\begin{matrix} C [rpm] = {1 / (8 \times magnetic pulse interval (s)} \times 60 & (2) \end{matrix}

[Switching Transmission Device]

The electric assist bicycle 10 is provided with, in a power transmission path between the power unit 20 including the motor M and the rear wheel 78, a switching transmission device 30 capable of switching a gear step among eight gear steps. In the present embodiment, the switching transmission device 30 has eight front gears, each having a different number of teeth, provided on the drive sprocket 80. One front gear is selected among the eight front gears by a user operation. The gear ratio of the electric assist bicycle 10 is determined according to (number of teeth of selected front gear)/(number of teeth of driven sprocket 81).

[Regulation on Assist Ratio]

According to the regulations of Japan, an upper limit value of an assist ratio is 2 until a vehicle speed reaches [10 km/h], and the assist ratio needs to be gradually decreased from 2 to 0 when the vehicle speed changes from [10 km/h] to 24 [km/h]. Therefore, when the electric assist function is on, the control device 40 needs to set the assist ratio so as not to exceed the regulation in Japan.

[Gear Step Estimation Process]

Next, the gear step estimation process of estimating the gear step applied in the switching transmission device 30 in the electric assist bicycle 10 will be described with reference to FIGS. 4 to 8. The gear step estimation process is performed in the control device 40 by causing the CPU 40a to execute a gear step estimation program stored in the storage medium ROM 40c. The gear step estimation program may be provided by a communication unit, or provided by being stored in a storage medium such as a CD-ROM, or provided as a gear step estimation device by being stored in a dedicated terminal.

As illustrated in FIG. 4, the control device 40 includes: a vehicle state acquisition unit 401 for receiving signals output from the motor rotation speed sensor SE1, the torque sensor SE2, the rear wheel rotation speed sensor SE3, the cadence sensor SE4, the inertial measurement unit 41, and the GNSS 43, thereby acquiring the state of the electric assist bicycle 10, including the vehicle speed V [km/h], the cadence C [rpm], and the pedal torque value Tq [W]; a gear ratio acquisition unit 402 for acquiring a detected gear ratio Rd described later; and a gear step estimation unit 403 for estimating the gear step selected by the switching transmission device 30.

As illustrated in FIGS. 5 to 8, the gear step estimation process starts to execute when the power supply of the electric assist bicycle 10 is turned on.

In the gear step estimation process, first, the process proceeds to step S110. In step S110, the preset gear ratios Ri (i=a natural number of 1 to 8) of the respective gear steps of the switching transmission device 30, that is, the first step to the eighth step in the present embodiment are acquired.

In the present embodiment, in step S110, the first to eighth preset gear ratios Ri (i=a natural number of 1 to 8) are acquired by calculating the preset gear ratio Ri for each gear step using the following equation (3).

$\begin{matrix} Preset gear ratio Ri = number of teeth of front gear / number of teeth of driven sprocket & (3) \end{matrix}$

(i=a natural number of 1 to 8)

Then, the process proceeds to step S120. In step S120, a timer for measuring the elapsed time t [ms] is reset to elapsed time t [ms]=0.

Then, the process proceeds to step S130. In step S130, the timer for measuring the elapsed time t [ms] starts to measure the elapsed time t [ms].

Then, the process proceeds to step S140. In step S140, based on the state of the electric assist bicycle 10 acquired by the vehicle state acquisition unit 401, including the vehicle speed V [km/h], the cadence C [rpm], and the pedal torque value Tq [W], it is determined whether at least one of the following three conditions is satisfied:

$vehicle speed V [km / h] = 0. [km / h]$

$cadence C [rpm] \leq 20 [rpm]$

- pedal torque value Tq [W]≤50.0 [W]. In a case where at least one of the three conditions is satisfied (step S140: YES), the process proceeds to step S151. In a case where none of the three conditions are satisfied (step S140: NO), the process proceeds to step S152.

In step S151, the gear ratio acquisition unit 402 calculates the detected gear ratio Rd as detected gear ratio Rd=0.0. Then, the process proceeds to step S160.

In step S152, the gear ratio acquisition unit 402 calculates the detected gear ratio Rd using the following equation (4). Then, the process proceeds to step S160.

