Abstract:
A bicycle transmission control apparatus comprises a control unit that provides a first signal to operate a first derailleur a gear shift distance from a first origin sprocket to a first destination sprocket. The control unit receives a condition signal that indicates a condition resulting from at least one of the first derailleur and a second derailleur; and an adjustment controller moves the first derailleur an adjustment distance less than the gear shift distance in response to the condition signal.

Description:
BACKGROUND OF THE INVENTION 
     The present invention is directed to bicycles and, more particularly, to an apparatus for adjusting a position of a bicycle derailleur. 
     Bicycle transmissions that comprise front and rear derailleurs are well known. The front derailleur shifts a chain among a plurality of front sprockets that are coaxially mounted to the pedal crank shaft, and the rear derailleur shifts the chain among a plurality of rear sprockets that are coaxially mounted to the rear wheel. It is also known to use electric motors to operate the front and rear derailleurs, wherein operating a button or lever on a shift control device mounted to the bicycle handlebar controls the motors. Such a system is shown in Japanese Patent Application No. 2002-87371. 
     The chain is oriented in very extreme angles when it engages the innermost front sprocket in combination with the outermost rear sprocket and when it engages the outermost front sprocket in combination with the innermost rear sprocket. Depending upon the design of the bicycle frame, such extreme angles may cause the chain to rub against the front derailleur cage. Even when the front derailleur is initially installed in a proper position, the derailleur may subsequently move over time, thereby again causing the chain to rub against the derailleur cage in such situations. Such contact causes noise, greater pedaling resistance, and excessive wear on the derailleur cage. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an apparatus for adjusting a position of a bicycle derailleur. In one embodiment, a bicycle transmission control apparatus comprises a control unit that provides a first signal to operate a first derailleur a gear shift distance from a first origin sprocket to a first destination sprocket. The control unit receives a condition signal that indicates a condition resulting from at least one of the first derailleur and a second derailleur; and an adjustment controller moves the first derailleur an adjustment distance less than the gear shift distance in response to the condition signal. Additional inventive features will become apparent from the description below, and such features alone or in combination with the above features may form the basis of further inventions as recited in the claims and their equivalents. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a particular embodiment of a bicycle; 
         FIG. 2  is a front view of particular embodiments of brake lever assemblies mounted to the bicycle handlebar; 
         FIG. 3  is a side view of the rear brake lever assembly; 
         FIG. 4  is a front view of the rear brake lever assembly; 
         FIG. 5  is a schematic diagram of the front and rear sprocket assemblies; 
         FIG. 6  is a schematic block diagram of a particular embodiment of a derailleur control apparatus; 
         FIG. 7  is a flow chart of a particular embodiment of the operation of the derailleur control apparatus; 
         FIG. 8  is a side view of another embodiment of a front brake lever assembly; 
         FIG. 9  is a schematic block diagram of a particular embodiment of a derailleur control apparatus used with the front brake lever assembly shown in  FIG. 8 ; 
         FIG. 10  is a flow chart of a particular embodiment of the operation of the derailleur control apparatus shown in  FIG. 9 ; 
         FIG. 11  is a schematic block diagram of another embodiment of a derailleur control apparatus; 
         FIG. 12  is a flow chart of a particular embodiment of the operation of the derailleur control apparatus shown in  FIG. 11 ; 
         FIG. 13  is a schematic block diagram of another embodiment of a derailleur control apparatus; and 
         FIG. 14  is a flow chart of a particular embodiment of the operation of the derailleur control apparatus shown in  FIG. 13 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       FIG. 1  is a side view of a bicycle  101  that includes particular embodiments of electrically controlled components. Bicycle  101  is a road bicycle comprising a diamond-shaped frame  102 , a front fork  98  rotatably mounted to frame  102 , a handlebar assembly  104  mounted to the upper part of fork  98 , a front wheel  106   f  rotatably attached to the lower part of fork  98 , a rear wheel  106   r  rotatably attached to the rear of frame  102 , and a drive unit  105 . A front wheel brake  107   f  is provided for braking front wheel  106   f , and a rear wheel brake  107   r  is provided for braking rear wheel  106   r.    
