Patent Publication Number: US-10317818-B2

Title: Image forming apparatus including detachably disposed drive unit

Description:
BACKGROUND 
     1. Field 
     The present disclosure relates to an image forming apparatus such as a copying machine, a multifunction machine, a printer, and a facsimile machine and particularly relates to an image forming apparatus including a rear-side frame member that is disposed, in a vertical or substantially vertical direction, on the rear side of an image forming apparatus body and a drive unit that includes a drive part that drives a component member of the image forming apparatus body. 
     2. Description of the Related Art 
     In general, a known image forming apparatus is configured, for example, as described below. 
       FIG. 23  is a schematic plan view illustrating a state in which a drive unit  20 X is to be disposed on an outer surface  110 Xa of a rear-side frame member  110 X of a known image forming apparatus  100 X.  FIG. 24  is a schematic perspective view, obliquely from above and on a rear side Y 2 , illustrating a state in which the drive unit  20 X illustrated in  FIG. 23  is disposed on the outer surface  110 Xa of the rear-side frame member  110 X. 
     As illustrated in  FIGS. 23 and 24 , in the known image forming apparatus  100 X, the drive unit  20 X that includes a drive part  21 X (for example, an electric drive part (specifically, a drive motor) that uses electric power for driving) is disposed on the outer surface  110 Xa of the rear-side frame member  110 X disposed on the rear side Y 2  of an image forming apparatus body  1 X so as to extend in a vertical or substantially vertical direction. The drive part  21 X drives a component member (for example, a toner supply member (not illustrated) of a toner storage part) of the image forming apparatus body  1 X. In addition, a large number of other component members that are not illustrated (for example, electric components, substrates, and wires that connect these component members to each other) are densely disposed on the outer surface  110 Xa of the rear-side frame member  110 X. Specifically, there is a case where the drive unit  20 X is disposed on the outer surface  110 Xa of the rear-side frame member  110 X and the electric components and/or the substrates (not illustrated) are disposed at the rear of the drive unit  20 X. 
     It is not easy, in the image forming apparatus  100 X in such a state, to perform maintenance work, such as cleaning and replacement, of the drive unit  20 X covered by the other component members (not illustrated) because the maintenance work is performed from the rear side Y 2  of the image forming apparatus body  1 X, which degrades maintainability of the drive unit  20 X. 
     In this respect, Japanese Unexamined Patent Application Publication No. 2006-243533 (hereinafter referred to as Patent Document 1) discloses (refer to paragraph [0034] and FIGS. 2 and 3 in Patent Document 1) a configuration in which a drive unit is detachably disposed on an inner surface of a rear-side frame member. 
     According to the configuration described in Patent Document 1, it is possible to perform maintenance work, such as cleaning and replacement, of the drive unit from the front side of an image forming apparatus body because the drive unit is detachably disposed on the inner surface of the rear-side frame member. As a result, it is possible to easily perform the maintenance work of the drive unit, which improves maintainability of the drive unit. 
     In the configuration described in Patent Document 1, however, a component member (for example, a unit for image formation, such as a photoreceptor unit) disposed in the image forming apparatus body easily interferes with a drive part of the drive unit because the drive unit is disposed on the inner surface of the rear-side frame member such that the drive part faces the inside of the image forming apparatus body. For example, the component member disposed in the image forming apparatus body is easily affected by the heat generated at the drive part. 
     SUMMARY 
     It is desirable to provide an image forming apparatus capable of avoiding interference between a component member disposed in an image forming apparatus body and a drive part of a drive unit while improving maintainability of the drive unit. 
     According to an aspect of the disclosure, an image forming apparatus includes a rear-side frame member that is disposed on a rear side of an image forming apparatus body so as to extend in a vertical or substantially vertical direction; and a drive unit that includes a drive part, the drive unit being detachably disposed on an inner surface of the rear-side frame member such that the drive part faces outward from the image forming apparatus body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic sectional view illustrating an internal structure of an image forming apparatus according to as embodiment of the present disclosure; 
         FIG. 2  is a schematic cross sectional view, from a rear side, illustrating a toner storage part illustrated in  FIG. 1 ; 
         FIG. 3  is a schematic cross sectional view, from the rear side, illustrating a portion including a toner replenishing member of the toner storage part illustrated in  FIG. 1 ; 
         FIG. 4  is a schematic longitudinal sectional view of the toner storage part illustrated in  FIG. 1 ; 
         FIG. 5  is a schematic perspective view, obliquely from above and on a front side, illustrating a state in which a drive unit is to be disposed on an inner surface of a rear-side frame member in the image forming apparatus according to the present embodiment; 
         FIG. 6  is a schematic plan view illustrating a state of the drive unit illustrated in  FIG. 5 ; 
         FIG. 7  is a schematic plan view illustrating a state in which the drive unit is disposed on the inner surface of the rear-side frame member in the image forming apparatus according to the present embodiment; 
         FIG. 8  is a schematic front view of the rear-side frame member illustrated in  FIGS. 5 to 7 ; 
         FIG. 9  is a schematic front view illustrating a state in which the drive unit illustrated in  FIG. 7  is attached to the rear-side frame member; 
         FIG. 10  is a schematic rear view of the rear-side frame member illustrated in  FIGS. 5 to 7 ; 
         FIG. 11  is a schematic rear view illustrating the state in which the drive unit illustrated in  FIG. 7  is attached to the rear-side frame member; 
         FIG. 12  is a schematic perspective view, obliquely from above and on the rear side, illustrating the state in which the drive unit illustrated in  FIG. 7  is attached to the rear-side frame member; 
         FIG. 13  is a schematic perspective view, obliquely from above and on the front side, illustrating the state in which the drive unit illustrated in  FIG. 7  is attached to the rear-side frame member; 
         FIG. 14  is a schematic rear view illustrating, for describing a configuration in which the drive unit is detachably disposed on the rear-side frame member, a state in which the drive unit is not yet attached to the rear-side frame member; 
         FIG. 15  is a schematic rear view of the drive unit illustrated in  FIG. 14 ; 
         FIG. 16  is a schematic rear view illustrating a state in which the drive unit illustrated in  FIG. 14  is attached to the rear-side frame member but not yet secured to the rear-side frame member by a pawl portion; 
         FIG. 17  is a schematic rear view illustrating a state in which the drive unit illustrated in  FIG. 14  is attached to the rear-side frame member and secured to the rear-side frame member by the pawl portion; 
         FIG. 18  is a schematic front view of the rear-side frame member illustrated in  FIGS. 14, 16, and 17 ; 
         FIG. 19  is a schematic front view illustrating a state in which the drive unit illustrated in  FIG. 16  that is attached to the rear-side frame member is not yet pawl-engaged with the rear-side frame member; 
         FIG. 20  is a schematic perspective view illustrating the drive unit illustrated in  FIGS. 14 to 17 and 19  and illustrating, as an enlargement, a projecting portion of the drive unit; 
         FIG. 21  is an enlarged schematic front view illustrating a portion including a lock portion and a guide groove illustrated in  FIG. 18 ; 
         FIG. 22  is a schematic sectional view of a portion including the lock portion and the guide groove illustrated in  FIG. 21 , taken along line XXII-XXII; 
         FIG. 23  is a schematic plan view illustrating a state in which a drive unit is to be disposed on an outer surface of a rear-side frame member of a known image forming apparatus; and 
         FIG. 24  is a schematic perspective view, obliquely from above and on a rear side, illustrating a state in which the drive unit illustrated in  FIG. 23  is disposed on the outer surface of the rear-side frame member. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. 
     Image Forming Apparatus 
       FIG. 1  is a schematic sectional view illustrating an internal structure of an image forming apparatus  100  according to an embodiment of the present disclosure. 
     The image forming apparatus  100  according to the present embodiment is a color-image forming apparatus having a configuration, which is commonly known as a tandem-type, in which a plurality of electrostatic latent image carriers (specifically, photoreceptor), on each of which a toner image is to be formed, are disposed substantially parallel to each other in a specific direction (in the present embodiment, a left-right direction X). The image forming apparatus  100  is, for example, an intermediate transfer-type color multifunction machine capable of forming a full-color image. The image forming apparatus  100  in the present embodiment is the tandem-type color-image forming apparatus; however, the image forming apparatus  100  may be a color-image forming apparatus of a different type. In addition, the image forming apparatus  100  in the present embodiment is the color-image forming apparatus; however, the image forming apparatus  100  may be a monochromatic-image forming apparatus. 
     The image forming apparatus  100  uses toners Ta, Tb, Tc, and Td (hereinafter referred to as Ta to Td) to form an image at an image forming part  30  provided in an image forming apparatus body  1  and collects waste toner discharged from the image forming part  30 , in a toner collection container  90  that is detachably attached to the image forming apparatus body  1 . Note that the one-dot chain line in  FIG. 1  indicates the toner collection container  90 . 
