Abstract:
In this invention, the charging units are in the separate construction for the main chargers and for the ozone ducts. When installing the process units, the ozone ducts are placed on the elastic sheets of the duct cases that are fixed to the main frame. The process units are slid while slanting the ozone ducts to the duct cases by the main chargers against the bias force of the elastic sheets. Fluctuation in manufacturing accuracy is absorbed by the elastic sheets and the maintenance efficiency when installing/removing the process units is improved by sliding the process units smoothly. Further, the charging units are supported certainly by the main frame.

Description:
The present application is a divisional of U.S. application Ser. No. 11/253,713 filed Oct. 20, 2005, the entire contents is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to an image forming apparatus to form images according to the electro-photographic system such as copying machines, printers and a charging unit fixing method in an image forming apparatus to make it easy to install/remove main chargers. 
     DESCRIPTION OF THE BACKGROUND 
     In electro-photographic type image forming apparatus such as copying machines, printers, etc., some of corona type chargers to charge photosensitive drums recover ozone generated by the corona discharge to conserve the environment around an image forming apparatus. In order to recover ozone generated in chargers, there are so far apparatus equipped with ozone recovery ducts on the back surfaces of chargers. 
     On the other hand, chargers or process cartridges with chargers incorporated are capable of installing or removing to/from the main body of the image forming apparatus by sliding for maintenance, etc. However, when tried to move chargers or process cartridges to the main body of an image forming apparatus by sliding them, ozone recovering ducts of chargers interfere with duct cases at the main body side of the apparatus and the smooth installing/removing of chargers or process cartridges are checked and the maintenance works can be impeded. Further, in a small sized image forming apparatus with downsized component parts arranged in narrow spaces, peripheral components are closely arranged each other and therefore, if chargers or process cartridges are slid by force, they come to contact peripheral components and may generate adverse effects. 
     So, an image forming apparatus and a method excellent in smooth sliding chargers or process cartridges for installing/removing to/from an image forming apparatus and highly precious installing chargers or process cartridges in the main body of the apparatus tightly to assure the excellent assembling and maintenance efficiency are demanded. 
     SUMMARY OF THE INVENTION 
     Therefore, effects of the present invention are to make it possible to smoothly slide chargers or process cartridges, improve the maintenance efficiency, and install chargers or process cartridges in the main body of the apparatus high preciously. 
     In order to achieve the above-mentioned effects, according to the embodiments of the present invention, it is characterized in that the apparatus is composed of a main frame to support image carriers; charging members that are installed to the main frame by sliding in the axial direction of the driving shafts of the image carriers to charge the image carriers; suction members that are fixed to the main frame at the rear side in the sliding direction of the charging members and have suction ports to suck ozone generated in the charging members; supporting members that are fixed to the main frame to support the charging members; ozone duct members placed on the supporting members in the state with the rear side ends inserted into the suction ports; and elastic members provided between the supporting members and the ozone duct members to bias the ozone duct members in the direction of the charging members installed to the main frame. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic construction diagram showing an image forming unit of a color copying machine in the embodiments of the present invention; 
         FIG. 2  is a schematic construction diagram showing a process unit in the embodiments of the present invention; 
         FIG. 3  is a schematic explanatory diagram showing the state of a claw and a locating cam of an ozone duct separately arranged in the embodiments of the present invention; 
         FIG. 4  is a schematic explanatory diagram showing the fit state of the claw and the locating cam of the ozone duct in the embodiments of the present invention; 
         FIG. 5  is a schematic perspective view showing the arrangement of the main frame in the embodiments of the present invention; 
         FIG. 6  is a flowchart showing the installation of process unit to the main frame in the embodiments of the present invention; and 
         FIG. 7  is a schematic explanatory diagram showing an ozone duct that is put in a duct case in the embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The embodiments of the present invention will be described below in detail referring to the attached drawings.  FIG. 1  is a schematic construction diagram showing an image forming unit  1  incorporated in the main body of a quadruple tandem type color copying machine  100  that is an image forming apparatus in the embodiments of the present invention. Image forming unit  1  has 4 sets of process units  2 Y,  2 M,  2 C and  2 K of yellow (Y), magenta (M), cyan (C) and black (K) arranged in parallel with along the lower side of a middle transfer belt  10 . Process units  2 Y,  2 M,  2 C and  2 K have photosensitive drums  11 Y,  11 M,  11 C and  11 K, which are image carriers, respectively. Process units  2 Y,  2 M,  2 C and  2 K are of cartridge type and are detachable integrally by sliding in parallel with the shafts of photosensitive drums  11 Y,  11 M,  11 C and  11 K along guides  3 Y,  3 M,  3 C and  3 K from the front side of main frame  101 . 
