Abstract:
The fixing device and image forming apparatus employ a horizontally moving claw for separating a sheet on which a toner image has been fixed. The claw moves in a horizontally reciprocating manner at a velocity between 0.001 mm/seconds to 0.1 mm/seconds. Moving at that speed, it has been found to reduce scratching of the fixing drum. The device and image forming apparatus also employ a claw having a width between 1.0 mm and 5.0 mm. The claw contacts the drum with a pressure in a range of 3.0×9.8 mN to 7.0×9.8 mN.

Description:
This application claims priority from Japanese Patent Application No. 2005-260424 filed on Sep. 8, 2005, which is incorporated hereinto by reference. 
   BACKGROUND OF THE INVENTION 
   The present invention relates to a fixing device which fixes a toner image on a recording material and to an image forming apparatus having the fixing device to form an image, such as a coping machine, a printer and a facsimile machine. 
   The image forming apparatus such as the coping machine, the printer, and the facsimile machine utilizing an electro photographic method forms an image on the recording material by transferring a toner image from a surface of an image carrier such as a photoreceptor and an intermediate transfer member and by fixing the transferred toner image. 
   In a fixing device commonly used for in the image forming apparatus, a nip area is formed by 2 rollers including a heat roller and a pressure roller, and the recording material is caused to pass through the nip area to be fixed. In the nip area in the fixing device, there has been occurred a problem that the recording material enwinds the heat roller. To solve the problem, a technology to cause separating claws to make contact with a heat roller surface is proposed. 
   The claw is effective to prevent enwinding, however the claw makes streak line scratches on the heat roller surface. These scratches on the heat roller appear on the image of the recording material as defects, which has been a problem for image forming apparatuses which are required to have high quality. As a technology considering this point of view, there is proposed a separation claw moving device by which the separation claws are able to move in a direction parallel to a rotation axis of the heat roller and may reciprocate in a claw moving area at a constant velocity. 
   [Patent Document 1] Japanese Patent Publication Laid-Open No. HEI 9-160390 
   However, though the separation claws move in the direction parallel to the rotation axis of the heat roller, if the moving velocity of the separation claw (a separation claw&#39;s moving distance along the surface of heat roller per unit time) is low, the scratches which are sufficient to generate the defects in the image on the recording material will occur on the heat roller surface. 
   Also, if the moving velocity of separation claw is high, a problem occurs in performance of separation. This aspect is explained using  FIG. 7 .  FIG. 7  is a drawing showing a status where the separation claws move along the surface of the heat roller. Numeral  1000  is the separation claw and numeral  1001  is the heat roller. The separation claws reciprocates along the surface of heat roller. If the moving velocity of separation claw  1000  is high, there is occurred a phenomenon that one side of separation claw  1000  is lifted (hereinafter called bias contact) as shown in  FIG. 7 . There is no problems in separation performance as long as separation claw  1000  is in contact with heat roller  1001  as shown in  FIG. 7(   a ), however in bias contact condition as shown in  FIG. 7(   b ), the separation claw cannot make contact sufficiently with the recording material adhering to the heat roller sufficiently, and preferable performance of separation cannot be exerted. 
   Therefore, an object of the present invention is to provide a fixing device and an image forming apparatus which prevents the defects of the image and the problem of separation performance of the separation claw, by focusing attention on the moving velocity of the separation claw. 
   SUMMARY OF THE INVENTION 
   To attain the aforesaid object, in the present invention, the moving velocity of the separation claw is made more appropriate. 
   That is, the fixing device related to the present invention includes, a fixing member to fix the toner image onto a recording material, a separation claw to separate the recording material from the fixing member, and a separation claw moving device to move the separation claw along a surface of the fixing member, and the moving velocity V of the separation claw caused by the separation claw moving device satisfies the formula below.
 
