Electric-assist bicycle

Abstract

To provide an electric assist bicycle capable of providing appropriate assistance. [Solution] The electric assist bicycle 1 comprises wheels 2 and 3, a control device 50, pedals 4, a rotating device 70 having a reduction gear 10 and a motor 40 that assists pedals 4, a first sensor 5 that detects the rotation speed of wheels 2 and 3, a second sensor 6 that detects the rotation speed of motor 40, and a fifth sensor 9 that detects the rotation speed of pedals 4. The control device 50 determines the gear ratio Gr of wheels 2 and 3 based on the rotation speed Nw of wheels 2 and 3, the rotation speed Nm of motor 40, and the reduction ratio grMDU of the rotating device 70. When the rotation speed Np of pedals 4 decreases and falls below the first rotation speed Npg1, the assist to pedals 4 is released. When the rotation speed Np of pedals 4 increases and exceeds the second rotation speed Npg2, the assist to pedals 4 is started, and the assist is started based on the changed gear ratio Gr between the release and start of the assist.

Description

[Technical Field]

[0001] This invention relates to an electric assist bicycle. [Background technology]

[0002] Electric assist bicycles are known that determine whether assistance is needed based on the pedaling force applied, and if assistance is needed, rotate the motor to provide assistance to the electric assist bicycle (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-90109 [Overview of the project] [Problems that the invention aims to solve]

[0004] In bicycles, including electric assist bicycles, when the pedal rotation speed is slower than the vehicle speed, such as when riding downhill, the pedals will spin freely, and the pedal rotation will not generate propulsion. In such cases, in electric assist bicycles, it is preferable that the motor does not provide assistance because the force the rider exerts on the pedals is not generating propulsion. However, when a strain-type torque sensor is used to detect pedaling force, pedaling force is detected even when pedaling downhill, so assistance may be generated when the pedal rotation speed is slower than the vehicle speed. For these reasons, appropriate assistance is required in electric assist bicycles.

[0005] Therefore, one of the objectives of the present invention is to provide an electric assist bicycle capable of providing appropriate assistance. [Means for solving the problem]

[0006] (1): The present invention comprises: a wheel; a control device; a pedal; a rotating device having a speed reducer and a motor that assists the pedal; a sensor that detects the rotation speed of the wheel; a sensor that detects the rotation speed of the motor; and a sensor that detects the rotation speed of the pedal. The control device specifies the gear ratio of the wheel based on the rotation speed of the wheel, the rotation speed of the motor, and the reduction ratio of the rotating device. Assistance for the pedal is canceled when the rotation speed of the pedal decreases and falls below a first rotation speed, assistance to the pedal is started when the rotation speed of the pedal increases and exceeds a second rotation speed, and the assistance is started based on the changed gear ratio during a period from the cancellation of the assistance to the start of the assistance.

[0007] (2): In the electrically power-assisted bicycle according to (1), the motor may be driven while the pedal is rotating during the period from the cancellation of the assistance to the start of the assistance.

[0008] (3): In the electrically power-assisted bicycle according to (2), driving of the motor may be canceled after determination by the control device.

[0009] (4): In the electrically power-assisted bicycle according to (3), during a period when the pedal is rotating between the cancellation of the assistance and the start of the assistance, the motor rotates with a first driving force, and after the pedal reaches a predetermined rotation speed, the motor assists the pedal with a second driving force, wherein the first driving force of the motor may be smaller than the second driving force of the motor.

[0010] (5): In the electrically power-assisted bicycle according to (4), during the period from the cancellation of the assistance to the start of the assistance, the motor is started with a third driving force, and the motor started with the third driving force rotates with the first driving force, wherein the first driving force and the second driving force may be smaller than the third driving force.

[0011] (6): In any of the electric assist bicycles described in (1) to (5), when the rotation speed of the pedal decreases and falls below a first rotation speed, the assist to the pedal is released, and when the rotation speed of the pedal increases and exceeds a second rotation speed, the assist to the pedal is started, and the first rotation speed and the second rotation speed are collectively referred to as the target rotation speed Npg, the number of teeth on the sprocket of the electric assist bicycle 1 is nsi, the number of teeth on the chainring of the electric assist bicycle 1 is nc, and the rotation speed of the wheel of the electric assist bicycle is Nw, the following formula (1) may be used to obtain the target rotation speed. Npg=k(n s i / n c )Nw···(1) (k=k1 (when the first rotational speed Npg1)) (k=k2(>k1)(in the case of the second rotational speed Npg2))

[0012] (7) In any of the electric assist bicycles described in (1) to (6), the aforementioned wheel may be designated as the first wheel, and a second wheel may be provided, wherein the gear ratio of the aforementioned wheel may be the ratio of the rotation speed of the second wheel to the rotation speed of the first wheel. [Brief explanation of the drawing]

[0013] [Figure 1] This is a side view showing an example of an electric assist bicycle according to an embodiment of the present invention. [Figure 2] Figure 1 is a block diagram showing the configuration of the control device, sensors, and motor of the electric assist bicycle. [Figure 3] Figure 2 shows an example of a table stored in the memory unit of the control device shown in Figure 2. [Figure 4] Figure 1 is a flowchart showing an example of the control flow by the control device installed in the electric assist bicycle. [Figure 5] This block diagram shows the functional configuration of the fourth computing unit in the electric assist bicycle shown in Figure 2. [Figure 6(a)]Figure 2 is a flowchart illustrating a part of the control system for the electric assist bicycle shown. [Figure 6(b)] This is a timing diagram to explain this control. [Figure 7] Figure 2 is a timing diagram illustrating other controls for the electric assist bicycle shown. [Figure 8] Figure 2 is a timing diagram illustrating other controls for the electric assist bicycle shown. [Figure 9] Figure 2 is a flowchart illustrating the gear ratio state determination process in an electric assist bicycle. [Figure 10(a)] Figure 2 is a diagram illustrating the detection and motor control during gear changes in an electric assist bicycle. [Figure 10(b)] This is an enlarged view of the part of Figure 10(a) where the gear changes from gear 9 to gear 8, and then, after the gear ratio state determination process shown in Figure 9, the gear is determined to be 8. [Figure 10(c)] This is an enlarged view of the part of Figure 10(a) where the gear changes from gear 2 to gear 1, and then, after the gear ratio state determination process shown in Figure 9, the gear is finalized as gear 1. [Figure 11] Figure 4 is a flowchart showing the gear update flow. [Modes for carrying out the invention]

[0014] The following examples illustrate embodiments for implementing the electric assist bicycle according to the present invention, along with the accompanying drawings. The embodiments illustrated below are provided to facilitate understanding of the present invention. This is not intended to limit the interpretation of the invention. The present invention can be modified and improved from the following embodiments without departing from its spirit. In addition, in the above-mentioned attached drawings, the dimensions of each component may be exaggerated or reduced, or hatching may be omitted, in order to facilitate understanding.

[0015] Figure 1 is a side view showing an electric assist bicycle according to the first embodiment. As shown in Figure 1, the electric assist bicycle 1 includes a frame F, a handle H, a saddle S, a transmission body TC, a chainring CR, a sprocket SP, a battery B, a motor drive unit (MDU) 100 as a rotating device (hereinafter referred to as "MDU100"), wheels (front wheel 2 and rear wheel 3), and pedals 4. The chainring CR is a gear that rotates together with the pedals 4 under predetermined conditions (for example, when the driving force of the MDU100 is transmitted to the pedals 4), and in this embodiment, it includes a single gear. The sprocket SP is attached to the rear wheel 3 and is configured as a multi-stage gear with multiple gears stacked on top of each other. That is, the sprocket SP has i gears (where i is a natural number of 2 or more). Therefore, the electric assist bicycle 1 has a gear ratio Gr corresponding to each gear of the sprocket SP. This gear ratio Gr will be described in detail later. The transmission unit TC spans the gears of the chainring CR and the gears of the sprocket SP. The MDU 100 includes a motor 40 and a control device 50 that controls the drive of the motor 40 in order to provide assistance to the electric assist bicycle 1.

[0016] When the rider sits on the saddle S of the electric assist bicycle 1 and pedals 4 to rotate the pedals 4, under predetermined conditions, driving force is transmitted to the wheels (typically the rear wheels 3) via the chainring CR, sprocket SP, and transmission TC, enabling forward movement. At this time, under predetermined conditions, the motor 40 of the MDU 100 rotates based on the control of the control device 50, and the force required by the rider to pedal 4 is reduced (assisted) by the rotation of this motor 40. The transmission TC may be a chain or a belt.

[0017] A first sensor 5 is positioned near the rotation axis of either the front wheel 2 or the rear wheel 3, for example, to detect the rotational speed Nw (rpm) of the wheels (front wheel 2 and rear wheel 3) and the vehicle speed Vb (km / h) of the electric assist bicycle 1. In this specification, "detecting the wheel rotation speed Nw (rpm) and the vehicle speed Vb (km / h) of the electric assist bicycle 1" may mean that the first sensor 5 itself calculates the wheel rotation speed Nw (rpm) and the vehicle speed Vb (km / h), or that the first sensor 5 outputs the necessary signals to the control device 50 to calculate the wheel rotation speed Nw (rpm) and the vehicle speed Vb (km / h), and the control device 50 calculates the wheel rotation speed Nw (rpm) and the vehicle speed Vb (km / h), or that the first sensor 5 outputs the necessary signals to another calculation device (not shown), and the calculation device that receives the output signals calculates the wheel rotation speed Nw (rpm) and the vehicle speed Vb (km / h) of the electric assist bicycle 1 and outputs them to the control device 50. Figure 1 shows an example in which the first sensor 5 is placed near the rotation axis of the rear wheel 3. As the first sensor 5, a known sensor capable of detecting the wheel rotation speed Nw (rpm) and the vehicle speed Vb (km / h) of the electric assist bicycle 1, or capable of outputting signals necessary to calculate the wheel rotation speed Nw (rpm) and the vehicle speed Vb (km / h) of the electric assist bicycle 1, can be used. The first sensor 5 may be, for example, a magnetic sensor or Hall sensor capable of detecting the wheel rotation speed Nw (rpm) and the vehicle speed Vb (km / h) of the electric assist bicycle 1, or an optical sensor capable of detecting the wheel rotation speed Nw (rpm) and the vehicle speed Vb (km / h) of the electric assist bicycle 1. Furthermore, the position in which the first sensor 5 is placed may be any position in which the wheel rotation speed Nw (rpm) and the vehicle speed Vb (km / h) of the electric assist bicycle 1 can be detected, for example, it may be placed at a position away from the rotation axis of the front wheel 2 or the rear wheel 3.

