Abstract:
An apparatus for controlling the operation of a bicycle transmission includes a shift command receiving unit that receives shift command signals corresponding to shift commands, and a shift command combining unit that combines a plurality of the shift command signals into a resultant shift command signal that would shift the bicycle transmission to the same state as if the plurality of shift commands all were executed individually. A method for controlling the operation of a bicycle transmission includes the steps of receiving shift command signals corresponding to shift commands, and combining a plurality of the shift command signals into a resultant shift command signal that would shift the bicycle transmission to the same state as if the plurality of shift commands all were executed individually.

Description:
BACKGROUND OF THE INVENTION 
     The present invention is directed to bicycles and, more particularly, to various features of a method and apparatus for controlling a bicycle transmission. 
     Bicycle transmissions that are operated by an electric motor or the like have recently become known. Such transmissions may be shifted automatically according to the bicycle speed shifted manually by the rider. Typically, a shift command is generated according to the bicycle speed or manual input by the rider, the motor is controlled by a transmission operating unit in response to the shift command, and the speed step of the transmission is set accordingly. 
     Shift commands sometimes are generated while the transmission is being operated. When prior art systems receive shift commands at this time, either the shift commands are ignored, or else the shift commands are saved and executed sequentially when the transmission operation is complete. If shift commands are ignored in the case of manual shifting, then the rider&#39;s intentions are not carried out. Furthermore, in such a system the rider must personally keep track of when shifting operations begin and end, which is very undesirable for a supposedly automated system. On the other hand, when the shift commands are saved and executed sequentially when the transmission operation is complete, there is a risk of wasted effort. More specifically, sometimes the rider enters a series of upshift and downshift commands, either because of changing conditions or because of initial misjudgment of the desired gear. If, for example, the rider wanted to enter a single upshift command but mistakenly entered two upshift commands and then entered a downshift command to correct the error, then in prior art systems the transmission would make a total of three shifts instead of one. Such a mode of operation creates unnecessary wear on the components, it requires more time to execute all of the shift commands, and it unnecessarily drains the power supply. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to various features of a method and apparatus for controlling a bicycle transmission. In one embodiment of the present invention, a shift command receiving unit is provided that receives shift command signals corresponding to shift commands, and a shift command combining unit is provided that combines a plurality of the shift command signals into a resultant shift command signal that would shift the bicycle transmission to the same state as if the plurality of shift commands all were executed individually. A method according to the present invention includes the steps of receiving shift command signals corresponding to shift commands, and combining a plurality of the shift command signals into a resultant shift command signal that would shift the bicycle transmission to the same state as if the plurality of shift commands all were executed individually. Additional inventive features will become apparent from the description below, and such features may be combined with the above features to provide additional benefits. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a bicycle that includes particular embodiments of electrically controlled bicycle transmissions; 
     FIG. 2 is a detailed view of particular embodiments of handlebar mounted components of the bicycle shown in FIG. 1; 
     FIG. 3 is a block diagram of a particular embodiment of a control unit; 
     FIG. 4 is a flow chart of a particular embodiment of an algorithm used to control the rear transmission; 
     FIG. 5 is a graph illustrating an example of the difference in operation between the present control unit and a prior art control unit; and 
     FIG. 6 is a flow chart of another embodiment of an algorithm used to control the rear transmission. 
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     FIG. 1 is a side view of a bicycle that includes particular embodiments of electrically controlled bicycle transmissions. The bicycle  1  is a sport bicycle of a mountain bike type, and it comprises a frame  2 , a front fork  3  rotatably mounted to frame  2 , a handlebar assembly  4  mounted to the upper part of fork  3 , a front wheel  5  rotatably attached to the lower part of fork  3 , a rear wheel  6  rotatably attached to the rear of frame  2 , a chain  7 , a front transmission  8 , a rear transmission  9 , and a saddle  11 . A front wheel brake  16  is provided for braking the front wheel  5 , and a rear wheel brake  17  is provided for braking the rear wheel  6 . As shown in FIG. 2, respective grips  12   a ,  12   b  and brake levers  13   a ,  13   b  are provided on both ends of handle  4 . Brake lever  13   b  is connected to the front wheel brake  16  for braking front wheel  5 , and brake lever  13   a  is connected to the rear wheel brake  17  for braking rear wheel  6 . 
