Patent Publication Number: US-9841726-B2

Title: Image forming apparatus

Description:
INCORPORATION BY REFERENCE 
     This application is based upon and claims the benefit of priority from the corresponding Japanese Patent Application No. 2016-082610 filed on Apr. 18, 2016, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     The present disclosure relates to an image forming apparatus including a unit, such as an intermediate transfer unit, which is horizontally attachable and detachable with respect to an apparatus main body. 
     Various image forming apparatuses have conventionally been proposed, among which there are ones that adopt an intermediate transfer method and include an endless-shaped intermediate transfer belt configured to rotate in a predetermined direction and a plurality of image forming portions arranged along the intermediate transfer belt, the image forming portions configured to form toner images, which are sequentially transferred onto the intermediate transfer belt to be superimposed one on another, to be then transferred altogether onto a recording medium. 
     In the image forming apparatuses adopting the intermediate transfer method as described above, the intermediate transfer belt needs to be replaced regularly, because its life is shorter than the life of the apparatus main body. For example, there is known an image forming apparatus which has an intermediate transfer unit that is drawable in the horizontal direction from the main body of the image forming apparatus. 
     SUMMARY 
     According to an aspect of the present disclosure, an image forming apparatus includes a unit and a lock mechanism for the unit. The unit is horizontally insertable and drawable with respect to a main body frame. The lock mechanism includes a lock member and a biasing member. The lock mechanism holds the unit in a state of being mounted in the main body frame, and the lock mechanisms is able to release hold of the unit. The lock member is arranged in the unit to be reciprocatable in a direction perpendicular to an inserting/drawing direction of the unit, and has an engagement projection engageable with an engaged portion formed in the main body frame. The biasing member biases the lock member in a first direction toward engagement of the engagement projection with the engaged portion. Along with insertion of the unit into the main body frame, the lock member moves in a second direction reverse to the first direction against biasing force of the biasing member, and when the unit is inserted to a predetermined position, the lock member is moved by the biasing force of the biasing member in the first direction and the engagement projection engages with the engaged portion. By moving the lock member in the second direction against the biasing force of the biasing member, engagement between the engagement projection and the engaged portion is released to make it possible to draw the unit out of the main body frame. 
     Further features and specific advantages of the present disclosure will become apparent from the following descriptions of preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic sectional view illustrating an internal configuration of an image forming apparatus according to an embodiment of the present disclosure; 
         FIG. 2  is a perspective view illustrating an intermediate transfer unit in a state of being inserted in a main body frame of the image forming apparatus; 
         FIG. 3  is a perspective view of the intermediate transfer unit inserted in the main body frame, as viewed from above; 
         FIG. 4  is a partial enlarged view illustrating a substantially central part of a side cover arranged at a drawing-side end part of the intermediate transfer unit, as seen from inside; 
         FIG. 5  is a plan view of an area around engagement projections of a lock member arranged inside the side cover, as seen from above; 
         FIG. 6  is a partial enlarged view illustrating the substantially central part of the side cover, as seen from outside; 
         FIG. 7  is a diagram illustrating a state in which an inclined surface of an engagement projection has come into contact with an engaged portion along with insertion of the intermediate transfer unit; 
         FIG. 8  is a diagram illustrating a state in which the engagement projection moves in a direction indicated by an arrow A on receiving reaction from the engaged portion along with further insertion of the intermediate transfer unit from the state illustrated in  FIG. 7 ; 
         FIG. 9  is a diagram illustrating a state in which the engagement projection has come into engagement with the engaged portion when the intermediate transfer unit is further inserted from the state illustrated in  FIG. 8 ; 
         FIG. 10  is a partial plan view of the intermediate transfer unit, illustrating a state in which engagement projections are engaged with engaged portions; 
         FIG. 11  is a sectional view of the vicinity of a unit-side connector of the intermediate transfer unit inserted in the main body frame; 
         FIG. 12  is a partial enlarged view illustrating a state after a switching portion in the state illustrated in  FIG. 6  has been operated; and 
         FIG. 13  is a partial plan view of the intermediate transfer unit, illustrating a state after the engagement between the engagement projection and the engaged portion is released. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.  FIG. 1  is a schematic sectional view of an image forming apparatus according to an embodiment of the present disclosure, and the image forming apparatus shown in the figure is a tandem-type color printer. In a main body of an image forming apparatus  100 , image forming portions Pa, Pb, Pc, and Pd are arranged in this order from an upstream side in a conveyance direction (a left side in  FIG. 1 ). The image forming portions Pa to Pd are provided corresponding to images of four different colors (cyan, magenta, yellow, and black), and sequentially form images of cyan, magenta, yellow, and black through charging, exposure, developing, and transfer steps. 
