Patent Publication Number: US-11040843-B2

Title: Image forming apparatus

Description:
FIELD 
     Embodiments described herein relate generally to an image forming apparatus. 
     BACKGROUND 
     An image forming apparatus includes a process unit that forms an image and a connection mechanism that transmits a driving force to the process unit. For maintenance or the like, the process unit is detached from the image forming apparatus. Therefore, the connection mechanism is configured to be detachably mounted on the process unit. 
     However, in the image forming apparatus, the structure of the connection mechanism is complex and is not easy to miniaturize. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating a configuration of an image forming apparatus according to a first embodiment; 
         FIG. 2  is an exploded perspective view illustrating a connection mechanism of the image forming apparatus; 
         FIG. 3  is a perspective view illustrating a first rotator and an engagement portion of the image forming apparatus; 
         FIG. 4  is a perspective view illustrating the connection mechanism of the image forming apparatus; 
         FIG. 5  is a flowchart illustrating an operation of the image forming apparatus; 
         FIG. 6  is a perspective view illustrating the connection mechanism of the image forming apparatus; 
         FIG. 7  is a perspective view illustrating the connection mechanism of the image forming apparatus; 
         FIG. 8  is a plan view illustrating the connection mechanism of the image forming apparatus; 
         FIG. 9  is a plan view illustrating the connection mechanism of the image forming apparatus; 
         FIG. 10  is a plan view illustrating the connection mechanism of the image forming apparatus; 
         FIG. 11  is a plan view illustrating the connection mechanism of the image forming apparatus; 
         FIG. 12  is a plan view illustrating the connection mechanism of the image forming apparatus; 
         FIG. 13  is a plan view illustrating the connection mechanism of the image forming apparatus; 
         FIG. 14  is a diagram illustrating a structure of the engagement portion according to a modification example; 
         FIG. 15  is an exploded perspective view illustrating a connection mechanism of an image forming apparatus according to a second embodiment; 
         FIG. 16  is a perspective view illustrating the connection mechanism of the image forming apparatus; 
         FIG. 17  is a perspective view illustrating the connection mechanism of the image forming apparatus; and 
         FIG. 18  is a perspective view illustrating the connection mechanism of the image forming apparatus. 
     
    
    
     DETAILED DESCRIPTION 
     In general, according to one embodiment, an image forming apparatus includes a process unit, a first rotator, a second rotator, a driving force transmission mechanism, and a displacement mechanism. The process unit forms an image. The first rotator is rotatable about a shaft in a first direction and a second direction reverse to the first direction. The second rotator is disposed in parallel to the first rotator. The second rotator is detachably connected to the process unit. The driving force transmission mechanism transmits a driving force of the first rotator to the second rotator to rotate the second rotator about a shaft when the first rotator is rotated in the first direction. The displacement mechanism releases the connection between the second rotator and the process unit by displacing the second rotator in a shaft direction when the first rotator is rotated in the second direction. 
     Hereinafter, an image forming apparatus according to an embodiment will be described with reference to the drawings. In each drawing, the same reference numerals are given to the same constituents. In each drawing, dimensions and a shape of each member are exaggerated or simplified for easy visibility. 
     First Embodiment 
     An image forming apparatus according to a first embodiment will be described. 
     As illustrated in  FIG. 1 , an image forming apparatus  10  according to the first embodiment includes a printer unit  11  which is an image forming unit. The printer unit  11  includes four process units  20 . The four process units  20  are process units  20 Y,  20 M,  20 C, and  20 K using Y (yellow) toner, M (magenta) toner, C (cyan) toner, and K (black) toner. The process units  20 Y,  20 M,  20 C, and  20 K are disposed in parallel along an intermediate transfer belt  18 . 
     The process unit  20  includes a photosensitive drum (photoreceptor)  22 , an electrostatic charger (charging device)  23 , an exposure scanning head (optical device)  24 , a development device  26 , and a photoreceptor cleaner  27 . 
     The photosensitive drum  22 , a photosensitive layer is coated on the surface of a conductive supporter with a cylindrical shape. The electrostatic charger  23  applies charges to the photosensitive drum  22  to charge the surface of the photosensitive drum  22 . The exposure scanning head  24  radiates light to the photosensitive drum  22  to form an exposure latent image. The development devices  26  of the process units  20 Y,  20 M,  20 C, and  20 K respectively have two-component developer including the Y (yellow) toner, M (magenta) toner, C (cyan) toner, and K (black) toner and carriers. The development device  26  develops the exposure latent image in accordance with the developer. The photoreceptor cleaner  27  removes the toner remaining on the photosensitive drum  22 . 