     Specifically, the image forming apparatus  100  forms an image, at the image forming part  30 , by using the toners Ta to Td that are supplied from respective toner storage parts (specifically, toner cartridges)  60   a ,  60   b ,  60   c , and  60   d  (hereinafter also referred to as  60   a  to  60   d ) detachably attached to the image forming apparatus body  1 . 
     The image forming apparatus  100  is an electrophotographic image forming apparatus and includes a plurality of (four in the present embodiment) image forming stations pa, pb, pc, and pd (hereinafter also referred to as pa to pd); an exposure device  4  (specifically, an exposure unit); a plurality of (four in the present embodiment) first transfer devices (specifically, first transfer units)  6   a ,  6   b ,  6   c , and  6   d  (hereinafter referred to as  6   a  to  6   d ); an intermediate transfer belt  7  as a toner image carrier that carries a toner image; a belt-cleaning device  9  (specifically, a belt-cleaning unit); a second transfer device  11  (specifically, a second transfer unit); a fixing device  12  (specifically, a fixing unit); a recording material storage part (specifically, a sheet-feeding device  13 ) that stores a recording material P, for example, a recording sheet; and a body frame  1   a . The body frame  1   a  supports component members, such as the image forming stations pa to pd, the exposure device  4 , the first transfer devices  6   a  to  6   d , the second transfer device  11 , and the fixing device  12 , of the image forming apparatus body  1  and constitutes a housing and a support frame of the image forming apparatus body  1 . In the present embodiment, the image forming stations pa to pd, the exposure device  4 , and the first transfer devices  6   a  to  6   d  constitute the image forming part  30 . Note that the second transfer device  11  and/or the fixing device  12  may also constitute the image forming part  30 . 
     The image forming apparatus  100  includes an image reading device  40  that is disposed on an upper portion of the image forming apparatus body  1 . The image reading device  40  includes an image reading part  41  for reading an image on a document G, a document transport part  42  that transports the document G, and a document placement table  43  on which the document G is placed. 
     The image reading device  40  reads, at the image reading part  41 , the document G transported by the document transport part  42  or reads, at the image reading part  41 , the document G placed on the document placement table  43 . The image on the document G read by the image reading device  40  is sent as image data to the image forming apparatus body  1 , or image data from an external apparatus is sent to the image forming apparatus body  1 . An image that is formed, in the image forming apparatus body  1 , in accordance with the image data is recorded on the recording material P. 
     A plurality of (four in the present embodiment) photoreceptors (specifically, photoreceptor drums)  2   a ,  2   b ,  2   c , and  2   d  (hereinafter also referred to as  2   a  to  2   d ), which act as electrostatic latent image carriers, charging devices (specifically, charging units)  3   a ,  3   b ,  3   c , and  3   d  (hereinafter also referred to as  3   a  to  3   d ), developing devices (specifically, developing units)  5   a ,  5   b ,  5   c , and  5   d  (hereinafter also referred to as  5   a  to  5   d ), and photoreceptor cleaning devices (specifically, photoreceptor cleaning units)  8   a ,  8   b ,  8   c , and  8   d  (hereinafter referred to as  8   a  to  8   d ) are included in the respective image forming stations pa to pd. The charging devices  3   a  to  3   d , the developing devices  5   a  to  5   d , and the photoreceptor cleaning devices  8   a  to  8   d  are disposed, in this order, around the respective photoreceptors  2   a  to  2   d.    
     The toner storage parts  60   a  to  60   d  are detachably connected to the corresponding developing devices  5   a  to  5   d  of the image forming stations pa to pd. The toner storage parts  60   a ,  60   b ,  60   c , and  60   d  store the black (B) toner Ta, the cyan toner Tb, the magenta (M) toner Tc, and the yellow (Y) toner Td, respectively. While the toners Ta to Td are supplied from the respective toner storage parts  60   a  to  60   d  to the corresponding developing devices  5   a  to  5   d , the image forming stations pa, pb, pc, and pd form a black (B) toner image, a cyan (C) toner image, a magenta (M) toner image, and a yellow (Y) toner image, respectively, on the photoreceptors  2   a ,  2   b ,  2   c , and  2   d , by using respective developing agents Da, Db, Dc, and Dd (hereinafter also referred to as Da to Dd) of each color in the developing devices  5   a  to  5   d . In the present embodiment, the developing agents Da to Dd are two-component developing agents that contain, as components, the respective toner Ta to Td and respective carriers Ca, Cb, Cc, and Cd (hereinafter referred to as Ca to Cd). 
     The toner collection container  90  and the toner storage parts  60   a  to  60   d  are detachable from the image forming apparatus body  1 . As a result, a user is enabled to replace the toner collection container  90  and the toner storage parts  60   a  to  60   d , as necessary. 
     Specifically, the image forming apparatus body  1  has insertion holes  1   aa ,  1   ab ,  1   ac , and  1   ad  (hereinafter referred to as  1   aa  to  1   ad ) extending in a depth direction Y and into which the respective toner storage parts  60   a  to  60   d  are inserted in the depth direction Y. The depth direction Y indicates a direction from an operation side (in the present embodiment, a front side Y 1  of the image forming apparatus body  1 ) of the image forming part  30  to a side opposite (in the present embodiment, the rear side Y 2  of the image forming apparatus body  1 ) to the operation side and a direction from the side opposite to the operation side of the image forming part  30  to the operation side. In the present embodiment, the direction from the rear side Y 2  of the image forming apparatus  100  to the front side Y 1  thereof is one direction side of the depth direction Y, and the direction from the front side Y 1  of the image forming apparatus  100  to the rear side Y 2  thereof is the other direction side of the depth direction Y. In addition, a right side X 1  in the left-right direction X in the view from the front side Y 1  is one side, and a left side X 2  in the left-right direction X in the view from the front side Y 1  is the other side. 
     The toner storage parts  60   a  to  60   d  are configured to be attached to the image forming apparatus body  1  by being inserted, in the depth direction Y toward the rear side Y 2 , into the respective insertion holes  1   aa  to  1   ad  of the image forming apparatus body  1 . In addition, the toner storage parts  60   a  to  60   d  are configured to be detached from the image forming apparatus body  1  by being extracted from the front side Y 1  (the operation side in the present embodiment) in the depth direction Y. The toner storage parts  60   a  to  60   d  have respective toner replenishing ports  64  (refer to  FIG. 4 , mentioned later). The toner replenishing port  64  communicate, while the corresponding toner storage parts  60   a  to  60   d  are attached to the image forming apparatus body  1 , with respective toner supply ports  551  (refer to  FIG. 4 ) of the developing device  5   a ,  5   b ,  5   c , and  5   d  via respective toner replenishing paths  61   a  (refer to  FIGS. 3 and 4 , mentioned later). 
     The toner storage parts  60   a  to  60   d  are disposed substantially parallel to each other in the left-right direction X, which is perpendicular to the depth direction Y. The image forming part  30  is disposed below the toner storage parts  60   a  to  60   d.    
     The charging devices  3   a  to  3   d  evenly charge the surfaces of the photoreceptors  2   a  to  2   d  corresponding thereto. The exposure device  4  exposes, to light, the surfaces of the photoreceptors  2   a  to  2   d  evenly changed by the charging devices  3   a  to  3   d  and thereby forms electrostatic latent images on the surfaces of the photoreceptors  2   a  to  2   d . The developing devices  5   a  to  5   d  include respective development tanks  51   a  to  51   d  that store the developing agents Da to Dd corresponding thereto. The developing devices  5   a  to  5   d  develop the electrostatic latent images, which have been formed on the surfaces of the photoreceptors  2   a  to  2   d  by the exposure device  4 , by using the respective developing agents Da to Dd, and thereby make the electrostatic latent images visible. 
     The first transfer devices  6   a  to  6   d  first transfer the toner images formed on the photoreceptors  2   a  to  2   d  onto the intermediate transfer belt  7 . 
     Each of the photoreceptor cleaning devices  8   a  to  8   d  is provided with a cleaning member (specifically, a cleaning blade). The photoreceptor cleaning devices  8   a  to  8   d  use the respective cleaning members to collect, as waste toner, residual toner that has not been transferred onto the intermediate transfer belt  7  by the first transfer devices  6   a  to  6   d  and that remains on the surfaces of the photoreceptors  2   a  to  2   d . Then, the photoreceptor cleaning devices  8   a  to  8   d  transport the waste toner to the toner collection container  90 . 
     The second transfer device  11  second transfers, onto the recording material P, the toner images that have been first transferred onto the intermediate transfer belt  7 . In the present embodiment, the second transfer device  11  is provided with a second transfer roller  11   a . The second transfer roller  11   a  electrostatically transfers, onto the recording material P, the toner images that have been transferred onto the intermediate transfer belt  7  by the first transfer devices  6   a  to  6   d , thereby forming unfixed toner images. 
     The belt-cleaning device  9  collects, as the waste toner, the residual toner that has not been transferred onto the recording material P by the second transfer device  11  and that remains on the intermediate transfer belt  7 . Then, the belt-cleaning device  9  transports the waste toner to the toner collection container  90 . 
