Patent Publication Number: US-8116663-B2

Title: Image forming apparatus with a secondary-transfer-roller releasing mechanism

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from the prior U.S. patent application Ser. No. 60/988,754, filed on 16 Nov. 2007, the entire contents of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to image forming apparatuses such as a copying machine and a printer, and, more particularly to an image forming apparatus with operability during maintenance improved. 
     BACKGROUND 
     An image forming apparatus includes a secondary transfer roller in order to bring an image bearing member such as a transfer belt and a recording medium into press contact with each other and transfer an image onto the recording medium. For example, when a jam occurs or when maintenance is necessary, the press-contact of the secondary transfer roller needs to be released to separate the secondary transfer roller from the transfer belt. 
     Concerning this point, in a mechanism proposed in JP-A-2006-11184, when a part of a housing is opened, a secondary transfer roller moves following the opening of the part of the housing and separates from a transfer belt. 
     However, in this technique, mechanisms associated with the part of the housing increases. Therefore, a large force is necessary to open the housing and operability is deteriorated. 
     To cope with this problem, provision of a lever exclusively used for separating the secondary transfer roller is proposed.  FIG. 5  is a diagram of a releasing mechanism for the secondary transfer roller by this related art. 
     As shown in  FIG. 5 , in the releasing mechanism in the past, when a release handle  101  is pulled up in a direction of an arrow X, an arm  102  pivots to push down a secondary transfer roller  11  and move the secondary transfer roller  11  along a track A. 
     However, a large force is necessary when a secondary-transfer-roller-side positioning member  109  climbs over a contact portion  106 A of a positioning member  106 . As a result, smooth release of the secondary transfer roller  11  cannot be realized. 
     SUMMARY 
     It is an object of the present invention to provide an image forming apparatus in which a secondary transfer roller can be smoothly released without being caught. 
     In an aspect of the present invention, an image forming apparatus includes: 
     a recording medium feeding mechanism that feeds recording media one by one; 
     a recording medium conveying path to convey the recording medium fed by the recording medium feeding mechanism to a recording medium discharging unit; 
     an image forming unit that is arranged further on an upstream side than the recording medium discharging unit on the recording medium conveying path and executes an image forming process to print an image based on image data on the recording medium conveyed through the recording medium conveying path; 
     a release handle pivotably locked to a support arm that slidably supports a secondary transfer roller of the image forming unit; and 
     an arm that separates, when the release handle is pulled, the secondary transfer roller from a secondary-transfer-roller positioning member using leverage. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram of a secondary-transfer-roller releasing mechanism according to a first embodiment of the present invention; 
         FIG. 2  is a diagram of a state in which a release handle is pulled up; 
         FIG. 3  is a diagram of a secondary-transfer-roller releasing mechanism according to a second embodiment of the present invention; 
         FIG. 4  is a diagram of a state in which a release handle is pulled up; 
         FIG. 5  is a diagram of a secondary-transfer-roller releasing mechanism according to a related art; and 
         FIG. 6  is a diagram of a configuration example of an image forming apparatus. 
     
    
    
     DETAILED DESCRIPTION 
     Throughout this description, the embodiments and examples shown should be considered as exemplars, rather than limitations on the apparatus and methods of the present invention. 
     Image forming apparatuses according to embodiments of the present invention are explained in detail below with reference to the accompanying drawings. 
     Overview of an Image Forming Apparatus 
       FIG. 6  is a diagram of a configuration example of an image forming apparatus. As shown in  FIG. 6 , an original stand  602  for original placement formed of a transparent material such as a glass plate is provided in an upper part of an apparatus main body  601 . A cover  603  is openably and closably set in the apparatus main body  601  to cover the original stand  602 . 