1×10 −3  mm/s≦ V≦ 0.1 mm/s
 
   Also, the image forming apparatus of the present invention forms the image by fixing a toner image transferred onto the recording material from an image carrying substance and includes the aforesaid fixing devices. 
   The fixing device and image forming apparatus of the present invention make it possible to realize excellent image forming by reducing defects in the image and to maintain separation performance of separation claw. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cross sectional drawing of an image forming apparatus showing an example embodiment of the present invention. 
       FIG. 2  is an explanatory drawing of a fixing device. 
       FIG. 3  is a plan view of separation claw moving device  100  observed from the top of fixing device  7 . 
       FIG. 4  is a plan view of separation claw moving device  100  observed from fixing member  71  side. 
       FIG. 5  is a drawing showing a cam mechanism to move separation claw  74 . 
       FIG. 6  is a drawing showing a drive system to move separation claw  74 . 
       FIG. 7  is a drawing to explain bias contact phenomenon of the separation claw. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   An embodiment of an image forming apparatus of the present invention will be described below. 
     FIG. 1  is a diagram explaining total configuration of the image forming apparatus. The image forming apparatus shown in  FIG. 1  is composed of duplex document automatic feeding device RADF and image forming apparatus main body A. 
   Duplex document automatic feeding device RADF is located in an upper part of image forming apparatus main body A and able to be opened and closed. A document on document feeding tray a is conveyed by sheet feeding roller b, separation roller c, registration roller d and conveyance drum e. 
   Image forming apparatus main body A is composed of image reading device  1 , control device  2 , image writing device  3 , image forming device  4 , recording material storing device  5 , conveyance transmission device  6 , fixing device  7 , sheet ejecting device  8 , and re-conveyance device  9 . 
   An optical system of image reading device  1  is composed of exposure unit  14  including a light source and a first mirror, V mirror unit  15  including a second mirror and a third mirror, lens  16 , and CCD image sensor  17 . Reading action for the document conveyed by duplex document automatic feeding device RADF is carried out while exposure unit  14  is located below slit exposure glass  13 . Reading action for the document placed on document glass  11  is carried out by moving exposure unit  14  and V mirror unit  15 . 
   An image of the document read by image reading device  1  is processed by control unit  2  and converted to signals as an image data and then stored in a memory. 
   Next, a process of forming an image on recording material P is explained. 
   Photoreceptor  21  is driven by an unillustrated main motor, electric voltage is applied to a surface of the photoreceptor  21  from an unillustrated power source, and the surface of the photoreceptor is charged in positive polarity by discharging of charging device  22  (+800V in the present embodiment). Next, optical writing in accordance with image information is carried out through image writing device  3  and an electrostatic latent image is formed on photoreceptor  21 . When the electrostatic latent image formed passes through developing device  23 , the toner charged in positive polarity in developing device  23  adheres onto the latent image portion by impressing positive polarity developing bias, then a toner image is formed on photoreceptor  21 . The toner image formed is transferred from photoreceptor  21  to recording material P by transfer device  24 A, then recording material P is separated by separating device  24 B. Remaining toner on photoreceptor  21  after transfer is removed by cleaning device  25 . The separated recording material P is conveyed to fixing device  7  composed of a pair of rollers including a pressure roller and a heat roller. As a result, the toner image is fixed on recording material P, then recording material P on which the image is formed is ejected by sheet ejecting device  8  to sheet ejection tray  81  which is located outside the apparatus. 
   Meanwhile, in case of duplex print, recording material P having an image formed on its first surface is conveyed to re-conveyance device  9  by conveyance path change over plate  82  to be reversed. Then after forming an image on the second surface again in image forming device  4 , recording material P is ejected to sheet ejection tray  81  which is located outside the apparatus. 
   In case of inverted ejection of sheet, recording material P is branched from an ordinary sheet path by conveyance path change over plate  82 . Then after being inverted by inverted ejection section  83  through switch back, recording material P is ejected by sheet ejection device  8  to sheet ejection tray  81  which is located outside the apparatus. 
     FIG. 2  is a detailed drawing of fixing device  7 . 
   Fixing device  7  fixes the toner image onto the recording material by making the recording material go through a nip area formed with fixing member  71  and pressure member  72 . 
   Fixing member  71  is a heat roller to melt the toner image on the recording material. Fixing member  71  is, for instance, a roller composed of a hollow aluminum core metal (thickness 14 mm) with a diameter of 70 mm whose outer circumference is covered by silicone rubber (thickness 2 mm) and is coated by PFA (perfluoroalkoxy 30 μm) having a halogen heater inside. 
   Pressure member  72  is, for instance, a roller in which a hollow aluminum core metal (thickness 2 mm) with a diameter of 60 mm whose outer circumference is covered by silicone rubber (thickness 2 mm, hardness 10° (measured by type A durometer of JIS K 6253/ISO 7619)) and is coated by PFA(perfluoroalkoxy 30 μm) is provided. Instead of PFA, PTFE (polytetrafluoroethylene) can be also used for coating. 
   Pressure member  72  is pressed to fixing member  71  with a line pressure of 29.4 N/cm by an unillustrated urging member such as a spring and forms a nip area with elastic distortion. At this stage, a distance of nip area in a lateral direction is about 10.5 mm depending on a line pressure and a hardness of the roller surface. 
   Fixing member  71  rotates at a circumferential velocity of 350 to 410 mm/s in a clockwise direction, and pressure member  72  is pressed against fixing member  71  to be driven to rotate. 
   Cleaning device  73  collects paper dust and toner adhering to the surface of fixing member  71  to clean the surface of fixing member  71 . Web  732  makes contact with the surface of fixing member  71  and winding roller  731  winds web  732 , and thereby toner and paper dust are collected from the surface of fixing member  71 . 
   Separation claw  74  is to separate the recording material adhering on the surface of fixing member  71  to prevent the recording material from wining around fixing member  71 . If separation claw  74  stationary contacts with fixing member  71  at the same position, separation claw  74  will cause the streak line scratch on the surface of fixing roller  71  therefore, separation claw  74  reciprocates left and right along a longitudinal direction of fixing member  71 . 
   Separation claw moving device  100  to move separation claw  74  along the surface of fixing member  71  is explained, referring to  FIG. 3  to  FIG. 5 . 
     FIG. 3  is a top plan view of separation claw moving device  100  observed from upper surface of fixing device  7 , and  FIG. 4  is a side plan view of separation claw moving device  100  observed from fixing member  71  side. 
   As  FIG. 3  shows, a plurality of separation claws is provided along the surface of fixing member  71 . The reason of provision of a plurality of separation claws is to separate recording material from fixing member  71  in good condition. Areas A enclosed by broken lines in  FIG. 4  are positions where separation claws  74  make contact with fixing member  71 . Though two separation claws  74  are shown in each of  FIG. 3  and  FIG. 4 , more than two separation claws  74  may also be provided along the surface of fixing member  71 . 
   An unillustrated opening is provided on a part of separation claw  74 . Separation claw retaining shaft  103  penetrates through the opening. The both ends of separation claw retaining shaft  103  are supported by U-shaped separation claw supporting section  102 . With this structure, separation claw  74  is supported by separation claw support section  102  through separation claw retaining shaft  103 . 
   Separation claw support section  102  is fixed on moving plate  101 , so that, if moving plat  101  moves in a longitudinal direction (a direction shown by arrows in  FIG. 3  and  FIG. 4 ), separation claw support section  102  also moves together with moving plate  101 . As  FIG. 3  shows, both ends of moving plate  101  are bent to form the shape of a U. Each of the bent portions at both ends of moving plate  101  has a plurality of openings (unillustrated) and a plurality of moving plate retaining shafts  107  penetrate through the openings. An end of moving plate retaining shaft  107  is supported by L-shaped moving plate support section  104 . Moving plate urging springs  105  are provided in the vicinity of each moving plate supporting shaft  107  so as to press moving plate  101 . 
   Moving plate  101  is provided with moving shaft  106 . By inserting moving shaft  106  to block channel  204 A to be hereinafter described, separation claws  74  can move in a longitudinal direction. 
     FIG. 5  is a diagram showing a cam mechanism to move separation claws  74 . 
   Numeral  201  shows a camshaft, numeral  202  shows a camshaft gearwheel provided on the camshaft and numeral  203  shows a cam provided on the camshaft. Drive power is transmitted to camshaft  201  through camshaft gearwheel  202  from power source. Cam  203  rotates together with camshaft  201  when camshaft  201  rotates. 
   Numeral  204  is a block which comes in contact with cam  203  and a U-shaped block channel  204 A is provided in a part of block  204 . Also block urging spring  205  is in contact with a part of block  204  to press block  204  rightward in  FIG. 5 . 
   A mechanism in which separation claw  74  moves along the surface of fixing member  71  is explained. Firstly, drive power is transmitted to camshaft  201  through camshaft gearwheel  202  from the power source, then camshaft  201  and cam  203  rotate. When cam  203  rotates, block  204 , which is in contact with cam  203  in area B enclosed by broken lines in  FIG. 5 , moves in a parallel direction to camshaft  201  following the shape of the cam. As moving shaft  106  is inserted in block channel  204 A of block  204 , moving plate  101  moves along with the movement of block  204 . With the above mechanism, separation claw  74  reciprocates in the longitudinal direction along the surface of fixing member  71  as shown by the broken lines in  FIG. 5 . 
     FIG. 6  is a diagram showing a drive system to move separation claw  74 . 
   Numeral  206  is a cleaning gearwheel provided on winding roller  731  (refer  FIG. 2 ). Numeral  208  is a motor, numeral  207  is a drive gearwheel provided on the motor. Drive gearwheel  207  is engaged with cleaning gearwheel  206  through a gearwheel. When drive gearwheel  207  rotates, cleaning device  73  can operates. Also camshaft gearwheel  202  to move separation claw  74  is engaged with drive gearwheel  207 , and by transmitting drive power of motor  208 , separation claw  74  reciprocates in the longitudinal direction along the surface of fixing member  71 . As stated above, the power source to operate winding roller  731  which constructs a part of cleaning device  73 , also moves separation claw  74 , so that there is no need to provide an additional drive motor to move separation claw  74 , which realizes cost reduction and space saving. 
   As explained using  FIG. 3  to  FIG. 6 , separation claw  74  reciprocates in the longitudinal direction (axial direction) along the surface of fixing member  71 . If the moving velocity of separation claw  74  is low, a scratch which can create a defect in the image on the recording material will occur on the surface of fixing member  71 . Therefore, the moving velocity of separation claw  74  which does not create defects in the image of the recording material is studied through experimental tests. The results are shown in Table 1 to Table 3. Meanwhile, the moving velocity of the separation claw means a moving distance of separation claw  74 , which moves along the surface of fixing member  71 , per unit time. 
   