     The toner collection container  90  is disposed on the front side Y 1  (operation side in the present embodiment) in the depth direction Y. The waste toner that has been transported from the photoreceptor cleaning devices  8   a  to  8   d  and the belt-cleaning device  9  is collected in the toner collection container  90 . 
     The intermediate transfer belt  7  is disposed opposite the photoreceptors  2   a  to  2   d . The intermediate transfer belt  7  is stretched over a drive roller  7   a  and a driven roller  7   b . When the driven roller  7   a  is rotationally driven, the intermediate transfer belt  7  is rotated (moved in a circular manner) in a predetermined rotation direction E. The second transfer device  11  and the belt-cleaning device  9  are disposed adjacent to the intermediate transfer belt  7  so as to be on the side of the drive roller  7   a  and on the side of the driven roller  7   b , respectively. 
     The exposure device  4  is configured to scan the surfaces of the photoreceptors  2   a  to  2   d , which are each rotationally driven in a predetermined direction, in a scanning direction (rotational axis direction of the photoreceptors) with four light beams (specifically, laser beams) from a light source portion  4   a  that includes a polygonal mirror. The exposure device  4  forms an electrostatic latent image on each of the surfaces of the photoreceptors  2   a  to  2   d  in accordance with externally input image data corresponding to a color image in which colors of a black (B) component, a cyan (C) component, a magenta (M) component, and a yellow (Y) component are used or in accordance with externally input image data corresponding to a monochromatic image in which a single color (for example, black) is used. 
     The fixing device  12  fixes, by using heat and pressure, the unfixed toner images transferred on the recording material P by the second transfer device  11  to the recording material P. Specifically, the fixing device  12  includes a heat source  12   c , such as a heater, a fixing roller  12   a , and a pressure roller  12   b  in pressure contact with the fixing roller  12   a . The operation of the heat source  12   c  is controlled to control the temperature of the fixing roller  12   a  so as to be maintained at a predetermined temperature. The fixing device  12  is configured to heat the fixing roller  12   a  to a predetermined fixing temperature by using the heat source  12   c  and then cause the recording material P on which unfixed images (specifically, the unfixed toner images) are formed to pass through a fixing nip part N so that the unfixed images (specifically, the unfixed toner images) are fixed to the recording material P as a result of heat and pressure applied at the fixing nip part N. 
     In the image forming apparatus  100  described above, image formation is performed as described below. First, the surfaces of the photoreceptors  2   a  to  2   d  are evenly charged by the respective charging devices  3   a  to  3   d , and each of the evenly charged surfaces of the photoreceptors  2   a  to  2   d  is exposed, by the exposure device  4 , to laser in accordance with the image data (image information). An electrostatic latent image is thereby formed on each of the photoreceptors  2   a  to  2   d.    
     Next, in the image forming apparatus  100 , the electrostatic latent images formed on the photoreceptors  2   a  to  2   d  are developed by the respective developing devices  5   a  to  5   d  to be visible as toner images. The visible toner images are transferred onto the intermediate transfer belt  7  by the first transfer devices  6   a  to  6   d  to which a bias voltage having a polarity opposite to the polarity of the toners Ta to Td is applied. The toner images are thereby formed on the intermediate transfer belt  7 . 
     Next, in the image forming apparatus  100 , the toner images formed on the intermediate transfer belt  7  are transported to the second transfer device  11  by the intermediate transfer belt  7  that is rotated in the predetermined rotation direction E. The recording material P pulled out from feeding rollers  13   a  of the sheet-feeding device  13  toward a transport path S and transported along the transport path S is transported by transport rollers  14  and resist rollers  15  to the second transfer device  11  in synchronization with the toner images on the intermediate transfer belt  7 . The toner images transported to the second transfer device  11  are transferred by the second transfer device  11  onto the recording material P transported to the second transfer device  11 . 
     Next, in the image forming apparatus  100 , the toner images transferred on the recording material P are transported to the fixing device  12 . When the toner images pass the fixing device  12 , heat and pressure are applied to the toner images on the recording material P to fuse and fix the toner images to the recording material P. Then, the recording material P to which the toner images are fixed by the fixing device  12  is placed on a discharge tray  17  by being discharged, by discharge rollers  16 , to the outside of the image forming apparatus body  1  to complete processes of the image formation. 
     The transport path S includes a reverse path Sr that guides, to the upstream of the resist rollers  15 , the recording material P transported by the discharge rollers  16  in a reverse direction, so that the recording material P is reversed. When image formation is intended to be performed not only on a front surface of the recording material P but also on a back surface thereof in the image forming apparatus  100 , the recording material P is reversed by being transported in the reverse direction from the discharge rollers  16  to the reverse path Sr and is re-guided to the resist rollers  15 . Then, after toner images are formed on and fixed to the back surface of the recording material P in the same manner as for the front surface of the recording material P, the recording material P is placed on the discharge tray  17  by being discharged to the outside of the image forming apparatus body  1 . 
     An electric power supply part  18  included in the image forming apparatus  100  illustrated in  FIG. 1  will be described later. 
     Toner Storage Part 
       FIG. 2  is a schematic cross sectional view, from the rear side Y 2 , illustrating the toner storage parts  60   a  to  60   d  illustrated in  FIG. 1 .  FIG. 3  is a schematic cross sectional view, from the rear side Y 2 , illustrating a portion including a toner replenishing member  622  of the toner storage parts  60   a  to  60   d  illustrated in  FIG. 2 . FIG.  4  is a schematic longitudinal sectional view of the toner storage parts  60   a  to  60   d  illustrated in  FIG. 1 . 
     Note that the toner storage parts  60   a  to  60   d  illustrated in  FIG. 1  have substantially identical configurations and are thus indicated by a single illustration in each of  FIGS. 2 to 4 .  FIGS. 2 to 4  each illustrate a state in which the toner storage parts  60   a  to  60   d  do not store the respective toners Ta to Td. 
     As illustrated in  FIGS. 2 to 4 , each of the toner storage parts  60   a  to  60   d  constitutes a long box-shaped container (specifically, a resin container) that extends in the depth direction Y. The toner storage parts  60   a  to  60   d  store the respective toners Ta to Td for replenishment and supply the respective toners Ta to Td to the developing devices  5   a  to  5   d  corresponding thereto. 
     The toner storage parts  60   a  to  60   d  include respective toner storage containers  61  and respective toner supply members  62 . The toner storage containers  61  store the toners Ta to Td corresponding thereto. The toner supply members  62  supply the respective toners Ta to Td stored in the toner storage containers  61  to the developing devices  5   a  to  5   d  corresponding thereto. In the present embodiment, each of the toner supply members  62  includes a toner stirring member  621  (refer to  FIG. 2 ) and the toner replenishing member  622 . The toner stirring members  621  stir the respective toners Ta to Td stored in the toner storage containers  61 . The toner replenishing members  622  replenish the respective toners Ta to Td stirred by the toner stirring members  621  to the developing devices  5   a  to  5   d  corresponding thereto. 
     The toner storage parts  60   a  to  60   d  communicate with the developing devices  5   a  to  5   d  corresponding thereto via the respective toner supply ports  551  (refer to  FIG. 4 ) of the cylindrical toner replenishing paths  61   a  (refer to  FIG. 4 ) extending vertically from the respective developing devices  5   a  to  5   d.    
     The image forming apparatus  100  includes a drive unit  20  (refer to  FIG. 4 ) including a drive part  21  (in the present embodiment, an electric drive part (specifically, a drive motor) that uses electric power for driving) (refer to  FIG. 4 ). The drive part  21  drives component members (in the present embodiment, the toner supply members  62  of the toner storage parts  60   a  to  60   d  (specifically, the toner stirring members  621  and the respective toner replenishing members  622 )) of the image forming apparatus body  1 . 
     Specifically, the drive unit  20  drives (rotationally drives in the present embodiment) the toner stirring members  621  and the toner replenishing members  622  of the toner supply members  62 . The drive unit  20  is provided with, on an output side thereof, output shaft portions  20   a  and  20   b  (refer to  FIG. 4 ) each having a structure that couples with the toner stirring member  621  and the toner replenishing member  622  corresponding thereto. Examples of the coupling structure include various types of structures. The present embodiment employs a fitting structure that includes a projection disposed on an output-side end surface of the drive unit  20  and a recess disposed on an output-side end surface of the toner supply member  62 , the output-side end surfaces facing each other. 
     Each toner stirring member  621  includes a rotary shaft  6211  (refer to  FIG. 2 ) axially supported in a longitudinal direction (the depth direction Y in the present embodiment) and a toner discharge member  6212  (refer to  FIG. 2 ) that is disposed on the rotary shaft  6211 . The toner discharge members  6212  stir and discharge the toners Ta to Td corresponding thereto. The rotary shafts  6211  rotate about respective axes to cause the toner stirring members  621  corresponding thereto to pump the respective toners Ta to Td stored in the toner storage containers  61  while stirring the toners Ta to Td by using the respective toner discharge members  6212  and to transport the toners Ta to Td to the respective toner replenishing members  622 . 
