Abstract:
A developer driving apparatus which drives a plurality of developing rollers via a gear chain including pivotable gears and one way gears. A reversible driving motor is coupled to a deceleration gear which directly drives a first swing drive gear and drives a second swing drive gear via an odd number of idler gears. Each swing drive gear is rotationally coupled with a respective swing gear having a center of rotation which is pivotable about a center of rotation of the respective swing drive gear. In a first position each swing gear drives one of the plurality of rollers via a respective one way gear and in a second position, each swing gear drives another of the plurality of rollers via a respective one way gear. A solenoid activated lever moves each swing gear between respective first and second positions.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of Korean Application No. 2002-35674 filed Jun. 25, 2002 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an apparatus for driving developers of a color image forming apparatus, and more particularly, to an apparatus for sequentially driving a plurality of developers separated a predetermined distance from a photosensitive body in a color image forming apparatus. 
     2. Description of the Related Art 
     In general, an electrophotographic printer such as a color laser printer includes an image forming apparatus which forms an electrostatic latent image on a photosensitive body and develops the electrostatic latent image with toner. Then, the developed image is transferred to paper by a predetermined transfer medium and is pressed and heated to completely fix the image on the paper. 
     FIG. 1 shows an example of an image forming apparatus of a color printer. Referring to FIG. 1, an image forming apparatus includes a photoreceptive drum  10  which is a photosensitive body, a charger  11  which charges the photosensitive drum  10 , a laser scanning unit (LSU)  12  as an exposing unit which forms an electrostatic latent image by scanning light onto the charged photoreceptive drum  10 , a development unit  13  which develops the electrostatic latent image with four colors of black (K), yellow (Y), magenta (M), and cyan (C), a transfer belt  14  on which four different color images developed on the photoreceptive drum  10  are sequentially overlapped, a first transfer roller  14   a  which transfers the image developed on the photoreceptive drum  10  to the transfer belt  14 , a second transfer roller  14   b  which transfers the image of four overlapping colors on the transfer belt  14  to paper, and a fusing unit  15  which presses and heats the paper to fix the transferred image on the paper. Developing rollers  13   a -K,  13   a -Y,  13   a -M, and  13   a -C of four developers  13 -K,  13 -Y,  13 -M, and  13 -C provided in the development unit  13  are arranged separated by a predetermined gap from the photoreceptive drum  10  and sequentially develop the electrostatic latent image on the photoreceptive drum  10  when a development bias voltage is applied to corresponding developing rollers. Reference numerals  16 ,  17 ,  18 , and  19  denote a paper cassette for storing a supply of paper, a blade for cleaning the photoreceptive drum  10 , an eraser, and a transfer path along which the paper is ejected, respectively. 
     The image forming apparatus having the above structure performs an image forming process as follows. First, when the charger  11  charges the photoreceptive drum  10 , the LSU  12  scans light to form an electrostatic latent image of an image to be developed with the first color. For example, when black is to be developed first, a predetermined bias voltage is applied to the black developing roller  13   a -K. Then, a development unit driving motor (not shown) drives the developing roller  13   a -K so that a toner adhering on the outer circumferential surface thereof is transferred to a portion of the photoreceptive drum  10  contacting the developing roller  13   a -K. The black image developed as above is transferred to the transfer belt  14  via a first transfer nip N 1 . Next, an electrostatic latent image for the second color is formed through the charging and exposing steps with respect to the photoreceptive drum  10 . For example, where yellow is to be developed secondly, a predetermined development bias voltage is applied to the yellow developing roller  13   a -Y and the developing roller  13   a -Y is driven to develop the electrostatic latent image on the photoreceptive drum  10 . The yellow developed as above is transferred onto the transfer belt  14  to overlap the black image previously transferred to the belt  14 . In the same manner, images of the third color, magenta, and the fourth color, cyan, are developed and transferred so that an image having a desired color is completely formed on the transfer belt  14 . Thereafter, the completed color image formed on the transfer belt  14  is transferred to paper supplied to a second transfer nip N 2  between the transfer belt  14  and the second transfer roller  14   b . As the paper passes through the fusing unit  15 , the color image is heated and pressed to be completely fixed onto the paper. 