     The printer unit  11  includes a backup roller  18   a , a driven roller  18   b , a tension roller (not illustrated), the intermediate transfer belt  18 , a plurality of primary transfer rollers  28 , and a secondary transfer roller  30 . The backup roller  18   a , the driven roller  18   b , and the tension roller (not illustrated) support the intermediate transfer belt  18 . The intermediate transfer belt  18  rotates in an arrow m direction. The primary transfer rollers  28  are provided at positions facing the photosensitive drums  22  with the intermediate transfer belt  18  interposed therebetween. The secondary transfer roller  30  is provided at a position facing the backup roller  18   a  with the intermediate transfer belt  18  interposed therebetween. 
     A paper feed unit (not illustrated) that supplies a sheet is provided below the printer unit  11 . The printer unit  11  includes a resist roller  31   a , a fixing device  32 , and a pair of paper discharge rollers  33 . The resist roller  31   a , the secondary transfer roller  30 , the fixing device  32 , and the pair of paper discharge rollers  33  are provided along a transport path along which the sheet is transported. 
     The primary transfer roller  28  primarily transfers toner images formed on the photosensitive drums  22  to the intermediate transfer belt  18 . The primary transfer rollers  28  of the process units  20 Y,  20 M,  20 C, and  20 K form Y (yellow), M (magenta), C (cyan), and K (black) toner images on the intermediate transfer belt  18  so that the toner images overlap to form a color toner image. 
     The secondary transfer roller  30  is driven and rotated by the intermediate transfer belt  18 . The secondary transfer roller  30  secondarily transfers the color toner image on the intermediate transfer belt  18  on the supplied sheet. 
     As illustrated in  FIG. 2 , the image forming apparatus includes a connection mechanism  100 . The connection mechanism  100  includes a first rotator  41 , a second rotator  42 , a driving force transmission mechanism  43 , a displacement mechanism  44 , a base substrate  45 , a first shaft  46 , a second shaft  47 , a stopper  48 , and a spring  49  (an urging member). 
     The first shaft  46  vertically protrudes from a main surface  45   a  of the base substrate  45  on the main surface  45   a . The first shaft  46  is inserted through the first rotator  41 . The second shaft  47  protrudes from a main surface  45   a  of the base substrate  45  to be orthogonal to the main surface  45   a . The second shaft  47  is inserted through the second rotator  42 . The second shaft  47  is formed to be away from the first shaft  46  in a diameter direction. The second shaft  47  is formed in parallel to the first shaft  46 . 
     Hereinafter, a protrusion direction of the first shaft  46  and the second shaft  47  is provisionally referred to as a “front F”. A reverse direction to the “front” is provisionally referred to as a “rear R”. 
     The first rotator  41  includes a first cylinder portion  51 . The first cylinder portion  51  includes a cylindrical main portion  52  and a cylindrical small-diameter portion  53  (see  FIG. 3 ). The outer diameter of the small-diameter portion  53  is less than the outer diameter of the main portion  52 . The small-diameter portion  53  extends from the rear end of the main portion  52  backwards. The first rotator  41  is mounted in the first shaft  46 . The first rotator  41  can rotate about a shaft using the first rotator  46  as a central shaft. Specifically, the first rotator  41  can rotate in a first direction R 1  which is a shaft circumference direction and a second direction R 2  which is a reverse shaft circumference direction to the first direction R 1 . 
     A flat portion (not illustrated) with which a contact protrusion  68  (to be described below) of an elastic piece  67  comes into contact may be formed on the outer circumferential surface of the small-diameter portion  53 . For example, the flat portion is a part of the outer circumferential surface of the small-diameter portion  53  and is a flat portion vertical to the diameter direction of the small-diameter portion  53 . 
     The second rotator  42  includes a second cylinder portion  54  with cylindrical shape. The second rotator  42  is mounted in the second shaft  47 . The second rotator  42  can rotate about a shaft using the second rotator  47  as a central shaft. The second rotator  42  can move in the shaft direction (the central shaft direction of the second rotator  42 ). 