     Each of the toner replenishing members  622  includes a rotary shaft  6221  axially supported in the longitudinal direction (the depth direction Y in the present embodiment) and a toner-transporting screw blade  6222  disposed, in a substantially spiral form, on an outer circumferential surface of the rotary shaft  6221 . The rotary shaft  6221  and the screw blade  6222  of each toner replenishing member  622  constitute a screw auger. 
     A coupling portion  63  (refer to  FIG. 4 ) is disposed on the rear side Y 2  of the toner stirring member  621  and the toner replenishing member  622  of each toner storage container  61 . 
     The coupling portions  63  engage and couple input sides (specifically, the rotary shafts  6211  and  6221 ) of the toner supply members  62  and output sides (specifically, the output shaft portions  20   a  and  20   b ) of the drive unit  20  with each other in a state in which the toner storage parts  60   a  to  60   d  are attached to the image forming apparatus body  1 . Thus, the toner supply members  62  (specifically the toner stirring members  621  and the toner replenishing members  622 ) are enabled to be rotated by being rotationally driven by the drive part  21  of the drive unit  20 . The toner replenishing ports  64  (refer to  FIGS. 3 and 4 ) through which the toners Ta to Td are replenished are disposed at the bottom surfaces of the toner storage parts  60   a  to  60   d  (the coupling portions  63  in the present embodiment) on the toner replenishing member  622  side in the left-right direction X. The toner replenishing paths  61   a  are disposed at positions corresponding to the respective toner replenishing ports  64 . 
     Responsive to the rotational driving of the drive part  21  of the drive unit  20 , the toner storage parts  60   a  to  60   d  transport the toners Ta to Td to the toner replenishing members  622  while stirring the toners Ta to Td by rotating the toner stirring members  621 . Then, the toner storage parts  60   a  to  60   d  transport the respective toners Ta to Td to the toner replenishing ports  64  by rotating the respective toner replenishing members  622 . As a result, the toner storage parts  60   a  to  60   d  are enabled to perform replenishing by dropping the toners Ta to Td stored in the toner storage containers  61  into the developing devices  5   a  to  5   d  through the respective toner replenishing ports  64 . 
     The toner storage parts  60   a  to  60   d  are provided with respective shutter mechanisms  65  (refer to  FIGS. 3 and 4 ) that are supported (for example, fitted in slide grooves) on outer surfaces of the corresponding toner storage parts  60   a  to  60   d  so as to be capable of sliding in a longitudinal direction (the depth direction Y in the present embodiment). The shutter mechanisms  65  open and close the respective toner replenishing ports  64 . The shutter mechanisms  65  may have a publicly known configuration, and detailed description thereof thus will be omitted. The shutter mechanisms  65  slide to open and close the toner replenishing ports  64  corresponding thereto by coming into contact with respective contact members (not shown) of the image forming apparatus body  1  in interlocking with insertion and extraction of the toner storage parts  60   a  to  60   d  corresponding thereto into and from the image forming apparatus body  1 . 
     Hereinafter, a toner storage part  60  as a representative of the toner storage parts  60   a  to  60   d  and a developing device  5  as a representative of the developing devices  5   a  to  5   d  will be described. 
     Drive Unit 
       FIG. 5  is a schematic perspective view, obliquely from above and on the front side Y 1 , illustrating a state in which the drive unit  20  is to be disposed on an inner surface  110   b  of a rear-side frame member  110  of the image forming apparatus  100  according to the present embodiment.  FIG. 6  is a schematic plan view illustrating a state of the drive unit  20  illustrated in  FIG. 5 .  FIG. 7  is a schematic plan view illustrating a state in which the drive unit  20  is disposed on the inner surface  110   b  of the rear-side frame member  110  of the image forming apparatus  100  according to the present embodiment. 
       FIG. 8  is a schematic front view of the rear-side frame member  110  illustrated in  FIGS. 5 to 7 .  FIG. 9  is a schematic front view illustrating a state in which the drive unit  20  illustrated in  FIG. 7  is attached to the rear-side frame member  110 .  FIG. 10  is a schematic rear view of the rear-side frame member  110  illustrated in  FIGS. 5 to 7 .  FIG. 11  is a schematic rear view illustrating the state in which the drive unit  20  illustrated in  FIG. 7  is attached to the rear-side frame member  110 . 
       FIG. 12  is a schematic perspective view, obliquely from above and on the rear side Y 2 , illustrating the state in which the drive unit  20  illustrated in  FIG. 7  is attached to the rear-side frame member  110 .  FIG. 13  is a schematic perspective view, obliquely from above and on the front side Y 1 , illustrating the state in which the drive unit  20  illustrated in  FIG. 7  is attached to the rear-side frame member  110 . 
     The image forming apparatus  100  according to the present embodiment includes the rear-side frame member  110  and the drive unit  20  (refer to  FIGS. 5 to 7, 9, and 11 to 13 ). The rear-side frame member  110  is disposed on the rear side Y 2  of the image forming apparatus body  1  so as to extend in or substantially in a vertical direction Z. The drive unit  20  includes the drive part  21  (refer to  FIGS. 5 to 7 and 11 to 13 ). The drive part  21  drives the component members (in the present embodiment, the toner supply member  62  of the toner storage part  60  (specifically, the toner stirring member  621  and the toner replenishing member  622 )) of the image forming apparatus body  1 . 
     The drive unit  20  is detachably disposed on the inner (front side Y 1 ) surface  110   b  (refer to  FIGS. 4 to 9 and 13 ) of the rear-side frame member  110  such that the drive part  21  faces outward from the image forming apparatus body  1 . 
     The image forming apparatus  100  according to the present embodiment enables maintenance work, such as cleaning and replacement, of the drive unit  20  to be performed from the front side Y 1  of the image forming apparatus body  1 , because the drive part  21  of the drive unit  20  is detachably disposed on the inner surface  110   b  of the rear-side frame member  110 . Thus, it is possible to easily perform the maintenance work of the drive unit  20 , which improves maintainability of the drive unit  20 . 
     Moreover, because the drive unit  20  is disposed on the inner surface  110   b  of the rear-side frame member  110  such that the drive part  21  faces outward from the image forming apparatus body  1 , it is possible to separate the drive part  21  of the drive unit  20  from the component members (component members for image formation, for example, the photoreceptors  2   a ,  2   b ,  2   c , and  2   d  and the charging devices  3   a ,  3   b ,  3   c , and  3   d ) disposed in the image forming apparatus body  1 . In the present embodiment, the drive part  21  is separated from the component members by a separation member such as a support member  22  (specifically, a drive unit body) on which the drive part  21  is disposed (refer to  FIGS. 4 to 7, 9, and 11 to 13 ). Thus, it is possible to avoid interference (specifically, contact), with the drive part  21  of the drive unit  20 , of the component members (for example, the component members for image formation, such as the photoreceptors  2   a ,  2   b ,  2   c , and  2   d  and the charging devices  3   a ,  3   b ,  3   c , and  3   d ) disposed in the image forming apparatus body  1 . For example, it is possible for the component members disposed in the image forming apparatus body to avoid an influence of heat generated at the drive part. 
     Specifically, the drive unit  20  includes the drive part  21  and the support member  22  that supports the drive part  21 . In the present embodiment, the support member  22  includes a drive transmission mechanism  22   a  (refer to  FIG. 4 ) that transmits a rotational drive force from the drive part  21  to the component members (in the present embodiment, the toner supply member  62  of the toner storage part  60  (specifically, the toner stirring member  621  and the toner replenishing member  622 )) of the image forming apparatus body  1 . The drive transmission mechanism  22   a  (specifically, gear train) is configured to rotate the toner stirring member  621  and the toner replenishing member  622  in directions opposite to each other. 
     The input side (specifically, the side of the drive unit  20  connected to a rotary shaft  21   a  refer to  FIG. 4 ) of the drive part  21 ) of the drive transmission mechanism  22   a  of the support member  22  is positioned on the rear side Y 2 . The output side (specifically, the side connected to the rotary shaft  6211  of the toner stirring member  621  and the rotary shaft  6221  of the toner replenishing member  622 ) of the drive transmission mechanism  22   a  of the support member  22  is positioned on the front side Y 1 . The input side of the drive transmission mechanism  22   a  is connected, on the rear side Y 2 , to the drive part  21  (specifically, the rotary shaft  21   a ) of the drive unit  20 . In other words, the drive part  21  of the drive unit  20  is secured to an outer (rear side Y 2 ) surface  22   b  (refer to  FIGS. 4, 11, and 12 ) of the support member  22 . The body side (specifically, the side opposite the rotary shaft  21   a ) of the drive part  21  is positioned on the rear side Y 2 . 
     The support member  22  is detachably secured to the rear-side frame member  110  such that the outer (rear side Y 2 ) surface  22   b  faces (specifically, in contact with) the inner surface  110   b  of the rear-side frame member  110 , by one or a plurality of securing members SC (in the present embodiment, two screws (refer to  FIGS. 9 and 13 )) that are coupled to respective portions to be secured (in the present embodiment, two female screw holes  110   c  (refer to  FIG. 8 )). 
