Abstract:
The present invention relates to a developing device for developing images formed on an image carrier comprising: a rotatably mounted roller-like toner carrier for holding a toner on the surface thereof; a plate-like regulating member for regulating an amount of the toner held on the toner carrier, the regulating member having at least one bent part, a first regulating part that is located such that it is in contact with the toner carrier and a second regulating part that is located such that it is in contact with the toner carrier at downstream side of the first regulating part with respect to the surface-moving direction of the toner carrier; and a casing for accommodating the toner, the toner carrier and the regulating member; wherein the regulating member is positioned between the toner carrier and the casing.

Description:
RELATED APPLICATIONS  
         [0001]    The present invention is based on Japanese Patent Application No. 2001-151,202, the contents of which are incorporated by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a developing device used in an image forming apparatus such as a copying machine or printer.  
           [0004]    2. Description of the Related Art  
           [0005]    Developing devices based on the two-component developing method that uses toner and a carrier as the developer and developing devices based on the single-component developing method that does not use a carrier and use only toner are known in the conventional art as developing devices used in image forming apparatuses such as copying machines and printers. As developing devices based on the single-component developing method, those based on the magnetic single-component developing method that includes a magnetic member inside the toner carrier and those based on the non-magnetic single-component developing method that uses a toner carrier that does not include a magnetic member are known.  
           [0006]    An example of the developing device using the single-component developing method is shown in FIG. 1. In this developing device, the toner (t) housed in the casing  1  of the system main unit is forwarded by a toner forwarding member  2  to a roller-like toner supply member  3 . The toner (t) is supplied to a roller-like toner carrier  4  via the rotation of the toner supply member  3 , and the toner carrier  4  further conveys the supplied toner (t) via the rotation thereof. A plate-like regulating member  5  is mounted to the casing  1  at one edge thereof, such that the other edge of the regulating member  5  is in pressure contact with the surface of the toner carrier  4 . This regulating member  5  regulates the amount of the toner (t) that is conveyed by the toner carrier  4  and at the same time charges the toner (t). The toner (t) that is regulated and charged in this way is guided by the toner carrier  4  to the developing area in which the toner carrier  4  faces the image carrier  6 , whereupon developing takes place.  
           [0007]    However, because only a single regulating member  5  is in pressure contact with the surface of the toner carrier  4 , problems exist, such as the fact that it is difficult to appropriately regulate the amount of the toner (t) conveyed by the toner carrier  4  and to appropriately charge the toner (t). In particular, the problem exists that it is difficult to reduce the amount of the toner (t) that is conveyed by the toner carrier  4  to the developing area and to charge the toner (t) appropriately.  
           [0008]    Systems have been proposed in recent years to address these problems, such as the system that includes two regulating members located inside the casing of the system main unit that are in pressure contact with the surface of the toner carrier, such that the amount of the toner held on the surface of the toner carrier and conveyed is regulated and the toner (t) is charged by the two regulating members, as disclosed by U.S. Pat. No. 6,343,201, and a system in which one edge of a regulating member is mounted to the system main unit and the other edge area of the regulating member is bent such that the regulating member is in contact with the surface of the toner carrier at two or more contact points, and the amount of the toner held on the surface of the toner carrier is regulated and the toner (t) is charged at each contact area, as disclosed by Japanese Laid-Open Patent Application H11-316499.  
           [0009]    However, the problems exist that (1) it is troublesome to install two regulating members inside the system main unit such that they are in pressure contact with the surface of the toner carrier in the manner disclosed in U.S. Pat. No. 6,343,201, and (2) construction of such a system is more costly due to the increased number of components. In addition, where the regulating member is attached to the system main unit at one edge thereof while the other edge area thereof is bent such that the regulating member is in contact with the surface of the toner carrier at two or more contact points, as disclosed by Japanese Laid-Open Patent Application H11-316499, the problem exists that one edge of the regulating member must be mounted to the system main unit using mounting members such as screws, which is inconvenient.  
         SUMMARY OF THE INVENTION  
         [0010]    An object of the present invention is to provide a developing device capable of regulating the toner amount such that the amount of toner conveyed by the toner carrier to the developing area is reduced, as well as of appropriately charging the toner.  
           [0011]    Another object of the present invention is to provide a developing device that comprises a reduced number of components and can accordingly be manufactured more easily and at a lower cost.  
           [0012]    Still another object of the present invention is to provide a developing device that does not entail the inconvenient task of mounting the regulating member to the system main unit using mounting members such as screws.  
