Patent Publication Number: US-2011070001-A1

Title: Steering Mechanism for Belt Unit

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from provisional U.S. Application 61/244,747 filed on Sep. 22, 2009, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     Embodiments described herein relate generally to a belt unit configured to regulate an endless belt mounted in copying machines, printers, or multi function peripherals so as not to meander during travel. 
     BACKGROUND 
     A belt unit mounted in a Multi Function Peripheral (MFP) or a printer needs to regulate a belt deviation. In order to regulate the belt deviation, there is a unit configured to sense the belt deviation and incline a steering roller. 
     In the belt unit having the steering roller, if the structure for sensing the belt deviation becomes complex, cost reduction of the belt unit may be hindered. 
     Therefore, in the field of the belt unit having the steering roller, development of a belt unit having a simplified structure for sensing the belt deviation and being capable of reliably regulating the belt deviation even at a low cost is desired. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic drawing showing a configuration of a principal portion of a transfer belt unit and a printer unit of an image forming apparatus; 
         FIG. 2  is a schematic perspective view showing the transfer belt unit; 
         FIG. 3  is a schematic plan view showing a self steering mechanism; 
         FIG. 4  is a schematic perspective view showing the self steering mechanism in a state in which a slide panel and a steering unit are separated; 
         FIG. 5  is a schematic plan view showing the slide panel; 
         FIG. 6  is a schematic plan view snowing the steering unit; 
         FIG. 7  is a schematic explanatory drawing showing a layout of a transfer belt and a sensing roller; 
         FIG. 8  is a schematic perspective view showing a first link; 
         FIG. 9  is a schematic plan view showing the first link; 
         FIG. 10  is a schematic explanatory drawing showing a second link; 
         FIG. 11  is a schematic explanatory drawing showing a drive of a second gear unit; 
         FIG. 12  is a schematic explanatory drawing showing a correction of the direction of travel of the transfer belt being deviated toward the front; 
         FIG. 13  is a schematic explanatory drawing showing a drive of a first gear unit; 
         FIG. 14  is a schematic explanatory drawing showing a correction of the direction of travel of the transfer belt being deviated toward the rear; and 
         FIG. 15  is a schematic plan view showing a self steering mechanism of a modification; 
     
    
    
     DETAILED DESCRIPTION 
     According to an embodiment, a belt unit includes a belt that is rotated, a belt comprising a rib formed on an inner periphery thereof, a plurality of supporting rollers configured to support the belt rotatably, a steering roller configured to contact with the inner periphery of the belt, a sensing roller configured to rotate in contact with the rib and a transmission configured to transmit a rotation of the sensing roller to the steering roller and configured to change an angle of the steering roller with respect to an axis of rotation of the belt. 
     The embodiment will be described below. As shown in  FIG. 1 , a printer unit  2  is provided under a transfer belt unit  1  of an image forming apparatus  100 . The printer unit  2  has image forming stations  11 K,  11 Y,  11 M, and  11 C for respective colors of black (K), yellow (Y), magenta (M) and cyan (C) arranged in tandem along a transfer belt  10  of the transfer belt unit  1 . The printer unit  2  has a laser exposure unit  17 . 
     The laser exposure unit  17  is configured to irradiate photoconductive drums  12 K,  12 Y,  12 M, and  12 C as image carriers of the image forming stations  11 K,  11 Y,  11 M, and  11 C for the respective colors with laser beams corresponding to image information. 
     The image forming station  11 K for black (K) of the printer unit  2  has a charger  13 K, a developing unit  14 K, a transfer roller  18 K, and a cleaner  16 K around the photoconductive drum  12 K rotating in the direction indicated by an arrow m. Configurations of the image forming stations  11 Y,  11 M,  11 C for yellow (Y), magenta (M) and cyan (C) are the same as the image forming station  11 K for black (K). 
     The transfer belt  10  has a rib  10   a  on one side in the width direction, for example, on the inner periphery of the front side. The rib  10   a  is formed by bonding a thin cord-shaped rubber on the inner periphery of the transfer belt  10 . The rib may be provided on both sides of the transfer belt  10  in the width direction. The plurality of the supporting rollers shown in  FIG. 2 , namely, a drive roller  20 , a driven roller  21 , and first to third tension rollers  22  to  24  support the transfer belt  10 . A steering roller  28  contacts the inner periphery of the transfer belt  10 . An axis of rotation γ of the transfer belt parallels to a shaft  20   a  of the drive roller  20 . 
