Abstract:
A drive transmission system includes a shaft member storing grease in a shaft outer circumferential small diameter section. A drive transmission gear is provided including a gear inner circumferential sliding section and a gear inner circumferential large diameter section. A gear moving device is provided to move the drive transmission gear reciprocally along the shaft member in a shaft direction. A restriction device is provided to restrict a movement range of the drive transmission gear along the shaft member in the shaft direction to enable the gear inner circumferential large diameter section to face the shaft outer circumferential small diameter section substantially continuously.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority pursuant to 35 USC §119 to Japanese Patent Application No. 2009-295908, filed on Dec. 25, 2009, the entire contents of which are hereby incorporated by reference herein. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a drive transmission system equipped with a stationary shaft member secured to an apparatus body and a drive transmission gear rotatable around the stationary shaft member, and in particular to a driving system and an image forming apparatus each equipped with the drive transmission system. 
         [0004]    2. Description of the Background Art 
         [0005]    In accordance with a demand for a longer-lasting, more durable image forming apparatus that employs an electro-photographic system, a drive transmission system that transmits a rotation driving force from a driving source to a rotation member such as a photo-conductive member is also required to be long-lasting and durable. In one such known exemplary drive transmission system, a stationary shaft member is secured to a casing of an apparatus body while a drive transmission gear rotates around the stationary shaft member to transmit a rotation driving force from a driving source to a rotation member via a drive transmission gear. In such a drive transmission system, in order for the drive transmission system can enjoy a longer life, durability of in order for the drive transmission system can enjoy a longer life, durability of a rotational sliding section existing between the drive transmission gear and the stationary shaft member must be improved. 
         [0006]    As a system that improves such durability of the rotational sliding section, a coupling drive mechanism serving as a drive transmission system is employed as described in Japanese Patent Application Laid Open No. 2001-82474 (JP-2001-82474-A). Specifically, a bearing member is provided in a rotational sliding section between a drive transmission gear and a stationary shaft member. However, the bearing member is rarely employed in the rotational sliding section in compact, inexpensive image forming apparatuses. 
         [0007]    Further, in a drive transmission system excluding such a bearing member in the rotational sliding section, an inner circumferential surface of the drive transmission gear generally slides while in frictional contact with an outer circumferential surface of the stationary shaft member when the drive transmission gear is rotated. Accordingly, the sliding section of the inner circumferential surface of the drive transmission gear (hereinafter referred to as a gear inner circumference sliding section) and that of the outer circumferential surface of the sliding section of the stationary shaft member (hereinafter referred to as a shaft outer circumferential sliding section) need improved durability. 
         [0008]    Further, it is known that one image forming apparatus in actual use employs a drive transmission system in which a grease groove filled with grease is provided on an outer circumferential surface of the stationary shaft member. 
         [0009]    For example, some conventional drive transmission systems include grease grooves on outer circumferential surfaces of stationary shaft members as shown in  FIGS. 11 and 12 , respectively, wherein  FIG. 11A  illustrates a section when viewed along a line B-B of  FIG. 11B , through which a rotation central line of a drive transmission system passes, and  FIG. 11B  illustrates a front view of the drive transmission system in a direction shown by an arrow A of  FIG. 11A , respectively. In a first conventional drive transmission system  200 , there are provided a stationary shaft member  61  secured to a frame  75  serving as a casing of an apparatus body and a drive transmission gear  64  rotating around the stationary shaft member  61 . As shown, an input gear for inputting a driving force to the drive transmission gear  64  and an output gear for outputting a driving force from the drive transmission gear  64  are also provided but omitted from  FIGS. 11A and 11B . 
         [0010]    In such a first conventional drive transmission system  200 , when a driving force is transmitted from an input gear, not shown, to the drive transmission gear  64 , the drive transmission gear  64  rotates in a direction shown by an arrow C. At that moment, a gear inner circumferential surface  64   f  of the drive transmission gear  64  slides on a shaft outer circumferential surface  61   f  of the stationary shaft member  61 . Further, a grease groove  62  filled with the grease  63  is provided on the shaft outer circumferential surface  61   f  in a shaft direction of the stationary shaft member  61 . When the drive transmission gear  64  rotates in a direction shown by an arrow C, a portion of the gear inner circumferential surface  64   f  to which the grease is attracted moves to a position facing the shaft outer circumferential surface  61   f . As a result, the grease  63  can enter a section between the gear inner circumference sliding section of the gear inner circumferential surface  64   f  and the shaft outer circumference of the shaft outer circumferential surface  61   f , thereby suppressing wear and improving durability of the gear inner circumference sliding section and the shaft outer circumferential surface sliding section. 
         [0011]    However, in such a first conventional drive transmission system  200 , the shaft direction in which the groove edge section  61   e  extends as a boundary between the shaft outer circumferential surface  61   f  and the grease groove  62 , and the direction in which the gear inner circumferential surface  64   f  moves in relation to the stationary shaft member  61  are orthogonal to each other. In such a situation, when the drive transmission gear  64  rotates, the groove edge section  61   e  contacts the gear inner circumferential surface  64   f  sliding around the stationary shaft member  61  in a counter direction, so that the gear inner circumferential surface  64   f  slides in friction with the groove edge section  61   e , and is susceptible to burn-out. 
         [0012]    A second conventional drive transmission system is then utilized to resolve such a problem, as described with reference to  FIG. 12 , which illustrates a cross section of a drive transmission gear  64  along its rotation central line  64   a.    
