Patent Publication Number: US-9429904-B2

Title: Image carrier unit and image forming apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image carrier unit including an image carrier capable of carrying an electrostatic image and image forming apparatus including the image carrier unit. 
     2. Description of the Related Art 
     There is widely used such an image forming apparatus configured to transfer a toner image formed on an image carrier to a sheet directly or through an intermediary of an intermediate transfer body and to fix the image to the sheet by heating and pressing the sheet to which the toner image has been transferred. In general, a photoconductive drum which is one exemplary image carrier is supplied to a user in a form of a process cartridge which is one exemplary image carrier unit. The process cartridge is configured such that a charging device, a developing device and others are built into a cartridge casing together with the photoconductive drum and to be able to replace them in a body. 
     Japanese Patent Application Laid-open Nos. 2004-170556 and 2009-75274 disclose an image forming apparatus in which a plurality of process cartridges is arrayed along an intermediate transfer belt. The plurality of process cartridges is configured to be able to be attached and to be replaced individually to/from a casing of the image forming apparatus by being moved in a rotational axis direction of the photoconductive drum. 
     The process cartridge disclosed in Japanese Patent Application Laid-open No. 2004-170556 is provided with an opening for making the photoconductive drum come into contact with the intermediate transfer belt and with a protection cover of the photoconductive drum for covering the opening. The protection cover prevents the photoconductive drum from being irradiated by light or from collecting dusts during processes of shipping and storage of the process cartridge. The protection cover engages with first and second engage portions disposed at both sides of the opening of a cartridge casing and is held to be able to move in the rotational axis direction of the photoconductive drum. 
     As shown in  FIG. 10A , a direction in which the engagement at a first engagement mechanism ( 71 L,  72 L) becomes shallow is opposite from a direction in which the engagement at a second engagement mechanism ( 71 R and  72 R) becomes shallow. Due to that, if the protection cover ( 10 ) is strongly pulled in a direction distant from the photoconductive drum  1 Bk (upward) as shown in  FIG. 10B , the protection cover deforms inwardly, the engagements of the first and second engagement mechanisms become shallow in the same time, and there is a possibility that the protection cover comes off from the process cartridge. 
     A drum cartridge disclosed in Japanese Patent Application Laid-open No. 2009-75274 is configured such that a protection cover abuts against a casing of an image forming apparatus and is automatically removed such that it is pushed out of a drum cartridge in attaching the drum cartridge to the casing of the image forming apparatus by moving the drum cartridge in a rotation axis direction of the photoconductive drum. 
     Because such a protection cover is so large as to cover an entire process cartridge, it is not preferable to use an excessive material as a protection cover attached only during a period from a packing state until when the process cartridge is attached to the image forming apparatus. If the whole process cartridge including the protection cover is large, it is troublesome during shipping, storage and handling. 
     SUMMARY OF THE INVENTION 
     An image carrier unit includes an image carrier capable of carrying an electrostatic image, a unit casing rotatably storing the image carrier with an opening for exposing a part of the image carrier, a protection cover covering the opening, and an engage mechanism configured to attach the protection cover slidably in a rotational axis direction of the image carrier to the unit casing. The engage mechanism includes a first engage mechanism including a first engage portion provided at a first end portion in a width direction orthogonal to the rotational axis direction of the protection cover and a first engaged portion provided in the unit casing and engaged with the first engage portion, and configured such that the first engage portion engages with the first engaged portion in orientation to one side in the width direction, and a second engage mechanism including a second engage portion provided at a second end portion in the width direction of the protection cover and a second engaged portion which is provided in the unit casing on a side opposite from the first engaged portion across the opening in the width direction, and configured such that the second engage portion engages with the second engaged portion in orientation to the one side in the width direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a section view schematically showing a configuration of an image forming apparatus of a first embodiment. 
         FIG. 2A  is a section view showing an overall configuration of a process cartridge of the first embodiment. 
         FIG. 2B  is an enlarged section view of a part of the configuration of the process cartridge. 
         FIG. 3A  is perspective view of the process cartridge before attaching to the image forming apparatus. 
         FIG. 3B  is a perspective view of the process cartridge being attached to the image forming apparatus. 
         FIG. 4A  illustrates a state in which the protection cover is attached to a unit casing of the process cartridge of the first embodiment. 
         FIG. 4B  illustrates a state in which the protection cover is removed out of the unit casing of the process cartridge of the first embodiment. 
         FIG. 5A  illustrates a state in which the protection cover approaches to a body frame in attaching the process cartridge of the first embodiment to the image forming apparatus. 
         FIG. 5B  illustrates a state in which an abutting portion of the protection cover abuts against an abutment portion of the body frame and is held by a holding portion in attaching the process cartridge of the first embodiment to the image forming apparatus. 
         FIG. 6A  illustrates a state in which the protection cover is attached to the process cartridge. 
         FIG. 6B  is a section view schematically showing a configuration of the protection cover. 
         FIG. 7A  illustrates a state in which no external force acts on the protection cover attached to the process cartridge. 
         FIG. 7B  illustrates a state in which an external force acts vertically in orientation to an opening to the protection cover attached to the process cartridge. 
         FIG. 7C  illustrates a state in which an external force acts by grasping the protection cover attached to the process cartridge. 
         FIG. 8  is a section view schematically showing a configuration of a process cartridge of a first comparative example. 
         FIG. 9A  illustrates a state in which no external force acts on a protection cover of a second comparative example attached to the process cartridge. 
         FIG. 9B  illustrates a state in which an external force acts vertically in orientation to an opening to a protection cover of a second comparative example attached to the process cartridge. 
         FIG. 10A  illustrates a state in which no external force acts on a protection cover of a third comparative example attached to the process cartridge. 
         FIG. 10B  illustrates a state in which an external force acts by grasping the protection cover attached of the third comparative example to the process cartridge. 
         FIG. 11A  illustrates a state in which a protection cover of a second embodiment is attached to the process cartridge. 
         FIG. 11B  is a section view schematically showing the protection cover of the second embodiment. 
         FIG. 12A  illustrates a state in which no external force acts on a protection cover of the second embodiment attached to the process cartridge. 
         FIG. 12B  illustrates a state in which an external force in an X-axis direction or an upward moment act to the protection cover of the second embodiment attached to the process cartridge. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Embodiments of the present invention will be described in detail below with reference to the drawings. 
