Abstract:
An organic photoconductive (OPC) unit of an image forming apparatus and a gear assembly arranged in the OPC unit. The gear assembly includes a drum gear formed on a flange of an OPC drum, a cleaning gear driven by a receiving power from the drum gear, and at least one idle gear interposed between the drum gear and the cleaning gear and transmitting the rotational force of the drum gear to the cleaning gear. Therefore, it is possible to drive a plurality of additional rollers with a single power source, and easy to connect the OPC drum with the gears when the OPC drum is fitted into the OPC unit. In addition, because the gear assembly is constructed in a compact form, it is possible to reduce the volume of the OPC unit.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of Korean Patent Application No. 2003-72887, filed on Oct. 20, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirely. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present general inventive concept relates to an image forming apparatus, and in particular, to a gear assembly to which power is easily and effectively transmitted from a main body of the image forming apparatus, and an optical photoconductive (OPC) drum unit provided with the gear assembly. 
   2. Description of the Related Art 
   In general, an OPC drum of a mono image forming apparatus is provided in one housing together with a developing roller, a toner transfer roller or the like, and a developing unit and an optical photoconductive (OPC) unit are not separately provided. 
   Therefore, a driving source of the OPC drum and a cleaning member for cleaning an electrification roller which electrifies the OPC drum, are usually fitted on the housing or other support member, and the developing member is driven by a separate driving source. In addition, waste toner is removed from the OPC drum by a cleaning blade, which is in contact with the OPC drum, and then freely drops; a waste toner transfer means is not separately provided. 
   In the case of recently developed color image forming apparatuses, an OPC unit and a developing unit are separately provided and the OPC unit comprises four color developing units, each for one of four colors, i.e., yellow, magenta, cyan and black. 
   Such color image forming apparatuses can be classified into a single path type and a multi-path type depending on the methods for forming and printing a color image on a recording medium. 
   A single path type image forming apparatus comprises a plurality of respective color developers and a plurality of OPC mediums. That is, a yellow developer, a magenta developer, a cyan developer and a black developer correspond to a first OPC medium, a second OPC medium, a third OPC medium and a fourth OPC medium, respectively, whereby individual color images are formed and then are transferred onto a single image transfer unit. Such a single path type image forming apparatus has an advantage in that the first to fourth OPC mediums can be constructed in a drum type that is easy to control rotational speed. However, because it is necessary to use a plurality of OPC mediums and to employ a plurality of laser scanning units (LSU), the volume of the image forming apparatus is increased and the price is high. 
   Contrary to this, in a multi-path type image forming apparatus, a plurality of developers selectively perform development on one OPC unit, in such a manner that during the first rotation of an OPC medium of the OPC unit, the yellow developer performs development, during the second rotation of the OPC medium, the magenta developer performs development, during the third rotation, the cyan developer performs development, and during the fourth rotation, the black developer performs development. Thereafter, an image, in which the colors are developed overlapping each other, is transferred to the image transfer unit at one time. 
   Such a multi-path type image forming apparatus has an advantage in that the entire volume can be reduced and the manufacturing costs can be lowered because only one OPC medium is used. However, because the OPC medium is formed in a belt type, there is a limit in properly controlling the rotational speed of the belt, and in the case of long-term use, the tension of the belt is weaken, whereby sometimes a defect may be caused in a color image. 
   Due to these problems of the prior art, there is a need to develop a drum type OPC medium to be used even in the multi-path type image forming apparatus. In particular, a need has been raised to develop an OPC unit in which yellow, magenta, cyan and black developers are fixed for stability in development, a cleaning roller that cleans an electrification roller and an auger that transfers waste are integrated within one OPC unit, and a power transmission system to effectively drive the cleaning roller and the auger. 
   SUMMARY OF THE INVENTION 
   Accordingly, the present general inventive concept has been made to solve the above-mentioned problems occurring in the prior art, and an aspect of the present general inventive concept is to provide a gear assembly built in an OPC unit in a compact form and capable of driving a cleaning roller and an auger roller with one driving source. 
   Another aspect of the present general inventive concept is to provide an OPC unit in which a gear assembly providing power transmission is completed concurrently with fitting an OPC drum into the OPC unit. 