           [0013]    The present invention relates to a developing device for developing images formed on an image carrier comprising: a rotatably mounted roller-like toner carrier for holding a toner on the surface thereof; a plate-like regulating member for regulating an amount of the toner held on the toner carrier, the regulating member having at least one bent part, a first regulating part that is located such that it is in contact with the toner carrier and a second regulating part that is located such that it is in contact with the toner carrier at downstream side of the first regulating part with respect to the surface-moving direction of the toner carrier; and a casing for accommodating the toner, the toner carrier and the regulating member; wherein the regulating member is positioned between the toner carrier and the casing. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1 is a basic explanatory drawing of a conventional developing device;  
         [0015]    [0015]FIG. 2 is a basic explanatory drawing of a developing device pertaining to one embodiment of the present invention,  
         [0016]    [0016]FIG. 3 is a basic explanatory drawing showing one example of a developing device including a sealing member that prevents toner from entering;  
         [0017]    [0017]FIG. 4 is perspective view showing one example of a regulating member near the bent part in which are-located ejection holes through which the accumulated toner is ejected;  
         [0018]    [0018]FIG. 5 is a basic explanatory drawing showing one example of a developing device that includes a rod member at the bent part of the regulating member such that the bent part of the regulating member is held in the engaging unit of the system main unit via the rod member.  
         [0019]    [0019]FIG. 6 is a basic explanatory drawing showing one example of a developing device in which a regulating member that is bent via two bent parts that extend along the axis of the toner carrier such that the regulating member has a trough configuration;  
         [0020]    [0020]FIG. 7 is a basic explanatory drawing showing one example of a developing device in which the toner carrier and the image carrier are each caused to rotate downward in the developing area in which the toner carrier and the image carrier face each other; and  
         [0021]    [0021]FIG. 8 is a basic explanatory drawing of a color image forming apparatus that uses four developing devices pertaining to the embodiment of the present invention and forms color images using toners of different colors, i.e., yellow, magenta, cyan and black, that are respectively housed in these four developing devices. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]    The developing device pertaining to an embodiment of the present invention is described below in specific terms with reference to the accompanying drawings.  
         [0023]    In the developing device pertaining to this embodiment, as shown in FIG. 2, a toner carrier  21  faces the image carrier  10  that rotates, and the toner carrier  21  is caused to rotate in the opposite direction from the direction of rotation of the image carrier  10  such that the toner carrier  21  and the image carrier  10  are respectively caused to rotate upward in the developing area in which they face each other.  
         [0024]    In addition, in this developing device, toner (t) is housed in a housing unit  20   a  of the casing  20  of the system main unit, and a toner forwarding member  22  having blade members  22   a  is rotatably mounted in the housing unit  20   a.    
         [0025]    Through the rotation of this toner forwarding member  22 , the blade members  22   a  supply the toner (t) housed in the housing unit  20   a  to a toner supply unit  20   b  via an opening  23   a . The toner supply unit  20   b  is separated from the housing unit  20   a  by a partition member  23 .  
         [0026]    Furthermore, a roller-like toner supply member  24  is located in the toner supply unit  20   b  such that it is in contact with the toner carrier  21 . Through the rotation of the toner supply member  24  in the direction opposite from the direction of rotation of the toner carrier  21 , the toner (t) in the toner supply unit  20   b  is supplied to the toner carrier  21  by the toner supply member  24 . The toner (t) that is not supplied to the toner carrier  21  and remains on the toner supply member  24  is scraped off from the toner supply member  24  by a scraper  25 .  
         [0027]    In this developing device, a regulating member  26 , which is bent into a letter V configuration via a bent part  26   a , which extends along the axis of the toner carrier  21 , is located below the toner carrier  21 . All edge areas of the V-shaped regulating member  26  that resides in the area between the scraper  25  and the image carrier  10  are in contact with the surface of the toner carrier  21 . The bent part  26   a  of the regulating member  26  is held in a groove-like engaging unit  27  that is located in the casing  20  of the system main unit at a position below the toner carrier  21 . The regulating member  26  is held sandwiched between the casing  20  of the system main unit and the toner carrier  21 .  
         [0028]    Because the bent part  26   a  is held in the groove-like engaging unit  27  and the regulating member  26  is sandwiched between the casing  20  of the system main unit and the toner carrier  21  in this way, the regulating member  26  is prevented from being dislodged when the toner (t) held on the toner carrier  21  is regulated and charged by the regulating member  26  that is in contact with the surface of the rotating toner carrier  21 , even if the regulating member  26  is not fixed to the casing  20  of the system main unit using screws or other means, as in the conventional apparatus. Incidentally, the part from the bent part  26   a  to the free edge that is located upstream in terms of the direction of rotation of the toner carrier will be termed the first regulating part, and the part from the bent part  26   a  to the free edge that is located downstream in terms of the direction of rotation of the toner carrier will be termed the second regulating part.  
         [0029]    The edge of the first regulating part that is in contact with the surface of the toner carrier  21  on the side of the scraper  25  is bent, and the toner (t) held on the toner carrier  21  is regulated and charged by the first regulating part. Subsequently, the toner (t) held on the toner carrier  21  is further regulated and charged by the second regulating part that is in contact with the surface of the toner carrier  21  on the side of the image carrier  10 .  
         [0030]    In this way, the toner (t) that is held onto and conveyed by the surface of the toner carrier  21  is simultaneously regulated and charged by each regulating part of the regulating member  26 , such that the amount of the toner (t) conveyed by the toner carrier  21  to the developing area is easily reduced to a small amount and the toner (t) is appropriately charged. In addition, if the edge of the first regulating part of the regulating member  26  is bent and then placed into contact with the surface of the toner carrier  21 , the pressure exerted by the first regulating part that is in contact with the surface of the toner carrier  21  becomes constant, and the toner (t) supplied to the toner carrier  21  can be uniformly regulated and charged.  
         [0031]    The toner (t) that is regulated and charged by the regulating member  26  is conveyed by the toner carrier  21  to the developing area in which the toner carrier  21  faces the image carrier  10 . In this developing area, the toner carrier  21  and the image carrier  10  are respectively caused to rotate upward, such that the toner (t) is supplied to the electrostatic latent image areas formed on the image carrier  10  from the toner carrier  21  and developing is preformed.  
         [0032]    The toner (t) that remains on the toner carrier  21  after the electrostatic latent image formed on the image carrier  10  is developed is separated therefrom by the sealing member  28  located in the casing  20  of the system main unit, and returns into the toner supply unit  20   b . New toner (t) is thereafter supplied by the toner supply member  24  to the toner carrier  21 .  
         [0033]    Where the toner (t) that is not supplied to the toner carrier  21  and remains on the toner supply member  24  is scraped off by the scraper  25  from the toner supply member  24  or the toner (t) held onto the toner carrier  21  is regulated by the first regulating part of the regulating member  26  and separated from the toner carrier  21 , toner (t) gradually accumulates on the back side of the regulating member  26 , i.e., the opposite side from the side of the first regulating part that is in connect with the toner carrier, which may cause the contact pressure of the first regulating part of the regulating member  26  to the toner carrier  21  to gradually increase, resulting in the loss of appropriate regulation by the regulating member  26 . Therefore, as shown in FIG. 3, it is preferred that a sealing member  29  that prevents the entrance of toner (t) be located opposite from the toner carrier  21  in the vicinity of the first regulating part of the regulating member  26  that is in contact with the surface of the toner carrier  21 . If this sealing member  29  is formed from an elastic material, the vibration of the regulating member  26  is reduced by the sealing member  29 .  
         [0034]    If the engaging unit  27  in which the bent part  26   a  of the regulating member  26  is held is formed from an elastic material, the vibration of the regulating member  26  is reduced by the engaging unit  27 . It is also possible to make this engaging unit  27  detachable such that it can be replaced where appropriate.  
         [0035]    In addition, if toner (t) separates from the surface of the toner carrier  21  in the area between the first regulating part and the second regulating part and accumulates in the bent part  26   a  of the regulating member  26 , the contact pressure applied by the second regulating part may gradually decrease due to the toner (t), resulting in the loss of appropriate regulation by the regulating member  26 . Therefore, as shown in FIG. 4, ejection holes  26   b  through which to eject the toner (t) accumulated in the bent part  26   a  may be created near the bent part  26   a  of the regulating member  26 .  
         [0036]    Moreover, as shown in FIG. 5, it is also acceptable if a rod member  26   c  is located in the bent part  26   a  of the regulating member  26  such that the bent part  26   a  of the regulating member  26  is held in the engaging unit  27  by this rod member  26   c . In this way, the regulating member  26  is further prevented from becoming dislodged. Furthermore, if a bias voltage that charges the toner (t) is impressed to the regulating member  26  via the rod member  26   c , the toner (t) becomes more appropriately charged.  
         [0037]    It is also acceptable if a regulating member  26  be used that is bent along two bent parts  26   a  that extend along the axis of the toner carrier  21  such that the regulating member  26  has a trough configuration, as shown in FIG. 6. Where this regulating member  26  is used as well, the regulating member  26  should be held in the engaging unit  27  located in the casing  20  of the system main unit at a position below the toner carrier  21  such that the regulating member  26  is held sandwiched between the casing  20  of the system main unit and the toner carrier  21 .  
         [0038]    In the developing device pertaining to the above embodiment, as described above, the toner carrier  21  and the image carrier  10  are each caused to rotate upward in the developing area in which they face each other, and a regulating member  26  that is bent into a letter V configuration via a bent part  26   a  is held in an engaging unit  27  located in the casing  20  of the system main unit at a position below the toner carrier  21 , such that the regulating member  26  is held between the casing  20  of the system main unit and the toner carrier  21 .  