     FIG. 2 is a view showing a structure of a driving apparatus of the development unit of FIG.  1 . FIG. 3 is a partial plan view of the driving apparatus of FIG.  2 . 
     Referring to FIGS. 1-3, the developing rollers  13   a -K,  13   a -Y,  13   a -M, and  13   a -C are arranged around the photoreceptive drum  10  to be sequentially separated from the photoreceptive drum  10  with a predetermined gap. A deceleration gear  31  which is a two-step gear is connected to a pinion gear  30  of a development unit driving motor (not shown). The deceleration gear  31  is connected to developing roller gears  20 -K,  20 -Y,  20 -M, and  20 -C via idle gears  32 ,  33 ,  34 , and  35  and electronic clutches  36 . The electronic clutches  36  are provided to correspond to the respective developing rollers  13   a . The idle gears  32 ,  33 ,  34 , and  35  are arranged in an appropriate number between the deceleration gear  31  and the electronic clutch  36  to transfer a rotational force of the gear  30  of the development unit driving motor to each of the electronic clutches  36 . A first gear  37  connected to the idle gear  32  or  35  and a second gear  38  connected to the developing roller gear  20  are provided at opposite ends of each of the electronic clutches  36 , as shown in FIG.  3 . When the electronic clutch  36  is turned on, the rotation of the first gear  37  is transferred to the second gear  38  and the developing roller gear  20 . When the electronic clutch  36  is turned off, the first gear  37  and the second gear  38  are disconnected. 
     In the operation of the driving apparatus of the development apparatus having the above structure, when the black developer  13 -K is to be used, the development unit driving motor and the gear  30  are rotated clockwise. According to the rotation of the development unit driving gear  30 , the first gears  37 -K and  37 -Y of the electronic clutches  36 -K and  36 -Y connected to the first idle gear  32  and the first gears  37 -M and  37 -C of the electronic clutches  36 -M and  36 -C connected to the second, third, and fourth idle gears  33 ,  34 , and  35  are rotated. Next, when the electronic clutch  36 -K for the black developer  13 -K is turned on, the rotation of the first gear  37 -K is transferred to the second gear  38 -K. Accordingly, the developing roller gear  20 -K and the developing roller  13   a -K are driven. Here, a development bias voltage is applied to the developing roller  13   a -K so that toner on the surface of the developing roller  13   a -K develops the electrostatic latent image of the photoreceptive drum  10 . 
     Next, to drive the yellow developing roller  13 -Y, the development bias voltage applied to the black developing roller  13 -K is cut off and the electronic clutch  36 -K is turned off. Then, a development bias voltage for yellow is applied to the yellow developing roller  13 -Y and the electronic clutch  36 -Y is turned on, so that the rotation power of the first gear  37 -Y is transferred to the second gear  38 -Y. Thus, the developing roller gear  20 -Y and the developing roller  13   a -Y are driven. The development of magenta and cyan are sequentially performed in a similar manner. 
     However, since the driving apparatus of the developers having the above structure requires a plurality of electronic clutches, a cost for material increases. 
     SUMMARY OF THE INVENTION 
     To solve the above and/or other problems, the present invention provides a developer driving apparatus of a color image forming apparatus which sequentially drives developers by a mechanical means instead of an electronic clutch. 
     Additional aspects and advantages of the invention will be set forth in part in the description which follows, and, in part, will be obvious from the description, or may be learned by practice of the invention. 