   Yet another aspect of the present invention is to provide a gear assembly which is excellent in gear-to-gear engagement efficiency and in which a secession of a gear cannot be easily caused, and an OPC unit provided with the same. 
   Additional aspects and advantages of the present general inventive concept 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 general inventive concept. 
   The foregoing and/or other aspects of the present general inventive concept are achieved by providing a gear assembly including a drum gear formed on a flange of an OPC drum, a cleaning gear driven by receiving power from the drum gear, and at least one idle gear interposed between the drum gear and the cleaning gear and transmitting the rotational force of the drum gear to the cleaning gear. 
   The gear assembly may further include an auger gear rotated by receiving power from the cleaning gear. According to this construction, it is possible to drive not only the cleaning roller that cleans an electrification roller, but also the auger roller that transfers waste toner using a single power source. In addition, the gear assembly may further include at least one idle gear interposed between the cleaning gear and the auger gear that transmits the rotational force of the cleaning gear to the auger gear. By adding the at least one idle gear in this manner, there is an advantage in that it is possible to freely tune the distance between the auger gear and the cleaning gear. 
   Each of the cleaning gear and the auger gear may be provided with a flange in a side thereof in order to prevent the at least one idle gear from slipping away from the gear assembly. As a result, it is possible to prevent the at least one idle gear interposed between the cleaning gear and the auger gear from slipping away from the gear assembly. 
   In addition, the at least one idle gear interposed between the drum gear and the cleaning gear may include a first idle gear engaged with the drum gear, a third idle gear engaged with the cleaning gear, and a second idle gear engaged with the first and third idle gears. 
   Here, the drum gear may include a helical gear and may have an outer diameter smaller than that of the OPC drum. According to this construction, it is possible to properly tune the rotational force of the cleaning gear and the auger gear by the rotation of the OPC drum. 
   The foregoing and/or other aspects of the present general inventive concept may also be achieved by providing a gear assembly including a drum gear formed on a flange of an OPC drum, the outer diameter of the drum gear being smaller than that of the OPC drum, a cleaning gear driven by receiving power from the drum gear, the cleaning gear being provided in a side of a housing assembly, an auger gear driven by receiving power from the cleaning gear, and at least one idle gear provided in a side of the housing assembly and interposed between the drum gear and the cleaning gear to transmit the rotational force of the drum gear to the cleaning gear. Accordingly, because all gears except the drum gear are arranged to be capable of being installed in the housing assembly, it is convenient in that the assembling of the gear assembly is completed concurrently with fitting the OPC drum into the housing assembly. 
   Here, the at least one idle gear may include a first idle gear engaged with the drum gear, a third gear engaged with the cleaning gear, and a second idle gear engaged with the first and third idle gears. As described above, each of the cleaning gear, the auger gear and the second idle gear is provided with a flange in a side thereof in order to prevent the at least one idle gear from slipping away from the gear assembly. 
   In order to maximize gear-to-gear power transmission efficiency, it is preferable that the drum gear, the first idle gear and the second idle gear include helical gears, respectively, and the gear assembly further includes at least one idle gear engaged with the cleaning gear and the auger gear. 
   The foregoing and/or other aspects of the present general inventive concept may also be achieved by providing an organic photoconductive (OPC) unit of an image forming apparatus including an OPC drum, a housing assembly to protect the OPC drum, the housing assembly including a cleaning roller and a auger roller that transfers waste toner, and a gear assembly that drives the OPC drum, the cleaning roller and the auger roller using one power source provided from a main body of an image forming apparatus. As a result, it is possible to construct an OPC unit of an image forming apparatus in a compact form. 
   The gear assembly may include a drum gear formed on a side of the OPC drum, a cleaning gear receiving power from the drum gear and rotating the cleaning roller, and an auger gear receiving power from the cleaning gear and rotating the auger gear. 