[0018] Furthermore, a fourth sensor 8 is positioned near the rotation axis of either the front wheel 2 or the rear wheel 3, for example, to detect a predetermined rotation angle An(deg) of the wheel. In this specification, "detecting a predetermined rotation angle An(deg) of the wheel" may mean that the fourth sensor 8 itself calculates the predetermined rotation angle An(deg) of the wheel, or that the fourth sensor 8 outputs a signal necessary to calculate the predetermined rotation angle An(deg) of the wheel to the control device 50, and the control device 50 calculates the predetermined rotation angle An(deg), or that the fourth sensor 8 outputs a signal necessary to calculate the predetermined rotation angle An(deg) of the wheel to another calculation device (not shown), and the calculation device that receives the output signal calculates the predetermined rotation angle An(deg) of the wheel and outputs it to the control device 50. Figure 1 shows an example in which the fourth sensor 8 is positioned near the rotation axis of the rear wheel 3. As the fourth sensor 8, a known sensor capable of detecting a predetermined rotation angle An(deg) of the wheel and outputting a signal necessary to calculate a predetermined rotation angle An(deg) of the wheel can be used. The fourth sensor 8 may be, for example, a magnetic sensor or Hall sensor capable of detecting a predetermined rotation angle An(deg) of the wheel, or an optical sensor capable of detecting a predetermined rotation angle An(deg) of the wheel. Furthermore, the position in which the fourth sensor 8 is placed may be any position in which the predetermined rotation angle An(deg) of the wheel can be detected, for example, it may be placed at a position away from the rotation axis of the front wheel 2 or the rear wheel 3.

[0019] In this embodiment, the fourth sensor 8 outputs a signal Sa to the fourth calculation unit 1540 of the control device 50, which will be described later, each time the wheel (e.g., the rear wheel 3) rotates by a predetermined rotation angle An(deg). That is, the fourth sensor 8 outputs a signal Sa to the fourth calculation unit 1540 of the control device 50 indicating that the wheel has rotated by a predetermined rotation angle An(deg). The predetermined rotation angle An(deg) is not particularly limited, but may be, for example, 30°, 120°, 90°, 60°, 45°, 15°, 10°, or any predetermined angle selected from the range of 1° to 360°.

[0020] Furthermore, the first sensor 5 and the fourth sensor 8 may be used as a common sensor.

[0021] Furthermore, in this embodiment, the electric assist bicycle 1 is equipped with a fifth sensor 9 that detects the actual rotation speed Np (rpm) of the pedal 4. The fifth sensor 9 is not particularly limited as long as it is capable of detecting the rotation speed Np (rpm) of the pedal 4, but in this embodiment, a cadence sensor is used as the fifth sensor 9. For example, the fifth sensor 9 may have a magnet attached to the crank arm that connects the pedal 4 and the crank shaft 23, and a sensor attached to the frame F, and the rotation speed Np (rpm) of the pedal 4 may be detected by the sensor attached to the frame F detecting the magnetic force from the magnet attached to the crank arm. In this specification, "detecting the rotational speed Np (rpm) of pedal 4" may mean that the fifth sensor 9 itself calculates the rotational speed Np (rpm) of pedal 4; or that the fifth sensor 9 outputs a signal necessary to calculate the rotational speed Np (rpm) of pedal 4 to the control device 50, and the control device 50 calculates the rotational speed Np (rpm) of pedal 4; or that the fifth sensor 9 outputs a signal necessary to calculate the rotational speed Np (rpm) of pedal 4 to another calculation device (not shown), and the calculation device that receives the output signal calculates the rotational speed Np (rpm) of pedal 4 and outputs it to the control device 50. In this embodiment, the fifth sensor 9 outputs a signal indicating the rotational speed Np (rpm) of pedal 4 to a determination unit 56 of the control device 50, which will be described later.

[0022] The MDU 100 and battery B are typically located around the crankshaft 23 connected to the pedal 4. As shown in Figure 1, the MDU 100 includes a rotating device 70, a control device 50, and a housing 60. The housing 60 is fixed to, for example, the frame F of the electric assist bicycle 1 and houses the rotating device 70, the control device 50, etc. The rotating device 70 includes a motor 40, a reduction gear 10, and a third sensor 7 as a torque sensor. In Figure 1, the rotating device 70 and the control device 50 are housed within the housing 60 and are not visible, so they are shown with dashed lines. The control device 50 may be partially or entirely located outside the housing 60. Battery B supplies power to the motor 40 and the control device 50, and this power operates the motor 40 and the control device 50.

[0023] The motor 40 of the rotating device 70 is driven by the control device 50 and assists the rotation of the pedal 4 via the reduction gear 10. In this specification, "rotation of the pedal 4" refers to the rotation (revolution) of the pedal 4 around the crankshaft 23. In this specification, "assist" includes reducing the force (pedaling force) required to rotate the pedal 4 (pedal the pedal 4) by human power. The motor 40 is not particularly limited, but for example, it may be a brushless DC motor having coils corresponding to three phases (U phase, V phase, and W phase).

[0024] As shown in Figure 1, the motor 40 is equipped with a second sensor 6 for detecting the rotational speed Nm(rpm) of the motor 40's rotor (hereinafter simply referred to as "motor 40 rotational speed Nm(rpm)"). In this specification, "detecting the motor 40 rotational speed Nm(rpm)" may mean that the second sensor 6 itself calculates the motor 40 rotational speed Nm(rpm), or that the second sensor 6 outputs a signal necessary to calculate the motor 40 rotational speed Nm(rpm) to the control device 50, and the control device 50 calculates the motor 40 rotational speed Nm(rpm), or that the second sensor 6 outputs a signal necessary to calculate the motor 40 rotational speed Nm(rpm) to another calculation device (not shown), and that the calculation device, upon receiving the output signal, calculates the motor 40 rotational speed Nm(rpm) and outputs it to the control device 50. Figure 1 shows an example in which the second sensor 6 is mounted on the motor 40, but the position of the second sensor 6 is not particularly limited as long as it is in a position where the rotational speed Nm (rpm) of the motor 40 can be detected. As the second sensor 6, any known sensor capable of detecting the rotational speed Nm (rpm) of the motor 40, or capable of outputting a signal necessary to calculate the rotational speed Nm (rpm) of the motor 40, can be used. The second sensor 6 may be, for example, a magnetic sensor or Hall sensor capable of detecting the rotational speed Nm (rpm) of the motor 40, or an optical sensor capable of detecting the rotational speed Nm (rpm) of the motor 40.

[0025] As shown in Figure 1, the crankshaft 23 penetrates the inside of the housing 60 of the MDU 100. Pedals 4 are fixed to one end and the other end of the crankshaft 23 in the direction of extension (axial or longitudinal direction). The crankshaft 23 rotates as the pedals 4 are pedaled and rotated. The third sensor 7 described above is a strain-type torque sensor that detects the pedaling force Tf(N) applied to the pedals 4 by detecting the strain of the crankshaft 23 that has been deformed due to the pedaling force applied to the pedals 4. Therefore, when the third sensor 7 detects the strain of the crankshaft 23, the pedaling force applied to the pedals 4 is detected, and the control device 50 controls the drive of the motor 40 based on this pedaling force, etc.

[0026] In this specification, "detecting the pedaling force Tf(N) applied to the pedal 4" may mean that the third sensor 7 itself calculates the pedaling force Tf(N), or that the third sensor 7 outputs a signal necessary for calculating the pedaling force Tf(N) to the control device 50, and the control device 50 calculates the pedaling force Tf(N), or that the third sensor 7 outputs a signal necessary for calculating the pedaling force Tf(N) to another calculation device (not shown), and the calculation device that receives the signal calculates the pedaling force Tf(N) and outputs it to the control device 50. Furthermore, the third sensor 7 may be located on the pedal 4, on the crank arm connecting the pedal 4 and the crank shaft 23, on the housing 60 of the MDU 100, or on any other location. In the electric assist bicycle 1, the output of the motor 40 is adjusted according to the pedaling force Tf(N), etc., detected by the third sensor 7.

[0027] The reduction gear 10 of the rotating device 70 includes multiple gears, multiple shafts, and multiple clutches (one-way clutches), etc. With this configuration, the reduction gear 10 has a predetermined reduction ratio grMDU, and can reduce the rotation of the motor 40 based on this reduction ratio grMDU. A chainring CR is fixed to one of the multiple gears in the reduction gear 10. The multiple clutches of the reduction gear 10 include gears fixed to the chainring (hereinafter referred to as "output gears"). The multiple clutches of the reduction gear 10 are configured to transmit rotation in one direction (forward direction) of the pedal 4 (crankshaft 23) and not to transmit rotation in the other direction (reverse direction).

[0028] For example, when pedal 4 is rotated in the opposite direction (the opposite direction to the direction in which pedal 4 is rotated to move the electric assist bicycle 1 forward), the crankshaft 23 rotates in the opposite direction relative to the output gear. In this case, the rotation of pedal 4 (crankshaft 23) is not transmitted to the output gear. That is, since the rotation of pedal 4 (crankshaft 23) is not transmitted to the chainring CR fixed to the output gear, the wheels are prevented from rotating in response to pedaling 4, and the force (pedaling force) applied by the driver to pedal 4 is prevented from becoming the propulsion force of the electric assist bicycle 1. In this way, when pedal 4 (crankshaft 23) rotates in the opposite direction relative to the output gear, the clutch (one-way clutch) of the reduction gear 10 prevents the motor 40's assist from being transmitted to pedal 4. Note that "rotation in the opposite direction relative to the output gear" may be simply referred to as "rotation in the opposite direction" from now on.

[0029] On the other hand, when the rotational speed of pedal 4 (crankshaft 23) in the forward direction reaches a certain number of rotations, the clutch connects the crankshaft 23 and the output gear, causing the crankshaft 23 and the output gear to rotate synchronously and integrally in the forward direction (hereinafter, this may be referred to as "synchronous forward rotation"). In this way, the rotation of pedal 4 (crankshaft 23) is transmitted to the output gear. As a result, the chainring CR, which is fixed to the output gear, rotates, and the sprocket SP and the rotation axis of the rear wheel 3 are connected via a transmission member TC that spans the gear of the chainring CR and the gear of the sprocket SP, thereby transmitting the driving force from the rotation of pedal 4 to the rear wheel 3. In other words, when the rotational speed of pedal 4 (crankshaft 23) in the forward direction reaches a certain number of rotations, the clutch of the reduction gear 10 makes it possible to transmit the rotational force of the motor 40 to pedal 4, and the force required to press pedal 4 is reduced (assisted) under predetermined conditions. In cases where such synchronized forward rotation occurs, typically the rotational speed Np (rpm) of pedal 4 is obtained by multiplying the gear ratio Gr, which corresponds to the current gear position of sprocket SP, by the rotational speed Nw (rpm) of the wheel.