     A fitting protrusion  42   a  that fits in a fitting concave  29   a  (fitting reception portion) of a coupling  29  of the process unit  20  is formed at the distal end of the second rotator  42 . The fitting protrusion  42   a  is formed to protrude on a distal end surface of the second rotator  42  forwards. The fitting protrusion  42   a  is formed in the diameter direction of the second rotator  42 . The fitting protrusion  42   a  can transmit a rotational driving force of the second rotator  42  to the coupling  29  when the fitting protrusion  42   a  fits in the fitting concave  29   a.    
     A structure in which the process unit and the second rotator are connected (connection structure) is not particularly limited to the structure illustrated in  FIG. 2 . For example, the connection structure may be the following configuration. The coupling of the process unit includes a fitting protrusion (fitting reception portion). The second rotator includes a fitting concave (fitting portion). The fitting protrusion of the process unit can be fitted in the fitting concave of the second rotator. The process unit and the second rotator are connected when the fitting protrusion fits in the fitting concave. 
     The driving force transmission mechanism  43  includes a first gear  56  and a second gear  57 . The first gear  56  is formed on the outer circumferential surface of the main portion  52  of the first rotator  41 . The first gear  56  is integrated with the first cylinder portion  51 . 
     The second gear  57  is formed on the outer circumferential surface of the second cylinder portion  54 . The second gear  57  is integrated with the second cylinder portion  54 . The first gear  56  and the second gear  57  can transmit a driving force of the first rotator  41  to the second rotator  42  in the mutual engagement state to rotate the second rotator  42  about the shaft. 
     The displacement mechanism  44  includes a slope portion  61  and an engagement portion  62 . 
     The slope portion  61  is formed on the outer circumferential surface of the second cylinder portion  54  of the second rotator  42 . The slope portion  61  is a convex portion formed in a helical shape about the central shaft of the second rotator  42 . The slope portion  61  protrudes outwards in the diameter direction of the second cylinder portion  54  from the outer circumferential surface of the second cylinder portion  54 . The slope portion  61  extends in a direction sloped in the shaft direction of the second rotator  42 . 
     As illustrated in  FIG. 3 , the engagement portion  62  includes a base portion  63 , an arm portion  64 , and an engagement protrusion  65 . The base portion  63  is formed in a cylindrical shape. The small-diameter portion  53  of the first cylinder portion  51  is inserted through an insertion hole  63   a  of the base portion  63 . An inner diameter of the insertion hole  63   a  is almost equal to the outer diameter of the small-diameter portion  53  or is greater than the outer diameter of the small-diameter portion  53 . 
     In the base portion  63 , an incision depth  66  with a U shape is formed. In the base portion  63 , the elastic piece  67  with a tongue shape is formed at the incision depth  66 . The elastic piece  67  extends in the circumferential direction of the base portion  63 . The contact protrusion  68  is formed on the inner circumferential surface of the elastic piece  67 . The contact protrusion  68  protrudes inwards in the diameter direction of the base portion  63  from the inner circumferential surface of the elastic piece  67 . For example, the contact protrusion  68  has a columnar shape. The central shaft direction of the columnar contact protrusion  68  is parallel to the diameter direction of the base portion  63 . The contact protrusion  68  is formed at a position close to the tip end of the elastic piece  67  in the extension direction. The shape of the contact protrusion is not limited to the columnar shape. The shape of the engagement protrusion may be a rectangular parallelepiped shape, a hemisphere shape, a polygonal pyramid shape, or the like. 
     The contact protrusion  68  comes into contact with the outer circumferential surface of the first rotator  41  in a pressed state by a bending elastic force of the elastic piece  67 . When the contact protrusion  68  comes into contact with the outer circumferential surface of the first rotator  41 , the engagement portion  62  easily rotates integrally with the first rotator  41  by friction between the contact protrusion  68  and the first rotator  41 . When the contact protrusion  68  comes into contact with a flat portion (not illustrated) of the outer circumferential surface of the small-diameter portion  53 , relative displacement of the engagement portion  62  to the first rotator  41  in the rotational direction rarely occurs. 
     The arm portion  64  extends to the outside side of the base portion  63  when the base portion  63  serves as a starting point. The arm portion  64  extends in a tangential direction of the cylindrical base portion  63 . The arm portion  64  is formed in a rectangular flat shape. The arm portion  64  is formed in a flat shape parallel to the central shaft direction of the base portion  63 . 
