Electric-assist bicycle and gear ratio determination method for electric-assist bicycle

Abstract

Provided are an electric-assist bicycle and a gear ratio determination method for an electric-assist bicycle that can reduce the risk of incorrect gear ratio determination and that identify a gear ratio with high accuracy.　In an electric-assist bicycle (1), the time from when a first gear ratio is changed to a second gear ratio until assisting of a pedal (4) corresponding to the second gear ratio is started is different from the time from when a third gear ratio is changed to a fourth gear ratio until assisting of the pedal (4) corresponding to the fourth gear ratio is started.

Description

Electrically assisted bicycle and method for determining gear ratio of electrically assisted bicycle

[0001] The present invention relates to an electrically assisted bicycle and a method for determining the gear ratio of an electrically assisted bicycle.

[0002] Patent document 1 discloses a technology for appropriately controlling the assist ratio of an electrically assisted bicycle that has a transmission and a motor, and in which the ratio between the motor's driving rotation speed and the pedal driving rotation speed changes in accordance with changes in the transmission's gear ratio.

[0003] JP 2013-241045 A

[0004] To determine the current gear ratio of an electrically assisted bicycle, it is necessary to measure the rotation speed of the motor and the rotation speed of the wheel. However, due to issues with the accuracy of the rotation speed sensor, situations can arise where it is unclear which of the adjacent gear ratios is correct. For example, even if the bicycle is set to gear 3, it may be impossible to determine whether the bicycle is set to gear 2 or gear 3 from the results of measuring the rotation speed of the motor and the rotation speed of the wheel. In this situation, if it is erroneously determined that the bicycle is set to gear 2, the electrically assisted bicycle may behave in an unexpected manner.

[0005] Therefore, an example of the objective of the present invention is to reduce the risk of erroneous judgment by provisionally judging both adjacent gear ratios as candidates when it is unclear which of the adjacent gear ratios is correct, and to determine the gear ratio with high accuracy.

[0006] In an electrically assisted bicycle that is one example of the present invention, the time from when the gear ratio is changed from a first to a second gear ratio until pedal assistance corresponding to the second gear ratio begins is different from the time from when the gear ratio is changed from a third to a fourth gear ratio until pedal assistance corresponding to the fourth gear ratio begins.

[0007] An example of an electric assist bicycle of the present invention is equipped with a control device, and the time from starting the control device after it has stopped until pedal assistance corresponding to the gear ratio begins is longer than the time from changing the gear ratio until pedal assistance corresponding to the changed gear ratio begins.

[0008] A method for determining the gear ratio of an electrically assisted bicycle, which is one example of the present invention, includes a first step of determining a candidate for the predetermined gear ratio before a first period has elapsed since the gear ratio was changed to the predetermined gear ratio, and a second step of determining the predetermined gear ratio from the candidate predetermined gear ratios after the first period has elapsed but before a second period has elapsed.

[0009] 8(a) is a side view of an electrically assisted bicycle equipped with a control device (motor control drive device); FIG. 9 is a diagram showing a part of an electrically assisted bicycle; FIG. 10 is a block diagram showing a schematic configuration of a control device, a first sensor, a second sensor, and a motor; FIG. 11 is a flowchart illustrating control in the present invention; FIG. 12 is a timing diagram illustrating control in the present invention; FIG. 13 is a timing diagram illustrating other control in the present invention; FIG. 14 is a flowchart illustrating gear ratio state determination processing; FIG. 15 is a simulation diagram illustrating detection during gear shifting and motor control in an electrically assisted bicycle; FIG. 16(a) is a simulation diagram showing an enlarged portion of FIG. 8(a) where gear 9 is changed to gear 8, and the process goes through the gear ratio state determination processing shown in FIG. 7 until gear 8 is confirmed; FIG. 17(a) is a simulation diagram showing an enlarged portion of FIG. 8(a) where gear 2 is changed to gear 1, and the process goes through the gear ratio state determination processing shown in FIG. 7 until gear 1 is confirmed.

[0010] FIG. 1 is a side view of an electrically assisted bicycle equipped with a control device (motor control drive device). The electrically assisted bicycle 1 includes a frame F, a handlebar H, a saddle S, a transmission body C, a battery B, a rotation device (MDU: motor drive unit) 100, a first wheel (front wheel) 2, a second wheel (rear wheel) 3, and pedals 4. When a rider sits on the saddle S of the electrically assisted bicycle 1 and rotates the bicycle by pedaling the pedals 4 with their feet, driving force is transmitted to a wheel (typically the rear wheel 3) via the transmission body C, with assistance from the rotation device 100 as needed, allowing the bicycle to travel forward. The transmission body C may be a chain or a belt.

[0011] A first sensor 5 for detecting the rotation speed of the wheel is disposed, for example, near the rotation axis of the front wheel 2 or the rear wheel 3. While FIG. 1 shows an example in which the first sensor 5 is disposed on the rear wheel 3, the first sensor 5 may be disposed in a position where it can detect the rotation speed or rotation angle of the wheel, for example, in a position away from the rotation axis of the front wheel 2 or the rear wheel 3. A known sensor capable of detecting the rotation speed of the wheel can be used as the first sensor 5. The first sensor 5 is, for example, a magnetic sensor (Hall sensor).

[0012] The rotating device 100 and the battery B are typically arranged around a crankshaft (not shown) connected to the pedals 4. The rotating device 100 has a motor M and a reducer G (see FIG. 2). The battery B supplies power to the motor M and the control device 50, causing the motor M and the control device 50 to operate.

[0013] Motor M is controlled by control device 50 and assists the rotation of pedal 4 via reducer G. In this specification, "rotation of pedal 4" refers to the rotation of pedal 4 around the crankshaft. In this specification, "assisting rotation of pedal 4" also includes reducing the force (pedaling force) required to rotate pedal 4 and move the bicycle forward. Motor M may be, for example, a brushless DC motor having coils corresponding to three phases (U phase, V phase, and W phase).