[0030] Furthermore, as shown in Figure 1, a clutch RC is provided on the rotation axis of the rear wheel 3. This clutch RC may be a one-way clutch such as a ratchet. The clutch RC is configured to transmit the rotation of the sprocket SP that rotates in the forward direction relative to the rotation direction of the rear wheel 3 to the rear wheel 3, but not the rotation of the sprocket SP that rotates in the opposite direction relative to the rotation direction of the rear wheel 3. As a result, when the wheel rotation speed Nw (rpm) increases, such as when driving downhill, the clutch RC disengages, preventing the pedal 4 from rotating quickly in accordance with the rapid rotation of the wheel. Also, when the wheel rotation speed Nw (rpm) increases, such as when driving downhill, the clutch RC of the rear wheel 3, described later, disengages, preventing the pedal 4 from rotating quickly in accordance with the rapid rotation of the wheel. As a result, the crankshaft 23 rotates in the opposite direction relative to the output gear. In this case as well, the rotation of the pedal 4 (crankshaft 23) is not transmitted to the output gear. Therefore, at the moment when the rotation of the sprocket SP, which rotates in the positive direction relative to the rotation direction of the rear wheel 3, is transmitted to the rear wheel 3, the metal members constituting the clutch RC of the rear wheel 3 come into contact with each other, and as a result, the rotational force of the pedal 4 and the rotational force of the motor 40 are transmitted to the rear wheel 3 via the chainring CR, sprocket SP, transmission body TC, and the clutch RC of the rear wheel 3.

[0031] Next, the control device 50 will be described in detail. Figure 2 is a block diagram showing the configuration of the control device 50, the first sensor 5, the second sensor 6, the third sensor 7, the fourth sensor 8, the fifth sensor 9, and the motor 40. As shown in Figure 2, the control device 50 includes a control circuit 50a and a drive circuit 50b. Note that the functions and configuration of the control device 50 shown in Figure 2 may be only a part of the overall functions and configuration of the control device 50. In other words, the control device 50 may include functions or configurations other than those shown in Figure 2.

[0032] The control circuit 50a is implemented by a program processing unit (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), A / D conversion circuit, D / A conversion circuit, clock generation circuit, and input / output I / F circuit are all connected to each other via a bus or dedicated line.

[0033] As shown in Figure 2, in this embodiment, the control circuit 50a includes, as a functional block, a first calculation unit 51, a second calculation unit 52, a third calculation unit 53, a fourth calculation unit 1540, an output adjustment unit 55, a determination unit 56, a memory unit 58, and a drive signal generation unit 59. The memory unit 58 may be all or part of the above-mentioned RAM, ROM, or other storage devices. The first calculation unit 51, the second calculation unit 52, the third calculation unit 53, the fourth calculation unit 1540, the determination unit 56, the output adjustment unit 55, and the drive signal generation unit 59 are realized, for example, in a program processing device as the control circuit 50a, by the processor executing various arithmetic processes according to various programs stored in the above-mentioned storage devices including the memory unit 58, and controlling peripheral circuits such as counters and A / D conversion circuits. In this embodiment, the various programs described above include a program that determines the current gear position of the sprocket SP (hereinafter sometimes referred to as "current gear") based on the rotational speed Nc (rpm) of the chainring CR and the rotational speed Nw (rpm) of the wheel (hereinafter sometimes referred to as "gear determination program"). The gear determination program will be described in detail later.

[0034] As described above, the second sensor 6 is, for example, a Hall sensor that detects the rotational speed Nm (rpm) of the motor 40. The gear determination program is configured to calculate the rotational speed Nc (rpm) of the chainring CR (i.e., the rotational speed Np (rpm) of the pedal 4) by multiplying the rotational speed Nm (rpm) of the motor 40 by the reciprocal of the reduction ratio grMDU of the reduction gear 10, and then determine the current gear based on the calculated rotational speed Nc (rpm) of the chainring CR and the rotational speed Nw (rpm) of the wheel.

[0035] In the present embodiment, in addition to the above-described program, the storage unit 58 stores data of the reduction ratio grMDU of the speed reducer 10 (hereinafter may be referred to as "reduction ratio data"), a table T of the gear ratio Gr of the electrically power assisted bicycle 1, data indicating the current gear, and the like. Note that the control circuit 50a may also have other functional blocks.

[0036] Here, the table T of the gear ratio Gr will be described. Figure 3 is a diagram showing an example of the table T. As described above, in the present embodiment, the chain ring CR includes a 1-speed gear, and the sprocket SP has an i-speed gear. Therefore, the number of teeth n of the chain ring CR c is a constant, and the number of teeth n of the sprocket SP s i varies depending on the gear stage (1st to i-th) of the sprocket SP. Here, the number of teeth of the sprocket SP when the sprocket SP is in the 1st gear is n s 1 and the number of teeth of the sprocket SP when the sprocket SP is in the 2nd gear is n s 2 and the number of teeth of the sprocket SP when the sprocket SP is in the 3rd gear is n s 3 and the number of teeth of the sprocket SP when the sprocket SP is in the i-th gear is n s i In the present embodiment, the gear ratio Gr of the electrically power assisted bicycle 1 is defined by the following formula (A). Gr = n s i / n c ...(A) As shown in Figure 3, in the table T, for each of the gear stages (1st to i-th) of the sprocket SP gear ratio Gr data based on formula (A) is associated therewith.

[0037] The gear ratio Gr may also be the ratio of the rotation speed of the second wheel to the rotation speed of the first wheel, assuming that the rear wheel 3 is the first wheel among wheels 2 and 3, and the front wheel 2 is the second wheel among wheels 2 and 3. Hereafter, the gear ratio Gr (wheel gear ratio Gr) of the electric assist bicycle 1 will be simply referred to as "gear ratio Gr".

[0038] As shown in Figure 2, the control circuit 50a receives signals output from the following: the first sensor 5, which detects the wheel rotation speed Nw and the vehicle speed Vb of the electric assist bicycle 1; the second sensor 6, which detects the rotor rotation speed Nm of the motor 40; the third sensor 7, which acts as a torque sensor; the fourth sensor 8, which detects a predetermined rotation angle An of the wheel; and the fifth sensor 9, which detects the rotation speed Np of the pedal 4. The first calculation unit 51 calculates the wheel rotation speed Nw (rpm) based on the signal input from the first sensor 5.

[0039] The third calculation unit 53 calculates the pedaling force Tf(N) applied to the pedal 4 based on the signal input from the third sensor 7, which is a strain-type torque sensor. Furthermore, based on the wheel rotation speed Nw(rpm) and vehicle speed Vb(km / h) calculated by the first calculation unit 51, it calculates the torque command value Tm(Nm), which is the target value for causing the motor 40 to exert a predetermined torque.

[0040] The second calculation unit 52 calculates the rotational speed Nm(rpm) of the motor 40 based on the signal input from the second sensor 6 (i.e., the signal indicating the rotational speed Nm(rpm) of the motor 40), and calculates the rotational speed Nc(rpm) of the chainring CR (i.e., the rotational speed Np(rpm) of the pedal 4) based on the calculated rotational speed Nm(rpm) of the motor 40 and the reduction ratio data stored in the memory unit 58 (data on the reduction ratio grMDU of the reduction gear 10). The rotational speed Nc(rpm) of the chainring CR is equal to the value obtained by multiplying the rotational speed Nm(rpm) of the motor 40 by the reciprocal of the reduction ratio grMDU of the reduction gear 10. Therefore, the second calculation unit 52 calculates the rotational speed Nc(rpm) of the chainring CR based on the following equation (B). Nc=Nm / grMDU...Formula (B)

[0041] Incidentally, a sensor that detects the rotational speed Nm (rpm) of the motor 40 (typically a Hall sensor) can sometimes detect the rotation angle with higher accuracy than a sensor that directly detects the rotational speed Np (rpm) of the pedal (crankshaft). Therefore, by calculating the rotational speed Np (rpm) of pedal 4 using equation (B), it is possible to obtain data on the rotational speed Np (rpm) of pedal 4 with higher accuracy (for example, at the time intervals desired for use in the software). One case in which the rotational speed can be obtained more accurately using a sensor that detects the rotational speed Nm (rpm) of the motor 40 is that, in the case of a sensor that directly detects the rotational speed Np (rpm) of the pedal, the distance between the magnet on the shaft connecting both pedals 4 and the magnetic sensor may change slightly due to the effect of the shaft being distorted by the pedaling force. On the other hand, since the sensor that detects the rotational speed Nm (rpm) of the motor 40 is fixed in the same position relative to the rotor of the motor 40, it is possible to obtain a substantially accurate magnetism at all times using the sensor that detects the rotational speed Nm (rpm) of the motor 40. Another case is the influence of the power of the rotating body being detected. In other words, in a sensor that detects the rotational speed Nm (rpm) of motor 40, the power source of the motor 40, which is the rotating body being detected, is electric, whereas in a sensor that directly detects the rotational speed Np (rpm) of the pedal, the power source of the rotating body being detected is human power. For example, if the detection period is 1 ms, the fluctuations per detection period will be smaller with electricity than with human power, making it usable as data within the software.

[0042] The fourth calculation unit 1540 receives a signal Sa from the fourth sensor 8 indicating the rotation angle An of the wheel, and uses the rotation speed Nc (rpm) of the chainring CR calculated by the second calculation unit 52 based on equation (B), and the rotation speed Nw (rpm) of the wheel calculated by the first calculation unit 51. Based on this, the current stage is determined using the stage determination program described later. The fourth calculation unit 1540 stores the data indicating the determined current stage in the storage unit 58. As a result, the data indicating the current stage that was already stored in the storage unit 58 is overwritten (updated) with the data calculated by the fourth calculation unit 1540.

