Patent Publication Number: US-2011076068-A1

Title: Fixing device, image forming apparatus, and method of removing residual toner

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is also based upon and claims the benefit of priority from U.S. provisional application 61/246,646, filed on Sep. 29, 2009; the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     Embodiments described herein relate generally to a technique for removing a toner remaining on a rotating member configured to heat the toner to be transferred onto a sheet. 
     BACKGROUND 
     In an image forming apparatus in the past, when a jam occurs, a heater for heating a fixing roller stops operation. When the heater stops the operation, the temperature of a sheet conveyed by the fixing roller gradually falls. When the temperature of the sheet falls, in some case, a toner transferred onto the sheet adheres to the fixing roller without being fixed on the sheet. 
     When printing is performed after jam treatment, it is likely that the residual toner adhering to the fixing roller is transferred onto the sheet and image quality is deteriorated. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a longitudinal sectional view of an image forming apparatus; 
         FIG. 2  is a block diagram of a driving unit; 
         FIG. 3  is an enlarged view of a fixing device, wherein a state before a peeling blade comes into contact with a heating belt is shown; 
         FIG. 4  is an enlarged view of the fixing device, wherein a state in which the peeling blade comes into contact with the heating belt is shown; 
         FIG. 5  is a flowchart for explaining a method of removing a residual toner; and 
         FIG. 6  is a sectional view of a peeling blade in a first modification. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a longitudinal sectional view of an image forming apparatus. An image forming apparatus  1  includes an image reading unit R and an image forming unit P. A controller  41  manages control of the entire image forming apparatus  1  including the image reading unit R and the image forming unit P. 
     The image reading unit R scans and reads images of a sheet document and a book document. 
     The image reading unit R includes a document table  5   a  configured to support an original document and an image sensor  5   b  configured to convert image information into image data. The image sensor  5   b  may be a CCD sensor. The image reading unit R irradiates illumination light, which is emitted from a lighting device  5   c , on an original document set on the document table  5   a  and converts, with the image sensor  5   b , reflected light reflected on the original document into an image signal. 
     The image forming unit P forms a developer image on a sheet on the basis of, for example, an image read from the original document by the image reading unit R or image data transmitted from an external apparatus to the image forming apparatus  1 . 
     The image forming unit P includes a sheet feeding unit  3 , photoconductive drums  11   a  to  11   d , developing devices  13   a  to  13   d , a transfer belt  15 , cleaners  17   a  to  17   d , a transfer device  19 , a fixing device  21 , and an exposure device  23 . 
     The photoconductive drums  11   a  to  11   d  carry latent images. The developing devices  13   a  to  13   d  supply toners to the latent images carried by the photoconductive drums  11   a  to  11   d  corresponding thereto and develop the latent images. The transfer belt  15  carries, in order, images of the toners carried by the photoconductive drums  11   a  to  11   d.    
     The cleaners  17   a  to  17   d  remove the toners remaining on the photoconductive drums  11   a  to lid corresponding thereto. The transfer device  19  transfers the images of the toners carried by the transfer belt  15  onto a sheet. The sheet may be plain paper or an OHP sheet that is a transparent resin sheet. 
     The exposure device  23  forms the latent images on the photoconductive drums  11   a  to  11   d . The fixing device  21  heats the sheet to thereby fix the toner images transferred onto the sheet. Details of the fixing device  21  are explained later. 
     The sheet feeding unit  3  includes cassettes  31 , pickup rollers  33 , separating mechanisms  35 , conveying rollers  37 , and an aligning roller  39 . The separating mechanisms  35  prevent two or more sheets from being extracted from the cassettes  31  by the pickup rollers  33  at a time. The conveying rollers  37  convey sheets separated by the separating mechanisms  35  to the aligning roller  39  one by one. 
     The aligning roller  39  feeds the sheet to a transfer position, where the transfer device  19  and the transfer belt  15  are in contact with each other, to be timed to coincide with the transfer of the images of the toners from the transfer belt  15  onto the sheet by the transfer device  19 . 
     A cover  1   a  moves between a closed position where the cover  1   a  closes an area for performing jam treatment and an opened position where the cover  1   a  projects from the image forming apparatus  1  and opens the area for performing the jam treatment. 