[0014] The second sensor 6 is a sensor, such as a Hall sensor, that detects the rotation speed of the motor M and is located near the motor M. Using a Hall sensor as the second sensor 6, rather than a cadence sensor attached near the crankshaft, is preferable because it allows for more accurate acquisition of the chainring rotation speed from the motor M rotation speed detected by the Hall sensor and allows for data acquisition at desired time intervals for use in software. The first reason why using a Hall sensor allows for more accurate acquisition of the rotation speed is that the Hall sensor is fixed so that it always maintains the same position relative to the rotor of the motor M, thereby always acquiring accurate magnetic data. In contrast, with a cadence sensor, the distance between the magnet on the shaft connecting the two pedals 4 and the magnetic sensor on the circuit board changes slightly due to distortion of the shaft caused by pedaling force. A second reason is the influence of the power of the rotating object being detected. That is, with a Hall sensor, the power of the rotating object being detected, the motor M, is electrically powered, whereas with a cadence sensor, the power of the rotating object being detected, the pedal 4, is manually powered. For example, if the detection cycle is set to 1 ms, the fluctuations per detection cycle are smaller for electricity than for human power, and can be used as data within the software.

[0015] FIG. 2 shows a portion of an electrically assisted bicycle. In general, bicycles experience differences in rotation speed depending on the number of gear teeth selected for the multi-stage (rear) gear sprocket 9 relative to the number of gear teeth on the crank (front) 8. For example, in this embodiment, the crank 8 has 44 gear teeth, and the gear sprocket 9 has nine gears, with the gear teeth numbers being 11-13-15-17-20-23-26-30-36. Examples of rear gear positions are: first gear position with 36 gear teeth, second gear position with 30 gear teeth, and third gear position with 26 gear teeth. Gear 1 is the lightest gear, and gear 9 is the heaviest gear. Table 1 shows the gear settings for this embodiment. Table 1 and the following tables are stored in the memory device of the control circuit 50a (see FIG. 3). The theoretical value of the rotation speed ratio R can be calculated using the number of rear gear teeth / number of front gear teeth. In Table 1, only the third decimal place is shown, but in actual calculations, the fourth decimal place and below are also used. In this embodiment, the lower limit of the threshold value used for determination is 90% of the theoretical value of the ratio of the rotation speeds, and the upper limit of the threshold value is 110% of the theoretical value of the ratio of the rotation speeds, but the upper and lower limits of the threshold value can be set arbitrarily.

[0016]

[0017] The actual rotation speed ratio R is N ｗ is the rotation speed of rear wheel 3 [rpm], N ｍ is the rotation speed [rpm] of the motor M, gr ＭＤＵ is the reduction ratio of the rotating device 100, which is expressed by the formula (1). ｍ / (gr ＭＤＵ ・N ｗ ) Equation (1) In the gear ratio state determination process described below, the control device 50 determines whether the rotation speed ratio R, i.e., the magnitude of equation (1), is included within a predetermined range (threshold range in Table 1) corresponding to each gear ratio.

[0018] 3 is a block diagram showing a schematic configuration of the control device, the first sensor, the second sensor, and the motor. The control device 50 has, for example, a control circuit 50a and a drive circuit 50b. The components of the control device 50 shown in FIG. 3 are only a part of the whole, and the control device 50 may have other components in addition to those shown in FIG. 3.

[0019] The control circuit 50a is realized by a program processing device (e.g., a microcontroller) having a configuration in which a processor such as a CPU, various storage devices such as RAM and ROM, and peripheral circuits such as a counter (timer), an A / D conversion circuit, a D / A conversion circuit, a clock generation circuit, and an input / output I / F circuit are connected to each other via a bus or dedicated lines.

[0020] The control circuit 50a has, for example, functional blocks including a rotation speed calculation unit 51, an i comparison unit 52, a threshold comparison unit 53, a gear ratio setting unit 54, an i setting unit 55, a C setting unit 56, a count threshold comparison unit 57, and a drive control signal generation unit 58. The rotation speed calculation unit 51, the i comparison unit 52, the threshold comparison unit 53, the gear ratio setting unit 54, the i setting unit 55, the C setting unit 56, the count threshold comparison unit 57, and the drive control signal generation unit 58 are realized, for example, by a program processing device serving as the control circuit 50a, in which a processor executes various arithmetic processes in accordance with programs stored in a memory and controls peripheral circuits such as a counter and an A / D conversion circuit. Note that the control circuit 50a may have other functions.

[0021] The drive control signal generating unit 58 generates a drive control signal Sd for driving the motor M based on the drive command signal, and controls the driving of the motor M. The drive control signal Sd is, for example, a PWM (Pulse Width Modulation) signal.

[0022] Based on the drive control signal Sd, the drive circuit 50b excites coils corresponding to the three phases (U phase, V phase, and W phase) of the motor M, thereby driving the motor M. The drive circuit 50b may include, for example, an inverter circuit that drives each coil, a pre-drive circuit that drives the inverter circuit in response to the drive control signal Sd, and a current detection circuit that detects the current flowing through each coil.

[0023] The control device 50 may be configured such that part or all of the control circuit 50a and part or all of the drive circuit 50b are packaged as a single integrated circuit device (IC), or such that the control circuit 50a and the drive circuit 50b are each packaged as separate integrated circuit devices.

[0024] The functions and operations of the rotation speed calculation unit 51, i comparison unit 52, threshold comparison unit 53, gear ratio setting unit 54, i setting unit 55, C setting unit 56 and count threshold comparison unit 57 will be explained using the flowchart of the gear ratio state determination process described later.

[0025] FIG. 4(a) is a flowchart illustrating the control according to the present invention, and FIG. 4(b) is a timing diagram illustrating this control. In step S1, the control device 50 detects whether the gear ratio has been changed from a first gear ratio to a second gear ratio. The time when the gear ratio is changed from the first gear ratio to the second gear ratio is set to t=t10. In step S2, the control device 50 performs a gear ratio state determination process, which will be described later. In step S3, the control device 50 controls the start of pedal assist corresponding to the second gear ratio. The time when pedal assist corresponding to the second gear ratio is started is set to t=t11. The time from when the gear ratio is changed from the first gear ratio to the second gear ratio until pedal assist corresponding to the second gear ratio is started is (t11-t10). The process ends here, but is repeated each time the gear ratio is changed.

[0026] For example, if the time when the gear ratio is changed from the third to the fourth gear ratio is t=t12 and the time when pedal assist corresponding to the fourth gear ratio starts is t=t13, the time from when the gear ratio is changed from the third to the fourth gear ratio to when pedal assist corresponding to the fourth gear ratio starts is (t13-t12). In the present invention, due to the gear ratio state determination process described below, the time (t11-t10) from when the gear ratio is changed from the first to the second gear ratio to when pedal assist corresponding to the second gear ratio starts is different from the time (t13-t12) from when the gear ratio is changed from the third to the fourth gear ratio to when pedal assist corresponding to the fourth gear ratio starts.

