roller  30 . In addition, the separation member  60  is movable in the second direction together with the casing  10  and the developing roller  30 . 
       FIG.  6    is an exploded perspective view of the separation member  60 . Of the casing  10 , only the lid  10 B at which the separation member  60  is disposed is illustrated in  FIG.  6   .  FIG.  7    is an exploded enlarged view of the shaft  61  and the first cam  62  in the separation member  60 .  FIGS.  8  and  9    are views for description of movement of the separation member  60  in the first direction relative to the casing  10  and the developing roller  30 .  FIG.  10    is a plan view of the developing cartridge  1  as viewed in the third direction. Hereinafter, the separation member  60  will be described with reference to  FIGS.  2  through  10   . 
     The separation member  60  includes the shaft  61  that extends along an axis (i.e., a second axis) extending in the first direction. The shaft  61  has a circular columnar shape. The shaft  61 , however, may have a rectangular columnar shape. The lid  10 B has a groove  10 B 1 , a hole  10 B 4 , and a hole  10 B 5  each penetrating the lid  10 B in the first direction. Each of the groove  10 B 1 , the hole  10 B 4 , and the hole  10 B 5  has a diameter greater than a diameter of the shaft  61 . The shaft  61  is inserted through the groove  10 B 1 , the hole  10 B 4 , and the hole  10 B 5 . The shaft  61  inserted into the groove  10 B 1 , the hole  10 B 4 , and the hole  10 B 5  is movable in the first direction relative to the lid  10 B of the casing  10  between a first position (a position illustrated in  FIG.  8   ) and a second position (a position illustrated in  FIG.  9   ). The shaft  61  in the second position is closer to the first outer surface  11  than the shaft  61  in the first position is to the first outer surface  11 . Note that, while the lid  10 B has two holes (i.e., the hole  10 B 4  and the hole  10 B 5 ) in the present embodiment, the lid  10 B may have at least one hole as long as the lid  10 B can movably support the shaft  61 . 
     Preferably, the shaft  61  is made of material having rigidity. For example, the shaft  61  is made of iron. Alternatively, the shaft  61  may be made of resin. 
     In the present embodiment, the casing  10  includes ring-shaped portions  10 B 2  and  10 B 3 . The ring-shaped portion  10 B 2  is formed at one end portion of the lid  10 B in the first direction, while the ring-shaped portion  10 B 3  is formed at another end portion of the lid  10 B in the first direction. Both the ring-shaped portions  10 B 2  and  10 B 3  are integrally formed at the lid  10 B. The through-hole penetrating the ring-shaped portion  10 B 2  is the hole  10 B 4 , and the through-hole penetrating the ring-shaped portion  10 B 3  is the hole  10 B 5 . The groove  10 B 1  formed along the first direction are exposed between the ring-shaped portion  10 B 2  and the ring-shaped portion  10 B 3 . That is, the shaft  61  inserted into the groove  10 B 1 , the hole  10 B 4 , and the hole  10 B 5  is exposed from the lid  10 B at a position between the ring-shaped portion  10 B 2  and the ring-shaped portion  10 B 3 . Since the shaft  61  has rigidity, a portion of the shaft  61  exposed from the lid  10 B will not be bent toward the second direction or the third direction (i.e., directions other than the first direction). 
     Incidentally, only one ring-shaped portion may be formed at the lid  10 B. Alternatively, an additional ring-shaped portion(s) may be disposed between the ring-shaped portions  10 B 2  and  10 B 3 . Although the shaft  61  is exposed at a position between the ring-shaped portions  10 B 2  and  10 B 3  in the first direction in the present embodiment, the shaft  61  may not be exposed from the lid  10 B. That is, the shaft  61  may be accommodated inside the lid  10 B. 
     As described above, the shaft  61  is supported by the lid  10 B so as to be movable in the first direction along the second axis. Accordingly, the shaft  61  can be easily disposed at the casing  10 . 
     The first cam  62  is disposed at one end portion  61 A of the shaft  61  in the first direction. The first cam  62  is made of rubber or resin, for example. As illustrated in  FIG.  7   , the first cam  62  has a hole  62 A penetrating the first cam  62  in the first direction. The one end portion  61 A of the shaft  61  has a diameter smaller than a diameter of a portion of the shaft  61  other than the one end portion  61 A. The one end portion  61 A of the shaft  61  is inserted into the hole  62 A. The one end portion  61 A inserted into the hole  62 A has a distal end exposed from the first cam  62  in the first direction, and a retaining ring  61 B is attached to the exposed distal end of the one end portion  61 A. With this configuration, the first cam  62  is fixed to the one end portion  61 A of the shaft  61 . Alternatively, the first cam  62  may be adhesively fixed to the shaft  61 . 
     The first cam  62  has a first inclined surface  621  that is non-parallel with the second axis. In the present embodiment, the first inclined surface  621  is positioned at a portion of a peripheral surface of the shaft  61  as illustrated in  FIG.  5   . More specifically, the first inclined surface  621  is positioned at one end portion of the shaft  61  in the second direction. The one end portion of the shaft in the second direction is closer to the developing roller  30  than another end portion of the shaft  61  in the second direction is to the developing roller  30 . The first cam  62  further has a contact surface  622  that faces the lid  10 B. The contact surface  622  is disposed at another portion of the peripheral surface of the shaft  61 , that is different from the portion of the peripheral surface at which the first inclined surface  621  is positioned. In other words, the contact surface  622  faces the casing  10 , i.e., an outer surface of the casing  10 . Since the contact surface  622  faces the lid  10 B, even if the first cam  62  tries to rotate about the shaft  61 , the contact surface  622  contacts the lid  10 B, thereby preventing rotation of the first cam  62 . Although the first inclined surface  621  is disposed at a portion of the peripheral surface of the shaft  61  in the present embodiment, the first inclined surface  621  may be disposed at the whole of the peripheral surface of the shaft  61 . 
     The first inclined surface  621  is inclined relative to the shaft  61  extending in the first direction and angled relative to the second axis. In other words, the first inclined surface  621  is inclined relative to a direction connecting the one end portion of the outer circumferential surface of the developing roller  30  and the other end portion of the outer circumferential surface of the developing roller  30 . An angle between the first inclined surface  621  and the first direction is greater than or equal to 43 degrees and smaller than or equal to 47 degrees. More preferably, the angle between the first inclined surface  621  and the first direction is about 45 degrees. 
     The first cam  62 , i.e., the first inclined surface  621  is positioned at the first outer surface  11  of the casing  10 . As the first inclined surface  621  extends in a direction away from the first outer surface  11  in the first direction, the first inclined surface  621  extends away from the developing roller  30  in the second direction. That is, the first inclined surface  621  is formed such that a distance between the shaft  61  (i.e., the second axis) and the first inclined surface  621  in a radial direction of the shaft  61  (i.e., the second direction) increases in a direction from the one end portion  61 A of the shaft  61  in the first direction toward the other end portion of the shaft  61  in the first direction. In other words, the first inclined surface  621  is inclined relative to the first direction such that the distance between the first inclined surface  621  and the shaft  61  in a direction perpendicular to the first axis increases from the one end portion  61 A of the shaft  61  in the first direction to the other end portion of the shaft  61  in the first direction. Further in other words, the first inclined surface  621  is inclined relative to the first direction such that a distance between the first inclined surface  621  and the developing roller  30  in the second direction increases or decreases relative to the casing  10  in the first direction. Further in other words, the first inclined surface  621  is inclined relative to the first direction such that one end of the first inclined surface  621  in the first direction is closer to the shaft  61  than another end of the first inclined surface  621  in the first direction is to the shaft  61  in the second direction. The first inclined surface  621  is inclined relative to the shaft  61  by an acute angle. 