     An opening and closing sensor  96  detects opening and closing of the cover  1   a . The opening and closing sensor  96  may be a switch of a push button type. When the cover  1   a  moves from the opened position to the closed position, the opening and closing sensor  96  outputs a signal. 
     The fixing device  21  is explained in detail below with reference to  FIGS. 1 and 2 .  FIG. 2  is a block diagram of a driving unit. 
     The fixing device  21  includes a heating roller  82 , a pressing roller  83 , a stretching and suspending roller  84 , a heating belt  85  as a rotating member, a heater  86 , a peeling blade  94 , and a driving unit  90 . 
     The pressing roller  83  comes into contact with the heating belt  85  and rotates in an arrow direction. The heating roller  82 , the stretching and suspending roller  84 , and the heating belt  85  rotate following the pressing roller  83 . 
     The heater  86  includes a coil. A magnetic flux is generated by high-frequency current applied to the coil. The magnetic flux generated by the heater  86  induces eddy-current in the heating belt  85 . The heating belt  85  generates heat. 
     The peeling blade  94  extends in a direction in which the heating belt  85  is located. The peeling blade  94  comes into contact with a sheet discharged from a nip position between the pressing roller  83  and the heating belt  85  and adhering to the heating belt  85 . The peeling blade  94  peels off the sheet, with which the peeling blade  94  comes into contact, from the heating belt  85 . 
     The driving unit  90  moves between a separated position where the driving unit  90  separates the peeling blade  94  from the heating belt  85  and a contact position where the driving unit  90  brings the peeling blade  94  into contact with the heating belt  85 . 
     The driving unit  90  includes a solenoid  91 , a return spring  92 , and a swinging shaft section  93 . The solenoid  91  includes a movable core  91 A. The controller  41  controls a power supply unit  42  to thereby control electric current flowing to a coil of the solenoid  91  to be turned on and off. 
     The controller  41  is connected to a timer  98  and performs various kinds of control on the basis of a count time of the timer  98 . 
     A distal end portion of the movable core  91 A is connected to a proximal end portion of the peeling blade  94 . The return spring  92  is located on the opposite side of the movable core  91 A across the peeling blade  94 . A distal end portion of the return spring  92  is connected to the proximal end portion of the peeling blade  94 . 
     The swinging shaft section  93  is located further on a distal end side of the peeling blade  94  than the return spring  92 . The peeling blade  94  swings around the swinging shaft section  93 . 
     The peeling blade  94  may be lubricated rubber. When the peeling blade  94  comes into contact with the heating belt  85 , a load applied to the heating belt  85  is small and deterioration in image quality is suppressed. 
     A method of removing a residual toner adhering to the heating belt  85  is explained with reference to  FIGS. 3 to 5 .  FIG. 3  is an enlarged view of the fixing device, wherein a state before the peeling blade comes into contact with the heating belt is shown.  FIG. 4  is an enlarged view of the fixing device, wherein a state in which the peeling blade comes into contact with the heating belt is shown.  FIG. 5  is a flowchart for explaining the method of removing a residual toner. 
     It is assumed that, in an initial state, the cover  1   a  is located in the opened position and jam treatment is being performed. As shown in  FIG. 3 , the peeling blade  94  is located in a position apart from the heating belt  85 . 
     In Act  101 , the controller  41  discriminates presence or absence of an output from the opening and closing sensor  96 . If an output from the opening and closing sensor  96  is present, the controller  41  proceeds to Act  102 . 
     In Act  102 , the controller  41  instructs the power supply unit  42  to energize the solenoid  91  and instructs the timer  98  to count time. 
     When electric current flows to the solenoid  91 , the movable core  91 A linearly moves in an arrow A direction in  FIG. 3 . When the movable core  91 A moves in the arrow A direction, the peeling blade  94  swings in the counterclockwise direction with the swinging shaft section  93  as a rotation axis. 
     When the peeling blade  94  further swings in the counterclockwise direction, as shown in  FIG. 4 , a distal end portion of the peeling blade  94  comes into contact with the heating belt  85 . 
     The peeling blade  94  may come into contact with the heating belt  85  in an area where the heating roller  82  and the heating belt  85  overlap. 