[0027] FIG. 5 is a timing diagram illustrating other control according to the present invention. Consider the case where the control device 50 is activated at time t=t20 from a stopped state. Pedal assist does not begin immediately upon activation, but rather after a predetermined time has elapsed. For example, assume that pedal assist corresponding to the gear ratio set at activation begins at time t=t21. Consider the case where the gear ratio is changed at time t=t22, a predetermined time after activation of the control device 50. As with the activation of the control device 50, pedal assist at the changed gear ratio is not applied immediately upon the change of the gear ratio, but is applied after a predetermined time has elapsed. For example, assume that pedal assist corresponding to the changed gear ratio begins at time t=t23. In the present invention, due to the gear ratio state determination process described below, the time from activation of the stopped control device 50 to the start of pedal assist corresponding to the gear ratio (t21-t20) is longer than the time from the change of the gear ratio to the start of pedal assist corresponding to the changed gear ratio (t23-t22).

[0028] Here, it is preferable that the time until pedal assist corresponding to the gear ratio starts is within the time required for one rotation of the wheel. Specifically, it is preferable that the times (t11-t10), (t13-t12), (t21-t20), and (t23-t22) are within the time required for one rotation of the rear wheel 3.

[0029] FIG. 6 is a timing diagram illustrating other control according to the present invention. Assume that the gear ratio is changed to a predetermined gear ratio at time t=t30. At time t=31, before the first period p1 has elapsed since the change to the predetermined gear ratio, the control device 50 determines (provisionally determines) a candidate for the predetermined gear ratio using a gear ratio state determination process described below. For example, gears 2 and 3 are determined (provisionally determined) as candidates. At time t=32, after the first period p1 has elapsed but before the second period p2 has elapsed, the control device 50 determines the predetermined gear ratio from the candidate predetermined gear ratios using a gear ratio state determination process described below. For example, from the two candidates (gears 2 and 3), it determines that gear 3 is the current gear ratio.

[0030] Here, it is preferable that the period including the first period p1 and the second period p2 is within the time required for one rotation of the wheel (rear wheel 3).

[0031] In addition, possible methods for checking whether a certain electrically assisted bicycle has the time relationship (time lag) that is a characteristic feature of the present invention include checking the display (display device) that shows the gear position, checking that the assist output is suppressed until the gear position is determined, and checking that a time lag occurs in the assist output due to motor current, etc.

[0032] FIG. 7 is a flowchart illustrating the gear ratio state determination process. The current gear ratio is set to gear 3. However, as described above, it may be impossible to determine whether the gear ratio is set to gear 2 or gear 3 based on the results of measuring the motor rotation speed and the wheel rotation speed. The situation in which it is unclear which of the adjacent gear ratios is correct can occur, for example, when the gear ratio is changed or when the system (control device 50) is started from a stopped state and pedaling begins. In the present invention, the gear ratio state determination process can provisionally determine or confirm the current gear. Example 1 illustrates a case in which the rotation speed ratio remains unchanged at R=0.63. Example 2 illustrates a case in which the rotation speed ratio changes from R=0.63 to R=0.55. Example 3 illustrates a case in which the rotation speed ratio changes from R=0.55 to R=0.63.

[0033] In Example 1, the rotation speed ratio remains unchanged at R = 0.63, and the count value C for gear 2 and gear 3 increases each time a vehicle speed pulse arrives. When the count value C exceeds the count threshold, gear 2 and gear 3 are "provisionally determined." A detailed description will be given below with reference to the flowchart. In this embodiment, a sensor that outputs 12 pulses (hereinafter referred to as vehicle speed pulses) per one rotation of the wheel is used as the first sensor 5.

[0034] In step S11, the rotation speed calculation unit 51 receives a signal indicating the rotation speed of the wheel (rear wheel 3) from the first sensor 5 and detects the timing to change the vehicle speed (whether a 1 / 12 vehicle speed pulse has arrived). Hereinafter, the timing to change the vehicle speed will be referred to as the vehicle speed change timing. At the vehicle speed change timing (when a 1 / 12 vehicle speed pulse has arrived), in step S12, the rotation speed calculation unit 51 calculates the rotation speed ratio R according to the above-mentioned equation (1) based on the signal from the first sensor 5 and the signal indicating the motor rotation speed from the second sensor 6. In the first embodiment, the rotation speed ratio R is assumed to be 0.63.

[0035] In step S13, the i comparison unit 52 compares i with Ngear. The initial value of i is 1, and Ngear is the number of gear ratios (number of gear sprocket stages), which is 9 in this embodiment. Here, since i<9, the process proceeds to step S14. In step S14, the threshold comparison unit 53 checks whether the rotation speed ratio R=0.63 is within the threshold range. According to Table 1, the threshold for i=1 is 0.736 to 0.900, and the rotation speed ratio R=0.63 is not within the threshold range, so the process proceeds to step S15. In step S15, the gear ratio setting unit 54 checks whether the gear ratio state of gear 1 is "provisional" or "determined." As shown in Table 2, the initial values ​​of the gear ratio states of all gears 1 to 9 are "undetermined," and the gear ratio state of gear 1 is also "undetermined," so the process proceeds to step S21. In step S21, the i setting unit 55 counts up i, and the process returns to step S13.

[0036] In step S13, the i comparison unit 52 compares i with Ngear. Since i=2, the process proceeds to step S14. In step S14, the threshold comparison unit 53 checks whether the rotation speed ratio R=0.63 is within the threshold range. From Table 1, the threshold for i=2 is 0.614 to 0.750, and since the rotation speed ratio R=0.63 is within the threshold range, the process proceeds to step S16. In step S16, the C setting unit 56 counts up the count value C of gear 2. Specifically, the count value C of gear 2 in Table 3 is changed from 0 to 1. In the tables shown below, including Table 3, the parts changed in this step are ＊ It is marked with. In step S17, the count threshold comparator 57 compares the count value C of gear 2 with the count threshold. The count threshold is a number indicating how many consecutive times the gear has satisfied the threshold, and is set to 6 in this embodiment. Since C<6, the process proceeds to step S15. Note that if gear determination is to be performed faster, the count threshold should be set to a small number, while if gear determination is to be performed more accurately, the count threshold should be set to a large number. The count threshold can be set arbitrarily. In step S15, the gear ratio setting unit 54 checks whether the gear ratio state of gear 2 is "provisionally determined" or "determined." As shown in Table 3, the gear ratio state of gear 2 is "undetermined," so the process proceeds to step S21. In step S21, the i setting unit 55 counts up i, and the process returns to step S13.

