Abstract:
An apparatus for controlling upshifting and downshifting of a bicycle transmission includes a running condition detecting mechanism that detects a running condition of the bicycle, a threshold value setting mechanism that sets at least one of an upshift threshold value and a downshift threshold value for the running condition, and a control mechanism. The control mechanism provides a signal that commands at least one of an upshift and a downshift when the running condition is beyond the corresponding upshift threshold value and downshift threshold value for a first predetermined time interval. In another embodiment, the control mechanism provides a signal that commands at least one of an upshift and a downshift when the running condition is beyond the corresponding one of the upshift threshold value and the downshift threshold value at both a first detection and a second detection, wherein the second detection occurs after the first detection. The control mechanism provides the signal after the second detection and not in a time interval between the first detection and the second detection.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is a division of copending application Ser. No. 10/267,535, filed Oct. 8, 2002. 

   BACKGROUND OF THE INVENTION 
   The present invention is directed to bicycles and, more particularly, to various features of an electronically controlled bicycle transmission. 
   Bicycle transmissions usually comprise either internally mounted transmissions or externally mounted transmissions. Internally mounted transmissions usually are built into the hub of the rear wheel, and externally mounted transmissions usually have a derailleur for switching a chain among a plurality of sprockets. A shift control device mounted to the bicycle frame and connected to the transmission by a shift control cable usually controls both types of transmissions. 
   The shift control device frequently comprises a shift lever mounted to the handlebars, and in many cases the shift lever is positioned close to the brake lever. The shifting operation is difficult when decelerating because it becomes necessary to operate the brake lever and the shift lever at the same time. For this reason, an automatic shift control device has been developed that automatically shifts gears (speed steps) in response to the bicycle&#39;s running conditions (e.g., wheel speed or crank revolutions). 
   Conventionally, bicycle wheel speed has been detected using a magnet mounted on the bicycle wheel and a reed switch mounted to the bicycle frame. The reed switch produces one pulse per wheel revolution, and the wheel speed may be determined from the interval between detected pulses and the wheel diameter. The automatic shift control device sets an upshift threshold value and a downshift threshold value for each speed step. The bicycle transmission upshifts to the next higher speed step when the detected speed exceeds the upshift threshold value. If the detected wheel speed subsequently falls below the downshift value, then the bicycle transmission downshifts back to the original speed step. Sometimes the upshift threshold value for a particular speed step is set to a slightly higher value than the downshift threshold value of the next higher speed step to create a well known hysteresis effect that minimizes chatter from frequent gear shifting when the wheel speed hovers around the shift points. 
   Chattering is prevented easily with the above technique when wheel speed is detected at relatively low frequencies such as one pulse per wheel revolution, since shift timing is controlled according to the different speeds set for upshifting and downshifting. But if, for example, attaching several magnets circumferentially around the bicycle wheel increases the wheel speed detection frequency per revolution, meaningless gear shifting may occur frequently. More specifically, if irregular crank revolutions occur while cycling up an incline, within a very short period of time a change might occur in which the wheel speed approaches the upshift threshold value so that the bicycle transmission upshifts against the rider&#39;s wishes, and immediately this is followed by a downshift. When such shifting actions occur repetitively, the pedal force required to maintain the desired speed changes frequently, thus causing the rider to pedal in a jerky fashion and reduce the stability of the ride. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to features of an automatic bicycle transmission that contribute to a reduction of some undesirable characteristics of known bicycle transmissions. In one embodiment of the present invention, an apparatus is provided for controlling upshifting and downshifting of a bicycle transmission. The apparatus comprises a running condition detecting mechanism that detects a running condition of the bicycle, a threshold value setting mechanism that sets at least one of an upshift threshold value and a downshift threshold value for the running condition, and a control mechanism. The control mechanism provides a signal that commands at least one of an upshift and a downshift when the running condition is beyond the corresponding upshift threshold value and downshift threshold value for a first predetermined time interval. 
