Abstract:
A control apparatus for controlling a drive member rotatably supported on a bicycle includes a mounting member for mounting the apparatus to the bicycle, a braking mechanism coupled to the mounting member for applying a braking force to the drive member; and a coupling mechanism adapted to couple the braking mechanism to a shift control mechanism so that the braking mechanism applies the braking force to the drive member upon actuation of the shift control mechanism.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention is directed to control devices for bicycle transmissions and, more particularly, to an apparatus that facilitates the gear shifting operation for the transmission.  
           [0002]    Bicycle transmissions known in the art include internal transmissions housed within the rear hub and external transmissions mounted on the rear hub around the crank spindle. Internal transmissions typically employ a planetary gear device and a clutch for selecting different power transmission paths through the planetary gear device. Such transmissions include the pushrod type and the rotary cam type. The pushrod type internal transmission comprises a pushrod slidingly mounted in the axial direction through the center of the hub spindle for moving the clutch axially to select the plurality of power transmission paths through the planetary gear device. A rotary cam type internal transmission includes a cam shaft with a plurality of cams arrayed in the axial direction, wherein the cam shaft is mounted for rotation around the hub spindle between the sun gears of the planetary gear device and the hub spindle. The rotational position of the cam shaft determines which sun gears are nonrotatably fixed to the hub spindle and which sun gears are free to rotate around the hub spindle. This, in turn, determines the power transmission path through the planetary gear device. External transmissions typically comprise a plurality of coaxially arranged sprockets that rotate with the pedals and/or the rear wheel and a corresponding front and/or rear derailleur for shifting a chain among the corresponding plurality of sprockets as the bicycle is being pedaled.  
           [0003]    In both types of transmissions, a shift control device attached to the handlebar, for example, is coupled to the transmission by means of a control cable having an inner wire that slides within an outer casing. Operating the shift control device in one direction causes displacement of the inner wire towards the shift control device, while moving the shift control device in the another direction causes displacement of the inner wire towards the transmission by means of a return spring provided to the shift control device or to the transmission.  
           [0004]    With an internal transmission, pedaling the bicycle causes substantial contact forces to be generated among the components that make up the planetary gear device. Thus, unless essentially no power is being transmitted to the rear wheel, such as when the rider stops pedaling or when the pedals are situated at the top or bottom deadpoint, the shifting operation will require the application of considerable force to the pushrod or cam shaft. When the shifting operation includes displacement of the inner wire towards the transmission by means of the return spring provided to the shift control device or to the transmission, very often the return spring is incapable of providing the required force until the pedals are situated at the top or bottom deadpoint or until the rider stops pedaling.  
           [0005]    With an external transmission, the bicycle must be pedaled in order to shift the transmission. Thus, optimum shifting occurs either when the pedals are situated at the top or bottom deadpoint or when the rider consciously reduces the pedaling force.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention is directed to a shift assist apparatus which helps to reduce the force applied to the transmission when a shifting operation is desired. In one embodiment of the present invention, a control apparatus for controlling a drive member rotatably supported on a bicycle includes a mounting member for mounting the apparatus to the bicycle, a braking mechanism coupled to the mounting member for applying a braking force to the drive member; and a coupling mechanism adapted to couple the braking mechanism to a shift control mechanism so that the braking mechanism applies the braking force to the drive member upon actuation of the shift control mechanism.  