[0043] When the signal Sa is input to the fourth calculation unit 1540 for the first time during one cycle of the control steps described later, and the current gear is calculated by the fourth calculation unit 1540, the determination unit 56 reads out table T and data indicating the current gear calculated by the fourth calculation unit 1540 from the storage unit 58 to identify the gear ratio Gr of the current gear. For example, as shown in Figure 3, if the current gear calculated by the fourth calculation unit 1540 is the i-th gear, the gear ratio Gr is n s i / n c Therefore, when the signal Sa is input to the fourth calculation unit 1540 for the first time during one cycle of the control steps described later, the determination unit 56 determines the gear ratio Gr(n) of the calculated current gear. s i / n c Based on the wheel rotation speed Nw (rpm) calculated by the first calculation unit 51, the first target rotation speed Npg1 (rpm) of the pedal 4 (hereinafter sometimes simply referred to as "first rotation speed Npg1") is calculated using the following formula (C). Npg1=k1(n s i / n c )Nw···(C) In equation (C), k1 is a positive constant less than 1. The value of k1 is not particularly limited, but for example, it may be between 0.70 and 0.80, or more specifically, 0.75. The determination unit 56 then determines the magnitude of the first rotational speed Npg1 (rpm) and the rotational speed Np (rpm) of the pedal 4 detected (measured) by the fifth sensor 9. Here, in equation (C), the first rotational speed Npg1 (rpm) is multiplied by a positive constant k1 less than 1 to calculate it. This suppresses the accidental disengagement of the assist due to the accuracy of the sensor during normal driving. Specifically, due to the accuracy of the sensor, a discrepancy (error) may occur between the detected (measured) rotational speed of the pedal 4 and the actual rotational speed of the pedal during normal driving, and this discrepancy may cause the assist to be disengaged. By multiplying by a positive constant k1 less than 1, the threshold (i.e., the first rotational speed Npg1) is lowered, making it possible to eliminate the effects of such errors.

[0044] Thus, when Nw is the rotational speed of the wheel, Nm is the rotational speed of the motor 40, Np is the rotational speed of the pedal 4, and grMDU is the reduction ratio of the reduction gear 10, the determination unit 56 calculates the gear ratio Gr(n s i / n c It is determined whether the magnitude of the above equation (B) (i.e., the rotational speed of pedal 4 Np (rpm)) falls within a predetermined range (Npg1 > Np) corresponding to ).

[0045] In this embodiment, the determination unit 56 outputs a first signal S1 to the output adjustment unit 55 if the rotation speed Nc (rpm) of the chainring CR output from the fifth sensor 9 (in other words, the rotation speed Np (rpm) of the pedal 4 calculated by the fifth sensor 9) is smaller than the first rotation speed Npg1 (rpm). Alternatively, the determination unit 56 may output the first signal S1 to the output adjustment unit 55 if the rotation speed Np (rpm) of the pedal 4 is less than or equal to the first rotation speed Npg1 (rpm).

[0046] Furthermore, when the signal Sa is input to the fourth calculation unit 1540 from the fourth sensor 8 for the second time during one cycle of the control steps described later, the determination unit 56 reads out the table T and data indicating the current gear from the storage unit 58, and determines the gear ratio Gr(n s i / n c Based on the wheel rotation speed Nw (rpm) calculated by the first calculation unit 51, the second target rotation speed Npg2 (rpm) of the pedal 4 is calculated using the following formula (D) (hereinafter, it may simply be referred to as "second rotation speed Npg2"). Npg2=k2(n s i / n c )Nw···(D) In equation (D), k2 is a positive constant less than 1 and greater than k1. The value of k2 is not particularly limited; for example, it may be between 0.80 and 0.90, or more specifically, 0.85. The determination unit 56 then determines the relative magnitude of the second rotational speed Npg2 (rpm) and the rotational speed Np (rpm) of the pedal 4 detected by the fifth sensor 9. Here, in equation (D), the second rotational speed Npg2 (rpm) is multiplied by a positive constant k2 less than 1. This prevents the phenomenon where, despite the pedal 4 not free-spinning due to the assist being deactivated and the vehicle in a normal driving state, the assist is not started (restarted) at the desired timing due to the accuracy of the sensor. Furthermore, in equation (D), the second rotational speed Npg2 (rpm) is multiplied by a constant k2 greater than k1. This creates a difference between the second rotational speed Npg2 and the first rotational speed Npg1, preventing the cycle of assist being deactivated and then reactivated from repeating undesirably in a short period of time.

[0047] In this embodiment, the determination unit 56 outputs the second signal S2 to the output adjustment unit 55 if the rotational speed Np (rpm) of the pedal 4 is greater than the second rotational speed Npg2 (rpm). Alternatively, the determination unit 56 may output the second signal S2 to the drive signal generation unit 59 if the rotational speed Np (rpm) of the pedal 4 is equal to or greater than the second rotational speed Npg2 (rpm).

[0048] Here, if we refer to the first rotational speed Npg1 (rpm) in equation (C) and the second rotational speed Npg2 (rpm) in equation (D) collectively as the target rotational speed Npg, then this target rotational speed Npg can be obtained using the constant k by the following equation (1). Npg=k(n s i / n c )Nw···(1) (k=k1 (when the first rotational speed is Npg1)) (k=k² (when the second rotational speed is Npg²)) In this embodiment, k1 <k2である。

[0049] As mentioned above, in this embodiment, the constant k2 in equation (D) is greater than the constant k1 in equation (C). Therefore, in this embodiment, the second rotational speed Npg2 (rpm) obtained using equation (D) tends to be greater than the first rotational speed Npg1 (rpm) obtained using equation (C), and if the gear ratio Gr (nsi / nc) and the wheel rotational speed Nw (rpm) are the same, the second rotational speed Npg2 (rpm) is greater than the first rotational speed Npg1 (rpm).

[0050] Furthermore, the determination unit 56 determines whether or not there is a change in the signal input from the fifth sensor 9 within a predetermined time. It determines whether or not a signal is input from the fifth sensor 9. As described above, in this embodiment, the fifth sensor 9 is arranged as a cadence sensor, and detects the rotation speed Np (rpm) of the pedal 4 by means of a magnet attached to the crank arm connecting the pedal 4 and the crank shaft 23, and a sensor attached to a predetermined location on the MDU 100 (for example, a non-rotating location within the MDU 100). For example, the fifth sensor 9 as a cadence sensor is configured such that the sensor attached to the MDU 100 detects the angle of the crank arm (cadence angle) with respect to the part of the MDU 100 to which the sensor is attached. In this case, determining whether or not there is a change in the signal input from the fifth sensor 9 within a predetermined time corresponds to determining the continuous rotation of the pedal 4 over a predetermined period. More specifically, if the signal input from the fifth sensor 9 (a signal indicating cadence angle) changes within a predetermined time, it can be determined that the pedal 4 is rotating for a predetermined time (the rotation of the pedal 4 has not stopped for a predetermined time). If the signal input from the fifth sensor 9 (a signal indicating cadence angle) does not change within a predetermined time, it can be determined that the pedal 4 is not rotating for a predetermined time. In determining whether or not there is a change in the signal indicating cadence angle, for example, the change in the signal indicating cadence angle The system may be configured to determine that the signal indicating the cadence angle has changed when the value indicating exceeds a predetermined threshold. The determination unit 56 may be configured to determine whether or not a signal is input from the fifth sensor 9 within a predetermined time.

[0051] When the second signal S2 is input from the determination unit 56 to the output adjustment unit 55, the output adjustment unit 55 outputs a fourth signal S4 indicating the torque command value Tm(Nm) calculated by the third calculation unit 53 (hereinafter may be referred to as "first torque command value Tm") to the drive signal generation unit 59. The control mode for driving the motor 40 based on the first torque command value Tm(Nm) is the normal output mode. By virtue of the driving force of the motor 40 in the normal mode (hereinafter may be referred to as "second driving force"), the cyclist can actually feel the assistance provided by the motor 40. On the other hand, when the first signal S1 is input from the determination unit 56 to the output adjustment unit 55, the output adjustment unit 55 outputs a third signal S3 indicating a torque command value obtained by suppressing the first torque command value Tm(Nm) calculated by the third calculation unit 53 (hereinafter may be referred to as "suppressed torque command value RTm(Nm)") to the drive signal generation unit 59.

[0052] Here, the suppressed torque command value RTm(Nm) may be, for example, a value (e.g., zero) that does not drive (stops) the motor 40, or may be a value indicating the torque of the motor 40 that is small enough such that the driving of the motor 40 is not transmitted to the output gear. For example, it may be a torque obtained by multiplying the smallest torque (Nm) of the motor 40 in the normal output mode by a number M smaller than 1 (0<M<1) (that is, a torque smaller than the torque in the normal output mode). That is, the suppressed torque command value RTm is a torque command value that causes the motor to output a torque to such an extent that the rider of the electrically assisted bicycle 1 does not actually feel that the motor 40 is assisting the electrically assisted bicycle 1 (in other words, to such an extent that the rider does not actually feel that propulsive force is applied to the electrically assisted bicycle 1). Therefore, when the third signal S3 indicating the suppressed torque command value RTm is input to the drive signal generation unit 59, the assistance provided by the motor 40 is canceled, and as a result, the rider of the electrically assisted bicycle 1 enters a state where they do not actually feel the assistance provided by the motor 40 (hereinafter may be referred to as "assistance canceled state"). In other words, this assistance canceled state is a state where the pedal 4 rotates together with the wheels. On the other hand, the state where the rider actually feels the assistance provided by the motor 40 is referred to as "assisted state". This assisted state is a state where the motor 40 outputs the second driving force based on the first torque command value Tm.

[0053] Hereinafter, among the suppression torque command values ​​RTm, the suppression torque command value that stops the motor 40 will be referred to as "first suppression torque command value RTm1," and the suppression torque command value that causes the motor 40 to exert a torque that is driven but whose assistance is not felt will be referred to as "second suppression torque command value RTm2."

[0054] Furthermore, when the control step enters the gear update flow GRF described later (at the time of entry), the determination unit 56 outputs the fifth signal S5 to the output adjustment unit 55. Also, while the control step is in the gear update flow GRF, the determination unit 56 outputs the sixth signal S6 to the output adjustment unit 55. When the output adjustment unit 55 receives the fifth signal S5 from the determination unit 56, it outputs the seventh signal S7 to the drive signal generation unit 59, indicating the torque command value (hereinafter sometimes referred to as "second torque command value Tm2") that causes the motor 40 to exert a third driving force. Also, when the output adjustment unit 55 receives the sixth signal S6 from the determination unit 56, it outputs the eighth signal S8 to the drive signal generation unit 59, indicating the torque command value (hereinafter sometimes referred to as "third torque command value Tm3") that causes the motor 40 to exert a first driving force.

[0055] Here, the first and third driving forces are driving forces that bring about the assist release state. The third driving force of the two driving forces is the driving force (starting torque) that starts the motor 40 which is stopped based on the first suppression torque command value RTm1. On the other hand, the first driving force of the two driving forces is the driving force for executing the gear update flow GRF. This is force (inertial torque). Therefore, even when the motor 40 is driven based on the third torque command value Tm3, which causes the motor 40 to exert a first driving force, and the second torque command value Tm2, ​​which causes the motor 40 to exert a third driving force, the driver will not feel the assistance from the motor 40, just as when the motor 40 is driven based on the suppression torque command value RTm.