   In another embodiment of the present invention, the apparatus again comprises a running condition detecting mechanism that detects a running condition of the bicycle, a threshold value setting mechanism that sets at least one of an upshift threshold value and a downshift threshold value for the running condition, and a control mechanism. The control mechanism provides a signal that commands at least one of an upshift and a downshift when the running condition is beyond the corresponding one of the upshift threshold value and the downshift threshold value at both a first detection and a second detection, wherein the second detection occurs after the first detection. The control mechanism provides the signal after the second detection and not in a time interval between the first detection and the second detection. 
   Additional inventive features will become apparent from the description below, and such features may be combined with the above features to provide additional inventions. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view of a bicycle that includes an embodiment of an automatically controlled bicycle transmission; 
       FIG. 2  is a detailed view of a particular embodiment of a handlebar mounted component of the bicycle transmission; 
       FIG. 3  is a block diagram of a particular embodiment of a shift control device; 
       FIG. 4  is a table showing a particular embodiment of upshift and downshift threshold values; 
       FIG. 5  is a flowchart of a particular embodiment of an algorithm for operating the bicycle transmission; 
       FIG. 6  is a flowchart of a particular embodiment of an algorithm for automatically operating the bicycle tranmission; 
       FIG. 7  is a flowchart of a particular embodiment of an algorithm for manually operating the bicycle transmission; 
     FIGS.  8 (A) and  8 (B) are graphs showing relationships between speed steps and wheel speed; 
       FIG. 9  is a side view of a bicycle that includes an alternative embodiment of an automatically controlled bicycle transmission; 
       FIG. 10  is a table showing another embodiment of upshift and downshift threshold values; and 
       FIG. 11  is a flowchart of an alternative embodiment of an algorithm for automatically operating the bicycle transmission. 
   

   DETAILED DESCRIPTION OF THE EMBODIMENTS 
     FIG. 1  is a side view of a bicycle that includes a particular embodiment of an automatically controlled bicycle transmission. The bicycle comprises a frame  1  having a double-loop-shaped frame body  2 , a saddle  11 , a front fork  3 , a handlebar part  4 , a driving part  5 , a front wheel  6  in which is installed a hub generator  12 , a rear wheel  7  in which is installed an internal gear changing hub  10 , and front and rear brake devices  8  (only the front brake device is shown in the drawing). The handlebar part  4  has a handlebar stem  14 , which is fixed to an upper part of the front fork  3 , and a handlebar  15  fixed to the handlebar stem  14 . Brake levers  16  and grips  17  are installed on the two ends of the handlebar  15 . Brake levers  16  operate the brake devices  8 . 
   A shift operation unit  9  is mounted on the right-side brake lever  16 . As shown in  FIG. 2 , the shift operation unit  9  has a control housing  20  formed integrally with the right-side (front-wheel) brake lever  16 , two control buttons  21  and  22  disposed next to each other to the left and right on the lower portion of the control housing  20 , a control dial  23  disposed above the control buttons  21  and  22 , and a liquid-crystal display component  24  disposed to the left of the control dial  23 . 
   The control buttons  21  and  22  are triangular push buttons. The control button  21  on the left side is a button for performing shifts to a higher speed step from a lower speed step (upshifts), while the control button  22  on the right side is a button for performing shifts to a lower speed step from a higher speed step (downshifts). The control dial  23  is used for switching among three shifting modes and a parking mode (P), and it has four stationary positions: P, A 1 , A 2 , and M. The shifting modes comprise an automatic shift  1  (A 1 ) mode, an automatic shift  2  (A 2 ) mode, and a manual shift (M) mode. The parking mode (P) is for locking the internal gear changing hub  10  and controlling the rotation of the rear wheel  7 . The automatic shift  1  and  2  modes are for automatically shifting the internal gear changing hub  10  by means of a bicycle speed signal from the hub generator  12 . The automatic shift  1  (A 1 ) mode is a shift mode primarily used when automatic shifting is performed on level terrain, and the automatic shift  2  (A 2 ) mode is a shifting mode primarily used when automatic shifting is performed on a hilly road. Accordingly, the shift timing for downshifts in the automatic shift  2  (A 2 ) mode is set ahead of those in the automatic shift  1  (A 1 ) mode, and the shift timing for upshifts is set behind those in the automatic shift  1  (A 1 ) mode. The manual shift mode is for shifting the internal gear changing hub  10  through the operation of the control buttons  21  and  22 . The current riding speed is displayed on the liquid-crystal display component  24 , as is the current speed step selected at the time of the shift. 