     The output side of the drive transmission mechanism  22   a  of the drive unit  20  is connected, on the front side Y 1 , to the output side (specifically, the rotary shafts  6211  and  6221 ) of the toner supply member  62 . 
     First Embodiment 
     Incidentally, due to the drive unit  20  that is detachably disposed on the inner surface  110   b  of the rear-side frame member  110  such that the drive part  21  faces outward from the image forming apparatus body  1 , the rear-side frame member  110  may interfere with the drive part  21  of the drive unit  20 . In order to avoid interference of the rear-side frame member  110  with the drive part  21  of the drive unit  20 , a gap may be provided between the rear-side frame member  110  and the drive part  21 ; however, in this case, the gap increases, in the image forming apparatus body  1 , a space having a size corresponding to the size of the gap. 
     Thus, it is desirable to suppress the interference of the rear-side frame member  110  with the drive part  21  of the drive unit  20  while achieving space-saving in the image forming apparatus body  1 . 
     In this respect, in the image forming apparatus  100  according to a first embodiment, the rear-side frame member  110  may be provided with an avoiding portion  120  ( FIGS. 4, 5, and 8 to 13 ) that avoids the interference of the rear-side frame member  110  with the drive part  21  of the drive unit  20 . 
     As a result, it is possible, due to the avoiding portion  120  of the rear-side frame member  110 , to suppress the interference of the rear-side frame member  110  with the drive part  21  of the drive unit  20 . Moreover, because a gap for avoiding the interference of the rear-side frame member  110  with the drive part  21  of the drive unit is not provided due to the provision of the avoiding portion  120 , it is possible to achieve space-saving in the image forming apparatus body  1  by a degree corresponding to the size of the gap. 
     Second Embodiment 
     In the image forming apparatus  100  according to a second embodiment, the avoiding portion  120  may be a through hole  121  (refer to  FIGS. 4, 5, and 8 to 13 ) through which the drive part  21  of the drive unit  20  passes. 
     As a result, it is possible to dispose the drive part  21  of the drive unit  20  in the through hole  121  of the rear-side frame member  110  in a non-contact manner. Thus, it is possible to effectively suppress the interference of the rear-side frame member  110  with the drive part  21  of the drive unit  20 . Moreover, because the through hole  121  enables the omission of a gap for avoiding the interference of the rear-side frame member  110  with the drive part  21  of the drive unit  20 , it is possible to achieve space-saving in the image forming apparatus body  1  by a degree corresponding to the size of the cap. 
     Specifically, non-limiting examples of the shape of the through hole  121  include a circular shape, an oval shape, and a polygonal shape. In the second embodiment, the through hole  121  has a substantially quadrangular shape. 
     Third Embodiment 
     Incidentally, other component members (for example, electric components, substrates, and wires for connecting these component members to each other) disposed on the rear-side frame member  110  (in particular, an outer (rear side Y 2 ) surface  110   a  (refer to  FIG. 12 ) of the rear-side frame member  110 ) sometimes interferes with the drive part  21  of the drive unit  20 . 
     Thus, it is desirable to avoid the interference of the other component members disposed on the rear-side frame member  110  with the drive part  21  of the drive unit  20 . 
     In this respect, in the image forming apparatus  100  according to a third embodiment, a surrounding portion  130  (refer to  FIGS. 4 to 7 and 10 to 12 ) that surrounds (specifically, surrounds in a non-contact manner) at least a portion of the circumference (in the third embodiment, the circumference excluding an upper portion thereof) of the drive part  21  of the drive unit  20  may be formed on the rear-side frame member  110  (in the third embodiment, the outer surface  110   a  of the rear-side frame member  110 ). 
     As a result, it is possible to protect, by using the surrounding portion  130  of the rear-side frame member  110 , the drive part  21  of the drive unit  20  from the component members around the drive part  21 . Thus, it is possible to avoid the interference of the other component members (for example, the electric components, the substrates, and the wires that connect these component members to each other) disposed on the rear-side frame member  110  (in the third embodiment, the outer surface  110   a  of the rear-side frame member  110 ) with the drive part  21  of the drive unit  20 . 
     Specifically, the surrounding portion  130  may have a shape that is substantially polygonal cylindrical, substantially circular cylindrical, or substantially oval cylindrical with at least a portion in a circumferential direction thereof notched when viewed from the rear side Y 2 . When a portion in the circumferential direction of the surrounding portion  130  is notched, the position of the portion to be notched may be at a position where the other component members are not disposed. Specifically, if the shape of the surrounding portion  130  is quadrangular, the surrounding portion  130  may include at least one of an upper plate, a lower plate, a right plate, and a left plate when viewed from the front side Y 1 . 
     In the third embodiment, the surrounding portion  130  includes a lower plate  131  (refer to  FIGS. 4, 6, 7, and 10 to 12 ), a right plate  132  (refer to  FIGS. 5 to 7 and 10 to 12 ), and a left plate  133  (refer to  FIGS. 5 to 7 and 10 to 12 ). 
     At least a part (for example, at least one of the plates) of the surrounding portion  130  may include one or a plurality of portions bent in a direction perpendicular to the depth direction Y. In the third embodiment, the lower plate  131  of the surrounding portion  130  includes two portions bent in the vertical direction Z. Specifically, the lower plate  131  includes two horizontal portions and an inclined portion formed between the horizontal portions. 
     The rear-side frame member  110  and the surrounding portion  130  are integral with each other. In the third embodiment, the lower plate  131 , the right plate  132 , and the left plate  133  of the surrounding portion  130  are integral with each other. 
     In the third embodiment, the surrounding portion  130  is disposed on the outer surface  110   a  of the rear-side frame member  110 ; however, the surrounding portion  130  may be disposed on the inner surface  110   b  of the rear-side frame member  110 . 
     Moreover, the shape of the whole circumference of the surrounding portion  130  may be substantially polygonal cylindrical, substantially circular cylindrical, or substantially oval cylindrical. In addition, an opening on the rear side Y 2  in the surrounding portion  130  may be closed. Specifically, a back surface plate that extends in both the left-right direction X and the vertical direction Z may be disposed on end surfaces on the rear side Y 2  of the lower plate  131 , the right plate  132 , and the left plate  133  so that the drive part  21  is covered by the lower plate  131 , the right plate  132 , the left plate  133 , and the back surface plate. The lower plate  131 , the right plate  132 , the left plate  133 , and the back surface plate may be integral with each other. 
     In addition, the surrounding portion  130  may be disposed on the drive unit  20  (specifically, the support member  22 ). 
     The drive unit  20  may be positioned by recess-projection engagement at the rear-side frame member  110 . Specifically, one (the rear-side frame member  110  in the third embodiment) of the drive unit  20  and the rear-side frame member  110  may be provided with one or a plurality of (two in the third embodiment) recessed portions  110   d   1  and  110   d   2  (refer to  FIG. 8 ) (through holes in the third embodiment). The other one (the support member  22  of the drive unit  20  in the third embodiment) of the drive unit  20  and the rear-side frame member  110  may be provided with projecting portions  22   c  and  22   c  (refer to  FIG. 9 ) (positioning pins in the third embodiment) that correspond to the recessed portions  110   d   1  and  110   d   2 , respectively. One (in the third embodiment, the recessed portion  110   d   2  on the left side when viewed from the front side) of the recessed portions  110   d   1  and  110   d   2  is an elongated hole extending in the left-right direction X. 
     Fourth Embodiment 
     In the image forming apparatus  100  according to a fourth embodiment, the avoiding portion  120  may be a recessed portion (not illustrated) that covers the drive part  21  of the drive unit  20 . 
     As a result, it is possible to dispose the drive part  21  of the drive unit  20  in the recessed portion of the rear-side frame member  110  in a non-contact manner. Thus, it is possible to effectively suppress the interference of the rear-side frame member  110  with the drive part  21  of the drive unit  20 . Moreover, because the recessed portion enables the omission of a gap for avoiding the interference of the rear-side frame member  110  with the drive part  21  of the drive unit  20 , it is possible to achieve space-saving in the image forming apparatus body  1  by a degree corresponding to the size of the gap. 
     Specifically, non-limiting examples of the recessed portion include a bottomed quadrangular cylindrical recessed portion, a bottomed circular cylindrical recessed portion, a bottomed oval cylindrical recessed portion, a circular arc-shaped recessed portion, a frustoconical recessed portion, and a truncated pyramid-shaped recessed portion. The recessed portion may have a through hole formed in a bottom surface (a top surface when viewed from the rear side Y 2 ) thereof. 