$\begin{matrix} Detected gear ratio Rd = vehicle speed V [km / h] \times (1000 / 60) / (circumferential length Ct [m] of rear wheel 78 / cadence C [rpm]) & (4) \end{matrix}$

In step S160, the detected gear ratio Rd calculated in step S151 or step S152 and the preset gear ratio Ri (i=a natural number of 1 to 8) of each gear step acquired in step S110 are acquired. Then, the process proceeds to step S170.

In step S170, it is determined whether or not there is any i value=m where ΔRi (=|Rd−Ri|)≤match determination allowable value. In the present embodiment, the match determination allowable value is a value that is different for each gear step and is calculated by Ri×0.05 (i=a natural number of 1 to 8). Therefore, according to the present embodiment, in step S170, it is determined whether or not there is any preset gear ratio Ri (i=a natural number of 1 to 8) has an error of 5[%] or less from the detected gear ratio Rd.

In step S170, in the case where there is an i value=m where ΔRi (=|Rd−Ri|)≤match determination allowable value (step S170: YES), the process proceeds to step S191, and the gear step directly read value D=m is stored in the storage medium RAM 40b. Then, the process proceeds to step S200.

This can calculate the detected gear ratio Rd based on the vehicle speed V and the cadence C, and estimate at any time which gear step of the switching transmission device 30 is selected by the user based on the detected gear ratio Rd.

In step S170, in the case where there is no i values=m where ΔRi (=|Rd−Ri|)≤match determination allowable value (step S170: NO), the process proceeds to step S180.

In step S180, it is determined whether the detected gear ratio Rd satisfies the following equation (5). In the present embodiment, the match determination allowable value is a value calculated by the preset gear ratio R8×0.05 of the fastest step (the eighth step in the present embodiment).

$\begin{matrix} Detected gear ratio Rd / preset gear ratio R 8 of fastest step (eighth step in present embodiment) > 1. + match determination allowable value & (5) \end{matrix}$

In step S180, in the case where the detected gear ratio Rd satisfies the above equation (5) (step S180: YES), the process proceeds to step S192, and the gear step directly read value D=9 is stored in the storage medium RAM 40b. Then, the process proceeds to step S200. In the present embodiment, the gear steps of the switching transmission device 30 are the first step to the eighth step, and the switching transmission device 30 does not have a ninth step. The gear step directly read value D=9 indicates that the detected gear ratio Rd is an illegal value.

Thus, in the case where the detected gear ratio Rd is an illegal value, the gear step directly read value D=9, and a mark indicating that the detected gear ratio Rd is an illegal value is used as one of the gear step directly read values D. This facilitates data processing, data management, display, and the like in the processing including the gear step estimation process and the illegal gear detection process described later.

In step S180, in the case where the detected gear ratio Rd does not satisfy the above equation (5) (step S180: NO), the process proceeds to step S193, and the gear step directly read value D=0 is stored in the storage medium RAM 40b. The gear step directly read value D=0 indicates that the gear step corresponding to the detected gear ratio Rd cannot be read and the gear step is unknown.

As described above, in the case where the gear step is unknown, the gear step directly read value D=0, and a mark indicating that the gear step is unknown is used as one of the gear step directly read values D. This facilitates data processing, data management, display, and the like in the processing including the gear step estimation process and the illegal gear detection process described later.

In step S200, it is determined whether data of the last 20 times on the gear step directly read value D is stored in the storage medium RAM 40b.

In step S200, in the case where data of the last 20 times on the gear step directly read value D is not stored in the storage medium RAM 40b (step S200: NO), the process returns to step S120.

In step S200, in the case where data of the last 20 times on the gear step directly read value D is stored in the storage medium RAM 40b (step S200: YES), the process proceeds to step S210 to acquire the gear step directly read value D of the last 20 times. Then, the process proceeds to step S220.

In step S220, with reference to the gear step directly read values D of the last 20 times, a gear step directly read value Dm having the largest number of appearances is estimated as the currently selected gear step, and the estimated gear step G=Dm. Then, the process proceeds to step S230.

In this way, with reference to the plurality of gear step directly read values D, the gear step directly read value Dm having the largest number of appearances is estimated as the currently selected gear step. This can reduce the frequency of erroneous estimation. In particular, this can avoid erroneous estimation due to a detection value error of the detected gear ratio Rd during the transition of the gear step. Accordingly, it is possible to estimate which gear step of the switching transmission device 30 is selected by the user with high accuracy.

