Patent Publication Number: US-9429907-B2

Title: Image forming apparatus having spacing configuration for process cartridge

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/520,430 filed Oct. 22, 2014, which is a continuation of U.S. patent application Ser. No. 13/429,506 filed Mar. 26, 2012, issued as U.S. Pat. No. 8,886,075 on Nov. 11, 2014, which claims priority from Japanese Patent Application No. 2011-186885 filed on Aug. 30, 2011, the entire contents of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     Aspects of the present invention relate to an image forming apparatus including a process cartridge which is detachably mounted to an apparatus body. 
     BACKGROUND 
     In related-art, there is disclosed an image forming apparatus including a process cartridge which is detachably mounted to an apparatus body. Further, there is disclosed a process cartridge which includes a first frame for supporting a photosensitive member and a second frame movably supported by the first frame to allow a developing roller to approach/separate from the photosensitive member (see, JP-A-2007-248618). 
     Meanwhile, the image forming apparatus may be shipped and transported in a state where the process cartridge is mounted thereon. In this case, if the photosensitive member and the developing roller are brought into contact with each other, a surface of the photosensitive member or a surface of the developing roller may be damaged or dents may be generated thereon due to a vibration during the transportation. For this reason, there is proposed a method for transporting an image forming apparatus in a state where a maintaining member (spacing member), which is disclosed in JP-A-2007-248618, is provided to the process cartridge to space the photosensitive member and the developing roller from each other. 
     SUMMARY 
     As the spacing member for spacing the photosensitive member and the developing roller from each other, there is known a related-art spacing member which is detachably provided to the process cartridge and is removed by a user before using the image forming apparatus. However, in the related-art spacing member, a driving force from an apparatus body may be inputted to drive the developing roller when a user forgets to remove the spacing member. Accordingly, there is a risk of an unnecessary stress being applied to developer. 
     Aspects of the present invention have been made to solve the above-described problems and an object thereof is to provide an image forming apparatus capable of preventing a stress from being applied to the developer due to the driving of the developing roller, and the like. 
     According to an aspect of the invention, there is provided an image forming apparatus including: a process cartridge, an apparatus body and a spacing member. The process cartridge is detachably mounted to the apparatus body. The process cartridge includes a photosensitive unit having a photosensitive member on which an electrostatic latent image is configured to be formed, a developing unit having a developing roller which is configured to contact with the photosensitive member to supply developer to the photosensitive member, and a driving input part into which a driving force from the apparatus body is configured to be inputted. The apparatus body includes a driving input member which is configured to move inwards and outwards in an axial direction of the developing roller and to input the driving force to the process cartridge when being engaged with the driving input part. The spacing member is attached to the process cartridge and is configured to space the photosensitive member and the developing roller. The spacing member includes a first cover part which is located between the driving input part and the driving input member and covers at least a portion of the driving input part. 
     According to the above configuration, since the spacing member includes the first cover part which is located between the driving input part and the driving input member and covers at least a portion of the driving input part, when the user forgets to remove the spacing member, the driving input member is not engaged with the driving input part by the presence of the first cover part. Accordingly, the developing roller is not driven. As a result, it is possible to prevent a stress from being applied to developer due to the driving of the developing roller, and the like. 
     The developing unit may be displaceably provided with respect to the photosensitive unit. Further, the spacing member may include a maintaining part which is engaged with both the photosensitive unit and the developing unit and is configured to maintain a position of the developing unit with respect to the photosensitive unit at a predetermined position. 
     According to the above configuration, it is possible to suppress rattling between the photosensitive unit and the developing unit during the transportation of the image forming apparatus. 
     The photosensitive unit may include a positioning part which is configured to position the developing unit by the developing unit being contacted thereto. Further, the maintaining part may be configured to maintain the developing unit to be spaced apart from the positioning part. 
     If the positioning part and the developing unit are brought into contact with each other during the transportation of the image forming apparatus, there is a possibility that wear is caused due to a friction therebetween. If the wear is caused, there is a risk that the position of the developing unit will not be accurately positioned. According to the above configuration, it is possible to suppress the wear between the positioning part and the developing unit during the transportation of the image forming apparatus. As a result, the position of the developing unit can be accurately positioned as in the time of shipping. 
     The image forming apparatus may further include a pair of rollers configured to convey a recording sheet. Further, a first roller of the pair of rollers may be supported by the process cartridge and a second roller of the pair of rollers may be supported by the apparatus body. Further, the spacing member may include a roller spacing part which is located between the first roller and the second roller and is configured to space the first roller and the second roller from each other. 
     There is a possibility that indentation such as dents is formed on the surface of the rollers having elasticity when the pair of rollers is pressed against each other during the transportation/storage of the image forming apparatus. According to the above configuration, the first roller and the second roller are spaced apart from each other, it is possible to prevent indentation from being formed on the surface of the roller. 
     The process cartridge may include a pair of bosses protruding outward in the axial direction. Further, the apparatus body may include a pair of guide walls configured to guide the bosses when the process cartridge is attached and detached. Further, the spacing member may include a boss engaging part which is located between the boss and the guide wall and is engaged with the boss. 