     According to an aspect of the present invention, a developer driving apparatus of a color image forming apparatus sequentially drives a plurality of developers for developing an electrostatic latent image formed on a photoreceptor body into predetermined colors. The developer driving apparatus comprises a reversible development unit driving motor which drives a developing roller of the developer, a deceleration gear which is rotated by being engaged with a gear of the development unit driving motor to provide a reduced angular velocity, a plurality of one-way gears which selectively receive a rotational driving force from the deceleration gear and rotate the corresponding developing roller according to a direction of rotation of the deceleration gear. Swing gears are adapted to selectively provide the driving force to the one-way gears by pivoting between the one-way gears. A swing drive gear supports and rotates the swing gear along a circumference of the swing drive gear. A swing arm pivotable about a shaft of the swing drive gear and having a first end connected to a shaft of the swing gear and a second end connected to a pivot unit positions the swing gear for engagement along a circumference of the swing drive gear. The swing arm and the pivot unit enable the swing gear to pivot between the pair of one-way gears according to a state of the pivot unit. 
     The swing gear pivot unit may comprise a plunger connected to the second end of the swing arm, and a solenoid into which the plunger is retracted and from which the plunger is partially ejected. The swing gear pivot unit may further comprise a spring which provides an elastic force to return the plunger to an original position when the solenoid is turned off. The spring may be positioned between the second end of the swing arm and the solenoid. 
     As the plunger is retracted into the solenoid when the solenoid is turned on, the swing arm pivots the swing gear from engagement with one of the pair of the one-way gears to engagement with the other of the pair of the one-way gears. 
     Each one-way gear comprises a first gear engaged with a respective swing gear, a second gear engaged with a respective developing roller gear, and a hub clutch arranged between the first and second gears to transfer a rotation force of the first gear to the second gear only when the first gear is rotated in one direction. 
     Idle gears are arranged in an odd number between the gear of the development unit driving motor and the swing drive gears to make the direction of rotation of the swing drive gears to be opposite. 
     The developer to be operated is determined according to the rotating direction of the development unit driving motor and the operation of the pivot unit. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and/or other aspects and advantages of the present invention will become more apparent by describing in detail preferred embodiments thereof with reference to the attached drawings in which: 
     FIG. 1 is a view illustrating a typical image forming apparatus of a color printer; 
     FIG. 2 is a view showing illustrating the driving apparatus of the development unit of FIG. 1; 
     FIG. 3 is a partial plan view illustrating a portion of the driving apparatus of FIG. 2; 
     FIG. 4 is a view illustrating a developer driving apparatus of a color image forming apparatus according to an embodiment of the present invention and for explaining an operation of the developer driving apparatus; 
     FIG. 5 is an exploded perspective view of a representative one-way gear of the apparatus illustrated in FIG. 4; and 
     FIG. 6 is a view for further explaining the operation of a developer driving apparatus of a color image forming apparatus according to the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the present embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. 
     FIG. 4 shows the structure of a developer driving apparatus of a color image forming apparatus according to an embodiment of the present invention. Here, the same reference designations are used for elements of the conventional apparatus having the same structure described above, and detailed descriptions thereof are omitted. Also, to aid in understanding the invention, references used for a plurality of elements having the same structure are distinguished by a suffix (K, Y, M, or C) where the elements are associated with a feature corresponding to a particular color of a developer. The suffixes K, Y, M and C correspond to black, yellow, magenta and cyan, respectively. Elements which do not correspond to a particular color and which have the same structure are indicated by a suffix A or B. 
     The developing rollers  13   a -K,  13   a -Y,  13   a -M, and  13   a -C are arranged around the photoreceptive drum  10  to sequentially contact a surface of the photoreceptive drum  10 . A deceleration gear  131  which is a two-step gear is connected to a pinion gear  30  of a development unit driving motor  101 . The deceleration gear  131  is selectively rotationally coupled with the developing roller gears  20 -K and  20 -Y, via a swing drive gear  140 A, a swing gear  150 A, and one-way gears  160 -K and  160 -Y, respectively. The deceleration gear  131  is further selectively rotationally coupled with the developing roller gears  20 -M and  20 -C via swing drive gear  140 B, swing gear  150 B, and one-way gears  160 -M and  160 -C, respectively. Idle gears  132 ,  133  and  134  are arranged between the deceleration gear  131  and the swing drive gear  140 B to adjust the driving arrangement between the developing rollers  13   a -K,  13   a -Y,  13   a -M, and  13   a -C and the photoreceptive drum  10 . Also, an odd number of the idle gears is provided so that respective rotation directions of the swing drive gears  140 A and  140 B are opposite to each other. 