     At the primary transferring position of a middle transfer belt  10  opposing to photosensitive drums  11 Y,  11 M,  11 C and  11 K, primary transferring voltage is applied by primary transferring rollers  21 ,  21 M,  21 C and  21 K and toner images on photosensitive drums  11 Y,  11 M,  11 C and  11 K are primarily transferred on the middle transferring belt. 
     Middle transfer belt  10  is stretched by a driving roller  10   c  and a secondary transferring roller  10   a . At the secondary transfer position where a secondary transfer roller  17  is arranged opposing to secondary transferring roller  19   a , a secondary transfer voltage is applied by secondary transfer roller  17  through a paper P and a toner image on middle transfer belt  10  is secondarily transferred on the paper P. At the downstream of secondary transferring roller  17  of middle transfer belt  10 , a belt cleaner  10   b  is provided. 
     As shown in  FIG. 2 , process units  2 Y,  2 M,  2 C and  2 K have charging units  14 Y,  14 M,  14 C and  14 K, developing units  13 Y,  13 M,  13 C and  13 K, photosensitive cleaners  12 Y,  12 M,  12 C and  12 K arranged in the vicinity of photosensitive drums  11 Y,  11 M,  11 C and  11 K along the rotating direction of arrow mark m of the drums. Exposure light is irradiated between the space from charging units  14 Y,  14 M,  14 C and  14 K to developing units  13 Y,  13 M,  13 C and  13 K around photosensitive drums  11 Y,  11 M,  11 C and  11 K by a laser exposure unit  50 , which is an exposure member. Further, at around photosensitive drums  11 Y,  11 M,  11 C and  11 K, charging units  14 Y,  14 M,  14 C and  14 K, developing units  13 Y,  13 M,  13 C and  13 K or photosensitive drum cleaners  12 Y,  12 M,  12 C and  12 K are detachable as a single body, respectively. 
     Next, charging units  14 Y,  14 M,  14 C and  14 K and their fixing status will be described in detail. Since charging units  14 Y,  14 M,  14 C and  14 K are in the same structure, common reference numerals will be used for explanation. As shown in  FIG. 2 , charging units  14 Y,  14 M,  14 C and  14 K are composed of a main charger  140  that is a charging member and an ozone duct  141  that is an ozone duct member, respectively. The frame of main charger  140  is made of stainless steel plate, etc. Ozone duct  141  is made of resin (ABS resin), etc. 
     Main charger  140  charges photosensitive drums  11 ,  11 M,  11 C and  11 K through the tip of a needle electrode  142  which has a needle shape boss on a thin metal plate. Main charger  140  and ozone duct  141  are formed in separate structures. When main charger  140  and ozone duct  141  are installed to main frame  101 , both of them fit each other and an ozone flow path R is formed on the back of the charging surface by needle electrode  142 . 
     As shown in  FIG. 3  and  FIG. 4 , a claw portion  150  that is an interference member and has an inclined surface  150   a  on the front side end of ozone duct  141 . At the position opposite to claw portion  150  of main charger  140 , a locating cam  151  that is a locating member is provided by protruding. Locating cam  151  fits inclined surface  150   a  of claw portion  150  when charging units  14 Y,  14 M,  14 C and  14 K are installed in the main body of the apparatus and fixes ozone duct  141  coupled with claw portion  150  on duct case  148  by inclined toward duct case  148 . 
     As shown in  FIG. 5 , at the rear side of main frame  101 , main duct  144  that is a suction member to suck ozone generated in charging units  14 Y,  14 M,  14 C and  14 K and other floating matters are provided. In main duct  144 , four suction ports  146  communicating to charging units  14 Y,  14 M,  14 C and  14 K are formed. Main duct  144  sucks ozone generated in charging units  14 Y,  14 M,  14 C and  14 K by vacuum sucking force and recovers in an ozone recovery unit provided in main duct  144 . 