     The image forming portions Pa, Pb, Pc, and Pd include photosensitive drums  1   a ,  1   b ,  1   c , and  1   d , respectively, which carry visible images (toner images) of respective colors. Further, an intermediate transfer belt  8 , which is rotated by drive means (unillustrated) in a counterclockwise direction in  FIG. 1 , is provided adjacent to the image forming portions Pa to Pd. The toner images formed on the photosensitive drums  1   a  to  1   d  are primarily transferred sequentially onto the intermediate transfer belt  8 , which moves in contact with the photosensitive drums  1   a  to  1   d , and the toner images are superimposed one on another on the intermediate transfer belt  8 . Then, the toner images primarily transferred onto the intermediate transfer belt  8  are secondarily transferred onto a sheet S, as an example of recording medium, by operation of a secondary transfer roller  9 . The sheet S onto which the toner images have been secondarily transferred is discharged to outside the image forming apparatus  100  after the toner images are fixed on the sheet S at a fixing device  15 . An image forming process is performed on each of the photosensitive drums  1   a  to  1   d  while making the photosensitive drums  1   a  to  1   d  rotate in a clockwise direction in  FIG. 1 . 
     Sheets S onto each of which a toner image is to be transferred are stored in a feeder  16  disposed in a lower part of the main body of the image forming apparatus  100 . A sheet S is conveyed via a sheet feeding roller  12  and a registration roller pair  13  to a nip portion between the secondary transfer roller  9  and a later-described drive roller  11  provided for driving the intermediate transfer belt  8 . The intermediate transfer belt  8  is made of a dielectric resin sheet, and mainly formed as a (seamless) belt having no seam. Furthermore, for the purpose of removing toner and the like remaining on a surface of the intermediate transfer belt  8 , a blade-shaped belt cleaner  19  is disposed on a downstream side of the secondary transfer roller  9 . 
     An image reader  22  is constituted by a scanning optical system, a condenser lens, a CCD sensor, and the like (none of which is illustrated), and the image reader  22  reads a document image to convert the document image into image data. The scanning optical system incorporates a scanner lamp, which illuminates a document for copying, and a mirror, which changes the optical path of light reflected from a document. The condenser lens collects light reflected from a document to form an image. The CCD sensor converts the formed image into electric signals. 
     Next, the image forming portions Pa to Pd will be described. Provided around and below the rotatably disposed photosensitive drums  1   a ,  1   b ,  1   c , and  1   d  are chargers  2   a ,  2   b ,  2   c , and  2   d  that charge the photosensitive drums  1   a ,  1   b ,  1   c , and  1   d , respectively, an exposure device  5  that exposes the photosensitive drums  1   a  to  1   d  with light based on image information, developing devices  3   a ,  3   b ,  3   c , and  3   d  that form a toner image on the photosensitive drums  1   a ,  1   b ,  1   c , and  1   d , respectively, and cleaning portions  7   a ,  7   b ,  7   c , and  7   d  that remove residual developer (toner) and the like remaining on the photosensitive drums  1   a ,  1   b ,  1   c , and  1   d , respectively. 
     In a copying operation, the image reader  22  reads image data of a document and converts the image data into an image signal. The charging devices  2   a  to  2   d  uniformly charge surfaces of the photosensitive drums  1   a  to  1   d . Then, the exposure device  5  irradiates the photosensitive drums  1   a  to  1   d  with light according to the image data, and thereby an electrostatic latent image is formed on each of the photosensitive drums  1   a  to  1   d  according to the image data. The developing devices  3   a  to  3   d  are each filled with a predetermined amount of two-component developer containing cyan, magenta, yellow, or black toner. Note that, the developing devices  3   a  to  3   d  are replenished with toner from toner containers  4   a  to  4   d  when the proportion of toner contained in the two-component developer in each of the developing devices  3   a  to  3   d  falls below a required value after later-described toner image formation. The toner contained in the developer in each of the developing devices  3   a  to  3   d  is supplied therefrom, and electrostatically adheres, onto a corresponding one of the photosensitive drums  1   a  to  1   d . Thereby, a toner image is formed on each of the photosensitive drums  1   a  to  1   d  corresponding to the electrostatic latent image formed by the exposure from the exposure device  5 . 
     Then, a predetermined transfer voltage is applied to primary transfer rollers  6   a  to  6   d  to thereby primarily transfer yellow, cyan, magenta, and black toner images formed on the photosensitive drums  1   a  to  1   d  onto the intermediate transfer belt  8 . Residual toner and the like left on the surface of each of the photosensitive drums  1   a ,  1   b ,  1   c , and  1   d  is removed by the cleaning portions  7   a ,  7   b ,  7   c , and  7   d , respectively. 