[0056] The relative magnitudes of the first driving force, the third driving force, and the second driving force that provides the assist state are as follows: 1st drive force < 3rd drive force < 2nd drive force Furthermore, the relative magnitudes of the driving forces exerted based on the first suppression torque command value RTm1 that stops the motor 40 (hereinafter referred to as the "fourth driving force" for convenience) are as follows. 4th drive force < 1st drive force < 3rd drive force < 2nd drive force Furthermore, the relative magnitudes of the driving forces exerted based on the second suppression torque command value RTm2 (hereinafter referred to as the "fifth driving force" for convenience) are as follows: 4th drive force < 5th drive force < 2nd drive force The relative magnitudes of the fifth, first, and third driving forces can be adjusted as appropriate.

[0057] The drive signal generation unit 59 generates a drive signal Sd to drive the motor 40 and outputs it to the drive circuit 50b. Specifically, when the fourth signal S4 is input, the drive signal generation unit 59 outputs a drive signal Sd to drive the motor 40 with a torque (second driving force) of the first torque command value Tm (Nm) indicated by the fourth signal S4; when the third signal S3 is input, the drive signal Sd to drive the motor 40 with a torque (third driving force) of the suppression torque command value RTm (Nm) indicated by the third signal S3; when the seventh signal S7 is input, the drive signal Sd to drive the motor 40 with a torque (third driving force) of the second torque command value Tm2 (Nm) indicated by the seventh signal S7; and when the eighth signal S8 is input, the drive signal Sd to drive the motor 40 with a torque (first driving force) of the third torque command value Tm3 (Nm) indicated by the eighth signal S8. The drive signal Sd is, for example, a PWM (Pulse Width Modulation) signal.

[0058] The drive circuit 50b drives the motor 40 by exciting the coils corresponding to the three phases (U phase, V phase, and W phase) of the motor 40, for example, if the motor 40 is a brushless DC motor having coils corresponding to three phases (U phase, V phase, and W phase). The drive circuit 50b may include, for example, an inverter circuit for driving each coil, a pre-drive circuit for driving the inverter circuit in accordance with the drive signal Sd, and a current detection circuit for detecting the current flowing through each coil.

[0059] Furthermore, the control device 50 described above 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 (IC), or the control circuit 50a and the drive circuit 50b may be packaged as separate integrated circuit devices.

[0060] Next, an example of the steps in control by the control device 50 will be described. Figure 4 is a flowchart showing an example of the steps in control by the control device 50. Note that the steps in control by the control device 50 are not limited to those shown in Figure 4. As shown in Figure 4, the steps in the control according to this embodiment include steps St1 to St9.

[0061] In this embodiment, for example, when the motor 40 is started to drive, the step of starting control may be started (START). Specifically, the step of starting control may be started when the drive signal generation unit 59 generates a drive signal Sd to drive the motor 40 and outputs it to the drive circuit 50b. At this time, the storage unit 58 stores the steps in the control. The gear position of the sprocket SP that was set immediately before the start (START) is stored as data indicating the current gear.

[0062] (Step St1) The control device 50 determines whether a signal Sa indicating that the wheel has rotated by a predetermined rotation angle An(deg) has been input to the fourth calculation unit 1540. If the control device 50 determines that the signal Sa has been input to the fourth calculation unit 1540, it advances the control step to step St2. If it determines that the signal Sa has not been input to the fourth calculation unit 1540, it returns the control step to step St1. Note that the signal Sa does not have to be a signal indicating that the wheel has rotated by a predetermined rotation angle An(deg); for example, it may be a signal transmitted at regular intervals from a predetermined timer.

[0063] (Step St2) The control device 50 determines (calculates) the current gear based on the rotational speed Nm (rpm) of the motor 40 calculated by the second calculation unit 52, the rotational speed Nw (rpm) of the wheels calculated by the first calculation unit 51, the reduction ratio data (data of the reduction ratio grMDU of the reduction gear 10) stored in the memory unit 58, and the gear determination program described later. The control device 50 overwrites (updates) the "data indicating the current gear" that was stored in the memory unit 58 up to this point (i.e., at the time of START) with the data indicating the current gear determined in this step, and advances the control step to step St3.

[0064] The following describes in detail the stage determination program executed in step St2.

[0065] In the gear determination program of this embodiment, the rotational speed Nm (rpm) of the motor 40 and the rotational speeds Nw (rpm) of the wheels 2 and 3 are measured to determine the current gear ratio (current gear). However, due to the accuracy of the sensors, a situation may occur where it is "unclear which of adjacent gear ratios is correct." For example, even when the gear is set to G3 (3rd gear), it may be impossible to determine whether the gear is set to G2 (2nd gear) or G3 (3rd gear) from the results of measuring the rotational speed Nm (rpm) of the motor 40 and the rotational speeds Nw (rpm) of the wheels 2 and 3. If it is incorrectly determined that the gear is set to G2 in this state, the electric assist bicycle 1 may behave in an unexpected manner. However, according to this embodiment, it is possible to determine with high accuracy which of adjacent gear ratios (gears) is correct. This point will be explained below.

[0066] As an example of the gear positions of the sprocket SP of the electric assist bicycle 1, the position with 36 teeth may be the 1st gear, the position with 30 teeth may be the 2nd gear, and the position with 26 teeth may be the 3rd gear. Gear G1 (1st gear) is the lightest, and gear G9 (9th gear) is the heaviest. Table 1 shows the gear (stage) settings of this embodiment. The tables shown below, including Table 1, may be stored, for example, in the memory unit 58 of the control circuit 50a (see Figure 2). The ratio of the number of teeth on the rear (sprocket SP) to the number of teeth on the front (chainring CR) (rear teeth / front teeth) corresponds to the ratio of the rotational speeds of the rear (rear wheel 3) and the front (front wheel 2) (theoretical value), and this theoretical value (i.e., the gear ratio Gr) is calculated based on the above formula (A) using the number of teeth (n s i ) / Front (chainring CR) gear teeth (n c The calculation can be performed using the formula shown. Although Table 1 only shows up to the third decimal place, the actual calculation uses up to the fourth decimal place. In this embodiment, the lower limit of the threshold used for determination is 90% of the theoretical value of the ratio of rotational speeds, and the upper limit of the threshold is 110% of the theoretical value of the ratio of rotational speeds, but the upper and lower limits of the threshold can be set arbitrarily.

[0067] [Table 1]

[0068] On the other hand, the ratio R of the actual rotational speeds is expressed by equation (E). R = Nm / (grMDU·Nw) ... Equation (E) In the gear ratio state determination process described later, the control device 50 determines whether the ratio R, i.e., the magnitude of equation (E), falls within a predetermined range (threshold range in Table 1) corresponding to each gear ratio Gr.

[0069] Figure 5 is a block diagram showing the functional configuration of the fourth calculation unit 1540. As shown in Figure 5, the fourth calculation unit 1540 has, as functional blocks, for example, a rotational speed calculation unit 1541, an i comparison unit 1542, a threshold comparison unit 1543, a gear ratio setting unit 1544, an i setting unit 1545, a C setting unit 1546, and a count threshold comparison unit 1547. The rotational speed calculation unit 1541, i comparison unit 1542, threshold comparison unit 1543, gear ratio setting unit 1544, i setting unit 1545, C setting unit 1546, and count threshold comparison unit 1547 are realized, for example, in a program processing device as a control circuit 50a, by the processor executing various calculation processes according to various programs stored in the above-mentioned storage devices including the storage unit 58, and controlling peripheral circuits such as counters and A / D conversion circuits. The fourth calculation unit 1540 may have other functional blocks. The functions and operations of the rotational speed calculation unit 1541, i comparison unit 1542, threshold comparison unit 1543, gear ratio setting unit 1544, i setting unit 1545, C setting unit 1546, and count threshold comparison unit 1547 will be explained using the flowchart of the gear ratio state determination process described later.

[0070] Figure 6(a) is a flowchart illustrating a part of the steps in the control of the electric assist bicycle 1 of this embodiment, and more specifically, it is a flowchart illustrating the control performed in step St2 of the electric assist bicycle 1. Figure 6(b) is a timing diagram illustrating the control shown in Figure 6(a).

[0071] As shown in Figure 6(a), in step St2, steps St1100, St1200, and St1300 are performed. In step St1100, the control device 50 detects whether the gear ratio (sprocket SP stage) has changed from the first gear ratio (first stage) to the second gear ratio (second stage). The time when the gear ratio changes from the first gear ratio to the second gear ratio is defined as t=t10 (see Figure 6(b)). In step St1200, the control device 50 performs the gear ratio state determination process described later. In step St1300, the control device 50 controls the pedal assist corresponding to the second gear ratio to start. The time when the pedal assist corresponding to the second gear ratio starts is defined as t=t11 (see Figure 6(b)). The time from when the gear ratio changes from the first to the second gear ratio until the pedal assist corresponding to the second gear ratio begins is (t11-t10). At this point, the processing of step St2 in this embodiment is completed, but in this embodiment, this processing is performed each time the gear ratio (stage) is changed.

[0072] For example, if we consider the time when the gear ratio changes from the third to the fourth gear ratio to be t=t12 (see Figure 6(b)), and the time when pedal assistance corresponding to the fourth gear ratio starts to be t=t13 (see Figure 6(b)), then the time from when the gear ratio changes from the third to the fourth gear ratio to when pedal assistance corresponding to the fourth gear ratio starts is (t13-t12). In this invention, due to the gear ratio state determination process described later, the time from when the gear ratio changes from the first to the second gear ratio to when pedal assistance corresponding to the second gear ratio starts (t11-t10) is different from the time from when the gear ratio changes from the third to the fourth gear ratio to when pedal assistance corresponding to the fourth gear ratio starts (t13-t12).

[0073] Figure 7 is a timing diagram illustrating other control mechanisms in this embodiment. Let's consider the case where the control device 50 is started at time t=t20 from a stopped state. Pedal assist does not start simultaneously with the start, but after a predetermined time. For example, let's assume that at time t=t21 shown in Figure 7, pedal assist corresponding to the gear ratio set at the time of start starts. Let's consider the case where the gear ratio is changed at time t=t22, after a predetermined time has elapsed since the control device 50 was started. Similar to the start of the control device 50, pedal assist for the changed gear ratio is not applied simultaneously with the change in gear ratio, but after a predetermined time. For example, let's assume that at time t=t23, pedal assist corresponding to the changed gear ratio starts. In this embodiment, due to the gear ratio state determination process described later, the time from the start 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 in gear ratio to the start of pedal assist corresponding to the changed gear ratio (t23-t22).

[0074] Here, the time until pedal assistance corresponding to the gear ratio begins may be, for example, within the time it takes for one wheel rotation. Specifically, the times (t11-t10), (t13-t12), (t21-t20), and (t23-t22) may be within the time it takes for one rotation of the rear wheel 3.