   A shift control unit  25  ( FIG. 3 ) for controlling shifting operations is housed inside the control panel  20 . In general, the shift control unit  25  comprises a microcomputer consisting of a CPU, a RAM, a ROM, and an I/O interface. As shown in  FIG. 3 , the shift control unit  25  is connected to the hub generator  12 , to an actuation position sensor  26  such as a potentiometer that senses the actuation position of the internal shifting hub  10 , to the control dial  23 , and to the control buttons  21  and  22 . The shift control unit  25  also is connected to a power supply  27  (for example, a battery), to a motor driver  28  for driving a motor  29 , to the liquid-crystal display component  24 , to a memory component  30 , and to other input/output components. The memory component  30  may be an EEPROM or another type of rewritable nonvolatile memory. Various types of data, such as passwords, tire diameter or thee like, are stored in the memory component  30 . Also stored in memory component  30  are data expressing respective relations between each speed step and the shifting speeds during the automatic shift  1  (A 1 ) mode and the automatic shift  2  (A 2 ) mode. The shift control unit  25  controls the motor  29  according to the various modes, and it also controls the display of the liquid-crystal display component  24 . 
   The hub generator  12  is, for example, a 28-pole AC generator that generates an alternating current signal in response to wheel speed. The shift control unit  25  detects a wheel speed S from the AC signals sent from hub generator 12 . Thus, wheel speed S can be detected 28 times per revolution, which results in much greater resolution that wheel speed detected using conventional magnets and reed switches. This permits real-time execution of shift control. 
   The drive unit  5  comprises a gear crank  18  rotatably supported by the frame body  2 , a chain  19  driven by the gear crank  18 , and the internal gear changing hub  10 . The internal gear changing hub  10  is a four-speed hub having four speed step positions and a lock position, and it is switched by shift motor  29  to the four speed step positions and to the lock position, for a total of 5 positions. As noted above, the lock position restricts the revolution of internal gear changing hub  10 . 
     FIG. 4  is a table showing a particular embodiment of upshift and downshift threshold values for automatic shift  1  (A 1 ) mode and automatic shift  2  (A 2 ) mode. More specifically, in this embodiment, the upshift threshold values in automatic shift  1  (A 1 ) mode are 13 km/h (step  1 - 2 ), 16 km/hr (step  2 - 3 ), and 19 km/h (step  3 - 4 ). The downshift threshold values are 12 km/h (step  2 - 1 ), 14 km/h (step  3 - 2 ), and 17 km/hr (step  4 - 3 ). In this embodiment, the upshift threshold values in automatic shift  2  (A 2 ) mode are 11 km/h (step  1 - 2 ), 14 km/hr (step  2 - 3 ), and 17 km/h (step  3 - 4 ). The downshift values are 10 km/h (step  2 - 1 ), 11 km/h (step  3 - 2 ), and 15 km/hr (step  4 - 3 ). 
     FIGS. 5 through 7  are flowcharts showing a particular embodiment of an algorithm for the operation of shift control unit  25 . As shown in  FIG. 5 , when the power is turned on (start), initialization occurs in step S 1 . Here, various operating parameters may be set (e.g., that a 26-inch diameter wheel is installed on the bicycle), the current speed step VP is read and set (e.g., to the second speed VP=2) from position sensor  26 , and various flags are set. In Step S 2 , a decision is made about whether or not control dial  23  is set to the parking (P) mode. In Step S 3 , a decision is made about whether or not control dial  23  is set to the automatic shift  1  (A 1 ) mode. In Step S 4 , a decision is made about whether or not control dial  23  is set to the automatic shift  2  (A 2 ) mode. In Step S 5 , a decision is made about whether or not control dial  23  is set to the manual shift (M) mode. In Step S 26 , a decision is made about whether to select some other process, such as inputting tire diameter, for example. 
