Patent Publication Number: US-2007098439-A1

Title: Image forming device

Description:
FIELD OF THE INVENTION  
      The present invention relates to an image forming device such as a copier, fax machine, printer, or a multifunction device that combines the functions of the foregoing.  
     BACKGROUND INFORMATION  
      In conventional image forming devices a drum unit comprising a photosensitive drum and a development unit comprising a development sleeve having an axis of rotation parallel to the axis of rotation of the photosensitive drum are coupled and in such state are inserted into and fitted inside an image forming device main body. In a process unit wherein the drum unit and the development unit are coupled, the timing for replacement of the drum unit and of the development unit are different, because the time for replacement of the drum unit is determined by degradation of the photosensitive drum, and time for replacement of the development unit is determined by lack of toner. Thus many image forming devices have been proposed in which the drum unit and the development unit are separate components and the drum unit and the development unit are each provided detachably on the image forming device main body.  
      Conventionally, for guiding such separate drum unit and development unit to their respective fixed positions within the image forming device main body, in a common configuration, guide grooves for the drum unit and for the development unit are provided on the main body frame, bosses of cylindrical or comparable shape are formed on the drum unit and on the development unit, and by inserting these bosses into the guide grooves and sliding, the units are positioned at their ultimate position.  
      However, in an image forming device having the drum unit and the development unit as separate components, there is the problem that when the drum unit and the development unit are fitted into the image forming device main body, an operation is required to match the boss parts formed on the drum unit and the development unit onto the groove parts formed in the main body frame, leading to complicated operations. Better operability has been demanded of the development unit in particular, as it must be removed from the image forming device main body each time a paper jam or similar matter is addressed.  
      As an example of the conventional art for guiding such separate drum unit and development unit to their respective fixed positions within the image forming device main body, a device is publicly known having a common insertion opening for the drum unit and the development unit and comprising a branching guide channel along which the drum unit and the development unit inserted through this common insertion opening are guided to their respective predetermined insertion opening.  
      Another publicly known device has insertion openings in the main body frame, and when the drum unit and development unit are fitted inside the image forming device main body, the drum unit is inserted through one insertion opening, and the development unit is inserted through the other two insertion openings.  
      In addition, there is a device constituted such that at least one of the drum unit and the development unit is provided detachably on the image forming device main body, and bosses for example protruding from the drum unit and development unit are inserted into corresponding guide grooves provided in the main body frame.  
      In all of these conventional examples, guide grooves for the drum unit and for the development unit are provided in the main body frame, bosses of cylindrical or comparable shape are formed on the drum unit and on the development unit, and they are positioned at their ultimate fixed positions by insertion of these bosses into the guide grooves and sliding.  
      But with such conventional art, in an image forming device in which the drum unit and the development unit are separate components, it is difficult to tell which unit should be inserted through which insertion opening when the drum unit and the development unit are to be fitted inside the image forming device main body, and trying to force one through the wrong insertion opening might cause breakage, etc. This is because the insertion openings for the units are of similar shape and are thus difficult for the operator to distinguish, and because in many cases the composition allows partial insertion even when insertion is made through the wrong insertion hole.  
      An object of the present invention is to provide an image forming device with improved operability at time of insertion and removal of the development unit.  
      Another object of the present invention is to provide an image forming device that makes it possible to prevent mis-operation when fitting the drum unit and the development unit.  
     SUMMARY OF THE INVENTION  
      The image forming device of the invention relating to claim  1  comprises a drum unit comprising a photosensitive drum and a development unit comprising a development sleeve disposed opposite the photosensitive drum when the units are coupled as separate components, wherein the drum unit and the development unit are each detachable from the image forming device main body.  
      This image forming device is configured such that a guide groove guiding the drum unit to a predetermined fitting position and a guides surface roughly parallel to the guide groove that guides the development unit to a predetermined fitting position are formed on the image forming device main body, a guide projection that fits into and moves along the guide groove is provided on the drum unit, and a development support part that is supported by and moves along the guide surfaces is provided on the development unit.  
      According to the invention relating to claim  1 , a guide groove that guides the drum unit and guide surface that supports the development unit are formed in the image forming device man body, a guide projection that fits into and moves along the guide groove is provided on the drum unit, and a development support part that is supported by and moves along the guide surface is provided on the development unit. When the development unit is inserted into the image forming device main body, it is sufficient simply to set the development support parts onto the guide surfaces and slide them. This improves the operability of the development unit, which is frequently removed at time of addressing paper jam or other such operation.  