     First Embodiment 
     Image Forming Apparatus 
       FIG. 1  is a section view schematically showing a configuration of an image forming apparatus  60  of the present embodiment. As shown in  FIG. 1 , the image forming apparatus  60  is a tandem type intermediate transfer full-color printer in which image forming portions  60 Y,  60 M,  60 C and  60 Bk are arrayed along an under surface of an intermediate transfer belt  61 . 
     In an image forming portion  60 Y, a yellow toner image is formed on a photoconductive drum  1 Y and is transferred to an intermediate transfer belt  61 . In an image forming portion  60 M, a magenta toner image is formed on a photoconductive drum  1 M and is transferred to the intermediate transfer belt  61 . Cyan and black toner images are formed respectively on the photoconductive drums  1 C and  1  Bk in the image forming portions  60 C and  60 Bk and are transferred to the intermediate transfer belt  61 . It is noted that these photoconductive drums  1 Y,  1 M,  1 C and  1 Bk are exemplary image carriers. It is also noted that while only the photoconductive drum  1 Bk among these photoconductive drums  1 Y,  1 M,  1 C and  1 Bk will be typically explained in the following explanation, configurations of the other photoconductive drums  1 Y,  1 M, and  1 C are the same with that of the photoconductive drum  1 Bk. 
     The four color toner images transferred to the intermediate transfer belt  61  are conveyed to a secondary transfer portion T2 and are secondarily transferred to a sheet S. A separation roller  63  separates the sheet S pulled out of a sheet cassette  62  one by one and sends to a registration roller  65 . The registration roller  65  feeds the sheet S to the secondary transfer portion T2 by synchronizing with the toner image on the intermediate transfer belt  61 . The sheet S on which the four color toner images are secondarily transferred is heated and pressed by a fixing device  9  to fix the toner images on a surface of the sheet S. 
     As shown in  FIG. 1 , the intermediate transfer belt  61  which is one exemplary intermediate transfer body is disposed, as a transfer medium, in contact with the photoconductive drum  1 Bk of a process cartridge  30  which is one exemplary image carrier unit. A rail RL is additionally provided in the image forming apparatus  60  and guides the process cartridge  30  in the rotational axis direction of the photoconductive drum  1 Bk. 
     (Image Forming Portion) 
       FIG. 2  illustrates a configuration of the process cartridge. As shown in  FIG. 1 , the image forming portions  60 Y,  60 M,  60 C and  60 Bk are constructed almost in the same manner except that the colors of the toner used in their developing devices are different as yellow, magenta, cyan and black. Then, the image forming portion  60 Bk will explained in the following explanation, and an overlapped explanation of the other image forming portions  60 Y,  60 M and  60 C will be omitted here. 
     As shown in  FIG. 1 , in the image forming portion  60 Bk a charging device  2 , an exposure device  68 , a developing device  3 , a transfer roller  4 , and a drum cleaning device  5  are disposed around the photoconductive drum  1 Bk. The photoconductive drum  1 Bk includes a photoconductive layer formed on an outer circumferential surface of an aluminum cylinder, and rotates at a predetermined processing speed. 
     The charging device  2  applies a vibration voltage, in which an AC voltage is superimposed on a negative DC voltage, to a charging roller to charge the photoconductive drum  1 Bk with homogeneous negative potential. The exposure device  68  scans a laser beam obtained by ON-OFF modulating a scan line image signal in which each color image is developed by a rotation mirror to draw an electrostatic image of an image on the surface of the photoconductive drum  1 Bk. 
     Developer containing toner and carrier is filled in a developer container  32  shown in  FIG. 2A . Agitating and conveying screws  28   a  and  28   b  agitate/circulate the developer within a developer container  32  to charge the toner to minus and the carrier to plus. A development sleeve  27  carries the developer by magnetic force of magnets disposed within the development sleeve  27 . A layer thickness restricting portion  29  restricts a layer thickness of the developer carried by the development sleeve  27 . The development sleeve  27  carries the charged developer in a napped state and frictionally slides around the photoconductive drum  1 Bk. When the vibration voltage, in which an AC voltage is superimposed on a DC voltage, is applied to the development sleeve  27 , the toner of the development sleeve  27  is transferred to the electrostatic image on the photoconductive drum  1 Bk and the electrostatic image on the photoconductive drum  1 Bk is developed as a toner image. 
     As shown in  FIG. 1 , new toner corresponding to an amount of toner consumed in the developing device  3  to form the image is replenished from a toner cartridge  605  to the developing device  3  through a toner conveying path not shown. 
     The transfer roller  4  is built in an intermediate transfer unit  6  including the intermediate transfer belt  61 . The transfer roller  4  presses the intermediate transfer belt  61  and forms a transfer portion between the photoconductive drum  1 Bk and the intermediate transfer belt  61 . The negative toner image carried on the photoconductive drum  1 Bk is transferred to the intermediate transfer belt  61  by applying a positive DC voltage to the transfer roller  4 . 
     The intermediate transfer belt  61  is suspended around and supported by a tension roller  7   c , a drive roller  66  which functions also as a secondary transfer roller, and tension rollers  7   a  and  7   b , and rotates in a direction of an arrow C by being driven by the drive roller  66 . A secondary transfer roller  67  is in contact with the intermediate transfer belt  61  whose inner surface is supported by the drive roller  66  and forms the secondary transfer portion T2. The toner image on the intermediate transfer belt  61  is transferred to the sheet S by a positive DC voltage applied to the secondary transfer roller  67 . 
     The drum cleaning device  5  is configured such that a cleaning blade  5   b  rubs the photoconductive drum  1 Bk to remove transfer residual toner attached on the surface of the photoconductive drum  1 Bk. A belt cleaning device  8  is configured such that a cleaning blade rubs the intermediate transfer belt  61  to recover transfer residual toner on the surface of the intermediate transfer belt  61 . 
     (Process Cartridge) 
     As shown in  FIG. 1 , the process cartridge  30  is what the photoconductive drum  1 Bk of the image forming portion  60 Bk, the developing device  3  and others are integrally unitized to be able to attach to/detach from the image forming apparatus  60 . The process cartridge  30  can be attached to a body frame (casing of the image forming apparatus) HF of the image forming apparatus  60  in a state in which a protection cover  10  described later is removed by moving the process cartridge  30  in the rotational axis direction of the photoconductive drum  1 Bk. 