     Each of the one-way gears  160  (K, Y, M, C) is arranged to correspond to a respective one of the developing roller gears  20  (K, Y, M, C). Referring now to FIG. 5, a representative one of the one-way gears  160  (K, Y, M, or C) will be described. To simplify the description of the representative one of the one-way gears, a suffix corresponding to color will not be used for individual features of the one-way gear, it being understood that the one-way gear shown and described with reference to FIG. 5 may be used for any one of the elements identified as  160 -K,  160 -Y,  160 -M or  160 -C in FIGS. 4 and 6. 
     The one-way gear  160 , as shown in FIG. 5, includes a first gear  162  adapted to engage with a respective one of the swing gears  150 A or  150 B, a second gear  164  adapted to engage a respective one of the developing roller gears  20 -K,  20 -Y,  20 -M and  20 -C, and a hub clutch  166  arranged between the first and second gears  162  and  164 . Inclined protrusions  164   a  and  166   a  are formed corresponding to each other on an inner surface of the second gear  164  and on one end of the hub clutch  166 , respectively. The inclined protrusions  164   a  and  166   a  are formed so that when the first gear  162  rotates clockwise (CW) as viewed in a direction of the arrow Z, the one-way gear  160  does not transfer power of the first gear  162  to the second gear  164  because the protrusions  166   a  of the hub clutch  166  slide along the protrusions  164   a  of the second gear  164 . However, when the first gear  162  is rotated counterclockwise (CCW), as viewed in the direction of the arrow Z, the protrusions  166   a  of the hub clutch  166  are engaged with the protrusions  164   a  of the second gear  164  so that the second gear  164  is rotated counterclockwise. Protrusions  166   b  provided on the hub clutch  166  engage protrusions  162   a  provided on the first gear  160  to rotationally couple the first gear  162  and the hub clutch  166 . Thus, the one-way gear  160  transfers a rotational force thereof to the second gear  164  according to the rotational direction of the first gear  162 . 
     Referring again to FIG. 4, the swing gear  150 A is provided between the swing drive gear  140 A and a pair of the one-way gears  160 -K and  160 -Y corresponding to the swing drive gear  140 A. A pivot arm  146 A is connected to a shaft  142 A of the swing drive gear  140 A. A first end of the pivot arm  146 A is connected to a shaft  152 A of the swing gear  150 A to support the swing gear  150 A in engagement along an outer circumference of the swing drive gear  140 A. A second end of the pivot arm  146 A is connected to a plunger  172 A of a solenoid  170 A. A spring  174 A is provided at the plunger  172 A to be compressed as the plunger  172 A is retracted into the solenoid  170 A when the solenoid  170 A is turned on. When the solenoid  170 A is turned off, the spring  174 A provides an elastic force so that the plunger  172 A is partially ejected from the solenoid  170 A. The swing arm  146 A makes the swing gear  150 A rotationally engaged with one of the two corresponding one-way gears  160 -K and  160 Y according to the operation of the solenoid  170 A. 