      The invention relating to claim  2  is an image forming device according to claim  1 , wherein the guide surface is formed more inwardly in the unit insertion width direction than the guide groove.  
      According to the invention relating to claim  2 , mis-insertion is prevented with the following constitution. The unit insertion widths of the guide groove and of the guide surface are different, preventing the fitting of the guide projection on the drum unit onto the guide surface or the insertion of the development support part of the development unit into the guide groove.  
      The image forming device of the invention relating to claim  3  comprises a drum unit comprising a photosensitive drum and a development unit comprising a development sleeve that is disposed opposite the photosensitive drum when the units are coupled, wherein the drum unit and development unit are separate components, and the drum unit and the development unit are each detachable from the image forming device main body.  
      Formed in the image forming device main body are a first guide groove, which guides the drum unit into a predetermined fitting position, and second guide groove roughly parallel to the first guide groove that guides the development unit into a predetermined fitting position. Provided on the drum unit are first guide projection that engages with the first guide groove and moves along the first guide groove, and provided on the development unit is a second guide projection that engages with the second guide groove and moves along the second guide groove. The first guide groove and the second guide groove have different unit insertion widths, and the first guide projection and the second guide projection have different diameters.  
      According to the invention relating to claim  3 , mis-insertion of the drum unit and development unit into the image forming device main body can be prevented, because the unit insertion widths of the first guide groove, which guides the drum unit, and of the second guide groove, which guides the development unit, are different, and because the first guide projection provided on the drum unit, and the second guide projection provided on the development unit have different diameters.  
      The invention relating to claim  4  is the image forming device according to claim  3 , wherein the unit insertion width of the first guide groove is greater than the unit insertion width of the second guide groove, and the diameter of the first guide projection is smaller than the diameter of the second guide projection.  
      According to the invention relating to claim  4 , because the unit insertion width of the first guide groove is greater than the unit insertion width of the second guide groove, and the diameter of the first guide projection is smaller than the diameter of the second guide projection, the difference in unit insertion width of the first and second guide groove and the difference in diameter between the first and second guide projection are obvious, effectively preventing mis-insertion of the units. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a cross-sectional side view of an image forming device;  
       FIG. 2  is an external view of the above when the front cover is open;  
       FIG. 3  is an external view of the main body frame with guide grooves and guide surfaces formed thereupon;  
       FIG. 4  is a side view of the main body frame with guide grooves and guide surfaces formed thereupon;  
       FIG. 5  is an external view of the state of the drum unit fitted in the image forming device main body;  
       FIG. 6  is an external view of the state of the development unit fitted in the image forming device main body;  
       FIG. 7  is a partial side view of the development unit;  
       FIG. 8  is an external view of the state of the drum unit and the development unit fitted in the image forming device main body;  
       FIG. 9  is a cross-sectional side view of the state of the drum unit and the development unit fitted in the image forming device main body;  
       FIG. 10  is an external view of the state of the development unit fitted in the image forming device main body;  
       FIG. 11  is an external view of the development unit inserted into the image forming device main body;  
       FIG. 12  is an external view of the state of the drum unit and the development unit fitted in the image forming device main body;  
       FIG. 13  is a plan view of the state of the drum unit and the development unit fitted in the image forming device main body;  
       FIG. 14  is a lateral view of the state of first and second guide groove formed in the main body frame;  
       FIG. 15  is a plan view of the drum unit and development unit;  
       FIG. 16  is an external view of the drum unit inserted into the image forming device main body;  
       FIG. 17  is a plan view of the drum unit inserted into the image forming device main body;  
       FIG. 18  is a plan view of the development unit inserted into the image forming device main body; and  
       FIG. 19  is an external view of the state of the drum unit and development unit fitted in the image forming device main body. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Embodiments of the present invention will be explained with reference to the drawings.  
      Overall configuration of the image forming device  
     First Embodiment  
       FIG. 1  is a lateral cross-sectional view of the image forming device according to an embodiment of the present invention.  