         [0013]    Specifically, in the second conventional drive transmission system  200 , there are provided a stationary shaft member  61  secured to a frame  75  serving as a casing of an apparatus body and a drive transmission gear  64  rotating around the stationary shaft member  61 . Further provided are an input gear  65  for inputting a driving force from a drive motor  500  to a drive transmission gear  64  and an output gear  69  for outputting a driving force from the drive transmission gear  64  to a driven section, not shown. The drive transmission gear  64  is a two-step gear having large- and small-diameter sections  77  and  79 , respectively. When the drive motor  500  operates and accordingly the input gear  65  rotates, a rotational driving force caused in this way is inputted to the large diameter section  77 , thereby rotating the drive transmission gear  64 . Owing to the rotation of the drive transmission gear  64 , the small diameter section  79  of the drive transmission gear  64  and the output gear  69  linked therewith rotate, so that a rotation driving force of the drive motor  500  is transmitted to the driven section. 
         [0014]    The large diameter section  77  of the drive transmission gear  64  and the input gear  65  employ helical gears, respectively. Thus, a thrusting force acts on the drive transmission gear  64  in a direction shown by arrow D in parallel to a rotation central line  64   a  when the input gear  65  and the drive transmission gear  64  rotate. Consequently, when the drive motor  500  operates and a rotation driving force caused in this way is inputted to the drive transmission gear  64 , the drive transmission gear  64  moves in a direction in which a thrusting force acts by an amount of thrusting allowance  68  and rotates there colliding with a washer  74 . 
         [0015]    When the drive motor  500  stops, the drive transmission gear  64  is biased by a biasing member in a direction opposite to the thrusting force acting direction, and separates from the washer by the amount of thrusting allowance  68 . By repeating such controlling of the drive motor  500 , the drive transmission gear  64  moves reciprocally in the thrusting direction of the shaft line direction. Further, a grease groove  62  filled with grease  63  is provided entirely around a shaft outer circumferential surface  61   f  of a cylindrical stationary shaft member  61 . When the driving motor  500  operates thereby moving the drive transmission gear  64  in the thrusting direction, a portion of the gear inner circumferential surface  64   f  facing the grease groove  62  while receiving the grease  63  therefrom while the motor is stopped is shifted to a different? position facing the shaft outer circumferential surface  61   f  on a thrusting direction side of the grease groove  621 . Thus, the grease  63  is attracted to the different position on the shaft outer circumferential surface  61   f . Subsequently, when the driving motor  500  stops and the drive transmission gear  64  moves in the opposite direction to the thrusting direction, the grease attraction portion on the shaft outer circumferential surface  61   f  faces the shaft outer circumferential surface  61   f  on a thrusting direction side than that facing the grease groove  62  during the stop condition. Thus, the grease  63  can be attracted to the portion on the gear inner circumferential surface  64   f . By repeating such controlling of the drive motor  500  and reciprocating the drive transmission gear  64  along the shaft line direction in this way, the grease in the grease groove  62  can be supplied in the thrusting direction. Thus, the grease  63  can enter between the gear inner circumferential surface  64   f  and the shaft outer circumferential surface  61   f . As a result, wear is suppressed in the gear inner circumference sliding section and the shaft outer circumference sliding section, so that durability can be improved. 
         [0016]    Further, since the groove edge section  61   e  serving as a boundary between the grease groove  62  and the shaft outer circumferential surface  61   f  is arranged in a sliding direction, the grease groove  62  and the shaft outer circumferential surface  61   f  do not slide in friction with each other, and burning does not occur therebetween when the drive transmission gear  64  rotates. 
         [0017]    However, since an inner diameter of a portion of a gear inner circumferential surface  64   f  facing a shaft outer circumferential surface  61   f  and that of a portion of a gear inner circumferential surface  64   f  facing a grease groove  62  are substantially the same, only an amount of grease equivalent to a capacity of the grease groove  62  can be filled in the grease groove  62  and cannot be continuously supplied for a long time period between the gear inner circumferential surface  64   f  and the shaft outer circumferential surface Elf. 
         [0018]    Further, when the grease is insufficiently supplied between the gear inner circumferential surface  64   f  and the shaft outer circumferential surface  61   f , sliding load increases therebetween, and accordingly a life of the drive transmission system becomes short. 
       SUMMARY OF THE INVENTION 
       [0019]    Accordingly, an object of the present invention is to provide a new and novel drive transmission system comprising a shaft member including an shaft outer circumferential sliding section on its outer circumferential surface, and a shaft outer circumferential small diameter section having a smaller diameter than that of the shaft outer circumferential sliding section as a groove circulating around its outer circumferential surface storing grease, and a drive transmission gear freely rotatably supported by the shaft member therearound. The drive transmission gear is rotated when a rotation driving force is input thereto. The drive transmission gear includes a gear inner circumferential sliding section on its inner circumferential surface. The gear inner circumferential sliding section contacts and slides on the shaft outer circumferential sliding section of the shaft member when the drive transmission gear rotates. A gear inner circumferential large diameter section having a large diameter than that of the gear inner circumferential sliding section on its inner circumferential surface is provided. A gear moving device is provided to move the drive transmission gear reciprocally along the shaft member in a shaft direction. A restriction device is provided to restrict a movement range of the drive transmission gear along the shaft member in the shaft direction to enable the gear inner circumferential large diameter section to face the shaft outer circumferential small diameter section substantially continuously. 
         [0020]    In another aspect, the gear moving device is a gear mechanism to provide a thrusting force to the drive transmission gear when rotating the drive transmission gear. 
         [0021]    In yet another aspect, the gear mechanism includes one of a helical gear, a wheel gear, a bevel gear, and a worm wheel. 
         [0022]    In yet another aspect, the drive transmission gear is a two-step gear having two gears, one of which is the gear mechanism. 
         [0023]    In yet another aspect, a diameter of an inner circumference surface of the drive transmission gear increases from the gear inner circumferential sliding section to the gear inner circumferential large diameter section forming a chamfered cross section therebetween. 
         [0024]    In yet another aspect, a diameter of an inner circumference surface of the drive transmission gear gradually increases from the gear inner circumferential sliding section to the gear inner circumferential large diameter section forming a cutaway cross section therebetween. 