     Drive unit  105  comprises a chain  95 , a front sprocket assembly  99   f  coaxially mounted with a crank  96  having pedals PD, an electrically controlled front derailleur  97   f  attached to a seat tube  102   a  of frame  102 , a rear sprocket assembly  99   r  coaxially mounted with rear wheel  106   r , and an electrically controlled rear derailleur  97   r . As shown in  FIG. 5 , front sprocket assembly  99   f  comprises two coaxially mounted sprockets F 1 -F 2 , and rear sprocket assembly  99   r  comprises ten sprockets R 1 -R 10  mounted for coaxial rotation with of rear wheel  106   r . The number of teeth on the laterally innermost front sprocket F 1  is less than the number of teeth on the laterally outermost front sprocket F 2 . The numbers of teeth on rear sprockets R 1 -R 10  gradually decrease from the laterally inner most rear sprocket R 1  to the laterally outermost rear sprocket R 10 . As a result, rear sprocket R 1  has the greatest number of teeth, and rear sprocket R 10  has the least number of teeth. Front derailleur  97   f  moves to two operating positions to switch chain  95  between front sprockets F 1  and F 2 , and rear derailleur  97   r  moves to ten operating positions to switch chain  95  among selected ones of the rear sprockets R 1 -R 10 . A front gear position sensor  133   f  ( FIG. 6 ) senses the operating position of front derailleur  97   f , and a rear gear position sensor  133   r  senses the operating position of rear derailleur  97   r . A battery or some other power source (not shown) powers front and rear derailleurs  97   f  and  97   r  as well as other electrical components described herein in a known manner. 
     Handlebar assembly  104  comprises a handlebar stem  111  and a drop-style handlebar  112 , wherein handlebar stem  111  is mounted to the upper part of fork  98 , and handlebar  112  is mounted to the forward end portion of handlebar stem  111 . As shown in  FIG. 2 , brake lever assemblies  113   f  and  113   r  are mounted at opposite sides of handlebar  112 . Brake lever assembly  113   f  controls the operation of front wheel brake  107   f , and brake lever assembly  113   r  controls the operation of rear wheel brake  107   r . A derailleur control device  110  is mounted to a central portion of handlebar  112 . 
     Brake lever assemblies  113   f  and  113   r  comprise respective brake brackets  115   f  and  115   r  mounted to the forward curved portions of handlebar  112 , and brake levers  116   f  and  116   r  pivotably mounted to brake brackets  115   f  and  115   r . Rear shift control devices  120   r  and  121   r  with switch levers  125  are mounted to the inner side of brake bracket  115   r  and to the rear side of brake lever  116   r , respectively, to control the operation of rear derailleur  97   r . In this embodiment, rear shift control devices  120   r  and  121   r  independently control the operation of rear derailleur  97   r  so that the rider may control the operation of rear derailleur  97   r  with the hand grasping brake bracket  115   r  or with the hand grasping brake lever  116   r . As shown in  FIG. 3 , the switch lever  125  mounted to brake lever bracket  115   r  rotates downward from a home position P 0  to a first position P 1  and rotates upward from home position P 0  to a second position P 2  to control the operation of rear derailleur  97   r . As shown in  FIG. 4 , the switch lever  125  mounted to the rear of brake lever  116   r  rotates laterally inward from a home position P 0  to a first position P 1  and rotates laterally outward from home position P 0  to a second position P 2  to control the operation of rear derailleur  97   r . Similarly, independent front shift control devices  120   f  and  121   f  with switch levers  125  are mounted to the inner side of brake bracket  115   f  and to the rear side of brake lever  116   f , respectively, to control the operation of front derailleur  97   f . The switch levers  125  mounted to brake lever bracket  115   f  and brake lever  116   f  operate in the same manner as switch levers  125  mounted to brake lever bracket  115   r  and brake lever  116   r . All of the switch levers  125  are biased toward the home position P 0 . 