      In this drawing, an image forming device  1  comprises, in an image forming device main body  2 , a paper feeding unit  4 , which feeds sheets of recording material P from a paper feeding tray  3 , a sheet transport unit  5 , which transports recording material P fed from the paper feeding unit  4  along sheet transport route R, an image forming unit  6 , which transfers a toner image to the recording material P that is transported by the sheet transport unit  5 , a fixing device  7 , which fixes on the recording material P the toner image transferred thereupon by this image forming unit  6 , and an ejection unit  9 , which ejects into paper ejection tray  8  the recording material P onto which the toner image has been fixed by this fixing device  7 . Examples of the recording material P include paper, plastic film, overhead projector transparencies, and the like.  
      The image forming unit  6  comprises a drum unit  10  having a photosensitive drum  11  and a development unit  20  having a development sleeve  22  (described below), and a transfer roller  19 , which transfers the toner image on the surface of the photosensitive drum  11  onto the recording material P. The drum unit  10  and the development unit  20  are constituted as separate unit, and each is detachable from the image forming device main body  2 .  
      The image forming device main body  2  is covered by an outer cover  35  (see  FIG. 2 ), and opening the front cover  35 A (see  FIG. 2 ) allows the drum unit  10  and the development unit  20  to be inserted into and removed from the image forming device main body  2 .  
      &lt;Configuration of the Drum Unit&gt; 
      As shown in  FIG. 1 , the drum unit  10  comprises the photosensitive drum  11 , which faces and is below the development unit  20  when the units are coupled together. The photosensitive drum  11  is rotatably supported in the drum unit  10  by a drum shaft  11 A. Arranged around the photosensitive drum  11  are a cleaner  12 , which removes toner remaining on the surface of the photosensitive drum  11 , a charger  13 , which puts a uniform electrostatic charge on the surface of the photosensitive drum  11 , and a decharger (not shown in the figures) that removes the residual electric charge. In addition, laser light can be beamed from an exposure device  14  onto the photosensitive drum  11 . Also, the drum unit  10  is inserted into and fitted in the image forming device main body  2  along the guide groove  37  provided on the side of main body frame  36  (see  FIG. 2 ).  
      That is, when the drum unit  10  is inserted into the image forming device main body  2 , the drum shaft  11 A as a guide projection of the photosensitive drum  11  is guided and supported along the guide groove  37 , which is formed in the main body frame  36  on both ends in the unit insertion width direction (drum axial direction). Formed at the end of the guide groove  37  in the insertion direction are final positioning points (see  FIG. 4 ) of the drum unit  10 . The drum unit  10  comprises, on drum shaft  11 A of the photosensitive drum  11 , a rotation-driven gear (not shown in the figures) that meshes with a rotation-drive gear (not shown in the figures) provided on the image forming device main body  2 .  
      &lt;Configuration of the Development Unit&gt; 
       FIG. 2  is a schematic oblique view of the image forming device in a case where the development unit  20  is to be inserted after that the drum unit  10  has been inserted.  
      The development unit  20  comprises at the lower part of the side facing the photosensitive drum  11 , a development sleeve  22 , which at time of fitting into the image forming device main body  2  faces the photosensitive drum  11  with a predetermined development gap therebetween. This development sleeve  22  supplies toner to the electrostatic latent image formed on the photosensitive drum  11 , thus developing the image. A toner storage container  21 , which stores toner that contains a magnetic substance, is provided in a position in the development unit  20  opposite the side facing the photosensitive drum  11 . A rear wall  23  that protrudes downward is formed on the lower part of this toner storage container  21 .  
      At both ends in the sleeve axial direction of the development unit  20  there is provided a development support part  24  that protrudes sideward (in the sleeve axial direction). And at both ends in the unit insertion width direction of the main body frame  36  of the image forming device main body  2  is a guide surface  38  roughly parallel to the guide groove  37 . The development unit  20  is inserted into the image forming device main body  2  with the development support parts  24  supported on the guide surface  38 . In a state of insertion into image forming device main body  2 , the development unit  20  is pressed toward the drum unit  10  by pressing means  30 , which is described below.  
      &lt;Configuration of the Main Body Frame&gt; 
      As shown in  FIG. 2 , one pair each of the guide groove  37  and guide surface  38  are formed on the main body frame  36 . Specifically, as shown in  FIG. 3  and  FIG. 4 , the guide groove  37  is formed in a groove shape in the main body frame  36 , the drum shaft  11 A of the photosensitive drum  11  is restricted in vertical motion by the guide groove  37  and is guided thereby to its predetermined fitting position (final position).  