         [0025]    In yet another aspect, a diameter of an inner circumference surface of the drive transmission gear gradually increases from the gear inner circumferential sliding section to the gear inner circumferential large diameter section forming a round shaped cross section therebetween. 
         [0026]    In yet another aspect, a drive source is provided to drive and rotate an objective, and a drive transmission device is provided to transmit a rotation driving force from the drive source to a rotation member. The drive transmission device includes the drive transmission system. 
         [0027]    In yet another aspect, an image forming apparatus includes an image formation section that forms an image on a recording medium by initially forming an image on an image bearer and finally transferring the image onto the recording medium, and the driving device that drives a driving objective arranged in an apparatus body. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0028]    A more complete appreciation of the present invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
           [0029]      FIGS. 1A and 1B  collectively illustrate an exemplary drive transmission system according to a first embodiment of the present invention; 
           [0030]      FIG. 2  schematically illustrates an exemplary printer according to one embodiment of the present invention; 
           [0031]      FIG. 3  illustrates an exemplary K-process unit included in the printer of  FIG. 2 ; 
           [0032]      FIG. 4  illustrates an exemplary drive transmission system for transmitting a driving force to a drive roller included in the printer of  FIG. 2 ; 
           [0033]      FIGS. 5A and 5B  collectively illustrate an exemplary drive transmission system according to a second embodiment of the present invention; 
           [0034]      FIGS. 6A and 6B  collectively illustrate an exemplary drive transmission system according to a third embodiment of the present invention; 
           [0035]      FIGS. 7A and 7B  collectively illustrate an exemplary drive transmission system according to a fourth embodiment of the present invention; 
           [0036]      FIGS. 8A and 8B  collectively illustrate an exemplary drive transmission system according to a fifth embodiment of the present invention; 
           [0037]      FIGS. 9A and 9B  collectively illustrate an exemplary drive transmission system according to a sixth embodiment of the present invention; 
           [0038]      FIGS. 10A and 10B  collectively illustrate an exemplary drive transmission system according to a seventh embodiment of the present invention; 
           [0039]      FIGS. 11A and 11B  collectively illustrate a first conventional drive transmission system; and 
           [0040]      FIG. 12  illustrates a second conventional drive transmission system. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0041]    Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, in particular in  FIGS. 1 to 3 , an exemplary printer as an image forming apparatus that employs an electrophotograph system is described. 
         [0042]    The fundamental configuration and operation of the printer without an inversion unit are described in detail in U52008/0226352-A1 in columns 0020 and 0021, and US2010/0192710-A9 in columns 0026 to 0038 filed by the applicant, and such description is incorporated therein. 
         [0043]    Specifically, the inversion unit  40  includes an external cover  45  and a swinging member  46 . The external cover  45  is swingably supported around a unit swing shaft  40   a  provided in the casing of the printer body  100  as shown by an arrow A in  FIG. 2 . With such swinging, the external cover  45  is open and closes together with a swinging member  46  installed therein. When the external cover  45  is open together with the swinging member  46 , a sheet feeding path  31 , a secondary transfer nip, a post transfer conveyance path  33 , a fixing nip, a post fixing conveyance path  35 , and a sheet ejection path  36  each formed between the inversion unit  40  and the printer body  100  are separated into two and exposed outside. Consequently, a sheet jamming on the sheet feeding path  31 , that in the secondary transfer nip, that on the post transfer conveyance path  33 , that in the fixing nip, that on the post fixing conveyance path  35 , and that on the sheet ejection path  36  can be readily removed. Further, the swing member  46  is supported by the external cover  45  to swing around a swing shaft, not shown, provided in the external cover  45  when the external cover  45  is open. Due to the swinging, a pre-inversion conveyance path  41  and the inversion conveyance path  44  are vertically separated into two and are exposed outside when the swinging member  46  is open with regard to the external cover  45 . Consequently, a sheet jamming on the pre-inversion conveyance path  41  and the inversion conveyance path  44  can be readily removed. 
         [0044]    An upper cover  50  arranged on the casing of the printer  100  is freely swingably supported around an upper cover swing shaft  51  as shown by an arrow B in  FIG. 2 . Thus, when the upper cover  50  swings counter clockwise in the drawing, the upper cover  50  becomes open with regard to the casing. Then, an upper opening appearing on the casing is largely exposed outside, so that the optical writing unit  70  is exposed. 
         [0045]    In the printer  100 , since the optical writing unit  70  is arranged above the four process units  1 K to  1 C as mentioned above, the four process units  1 K to  1 C cannot be recognized from above only by opening the upper cover  50 . Further, since the optical writing unit  70  is visually obstacle, maintenance for the process units is impossible thru the upper opening appearing as the upper cover  50  is open if no countermeasure is taken. Thus, the optical writing unit  70  is detachable to the casing of the printer  100 . When, any one of the four process units  1 K to  1 C is to be replaced, the upper cover  50  is open and the optical writing unit  70  is detached to expose the process units  1 K to  1 C, so that an intended process unit  1  can be detached and is replaced. To open the upper cover  50  and detach the process unit  1  from the apparatus body, an optical writing unit  70  can be secured to the upper cover  50  so that the optical writing unit  70  separates from above the process units  1 K to  1 C together with the upper cover  50  when the upper cover  50  is open. 
         [0046]    Now, a driving device  300  that drives a belt driving roller  18  for rotating an intermediate transfer belt is described with reference to  FIG. 4 . When the driving motor  500  of the driving system  300  operates, an input gear  65  secured to a rotational shaft of the driving motor  500  rotates and transmits a rotation driving force to the driving roller gear  18   g  via a drive transmission gear  64  and an output gear  69 . 