     According to the above configuration, it is possible to suppress the rattling between the apparatus body and the process cartridge during the transportation of the image forming apparatus. Further, since the boss engaging part is arranged between the boss and the guide wall, it is possible to suppress the wear between the boss and the guide wall during the transportation of the image forming apparatus. 
     The apparatus body may include a cover configured to open and close a mounting part to which the process cartridge is mounted. Further, the spacing member may include an interposing part which is located between the process cartridge and the cover. 
     According to the above configuration, it is possible to suppress the rattling between the process cartridge and the cover during the transportation of the image forming apparatus. 
     The driving input member may be configured to be movable inwards and outwards in the axial direction elastically. 
     According to the above configuration, it is possible to prevent a large force from being applied to the driving input member itself or the first cover part (process cartridge), even in a case where the driving input member advances to engage with the driving input part and is brought into contact with the first cover part. 
     The process cartridge may include a cartridge side electrode which is electrically connected to a body side electrode provided to the apparatus body. Further, the spacing member may include a second cover part which is located between the body side electrode and the cartridge side electrode and is configured to cover at least a portion of the cartridge side electrode. 
     According to the above configuration, since the second cover part covers at least a portion of the cartridge side electrode, both electrodes are not brought into contact with each other. Accordingly, it is possible to suppress the wear of both electrodes during the transportation of the image forming apparatus. 
     According to the present invention, since the spacing member includes the first cover part to cover at least a portion of the driving input part, the developing roller is not driven when the user forgets to remove the spacing member. Thereby, it is possible to prevent a stress from being applied to the developer due to the driving of the developing roller, and the like. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a sectional view illustrating a schematic configuration of a laser printer as an example of an image forming apparatus; 
         FIG. 2  is a perspective view of a photosensitive unit and a developing unit; 
         FIG. 3  is an enlarged sectional view of the laser printer; 
         FIG. 4  is an enlarged sectional view of an inner configuration of the body casing; 
         FIG. 5A  is a perspective view of a spacing member as viewed from a left side and 
         FIG. 5B  is a perspective view of the spacing member as viewed from a right side; 
         FIG. 6  is a perspective view of a right side portion of the spacing member as viewed from an inner side; 
         FIG. 7A  is a perspective view of a process cartridge as viewed from the left side and  FIG. 7B  is a perspective view of the process cartridge in a state where the spacing member is attached thereto; 
         FIG. 8A  is a perspective view of a process cartridge as viewed from the right side and  FIG. 8B  is a perspective view of the process cartridge in a state where the spacing member is attached thereto; 
         FIG. 9A  is a side view of the process cartridge to which the spacing member is attached as viewed from the left side and  FIG. 9B  is a side view of the process cartridge as viewed from the right side; and 
         FIG. 10  is an enlarged sectional view of the laser printer on which the process cartridge having the spacing member is attached. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, an exemplary embodiment of the present invention will be described suitably by referring to the accompanying drawings. In the following description, first, a laser printer  1  as an example of an image forming apparatus according to the exemplary embodiment will be described briefly. Subsequently, configurations of the characteristic parts of the present invention will be described in detail. 
     Further, a direction used in the following description refers to a direction with reference to a user using the laser printer  1 . That is, a right side in  FIG. 1  is referred to as a “front side,” a left side in  FIG. 1  is referred to as a “rear side,” a front side in  FIG. 1  is referred to as a “left side” and a back side in  FIG. 1  is referred to as a “right side.” Further, an upper-lower direction in  FIG. 1  is referred to as “upper-lower.” 
     &lt;Schematic Configuration of Laser Printer&gt; 
     As illustrated in  FIG. 1 , the laser printer  1  mainly includes a sheet feeding unit  3  for feeding a sheet S as an example of a recording sheet, an exposure unit  4 , a process cartridge  5  for transferring a toner image (developer image) on the sheet S and a fixing unit  8  for thermally fixing the toner image on the sheet S, which are provided with a body casing  2  as an example of an apparatus body. 
     The sheet feeding unit  3  is provided in a lower portion of the body casing  2  and mainly includes a sheet feeding tray  31 , a sheet pressing plate  32 , a sheet feeding mechanism  33  and a register roller  34  as an example of a pair of rollers. The sheet S accommodated in the sheet feeding tray  31  is transmitted upward by the sheet pressing plate  32  and fed toward the process cartridge  5  by the sheet feeding mechanism  33 . And then, the sheet S passes through the register roller  34  and is conveyed between a photosensitive drum  61  and a transfer roller  63 . 
     The exposure unit  4  is provided in an upper portion of the body casing  2  and includes a laser emitting unit (not illustrated), a polygon mirror, lens and a reflector mirror which are illustrated without reference numerals. In this exposure unit  4 , a laser beam (see, chained line) based on an image data emitted from the laser emitting unit scans the surface of the photosensitive drum  61  in a high speed. In this way, the surface of the photosensitive drum  61  is exposed. 