     The engagement protrusion  65  is formed on one surface  64   a  of the arm portion  64 . The engagement protrusion  65  is a convex portion that protrudes from the surface  64   a  of the arm portion  64  to be vertical to the surface  64   a . For example, the engagement protrusion  65  is formed in a rectangular parallelepiped shape. 
     The shape of the engagement protrusion is not limited to the rectangular parallelepiped shape. The shape of the rectangular parallelepiped shape may be a columnar shape, a hemisphere shape, a polygonal pyramid shape, or the like. 
     As illustrated in  FIG. 1 , for example, the spring  49  is a coil spring. The spring  49  urges the second rotator  42  toward the process unit  20  with a reactive force on the main surface  45   a  of the base substrate  45 . 
     Next, an operation of the image forming apparatus  10  will be described. 
     First, an operation in normal working of the image forming apparatus  10  will be described. 
     The coupling  29  illustrated in  FIG. 2  is contained in the process unit  20 . The fitting concave  29   a  of the coupling  29  is exposed to a connection surface  21  (see  FIG. 8 ). 
     As illustrated in  FIG. 4 , the first rotator  41  is rotated in the first direction R 1  by a driving source (not illustrated). At this time, the engagement portion  62  can be rotated in the first direction R 1  along with the first rotator  41 . The rotation of the engagement portion  62  in the first direction R 1  is regulated when the arm portion  64  comes into contact with the stopper  48 . 
     The driving force of the first rotator  41  in the first direction R 1  is transmitted to the second rotator  42  by the driving force transmission mechanism  43  (the first gear  56  and the second gear  57 ). Therefore, the second rotator  42  is driven by the first rotator  41  to be rotated in an arrow direction. 
     When the fitting protrusion  42   a  of the second rotator  42  fits in the fitting concave  29   a  of the coupling  29  (which is not illustrated), a rotational driving force of the second rotator  42  is transmitted to the coupling  29 . A position of the second rotator  42  connected to the coupling  29  is referred to as a “connection position”. 
     Next, an operation when the process unit  20  is detached for maintenance or the like will be described. 
     As illustrated in  FIG. 5 , a home switch, a setting switch, a maintenance switch, and a process unit (PU) exchange switch on a control panel (not illustrated) are pressed in sequence. 
     Thus, as illustrated in  FIG. 6 , the first rotator  41  is rotated in the second direction R 2  by a driving source (not illustrated). That is, the first rotator  41  is rotated in the reverse direction to that of the normal working. The engagement portion  62  is rotated in the second direction R 2  along with the first rotator  41 . Thus, the arm portion  64  becomes closes to the second rotator  42 . The engagement protrusion  65  can engage with the slope portion  61 . 
     The driving force of the first rotator  41  in the second direction R 2  is transmitted to the second rotator  42  by the first gear  56  and the second gear  57 . Therefore, the second rotator  42  is driven by the first rotator  41  to be rotated in the arrow direction. 
     When the engagement protrusion  65  engages with the slope portion  61  and the second rotator  42  is rotated in the arrow direction for a predetermined time (see  FIG. 5 ), as illustrated in  FIG. 7 , the second rotator  42  is displaced in the shaft direction of the second rotator  42  in a direction (backwards) away from the process unit  20  (see  FIG. 2 ) along the slope of the slope portion  61 . Thus, the second rotator  42  is dislocated from the coupling  29 . When the second gear  57  is dislocated from the first gear  56 , the second rotator  42  losses the driving force and thus stops. 
     The position of the second rotator  42  dislocated from the coupling  29  is referred to as a “connection release position”. 
     After the second rotator  42  is dislocated from the coupling  29 , the rotation of the first rotator  41  is stopped. The process unit (PU) which is in an exchange state is displayed on the control panel (not illustrated) (see  FIG. 5 ). 
     Since the second rotator  42  is dislocated from the coupling  29 , the process unit  20  is detached from the image forming apparatus  10  to be supplied for maintenance. 
     Next, an operation when the process unit  20  is mounted in the image forming apparatus  10  after end of the maintenance will be described. 
     As illustrated in  FIG. 8 , a slope portion  21   a  is formed on the connection surface  21  of the process unit  20 . 
     First, a normal operation when the process unit is mounted will be described. 
