Patent Publication Number: US-2003233900-A1

Title: Rotary transmission device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001] This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2002-127245, filed Apr. 26, 2002; and No. 2002-231121, filed Aug. 8, 2002, the entire contents of both of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002] 1. Field of the Invention  
       [0003] The present invention relates to a gear structure used in, for example, a rotary transmission mechanism of a camera or the like.  
       [0004] 2. Description of the Related Art  
       [0005] Heretofore, the so-called stepped gears, in which different spur gears are coaxially stacked and arranged, are provided in a rotary transmission mechanism of a camera or the like by gears. In such stepped gears, one of the spur gears may be formed by a molding technique in compliance with a use purpose such as torque to be transmitted, and the other spur gear to which high torque is applied may be formed of a metallic material. According to means for producing the stepped gears, a round boss is formed on one rotation axis of the one spur gear, and a round hole is oppositely formed on the same rotation axis of the other spur gear. Then, the round boss is pressed into the round hole, thereby producing the stepped gears which are integrally stacked and arranged.  
       [0006] However, if the large torque is applied between the gears of the stepped gears, a problem occurs in which the so-called slip is caused between the spur gears, so that stable transmission of a driving force is difficult.  
       [0007] Therefore, a pressing structure has been employed in which the round boss and the round hole formed in the spur gears are replaced with, for example, oval bosses and holes. Then, these oval bosses are pressed into the oval holes so that the gears may be integrally stacked and arranged, thereby increasing rigidity in a rotating direction. In this pressing structure, even if the relatively high torque is applied between the gears, and the stable transmission of the driving force can be achieved without causing the slip between them.  
       [0008] However, in the above pressing structure, its configuration becomes complicated, and hence, when the stepped gears are formed of the metallic material, it is necessary to carry out complicated machining such as milling for their processing. In consequence, such a structure has an inconvenience that the production of the gears is very troublesome and costly.  
       [0009] The conventional stepped gears have a disadvantage that the increase of the torque to be applied might cause the slip between the gears, and if they are constituted so as to prevent the slip, the processing becomes troublesome and costly.  
       BRIEF SUMMARY OF THE INVENTION  
       [0010] A feature of the present invention is therefore to provide a gear structure having a simple constitution, realizing convenient, inexpensive and easy production, and enabling stable and highly accurate transmission of a driving force.  
       [0011] According to the first feature of the present invention, there is provided a rotary transmission device comprising:  
       [0012] a first rotary member having a plurality of radial concave portions around a rotary central axis in the vicinity of the rotary central axis; and  
       [0013] a second rotary member formed as a gear, a tooth width of each tooth of the gear being reduced from a tip of the tooth to a halfway point of a tooth height, a tooth portion of from the halfway point of the tooth height to a tooth root being fitted into the plurality of concave portions, whereby the second rotary member does not relatively rotate with the first rotary member.  
       [0014] According to the second feature of the present invention, there is provided a rotary transmission device comprising:  
       [0015] a first rotary member having a plurality of radial concave portions around a rotary central axis in the vicinity of the central axis; and  
       [0016] a second rotary member which is a gear, having a thin portion as a gear portion in which a tooth width of each tooth of the gear is additionally processed to reduce the tooth width from a tip of the tooth to a halfway point of a tooth height, and a plurality of thick portions which are tooth portions and are not additionally processed from the halfway point of the tooth height to a tooth root, the plurality of thick portions being fitted into the plurality of concave portions, respectively, whereby the second rotary member does not relatively rotate with the first rotary member.  
       [0017] According to the third feature of the present invention, there is provided a gear mechanism comprising:  
       [0018] a first gear;  
       [0019] a second gear to engage with the first gear;  
       [0020] a first outer peripheral surface portion provided to rotate coaxially and integrally with the first gear; and  
       [0021] a second outer peripheral surface portion provided to rotate coaxially and integrally with the second gear,  
       [0022] wherein to keep a space between axes of the first gear and the second gear at a certain distance, the first outer peripheral surface portion and the second outer peripheral surface portion are allowed to contact or adjoin each other, so that the first gear engages with the second gear.  