     A scan unit (not shown) that optically scans an image of an original placed on the original stand  602  is provided on a lower surface side of the original stand  602  in the inside of the apparatus main body  601 . The scan unit includes, for example, a carriage  604 , reflection mirrors  606 ,  607 , and  608  that reflect light of an exposure lamp  605  reflected on the original, a lens block for magnification  609  that magnifies the reflected light, and a CCD (Charge Coupled Device)  610 . The carriage  604  includes the exposure lamp  605  that irradiates light toward the original stand  602 . The carriage  604  can reciprocatingly move along a lower surface of the original stand  602 . 
     The carriage  604  reciprocatingly moves while lighting the exposure lamp  605  to thereby expose the original placed on the original stand  602  to light. A reflected light image of the original, which is placed on the original stand  602 , formed by this exposure is projected on the CCD  610  through the reflection mirrors  606 ,  607 , and  608  and the lens block for magnification  609 . The CCD  610  outputs image data corresponding to the reflected light image of the original projected thereon. 
     An image forming unit  220  is provided below the scan unit in the inside of the apparatus main body  601 . The image forming unit  220  includes, for example, a print engine (not shown) and a process unit (not shown). 
     The print engine includes an exposing unit  611 . The process unit includes photoconductive drums  621 ,  622 ,  623 , and  624  arranged along the exposing unit  611 . 
     Further, the process unit includes an endless transfer belt  12  arranged to be opposed to the exposing unit  611  across the photoconductive drums  621 ,  622 ,  623 , and  624 . 
     Moreover, the process unit includes a drive roller  626  that drives the transfer belt  12  and primary transfer rollers  641 ,  642 ,  643 , and  644  arranged to be opposed to the photoconductive drums  621 ,  622 ,  623 , and  624  across the transfer belt  12 . 
     Furthermore, the process unit includes a transfer roller driving unit that drives the primary transfer rollers  641 ,  642 ,  643 , and  644 . 
     The transfer belt  12  is laid over the drive roller  626 , guide rollers  627 ,  628 , and  629 , and a driven roller  10  and receives power from the drive roller  626  to rotationally travel in the counterclockwise direction. The guide roller  627  is provided to freely move up and down. The guide roller  627  receives pivoting of a cam  631  to move to the transfer belt  12  side. Consequently, the guide roller  627  changes a position of the transfer belt  12  to the photoconductive drums  621 ,  622 ,  623 , and  624  side. 
     The image forming unit  220  executes an image forming process for forming an image based on image data (an image signal outputted from the CCD  610 ) and printing the image on a recording medium being conveyed. The image signal outputted from the CCD  610  is appropriately processed and, then, supplied to the exposing unit  611 . 
     The exposing unit  611  emits a laser beam B 1  corresponding to an image signal of a yellow color to the photoconductive drum  621  for the yellow color. The exposing unit  611  emits a laser beam B 2  corresponding to an image signal of a magenta color to the photoconductive drum  622  for the magenta color. The exposing unit  611  emits a laser beam B 3  corresponding to an image signal of a cyan color to the photoconductive drum  623  for the cyan color. The exposing unit  611  emits a laser beam B 4  corresponding to an image signal of a black color to the photoconductive drum  624  for the black color. 
     The primary transfer rollers  641 ,  642 ,  643 , and  644  are moved (lowered) to the transfer belt  12  side to thereby bring the transfer belt  12  into contact with the photoconductive drums  621 ,  622 ,  623 , and  624  and transfer visible images on the photoconductive drums  621 ,  622 ,  623 , and  624  onto the transfer belt  12 . 
     A drum cleaner, a charge removing lamp, a charging unit, and a developing unit, which are not shown in the figure, are disposed in order around the photoconductive drum  621 . The drum cleaner has a drum cleaning blade that is in contact with the surface of the photoconductive drum  621 . The drum cleaner scrapes off a developing material remaining on the surface of the photoconductive drum  621  using the drum cleaning blade. 