     Fifth Embodiment 
     In the image forming apparatus  100  according to a fifth embodiment, the drive part  21  of the drive unit  20  may be an electric drive part. A connector  23  (refer to  FIGS. 4 to 7, 9, and 13 ) electrically connected to the drive part  21  may be disposed on the drive unit  20  (the support member  22  in the fifth embodiment) such that a connected side thereof faces the front side Y 1  of the image forming apparatus body  1 . The drive part  21  may be electrically connected to the image forming apparatus body  1  via the connector  23 . The drive part  21  electrically drives component members (in the fifth embodiment, the toner supply member  62  of the toner storage part  60  (specifically, the toner stirring member  621  and the toner replenishing member  622 )). 
     As a result, it is possible to attach and detach the drive part  21 , which is the electric drive part, to and from the connector  23  easily from the front side Y 1  of the image forming apparatus body  1 . Thus, it is possible to improve the efficiency of attaching and detaching the drive part  21  to and from the connector  23 . Moreover, it is possible to attach and detach the drive part  21  to and from the connector  23  when attaching or detaching the drive unit  20  to or from the rear-side frame member  110  from the front side Y 1  of the image forming apparatus body  1 . Thus, it is possible to improve the efficiency of attaching and detaching the drive part  21  to and from the connector  23 . 
     Specifically, the image forming apparatus body  1  may include the electric power supply part  18  (specifically, a drive circuit board) (refer to  FIG. 1 ) that supplies electric power to the drive part  21  of the drive unit  20 . A connector  19  (refer to  FIG. 13 ) may be electrically connected to the output side of the electric power supply part  18 . The connector  19  extending from the electric power supply part  18  via wires  19   a  (refer to  FIG. 13 ) is disposed in the vicinity of the connector  23  of the drive part  21  on the front side Y 1  of the drive unit  20 . 
     In the fifth embodiment, the connector  23  of the drive part  21  of the drive unit  20  is positioned (refer to  FIGS. 4, 9, and 13 ) above the output shaft portions  20   a  and  20   b  each having the structure that couples with the toner supply member  62  (specifically, the toner stirring member  621  and the toner replenishing member  622 ). 
     As a result, it is possible to effectively suppress the interference of the connector  23  and/or wires  23   a  (refer to  FIG. 4 ) of the connector  23  with the output shaft portions  20   a  and  20   b  and the interference of the connector  19  and/or the wires  19   a  of the connector  19  with the toner storage part  60 . Moreover, it is possible to more easily attach and detach the drive part  21  to and from the connector  23 . 
     In the fifth embodiment, the toner replenishing port  64  and the toner supply port  551  are disposed on the rear side Y 2  of the toner storage part  60  and the developing device  5 , respectively. In this case, a toner from the toner replenishing port  64  and/or the toner supply port  551  sometimes causes a toner stain on the rear side Y 2 . As a result, the toner sometimes causes contact failure between the connector  23  and the connector  19 . Thus, the toner replenishing port  64  and the toner supply port  551  may be disposed on the front side Y 1  of the toner storage part  60  and the developing device  5 , respectively. As a result, it is possible to avoid a toner stain caused, on the rear side Y 2 , by the toner from the toner replenishing port  64  and/or the toner supply port  551 , which makes it possible to avoid contact failure caused between the connector  23  and the connector  19  by the toner. 
     Moreover, the toner replenishing port  64  and the toner supply port  551  disposed on the rear side Y 2  of the toner storage part  60  and the developing device  5 , respectively, may be disposed such that the connector  23  and the connector  19  do not overlap (specifically, deviated in the left-right direction X and/or the depth direction Y from) the toner replenishing port  64  and the toner supply port  551  in the vertical direction Z. For example, the connector  23  may be disposed on toe right side X 1  of the drive unit  20  while the toner replenishing port  64  is disposed on the left side X 2  of the toner storage part  60 . As a result, even when the toner from the toner replenishing port  64  and/or the toner supply port  551  causes a toner stain on the rear side Y 2 , it is possible to avoid the contact failure caused by the toner, between the connector  23  (in particular, the connector  23  disposed below the toner replenishing port  64 ) and the connector  19 . 
     Sixth Embodiment 
     Incidentally, in the first to fifth embodiments, the securing members SC such as screws are used to detachably attach) the drive unit  20  to the rear-side frame member  110 . In this case, a tool is used to attach and detach the securing members SC, which increases the complexity of attaching and detaching the drive unit  20  to and from the rear-side frame member  110 . 
     Therefore, it is desirable to improve the efficiency of attaching and detaching the drive unit  20  to and from the rear-side frame member  110 . 
     In this respect, in each of a sixth embodiment and seventh to eleventh embodiments (described later), the drive unit  20  in the first to fifth embodiments is detachably disposed on the rear-side frame member  110 . 
       FIG. 14  is a schematic rear view illustrating, for describing a configuration in which the drive unit  20  is detachably disposed on the rear-side frame member  110 , a state in which the drive unit  20  is not yet attached to the rear-side frame member  110 .  FIG. 15  is a schematic rear view of the drive unit  20  illustrated in  FIG. 14 .  FIG. 16  is a schematic rear view illustrating a state in which the drive unit  20  illustrated in  FIG. 14  is attached to the rear-side frame member  110  but not yet secured to the rear-side frame member  110  by a pawl portion  25 . 
       FIG. 17  is a schematic rear view illustrating a state in which the drive unit  20  illustrated in  FIG. 14  is attached to the rear-side frame member  110  and secured to the rear-side frame member  110  by the pawl portion  25 .  FIG. 18  is a schematic front view of the rear-side frame member  110  illustrated in each of  FIGS. 14, 16, and 17 .  FIG. 19  is a schematic front view illustrating a state in which the drive unit  20  illustrated in  FIG. 16  that is attached to the rear-side frame member  110  is not yet pawl-engaged with the rear-side frame member  110 . 
       FIG. 20  is a schematic perspective view illustrating the drive unit  20  illustrated in each of  FIGS. 14 to 17 and 19  and illustrating, as an enlargement, a projecting portion  26  of the drive unit  20 . 
     Note that members in the image forming apparatus  100  according to each of the sixth to eleventh embodiments having substantially identical configurations as those of the component members of the image forming apparatus  100  according to the first to fifth embodiments are given like reference numerals, and description of such members will be omitted. 
     In the image forming apparatus  100  according to the sixth embodiment, the drive unit  20  (refer to  FIGS. 14 to 17, 19, and 20 ) may be configured to be detachably secured to the rear-side frame member  110  by being rotated about a rotational axis (specifically, a rotary shaft  24  (refer to  FIGS. 14 to 17 )) extending in a direction perpendicular or substantially perpendicular to the rear-side frame member  110 . 
     Specifically, the drive unit  20  may be configured to be attached to the rear-side frame member  110  by being rotated in one direction (in the sixth embodiment, clockwise when viewed from the rear side Y 2  in  FIG. 16  and counter-clockwise when viewed from the front side Y 1  in  FIG. 19 ) about the rotational axis (specifically, the rotary shaft  24 ) and to be detached from the rear-side frame member  110  by being rotated in the other direction (in the sixth embodiment, counter-clockwise when viewed from the rear side Y 2  in  FIG. 16  and clockwise when viewed from the front side Y 1  in  FIG. 19 ) about the rotational axis (specifically, the rotary shaft  24 ). 
     As a result, it is possible to easily attach and detach the drive unit  20  to and from the rear-side frame member  110 . Thus, it is possible to improve the efficiency of attaching and detaching the drive unit  20  to and from the rear-side frame member  110 . 
     Specifically, the outer (rear side Y 2 ) surface  22   b  (refer to  FIGS. 14 to 17 and 20 ) of the support member  22  of the drive unit  20  has a shape extending along the inner (front side Y 1 ) surface  110   b  (refer to  FIGS. 18 and 19 ) of the rear-side frame member  110 . The rotary shaft  24  is disposed on the outer (rear side Y 2 ) surface  22   b  of the support member  22  and has a projecting shape that projects toward the front side Y 1 . 
     Non-limiting examples of the projecting shape of the rotary shaft  24  include a columnar projecting shape and a cylindrical projecting shape. In the sixth embodiment, the projecting shape of the rotary shaft  24  is the columnar projecting shape. 
     The rear-side frame member  110  is provided with an insertion portion  110   e  (refer to  FIGS. 14 and 16 to 18 ) into which the rotary shaft  24  of the support member  22  of the drive unit  20  is inserted so as to be rotatable about the axis of the rotary shaft  24 . The insertion portion  110   e  may be a through hole or a bottomed hole (recessed portion). 
     In the sixth embodiment, the insertion portion  110   e  is a through hole. The diameter of the insertion portion  110   e  is slightly larger (larger by a predetermined distance) than the diameter of the rotary shaft  24  by a degree that ensures insertion of the rotary shaft  24 . 
     Seventh Embodiment 
     In the image forming apparatus  100  according to a seventh embodiment, the drive unit  20  may be configured to be detachably secured, by pawl engagement, to the rear-side frame member  110 . 
     As a result, it is possible to detachably engage, by pawl engagement, the drive unit  20  and the rear-side frame member  110  with each other, which makes it easy to achieve a configuration in which the drive unit  20  is detachably secured to the rear-side frame member  110 . 