In step S230, it is determined whether the estimated gear step G estimated in step S220 is 9, that is, the estimated gear step G=9.

In step S230, in the case where it is determined that the estimated gear step G estimated in step S220 is 9, that is, the estimated gear step G=9 (step S230: YES), the process proceeds to step S300 to execute the illegal gear detection process. Details of the illegal gear detection process in step S300 will be described later.

In step S230, in the case where it is determined that the estimated gear step G estimated in step S220 is not 9, that is, the estimated gear step G is not 9 (step S230: NO), the process proceeds to step S240 to reset an illegal value continuation time te [s] described later to illegal value continuation time te [s]=0. Then, the process proceeds to step S250.

In step S250, it is determined whether the estimated gear step G estimated in step S220 is 0, that is, the estimated gear step G=0.

In step S250, in the case where it is determined that the estimated gear step G estimated in step S220 is 0, that is, the estimated gear step G=0 (step S250: YES), the process proceeds to step S261. In step S261, the last estimated gear step G saved in the storage medium ROM 40c is output to the portable terminal 8. Then, the display unit 8a of the portable terminal 8 displays the estimated gear step G as the selected gear step. Then, the process proceeds to step S270.

Thus, the estimated gear step G estimated immediately before is estimated as the estimated gear step G in the case where the last estimated gear step G estimated in step S220 is 0, that is, the gear step is unknown. Thereby, the last estimated gear step G estimated is estimated as the estimated gear step G even in the case where, for example, the electric assist bicycle 10 is temporarily in an idle state. This can reduce the strange feeling of the user in the estimation result of the gear step.

In step S250, in the case where it is determined that the estimated gear step G estimated in step S220 is not 0, that is, the estimated gear step G is not 0, in other words, the estimated gear step G is 1 to 8 in consideration of step S230 (step S250: NO), the process proceeds to step S262. In step S262, the estimated gear step G estimated in step S220 is output to the portable terminal 8. The display unit 8a of the portable terminal 8 displays the estimated gear step G as the selected gear step. Then, the process proceeds to step S263. In step S263, the estimated gear step G estimated in step S220 is stored in the storage medium ROM 40c. Then, the process proceeds to step S270.

As a result, even an electric assist bicycle 10 without a shift indicator function can be retrofitted to have a shift indicator function by outputting the estimated gear step G to the portable terminal 8.

In step S270, it is determined whether the elapsed time t [ms] measured in step S130 is elapsed time t [ms]≥50 [ms] or more. In step S270, the standby state is maintained until the elapsed time t [ms]≥50 [ms] or more (step S270: loop of NO), and the process proceeds to step S280 when the elapsed time t [ms]≥50 [ms] or more.

In step S280, it is determined whether the power supply of the electric assist bicycle 10 is turned off. In step S280, in the case where the power supply of the electric assist bicycle 10 is not turned off (step S280: NO), the process returns to step S120, and in the case where the power supply of the electric assist bicycle 10 is turned off (step S280: YES), the process proceeds to step S290.

The processes of step S170 to step S280 are performed by, for example, the gear step estimation unit 403.

In step S290, the illegal state detection count En [times] is reset to illegal state detection count En [times]=0 [times], and the series of processes is ended.

In this way, until the power supply of the electric assist bicycle 10 is turned off, the gear step directly read value D is acquired every predetermined time (50 [ms] in the present embodiment), and it is estimated at any time which gear step of the switching transmission device 30 is selected by the user.

Incidentally, the user often changes the gear step in the case where the user causes the electric assist bicycle to idle for a predetermined time and then stop. In the gear step estimation process, as described above, in step S140 and step S151, it is calculated that the detected gear ratio Rd=0.0 in the case where any one of the three conditions including vehicle speed V [km/h]=0.0 [km/h], cadence C [rpm]≤20 [rpm], and pedal torque value Tq [W]≤50.0 [W] is satisfied. Accordingly, the estimated gear step G=0 in the case where the user causes the electric assist bicycle 10 to idle for a predetermined time and then stop. Thus, it is calculated that the detected gear ratio Rd=0.0 and it is estimated that the estimated gear step G=0 in the case where the user causes the electric assist bicycle 10 to idle for a predetermined time and then stop. This can reset the detected gear ratio Rd and the estimated gear step G.