     The process cartridge  5  is disposed lower to the exposure unit  4  and is configured to be detachably mounted to the body casing  2  through an opening created by opening a front cover  21  as an example of a cover provided to the body casing  2 . The process cartridge  5  includes a photosensitive unit  6  and a developing unit  7 . 
     The photosensitive unit  6  mainly includes the photosensitive drum  61  as an example of a photosensitive member, a scorotron-type charger  62  including a corona wire and a grid which are illustrated without reference numerals, and the transfer roller  63 . 
     The developing unit  7  is configured to be detachably mounted to the photosensitive unit  6 . The developing unit  7  is configured to be detachably mounted to the body casing  2  in a state of being mounted to the photosensitive unit  6 . That is, the developing unit  7  is detachably mounted to the body casing  2  as a part of the process cartridge  5 . The developing unit  7  mainly includes a developing roller  71 , a supply roller  72 , a thickness restricting blade  73 , a toner accommodating part  74  for accommodating a toner as an example of developer and an agitator  75 . 
     In the process cartridge  5 , the surface of the photosensitive drum  61  is uniformly charged by the charger  62  and then exposed by a high speed scanning of a laser beam from the exposure unit  4 . In this way, an electrostatic latent image based on the image data is formed on the photosensitive drum  61 . Further, the toner in the toner accommodating part  74  is first supplied to the supply roller  72  while being agitated by the agitator  75  and then supplied from the supply roller  72  to the developing roller  71 . The toner enters between the developing roller  71  and the thickness restricting blade  73  by the rotation of the developing roller  71  to be supported on the developing roller  71  as a thin layer having a constant thickness. 
     The toner supported on the developing roller  71  is supplied from the developing roller  71  to the electrostatic latent image formed on the photosensitive drum  61 . Thereby, the electrostatic latent image becomes a visible image and the toner image is formed on the photosensitive drum  61 . Thereafter, as the sheet S is conveyed through between the photosensitive drum  61  and the transfer roller  63 , the toner image on the photosensitive drum  61  is transferred onto the sheet S. 
     The fixing unit  8  is located rear to the process cartridge  5  and mainly includes a heating unit  81  and a pressing roller  82 . The heating unit  81  has a halogen heater, a fixation belt and a nip plate which are illustrated without reference numeral. The pressing roller  82  is configured to hold the fixation belt between the nip plate of the heating unit  81 . In the fixing unit  8 , the toner image transferred onto the sheet S is thermally fixed while the sheet S passes through between the heating unit  81  and the pressing roller  82 . The sheet S onto which the toner image is thermally fixed is discharged onto a sheet discharge tray  22  by a sheet discharge roller  23 . 
     &lt;Configuration of Process Cartridge&gt; 
     Next, a configuration of the process cartridge  5  (photosensitive unit  6  and developing unit  7 ) related to a characteristic part of the present invention will be described. 
     As illustrated in  FIG. 2 , the developing unit  7  further includes a developing frame  70 , a coupling  76  as an example of a driving input part and a cover body  77 , in addition to the developing roller  71  and the supply roller  72  mentioned above. 
     The developing frame  70  is a member which rotatably supports the developing roller  71  or the supply roller  72  and defines the toner accommodating part  74 . 
     As illustrated in  FIGS. 3 and 9B , a pressed part  70 A protruding outwards in the left-right direction (axial direction of the developing roller  71 ) is provided to a front side of outer surfaces of the left and right side walls of the developing frame  70 . The pressed part  70 A is a portion which is pressed by a pressing member  64  (will be described later) of the photosensitive unit  6  when the developing unit  7  is mounted to the photosensitive unit  6 . 
     Further, as illustrated in  FIG. 8A , a convex part  70 S protruding outwards in the left-right direction is provided upper to the pressed part  70 A to a right side wall of the developing frame  70 . A right convex part engaging part  143  (see,  FIG. 8B ) of a spacing member  100 , which will be described later, is configured to be engaged with the convex part  70 S. 
     Returning back to  FIG. 2 , the coupling  76  is a member into which a driving force from the body casing  2  is inputted. The coupling  76  is rotatably supported on a left side wall of the developing frame  70 . The driving force inputted into the coupling  76  is transmitted to the developing roller  71 , the supply roller  72  and the agitator  75  via a known driving force transmitting mechanism which is not illustrated. The driving force transmitting mechanism is provided to a left side surface of the developing frame  70 , and an example thereof is a plurality of gears. Thereby, the developing roller  71 , the supply roller  72  and the agitator  75  can be driven. 
     The cover body  77  is a member which is mounted to a left side wall of the developing frame  70  to cover the coupling  76  or the driving force transmitting mechanism mentioned above. A convex part  77 S protruding outwards in the left-right direction is provided to a front side in an outer surface of the cover body  77 . A left convex part engaging hole  112  (see,  FIGS. 5A, 5B ) of the spacing member  100  can be engaged with the convex part  77 S. 