     The first cam  62  is formed like the half of a cone centered on the second axis. In other words, the first cam  62  has a portion of a circumferential surface of the cone serving as the first inclined surface  621 . 
     Note that the first cam  62  may have a pyramid shape instead of a cone shape. In this case, the second axis passes through a vertex and the center of a bottom surface of the pyramid, and a portion of a lateral surface of the pyramid serves as the first inclined surface  621 . Further, while the first inclined surface  621  is smoothly inclined relative to the shaft  61  in the present embodiment, the first inclined surface  621  may have protrusions and recessed portions, such as steps. Alternatively, the first inclined surface  621  may be curved. 
     The second cam  63  is disposed at another end portion of the shaft  61  in the first direction. The second cam  63  is made of rubber or resin, for example. Similar to the first cam  62  described with reference to  FIG.  7   , the second cam  63  is fixed to the other end portion of the shaft  61  in the first direction. 
     The second cam  63  has a second inclined surface  631  that is non-parallel with the second axis. In the present embodiment, the second inclined surface  631  is positioned at the whole peripheral surface of the shaft  61 , as illustrated in  FIG.  4   . Incidentally, the second inclined surface  631  may be disposed at a portion of the peripheral surface of the shaft  61 . In this case, the second inclined surface  631  is positioned at the one end portion of the shaft  61  in the second direction, i.e., the end portion positioned closer to the developing roller  30  than the other end portion to the developing roller  30 . 
     The second inclined surface  631  is inclined relative to the shaft  61  that extends in the first direction and angled relative to the second axis. In other words, the second inclined surface  631  is inclined relative to the direction connecting the one end portion of the outer circumferential surface of the developing roller  30  and the another end portion of the outer circumferential surface of the developing roller  30 . An angle between the second inclined surface  631  and the first direction is greater than or equal to 43 degrees and smaller than or equal to 47 degrees. More preferably, the angle between the second inclined surface  631  and the first direction is about 45 degrees. 
     The second inclined surface  631  is formed such that a distance between the shaft  61  (i.e., the second axis) and the second inclined surface  631  in the radial direction of the shaft  61  (i.e., the second direction) increases in the direction from the one end portion  61 A of the shaft  61  in the first direction to the other end portion of the shaft  61  in the first direction. In other words, the second inclined surface  631  is inclined relative to the first direction such that the distance between the second inclined surface  631  and the shaft  61  in a direction perpendicular to the first axis increases from the one end portion  61 A of the shaft  61  in the first direction to the other end portion of the shaft  61  in the first direction. Further in other words, the second inclined surface  631  is inclined relative to the first direction such that a distance between the second inclined surface  631  and the developing roller  30  in the second direction increases or decreases relative to the casing  10  in the first direction. Further in other words, the second inclined surface  631  is inclined relative to the first direction such that one end of the second inclined surface  631  in the first direction is closer to the shaft  61  than another end of the second inclined surface  631  in the first direction is to the shaft  61  in the second direction. The second inclined surface  631  is inclined relative to the shaft  61  by an acute angle. That is, the first inclined surface  621  of the first cam  62  and the second inclined surface  631  of the second cam  63  are inclined in the same direction relative to the first direction. 
     A radial distance from the second axis to the second inclined surface  631  increases as a distance from the first inclined surface  621  to the second inclined surface  631  increases, and a radial distance from the second axis to the first inclined surface  621  decreases as a distance from the first inclined surface  621  to the second inclined surface  631  increases. 
     The second cam  63  has a cone shape centered on the second axis. In other words, the second cam  63  has a portion of a circumferential surface of the cone serving as the second inclined surface  631 . 
     The second cam  63  may have a pyramid shape, not a cone shape. In this case, the second axis passes through a vertex and the center of a bottom surface of the pyramid, and a portion of a lateral surface of the pyramid serves as the second inclined surface  631 . In the present embodiment, the second inclined surface  631  is smoothly inclined relative to the shaft  61 . However, the second inclined surface  631  may have protrusions or recessed portions, such as steps. Alternatively, the second inclined surface  631  may be curved. 
     As illustrated in  FIGS.  8  and  9   , both the first cam  62  and the second cam  63  are movable in the first direction together with the shaft  61 . That is, both the first cam  62  and the second cam  63  are axially movable together with the shaft  61  along the second axis in response to axial movement of the shaft  61  in the first direction. When the shaft  61  moves from the first position to the second position in the first direction, the second cam  63  approaches the lid  10 B, and the first cam  62  recedes from the lid  10 B. When the shaft  61  moves from the second position to the first position in the first direction, the second cam  63  recedes from the lid  10 B, and the first cam  62  approaches the lid  10 B. In other words, when the shaft  61  moves from the first position to the second position in the first direction, the second cam  63  approaches the casing  10 , and the first cam  62  moves away from the casing  10 . When the shaft  61  moves from the second position to the first position in the first direction, the second cam  63  moves away from the casing  10 , and the first cam  62  approaches the casing  10 . 
     In the present embodiment, the contact surface  622  of the first cam  62  faces the lid  10 B, and this configuration prevents the first cam  62  from rotating. Accordingly, the shaft  61  to which the first cam  62  is fixed, and the second cam  63  fixed to the shaft  61  are also not rotatable relative to the lid  10 B. That is, the shaft  61  inserted through the hole  10 B 5  and the hole  10 B 4  is not rotatable about the second axis extending in the first direction relative to the lid  10 B of the casing  10 . However, the shaft  61  may be rotatable about the second axis extending in the first direction relative to the lid  10 B. In a case where the shaft  61  is configured so as to be rotatable relative to the first cam  62  and the second cam  63 , only the shaft  61  rotates relative to the lid  10 B, the first cam  62  and the second cam  63 , and the first cam  62  and the second cam  63  do not rotate. Alternatively, the shaft  61  may be rotatable about the second axis together with the first cam  62  and the second cam  63 . 
     The separation member  60  further includes a coil spring  64 . The coil spring  64  is positioned at the other end portion of the shaft  61  in the first direction. Specifically, the shaft  61  is inserted into the coil spring  64 . The coil spring  64  is positioned between the second cam  63  and the lid  10 B in the first direction. One end of the coil spring  64  in the first direction is in contact with the lid  10 B through, for example, a washer  65 . Another end of the coil spring  64  in the first direction is in contact with the second cam  63 . That is, the one end of the coil spring  64  is connected to the casing  10 , while the another end of the coil spring  64  is connected to the second inclined surface  631 . The coil spring  64  is covered with a cover  66  in a circumferential direction of the shaft  61 . Although the coil spring  64  is connected to the shaft  61  through the second cam  63 , the coil spring  64  may be directly connected to the shaft  61 . 