     A secondary transfer roller  30  opposes the transfer belt  10  at a secondary transfer position. At the secondary transfer position, a toner image on the transfer belt  10  is secondarily transferred to a sheet P by a transfer bias supplied to the secondary transfer roller  30 . The structure of the transfer belt unit  1  is not limited thereto. 
     When the image forming apparatus  100  starts a printing, for example, at the image forming station  11 K for black (K), the photoconductive drum  12 K rotates in the direction indicated by the arrow m. In association with the rotation of the photoconductive drum  12 K, the charger  13 K charges the photoconductive drum  12 K uniformly. The laser exposure unit  17  irradiates the photoconductive drum  12 K with an exposure light corresponding to the image information in black (K) and forms an electrostatic latent image on the photoconductive drum  12 K. The developing unit  14 K then forms a toner image on the photoconductive drum  12 K. The transfer roller  18 K primarily transfers the toner image on the photoconductive drum  12 K onto the transfer belt  10  rotating in the direction indicated by an arrow s. After the primary transfer, the cleaner  16 K cleans residual toner on the photoconductive drum  12 K. 
     The image forming stations  11 Y,  11 M,  11 C for yellow (Y), magenta (M) and cyan (C) form toner images on the photoconductive drums  12 Y,  12 M, and  12 C in the same manner as the image forming station  11 K for black (K). The respective toner images in yellow (Y), magenta (M), cyan (C) on the photoconductive drums  12 Y,  12 M, and  12 C are multiply transferred to the transfer belt  10  in sequence to form a full color toner image. 
     The full color toner image on the transfer belt  10  is then secondarily transferred from the transfer belt  10  to the sheet P by the secondary transfer roller  30 . The sheet P reaches the secondary transfer position synchronously with the full color toner image on the transfer belt  10  reaching the secondary transfer position. The sheet P having the full color toner image is subjected to fixation, and then the image forming apparatus  100  finishes the printing. 
     The transfer belt  10  has a self steering mechanism  27  on the inner periphery thereof. As shown in  FIG. 3  to  FIG. 6 , the self steering mechanism  27  has a slide panel  32  and a steering unit  33  provided with the steering roller  28 . The slide panel  32  supports and fixes a circular arc shaped fixed gear  63 . The slide panel  32  has slits  36   a  and  36   b  for rotating the steering unit  33 . The slide panel  32  rotates about supporting points  37   a  and  37   b  with respect to a main body of the image forming apparatus  100 . An axial line π passing through the supporting points  37   a  and  37   b  parallels to the shaft  20   a  of the drive roller  20 . As shown in  FIG. 1 , a spring  38  as a pusher is provided between the slide panel  32  and a regulating panel  38   a . The spring  38  pushes the slide panel  32  upward about the supporting points  37   a  and  37   b . By pushing the slide panel  32  upward, the steering roller  28  provides a tension to the transfer belt  10 . 
     The steering unit  33  has a steering supporting panel  40  as a steering supporter. The steering supporting panel  40  has side frames  41   a  and  41   b , and inner frames  42   a  and  42   b . The side frames  41   a  and  41   b  support the steering roller  28 . The inner frames  42   a  and  42   b  support a worm shaft  62 . A shaft  28   a  of the steering roller  28  parallels to the worm shaft  62 . 
     The shaft  28   a  of the steering roller  28  supports a first sensing roller  47  and a second sensing roller  48  as sensing rollers, for example, on the front side. Diameters of the first sensing roller  47  and the second sensing roller  48  are smaller than the diameter of the steering roller  28 . As shown in  FIG. 7 , the first sensing roller  47  and the second sensing roller  48  are apart from the inner periphery of the transfer belt  10 . The rib  10   a  is located in a gap a between the first sensing roller  47  and the second sensing roller  48 . The gap α is larger than a width □ of the rib  10   a . When the transfer belt  10  is not deviated and the transfer belt is at a normal position, the rib  10   a  comes apart from the first sensing roller  47  and the second sensing roller  48 . The first sensing roller  47  has a first gear  47   a . The second sensing roller  48  has a fifth gear  48   a.    
     A first link  70  and a second link  80  as transmissions are provided from the first sensing roller  47  or the second sensing roller  48  to the steering supporting panel  40 . The first link  70  transmits the rotation of the first sensing roller  47  or the second sensing roller  48  to a worm gear  60 . The second link  80  transmits the rotation of the first sensing roller  47  and the second sensing roller  48  from the worm gear  60  to the steering roller  28  via the steering supporting panel  40 . 