     The photosensitive unit  6  further includes a photosensitive frame  60 , a driven roller  34 A as an example of a first roller of a pair of register rollers  34 , a pressing member  64 , a wire electrode  65  and a gird electrode  66  (see,  FIG. 9B ) as an example of a cartridge side electrode, in addition to the photosensitive drum  61  and the charger  62  mentioned above. 
     The photosensitive frame  60  is a member configured to rotatably support the photosensitive drum  61  or the driven roller  34 A and form a concave detaching part  60 A to which the developing unit  7  is detachably mounted. A positioning part  60 B protruding upward is provided to both left and right sides at a front end of a lower wall of the detaching part  60 A. An upper end of the positioning part  60 B has an approximately hemi-spherical shape. 
     As illustrated in  FIG. 3 , a front side of the developing unit  7  is brought into contact with the upper end of the positioning part  60 B from the upper side when the developing unit  7  is mounted to the photosensitive unit  6 . Thereby, the developing unit  7  can be positioned with respect to the photosensitive unit  6 . 
     As illustrated in  FIG. 2 , a concave engaging part  60 C opening toward the front side is provided near a central portion in the front-rear direction to the left and right side walls of the photosensitive frame  60 . A shaft  71 A of the developing roller  71  is engaged with the concave engaging part  60 C when the developing unit  7  is mounted to the photosensitive unit  6  (see,  FIG. 9 ). 
     Further, a pair of bosses  60 D protruding outwards in the left-right direction is provided to the front ends of the left and right side walls of the photosensitive frame  60 . The bosses  60 D have an approximately cylindrical shape. 
     The pressing member  64  is a member which presses the developing unit  7  mounted to the photosensitive unit  6  toward the rear to urge the developing roller  71  to the photosensitive drum  61 . The pressing member  64  is provided adjacent to the positioning part  60 B, obliquely at the front side of the positioning part  60 B and outside of the positioning part  60 B in the left-right direction. The pressing member  64  mainly includes a pressing arm  64 A and a coil spring  64 B, as illustrated in  FIG. 3 . 
     The pressing arm  64 A is supported by the photosensitive frame  60  to swing in the front-rear direction around a lower end thereof. Further, the coil spring  64 B is disposed between the pressing arm  64 A and the photosensitive frame  60  and urges a portion of the pressing arm  64 A which is located at a rear side and farther to the rear than a swing axis thereof in an approximately upper direction. 
     The pressing member  64  presses the pressed part  70 A of the developing unit  7  obliquely toward the rear and lower side when the developing unit  7  is mounted to the photosensitive unit  6 . Thereby, the entire developing unit  7  is urged obliquely toward the rear and lower side and thus the developing roller  71  is urged toward the photosensitive drum  61 . Further, as the entire developing unit  7  is urged obliquely toward the rear and lower side, a front side of the developing frame  70  is pressed against the upper end of the positioning part  60 B. In this way, the position of the developing unit  7  can be securely positioned. 
     The driven roller  34 A is disposed upper to a pressing roller  34 B as an example of a second roller of the pair of register roller  34  supported by the body casing  2  when the process cartridge  5  is mounted to the body casing  2 . In the register roller  34 , the driven roller  34 A is rotationally driven by the rotation driving of the pressing roller (e.g., driving roller)  34 B and thus sheet S is conveyed toward between the photosensitive drum  61  and the transfer roller  63 . 
     As illustrated in  FIG. 9B , the wire electrode  65  and the grid electrode  66  are electrically connected to a first electrode  25  and a second electrode  26  (see,  FIG. 4 ) which are provided to the body casing  2 . The wire electrode  65  and the grid electrode  66  are arranged to an upper portion of the rear side of a right side wall of the photosensitive frame  60 . 
     More specifically, the wire electrode  65  is electrically connected to the corona wire of the charger  62 . The wire electrode  65  is electrically connected to the first electrode  25  when the process cartridge  5  is mounted to the body casing  2 . Further, the grid electrode  66  is electrically connected to the grid of the charger  62 . The grid electrode  66  is electrically connected to the second electrode  26  when the process cartridge  5  is mounted to the body casing  2 . 
     &lt;Configuration of Body Casing&gt; 
     Next, a configuration of the body casing  2  related to a characteristic part of the present invention will be described. As illustrated in  FIG. 4 , the body casing  2  includes a mounting part  2 A, a pair of left and right guides  24  (only one thereof is illustrated), the first electrode  25  and the second electrode  26  as an example of a body side electrode and a driving input member  27  (see,  FIGS. 7A and 7B ). 
     The mounting part  2 A is a portion inside the body casing  2 , to which the process cartridge  5  is mounted. The mounting part  2 A is formed between the left and right side walls of the body casing  2 . The mounting part  2 A is configured to be opened and closed by the front cover  21 . 
     The guides  24  are configured to guide the process cartridge  5  up to a mounting position (position illustrated in  FIG. 1 ) and respectively provided to an inner surface of the left and right side walls of the body casing  2 . In the present exemplary embodiment, the guides  24  mainly include a drum guide  24 A for guiding a drum shaft  61 A and a boss guide  24 B as an example of a pair of guide walls for guiding the bosses  60 D when the process cartridge  5  is attached or detached. 
