Patent Publication Number: US-8537192-B2

Title: Exposure device, image forming apparatus and mirror adjusting method

Description:
This application is also based upon and claims the benefit of priority from U.S. provisional application 61/326,555, filed on Apr. 21, 2010; the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     Embodiments described herein relate generally to an exposure device, an image forming apparatus and a mirror adjusting method. 
     BACKGROUND 
     In an optical system in which light emitted from a light source reaches an object, a mirror is used. When a position where the mirror is mounted is shifted, or the light incident on the mirror is deviated, the direction (angle) of the mirror is required to be adjusted in order to cause the light reflected by the mirror to be sent in a specified direction. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view showing an inner structure of an image forming apparatus. 
         FIG. 2  is a view showing a structure of a printer part. 
         FIG. 3  is a view showing a structure of a part of an exposure device. 
         FIG. 4  is an enlarged view of an area R 1  of  FIG. 2 . 
         FIG. 5  is an enlarged view of an area R 2  of  FIG. 2 . 
         FIG. 6  is an exploded view of a mirror unit of a first embodiment. 
         FIG. 7  is a view showing a structure of adjusting a direction of a mirror in the first embodiment. 
         FIG. 8  is a view for explaining a method of adjusting the direction of the mirror in the first embodiment. 
         FIG. 9  is an outer appearance view of a mirror unit of a second embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     According to an embodiment, an exposure device includes a mirror to reflect light used for exposure of an object, a holder to hold the mirror, an adhesive that bonds the mirror to the holder and elastically deforms, and an adjusting tool that pushes the mirror to change a direction of the mirror. 
     First Embodiment 
       FIG. 1  is a view showing an inner structure of an image forming apparatus of a first embodiment.  FIG. 2  is a view showing a structure of a printer part. A document table is provided at an upper part of a main body  11  of an image forming apparatus  10 , and an auto document feeder  12  is provided over the document table. The auto document feeder  12  feeds a document to the document table. An operation panel  13  is provided at an upper part of the main body  11 . The operation panel  13  includes an operation part  14  including various keys and a display part  15 . 
     A scanner  16  reads a document placed on the document table and generates image data. A printer part  17  forms an image corresponding to inputted image data onto a sheet. The image data includes image data generated by the scanner  16 , and image data transmitted from an external equipment such as a PC (Personal Computer) to the image forming apparatus  10 . 
     The printer part  17  includes image forming parts  20 Y,  20 M,  20 C and  20 K of respective colors of yellow (Y), magenta (M), cyan (C) and black (K). The image forming parts  20 Y to  20 K are disposed along an intermediate transfer belt  21 . 
     The image forming parts  20 Y to  20 K include photoconductive drums  22 Y to  22 K. A charging charger  23 Y, a developing unit  24 Y, a primary transfer roller  25 Y, a cleaner  26 Y and a blade  27 Y are disposed around the photoconductive drum  22 Y. Similarly to the photoconductive drum  22 Y, a charging charger and the like are disposed around the photoconductive drums  22 M to  22 K. 
     A laser beam irradiated from an exposure device  19  and corresponding to yellow reaches an exposure position of the photoconductive drum  22 Y. An electrostatic latent image is formed on the surface of the photoconductive drum  22 Y by the laser beam. The charging charger  23 Y charges the surface of the photoconductive drum  22 Y. The developing unit  24 Y supplies toner to the photoconductive drum  22 Y. The cleaner  26 Y uses the blade  27 Y and removes toner remaining on the surface of the photoconductive drum  22 Y. 
