Bicycle shift control apparatus that prevents undesirable chain angles

Abstract

A shift control apparatus is provided for a bicycle having a plurality of front sprockets and a plurality of rear sprockets, wherein a front derailleur shifts a chain among the plurality of front sprockets and a rear derailleur shifts the chain among the plurality of rear sprockets. The apparatus comprises a shift unit that provides signals for shifting the front derailleur and the rear derailleur; and a prohibiting unit operatively coupled to the shift unit and providing signals so that the chain is prohibited from engaging at least one of i) a laterally innermost front sprocket in combination with a laterally outermost rear sprocket, and ii) a laterally outermost front sprocket in combination with a laterally innermost rear sprocket.

1. A shift control apparatus for a bicycle having a plurality of front sprockets and a plurality of rear sprockets, wherein a front derailleur shifts a chain among the plurality of front sprockets and a rear derailleur shifts the chain among the plurality of rear sprockets, wherein the apparatus comprises:
 a velocity signal circuit that generates a velocity signal indicating a traveling velocity of the bicycle;  
 a shift unit that provides signals for shifting the front derailleur and the rear derailleur; 
 wherein the shift unit gives priority to shifting the rear derailleur to achieve a destination gear ratio unless the velocity signal indicates that the bicycle is accelerating or decelerating rapidly, whereupon the shift unit gives priority to shifting the front derailleur to achieve the destination gear; and 
 a prohibiting unit operatively coupled to the shift unit and providing  so that, when one of the front derailleur or the rear derailleur is shifted, the prohibiting unit provides signals to shift the front derailleur or the rear derailleur so that the chain is prohibited from engaging at least one prohibited sprocket combination comprising at least one of i) a laterally innermost front sprocket in combination with a laterally outermost rear sprocket, and ii) a laterally outermost front sprocket in combination with a laterally innermost rear sprocket; 
 wherein the prohibiting unit detects when the front derailleur and the rear derailleur are positioned such that shifting the front derailleur or the rear derailleur to execute a shift command would cause the front derailleur and the rear derailleur to engage the at least one prohibited sprocket combination. 
 
     
     
       2. The apparatus according to  claim 1  wherein the prohibiting unit cooperates with the shift unit so that the chain is prohibited from engaging the laterally innermost front sprocket in combination with the laterally outermost rear sprocket. 
     
     
       3. The apparatus according to  claim 2  wherein the plurality of front sprockets comprise a first front sprocket, a second front sprocket and a third front sprocket, wherein the first front sprocket comprises the laterally innermost front sprocket, wherein the third front sprocket comprises the laterally outermost front sprocket, wherein the second front sprocket is disposed between the first front sprocket and the third front sprocket, and wherein the prohibiting unit cooperates with the shift unit so that the chain is prohibited from engaging the second front sprocket in combination with the laterally innermost rear sprocket. 
     
     
       4. The apparatus according to  claim 2  wherein the plurality of front sprockets comprise a first front sprocket, a second front sprocket and a third front sprocket, wherein the first front sprocket comprises the laterally innermost front sprocket, wherein the third front sprocket comprises the laterally outermost front sprocket, wherein the second front sprocket is disposed between the first front sprocket and the third front sprocket, and wherein the prohibiting unit cooperates with the shift unit so that chain is prohibited from engaging the second front sprocket in combination with the laterally outermost rear sprocket. 
     
     
       5. The apparatus according to  claim 2  wherein the prohibiting unit cooperates with the shift unit so that the chain is prohibited from engaging the laterally innermost front sprocket in combination with a rear sprocket adjacent to the laterally outermost rear sprocket. 
     
     
       6. The apparatus according to  claim 5  wherein the plurality of front sprockets comprise a first front sprocket, a second front sprocket and a third front sprocket, wherein the first front sprocket comprises the laterally innermost front sprocket, wherein the third front sprocket comprises the laterally outermost front sprocket, wherein the second front sprocket is disposed between the first front sprocket and the third front sprocket, and wherein the prohibiting unit cooperates with the shift unit so that the chain is prohibited from engaging the second front sprocket in combination with the laterally innermost rear sprocket. 
     