       [0023] According to the fourth feature of the present invention, there is provided a gear mechanism comprising:  
       [0024] a first gear;  
       [0025] a second gear to engage with the first gear;  
       [0026] a first outer peripheral surface portion provided coaxially and integrally with the first gear; and  
       [0027] a second outer peripheral surface portion to rotate coaxially and integrally with the second gear,  
       [0028] wherein to keep a space between axes of the first gear and the second gear at a certain distance, the first outer peripheral surface portion and the second outer peripheral surface portion are allowed to contact or adjoin each other, so that the first gear engages with the second gear.  
       [0029] Advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.  
     
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
     [0030] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention.  
     [0031]FIG. 1 is an exploded perspective view showing by exploding a gear structure according to a first embodiment of the present invention;  
     [0032]FIG. 2 is a perspective view showing essential portions of a first gear of FIG. 1;  
     [0033]FIG. 3 is a plan view showing the first gear and a second gear of FIG. 1 stacked and arranged;  
     [0034]FIG. 4 is a sectional view showing by sectioning the essential portions of FIG. 3;  
     [0035]FIG. 5 is a sectional view showing the gear structure of FIG. 1 in a state incorporated in a device body;  
     [0036]FIG. 6 is an exploded perspective view showing by exploding a gear structure according to a second embodiment of the present invention;  
     [0037]FIG. 7 is an exploded perspective view showing by exploding a gear structure according to a third embodiment of the present invention;  
     [0038]FIG. 8 is an exploded perspective view of a gear structure and its peripheral portions according to a fourth embodiment of the present invention; and  
     [0039]FIG. 9 is a sectional view of the gear structure of FIG. 8. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0040] Embodiments of the present invention will hereinafter be described in detail in reference to the drawings.  
     [0041]FIG. 1 is a perspective view showing a gear structure regarding a first embodiment of the present invention. In FIG. 1, a first gear  10  constitutes, for example, a driving side member as a transmission member, and is rotated and driven, for example, by a driving force transmitted from a driving source not shown. On the above first gear  10 , for example, a second gear  12  having a smaller diameter, which constitutes a driven side member as a transmission member, is integrally stacked so as to be arranged in a combined state.  
     [0042] In the first gear  10 , a plurality of teeth  22 , which is a gear portion having a predetermined tooth top external diameter by, for example, molding, is formed at predetermined intervals. A pressing hole  24  is formed in the center of the first gear  10 . Further, a plurality of concave fitting portions  26  is formed at predetermined intervals at one end of the pressing hole  24  in the first gear  10 , as shown in FIG. 2.  
     [0043] On the other hand, the second gear  12  is formed of, for example, a metallic material, and a shaft fitting hole  30  is provided in its central portion. A plurality of teeth  32 , which constitutes a gear portion having a predetermined tooth top external diameter, is formed at predetermined intervals around the shaft fitting hole  30  of the second gear  12 .  
     [0044] On one side of the second gear  12 , a convex pressing portion  34 , which is formed by cutting each teeth  32 , for example, into a smaller diameter from a tooth top external diameter, is coaxially formed around the shaft fitting hole  30 . The pressing portion  34  is coaxially formed correspondingly to the pressing hole  24  formed in the first gear  10 .  
     [0045] Furthermore, the second gear  12  is provided with a plurality of regulating portions  36  between its teeth  32  and pressing portion  34 . The regulating portions  36  are formed at predetermined intervals correspondingly to the plurality of concave fitting portions  26  formed in the first gear  10  mentioned above.  
     [0046] In addition, the regulating portions  36  are, for example, formed in each teeth  32  in a stepped shape cut into a smaller diameter by predetermined dimensions than a tooth top external diameter in its tooth width direction. Further, the regulating portion  36  is formed in a shape provided, in its central portion, with an inclined surface  38  inclined in an axial direction. The provision of the inclined surface  38  makes it easy to find a rotating direction position during a pressing operation.  