     The first electrode  25  and the second electrode  26  are respectively provided to an inner surface of the right wall of the body casing  2 . Further, a bias applying device (not illustrated) is provided inside the body casing  2 . When the charger  62  of the process cartridge  5  is driven during image formation, the bias applying device applies a predetermined bias to the wire electrode  65  (corona electrode) via the first electrode  25  and applies a predetermined bias to the grid electrode  66  (grid) via the second electrode  26 . 
     As illustrated in  FIG. 7A , the driving input member  27  is a member inputting a driving force from a motor (not illustrated) provided within the body casing  2  to the coupling  76  of the process cartridge  5 . The driving input member  27  is supported by a left side wall of the body casing  2  and is configured to move inwards and outwards in the left-right direction. The driving input member  27  can be operated by a known mechanism. Specifically, the driving input member  27  advances inwards in the left-right direction in accordance with an operation for closing the front cover  21 . And thus, the driving input member  27  is engaged with the coupling  76  of the mounted process cartridge  5  to transmit the driving force. Further, the driving input member  27  retreats outwards in the left-right direction in accordance with an operation for opening the front cover  21  and thus is disengaged from the coupling  76 . 
     In the present exemplary embodiment, the driving input member  27  is configured to be movable inwards and outwards in the left-right direction elastically by the action of a spring  27 B. Thereby, even if the driving input member  27  advancing inwards in the left-right direction is subjected to a force directed outwards in the left-right direction, it is possible to reduce the force applied on the driving input member  27  by contraction of the spring  27 B. 
     &lt;Detailed Configuration of the Spacing Member&gt; 
     The laser printer  1  according to the present exemplary embodiment is shipped from a factory in a state where the process cartridge  5  is mounted thereon. At this time, the spacing member  100  illustrated in  FIG. 5  is mounted to the process cartridge  5  in order to space the photosensitive drum  61  and the developing roller  71  from each other (see,  FIG. 7B  and  FIG. 8B ). 
     As an example, the spacing member  100  is made of polypropylene resin and is configured by a single member. The spacing member  100  includes a left part  101  attached to a left side of the process cartridge  5 , a right part  102  attached to a right side thereof and a connecting part  103  which extends in the left-right direction and connects the front upper ends of the left part  101  and the right part  102  with each other. 
     Two engaging claws  104  protruding inwards in the left-right direction are respectively provided to each of the left part  101  and the right part  102 . That is, a total of four engaging claws  104  are provided. When the spacing member  100  is attached to the process cartridge  5 , each of the engaging claws  104  is engaged with the photosensitive frame  60 . Accordingly, it is possible to prevent the spacing member  100  from being separated from the process cartridge  5  due to a vibration during the transportation. 
     The spacing member  100  includes a first spacing part  110 , a first cover part  120 , a second cover part  130 , a maintaining part  140 , a second spacing part  150  as an example of a roller spacing part and an interposing part  160  as functioning parts corresponding to the characteristic part of the present invention. 
     In the following description, a state where the spacing member  100  is attached to the process cartridge  5  is referred to as an attached state and a state where the spacing member  100  is not attached to the process cartridge  5  is referred to as a detached state. 
     The first spacing part  110  is configured to space the photosensitive drum  61  apart from the developing roller  71 . The first spacing part includes a drum engaging hole  111 , the left convex part engaging hole  112  and a left first wall  113  which are provided to the left part  101 . The first spacing part also includes a convex engaging part  114  which is provided to the right part  102 . 
     The drum engaging hole  111  is a through hole which is engaged with the drum shaft  61 A of the photosensitive drum  61  and provided to a rear end of the left part  101 . In the present exemplary embodiment, the drum engaging hole  111  is also provided to a rear end of the right part  102 . 
     The left convex part engaging hole  112  is a through hole which is engaged with the convex part  77 S of the process cartridge  5  and provided to an upper portion of a front side of the left part  101 . 
     The left first wall  113  is a portion of the wall constituting the left part  101  between the drum engaging hole  111  and the left convex part engaging hole  112 . As illustrated in  FIG. 7B , the left side wall  113  have a length L 1  (shortest length from the drum engaging hole  111  to the left convex part engaging hole  112 ) slightly longer than a shortest length L 2  from the drum shaft  61 A to the convex part  77 S in a detached state. 
     As illustrated in  FIG. 6 , the convex engaging part  114  is a portion which is engaged between the shaft  71 A of the developing roller  71  and the rear wall of the concave engaging part  60 C. The convex engaging part  114  is provided at a front side of the drum engaging hole  111  to protrude from an inner surface of the right part  102  inwardly in the left-right direction. The convex engaging part  114  has a length L 3  in a substantially longitudinal direction slightly longer than a shortest length L 4  (see,  FIG. 8A ) from the shaft  71 A to the rear wall of the concave engaging part  60 C in the detached state. 