     The charge removing lamp removes charges remaining on the surface of the photoconductive drum  621 . The charging unit applies high voltage to the photoconductive drum  621  to thereby charge the surface of the photoconductive drum  621  with electrostatic charges. The laser beam B 1  emitted from the exposing unit  611  is irradiated on the charged surface of the photoconductive drum  621 . An electrostatic latent image is formed on the surface of the photoconductive drum  621  by the irradiation of the laser beam B 1 . The developing unit supplies a developing material (a toner) of the yellow color to the surface of the photoconductive drum  621  to thereby visualize the electrostatic latent image on the surface of the photoconductive drum  621 . 
     Similarly, the other photoconductive drums  622 ,  623 , and  624  visualize electrostatic latent images on the surfaces thereof using developing materials of colors corresponding thereto. 
     A cleaner  636  is provided in a position opposed to the drive roller  626  of the image forming unit  220  across the transfer belt  12 . The cleaner  636  has a cleaning blade  636   a  that is in contact with the transfer belt  12 . The cleaner  636  scrapes off the developing materials remaining on the transfer belt  12  using the cleaning blade  636   a.    
     A printing mode is changed as described below. Hooks  671 ,  672 ,  673 , and  674  are provided near the primary transfer rollers  641 ,  642 ,  643 , and  644 . The hooks  671 ,  672 ,  673 , and  674  engage with shafts of the primary transfer rollers  641 ,  642 ,  643 , and  644  to lift the shafts while pivoting and move the primary transfer rollers  641 ,  642 ,  643 , and  644  in a direction away from the photoconductive drums  621 ,  622 ,  623 , and  624 . Printing modes such as a full-color mode, a totally separated mode, and a monochrome mode are changed by moving none of the primary transfer rollers  641 ,  642 ,  643 , and  644  or changing a combination of the primary transfer rollers to be moved. 
     A storing mechanism and a feeding mechanism for a recording medium are explained. Plural recording media cassettes  650  that store recording media are provided below the exposing unit  611 . A large number of recording media P of recording media types different from one another are stored in the recording media cassettes  650  in a stacked state. Recording medium feeding mechanisms  221  that feed the recording media in the recording media cassettes  650  one by one from above are respectively provided in outlet portions (on the right side in the figure) of the recording media cassettes  650 . The recording media P are extracted one by one from any one of the recording media cassettes  650  by each of the recording medium feeding mechanisms  221 . The recording medium feeding mechanism  221  for extraction includes a pickup roller  651 , a recording medium feeding roller  652   a , and a separating roller  652   b . The recording medium feeding mechanism  221  separates the recording media P extracted from the recording media cassette  650  one by one and feeds the recording medium P to a recording medium conveying path  653 . 
     A conveying path for a recording medium is explained. The recording medium conveying path  653  extends to a recording medium discharge port  654  in an upper part through the driven roller  10  of the image forming unit  220 . The recording medium discharge port  654  faces a recording medium discharging unit  655  that continues to an outer peripheral surface of the apparatus main body  601 . Conveying rollers  656  are respectively provided near the recording medium feeding mechanisms  221  on a start end side of the conveying path  653 . When a recording medium is fed by any one of the recording medium feeding mechanisms  221 , the fed recording medium is conveyed to the recording medium discharging unit  655  through the recording medium conveying path  653 . 
     A secondary transfer roller  11  is provided in a position opposed to the driven roller  10  across the transfer belt  12  along the recording medium conveying path  653 . Registration rollers  658  are provided in a position in a conveying direction before the driven roller  10  and the secondary transfer roller  11 . 
     The registration rollers  658  feed the recording medium P into between the transfer belt  12  and the secondary transfer roller  11  at timing synchronizing with a transfer operation, which is an operation for transferring an image formed by a developing material (a toner) onto a recording medium, by the transfer belt  12  and the secondary transfer roller  11 . The secondary transfer roller  11  transfers a visible image formed by the developing material (the toner), which is transferred onto the transfer belt  12 , onto the recording medium P and prints the visible image while holding the recording medium P, which is fed from the registration rollers  658 , between the secondary transfer roller  11  and the transfer belt  12  on the driven roller  10 . In this way, the registration rollers  658  convey the recording medium P to the image forming unit  220  including the transfer belt  12  and the secondary transfer roller  11  in synchronization with the transfer operation of the image forming unit  220 . 