     Specifically, one (in the seventh embodiment, the drive unit  20 ) of the drive unit  20  and the rear-side frame member  110  may be provided with the pawl portion  25  (refer to  FIGS. 14 to 17, 19, and 20 ), and the other one (in the seventh embodiment, the rear-side frame member  110 ) of the drive unit  20  and the rear-side frame member  110  may be provided with a pawl lock portion  140  (refer to  FIGS. 14 and 16 to 19 ) to be locked with the pawl portion  25 . 
     More specifically, the support member  22  of the drive unit  20  is provided with a plurality of (two in the seventh embodiment) pawl portions  25   a  ( 25 ) and  25   b  ( 25 ). Each of the pawl portions  25   a  ( 25 ) and  25   b  ( 25 ) includes a first pawl portion  251  (refer to  FIGS. 14 to 17, 19, and 20 ) and a second pawl portion  252  (refer to  FIGS. 14 to 17, 19 , and  20 ). Each first pawl portion  251  is disposed on the support member  22  so as to project from the support member  22  toward the rear side Y 2 . Each second pawl portion  252  is bent, at the right angle or a substantially right angle, at a top end portion of the first pawl portion  251  corresponding thereto outwardly in the radial direction of the axis of the rotary shaft  24 . 
     The rear-side frame member  110  is provided with pawl lock portions  140   a  ( 140 ) and  140   b  ( 140 ) (refer to  FIGS. 14 and 16 to 19 ) that lock the pawl portions  25   a  ( 25 ) and  25   b  ( 25 ) of the support member  22  of the drive unit  20 . The pawl lock portions  140   a  ( 140 ) and  140   b  ( 140 ) may be through holes or bottomed holes (recessed grooves). In the seventh embodiment, the pawl lock portions  140  are through holes. 
     Each of the pawl lock portions  140   a  ( 140 ) and  140   b  ( 140 ) includes a first pawl lock portion  141  (refer to FIGS.  14  and  16  to  19 ) and a second pawl lock portion  142  (refer to  FIGS. 14 and 16 to 19 ). Each first pawl lock portion  141  is configured such that both the corresponding first pawl portion  251  and the corresponding second pawl portion  252  are inserted therethrough. When rotated about the rotary shaft  24 , each second pawl lock portion  142  is inserted by the first pawl portion  251  corresponding thereto and locks the second pawl portion  252  corresponding thereto. Thus, it is possible to secure the drive unit  20  in the rotational axis direction of the drive unit  20 . 
     Each first pawl portion  251  has a circular arc shape that coincides with a locus of rotation about the axis of the rotary shaft  24 . Each second pawl portion  252  has a plate shape extending in the left-right direction X and an up-down direction Z. 
     A distance between each second pawl portion  252  and the support member  22  is slightly larger (larger by a predetermined distance) than a thickness of the rear-side frame member  110  by a degree that ensures engagement of each second pawl portion  252  with the rear-side frame member  110 . 
     The size of each first pawl lock portion  141  slightly larger (larger by a predetermined distance) than the size of the first pawl portion  251  and the size of the second pawl portion  252  by a degree that ensures insertion of the first pawl portion  251  and the second pawl portion  252 . Each second pawl lock portion  142  has a circular arc shape that coincides with the locus of the rotation about the axis of the rotary shaft  24 . The size of each second pawl lock portion  142  is slightly larger (larger by a predetermined distance) than the size of the first pawl portion  251  by a degree that ensures insertion of the first pawl portion  251 . 
     In the seventh embodiment, the rotational axis (specifically, the rotary shaft  24 ) and the two second pawl portions  252  and  252  of the drive unit  20  are disposed on the support member  22  such that virtual straight lines that connect the rotational axis and the second pawl portions  252  and  252  form a triangular shape. 
     As a result, it is possible to effectively engage the drive unit  20  with the rear-side frame member  110 . 
     Eighth Embodiment 
     Incidentally, the rotational position of the drive unit  20  about the rotational axis (specifically, the rotary shaft  24 ) may be restricted by pawl engagement (for example, the aforementioned pawl engagement); however, in this case, it may not be possible to accurately restrict the rotation of the drive unit  20 . 
     Therefore, it is desirable to improve accuracy in the rotational position of the drive unit  20 . 
     In this respect, in the image forming apparatus  100  according to the eighth embodiment, the rotation of the drive unit  20  about the rotational axis (specifically, the rotary shaft  24 ) may be restricted by recess-projection engagement with the rear-side frame member  110 . 
     As a result, it is possible, due to the recess-projection engagement, to accurately restrict the rotation of the drive unit  20  about the rotational axis (specifically, the rotary shaft  24 ), which makes it possible to improve accuracy in the rotational position of the drive unit  20 . 
     Ninth Embodiment 
     In the image forming apparatus  100  according to a ninth embodiment, one (in the ninth embodiment, the drive unit  20 ) of the drive unit  20  and the rear-side frame member  110  may be provided with the projecting portion  26  (refer to  FIGS. 14 to 17 and 20 ), and the other one (in the ninth embodiment, the rear-side frame member  110 ) of the drive unit  20  and the rear-side frame member  110  may be provided with a lock portion  110   f  (refer to  FIGS. 14 and 16 to 18 ) that is locked with the projecting portion  26 . The rotation of the drive unit  20  of the image forming apparatus  100  about the rotational axis (specifically, the rotary shaft  24 ) is restricted by the engagement between the projecting portion  26  and the lock portion  110   f.    
     As a result, it is possible to easily provide the projecting portion  26  on one (the drive unit  20  in the ninth embodiment) of the drive unit  20  and the rear-side frame member  110 , and it is also possible to easily provide the lock portion  110   f  on the other one (the rear-side frame member  110  in the ninth embodiment) of the drive unit  20  and the rear-side frame member  110 . Thus, it is possible to easily achieve the engagement between the drive unit  20  and the rear-side frame member  110 . 
     Specifically, the projecting portion  26  is disposed on the outer (rear side Y 2 ) surface  22   b  of the support member  22  of the drive unit  20 . The projecting portion  26  has a projecting shape that projects toward the front side Y 1 . 
     Non-limiting examples of the shape of the projecting portion  26  include a semi-spherical (semi-circular in the side view) shape, a circular arc shape in the side view, an oval arc shape in the side view, a conical (triangular in the side view) shape, a pyramid (triangular in the side view) shape, a frustoconical shape (trapezoidal in the side view), and a truncated pyramid shape (trapezoidal in side view). In the ninth embodiment, the shape of the projecting portion  26  is substantially semi-spherical (substantially semi-circular in side view). 
     The lock portion  110 ′ is disposed on the inner surface  110   b  of the rear-side frame member  110 . The lock portion  110   f  may be a through hole or a bottomed hole (recessed portion). In the ninth embodiment, the lock portion  110   f  is a through hole. 
     Specifically, the projecting portion  26  may be disposed on the rear-side frame member  110  so as to be at a position (specifically, opposite the rotational axis (specifically, the rotary shaft  24 ) of the drive unit  20  with the drive part  21  interposed therebetween) as far as possible from the rotational axis (specifically, the rotary shaft  24 ) of the drive unit  20 . 
     As a result, it is possible to accurately restrict the rotation of the drive unit  20  about the rotational axis (specifically, the rotary shaft  24 ). 
     Tenth Embodiment 
     In the image forming apparatus  100  according to a tenth embodiment, the other one (the rear-side frame member  110  in the tenth embodiment) of the drive unit  20  and the rear-side frame member  110  may be further provided with a guide groove  110   g  (refer to  FIG. 18 ) that guides the projecting portion  26  to the lock portion  110   f.    
     As a result, it is possible to guide the projecting portion  26  to the lock portion  110   f  along the guide groove  110   g , which ensures locking of the projecting portion  26  to the lock portion  110   f.    
     Specifically, the lock portion  110   f  and the guide groove  110   g  are configured as illustrated in  FIGS. 21 and 22 . 
       FIG. 21  is an enlarged schematic front view illustrating a portion including the lock portion  110   f  and the guide groove  110   g  illustrated in  FIG. 18 .  FIG. 22  is a schematic sectional view of a portion including the lock portion  110   f  and the guide groove  110   g  illustrated in  FIG. 21 , taken along line XXII-XXII. 
     The guide groove  110   g  is disposed on the inner surface  110   b  of the rear-side frame member  110 . The lock portion  110   f  communicates with one end (a guide outlet end that guides the projecting portion  26  to the lock portion  110   f ) of the guide groove  110   g.    
     The guide groove  110   g  has a circular arc shape that coincides with the locus of the rotation of the drive unit  20  about the rotational axis (specifically, the axis of the rotary shaft  24 ). 
     As a result, it is possible to ensure guiding of the projecting portion  26  along the guide groove  110   g  having the circular arc shape that coincides with the locus of the rotation of the drive unit  20 . 
     The guide groove  110   g  has a width Wa (refer to  FIG. 21 ) that increases as a distance from the lock portion  110   f  increases. 