     The coil spring  64  is an elastic member configured to extend and contract in the first direction between a first length and a second length shorter than the first length. As will be described later in detail, the second cam  63  is pressed by a pressing force applied in a direction from the other end portion of the shaft  61  to the one end portion  61 A of the shaft  61  in the first direction. Accordingly, the shaft  61  moves from the first position illustrated in  FIG.  8    to the second position illustrated in  FIG.  9    together with the first cam  62  and the second cam  63 . When the shaft  61  moves from the first position to the second position, the coil spring  64  is compressed from the first length to the second length. When the pressing force applied to the second cam  63  is released, the coil spring  64  is restored from the second length to the first length due to a restoring force of the coil spring  64 , whereby the shaft  61  moves back, from the second position to the first position, together with the first cam  62  and the second cam  63 . In this way, the shaft  61 , the first cam  62 , and the second cam  63  are movable in the first direction relative to the casing  10  due to the pressing force applied in the first direction and the elastic force (restoring force) of the coil spring  64 . 
     &lt;1.3. Drawer&gt; 
       FIG.  11    is a perspective view of the drawer  2 .  FIG.  12    is a plan view of the drawer  2  as viewed in the third direction.  FIG.  13    is a perspective view of the drawer  2  and the developing cartridges  1 , illustrating a state where the developing cartridges  1  are attached to the corresponding slots  2 A of the drawer  2 .  FIG.  14    is a plan view of the drawer  2  and the developing cartridges  1  as viewed in the third direction, and illustrating the state where the developing cartridges  1  are attached to the corresponding slots  2 A of the drawer  2 .  FIG.  15    is a plan view of the drawer  2  and the developing cartridges  1  as viewed in the first direction, and illustrating the state where the developing cartridges  1  are attached to the corresponding slots  2 A of the drawer  2 . 
     The drawer  2  includes a frame  200 . The frame  200  includes the four slots  2 A. The developing cartridges  1  are respectively attachable to the corresponding slots  2 A. The drawer  2  also includes the photosensitive drums  21 . Each of the photosensitive drums  21  is disposed corresponding to each of the four slots  2 A. Each of the photosensitive drums  21  is rotatable about the rotational axis (the drum axis) extending in the first direction. In a state where each developing cartridge  1  is attached to the corresponding slot  2 A, the frame  200  movably supports the separation member  60  of each developing cartridge  1 . Each of the developing cartridges  1  is attachable to the corresponding slot  2 A of the drawer  2  such that the outer circumferential surface of the developing roller  30  faces the outer circumferential surface of the photosensitive drum  21 . More specifically, each of the developing cartridge  1  is attachable to the corresponding slot  2 A of the drawer  2  in a state where the outer circumferential surface of the developing roller  30  contacts the outer circumferential surface of the photosensitive drum  21 . 
     Note that the drawer  2  includes a conventional (well-known) urging member. In a state where each developing cartridge  1  is attached to the slot  2 A, the developing roller  30  of each developing cartridge  1  and the corresponding photosensitive drum  21  are in contact with each other in the second direction due to an urging force applied by the conventional urging member. The drawer  2  which the developing cartridge  1  has been attached to each slot  2 A is attached to the main frame  101  (see  FIG.  1   ). 
     In a state where each developing cartridge  1  is attached to the frame  200  of the drawer  2 , the frame  200  is configured to move the developing roller  30  of the attached developing cartridge  1  in the second direction. That is, in response to movement in the first direction of the separation member  60  in a state where the outer circumferential surface of the developing roller  30  is in contact with the outer circumferential surface of the photosensitive drum  21 , the frame  200  can move the developing roller  30  in the second direction in which the developing roller  30  moves away from the corresponding photosensitive drum  21 . 
     The frame  200  of the drawer  2  includes a first side frame  201  and a second side frame  202 . The first side frame  201  and the second side frame  202  are spaced apart from each other in the first direction. The four photosensitive drums  21  are disposed at positions between the first side frame  201  and the second side frame  202  in the first direction. When the developing cartridges  1  are attached to the slots  2 A, the developing cartridges  1  are positioned between the first side frame  201  and the second side frame  202  in the first direction. In this state, the first outer surface  11  of each developing cartridge  1  faces the first side frame  201  in the first direction, and the second outer surface  12  of each developing cartridge  1  faces the second side frame  202  in the first direction. 
     The first side frame  201  has a first recessed portion  201 A formed corresponding to each of the four slots  2 A. Each of the first recessed portions  201 A penetrates the first side frame  201  in the first direction and recessed toward the corresponding photosensitive drum  21  in the third direction. In a state where each developing cartridge  1  is attached to the corresponding slot  2 A of the drawer  2 , the IC chip  51  of each developing cartridge  1  covered with a cover  45  is positioned in the corresponding first recessed portion  201 A, as illustrated in  FIGS.  13  and  14   . 
     The second side frame  202  has second recessed portions  202 A. Similar to the first recessed portions  201 A, each second recessed portion  202 A is formed corresponding to each slot  2 A. Each of the second recessed portions  202 A penetrates the second side frame  202  in the first direction to expose a portion of the developing cartridge  1  to the outside of the drawer  2 , and is open toward a direction away from the corresponding photosensitive drum  21  in the third direction. In a state where each developing cartridge  1  is attached to the corresponding slot  2 A of the drawer  2 , the second cam  63  of each developing cartridge  1  is positioned in the corresponding second recessed portions  202 A, as illustrated in  FIGS.  13  through  15   . 
     The second side frame  202  further has through-holes  202 B. Each through-holes  202 B is formed corresponding to each of the slots  2 A. Each of the through-holes  202 B penetrates the second side frame  202  in the first direction. In a state where each developing cartridge  1  is attached to the corresponding slot  2 A of the drawer  2 , the coupling hole  411  of the coupling  41  of each developing cartridge  1  is exposed from the corresponding through-hole  202 B, as illustrated in  FIGS.  13  through  15   . The drive shaft of the image forming apparatus  100  is inserted into each coupling hole  411  through the corresponding through-hole  202 B. Accordingly, the drive shafts and the corresponding couplings  41  are coupled with each other so as not to rotate relative to each other. 
     The drawer  2  has a first receiving surface  22  and a second receiving surface  23  for each slot  2 A. The first receiving surface  22  is spaced apart from the second receiving surface  23  in the first direction. That is, the first receiving surface  22  is positioned at one end portion of each slot  2 A in the first direction, while the second receiving surface  23  is positioned at another end portion of each slot  2 A in the first direction. 
     Each of the first receiving surface  22  is positioned at a surface of the first side frame  201  that faces the second side frame  202 . The first receiving surface  22  is inclined relative to the first direction. More specifically, the first receiving surface  22  is disposed so as to face the first cam  62  of the developing cartridge  1  attached to the slot  2 A of the drawer  2  in the second direction. The first receiving surface  22  contacts the first inclined surface  621  of the first cam  62  as illustrated in  FIG.  14   . The first receiving surface  22  is formed such that a distance between the first receiving surface  22  and the developing cartridge  1  in the second direction increases in a direction away from the first side frame  201  in the first direction (i.e., a direction from the first side frame  201  to the second side frame  202  in the first direction). 