     The worm gear  60  has a worm  61 , the worm shaft  62  configured to coaxially support the worm  61 , and the fixed gear  63  engaging the worm  61 . As shown in  FIG. 8  and  FIG. 9 , the first link  70  has a first gear unit  71  configured to transmit the rotation of the first sensing roller  47  to the worm shaft  62 . The first link  70  has a second gear unit  75  configured to transmit the rotation of the second sensing roller  48  to the worm shaft  62 . 
     The first gear unit  71  has a second gear  72  provided on a shaft  72   c  in parallels to the shaft  28   a  and engaging the first gear  47   a  of the first sensing roller  47 , a second deceleration gear  72   a  coaxial with the second gear  72 , a third gear  73  provided on a shaft  73   c  parallels to the shaft  28   a  and engaging the second deceleration gear  72   a , a third deceleration gear  73   a  coaxial with the third gear  73 , and a fourth gear  74  coaxial with the worm shaft  62  and engaging the third deceleration gear  73   a . The fourth gear  74  has a first one-way clutch  74   a  and transmits only a rightward rotation viewed from the front to the worm shaft  62 . 
     The second gear unit  75  has a sixth gear  76  provided on a shaft  76   c  parallels to the shaft  28   a  and engaging the fifth gear  48   a  of the second sensing roller  48 , a sixth deceleration gear  76   a  coaxial with the sixth gear  76 , a seventh gear  77  provided on a shaft  77   c  parallels to the shaft  28   a  and engaging the sixth deceleration gear  76   a , an eighth gear  78  provided on a shaft  78   c  parallels to the shaft  28   a  and engaging the seventh gear  77 , an eighth deceleration gear  78   a  coaxial with the eighth gear  78 , and a ninth gear  79  coaxial with the worm shaft  62  and engaging the eighth deceleration gear  78   a . The ninth gear  79  has a second one-way clutch  79   a  and transmits only a leftward rotation viewed from the front to the worm shaft  62 . 
     The second link  80  has the slide panel  32  having the slits  36   a  and  36   b , the worm shaft  62 , the worm  61  configured to rotate with the rotation of the worm shaft  62 , the fixed gear  63  engaging the worm  61 , and the steering supporting panel  40  configured to slide on the slide panel  32  integrally with the worm shaft  62 . The slits  36   a  and  36   b  of the slide panel  32  are configured to guide pins  40   a  and  40   b  of the steering supporting panel  40 . The pins  40   a  and  40   b  are provided with pin stoppers  40   c  and  40   d.    
     In the second link  80 , as shown in  FIG. 10 , if the worm shaft  62  is rotated rightward viewed from the front, the worm  61  engages the fixed gear  63 , and advances in the direction indicated by an arrow v, which is parallel to the axial line π passing through the supporting points  37   a  and  37   b  of the slide panel  32 . The worm  61  moves linearly in the rear direction of the axial line π passing through the supporting points  37   a  and  37   b  of the slide panel  32  along the fixed gear  63  and moves in the direction of rotation with respect to the axial line π passing through the supporting points  37   a  and  37   b  of the slide panel  32 . 
     With the advancement of the worm  61  in the direction indicated by the arrow v, the pins  40   a  and  40   b  of the steering supporting panel  40  which supports the worm shaft  62  slide in the slits  36   a  and  36   b , and move the steering supporting panel  40  toward the rear side while rotating the steering supporting panel  40  in the direction indicated by an arrow x as a first direction. The steering roller  28  rotates together with the steering supporting panel  40  in the direction indicated by the arrow x, and moves toward the rear side. The axis of rotation of the steering roller  28  inclines respect to the axial line π passing through the supporting points  37   a  and  37   b  of the slide panel  32 . The steering roller  28  changes an angle respect to the axial line π passing through the supporting points  37   a  and  37   b  and inclines in the direction indicated by a broken line δ. 
     If the worm shaft  62  is rotated leftward viewed from the front, the worm  61  engages the fixed gear  63 , and advances in the direction indicated by an arrow w, which is parallel to the axial line π passing through the supporting points  37   a  and  37   b  of the slide panel  32 . The worm  61  moves linearly in the front direction of the axial line π passing through the supporting points  37   a  and  37   b  of the slide panel  32  along the fixed gear  63 , and moves in the direction of rotation with respect to the axial line π passing through the supporting points  37   a  and  37   b  of the slide panel  32 . 
     With the advancement of the worm  61  in the direction indicated by the arrow w, the pins  40   a  and  40   b  of the steering supporting panel  40  which supports the worm shaft  62  slide in the slits  36   a  and  36   b , and move the steering supporting panel  40  toward the front side while rotating the steering supporting panel  40  in the direction indicated by an arrow y as a second direction. The steering roller  28  rotates together with the steering supporting panel  40  in the direction indicated by the arrow y, and moves toward the front side. The axis of rotation of the steering roller  28  inclines respect to the axial line π passing through the supporting points  37   a  and  37   b  of the slide panel  32 . The steering roller  28  changes the angle respect to the axial line π passing through the supporting points  37   a  and  37   b  and inclines in the direction indicated by a broken line θ. 