[Illegal Gear Detection Process]

Next, details of the illegal gear detection process in step S300 will be described with reference to FIG. 8. The illegal gear detection process is performed by, for example, the gear step estimation unit 403.

In the illegal gear detection process, first, the process proceeds to step S310. In step S310, it is determined whether the illegal value continuation time te [s]=0.

In step S310, in the case where the illegal value continuation time te [s]=0 (step S310: YES), the process proceeds to step S311. In step S311, the measurement of the illegal value continuation time te [s] is started. Then, the process proceeds to step S320.

In step S310, in the case where the illegal value continuation time te [s] is not 0 (step S310: NO), the process proceeds to step S320.

In step S320, in step S310, it is determined whether the illegal value continuation time te [s]≥5 [s], that is, whether the illegal value continuation time te [s] exceeds 5 seconds.

In step S320, in the case where the illegal value continuation time te [s]≥5 [s](step S310: YES), the process proceeds to step S321. At step S321, the illegal state detection count En [times] is set to En+1 [times]. That is, the illegal state detection count En [times] is added by 1 [time]. Then, the process proceeds to step S330.

In step S320, in the case where the illegal value continuation time te [s]≥5 [s] is not satisfied (step S310: NO), the process proceeds to step S330.

In step S330, it is determined whether the illegal state detection count En [times]≥3 [times], that is, the illegal state detection count En [times] is 3 [times] or more.

In step S330, in the case where the illegal state detection count En [times]≥3 [times], that is, the illegal state detection count En [times] is 3 [times] or more (step S330: YES), the process proceeds to step S340.

In step S340, illegality determination process is executed. The illegality determination process executes at least one of the following (i) to (iii). In the present embodiment, the following (i) to (iii) are executed in order. Then, the process proceeds to step S341.

- (i) Determining an abnormal occurrence in the power transmission mechanism T.

In the present embodiment, it is determined that an illegal gear is mounted on the power transmission mechanism T.

- (ii) Generating information for limiting or prohibiting a drive using the power transmission mechanism T.

In the present embodiment, information for prohibiting the drive of the motor M is generated.

- (iii) Generating information for reporting to at least one of the rider (user) of the electric assist bicycle 10, the party which mounts the vehicle body and the power unit 20, the party which manufactures the electric assist bicycle 10, the party which manufactures the power unit 20, the party which manages the electric assist bicycle 10, the party which manages the power unit 20, the party which certifies the electric assist bicycle 10, or the regulatory party of the electric assist bicycle 10.

In the present embodiment, information for reporting to the rider (user) on the electric assist bicycle 10 that an illegal gear is mounted on the power transmission mechanism T is generated.

In step S341, a signal including the information for prohibiting the drive of the motor M generated in the process of (ii) of step S340 is output. When the signal including the information for prohibiting the drive of the motor M is output in step S341, the assist by the motor M is prohibited in the electric assist bicycle 10. The user cannot cancel the assist prohibited state. For example, the assist prohibited state cannot be cancelled unless the vehicle is brought into a shop or the like and operated with a dedicated device. Then, the process proceeds to step S342.

In step S342, the signal generated in the process of (iii) of step S340 and including the information for reporting that an illegal gear is mounted in the power transmission mechanism T is output to the portable terminal 8. Then, the display unit 8a of the portable terminal 8 displays that an illegal gear is mounted on the power transmission mechanism T. For example, in the display unit 8a of the portable terminal 8, “error” is displayed in a region indicating the selected gear step.

In this way, with the process of (i) in step S340, the state of the electric assist bicycle 10 not complying with the regulations can be detected. With the process of (ii), it is possible to avoid using the electric assist bicycle 10 in the state of not complying with the regulations. With the processing of (iii), the user or the like can recognize that remodeling and improvement causing the regulation non-compliance state are performed on the electric assist bicycle 10.

On the other hand, in step S330, in the case where it is not satisfied that the illegal state detection count En [times]≥3 [times], that is, the illegal state detection count En [times] is 2 [times] or less (step S330: NO), the process proceeds to step S360.

In step S360, the estimated gear step G saved in the storage medium ROM 40c as the last gear step in the last step S263 is output to the portable terminal 8. Then, the display unit 8a of the portable terminal 8 displays the estimated gear step G as the selected gear step. Then, the process proceeds to step S370.