      The guide surface  38  is formed in a shape having steps at a position below and more inwardly in the unit insertion width direction than the guide groove  37 . This guide surface  38  is constituted to support the development support part  24  of the development unit  20 , and the space above the guide surface  38  is open. With such a constitution, to insert the development unit  20  into the image forming device main body  2 , in a state with the development support part  24  resting on the guide surface  38 , the development unit  20  is slid and guided to its predetermined fitting position.  
      As stated above, the guide surface  38  is formed more inwardly than the guide groove  37  in the unit insertion width direction, so the unit insertion width of the guide groove  37  is greater than the unit insertion width of the guide surface  38 . Therefore, when the drum unit  10  is to be inserted into the image forming device main body  2 , the drum shaft  11 A of the drum unit  10  cannot be placed onto the guide surface  38  by mistake, because the unit insertion width of the guide surface  38  is smaller. Because the unit insertion width of the guide groove  37  is larger, the development support part  24  of the development unit  20  cannot be inserted into the guide groove  37  by mistake. Thus, mis-insertion is prevented.  
      &lt;Operation of the Guide Grove and Guide Surface&gt; 
       FIG. 5  shows the state of the drum unit  10  inserted into the image forming device main body  2  to its final position. More specifically, the drum shaft  11 A of the photosensitive drum  11  has been inserted through the opening  37 A of the guide groove  37 , and, while moving within the guide groove  37 , has been guided to the final position inside the image forming device main body  2 .  
       FIG. 6  shows a state where the development unit  20  has been inserted to its final position inside the image forming device main body  2 , and  FIG. 7  shows an enlarged view of the side of the development unit  20 . A development support part  24  is provided at each of the two ends of the development unit  20  in the sleeve axial direction, and the side that comes into contact with the guide surface  38  is formed in an arc. When the development unit  20  is inserted into the image forming device main body  2 , it comes into contact with the guide surface  38  in the range indicated by the alternating long and short dashed line in  FIG. 7 , and at its final stopping position, it is in linear contact near point A in  FIG. 7 .  
      In this way, upon insertion of the development unit  20  into the image forming device main body  2 , the development support part  24  can be inserted into the image forming device main body  2  and guided to its predetermined final position simply by placing it onto the guide surface  38  from above and sliding. However, because the development unit  20  is slid in a state of resting on the guide surface  38 , when it is fitted in its final position inside the image forming device main body  2 , there must be means for pushing toward the drum unit  10  and means for pressing down to ensure that the development unit  20  does not escape upward.  
      Thus according to the configuration shown in  FIG. 8  through  FIG. 10 , the development unit  20  is pressed toward the drum unit  10  and prevented from escaping upward.  
      First, in  FIG. 8  and  FIG. 9 , pressing means  30  having a pressing member  31  and a spring  32  is provided on the unit insertion opening side of image forming device main body  2 . The pressing member  31  is provided slidingly in the unit insertion direction (the front-rear direction) with respect to the image forming device main body  2 , and the pressing member  31  is impelled toward the front by the impelling force of the spring  32 . As described above, the rear wall  23  protrudes downward below the toner storage container  21 , and this rear wall  23  is made to come into contact with the pressing member  31 . Because of this, the development unit  20  is pressed toward the drum unit  10  through the rear wall  23  by the impelling force of the spring  32 .  
      In  FIG. 10 , a boss is provided in a manner projecting inwardly in the unit insertion direction from the main body frame  36  at a position near its final position when the development unit  20  has been inserted into the image forming device main body  2 . With the development unit  20  inserted into the image forming device main body  2  and fitted into its final position, the upper edge face of the development support part  24  is in contact with the boss  33 . Thus in a state where the development unit  20  is fitted into the image forming device main body  2 , the development unit  20  is prevented from escaping upward.  
      Thus with such a configuration, for insertion of the development unit  20  into the image forming device main body  2 , it is sufficient simply to set the development support part  24  onto the guide surface  38  from above and slide, so as with the drum unit  10 , there is no need for a complicated operation such as, for example, making a development support part  24  match with a groove.  