           [0007]    In a specific embodiment of the present invention, the apparatus includes a mounting member for mounting the apparatus to the bicycle; a rotary member rotatably supported to the mounting member; a first braking member; a first cam member coupled to the mounting member; a second cam member coupled to the rotary member for rotation therewith; wherein at least one of the first cam member and the second cam member moves the first braking member when the first cam member and the second cam member rotate relative to each other; a coupling pawl coupled to the rotary member; a pawl biasing member for biasing the coupling pawl toward a coupled position for coupling the rotary member for rotation with the drive member; and a pawl control member for retaining the coupling pawl in a decoupled position. In this embodiment, the pawl control member is adapted to couple to a shift control mechanism so that the coupling pawl is allowed to move toward the coupled position upon actuation of the shift control mechanism. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a side view of a bicycle that includes a particular embodiment of a shift assist apparatus according to the present invention;  
         [0009]    [0009]FIG. 2 is a perspective view of the shift assist apparatus disassembled from the front sprocket assembly;  
         [0010]    [0010]FIG. 3 is a partial cross sectional view of the shift assist apparatus mounted to the bottom bracket assembly;  
         [0011]    [0011]FIG. 4 is a view taken along line IV-IV in FIG. 3;  
         [0012]    [0012]FIG. 5 is an exploded view of the shift assist apparatus;  
         [0013]    [0013]FIG. 6 is a perspective view of a particular embodiment of the first and second cam disks used in the shift apparatus; and  
         [0014]    FIGS.  7 (A)- 7 (C) are diagrams illustrating the operation of the first and second cam disks. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0015]    [0015]FIG. 1 is a side view of a bicycle  10  that includes a particular embodiment of a shift assist apparatus  50  according to the present invention. Bicycle  10  includes a frame  12  having a front fork  13 ; a front wheel  14  mounted on the front fork  13 ; and a rear wheel  16  mounted on the rear of the frame  12 . As shown in FIG. 3, a crank spindle  20  is rotatably supported in a bottom bracket  19  threadably fastened to the hanger portion  15  of the frame  12 . The two ends of the crank spindle  20  have nonrotatably mounted thereon a pair of left and right crank arms  24  and  26 , each having a pedal  22  mounted to its distal end.  
         [0016]    The crank arm  26  on the right side (as viewed from the back) is assembled with a front sprocket portion  28  having two (a large and a small) sprocket plates  28   c ,  28   d  mounted thereon, a centrally disposed boss portion  28   a  for nonrotatable mounting to the crank spindle  20 , and an outer peripheral sprocket mounting portion  28   b.  A sprocket cover  29  is mounted on the outside peripheral portion of the front sprocket portion  28 , and a chain  30  may be engaged around either of the sprocket plates  28   c,    28   d.    
         [0017]    An internally geared hub  32  is mounted on the rear wheel  16 . The internally geared hub  32  is coupled by means of a control cable  38  to a shift control device  36  attached to the handlebar  34 . The internally geared hub  32  may be, for example, a four-speed rotary cam type hub having a rear sprocket  40  non-rotatably coupled to the right side thereof. The chain  30  is engaged around the rear sprocket  40  so that rotational force of the crank arms  24  and  26  is transmitted to the internally geared hub  32 .  
         [0018]    As shown in FIG. 2, the control cable  38  comprises an inner wire  42  coupling the operating member of the shift control device  36  to the operating member of the internally geared hub  32 , and an outer casing  44  covering the inner wire  42 . The outer casing  44  is disposed on the outside of the inner wire  42  so as to be capable of relative motion with respect to the inner wire  42 . The outer casing  44  is divided into a first casing  44   a  that extends from shift control device  36  to the shift assist apparatus  50 , and a second casing  44   b  that extends from the shift assist apparatus  50  to the internally geared hub  32 . The two ends of the first casing  44   a  are immoveable with respect to the frame  12 , and the internally geared hub  32  end of the second casing  44   b  is immoveable with respect to the frame  12 . The shift assist apparatus  50  end of the second casing  44   b  is retained to a translating member  80  and can move along with it as described below.  