     
       
             
             
             
             
             
             
             
             
             
           
         
             
               TABLE 1 
             
             
                 
             
             
               Material 
               Surface 
                 
                 
                 
                 
                 
                 
                 
             
             
               Of 
               Of 
             
             
               separation 
               fixing 
               Contact 
               Contact 
             
             
               claw 
               member 
               load 
               width 
               V1 
               V2 
               V3 
               V4 
               V5 
             
             
                 
             
           
           
             
               PEEK 
               PFA 
                1 × 9.8 
               1.0 
               A 
               A 
               A 
               A 
               A 
             
             
                 
               Tube 
                1 × 9.8 
               1.5 
               A 
               A 
               A 
               A 
               A 
             
             
                 
                 
                1 × 9.8 
               3.0 
               A 
               A 
               A 
               A 
               A 
             
             
                 
                 
                1 × 9.8 
               4.5 
               A 
               A 
               A 
               A 
               A 
             
             
                 
                 
                5 × 9.8 
               1.0 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
                5 × 9.8 
               1.5 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
                5 × 9.8 
               3.0 
               C 
               B 
               A 
               A 
               A 
             
             
                 
                 
                5 × 9.8 
               4.5 
               B 
               A 
               A 
               A 
               A 
             
             
                 
                 
               10 × 9.8 
               1.0 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
               10 × 9.8 
               1.5 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
               10 × 9.8 
               3.0 
               C 
               B 
               A 
               A 
               A 
             
             
                 
                 
               10 × 9.8 
               4.5 
               C 
               A 
               A 
               A 
               A 
             
             
                 
                 
               20 × 9.8 
               1.0 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
               20 × 9.8 
               1.5 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
               20 × 9.8 
               3.0 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
               20 × 9.8 
               4.5 
               C 
               B 
               A 
               A 
               A 
             
             
                 
               PTEF 
                1 × 9.8 
               1.0 
               A 
               A 
               A 
               A 
               A 
             