[0037] In step S13, the i comparison unit 52 compares i with Ngear. Since i=3, the process proceeds to step S14. In step S14, the threshold comparison unit 53 checks whether the rotation speed ratio R=0.63 is within the threshold range. According to Table 1, the threshold for i=3 is 0.532 to 0.650, and since the rotation speed ratio R=0.63 is within the threshold range, the process proceeds to step S16. In step S16, the C setting unit 56 counts up the count value C of gear 3. Specifically, the count value C of gear 3 in Table 4 is changed from 0 to 1. In step S17, the count threshold comparator 57 compares the count value C of gear 3 with the count threshold (6 in this embodiment). Since C<6, the process proceeds to step S15. In step S15, the gear ratio setting unit 54 checks whether the gear ratio state of gear 3 is "provisional" or "determined." As shown in Table 4, the gear ratio state of gear 3 is "undetermined," so the process proceeds to step S21. In step S21, the i setting unit 55 counts up i, and the process returns to step S13.

[0038] In step S13, the i comparison unit 52 compares i with Ngear. Since i=4, the process proceeds to step S14. In step S14, the threshold comparison unit 53 checks whether the rotation speed ratio R=0.63 is within the threshold range. According to Table 1, the threshold for i=4 is 0.470 to 0.535, and since the rotation speed ratio R=0.63 is not within the threshold range, the process proceeds to step S15. In step S15, the gear ratio setting unit 54 checks whether the gear ratio state of gear 4 is "provisionally determined" or "determined." As shown in Table 4, the gear ratio state of gear 4 is "undetermined," so the process proceeds to step S21. In step S21, the i setting unit 55 counts up i and returns to step S13.

[0039] Since i=5 to 9 are the same as the case of i=4 described above, in step S21 the i setting unit 55 counts up i and skips to i=10.

[0040] In step S13, the i comparison unit 52 compares i with Ngear. Since i=10, the process proceeds to step S22. In step S22, the i setting unit 55 resets i=1, and then the process proceeds to step S23. In step S23, the gear ratio setting unit 54 checks whether there is at least one gear ratio state that is "provisional" or "confirmed" among the gear ratio states of all gears. As shown in Table 4, the gear ratio states of all gears are "undetermined," so the process proceeds to step S24. In step S24, the gear ratio setting unit 54 sets the gear ratio states of all gears to "undetermined." In Example 1, since the gear ratio states of all gears are already "undetermined," nothing is done and the process returns to step S11.

[0041] In step S11, the rotation speed calculation unit 51 receives a signal indicating the rotation speed of the wheel (rear wheel 3) from the first sensor 5 and detects the timing of a vehicle speed change (whether a 2 / 12 vehicle speed pulse has arrived). At the timing of the vehicle speed change (when a 2 / 12 vehicle speed pulse has arrived), in step S12, the rotation speed calculation unit 51 calculates the rotation speed ratio R based on the signal from the first sensor 5 and the signal indicating the motor rotation speed from the second sensor 6. In the first embodiment, the rotation speed ratio R is assumed to remain unchanged at 0.63. Therefore, when i=1, steps S12 to S21 are the same as in the case of the 1 / 12 vehicle speed pulse described above. Therefore, in step S21, the i setting unit 55 counts up i and skips until i=2.

[0042] In step S13, the i comparison unit 52 compares i with Ngear. Since i=2, the process proceeds to step S14. In step S14, the threshold comparison unit 53 checks whether the rotation speed ratio R=0.63 is within the threshold range. According to Table 1, the threshold for i=2 is 0.614 to 0.750, and since the rotation speed ratio R=0.63 is within the threshold range, the process proceeds to step S16. In step S16, the C setting unit 56 counts up the count value C of gear 2. Specifically, the count value C of gear 2 in Table 5 is changed from 1 to 2. In step S17, the count threshold comparator 57 compares the count value C of gear 2 with the count threshold (6 in this embodiment). Since C<6, the process proceeds to step S15. In step S15, the gear ratio setting unit 54 checks whether the gear ratio state of gear 2 is "provisional" or "determined." As shown in Table 5, the gear ratio state of gear 2 is "undetermined," so the process proceeds to step S21. In step S21, the i setting unit 55 counts up i, and the process returns to step S13.

[0043] In step S13, the i comparison unit 52 compares i with Ngear. Since i=3, the process proceeds to step S14. In step S14, the threshold comparison unit 53 checks whether the rotation speed ratio R=0.63 is within the threshold range. According to Table 1, the threshold for i=3 is 0.532 to 0.650, and since the rotation speed ratio R=0.63 is within the threshold range, the process proceeds to step S16. In step S16, the C setting unit 56 counts up the count value C of gear 3. Specifically, the count value C of gear 3 in Table 6 is changed from 1 to 2. In step S17, the count threshold comparator 57 compares the count value C of gear 3 with the count threshold (6 in this embodiment). Since C<6, the process proceeds to step S15. In step S15, the gear ratio setting unit 54 checks whether the gear ratio state of gear 3 is "provisional" or "determined." As shown in Table 6, the gear ratio state of gear 3 is "undetermined," so the process proceeds to step S21. In step S21, the i setting unit 55 counts up i and returns to step S13.

[0044] Similarly, at the subsequent vehicle speed change timings (when the 3 / 12, 4 / 12, and 5 / 12 vehicle speed pulses arrive), as shown in Table 7, the C setting unit counts up the count values ​​C for gears 2 and 3.

[0045] The flow for each vehicle speed change timing (3 / 12, 4 / 12, 5 / 12 vehicle speed pulse) is the same as that described above. Also, in the flow for the vehicle speed change timing (6 / 12 vehicle speed pulse), when i=1, steps S12 to S21 are the same as those for each vehicle speed change timing (1 / 12, 2 / 12, 3 / 12, 4 / 12, 5 / 12 vehicle speed pulse) described above, so in step S21, the i setting unit 55 counts up i and skips until i=2.