     A swing gear  150 B is provided between the swing drive gear  140 B and a pair of the one-way gears  160 -M and  160 -C corresponding to the swing drive gear  140 B. A pivot arm  146 B is connected to a shaft  142 B of the swing drive gear  140 B. A first end of the pivot arm  146 B is connected to a shaft  152 B of the swing gear  150 B to support the swing gear  150 B in engagement along an outer circumference of the swing drive gear  140 B. A second end of the pivot arm  146 B is connected to a plunger  172 B of a solenoid  170 B. A spring  174 B is provided at the plunger  172 B to be compressed as the plunger  172 B is retracted into the solenoid  170 B when the solenoid  170 B is turned on. When the solenoid  170 B is turned off, the spring  174 B provides an elastic force so that the plunger  172 B is partially ejected from the solenoid  170 B. The swing arm  146 B makes the swing gear  150 B rotationally engaged with one of the two corresponding one-way gears  160 -M and  160 C according to the operation of the solenoid  170 B. 
     The operation of the developer driving apparatus of an image forming apparatus having the above structure according to the present invention is described below with reference to FIGS. 4,  5  and  6 . 
     Referring particularly to FIG. 5, in a case of using the black developer  13 -K (FIG.  1 ), when the solenoid  170 A is turned off, the swing arm  146 A is rotated by the elastic force of the spring  174 A with respect to the swing drive gear shaft  142 A so that the swing gear  150 A engages the one-way gear  160 -K. Here, when the development unit driving motor is rotated counterclockwise, the swing gear  150 A is rotated clockwise via the gears  131  and  140 A. The first gear  162 -K of the one-way gear  160 -K engaged with the swing gear  150 A is rotated counterclockwise. Then, the protrusions  162   a -K of the hub clutch  166 -K are engaged with the protrusions  164   a -K of the second gear  164 -K to rotate the second gear  164 -K counterclockwise. Thus, the developer roller gear  20 -K engaged with the second gear  164 -K is rotated clockwise. Next, the developing roller  13   a -K to which a development bias voltage is applied develops the electrostatic latent image on the photoreceptive drum  10 . Here, the yellow developing roller gear  20 -Y being separated from the swing gear  150 A does not receive the rotational force of the development unit driving motor  101 . 
     Next, the operation of the magenta developing roller gear  20 -M and the cyan developing roller for a counterclockwise rotation of the development unit driving motor  101  and the deceleration gear  131  will be described. The swing gear  150 B is rotationally coupled with the deceleration gear  131  via a plurality of the idle gears  132 ,  133 , and  134  and the swing drive gear  140 B as described above. 
     The counterclockwise rotational force of the development unit driving motor  101  rotates the swing gear  150 B counterclockwise via the deceleration gear  131  and the idle gears  132 ,  133  and  134  and the swing drive gear  140 B. The swing gear  150 B rotates the first gear  162 -M of the one-way gear  160 -M clockwise. When the first gear  162 -M is rotated clockwise, the protrusions  162   a -M of the hub clutch  166 -M slide along the protrusions  164   a -M of the second gear  164 -M and do not transfer the rotational force of the first gear  162 -M to the second gear  164 -M. Thus, the magenta developing roller gear  20 -M is maintained in a stop state. Also, the one-way gear  160 -C connected to the cyan developing roller gear  20 -C is separated from the swing gear  150 B and is maintained in a stop state. 
     Next, when the yellow developing roller  13   a -Y is driven, the development bias voltage applied to the black developing roller  20 -K is turned off and the solenoid  170 A is turned on. The plunger  172 A compresses the spring  174 A and the plunger  172 A is retracted into the solenoid  170 A to rotate the swing arm  146 A with respect to the shaft  142 A of the swing drive gear  140   a , as indicated by the dashed lines in FIG.  4 . Here, the swing gear  150 A is engaged with the first gear  162 -Y of the one-way gear  160 -Y to rotate the first gear  162 -Y counterclockwise. Accordingly, the protrusions  162   a -Y of the hub clutch  166 -Y are engaged with the protrusions  164   a -Y of the second gear so that the second gear  164 -Y is rotated counterclockwise. Thus, the developing roller gear  20 -Y engaged with the second gear  164 -Y is rotated clockwise as shown in FIG.  4 . Here, the developing roller  13   a -Y to which a development bias voltage is applied develops the electrostatic latent image of the photoreceptive drum  10 . 