         [0047]    The driving system  300  includes plural image formation section drive transmission gears  25 K to  25 C which transmit driving forces to respective four process units  1 K to  1 C. The K-use image formation section drive transmission gear  25 K that transmits the driving force to the K-use process unit  1 K meshes with the input gear  65  via its large diameter gear section. When the driving motor  500  operates and the input gear  65  rotates, the rotation driving force is inputted to the K-use image formation section drive transmission gear  25 K. The rotation driving force is then transmitted to respective rotation driving members of a photoconductive member  2 K, a charge roller, an agitator  8 K, a stirring paddle  9 K, a toner supply roller  10 K, and a developing roller  11 K or the like arranged in the K-use process unit  1 K. 
         [0048]    Further, the Y to C-use image formation section drive transmission gears  25 Y to  25 C, which transmission driving forces to the Y to C-use process units  1 Y to  1 C, rotate as a second driving motor  520  operates, respectively. Specifically, when the second driving motor  520  operates, a second input gear  521  secured to a rotational shaft of the second driving motor  520 , and accordingly the M use image formation section drive transmission gear  25 M that meshes with the second input gear  521  rotate. Further, the image formation section drive transmission gear  25 M transmits and rotates the C and Y use image formation section drive transmission gears  25 C and  25 Y via two idler gears  530 . As a result, the respective rotation driving members constituting the Y to C use process units  1 Y to  1 C receive the rotation driving force. When image formation is executed in a monochrome mode only using black toner, the photo-conductive members  2 Y to  2 C separate from the intermediate transfer belt  16  while the second driving motor  520  enters a halt condition. 
         [0049]    Now, a first embodiment of a drive transmission system  200  that transmits a rotation driving force from a driving motor  500  provided in a driving device  300  to the drive roller gear  18   g  is described with reference to  FIGS. 1A and 1B , which illustrate stopping and operating conditions of the driving motor  500 , respectively. 
         [0050]    As shown, the drive transmission system  200  includes a stationary shaft member  61  that is arranged horizontally. One end of the stationary shaft member  61  is screwed into a bracket  73 , while the other end having a smaller diameter being inserted and held by a holder opening formed on a frame  75 . A washer fits to the shaft small diameter section  61   a , and is sandwiched by a thrusting surface  61   c  formed on the side of a shaft large diameter section  61   b  to serve as a boundary between the small and large diameter sections  61   a  and  61   b  of the stationary shaft member  61 , and an end face of the frame  75 . A drive transmission gear  64  is attached to the shaft large diameter section so that a gear inner circumferential surface  64   f  thereof faces a shaft outer circumferential surface  61   f  of the stationary shaft member  61 . The drive transmission gear  64  of the drive transmission system  200  includes two steps of smaller and larger diameter gear sections  79  and  77 . The large gear section  77  is a helical type and is linked with an input gear  65  of a helical gear. Whereas the small gear section  79  is a flat type and is linked with an output gear  69 . When the input gear  65  and the drive transmission gear  64  rotate as a result of the linkage between the helical gears of the input gear and  65  and the larger diameter gear section  77 , a thrusting force acts in a direction in parallel to a rotational center line  64   a  of the drive transmission gear  64  as shown by an arrow D in  FIG. 1B . 
         [0051]    A gear inner circumference sliding section  67  is formed on the gear inner circumferential surface  64   f  of the drive transmission gear  64  to contact and slide on the shaft outer circumferential surface  61   f  when the drive transmission gear  64  rotates. Further, a gear inner circumference large diameter section  76  having a larger diameter than that of the gear inner circumference sliding section  67  is formed on the gear inner circumferential surface  64   f  in the opposite direction to that of the arrow D regarding the gear inner circumference sliding section  67 . A grease transfer surface  80  is formed perpendicular to the rotation central line  64   a  between a sliding section large diameter side edge  78  of the gear inner circumference sliding section  67  and the gear inner circumference large diameter section  76 . 
         [0052]    In such a situation, when the printer is expected to be compact and low cost, a private use-bearing member is hardly provided in the sliding section between the drive transmission gear  64  and the stationary shaft member  61 . Then, a grease groove  62  having a smaller outer diameter than that of the shaft outer circumferential surface  61   f  is provided on the stationary shaft member  61 . During a stop condition as shown in  FIG. 1A , the grease groove  62  is located on the side of the bracket  73  of the sliding section large diameter side edge  78  being distanced therefrom by a grease groove distance  72 . The grease groove distance  72  is greater than a width of a thrusting allowance  68 . With such a configuration, even when the drive transmission gear  64  starts rotation as shown in  FIG. 1B  and moves in the direction shown by the arrow D thereby causing the thrusting force to work on after the stopping condition as shown in  FIG. 1A , the grease groove  62  does not (closely?) face the gear inner circumference sliding section  67 . Thus, an excessive amount of grease  63  than a capacity of the grease groove  62  is prevented from being abraded by a section of the gear inner circumference sliding section  67 . As a result, the grease  63  can be continuously supplied between the gear inner circumference sliding section  67  and the shaft outer circumferential surface  61   f  for a longer time period than before. 
         [0053]    Further, burning can be avoided or suppressed even when the drive transmission gear  64  rotates and the gear inner circumferential surface  64   f  slides in friction with the groove edge section  61   e . Because, the groove edge section  61   e  serving as a boundary between the grease groove  62  and the shaft outer circumferential surface  61   f  is formed in a sliding direction. It is also true in the second conventional example of  FIG. 12 . However, even if the groove edge section  61   e  is formed in the sliding direction, stress more highly likely occurs at the sliding section between the gear inner circumferential surface  64   f  and the groove edge section  61   e  in comparison with a configuration where only the shaft outer circumferential surface  61   f  slides on the gear inner circumferential surface  64   f  as in the first embodiment. As a result, burning readily occurs when the stress concentrates on the sliding section. 