         [0019]    As shown in FIGS.  2  to  5 , in this embodiment shift assist apparatus  50  is arranged around the crank spindle  20  between the front sprocket portion  28  and the frame  12 , and it is provided for the purpose of braking the crank spindle  20  during shift operations to lower the tension on the chain  30 . This, in turn, decreases the contact forces created within hub  32  to facilitate the shifting operation. To that end, the shift assist apparatus  50  comprises a braking mechanism  51  mounted to the frame  12  and a coupling mechanism  52  for coupling and decoupling the braking mechanism  51  for rotation with crank spindle  20 . The braking mechanism  51  comprises a bracket  53  nonrotatably mounted on the frame  12  about the crank spindle  20 ; a fixed portion  54  including a plurality of first friction disks  57  nonrotatably mounted on bracket  53 , each having a first friction face  57   a;  a rotary portion  55  including a plurality of second friction disks  59  nonrotatably mounted to a rotary member  58 , each having a second friction face  59   a;  and a braking force regulating portion  56  for varying braking force during the course of a single rotation of the crank spindle  20 .  
         [0020]    Bracket  53  is attached to hanger portion  15  by means of the bottom bracket  19 . Bracket  53  comprises a bracket body  60  having a round opening and a cover member  61  for covering the opening. The bracket body  60  comprises a first cylindrical portion  62  having the form of a bottomed hollow cylinder, an attachment cylinder  63  having the form of a bottomed hollow cylinder of smaller diameter than a first cylindrical portion  62 , a guide portion  64  formed on the back face of first cylindrical portion  62 , and a frame detent portion  65  extending radially outwardly from the outer peripheral face of the first cylindrical portion  62 . Frame detent portion  65  bends so as to extend parallel to the crank spindle  20 , and a semicircular recess  65   a  formed at the distal end of frame detent portion  65  engages the seat tube  17  to ensure that bracket  53  is nonrotatably fixed to frame  1 .  
         [0021]    First splines  66  for nonrotatably supporting the first friction disks  57  of the braking mechanism  51  are circumferentially formed on the inside peripheral surface of the first cylindrical portion  62 . The fixed portion  54 , rotary portion  55  and braking force regulating portion  56  are accommodated within the first cylindrical portion  62 . The attachment cylinder  63  projects slightly outward from the back face of the first cylindrical portion  62 , and it is fastened to hanger portion  15  by the flanged portion of bottom bracket  19  that extends through its center hole  63   a.  The guide portion  64  is disposed at a radially outward portion of first cylindrical portion  62 , and in this embodiment it has the shape of a partial circular arc intersecting a chord. The inner wire  42  of control cable  38  extends through the guide portion  64 . An outer detent portion  67  for supporting one end of the first casing  44   a  is formed at the shift control device  36  end of guide portion  64 . On the hub  32  side of guide portion  64  is formed a guide hole  68  of rectangular cross section for slidingly guiding a translating member  80  of the coupling mechanism  52  in the direction of cable passage.  
         [0022]    The cover member  61  is a tubular flange member having at its center a second cylindrical portion  70  of smaller diameter than the first cylindrical portion  62 . The cover member  61  is detachably fastened to the end face of the first cylindrical portion  62  by means of a plurality of bolts  71 . A sealing member  72  is installed between the inner rim of the cover member  61  and the boss portion  28   a  of the front sprocket portion  28  to prevent water or foreign matter from entering.  
         [0023]    The fixed portion  54  comprises, for example, three first friction disks  57 . First friction faces  57   a  are formed on the two sides of each first friction disk  57 , and splines  57   b  are formed on the outer peripheral edges thereof for nonrotatably mating with splines  66  of the first cylindrical portion  62 . The rotary portion  55  comprises a cylindrical rotary member  58  rotatably mounted on the outside peripheral face of the second cylindrical portion  70  of cover member  70  and, for example, three second friction disks  59  disposed in alternating arrangement with the first friction disks  57 . Second splines  58   a  are formed on the outer peripheral surface of the rotary member  58 . Second friction faces  59   a  are formed on the two sides of each second friction disk  59 , and splines  59   b  are formed on the inner peripheral edges of each second friction disk  59  for nonrotatably mating with the splines  58   a  on rotary member  58 .  