     A toner cartridge  28  is provided above the image forming parts  20 Y to  20 K. The toner cartridge  28  supplies toner to the developing units  24 Y,  24 M,  24 C and  24 K. The toner cartridge  28  includes toner cartridges  28 Y,  28 M,  28 C and  28 K containing toners of the respective colors of yellow (Y), magenta (M), cyan (C) and black (K). 
     The intermediate transfer belt  21  is stretched over a drive roller  31  and driven rollers  32  and  33 , and is in contact with the photoconductive drums  22 Y to  22 K. The primary transfer roller  25 Y applies a primary transfer voltage to the intermediate transfer belt  21  and transfers the toner image of the photoconductive drum  22 Y to the intermediate transfer belt  21 . The toner images of the photoconductive drums  22 M to  22 K are also transferred to the intermediate transfer belt  21  by the primary transfer roller. 
     A secondary transfer roller  34  is provided at a position opposite to the drive roller  31 . When a sheet S passes between the drive roller  31  and the secondary transfer roller  34 , the secondary transfer roller  34  applies a secondary transfer voltage to the intermediate transfer belt  21 , and transfers the toner images on the intermediate transfer belt  21  to the sheet S. A belt cleaner  35  is provided at a position opposite to the driven roller  33 . 
     The exposure device  19  irradiates and scans a laser beam corresponding to image information to the photoconductive drums  22 Y to  22 K. Electrostatic latent images corresponding to the respective colors (Y, M, C, K) are formed on the photoconductive drums  22 Y to  22 K by the laser beam. 
     The main body  11  includes plural paper feed cassettes  18 . The paper feed cassettes  18  contain plural sheets. A separation roller  36  takes out the sheet S contained in the paper feed cassette  18 . A conveyance roller  37  conveys the sheet from the paper feed cassette  18  to the secondary transfer roller  34 . 
     A fixing unit  38  heats the sheet S conveyed from the secondary transfer roller  34 , and fixes the image to the sheet S. The sheet passing through the fixing unit  38  is discharged to a tray  39 . 
     In this embodiment, a direction of a mirror is adjusted, and as the mirror, there is a mirror used in the exposure device  19 .  FIG. 3  is an outer appearance view of a part of the exposure device  19 , and mirrors are arranged in portions surrounded by areas R 1  and R 2 . 
       FIG. 4  is an enlarged view of the area R 1  of  FIG. 3 . A mirror  101  reflects a laser beam L scanned by a polygon mirror to a condenser lens  102 . The condenser lens  102  focuses the laser beam L from the mirror  101  on a horizontal synchronization sensor  103 . 
     The horizontal synchronization sensor  103  receives the laser beam L, and outputs a horizontal synchronization signal. A case  104  of the exposure device  19  holds the mirror  101 , and can be formed of, for example, resin. 
       FIG. 5  is an enlarged view of the area R 2  of  FIG. 3 . Mirrors  105  and  106  reflect a laser beam from a corresponding light source to a polygon mirror  107 . A case  108  of the exposure device  109  holds the mirrors  105  and  106 , and can be formed of, for example, metal (aluminum die casting). 
     A structure of adjusting the direction of the mirror will be described.  FIG. 6  is an exploded view of a mirror unit. In  FIG. 6 , an X-axis, a Y-axis and a Z-axis are axes perpendicular to each other. The relation between the X-axis, the Y-axis and the Z-axis is the same also in  FIG. 7  and  FIG. 8 . 
     A holder  220  holds a mirror  210 . The mirror  210  corresponds to the mirror  101 ,  105  or  106  explained in  FIG. 4  and  FIG. 5 . A surface  211  of the mirror  210  is a reflecting surface to reflect a laser beam. In this embodiment, although the surface  211  of the mirror  210  is a flat surface, the surface  211  may be a curved surface. The curved surface may be a concave surface or a convex surface. 