     A front upshift switch  131   f  ( FIG. 6 ) and a front downshift switch  132   f  are mounted in each front shift control device  120   f  and  121   f . The front upshift switches  131   f  operate when switch levers  125  in front shift control devices  120   f  and  121   f  rotate from position P 0  to position P 1 , and the front downshift switches  132   f  operate when switch levers  125  in front shift control devices  120   f  and  121   f  rotate from position P 0  to position P 2 . Similarly, a rear upshift switch  131   r  and a rear downshift switch  132   r  are mounted in each rear shift control device  120   r  and  121   r . The rear upshift switches  131   r  operate when switch levers  125  in rear shift control devices  120   r  and  121   r  rotate from position P 0  to position P 1 , and the rear downshift switches  132   r  operate when switch levers  125  in rear shift control devices  120   r  and  121   r  rotate from position P 0  to position P 2 . Of course, many different switch combinations that operate in many different ways may be provided to suit different applications. 
     As shown in  FIGS. 2 and 6 , derailleur control device  110  comprises a case  126  mounted onto the central portion of handlebar  112 . Mounted within case  126  are a control unit  130  and a liquid crystal display (LCD)  135  for displaying riding parameters and other information. Front derailleur  97   f , rear derailleur  97   r , front upshift switch  131   f , front downshift switch  132   f , rear upshift switch  131   r , rear downshift switch  132   r , front gear position sensor  133   f , rear gear position sensor  133   r  and other I/O units are connected to control unit  130  through appropriate methods such as wired or wireless devices. A storage unit such as a memory  138  stores various parameters used in the operation of control unit  130 . For example, the operating (sprocket) positions (FP, RP) based on the front sprockets FS (S=1, 2) and rear sprockets RS (S=1-10) for the front and rear derailleurs  97   f  and  97   r  are stored in accordance with values detected by gear position sensors  133   f  and  133   r . As shown in  FIGS. 1 and 6 , a speed sensor  122  is mounted to fork  98  to sense the passage of a magnet  123  mounted to a spoke  106   s  of front wheel  106   f  and to provide speed indicating signals to control unit  130  through a wired or wireless method. 
     In this embodiment, control unit  130  comprises a programmed microprocessor. Control unit  130  includes a gear shift controller  130   a , an adjustment controller  130   b  and a return controller  130   c . Gear shift controller  130   a  provides signals to control the operation of front derailleur  97   f  and rear derailleur  97   r  to shift chain  95  the distance from an origin sprocket to a destination sprocket in accordance with signals received from front and rear upshift switches  131   f  and  131   r , front and rear downshift switches  132   f  and  132   r , and front and rear gear position sensors  133   f  and  133   r . In this embodiment, adjustment controller  130   b  adjusts the position of front derailleur  97   f  in a manner discussed below. Return controller  130   c  returns front derailleur  97   f  to a position it had prior to movement by adjustment controller  130   b  under conditions described below. Control unit  130  also displays speed, gear positions, and running distance on LCD  135  based on signals received from speed sensor  122  and gear position sensors  133   f  and  133   r.    
       FIG. 7  is a flow chart of a particular embodiment of the operation of control unit  130 . Initialization is carried out in a step S 1  when power is supplied to control unit  130 . In this step, various flags and variables are reset. It is then determined in a step S 2  whether or not a front upshift switch  131   f  has been turned on as a result of a switch lever  125  in front shift control device  120   f  or  121   f  rotating from position P 0  to position P 1 . If so, it is then determined in a step S 10  whether or not front derailleur  97   f  currently is at the operating position for sprocket F 2  based on signals from front gear position sensor  133   f . If so, then no further upshifting is possible, the upshift request is ignored, and processing continues in a step S 3 . Otherwise, control unit  130  provides a signal so that front derailleur  97   f  switches chain  95  from sprocket F 1  to sprocket F 2  in step S 11 . 
     It is then determined in a step S 12  whether or not rear derailleur  97   r  currently is at the operating position for one of sprockets R 1 -R 3  based on signals from rear gear position sensor  133   r . If not, then chain  95  is not at a very high incline relative to front sprocket F 2 , it is assumed that fine tuning of the position of front derailleur  97   f  is not required, and processing simply continues at step S 3 . On the other hand, if rear derailleur  97   r  currently is at the operating position for one of sprockets R 1 -R 3 , then chain  95  is at a relatively high incline relative to front sprocket F 2 , which may cause undesirable contact between chain  95  and the chain guide of front derailleur  97   f , and it is assumed that fine tuning of the position of front derailleur  97   f  is in order. Such fine tuning is performed in a step S 13 , and it comprises moving front derailleur  97   f  laterally inward by a distance less than the distance between front sprockets F 1  and F 2 . More specifically, front derailleur  97   f  may be moved laterally inward a small distance, e.g., from approximately 0.5 mm to approximately 2 mm (or more or less, depending upon the application), preferably 1 mm. 