      Such a configuration improves the operability of the development unit  20 , which is frequently removed from the image forming device main body  2  because of paper jams or other such reason. Because the drum unit  10  is guided by the guide groove  37  and the development unit  20  is placed onto the guide surface  38  and is guided, operations are easily explained.  
     Second Embodiment 2  
      An explanation will now be given of a second embodiment. The overall configuration of the image forming device in this second embodiment is the same as the configuration of the first embodiment shown in  FIG. 1 .  FIG. 11  is a schematic oblique view of a case of an imaging forming device where after the drum unit  10  has been inserted, the development unit  20  is to be inserted into image forming device main body  2 , and  FIG. 12  is a perspective view of a state where the drum unit  10  and the development unit  20  have been inserted.  
      In  FIG. 11  and  FIG. 12 , the image forming device main body  2  is covered by an outer cover  35 , and when a front cover  35 A thereof is opened, the drum unit  10  and the development unit  20  can be inserted into or removed from the image forming device main body  2 .  
      &lt;Configuration of the Drum Unit&gt; 
      As shown in  FIG. 1  and  FIG. 11  to  FIG. 13 , the drum unit  10  comprises the photosensitive drum  11  on the lower part of the side opposite the development unit  20  when the units are coupled together. This photosensitive drum  11  is rotatably supported rotatably on the drum unit  10  by a drum shaft  11 A as a first guide projection. Provided in the vicinity of the photosensitive drum  11  are a cleaner  12 , which removes toner remaining on the surface of the photosensitive drum  11 , a charger  13 , which puts a uniform electrostatic charge on the surface of the photosensitive drum  11 , and a decharger (not shown in the figures) that removes the residual electric charge. In addition, laser light can be beamed from the exposure device  14  onto the photosensitive drum  11 . The drum unit  10  can be inserted into the image forming device main body  2  along a first guide groove  137  provided on a main body frame  136  described below.  
      For example, when the drum unit  10  is to be inserted into the image forming device main body  2 , the drum shaft  11 A of the photosensitive drum  11  is guided along a first guide groove  137  formed on both ends in the unit insertion width direction (the drum axial direction) of the main body frame  136 . At the end of the first guide groove  137  in the insertion direction is a final positioning point (see  FIG. 14 ) of the drum unit  10 . Further, the drum shaft  11 A of the photosensitive drum  11  is given a diameter allowing smooth entry into the first guide groove  137 .  
      In the drum unit  10 , rotation-driven gears (not shown in the figures) that mesh with rotation-drive transmission gears (not shown in the figures) provided on the image forming device main body  2  side are provided on the drum shaft  11 A of the photosensitive drum  11 .  
      &lt;Configuration of the Development Unit&gt; 
      As shown in  FIG. 1  and  FIG. 11  to  FIG. 13 , the development unit  20  comprises, at a lower portion of the side that faces the photosensitive drum  11 , a development sleeve  22 , which faces the photosensitive drum  11  with a predetermined development gap therebetween when the development unit  20  is fitted into the image forming device main body  2 . This development sleeve  22  carries out development by supplying toner to the electrostatic latent image formed on the photosensitive drum  11 . Provided in a position opposite the side facing the photosensitive drum  11  in the development unit  20  is a toner storage container  21 , which stores toner that includes a magnetic substance.  
      Provided on both ends of the development unit  20  in the sleeve axial direction are guide pins  123  and  124  (one pair each on left and right) as second guide projections that protrude sideward (in the sleeve axial direction). A second guide groove  138 , roughly parallel to the first guide groove  137  referred to above, is formed on the main body frame  136  on both ends in the unit insertion width direction of the image forming device main body  2 . The unit insertion width of the first guide grooves  137  is greater than the unit insertion width of the second guide grooves  138 .  
      The development unit  20 , when fitted into the image forming device main body  2 , is guided with the guide pins  123  and  124  in the second guide groove  138 . The guide pins  123  and  124  may, for example, have the same diameter, which is of a size that smoothly fits into the second guide groove  138 . In addition, these guide pins  123  and  124  have a greater diameter than that of the drum shaft  11 A of the photosensitive drum  11 .  
      The above explanation assumes that two guide pins  123  and  124  are protrusions provided on the development unit  20 , but it is also permissible to have just one of these guide pins.  