In step S370, the illegal value continuation time te [s] is reset to illegal value continuation time te [s]=0. Then, the process proceeds to step S380.

In step S380, the measurement of the illegal value continuation time te [s] is started again. Then, the illegal gear detection process is ended, and the process proceeds to step S270 of the gear step estimation process.

FIG. 9 is a time-series change graph illustrating a first example of executing the above-described gear step estimation process in the electric assist bicycle 10.

In FIG. 9, the uppermost graph is a graph representing a time series of the vehicle speed V [km/h]. The second graph from the top is a graph illustrating a time series of the cadence C [rpm]. The third graph from the top is a graph illustrating a time series of the detected gear ratio Rd calculated in step S151 or step S152 of the gear step estimation process. The fourth graph from the top is a graph illustrating a time series of the estimated gear step G estimated in the gear step estimation process.

Further, in FIG. 9, the fifth graph from the top is a graph illustrating a time series of the number of appearances of the gear step directly read value D=0 for the gear step directly read values D of the last 20 times in step S220 of the gear step estimation process. The sixth graph from the top is a graph illustrating a time series of the number of appearances of the gear step directly read value D=1 for the gear step directly read values D of the last 20 times in step S220 of the gear step estimation process. The seventh graph from the top is a graph illustrating a time series of the number of appearances of the gear step directly read value D=2 for the gear step directly read values D of the last 20 times in step S220 of the gear step estimation process. The eighth graph from the top is a graph illustrating a time series of the number of appearances of the gear step directly read value D=3 for the gear step directly read values D of the last 20 times in step S220 of the gear step estimation. The ninth graph from the top is a graph illustrating a time series of the number of appearances of the gear step directly read value D=4 for the gear step directly read values D of the last 20 times in step S220 of the gear step estimation process. The 10-th graph from the top is a graph illustrating a time series of the number of appearances of the gear step directly read value D=5 for the gear step directly read values D of the last 20 times in step S220 of the gear step estimation. The 11-th graph from the top is a graph illustrating a time series of the number of appearances of the gear step directly read value D=6 for the gear step directly read values D of the last 20 times in step S220 of the gear step estimation process. The 12-th graph from the top is a graph illustrating a time series of the number of appearances of the gear step directly read value D=7 for the gear step directly read values D of the last 20 times in step S220 of the gear step estimation process. The 13-th graph from the top is a graph illustrating a time series of the number of appearances of the gear step directly read value D=8 for the gear step directly read values D of the last 20 times in step S220 of the gear step estimation process. The 14-th graph from the top is a graph illustrating a time series of the number of appearances of the gear step directly read value D=9 for the gear step directly read values D of the last 20 times in step S220 of the gear step estimation process.

Therefore, the fourth graph from the top illustrates the gear step directly read value Dm having the largest number of appearances as the estimated gear step G=Dm based on the fifth to 14-th graphs from the top.

For example, in FIG. 9, at a time point TO, the cadence C [rpm] starts to increase, and the vehicle speed V [km/h] also starts to increase subsequently. Then, at a time point T1, the number of appearances of the gear step directly read value D=1 is the largest among the gear step directly read values D of the last 20 times, and it is estimated that the estimated gear step G=1.

Then, at a time point T2, the number of appearances of the gear step directly read value D=2 is the largest among the gear step directly read values D of the last 20 times, and it is estimated that the estimated gear step G=2. Similarly, at a time point T3, the number of appearances of the gear step directly read value D=3 is the largest, and it is estimated that the estimated gear step G=3; at a time point T4, the number of appearances of the gear step directly read value D=4 is the largest, and it is estimated that the estimated gear step G=4; and at a time point T5, the number of appearances of the gear step directly read value D=5 is the largest, and it is estimated that the estimated gear step G=5.

The cadence C [rpm] is rapidly decreases when a time point T6 is passed. The cadence C [rpm] temporarily increases between the time point T6 and a time point T7, but the cadence C [rpm] is close to zero most of the time. This indicates that the user stops the pedal operation on the electric assist bicycle 10 and the electric assist bicycle 10 is in the idle state. When the electric assist bicycle 10 is in the idle state, the vehicle speed V [km/h] and the cadence C [rpm] are no longer correlated with each other. Therefore, for most of the period between the time point T6 and the time point T7, the number of appearances of the gear step directly read value D=0 is the largest, and it is estimated that the estimated gear step G=0, that is, the gear step is unknown. At this time, as described above, in step S261, the last saved estimated gear step G=5 is output to the portable terminal 8 as the selected gear step.