         [0000]    By contrast, in the drive transmission system  200  of the first embodiment of  FIG. 1 , the grease groove  62  does not (closely) face the gear inner circumference sliding section  67 . Thus, since the groove edge section  61   e  serving as a boundary between the grease groove  62  and the shaft outer circumferential surface  61   f  does not either (closely) face or slide in friction with the gear inner circumferential surface  64   f , the stress does not concentrate, so that the burning can be avoided or suppressed. 
         [0054]    Further, the grease  63  filled in a space formed between the gear inner circumference large diameter section  76  and the grease groove  62  is transferred onto the grease transfer surface  80  while the motor is stopped. Thus, when both the input gear  65  and the drive transmission gear  64  rotate, and the thrusting force acts in the direction of the arrow D of  FIG. 1B , the grease transfer surface  80  moves toward the washer  74 . Specifically, the grease  63  transferred onto the grease transfer surface  80  moves to the shaft outer circumferential surface  61   f  and is supplied all around the shaft outer circumferential surface  61   f  as the drive transmission gear  64  rotates. As a result, wearing of both the shaft outer circumferential surface  61   f  and the gear inner circumference sliding section  67  can be avoided or suppressed. 
         [0055]    Whereas in a case where a gear inner circumferential surface  64  having the same inner diameter faces the grease groove  62  as in the second conventional drive transmission system  200  of  FIG. 12 , only a limited amount of the grease  63  can be filled therein. Because, a gap is narrow at a section facing the grease groove  62 . Further, almost all of the grease  63  is extracted from the grease groove  62  by the gear inner circumferential surface  64   f  facing the grease groove  62 . 
         [0000]    Thus, the grease  63  cannot continuously be supplied between the gear inner circumferential surface  64   f  and the shaft outer circumferential surface  61   f  for a long time period. 
         [0056]    By contrast, in the first embodiment of the drive transmission system  200  of  FIG. 1 , by arranging the gear inner circumference large diameter section  76  to face the grease groove  62 , an amount of the grease  63  exceeding the capacity of the grease groove  62  can be filled into a space formed by the gear inner circumference large diameter section  76 . 
         [0000]    Further, the bracket  73 , the frame  75 , and the washer  74  collectively serving as a restriction device restricts movement of the drive transmission gear  64  in the shaft direction of the stationary shaft member  61  so that the gear inner circumferential large diameter section  76  can face the grease groove  62  continuously. Thus, the amount of the grease  63  exceeding the capacity of the grease groove  62  is prevented from being extracted from the grease groove  62  by the gear inner circumferential surface  64   f  of the drive transmission gear  64 . As a result, the grease  63  can be continuously supplied for a long time period between the gear inner circumference sliding section  67  and the shaft outer circumferential surface  61   f . The above-mentioned supplying of the grease  63  to both the gear inner circumference sliding section  67  and the shaft outer circumferential surface  61   f  is actually executed in the below described manner. Specifically, the grease  63  in the grease groove  62  is transferred onto the grease transfer surface  80  during the stop condition and is supplied to the shaft outer circumferential surface  61   f  when the drive transmission gear  64  and the grease transfer surface  80  move in the shaft direction during the operation condition. The drive transmission gear  64  returns to its original position and the grease transfer surface  80  approaches the grease groove  62  during the next stop condition, so that the grease  63  is transferred onto the grease transfer surface  80  again. In this way, due to repetitious movement of the drive transmission gear  64  in the shaft directions during the rotating and stopping conditions, the grease  63  filled in the grease groove  62  is supplied to both the gear inner circumference sliding section  67  and the shaft outer circumferential surface  61   f.    
         [0057]    Further, since the groove edge section  61   e  extends in a direction perpendicular to the sliding direction in the first conventional example of  FIGS. 11A and 11B , the gear inner circumferential surface  64   f  scrapes against the groove edge section  61   e , the inner circumferential surface of the drive transmission gear  64  and the groove edge section  61   e  of the stationary shaft member  61  are scrapped off, thereby a foreign substance appears sometimes as the drive transmission gear  64  rotates. Similarly, when stress concentrates on the sliding section between the gear inner circumferential surface  64   f  and the groove edge section  61   e  in the first conventional example, the inner circumferential surface of the drive transmission gear  64  and the groove edge section  61   e  of the stationary shaft member  61  are scrapped off, thereby a foreign substance appears sometimes. When the foreign substance appears, the foreign substance necessarily contacts and slides on the gear inner circumference sliding section  67  even if the grease  63  remains between the gear inner circumference sliding section  67  and the shaft outer circumferential surface  61   f . As a result, since the grease  63  is not attracted to the foreign substance, a noise occurs sometimes. By contrast, in the first embodiment of the drive transmission system  200 , since the gear inner circumferential surface  64   f  does not face the groove edge section  61   e , the inner circumferential surface of the drive transmission gear  64  and the groove edge section  61   e  of the stationary shaft member  61  are prevented from being scrapped off, and the noise is not generated by the foreign substance. 
         [0058]    When producing the above-mentioned stationary shaft member  61  of the first conventional drive transmission system  200 , a process needs milling. Specifically, to form the grease groove  62  in a shaft direction, a shaft member is set again onto a milling process machine and a milling process is then to be executed after the shaft member is produced using a lathe. Thus, two preparatory steps are needed, so that part cost and production time increase. By contrast, if a circular grease groove  62  is formed entirely around the shaft as in the stationary shaft member  61  of the drive transmission system  200  of the first embodiment, parts can be produced by one preparatory step using the lathe. Thus, a productivity of the stationary shaft member  61  of the first embodiment is more effective than that of the first conventional example. 
         [0059]    Now, a second embodiment of the drive transmission system  200  is described with reference to  FIGS. 5A and 5B , which illustrate situations where a driving motor  500  stops and operates, respectively. 