     
       7. The apparatus according to  claim 5  wherein the plurality of front sprockets comprise a first front sprocket, a second front sprocket and a third front sprocket, wherein the first front sprocket comprises the laterally innermost front sprocket, wherein the third front sprocket comprises the laterally outermost front sprocket, wherein the second front sprocket is disposed between the first front sprocket and the third front sprocket, and wherein the prohibiting unit cooperates with the shift unit so that chain is prohibited from engaging the second front sprocket in combination with the laterally outermost rear sprocket. 
     
     
       8. The apparatus according to  claim 1  wherein the prohibiting unit cooperates with the shift unit so that the chain is prohibited from engaging the laterally outermost front sprocket in combination with the laterally innermost rear sprocket. 
     
     
       9. The apparatus according to  claim 8  wherein the plurality of front sprockets comprise a first front sprocket, a second front sprocket and a third front sprocket, wherein the first front sprocket comprises the laterally innermost front sprocket, wherein the third front sprocket comprises the laterally outermost front sprocket, wherein the second front sprocket is disposed between the first front sprocket and the third front sprocket, and wherein the prohibiting unit cooperates with the shift unit so that the chain is prohibited from engaging the second front sprocket in combination with the laterally innermost rear sprocket. 
     
     
       10. The apparatus according to  claim 8  wherein the plurality of front sprockets comprise a first front sprocket, a second front sprocket and a third front sprocket, wherein the first front sprocket comprises the laterally innermost front sprocket, wherein the third front sprocket comprises the laterally outermost front sprocket, wherein the second front sprocket is disposed between the first front sprocket and the third front sprocket, and wherein the prohibiting unit cooperates with the shift unit so that chain is prohibited from engaging the second front sprocket in combination with the laterally outermost rear sprocket. 
     
     
       11. The apparatus according to  claim 8  wherein the prohibiting unit cooperates with the shift unit so that the shift unit prohibits the chain from engaging the laterally outermost front sprocket in combination with a rear sprocket adjacent to the laterally innermost rear sprocket. 
     
     
       12. The apparatus according to  claim 11  wherein the plurality of front sprockets comprise a first front sprocket, a second front sprocket and a third front sprocket, wherein the first front sprocket comprises the laterally innermost front sprocket, wherein the third front sprocket comprises the laterally outermost front sprocket, wherein the second front sprocket is disposed between the first front sprocket and the third front sprocket, and wherein the prohibiting unit cooperates with the shift unit so that the chain is prohibited from engaging the second front sprocket in combination with the laterally innermost rear sprocket. 
     
     
       13. The apparatus according to  claim 11  wherein the plurality of front sprockets comprises a first front sprocket, a second front sprocket and a third front sprocket, wherein the first front sprocket comprises the laterally innermost front sprocket, wherein the third front sprocket comprises the laterally outermost front sprocket, wherein the second front sprocket is disposed between the first front sprocket and the third front sprocket, and wherein the prohibiting unit cooperates with the shift unit so that chain is prohibited from engaging the second front sprocket in combination with the laterally outermost rear sprocket. 
     
     
       14. The apparatus according to  claim 1  wherein the prohibiting unit cooperates with the shift unit so that the chain is prohibited from engaging i) a laterally innermost front sprocket in combination with a laterally outermost rear sprocket, and ii) a laterally outermost front sprocket in combination with a laterally innermost rear sprocket. 
     
     
       15. The apparatus according to  claim 14  wherein the plurality of front sprockets comprise a first front sprocket, a second front sprocket and a third front sprocket, wherein the first front sprocket comprises the laterally innermost front sprocket, wherein the third front sprocket comprises the laterally outermost front sprocket, wherein the second front sprocket is disposed between the first front sprocket and the third front sprocket, and wherein the prohibiting unit cooperates with the shift unit so that the chain is prohibited from engaging the second front sprocket in combination with the laterally innermost rear sprocket. 
     
     
       16. The apparatus according to  claim 14  wherein the plurality of front sprockets comprise a first front sprocket, a second front sprocket and a third front sprocket, wherein the first front sprocket comprises the laterally innermost front sprocket, wherein the third front sprocket comprises the laterally outermost front sprocket, wherein the second front sprocket is disposed between the first front sprocket and the third front sprocket, and wherein the prohibiting unit cooperates with the shift unit so that chain is prohibited from engaging the second front sprocket in combination with the laterally outermost rear sprocket. 
     