     The intermediate transfer belt  8  is wound around and between a tension roller  10  and the drive roller  11 , which are located on an upstream side and a downstream side, respectively. When the intermediate transfer belt  8  starts to rotate in the counterclockwise direction along with rotation of the drive roller  11  caused by a driving motor (unillustrated), a sheet S is conveyed from the registration roller pair  12   b  at a predetermined timing to a nip portion (a secondary transfer nip portion) between the drive roller  11  and the secondary transfer roller  9  provided adjacent to the drive roller  11 . Then, a full color image on the intermediate transfer belt  8  is secondarily transferred onto the sheet S. The sheet S onto which the toner image has been transferred is conveyed through a sheet conveyance path  14  to the fixing device  15 . 
     The sheet S, which has been conveyed to the fixing device  15 , is heated and pressurized by a fixing roller pair  15   a , whereby the toner image is fixed on a surface of the sheet S, and a predetermined full-color image is formed. The sheet S on which the full-color image has been formed is directed toward one of a plurality of conveying directions branched from a branch portion  17 . When forming an image only on one side of the sheet S, the sheet S is discharged as it is by a discharge roller pair  18  onto a delivery tray  20 . 
       FIG. 2  is a perspective view illustrating a state in which an intermediate transfer unit  30  is inserted in a main body frame  101  of the image forming apparatus  100  illustrated in  FIG. 1 .  FIG. 3  is a perspective view of the intermediate transfer unit  30  inserted in the main body frame  101 , as viewed from above. Such elements in  FIGS. 2 and 3  having counterparts in  FIG. 1  are given the same reference signs as their counterparts, and descriptions thereof will be omitted. 
     As illustrated in  FIG. 2 , the main body frame  101  includes a front face frame  23   a  and a rear face frame  23   b , a pair of side panel frames  23   c  and  23   d , which are arranged opposite from each other, and an upper face frame  23   e , which is arranged above the front face frame  23   a , the rear face frame  23   b , and the side panel frames  23   c  and  23   d . Note that the upper face frame  23   e  is not illustrated in  FIG. 3 , but only rail guides  24  provided on the upper face frame  23   e  are illustrated. 
     As illustrated in  FIG. 3 , the intermediate transfer unit  30  includes components such as a pair of side covers  31  and  32 , two connecting frames  33 , which are fixed to the side covers  31  and  32  so as to extend like bridges between the side covers  31  and  32 , a plurality of suspension rollers including the drive roller  11  and the tension roller  10 , which are supported between the side covers  31  and  32 , and the intermediate transfer belt  8 , which is endless-shaped and stretched between these suspension rollers. The connecting frames  33  are each provided with a grip member  37  for carrying the intermediate transfer unit  30 . 
     The connecting frames  33  are further provided with rail portions (unillustrated) which engage with the rail guides  24  provided on a lower surface of the upper face frame  23   e . By inserting the rail portions along the rail guides  24 , the intermediate transfer unit  30  is supported to be slidable with respect to the upper face frame  23   e.    
       FIG. 4  is a partial enlarged view of a substantially central part of the side cover  31  in its longitudinal direction, as seen from inside, the side cover  31  being arranged at a drawing-side end part (the near side in the sheet on which  FIG. 3  is drawn) of the intermediate transfer unit  30  illustrated in  FIG. 3 .  FIG. 5  is a plan view of an area around engagement projections  41   a  and  41   b  of a lock member  41 , as seen from above, the lock member  41  being arranged in the side cover  31 .  FIG. 6  is a partial enlarged view illustrating the substantially central part of the side cover  31  in its longitudinal direction, as seen from outside. A detailed description will be given of the intermediate transfer unit  30  with reference to  FIG. 4  to  FIG. 6 . 
     As illustrated in  FIG. 4 , the side cover  31  is provided with a lock mechanism  40 , which holds the intermediate transfer unit  30  in a state of being mounted in the main body frame  101 , and is able to release the hold of the intermediate transfer unit  30 . The lock mechanism  40  includes the lock member  41 , which is provided to be slidable along the longitudinal direction (a left-right direction in  FIG. 4 ) of the side cover  31 , and a compression spring  43 , which biases the lock member  41  in one direction (a leftward direction in  FIG. 4 ). 