     As illustrated in  FIG. 8 , the process unit  20  is advanced in a mounting direction (see an arrow). Normally, the second rotator  42  is at the connection release position (evacuated position). 
     As illustrated in  FIGS. 9 and 10 , when the coupling  29  reaches a position corresponding to the second rotator  42 , the second rotator  42  is advanced by the urging force of the spring  49  and the fitting protrusion  42   a  fits in the fitting concave  29   a  (see  FIG. 7 ). 
     Next, an operation when the second rotator is advanced and the process unit is mounted will be described. 
     As illustrated in  FIG. 11 , the connection mechanism  100  operates as the follows when the second rotator  42  is at the advanced position. The process unit  20  is advanced in the mounting direction (see an arrow). 
     As illustrated in  FIGS. 12 and 13 , the distal end of the second rotator  42  comes into contact with the slope portion  21   a  of the process unit  20  to retreat along the slope of the slope portion  21   a.    
     As illustrated in  FIGS. 9 and 10 , when the coupling  29  reaches the position corresponding to the second rotator  42 , the second rotator  42  is advanced by the urging force of the spring  49  and the fitting protrusion  42   a  fits in the fitting concave  29   a  (see  FIG. 7 ). 
     As illustrated in  FIG. 6 , the image forming apparatus  10  includes the connection mechanism  100  that includes the displacement mechanism  44 . The displacement mechanism  44  displaces the second rotator  42  in a shaft direction away from the process unit  20  when the first rotator  41  is rotated in the second direction R 2  (the reverse direction to that in the normal working). Thus, the connection between the second rotator  42  and the process unit  20  is released. The image forming apparatus  10  can be miniaturized since the connection between the second rotator  42  and the process unit  20  is released by the connection mechanism  100  with a simple configuration. 
     The displacement mechanism  44  can displace the second rotator  42  along the slope of the slope portion  61  in the direction away from the process unit  20  by rotating the first rotator  41  in the second direction R 2 . Since the displacement mechanism  44  displaces the second rotator  42  using the slope portion  61 , the structure of the connection mechanism  100  can be simplified. 
     Since the slope portion  61  is formed in the helical direction about the shaft of the second rotator  42 , the second rotator  42  can be displaced in the direction away from the process unit  20  in a broad range in the rotational direction. 
     The engagement portion  62  includes the base portion  63 , the arm portion  64 , and the engagement protrusion  65 . The engagement portion  62  does not engage with the second rotator  42  when the first rotator  41  is rotated in the first direction R 1 . The engagement portion  62  engages with the slope portion  61  of the second rotator  42  when the first rotator  41  is rotated in the second direction R 2 . Accordingly, even in the simple structure, the second rotator  42  can be displaced in the direction away from the process unit  20  only when the first rotator  41  is rotated in the second direction R 2 . 
     When the first rotator  41  is rotated in the second direction R 2 , the engagement portion  62  is rotated in a direction in which the engagement protrusion  65  approaches the second rotator  42  along with the first rotator  41 . Therefore, even in the simple structure, the second rotator  42  can be displaced in the direction away from the process unit  20  only when the first rotator  41  is rotated in the second direction R 2 . 
     The engagement portion  62  includes the elastic piece  67  that comes into contact with the outer circumferential surface of the first rotator  41 . Therefore, the engagement portion  62  is easily rotated integrally with the first rotator  41  by friction with the first rotator  41 . Therefore, it is possible to reliably operate the engagement portion  62 . 
     Since the connection mechanism  100  includes the spring  49 , the second rotator  42  is pressed toward the process unit  20  to be connectable to the coupling  29 . 
     An engagement portion which is a modification example of the engagement portion  62  illustrated in  FIG. 3  will be described. 
     As illustrated in  FIG. 14 , an engagement portion  162  which is the modification example includes a base portion  163 , the arm portion  64 , the engagement protrusion  65 , a contactor  168 , and an urging body  169 . The engagement portion  162  is different from the engagement portion  62  illustrated in  FIG. 3  in that the contactor  168  and the urging body  169  are included. 
     An urging force of the urging body  169  is denoted by “F”. “Fx” denotes a diameter direction component of the urging force F and is a force by which the contactor  168  dampens the first rotator  41 . “Fy” denotes a component in a tangential direction of the urging force F (a tangential direction at a point at which the contactor  168  comes into contact with the first rotator  41 ). The point at which the contactor  168  comes into contact with the first rotator  41  is referred to as a “contact point of the contactor  168 ”. 