     As shown in  FIG. 2A , the process cartridge  30  is constructed by connecting a drum unit  33  with the developing device  3 . The drum unit  33  includes a photoconductive drum container (unit casing)  31 , the photoconductive drum  1 Bk, the charging device  2 , the cleaning blade  5   b , and a toner discharge screw  5   c . The toner discharge screw  5   c  conveys the transfer residual toner scraped by the cleaning blade  5   b  to a cleaner recovery space  5   a  to convey a recovery toner container not shown. 
     The exposure device  68  shown in  FIG. 1  performs scanning exposure of the laser beam to the surface of the photoconductive drum  1 Bk through an opening located at an under surface of the process cartridge  30 . A large opening  30   a  for making the photoconductive drum  1 Bk come into contact with the intermediate transfer belt  61  shown in  FIG. 1  is made through an upper surface of the process cartridge  30 , and the photoconductive drum  1 Bk is exposed upward. 
     As shown also in  FIGS. 3A and 3B , the process cartridge  30  includes the photoconductive drum  1 Bk capable of carrying the electrostatic image, the photoconductive drum container  31  rotatably storing the photoconductive drum  1 Bk with the opening  30   a  for exposing a part of the photoconductive drum  1 Bk, the protection cover  10  covering the opening  30   a , and an engage mechanism  100  slidably attaching the protection cover  10  to the photoconductive drum container  31  in the rotational axis direction of the photoconductive drum  1 Bk. 
     (Protection Cover) 
       FIG. 3A  is a perspective view of the process cartridge  30  before attaching to the image forming apparatus  60  of the present embodiment.  FIG. 3B  is a perspective view of the process cartridge  30  during when it is attached to the image forming apparatus  60  of the present embodiment.  FIG. 6A  illustrates a state in which the protection cover  10  is attached to the process cartridge  30 .  FIG. 6B  is a section view schematically showing a configuration of the protection cover  10 . Here, in the present embodiment, the rotational axis direction of the photoconductive drum  1 Bk will be defined as a Y-axis direction, a width direction orthogonal to the rotational axis direction of the photoconductive drum  1 Bk, i.e., a moving direction of the intermediate transfer belt  61  in contact with the photoconductive drum  1 Bk, is defined as an X-axis direction, and a vertical direction orthogonal to these X and Y-axes directions will be defined as a Z-axis direction. 
     As shown in  FIG. 3A , the process cartridge  30  is attached with the protection cover  10  and the photoconductive drum  1 Bk is covered by the protection cover  10  (see  FIG. 3B ) right after when the process cartridge  30  is unpacked. As shown in  FIGS. 3A and 4A , the protection cover  10  is fixed to the photoconductive drum container  31  by locking a hook  43  made of resin spring and provided to the photoconductive drum container  31  of the process cartridge  30  by an engagement hole  13  in a manner of snap-fit. Due to that, even if the process cartridge  30  is slanted in various directions including a longitudinal direction, the protection cover  10  will not readily come off. It is noted that as shown in  FIGS. 3B and 4B , the hook  43  is configured such that it deflects and the protection cover  10  is unlocked from the opening  13  when a manipulation force in a direction of an arrow P increases more than a predetermined degree. 
     As shown in  FIG. 3A , a positioning mark  41  is marked at a positioning portion (abutment portion)  40  of the protection cover  10 . The positioning portion  40  is provided at an inner side end in the Y-axis direction of the protection cover  10  and is formed into a shape of a flange projecting upward. The positioning portion  40  is also formed such that its profile is circular arc when seen from the Y-axis direction. A user (or a service technician) sets the process cartridge  30  into the image forming apparatus  60  by positioning the positioning mark  41  of the protection cover  10  at a positioning mark IM marked on the body frame HF of the image forming apparatus  60  (see  FIG. 1 ). The hook  43  comes off from the opening  13  and the process cartridge  30  is inserted into the image forming apparatus  60  while leaving the protection cover  10  by pushing a grip  42  in a direction of an arrow P in the state in which the positioning mark  41  is positioned at the mark IM. 
     That is, the protection cover  10  includes the positioning portion  40  that abuts against the body frame HF and moves the protection cover  10  in the Y-axis direction with respect to the photoconductive drum container  31  when the photoconductive drum container  31  is moved in the Y-axis direction to attach to the body frame HF. 
     As shown in  FIG. 3B , the process cartridge  30  moves inside by being guided by the rail RL (see  FIG. 1 ) of the image forming apparatus  60 . The process cartridge  30  is moved in the direction of the arrow P while attaching the protection cover  10  to attach to the image forming apparatus  60 . During such process, the positioning portion  40  abuts against the body frame HF of the image forming apparatus  60  and the protection cover  10  is left at a front side. 
     Here, as shown in  FIG. 5A , the body frame HF includes an abutted portion  15  against which the positioning portion  40  of the protection cover  10  abuts in attaching the process cartridge  30  to the body frame HF by moving in the Y-axis direction and a holding portion  14  configured to hold the protection cover  10  that has been attached to the process cartridge  30 . The holding portion  14  is formed of a fitting portion configured to hold the protection cover  10  by fitting the positioning portion  40  of the protection cover  10 . In the present embodiment, the holding portion  14  is a rectangular concave portion formed in the body frame HF and is provided with a plurality of holding projections  16  projecting in orientation to inside at part of an inner surface  14   a . The abutment portion  15  is provided inside in the Y-axis direction of the holding portion  14 . 
     Therefore, when the photoconductive drum container  31  is attached to the body frame HF by moving the photoconductive drum container  31 , to which the protection cover  10  is attached, in the Y-axis direction, the protection cover  10  is removed from the photoconductive drum container  31  by being moved in the Y-axis direction with respect to the photoconductive drum container  31  by abutting the positioning portion  40  of the protection cover  10  against the abutment portion  15  of the body frame HF. At this time, a peripheral side surface of the positioning portion  40  is fitted into the holding projections  16  and the protection cover  10  is held by the body frame HF. Thereby, the protection cover  10  is held by the body frame HF, and it is possible to prevent the protection cover  10  from dropping right after when the photoconductive drum container  31  is attached and when the protection cover  10  is removed out of the photoconductive drum container  31  when the photoconductive drum container  31  is completely attached to the body frame HF. Accordingly, this arrangement makes it possible to improve workability of a replacement work of the process cartridge  30  by preventing the unintentional drop of the protection cover  10 . 