     The holder  220  includes a containing part  221  to contain the mirror  210 . The holder  220  includes four projections  222  and  223  in an area surrounding the mirror  210 . The projections  222  and  223  protrude to the inside of the holder  220 , and contact the outer edge (side surface) of the mirror  210 . 
     The two projections  222  contact the mirror  210 , so that the mirror  210  can be positioned in the Y direction. The two projections  223  contact the mirror  210 , so that the mirror  210  can be positioned in the Z direction. 
     In this embodiment, although the projections  222  and  223  are provided at the positions corresponding to the four sides of the mirror  210 , the positions where the projections  222  and  223  are provided and the number thereof can be appropriately set. It is sufficient if the mirror  210  can be positioned in at least one of the Y direction and the Z direction. 
     For example, only the projections  222  may be provided, or only the projections  223  may be provided. In this embodiment, although the two projections  222  are opposite to each other in the Y direction, the two projections  222  may not be opposite to each other in the Y direction. The two projections  223  may also not be opposite to each other in the Z direction. 
     The holder  220  includes three first cylindrical parts  224  at the inside of the containing part  221 . The first cylindrical part  224  extends in the X direction, and a screw groove  225  is formed on the inner surface of the first cylindrical part  224 . Three second cylindrical parts  226  are provided on the outer surface of the holder  220 , and the second cylindrical parts  226  extend in the X direction. 
     The second cylindrical part  226  is provided on an extended line of the first cylindrical part  224 . The screw groove  225  passes through the holder  220 , and is also formed on the inner peripheral surface of the second cylindrical part  226 . 
     A pin  230  as an adjusting tool includes a screw part  231  engaging with the screw groove  225 . A tip  232  of the pin  230  is formed of a curved surface (hemisphere face). The pin  230  is inserted into the screw groove  225  from the side of the second cylindrical part  226 . When the pin  230  rotates in the state where the screw part  231  and the screw groove  225  are engaged with each other, the tip  232  of the pin  230  protrudes from the tip of the first cylindrical part  224  (see  FIG. 7 ). 
     When the position where the screw groove  225  engages with the screw part  231  is changed, the pin  230  can be moved in the X direction with respect to the holder  220 . When the pin  230  is moved in the X direction, the protrusion amount of the pin  230  from the first cylindrical part  224  can be changed. 
     The tip  232  of the pin  230  protruding from the first cylindrical part  224  contacts the mirror  210 . Specifically, the tip  232  of the pin  230  contacts a rear surface of the mirror  210 . The rear surface of the mirror  210  is the surface opposite to the front surface (reflecting surface)  211  in the X direction. The rear surface of the mirror  210  is a flat surface. 
     As shown in  FIG. 7 , an adhesive  240  is applied to the containing part  221 . The thickness (length in the X direction) of the layer of the adhesive  240  is equal to the length of the first cylindrical part  224  in the X direction. Accordingly, the adhesive  240  does not enter the inside of the first cylindrical part  224  and does not contact the pin  230 . 
     The adhesive  240  applied to the containing part  221  contacts the rear surface of the mirror  210 . The adhesive  240  bonds the mirror  210  to the holder  220 . The adhesive  240  used in this embodiment can elastically deform after the adhesive  240  is cured. 
     As the adhesive  240 , for example, the adhesive shown in Table 1 can be used. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Manufacturing  
                 Product  
                   