     In any event, it is then determined in step S 3  whether or not a front downshift switch  132   f  has been turned on as a result of a switch lever  125  in front shift control device  120   f  or  121   f  rotating from position P 0  to position P 2 . If so, it is then determined in a step S 16  whether or not front derailleur  97   f  currently is at the operating position for sprocket F 1 . If so, then no further downshifting is possible, the downshift request is ignored, and processing continues in a step S 4 . Otherwise, control unit  130  provides a signal so that front derailleur  97   f  switches chain  95  from sprocket F 2  to sprocket F 1  in a step S 17 . 
     It is then determined in a step S 18  whether or not rear derailleur  97   r  currently is at the operating position for one of sprockets R 8 -R 10 . If not, then chain  95  is not at a very high incline relative to front sprocket F 1 , it is assumed that fine tuning of the position of front derailleur  97   f  is not required, and processing simply continues at step S 4 . On the other hand, if rear derailleur  97   r  currently is at the operating position for one of sprockets R 8 -R 10 , then chain  95  is at a relatively high incline relative to front sprocket F 1 , which may cause undesirable contact between chain  95  and the chain guide of front derailleur  97   f , and it is assumed that fine tuning of the position of front derailleur  97   f  is in order. Such fine tuning is performed in a step S 19 , and it comprises moving front derailleur  97   f  laterally outward by a distance such as the distance noted above for step S 13 . 
     In any event, it is then determined in step S 4  whether or not a rear upshift switch  131   r  has been turned on as a result of a switch lever  125  in rear shift control device  120   r  or  121   r  rotating from position P 0  to position P 1 . If so, it is then determined in a step S 22  whether or not rear derailleur  97   r  currently is at the operating position for sprocket R 10  based on signals from rear gear position sensor  133   r . If so, then no further upshifting is possible, the upshift request is ignored, and processing continues in a step S 5 . Otherwise, control unit  130  provides a signal so that rear derailleur  97   r  switches chain  95  to the next higher rear sprocket in a step S 23 . 
     It now must be determined whether or not the rear upshift has caused chain  95  to be at a relatively high incline, which would be the case if front derailleur  97   f  currently is at the operating position for sprocket F 1  and rear derailleur  97   r  currently is at the operating position for one of sprockets R 8 -R 10 . Accordingly, it is determined in a step S 24  whether or not rear derailleur  97   r  currently is at the operating position for one of sprockets R 8 -R 10 . If so, it is then determined in a step S 25  whether or not front derailleur  97   f  currently is at the operating position for sprocket F 1 . If so, then chain  95  currently is at a relatively high incline relative to front sprocket F 1 , and it is assumed that fine tuning of the position of front derailleur  97   f  is in order. Such fine tuning is performed in a step S 26  by moving front derailleur  97   f  laterally outward by a distance such as the distance noted above for step S 13 . Processing then continues at step S 5 . On the other hand, if front derailleur  97   f  is not positioned at sprocket F 1 , then chain  95  currently is engaging front sprocket F 2 , it is assumed that fine tuning of the position of front derailleur  97   f  is not required, and processing simply continues at step S 5 . 
     If it is determined in step S 24  that rear derailleur  97   r  currently is not at the operating position for one of sprockets R 8 -R 10 , it now must be determined whether or not the rear upshift eliminated a previously high incline of chain  95 , which would be the case if front derailleur  97   f  currently is at the operating position for sprocket F 2  and rear derailleur  97   r  previously was at the operating position for any one of sprockets R 1 -R 3 . Accordingly, it is determined in a step S 27  whether or not rear derailleur  97   r  currently is at the operating position for sprocket R 4 . If so, it is then determined in a step S 28  whether or not front derailleur  97   f  currently is at the operating position for sprocket F 1 . If not, then front derailleur  97   f  currently is at the operating position for sprocket F 2 , rear derailleur  97   r  previously was at the operating position for sprocket R 3 , and chain  95  previously was at a relatively high incline relative to front sprocket F 2 . It also is assumed that front derailleur  97   f  previously was adjusted to accommodate that high incline, but now such adjustment no longer is necessary. Accordingly, return controller  130   c  cancels the previous adjustment by moving front derailleur  97   f  laterally outwardly to the unadjusted operating position for sprocket F 2 , and processing continues at step S 5 . On the other hand, if it is determined in step S 27  that rear derailleur  97   r  currently is not positioned at sprocket R 4 , or if it is determined that front derailleur  97   f  currently is positioned at sprocket F 1 , then no further action is required, so processing simply continues at step S 5 . 