   When the control dial  23  has been turned to the P position and set to the parking (P) mode, then the process moves from Step S 2  to Step S 7 . In Step S 7 , the parking (P) process is executed. In this process, various routines are executed by operating buttons  21 ,  22 . Such routines may include a password registration routine for registering a password that will clear the locked status of internal gear changing hub  10 , or a password input process for inputting and referencing the password for clearing the locked status, and so on. When the control dial  23  has been turned to the A 1  position and set to the automatic shift  1  (A 1 ) mode, then the process moves from Step S 3  to Step S 8  to execute the automatic shift  1  (A 1 ) process shown in FIG.  8 . If control dial  23  has been turned to the A 2  position and set to the automatic shift  2  (A 2 ) mode, then the process moves from Step S 4  to Step S 9 . In Step S 9 , an automatic shift  2  (A 2 ) process is executed, similar to the automatic shift  1  process. If the control dial  23  is turned to the M position and set to the manual shift mode, then the process moves from Step S 5  to Step S 10  to execute the manual shift (M) process shown in FIG.  7 . If other processes are selected, the process moves from Step S 6  to Step S 11 , and the selected process is executed. 
     FIG. 6  is a flowchart illustrating a particular embodiment of the process of Step S 8  from FIG.  5 . In general, the desired speed step VP of internal gear changing hub  10  is set according to wheel speed S. When the wheel speed S has departed from the desired range, a shift is made in the direction of the closest speed step, one at a time. More specifically, the current speed step VP of internal gear changing hub  10  is acquired from position sensor  26  and stored in Step S 21 , and the current wheel speed S of the bicycle is acquired from the speed signal from the hub generator  12  and stored in Step S 22 . In Step S 23 , a decision is made whether or not the current wheel speed S is greater than the upshift threshold value U (VP) for the current speed step VP as set forth in the table shown in FIG.  4 . In Step S 24 , a decision is made whether or not the current wheel speed S is less than the downshift threshold value D (VP) for the current speed step VP as set forth in the table shown in FIG.  4 . 
   When the current wheel speed S exceeds the upshift threshold value U (VP) for the current speed step, the process moves from Step S 23  to Step S 25 . For example, when VP=2 (second gear), the process moves from Step S 23  to Step S 25  whenever the wheel speed S is greater than 16 km/h. In Step S 25 , a decision is made whether or not a time interval T 1  has passed since the decision at Step S 23 . If not, the wheel speed S is acquired again in Step S 26 . In Step S 27 , a decision is made as to whether the reacquired current wheel speed S exceeds the upshift threshold value U (VP) for the current speed step. If wheel speed S does not exceed the upshift threshold value U (VP), the process moves to Step S 24  to cancel the potential upshift operation. On the other hand, if the wheel speed S still exceeds the upshift threshold value U (VP) in Step  27 , then the process returns to Step S 25 , where again a decision is made as to whether the time interval T 1  has passed since the decision at Step S 23 . 
   If it is determined in Step  25  that time interval T 1  has passed since the decision in Step S 23 , then the process moves from Step S 25  to Step S 28 , where a decision is made whether or not the current speed step is equal to four. If so, since internal gear changing hub  10  has only four speed steps, then the process will flow to Step S 24  without doing anything. However, note that the upshift threshold value for speed step four has been set at the normally unthinkable level of 255, so normally the process does not advance as far as this routine. At speed steps below step four, the process moves to Step S 29  wherein VP is incremented by one, shift control unit  25  commands motor  29  to upshift internal gear changing hub  10  by one speed step, and the process continues in Step S 24 . 
   If the current wheel speed S is less than the downshift threshold value D (VP) for the current speed step shown in the table in  FIG. 4 , then the process moves from Step S 24  to Step S 30 . For example, when VP=2, the process moves from Step S 24  to Step S 30  whenever the wheel speed S is below 12 km/h. In Step S 30 , a decision is made whether or not the current speed step is equal to one. If so, nothing further is done and the process returns to the main routine. If the current speed step is step two or greater, then the process moves to Step S 31  wherein VP is decremented by one, shift control unit  25  commands motor  29  to downshift internal gear changing hub  10  by one speed step, and the process returns to the main routine. 