         [0060]    As shown, the second embodiment is only different from the first embodiment by that an input gear  65  is constituted by a worm gear, while a large diameter gear section  77  is constituted by a wheel gear in a drive transmission system  200 . Therefore, only the difference is herein below described. As shown, the large diameter gear section  77  is linked with the input gear  65 . The worm gear of the input gear  65  has a prescribed lead angle. For example, when the lead angle is 16 degrees, a lead angle of the large diameter gear section  77  of the wheel gear becomes 74 degrees. When the input gear  65  rotates in a direction shown by an arrow E, a thrusting force acts on the drive transmission gear  64  in a direction shown by an arrow D. A small diameter gear section  79  employs a flat gear as in the first embodiment, and is linked with an output gear  69 . When a rotation driving force is transmitted from the input gear  65 , the thrusting force is applied to the large diameter gear section  77 , and accordingly the drive transmission gear  64  moves toward a washer  74 . Thus, a grease transfer surface  80  of the drive transmission gear  64  also moves toward the washer  74 . Consequently, grease  63  transferred onto the grease transfer surface  80  moves to a shaft outer circumferential surface  61   f , and is supplied all around the shaft outer circumferential surface  61   f  when the drive transmission gear  64  rotates. As a result, wear can be suppressed or avoided between the shaft outer circumferential surface  61   f  and the gear inner circumference sliding section  67 . 
         [0061]    Further, similar to the drive transmission system  200  of the second embodiment, a bracket  73 , a frame  75 , and the washer  74  collectively serving as a restriction device restricts movement of the drive transmission gear  64  in the shaft direction of the stationary shaft member  61  so that the gear inner circumferential large diameter section  76  can face a grease groove  62  continuously. Thus, the amount of the grease  63  exceeding the capacity of the grease groove  62  is prevented from being extracted from the grease groove  62  by the gear inner circumferential surface  64   f  of the drive transmission gear  64 , so that the grease  63  can be continuously supplied for a long time period between the gear inner circumference sliding sections  67  and the shaft outer circumferential surface  61   f.    
         [0062]    Further, since the gear inner circumferential surface  64   f  does not face a groove edge section  61   e  of the stationary shaft member  61 , the inner circumferential surface of the drive transmission gear  64  and the groove edge section  61   e  are prevented from being scrapped off, and noise is not generated by foreign substances. 
         [0063]    Now, a third embodiment of the drive transmission system  200  is described with reference to  FIGS. 6A and 6B , which illustrate situations where a driving motor  500  stops and operates, respectively. 
         [0064]    As shown, the third embodiment is only different from the first embodiment by that a large diameter gear section  77  of a drive transmission gear  64  and an input gear  65  employ bevel gears, respectively, while a wave washer is employed in a drive transmission system  200 . Thus, only the difference is herein below described. As shown, the large diameter gear section  77  is linked with the input gear  65 . The input gear  65  has a corn angle. A small diameter gear section  79  employs a flat gear as in the first embodiment, and is linked with an output gear  69 . As the drive transmission gear  64  moves toward the wave washer  74 , a grease transfer surface  80  of the drive transmission gear  64  moves toward the washer  74 . When a rotation driving force is transmitted from the input gear  65 , a thrusting force is applied to the large diameter gear section  77 , and accordingly, the drive transmission gear  64 , and the grease transfer surface  80  of the drive transmission gear  64  move toward the wave washer  74 . At this moment, the wave washer receiving prescribed pressurization in a thrusting allowance  68  elastically deforms while the motor is stopped. Accordingly, due to a reactive force to the elastic deformation, an amount of movement of the bevel gear of the large diameter gear section  77  in the thrusting force working on direction D is restricted to be equal to or less than a half of a gear meshing width which is capable of preventing skipping of a teeth thereof. Owing to the above, grease  63  transferred onto the grease transfer surface  80  moves to a shaft outer circumferential surface  61   f  as the grease transfer surface  80  moves toward the washer  74 . Thus, when the drive transmission gear  64  rotates, the grease  63  is supplied all around the shaft outer circumferential surface  61   f . As a result, wear can be suppressed or avoided between the shaft outer circumferential surface  61   f  and the gear inner circumference sliding section  67 . Further, with the reactive force of the wave washer  74 , the drive transmission gear  64  moves in a direction in which the bevel gear  65  of the large diameter gear section  77  tightly meshed with the bevel gear of the input gear  65 . 
         [0065]    Further, similar to the above-mentioned several embodiments, a bracket  73 , a frame  75 , and the washer  74  collectively serving as a restriction device restricts movement of the drive transmission gear  64  in the shaft direction of the stationary shaft member  61  so that the gear inner circumferential large diameter section  76  can face a grease groove  62  continuously as in the drive transmission system  200  of the third embodiment. Thus, the amount of the grease  63  exceeding the capacity of the grease groove  62  is prevented from being extracted from the grease groove  62  by the gear inner circumferential surface  64   f  of the drive transmission gear  64 , so that the grease  63  can be continuously supplied for a long time period between the gear inner circumference sliding sections  67  and the shaft outer circumferential surface  61   f . Further, since the gear inner circumferential surface  64   f  does not face a groove edge section  61   e  of the stationary shaft member  61 , the inner circumferential surface of the drive transmission gear  64  and the groove edge section  61   e  are prevented from being scrapped off, and noise is not generated by foreign substance. 
         [0066]    Now, a fourth embodiment of the drive transmission system  200  is described with reference to  FIGS. 7A and 7B , which illustrate situations where a driving motor  500  stops and operates, respectively. 