         [0024]    The braking force regulating portion  56  comprises a rotary cam mechanism  75  arranged coaxially with the friction disks  57  and  59  for varying the pressing force exerted on friction disks  57  and  59  in response to rotation of the rotary member  58 . The rotary cam mechanism  75  comprises a first cam disk  76 , a second cam disk  77  adjacent to first cam disk  76 , and a corrugated plate spring  78  for biasing the first and second cam disks  76  and  77  together. As shown in FIG. 6, splines  76   a  are formed on the inner peripheral surface of first cam disk  76  for nonrotatably mating with the splines  58   a  formed on the outer peripheral surface of rotating member  58 , and four first cam projections  76   b,    76   c,    76   d,    76   e  facing second cam disk  77  extend circumferentially around first cam disk  76 . Each cam projection  76   b - 76   e  includes a first ramp  76   g  extending in the axial direction toward the second cam disk  77 , a transition portion  76   f  (indicated by hatching in FIG. 6) extending from the first ramp  76   g  in a circumferential direction, and a second ramp  76   h  extending from the transition portion  76   f  away from the second cam disk  77 . The four first cam projections  76   b - 76   e  are arranged such that their transition portions  76   f  are situated at different locations 90° apart in the circumferential direction.  
         [0025]    Splines  76   a  are formed on the outer peripheral surface of second cam disk  77  for nonrotatably mating with splines  66  formed on the inner peripheral surface of first cylindrical portion  62 , and four second cam projections  77   b,    77   c,    77   d,    77   e  facing first cam disk  76  extend circumferentially around second cam disk  77 . In this embodiment, the second cam projections  77   b - 77   e  have greater circumferential extension than do the first cam projections  76   b - 76   e.  Each cam projection  77   b - 77   e  includes a first ramp  77   g  extending in the axial direction toward the first cam disk  76 , a transition portion  77   f  (indicated by hatching in FIG. 6) extending from the first ramp  77   g  in a circumferential direction, and a second ramp  77   h  extending from the transition portion  77   f  away from the first cam disk  76 . The four second cam projections  77   b - 77   e  are arranged such that their transistion portions  77   f  are situated at different locations 90° apart in the circumferential direction.  
         [0026]    The second cam disk  77 , through relative motion with respect to the first cam disk  76 , can move axially with respect to the first cam disk  76  in the direction of the crank spindle  20  so as to press together the two sets of friction disks  57  and  59 . A guide member  79  is attached to the inside side wall of cover member  61  so that the two cam disks  76 ,  77  are smoothly displaceable in the axial direction. By arranging the two sets of cam projections  76   b  - 76   e  and  77   b - 77   e  in this way, the two sets of cam projections  76   b - 76   e  and  77   b - 77   e  are constantly in contact and resist tilting even when undergoing relative motion.  
         [0027]    The rotary member  58  is selectively coupled for rotation with crank spindle  20  by means of the coupling mechanism  52 . As shown in FIG. 5, a pawl shaft  58   b  projects from the side of the rotary member  58  for rotatably supporting a coupling pawl  81 , and a spring post  58   c  projects from the side of the rotary member  58  for mounting a helical torsion spring  82  that biases the coupling pawl  81  radially inwardly. The translating member  80  has a rectangular rod configuration, and it is slidingly supported within guide hole  68 . A catch projection  80   b  is formed at the first end of translating member  80 . The distal end of catch projection  80   b  is bent into a hook for engaging a hook-shaped catch projection  81   a  of coupling pawl  81  for holding coupling pawl  81  in a decoupled position shown in FIG. 4. A detent portion  80   a  is formed at a first end of translating member  80  for terminating an end of the second casing  44   b.    