[0075] Figure 8 is a timing diagram illustrating other control methods in this embodiment. Assume that the gear ratio is changed to a predetermined gear ratio at time t=t30 shown in Figure 8. At time t=t31, before the first period p1 has elapsed after the gear ratio has been changed to the predetermined gear ratio, the control device 50 determines (provisionally determines) candidates for the predetermined gear ratio by the gear ratio state determination process described later. For example, gears G2 and G3 (2nd and 3rd gears) are determined (provisionally determined) as candidates. At time t=t32, after the first period p1 has elapsed and before the second period p2 has elapsed, the control device 50 determines the predetermined gear ratio from the candidates for the predetermined gear ratio by the gear ratio state determination process described later. For example, it determines that gear G3 (3rd gear) is the current gear ratio (current gear) from the two candidates (gears G2 and G3).

[0076] Here, the period including the first period p1 and the second period p2 is preferably, for example, within the time it takes for one rotation of the wheel (rear wheel 3).

[0077] Furthermore, possible methods for confirming whether a particular electric assist bicycle exhibits the time relationship (time lag) of the present invention include checking the display (display device) that shows the gear position, confirming that the assist output is suppressed until the gear position is determined, and confirming that a time lag occurs in the assist output due to motor current, etc.

[0078] Figure 9 is a flowchart illustrating the gear ratio state determination process (step St1200 shown in Figure 6(a)). In the following explanation, we assume that the current gear ratio (current stage) is set to gear G3 (3rd stage). However, as mentioned above, it is sometimes impossible to determine whether the current stage is set to gear G2 (2nd stage) or gear G3 (3rd stage) from the results of measuring the motor rotation speed and wheel rotation speed. The situation of "not knowing which of adjacent gear ratios is correct" can occur, for example, when changing the gear ratio, and when starting the system (control device 50) from a stopped state and beginning to pedal. According to the electric assist bicycle 1, the gear ratio state determination process shown in Figure 9 can provisionally determine or confirm which gear (stage) the current stage is. Example 1 shows the case where the rotational speed ratio does not change at R=0.63, Example 2 shows the case where the rotational speed ratio changes from R=0.63 to R=0.55, and Example 3 shows the case where the rotational speed ratio changes from R=0.55 to R=0.63.

[0079] In Example 1, the rotation speed ratio remains constant at R=0.63. Each time a signal indicating the vehicle speed of the electric assist bicycle 1 (vehicle speed pulse) is received, the count value C of gear G2 (2nd gear) and gear G3 (3rd gear) increases. When the count value C exceeds the count threshold, gear G2 (2nd gear) and gear G3 (3rd gear) are "provisionally determined". The following will be explained in detail according to the flowchart in Figure 9. In this embodiment, the first sensor 5 is a sensor that outputs 12 pulses (hereinafter referred to as vehicle speed pulses) during one rotation of the wheel. Hereinafter, the nth pulse out of the 12 pulses will be referred to as n (=1~12) / 12 pulses. Therefore, for example, the 1 / 12 vehicle speed pulse refers to the first vehicle speed pulse out of the 12 vehicle speed pulses.

[0080] In step St1211, the rotation speed calculation unit 1541 receives a signal from the first calculation unit 51 indicating the rotation speed Nw (rpm) of the wheel 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 arrives), in step S1212, the rotation speed calculation unit 1541 calculates the rotation speed ratio R (ratio of actual rotation speeds) according to the above-described equation (E) based on the signal from the first calculation unit 51 and the signal from the second calculation unit 52 indicating the rotation speed Nm (rpm) of the motor 40. In Example 1, the ratio R = 0.63.

[0081] In step St1213, the i comparison unit 1542 compares i with Ngear (=9). The initial value of i is 1, and Ngear is the number of gear ratios (number of stages on the sprocket SP), which in this embodiment is 9. Here, i ≠ 9, so the process proceeds to step St1214. In step St1214, the threshold comparison unit 1543 checks whether the ratio R=0.63 is within the threshold range. From Table 1, the threshold for i=1 is 0.736~0.900, and the ratio R=0.63 is not within the threshold range, so the process proceeds to step St1215. In step St1215, the gear ratio setting unit 1544 checks whether the gear ratio state of gear G1 is "provisional determination" or "confirmed". As shown in Table 2, the initial value of the gear ratio state for all gears G1~9 is "undetermined", and the gear ratio state of gear G1 is also "undetermined", so the process proceeds to step St1221. [Table 2] In step St1221, the i setting unit 1545 increments i and returns to step St1213.

[0082] In step St1213, the i comparison unit 1542 compares i with Ngear (=9). Since i=2, the process proceeds to step St1214. In step St1214, the threshold comparison unit 1543 checks whether the ratio R=0.63 is within the threshold range. From Table 1, the threshold for i=2 is 0.614~0.750, and since the ratio R=0.63 is within the threshold range, the process proceeds to step St1216. In step St1216, the C setting unit 1546 increments the count value C of gear G2 (2nd stage). Specifically, it changes the count value C of gear G2 (2nd stage) in Table 3 from 0 to 1. In the tables shown below, including Table 3, the parts changed in this step are marked with an asterisk (*). [Table 3] In step St1217, the count threshold comparison unit 1547 compares the count value C of gear G2 with the count threshold. The count threshold is a number indicating how many times consecutively that gear (stage) has met the threshold, and in this embodiment, the threshold is set to 6. Since C < 6, the process proceeds to step St1215. Note that to make the gear (stage) determination faster, the count threshold should be a smaller number, while to make the gear (stage) determination more accurate, the count threshold should be a larger number. The count threshold can be set arbitrarily. In step St1215, the gear ratio setting unit 1544 checks whether the gear ratio state of gear G2 is "provisional determination" or "confirmed". As shown in Table 3, the gear ratio state of gear G2 is "undetermined", so the process proceeds to step St1221. In step St1221, the i setting unit 1545 counts up i and returns to step St1213.

[0083] In step St1213, the i comparison unit 1542 compares i with Ngear (=9). Since i=3, the process proceeds to step St1214. In step St1214, the threshold comparison unit 1543 checks whether the ratio R=0.63 is within the threshold range. From Table 1, the threshold for i=3 is 0.532~0.650, and since the ratio R=0.63 is within the threshold range, the process proceeds to step St1216. In step St1216, the C setting unit 1546 increments the count value C of gear G3 (3rd stage). Specifically, it changes the count value C of gear G3 in Table 4 from 0 to 1. [Table 4] In step St1217, the count threshold comparison unit 1547 compares the count value C of gear G3 (3rd stage) with the count threshold (6 in this embodiment). Since C < 6, the process proceeds to step St1215. In step St1215, the gear ratio setting unit 1544 checks whether the gear ratio state of gear G3 is "provisional determination" or "confirmed". As shown in Table 4, the gear ratio state of gear G3 is "undetermined", so the process proceeds to step St1221. In step St1221, the i setting unit 1545 counts up i and returns to step St1213.

[0084] In step St1213, the i comparison unit 1542 compares i with Ngear (=9). Since i=4, the process proceeds to step St1214. In step St1214, the threshold comparison unit 1543 checks whether the ratio R=0.63 is within the threshold range. From Table 1, the threshold for i=4 is 0.470~0.575, and since the ratio R=0.63 is not within the threshold range, the process proceeds to step St1215. In step St1215, the gear ratio setting unit 1544 checks whether the gear ratio state of gear G4 is "provisional" or "confirmed". As shown in Table 4, the gear ratio state of gear G4 is "undetermined", so the process proceeds to step St1221. In step St1221, the i setting unit 1545 counts up i and returns to step St1213.

[0085] Since i=5 to 9 is the same as in the case of i=4 described above, in step St1221, the i setting unit 1545 counts up i and skips until i=10.

[0086] In step St1213, the i comparison unit 1542 compares i with Ngear (=9). Since i=10, the process proceeds to step St1222. In step St1222, the i setting unit 1545 resets i to 1, and then the process proceeds to step St1223. In step St1223, the gear ratio setting unit 1544 checks whether there is at least one gear ratio state that is either "provisionally determined" or "confirmed" among all gear (stage) gear ratio states. See Table 4. Therefore, since the gear ratio state for all gears is "undetermined", the process proceeds to step St1224. In step St1224, the gear ratio setting unit 1544 sets the gear ratio state for all gears to "undetermined". In Example 1, since the gear ratio state for all gears is already "undetermined", nothing is done and the process returns to step St1211.

[0087] In step St1211, the rotation speed calculation unit 1541 receives a signal from the first calculation unit 51 indicating the rotation speed Nw (rpm) of the wheel and detects the vehicle speed change timing (whether a 2 / 12 vehicle speed pulse has arrived). At the vehicle speed change timing (when a 2 / 12 vehicle speed pulse arrives), in step St1212, the rotation speed calculation unit 1541 calculates the ratio R based on the signal from the first calculation unit 51 and the signal from the second calculation unit 52 indicating the rotation speed Nm (rpm) of the motor 40. In Embodiment 1, the ratio R is assumed to remain unchanged at 0.63, so when i=1, steps St1212 to St1221 are the same as in the case of the 1 / 12 vehicle speed pulse described above. Therefore, in step St1221, the i setting unit 1545 counts up i and skips until i=2.

[0088] In step St1213, the i comparison unit 1542 compares i with Ngear (=9). Since i=2, the process proceeds to step St1214. In step St1214, the threshold comparison unit 1543 checks whether the ratio R=0.63 is within the threshold range. From Table 1, the threshold for i=2 is 0.614~0.750, and since the ratio R=0.63 is within the threshold range, the process proceeds to step St1216. In step St1216, the C setting unit 1546 increments the count value C of gear G2 (2nd stage). Specifically, it changes the count value C of gear G2 (2nd stage) in Table 5 from 1 to 2. [Table 5] In step St1217, the count threshold comparison unit 1547 compares the count value C of gear G2 (2nd stage) with the count threshold (6 in this embodiment). Since C < 6, the process proceeds to step St1215. In step St1215, the gear ratio setting unit 1544 checks whether the gear ratio state of gear G2 is "provisional determination" or "confirmed". As shown in Table 5, the gear ratio state of gear G2 is "undetermined", so the process proceeds to step St1221. In step St1221, the i setting unit 1545 counts up i, and the process proceeds to step St121 Return to step 3.