     The process cartridge  30  is lifted by a slope by a final 10 mm in the insertion process to make the photoconductive drum  1 Bk come into contact with the intermediate transfer belt  61 . When the process cartridge  30  is completely inserted, the protection cover  10  is held by the holding portion  14  of the body frame HF while keeping an initial position. The user takes the protection cover  10  out of the body frame HF by pulling in orientation to the front side. 
     As shown in  FIG. 3A , the engage mechanism  100  includes first and second engage mechanisms  101  and  102 . 
     The first engage mechanism  101  includes a first engage portion  101   a  provided at a first end portion  10   a  in the X-axis direction of the protection cover  10  and a first engaged portion  101   b  provided in the photoconductive drum container  31  and engaged with the first engage portion  101   a  and is configured such that the first engage portion  101   a  engages with the first engaged portion  101   b  in orientation to one side X1 in the X-axis direction. That is, the first engage mechanism  101  is configured such that the first engage portion  101   a  formed convexly in orientation to one side X1 in the X-axis direction engages with the first engaged portion  101   b  formed concavely opened in orientation to another side X2 in the X-axis direction. Here, the engagement of the first engage portion  101   a  with the first engaged portion  101   b  means that the first engage portion  101   a  of the convex shape fits into the first engaged portion  101   b  of the concave shape in one side X1 in the X-axis direction. 
     Still further, the first engage portion  101   a  includes a plurality of first convex portions (first engage members)  11 R 1  through  11 R 4  disposed at a plurality of places with certain intervals along the Y-axis direction. The first engaged portion  101   b  also includes a first concave portion  34 R along the Y-axis direction. It is noted that because all of the first convex portions  11 R 1  through  11 R 4  are constructed and act in the same manner, one convex portion will be explained typically by denoting as  11 R in the following explanation. 
     The second engage mechanism  102  includes a second engage portion  102   a  provided at a second end portion  10   b  of the protection cover  10  and a second engaged portion  102   b  formed into a shape of a groove for example and provided in the photoconductive drum container  31  on a side opposite from the first engaged portion  101   b  across the opening  30   a  in the X-axis direction, and is configured such that the second engage portion  102   a  engages with the second engaged portion  102   b  in orientation to one side X1 in the X-axis direction. That is, the second engage mechanism  102  is configured such that the second engage portion  101   a  formed into a convex shape in orientation to one side X1 in the X-axis direction engages with the second engaged portion  101   b  formed into a concave shape opening in orientation to the other side X2 in the X-axis direction. Here, the engagement of the second engage portion  102   a  with the second engaged portion  102   b  means that the second engage portion  102   a  of the convex shape fits into the second engaged portion  102   b  of the concave shape in orientation to one side X1 in the X-axis direction. 
     The second engage portion  102   a  also includes a plurality of second convex portions (second engage members)  11 L 1  through  11 L 4  disposed at a plurality of places at certain intervals along the Y-axis direction. The second engaged portion  102   b  also includes a second concave portion  34 L along the Y-axis direction. It is noted that because all of the second convex portions  11 L 1  through  11 L 4  are constructed and act in the same manner, one convex portion will be explained typically by denoting as  11 L in the following explanation. 
     As shown in  FIG. 6A , the protection cover  10  can be moved in the rotational axis direction of the photoconductive drum  1 Bk in a state in which the first projection  11 R is engaged with the first concave portion  34 R and the second projection  11 L is engaged with the second concave portion  34 L. 
     The protection cover  10  is provided with the plurality of first engage members  11 R 1  through  11 R 4  and the plurality of second engage members  11 L 1  through  11 L 4  arrayed in the longitudinal direction (in the Y-axis direction, rotational axis direction) at both ends in the X-axis direction thereof. Because the first engage members  11 R 1  through  11 R 4  and the second engage members  11 L through  11 L 4  engage at a plurality of positions in the longitudinal direction, the protection cover  10  functions also as a rail guiding the insertion in the Y-axis direction of the process cartridge  30  while restricting the position of the process cartridge  30  in the Z-axis direction in attaching to the image forming apparatus  60 . 
     By the way, the protection cover  10  is a part attached to the process cartridge  30  only during a period until when the process cartridge  30  is attached to the image forming apparatus  60  undergoing a storage condition after when the process cartridge  30  is manufactured and is packed. In order to let the user understand that the process cartridge  30  is a component used by removing the protection cover  10 , the protection cover  10  is colored by conspicuous color such as orange fluorescent color which is obviously different from surrounding parts within the image forming apparatus  60 . 
     Therefore, there is a possibility that a user who handles the process cartridge  30  for the first time erroneously removes the protection cover  10  immediately from the process cartridge  30  in taking out the process cartridge  30  by unpacking the process cartridge  30 . There is also another possibility that the user removes the protection cover  10  from the process cartridge  30  in a stage before inserting the process cartridge  30  to the image forming apparatus  60 . 
     However, the protection cover  10  is a part that functions also as a guide in inserting the process cartridge  30  to the image forming apparatus  60  and is automatically removed from the process cartridge  30 . Therefore, if the protection cover  10  is removed before inserting the process cartridge  30  to the image forming apparatus  60 , the chance of using the protection cover  10  as the insertion guide in setting the process cartridge  30  in the image forming apparatus  60  is lost and the original role of the protection cover  10  cannot be achieved. If the process cartridge  30  is inserted into the image forming apparatus  60  in a state in which the protection cover  10  is removed, there is a possibility that the photoconductive drum  1 Bk collides against peripheral devices and structures and the photoconductive drum  1 Bk is damaged in the processes of positioning and inserting the process cartridge  30  into the image forming apparatus  60 . 
     Still further, if the protection cover  10  is tried to be forcibly removed from the process cartridge  30 , there is a possibility that the photoconductive drum  1 Bk is damaged by colliding against the protection cover  10  and tools by momentum in removing the protection cover  10 . 
     (Engagement Structure of Present Embodiment) 
       FIGS. 7A, 7B, and 7C  illustrate engagement states of the protection cover  10  with the process cartridge  30 .  FIG. 7A  illustrates a state in which the protection cover  10  is attached.  FIG. 7B  illustrates a state in which the protection cover  10  is pressed downward, and  FIG. 7C  illustrates a state in which the protection cover  10  is grasped from the X-axis direction. 