[0046] In step S13, the i comparison unit 52 compares i with Ngear. Since i=2, the process proceeds to step S14. In step S14, the threshold comparison unit 53 checks whether the rotation speed ratio R=0.63 is within the threshold range. According to Table 1, the threshold for i=2 is 0.614 to 0.750, and since the rotation speed ratio R=0.63 is within the threshold range, the process proceeds to step S16. In step S16, the C setting unit 56 counts up the count value C of gear 2. Specifically, the count value C of gear 2 in Table 8 is changed from 5 to 6. In step S17, the count threshold comparator 57 compares the count value C of gear 2 with the count threshold (6 in this embodiment). Since 6≦C, the process proceeds to step S18. In step S18, the gear ratio setting unit 54 checks whether the gear ratio state of gear 2 is "excluded." As shown in Table 8, the gear ratio state of gear 2 is "undetermined," so the process proceeds to step S19. In step S19, as shown in Table 9, the gear ratio setting unit 54 changes the gear ratio state of gear 2 from "undetermined" to "provisional determination."

[0047] Similarly, in the loop of the vehicle speed change timing (6 / 12 vehicle speed pulse), the count value C for gear 3 also becomes 6, so as shown in Table 10, the gear ratio setting unit 54 also changes the gear ratio state of gear 3 to "provisional determination."

[0048] Since i=4 to 9 are the same as the cases of the above-mentioned vehicle speed change timings (1 / 12, 2 / 12, 3 / 12, 4 / 12, 5 / 12 vehicle speed pulses), in step S21, the i setting unit 55 counts up i and skips until it reaches i=10.

[0049] In step S13, the i comparison unit 52 compares i with Ngear. Since i=10, the process proceeds to step S22. In step S22, the i setting unit 55 resets i=1, and then the process proceeds to step S23. In step S23, the gear ratio setting unit 54 checks whether there is at least one gear ratio state that is "provisional" or "confirmed" among the gear ratio states of all gears. As shown in Table 10, the gear ratio states of gears 2 and 3 are "provisional," so the process proceeds to step S25. In step S25, the gear ratio setting unit 54 checks whether there is one "provisional" gear ratio state and whether the gear ratio states above and below this state are "excluded." As shown in Table 10, there are two gears with "provisional" gear ratio states, gears 2 and 3, so the process returns to step S11.

[0050] Similarly, at subsequent vehicle speed change timings (7 / 12, 8 / 12, and 9 / 12 vehicle speed pulses), the C setting unit increments the count value C for gears 2 and 3, as shown in Table 11. In Example 1, the rotational speed ratio R remains unchanged at 0.63, so the gear ratio state remains unchanged and the loop continues. Therefore, the gear ratio state is not determined, and both gears 2 and 3 remain in a provisional determination state. As a result, by provisionally determining both adjacent gear ratios (gears 2 and 3) as candidates, the risk of erroneous determination can be reduced. However, if the count value C reaches the count threshold, further increments are not necessary. That is, in Table 11, the count value C for gears 2 and 3 may stop at 6.

[0051] In Example 1, the control device 50 determines one or more numerical ranges that include the gear ratio calculated by equation (1) from among the numerical ranges corresponding to multiple gear ratios (gears 1 to 9) as shown in Table 1 (step S14), and one or more gear ratios (gears 2, 3) corresponding to the one or more numerical ranges are candidates for the predetermined gear ratio.

[0052] In Example 2, when the rotation speed ratio changes from the state in Example 1 (R = 0.63) to R = 0.55, and the first vehicle speed pulse arrives after the change, Gear 2 deviates from the threshold (NO in step S14). Because Gear 2 was provisionally determined (YES in step S15), Gear 2 is "excluded" (step S20). Because R = 0.55 is included in the thresholds of both Gear 3 and Gear 4 (step S14), the count values ​​C for Gear 3 and Gear 4 increase (step S16) and exceed the count threshold (YES in step S17). As a result, Gear 3 and Gear 4 are "provisionally determined" (step S19). A detailed description is given below with reference to the flowchart.

[0053] In step S11, the rotation speed calculation unit 51 receives a signal indicating the rotation speed of the wheel (rear wheel 3) from the first sensor 5 and detects the timing of a vehicle speed change (whether a 10 / 12 vehicle speed pulse has arrived). At the timing of the vehicle speed change (when a 10 / 12 vehicle speed pulse has arrived), in step S12, the rotation speed calculation unit 51 calculates the rotation speed ratio R based on the signal from the first sensor 5 and the signal indicating the motor rotation speed from the second sensor 6. In the second embodiment, the rotation speed ratio R is assumed to be 0.55.

[0054] In step S13, the i comparison unit 52 compares i with Ngear. Since i=1, the process proceeds to step S14. In step S14, the threshold comparison unit 53 checks whether the rotation speed ratio R=0.55 is within the threshold range. According to Table 1, the threshold for i=1 is 0.736 to 0.900, and since the rotation speed ratio R=0.55 is not within the threshold range, the process proceeds to step S15. In step S15, the gear ratio setting unit 54 checks whether the gear ratio state of gear 1 is "provisionally determined" or "determined." As shown in Table 11, the gear ratio state of gear 1 is "undetermined," so the process proceeds to step S21. In step S21, the i setting unit 55 counts up i and returns to step S13.

[0055] In step S13, the i comparison unit 52 compares i with Ngear. Since i=2, the process proceeds to step S14. In step S14, the threshold comparison unit 53 checks whether the rotation speed ratio R=0.55 is within the threshold range. According to Table 1, the threshold for i=2 is 0.614 to 0.750, and since the rotation speed ratio R=0.55 is not within the threshold range, the process proceeds to step S15. In step S15, the gear ratio setting unit 54 checks whether the gear ratio state of gear 2 is "provisional" or "definite." As shown in Table 11, the gear ratio state of gear 2 is "provisional," so the process proceeds to step S20. In step S20, as shown in Table 12, the gear ratio setting unit 54 changes the gear ratio state of gear 2 from "provisional" to "exclude," and the C setting unit 56 resets the count value C (to zero). In step S21, the i setting unit 55 counts up i, and the process returns to step S13.

[0056] In step S13, the i comparison unit 52 compares i with Ngear. Since i=3, the process proceeds to step S14. In step S14, the threshold comparison unit 53 checks whether the rotation speed ratio R=0.55 is within the threshold range. According to Table 1, the threshold for i=3 is 0.532 to 0.650, and since the rotation speed ratio R=0.55 is within the threshold range, the process proceeds to step S16. In step S16, the C setting unit 56 counts up the count value C of gear 3. Specifically, the count value C of gear 3 in Table 13 is changed from 9 to 10. In step S17, the count threshold comparator 57 compares the count value C of gear 3 with the count threshold (6 in this embodiment). Since 6≦C, the process proceeds to step S18. In step S18, the gear ratio setting unit 54 checks whether the gear ratio state of gear 3 is "excluded." As shown in Table 13, the gear ratio state of gear 3 is "provisional determination," so the process proceeds to step S19. In step S19, the gear ratio state of gear 3 is already "provisional determination," so nothing is done and the process proceeds to step S21. In step S21, the i setting unit 55 counts up i, and the process returns to step S13.