     The second receiving surface  23  is positioned at each second recessed portion  202 A formed at the second side frame  202 . The second receiving surface  23  is inclined relative to the first direction in the same direction as the first receiving surface  22 . More specifically, the second receiving surface  23  is disposed such that the second receiving surface  23  faces the second cam  63  of the developing cartridge  1  attached to each slot  2 A of the drawer  2 . The second receiving surface  23  contacts the second inclined surface  631  of the second cam  63  as illustrated in  FIG.  14   . The second receiving surface  23  is formed such that a distance between the second receiving surface  23  and the developing cartridge  1  in the second direction increases in the direction away from the first side frame  201  in the first direction (i.e., a direction from the first side frame  201  to the second side frame  202  in the first direction). 
     As will be described below in detail, when the separation member  60  of the developing cartridge  1  attached to each slot  2 A moves in the first direction, each of the first receiving surface  22  and the second receiving surface  23  is configured to guide (move) the developing cartridge  1  in the second direction relative to the frame  200  while the first inclined surface  621  is in contact with the first receiving surface  22  and the second inclined surface  631  is in contact with the second receiving surface  23 , respectively. 
     &lt;1.4. Separation Movement by Separation Member  60 &gt; 
     Next, movement of the developing cartridge according to the present embodiment in the image forming apparatus  100  when the image forming apparatus  100  is switched between the contact state and the separation state will be described. 
       FIGS.  16 A and  16 B  are views for description of separation movement of the developing cartridge  1  performed by the separation member  60 .  FIG.  16 A  illustrates the developing cartridge  1  in the contact state of the image forming apparatus  100 .  FIG.  16 B  illustrates the developing cartridge  1  in the separation state of the image forming apparatus  100 .  FIG.  17    is a perspective view of the developing cartridge  1  and the photosensitive drum  21 , and illustrating a state where the developing roller  30  and the photosensitive drum  21  are in contact with each other.  FIG.  18    is a perspective view of the developing cartridge  1  and the photosensitive drum  21 , and illustrating a state where the developing roller  30  and the photosensitive drum  21  are separated from each other. 
     When each developing cartridge  1  is attached to the corresponding slot  2 A of the drawer  2 , the developing roller  30  of each developing cartridge  1  contacts the corresponding photosensitive drum  21 , as illustrated in  FIG.  17   . That is, the image forming apparatus  100  is in the contact state. In this contact state of the image forming apparatus  100 , as illustrated in  FIG.  16 A , the first inclined surface  621  of the first cam  62  is in contact with the first receiving surface  22 , and the second inclined surface  631  of the second cam  63  is in contact with the second receiving surface  23 . In other words, the first inclined surface  621  and the second inclined surface  631  engages the frame  200 . 
     More precisely, at the time of attachment of the developing cartridge  1  to the drawer  2 , the first inclined surface  621  is out of contact with the first receiving surface  22 , and the second inclined surface  631  is out of contact with the second receiving surface  23 . Then, as the developing cartridge  1  moves by a predetermined distance in the first direction, the first inclined surface  621  is brought into contact with the first receiving surface  22 , and the second inclined surface  631  is brought into contact with the second receiving surface  23 . Incidentally, the first inclined surface  621  may contact the first receiving surface  22  and the second inclined surface  631  may contact the second receiving surface  23  at the time of attachment of the developing cartridge  1  to the drawer  2 . 
     The first inclined surface  621  extends radially outward of the shaft  61  in the direction from the first cam  62  toward the second cam  63  in the first direction. The first receiving surface  22  contacts a portion of the first inclined surface  621 . A distance between the portion of the first inclined surface  621  and the shaft  61  in the radial direction of the shaft  61  is smaller than a distance between the remaining portion of the first inclined surface  621  and the shaft  61  in the radial direction of the shaft  61 . Similarly, the second inclined surface  631  extends radially outward of the shaft  61  in the direction from the first cam  62  toward the second cam  63  in the first direction. The second receiving surface  23  contacts a portion of the second inclined surface  631 . A distance between the portion of the second inclined surface  631  and the shaft  61  in the radial direction of the shaft  61  is smaller than a distance between the remaining portion of the second inclined surface  631  and the shaft  61  in the radial direction of the shaft  61 . 
     As described above, each of the first cam  62  and the second cam  63  has a cone shape. Thus, even if the shaft  61  rotates about the second axis, the first inclined surface  621  and the second inclined surface  631  can reliably contact (engage) the first receiving surface  22  and the second receiving surface  23 , respectively. 
     The image forming apparatus  100  includes a driving unit  103  and a pressing member  104 . The driving unit  103  is configured to move the pressing member  104  in the first direction. The driving unit  103  is, for example, a motor. The pressing member  104  has a circular columnar shape or a rectangular columnar shape and extends in the first direction. The pressing member  104  is movable in the first direction between a contact position and a non-contact position through the second recessed portion  202 A formed in the second side frame  202  to apply the pressing force from the outside of the frame  200  to the second cam  63 . The pressing member  104  in the contact position contacts the second cam  63  of the developing cartridge  1  attached to slot  2 A of the drawer  2 , while the pressing member  104  in the non-contact position does not contact the second cam  63 . 
     In order to separate the developing roller  30  from the photosensitive drum  21 , the driving unit  103  moves the pressing member  104  toward the direction from the second cam  63  to the first cam  62  in the first direction. Accordingly, the second cam  63  is pressed by the pressing member  104  toward the direction from the second cam  63  to the first cam  62  in the first direction. When the second cam  63  receives pressing force from the pressing member  104  through the second recessed portion  202 A, the shaft  61 , the first cam  62 , and the second cam  63  move toward the direction from the second cam  63  to the first cam  62  in the first direction relative to the casing  10  and the developing roller  30 . 
     In this instance, the first inclined surface  621  of the first cam  62  moves toward the direction from the second cam  63  to the first cam  62  in the first direction while maintaining contact with the first receiving surface  22 . As described above, the first inclined surface  621  is formed so as to extend radially outward of the shaft  61  in the direction from the first cam  62  to the second cam  63 . Therefore, when the first cam  62  moves toward the direction from the second cam  63  to the first cam  62  in the first direction, a portion of the first inclined surface  621  contacting the first receiving surface  22  recedes from the shaft  61  in the radial direction of the shaft  61 . The first inclined surface  621  and the first receiving surface  22  face each other in the second direction. That is, when the first inclined surface  621  moves toward the direction from the second cam  63  to the first cam  62  in the first direction, the first inclined surface  621  also moves toward a direction away from the first receiving surface  22  in the second direction, as illustrated in  FIG.  16 B . 
     Similar to the first inclined surface  621 , the second inclined surface  631  of the second cam  63  moves toward the direction from the second cam  63  to the first cam  62  in the first direction while contacting the second receiving surface  23 . As described above, the second inclined surface  631  is formed such that the second inclined surface  631  extends radially outward of the shaft  61  in the direction from the first cam  62  to the second cam  63 . Accordingly, when the second cam  63  moves toward the direction from the second cam  63  to the first cam  62  in the first direction, a portion of the second inclined surface  631  contacting the second receiving surface  23  comes away from the shaft  61  in the radial direction of the shaft  61 . The second inclined surface  631  and the second receiving surface  23  face each other in the second direction. That is, when the second inclined surface  631  moves toward the direction from the second cam  63  to the first cam  62  in the first direction, the second inclined surface  631  also moves toward a direction away from the second receiving surface  23  in the second direction, as illustrated in  FIG.  16 B . 