[0089] In step St1213, the i comparison unit 1542 compares i with Ngear (=9). Since i=3, the process proceeds to step St1214. In step St1214, the threshold comparison unit 1543 checks whether the ratio R=0.63 is within the threshold range. From Table 1, the threshold for i=3 is 0.532~0.650, and since the ratio R=0.63 is within the threshold range, the process proceeds to step St1216. In step St1216, the C setting unit 1546 increments the count value C of gear G3 (3rd stage). Specifically, it changes the count value C of gear G3 (3rd stage) in Table 6 from 1 to 2. [Table 6] In step St1217, the count threshold comparison unit 1547 compares the count value C of gear G3 (3rd gear) with the count threshold (6 in this embodiment). Since C < 6, the process proceeds to step St1215. In step St1215, the gear ratio setting unit 1544 checks whether the gear ratio state of gear G3 is "provisional determination" or "confirmed". As shown in Table 6, the gear ratio state of gear G3 is "undetermined", so the process proceeds to step St1221. In step St1221, the i setting unit 1545 counts up i and returns to step St1213.

[0090] Similarly, at subsequent vehicle speed change timings (when the 3 / 12, 4 / 12, and 5 / 12 vehicle speed pulses arrive), the C setting unit increments the count value C for gears G2 and G3, as shown in Table 7. [Table 7]

[0091] The flow for each vehicle speed change timing (3 / 12, 4 / 12, 5 / 12 vehicle speed pulse) is the same as described above. Also, in the flow for the vehicle speed change timing (6 / 12 vehicle speed pulse), when i=1, steps St1212 to St1221 are the same as for each vehicle speed change timing (1 / 12, 2 / 12, 3 / 12, 4 / 12, 5 / 12 vehicle speed pulse) described above, so in step St1221, the i setting unit 1545 counts up i and skips until i=2.

[0092] In step St1213, the i comparison unit 1542 compares i with Ngear (=9). Since i=2, the process proceeds to step St1214. In step St1214, the threshold comparison unit 1543 checks whether the ratio R=0.63 is within the threshold range. From Table 1, the threshold for i=2 is 0.614~0.750, and since the ratio R=0.63 is within the threshold range, the process proceeds to step St1216. In step St1216, the C setting unit 1546 increments the count value C of gear G2 (2nd stage). Specifically, it changes the count value C of gear G2 in Table 8 from 5 to 6. [Table 8] In step St1217, the count threshold comparison unit 1547 compares the count value C of gear G2 (2nd stage) with the count threshold (6 in this embodiment). Since 6 ≤ C, the process proceeds to step St1218. In step St1218, the gear ratio setting unit 1544 checks whether the gear ratio state of gear G2 is "excluded". As shown in Table 8, the gear ratio state of gear G2 is "undetermined", so the process proceeds to step St1219. In step St1219, as shown in Table 9, the gear ratio setting unit 1544 changes the gear ratio state of gear G2 (2nd stage) from "undetermined" to "provisional determination". [Table 9]

[0093] Similarly, in the vehicle speed change timing (6 / 12 vehicle speed pulse) loop, the count value C of gear G3 also becomes 6, so as shown in Table 10, the gear ratio setting unit 1544 also changes the gear ratio state of gear G3 (3rd stage) to "provisional determination". [Table 10]

[0094] Since i=4 to 8 is the same as the vehicle speed change timings (1 / 12, 2 / 12, 3 / 12, 4 / 12, 5 / 12 vehicle speed pulses) described above, in step St1221, the i setting unit 1545 counts up i and skips until i=9.

[0095] In step St1213, the i comparison unit 1542 compares i with Ngear (=9). Since i=9, the process proceeds to step St1222. In step St1222, the i setting unit 1545 resets i to 1, and then the process proceeds to step St1223. In step St1223, the gear ratio setting unit 1544 checks whether there is at least one gear ratio state that is either "provisionally determined" or "confirmed" among all the gear (stage) gear ratio states. As shown in Table 10, the gear ratio state for gears G2 and G3 is "provisionally determined," so the process proceeds to step St1225. In step St1225, the gear ratio setting unit 1544 checks whether there is one gear ratio state that is "provisionally determined," and whether the gear ratio states above and below it are "excluded." As shown in Table 10, there are two gears with a gear ratio state that are "provisionally determined," namely gears G2 and G3, so the process returns to step St1211.

[0096] Similarly, at subsequent vehicle speed change timings (when the 7 / 12, 8 / 12, and 9 / 12 vehicle speed pulses arrive), as shown in Table 11, the C setting unit increments the count value C for gears G2 and G3. In Example 1, the ratio R remains unchanged at 0.63, so there is no change in the gear ratio state, and the loop continues. Therefore, the gear ratio state is never finalized, and both gears G2 and G3 are in a provisional determination state. As a result, by provisionally determining both adjacent gear ratios (gears G2 and G3) as candidates, the risk of misdetermination can be reduced. However, if the count value C reaches the count threshold, further incrementing is not necessary. That is, in Table 11, the count value C for gears G2 and G3 can be stopped at 6. stomach. [Table 11]

[0097] In Example 1, the control device 50 determines one or more numerical ranges that include the gear ratio calculated by formula (1) from among the numerical ranges corresponding to multiple gear ratios (gears G1 to G9) as shown in Table 1 (step St1214), and one or more gear ratios (gears G2, G3) corresponding to one or more numerical ranges are candidates for the predetermined gear ratio.

[0098] In Example 2, the rotational speed ratio changes from the state in Example 1 (R=0.63) to R=0.55. When the first vehicle speed pulse arrives after the rotational speed ratio change, gear G2 (2nd stage) deviates from the threshold (NO in step St1214). Since gear G2 (2nd stage) was in a provisional judgment (YES in step St1215), gear G2 (2nd stage) is "excluded" (step St1220). Since R=0.55 is included in the thresholds of both gear G3 (3rd stage) and gear G4 (4th stage) (step St1214), the count value C of gear G3 (3rd stage) and gear G4 (4th stage) increases (step St1216), exceeding the count threshold (YES in step St1217). As a result, gear G3 (3rd stage) and gear G4 (4th stage) become "provisionally judged" (step St1219). The following is a detailed explanation following the flowchart.

[0099] In step St1211, the rotation speed calculation unit 1541 receives a signal from the first sensor 5 indicating the rotation speed of the wheel (rear wheel 3) and detects the vehicle speed change timing (whether a 10 / 12 vehicle speed pulse has arrived). At the vehicle speed change timing (when a 10 / 12 vehicle speed pulse arrives), in step St1212, the rotation speed calculation unit 1541 calculates the ratio R based on the signal from the first calculation unit 51 and the signal from the second calculation unit 52 indicating the rotation speed Nm (rpm) of the motor 40. In Example 2, the ratio R = 0.55.

[0100] In step St1213, the i comparison unit 1542 compares i with Ngear (=9). Since i=1, the process proceeds to step St1214. In step St1214, the threshold comparison unit 1543 checks whether the ratio R=0.55 is within the threshold range. From Table 1, the threshold for i=1 is 0.736~0.900, and since the ratio R=0.55 is not within the threshold range, the process proceeds to step St1215. In step St1215, the gear ratio setting unit 1544 checks whether the gear ratio state of gear G1 is "provisional" or "confirmed". As shown in Table 11, the gear ratio state of gear G1 is "undetermined", so the process proceeds to step St1221. In step St1221, the i setting unit 1545 counts up i and returns to step St1213.

[0101] In step St1213, the i comparison unit 1542 compares i with Ngear (=9). Since i=2, the process proceeds to step St1214. In step St1214, the threshold comparison unit 1543 checks whether the ratio R=0.55 is within the threshold range. From Table 1, the threshold for i=2 is 0.614~0.750, and the ratio R=0.55 is not within the threshold range, so the process proceeds to step St1215. In step St1215, the gear ratio setting unit 1544 checks whether the gear ratio state of gear G2 is "provisional" or "confirmed". As shown in Table 11, the gear ratio state of gear G2 is "provisional", so the process proceeds to step St1220. In step St1220, as shown in Table 12, the gear ratio setting unit 1544 changes the gear ratio state of gear G2 from "provisional determination" to "excluded," and the C setting unit 1546 resets the count value C (to zero). [Table 12] In step St1221, the i setting unit 1545 increments i and returns to step St1213.

[0102] In step St1213, the i comparison unit 1542 compares i with Ngear (=9). Since i=3, the process proceeds to step St1214. In step St1214, the threshold comparison unit 1543 checks whether the ratio R=0.55 is within the threshold range. From Table 1, The threshold for i=3 is 0.532~0.650, and the ratio R=0.55 is within the threshold range, so the process proceeds to step St1216. In step St1216, the C setting unit 1546 increments the count value C of gear G3 (3rd stage). Specifically, it changes the count value C of gear G3 (3rd stage) in Table 13 from 9 to 10. [Table 13] In step St1217, the count threshold comparison unit 1547 compares the count value C of gear G3 with the count threshold (6 in this embodiment). Since 6 ≤ C, the process proceeds to step St1218. In step St1218, the gear ratio setting unit 1544 checks whether the gear ratio state of gear G3 (3rd stage) is "excluded". As shown in Table 13, the gear ratio state of gear G3 (3rd stage) is "provisional determination", so the process proceeds to step St1219. In step St1219, since the gear ratio state of gear G3 (3rd stage) is already "provisional determination", nothing is done, and the process proceeds to step St1221. In step St1221, the i setting unit 1545 counts up i and returns to step St1213.

[0103] In step St1213, the i comparison unit 1542 compares i with Ngear (=9). Since i=4, the process proceeds to step St1214. In step St1214, the threshold comparison unit 1543 checks whether the ratio R=0.55 is within the threshold range. From Table 1, the threshold for i=4 is 0.470~0.575, and since the ratio R=0.55 is within the threshold range, the process proceeds to step St1216. In step St1216, the C setting unit 1546 increments the count value C of gear G4 (4th stage). Specifically, it changes the count value C of gear G4 in Table 14 from 0 to 1. [Table 14] In step St1217, the count threshold comparison unit 1547 compares the count value C of gear G4 (4th stage) with the count threshold (6 in this embodiment). Since C < 6, the process proceeds to step St1215. In step St1215, the gear ratio setting unit 1544 checks whether the gear ratio state of gear G4 (4th stage) is "provisional determination" or "confirmed". As shown in Table 14, the gear ratio state of gear G4 (4th stage) is "undetermined", so the process proceeds to step St1221. In step St1221, the i setting unit 1545 counts up i and returns to step St1213.

[0104] Since i=5 to 9 is the same as in the case of i=1 described above, in step St1221, the i setting unit 1545 counts up i and skips until i=10.

[0105] In step St1213, the i comparison unit 1542 compares i with Ngear (=9). Since i=10, the process proceeds to step St1222. In step St1222, the i setting unit 1545 resets i to 1, and then the process proceeds to step St1223. In step St1223, the gear ratio setting unit 1544 checks whether there is at least one gear ratio state that is either "provisionally determined" or "confirmed" among all the gear (stage) gear ratio states. As shown in Table 14, there is one gear G3 whose gear ratio state is "provisionally determined," so the process proceeds to step St1225. In step St1225, the gear ratio setting unit 1544 checks whether there is one gear ratio state that is "provisionally determined," and whether the gear ratio states above and below it are "excluded." As shown in Table 14, the only gear whose gear ratio state is "provisionally determined" is gear G3. Furthermore, the gear ratio state of gear G2 above gear G3 is "excluded," and the gear ratio state of gear G4 below gear G3 is "undetermined." Therefore, we return to step St1211.