     As a result, it is possible, at the other end opposite the lock portion  110   f  (a guide inlet end that guides the projecting portion  26  to the lock portion  110   f ) of the guide groove  110   a , to easily receive the projecting portico  26  in the other end (guide inlet end) of the guide groove  110   g  in a radial direction R (refer to  FIGS. 20 and 21 ) of the rotary shaft  24 . 
     Incidentally, a size Wb (refer to  FIG. 21 ) of the lock portion  110   f  in the radial direction R may be equal or substantially equal to a size Wc (refer to  FIG. 20 ) of the projecting portion  26  in the radial direction R; however, in this case, if there is a dimensional difference between the rotary shaft  24  and the projecting portion  26 , it is difficult to tolerate the dimensional difference. In this case, it is not possible to ensure the engagement of the projecting portion  26  with the lock portion  110   f.    
     Thus, it is desirable to tolerate the dimensional difference between the rotary shaft  24  and the projecting portion  26 . 
     In this respect, the size Wb of the lock portion  110   f  in the radial direction R is slightly larger (larger by a predetermined distance that enables toleration of the dimensional difference between the rotary shaft  24  and the projecting portion  26 ) than the size Wc of the projecting portion  26  in the radial direction R. 
     As a result, even if there is a dimensional difference between the rotary shaft  24  and the projecting portion  26 , it is possible to tolerate the dimensional difference, which ensures engagement of the projecting portion  26  with the lock portion  110   f.    
     The lock portion  110   f  has, for example, a shape (commonly known as an oval shape) having two substantially straight line portions that face each other and extend in the radial direction R with a gap interposed therebetween, the gap being slightly larger (larger by a predetermined distance that ensures insertion of the projecting portion  26 ) in a circumferential direction M (refer to  FIG. 21 ) of the rotary shaft  24  than the size of the projecting portion  26 ; and circular arc portions that are connected to both ends of the substantially parallel straight line portions so as to correspond to the circular arc shape of the projecting portion  26 . 
     The width Wa of the guide groove  110   g  is equal or substantially equal, at one end (guide outlet end) of the guide groove  110   g  on the lock portion  110   f  side, to the size Wb of the lock portion  110   f  in the radial direction R. 
     As a result, it is possible to smoothly move the projecting portion  26  from the one end (guide outlet end) of the guide groove  110   g  to the lock portion  110   f.    
     The width Wa of the guide groove  110   g  is larger (larger by a predetermined distance that enables the projecting portion  26  to be smoothly guided from the other end (guide inlet end) of the guide groove  110   g  along the guide groove  110  at the other end (guide inlet end) of the guide groove  110   g  than the size Wb of the lock portion  110   f.    
     As a result, it is possible to smoothly guide the projecting portion  26  from the other end (guide inlet end) of the guide groove  110   g  along the guide groove  110   g.    
     The guide groove  110   g  has a depth D (refer to  FIG. 22 ) that increases as a distance from the lock portion  110   f  increases. 
     As a result, it is possible, at the other end (guide inlet end) of the guide groove  110   g , to easily receive the projecting portion  26  in the guide groove  110   g  in a thickness direction H (depth direction Y). 
     The guide groove  110   g  may be inclined linearly or may have curved shape projecting upward or projecting downward. In the tenth embodiment, the guide groove  110   g  is inclined linearly. 
     Eleventh Embodiment 
     In the image forming apparatus  100  according to an eleventh embodiment, the other one (in the eleventh embodiment, the inner surface  110   b  of the rear-side frame member  110 ) of the drive unit  20  and the rear-side frame member  110  may be provided with a temporary placement portion  110   h  (refer to  FIGS. 18, 21, and 22 ) for temporarily placing the projecting portion  26  thereon. 
     As a result, it is possible to temporarily place the projecting portion  26  on the temporary placement portion  110   h  before the projecting portion  26  is guided along the guide groove  110   g , which ensures guiding of the projecting portion  26  to the vicinity of the other end (guide inlet end) of the guide groove  110   g.    
     The temporary placement portion  110   h  may be a through hole or may be a bottomed hole (recessed portion). In the eleventh embodiment, the temporary placement portion  110   h  is a through hole. 
     The temporary placement portion  110   h  communicates with the other end (guide inlet end) of the guide groove  110   g . The temporary placement portion  110   h  has a size Wd (refer to  FIG. 21 ) in the radial direction R. The size Wd is equal or substantially equal to the width Wa of the other end (guide inlet end) of the guide groove  110   a.    
     As a result, it is possible to smoothly move the projecting portion  26  from the other end (guide inlet end) of the guide groove  110   g  into the guide groove  110   g.    
     The temporary placement portion  110   h  includes an inclined portion  110   ha  (refer to  FIGS. 21 and 22 ) that communicates with the guide groove  110   g . The height of the inclined portion  110   ha  in the thickness direction H (depth direction Y) gradually increases toward the guide groove  110   g.    
     As a result, it is possible to more smoothly move the projecting portion  26  from the temporary placement portion  110  to the guide groove  110   g  via the inclined portion  110   ha.    
     An example of the shape of the temporary placement portion  110   h  is a shape (commonly known as an oval shape) having two substantially straight line portions that face each other and extend in the radial direction R with a gap interposed therebetween, the gap being larger (larger by a predetermined distance that ensures placing of the projecting portion  26  in the vicinity of the other end (guide inlet end) of the guide groove  110   g ) in the circumferential direction M than the size of the projecting portion  26 ; and circular arc portions that are connected to both ends of the two straight line portions so as to correspond to the circular arc shape of the projecting portion  26 . 
     Attaching/Detaching of Drive Unit to/from Rear-side Frame Member 
     In the aforementioned image forming apparatus  100 , the drive unit  20  is attached to the rear-side frame member  110  from the front side Y 1  as described below. First, the rotary shaft  24  of the drive unit  20  is inserted, toward the rear side Y 2 , into the insertion portion  110   e  of the rear-side frame member  110 . Then, the projecting portion  26  of the drive unit  20  is temporarily placed on the temporary placement portion  110   h  of the rear-side frame member  110 . Next, the drive unit  20  is rotated in one direction (in the eleventh embodiment, clockwise when viewed from the rear side Y 2  in  FIG. 16  and counter-clockwise when viewed from the front side Y 1  in  FIG. 19 ) about the rotary shaft  24 , and at the same time, the projecting portion  26  is moved from the temporary placement portion  110   h  toward the lock portion  110   f  along the guide groove  110   g  so that the pawl portions  25   a  ( 25 ) and  25   b  ( 25 ) of the drive unit  20  are locked with the pawl lock portions  140   a  ( 140 ) and  140   b  ( 140 ) of the rear-side frame member  110 , respectively. Then, the projecting portion  26  of the drive unit  20  is locked with the lock portion  110   f  of the rear-side frame member  110 . Thus, the drive unit  20  is attached to the rear-side frame member  110 . 
     The drive unit  20  is detached from the rear-side frame member  110  from the front side Y 1  as described below. First, the drive unit  20  is pulled slightly toward the front side Y 1  to release the engagement between the projecting portion  26  of the drive unit  20  and the lock portion  110   f  of the rear-side frame member  110 , and at the same time, the drive unit  20  is rotated in the other direction (in the eleventh embodiment, counter-clockwise when viewed from the rear-side Y 2  in  FIG. 16  and clockwise when viewed from the front side Y 1  in  FIG. 19 ) about the rotary shaft  24 . Next, the projecting portion  26  of the drive unit  20  is moved from the lock portion  110   f  of the rear-side frame member  110  toward the temporary placement portion  110   h  along the guide groove  110   g , and at the same time, the engagement of each of the pawl portions  25   a  ( 25 ) and  25   b  (n) of the drive unit  20  with the respective pawl lock portions  140   a  ( 140 ) and  140   b  ( 140 ) of the rear-side frame member  110  is released. Then, the rotary shaft  24  of the drive unit  20  is extracted from the insertion portion  110   e  of the rear-side frame member  110  toward the front side Y 1 . Thus, the drive unit  20  is detached from the rear-side frame member  110 . 
     In the embodiments, a drive device that drives a toner storage part (specifically, a toner cartridge) is presented as an example of the drive unit according to the present disclosure; however, the drive unit according to the present disclosure is also employed as a drive device that drives various types of devices and units used in an image forming apparatus, for example, as a transfer unit and a process unit that includes a developing device, a fixing device, and a photoreceptor. 
     The present disclosure is not limited to the embodiments described above and can be carried out in other various forms. Therefore, such embodiments are merely examples in all aspects and are not to be restrictively interpreted. The scope of the present disclosure is indicated by the claims and is not restricted by the content of the specification. Further, all modifications and alterations belonging to a scope equivalent to the claims are included in the scope of the present disclosure. 
     The present disclosure contains subject matter related to that disclosed in Japanese Priority Patent Application JP 2017-080830 filed in the Japan Patent Office on Apr. 14, 2017, the entire contents of which are hereby incorporated by reference. 
     It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.