     As the first cam  62  and the second cam  63  move in the second direction while moving in the first direction, the shaft  61  also moves in the same manner. When the shaft  61 , the first cam  62 , and the second cam  63  move in the second direction, the casing  10  and the developing roller  30  also move in the second direction, as illustrated in  FIG.  16 B . In other words, the first cam  62  and the second cam  63  are movable together with the casing  10  and the developing roller  30  in a direction non-parallel with the second axis in response to the axial movement of the shaft  61  along the second axis. Further in other words, each of the first inclined surface  621  and the second inclined surface  631  provides a camming movement in response to the axial movement of the shaft  61  along the second axis. This movement causes the developing roller  30  to be separated from the photosensitive drum  21  in the second direction against the urging force of the conventional urging member (not illustrated) provided in the drawer  2 , as illustrated in  FIG.  18   . Accordingly, the image forming apparatus  100  is brought into the separation state. 
     The movement of the shaft  61 , the first cam  62 , and the second cam  63  in the first direction cause expansion and contraction of the coil spring  64  in the first direction. As described above, the coil spring  64  has the first length when the shaft  61  is positioned at the first position, as illustrated in  FIG.  8   . To the contrary, the coil spring  64  has the second length shorter than the first length when the shaft  61  is positioned at the second position, as illustrated in  FIG.  9   . The coil spring  64  is compressed from the first length to the second length due to the pressing force of the pressing member  104 , and extends from the second length to the first length when the pressing force acting on the separation member  60  by the pressing member  104  is released. 
     When the shaft  61  moves back from the second position to the first position together with the first cam  62  and the second cam  63 , a portion of the first inclined surface  621  contacting the first receiving surface  22  approaches the shaft  61  in the second direction due to mechanism which is reverse of the mechanism described above. Similarly, a portion of the second inclined surface  631  contacting the second receiving surface  23  approaches the shaft  61  in the second direction. These movements of the shaft  61 , the first cam  62 , and the second cam  63  cause the casing  10  and the developing roller  30  to move in the second direction, thereby allowing the developing roller  30  to approach the photosensitive drum  21  in the second direction. As a result, the outer circumferential surface of the developing roller  30  comes into contact with the outer circumferential surface of the photosensitive drum  21  due to the urging force of the conventional urging member (not illustrated) provided in the drawer  2 . Thus, the image forming apparatus  100  is brought into the contact state. 
     &lt;1.5. Advantageous Effects of First Embodiment&gt; 
     In the present embodiment, the first cam  62  and the second cam  63  are disposed at both ends of the shaft  61  in the first direction, respectively. This configuration can prevent one of ends of the casing  10  and the developing roller  30  in the first direction from being inclined while the image forming apparatus  100  is switched between the separation state and the contact state in comparison with a case where only one of the first cam  62  and the second cam  63  is disposed at the shaft  61 . 
     As described above, the pressing force directed in the first direction causes the shaft  61  to move in the first direction relative to the casing  10  and the developing roller  30 . When the first inclined surface  621  contacts the first receiving surface  22  due to the movement of the shaft  61  in the first direction, the first inclined surface  621  moves in the second direction along the first receiving surface  22 . The casing  10  and the developing roller  30  also move in the second direction in accordance with the movement of the first inclined surface  621  in the second direction. With this configuration, the developing cartridge  1  is movable in the second direction by the driving force directed in the first direction, not by driving force acting on both ends of the developing cartridge  1 . In addition, the developing cartridge  1  has the first inclined surface  621  and the shaft  61 . Thus, compared to a case where the drum cartridge includes a shaft, the shaft  61  does not interrupt attachment of the developing cartridge  1  to the slot  2 A and detachment of the developing cartridge  1  from the slot  2 A. 
     Further, when the shaft  61  is to move in the first direction, the driving force from both ends of the shaft  61  in the first direction is not required. That is, the developing cartridge  1  is movable due to the driving force applied from one end of the shaft  61  in the first direction. 
     In the present embodiment, the image forming apparatus  100  further includes a driving source disposed at one side the main frame  101  at which one end of the developing cartridge  1  and the drawer  2  in the first direction is positioned. The driving source is configured to drive the developing roller  30  and the photosensitive drum  21  to rotate. The driving unit  103 , that serves as a driving source used to move the pressing member  104  in the first direction, can be disposed in the vicinity of the driving source. With this arrangement, the driving sources of the image forming apparatus  100  (i.e., the driving unit  103  and the driving source for driving the developing roller  30  and the photosensitive drum  21 ) can be collectively arranged on one side of the developing cartridge  1  and the drawer  2 . Accordingly, downsizing of the image forming apparatus  100  can be realized. Further, since the components for moving the developing cartridge  1  need not be disposed on both ends of the drawer  2  in the first direction, the configuration of the drawer  2  can be simplified, and the drawer  2  can be downsized. 
     2. Second Embodiment 
     Next, a developing cartridge  1  according to a second embodiment will be described with reference to  FIGS.  19  through  20 B , wherein like parts and components are designated with the same reference numerals as those shown in the first embodiment to avoid duplicating description. 
     In the first embodiment, each of the first inclined surface  621  and the second inclined surface  631  is inclined relative to the first direction at a constant angle. To the contrary, in the second embodiment, each of the first inclined surface  621  and the second inclined surface  631  has at least two inclined surfaces defining different angles. Hereinafter, different points of the second embodiment from the first embodiment will be described. 
       FIG.  19    is a plan view of the developing cartridge  1  according to the second embodiment as viewed in the third direction. 
     The first inclined surface  621  of the first cam  62  has a sloped surface  621 A and a sloped surface  621 B. The sloped surface  621 A and the sloped surface  621 B are arrayed with each other in the first direction. The sloped surface  621 A is positioned farther from the second cam  63  than the sloped surface  621 B is from the second cam  63  in the first direction. Further, the sloped surface  621 A provides an inclination relative to the first direction steeper than an inclination of the sloped surface  621 B relative to the first direction. Specifically, the sloped surface  621 A is inclined relative to the first direction to define an acute angle between the sloped surface  621 A and the first direction; the sloped surface  621 B is also inclined relative to the first direction to define an acute angle between the sloped surface  621 B and the first direction; and an angle between the sloped surface  621 A and the first direction is greater than an angle between the sloped surface  621 B and the first direction. 
     The angle between the sloped surface  621 A and the first direction is greater than or equal to 43 degrees and smaller than or equal to 47 degrees. More preferably, the angle between the sloped surface  621 A and the first direction is 45 degrees. The angle between the sloped surface  621 B and the first direction is greater than or equal to 12 degrees and smaller than or equal to 17 degrees. Preferably, the angle between the sloped surface  621 B and the first direction is greater than or equal to 14 degrees and smaller than or equal to 15 degrees. More preferably, the angle between the sloped surface  621 B and the first direction is 14 degrees or 15 degrees. 