     Returning back to  FIG. 5A , the first cover part  120  is a part of the left first wall  113  and is arranged to cover the coupling  76  from the outside in the left-right direction, in an attached state (see,  FIG. 7B ). 
     The second cover part  130  is a portion of a rear end of the right part  102  that protrudes upwards and is arranged to cover the wire electrode  65  and the grid electrode  66  from the outside in the left-right direction, in the attached state (see,  FIG. 8A ). 
     The maintaining part  140  is configured to maintain the position of the developing unit  7  with respect to the photosensitive unit  6  in a predetermined position and includes a boss engaging part  141 , the left convex part engaging hole  112 , a left maintaining wall  142 , a right convex part engaging part  143  (see,  FIG. 6 ) and a left maintaining wall  144 . 
     The boss engaging part  141  is an approximately cylindrical part which is engaged with the boss  60 D of the photosensitive frame  60  and is provided to protrude from the front ends of the left part  101  and the right part  102  toward both sides in the left-right direction. 
     The left maintaining wall  142  is a portion of the wall constituting the left part  101  between the boss engaging part  141  and the left convex part engaging hole  112 . As illustrated in  FIG. 7B , a shortest length L 5  from an inner peripheral surface of the boss engaging part  141  of the left maintaining wall  142  to the left convex part engaging hole  112  is set such that the convex part  77 S (developing unit  7 ) engaged with the left convex part engaging hole  112  is spaced apart from the positioning part  60 B of the photosensitive unit  6 , in the attached state (see, also  FIG. 10 ). 
     As illustrated in  FIG. 6 , the right convex part engaging part  143  is a cylindrical part which is engaged with the convex part  70 S of the process cartridge  5  and is provided to protrude obliquely from the rear and upper side of the boss engaging part  141  inwards in the left-right direction. 
     The right maintaining wall  144  is a portion of the wall constituting the right part  102  between the boss engaging part  141  and the right convex part engaging hole  143 . As illustrated in  FIG. 8B , a shortest length L 6  from an inner peripheral surface of the boss engaging part  141  of the right maintaining wall  144  to an inner peripheral surface of the right convex part engaging part  143  is set such that the convex part  70 S (developing unit  7 ) engaged with the right convex part engaging hole  143  is spaced apart from the positioning part  60 B of the photosensitive unit  6  in the attached state (see, also  FIG. 10 ). Further, as illustrated in  FIG. 6 , a rib  145  is provided to an inner surface of the right maintaining wall  144  to protrude toward inwards in the left-right direction. 
     As illustrated in  FIG. 5A , the second spacing part  150  is configured such that the register rollers  34  (driven roller  34 A and driving roller  34 B) are spaced apart from each other. A concave part  105  (see,  FIG. 6 ) accommodating both left and right ends of the driven roller  34 A is formed to a lower portion of the left part  101  and the right part  102  around a central portion thereof in the front and rear directions, in the attached state. The second spacing part  150  is provided to extend from a rear edge of the concave part  105  toward the front side in an approximately bow shape as viewed from the side. 
     The second spacing part  150  is formed to be wide in the left-right direction (that is, thicker than the wall constituting the left part  101  and the right part  102 ) and is arranged to cover both left and right ends of the driven roller  34 A from the below in the attached state. 
     The interposing part  160  is configured to prevent contact between the process cartridge  5  and the front cover  21 . The interposing part  160  is formed to extend from the front ends of the left part  101  and the right part  102  toward the inside in the left-right direction in a substantially plate shape. 
     &lt;Explanation of Function of Spacing Member&gt; 
     Next, the function of each part of the spacing member  100  will be described. 
     When the spacing member  100  is attached to the process cartridge  5 , in the left part  101 , the drum engaging hole  111  is engaged with the drum shaft  61 A, the left convex part engaging hole  112  is engaged with the convex part  77 S and the boss engaging part  141  is engaged with the boss  60 D, as illustrated in  FIG. 7 . Further, the left end of the driven roller  34 A is engaged with the second spacing part  150 , as illustrated in  FIG. 9A . 
     Further, in the right part  102 , the convex engaging part  114  is engaged between the shaft  71 A and the concave engaging part  60 C and the right convex part engaging part  143  is engaged with the convex part  70 S while the drum engaging hole  111  is engaged with the drum shaft  61 A and the boss engaging part  141  is engaged with the boss  60 D, as illustrated in  FIG. 8B . Further, the right end of the driven roller  34 A is engaged with the second spacing part  150 , as illustrated in  FIG. 9B . Thereby, the spacing member  100  is attached to the process cartridge  5 . 
     As mentioned above, since the length L 1  of the left side wall  113  is set longer than the shortest length L 2  from the drum shaft  61 A to the convex part  77 S in the detached state, the convex part  77 S (developing unit  7 ) in the attached state is spaced farther apart from the drum shaft  61 A than in the detached state by support of the left side wall  113 . Further, since the length L 3  of the convex engaging part  114  is set longer than the shortest length L 4  from the shaft  71 A to the rear wall of the concave engaging part  60 C in the detached state, the convex engaging part  114  is engaged between the shaft  71 A and the rear wall of the concave engaging part  60 C. Accordingly, the shaft  71 A (developing unit  7 ) in the attached state is spaced farther apart from the drum shaft  61 A than in the detached state. 