     On an upper surface of the lock member  41 , the engagement projections  41   a  and  41   b  are formed which each engage with a corresponding one of engaged portions  50  (see  FIG. 7 ) of the main body frame  101 . The engagement projections  41   a  and  41   b  project through openings  31   a  and  31   b , respectively, which are formed in an upper surface of the side cover  31 . As illustrated in  FIG. 5 , in each of the engagement projections  41   a  and  41   b , there is formed an inclined surface  45 , which is inclined in a direction (a left-right direction in  FIG. 5 ) perpendicular to an inserting direction of the intermediate transfer unit  30 . 
     Further, on a side surface of the lock member  41  on an upstream side with respect to the inserting direction of the intermediate transfer unit  30 , there is formed a switching portion  41   c  (see  FIG. 6 ) for moving the lock member  41  in a direction reverse to the biasing direction of the compression spring  43 . As illustrated in  FIG. 6 , the switching portion  41   c  is exposed via an operation window  31   d , which is formed in an outer side surface (on the near side in the sheet on which  FIG. 3  is drawn) of the side cover  31 . Here, the switching portion  41   c  is a pressed portion (operated portion) which is made to reciprocate to switch a state of the lock member  41 . The shape of the switching portion  41   c  is not limited to the shape in the present embodiment, but it may have, for example, a lever shape or a handle shape. 
     In the upper surface of the side cover  31 , on an upstream side (the far side in the sheet on which  FIG. 4  is drawn) of the engagement projections  41   a  and  41   b  with respect to the inserting direction of the intermediate transfer unit  30 , there is formed an upstanding wall portion  31   c . On an inner surface of the upstanding wall portion  31   c , there are provided a unit-side connector  47 , a grounding spring  48 , and two positioning pins  49 . The unit-side connector  47  is connected to a main-body-side connector  46  (see  FIG. 11 ), which is provided in the main body frame  101 . The grounding spring  48  contacts the main body frame  101 , which is made of metal, and thereby the intermediate transfer unit  30  is grounded (earthed). The positioning pins  49  are inserted into positioning holes (unillustrated) provided in the main body frame  101  for positioning of the intermediate transfer unit  30  with respect to the main body frame  101 . 
     Next, a description will be given of an operation of inserting the intermediate transfer unit  30  into the main body frame  101 .  FIG. 7  to  FIG. 9  are diagrams illustrating a mechanism how the engagement projection  41   a  and a corresponding one of the engaged portions  50  come into engagement with each other along with the insertion of the intermediate transfer unit  30 ,  FIG. 10  is a partial plan view of the intermediate transfer unit  30 , illustrating a state in which the engagement projections  41   a  and  41   b  are engaged with the engaged portions  50 , and  FIG. 11  is a sectional view of an area in the vicinity of the unit-side connector  47  of the intermediate transfer unit  30  inserted in the main body frame  101 . Although a description will be omitted herein, the engagement projection  41   b  also engages with a corresponding one of the engaged portions  50  in the same mechanism illustrated in  FIG. 7  to  FIG. 9 . 
     To insert the intermediate transfer unit  30  into the main body frame  101 , the intermediate transfer unit  30  is inserted along the rail guides  24  (see  FIG. 3 ), with the side cover  32  in the lead. When the intermediate transfer unit  30  is inserted to a predetermined position, as illustrated in  FIG. 7 , the inclined surface  45  of the engagement projection  41   a  projecting from the upper surface of the side cover  31  comes into contact with the engaged portion  50  of the main body frame  101 . 
     When the intermediate transfer unit  30  is further inserted from the state illustrated in  FIG. 7 , the inclined surface  45  receives drag force P from the engaged portion  50  due to reaction as illustrated in  FIG. 8 . At this time, the inclination of the inclined surface  45  causes the drag force P to be divided into a force component P 1  in a direction toward an upstream side in the inserting direction and a force component P 2  in a direction perpendicular to the inserting direction. Since the lock member  41  is supported to be slidable in the direction (the longitudinal direction of the side cover  31 ) which is perpendicular to the inserting direction, the lock member  41  is caused by the force component P 2  to slide in a direction indicated by an arrow A against the biasing force of the compression spring  43  (see  FIG. 4 ). 
     Then, when the lock member  41  slides until the engaged portion  50  leaves the inclined surface  45 , action of the force component P 2  is lost. Thus, as illustrated in  FIG. 9 , the biasing force of the compression spring  43  causes the lock member  41  to slide in a direction indicated by an arrow A′, and the engagement projection  41   a  and the engaged portion  50  engage with each other. Thereby, as illustrated in  FIG. 10 , an engagement state is achieved in which the engagement projections  41   a  and  41   b  each overlap with the corresponding one of the engaged portions  50  in an inserting/drawing direction of the intermediate transfer unit  30  (an up-down direction in  FIG. 10 ), to restrict the drawing of the intermediate transfer unit  30 . 