     The ratio of a length of the sloped surface  621 A in the first direction to a length of the sloped surface  621 A in the radial direction of the shaft  61  (i.e., the second direction) is, for example, 1:1 (one to one). Further, the ratio of a length of the sloped surface  621 B in the first direction to a length of the sloped surface  621 B in the radial direction of the shaft  61  (i.e., the second direction) is, for example, 4:1 (four to one). 
     The second inclined surface  631  of the second cam  63  has a sloped surface  631 A and a sloped surface  631 B. The sloped surface  631 A and the sloped surface  631 B are arrayed with each other in the first direction. The sloped surface  631 A is positioned closer to the first cam  62  (i.e., the first inclined surface  621 ) than the sloped surface  631 B is to the first cam  62  (i.e., the first inclined surface  621 ) in the first direction. Further, the sloped surface  631 A provides an inclination relative to the first direction steeper than an inclination of the sloped surface  631 B relative to the first direction. Specifically, the sloped surface  631 A is inclined relative to the first direction to define an acute angle between the sloped surface  631 A and the first direction; the sloped surface  631 B is also inclined relative to the first direction to define an acute angle between the sloped surface  631 B and the first direction; and an angle between the sloped surface  631 A and the first direction is greater than an angle between the sloped surface  631 B and the first direction. 
     The angle between the sloped surface  631 A and the first direction is greater than or equal to 43 degrees and smaller than or equal to 47 degrees. More preferably, the angle between the sloped surface  631 A and the first direction is 45 degrees. The angle between the sloped surface  631 B and the first direction is greater than or equal to 12 degrees and smaller than or equal to 17 degrees. Preferably, the angle between the sloped surface  631 B and the first direction is greater than or equal to 14 degrees and smaller than or equal to 15 degrees. More preferably, the angle between the sloped surface  631 B and the first direction is 14 degrees or 15 degrees. 
     The ratio of a length of the sloped surface  631 A in the first direction to a length of the sloped surface  631 A in the radial direction of the shaft  61  (i.e., the second direction) is, for example, 1:1 (one to one). The ratio of a length of the sloped surface  631 B in the first direction to a length of the sloped surface  631 B in the radial direction of the shaft  61  (i.e., the second direction) is, for example, 4:1 (four to one). 
     It is preferable that the sloped surface  621 A and the sloped surface  631 A are inclined relative to the first direction so as to define angles the same as each other. Further, it is also preferable that the sloped surface  621 B and the sloped surface  631 B are inclined relative to the first direction so as to define angles the same as each other. 
     &lt;2.1. Separation Movement by Separation Member  60 &gt; 
     Movement of the developing cartridge  1  according to the second embodiment in the image forming apparatus  100  when the image forming apparatus  100  is switched between the contact state and the separation state will next be described. 
       FIGS.  20 A and  20 B  are views for description of separation movement of the developing cartridge  1  performed by the separation member  60 .  FIG.  20 A  illustrates the developing cartridge  1  in the contact state of the image forming apparatus  100 .  FIG.  20 B  illustrates the developing cartridge  1  in the separation state of the image forming apparatus  100 . 
     In the contact state of the image forming apparatus  100  where the developing roller  30  of the developing cartridge  1  is in contact with the photosensitive drum  21 , the sloped surface  621 A of the first inclined surface  621  contacts the first receiving surface  22  and the sloped surface  631 A of the second inclined surface  631  contacts the second receiving surface  23 , as illustrated in  FIG.  20 A . 
     More precisely, at the time of attachment of the developing cartridge  1  to the drawer  2 , the sloped surface  621 A is separated from the first receiving surface  22 , and the sloped surface  631 A is separated from the second receiving surface  23 . Then, as the developing cartridge  1  moves by a predetermined distance in the first direction, the sloped surface  621 A is brought into contact with the first receiving surface  22 , and the sloped surface  631 A is brought into contact with the second receiving surface  23 . Incidentally, the sloped surface  621 A may contact the first receiving surface  22 , and the sloped surface  631 A may contact the second receiving surface  23  at the time of attachment of the developing cartridge  1  to the drawer  2 . 
     When the second cam  63  is pressed by the pressing member  104  toward the first cam  62  in the first direction, the shaft  61 , the first cam  62 , and the second cam  63  move in the first direction relative to the casing  10  and the developing roller  30 . At this time, the sloped surface  621 A of the first inclined surface  621  moves toward the direction from the second cam  63  to the first cam  62  in the first direction while contacting the first receiving surface  22 . In addition, the sloped surface  631 A of the second inclined surface  631  moves toward the direction from the second cam  63  to the first cam  62  in the first direction while contacting the second receiving surface  23 . Thus, the first inclined surface  621  also moves toward the direction away from the first receiving surface  22  in the second direction, as illustrated in  FIG.  20 B . In addition, the second inclined surface  631  also moves in the direction away from the second receiving surface  23  in the second direction, as illustrated in  FIG.  20 B . Through this movement, the developing roller  30  moves away from the photosensitive drum  21  in the second direction (see  FIG.  18   ). 
     When the shaft  61 , the first cam  62  and the second cam  63  further move toward the direction from the second cam  63  to the first cam  62  in the first direction, the sloped surface  621 B of the first inclined surface  621  contacts the first receiving surface  22  to move toward the direction from the second cam  63  to the first cam  62  in the first direction along the first receiving surface  22 . Further, the sloped surface  631 B of the second inclined surface  631  contacts the second receiving surface  23  to move toward the direction from the second cam  63  to the first cam  62  in the first direction along the second receiving surface  23 . 
     When the shaft  61  moves back from the second position to the first position together with the first cam  62  and the second cam  63 , a portion of the first inclined surface  621  contacting the first receiving surface  22  approaches the shaft  61  in the second direction due to mechanism which is reverse of the mechanism described above. Similarly, a portion of the second inclined surface  631  contacting the second receiving surface  23  approaches the shaft  61  in the second direction. Accordingly, the casing  10  and the developing roller  30  move in the second direction so that the developing roller  30  approaches the photosensitive drum  21  in the second direction. Thus, the image forming apparatus  100  is brought into the contact state. 
     &lt;2.2. Advantageous Effects of Second Embodiment&gt; 
     As described above, the pressing force from the pressing member  104  causes the shaft  61  to move in the first direction relative to the casing  10  and the developing roller  30 . When the first inclined surface  621  contacts the first receiving surface  22  due to the movement of the shaft  61  in the first direction, the first inclined surface  621  moves in the second direction along the first receiving surface  22 . The casing  10  and the developing roller  30  also move in the second direction, in accordance with the movement of the first inclined surface  621  in the second direction. With this configuration, the developing cartridge  1  is movable in the second direction by the driving force directed in the first direction, not by driving force acting on both ends of the developing cartridge  1 . In addition, the developing cartridge  1  has the first inclined surface  621  and the shaft  61 . Thus, compared to a case where the drum cartridge includes a shaft, the shaft  61  does not interrupt attachment of the developing cartridge  1  to the slot  2 A and detachment of the developing cartridge  1  from the slot  2 A. 
     Further, when the shaft  61  is to move in the first direction, the driving force from both ends of the shaft  61  in the first direction is not required. That is, the developing cartridge  1  is movable due to the driving force applied from one end of the shaft  61  in the first direction. 