     As shown in  FIG. 2B , depth directions of the grooves of the first and second concave portions  34 R and  34 L of the process cartridge  30  orient in the same direction. 
     As shown in  FIG. 6B , projecting directions of the claws of the first and second convex portions  11 R and  11 L of the protection cover  10  are the same. As shown also in  FIG. 3B , the projecting directions of the claws of the first and second convex portions  11 R and  11 L of the protection cover  10  orient both in the direction of X1 in  FIG. 3B . 
     Because the first convex portion  11 R is engaged with the first concave portion  34 R and the second convex portion  11 L is engaged with the second concave portion  34 L in the same time, the protection cover  10  is slidable in the Y-axis direction while being restricted so as not to deviate from the process cartridge  30  in the Z-axis direction. 
     The process cartridge  30  also includes a restricting portion  80  in the present embodiment. The restricting portion  80  is provided either at the photoconductive drum container  31  or the protection cover  10  and is configured to restrict the protection cover  10  attached to the photoconductive drum container  31  from moving in the other side X2 in the X-axis direction of the protection cover  10  by abutting against the photoconductive drum container  31  or the protection cover  10 . 
     As shown in  FIG. 7A , the restricting portion  80  is provided on the photoconductive drum container  31  so as to face the opening  34   a  of the second concave portion  34 L, which is formed into a concave shape, in the X-axis direction when seen from the Y-axis direction and is configured to restrict the move in the X-axis direction of the second convex portion  11 L engaged with the second concave portion  34 L between the second concave portion  34 L and the restricting portion  80 . Still further, the second concave portion  34 L is formed such that it opens in orientation to the photoconductive drum  1 Bk side in the X-axis direction, and the restricting portion  80  is disposed between the second concave portion  34 L and the photoconductive drum  1 Bk in the X-axis direction. 
     As shown in  FIG. 6A , the restricting portion  80  provided in the process cartridge  30  abuts against an inner surface  10   c  facing the other side X2 in the X-axis direction of the protection cover  10  at the position close to the second concave portion  34 L and restricts the protection cover  10  from being shifted in the X-axis direction and coming off. 
     As shown in  FIG. 7A , the first and second convex portions  11 R and  11 L provided at the both end portions in the X-axis direction of the protection cover  10  orient in the same direction from each other in the present embodiment. The first and second convex portions  11 R and  11 L projecting in the same direction in the protection cover  10  engage with the first and second concave portions  34 R and  34 L concaved in the same direction in the photoconductive drum container  31 . 
     When the protection cover  10  is pressed downward (in the Z-axis direction) by a force F as shown in  FIG. 7B , while a degree of the engagement of the first convex portion  11 R becomes less, a degree of the engagement of the second convex portion  11 L increases, so that the protection cover  10  will not come off from the photoconductive drum container  31 . Even when the protection cover  10  is twisted upward with a moment M, while a degree of the engagement of the first convex portion  11 R is lessened, a degree of the engagement of the second convex portion  11 L increases, so that the protection cover  10  will not come off from the photoconductive drum container  31 . Here, ‘the engagement becomes shallow or is lessened’ means that a degree of the engagement (a degree of entry entering a groove bottom direction) of each of the convex portions  11 R and  11 L with each of the concave portions  34 R and  34 L is lessened. ‘The engagement is deepened’ means that a degree of the engagement (a degree of entry entering the groove bottom direction) of each of the convex portions  11 R and  11 L with each of the concave portions  34 R and  34 L increases. 
     In a case where a force F′ is applied to the both ends in the X-axis direction of the protection cover  10  by gripping the protection cover  10  in the X-axis direction as shown in  FIG. 7C , the inner surface  10   c  of the protection cover  10  abuts against the restricting portion  80  of the photoconductive drum container  31  and each of the convex portions  11 R and  11 L cannot move in a direction in which the engagement is lessened. The restricting portion  80  provided on the photoconductive drum container  31  prevents the protection cover  10  from deviating in the X-axis direction. 
     The case where the moment M acts on the protection cover  10  happens in a case where the user tries to removes the protection cover  10  at first by erroneously considering the protection cover  10  as a packing member. The case where the force F′ acts on the protection cover  10  is a case where the user tries to remove the protection cover  10  at first. Such cases are readily assumable, and the narrower the area covered by the protection cover  10  on the process cartridge  30 , the higher the possibility of deviation of each of the convex portions  11 R and  11 L is. 
     Effects of the Present Embodiment 
     According to the present embodiment, the engagements of the first and second convex portions  11 R and  11 L engaging respectively at the both right and left sides seen from the inserting direction (Y-axis direction) of the protection cover  10  and the process cartridge  30  orient in the same direction X1 in the horizontal direction (X-axis direction) and the protection cover  10  is restricted from deviating in the vertical direction (Z-axis direction) by engaging the convex portions  11 R and  11 L respectively with the concave portions  34 R and  34 L. 
     According to the present embodiment, because the first and second convex portions  11 R and  11 L orient in the same direction, either one of the convex portions  11 R and  11 L bites in a direction of increasing a degree of engagement when an external force F or a moment M acts on the protection cover  10 , the protection cover  10  is not readily removed. Even if the protection cover  10  is a size protecting a minimum necessary size of the opening  30   a , the protection cover  10  will not be removed unintentionally during the replacement work of the process cartridge  30 . Or, even if one tries to remove the protection cover  10  forcibly from the process cartridge  30  by performing an unanticipated operation, the protection cover  10  is hardly removed. The present embodiment makes it possible to realize such engagement structure of the protection cover  10  by the simple structure. 
     According to the present embodiment, because the protection cover  10  is hardly removed even if the user erroneously tries to remove the protection cover  10 , there is less possibility of damaging the photoconductive drum  1 Bk by removing the protection cover  10 . Because the protection cover  10  can be utilized as the insertion guide of the process cartridge  30  while steadily exhibiting the function of the insertion guide originally given to the protection cover  10 , the works for setting and replacing the process cartridge  30  of the user can be made ready. 