     An accommodation hole  170  that accommodates the contactor  168  and the urging body  169  is formed in the inner circumferential surface of an insertion hole  163   a  of the base portion  163 . The accommodation hole  170  is sloped in the diameter direction of the insertion hole  163   a  when viewed in a direction parallel to the shaft direction of the insertion hole  163   a  (see  FIG. 14 ). Fy is oriented in the same direction as a tangential direction component of the first direction R 1  at the contact point of the contactor  168 . A direction in which the accommodation hole  170  is formed (a depth direction) is a direction sloped on the upstream side of the first direction R 1  with respect to the diameter direction of the insertion hole  163   a.    
     The contactor  168  is a sphere. For example, the contactor  168  is made of a metal such as stainless steel. The contactor  168  comes into contact with the outer circumferential surface of the first rotator  41  to be pressed by the urging force of the urging body  169 . When the contactor  168  comes into contact with the outer circumferential surface of the first rotator  41 , the engagement portion  162  is easily rotated integrally with the first rotator  41  by friction between the contactor  168  and the first rotator  41 . 
     The contactor  168  is retained to be revolvable between the urging body  169  and the first rotator  41 . 
     For example, the urging body  169  is a coil spring. The urging body  169  is accommodated in the accommodation hole  170 . The urging body  169  urges the contactor  168  toward the first rotator  41  with a reactive force on the bottom of the accommodation hole  170 . A direction of the urging force by the urging body  169  is parallel to the direction in which the accommodation hole  170  is formed. 
     Contact resistance of the engagement portion  162  to the first rotator  41  when the first rotator  41  is rotated in the second direction R 2  is greater than contact resistance of the engagement  162  to the first rotator  41  when the first rotator  41  is rotated in the first direction R 1 . Therefore, in the normal working, the contact resistance is relatively small. When the first rotator  41  is rotated in a direction reverse to that of the normal working (the second direction R 2 ), the contact resistance is greater than in the normal working. Accordingly, the engagement portion  162  which is the modification example can suppress abrasion of the engagement portion  162  in the normal working. When the first rotator  41  is rotated in the direction reverse to that of the normal working (the second direction R 2 ) with regard to the engagement portion  162 , the engagement portion  162  can reliably be rotated and moved. 
     When the first rotator  41  is rotated, the contactor  168  comes into contact with the outer circumferential surface of the first rotator  41  to revolve with the rotation of the first rotator  41 . 
     Since the contactor  168  which is a revolvable sphere is used in the engagement portion  162 , it is possible to suppress abrasion of the contactor  168  when the first rotator  41  is rotated. When the contactor  168  is made of a metal, the abrasion due to contact with the first rotator  41  can be suppressed. 
     Second Embodiment 
     An image forming apparatus according to a second embodiment will be described. The same reference numerals are given to common configurations to those of the first embodiment and the description thereof will be omitted. 
     As illustrated in  FIG. 15 , a connection mechanism  200  of an image forming apparatus  210  is different from the connection mechanism  100  illustrated in  FIG. 2  in that a displacement mechanism  244  is included instead of the displacement mechanism  44 . 
     The displacement mechanism  244  includes an outer tube body  260 , a one-way bearing  263  (one-way clutch), and an engagement portion  262 . 
     The one-way bearing  263  is formed in a cylindrical shape. The one-way bearing  263  has a structure for transmitting a rotational force in only one direction. A known structure can be adopted for the one-way bearing  263 . A second cylinder portion  254  of the second rotator  242  is inserted through the one-way bearing  263 . 
     The outer tube body  260  is formed in a cylindrical shape. The one-way bearing  263  and the second cylinder portion  254  of the second rotator  242  is inserted through the outer tube body  260 . A slope portion  261  is formed on the outer circumferential surface of the outer tube body  260 . The slope portion  261  is a convex portion formed in a helical shape about the central shaft of the second rotator  242 . 
     Since the outer tube body  260  is inserted through the one-way bearing  263 , the outer tube body  260  operates as follows. The outer tube body  260  is not rotated when the second rotator  242  is driven and rotated with the rotation of the first rotator  41  in the first direction R 1 . The outer tube body  260  is rotated along with the second rotator  242  when the second rotator  242  is driven and rotated with the rotation of the first rotator  41  in the second direction R 2 . 