After the time point T7 is passed, the cadence C [rpm] rapidly increases, and the vehicle speed V [km/h] also starts to increase subsequently. Immediately after time point T7, the number of appearances of the gear step directly read value D=0 is the largest among the gear step directly read values D of the last 20 times, and the estimated gear step G=0 remains unchanged. However, after a predetermined time has elapsed and it reaches a time point T8, the number of appearances of the gear step directly read value D=4 is the largest, and the estimated gear step G transitions to 4. The reason is considered as that the correlation between the vehicle speed V [km/h] and the cadence C [rpm] is still low immediately after the electric assist bicycle 10 transitions from the idle state to pedal-powered driving, and that the user switched the gear step from the fifth step to the fourth step between the time point T7 and the time point T8.

Then, at a time point T9, the number of appearances of the gear step directly read value D=5 is the largest among the gear step directly read values D of the last 20 times, and it is estimated that the estimated gear step G=5. Similarly, at a time point T10, the number of appearances of the gear step directly read value D=6 is the largest, and it is estimated that the estimated gear step G=6; at a time point T11, the number of appearances of the gear step directly read value D=7 is the largest, and it is estimated that the estimated gear step G=7; and at a time point T12, the number of appearances of the gear step directly read value D=8 is the largest, and it is estimated that the estimated gear step G=8.

After a time point T13, both the vehicle speed V [km/h] and the cadence C [rpm] decrease. Between the time point T13 and a time point T14, it is considered that the pedal torque value Tq [W] decreases and the pedal is substantially idling. Therefore, during the period from the time point T13 to the time point T14, the vehicle speed V [km/h] and the cadence C [rpm] are correlated with each other. For most of the period between the time point T6 and the time point T7, the number of appearances of the gear step directly read value D=0 is the largest, and it is estimated that the estimated gear step G=0, that is, the gear step is unknown.

When the time point T14 is passed, the cadence C [rpm] rapidly increases, the vehicle speed V [km/h] also starts to increase, the number of appearances of the gear step directly read value D=1 is the largest among the gear step directly read values D of the last 20 times, and it is estimated that the estimated gear step G=1. Then, at a time point T15, the number of appearances of the gear step directly read value D=2 is the largest among the gear step directly read values D of the last 20 times, and it is estimated that the estimated gear step G=2.

FIG. 10 is a time-series change graph illustrating a second example of executing the above-described gear step estimation process in the electric assist bicycle 10. Here, only the difference from the first example described above will be described in detail, and the description of the same aspect as the first example will be omitted or simplified.

In this example, the number of appearances of the gear step directly read value D=9 is the largest between the time point T12 and the time point T13, and it is estimated that the estimated gear step G=9. In this case, the above-described illegal gear detection process is executed, and, the illegal state detection count En [times] is counted as 1 [time] by the above-described step S321 in the case where the time from the time point T12 to the time point T13 is 5 [s] or more. At this time, as described above, in step S360, the last saved estimated gear step G=7 is output to the portable terminal 8 as the selected gear step. Then, when the illegal state detection count En [times] becomes 3 [times] or more before the power supply of the electric assist bicycle 10 is turned off, the above-described step S340 to step S342 are executed, the assist by the motor M is prohibited in the electric assist bicycle 10, and “error” is displayed in the region indicating the selected gear step on the display unit 8a of the portable terminal 8.

Although an embodiment of the present disclosure has been described above with reference to the accompanying drawings, it is needless to say that the present invention is not limited to the embodiment. It is apparent that those skilled in the art can conceive of various modifications and changes within the scope described in the claims, and it is understood that such modifications and changes naturally fall within the technical scope of the present invention. In addition, the constituent elements in the above embodiments may be freely combined without departing from the gist of the invention.

For example, in the present embodiment, although the electric assist bicycle 10 is exemplified as a vehicle, the present invention is not limited thereto, and the vehicle may be a two-wheeled vehicle without input from the crank pedal 79, or a three-wheeled vehicle or a four-wheeled vehicle instead of a two-wheeled vehicle.