     When the peeling blade  94  swings in the counterclockwise direction, the return spring  92  stretches. The peeling blade  94  swings in the counterclockwise direction while being pulled by the return spring  92  in the clockwise direction with the swinging shaft section  93  as the rotation axis. 
     In Act  103 , the controller  41  discriminates whether the time counted by the timer  98  reaches T 1 . When time required by the heating belt  85  to rotate once is represented as T 2 , T 1  may be equal to or longer than T 2 . 
     In a state in which the peeling blade  94  is in contact with the heating belt  85 , the heating belt  85  rotates at least once, whereby a residual toner remaining on the heating belt  85  moves to the peeling blade  94 . 
     When the heating belt  85  rotates, the controller  41  may control the power supply unit  42  and energize the heater  86 . Timing of temperature rising processing for the heating belt  85 , the temperature of which falls during the jam treatment, and timing of removal processing for the residual toner adhering to the heating belt  85  are the same. Therefore, a preparation time for printing is reduced. 
     If the time counted by the timer  98  reaches T 1  in Act  103 , the controller  41  proceeds to Act  104 . 
     In Act  104 , the controller  41  instructs the power supply unit  42  to inhibit the energization to the solenoid  91 . When the electric current stops flowing to the solenoid  91 , with spring force of the return spring  92 , the peeling blade  94  swings in the clockwise direction with the swinging shaft section  93  as the rotation axis. When the peeling blade  94  further swings, the peeling blade  94  returns to the separated position shown in  FIG. 3 . 
     In Act  104 , the controller  41  resets the timer  98 . 
     First Modification 
       FIG. 6  is a sectional view of a peeling blade in a first modification. Components having functions same as those in the embodiment are denoted by the same reference numerals and signs. The peeling blade  101  includes a substrate  102  and a contact section  103 . The substrate  102  may be SUS. 
     The return spring  92  is connected to one end face in the thickness direction of the substrate  102 . The movable core  91 A is connected to the other end face. The contact section  103  covers a front end side of the substrate  102 . The contact section  103  may be lubricated rubber. The lubricated rubber may be fluorine resin. 
     The contact section  103  includes a taper section  103 A, the thickness of which gradually decreases from a rear end portion to a front end portion thereof. The taper section  103 A of the contact section  103  includes a storage opening  103 B. The storage opening  103 B stores a residual toner moved from the heating belt  85  to the peeling blade  101 . The storage opening  103 B prevents the residual toner once moved to the peeling blade  101  from falling. 
     Second Modification 
     The driving unit  90  is not limited to the solenoid  91  and may be another driving mechanism. The other driving mechanism may be a link mechanism or an air cylinder. 
     The peeling blade  94  is fixed to the link mechanism. The link mechanism rotates, whereby the peeling blade  94  operates. 
     The peeling blade  94  is fixed to a distal end portion of a piston rod of the air cylinder. The piston rod moves back and forth, whereby the peeling blade  94  operates. 
     The peeling blade  94  and the movable core  91 A may be located on the same axis. The peeling blade  94  may be fixed to the distal end portion of the movable core  91 A. When the movable core  91 A moves in a direction away from the solenoid  91 , the peeling blade  94  comes into contact with the heating belt  85 . When the movable core  91 A moves in a direction approaching the solenoid  91 , the peeling blade  94  separates from the heating belt  85 . 
     Third Modification 
     Timing when the peeling blade  94  operates may be timing other than timing immediately after the jam treatment. 
     The timing when the peeling blade  94  operates may be timing when image density detected by pixel count exceeds a threshold. For example, in the case of color printing, plural kinds of toners are stacked on a sheet. Therefore, the image density rises and the toners tend to adhere to the heating belt  85 . The toners adhering to the heating belt  85  during the color printing move to the peeling blade  94 . 
     Fourth Modification 
     The heating roller  82  and the heating belt  85  may be replaced with a heat generating roll. The heat generating roll includes, in a surface layer section, a conductive layer in which eddy-current is generated by a magnetic flux from the heater  86 . The peeling blade  94  moves between a contact position where the peeling blade  94  comes in to contact with the heat generating roll and a separated position where the peeling blade  94  separates from the heating roll. 
     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 invention. 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 sprit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.