     The engagement portion  262  includes a pair of arm portions  264  and engagement protrusions  265 . The arms  264  protrude from the main surface  45   a  of the base substrate  45  to be vertical to the main surface  45   a . The arms  264  are formed closely to the second shaft  47 . The one pair of arms  264  are formed at positions at which the arms  264  face each other with the second shaft  47  interposed therebetween. 
     The engagement protrusion  265  is formed in one surface  264   a  of the arm  264 . The surface  264   a  is a surface facing the second shaft  47 . The engagement protrusion  265  is a convex portion that protrudes to be vertical to the surface  264   a  of the arm portion  264 . The engagement protrusion  265  is formed at a position at which the engagement protrusion  265  can engage with the slope portion  261 . The engagement protrusion  265  is formed at the distal end of the arm portion  264  in the extension direction. 
     Next, an operation of the image forming apparatus  210  will be described. 
     First, an operation in normal working of the image forming apparatus  210  will be described. 
     As illustrated in  FIG. 16 , the first rotator  41  is rotated in the first direction R 1 . The second rotator  242  is driven by the first rotator  41  to be rotated in an arrow direction. A driving force of the second rotator  242  is transmitted to the process unit  20  via the coupling  29  (see  FIG. 15 ). 
     As described above, the outer tube body  260  is not rotated in accordance with the function of the one-way bearing  263 . Since the displacement mechanism  244  does not function, the second rotator  242  maintains the connection state to the process unit  20 . 
     Next, an operation when the process unit  20  is detached for maintenance or the like will be described. 
     As illustrated in  FIG. 17 , the first rotator  41  is rotated in the second direction R 2 . The second rotator  242  is driven by the first rotator  41  to be rotated in the arrow direction. 
     As described above, the outer tube body  260  is rotated along with the second rotator  242  in accordance with the function of the one-way bearing  263 . 
     When the engagement protrusion  265  engages with the slope portion  261  and the second rotator  242  is rotated in the arrow direction (see  FIG. 17 ), as illustrated in  FIG. 18 , the second rotator  242  is displaced along the slope of the slope portion  261  in the shaft direction of the second rotator  242  in a direction (backwards) away from the process unit  20  (see  FIG. 15 ). Thus, the second rotator  242  is dislocated from the coupling  29 . When the second gear  57  is dislocated from the first gear  56 , the second rotator  242  losses the driving force and thus stops. 
     After the second rotator  242  is dislocated from the coupling  29 , the rotation of the first rotator  41  is stopped. 
     Since the second rotator  242  is dislocated from the coupling  29 , the process unit  20  is detached from the image forming apparatus  210  to be supplied for maintenance. 
     The image forming apparatus  210  includes the displacement mechanism  244  that includes the outer tube body  260 . The outer tube body  260  is not rotated when the second rotator  242  is driven and rotated with the rotation of the first rotator  41  in the first direction R 1 . The outer tube body  260  is rotated along with the second rotator  242  when the second rotator  242  is driven and rotated with the rotation of the first rotator  41  in the second direction R 2 . Therefore, it is not necessary to mount or separate the engagement portion  262  on or from the second rotator  242 . The image forming apparatus  10  can be miniaturized since the connection between the second rotator  42  and the process unit  20  is released by the connection mechanism  100  with a simple configuration. 
     In the image forming apparatus  10 , the fitting protrusion  42   a  is a convex portion and the fitting concave portion  29   a  is a concave portion. However, a structure of the fitting reception portion and the fitting portion is not limited to the illustrated structure as long as the rotational driving force can be transmitted. For example, the fitting reception portion may be a concave portion and the fitting portion may be a convex portion. 
     The image forming apparatus may be a monochromic image forming apparatus. The number of process units is not limited. The image forming apparatus may include a plurality of printer units. 
     According to at least one of the above-described embodiments, the displacement mechanism displaces the second rotator in the shaft direction away from the process unit when the first rotator is rotated in the second direction (the reverse direction to that of the normal working). Thus, the connection between the second rotator and the process unit is released. The image forming apparatus can be miniaturized since the connection between the second rotator and the process unit is released by the connection mechanism with a simple configuration. 
     While certain embodiments have been described these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms: furthermore various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and there equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention.