Patent Publication Number: US-7917054-B2

Title: Image developing apparatus and image forming apparatus using the apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of Ser. No. 12/081,641, filed Apr. 18, 2008, which application is a divisional application of Ser. No. 11/439,254, filed May 24, 2006, now U.S. Pat. No. 7,386,248. This application also claims benefit under 35 U.S.C. §119(a) of Korean Patent Application No. 2005-112051, filed Nov. 22, 2005, in the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image developing apparatus and to an image forming apparatus using the image developing apparatus. More particularly, the present invention relates to an image developing apparatus and to an image forming apparatus, which prevent contamination of a charging roller or blocking of a light path by scattered toner during the developing process. 
     2. Description of the Related Art 
     An electrophotograph image forming apparatus forms an image on a recording medium, by use of an electrophotograph image forming method. The electrophotograph image forming apparatus may be an electrophotograph duplicator, an electrophotograph printer (for example, a laser beam printer), a facsimile and a MFP (multifunction printer). 
     The electrophotograph image forming apparatus such as the above-mentioned printer forms an electrostatic latent image by selectively exposing a photoconductive drum that is charged by a charging unit. The electrostatic latent image is developed with a developing agent in a developing unit. The image developed by the developing agent is scanned on the recording medium to record the image. 
     The electrophotograph image forming apparatus uses a process cartridge. The process cartridge may integrate the abovementioned charging unit and developing unit, or a cleaning unit and a photoconductive drum into one cartridge. This makes the cartridge attachable and detachable with respect to the image forming apparatus. Alternatively, at least one of the charging unit, the developing unit and the cleaning unit, and one photoconductive drum are integrated into one cartridge, and made attachable and detachable with respect to the image forming apparatus. 
       FIG. 1  is a fragmentary sectional view of a developing unit of a conventional image forming apparatus. 
     Referring to  FIG. 1 , a developing unit  10  includes an upper case  11  and a lower case  13 . The inside of the upper case  11  is formed with a charging roller  15  and a photoconductive drum  17 . The charging roller  15  charges a surface of the photoconductive drum  17  at a predetermined voltage, and the charged surface of the charging roller  17  is exposed to light irradiated from a light scanning unit  19 , for example, a laser beam to form an electrostatic latent image on the surface of the charging roller  17 . 
     The rear side of the upper case  11  is formed with a light passage hole (not shown) so that the light irradiated from the light scanning unit  19  can pass through and scan the surface of the photoconductive drum  17 . 
     The inside of the lower case  13  includes a developing roller  21  for supplying toner to the electrostatic latent image formed on the surface of the photoconductive drum  17  and developing the latent image as a visible image. One side of the developing roller  21  is formed with a supplying roller  22  supplying the developing roller  21  with a toner (TI). An upper side of the lower case  21  has a regulating blade  23  regulating a toner layer of the developing roller  21 , and the regulating blade  23  is supported by a blade bracket  25 . 
     The abovementioned developing unit  10  operates as follows. The surface of the photoconductive drum  17  is charged through the charging roller  15  at a predetermined voltage. If a predetermined light is irradiated from the light scanning unit  19  on the charged surface of the charging roller  17  in the charged state, the electrostatic latent image is formed in the surface of the photoconductive drum  17 . 
     The rotating surface of the developing roller  21  is supplied with the toner layer through the supplying roller  22 . The toner layer is formed with a uniform thickness by regulating the thickness using a regulating blade  23 . 
     The toner attached to the surface of the developing roller  21  moves to the photoconductive drum  17  by potential differences, and is applied on the electrostatic latent image to form a toner image. The photoconductive drum  17  and the developing roller  21  are not in contact, and positioned to provide a predetermined gap (D) therebetween. The toner formed on the surface of the developing roller  21  jumps the gap (D) between the photoconductive drum  17  and the developing roller  21 , and moves to the photoconductive drum  17 . 
     As discussed above, the photoconductive drum  17  and the developing roller  21  are not in contact, so the toner is not perfectly transferred, and the toner may be scattered. The scattered toner may contaminate the charging roller  15  and influence charging, thereby causing a defective image problem. 
     The scattered toner is attached to the upper side of the regulating blade  25 , the inside of the upper case  11  or the external surface of the upper side of the lower case  13 , and blocks a path of light irradiated from the light scanning unit  19 , thereby causing image problems. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention is to solve at least the above problems and/or disadvantages of the related art and to provide at least the advantages described below. Accordingly, an aspect of the present invention is to provide an image developing apparatus, which prevents image defects by preventing contamination of the charging roller or preventing the blocking of the light path caused by toner scattering. 
     An aspect of the present invention is to provide an image forming apparatus employed with the abovementioned image developing apparatus. 
     In order to achieve the above-described aspects of the present invention, an image developing apparatus is provided comprising: an upper case; a lower case disposed on a lower side of the upper case and internally housing a developing agent, and having an opening; a photoconductive drum disposed on the upper case for forming an electrostatic latent image on a surface thereof; a charging roller disposed on one side of an outer circumference of the photoconductive drum, for charging the photoconductive drum; a developing roller having one part exposed through the opening of the lower case to cooperate with the photoconductive drum for developing the electrostatic latent image; and a scattering preventing unit disposed between the photoconductive drum and the developing roller, to prevent scattering of the developing agent supplied by the developing roller. 
     The scattering preventing unit includes a blocking curtain which covers a part of the opening on one side in contact with the outer circumference of the photoconductive drum, and a fixing bracket which supports the blocking curtain. 
     The blocking curtain is formed of soft materials, for example, Urethane. 
     The blocking curtain includes a supporting portion supported on the fixing bracket, and a bending portion having one end of the supporting portion bent to contact with the photoconductive drum. The bending portion is bent along the rotation direction of the photoconductive drum. The bending portion is bent to correspond to the outer circumference of the photoconductive drum. 
     The fixing bracket is disposed towards the opening on an upper side of the lower case. 
     The fixing bracket is additionally included with a regulating blade for regulating a thickness of a developing agent layer formed on a surface of the developing roller. 
     The photoconductive drum and the developing roller are disposed with a predetermined gap therebetween. The developing agent is a 1-component nonmagnetic toner. 
     In order to achieve the above-described aspects of the present invention, an image developing apparatus is provided comprising: an image developing apparatus comprising: a photoconductive drum for forming an electrostatic latent image on surface thereof; a charging roller disposed on one side of the photoconductive drum for charging the photoconductive drum; a developing roller disposed on the other side of the photoconductive drum for supplying a developing agent to develop the electrostatic latent image; and a scattering preventing unit disposed between the photoconductive drum and the developing roller to prevent scattering of the developing agent supplied by the developing roller. The scattering preventing unit covers an upper side of the developing roller, and includes a blocking curtain whose one side is in contact with an outer circumference of the photoconductive drum, and a fixing bracket which supports the blocking curtain. 
     In order to achieve the above-described aspects of the present invention, there is provided an image developing apparatus is provided comprising: an image forming apparatus comprising: at least one developing unit; and a transferring unit disposed on one side of the developing unit to transfer a developing agent image developed through the developing unit on a recording medium. The developing unit comprises: an upper case; a lower case disposed on a lower side of the upper case and internally housing a developing agent and formed with an opening; a photoconductive drum disposed on the upper case for forming an electrostatic latent image on a surface of the photoconductive drum; a charging roller disposed on one side of the photoconductive drum for charging the photoconductive drum; a developing roller having one part is exposed through the opening of lower case to cooperate with the photoconductive drum, and developing the electrostatic latent image; and a scattering preventing unit disposed between the photoconductive drum and the developing roller to prevent scattering of the developing agent supplied by the developing roller. 
     The scattering preventing unit includes a blocking curtain which covers an upper side of the developing roller whose one side is in contact with an outer circumference of the photoconductive drum, and a fixing bracket which supports the blocking curtain. 
     The scattering preventing unit is made of soft materials, for example, Urethane. 
     The scattering preventing unit includes a supporting portion supported on the fixing bracket, and a bending portion having one end of the supporting portion for contacting with the photoconductive unit. The bending portion is bent along a rotation direction of the photoconductive drum. The bending portion is curved to correspond to the outer circumference of the photoconductive drum. 
     The fixing bracket is disposed towards the opening of the lower case on an upper side of the lower case. 
     The fixing bracket additionally includes a regulating blade for regulating a developing agent layer formed on a surface of the developing roller. 
     The photoconductive drum and the developing roller are spaced a predetermined gap. The developing agent is a 1-component nonmagnetic toner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       The above aspect and other features of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawing figures, wherein; 
         FIG. 1  is a fragmentary sectional view of a developing unit of a conventional image forming apparatus; 
         FIG. 2  is a side view of an image forming device according to an embodiment of the present invention; 
         FIG. 3  is a perspective view of a developing unit structure according to the embodiment of the present invention; 
         FIG. 4  is an exploded perspective view showing the photoconductive drum separated from the structure of  FIG. 3 ; and 
         FIG. 5  is a view taken along IV-IV′ of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawing figures. 
     In the following description, same drawing reference numerals are used for the same elements even in different drawings. The matters defined in the description such as a detailed construction and elements are provided to assist in a comprehensive understanding of the invention. Thus, it is apparent that the present invention can be carried out without those defined matters. Also, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. 
       FIG. 2  is a structural diagram of a complete image forming device according to an embodiment of the present invention. 
     Referring to  FIG. 2 , the image forming apparatus includes a developing unit  110  for each of the four colors (black, cyan, magenta and yellow) inside a main body  101 . The developing unit  110  includes a photoconductive drum  111 , a charging roller  113 , a developing roller  115 , a supplying roller  116  and a developing agent case  117 . 
     The photoconductive drum  111  has a surface charged at a uniform potential by the charging roller  113 . Likewise, if a predetermined light, for example, from one or more laser beams, is scanned on the photoconductive drum  111  charged with a predetermined potential on the surface thereof, through a light scanning unit  105 , an electrostatic latent image is formed on the photoconductive drum  111 . 
     The electrostatic latent image formed on the photoconductive drum  111  is developed as a visible image by a developing agent being transferred by the developing roller  115 . 
     A scanning unit  130  comprises a belt  131  driving on treads, in contact with the photoconductive drum  111 , rollers  133   a  through  133   d  rotatably supporting the belt  131  and transferring rollers  135  installed inside the belt  131  to correspond to the photoconductive drum  111 . 
     As above-mentioned, if the electrostatic latent image is developed as the visible image on the photoconductive drum  101  by the developing agent being supplied by the developing roller  115 , a recording medium  103  is transferred by the belt  131  and the transferred recording medium  103  is scanned with a color image in duplicate, so that a perfect image is implemented. 
     A paper supplying unit  150  includes a supplying cassette  151  loaded with a plurality of pages or sheets of recording medium  103 , a pickup roller  153  for picking up the recording medium  103  of the paper supplying cassette  151 , and a feeding roller  155  for feeding the picked-up recording medium  103 . 
     A fixing unit  170  applies heat and pressure on the recording medium  103  having passed through the belt  131  and the transferring rollers  135 , and fixes the color image on the recording medium  103 . The fixing unit  170  comprises a heating roller  171  and a pressurizing roller  173 . 
     The recording medium  103  is transferred by an exit or discharge roller  161  out of the main body  101  through an exit port  101   a.    
       FIG. 3  is a perspective diagram of a developing unit structure according to the embodiment of the present invention,  FIG. 5  is a perspective view showing a partially separated structure of  FIG. 3  and  FIG. 4  is a view taken along IV-IV′ of  FIG. 3 . 
     Referring to  FIGS. 3 through 5 , a developing case forming an external appearance of the developing unit  110  comprises an upper case  117   a  and a lower case  117   b . The upper case  117   a  is formed with the photoconductive drum  111  and the charging roller  113 . A rear side of the upper case  117   a  is formed with a light passage hole  117   a ′ through which light irradiated from the light scanning unit  105  passes. 
     The lower case  117   b  internally houses a developing unit, for example, 1-component nonmagnetic toner (T), and an opening  117   b ′ is formed at a side facing the photoconductive drum  111 . Inside the lower case  117   b  is formed with a portion of an outer circumference of the developing roller  115  exposed through the opening  117   b ′ as shown in  FIG. 5 . The developing roller  115  does not contact the photoconductive drum  111 . The developing roller  115  and the photoconductive drum  111  are spaced apart by a predetermined gap (G). One side of the developing roller  115  is formed with the supplying roller  116  for supplying the toner (T) to the developing roller  115 . 
     A scattering preventing unit  210  is formed with the upper side of the lower case  117   b  facing towards the opening  117   b ′ as shown in  FIG. 5 . The scattering preventing unit  210  covers a part of the opening  117   b ′ and includes a blocking curtain  211  whose one end is in contact with an outer circumference of the photoconductive drum  111 , and a fixing bracket  213  supported on the upper side of the lower case  117   b  to support the blocking curtain  211 . 
     The fixing bracket  213  is additionally formed with a regulating blade  221  for regulating a uniform thickness of a toner layer formed on the surface of the developing roller  115 . 
     The blocking curtain  211  may be made of soft materials, for example, Urethane. The blocking curtain  211  includes a supporting portion  211   a  supported by the fixing bracket  213  and a bending portion  211   b  in contact with the outer circumference of the photoconductive drum  111 . The bending portion  211   b  may be bent along the rotation direction of the photoconductive drum  111  (illustrated as a clockwise direction in  FIG. 5 ) and be curved to correspond to the outer circumference of the photoconductive drum  111 . 
     An operation of the above-structured developing unit will be described as below. 
     For example, approximately −700V bias supplying voltage and −600V bias supplying voltage are supplied to the supplying roller  116  and the developing roller  115 , respectively. 100V voltage differences are maintained between the supplying roller  116  and the developing roller  115 . If a toner supplying member (not shown) is driven in this state, the 1-component nonmagnetic toner (T) is supplied to the supplying roller  116 . 
     The supplied toner (T) is attached to the surface of the supplying roller  116  and rotates together, to pass through a contact surface between the supplying roller  116  and the developing roller  115 . The 1-component nonmagnetic toner (T) is charged by the medium of friction contact force between the supplying roller  116  and the developing roller  115 . The charged toner moves towards the developing roller  115  from the supplying roller  116  within an electric field that is maintained at a uniform voltage difference. A toner layer is formed on the surface of the developing roller  115 . 
     The toner layer formed on the surface of the developing roller  115  is maintained entirely at a uniform thickness by the regulating blade  221  and the rotation of the developing roller  115 . That is, the surface of the developing roller  115  is formed with the uniform toner layer applied with the charged toner. The toner moves towards the photoconductive drum  111  by the voltage differences between the developing roller  115  and the photoconductive drum  111 . The toners are applied on the electrostatic latent image and form the visible image. After that, the visible image is transferred to a recording medium by the high voltage scanning unit  130  (refer to  FIG. 2 ). 
     In the above description, values of voltage supplied to each roller are one example provided to help easy explanation, and are not limited to the abovementioned voltage value. 
     While the development operation is performed, the toner (T) may be attached to the charging roller  113  and scattered inside the upper case  117   a  or the upper side of the fixing bracket  213 . Charging problems may be caused or a light path may be blocked, to trigger image defects. The scattering preventing unit  210  of the present invention is provided to reduce or prevent the above-mentioned problem. 
     That is, a part of opening  117   b ′ of the lower case  117   b  is blocked by the blocking curtain  211 , so that scattering of the toner (T) is prevented. The blocking curtain  211  is bent along the rotation direction of the photoconductive drum  111 , without disturbing the rotation of the photoconductive drum  111 . The blocking curtain  211  is made of a soft material such as Urethane, so that it does not damage the photoconductive drum  111 , such as by scratching, even when in contact therewith. 
     As mentioned above, an embodiment of the present invention efficiently prevents triggering of the effects that cause image defects, by solving problems of contaminating a charging roller or blocking a light path caused by toner scattering. 
     While the invention has been shown and described with reference to certain embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.