     The front transmission  8  is a mechanical unit attached in the central lower part of frame  2  for transmitting the drive force generated by the rider to the rear transmission  9  via the chain  7 . The front transmission  8  comprises three sprockets  37  of various sizes and a front derailleur  33 . The three sprockets  37  are installed on a gear crank  31  that is rotated when the rider pushes pedals  32   a  and  32   b . The gear crank  31  comprises a crankshaft  34  that passes horizontally and rotatably through the central lower part of frame  2 , a right crank  35 , and a left crank  36 . One end of the right crank  35  is connected to the right side of crankshaft  34 , and the three sprockets  37  are attached to the right crank  35 . One end of the left crank  36  is connected to the left side of crankshaft  34 . The other ends of right crank  35  and left crank  36  rotatably support pedals  32   a  and  32   b , respectively. The front derailleur  33  engages the chain  7  with one of the three sprockets  37  and can be moved by a motor (not shown in the figures) that is controlled by a transmission control unit  15  described below. A front derailleur position sensor (not shown in the figures) detects the position of front derailleur  33  and hence the current speed step of front transmission  8 . 
     The rear transmission  9  serves to transmit the driving force transmitted by the chain  7  to the rear wheel  6 . The rear transmission  9  comprises a rear sprocket wheel  41  and a rear derailleur  42 . In this embodiment, rear sprocket wheel  41  comprises seven sprockets  43  of different sizes that are mounted concentrically with the hub portion of rear wheel  6 . Rear derailleur  42  engages chain  7  with one of the seven sprockets  43  and can be moved by a motor (not shown in the figures) that is controlled by transmission control unit  15 . A rear derailleur position sensor (not shown in the figures) detects the position of rear derailleur  42  and hence the current speed step of rear transmission  9 . 
     As shown in FIG. 2, shift command units  14   a ,  14   b  are provided inwardly of grips  12   a ,  12   b  and brake levers  13   a ,  13   b , respectively. Transmission control unit  15  is attached to the central portion of handlebar assembly  4 , and it is connected to the shift command units  14   a ,  14   b . The shift command units  14   a ,  14   b  are used for shifting the front transmission  8  and rear transmission  9 . A rear upshift button  18   a  and a rear downshift button  19   a  are provided in the shift command unit  14   a , and a front upshift button  18   b  and a front downshift button  19   b  are provided in the shift command unit  14   b . In this embodiment, the upshift buttons  18   a  and  18   b  provide signals for upshifting the front and rear transmissions  8  and  9  by one speed step. Similarly, the downshift buttons  19   a  and  19   b  provide signals for downshifting the front and rear transmissions  8  and  9  by one speed step. 
     The transmission control unit  15  controls the front transmission  8  and rear transmission  9  according to the signals provided by the shift command units  14   a  and  14   b . As shown in FIG. 3, the transmission control unit  15 , comprises a control unit  23  having a CPU  21  and memory  22 , a display unit  24  for displaying the current speed step, a power switch  25 , and a mode switch  26 . The control unit  23  controls the transmission control unit  15  with the CPU  21  according to the information stored in the memory  22 . The mode switch  26  changes an operating mode of transmission control unit  15 . As shown in FIG. 2, the transmission control unit  15  includes a box-like housing  27 . The display unit  24 , the power switch  25 , and the mode switch  26  are arranged on the upper surface of housing  27 . The transmission control unit  15  is connected to the front transmission  8  and to the rear transmission  9  by a connector unit  28 . 
     FIG. 4 is a flow chart of a particular embodiment of an algorithm used to control the rear transmission  9 . The algorithm used to control the front transmission  8  is the same, except the number of speed steps is less, so the explanation thereof is omitted. The algorithm is invoked when the rider turns on the power switch  25  of transmission control unit  15 . 
     Initial setting of transmission control unit  15  is conducted in step S 1 . This initial setting includes the initialization of a count value location (OP) in the memory  22  to zero. The OP value is incremented or decremented according to the operation of shift command unit  14   a . In step S 2 , the current position of rear derailleur  42  is obtained from the position sensor for rear derailleur  42  and stored in a location (SH) in memory  22 . For example, SH is set to three when the rear transmission  9  is in the third speed step position. 
     In step S 3 , a decision is made whether or not the rear upshift button  18   a  of shift command unit  14   a  has been pushed. If so, the program proceeds to step S 4  wherein the value of OP is incremented by one, and the program proceeds to step S 7 . If the rear upshift button  18   a  has not been pushed, then the value of OP remains the same, and the program proceeds to step S 5 . In step S 5 , a decision is made whether or not the rear downshift button  19   a  of gear change operation unit  14   a  has been pushed. If so, the program proceeds to step S 6  wherein the value of OP is decremented by one, and then the program proceeds to step S 7 . If the rear downshift button  19   a  has not been pushed, then the value of OP remains the same, and the program proceeds to step S 7 . In step S 7 , a decision is made by the derailleur position sensor or the like whether or not the rear derailleur  42  is being shifted. If rear derailleur  42  is presently being shifted, the program returns to step S 3 . The value of OP again will be incremented or decremented depending upon the activity of rear upshift button  18   a  and rear downshift button  19   a  in the manner noted above. This series of steps continue as long as rear derailleur  42  is being shifted. 