     
       17. The apparatus according to  claim 14  wherein the plurality of front sprockets comprise a first front sprocket, a second front sprocket and a third front sprocket, wherein the first front sprocket comprises the laterally innermost front sprocket, wherein the third front sprocket comprises the laterally outermost front sprocket, wherein the second front sprocket is disposed between the first front sprocket and the third front sprocket, and wherein the prohibiting unit cooperates with the shift unit so that the chain is prohibited from engaging i) the second front sprocket in combination with the laterally innermost rear sprocket, and ii) the second front sprocket in combination with the laterally outermost rear sprocket. 
     
     
       18. The apparatus according to  claim 14  wherein the prohibiting unit cooperates with the shift unit so that the chain is prohibited from engaging i) the laterally innermost front sprocket in combination with a rear sprocket adjacent to the laterally outermost rear sprocket, and ii) the laterally outermost front sprocket in combination with a rear sprocket adjacent to the laterally innermost rear sprocket. 
     
     
       19. The apparatus according to  claim 18  wherein the plurality of front sprockets comprise a first front sprocket, a second front sprocket and a third front sprocket, wherein the first front sprocket comprises the laterally innermost front sprocket, wherein the third front sprocket comprises the laterally outermost front sprocket, wherein the second front sprocket is disposed between the first front sprocket and the third front sprocket, and wherein the prohibiting unit cooperates with the shift unit so that the chain is prohibited from engaging the second front sprocket in combination with the laterally innermost rear sprocket. 
     
     
       20. The apparatus according to  claim 18  wherein the plurality of front sprockets comprise a first front sprocket, a second front sprocket and a third front sprocket, wherein the first front sprocket comprises the laterally innermost front sprocket, wherein the third front sprocket comprises the laterally outermost front sprocket, wherein the second front sprocket is disposed between the first front sprocket and the third front sprocket, and wherein the prohibiting unit cooperates with the shift unit so that chain is prohibited from engaging the second front sprocket in combination with the laterally outermost rear sprocket. 
     
     
       21. The apparatus according to  claim 20  wherein the plurality of front sprockets comprise a first front sprocket, a second front sprocket and a third front sprocket, wherein the first front sprocket comprises the laterally innermost front sprocket, wherein the third front sprocket comprises the laterally outermost front sprocket, wherein the second front sprocket is disposed between the first front sprocket and the third front sprocket, and wherein the prohibiting unit cooperates with the shift unit so that the chain is prohibited from engaging i) the second front sprocket in combination with the laterally innermost rear sprocket, and ii) the second front sprocket in combination with the laterally outermost rear sprocket. 
     
     
       22. The apparatus according to  claim 1  further comprising riding condition sensing means for sensing a riding condition of the bicycle, wherein the shift unit cooperates with the riding condition sensing means to automatically operate the front derailleur and the rear derailleur in accordance with the riding condition. 
     
     
       23. The apparatus according to  claim 1  further comprising a manually operated shift control device that provides shift command signals to the shift unit, wherein the shift unit operates the front derailleur and the rear derailleur in response to the shift command signals. 
     
     
       24. The apparatus according to  claim 1  wherein the shift unit is adapted to attempt to engage the chain with at least one of i) a laterally innermost front sprocket in combination with a laterally outermost rear sprocket and ii) a laterally outermost front sprocket in combination with a laterally innermost rear sprocket, but the prohibiting unit causes the shift unit to engage the chain with a different front sprocket than the attempted front sprocket. 
     
     
       25. The apparatus according to claim 1 further comprising a manually-operated shift control device having shift switches to provide command signals to the shift unit to shift the front derailleur and the rear derailleur, wherein the shift control device includes:
 front derailleur shift switches dedicated to the operation of the front derailleur to provide command signals to the shift unit to shift only the front derailleur; and   rear derailleur shift switches dedicated to the operation of the rear derailleur to provide command signals to the shift unit to shift only the rear derailleur.   
     
     
       26. The apparatus according to claim 1 wherein the shift unit shifts the rear derailleur in priority over the front derailleur to achieve the destination gear ratio when the velocity signal passes a first threshold value, and wherein the shift unit shifts the front derailleur in priority over the rear derailleur to achieve the destination gear ratio when the velocity signal passes a different second threshold value.