Patent Publication Number: US-7899387-B2

Title: Drive switching mechanism and image forming apparatus including same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2006-222183 filed Aug. 17, 2006. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates to a drive switching mechanism and an image forming apparatus including such mechanism. 
     2. Related Art 
     An image forming apparatus such as a printer, copier, or facsimile machine provided with a sheet turnover unit, including a drive switching unit for reversing the paper driving direction is known. 
     SUMMARY 
     An aspect of the present invention resides in a drive switching mechanism including a first gear, a second gear, a support member for movably supporting the first gear and the second gear, and a switching unit that moves the support member to reverse an output direction of the first gear and the second gear. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present invention will be described in detail based on the following figures, wherein: 
         FIG. 1  is a cross sectional diagram of an image forming apparatus according to an exemplary embodiment of the present invention; 
         FIG. 2  is a cross sectional diagram illustrating a configuration of a drive switching device and its periphery, when a sheet turnover unit embodied herein is detached from the image forming apparatus main body; 
         FIGS. 3A and 3B  outline the drive switching device embodied herein, wherein  FIG. 3A  is a front view and  FIG. 3B  is a side view of the drive switching device; 
         FIG. 4  is a cross sectional diagram illustrating the configuration of the drive switching device and its periphery, when the sheet turnover unit embodied herein is attached to the image forming apparatus main body; and 
         FIG. 5  is a cross sectional diagram illustrating a configuration of the drive switching device and its periphery, when a sheet turnover unit embodied according to a second exemplary embodiment of the invention is detached from the image forming apparatus main body. 
     
    
    
     DETAILED DESCRIPTION 
     Then, exemplary embodiments of the present invention are described based on the drawings. 
       FIG. 1  shows an outline of an image forming apparatus  10  embodied herein according to the present invention. The image forming apparatus  10  has an image forming apparatus main body  12 . An image forming unit  14  is installed inside the image forming apparatus main body  12  and an output tray  16  is provided on the top of the image forming apparatus main body  12 . In the lower part of the image forming apparatus main body  12 , a paper feeder  18  which will be described later is installed. A sheet turnover unit  22  is removably attached to the rear side (left side in  FIG. 1 ) of the apparatus main body  12 . The sheet turnover unit  22  has a sheet turnover unit main body  24  in which a reverse path  50  which will be described later is provided. 
     The image forming unit  14  is, for example, of an electrophotographic type, and composed of the following: an image carrying body  26  made of a photoreceptor; a charging device  28  that charges the image carrying body  26  evenly, wherein the charging device  28  is formed of, for example, a charging roller; an optical projection device  30  that, by light irradiation, projects a latent image onto the image carrying body  26  charged by the charging member  28 ; a development device  32  that applies a developer to a latent image formed on the image carrying body  26  by the optical projection device  30 , thus making the latent image visible; a transfer device  34  that transfers a developer image created by the development device  32  onto a sheet, wherein the transfer device  34  is formed of, for example, a transfer roller; a cleaning device  36  that clears remaining developer particles from the image carrying body  26 , wherein the cleaning device  36  is formed of, for example, a blade; and a fixing device  38  that fuses and fixes the developer image on the sheet, transferred by the transfer device  34 , to the sheet, wherein the fixing device  38  is formed of, for example, a pressure roller and a heating roller. The optical projection device  30  is formed of, for example, a scan-type laser illumination device. This device is placed in parallel with a paper cassette  20  in the paper feeder  18  and nearer to the front (right side in  FIG. 1 ) of the image forming apparatus main body  12 , and emits light that passes across the development device  32  and irradiates the image carrying body  26 . The development device  32  includes a development roller  42  positioned in contact with the outer surface of the image carrying body  26 . 
     A process cartridge  40  is a cartridge in which the image carrying body  26 , the charging device  28 , the development device  32 , and the cleaning device  36  are integrated. The process cartridge  40  is positioned directly under the output tray  16  and this cartridge is removably installed in the apparatus main body  12 . 
     In the apparatus main body  12 , for example, registration rollers  44  are placed upstream of the transfer device  34  (beneath the transfer device  34  in  FIG. 1 ). From the paper feeder  18 , a sheet guided onto a transport path  45  and transported is temporarily stopped by the registration rollers  44 . The sheet is moved into the image forming unit  14  at appropriate timing. After an image is produced on the sheet, the sheet is outputted by output rollers  46  to the output tray  16 . 
     In the case of both-side printing, however, the sheet gets back to the reverse path  50 . Specifically, there is a two-way divergence just before the output rollers  46  and a switching pawl (not shown) is provided at the divergence. The reverse path  50  is formed for going back from the divergence to the registration rollers  44 . Transport rollers  52   a  to  52   c  are provided along the reverse path  50 . In the case of both-side printing, the switching pawl (not shown) is placed to a position to open the reverse path  50  and the output rollers  46  rotate reversely when a part of the sheet has been outputted out of the apparatus main body  12 . The sheet is reversed and guided to the reverse path  50  in the opposite direction to the output tray  16 . The sheet is transported again to pass the registration rollers  44 , a nip between the transfer device and the image carrying body  26 , and to the fixing device  38 , and then outputted to the output tray  16 . 