   The gear assembly may further include at least one idle gear that transmits the rotational force of the drum gear to the cleaning gear between the drum gear and the cleaning gear, and at least one idle gear interposed between the cleaning gear and the auger gear to transmit the rotational force of the cleaning gear to the auger gear. According to this construction, it is possible to freely tune the distance between the drum gear and the cleaning gear and the distance between the cleaning gear and the auger gear. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and/or other aspects and advantages of the present general inventive concept will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
       FIG. 1  is a perspective view illustrating an OPC unit according to an embodiment of the present general inventive concept; 
       FIG. 2  is an exploded perspective view of the OPC unit shown in  FIG. 1 ; 
       FIG. 3  is a perspective view illustrating a gear assembly according to an embodiment of the present general inventive concept; 
       FIG. 4  is a front elevational view illustrating a state in which the gear assembly shown in  FIG. 3  is installed in a housing assembly; 
       FIG. 5  is a perspective view illustrating first to third idle gears included in the gear assembly shown in  FIG. 3 ; and 
       FIG. 6  is a perspective view illustrating a cleaning gear, a fourth idle gear and an auger gear included in the gear assembly shown in  FIG. 3 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Reference will now be made in detail to the embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present general inventive concept by referring to the figures. 
     FIG. 1  is a perspective view illustrating an OPC unit according to an embodiment of the present general inventive concept, and  FIG. 2  is an exploded perspective view of the OPC unit shown in  FIG. 1 . 
   As can be seen from  FIGS. 1 and 2 , the inventive OPC unit  100  can include a housing assembly  102 , an OPC drum  200 , and a gear assembly  300 . 
   The housing assembly  102  may include a main housing  130 , a first sub-housing  140 , a second sub-housing  160 , a bracket  120  and a handle  110 , as shown in  FIG. 2 . 
   The main housing  130  may be formed with a main opening  137 , and first to fourth sub-openings  132 ,  134 ,  136  and  138 . The main opening  137  can be an open space occupying about half of the main housing  130 , into which an OPC drum  200  is fitted. As can be seen from  FIG. 2 , a drum axle  212  can be inserted into a pair of slits  139  along the main opening  130 , and then brackets  120  may be secured to the main housing, whereby the OPC unit  100  is completed. 
   The first sub-opening  132  may be formed on the upper end of the main housing  130 , where an image transfer unit (not shown) is mounted, and the first sub-opening  132  can serve as a passage that transfers an image developed on the OPC drum  200  onto the image transfer unit. 
   The second sub-opening  134  can be formed below the lower end of the first sub-opening  132 , as can be seen from  FIG. 2 , and the second sub-opening  134  can be provided with a cleaning blade  135  at the lower end thereof. The first sub-housing  140  to be described later can be assembled in the second opening  134  to transfer waste toner, which is removed from the OPC drum  200  by the cleaning blade  135 , into a waste toner sump (not shown). 
   The third sub-opening  136  can be formed in the bottom of the main housing  130  in a rectangular shape. A laser scanning unit (LSU) (not shown), which forms an image on the OPC drum using laser beam, can be positioned at the bottom end of the third opening  136  and to form an image to be transferred on the OPC drum  200  through the third sub-opening  136 . 
   The fourth sub-opening  138  can be formed between the second sub-opening  134  and the third sub-opening  136 , and the sub-housing  160  and an electrification roller unit  150  as shown in  FIG. 2  can be mounted in the fourth sub-opening  110 . That is, the electrification roller unit  150  consisting of an electrification roller  151  and a cleaning roller  152  and can be mounted through the fourth sub-opening  138  to be in contact with the OPC drum  200 , and the second sub-housing  160  can be connected to the main housing  130 , thereby enclosing the fourth sub-opening  138 . 
   An auger roller  142  can be mounted inside of the first sub-housing  140  to transfer waste toner toward a waste toner drop hole  146  and an auger roller gear  370  can be provided on a side of the auger roller  142 . A carriage space  148  can be formed inside of the first sub-housing  140 , which is capable of temporarily carrying the waste toner removed from the OPC drum  200 . The first sub-housing  140  can be connected to the main housing  130 , thereby enclosing the second sub-opening  134 . 
   The second sub-housing  160  can be provided with an electrostatic elimination light guide  162  in a side thereof and formed with a plurality of ribs  166  on the inner surface. In addition, a plurality of screw holes  164  can be formed in the second sub-housing for a screw connection. The electrostatic elimination light guide  162  serves to guide electrostatic elimination light to the OPC drum  200  to eliminate static electricity from the OPC drum  200  and it is desirable to form the light guide to be transparent or semi-transparent. The plurality of ribs  166  prevent the toner removed by the cleaning roller  152  from being scattered due to the rotation of the OPC drum  200 , the electrification roller  151  and the cleaning roller  152 . 