[0057] In step S13, the i comparison unit 52 compares i with Ngear. Since i=4, the process proceeds to step S14. In step S14, the threshold comparison unit 53 checks whether the rotation speed ratio R=0.55 is within the threshold range. According to Table 1, the threshold for i=4 is 0.470 to 0.575, and since the rotation speed ratio R=0.55 is within the threshold range, the process proceeds to step S16. In step S16, the C setting unit 56 counts up the count value C of gear 4. Specifically, the count value C of gear 4 in Table 14 is changed from 0 to 1. In step S17, the count threshold comparator 57 compares the count value C of gear 4 with the count threshold (6 in this embodiment). Since C<6, the process proceeds to step S15. In step S15, the gear ratio setting unit 54 checks whether the gear ratio state of gear 4 is "provisional" or "determined." As shown in Table 14, the gear ratio state of gear 4 is "undetermined," so the process proceeds to step S21. In step S21, the i setting unit 55 counts up i, and the process returns to step S13.

[0058] Since i=5 to 9 are the same as the case of i=1 described above, in step S21 the i setting unit 55 counts up i and skips to i=10.

[0059] In step S13, the i comparison unit 52 compares i with Ngear. Since i=10, the process proceeds to step S22. In step S22, the i setting unit 55 resets i=1, and then the process proceeds to step S23. In step S23, the gear ratio setting unit 54 checks whether there is one or more gear ratio states that are "provisional" or "confirmed" among the gear ratio states of all gears. As shown in Table 14, the gear ratio state of gear 3 is "provisional," so the process proceeds to step S25. In step S25, the gear ratio setting unit 54 checks whether there is one "provisional" gear ratio state and whether the gear ratio states above and below this state are "excluded." As shown in Table 14, there is only one gear whose gear ratio state is "provisional judgment", that is, gear 3, and the gear ratio state of gear 2 above gear 3 is "excluded", and the gear ratio state of gear 4 below gear 3 is "undetermined", so the process returns to step S11.

[0060] Similarly, at the subsequent vehicle speed change timings (when the 11 / 12, 12 / 12, 1 / 12, and 2 / 12 vehicle speed pulses arrive), as shown in Table 15, the C setting unit 56 counts up the count value C for gears 3 and 4.

[0061] The flow for each vehicle speed change timing (11 / 12, 12 / 12, 1 / 12, 2 / 12 vehicle speed pulse) is the same as that described above, so in step S16 of the loop for the vehicle speed change timing (3 / 12 vehicle speed pulse), as shown in Table 16, skip is made until the count value C for gear 4 becomes 6.

[0062] In step S17, the count threshold comparator 57 compares the count value C of gear 4 with the count threshold (6 in this embodiment). Since 6≦C, the process proceeds to step S18. In step S18, the gear ratio setting unit 54 checks whether the gear ratio state of gear 4 is "excluded." As shown in Table 16, the gear ratio state of gear 4 is "undetermined," so the process proceeds to step S19. In step S19, as shown in Table 17, the gear ratio setting unit 54 changes the gear ratio state of gear 4 from "undetermined" to "provisional determination." In step S21, the i setting unit 55 counts up i, and the process returns to step S13.

[0063] Since i=5 to 9 are the same as when i=4 in the first embodiment, in step S21 the i setting unit 55 counts up i and skips to i=10.

[0064] In step S13, the i comparison unit 52 compares i with Ngear. Since i=10, the process proceeds to step S22. In step S22, the i setting unit 55 resets i=1, and then the process proceeds to step S23. In step S23, the gear ratio setting unit 54 checks whether there is at least one gear ratio state that is "provisional" or "confirmed" among the gear ratio states of all gears. As shown in Table 17, the gear ratio states of gears 3 and 4 are "provisional," so the process proceeds to step S25. In step S25, the gear ratio setting unit 54 checks whether there is one "provisional" gear ratio state and whether the gear ratio states above and below this gear ratio state are "excluded." As shown in Table 17, there are two gears, gears 3 and 4, that are in the "provisional" gear ratio state, so the process returns to step S11. In Example 2, the gear ratio state is not confirmed, and both gears 3 and 4 are in the provisionally determined state. As a result, by provisionally determining both of the adjacent gear ratios (gears 3 and 4) as candidates, the risk of erroneous determination can be reduced.

[0065] In Example 3, when the rotation speed ratio changes from the state in Example 2 (R = 0.55) to R = 0.63, and the first vehicle speed pulse arrives after the change, gear 4 deviates from the threshold (NO in step S14). Because gear 4 was provisionally determined (YES in step S15), gear 4 is "excluded" (step S20). At this time, gear 3 has not yet been "excluded," and gear 3 is the only provisionally determined or confirmed gear ratio (YES in step S23). Because gears 2 and 4 above and below gear 3 have been "excluded," gear 3 is "confirmed" (YES in step S25). A detailed description will be given below with reference to the flowchart.

[0066] In step S11, the rotation speed calculation unit 51 receives a signal indicating the rotation speed of the wheel (rear wheel 3) from the first sensor 5 and detects the timing of a vehicle speed change (whether a 4 / 12 vehicle speed pulse has arrived). At the timing of the vehicle speed change (when a 4 / 12 vehicle speed pulse has arrived), in step S12, the rotation speed calculation unit 51 calculates the rotation speed ratio R based on the signal from the first sensor 5 and the signal indicating the motor rotation speed from the second sensor 6. In the third embodiment, the rotation speed ratio R is assumed to be 0.63.

[0067] In step S13, the i comparison unit 52 compares i with Ngear. Since i=1, the process proceeds to step S14. In step S14, the threshold comparison unit 53 checks whether the rotation speed ratio R=0.63 is within the threshold range. According to Table 1, the threshold for i=1 is 0.736 to 0.900, and since the rotation speed ratio R=0.63 is not within the threshold range, the process proceeds to step S15. In step S15, the gear ratio setting unit 54 checks whether the gear ratio state of gear 1 is "provisionally determined" or "determined." As shown in Table 17, the gear ratio state of gear 1 is "undetermined," so the process proceeds to step S21. In step S21, the i setting unit 55 counts up i and returns to step S13.