     According to the present embodiment, because the process cartridge  30  is configured to be able to replace the developing device  3  and the drum unit  33  in a body, readiness of maintenance is improved and the works for setting and replacing the process cartridge  30  of the image forming apparatus  60  can be performed readily. Because the protection cover  10  for protecting the photoconductive drum  1 Bk is provided in a new process cartridge  30 , there will be no such a case where the surface of the photoconductive drum  1 Bk is unintentionally touched or damaged in handling the process cartridge  30 . Because the protection cover  10  is utilized not only as the protection member but also as the guide member in attaching the process cartridge  30  to the body frame HF of the image forming apparatus  60 , the works for setting and replacing the process cartridge  30  are improved. 
     According to the present embodiment, even if the protection cover  10  is a size of protecting the minimum necessary size of the opening  30   a , the protection cover  10  is hardly removed unintentionally during the replacement work of the process cartridge  30 . The present embodiment makes it possible to realize the engagement structure of the protection cover  10  that is hardly removed even if it is tried to be forcibly removed by an unanticipated operation by the simple configuration. Because the present embodiment also makes it possible to exhibit the original effect of using the protection cover  10  as the insertion guide of the process cartridge  30 , the works for setting and replacing the process cartridge  30  of the user can be readily realized. It is also possible to prevent such problem that the photoconductive drum  1 Bk is damaged by an erroneous operation of the user. 
     First Comparative Example 
       FIG. 8  illustrates a configuration of a process cartridge  50  of a first comparative example. As shown in  FIG. 8 , in the first comparative example, a protection cover  51  is attached to the process cartridge  50  so as to cover an opening  55  for exposing the photoconductive drum  1 Bk to the outside. In the same manner with the first embodiment, the protection cover  51  is slidable in the longitudinal direction of the photoconductive drum container  53  (the inserting direction of the process cartridge  50 ) by engaging a casing of the process cartridge  50  with the protection cover  51  through engagement claws  52 R and  52 L. 
     Engagement grooves  54 R and  54 L formed into a shape of a crank are provided to the photoconductive drum container  53  across the opening  55 . Each of the engagement grooves  54 R and  54 L is formed into the shape of the crank such that opening sides of the grooves approach with each other. 
     The protection cover  51  is provided with the engagement claws  52 R and  52 L in the shape of the crank corresponding to the engagement grooves  54 R and  54 L. The protection cover  51  slidable in the rotational axis direction of the photoconductive drum  1 Bk (the inserting direction of the process cartridge  50 ) by engaging the engagement claw  52 R with the engagement groove  54 R and the engagement claw  52 L with the engagement groove  54 L. 
     Because the engagement grooves  54 R and  54 L formed into the shape of the crank hold the engagement claws  52 R and  52 L formed into the shape of the crank in the first comparative example, looseness between the protection cover  51  and the photoconductive drum container  53  is reduced. However, because the engagement claws  52 R and  52 L are configured such that they engage outwardly from each other, the protection cover  51  deflects convexly to the outside and the engagements with the engagement claws  52 R and  52 L are readily disengaged in a case where the user grasps and holds the protection cover  51  so as to add a force F1. For example, in a case where the user unpacks the process cartridge  50  and grasps and holds the protection cover  51  so as to add the force F1 as a load, the protection cover  51  deflects convexly to the outside and the engagement claws  52 L and  52 R are readily disengaged. If engagement claws  52 L and  52 R are disengaged, there is a possibility that the user misunderstand that the protection cover  51  is a member that should be removed before inserting the process cartridge  50  into the body frame HF of the image forming apparatus  60 . The user also tends to misunderstand that a process of inserting the process cartridge  50  into the image forming apparatus  60  after removing the protection cover  51  is correct if the protection cover  51  can be readily removed. 
     There is also another problem that because a depth of the engagement of the engagement claws  52 R and  52 L and the engagement grooves  54 R and  54 L formed respectively into the shape of the crank is deepened, space utilization for storing parts of the process cartridge  50  is worsened. 
     With regard this problem, according to the image forming apparatus  60  of the first embodiment described above, the first and second convex portions  11 R and  11 L orient in the same direction, so that the protection cover  10  will not be readily removed because either one convex portion  11 R or  11 L bites into a direction in which the degree of engagement increases even if an external force F or a moment M acts on the protection cover  10 . Still further, because the both of the first and second engage mechanisms  101  and  102  can engage by the engagement operation only in one side X1 in the X-axis direction, it is possible to make the depth of the engagement shallow and to improve the space utilization as compared to the case of engaging the engagement claws  52 R and  52 L form into the shape of the crank of the first comparative example. 
     Second Comparative Example 
       FIGS. 9A and 9B  illustrate an engagement structure of the protection cover  10  of a second comparative example.  FIG. 9A  illustrates a state in which the protection cover  10  is attached and  FIG. 9B  is illustrates a state in which the protection cover  10  is pressed downward. As shown in  FIG. 9A , the protection cover  10  is additionally provided with the engagement claws  71 R and  71 L formed into a shape of a hook corresponding to engagement grooves  72 R and  72 L of a photoconductive drum container  70 . Each of the engagement claws  71 R and  71 L is formed such that a front edge thereof faces the inside. The protection cover  10  is slidable in the rotational axis direction of the photoconductive drum  1 Bk (the insertion direction of the process cartridge) by engaging the engagement claw  71 R with the engagement groove  72 R and the engagement claw  71 L with the engagement groove  72 L. 
     Because the engagement claws  71 R and  71 L formed in the shape of the hook which is simpler than the shape of the crank are used in the second comparative example, it is possible to attach the protection cover  10  which is less costly than the protection cover  51  of the first comparative example. Still further, the protection cover  10  of the second comparative example enables to assure a large degree of engagement in the horizontal direction, so that the protection cover  10  will be hardly removed from the photoconductive drum container  70  as compared to that of the first comparative example. 
     As shown in  FIG. 9B , because the engagement claws  71 R and  71 L are formed in orientation to the inside with each other in the second comparative example, the protection cover  10  deflects and a distance between the engagement claws  71 R and  71 L is opened and the engagement claws  71 R and  71 L are disengaged if the user presses the protection cover  10  by a force F from above the protection cover  10 . 
     With regard this problem, according to the image forming apparatus  60  of the first embodiment described above, the first and second convex portions  11 R and  11 L orient in the same direction, so that the protection cover  10  will not be readily removed because either one convex portion  11 R or  11 L bites into a direction in which the degree of engagement increases even if an external force F or a moment M acts on the protection cover  10 . 