             
                 
               coat 
                1 × 9.8 
               1.5 
               A 
               A 
               A 
               A 
               A 
             
             
                 
                 
                1 × 9.8 
               3.0 
               A 
               A 
               A 
               A 
               A 
             
             
                 
                 
                1 × 9.8 
               4.5 
               A 
               A 
               A 
               A 
               A 
             
             
                 
                 
                5 × 9.8 
               1.0 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
                5 × 9.8 
               1.5 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
                5 × 9.8 
               3.0 
               C 
               B 
               A 
               A 
               A 
             
             
                 
                 
                5 × 9.8 
               4.5 
               B 
               A 
               A 
               A 
               A 
             
             
                 
                 
               10 × 9.8 
               1.0 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
               10 × 9.8 
               1.5 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
               10 × 9.8 
               3.0 
               C 
               B 
               A 
               A 
               A 
             
             
                 
                 
               10 × 9.8 
               4.5 
               C 
               A 
               A 
               A 
               A 
             
             
                 
                 
               20 × 9.8 
               1.0 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
               20 × 9.8 
               1.5 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
               20 × 9.8 
               3.0 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
               20 × 9.8 
               4.5 
               C 
               C 
               A 
               A 
               A 
             
             
                 
             
           
        
       
     
   
   
     
       
             
             
             
             
             
             
             
             
             
           
         
             
               TABLE 2 
             
             
                 
             
             
               Material 
               Surface 
                 
                 
                 
                 
                 
                 
                 
             
             
               Of 
               Of 
             
             
               separation 
               fixing 
               Contact 
               Contact 
             
             
               claw 
               member 
               load 
               width 
               V1 
               V2 
               V3 
               V4 
               V5 
             
             
                 
             
           
           
             
               PEEK 
               PFA 
                1 × 9.8 
               1.0 
               A 
               A 
               A 
               A 
               A 
             
             
                 
               Tube 
                1 × 9.8 
               1.5 
               A 
               A 
               A 
               A 
               A 
             
             
                 
                 
                1 × 9.8 
               3.0 
               A 
               A 
               A 
               A 
               A 
             
             
                 
                 
                1 × 9.8 
               4.5 
               A 
               A 
               A 
               A 
               A 
             
             
                 
                 
                5 × 9.8 
               1.0 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
                5 × 9.8 
               1.5 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
                5 × 9.8 
               3.0 
               B 
               B 
               A 
               A 
               A 
             
             
                 
                 
                5 × 9.8 
               4.5 
               B 
               A 
               A 
               A 
               A 
             
             
                 
                 
               10 × 9.8 
               1.0 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
               10 × 9.8 
               1.5 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
               10 × 9.8 
               3.0 
               B 
               B 
               A 
               A 
               A 
             
             
                 
                 
               10 × 9.8 
               4.5 
               B 
               A 
               A 
               A 
               A 
             
             
                 
                 
               20 × 9.8 
               1.0 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
               20 × 9.8 
               1.5 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
               20 × 9.8 
               3.0 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
               20 × 9.8 
               4.5 
               C 
               B 
               A 
               A 
               A 
             
             
                 
               PTEF 
                1 × 9.8 
               1.0 
               A 
               A 
               A 
               A 
               A 
             
             
                 
               coat 
                1 × 9.8 
               1.5 
               A 
               A 
               A 
               A 
               A 
             
             
                 
                 
                1 × 9.8 
               3.0 
               A 
               A 
               A 
               A 
               A 
             
             
                 
                 
                1 × 9.8 
               4.5 
               A 
               A 
               A 
               A 
               A 
             
             
                 
                 
                5 × 9.8 
               1.0 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
                5 × 9.8 
               1.5 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
                5 × 9.8 
               3.0 
               B 
               B 
               A 
               A 
               A 
             
             
                 
                 
                5 × 9.8 
               4.5 
               B 
               A 
               A 
               A 
               A 
             
             
                 
                 
               10 × 9.8 
               1.0 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
               10 × 9.8 
               1.5 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
               10 × 9.8 
               3.0 
               B 
               B 
               A 
               A 
               A 
             
             
                 
                 
               10 × 9.8 
               4.5 
               B 
               A 
               A 
               A 
               A 
             
             
                 
                 
               20 × 9.8 
               1.0 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
               20 × 9.8 
               1.5 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
               20 × 9.8 
               3.0 
               C 
               B 
               A 
               A 
               A 
             
             
                 
                 
               20 × 9.8 
               4.5 
               C 
               B 
               A 
               A 
               A 
             
             
                 
             
           
        
       
     
   
   
     
       
             
             
             
             
             
             
             
             
             
           
         
             
               TABLE 3 
             
             
                 
             
             
               Material 
               Surface 
                 
                 
                 
                 
                 
                 
                 
             
             
               Of 
               Of 
             
             
               separation 
               fixing 
               Contact 
               Contact 
             
             
               claw 
               member 
               load 
               width 
               V1 
               V2 
               V3 
               V4 
               V5 
             
             
                 
             
           
           
             
               PEEK 
               PFA 
                1 × 9.8 
               1.0 
               A 
               A 
               A 
               A 
               A 
             
             
                 
               Tube 
                1 × 9.8 
               1.5 
               A 
               A 
               A 
               A 
               A 
             
             
                 
                 
                1 × 9.8 
               3.0 
               A 
               A 
               A 
               A 
               A 
             
             
                 
                 
                1 × 9.8 
               4.5 
               A 
               A 
               A 
               A 
               A 
             
             
                 