[0068] In step S13, the i comparison unit 52 compares i with Ngear. Since i=2, the process proceeds to step S14. In step S14, the threshold comparison unit 53 checks whether the rotation speed ratio R=0.63 is within the threshold range. According to Table 1, the threshold for i=2 is 0.614 to 0.750, and since the rotation speed ratio R=0.63 is within the threshold range, the process proceeds to step S16. In step S16, the C setting unit 56 counts up the count value C of gear 2. Specifically, the count value C of gear 2 in Table 18 is changed from 0 to 1. In step S17, the count threshold comparator 57 compares the count value C of gear 2 with the count threshold (6 in this embodiment). Since C<6, the process proceeds to step S15. In step S15, the gear ratio setting unit 54 checks whether the gear ratio state of gear 2 is "provisional" or "determined." As shown in Table 18, the gear ratio state of gear 2 is "exclusion," so the process proceeds to step S21. In step S21, the i setting unit 55 counts up i and returns to step S13.

[0069] In step S13, the i comparison unit 52 compares i with Ngear. Since i=3, the process proceeds to step S14. In step S14, the threshold comparison unit 53 checks whether the rotation speed ratio R=0.63 is within the threshold range. According to Table 1, the threshold for i=3 is 0.532 to 0.650, and since the rotation speed ratio R=0.63 is within the threshold range, the process proceeds to step S16. In step S16, the C setting unit 56 counts up the count value C of gear 3. Specifically, the count value C of gear 3 in Table 19 is changed from 15 to 16. In step S17, the count threshold comparator 57 compares the count value C of gear 3 with the count threshold (6 in this embodiment). Since 6≦C, the process proceeds to step S18. In step S18, the gear ratio setting unit 54 checks whether the gear ratio state of gear 3 is "excluded." As shown in Table 19, the gear ratio state of gear 3 is "provisional determination," so the process proceeds to step S19. In step S19, the gear ratio state of gear 3 is already "provisional determination," so nothing is done and the process proceeds to step S21. In step S21, the i setting unit 55 counts up i and returns to step S13.

[0070] In step S13, the i comparison unit 52 compares i with Ngear. Since i=4, the process proceeds to step S14. In step S14, the threshold comparison unit 53 checks whether the rotation speed ratio R=0.63 is within the threshold range. According to Table 1, the threshold for i=4 is 0.470 to 0.575, and since the rotation speed ratio R=0.63 is not within the threshold range, the process proceeds to step S15. In step S15, the gear ratio setting unit 54 checks whether the gear ratio state of gear 4 is "provisional" or "definite." As shown in Table 19, the gear ratio state of gear 4 is "provisional," so the process proceeds to step S20. In step S20, as shown in Table 20, the gear ratio setting unit 54 changes the gear ratio state of gear 4 from "provisional" to "exclude," and the C setting unit 56 resets the count value C (to zero). In step S21, the i setting unit 55 counts up i, and the process returns to step S13.

[0071] Since i=5 to 9 are the same as the case of i=1 described above, in step S21 the i setting unit 55 counts up i and skips to i=10.

[0072] In step S13, the i comparison unit 52 compares i with Ngear. Since i=10, the process proceeds to step S22. In step S22, the i setting unit 55 resets i=1, and then the process proceeds to step S23. In step S23, the gear ratio setting unit 54 checks whether there is at least one gear ratio state that is "provisional" or "confirmed" among the gear ratio states of all gears. As shown in Table 20, the gear ratio state of gear 3 is "provisional," so the process proceeds to step S25. In step S25, the gear ratio setting unit 54 checks whether there is one gear ratio state that is "provisional," and whether the gear ratio states above and below this gear ratio state are "excluded." As shown in Table 20, there is only one gear that is in a "provisional" gear ratio state, gear 3, and the gear ratio state of gear 2 above gear 3 is "excluded," and the gear ratio state of gear 4 below gear 3 is also "excluded," so the process proceeds to step S26. In step S26, as shown in Table 21, the gear ratio setting unit 54 changes the gear ratio state of gear 3 from "provisional" to "determined." In this way, in the third embodiment, it is possible to determine with high accuracy that the current gear ratio is gear 3.

[0073] The control device 50 determines that the gear ratio is set when the rotation speed ratio R is within the threshold range of Table 1 for a predetermined period (the time it takes for the wheels (rear wheels 3) to make one rotation). However, the gear ratio state determination process continues even after the determination. If the driver changes the gear ratio, the gear ratio determined before the change no longer satisfies equation (1). At this time, the control device 50 detects that the gear ratio has been changed and limits the motor output. After the motor output has been limited, if it is determined that the predetermined gear ratio is set according to the gear ratio state determination process, the control device 50 releases the limit on the motor output.

[0074] To summarize the first to third embodiments, the control device 50 is configured as follows. Based on a signal indicating the rotation speed of the wheels from the first sensor and a signal indicating the rotation speed of the motor from the second sensor, the rotation speed ratio R is calculated according to Equation (1) (steps S11 and S12). If the rotation speed ratio R for one or more of all the gear ratios (gears 1 to 9) is within the threshold range for a predetermined number of times (count threshold, 6 in this embodiment) or more (step S17), one or more gear ratios are provisionally determined (step S19). If the rotation speed ratio R for a provisionally determined gear ratio is no longer within the threshold range (step S15), the gear ratio is excluded (step S20). If both gear ratios adjacent to a provisionally determined gear ratio are excluded (step S25), the provisionally determined gear ratio is determined to be the correct gear ratio (step S26).

[0075] FIG. 8(a) is a simulation diagram illustrating gear shift detection and motor control for an electrically assisted bicycle. The vertical axis represents the gear determination status in the software in terms of voltage output, and the horizontal axis represents time. "Uncoupled" refers to cases where assist output is suppressed at the beginning of pedaling or when a gear change is detected and the assist output is suppressed. As shown in FIG. 8(a), the time ta from shifting from gear 9 to gear 8 and completing the above-described gear ratio state determination process until gear 8 is confirmed is longer than the time tb from shifting from gear 8 to gear 7 and confirming gear 7. A similar magnitude relationship holds, with the time tc from shifting from gear 2 to gear 1 and confirming gear 1 being the shortest. This is because heavier gears have a smaller difference in the number of teeth between the upper and lower gears, and therefore take longer to confirm the gear than lighter gears. For example, as shown in Table 1, gear 9 has 11 teeth and gear 8 has 13 teeth, so the difference in the number of teeth between gears 9 and 8 is 2, while gear 2 has 30 teeth and gear 1 has 36 teeth, so the difference in the number of teeth between gears 2 and 1 is 6. Note that the time taken to change from gear 9 to gear 8 and to be fixed as gear 8 is the same as the time taken to change from gear 8 to gear 9 and to be fixed as gear 9.