     The paper feeder  18  includes the paper cassette  20 , a pickup roller  54 , a feed roller  56 , and a retard roller  58 . The pickup roller  54  abuts on a top one of sheets stacked in the paper cassette  20  and picks up the sheet. The feed roller  56  and the retard roller  58  are positioned to contact with each other, downstream of the pickup roller  54 , and work together for sheet by sheet feeding to feed only the top sheet picked up by the pickup roller  54 . 
     Then, an example of a drive switching mechanism  60  is explained based on  FIGS. 2 through 4 . 
     As shown in  FIG. 2 , a forward rotary motor  62  as a drive unit is installed in the image forming apparatus main body  12 . A forward rotary motor gear  64  is positioned on the forward rotary motor  62 . This forward rotary motor  62  is a motor running in only one direction (as indicated by arrow A in  FIG. 2 ). In the apparatus main body  12 , further, a first idler gear  66 , a first connecting gear  68 , a second connecting gear  70 , a feed gear  72 , a transport gear  74 , a sway gear train  76 , and an output gear  86  are positioned. 
     The first idler gear  66  is provided on the drive side of the sway gear train  76  and positioned to interlock with a part of the sway gear train  76  when the sway gear train  76  is in a predefined position. The first connecting gear  68  is positioned to interlock with the second connecting gear  70  and the feed gear  72  provided coaxially with the feed roller  56 . The second connecting gear  70  is positioned to interlock with the transport gear  74  provided coaxially with one of the transport rollers  52   c . Thus, the forward rotary motor  62  is arranged to rotate the feed roller  56  in a forward direction (as indicated by arrow B in  FIG. 2 ) via the forward rotary motor gear  64 , the first idler gear  66 , the first connecting gear  68 , and the feed gear  72 , and rotate the transport rollers  52   c  in a forward direction (as indicated by arrow C in  FIG. 2 ) via the forward rotary motor gear  64 , the first idler gear  66 , the first connecting gear  68 , the second connecting gear  70 , and the transport gear  74 . 
     The output gear  86  is provided coaxially with one of the output rollers  46 . The output gear  86  is provided on the load side of the sway gear train  76  and positioned to interlock with a part of the sway gear train  76  when the sway gear train  76  is in a predefined position. 
     In the sheet turnover unit main body  24 , a forward/reverse rotary motor  88  as a drive unit, a forward/reverse rotary motor gear  90 , and a second idler gear  92  are installed. The forward/reverse rotary motor  88  is a motor running in two directions; i.e., it is rotatable in both forward and reverse directions (as indicated by arrows D and E in  FIG. 2 ). The second idler gear  92  is positioned to interlock with the forward/reverse rotary motor gear  90 . This second idler gear  92  is provided on the drive side of the sway gear train  76  and designed to interlock with a part of the sway gear train  76  when the sheet turnover unit  22  is attached to the image forming apparatus main body  12 , as will be described later. 
     In the sheet turnover unit main body  24 , a forward rotary motor running only in one direction may be installed and a drive direction reversing unit may be provided so that the direction of the drive interlocked with the forward rotary motor can be reversed. An additional gear train may be provided that interlocks with the forward rotary motor  62  when the sheet turnover unit is attached to the image forming apparatus main body  12  and the drive direction reversing unit may be provided in the sheet turnover unit main body  24  so that the direction of the drive interlocked with the additional gear train can be reversed. 
     On the inner side (right side in  FIG. 2 ) of the sheet turnover unit main body  24 , a rack  96  like an elongated bar is provided which protrudes horizontally from the sheet turnover unit main body  24 . 
     Also as shown in  FIGS. 3A and 3B , the drive switching mechanism  60  includes the sway gear train  76 , a sway gear train supporting member  84 , and a switching unit  94 . The sway gear train  76  is made up of a first sway idler gear  78  as a first gear, a second sway idle gear  80  as a second gear, and a sway fulcrum gear  82 . 
     The sway gear train supporting member  84  is formed in a substantially triangle shape with round vertices and a pinion gear  84   a  is provided in the vicinity of one vertex. The pinion gear  84   a  is formed in a partially cut circle like a D shape and provided integrally with the sway gear train supporting member  84 . The sway gear train supporting member  84  is provided with a support axis  78   a  and a support axis  80   a . The first sway idler gear  78  and the second sway idler gear  80  are rotatably supported on the support axis  78   a  and the support axis  80   a , respectively. 
     The sway fulcrum gear  82  is positioned to engage with the first sway idler gear  78  and the second sway idler gear  80  and rotatably supported on a support axis  82   a  provided in the sway gear train supporting member  84 . The support axis  82   a  is provided in the center of rotation of the pinion gear  84   a  and coaxially supports the pinion gear  84   a  and the sway fulcrum gear  82 . One end of the support axis  82   a  is rotatably provided in the image forming apparatus main body  12 . 