                 
                5 × 9.8 
               1.0 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
                5 × 9.8 
               1.5 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
                5 × 9.8 
               3.0 
               B 
               B 
               A 
               A 
               A 
             
             
                 
                 
                5 × 9.8 
               4.5 
               B 
               A 
               A 
               A 
               A 
             
             
                 
                 
               10 × 9.8 
               1.0 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
               10 × 9.8 
               1.5 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
               10 × 9.8 
               3.0 
               C 
               B 
               A 
               A 
               A 
             
             
                 
                 
               10 × 9.8 
               4.5 
               B 
               A 
               A 
               A 
               A 
             
             
                 
                 
               20 × 9.8 
               1.0 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
               20 × 9.8 
               1.5 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
               20 × 9.8 
               3.0 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
               20 × 9.8 
               4.5 
               C 
               B 
               A 
               A 
               A 
             
             
                 
               PTEF 
                1 × 9.8 
               1.0 
               A 
               A 
               A 
               A 
               A 
             
             
                 
               coat 
                1 × 9.8 
               1.5 
               A 
               A 
               A 
               A 
               A 
             
             
                 
                 
                1 × 9.8 
               3.0 
               A 
               A 
               A 
               A 
               A 
             
             
                 
                 
                1 × 9.8 
               4.5 
               A 
               A 
               A 
               A 
               A 
             
             
                 
                 
                5 × 9.8 
               1.0 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
                5 × 9.8 
               1.5 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
                5 × 9.8 
               3.0 
               B 
               B 
               A 
               A 
               A 
             
             
                 
                 
                5 × 9.8 
               4.5 
               B 
               A 
               A 
               A 
               A 
             
             
                 
                 
               10 × 9.8 
               1.0 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
               10 × 9.8 
               1.5 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
               10 × 9.8 
               3.0 
               C 
               B 
               A 
               A 
               A 
             
             
                 
                 
               10 × 9.8 
               4.5 
               B 
               A 
               A 
               A 
               A 
             
             
                 
                 
               20 × 9.8 
               1.0 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
               20 × 9.8 
               1.5 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
               20 × 9.8 
               3.0 
               C 
               C 
               A 
               A 
               A 
             
             
                 
                 
               20 × 9.8 
               4.5 
               C 
               C 
               A 
               A 
               A 
             
             
                 
             
           
        
       
     
   
   As the factors to create the scratches on the surface of fixing member  71 , moving velocity of separation claw  74 , a material of separation claw  74 , a surface layer of fixing material  71 , a contact load on separation claw  74 , and a contact width of separation claw  74  are presumed. Therefore, the experimental tests were carried out combining these factors. The moving velocity of separation claw  74  was varied in 5 steps, i.e. V 1  (5×10 4  mm/s), V 2  (7.5×10 −4  mm/s), V 3  (1×10 −3  mm/s), V 4  (1.6×10 −3  mm/s) and V 5  (2×10 −3  mm/s). As the materials of separation claw, 3 kinds i.e. PEEK (polyehter etherketone), PAI (polyamidoimide) and PI (polyimide) were used. As the surface layer of fixing member  71 , PFA tube and PTFE coating were used. The contact load of separation claw  74  was varied in 4 steps i.e. 1×9.8 mN, 5×9.8 mN, 10×9.8 mN and 20×9.8 mN, and the contact width of separation claw  74  was varied in 4 steps i.e. 1 mm, 1.5 mm, 3 mm and 4.5 mm, in the experimental test. The image on the 100,000th solid black print was used for evaluation. In the tables, A means that no image defects caused by separation claw  74  exist, B means that slight image defects caused by separation claw  74  exist and C means that image defects caused by separation claw  74  exist. As the results of the experiments in the table 1 to table 3 show, it was found that if the velocity of separation claw  74  is not less than 1×10 −3  mm/s, no image defects exist irrespective of combination of the materials of separation claw  74 . 
   On the other hand, if the velocity of separation claw  74  is high, the aforesaid bias contact phenomenon and a problem in separation performance of the separation claw occurred. Thus, the moving velocity of separation claw to reduce the bias contact phenomenon and to maintain separation performance was studied through experimental tests. The results are shown in the Table 4. 
                                             TABLE 4                       Moving velocity of the               separation claw (mm/s)   Bias contact phenomenon                                        0.01   A           0.05   A           0.06   A           0.08   A           0.1   A           0.12   B           0.15   C           0.2   C           0.3   C                        
A: Not occurred, B: Slightly occurred, C: Occurred
 