         [0067]    As shown, the fourth embodiment is only different from the first embodiment by that a large diameter gear section  77  of a drive transmission gear  64  as a two-step gear employs a worm gear and an input gear  65  employs a wheel gear in a drive transmission system  200 . Therefore, only the difference is herein below described. As shown, the large diameter gear section  77  is linked with the input gear  65 . The wheel gear of the input gear  65  has a lead angle. For example, when the lead angle is 74 degrees, a lead angle of the large diameter gear section  77  of the worm gear becomes 16 degrees. When the input gear  65  rotates in a direction shown by an arrow E, a thrusting force acts on the drive transmission gear  64  in a direction shown by an arrow D. A small diameter gear section  79  employs a flat gear as in the first embodiment, and is linked with an output gear  69 . When a rotation driving force is transmitted from the input gear  65 , a thrusting force is applied to the large diameter gear section  77 , and accordingly, the drive transmission gear  64  moves toward a washer  74 . 
         [0000]    Thus, a grease transfer surface  80  formed on the drive transmission gear  64  also moves toward the washer  74 . Consequently, grease  63  transferred onto the grease transfer surface  80  moves to a shaft outer circumferential surface  61   f . When the drive transmission gear  64  rotates, the grease  63  is supplied all around the shaft outer circumferential surface  61   f . As a result, wear can be suppressed or avoided between the shaft outer circumferential surface  61   f  and the gear inner circumference sliding section  67 . 
         [0068]    Further, similar to the above-mentioned several embodiments, a bracket  73 , a frame  75 , and the washer  74  collectively serving as a restriction device restricts movement of the drive transmission gear  64  in the shaft direction of the stationary shaft member  61  so that the gear inner circumferential large diameter section  76  can face a grease groove  62  continuously as in the drive transmission system  200  of the fourth embodiment. Thus, the amount of the grease  63  exceeding the capacity of the grease groove  62  is prevented from being extracted from the grease groove  62  by the gear inner circumferential surface  64   f  of the drive transmission gear  64 , so that the grease  63  can be continuously supplied for a long time period between the gear inner circumference sliding sections  67  and the shaft outer circumferential surface  61   f.    
         [0000]    Further, since the gear inner circumferential surface  64   f  does not face the groove edge section  61   e  of the stationary shaft member  61 , the inner circumferential surface of the drive transmission gear  64  and the groove edge section  61   e  are prevented from being scrapped off, and noise is not generated by foreign substance. 
         [0069]    Now, a fifth embodiment of the drive transmission system  200  is described with reference to  FIGS. 8A and 8B , which illustrate situations where a driving motor  500  stops and operates, respectively. 
         [0070]    In the above-mentioned drive transmission system  200  of the first embodiment, the grease transfer surface  80  is formed on a plane perpendicular to a rotation central line  64   a  between the sliding section large diameter side edge  78  of the gear inner circumferential surface  67  and the gear inner circumferential large diameter section  76 . However, a grease transfer surface  80  of the drive transmission system  200  of the fifth embodiment is inclined with regard to the rotation central line  64   a . Therefore, only such a difference is herein below described. As shown, a large diameter gear section  77  and an input gear  65  are constituted by helical gears, respectively. When the input gear  65  and the drive transmission gear  64  rotate, a thrusting force acts on the drive transmission gear  64  in a direction in parallel to the rotation central line  64   a  thereof as shown by an arrow D. 
         [0071]    Grease  63  filled in a space formed between the gear inner circumference large diameter section  76  and the grease groove  62  is transferred onto the grease transfer surface  80  of the slant plane between the sliding section large diameter side edge  78  and the gear inner circumference large diameter section  76  while the motor is stopped. When the input gear  65  and the drive transmission gear  64  rotate, and a thrusting force acts on the drive transmission gear  64  in a direction shown by the arrow D in parallel to the rotation central line  64   a , the slant grease transfer surface  80  of the drive transmission gear  64  moves toward the washer  74 . As a result, the grease  63  transferred onto the slant grease transfer surface  80  moves to the shaft outer circumferential surface  61   f  and is supplied to all around the shaft outer circumferential surface  61   f  as the drive transmission gear  64  rotates. As a result, wearing can be avoided or suppressed between the shaft outer circumferential surface  61   f  and the gear inner circumference sliding section  67 . 
         [0072]    Further, similar to the above-mentioned several embodiments, a bracket  73 , a frame  75 , and the washer  74  collectively serving as a restriction device restricts movement of the drive transmission gear  64  in the shaft direction of the stationary shaft member  61  so that the gear inner circumferential large diameter section  76  can face a grease groove  62  continuously as in the drive transmission system  200  of the fifth embodiment. Thus, the amount of the grease  63  exceeding the capacity of the grease groove  62  is prevented from being extracted from the grease groove  62  by the gear inner circumference  64   f  of the drive transmission gear  64 , so that the grease  63  can be continuously supplied for a longer time period between the gear inner circumference sliding sections  67  and the shaft outer circumferential surface  61   f  than before. 
         [0000]    Further, since the gear inner circumferential surface  64   f  does not face the groove edge section  61   e , the inner circumferential surface of the drive transmission gear  64  and the groove edge section  61   e  of the stationary shaft member  61  are prevented from being scrapped off, and noise is not generated by foreign substance. 
         [0073]    Now, a sixth embodiment of the drive transmission system  200  is described with reference to  FIGS. 9A and 9B , which illustrate situations where a driving motor  500  stops and operates, respectively. 
         [0074]    In the above-mentioned drive transmission system  200  of the first embodiment, the grease transfer surface  80  is formed on the plane perpendicular to the rotation central line  64   a  between the sliding section large diameter side edge  78  of the gear inner circumference sliding section  67  and the gear inner circumferential large diameter section  76 . However, a grease transfer surface  80  of the drive transmission system  200  of the sixth embodiment has an R letter shape in the sixth embodiment of the drive transmission system  200  as only a difference therefrom. Therefore, only such a difference is herein below described. As shown, a large diameter gear section  77  and the input gear  65  are constituted by helical gears as in the first embodiment. When the input gear  65  and the drive transmission gear  64  rotate, a thrusting force acts on the drive transmission gear  64  in a direction in parallel to the rotation central line  64   a  thereof as shown by an arrow D. 