[0076] FIG. 8( b ) is an enlarged simulation diagram of the portion of FIG. 8( a ) in which gear 9 is changed to gear 8, and gear 8 is confirmed through the gear ratio state determination process shown in FIG. 7 . Immediately after gear 9 is changed to gear 8, the assist output is suppressed. Next, gear 8 is tentatively determined, and the voltage output becomes the voltage level of gear 8. Next, gears 8 and 7 are tentatively determined, and the voltage output becomes the voltage level between gears 8 and 7. Next, gear 7 is excluded, and only gear 8 is tentatively determined, so the voltage output becomes the voltage level of gear 8. Next, gear 9 is also tentatively determined, and since gears 8 and 9 are tentatively determined, the voltage output becomes the voltage level between gears 8 and 9. Finally, gear 9 is excluded, gear 8 is confirmed, and the voltage output becomes the voltage level of gear 8.

[0077] 8(c) is an enlarged simulation diagram of the portion of FIG. 8(a) in which gear 2 is changed to gear 1, and gear 1 is confirmed through the gear ratio state determination process shown in FIG. 7. Immediately after changing from gear 2 to gear 1, the assist output is suppressed. Next, gear 1 is tentatively determined, and the voltage output becomes the voltage level of gear 1. As described above, since there is a large difference in the number of teeth between gears 2 and 1, the determination is not ambiguous.

[0078] 1...electrically assisted bicycle, 2...first wheel (front wheel), 3...second wheel (rear wheel), 4...pedal, 5...first sensor, 6...second sensor, 8...crank (front), 9...(rear) gear sprocket, 50...control device, 50a...control circuit, 50b...drive circuit, 51...rotation speed calculation unit, 52...i comparison unit, 53...threshold comparison unit, 54...gear ratio setting unit, 55...i setting unit, 56...C setting unit, 57...count threshold comparison unit, 58...drive control signal generation unit, 100...rotation device (MDU: motor drive unit)

Claims

1. The time from when the gear ratio is changed from the first gear ratio to the second gear ratio until the assist of the pedal corresponding to the second gear ratio starts is different from the time from when the gear ratio is changed from the third gear ratio to the fourth gear ratio until the assist of the pedal corresponding to the fourth gear ratio starts, an electric assist bicycle.

2. A rotating device having a wheel, a control device, a speed reducer, and a motor for assisting the pedal, a first sensor for detecting the rotational speed of the wheel, and a second sensor for detecting the rotational speed of the motor, and N ｗ is the rotational speed [rpm] of the wheel, N ｍ is the rotational speed [rpm] of the motor, gr ＭＤＵ is defined as the reduction ratio of the rotating device, and Equation (1) is defined as: N ｍ / (gr ＭＤＵ ·N ｗ ) Equation (1) The control device determines whether the magnitude of Equation (1) is included within a predetermined range corresponding to the reduction ratio. The electric assist bicycle according to claim 1.

3. An electric assist bicycle comprising a control device, wherein the time from when the stopped control device is activated until the assist of the pedal corresponding to the gear ratio starts is longer than the time from when the gear ratio is changed until the assist of the pedal corresponding to the changed gear ratio starts.

4. A rotating device having a wheel, a speed reducer, and a motor for assisting the pedal, a first sensor for detecting the rotational speed of the wheel, and a second sensor for detecting the rotational speed of the motor, N ｗ Let N be the rotational speed [rpm] of the wheel, N ｍ let gr be the rotational speed [rpm] of the motor, ＭＤＵ define Equation (1) using the reduction ratio of the rotating device, N ｍ / (gr ＭＤＵ · N ｗ ) Equation (1) The control device determines whether the magnitude of Equation (1) is included within a predetermined range corresponding to the reduction ratio. The electric assist bicycle according to claim 3.

5. The electric assist bicycle according to any one of claims 1 to 4, wherein the time until the assist of the pedal corresponding to the gear ratio starts is within the time taken for one rotation of the wheel.

6. The control device calculates the ratio of the rotational speeds according to formula (1) based on the signal indicating the rotational speed of the wheel from the first sensor and the signal indicating the rotational speed of the motor from the second sensor, and for one or more of all the gear ratios, when the ratio of the rotational speeds is within the threshold range a predetermined number of times or more, tentatively determines the one or more gear ratios, and for a gear ratio that has been tentatively determined, when the ratio of the rotational speeds is no longer within the threshold range, excludes the gear ratio, and when both of the two gear ratios adjacent to the tentatively determined one gear ratio are excluded, determines the tentatively determined one gear ratio as the gear ratio. The electric assist bicycle according to claim 2 or 4.

7. A method for determining the gear ratio of an electric assist bicycle, comprising a first step of determining a candidate for the predetermined gear ratio before the elapse of a first period after the change to the predetermined gear ratio, and a second step of determining the predetermined gear ratio from the candidates for the predetermined gear ratio after the elapse of the first period and before the elapse of a second period.

8. The electric assist bicycle includes a rotating device having a wheel, a control device, a speed reducer, and a motor for assisting the pedals, a first sensor for detecting the rotational speed of the wheel, and a second sensor for detecting the rotational speed of the motor, and N ｗ Let N be the rotational speed [rpm] of the wheel, and N ｍ Let N be the rotational speed [rpm] of the motor, and gr ＭＤＵ Let gr be the reduction ratio of the rotating device, and define Equation (1): N ｍ / (gr ＭＤＵ · N ｗ ) Equation (1) In the first step, the control device determines one or more numerical ranges including the reduction ratio calculated by Equation (1) among the numerical ranges corresponding to a plurality of reduction ratios, and one or more reduction ratios corresponding to the one or more numerical ranges are candidates for the predetermined reduction ratio. The method for determining the reduction ratio of the electric assist bicycle according to claim 7.

9. The method for determining the gear ratio of an electric assist bicycle according to claim 7 or 8, wherein the period including the first period and the second period is within the time taken for one rotation of the wheel.

Images