     A heat roller  659  for thermal fixing and a press contact roller  660  that is in contact with the heat roller  659  are provided in a position further on a downstream side than the secondary transfer roller  11  on the recording medium conveying path  653 . The image transferred onto the recording medium P is fixed by the heat roller  659  and the press contact roller  660 . Recording medium discharging rollers  661  are provided at a terminal end of the recording medium conveying path  653 . 
     An automatic duplex unit (hereinafter referred to as ADU)  222  may be provided in the apparatus main body  601 . The ADU  222  is set to couple a sub-conveying path  662 , which is a path to convey the recording medium P in the ADU  222 , to the terminal end of the recording medium conveying path  653  and an inlet of the registration rollers  658 . The sub-conveying path  662  branches from a downstream side relative to the image forming unit  220  on the recording medium conveying path  653  (the terminal end of the recording medium conveying path  653 ) and merges into an upstream side relative to the image forming unit  220  on the recording medium conveying path  653  (an upstream side position of the registration rollers  658 ). 
     The sub-conveying path  662  reverses the front and the back of the recording medium P for duplex printing. Recording medium feeding rollers  663 ,  664 , and  665  are provided in the sub-conveying path  662 . The ADU  222  reversely feeds the recording medium P conveyed from the image forming unit  220  to the recording medium discharging unit  655 , conveys the recording medium P through the sub-conveying path  662 , and merges the recording medium P into the recording medium conveying path  653  on an upstream side of the image forming unit  220 . When the recording medium P is conveyed in this way, the front and the back of the recording medium P is reversed. 
     The recording medium P returned to the upstream side of the image forming unit  220  through the sub-conveying path  662  merges into the recording medium conveying path  653 . Then, in synchronization with the transfer operation of the image forming unit  220 , the recording medium P is fed into a transfer position, where the transfer belt  12  and the secondary transfer roller  11  are in contact, by the registration rollers  658 . In this way, the visible image on the transfer belt  12  is transferred onto the rear surface of the recording medium P as well and printed thereon. 
     When duplex printing is designated by, for example, an operation panel  724  provided in the apparatus main body  601  or a computer or the like connected to the apparatus main body  601  through a network, the sub-conveying path  662  of the ADU  222  changes to a state for performing an operation for reversing the front and the back of the recording medium P. 
     Devices additionally provided in the image forming apparatus are explained. In the example of the apparatus main body  601  shown in  FIG. 6 , two recording media cassettes  650  are provided as feeding sources of recording media. Three or more recording media cassettes  650  may be provided in the apparatus main body  601 . Besides, although not shown in the figure, a manual-feed recording medium feeding mechanism (hereinafter referred to as SFB) or a large-capacity recording medium feeder (hereinafter referred to as LCF) as a recording medium feeding mechanism, which can store several thousand recording media in a stacked state, can also be provided. The SFB or the LCF is set in the apparatus main body  601  such that a path of the SFB or the LCF for feeding recording media merges into the recording medium conveying path  653 . 
     A recording medium type sensor  223  may be provided in the apparatus main body  601 . The recording medium type sensor  223  is arranged in a position on the upstream side relative to the image forming unit  220  on the recording medium conveying path  653  and further on the upstream side than the registration rollers  658 . The recording medium type sensor  223  detects a recording medium type of the recording medium P conveyed through the recording medium conveying path  653 . 
     As the recording medium type sensor  223 , for example, a publicly-known sensor that judges a type of the recording medium P by detecting the thickness and the light transmittance of the recording medium P can be used. 