         [0028]    A catch ring  85  forming an abutment  85   a  is attached to and rotates with boss portion  28   a  of front sprocket portion  28  of crank arm  26 . The catch ring  85  is nonrotatably fixed to boss portion  28   a  by suitable fixing means such as interlocking serrations or by some other means. As described below, translation member  80  translates within guide hole  68  between a pawl engaging position and a pawl disengaging position. In the pawl disengaging position, depicted in FIG. 4, catch projection  80   b  engages catch projection  81   a  of coupling pawl  81  to thereby hold coupling pawl  81  in a decoupled position. In the pawl disengaging position, further towards the lower left in FIG. 4, the coupling pawl  81  pawl is allowed to move radially inwardly toward a coupled position, wherein a catch recess  81   b  of coupling pawl  81  abuts against abutment  85   a  formed on catch ring  85 . In the coupled position, coupling pawl  81  and thereby rotary member  58  rotate together with catch ring  85 . A return projection  86  is formed on the interior side wall of bracket  53 . The return projection  86  has a sloping face  86   a  for contacting the catch hook  81   a  of the coupling pawl  81  to return the coupling pawl  81  to the decoupled position.  
         [0029]    An annular recess  80   c  is formed at a second end of translating member  80  for supporting a coil spring  83  that biases the translating member  80  towards the pawl disengaging position. The translating member  80  is normally situated at the pawl engaging position because of the pressing force of the second casing  44   b,  but during a shift operation the inner wire  42  undergoes displacement towards hub  32  so that the pressing force of the second casing  44   b  is diminished, whereupon the translating member  80  moves to the pawl disengaging position because of the biasing force of the coil spring  83 . When the shift operation is complete, translating member  80  returns to the pawl engaging position because of the pressing force of the second casing  44   b.    
         [0030]    Assembly of shift assist apparatus  50  is as follows. Translating member  80  is first arranged at the bottom of the guide hole  68  and temporarily secured at this location by means of a fastening bolt  90  depicted in FIG. 3. While pushing towards the shift control device  36 , the attachment cylinder  63  of the bracket  53  is attached to the bottom bracket  19 , and the bottom bracket  19  is threaded into the hanger portion  15 . At this time, the frame detent portion  65  is fixed to the seat tube  17  so that bracket  53  is nonrotatably mounted on the frame  12  about the crank spindle  20 .  
         [0031]    The control cable  38  is then installed in the shift assist apparatus  50 . More specifically, a first end of the inner wire  42  (sheathed by the first casing  44   a ) is attached to the shift control device  36 , while a second end of inner wire is passed through translating member  80  such that the first casing  44   a  is terminated in the outer detent portion  67  of the guide portion  64 . The second casing  44   b  is then slipped onto the inner wire  42 , the inner wire  42  is secured to the operating member of the internally geared hub  32 , and the second casing  44   b  is terminated in the outer detent portion  80   a  of the translating member  80 . The operating member of the internally geared hub  32  is adjusted appropriately. A check is then performed to verify that the catch projection  80   b  of translating member  80  properly mates with the catch projection  81   a  of the coupling pawl  81 .  
         [0032]    Finally, the left and right crank arms  24  and  26  are arranged on both ends of the crank spindle  20 , and the chain  30  is installed on one of the sprocket plates  28   c  and  28   d.  The temporary fastening bolt  90  is then removed, thus allowing the translating member  80  to undergo translating motion. A check is then performed to verify that the shift assist apparatus  50  operates normally when a shift operation is performed in the loaded state.  