     The steering roller  28  rotates on a plane parallel to a plane including the axial line π passing through the supporting points  37   a  and  37   b  and inclines respect to the axial line π. During the rotation of the worm shaft  62 , the steering roller  28  slides in the plane parallel to the plane including the axial line π in the direction indicated by the arrow v and rotates in the direction indicated by the arrow x or, alternatively, slides in the plane parallel to the plane including the axial line π in the direction indicated by the arrow w and rotates in the direction indicated by the arrow y. The rotation of the steering roller  28  in the plane parallel to the plane including the axial line π does not have an axis of rotation at a constant position. The steering roller  28  rotates in the plane parallel to the plane including the axial line π about the pins  40   a  and  40   b  of the steering supporting panel  40  sliding in the slits  36   a  and  36   b  as supporting shafts. 
     Subsequently, an operation of the self steering mechanism  27  will be described. During printing, if the transfer belt  10  does not meander, and rotates and travels at the normal position, the rib  10   a  of the transfer belt  10  moves apart from both the first sensing roller  47  and the second sensing roller  48 . If the transfer belt  10  rotates and travels at the normal position, the self steering mechanism  27  is not activated. If the transfer belt  10  meanders during printing and is deviated toward the front side or the rear side, the self steering mechanism  27  senses the deviation of the transfer belt  10 , inclines the shaft  28   a  of the steering roller  28  respect to the axial line π passing through the supporting points  37   a  and  37   b , and corrects the direction of travel of the transfer belt  10 . 
     (Meandering on the Front Side) 
     Referring now to  FIG. 11  and  FIG. 12 , for example, correction of the direction of travel of the transfer belt  10  when the transfer belt  10  meanders on the front side will be described. The directions of rotation of the respective gears described here are the directions of rotation when viewed from the front side. (1) If the transfer belt  10  traveling in the direction indicated by the arrow s is deviated toward the front side, a side surface of the rib  10   a  on the front side as a second side surface, contacts with the second sensing roller  48  and rotates the second sensing roller  48  and the fifth gear  48   a  leftward (r 1 ). (2) The sixth gear  76  engaging the fifth gear  48   a  and the sixth deceleration gear  76   a  rotate rightward (r 2 ). (3) The seventh gear  77  engaging the sixth deceleration gear  76   a  rotates leftward (r 3 ). (4) The eighth gear  78  engaging the seventh gear  77  and the eighth deceleration gear  78   a  rotate rightward (r 4 ). 
     (5) The ninth gear  79  engaging the eighth deceleration gear  78   a  rotates leftward (r 5 ) and transmits the leftward rotation (r 5 ) to the worm shaft  62 . (6) If the worm shaft  62  rotates leftward, the worm  61  advances along the fixed gear  63  in the direction indicated by the arrow w. (7) The steering supporting panel  40  is maintained at a position parallel to the slide panel  32  having the supporting points  37   a  and  37   b  via the worm shaft supporting the worm  61 , rotates in the direction indicated by the arrow y along the slits  36   a  and  36   b  about the pins  40   a  and  40   b  as supporting shafts, and moves toward the front. The steering supporting panel  40  rotates in a plane of the slide panel  32 . (8) The steering roller  28  rotating integrally with the steering supporting panel  40  changes the angle with respect to the axial line π passing through the supporting points  37   a  and  37   b  in a plane parallel to the slide panel  32 , and inclines as indicated by the broken line θ. (9) The inclined steering roller  28  generates a force to transport the transfer belt  10  in the direction vertical to the broken line θ. (10) The transfer belt  10  slides toward the rear as a fourth direction, by the transporting force in the direction vertical to the broken line θ by the steering roller  28 , and corrects the direction of travel. 
     If the steering roller  28  is inclined and the direction of travel of the transfer belt  10  is corrected to the normal direction, the rib  10   a  of the transfer belt  10  moves apart from the second sensing roller  48 . The second sensing roller  48  stops rotating. 