     Also in the second embodiment, the image forming apparatus  100  further includes a driving source disposed at one side the main frame  101  at which one end of the developing cartridge  1  and the drawer  2  in the first direction is positioned. The driving source is configured to drive the developing roller  30  and the photosensitive drum  21  to rotate. The driving unit  103 , that serves as a driving source used to move the pressing member  104  in the first direction, can be disposed in the vicinity of the driving source. With this arrangement, the driving sources of the image forming apparatus  100  (i.e., the driving unit  103  and the driving source for driving the developing roller  30  and the photosensitive drum  21 ) can be collectively arranged on one side of the developing cartridge  1  and the drawer  2 . Accordingly, downsizing of the image forming apparatus  100  can be realized. Further, since the components for moving the developing cartridge  1  need not be disposed on both ends of the drawer  2  in the first direction, the configuration of the drawer  2  can be simplified, and the drawer  2  can be downsized. 
     The sloped surface  621 A of the first inclined surface  621  that first contacts the first receiving surface  22  during the movement of the first cam  62  toward the direction from the second cam  63  to the first cam  62  in the first direction is steeper than the sloped surface  621 B. Similarly, the sloped surface  631 A of the second inclined surface  631  that first contacts the second receiving surface  23  during the movement of the second cam  63  toward the direction from the second cam  63  to the first cam  62  in the first direction is steeper than the sloped surface  631 B. With this configuration, in the beginning of the movement of the separation member  60  in the first direction, the amount of movement of the separation member  60  in the second direction can be increased. Thus, the developing roller  30  can be separated from the photosensitive drum  21  while reducing amount of movement of the separation member  60  in the first direction. 
     Further, the sloped surface  621 B whose inclination relative to the first direction is smaller than the sloped surface  621 A contacts the first receiving surface  22 , and the sloped surface  631 B whose inclination relative to the first direction is smaller than the sloped surface  631 A contacts the second receiving surface  23 . Accordingly, the separation member  60  can move in the first direction with less amount of movement in the second direction. This configuration can reduce driving load of the pressing member  104 . 
     3. Third Embodiment 
     &lt;3.1. Developing Cartridge&gt; 
     Next, a developing cartridge  1  according to a third embodiment will be described with reference to  FIGS.  21  through  25   , wherein like parts and components are designated with the same reference numerals as those shown in the first and second embodiments to avoid duplicating description. The developing cartridge  1  according to the third embodiment differs from the developing cartridges  1  in the first and second embodiments in that the shape of the casing  10  and the separation member  60  are different from those of in the first and second embodiments. 
       FIG.  21    is a perspective view of the developing cartridge  1  according to the third embodiment.  FIG.  22    is a perspective view of the developing cartridge  1  according to the third embodiment in which a portion of the developing cartridge  1  is exploded. As illustrated in  FIGS.  21  and  22   , the casing  10  of the developing cartridge  1  in the present embodiment includes a first cover  45  and a second cover  46 . The first cover  45  is positioned at one end in the first direction of the casing  10 , while the second cover  46  is positioned at another end in the first direction of the casing  10 . The first cover  45  holds the IC chip  51 . The second cover  46  covers a plurality of gears of the gear portion  40 . 
     The developing cartridge  1  according to the present embodiment also includes the separation member  60 . The separation member  60  is a member for switching a state of the image forming apparatus  100  between the contact state and the separation state. The separation member  60  is disposed at the lid  10 B of the developing cartridge  1 . The separation member  60  is movable in the first direction relative to the casing  10  and the developing roller  30 . In addition, the separation member  60  is movable in the second direction together with the casing  10  and the developing roller  30 . 
     As illustrated in  FIGS.  21  and  22   , the separation member  60  includes a shaft  61 , a first cam  62 , a second cam  63 , and a coil spring  64  as an example of an elastic member. Since the configuration of the shaft  61  is the same as that in the first and second embodiments, description as to the shaft  61  will be omitted. 
     The first cam  62  is positioned at the one end in the first direction of the shaft  61 .  FIG.  23    is a perspective view of the first cam  62 . As illustrated in  FIG.  23   , the first cam  61  has a first inclined surface  621  inclined relative to the shaft  61  that extends in the first direction. The first inclined surface  621  is positioned at only a portion of the peripheral surface of the shaft  61 . In other words, the first inclined surface  621  is provided at only a portion of the peripheral surface in the circumferential direction of the shaft  61 , not the entire portion of the peripheral surface of the shaft  61  centered on the axis of the shaft  61  (i.e., the second axis). With this configuration, a portion of the first cam  62  other than the first inclined surface  621  can be restrained from protruding outward. More specifically, a back surface of the first cam  62  (that is, a surface of the first cam  62  that faces the lid  10 B and the first cover  45 ) can be a flat surface. As a result, a space for positioning the first cover  45  that holds the IC chip  51  can be made larger. 
     The second cam  63  is positioned at the other end in the first direction of the shaft  61 .  FIG.  24    is a perspective view of the second cam  63 . As illustrated in  FIG.  24   , the second cam  63  has a second inclined surface  631  inclined relative to the shaft  61  extending in the first direction. The second inclined surface  631  is positioned at only a portion of the peripheral surface of the shaft  61 . In other words, the second inclined surface  631  is positioned at only a portion of the peripheral surface in the circumferential direction of the shaft  61 , but not the entire portion of the peripheral surface of the shaft  61  centered on the axis of the shaft  61  (i.e., the second axis). This configuration can suppress a portion of the second cam  63  other than the second inclined surface  631  from protruding outward. Specifically, a back surface of the second cam  63  (that is, a surface of the second cam  63  that faces the lid  10 B and the second cover  46 ) can be a flat surface. In this way, a space for positioning the second cover  46  that accommodates the plurality of gears of the gear portion  40  can be made larger. 
     Further, in the present embodiment, the second cam  63  includes a first protrusion  632  and a second protrusion  633 . 
     The first protrusion  632  extends from the axis of the shaft  61  (i.e., the second axis) radially outward and in the third direction toward the developing roller  30 . The first protrusion  632  is positioned closer to the developing roller  30  than the second inclined surface  631  is to the developing roller  30 . However, the first protrusion  632  may extend in a direction different from the direction described above. The first protrusion  632  is movable in the first direction together with the second inclined surface  631  relative to the casing  10 . 
     The first protrusion  632  has a positioning surface  632   a . The positioning surface  632   a  is a surface of the first protrusion  632  that faces in the first direction.  FIG.  25    is a cross-sectional view of a portion in the vicinity of the second cam  63  in a state in which the developing cartridge  1  is attached to the drawer  2 . As illustrated in  FIG.  25   , in a state where the developing cartridge  1  to the drawer  2 , the positioning surface  632   a  is in contact with an inner surface of the second side frame  202  of the drawer  2  in the first direction. This contact between the positioning surface  632   a  and the second side frame  202  causes the coil spring  64  to be slightly compressed in the first direction than that in a state prior to attachment of the developing cartridge  1  to the drawer  2 . That is, by contacting the positioning surface  632   a  with the second side frame  202 , the second cam  63  is positioned relative to the drawer  2  in the first direction. 
     Accordingly, the shaft  61  and the first cam  62  are also positioned relative to the drawer  2  in the first direction. As a result, the first inclined surface  621  and the second inclined surface  631  can be accurately positioned relative to the drawer  2  in the first direction, thereby suppressing deviation in positions in the first direction of the first inclined surface  621  and the second inclined surface  631  relative to the drawer  2 . 