     [0047] In such constitution, when the first gear  10  and second gear  12  are stacked and arranged, the pressing portion  34  of the second gear  12  is pressed into the pressing hole  24  of the first gear  10 , as shown in FIGS. 3 and 4. At this point, the regulating portions  36  of the second gear  12  are fitted into the fitting portions  26  of the first gear  10 . In this way, positions of the first and second gears  10  and  12  in the direction of the rotation axis are decided by the mutual function of the pressing hole  24  and pressing portion  34 . Then, they are integrated in a stacked state and thus combined, while the fitting portions  26  and regulating portions  36  function to decide the position in the rotating direction between the gears.  
     [0048] The shaft fitting hole  30  of the second gear  12  stacked and arranged is, for example, fitted into by a support shaft  42  provided for a film winding device body  40 , as shown in FIG. 5. At an end of the support shaft  42 , a presser plate  44  is provided, which is a presser plate to regulate the first and second gears  10  and  12  in the axial direction.  
     [0049] In this state, the first gear  10  is rotated and driven on the device body  40  via the support shaft  42 , by a driving force transmitted from the driving source (not shown). Here, the second gear  12  is integrally rotated and driven in conjunction with the rotation of the first gear  10 , thereby rotating and driving, for example, a driving portion in the device body  40 , and performing a desired operation.  
     [0050] In this way, in the above gear structure, the teeth  32  constituting the gear portion of the second gear  12  are provided, in a partial area in a tooth width direction, with the regulating portions  36  forming a shape which is cut to have a diameter smaller than an external diameter of a tooth top. Further, the first gear  10  is provided with the fitting portions  26  into which the regulating portions  36  of the second gear  12  are fitted. Moreover, the regulating portions  36  of the second gear  12  are built to fit into the fitting portions  26  of the first gear  10  so that they are integrally stacked and arranged.  
     [0051] In this way, the regulating portions  36  are formed in the teeth  32  of the second gear  12 , and the fitting portions  26  into which the regulating portions  36  are fitted are formed in the first gear  10  so that they are fitted and integrated, thereby making it possible to form the regulating portions  36  provided in the second gear  12  into a shape capable of surely preventing a slip merely by cutting the partial area of the teeth  32 , and achieving simple and easy production. In other words, when the second gear  12  is formed of, for example, a metallic material, it is possible to, after once forming the teeth  32  having the tooth top external diameter, produce the partial area of the tooth top by the machining of simply cutting into the cut shape mentioned above, thereby enabling simple and easy processing.  
     [0052] Furthermore, the above gear structure is constituted in a manner that the regulating portions  136  and the pressing portion  34  are coaxially provided in the second gear  12 , and the fitting portions  26  and the pressing hole  24  are coaxially provided in the first gear  10 , so that the pressing portion  34  of the second gear  12  is pressed into the pressing hole  24  of the first gear  10 , and the regulating portions  36  are fitted into the fitting portions  26 , thereby integrally arranging and stacking them.  
     [0053] In this way, the first gear  10  and the second gear  12  are integrally stacked and arranged while the position of each gear of the gear structure is decided in the rotating direction and axial direction by the regulating portions  36  and the fitting portions  26 , and by the pressing portion  34  and the pressed portion  24 , thereby enabling a rigid combination arrangement.  
     [0054] It should be noted that in the embodiment described above, such constitution has been described as an example that the fitting portions  26  of the first gear  10  are formed in about the same shape as the regulating portions  36  of the second gear  12  to decide the position in the rotating direction, but it is not limited to this, and it is also possible to configure the shape of the fitting portions  26  of the first gear  10  in a manner that, for example, the shape except in the rotation axis direction for deciding position has a larger diameter.  