     It is determined in step S 5  whether or not a rear downshift switch  132   r  has been turned on as a result of a switch lever  125  in rear shift control device  120   r  or  121   r  rotating from position P 0  to position P 2 . If so, it is then determined in a step S 30  whether or not rear derailleur  97   r  currently is at the operating position for sprocket R 1 . If so, then no further downshifting is possible, the downshift request is ignored, and processing continues at step S 2 . Otherwise, control unit  130  provides a signal so that rear derailleur  97   r  switches chain  95  to the next lower rear sprocket in a step S 31 . 
     It now must be determined whether or not the rear downshift has caused chain  95  to be at a relatively high incline, which would be the case if front derailleur  97   f  currently is at the operating position for sprocket F 2  and rear derailleur  97   r  currently is at the operating position for one of sprockets R 1 -R 3 . Accordingly, it is determined in a step S 32  whether or not rear derailleur  97   r  currently is at the operating position for one of sprockets R 1 -R 3 . If so, it is then determined in a step S 33  whether or not front derailleur  97   f  currently is at the operating position for sprocket F 2 . If so, then chain  95  currently is at a relatively high incline relative to front sprocket F 2 , and it is assumed that fine tuning of the position of front derailleur  97   f  is in order. Such fine tuning is performed in a step S 34  by moving front derailleur  97   f  laterally inward by a distance such as the distance noted above for step S 13 . Processing then continues at step S 2 . On the other hand, if front derailleur  97   f  is not positioned at sprocket F 2 , then chain  95  currently is engaging sprocket F 1 , it is assumed that fine tuning of the position of front derailleur  97   f  is not required, and processing simply continues at step S 2 . 
     If it is determined in step S 32  that rear derailleur  97   r  currently is not at the operating position for one of sprockets R 1 -R 3 , it now must be determined whether or not the rear downshift eliminated a previously high incline of chain  95 , which would be the case if front derailleur  97   f  currently is at the operating position for sprocket F 1  and rear derailleur  97   r  previously was at the operating position for any one of sprockets R 8 -R 10 . Accordingly, it is determined in a step S 35  whether or not rear derailleur  97   r  currently is at the operating position for sprocket R 7 . If so, it is then determined in a step S 36  whether or not front derailleur  97   f  currently is at the operating position for sprocket F 2 . If not, then front derailleur  97   f  currently is at the operating position for sprocket F 1 , rear derailleur  97   r  previously was at the operating position for sprocket R 8 , and chain  95  previously was at a relatively high incline relative to front sprocket F 1 . It also is assumed that front derailleur  97   f  previously was adjusted to accommodate that high incline, but now such adjustment no longer is necessary. Accordingly, return controller  130   c  cancels the previous adjustment by moving front derailleur  97   f  laterally inwardly to the unadjusted operating position for sprocket F 1 , and processing continues at step S 2 . On the other hand, if it is determined in step S 35  that rear derailleur  97   r  currently is not positioned at sprocket R 7 , or if it is determined that front derailleur  97   f  currently is positioned at sprocket F 2 , then no further action is required, so processing simply continues at step S 2 . 
       FIG. 8  is a side view of another embodiment of front brake lever assembly  113   f , and  FIG. 9  is a schematic block diagram of a particular embodiment of a derailleur control apparatus used with front brake lever assembly  113   f  shown in  FIG. 8 . In this embodiment, a manually operated disabling switch  140  is mounted to brake bracket  115   f , and disabling switch  140  provides signals to a disabling unit  130   d  in control unit  130  so that disabling unit  130   d  can selectively enable and disable the operation of adjustment controller  130   a . That may be desirable when the number of rear sprockets is reduced, for example. Disabling the operation of adjustment controller  130   b  reduces power consumption and unnecessary wear on the components. 