     When the SFB or the LCF is set, the recording medium type sensor  223  is arranged further on the downstream side than a merging point of the recording medium feeding path from the SFB or the LCF and the recording medium conveying path  653 . By arranging the recording medium type sensor  223  in this way, it is possible to detect, with one recording medium type sensor  223 , types of the recording media P conveyed on the recording medium conveying path  653  from all the recording medium feeding sources. Secondary-transfer-roller releasing mechanism 
     First Embodiment 
       FIG. 1  is a diagram of a secondary-transfer-roller releasing mechanism according to this embodiment. As shown in  FIG. 1 , a roller guide  108  supports a rotating shaft of the secondary transfer roller  11 . A positioning spring  107  slidably supports the roller guide  108 . A broken line A indicates a track of pivoting of the secondary transfer roller  11 . A supporting frame  104  supports the positioning spring  107 . The positioning spring  107  pushes the secondary transfer roller  11  in a direction of the driven roller  10  and brings the secondary transfer roller  11  into press contact with the driven roller  10  and the transfer belt  12 . 
     A driven-roller supporting frame  110 , which supports the driven roller  10 , supports a secondary-transfer-roller positioning member  106 . The secondary-transfer-roller positioning member  106  comes into contact with a secondary-transfer-roller-side positioning member  109  and positions the secondary transfer roller  11  in a predetermined position. 
     The supporting frame  104  pivotably supports a pivoting arm  102  at a pivotal fulcrum  103 . The pivoting arm  102  is locked to a release handle  101  and a fixed fulcrum  105 . A housing frame pivotably supports the supporting frame  104 . 
     The pivoting arm  102  locks a first coupling arm  201 A to the fixed fulcrum  105 . The first coupling arm  201 A pivotably locks a second coupling arm  201 B to a first coupling point  202 A. The second coupling arm  201 B pivotably locks a third coupling arm  201 C to a second coupling point  202 B. The supporting frame  104  pivotably locks the third coupling arm  201 C to a third coupling point  202 C. The third coupling arm  201 C brings a contact portion of the third coupling arm  201 C, which is one end on the opposite side of the second coupling point  202 B relative to the third coupling point  202 C, into contact with the secondary-transfer-roller-side positioning member  109 . 
     With a power point set in the second coupling point  202 B, a fulcrum set in the third coupling point  202 C, and an action point set in the contact portion of the third coupling arm  201 C, the third coupling arm  201 C pushes down the secondary transfer roller  11  using leverage. 
     When the release handle  101  is pulled up in an arrow X direction, the first coupling arm  201 A pivots in the arrow X direction following the release handle  101 . When the first coupling arm  201 A pivots in the arrow X direction, the second coupling arm  201 B moves in an arrow Y direction. 
       FIG. 2  is a diagram of a state in which the release handle  101  is pulled up. As shown in  FIG. 2 , when the second coupling arm  201 B moves in the arrow Y direction, the third coupling arm  201 C pivots around the third coupling point  202 C and pushes the secondary-transfer-roller-side positioning member  109  to push down the secondary transfer roller  11  in an arrow Z direction. 
     When the secondary transfer roller  11  is pushed down in the arrow z direction, the secondary-transfer-roller-side positioning member  109  separates from a contact portion  106 A of the secondary-transfer-roller positioning member  106 . Therefore, the track of the secondary transfer roller  11  falls to a broken line B. When the secondary transfer roller  11  is released, the secondary-transfer-roller-side positioning member  109  is not caught in the contact portion  106 A. Therefore, it is possible to smoothly release the secondary transfer roller  11 . 
     As explained above, the image forming apparatus according to this embodiment includes the coupling arm that moves, when the release handle  101  is pulled up, in association with the movement of the release handle  101  and separates the secondary transfer roller  11  from the secondary-transfer-roller positioning member  106 . Therefore, the image forming apparatus according to this embodiment has an effect that, when the secondary transfer roller  11  is released, the secondary-transfer-roller-side positioning member  109  is not caught in the contact portion  106 A and the secondary transfer roller  11  can be smoothly released. 
     Second Embodiment 
       FIG. 3  is a diagram of a secondary-transfer-roller releasing mechanism according to a second embodiment of the present invention. As shown in  FIG. 3 , the roller guide  108  supports the rotating shaft of the secondary transfer roller  11 . The positioning spring  107  slidably supports the roller guide  108 . The broken line A indicates the track of pivoting of the secondary transfer roller  11 . The supporting frame  104  supports the positioning spring  107 . The positioning spring  107  pushes the secondary transfer roller  11  in a direction of the driven roller  10  and brings the secondary transfer roller  11  into press contact with the driven roller  10  and the transfer belt  12 . 