     In the meantime, the black developing roller gear  20 -K and the cyan developing roller gear  20 -C are in a stop state, being disengaged from the swing drive gears  150 A and  150 B, respectively. Also, the magenta developing roller gear  20 -M is in a stop state by the operation of the one-way gear  160 -M. 
     Referring now to FIG. 6, when the magenta developing roller  13   a -M is driven, the solenoid  170 A is turned off and the swing arm  146 A is rotated counterclockwise by the elastic force of the spring  174 A and the rotational force of the swing drive gear  140 A so that the swing gear  150 A is engaged with the one-way gear  160 -K. Also, the bias voltage applied to the yellow developing roller  13   a -Y is turned off. Meanwhile, the development unit driving motor  101  is rotated in a reverse direction, that is, clockwise, to rotate the development unit driving gear  30  clockwise as shown in FIG.  6 . The swing gear  150 B rotationally engages the one-way gear  160 -M in a state in which the solenoid  170 B is turned off. Here, the development unit driving motor rotates the swing gear  150 B clockwise via the gears  131 ,  132 ,  133 ,  134 , and  140 B. As the first gear  162   a -M of the one-way gear  160 -M engaged with the swing gear  150 B is rotated counterclockwise, the protrusions  166   a -M of the hub clutch  166 -M and the protrusions  164   a -M of the second gear  164  engage with each other, so that the second gear  164 -M is rotated counterclockwise. Thus, the developing roller gear  20 -M engaged with the second gear  164 -M is rotated clockwise. Next, the developing roller  13   a -M to which the development bias voltage is applied develops the electrostatic latent image on the photoreceptive drum  10 . Meanwhile, the cyan developing roller gear  20 -C being separated from the swing gear  150 B is maintained in a stop state due to not receiving a rotational force from the development unit driving motor  101 . 
     Next, the operation of the black developing roller  20 -K engaged with the swing gear  150 A for a clockwise rotation of the development unit driving motor will be described. In this case, the solenoid  170 A is turned off. 
     The clockwise rotational force of the development unit driving motor rotates the swing gear  150 A counterclockwise via the swing drive gear  140 A. The swing gear  150 A rotates the first gear  162 -K of the one-way gear  160 -K clockwise. When the first gear  162 -K is rotated clockwise, the protrusions  162   a -K of the hub clutch slide along the protrusions  164   a -K of the second gear so that the rotational force of the first gear  162 -K is not transferred to the second gear  164 -K. Thus, the black developing roller gear  20 -K is maintained in a stop state. Also, the one-way gear  160 -Y engaged with the yellow developing roller gear  20 -Y, being separated from the swing gear  150 A, is maintained in a stop state. 
     Next, continuing to refer to FIG. 6, when the cyan developing roller  13   a -C is driven, the development bias voltage applied to the magenta developing roller  13   a -M is turned off and the solenoid  170 B is turned on. The plunger  172 B retracts into the solenoid  170 B while compressing the elastic spring  174 B to rotate the swing arm  150 B with respect to the shaft  142 B of the swing drive gear  140 B. Here, the swing gear  150 B engages with the first gear  162 -C of the one-way gear  160 -C to rotate the first gear  162 -C counterclockwise. Accordingly, the protrusions  166   a -C of the hub clutch  166 -C and the protrusions  164   a -C of the second gear  164  are engaged with each other to rotate the second gear  164 -C counterclockwise. Thus, the developing roller gear  20 -C engaged with the second gear  164 -C rotates clockwise. Here, a development bias voltage is applied to the developing roller  13   a -C so that toner on the surface of the developing roller  13   a -C develops the electrostatic latent image of the photoreceptive drum  10 . 
     As described above, the developer driving apparatus of a color image forming apparatus according to the present invention reduces a cost of manufacture of a color image forming apparatus by using inexpensive solenoids and one-way gears. 
     Although an embodiment of the present invention has been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.