     If it is determined in Step S 7  that rear derailleur  42  is not being shifted (e.g., the rear derailleur  42  has completed a prior shifting operation), the program proceeds to step S 8 . In step S 8 , a decision is made whether or not the OP value resulting from the combined operations of rear upshift button  18   a  and/or rear downshift button  19   a  during shifting of the rear derailleur  42  (Steps S 3 -S 7 ) is positive, negative, or zero. As discussed below, derailleur  42  is further adjusted, if necessary, according to this determination. 
     When OP equals zero, either no further shift commands were issued during the operation of rear derailleur  42 , or else rear upshift button  18   a  and rear downshift button  19   a  were operated in a manner to cancel each other out. In either case, the program returns to step S 2 . 
     A negative OP value indicates that the rider wants a net downshift by some amount. In this case, the program proceeds to step S 9 , and it is determined whether or not the current speed step (SH) for rear derailleur  42  equals one. A current speed step of one indicates that the chain  7  already is engaged with the sprocket  43  corresponding to the lowest speed step, and chain  7  cannot be shifted further. Accordingly, no further adjustment of derailleur  42  is performed, OP is reset to zero in Step S 10 , and the program returns to step S 2 . On the other hand, when SH is not equal to one, rear derailleur  42  is operated to shift chain  7  to the sprocket  43  corresponding to the next lower speed step, the value of SH is decremented by one, the value of OP is incremented by one, and the process returns to step S 2 . 
     A positive OP value indicates that the rider wants a net upshift by some amount. In this case, the program proceeds to step S 12 , and it is determined whether or not the current speed step (SH) for rear derailleur  42  equals seven. A current speed step of seven indicates that the chain  7  already is engaged with the sprocket  43  corresponding to the highest speed step, and chain  7  cannot be shifted further. Accordingly, no further adjustment of derailleur  42  is performed, OP is reset to zero in Step S 13 , and the program returns to step S 2 . On the other hand, when SH is not equal to seven, rear derailleur  42  is operated to shift chain  7  to the sprocket  43  corresponding to the next higher speed step, the value of SH is incremented by one, the value of OP is decremented by one, and the process returns to step S 2 . 
     In summary, in this embodiment the rider can command a shift to a desired speed step by pushing the upshift buttons  18   a ,  18   b  or downshift buttons  19   a ,  19   b  of the shift command units  14   a ,  14   b  at any time. When the shift command unit  14   a  is operated during shifting of the rear transmission  9  or when the shift command unit  14   b  is operated during shifting of the front transmission  8 , the transmission control unit  15  stores the information for the shift commands as OP count values in memory  22 . More specifically, when the upshift buttons  18   a ,  18   b  are pushed, the OP counts are incremented, whereas when the downshift buttons  19   a ,  19   b  are pushed, the OP counts are decremented. When a plurality of shift commands are issued by the shift command units  14   a ,  14   b , the OP count values are adjusted accordingly to produce resultant OP values. When the shifting action of the relevant front transmission  8  or rear transmission  9  is completed, the transmission control unit  15  conducts appropriate adjustment of front derailleur  33  and/or rear derailleur  42  based on the corresponding OP values at this point of time. Thus, the shift commands conducted by the rider during shifting are fully taken into account. Furthermore, when a plurality of shift commands are conducted during shifting, the gear change operations to the final speed step in this process can be conducted with a minimum action. 
     FIG. 5 is a graph illustrating an example of the difference in operation between the present transmission control unit  15  and a prior art control unit. Assume the rider twice pushes the rear upshift button  18   a  and then once pushes the rear downshift button  19   a  as the rear derailleur  42  is being upshifted from the third speed step to the fourth speed step. If all of the shift commands were carried out in sequence, upon completion of the shifting action A, a shifting action B would be carried out from the fourth speed step to the fifth speed step, a shifting action C would be carried out from the fifth speed step to the sixth speed step, and a shifting action D would be carried out from the sixth speed step to the fifth speed step. However, since the rider only wanted to shift to the fifth speed step, the shifting actions C and D were superfluous. In the present embodiment, the final speed step which results from issuing multiple shift commands is detected in advance, and the operation of the derailleur to that final speed step is conducted. In this example, only shifting action B is conducted after completing shifting action A. 