     According to these configurations, the developing roller  71  supported by the developing unit  7  (developing frame  70 ) is spaced apart from the photosensitive drum  61  (see,  FIG. 10 ). As a result, it is possible to prevent the surface of the photosensitive drum  61  or the developing roller  71  to be damaged or dents to be generated thereon during the transportation of the laser printer  1  on which the process cartridge  5  is mounted. 
     Meanwhile, in a case where the developing unit  7  can be attached or detached from the photosensitive unit  6 , there is a slight rattling between the developing unit  7  and the photosensitive frame  60 . However, in the present exemplary embodiment, the spacing member  100  as a single member is engaged with both the photosensitive unit  6  and the developing unit  7 . Specifically, the boss engaging part  141  is engaged with the boss  60 D (photosensitive unit  6 ) and the left convex part engaging hole  112  and the right convex part engaging part  143  are engaged with the convex parts  77 S,  70 S (developing unit  7 ). Accordingly, the developing unit  7  is maintained in a predetermined position with respect to the photosensitive unit  6 . Thereby, it is possible to suppress the rattling between the photosensitive unit  6  and the developing unit  7  during the transportation of the laser printer  1 . 
     Further, in the present exemplary embodiment, the convex part  77 S engaged with the left convex part engaging hole  112  is spaced apart from the positioning part  60 B of the photosensitive unit  6  by the support of the left maintaining wall  142 . Furthermore, the convex part  70 S engaged with the right convex part engaging part  143  is spaced apart from the positioning part  60 B by the support of the right maintaining wall  144 . Consequently, the front portion of the developing unit  7  is maintained in a state of being spaced apart from the positioning part  60 B (see,  FIG. 10 ). Thereby, it is possible to suppress the wear between the positioning part  60 B and the developing unit  7  during the transportation of the laser printer  1 . Accordingly, when the spacing member  100  is removed (when the laser printer  1  is used), the position of the developing unit  7  can be accurately positioned as in the time of shipping. 
     As illustrated in  FIG. 8B , the right maintaining wall  144  is disposed at a position spaced apart from a right side surface of the developing unit  7  in the attached state. However, since the rib  145  (see,  FIG. 6 ) is provided to an inner surface of the right maintaining wall  144  in the present exemplary embodiment, the rigidity of the right maintaining wall  144  is improved. Accordingly, since the right maintaining wall  144  can be supported without being flexed, it is possible to space the convex part  70 S and the boss  60 D from each other. 
     As illustrated in  FIG. 10 , when the process cartridge  5  to which the spacing member  100  is attached is mounted to the body casing  2 , the second spacing part  150  is located between the driven roller  34 A and the driving roller  34 B. Thereby, the driven roller  34 A and the driving roller  34 B are spaced apart from each other. Accordingly, it is possible to prevent an indentation from being caused on the surface of the register rollers  34  during the transportation of the laser printer  1 . 
     Further, when the process cartridge  5  to which the spacing member  100  is attached is mounted to the body casing  2 , a peripheral wall of the boss engaging part  141  having an approximately cylindrical shape is located between the boss  60 D and the boss guide  24 B (see,  FIG. 4 ). Thereby, it is possible to suppress the rattling between the boss guide  24 B (body casing  2 ) and the process cartridge  5  during the transportation of the laser printer  1 . Further, since the boss engaging part  141  is located between the boss  60 D and the boss guide  24 B, it is also possible to suppress the wear between the boss  60 D and the boss guide  24 B during the transportation of the laser printer  1 . 
     Since the interposing part  160  is located between the process cartridge  5  and the front cover  21  when the front cover  21  is closed, the contact between the process cartridge  5  and the front cover  21  is prevented. Thereby, it is possible to suppress the rattling between the process cartridge  5  and the front cover  21  during the transportation of the laser printer  1 . 
     As illustrated in  FIG. 7B , when the process cartridge  5  to which the spacing member  100  is attached is mounted to the body casing  2 , the first cover part  120  is located between the coupling  76  and the driving input member  27  to cover almost the entire of the coupling  76 . Accordingly, even in a case where the front cover  21  is closed, the driving input member  27  cannot be engaged with the coupling  76 . Thereby, a driving force from the driving input member  27  is not transmitted to the coupling  76  (process cartridge  5 ). 
     Since the first cover part  120  thus configured is provided in this exemplary embodiment, even if a user forgets to remove the spacing member  100  in a case of using the laser printer  1 , the developing roller  71  or the agitator  75  is not driven. Thereby, it is possible to prevent a stress from being applied to the toner due to the driving of the developing roller  71  or the agitator  75 . 