     Process units  2 Y,  2 M,  2 C and  2 K are normally set in main frame  101  based on the driving shafts of photosensitive drums  11 Y,  11 M,  11 C and  11 K. Therefore, ozone ducts  141  for charging units  14 Y,  14 M,  14 C and  14 K arranged opposing to photosensitive drums  11 Y,  11 M,  11 C and  11 K get loose from the supporting members on main frame  101  if there is fluctuation in manufacturing accuracy of process units  2 Y,  2 M,  2 C and  2 K. In order to absorb this fluctuation, an elastic sheet  147  made of a sponge that is an elastic member is placed between charging units  14 Y,  14 M,  14 C and  14 K and main frame  101 . 
     In main frame  101 , duct cases  148  that are supporting members are fixed by welding on a metallic sheet partition plate  101   a  provided between laser exposure unit  50  and process units  2 Y,  2 M,  2 C and  2 K. Furthermore, elastic sheet  147  is bonded on duct cases  148 . Ozone duct  141  is kept put on elastic sheet  147 . Zone duct  141  is biased in the direction of main charger  140  by elastic sheet  147  between main charger  140  and duct case  148  and fixed without looseness in the main body of the apparatus. 
     Further, the rear side end of ozone duct  141  is inserted into a suction port  146  of main duct  144  and charging units  14 Y,  14 M,  14 C and  14 K are thus inserted into main duct  144 . 
     Next, actions will be described. First, referring to the flowchart shown in  FIG. 6 , the installation of process units  2 Y,  2 M,  2 C and  2 K into main frame  101  will be described. Before installing process units  2 Y,  2 M,  2 C and  2 K, ozone duct  141  is placed on duct case  148  in the state with its rear side end inserted into suction port  146  of main duct  144  (Step  200 ). At this time, the rear side end of ozone duct  141  is defined to suction port  146  of main duct  144 . On the other hand, ozone duct  148  is biased upward above duct case  148  by elastic sheet  147  as shown in  FIG. 7 . 
     Then, process units  2 Y,  2 M,  2 C and  2 K are slid into main frame  101  from the front side along guides  3 Y,  3 M,  3 C and  3 K (Step  201 ). At this time, in charging units  14 Y,  14 M,  14 C and  14 K, main charger  140  slides while pushing ozone duct  141  to duct case  148  side against the bias force of elastic sheet  147 . At this time, ozone duct  141  is only placed on duct case  148  and elastic sheet  147  exists between ozone duct  141  and duct case  148 . Accordingly, even if main charger  140  and ozone duct  148  somewhat interfere with each other for fluctuation in manufacturing accuracy, main charger  140  of process units  2 Y,  2 M,  2 C and  2 K can be smoothly slide without receiving a large resistance from ozone duct  141 . 
     Thereafter, photosensitive drums  11 Y,  11 M,  11 C and  11 K fit the driving shafts and the installation of process units  2 Y,  2 ,  2 C and  2 K to main frame  101  is completed (Step  202 ). At this time, charging units  14 Y,  14 M,  14 C and  14 K are slid in the arrow direction and claw  150  of ozone duct  141  contacts locating cam  151  of main charger  140 . With the sliding of process units  2 Y,  2 M,  2 C and  2 K, locating cam  151  presses down inclined surface  150   a  of claw  150  in the arrow direction t against the bias force of elastic sheet  147 . 
     When the installation of process units  2 Y,  2 M,  2 C and  2 K to main frame  101  is completed, ozone duct  141  is slanted in the direction of duct case  148  and fixed at above duct case  148 . In this fixed state, ozone duct  141  is always receiving the bias force of elastic sheet  147  in the direction of main charger  140 . Accordingly, even if the manufacturing accuracy fluctuates, charging units  14 Y,  14 M,  14 C and  14 K are firmly fixed to main frame  101  without becoming loose. Further, charging units  14 Y,  14 M,  14 C and  14 K are certainly connected to suction port  146  of main duct  144 . 