     (Meandering on the Rear Side) 
     Referring now to  FIG. 13  and  FIG. 14 , for example, the correction of the direction of travel of the transfer belt  10  when the transfer belt  10  meanders on the rear side will be described. The directions of rotation of the respective gears described here are the directions of rotation when viewed from the front side. (11) If the transfer belt  10  traveling in the direction indicated by the arrow s is deviated toward the rear side, a side surface of the rib  10   a  on the rear side as a first side surface, contacts with the first sensing roller  47  and rotates the first sensing roller  47  and the first gear  47   a  leftward (r 6 ). (12) The second gear  72  engaging the first gear  47   a  and the second deceleration gear  72   a  rotate rightward (r 7 ). (13) The third gear  73  engaging the second deceleration gear  72   a  and the third deceleration gear  73   a  rotate leftward (r 8 ). (14) The fourth gear  74  engaging the third deceleration gear  73   a  rotates rightward (r 9 ) and transmits the rightward rotation to the worm shaft  62 . 
     (15) If the worm shaft  62  rotates rightward, the worm  61  advances along the fixed gear  63  in the direction indicated by the arrow v. (16) The steering supporting panel  40  is maintained at a position parallel to the slide panel  32  having the supporting points  37   a  and  37   b  via the worm shaft  62  supporting the worm  61 , rotates in the direction indicated by the arrow x along the slits  36   a  and  36   b  about the pins  40   a  and  40   b  as supporting shafts, and moves toward the rear. The steering supporting panel  40  rotates in the plane of the slide panel  32 . (17) The steering roller  28  rotating integrally with the steering supporting panel  40  changes the angle respect to the axial line π passing through the supporting points  37   a  and  37   b  in the plane parallel to the slide panel  32 , and inclines as indicated by the broken line δ. (18) The inclined steering roller  28  generates a force to transport the transfer belt  10  in the direction vertical to the broken line δ. (19) The transfer belt  10  slides toward the front as a third direction, by the transporting force in the direction vertical to the broken line δ by the steering roller  28 , and corrects the direction of travel. 
     If the steering roller  28  is inclined and the direction of travel of the transfer belt  10  is corrected to the normal direction, the rib  10   a  of the transfer belt  10  moves apart from the first sensing roller  47 . The first sensing roller  47  stops rotating. 
     The angle of inclination of the steering roller  28  for correcting the direction of travel of the transfer belt  10  to the normal direction is, for example, set to ±3° at maximum. If the tension of the transfer belt  10  is varied during the travel of the transfer belt  10 , the spring  38  swings the slide panel  32  about the supporting points  37   a  and  37   b  on the side of the steering roller  28 ′ to provide an adequate tension to the transfer belt  10 . The steering roller  28  is contacted with the transfer belt  10  with the adequate tension, so that sensing of the deviation of the transfer belt  10  by the first sensing roller  47  and the second sensing roller  48  is ensured. 
     According to the embodiment, the rib  10   a  is contacted with the first sensing roller  47  or the second sensing roller  48  on the front side of the transfer belt  10  to sense the meandering of the transfer belt  10 . The rotation of the first sensing roller  47  or the second sensing roller  48  transmits to the steering roller  28  using the worm gear  60 . Steering is performed by rotating the steering roller  28  in the plane parallel to the plane including the axial line π passing through the supporting points  37   a  and  37   b  in the direction parallel to the axial line π passing through the supporting points  37   a  and  37   b  of the slide panel  32  and in the direction of rotation with respect to the axial line π passing through the supporting points  37   a  and  37   b  of the slide panel  32 , whereby the direction of travel of the transfer belt  10  is corrected. 
     According to the embodiment, the meandering of the transfer belt  10  can be sensed on the one side of the transfer belt. The transfer belt  10  can be formed into a transfer belt with a one-side rib, and a configuration to transmit driving of the sensing roller to the steering roller can be simplified. The cost and weight of the steering mechanism for reliably correcting the deviation of the transfer belt are reduced. 
     The fixed gear may simply have a shape which prevents the worm and the fixed gear from being disengaged when the rotating worm moves along the fixed gear. For example, in a modification shown in  FIG. 15 , a fixed gear  93  of a worm gear  90  is formed into a wheel shape. A worm  91  engaging the fixed gear  93 , which is to be fixed to the slide panel  32 , moves toward the front side or rear side along the fixed gear  93  during rotation thereof. While rotating the steering supporting panel  40  supporting a worm shaft  92 , the worm  91  moves toward the front side or the rear side, rotates the steering roller  28  in the plane parallel to the plane including the axial line π passing through the supporting points  37   a  and  37   b  together with the steering supporting panel  40 , and inclines the steering supporting panel  40  respect to the axial line π passing through the supporting points  37   a  and  37   b.    
     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 apparatus and methods described herein may be embodied in a variety of other forms: furthermore various omissions, substitutions and changes in the form of the apparatus and methods 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 of modifications as would fall within the scope and spirit of the invention.