         [0075]    Grease  63  filled in a space formed between the gear inner circumference large diameter section  76  and the grease groove  62  is transferred onto the grease transfer surface  80  of the R letter shape plane between the sliding section large diameter side edge  78  and the gear inner circumference large diameter section  76  while the motor is stopped. When the input gear  65  and the drive transmission gear  64  rotate and the thrusting force acts on the drive transmission gear  64  in a direction shown by the arrow D parallel to the rotation central line  64   a  thereof, the R-shaped grease transfer surface  80  of the drive transmission gear  64  moves toward the washer  74 . As a result, the grease  63  transferred onto the R letter shape grease transfer surface  80  moves to the shaft outer circumferential surface  61   f  and is supplied all around the shaft outer circumferential surface  61   f  as the drive transmission gear  64  rotates. As a result, wearing can be avoided or suppressed between the shaft outer circumferential surface  61   f  and the gear inner circumference sliding section  67 . 
         [0076]    Further, similar to the above-mentioned several embodiments, a bracket  73 , a frame  75 , and the washer  74  collectively serving as a restriction device restricts movement of the drive transmission gear  64  in the shaft direction of the stationary shaft member  61  so that the gear inner circumferential large diameter section  76  can face a grease groove  62  continuously as in the drive transmission system  200  of the sixth embodiment. Thus, the amount of the grease  63  exceeding the capacity of the grease groove  62  is prevented from being extracted from the grease groove  62  by the gear inner circumferential surface  64   f  of the drive transmission gear  64 , so that the grease  63  can be continuously supplied for a longer time period between the gear inner circumference sliding sections  67  and the shaft outer circumferential surface  61   f  than before. Further, since the gear inner circumferential surface  64   f  does not face the groove edge section  61   e  of the stationary shaft member  61 , the inner circumferential surface of the drive transmission gear  64  and the groove edge section  61   e  are prevented from being scarped off, and noise is not generated by foreign substance. 
         [0077]    Now, a seventh embodiment of the drive transmission system  200  is described with reference to  FIGS. 10A and 10B , which illustrate situations where a driving motor  500  stops and operates, respectively. 
         [0078]    In the above-mentioned drive transmission system  200  of the first embodiment, the grease transfer surface  80  is formed on the plane perpendicular to the rotation central line  64   a  between the sliding section large diameter section edge  78  of the gear inner circumference sliding section  67  and the gear inner circumferential large diameter section  76 . However, a grease transfer surface  80  of the drive transmission system  200  of the seventh embodiment is an envelope state as only a difference therefrom. Therefore, only such a difference is herein below described. As shown, a large diameter gear section  77  and an input gear  65  are constituted by helical gears in the first embodiment. When the input gear  65  and the drive transmission gear  64  rotate, a thrusting force acts on the drive transmission gear  64  in a direction in parallel to the rotation central line  64   a  thereof as shown by an arrow D. 
         [0079]    Grease  63  filled in a space formed between a gear inner circumference large diameter section  76  and a grease groove  62  is transferred onto the envelope state grease transfer surface  80  between a sliding section large diameter side edge  78  and a gear inner circumference large diameter section  76  while the motor is stopped. When the input gear  65  and the drive transmission gear  64  rotate and the thrusting force acts on the drive transmission gear  64  in a direction shown by the arrow. D in parallel to the rotation central line  64   a  thereof, the envelope state grease transfer surface  80  of the drive transmission gear  64  moves toward the washer  74 . 
         [0080]    As a result, the grease  63  transferred onto the envelope state grease transfer surface  80  moves to the shaft outer circumferential surface  61   f  and is supplied to all around the shaft outer circumferential surface  61   f  as the drive transmission gear  64  rotates. As a result, wearing can be avoided or suppressed between the shaft outer circumferential surface  61   f  and the gear inner circumference sliding section  67 . 
         [0081]    As mentioned heretofore, by making the grease transfer surface  80  being inclined or in an R shape or an envelope shape, the grease transfer surface  80  can serve as a guide for conveying the grease  63  onto the shaft outer circumferential surface  61   f , so that the grease can readily move to the sliding section between the shaft outer circumferential surface  61   f  and the gear inner circumferential surface  64   f.    
         [0082]    Further, similar to the above-mentioned several embodiments, a bracket  73 , a frame  75 , and the washer  74  collectively serving as a restriction device restricts movement of the drive transmission gear  64  in the shaft direction of the stationary shaft member  61  so that the gear inner circumferential large diameter section  76  can face a grease groove  62  continuously as in the drive transmission system  200  of the seventh embodiment. Thus, the amount of the grease  63  exceeding the capacity of the grease groove  62  is prevented from being extracted from the grease groove  62  by the gear inner circumferential surface  64   f  of the drive transmission gear  64 , so that the grease  63  can be continuously supplied for a longer time period between the gear inner circumference sliding sections  67  and the shaft outer circumferential surface  61   f  than before. 
         [0083]    Further, since the gear inner circumferential surface  64   f  does not face the groove edge section  61   e , the inner circumferential surface of the drive transmission gear  64  and the groove edge section  61   e  of the stationary shaft member  61  are prevented from being scrapped off, and noise is not generated by foreign substance. 
         [0084]    Numerous additional modifications and variations of the present invention are possible in latent image of the above teachings. It is therefore to be understood that within the scope of the appended claims, the present invention may be practiced otherwise that as specifically described herein. 
       ADVANTAGE 
       [0085]    According to one embodiment of the present invention, since the grease  63  can be continuously supplied for a longer time period between the gear inner circumference sliding sections and the shaft outer circumferential surface than before, they can enjoy long lives.