     After thus installing process units  2 Y,  2 M,  2 C and  2 K to main frame  101 , the image forming operation starts and various images are obtained. While the image formation is executed, in the ozone flow path R of charging units  14 Y,  14 M,  14 C and  14 K, the air flow toward suction port  146  at the rear side is generated by the vacuum suction force of main duct  144 . As a result, the ozone generated by the corona discharge of needle electrode  142  or other floating matters, etc. are sucked in the main duct  144  and recovered in the ozone recovery unit. 
     When the maintenance works including exchange or cleaning of process units  2 Y,  2 M,  2 C and  2 K become necessary while the image forming is being executed, move process units  2 Y,  2 M,  2 C and  2 K by sliding to the front side. Charging units  14 Y,  14 M,  14 C and  14 K are slid in the direction reverse to the arrow direction s and locating cam  151  of main charger  140  is separated from claw  150  of ozone duct  141 . 
     When process units  2 Y,  2 M,  2 C and  2 K are taking out, in charging units  14 Y,  14 M,  14 C and  14 K, main charger  140  only is taken out from main frame  101 . Ozone duct  141  is placed on duct case  148  in the state inserted into suction port  146  of main duct  144 . When process units  2 Y,  2 M,  2 C and  2 K are taken out, charging units  14 Y,  14 M,  14 C and  14 K can be slid smoothly without receiving a large resistance from ozone duct  141  by elastic sheet  147  that is present between ozone duct  141  and duct case  148 . After completing the maintenance, while pressing ozone duct  141  to duct case  148  side against the bias force of charging elastic sheet  147  again, install process units  2 Y,  2 M,  2 C and  2 K by sliding into main frame  101  from the front side. 
     According to this embodiment, charging units  14 Y,  14 M,  14 C and  14 K are in separate structures depending on main charger  140  that is slid and moved or ozone duct  141  that is placed on duct case  148  of main frame  101  when process units  2 Y,  2 M,  2 C and  2 K are slid. Further, elastic sheet  147  is present between ozone duct  141  and duct case  148 . Accordingly, even if main charger  140  interfere somewhat ozone duct  148  for fluctuation in manufacturing accuracy of process units  2 Y,  2 M,  2 C and  2 K when sliding process units  2 Y,  2 M,  2 C and  2 K, and main charger  140  can be slid smoothly without receiving a large resistance from ozone duct  141 , and the inverse influence to peripheral components can be prevented. Thus, process units  2 Y,  2 ,  2 C and  2 K are moved smoothly during the maintenance operation and the maintenance efficiency can be promoted. 
     Further, according to this embodiment, locating cam  151  is provided to main charger  140  and claw  150  of ozone duct  141  is slanted and ozone duct  141  is fixed above duct case  148  when completing the installation of process units  2 Y,  2 M,  2 C and  2 K. Further, ozone duct  141  is fixed above duct case  148  in the state always biased in the direction of main charger  140  by elastic sheet  147 . Accordingly, only when main charger  140  is installed to main frame  101 , charging units  14 Y,  14 M,  14 C and  14 K can be fixed on duct case  148  without using screws or other fixing members. In addition, even if manufacturing accuracy of components is fluctuated, charging units  14 Y,  14 M,  14 C and  14 K can be surely fixed to main frame  101  without causing looseness and furthermore, ozone or other floating matters can be surely recovered and the environmental preservation is obtained. 
     Further, the present invention is not restricted to the embodiment described above but can be modified variously within the scope of the invention. For example, image carriers, charging units may not be unitized but can be of type constructed in a single unit. Further, the frame of main charger or material of ozone duct is also not restricted. In addition, the elastic member is able to slide to the main charger smoothly and its material and shape, etc. are optional provided that charging units can be fixed without loose to supporting members. Accordingly, the elastic member may not be provided for whole surface between, for example, ozone duct members and supporting members and can be provided on the peripheral edges only or only parts of them. 
     According to the present invention as described above in detail, as an elastic member is provided between the supporting member and the ozone duct member, it is possible to slide charging members smoothly without causing adverse influences to peripheral units and improve the maintenance efficiency regardless of fluctuation in manufacturing accuracy. Further, only when charging members are installed to the main frame without using exclusive fixing members, charging units can be fixed easily to the main frame. Furthermore, regardless of fluctuation in manufacturing accuracy, the charging units do not generate slackness to the main frame.