                   
                   
               
               
                 company 
                 name 
                 Main ingredient 
                 Bonding strength 
                 Extension 
               
               
                   
               
             
            
               
                 Cemedine  
                 PM100 
                 Modified silicone 
                 0.91 [N/mm{circumflex over ( )}2] 
                 200[%] 
               
               
                 Co., Ltd. 
                 PM155 
                 Epoxy + Modified  
                  2.1 [N/mm{circumflex over ( )}2] 
                 180[%] 
               
               
                   
                   
                 silicone 
                   
                   
               
               
                   
                 PM165 
                 Modified silicone 
                  2.1 [N/mm{circumflex over ( )}2] 
                 100[%] 
               
               
                   
                 PM300 
                 Ethyl  
                  2.0 [N/mm{circumflex over ( )}2] 
                 170[%] 
               
               
                   
                   
                 cyanoacrylate 
                   
                   
               
               
                   
                 PM200 
                 Epoxy + Modified  
                  5.4 [N/mm{circumflex over ( )}2] 
                 140[%] 
               
               
                   
                   
                 silicone 
                   
                   
               
               
                   
                 Super X 
                 Acrylic modified  
                  3.7 [N/mm{circumflex over ( )}2] 
                 220[%] 
               
               
                   
                   
                 silicone 
                   
                   
               
               
                 ThreeBond  
                 1530 
                 Special polymer 
                  5.9 [MPa] 
                 280[%] 
               
               
                 Co., Ltd. 
                   
                 containing silyl  
                   
                   
               
               
                   
                   
                 group 
                   
                   
               
               
                   
                 1530B 
                 Special polymer 
                  3.0 [MPa] 
                 380[%] 
               
               
                   
                   
                 containing silyl  
                   
                   
               
               
                   
                   
                 group 
                   
                   
               
               
                   
                 1530C 
                 Special polymer 
                  4.1 [MPa] 
                 200[%] 
               
               
                   
                   
                 containing silyl  
                   
                   
               
               
                   
                   
                 group 
                   
                   
               
               
                   
                 1532 
                 Modified silicone 
                  1.8 [MPa] 
                 360[%] 
               
               
                   
               
            
           
         
       
     