     The driven-roller supporting frame  110 , which supports the driven roller  10 , supports the secondary-transfer-roller positioning member  106 . The secondary-transfer-roller positioning member  106  comes into contact with the secondary-transfer-roller-side positioning member  109  and positions the secondary transfer roller  11  in a predetermined position. 
     The supporting frame  104  pivotably supports the pivoting arm  102  at the pivotal fulcrum  103 . The pivoting arm  102  is locked to the release handle  101  and the fixed fulcrum  105 . The housing frame pivotably supports the supporting frame  104 . The image forming apparatus according to this embodiment can include only one pivoting arm  102  or can include one pivoting arm  102  at each of ends of the secondary transfer roller  11 , two pivoting arms  102  in total. 
     The pivoting arm  102  has a push-down spatula  301  on the opposite side of the fixed fulcrum  105  across the pivotal fulcrum  103 . The push-down spatula  301  has a curved section  302 A in a distal end thereof. The curved section  302 A is in contact with the secondary-transfer-roller-side positioning member  109 . 
     The push-down spatula  301  has length enough to set the curved section  302 A in contact with the secondary-transfer-roller-side positioning member  109 . A distance L 0  from the distal end of the push-down spatula  301  to the pivotal fulcrum  103  is larger than a distance L 1  from the curved section  302 A to the pivotal fulcrum  103 . 
     A curvature radius of the curved section  302 A is desirably larger than a radius of the secondary-transfer-roller-side positioning member  109 . When the curvature radius of the curved section  302 A is smaller than the radius of the secondary-transfer-roller-side positioning member  109 , a large force may be required during a release operation. 
     When the release handle  101  is pulled up in the arrow X direction, the pivoting arm  102  pivots in an arrow T direction around the pivotal fulcrum  103  in association with the movement of the release handle  101 . With a power point set in the release handle  101 , a fulcrum set in the pivotal fulcrum  103 , and an action point set in the curved section  302 A, the pivoting arm  102  pushes down the secondary transfer roller  11  using leverage. 
       FIG. 4  is a diagram of a state in which the release handle  101  is pulled up. As shown in  FIG. 4 , when the pivoting arm  102  pivots in the arrow T direction around the pivotal fulcrum  103 , the push-down spatula  301  pushes down the secondary transfer roller  11  in an arrow U direction. 
     When the secondary transfer roller  11  is pushed down in the arrow U direction, the secondary-transfer-roller-side positioning member  109  separates from the contact portion  106 A of the secondary-transfer-roller positioning member  106 . Therefore, the track of the secondary transfer roller  11  falls to the broken line B. When the secondary transfer roller  11  is released, the secondary-transfer-roller-side positioning member  109  is not caught in the contact portion  106 A. Therefore, it is possible to smoothly release the secondary transfer roller  11 . 
     As explained above, the image forming apparatus according to this embodiment includes the pivoting arm  102  having the push-down spatula  301  that moves, when the release handle  101  is pulled up, in association with the movement of the release handle  101  and separates the secondary transfer roller  11  from the secondary-transfer-roller positioning member  106 . Therefore, the image forming apparatus according to this embodiment has an effect that it is possible to manufacture at lower cost a releasing mechanism in which, when the secondary transfer roller  11  is released, the secondary-transfer-roller-side positioning member  109  is not caught in the contact portion  106 A and the secondary transfer roller  11  can be smoothly released. 
     Although exemplary embodiments of the present invention have been shown and described, it will be apparent to those having ordinary skill in the art that a number of changes, modifications, or alterations to the invention as described herein may be made, none of which depart from the spirit of the present invention. All such changes, modifications, and alterations should therefore be seen as within the scope of the present invention.