     [0055] Furthermore, in the embodiment described above, such constitution has been described as an example that the regulating portions  36  are formed in all the teeth  32  of the second gear  12  so that all these regulating portions may fit into the fitting portions provided in the first gear, but it is not limited to this. Alternatively, it is also possible to constitute in such a manner that the regulating portions  36  are provided only in one or more desired teeth  32 , and the regulating portions  36  are fitted into the fitting Portions  26  of the first gear  10  so as to decide the position in the rotation axis direction.  
     [0056] Still further, in the embodiment described above, such constitution has been described as an example that only the position in the rotation axis direction is decided by means of the regulating portions  36  and the fitting portions  26 , but it is also possible to constitute in a manner that the position in the rotation axis direction is decided by means of the regulating portions  36  and the fitting portions  26 , and at the same time, the position in the rotation axis direction is decided by pressing. In this case, the pressing hole  24  of the first gear  10  and the regulating portions  36  of the second gear  12  are used not for pressing but for deciding the position in the diameter direction.  
     [0057] Further yet, in the embodiment described above, such constitution has been described as an example that the first gear  10  is molded and the second gear  12  is formed of a metallic material, but it is not limited to this, but alternatively, it is also possible to constitute in such a manner that, for example, the first gear  10  is formed of a metallic material and the second gear  12  is molded, or that both the first and second gears  10  and  12  are formed of the same material.  
     [0058] In addition, in the embodiment described above, such constitution has been described as an example that the first gear  10  is rotated and driven by the driving source (not shown), but it is not limited to this, and it is also possible to constitute in such a manner that the second gear  12  is rotated and driven as a driving side member by the driving force transmitted from the driving source (not shown).  
     [0059] Moreover, the present invention is not limited to the embodiment described above, but alternatively, it is also possible to constitute as shown in FIGS. 6 and 7, whereby about the same effect can be expected. In addition, in the embodiments described below, the same portions as those in the first embodiment described above are given the same reference numerals for the sake of convenience and will not be described.  
     [0060]FIG. 6 is an exploded perspective view showing by exploding a gear structure according to a second embodiment of the present invention.  
     [0061] As shown in FIG. 6, the gear structure according to the second embodiment is constituted to form the driving side member with a pulley  50  and form the driven side member with the second gear  12 . More specifically, in the pulley  50 , a pressing hole  52  into which the pressing portion  34  of the second gear  12  is pressed and fitting portions  54  into which the regulating portions  36  of the second gear  12  are fitted are each formed. Then, the pressing portion  34  and regulating portions  36  of the second gear  12  are pressed and fitted into the pressing hole  52  and fitting portions  54  so that the members are integrally stacked and arranged. In this case, a driving belt  58  is wound and hung around the pulley  50 , and the pulley  50  is rotated and driven via this driving belt  58 , and in conjunction with this, the second gear  12  is rotated and driven.  
     [0062]FIG. 7 is an exploded perspective view showing by exploding a gear structure according to a third embodiment of the present invention.  
     [0063] The third embodiment shown in FIG. 7 is constituted in such a manner that the driven side member is formed by a bladed wheel  16  and the driving side member is formed by the second gear  12 . More specifically, in the bladed wheel  60 , a pressing hole  62  into which the pressing portion  34  of the second gear  12  is pressed and fitting portions  64  into which the regulating portions  36  of the second gear  12  are fitted are each formed, and the pressing portion  34  and regulating portions  36  of the second gear  12  are pressed and fitted into the pressing hole  62  and fitting portions  64  so that the members are integrally stacked and arranged. The second gear  12  is engaged with an unshown driving source in a manner that a driving force can be transmitted, and in conjunction with the rotation and driving, the bladed wheel  60  is rotated and driven.  
     [0064] This bladed wheel  60  is provided, for example, in an optical path of a light emitting portion and a light receiving portion of a photointerruptor, and is used to, in conjunction with the rotation, intermittently interrupt the optical path of the light emitting portion and light receiving portion.  
     [0065] Next, a forth embodiment of the present invention will be described.  
     [0066]FIG. 8 is an exploded perspective view of a gear structure and its peripheral portions according to the fourth embodiment of the present invention, and FIG. 9 is a sectional view of the gear structure of FIG. 8.  