     In this embodiment, disabling switch  140  comprises an on/off push button such that disabling unit  130   d  disables the operation of adjustment controller  130   b  when disabling switch provides an “on” signal and correspondingly enables the operation of adjustment controller  130   b  when disabling switch  140  provides an “off” signal. The other components shown in  FIGS. 8 and 9  are the same as those disclosed for the first embodiment and will not be described further. 
       FIG. 10  is a flow chart of a particular embodiment of the operation of the derailleur control apparatus shown in  FIG. 9 . The operation is the same as that show in  FIG. 7  except for the following differences. 
     After initialization is performed in step S 1 , it is determined in a step S 41  whether or not disabling switch  140  is providing an “on” signal, thus indicating a desire to disable the operation of adjustment controller  130   b . If so, then a disabled flag PF is turned on (set to one) in a step S 42 . The disabled flag PF is reset during the initialization performed in step S 1  and at any time when disabling switch  140  is turned off. In any event, it is then determined in step S 2  whether or not a front upshift switch  131   f  has been turned on as a result of a switch lever  125  in front shift control device  120   f  or  121   f  rotating from position P 0  to position P 1 . If so, it is then determined in step S 10  whether or not front derailleur  97   f  currently is at the operating position for sprocket F 2  based on signals from front gear position sensor  133   f . If so, then no further upshifting is possible, the upshift request is ignored, and processing continues at step S 3 . Otherwise, control unit  130  provides a signal so that front derailleur  97   f  switches chain  95  from sprocket F 1  to sprocket F 2  in step S 11 . 
     It is then determined in a step S 43  whether or not disabled flag PF is turned on. If so, then the adjustment process is bypassed, and processing simply continues at step S 3 . Otherwise, adjustment processing continues at step S 12  as in the first embodiment. 
     In any event, it is then determined in step S 3  whether or not a front downshift switch  132   f  has been turned on as a result of a switch lever  125  in front shift control device  120   f  or  121   f  rotating from position P 0  to position P 2 . If so, it is then determined in step S 16  whether or not front derailleur  97   f  currently is at the operating position for sprocket F 1 . If so, then no further downshifting is possible, the downshift request is ignored, and processing continues at step S 4 . Otherwise, control unit  130  provides a signal so that front derailleur  97   f  switches chain  95  from sprocket F 2  to sprocket F 1  in step S 17 . 
     It is then determined in a step S 44  whether or not disabled flag PF is turned on. If so, then the adjustment process is bypassed, and processing simply continues at step S 4 . Otherwise, adjustment processing continues at step S 18  as in the first embodiment. 
     In any event, it is then determined in step S 4  whether or not a rear upshift switch  131   r  has been turned on as a result of a switch lever  125  in rear shift control device  120   r  or  121   r  rotating from position P 0  to position P 1 . If so, it is then determined in step S 22  whether or not rear derailleur  97   r  currently is at the operating position for sprocket R 10 . If so, then no further upshifting is possible, the upshift request is ignored, and processing continues at step S 5 . Otherwise, control unit  130  provides a signal so that rear derailleur  97   r  switches chain  95  to the next higher rear sprocket in step S 23 . 
     It is then determined in a step S 45  whether or not disabled flag PF is turned on. If so, then the adjustment process is bypassed, and processing simply continues at step S 5 . Otherwise, adjustment processing continues at step S 24  as in the first embodiment. 
     In any event, it is determined in step S 5  whether or not a rear downshift switch  132   r  has been turned on as a result of a switch lever  125  in rear shift control device  120   r  or  121   r  rotating from position P 0  to position P 2 . If so, it is then determined in step S 30  whether or not rear derailleur  97   r  currently is at the operating position for sprocket R 1 . If so, then no further downshifting is possible, the downshift request is ignored, and processing continues at step S 2 . Otherwise, control unit  130  provides a signal so that rear derailleur  97   r  switches chain  95  to the next lower rear sprocket in step S 31 . 