   As shown in  FIG. 2 , the brackets  120  can be mounted on the opposite sides of the main housing  130  via a plurality of screws and each bracket may include a shock absorbing bar  122 , a coil spring  124 , and a support member  126 . The shock absorbing bar  122  can be in contact with the image transfer unit (not shown) when the image transfer unit is seated on the top end of the housing assembly  102 , the coil spring  124  can elastically support the bottom of the shock absorbing bar  122 , and the support member  126  can receive the coil spring  124  and the shock absorbing bar  122  and be secured on the main housing  130 . As a result, when the image transfer unit (not shown) is seated on the top end of the housing assembly  102 , the bracket  120  absorbs an impact. 
   The handle  110  can be provided with openings  114 , so that it can be hingedly connected to the opposite sides of the main housing  130 , and can include an anti-slip part  116  and a lateral leg part  112  at each end thereof. Each of the lateral leg parts  112  can be formed with a hook part  117  to be latched in a flange seating part  131  in the main housing  130 . 
   As shown in  FIG. 2 , the OPC drum  200  is a cylindrical drum and an image will be formed on the OPC drum  200 . A flange  230  is fitted onto each side of the OPC drum  200  and the drum axle  212  extends through the center of the flange. Such an OPC drum  200  is inserted into the housing assembly and rotates the gear assembly  300  (see  FIG. 1 ), which will be described later, while the OPC drum  200  is being rotated. 
     FIG. 3  is a perspective view illustrating an embodiment of a gear assembly according to the present general inventive concept,  FIG. 4  is a front elevational view illustrating a state in which the gear assembly shown in  FIG. 3  is installed in a housing assembly,  FIG. 5  is a perspective view illustrating first to third idle gears included in the gear assembly shown in  FIG. 3 , and  FIG. 6  is a perspective view illustrating a cleaning gear, a fourth idle gear and an auger gear included in the gear assembly shown in  FIG. 3 . 
   As shown in  FIGS. 3 to 6 , the gear assembly  300  according this embodiment can include a drum gear  310 , first to fourth idle gears  320 ,  330 ,  340  and  360 , a cleaning gear  350  and an auger gear  370 . 
   The drum gear  310  can be projectingly formed on a flange  230  provided on a side of an OPC drum  200 , and an outer diameter d of the drum gear  310  is smaller than the outer diameter D of the OPC drum  200 , as shown in  FIGS. 3 and 4 . The drum gear  310  can engage with the first idle gear  320  on the top end of the first idle gear  320 . As shown in  FIG. 4 , when the drum gear  310  is mounted in the housing assembly  102 , one side of the drum gear  310  can project toward the main opening  137  and the other side can project toward a power source insertion part  133  so that it engages with the power source (not shown) installed on the main body and thereby rotates. In addition, as shown in  FIG. 3 , it is an aspect that the drum gear  310  is a helical gear. 
   The first to third idle gears  320 ,  330 ,  340  can engage with the drum gear  310  and the cleaning gear  350 , as shown in  FIGS. 3 to 5 , and hence serve to transmit the rotational force of the drum gear  310  to the cleaning gear  350 . Furthermore, the first idle gear  320  engages with the drum gear  310  and can be a helical gear. The second idle gear  330  rotates in the state of being engaged with the first idle gear  320  and the third idle gear  340  and can be provided with a flange  332  (see  FIG. 5 ) on a side thereof, thereby preventing the first idle gear  320  and the third gear  340  from slipping away from the housing assembly  102 . The second idle gear  330  can be a double gear, which can be divided into a helical gear section  334  engaging with the first idle gear  320  and a plain gear section  336  engaging with the third idle gear  340 . Because the plain gear section  336  is more deeply positioned toward the housing assembly  102  than the helical gear section  334  (in the direction indicated by arrow A in  FIG. 5 ), it is also possible to install the third idle gear  340  more deeply toward the housing assembly (in the direction A), whereby the volume of the OPC unit  100  can be reduced. The third idle gear  340  rotates in the state of being engaged with the second idle gear  330  and the cleaning gear  350  and can be divided into a gear section  346  and a ring section  342  (see  FIG. 5 ). The gear section  346  can include a plain gear engaging with the second idle gear  320  and the cleaning gear  350 , and the ring section  342  can project from the front of the gear section  342  as shown in  FIGS. 4 and 5 , thereby being caught by the inner side  335  of the helical gear section  334  in the second idle gear  330 , whereby the third idle gear  340  is prevented from slipping away from the housing assembly  102  (see  FIG. 5 ). 