     [0067] In FIGS. 8 and 9, a pinion gear (drive gear)  76  as the first gear is pressed into a motor shaft  74 , which is extended from a motor bearing  72  projecting from and formed on the surface of a motor  70 . Further, under the pinion gear  76 , an interaxial distance maintaining disc  78  is formed. The interaxial distance maintaining disc  78  is constituted as a first outer peripheral surface portion which is coaxially provided to rotate with the pinion gear  76 . This enables the pinion gear  76  and the interaxial distance maintaining disc  78  to turn integrally with the motor shaft  74 .  
     [0068] A bottom board hole  80  having a diameter larger than the diameter of the pinion gear  76  is formed on a bottom board  78 . The pinion gear  76  is inserted through the bottom board hole  80 . Further, motor fixing screws  86 ,  86  are tightened into screw holes  84 ,  84  of the motor  70  via screw fixing holes  82 ,  82 , thereby fixing the motor  70  on the bottom board  86 .  
     [0069] The bottom board  86  is also provided with a support shaft  90 . A driven gear  92  as the second gear, which is engaged with the pinion gear  76  mentioned above, and an interaxial distance maintaining member  94  as a second outer peripheral surface portion, are each mounted on the support shaft  90  in a state capable of turning.  
     [0070] The interaxial distance maintaining member  94  has a disc shape, and in its central portion, a gear fixing hole  96  is formed into which the support shaft  90  is pressed into. Further, a gear fixing portion  98  is provided around the gear fixing hole  96 . The gear fixing portion  98  is formed into a partially cut disc shape (almost D shape) to fix the driven gear  92 . The driven gear  92  can turn integrally with the interaxial distance maintaining member  94  by pressing its central portion into the gear fixing portion  98 .  
     [0071] It has been described that the driven gear  92  is pressed into the interaxial distance maintaining member  94 , which is not limited to this. For example, they may be bonded with an adhesive or the like, and may be constituted so that the driven gear  92  and the interaxial distance maintaining member  94  can turn integrally.  
     [0072] Furthermore, a C ring  100 , which is a so-called C-shaped spring member, is fitted and fixed at an end portion of the support shaft  90 . This C ring  100  prevents the driven gear  92  and the interaxial distance maintaining member  94  from coming off from the support shaft  90 .  
     [0073] In the gear structure having such constitution, assembling of the gears is done in the following manner.  
     [0074] Specifically, first, the interaxial distance maintaining member  94 , and the driven gear  92  fixed on the interaxial distance maintaining member  94  are inserted through by the support shaft  90  provided on the bottom board  78 . Then, the interaxial distance maintaining member  94  and the driven gear  92  are fixed on a boss of the support shaft  90 , and in this state, the C ring  100  is fitted and fixed at the end portion of the support shaft  90 .  
     [0075] On the other hand, the motor shaft  74  extended from the motor bearing  72  of the motor  70  is pressed into the pinion gear  76  with which the interaxial distance maintaining disc  78  is coaxially provided. Then, the interaxial distance maintaining disc  78 , and the motor shaft  74  on which the pinion gear  76  is mounted are inserted through the bottom board hole  80  formed on the bottom board  78 .  
     [0076] Here, an interaxial distance maintaining circumferential surface  78   a  of the interaxial distance maintaining disc  78 , which is the first outer peripheral surface portion, and an interaxial distance maintaining circumferential surface  94   a  of the interaxial distance maintaining member  94 , which is the second outer peripheral surface portion, contact each other. At this point, as to the interaxial distance maintaining circumferential surface  78   a  and the interaxial distance maintaining circumferential surface  94   a , position is decided between the screw fixing holes  82 ,  82  formed on the bottom board  78  and the screw holes  84 ,  84  formed on the motor  70 . Then, the motor fixing screws  86 ,  86  are tightened, thereby fixing the motor  70  on the bottom board  78  while the interaxial distance maintaining circumferential surface  78   a  and the interaxial distance maintaining circumferential surface  94   a  are contacting each other.  