Further, for example, although a case where a non-electric assist bicycle after sale is retrofitted with the assist device has been described in the present embodiment described above, the present invention is not necessarily limited to a non-electric assist bicycle after sale, and can also be applied to a completed vehicle obtained by mounting, at a dealer or the like, the assist device to a new non-electric assist bicycle. The present invention can also be applied to a completed vehicle manufactured in a factory for mounting the assist device which is the same site where the vehicle body is manufactured (that is, an electric assist bicycle completed vehicle factory).

For example, in the present embodiment, the gear step estimation process is constantly executed from when the power supply of the electric assist bicycle 10 is turned on to when the power supply is turned off, but the electric assist bicycle 10 may enter a standby state without executing the gear step estimation process in the case where, for example, the pedal torque value Tq [W] is below a predetermined value, for example, in the case where the pedal torque value Tq [W]≤50.0 [W]. Further, for example, in the present embodiment, the process proceeds to step S151 in the case where step S140 is YES in the gear step estimation process, but the process may return to step S140 and wait until step S140 becomes NO in the case where step S140 is YES. In this case, until step S140 becomes NO, the selected gear step may be assumed to be the estimated gear step G that is last estimated, and the display unit 8a of the portable terminal 8 may display the estimated gear step G that is last estimated as the selected gear step.

Further, for example, in the present embodiment, the execution of the gear step estimation process is started when the power supply of the electric assist bicycle 10 is turned on, and in step S110, the preset gear ratios Ri (i=a natural number of 1 to 8) of the first to eighth steps are acquired by calculating the preset gear ratio Ri (i=a natural number of 1 to 8) for each gear step using the above-described equation (3), but the preset gear ratio Ri of each gear step may be stored in advance in the storage medium ROM 40c in a dealer or the like of the electric assist bicycle 10.

Further, for example, in the present embodiment, in the gear step estimation process, when the estimated gear step G=0 (step S250: YES), the last saved estimated gear step G is output to the portable terminal 8 as the selected gear step (step S261), but step S261 may also output to the portable terminal 8 that the estimated gear step G=0. In this case, the area indicating the selected gear step on the display unit 8a of the portable terminal 8 may display nothing.

In addition, for example, the gear step estimation process may further include a step of executing at least one of the following (i) to (iii) before or after step S261 in the case where the estimated gear step G=0 in step S250 (step S250: YES).

- (i) Determining an abnormal occurrence in the power transmission path
- (ii) Generating information for limiting or prohibiting a drive using the power transmission path
- (iii) Generating information for reporting to at least one of the rider (user) of the electric assist bicycle 10, the party which manufactures the electric assist bicycle 10, the party which manages the electric assist bicycle 10, the party which certifies the electric assist bicycle 10, and the regulatory party of the electric assist bicycle 10

Further, for example, in the present embodiment, it is estimated that the estimated gear step G=0 in the case where the user stops the electric assist bicycle 10 after causing the electric assist bicycle 10 to idle for a predetermined time, but the estimated gear step G may be estimated as a preset initial value without being limited to the estimated gear step G=0 when the vehicle speed V of the power-assisted bicycle becomes a predetermined threshold or less. Thus, the estimated gear step G is estimated as the initial value in the case where the user causes the electric assist bicycle 10 to idle for a predetermined time and then stop. This can reset the detected gear ratio Rd and the estimated gear step G.

For example, in the present embodiment, the illegal gear detection process is performed, for example, by the gear step estimation unit 403, but the control device 40 may be provided with an illegal gear detection unit for performing the illegal gear detection process separate from the gear step estimation unit 403.

In the present specification, at least the following matters are described. In the parentheses, the corresponding constituent elements and the like in the above embodiment are shown as an example, but the present invention is not limited thereto.

(1) A gear step estimation method of estimating a gear step of a switching transmission device (switching transmission device 30) in a vehicle (electric assist bicycle 10) including

- a power source (motor M), and
- the switching transmission device provided in a power transmission path between the power source and a wheel (rear wheel 78), and capable of switching the gear step among n gear steps (n is a natural number of 2 or more),
- the gear step estimation method including:
- a step of acquiring, at a first time, a first gear ratio (detected gear ratio Rd) that is a gear ratio of a transmission section including the switching transmission device, the transmission section being a whole or a part of the power transmission path;
- a step of comparing the acquired first gear ratio with n reference values (preset gear ratios Ri) set within a range of possible gear ratios taken by the n gear steps; and
- a step of estimating the gear step of the switching transmission device as an m-step (m is a natural number of 1 or more and n or less) in a case where the first gear ratio matches an m-th reference value from a smallest among the n reference values.