     It is then determined in a step S 46  whether or not disabled flag PF is turned on. If so, then the adjustment process is bypassed, and processing simply continues at step S 41 . Otherwise, adjustment processing continues at step S 32  as in the first embodiment. 
       FIG. 11  is a schematic block diagram of another embodiment of a derailleur control apparatus. In this embodiment, a voltage sensor  142  provides signals to a disabling unit  130   e  in control unit  130  so that disabling unit  130   e  can selectively enable and disable the operation of adjustment controller  130   a  when a power supply voltage, for example, falls below a desired value to avoid further drain on the power supply and possible malfunction of the components. 
       FIG. 12  is a flow chart of a particular embodiment of the operation of the derailleur control apparatus shown in  FIG. 11 . The operation is the same as that show in  FIG. 10  except for the following differences. 
     After initialization is performed in step S 1 , it is determined in a step S 40  whether or not voltage sensed by voltage sensor  142  has fallen below a selected threshold value (e.g., 50% of a fully charged state). If so, then a disabled flag PF is turned on (set to one) in a step S 42 . Processing then continues in the same manner as that shown in  FIG. 10 . 
       FIG. 13  is a schematic block diagram of another embodiment of a derailleur control apparatus. In this embodiment, a contact sensor  143  provides signals to control unit  130  so that control unit  130  may determine whether or not to perform adjustment processing. In this embodiment, contact sensor  143  may comprise a vibration sensor that senses unusual vibration of front derailleur  97   f . Contact sensor  143  also may comprise a sound wave sensor that senses unusual noise that may arise from contact between chain  95  and front derailleur  97   f . The other components shown in  FIG. 13  are the same as those disclosed for the first embodiment and will not be described further. 
       FIG. 14  is a flow chart of a particular embodiment of the operation of the derailleur control apparatus shown in  FIG. 13 . The operation is the same as that show in  FIG. 7  except for the following differences. 
     After initialization is performed in step S 1 , it is then determined in step S 2  whether or not a front upshift switch  131   f  has been turned on as a result of a switch lever  125  in front shift control device  120   f  or  121   f  rotating from position P 0  to position P 1 . If so, it is then determined in step S 10  whether or not front derailleur  97   f  currently is at the operating position for sprocket F 2 . If so, then no further upshifting is possible, the upshift request is ignored, and processing continues at step S 3 . Otherwise, control unit  130  provides a signal so that front derailleur  97   f  switches chain  95  from sprocket F 1  to sprocket F 2  in step S 11 . 
     It is then determined in a step S 51  whether or not undesirable contact between chain  95  and front derailleur  97   f  is being sensed by contact sensor  143 . If so, then front derailleur  97   f  is adjusted laterally inward in step S 13  as in the first embodiment. 
     In any event, it is then determined in step S 3  whether or not a front downshift switch  132   f  has been turned on as a result of a switch lever  125  in front shift control device  120   f  or  121   f  rotating from position P 0  to position P 2 . If so, it is then determined in a step S 16  whether or not front derailleur  97   f  currently is at the operating position for sprocket F 1 . If so, then no further downshifting is possible, the downshift request is ignored, and processing continues at step S 4 . Otherwise, control unit  130  provides a signal so that front derailleur  97   f  switches chain  95  from sprocket F 2  to sprocket F 1  in step  17 . 
     It is then determined in a step S 52  whether or not undesirable contact between chain  95  and front derailleur  97   f  is being sensed by contact sensor  143 . If so, then front derailleur  97   f  is adjusted laterally outward in step S 19  as in the first embodiment. 
     In any event, it is then determined in step S 4  whether or not a rear upshift switch  131   r  has been turned on as a result of a switch lever  125  in rear shift control device  120   r  or  121   r  rotating from position P 0  to position P 1 . If so, it is then determined in a step S 22  whether or not rear derailleur  97   r  is at the operating position for sprocket R 10 . If so, then no further upshifting is possible, the upshift request is ignored, and processing continues at step S 5 . Otherwise, control unit  130  provides a signal so that rear derailleur  97   r  switches chain  95  to the next higher rear sprocket in step S 23 . 