     The bonding strength shown in Table 1 includes tensile bonding strength and shear bonding strength. The tensile bonding strength is a tensile load per unit area when the adhesion is broken when a tensile force acts in a direction perpendicular to the adhesive surface of the adhesive. The shear bonding strength is the magnitude of force when the adhesion is broken when the force acts in a direction parallel to the adhesive surface of the adhesive. 
     The movement amount of the mirror  210  when the direction of the mirror  210  is adjusted, the bonding strength and the extension of the adhesive  240  are considered, and the specific adhesive  240  can be determined. 
     After the holder  220  and the mirror  210  are bonded to each other by the adhesive  240 , when at least one pin  230  of the three pins  230  is moved in the X direction, the direction of the mirror  210  can be changed. 
     Specifically, when the pin  230  is moved in the X direction and pushes the mirror  210 , the direction of the mirror  210  can be changed. The adhesive  240  to bond the mirror  210  to the holder  220  is deformed according to the change of the direction of the mirror  210 . A part of the adhesive  240  expands according to the displacement of the mirror  210 . 
     In  FIG. 8 , among the three pins  230 , only one pin  230  positioned above is moved in an arrow D (X) direction. Before the pin  230  is moved in the arrow D (X) direction, a laser beam L 1  incident on the mirror  210  is reflected by the mirror  210  and advances along an optical path L 2 . 
     After the pin  230  is moved in the arrow D (X) direction, the laser beam L 1  incident on the mirror  210  is reflected by the mirror  210  and advances along a light path L 3 . As shown in  FIG. 8 , the direction of the mirror  210  is changed by moving the pin  230  in the arrow D (X) direction, and the movement direction of the laser beam reflected by the mirror  210  can be changed. 
     According to this embodiment, among the three pins  230 , at least one pin  230  is moved in the X direction and pushes the mirror  210 , so that the direction of the mirror  210  can be changed. When the three pins  230  are used, the direction of the mirror  210  can be changed in various directions. 
     Since the tip  232  of the pin  230  is formed of the curved surface (convex surface), even if the direction of the mirror  210  is changed, a part of the tip  232  can be kept to contact the mirror  210 . When the three pins  230  are moved in the same direction by the same amount, the mirror  210  can be moved in the X direction without changing the direction of the mirror  210 . 
     Even if the pin  230  pushes the mirror  210 , since the mirror  210  and the holder  220  remain to be bonded by the adhesive  240 , the mirror  210  does not come off from the holder  220 . The pin  230  can be held at a desired position by engaging the screw part  231  of the pin  230  with the screw groove  225 . 
     The protrusion amount of the pin  230  from the first cylindrical part  224  can be finely adjusted according to the rotation amount of the pin  230 . When the protrusion amount of the pin  230  is finely adjusted, the direction of the mirror  210  can be finely adjusted. 
     In this embodiment, although the adhesive  240  is applied to the whole area of the containing part  221  except for the first cylindrical parts  224 , the area to which the adhesive  240  is applied can be appropriately set. It is sufficient if the adhesive  240  bonds the mirror  210  to the holder  220 , and can allow the movement of the mirror  210  by the elastic deformation. The adhesive  240  can be applied to only a partial area of the area of the containing part  221  except for the first cylindrical parts  224   
     Second Embodiment 
     A mirror unit of a second embodiment will be described.  FIG. 9  is an outer appearance view of the mirror unit. 
     In the first embodiment, the adhesive  240  is applied to the containing part  221  of the holder  220 . However, in this embodiment, as shown in  FIG. 9 , an adhesive  240  is applied to an outer edge of a mirror  210 . 
     In this embodiment, the adhesive  240  is not applied to the containing part  221  of the holder  220 . Accordingly, in the holder  220  of this embodiment, the first cylindrical parts  224  explained in the first embodiment can be omitted. Besides, in this embodiment, the projections  222  and  223  explained in the first embodiment are omitted. 
     As shown in  FIG. 9 , the adhesive  240  is applied to four places of the outer edge of the mirror  210 . The adhesive  240  bonds the mirror  210  to the holder  220 . The adhesive  240  is applied to the four places, so that the mirror  210  can be positioned in the Y-Z plane. 
     In this embodiment, although the adhesive  240  is applied to two positions opposite to each other in the Z direction and two positions opposite to each other in the Y direction, the position to which the adhesive  240  is applied can be appropriately set. It is sufficient if the adhesive  240  bonds the mirror  210  to the holder  220 , and allows the movement of the mirror  210  by the elastic deformation. 
     According to this embodiment, the pin  230  is moved in the X direction and pushes the mirror  210 , so that the direction of the mirror  210  can be changed. 
     In the first embodiment and the second embodiment, although the pin  230  provided with the screw part  231  is used, a pin provided with another structure may be used. It is sufficient if the pin can be moved in the X direction, and can be fixed to the holder  220  at specified positions (plural positions) in the X direction. 
     For example, the pin  230  is provided with a plate spring, and plural grooves engaging with the plate spring are provided in the holder  220 . The position of the pin in the X direction can be adjusted by changing the position where the plate spring engages with the groove. The direction of the mirror  210  can be adjusted by adjusting the position of the pin in the X direction. 
     In the first embodiment and the second embodiment, although the three pins  230  are used and the direction of the mirror  210  is adjusted, the positions where the pins  230  are disposed and the number thereof can be appropriately set. 
     Specifically, one pin  230  is used, and the direction of the mirror  210  can be adjusted. For example, in a structure in which the tip  232  of the pin  230  contacts a portion deviated from the center of the mirror  210 , when the pin  230  pushes the mirror  210 , the direction of the mirror  210  can be changed. The center of the mirror  210  is the center of the mirror  210  on the Y-Z plane. 
     Even when two pins  230  are used, the direction in which the direction of the mirror  210  is changed can be changed according to the positions where the two pins  230  are disposed. 
     In addition to the structure of the first embodiment and the second embodiment, the holder  220  can be provided with a stopper. The stopper contacts the mirror  210 , and prevents the mirror  210  from being displaced by a specified amount or more. The stopper can be provided on the surface of the holder  220  on which the containing part  221  is formed. 
     The movement amount of the pin  230  in the X direction can be limited by using the second cylindrical part  226 . Specifically, the length of the second cylindrical part  226  in the X direction and the length of the pin  230  in the X direction are appropriately determined, so that the protrusion amount (maximum value) of the pin  230  from the first cylindrical part  224  can be determined. When the protrusion amount (maximum value) of the pin  230  is determined, it is possible to prevent the pin  230  from pushing the mirror  310  until the adhesion of the adhesive  240  is broken. 
     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 embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit 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.