   The velocity of separation claw  74  was varied in 9 steps in the experimental tests. As the results in Table 4 show, it was found that if the velocity of separation claw  74  is not more than 0.1 mm/s, the bias contact phenomenon does not occur. 
   Also, the occurrence rate of scratch can be reduced, by adjusting the contact load and the contact width of separation claw  74 . Therefore, Table 5 shows the results of the experimental test where the contact width and the contact load were varied. 
   The contact load of separation claw  74  was in a range of 1×9.8 mN to 5×9.8 mN and the contact width of separation claw  74  was varied in 6 steps i.e. 0.5 mm, 1.0 mm, 1.5 mm, 3.0 mm, 4.5 mm and 5.0 mm to carry out the experimental test. Also, 3 kinds of the material of separation claw i.e. 74 PEEK, PAI and PI, and 2 kinds of the surface layer of the fixing member PFA tube and PTFE coating were used. 
   The contact efficiency in Table 5 is an index indicates whether or not separation claw  74  and the fixing member are in stable contact. If the contact load is low and the contact width of separation claw  74  is narrow, defects such as bias contact occur. Also, if the contact load is low, sheet separation performance decreases. In Table 5, “A” means separation claw  74  and the fixing member are in stable contact, “B” means the contact is rather unstable and “C” means the contact is unstable and defects occur. 
   The occurrence rate of scratches in Table 5 is an index indicates whether or not separation claw  74  cuts into the fixing member. For example, if the contact load is high, scratches occur on the fixing member in a process of releasing of guide plate (not illustrated) of separation claw  74  from contact. In Table 5, “A” means no adverse affect by separation claw  74  to the fixing member, “B” means there is a possibility of occurring scratches and “C” means scratches occur on the fixing member. Meanwhile, if the width of separation claw is lager than 5.0 mm, other mechanisms need to be modified. 
   From the results of Table 5, by setting contact load P of separation claw  74  as 3.0×9.8 mN≦P≦7.0×9.8 mN and by setting the width W of claw  74  as 1.0 mm≦W≦5.0 mm, scratches on the fixing member can be prevented and defects in images can be reduced. Also, the experimental test of Table 5 was carried out while separation claw  74  is fixed however, by setting the moving velocity of separation claw  74  in the aforesaid range, it is needless to say that better images with less defects can be formed. 
   
     
       
             
             
             
             
             
           
         
             
                 
               TABLE 5 
             
             
                 
                 
             
             
                 
               Contact 
               Contact 
               Contact 
               Occurrence rate 
             
             
                 
               load 
               width 
               efficiency 
               of scratch 
             
             
                 
                 
             
           
           
             
                 
                 1 × 9.8 
               0.5 
               C 
               A 
             
             
                 
                 1 × 9.8 
               1.0 
               C 
               A 
             
             
                 
                 1 × 9.8 
               1.5 
               C 
               A 
             
             
                 
                 1 × 9.8 
               3.0 
               C 
               A 
             
             
                 
                 1 × 9.8 
               4.5 
               C 
               A 
             
             
                 
                 1 × 9.8 
               5.0 
               C 
               A 
             
             
                 
               1.5 × 9.8 
               0.5 
               C 
               A 
             
             
                 
               1.5 × 9.8 
               1.0 
               B 
               A 
             
             
                 
               1.5 × 9.8 
               1.5 
               B 
               A 
             
             
                 
               1.5 × 9.8 
               3.0 
               B 
               A 
             
             
                 
               1.5 × 9.8 
               4.5 
               B 
               A 
             
             
                 
               1.5 × 9.8 
               5.0 
               B 
               A 
             
             
                 
                 2 × 9.8 
               0.5 
               C 
               A 
             
             
                 
                 2 × 9.8 
               1.0 
               C 
               A 
             
             
                 
                 2 × 9.8 
               1.5 
               B 
               A 
             
             
                 
                 2 × 9.8 
               3.0 
               B 
               A 
             
             
                 
                 2 × 9.8 
               4.5 
               B 
               A 
             
             
                 
                 2 × 9.8 
               5.0 
               B 
               A 
             
             
                 
               2.5 × 9.8 
               0.5 
               C 
               A 
             
             
                 
               2.5 × 9.8 
               1.0 
               C 
               A 
             
             
                 
               2.5 × 9.8 
               1.5 
               B 
               A 
             
             
                 
               2.5 × 9.8 
               3.0 
               B 
               A 
             
             
                 
               2.5 × 9.8 
               4.5 
               B 
               A 
             
             
                 
               2.5 × 9.8 
               5.0 
               B 
               A 
             
             
                 
                 3 × 9.8 
               0.5 
               C 
               A 
             
             
                 
                 3 × 9.8 
               1.0 
               A 
               A 
             
             
                 
                 3 × 9.8 
               1.5 
               A 
               A 
             
             
                 
                 3 × 9.8 
               3.0 
               A 
               A 
             
             
                 
                 3 × 9.8 
               4.5 
               A 
               A 
             
             
                 
                 3 × 9.8 
               5.0 
               A 
               A 
             
             
                 
               3.5 × 9.8 
               0.5 
               C 
               A 
             
             
                 
               3.5 × 9.8 
               1.0 
               A 
               A 
             
             
                 
               3.5 × 9.8 
               1.5 
               A 
               A 
             
             
                 
               3.5 × 9.8 
               3.0 
               A 
               A 
             
             
                 
               3.5 × 9.8 
               4.5 
               A 
               A 
             
             
                 
               3.5 × 9.8 
               5.0 
               A 
               A 
             
             
                 
                 4 × 9.8 
               0.5 
               C 
               A 
             
             
                 
                 4 × 9.8 
               1.0 
               A 
               A 
             
             
                 
                 4 × 9.8 
               1.5 
               A 
               A 
             
             
                 
                 4 × 9.8 
               3.0 
               A 
               A 
             
             
                 
                 4 × 9.8 
               4.5 
               A 
               A 
             
             
                 
                 4 × 9.8 
               5.0 
               A 
               A 
             
             
                 
               4.5 × 9.8 
               0.5 
               C 
               A 
             
             
                 
               4.5 × 9.8 
               1.0 
               A 
               A 
             
             
                 
               4.5 × 9.8 
               1.5 
               A 
               A 
             
             
                 
               4.5 × 9.8 
               3.0 
               A 
               A 
             
             
                 
               4.5 × 9.8 
               4.5 
               A 
               A 
             
             
                 
               4.5 × 9.8 
               5.0 
               A 
               A 
             
             
                 
                 5 × 9.8 
               0.5 
               C 
               A 
             
             
                 