     It is then determined in a step S 53  whether or not undesirable contact between chain  95  and front derailleur  97   f  is being sensed by contact sensor  143 . If so, then front derailleur  97   f  is adjusted laterally outward in step S 26  as in the first embodiment. Otherwise, processing continues at step S 27  as in the first embodiment. 
     In any event, it is determined in step S 5  whether or not a rear downshift switch  132   r  has been turned on as a result of a switch lever  125  in rear shift control device  120   r  or  121   r  rotating from position P 0  to position P 2 . If so, it is then determined in a step S 30  whether or not rear derailleur  97   r  currently is at the operating position for sprocket R 1 . If so, then no further downshifting is possible, the downshift request is ignored, and processing continues at step S 2 . Otherwise, control unit  130  provides a signal so that rear derailleur  97   r  switches chain  95  to the next lower rear sprocket in step S 31 . 
     It is then determined in a step S 54  whether or not undesirable contact between chain  95  and front derailleur  97   f  is being sensed by contact sensor  143 . If so, then front derailleur  97   f  is adjusted laterally inward in step S 34  as in the first embodiment. Otherwise, processing continues at step S 35  as in the first embodiment. 
     While the above is a description of various embodiments of inventive features, further modifications may be employed without departing from the spirit and scope of the present invention. For example, in the embodiment described in  FIG. 7 , a previous adjustment of front derailleur  97   f  was canceled whenever rear derailleur  97   r  shifted one gear up from rear sprocket R 3  or one gear down from rear sprocket R 8 . However, such cancellation may occur when rear derailleur  97   r  shifts even more one gear up or down than that disclosed in  FIG. 7 . In that case, it would be determined in step S 27  in  FIG. 7  whether or not rear derailleur  97   r  currently is in the operating position for sprocket R 5 , and it would be determined in step S 35  whether or not rear derailleur  97   r  currently is in the operating position for sprocket R 6 . That further reduces power consumption caused by frequent operation of front derailleur  97   f.    
     In the above embodiments, adjustment of front derailleur  97   f  occurred at the same time gear shifting occurred. However, it is possible to delay the adjustment operation until after a predetermined time interval from the detection of a questionable sprocket combination, or after a predetermined crank rotation interval from the detection of the questionable sprocket combination. If desired, such delays may be applied only to situations where the front and/or rear derailleur takes more time to complete the shifting operation, such as when the front derailleur performs an upshift operation. Such time delays increase the probability that the gear shift operation has in fact completed and front derailleur  97   f  may be adjusted with more precision. 
     While the above embodiments included only two front sprockets F 1  and F 2 , a three-stage front sprocket assembly  99   f  comprising front sprockets F 1 -F 3  may be employed. In this case, adjustment processing may be disabled when front derailleur  97   f  is in the operating position for sprocket F 2 . 
     While adjustment processing was performed when front derailleur  97   f  was in the operating position for front sprocket F 1  and rear derailleur  97   r  was in the operating position for any one of rear sprockets R 8 -R 10 , or when front derailleur  97   f  was in the operating position for front sprocket F 2  and rear derailleur  97   r  was in the operating position for any one of rear sprockets R 1 -R 3 , adjustment may be accomplished for many sprocket combinations, such as when front derailleur  97   f  is in the operating position for front sprocket F 1  and rear derailleur  97   r  is in the operating position only for rear sprocket R 10 , or when front derailleur  97   f  is in the operating position for front sprocket F 2  and rear derailleur  97   r  is in the operating position only for rear sprocket R 1 . Similarly, adjustment may be accomplished when front derailleur  97   f  is in the operating position for front sprocket F 1  and rear derailleur  97   r  is in the operating position only for rear sprockets R 9  and R 10 , or when front derailleur  97   f  is in the operating position for front sprocket F 2  and rear derailleur  97   r  is in the operating position only for rear sprockets R 1  and R 2 . 
     While the described embodiments were applied to a road bicycle, the bicycle may have any configuration. Also, while the above embodiments described an electronically controlled rear derailleur  97   r , a manually controlled rear derailleur also may be used. 
     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. The structures and functions of one embodiment may be adopted in another embodiment. It is not necessary for all advantages to be present in a particular embodiment at the same time. Every feature that 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 or emphasis on a particular structure or feature.