   The explanation for Step S 9  in  FIG. 5 , the automatic shift  2  (A 2 ) process, will be omitted because the details of that process are identical to those for the automatic shift  1  (A 1 ) process, with the exception that the threshold values are different. 
     FIG. 7  is a flowchart of a particular embodiment of an algorithm for manually operating the bicycle transmission (Step S 10  in FIG.  5 ). In Step S 10 , shifting is done one step at a time using control buttons  21  and  22 . In Step S 41 , the operating position VP is acquired and stored from position sensor  26 . In Step S 42 , a decision is made whether or not control button  21  has been operated or not. In Step S 43 , a decision is made to whether or not control button  22  has been operated or not. If control button  21  has been operated, the process moves from Step S 42  to Step S 44 , where a decision is made whether or not the current speed step VP is equal to four. If the current speed step VP is not equal to four, then the process moves to Step S 45  wherein VP is incremented by one and shift control unit  25  commands motor  29  to upshift internal gear changing hub  10  by one speed step to the next higher step. If the current speed step VP equals 4, then this process is skipped. When control button  22  is operated, the process moves from Step S 43  to Step S 46 , where a decision is made whether or not the current speed step VP is equal to one. If the current speed step VP is not equal to one, the process moves to Step S 47  wherein VP is decremented by one and shift control unit  25  commands motor  29  to downshift internal gear changing hub  10  by one speed step to the next lower step. If the current speed step VP equals one, then this process is skipped. 
   FIGS.  8 (A) and  8 (B) are graphs that compare an example of the bicycle gear shift operation using the teachings discussed herein (FIG.  8 (A)) with that of a conventional example (FIG.  8 (B)). In FIGS.  8 (A) and  8 (B), speed is shown on the vertical axis and time is shown on the horizontal axis. In the case of automatic shift  1  (A 1 ) processing, as shown in FIG.  8 (A), if the current speed step is one, for example, and the upshift threshold value U ( 1 ) is exceeded (e.g., 13 km/h), a determination will be made in Step S 27  in  FIG. 6  that the upshift threshold value U ( 1 ) has been exceeded during the predetermined time interval T 1 . However, the hatching in FIG.  8 (A) indicates a region where the wheel speed S does not exceed the upshift threshold value U ( 1 ), which results in a decision of “No” in Step S 27  of FIG.  6 . When this occurs, the potential upshift from speed step one to speed step two is cancelled, and no upshift occurs. 
   If the wheel speed S again exceeds upshift threshold value U ( 1 ), and if this threshold value U ( 1 ) is exceeded for the entire time interval T 1 , then the decision from Step S 27  will be “yes” for the entire time interval T 1 . Similarly, the decision from Step S 25  will be “yes” after time interval T 1  passes, and an upshift will be executed in Step S 29  from speed step one to speed step two. 
   However in the case of the prior art, as shown in FIG.  8 (B), whenever the wheel speed exceeds the upshift threshold value U ( 1 ), the transmission upshifts to speed step two, and whenever the wheel speed falls below the downshift threshold value D ( 2 ) (e.g., 12 km/h), the transmission downshifts again to speed step one. When the wheel speed again exceeds upshift threshold value U ( 1 ), the transmission again upshifts, thus bringing about frequent upshifts against the intentions of the rider. 
   The teachings herein smooth out the gear shifting operation by filtering out transient conditions (using time interval T 1 ) where gear shifting would occur in the prior art. This reduces unnecessary shifting and reduces discomfort on the rider. The teachings herein also produce the unexpected benefit that, by waiting for the passage of time interval T 1  before allowing the shifting operation to occur, the actual speed at which upshifting will occur will be faster as acceleration increases. The net effect is a change in the upshift threshold value in response to acceleration, even though the table values remain the same. 