                 5 × 9.8 
               1.0 
               A 
               A 
             
             
                 
                 5 × 9.8 
               1.5 
               A 
               A 
             
             
                 
                 5 × 9.8 
               3.0 
               A 
               A 
             
             
                 
                 5 × 9.8 
               4.5 
               A 
               A 
             
             
                 
                 5 × 9.8 
               5.0 
               A 
               A 
             
             
                 
               5.5 × 9.8 
               0.5 
               C 
               A 
             
             
                 
               5.5 × 9.8 
               1.0 
               A 
               A 
             
             
                 
               5.5 × 9.8 
               1.5 
               A 
               A 
             
             
                 
               5.5 × 9.8 
               3.0 
               A 
               A 
             
             
                 
               5.5 × 9.8 
               4.5 
               A 
               A 
             
             
                 
               5.5 × 9.8 
               5.0 
               A 
               A 
             
             
                 
                 6 × 9.8 
               0.5 
               C 
               A 
             
             
                 
                 6 × 9.8 
               1.0 
               A 
               A 
             
             
                 
                 6 × 9.8 
               1.5 
               A 
               A 
             
             
                 
                 6 × 9.8 
               3.0 
               A 
               A 
             
             
                 
                 6 × 9.8 
               4.5 
               A 
               A 
             
             
                 
                 6 × 9.8 
               5.0 
               A 
               A 
             
             
                 
               6.5 × 9.8 
               0.5 
               C 
               A 
             
             
                 
               6.5 × 9.8 
               1.0 
               A 
               A 
             
             
                 
               6.5 × 9.8 
               1.5 
               A 
               A 
             
             
                 
               6.5 × 9.8 
               3.0 
               A 
               A 
             
             
                 
               6.5 × 9.8 
               4.5 
               A 
               A 
             
             
                 
               6.5 × 9.8 
               5.0 
               A 
               A 
             
             
                 
                 7 × 9.8 
               0.5 
               C 
               A 
             
             
                 
                 7 × 9.8 
               1.0 
               A 
               A 
             
             
                 
                 7 × 9.8 
               1.5 
               A 
               A 
             
             
                 
                 7 × 9.8 
               3.0 
               A 
               A 
             
             
                 
                 7 × 9.8 
               4.5 
               A 
               A 
             
             
                 
                 7 × 9.8 
               5.0 
               A 
               A 
             
             
                 
               7.5 × 9.8 
               0.5 
               C 
               A 
             
             
                 
               7.5 × 9.8 
               1.0 
               A 
               A 
             
             
                 
               7.5 × 9.8 
               1.5 
               A 
               A 
             
             
                 
               7.5 × 9.8 
               3.0 
               A 
               A 
             
             
                 
               7.5 × 9.8 
               4.5 
               A 
               A 
             
             
                 
               7.5 × 9.8 
               5.0 
               A 
               A 
             
             
                 
                 8 × 9.8 
               0.5 
               C 
               A 
             
             
                 
                 8 × 9.8 
               1.0 
               A 
               A 
             
             
                 
                 8 × 9.8 
               1.5 
               A 
               A 
             
             
                 
                 8 × 9.8 
               3.0 
               A 
               A 
             
             
                 
                 8 × 9.8 
               4.5 
               A 
               A 
             
             
                 
                 8 × 9.8 
               5.0 
               A 
               A 
             
             
                 
               8.5 × 9.8 
               0.5 
               C 
               A 
             
             
                 
               8.5 × 9.8 
               1.0 
               A 
               A 
             
             
                 
               8.5 × 9.8 
               1.5 
               A 
               A 
             
             
                 
               8.5 × 9.8 
               3.0 
               A 
               A 
             
             
                 
               8.5 × 9.8 
               4.5 
               A 
               A 
             
             
                 
               8.5 × 9.8 
               5.0 
               A 
               A 
             
             
                 
                 9 × 9.8 
               0.5 
               C 
               A 
             
             
                 
                 9 × 9.8 
               1.0 
               A 
               A 
             
             
                 
                 9 × 9.8 
               1.5 
               A 
               A 
             
             
                 
                 9 × 9.8 
               3.0 
               A 
               A 
             
             
                 
                 9 × 9.8 
               4.5 
               A 
               A 
             
             
                 
                 9 × 9.8 
               5.0 
               A 
               A 
             
             
                 
               9.5 × 9.8 
               0.5 
               C 
               A 
             
             
                 
               9.5 × 9.8 
               1.0 
               A 
               A 
             
             
                 
               9.5 × 9.8 
               1.5 
               A 
               A 
             
             
                 
               9.5 × 9.8 
               3.0 
               A 
               A 
             
             
                 
               9.5 × 9.8 
               4.5 
               A 
               A 
             
             
                 
               9.5 × 9.8 
               5.0 
               A 
               A 
             
             
                 
                10 × 9.8 
               0.5 
               C 
               A 
             
             
                 
                10 × 9.8 
               1.0 
               A 
               A 
             
             
                 
                10 × 9.8 
               1.5 
               A 
               A 
             
             
                 
                10 × 9.8 
               3.0 
               A 
               A 
             
             
                 
                10 × 9.8 
               4.5 
               A 
               A 
             
             
                 
                10 × 9.8 
               5.0 
               A 
               A 
             
             
                 
               10.5 × 9.8  
               0.5 
               C 
               B 
             
             
                 
               10.5 × 9.8  
               1.0 
               A 
               B 
             
             
                 
               10.5 × 9.8  
               1.5 
               A 
               B 
             
             
                 