According to (1), it is possible to estimate at any time which gear step of the switching transmission device is selected by the user. In addition, even a vehicle without a shift indicator function can be easily retrofitted to have a shift indicator function. The reference value may be a single value or may be values having an upper limit value and a lower limit value.

(2A) The gear step estimation method according to (1), further including:

- a step of acquiring, at a second time after the first time, a second gear ratio (detected gear ratio Rd) that is a gear ratio of the transmission section;
- a step of comparing the acquired second gear ratio with the n reference values;
- a step of estimating the gear step of the switching transmission device as a p-step (p is a natural number of 1 or more and n or less) in a case where the second gear ratio matches a p-th reference value from the smallest among the n reference values; and
- a step of estimating, based on the m-step estimated at the first time and the p-step estimated at the second time, the gear step of the switching transmission device as the m-step or the p-step.

(2B) The gear step estimation method according to (1), further including:

- a step of acquiring, at a second time after the first time, a second gear ratio (detected gear ratio Rd) that is a gear ratio of the transmission section;
- a step of comparing the acquired second gear ratio with the n reference values;
- a step of estimating the gear step of the switching transmission device as a p-step (p is a natural number of 1 or more and n or less) in a case where the second gear ratio matches a p-th reference value from the smallest among the n reference values; and
- a step of estimating, based on the m-step estimated at the first time and the p-step estimated at the second time, the gear step of the switching transmission device at the second time, a current time after the second time, or any time between the second time and the current time as the m-step or the p-step.

According to (2A) and (2B), based on the m-step estimated at the first time and the p-step estimated at the second time, the gear step of the switching transmission device is estimated as the m-step or the p-step. This can reduce the frequency of erroneous estimation.

(3A) The gear step estimation method according to (2A) or (2B), further including: a step of acquiring, at a third time after the second time, a third gear ratio (detected gear ratio Rd) that is a gear ratio of the transmission section;

- a step of comparing the acquired third gear ratio with the n reference values;
- a step of estimating the gear step of the switching transmission device as a q-step (q is a natural number of 1 or more and n or less) in a case where the third gear ratio matches a q-th reference value from the smallest among the n reference values; and
- a step of estimating, based on the m-step estimated at the first time, the p-step estimated at the second time, and the q-step estimated at the third time, the gear step of the switching transmission device as a gear step having a largest number of appearances among the m-step, the p-step and the q-step.

(3B) The gear step estimation method according to (2A) or (2B), further including:

- a step of acquiring, at a third time after the second time, a third gear ratio (detected gear ratio Rd) that is a gear ratio of the transmission section;
- a step of comparing the acquired third gear ratio with the n reference values;
- a step of estimating the gear step of the switching transmission device as a q-step (q is a natural number of 1 or more and n or less) in a case where the third gear ratio matches a q-th reference value from the smallest among the n reference values; and
- a step of estimating, based on the m-step estimated at the first time, the p-step estimated at the second time, and the q-step estimated at the third time, the gear step of the switching transmission device at the third time, a current time after the third time, or any time between the third time and the current time as a gear step having a largest number of appearances among the m-step, the p-step and the q-step.

According to (3A) and (3B), based on the m-step estimated at the first time, the p-step estimated at the second time, and the q-step estimated at the third time, the gear step of the switching transmission device is estimated as the gear step having the largest number of appearances among the m-step, the p-step, and the q-step. This can reduce the frequency of erroneous estimation. In particular, this can avoid erroneous estimation due to a detection value error of the detected gear ratio during the transition of the gear step.

(4) The gear step estimation method according to (3A) or (3B), further including: a step of estimating the gear step of the switching transmission device as the gear step last estimated as the gear step of the switching transmission device, when no gear step has the largest number of appearances.

According to (4), the gear step of the switching transmission device is estimated as the gear step last estimated as the gear step of the switching transmission device, when no gear step has the largest number of appearances. This can reduce the strange feeling of the user in the estimation result of the gear step.

(5) The gear step estimation method according to (1), further including:

- a step of estimating, at a fourth time, the gear step of the switching transmission device as a gear step having a largest number of appearances, in a case where the gear step is estimated a plurality of times for a predetermined period before the fourth time.