     The second protrusion  633  extends radially outward and away from the developing roller  30  from the axis of the shaft  61  (i.e., the second axis). The second protrusion  633  is positioned farther from the developing roller  30  than the second inclined surface  631  is from the developing roller  30 . In other words, the second protrusion  633  is positioned opposite to the first protrusion  632  with respect to the second inclined surface  631 . However, the second protrusion  633  may extend in a direction other than the direction described above. 
     The second protrusion  633  is movable in the first direction together with the second inclined surface  631  and the first protrusion  632  relative to the casing  10 . Further, the second protrusion  633  is incapable of rotating relative to the second inclined surface  631  and the first protrusion  632 . 
     A distal end portion of the second protrusion  633  is inserted into the second cover  46 . In a case where the second cam  63  tries to rotate about the second axis, the distal end portion of the second protrusion  633  makes contact with an inner surface of the second cover  46 . Consequently, rotation of the second cam  63  about the second axis is stopped, thereby causing rotation of the shaft  61  and the first cam  62  about the second axis to be also stopped. In this way, the second protrusion  633  can restrict the rotations of the shaft  61 , the first cam  62 , and the second cam  63  about the second axis. Therefore, the first inclined surface  621  and the second inclined surface  631  can reliably contact the frame  200  of the drawer  2  despite the fact that both the first inclined surface  621  and the second inclined surface  631  are positioned at only portions of the peripheral surface of the shaft  61 . 
     &lt;3.2. Drawer&gt; 
     Different from the drawer  2  in the first and second embodiments, the drawer  2  according to the third embodiment includes first guide rollers  24  instead of the first receiving surfaces  22 , and second guide rollers  25  instead of the second receiving surfaces  23 . The differences between the drawer  2  in the third embodiment and the drawer  2  in the first and second embodiments will be only described while omitting the duplicating description as to the same components in the drawer  2  among the first to third embodiments. The drawer  2  is an example of a drum cartridge. 
       FIG.  26    is a plan view of the drawer  2  to which the developing cartridges  1  are attached as viewed in the third direction. As illustrated in  FIG.  26   , the frame  200  of the drawer  2  includes a first side frame  201  and a second side frame  202 . In a state where the developing cartridges  1  are attached to the drawer  2 , the first outer surfaces  11  of the developing cartridges  1  face the first side frame  201  in the first direction, and the second outer surfaces  12  of the developing cartridges  1  face the second side frame  202  in the first direction. 
     As indicated by a broken line in an enlarged view in  FIG.  26   , the first side frame  201  includes the first guide rollers  24 . That is, the first guide rollers  24  are positioned at the one end portion in the first direction of the frame  200 . More specifically, of the surface of the first side frame  201  that faces the second side frame  202 , each of the first guide rollers  24  is at a position where the first guide roller  24  faces the first cam  62  of the corresponding developing cartridge  1  attached to the slot  2 A in the second direction. 
       FIG.  27    is an exploded perspective view of the first guide roller  24  and a bearing  26  that holds the first guide roller  24 . As illustrated in  FIG.  27   , the first guide roller  24  has an outer circumferential surface  240 . The outer circumferential surface  240  has a hollow cylindrical shape and extends in the third direction. Both end portions in the third direction of the first guide roller  24  are rotatably supported by the bearing  26 . This configuration enables the first guide roller  24  to rotate about a center axis extending in the third direction. 
     As indicated by a broken line in another enlarged view in  FIG.  26   , the second side frame  202  includes the second guide rollers  25 . In other words, the second guide rollers  25  are positioned at the other end portion in the first direction of the frame  200 . Specifically, of the surface of the second side frame  202  that faces the first side frame  201 , each of the second guide rollers  25  is at a position where the second guide roller  25  faces the second cam  63  of the corresponding developing cartridge  1  attached to the slot  2 A in the second direction. 
       FIG.  28    is an exploded perspective view of the second guide roller  25  and a bearing  27  that holds the second guide roller  25 . As illustrated in  FIG.  28   , the second guide roller  25  has an outer circumferential surface  250  having a hollow cylindrical shape and extending in the third direction. The bearing  27  rotatably supports one end portion and another end portion in the third direction of the second guide roller  25 . With this configuration, the second guide roller  25  is rotatable about a center axis extending in the third direction. 
     When the second cam  63  receives a pressing force directed in the first direction to move the separation member  60  in a direction from the second cam  63  toward the first cam  62 , the first inclined surface  621  of the first cam  62  comes into contact with the first guide roller  24 . Similarly, the second inclined surface  631  of the second cam  63  comes into contact with the second guide roller  25 . The first cam  62  moves in the second direction due to guide of the first guide roller  24  while moving in the first direction. At the same time, while moving in the first direction, the second cam  63  is guided by the second guide roller  25  to also move in the second direction. 
     Here, the first guide roller  24  is configured to guide the first inclined surface  621  by rotating about the center axis extending in the third direction in a state where the first guide roller  24  is in contact with the first inclined surface  621 . Further, the second guide roller  25  is configured to guide the second inclined surface  631  by rotating about the center axis extending in the third direction in a state where the second guide roller  25  is in contact with the second inclined surface  631 . These rotations of the first guide roller  24  and the second guide roller  25  can decrease frictional resistance between the separation member  60  and the frame  200 , whereby the separation member  60  can more smoothly move relative to the frame  200 . 
     Note that it is preferable that the first guide roller  24  and the second guide roller  25  are made of metal. In a case where the first guide roller  24  and the second guide roller  25  are made of metal, abrasion of the first guide roller  24  and the second guide roller  25  caused by friction can be suppressed in comparison with a case where the first guide roller  24  and the second guide roller  25  are made of resin. Accordingly, the first guide roller  24  and the second guide roller  25  can more accurately guide the separation member  60 . 
     4. Modification 
     While the description has been made in detail with reference to the embodiments, it would be apparent to those skilled in the art that various changes and modifications may be made thereto. 
     In the above-described embodiments, the separation member  60  includes the first cam  62  and the second cam  63 . The separation member  60 , however, may include at least one of the first cam  62  and the second cam  63 . In addition, the separation member  60  may have at least one of the first inclined surface  621  and the second inclined surface  631 . In other words, in a case where only the first cam  62  is provided, only the first inclined surface  621  is provided in the separation member  60 . On the other hand, in a case where only the second cam  63  is provided, only the second inclined surface  631  is provided in the separation member  60 . Alternatively, the first inclined surface  621  and the second inclined surface  631  may be formed without providing the first cam  62  and the second cam  63 . For example, the first inclined surface  621  and the second inclined surface  631  may be formed by machining the shaft  61  so that the peripheral surfaces of the end portions of the shaft  61  are inclined relative to the first direction. 
     Although the coil spring  64  serves as an example of the elastic member in the above-described embodiments, the elastic member is not limited to the coil spring  64 . For example, material having elasticity, such as a leaf spring, a torsion spring, a rubber, a sponge, or the like can be employed as the elastic member. 
     Further, various features appearing in the above-described embodiments and the modifications may be suitably combined together avoiding conflicting combination.