         [0033]    Operation of the shift assist apparatus  50  during shift operations is as follows. When the inner wire  42  is pulled towards the shift control device  36  such as occurs, for example, when shift control device  36  is operated to shift the internally geared hub  32  from a lower speed to a higher speed, the second casing  44   b  maintains a pressing force on the translating member  80  so that the translating member  80  of the shift assist apparatus  50  is maintained in the engaged position. However, when shift control device  36  is operated such that the inner wire  42  is returned towards the internally geared hub  32  to shift the internally geared hub  32  from a higher speed to a lower speed speed, the pressing force of the second casing  44   b  on the translating member  80  drops to a low level due to displacement of the inner wire  42  towards the internally geared hub  32 . As a result, the translating member  80  of the shift assist apparatus  50  moves to the left in FIG. 4 from the engaged position to the disengaged position. When translating member  80  moves to the disengaged position, the coupling pawl  81  becomes disengaged from the translating member  80 , and coupling pawl  81  moves radially inwardly from the decoupled position to the coupled position. In this position, the catch recess  81   b  of coupling pawl  81  engages the coupling projection  85   a  of the catch ring  85 , whereupon the rotary member  58 , second friction disks  59  and first cam disk  76  rotate together with the crank spindle  20 .  
         [0034]    FIGS.  7 (A)- 7 (C) are diagrams illustrating the operation of the first and second cam disks  76  and  77 . During the first half of the rotation, the transition portions  76   f,    77   f  of first and second cam disks  76  and  77  gradually overlap so that the first and second cam disks  76  and  77  move axially away from each other. This creates a progressively increasing pressing force on the first and second friction disks  57  and  59  which, in turn, creates a progressively increasing braking force on rotary member  58  and crank spindle  20 . This results in less tension being applied to chain  30  and hub  32 , thereby facilitating the shifting operation by reducing contact forces in the planetary gear mechanism within hub  32 . The gradual increase in braking force reduces the chance that the rider will experience any discomfort.  
         [0035]    When the transition portions  76   f  and  77   f  subsequently pass each other, the first and second cam disks  76  and  77  move progressively closer together because of the biasing force of the corrugated plate spring  78 . The pressing force on the first and second friction disks  57  and  59  diminish accordingly so that the braking force on crank spindle  20  gradually decreases. When the crank spindle  20  has undergone one rotation and the coupling pawl  81  rides up over the return projection  86 , the coupling pawl  81  is returned to the decoupled position and held in the decoupled position by the engagement of catch projection  80   b  of translating member  80 , which has now returned to the engaged position under the pressing force of the second casing  44   b,  and catch projection  81   a  of coupling pawl  81 . At this time, braking of the crank spindle  20  is completely released.  
         [0036]    While the above is a description of various embodiments of the present invention, further modifications may be employed without departing from the spirit and scope of the present invention. For example, the size, shape, location or orientation of the various components may be changed as desired. Components that are shown directly connected or contacting each other may have intermediate structures disposed between them. The functions of one element may be performed by two, and vice versa.  
         [0037]    Whereas in the described embodiment the front sprocket portion  28  is the drive apparatus that is braked, a different drive apparatus could be braked. For example, the rear sprocket  40  could be braked rather than the front sprocket portion  28 . The braking mechanism  51  and the crank spindle  20  may be directly linked. The braking mechanism  51  may be situated at the left in FIG. 3, with the braking mechanism  51  coupled with the left end of the crank spindle  20 . Instead of the braking mechanism  51  being fastened to the frame  12 , the braking mechanism could instead be fastened to the crank spindle  20  to effect coupling/decoupling with the frame  12 .  
         [0038]    In the described embodiment the coupling member coupling the shift control device to the internal gearshift was a control cable, but the coupling member could instead be a metal rod, hydraulic/pneumatic system, etc. While the braking mechanism was illustrated as multiple friction disks, the braking mechanism could instead employ a different braking structure including a drum or a caliper. Of course, the invention may also be implemented in an external gearshift apparatus comprising a derailleur and a plurality of sprockets.  
         [0039]    It is not necessary for all advantages to be present in a particular embodiment at the same time. Every feature which is unique from the prior art, alone or in combination with other features, also should be considered a separate description of further inventions by the applicant, including the structural and/or functional concepts embodied by such feature(s). Thus, the scope of the invention should not be limited by the specific structures disclosed or the apparent initial focus on a particular structure or feature.