     At this time, the positioning pins  49  provided on the side cover  31  are inserted into the positioning holes (unillustrated) formed in the main body frame  101 , and, as illustrated in  FIG. 11 , the unit-side connector  47  is connected to the main-body-side connector  46 . Further, the grounding spring  48  comes into contact with the main body frame  101 , and thereby the intermediate transfer unit  30  is grounded. Further, a unit-side coupling (unillustrated) fixed to one end of a rotation shaft of the drive roller  11  is coupled to a drive output coupling (unillustrated) of the main body of the image forming apparatus  100  to make it possible to input driving force to the drive roller  11 . In this manner, mounting of the intermediate transfer unit  30  with respect to the main body frame  101  is completed. 
     Next, a description will be given of an operation of drawing the intermediate transfer unit  30  out of the main body frame  101 .  FIG. 12  is a partial enlarged view of the side cover  31 , illustrating a state after the switching portion  41   c  in the state illustrated in  FIG. 6  has been operated.  FIG. 13  is a partial plan view of the intermediate transfer unit  30  in a state after the engagement between the projections  41   a  and  41   b  with the engaged portions  50  has been released. 
     To draw the intermediate transfer unit  30  out of the main body frame  101 , a user grips the switching portion  41   c , which is exposed through the operation window  31   d  of the side cover  31 , to slide the lock member  41  in the direction indicated by the arrow A against the biasing force of the compression spring  43 , as illustrated in  FIG. 12 . Thereby, as illustrated in  FIG. 13 , the engagement projections  41   a  and  41   b  are brought out of engagement with the engaged portions  50  into an engagement-released state in which the engagement projections  41   a  and  41   b  do not overlap with the engaged portions  50  in the inserting/drawing direction of the intermediate transfer unit  30  (the up-down direction in  FIG. 13 ), and it becomes possible to draw the intermediate transfer unit  30  out of the main body frame  101 . 
     Then, the user, gripping the switching portion  41   c , pulls the intermediate transfer unit  30  frontward along the rail guides  24  of the image forming apparatus  100 , and thereby the drawing out of the intermediate transfer unit  30  is completed. 
     According to this configuration, in mounting the intermediate transfer unit  30  in the image forming apparatus  100 , the engagement projections  41   a  and  41   b  of the lock member  41  come into engagement with the engaged portions  50  of the main body frame  101  only with the operation of inserting the intermediate transfer unit  30 . Further, in detaching the intermediate transfer unit  30  from the image forming apparatus  100 , the engagement of the engagement projections  41   a  and  41   b  with the engaged portions  50  can be released just by gripping the switching portion  41   c.    
     Thus, through a simple operation without fastening a screw, operating a rotary lever, or the like, the user can have the intermediate transfer unit  30  securely held in the main body frame  101  and release the hold of the intermediate transfer unit  30 . As a result, the user can perform a smooth operation of replacing the intermediate transfer unit  30 . 
     It should be understood that the present disclosure is not limited to the above embodiments, and various modifications are possible within the scope of the present disclosure. For example, in the embodiment described above, the intermediate transfer unit  30  is inserted or drawn in a direction (a direction perpendicular to a surface of the sheet on which  FIG. 1  is drawn) parallel to a drive shaft, but the intermediate transfer unit  30  may be inserted and drawn out in a direction (a left-right direction in  FIG. 1 ) perpendicular to the drive shaft. Further, the present disclosure is applicable to any unit besides the intermediate transfer unit  30 , as long as it is a unit that is horizontally inserted into, and drawn out of, the main body of the image forming apparatus  100 . 
     Further, in the above-described embodiment, when the intermediate transfer unit  30  is inserted into the main body frame  101 , the engagement projections  41   a  and  41   b  are moved by using the inclined surfaces  45 , which are formed in the engagement projections  41   a  and  41   b , but the inclined surfaces  45  may be formed on the engaged portions  50 . 
     Further, application of the present disclosure is not limited to tandem color printers dealt with in the above embodiment, but the present disclosure is applicable to any image forming apparatus, such as a facsimile machine and a laser printer, which is provided with a unit that is horizontally drawn out, and inserted into, the main body of the image forming apparatus. 
     The present disclosure can be used in an image forming apparatus provided with a unit horizontally detachable and attachable with respect to the apparatus main body. By using the present disclosure, it is possible to provide an image forming apparatus capable of, with a simple device, both locking and unlocking a unit horizontally detachable and attachable with respect to an apparatus main body to and from the apparatus main body.