     FIG. 6  shows that the cleaning gear  350  has a smooth surface and is a non-auger member. The cleaning gear  350  can engage with the third idle gear  340  and the fourth idle gear  360  as shown in  FIGS. 3 ,  4  and  6 , whereby the cleaning gear  350  receives power from the third idle gear  340  and transmits it to the fourth idle gear  360 . One side of the cleaning gear  350  is provided with a flange  352  that prevents the fourth idle gear  360  (see  FIG. 6 ) from slipping away from the housing assembly  102  and rotates the cleaning roller  152  to clean the electrification roller  151 . The center part of the cleaning gear  350  can be cut to form a “D” hole in order to enhance the rotational force transmission efficiency. 
   The fourth idle gear  360  is installed in a side of the housing assembly  102  and transmits rotational force received from the cleaning gear  350  to the auger gear  370 . In addition, the fourth idle gear  360  can include a plain gear and can be cut to form a “D” hole so that the end of the auger roller  142  can be fitted into the “D” hole. 
   The auger gear  370  drives the auger roller  142  that transfers waste toner and receives power from the fourth idle gear  360 . One side of the auger gear  370  can be provided with a flange  372  so that the fourth idle gear  360  cannot slip away from the housing assembly  102 . 
   The operational relation of the inventive gear assembly constructed as described above will be described in detail. 
   Firstly, if the OPC unit  100  is mounted in a main body of an image forming apparatus (not shown), a power source (not shown) can be inserted into a power source insertion part  133  in the housing assembly  102  and transmits a driving force to the drum gear  310  of the OPC drum  200 . 
   When the drum gear  310  is rotated due to the transmitted power, the OPC drum  200  itself rotates and an image is formed on the OPC drum  200 . The rotational force is transmitted to the cleaning gear  350  through the first idle gear  320  engaged with the drum gear  310 , the second idle gear  330  engaged with the first idle gear  320 , and the third idle gear  340  engaged with the second idle gear  330 . By this, the cleaning roller  152  rotates in a direction identical to that of the electrification roller  151  and cleans the surface of the electrification roller  151 . 
   As the cleaning gear  350  rotates, the fourth idle gear  360  is rotated and the fourth idle gear  360  rotates the auger gear  370 . Therefore, toner removed from the surface of the OPC drum  200  by a cleaning blade  135  (see  FIG. 2 ) is moved toward the toner drop hole  146  and then drops into a waste toner sump (not shown). 
   As described above, because a gear assembly according to the present general inventive concept and an OPC unit provided with the same are constructed in such a manner that gears to drive a cleaning gear and an auger gear are provided on one side of the housing assembly in a compact form, it is possible to reduce the entire volume of the OPC unit and it is also possible to drive the cleaning roller and the auger roller with one driving source. 
   According to the present general inventive concept, because a gear assembly providing power transmission is completed concurrently with fitting an OPC drum into an OPC unit, it is easy to assemble the OPC drum and to connect the drum gear with other gears. 
   Furthermore, according to the present general inventive concept, there are advantages in that it is easy to connect a gear that transmits power from a power source to an OPC unit, in that gear-to-gear engagement efficiency can be enhanced, and in that a slipping away of a gear from the housing assembly does not occur. 
   Still yet, an OPC unit according to the present general inventive concept includes a gear assembly which can be constructed in such a manner that an auger roller that transfers waste toner and an electrification roller can be driven without a separate power source, whereby it is possible to employ, in a multi-path type color image forming apparatus, a fixed type developer that is easy to control a rotational force and to enlarge the OPC drum. 
   Although a few embodiments of the present general inventive concept have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the general inventive concept, the scope of which is defined in the appended claims and their equivalents.