               10.5 × 9.8  
               3.0 
               A 
               B 
             
             
                 
               10.5 × 9.8  
               4.5 
               A 
               B 
             
             
                 
               10.5 × 9.8  
               5.0 
               A 
               B 
             
             
                 
                11 × 9.8 
               0.5 
               C 
               B 
             
             
                 
                11 × 9.8 
               1.0 
               A 
               B 
             
             
                 
                11 × 9.8 
               1.5 
               A 
               B 
             
             
                 
                11 × 9.8 
               3.0 
               A 
               B 
             
             
                 
                11 × 9.8 
               4.5 
               A 
               B 
             
             
                 
                11 × 9.8 
               5.0 
               A 
               B 
             
             
                 
               11.5 × 9.8  
               0.5 
               C 
               B 
             
             
                 
               11.5 × 9.8  
               1.0 
               A 
               B 
             
             
                 
               11.5 × 9.8  
               1.5 
               A 
               B 
             
             
                 
               11.5 × 9.8  
               3.0 
               A 
               B 
             
             
                 
               11.5 × 9.8  
               4.5 
               A 
               B 
             
             
                 
               11.5 × 9.8  
               5.0 
               A 
               B 
             
             
                 
                12 × 9.8 
               0.5 
               C 
               B 
             
             
                 
                12 × 9.8 
               1.0 
               A 
               B 
             
             
                 
                12 × 9.8 
               1.5 
               A 
               B 
             
             
                 
                12 × 9.8 
               3.0 
               A 
               B 
             
             
                 
                12 × 9.8 
               4.5 
               A 
               B 
             
             
                 
                12 × 9.8 
               5.0 
               A 
               B 
             
             
                 
               12.5 × 9.8  
               0.5 
               C 
               B 
             
             
                 
               12.5 × 9.8  
               1.0 
               A 
               B 
             
             
                 
               12.5 × 9.8  
               1.5 
               A 
               B 
             
             
                 
               12.5 × 9.8  
               3.0 
               A 
               B 
             
             
                 
               12.5 × 9.8  
               4.5 
               A 
               B 
             
             
                 
               12.5 × 9.8  
               5.0 
               A 
               B 
             
             
                 
                13 × 9.8 
               0.5 
               C 
               B 
             
             
                 
                13 × 9.8 
               1.0 
               A 
               B 
             
             
                 
                13 × 9.8 
               1.5 
               A 
               B 
             
             
                 
                13 × 9.8 
               3.0 
               A 
               B 
             
             
                 
                13 × 9.8 
               4.5 
               A 
               B 
             
             
                 
                13 × 9.8 
               5.0 
               A 
               B 
             
             
                 
               13.5 × 9.8  
               0.5 
               C 
               B 
             
             
                 
               13.5 × 9.8  
               1.0 
               A 
               B 
             
             
                 
               13.5 × 9.8  
               1.5 
               A 
               B 
             
             
                 
               13.5 × 9.8  
               3.0 
               A 
               B 
             
             
                 
               13.5 × 9.8  
               4.5 
               A 
               B 
             
             
                 
               13.5 × 9.8  
               5.0 
               A 
               B 
             
             
                 
                14 × 9.8 
               0.5 
               C 
               C 
             
             
                 
                14 × 9.8 
               1.0 
               A 
               C 
             
             
                 
                14 × 9.8 
               1.5 
               A 
               C 
             
             
                 
                14 × 9.8 
               3.0 
               A 
               C 
             
             
                 
                14 × 9.8 
               4.5 
               A 
               C 
             
             
                 
                14 × 9.8 
               5.0 
               A 
               C 
             
             
                 
               14.5 × 9.8  
               0.5 
               C 
               C 
             
             
                 
               14.5 × 9.8  
               1.0 
               A 
               C 
             
             
                 
               14.5 × 9.8  
               1.5 
               A 
               C 
             
             
                 
               14.5 × 9.8  
               3.0 
               A 
               C 
             
             
                 
               14.5 × 9.8  
               4.5 
               A 
               C 
             
             
                 
               14.5 × 9.8  
               5.0 
               A 
               C 
             
             
                 
                15 × 9.8 
               0.5 
               C 
               C 
             
             
                 
                15 × 9.8 
               1.0 
               A 
               C 
             
             
                 
                15 × 9.8 
               1.5 
               A 
               C 
             
             
                 
                15 × 9.8 
               3.0 
               A 
               C 
             
             
                 
                15 × 9.8 
               4.5 
               A 
               C 
             
             
                 
                15 × 9.8 
               5.0 
               A 
               C 
             
             
                 
               15.5 × 9.8  
               0.5 
               C 
               C 
             
             
                 
               15.5 × 9.8  
               1.0 
               A 
               C 
             
             
                 
               15.5 × 9.8  
               1.5 
               A 
               C 
             
             
                 
               15.5 × 9.8  
               3.0 
               A 
               C 
             
             
                 
               15.5 × 9.8  
               4.5 
               A 
               C 
             
             
                 
               15.5 × 9.8  
               5.0 
               A 
               C 
             
             
                 
                 
             
           
        
       
     
   
   From the above results, if the velocity of separation claw  74  is set in a range of 1×10 −3  mm/s≦V≦0.1 mm/s, excellent image forming where defects are reduced can be realized, and separation performance by the separation claw can be well maintained. 
   Meanwhile, the present invention is not to be considered limited to the embodiments shown in the drawings and described in the specification, and it can naturally exhibit its effect even for other embodiments of fixing devices and image forming apparatuses.