     Thus, the sway gear train supporting member  84  movably supports the first sway idler gear  78  and the second sway idler gear  80 . 
     The switching unit  94  includes the above pinion gear  84   a  and the rack  96  that is engaged with the pinion gear  84   a . By the engagement of the pinion gear  84   a  and the rack  96 , translatory movement of the rack  96  is converted into rotary motion of the pinion gear  84   a  and, thereby, the sway gear train supporting member  84  turns. 
     When the sheet turnover unit  22  is detached from the image forming apparatus main body  12 , as shown in  FIG. 2 , the forward rotary motor gear  64 , the first idler gear  66 , the first sway idler gear  78 , the sway fulcrum gear  82 , the second sway idler gear  80 , and the output gear  86  are interlocked together. Thus, the output rollers  46  are driven to rotate in a forward direction (as indicated by arrow F in  FIG. 2 ) by the drive of the forward rotary motor  62 . 
     As shown in  FIG. 4 , when attaching the sheet turnover unit  22  to the image forming apparatus main body  12  begins, the rack  96  and the pinion gear  84   a  are engaged and the sway gear train supporting member  84  turns on the support axis  82   a  (moves in a direction indicated by arrow H in  FIG. 4 ). At this time, the first sway idler gear  78  and the first idler gear  66  are disengaged and the second sway idler gear  80  and the output gear  86  are disengaged. Upon completion of attaching the sheet turnover unit  22 , by a given amount of rotation of the pinion gear  84   a  turned by the lateral movement of the rack  96 , the first sway idler gear  78  and the output gear  86  are interlocked and the second sway idler gear  80  and the second idler gear  92  are interlocked. Thereby, the forward/reverse rotary motor gear  90 , the second idler gear  92 , the second sway idler gear  80 , the sway fulcrum gear  82 , the first sway idler gear  78 , and the output gear  86  are interlocked together. Thus, the output rollers  46  are driven to rotate in both forward and reverse directions (as indicated by arrows F and G in  FIG. 2 ) by the drive of the forward/reverse rotary motor  88 . 
     In this way, switching of the drive that drives the output rollers  46  can be performed by attaching/detaching the sheet turnover unit  22  to/from the image forming apparatus main body  12 . Specifically, by the engagement of the rack  96  of the sheet turnover unit  22  and the pinion gear  84   a , the sway gear train supporting member  84  turns. This turning moves the first sway idler gear  78  and the second sway idler gear  80  to reverse the output direction of the drive switching mechanism  60 . In this way, the input and output gears in the drive switching mechanism  60  are used to transmit the drive. This avoids useless idle running of at least the input and output gears and can suppress vibration and noise. 
     By use of the rack  96  and the pinion gear  84   a  as the switching unit, the first sway idler gear  78  and the second sway idler gear  80  can be moved to a greater extent than the amount of movement of the sheet turnover unit  22 . This makes it easy to lay out gear trains in various ways. Moreover, by changing the gear ratio between the rack  96  and the pinion gear  84   a , the amount of movement of the sheet turnover unit main body  24  and the amount of rotation of the sway gear train supporting member  84  can be adjusted easily. 
     When the sheet turnover unit  22  is attached to the image forming apparatus main body  12 , the output rollers  46  can be rotated in both forward and reverse directions by the forward/reverse rotary motor  88  within the sheet turnover unit main body  24 . Accordingly, the structure inside the image forming apparatus main body  12  can be simplified, as compared with the image forming apparatus main body  12  incorporating the switching unit. When the sheet turnover unit  22  is not in use, noise and power consumption can be suppressed, as compared with the image forming apparatus main body  12  incorporating another motor for reversing the rotation of the output rollers  46 . 
     Next, a second exemplary embodiment is described based on  FIG. 5 . 
     The sheet turnover unit main body  24  configured according to the second exemplary embodiment includes the following: a forward/reverse rotary motor  88 , as a drive unit, which is rotatable in both forward and reverse directions (as indicated by arrows D and E in  FIG. 5 ); a forward/reverse rotary motor gear  90 ; a second idler gear  92 ; a second connecting gear  70 ; and a transport gear  74 . The second connecting gear  70  is positioned to interlock with the transport gear  74  provided coaxially with one of the transport rollers  52   c . The second connecting gear  70  is designed to interlock with the first connecting gear  68  when the sheet turnover unit  22  is attached to the image forming apparatus main body  12 . 
     In this way, by providing the second connecting gear  70  and the transport gear  74  in the sheet turnover unit main body  24 , useless rotation of the transport rollers  52   c  can be prevented when the sheet turnover unit  22  is detached. When the sheet turnover unit  22  is detached, the image forming apparatus main body  12  can be more compact. 
     As described hereinbefore, the present invention can be applied to a drive switching device and an image forming apparatus including such device for which vibration and noise have to be suppressed. 
     The present invention may be embodied in other specific forms without departing from its spirit or characteristics. The described exemplary embodiments are to be considered in all respects only as illustrated and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.