     It is clear that the burden on the transmission components is reduced, and shifting to the final target speed step can be conducted within a short time. Furthermore, because the front derailleur  33  and rear derailleur  42  are driven from a battery, the reduction in the number of operations by these components makes it possible to suppress the exhaustion of the battery due to gear change operations. 
     In the above-described embodiment, the shift commands issued by the rider were input using shift command units  14   a ,  14   b  that had upshift buttons  18   a ,  18   b  and downshift buttons  19   a ,  19   b  for upshifting and downshifting the front transmission  8  and rear transmission  9 . However, the bicycle  1  also may have shift command units  14   a ,  14   b  comprising shift buttons that directly indicate the speed step number of the front transmission  8  and rear transmission  9 . In such a case, when a shift button is pushed, the transmission control unit  15  moves front derailleur  33  and/or rear derailleur  42  to the desired speed stage. FIG. 6 is a flow chart of an embodiment of an algorithm used to control the rear transmission in such an arrangement. The front transmission  8  may be controlled in the same manner, except for the number of speed steps. 
     When the rider turns on the power switch S 25 , processing proceeds to Step S 51 . At that time, various control flags are set, and a direct step (DS) location in the memory  22  is set to a value corresponding to the current operating position of the shift button of the shift command unit  14   a . Thus, in this embodiment, DS is set to one when the rider operates the shift button of the first speed step, and DS is set to three when the rider operates the shift button of the third speed step. 
     In step S 52 , the current position of rear derailleur  42  is obtained from the position sensor for rear derailleur  42  and stored in a location (SH) in memory  22 . In step S 53 , a decision is made whether or not a shift button of shift command unit  14   a  has been pushed. If so, the program proceeds to step S 54  wherein DS is set to the value of the shift button, and the program proceeds to step S 55 . On the other hand, if the shift button has not been pushed, then the program proceeds directly to step S 55 . In step S 55 , a decision is made by the derailleur position sensor or the like whether or not the rear derailleur  42  is being shifted. If rear derailleur  42  is presently being shifted, the program returns to step S 53  to check whether or not the shift button has been pushed again. If so, then DS is set to the new value corresponding to the shift button. 
     If rear derailleur  42  is not being shifted (e.g., the rear derailleur  42  has completed a prior shifting operation), then the program proceeds to step S 56 . In step S 56 , a decision is made whether or not DS is equal to, less than, or greater than SH. If DS equals SH, then no change is necessary either because no shift command was issued or else the final shift command in a series of shift commands resulted in the request for the current speed step. In this case, the program proceeds to step S 57  wherein DS is set to SH (which is a redundant action in this case) and then returns to step S 52 . 
     When DS is less than SH, the program proceeds to Step S 58 . In step S 58 , rear derailleur  42  shifts chain  7  to a sprocket  43  corresponding to one speed step less than the current speed step, SH is decremented, and the program proceeds to Step S 59 . In step S 59  it is determined whether DS is equal to SH. If so, then the program proceeds to Step S 57 . Otherwise, the program proceeds to Step S 52  wherein it can be determined whether a shift button has been pressed again. 
     When DS is greater than SH, the program proceeds to Step S 60 . In step S 60 , rear derailleur  42  shifts chain  7  to the sprocket  43  corresponding to one speed step higher than the current speed step, SH is incremented, and the program proceeds to Step S 61 . In step S 61  it is determined whether DS is equal to SH. If so, then the program proceeds to Step S 57 . Otherwise, the program proceeds to Step S 52  wherein it can be determined whether a shift button has been pressed again. 
     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 described embodiment the bicycle  1  had manually operated front and rear transmissions, and the rider operated the front and rear transmissions  8  and  9  using the shift command units  14   a  and  14   b . However, the bicycle  1  may have a configuration in which the transmission control unit  15  automatically shifts the transmissions according to the speed of bicycle  1  in an automatic mode of operation, and mode switch  26  can be used to switch from automatic to manual modes of operation. In the automatic shifting mode, the speed of bicycle  1  may be detected from a speed sensor that detects the rotation of front wheel  5  or rear wheel  6 , and the transmission control unit  15  may conduct automatic shifting according to the bicycle speed. The transmission control unit  15  downshifts when the speed is low and upshifts up when the speed is high. 
     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 on a particular structure or feature.