      &lt;Configuration of the Guide Grooves and Guide Projections&gt; 
      As shown in  FIG. 14 , one pair each of a first guide groove  137  and second guide groove  138  are formed in the above-described main body frame  136 . That is, as shown in  FIG. 12  to  FIG. 14 , the first guide groove  137  has a wide support surface  137   a , on which the drum shaft  11 A of the photosensitive drum  11  is placed, and a guide member  137   b , which covers the upper surface of drum shaft  11 A so as to come in contact therewith at the end of this support surface  137   a  in the unit insertion width direction. The drum shaft  11 A of the photosensitive drum  11 , while making contact with the upper and lower surfaces of this first guide groove  137 , is guided as far as the predetermined fitting position (final position).  
      The second guide groove  138 , having a three-sided box cross-sectional shape, is formed roughly parallel to the first guide groove  137 , below and more inwardly in the unit insertion width direction than the first guide groove  137 . Because of this, in inserting the development unit  20  into the image forming device main body  2 , the guide pins  123  and  124  are inserted into the guide groove  138 , and in such a state the development unit  20  is slid and guided to its predetermined fitting position.  
      As shown in  FIG. 15 , the diameter of the drum shaft  11 A of the drum unit  10  is smaller than the diameter of the diameter of the guide pins  123  and  124  of the development unit  20 . And correspondingly, the groove diameter of first guide groove  137  is smaller than the groove diameter of second guide groove  138  (see  FIG. 14 ).  
      Such a constitution makes it impossible to mistakenly put the large-diameter guide pins  123  and  124  of the development unit  20  into the small-groove-diameter first guide groove  137 , preventing mis-insertion of the development unit  20  into the image forming device main body  2 . Even so, there still remains the danger that the small-diameter drum shaft  11 A of the drum unit  10  will be misinserted into the large-groove-diameter second guide groove  138 . Thus, as shown in  FIG. 15 , length L 1  of the drum unit  10  in the axial direction of the drum shaft  11 A is longer than length L 2  of the development unit  20  in the axial direction of the guide pins  123  and  124 .  
       FIG. 16  and  FIG. 17  show a state where the drum unit  10  is to be inserted into the image forming device main body  2 , and  FIG. 18  shows a state where the development unit  20  is to be inserted into the image forming device main body  2 .  
      In  FIG. 16  to  FIG. 18 , so as to correspond with the length L 1  of the drum unit  10  in the axial direction of the drum shaft  11 A and the length L 2  of the development unit  20  in the axial direction of the guide pins  123  and  124 , the unit insertion width L 1 ′ of the first guide groove  137  along which the drum unit  10  is guided into the image forming device main body  2  is made larger than the unit insertion width L 2 ′ of the second guide groove  138  along which the development unit  20  is guided into the image forming device main body  2 .  
      Thus when inserting the drum unit  10  into the image forming device main body  2 , because the insertion widths of units  10  and  20  are different, it is impossible to mistakenly put the drum shaft  11 A of the drum unit  10  into the second guide groove  138 . And when inserting the development unit  20  into the image forming device main body  2 , because the unit insertion widths are different and the diameter of the guide pins  123  and  124  is greater than the groove diameter of the first guide groove  137 , it is also impossible to mistakenly put the guide pins the  123  and  124  of the development unit  20  into the first guide grooves  137 . Thus mis-insertion of the drum unit  10  and the development unit  20  into the image forming device main body  2  is prevented.  
      When inserting either the drum unit  10  or the development unit  20  into the image forming device main body  2 , an operator can easily confirm the difference between the unit insertion width of the first guide groove  137  and the unit insertion width of the second guide groove  138 , and moreover can easily confirm the difference between the diameters of the drum shaft  11 A and of the guide pins  123  and  124 . This allows the operator to insert the drum unit  10  and the development unit  20  into the image forming device main body  2  without error, each from the correct insertion openings.  
       FIG. 10  shows a state where the drum unit  10  and the development unit  20  have been inserted as far as their final position inside the image forming device main body  2 . That is, the drum shaft  11 A of the photosensitive drum  11  is inserted through the opening  137 A of the first guide groove  137  (see  FIG. 14 ) and is guided along the first guide groove  137  as far as its final position inside the image forming device main body  2 . And the guide pins  123  and  124  of the development unit  20  are inserted through the opening  138 A of second guide groove  138  (see  FIG. 14 ) and are guided along the second guide groove  138  as far as their final positions inside the image forming device main body  2 .