     [0077] As described above, the interaxial distance maintaining disc  78  (interaxial distance maintaining circumferential surface  78   a ) and the interaxial distance maintaining member  94  (interaxial distance maintaining circumferential surface  94   a ) contact each other so as to rotate. At the same time, the pinion gear  76  as the first gear and the driven gear  92  as the second gear engage with each other.  
     [0078] It should be noted that a backlash portion formed between the teeth of the pinion gear  76  and the teeth of the driven gear  92  may be at a contact strength level in which the surfaces of the interaxial distance maintaining circumferential surface  78   a  and the interaxial distance maintaining circumferential surface  94   a  would relatively move to be able to slide. This contact strength should rather be as little as possible, and the strength is preferably 0.  
     [0079] Now, as shown in FIG. 9, if a center distance to be obtained is L, this distance L is a distance from an axial center of the motor shaft  74  to an axial center of the support shaft  90 . Then, the distance from an axial center of the interaxial distance maintaining disc  78  to the interaxial distance maintaining circumferential surface  94   a  of the first outer peripheral surface portion, that is, a radius, is R 1 , and the distance from the center of the interaxial distance maintaining member  94  to the interaxial distance maintaining circumferential surface  94   a  of the second outer peripheral surface portion, that is, a radius, is R 2 . This shows that R 1 +R 2  =L, and that the sum of the radius R 1  of the interaxial distance maintaining disc  78  and the radius R 2  of the interaxial distance maintaining member  94  in a state where they contact each other will be the desired distance L.  
     [0080] Therefore, if the interaxial distance maintaining disc  78  (interaxial distance maintaining circumferential surface  78   a ) and the interaxial distance maintaining member  94  (interaxial distance maintaining circumferential surface  94   a ) are made to contact each other so as to fix the motor  70 , it is possible to set and keep a space between the axes of the gears at a desired certain distance. Thus, an efficient transmission of the driving force can be achieved.  
     [0081] However, even if the contact between the interaxial distance maintaining circumferential surface  78   a  and the interaxial distance maintaining circumferential surface  94   a  is severed when the screws  86  are tightened, that is, even if their axes move away, no functional problem occurs as long as a distance between the axes is slightly increases. More specifically, the outer peripheral surfaces only need to contact or adjoin each other. In other words, the gears would never be set in a direction to decrease the backlash, and the backlash does not vanish.  
     [0082] It should be noted that, in the fourth embodiment described above, as to the relationship of the diameter size between the pinion gear  76  and the interaxial distance maintaining disc  78  and between the driven gear  92  and the interaxial distance maintaining member  94 , as long as the interaxial distance maintaining portion  78  and the interaxial distance maintaining member  94  are built to contact, their size may be larger or smaller than the diameter of the respective gears.  
     [0083] Furthermore, in the fourth embodiment described above, the pinion gear  76 , interaxial distance maintaining disc  78 , driven gear  92  and interaxial distance maintaining portion  94  are constituted of materials such as plastics, aluminum and brass.  
     [0084] Still further, in FIGS. 8 and 9, the interaxial distance maintaining member  94  is illustrated as it has a stepped portion to have an opening in between with the driven gear  92 , and this is provided so that the interaxial distance maintaining member  94  and the interaxial distance maintaining disc  78 , and the driven gear  92  and the pinion gear  76  will surely catch each other. Therefore, no opening may be provided between the interaxial distance maintaining member  94  and the driven gear  92 .  
     [0085] It should be noted that the gear structure in the present invention is not limited to involute gears, but is also very useful in cycloid gears that do not permit deviation between axes.  
     [0086] Therefore, the present invention is not limited to the above embodiments, but alternatively, various modifications can be made and obtained without departing from its gist at the stage of execution. Further, the invention at various stages is included in each of the above embodiments, and the proper combination of a plurality of disclosed constituent requirements makes it possible to extract various kinds of invention.  
     [0087] Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general invention concept as defined by the appended claims and their equivalents.