     In the present exemplary embodiment, the driving input member  27  is configured to be elastically movable in the left-right direction under the action of the spring  27 B. Accordingly, even if the driving input member  27  advances to engage with the coupling  76  and is brought into contact with the first cover part  120  by closing the front cover  21 , the spring  27 B is contracted to prevent a large force from being applied to the driving input member  27  itself or the first cover part  120  (process cartridge  5 ). 
     Further, as illustrated in  FIG. 8B , when the process cartridge  5  to which the spacing member  100  is attached is mounted to the body casing  2 , the second cover part  130  is located between the first electrode  25  and the wire electrode  65  and between the second electrode  26  and the grid electrode  66  to cover almost the entirety of the wire electrode  65  and the grid electrode  66 . Accordingly, each pair of the electrodes  65  and  66  is not brought into contact with each other. Thereby, it is possible to suppress the wear of each electrode  65  and  66  during the transportation of the laser printer  1 . 
     In the laser printer  1  including the process cartridge  5  to which the spacing member  100  is attached, the spacing member  100  is removed by a user when used. As the spacing member  100  is removed from the process cartridge  5 , the developing roller  71  is urged to the photosensitive drum  61  by the action of the pressing member  64 , as illustrated in  FIG. 3 . Further, since the front side of the developing unit  7  is brought into contact with the upper end of the positioning part  60 B, the developing unit  7  is positioned with respect to the photosensitive unit  6  in a state of being used. 
     Thereafter, when the process cartridge  5  is mounted to the body casing  2  again, the driven roller  34 A is brought into contact with the driving roller  34 B and the driven roller  34 A can be rotated in accordance with the rotation of the driving roller  34 B. Further, since the wire electrode  65  is electrically connected to the first electrode  25  and the grid electrode  66  is electrically connected to the second electrode  26 , it is possible to apply a bias to the process cartridge  5 . 
     Thereafter, when the front cover  21  is closed, the driving input member  27  advances inwards in the left-right direction and is engaged with the coupling  76 . Thereby, it is possible to input the driving force to the process cartridge  5 , specifically, the developing roller  71  or the agitator  75 . 
     Although the exemplary embodiment of the present invention has been described above, the present invention is not limited to the above-described exemplary embodiment. The specific configuration thereof may be suitably modified without departing from the gist of the present invention. 
     Although the first cover part  120  is configured to cover almost the entirety of the coupling  76  (driving input part) in the above-described exemplary embodiment, the present invention is not limited thereto. That is, the first cover part may be configured to cover at least a portion of the driving input part, as long as the first cover part is provided to suppress the engagement of the driving input part and the driving input member of the apparatus body. 
     Further, although the second cover part  130  is configured to cover the entirety of the wire electrode  65  and the grid electrode  66  (cartridge side electrode) in the above-described exemplary embodiment, the present invention is not limited to this. That is, the second cover part may be configured to cover at least a portion of the cartridge side electrode, as long as the second cover part is provided to suppress the contact of the cartridge side electrode and the body side electrode. 
     Although an electrode for applying a bias to the charger  62  is illustratively described as the cartridge side electrode and the body side electrode in the above-described exemplary embodiment, the present invention is not limited to this. For example, the cartridge side electrode and the body side electrode may be an electrode for applying a bias to the photosensitive member or the developing roller or an electrode for grounding the photosensitive member. 
     Although the spacing member  100  is configured by a single member in the above-described exemplary embodiment, the present invention is not limited thereto. That is, the spacing member of the present invention may be configured by multiple members. In this case, a part for preventing a rattling, for example, the interposing part  160  in the above-described exemplary embodiment may be formed by an elastic member (material). 
     Although the coupling  76  as an example of the driving input part is provided to the developing unit  7  in the above-described exemplary embodiment, the present invention is not limited to this. For example, the coupling may be provided to the photosensitive unit. Further, the driving input part may be respectively provided to the photosensitive unit and the developing unit. 
     Although the first spacing part  110 , that is, a configuration for spacing the photosensitive drum  61  and the developing roller  71  is illustratively described in the above-described exemplary embodiment, the present invention is not limited to this configuration. For example, the spacing member may include a spacer which is interposed between the photosensitive member and the developing roller to space the photosensitive member and the developing roller from each other. 
     Although the developing unit  7  is detachably mounted to the photosensitive unit  6  in the above-described exemplary embodiment, the present invention is not limited thereto. For example, as in the process cartridge disclosed in JP-A-2007-248618, the developing unit may be swingably (displaceably) supported by the photosensitive unit to allow the developing roller to approach and separate from the photosensitive member, instead of being detachably mounted thereon. 
     Although the laser printer  1  for forming a monochrome image is illustratively described as an image forming apparatus in the above-described exemplary embodiment, the present invention is not limited to this. For example, the present invention may be applied to a printer for forming a color image. Further, the image forming apparatus is not limited to a printer. For example, the present invention may be applied to a copying machine or a multifunction machine including a document reading device such as a flatbed scanner. 
     Although the sheet S such as a plain sheet or a postcard is illustratively described as a recording sheet in the above-described exemplary embodiment, the present invention is not limited to this. For example, the present invention may also be applied to an OHP sheet.