     Comparative Example 
       FIGS. 10A and 10B  illustrate an engagement structure of the protection cover  10  of a third comparative example.  FIG. 10A  illustrates a state in which the protection cover  10  is attached, and  FIG. 10B  illustrates a state in which the protection cover  10  is grasped. As shown in  FIG. 10A , the protection cover  10  is additionally provided with engagement claws  71 R and  71 L corresponding to engagement grooves  72 R and  72 L of the photoconductive drum container  70 . The engagement claws  71 R and  71 L are formed such that their front ends face outside from each other. 
     As shown in  FIG. 10B , because the engagement claws  71 R and  71 L are formed to face outside from each other in the third comparative example, the protection cover  10  deflects and a distance between the engagement claws  71 R and  72 L becomes narrow and are disengaged in a case where the user grasps the protection cover  10  from both sides thereof by a force F. 
     With regard this problem, according to the image forming apparatus  60  of the first embodiment described above, the first and second convex portions  11 R and  11 L orient in the same direction, so that the protection cover  10  will not be readily removed because either one convex portion  11 R or  11 L bites into a direction in which the degree of engagement increases even if the external force F or the moment M acts on the protection cover  10 . 
     Fourth Comparative Example 
     As disclosed in Japanese Patent Application Laid-open No. 2009-75274, a cylindrical protection cover covering an outer periphery of the process cartridge is provided in a fourth comparative example. The protection cover is not be removed unintentionally even if a force acts from any direction in the fourth comparative example. However, it is costly and wasteful in terms of resources to use such cylindrical protection cover as the part which is used only in setting the process cartridge. There is another problem that because a packing size in shipping the product increases, a distribution cost increases. 
     With regard this problem, according to the image forming apparatus  60  of the first embodiment described above, the first and second convex portions  11 R and  11 L orient in the same direction, so that the protection cover  10  will not be readily removed because either one convex portion  11 R or  11 L bites into a direction in which the degree of engagement increases even if an external force F or a moment M acts on the protection cover  10 . Still further, because the protection cover  10  covers only the opening  30   a , it is possible to reduce the size as compared to the case of covering the entire process cartridge of the fourth comparative example. This arrangement makes it possible to reduce the packing size and to cut the distribution cost. 
     Second Embodiment 
       FIG. 11A  illustrates a state in which a protection cover  10  of a second embodiment is attached to the process cartridge  30 .  FIG. 11B  which no external force acts on the protection cover  10  attached to the photoconductive drum container  31  of the process cartridge  30  of the second embodiment.  FIG. 12B  illustrates a state in which an external force F′ in the X-axis direction or a moment M acts on the protection cover  10  attached to the photoconductive drum container  31  of the second embodiment. 
     As shown in  FIG. 6A , the structure (the restricting portion  80 ) blocking the respective engagements of the convex portions  11 R and  11 L with the concave portions  34 R and  34 L from becoming shallow is provided on the side of the process cartridge  30  in the first embodiment. In contrary, a protection portion (restricting portion)  20  is provided on the side of the protection cover  10  as a structure blocking the respective engagements of the convex portions  11 R and  11 L with the concave portions  34 R and  34 L from becoming shallow in the second embodiment. The configuration of the second embodiment is the same with the first embodiment other than that structure, so that the same reference numerals in  FIGS. 1 through 7C  will be assigned to the components of the second embodiment common with those of the first embodiment in  FIGS. 11A through 12B  and an overlapped explanation will be omitted here. 
     (Engagement Structure of the Present Embodiment) 
     As shown in  FIG. 11A , the first and second concave portions  34 R and  34 L of the photoconductive drum container  31  and the first and second convex portions  11 R and  11 L of the protection cover  10  are the same with those of the first embodiment. The protection cover  10  is slidable in the Y-axis direction whole being restricted so as not to deviate in the Z-axis direction from the photoconductive drum container  31  in the same manner as shown in  FIGS. 3A and 3B  by engaging the second convex portion  11 L with the second concave portion  34 L in the same time of engaging the first convex portion  11 R with the first concave portion  34 R. The pluralities of respective convex portions  11 R and  11 L are disposed in the longitudinal direction of the process cartridge  30 . 
     As shown in  FIG. 12A , the protection cover  10  includes a protection portion  20  covering a projection  37  forming the second concave portion  34 L by turning around an outside in the X-axis direction of the second convex portion  11 L. The protection cover  10  includes the protection portion  20  disposed adjacent the second convex portion  11 L. Among a projection  36  forming the first concave portion  34 R and a projection  37  forming the second concave portion  34 L, the projection  37  which is not covered by the protection cover  10  is covered by the protection portion  20  in the present embodiment. The protection portion  20  is provided so as to cover the second convex portion  11 L exposed out of the protection cover  10  among the first and second convex portions  11 L and  11 R. As shown in  FIG. 11B , the protection portion  20  is a flange formed on an imaginary line  20   b  extended from a front end of the second convex portion  11 L to an imaginary line  11   a  and protects the second convex portion  11 L so as not to be exposed. 
     That is, the protection cover  10  includes a cover body  10   d , the first convex portion  11 R forming the first engage portion at a first end portion  10   a , a first connecting portion  10   e  connecting the cover body  10   d  with the first convex portion  11 R, the second convex portion  11 L forming the second engage portion at a second end portion  10   b , a second connecting portion  10   f  connecting the cover body  10   d  with the second convex portion  11 L and supporting the second convex portion  11 L such that the second convex portion  11 L is positioned on the opening  34   a  side of the second concave portion  34 L, the flange forming the protection portion  20  at the second end portion  10   b , and a third connecting portion  10   g  connecting the cover body  10   d  with the flange. 
     The third connecting portion  10   g  extends in the X-axis direction so as to straddle the second concave portion  34 L from the cover body  10   d  such that the flange is positioned on a side opposite from the opening  34   a  of the second concave portion  34 L and covers the second concave portion  34 L from an outside in a state in which the protection cover  10  is attached to the photoconductive drum container  31 . This arrangement makes it possible to prevent the protection cover  10  from being removed by a foreign matter inserted into the second engage mechanism  102  because the second concave portion  34 L is prevented from being exposed to the outside. 