   In this embodiment, when the wheel speed S is detected to be lower than the downshift threshold value (VP), motor  29  is controlled so that a downshift occurs without delay. This minimizes the burden on the rider, since it is desirable to shift to a lower gear as soon as possible, such as when riding up hills. The effect is further improved when wheel speed is detected frequently, as in the above embodiment. 
   While the above is a description of various embodiments of inventive features, further modifications maybe employed without departing from the spirit and scope of the present invention. For example, the aforementioned embodiment included an internally mounted gear shifting hub as the gear shift device, but the invention also can be applied to the control of externally mounted gear shifting mechanisms such as those that include multiple sprockets and a derailleur. Also, while the above embodiment used a motor to control the shifting operation, solenoids, electricity, hydraulics, compressed air cylinders, and other actuators can be used to control the gear shifting device. 
   The above embodiment used wheel speed as the running condition, but it is also possible to use crank revolutions as the running condition. In this case, as shown in  FIG. 9 , a magnet or other detectable element  113  is mounted on the bicycle&#39;s gear crank  18 , and a revolution detector  112  comprising, for example, a reed switch for detecting the passage of detectable element  113  is mounted on bicycle frame  2 . This arrangement allows the number of crank revolutions to be detected. Several detectable elements  113  may be mounted at intervals along the periphery of gear crank  18 . As shown in  FIG. 10 , the upper and lower threshold values for each speed step may be set in terms of crank revolutions. In  FIG. 10 , the same values have been set for every speed step, but they may also be different. Processing would be similar to that shown in  FIG. 6 , with crank revolutions substituted for wheel speed. In other words, when the number of crank rotations is above the upshift threshold value, a decision is made whether or not a predetermined time interval T 1  has passed. If the number of crank rotations fall below the upshift threshold value even temporarily (namely, when the pedals are being lightly pumped), the upshift is canceled, and if the number of crank rotations remain above the upshift threshold value (namely, when the pedals are being heavily pumped), the upshift is implemented. 
   The above embodiment included an analysis only over a predetermined time interval T 1 , but various time intervals could be used in various combinations to produce desirable advantages. For example, it is also possible to analyze the running condition after a predetermined time interval T 2  and then determine whether or not to upshift based on the detection results.  FIG. 11  is a flowchart of such an embodiment. In this embodiment, the current speed step and wheel speed are acquired and stored in Steps S 51  and S 52 , as was done in Steps S 21  and S 22  in FIG.  6 . If it is ascertained in step S 53  that the current wheel speed S is greater than the upshift threshold value U (VP) (e.g., 16 km/h according to the table shown in  FIG. 4 ) for the current speed step (e.g., VP=2), then the process moves from Step S 53  to Step S 55 . In Step  55 , the process is delayed until a predetermined time interval T 2  passes. In this embodiment, T 2  is less than T 1 . Once the predetermined time interval T 2  has passed, the process moves to Step S 56 , where again a decision is made whether or not the upshift threshold value U (VP) is exceeded by the wheel speed S. If the wheel speed S is less than the upshift threshold value U (VP), then the process moves to Step S 54 , and the potential upshift operation is canceled. If the wheel speed S exceeds the upshift threshold value U (VP), then the process moves to Step S 57  to determine whether or not the current speed step equals four. If the current speed step equals four, then again nothing is done and the process moves to Step S 54 . If the current speed step is less than four, then the process moves to Step S 58  and waits for the passage of predetermined time interval T 1  from the decision of Step S 53 . When the predetermined time interval T 1  has passed, the process moves to Step S 59  where VP is incremented by one and shift control unit  25  operates motor  29  to cause internal gear changing hub  10  to upshift by one speed step. 
   When the current wheel speed S is below the downshift threshold value D (VP) for the current speed step according to  FIG. 4 , the process moves to Steps S 60  and S 61  to downshift hub  10  in the same manner as the first embodiment. 
   In other embodiments, it is also possible to arrange things so that no upshift will be executed unless the average wheel speed or crank revolution value exceeds the upshift threshold value. 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 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.