         [0039]    However, the developing device of the present invention is not limited to the above embodiment, and other implementations are possible. For example, as shown in FIG. 7, the toner carrier  21  and the image carrier  10  may each be caused to rotate downward in the developing area in which they face each other, and the bent part  26   a  of the regulating member  26  bent into a letter V configuration may be held in a groove-like engagement unit  27  located in the casing  20  of the system main unit at a position above the area at which the toner (t) inside the toner supply unit  20   b  is supplied to the toner carrier  21  by the toner supply member  24 , such that the regulating member  26  is held between the casing  20  of the system main unit and the toner carrier  21 .  
         [0040]    In the developing device of the present invention, it is preferred that a member comprising an SUS plate member having a thickness ranging from 40 to 80 μm be used as the regulating member  26 , and where the regulating member  26  is bent at the bent part  26   a  in order to form it into a letter V configuration, as described above, it is preferred that the angle of the V shape range from 50 to 80 degrees.  
         [0041]    A color image forming apparatus in which the developing device of the above embodiment is employed will now be described in detail with reference to the accompanying drawings.  
         [0042]    Here, the color image forming apparatus uses four developing devices A 1  through A 4  described in connection with the above embodiment, as shown in FIG. 8, and these four developing devices A 1  through A 4 , respectively house toners of different colors, i.e., yellow, magenta, cyan and black.  
         [0043]    These four developing devices A 1  through A 4  are held on a holder  40  that rotates, and the positions of each developing device A 1  through A 4  are changed by rotating the holder  40  such that the toner carrier  21  of each developing device A 1  through A 4  is sequentially guided to the position at which it faces the image carrier  10 . In the developing area in which each toner carrier  21  and the image carrier  10  face each other, the toner carrier  21  and the image carrier  10  are respectively caused to rotate upward.  
         [0044]    When forming a color image using this color image forming apparatus, for example, the toner carrier  21  in the first developing device A 1 , in which is housed yellow toner, is first positioned such that it faces the image carrier  10 , the image carrier  10  is caused to rotate, the surface thereof is uniformly charged by a charger  41 , and exposure of the charged image carrier  10  is performed by an exposure device  42  in accordance with image signals to form an electrostatic latent image on the surface of the image carrier  10 .  
         [0045]    Next, in the developing area in which the image carrier  10 , on which has been formed an electrostatic latent image as described above, and the toner carrier  21  of the first developing device A 1  face each other, the toner carrier  21  and the image carrier  10  are respectively caused to rotate upward, the yellow toner is supplied from the toner carrier  21  to the electrostatic latent image area formed on the image carrier  10  to form on the image carrier  10  a yellow toner image that corresponds to the electrostatic latent image.  
         [0046]    While the yellow toner image formed on the image carrier  10  in this way is transferred to an intermediate transfer unit  43 , which has a continuous belt configuration and is suspended above the image carrier  10 , the yellow toner remaining on the image carrier  10  after the transfer is removed therefrom by a cleaning device  44 .  
         [0047]    The holder  40  is then caused to rotate such that the toner carrier  21  of the second developing device A 2 , in which magenta toner is housed, faces the image carrier  10 , and a magenta toner image is formed on the surface of the image carrier  10  in the same manner as with the first developing device A 1 , the magenta toner image is transferred to the intermediate transfer unit  43  on which the yellow toner image was transferred, and the magenta toner remaining on the image carrier  10  after the transfer is removed therefrom by the cleaning device  44 .  
         [0048]    A cyan toner image is then formed, through the same operation, on the surface of the image carrier  10  by the third developing device A 3  in which cyan toner is housed, and after this cyan toner image is transferred to the image transfer unit  43 , a black toner image is formed on the surface of the image carrier  10  by the fourth developing device A 4  in which black toner is housed, and this black toner image is transferred to the intermediate transfer unit  43 . A multi-color toner image is thus formed via the transfer of the yellow, magenta, cyan and black toner images onto the intermediate transfer unit  43 .  
         [0049]    A recording sheet  46  is then guided by forwarding rollers  47  from a paper cassette  45  located in the bottom part of the color image forming apparatus to the area in which the intermediate transfer unit  43  and the transfer roller  48  face each other, and the multi-color toner image formed on the intermediate transfer unit  43  is transferred onto the recording sheet  46 . The multi-color toner image transferred onto the recording sheet  46  is fused thereto by a fusing device  49  and the recording sheet  46  is ejected. The toner that was not transferred and remains on the intermediate transfer unit  43  is removed from the intermediate transfer unit  43  by a cleaning device  50 .  
         [0050]    Although the present invention has been fully described by way of examples, it is to be noted that various changes and modification will be apparent to those skilled in the art. Therefore, unless otherwise such changes and modifications depart from the scope of the present invention, they should be construed as being included therein.