     The protection portion  20  is provided in the protection cover  10  such that it is positioned in terms of the X-axis direction with respect the second concave portion  34 L on the side opposite from the opening  34   a  of the second concave portion  34 L, and restricts the protection cover  10  from moving to the other side X2 in the width direction by abutting against a surface on an opposite side from the opening  34   a  of the second concave portion  34 L in the X-axis direction. This arrangement makes it possible to suppress the second convex portion  11 L from abutting against the photoconductive drum  1 Bk when the protection cover  10  deflects. 
     The first connecting portion  10   e  extends in the X-axis direction so as to straddle the first concave portion  34 R from the cover body  10   d  and covers the first concave portion  34 R from an outside in a state in which the protection cover  10  is attached to the photoconductive drum container  31 . This arrangement makes it possible to prevent the protection cover  10  from being removed by a foreign matter inserted into the first engage mechanism  101  because the first concave portion  34 R is prevented from being exposed to the outside. 
     Effect of the Present Embodiment 
     As shown in  FIG. 12A , the protection portion  20  is formed integrally with the protection cover  10 . The protection portion  20  abuts from the X-axis direction against a surface on a side opposite from a direction in which the engagement becomes shallow in the projection  37  where the second concave portion  34 L is formed and restricts moves of the protection cover  10 . 
     As shown in  FIG. 12B , because the protection portion  20  abutting against the projection  37  receives an external force F′ in the X-axis direction in the present embodiment, the external force F′ acting on the protection cover  10  will not directly act on the second convex portion  11 L and the protection cover  10  hardly deflects. For instance, the external force F′ acts on the protection cover  10  when the user holds the process cartridge  30  by grasping the protection cover  10  by the both ends in the X-axis direction. Such a scene is readily imaginable. 
     As shown in  FIG. 12B , a deflection of the first convex portion  11 R is backed up by the projection  36  of the first concave portion  34 R and a deflection of the second convex portion  11 L is backed up by the projection  37  of the second concave portion  34 L in the present embodiment. Accordingly, this arrangement makes it possible to reduce a possibility of the protection cover  10  from being removed in a case where the external force F′ acts on the protection cover  10  and to steadily exhibit the function as the insertion guide originally given to the protection cover  10 . 
     According to the present embodiment, it is possible to reduce the possibility of the protection cover  10  from being removed even in a case where the external force F′ acts on the protection portion  20  from the X-axis direction. Because the flange-like protection portion  20  and the third connecting portion  10   g  enhance flexural rigidity of the second end portion  10   b  of the protection cover  10 , the protection portion  20  also receives a moment M of disengaging the first convex portion  11 R from the first concave portion  34 R and the moment M does not act only to the second convex portion  11 L and the protection cover  10  is hardly removed. Because the protection portion  20  restricts the projection  37 , the protection cover  10  is hardly shifted in the X-axis direction even if the engagement of the convex portions  11 R and  11 L becomes shallow. 
     According to the present embodiment, because the protection portion  20  is provided on the protection cover  10  side, a degree of freedom is large in terms of parts design and parts processing more than the case of the first embodiment in which the restricting portion  80  is provided on the process cartridge  30  side. The protection cover  10  has a relatively simple shape as compared to the photoconductive drum container  31  and is a component not requiring much precision. Accordingly, there is less restriction in terms of the parts design and parts processing and the degree of freedom is high to provide the protection portion  20  to the protection cover  10 . 
     OTHER EMBODIMENTS 
     The image forming apparatus  60  of the first and second embodiments described above can be carried out by another embodiment in which a part or the whole of the configuration of the embodiments are replaced with their substitutive configuration as long as the engagement direction of the first and second engage mechanisms  101  and  102  are the same. 
     Accordingly, the image forming apparatus  60  can be carried out regardless of one drum type, or a tandem type or an intermediate transfer type or a recording medium conveying type. It is also possible to carry out regardless a number of photoconductive drums, a charging method, an electrostatic image forming method, a transfer method, a fixing method, and others. While only a main part related to formation and transfer of toner images has been explained here, the present invention can be carried out in image forming apparatuses of various uses such as a printer, various printing machines, a copier, a facsimile, and a multi-function machine by adding necessary devices, equipment, and a casing structure. 
     The image forming apparatus  60  may be also carried out not only in the system in which the photoconductive drums  1 Y,  1 M,  1 C, and  1 Bk are exposed from below as shown in  FIG. 1  (the system in which the protection cover  10  covers an upper surface of the process cartridge  30 ), but also in a system in which the photoconductive drums  1 Y,  1 M,  1 C, and  1 Bk are exposed from above (a system in which the protection cover  10  covers a lower surface of the process cartridge  30 ). 
     It is also possible to carry out the invention not only in the case of orienting the both of the convex portions (engagement claws)  11 R and  11 L of the protection cover  10  in one direction X1 (orient in the left side) in the X-axis direction seen from the direction inserting the process cartridge  30  but also in a case of orienting the both of them in the other side X2 (orient in the right side) in the X-axis direction. 
     The present invention may be also carried out not only in the case in which the process cartridge  30  contains the drum cleaning device  5 , but also in a case in which the drum cleaning device  5  is provided as an independent replacement unit. The present invention may be carried out also in a case in which the drum cleaning device  5  and the charging device  2  are set as an independent replacement unit and the photoconductive drums  1 Y,  1 M,  1 C and  1 Bk and the developing device  3  are gathered as one process cartridge  30 . 
     Still further, while the both of the restricting portion  80  and the protection portion  20  are provided on the second engage mechanism  102  side in the embodiments described above, the present invention is not limited to that case and the restricting portion  80  and the protection portion  20  may be provided on the first engage mechanism  101  side. 
     Still further, while the first engage portion formed on the protection cover  10  is provided as the first convex portion  11 R, the second engage portion as the second convex portion  11 L, the first engaged portion formed on the photoconductive drum container  31  as the first concave portion  34 R and the second engaged portion as the second concave portion  34 L in the embodiments described above, the present invention is not limited to such a case. 
     Still further, while the first convex portion  11 R includes the plurality of first engage members  11 R 1  through  11 R 4  and the second convex portion  11 L includes the plurality of second engage members  11 L through  11 L 4  in the embodiments described above, the present invention is not limited to such a case. For instance, it is also possible to configure such that a number of the engage members of at least one of the first and second convex portion  11 R and  11 L is singular. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No 2013-182006, filed Sep. 3, 2013 which is hereby incorporated by reference herein in its entirety.