[0106] Similarly, at subsequent vehicle speed change timings (when 11 / 12, 12 / 12, 1 / 12, and 2 / 12 vehicle speed pulses arrive), the C setting unit 1546 increments the count value C of gears G3 and G4, as shown in Table 15. [Table 15]

[0107] Since the flow for each vehicle speed change timing (11 / 12, 12 / 12, 1 / 12, 2 / 12 vehicle speed pulses) is the same as described above, in step St1216 of the loop for the vehicle speed change timing (3 / 12 vehicle speed pulse), skip until the count value C of gear G4 becomes 6, as shown in Table 16. [Table 16]

[0108] In step St1217, the count threshold comparison unit 1547 compares the count value C of gear G4 (4th gear) with the count threshold (6 in this embodiment). Since 6 ≤ C, the process proceeds to step St1218. In step St1218, the gear ratio setting unit 1544 checks whether the gear ratio state of gear G4 is "excluded". As shown in Table 16, the gear ratio state of gear G4 is "undetermined", so the process proceeds to step St1219. In step St1219, as shown in Table 17, the gear ratio setting unit 1544 changes the gear ratio state of gear G4 (4th gear) from "undetermined" to "provisional determination". [Table 17] In step St1221, the i setting unit 1545 increments i and returns to step St1213.

[0109] Since i=5 to 9 is the same as in the case of i=4 in Example 1, in step St1221, the i setting unit 1545 counts up i and skips until i=10.

[0110] In step St1213, the i comparison unit 1542 compares i with Ngear (=9). Since i=10, the process proceeds to step St1222. In step St1222, the i setting unit 1545 resets i to 1, and then the process proceeds to step St1223. In step St1223, the gear ratio setting unit 1544 checks whether there is at least one gear ratio state that is either "provisionally determined" or "confirmed" among all the gear (stage) gear ratio states. As shown in Table 17, the gear ratio state for gears G3 and G4 is "provisionally determined," so the process proceeds to step St1225. In step St1225, the gear ratio setting unit 1544 checks whether there is one gear ratio state that is "provisionally determined," and whether the gear ratio states above and below it are "excluded." As shown in Table 17, there are two gears with a gear ratio state that are "provisionally determined," namely gears G3 and G4, so the process returns to step St1211. In Example 2, the gear ratio state is not determined, and both gears G3 and G4 are in a provisional state. As a result, by provisionally determining both adjacent gear ratios (gears G3 and G4) as candidates, the risk of misjudgment can be reduced.

[0111] In Example 3, the rotational speed ratio changes from the state in Example 2 (R=0.55) to R=0.63, and when the first vehicle speed pulse arrives after the change, gear G4 (4th gear) deviates from the threshold (NO in step St1214). Since gear G4 (4th gear) was in a provisional judgment (YES in step St1215), gear G4 (4th gear) is "excluded" (step St1220). At this time, gear G3 (3rd gear) has not yet been "excluded", and the only gear ratio that is provisionally judged or confirmed is gear G3 (3rd gear) (YES in step St1223). Since gears G2 and G4 above and below gear G3 (3rd gear) are "excluded", gear G 3 (stage 3) is "confirmed" (YES in step St1225). The following explains this in detail according to the flowchart.

[0112] In step St1211, the rotation speed calculation unit 1541 receives a signal from the first sensor 5 indicating the rotation speed of the wheel (rear wheel 3) and detects the vehicle speed change timing (whether a 4 / 12 vehicle speed pulse has arrived). At the vehicle speed change timing (when a 4 / 12 vehicle speed pulse arrives), in step St1212, the rotation speed calculation unit 1541 calculates the ratio R based on the signal from the first calculation unit 51 and the signal from the second calculation unit 52 indicating the rotation speed Nm (rpm) of the motor 40. In Example 3, the ratio R = 0.63.

[0113] In step St1213, the i comparison unit 1542 compares i with Ngear (=9). Since i=1, the process proceeds to step St1214. In step St1214, the threshold comparison unit 1543 checks whether the ratio R=0.63 is within the threshold range. From Table 1, the threshold for i=1 is 0.736~0.900, and since the ratio R=0.63 is not within the threshold range, the process proceeds to step St1215. In step St1215, the gear ratio setting unit 1544 checks whether the gear ratio state of gear G1 is "provisional" or "confirmed". As shown in Table 17, the gear ratio state of gear G1 is "undecided", so the process proceeds to step St1221. In step St1221, the i setting unit 1545 counts up i and returns to step St1213.

[0114] In step St1213, the i comparison unit 1542 compares i with Ngear (=9). Since i=2, the process proceeds to step St1214. In step St1214, the threshold comparison unit 1543 checks whether the ratio R=0.63 is within the threshold range. From Table 1, the threshold for i=2 is 0.614~0.750, and since the ratio R=0.63 is within the threshold range, the process proceeds to step St1216. In step St1216, the C setting unit 1546 increments the count value C of gear G2 (2nd stage). Specifically, it changes the count value C of gear G2 in Table 18 from 0 to 1. [Table 18] In step St1217, the count threshold comparison unit 1547 compares the count value C of gear G2 (2nd stage) with the count threshold (6 in this embodiment). Since C < 6, the process proceeds to step St1215. In step St1215, the gear ratio setting unit 1544 checks whether the gear ratio state of gear G2 (2nd stage) is "provisional determination" or "confirmed". As shown in Table 18, the gear ratio state of gear G2 (2nd stage) is "excluded", so the process proceeds to step St1221. In step St1221, the i setting unit 1545 counts up i and returns to step St1213.

[0115] In step St1213, the i comparison unit 1542 compares i with Ngear (=9). Since i=3, the process proceeds to step St1214. In step St1214, the threshold comparison unit 1543 checks whether the ratio R=0.63 is within the threshold range. From Table 1, the threshold for i=3 is 0.532~0.650, and since the ratio R=0.63 is within the threshold range, the process proceeds to step St1216. In step St1216, the C setting unit 1546 increments the count value C of gear G3 (3rd stage). Specifically, it changes the count value C of gear G3 in Table 19 from 15 to 16. [Table 19] In step St1217, the count threshold comparison unit 1547 compares the count value C of gear G3 (3rd stage) with the count threshold (6 in this embodiment). Since 6 ≤ C, the process proceeds to step St1218. In step St1218, the gear ratio setting unit 1544 checks whether the gear ratio state of gear G3 is "excluded". As shown in Table 19, the gear ratio state of gear G3 (3rd stage) is "provisional determination", so the process proceeds to step St1219. In step St1219, since the gear ratio state of gear G3 (3rd stage) is already "provisional determination", nothing is done, and the process proceeds to step St1221. In step St1221, the i setting unit 1545 counts up i and returns to step St1213.

[0116] In step St1213, the i comparison unit 1542 compares i with Ngear (=9). Since i=4, the process proceeds to step St1214. In step St1214, the threshold comparison unit 1543 checks whether the ratio R=0.63 is within the threshold range. From Table 1, the threshold for i=4 is 0.470~0.575, and the ratio R=0.63 is not within the threshold range. Therefore, the process proceeds to step St1215. In step St1215, the gear ratio setting unit 1544 checks whether the gear ratio state of gear G4 (4th gear) is "provisional determination" or "confirmed". As shown in Table 19, the gear ratio state of gear G4 (4th gear) is "provisional determination", so the process proceeds to step St1220. In step St1220, as shown in Table 20, the gear ratio setting unit 1544 changes the gear ratio state of gear G4 (4th gear) from "provisional determination" to "excluded", and the C setting unit 1546 resets the count value C (to zero). [Table 20] In step St1221, the i setting unit 1545 increments i and returns to step St1213.

[0117] Since i=5 to 9 is the same as in the case of i=1 described above, in step St1221, the i setting unit 1545 counts up i and skips until i=10.

[0118] In step St1213, the i comparison unit 1542 compares i with Ngear (=9). Since i=10, the process proceeds to step St1222. In step St1222, the i setting unit 1545 resets i to 1 and then proceeds to step St1223. In step St1223, the gear ratio setting unit 1544 checks whether there is at least one gear ratio state that is either "provisionally determined" or "confirmed" among all gear (stage) gear ratio states. As shown in Table 20, the gear ratio state of gear G3 is "provisionally determined," so the process proceeds to step St1225. In step St1225, the gear ratio setting unit 1544 checks whether there is one gear ratio state that is "provisionally determined," and whether the gear ratio states above and below it are "excluded." As shown in Table 20, the only gear with a "provisional determination" gear ratio state is gear G3, and the gear ratio state of gear G2 above gear G3 is "excluded," and the gear ratio state of gear G4 below gear G3 is also "excluded," so the process proceeds to step St1226. In step St1226, as shown in Table 21, the gear ratio setting unit 1544 changes the gear ratio state of gear G3 (3rd gear) from "provisional determination" to "confirmed." [Table 21] Thus, in Example 3, it is possible to determine with high accuracy that the current gear ratio is gear G3.

[0119] In this embodiment, in steps St3 and St9 of Figure 4, the control device 50 determines that the gear ratio Gr (stage) is such that the rotational speed ratio R (actual rotational speed ratio) is within the threshold range in Table 1 for a predetermined period (for example, the time it takes for one wheel (rear wheel 3) to rotate). However, the gear ratio state determination process continues even after the determination. If the driver changes the gear ratio Gr (stage), the gear ratio (stage) determined before the change no longer satisfies equation (1). At this time, the control device 50 detects that the gear ratio Gr has been changed.

[0120] To summarize Examples 1 to 3, the fourth calculation unit 1540 is configured as follows: Based on the signal from the first calculation unit 51 indicating the rotational speed Nw (rpm) of the wheel and the signal from the second calculation unit 52 indicating the rotational speed Nm (rpm) of the motor 40, the rotational speed ratio R (ratio of actual rotational speeds) is calculated according to formula (E) (steps St1211 and St1212). For one or more of the gear ratios Gr (gears G1 to G9), if the ratio R is within the threshold range for a predetermined number of times (count threshold, 6 in this embodiment) or more (step St1217), one or more gear ratios Gr (stages) are tentatively determined (step St1219). For gear ratios Gr (stages) that have been tentatively determined, if the ratio R is no longer within the threshold range (step St1215), that gear ratio Gr (stage) is excluded (step St1220). If two gear ratios Gr(stage) adjacent to one provisionally determined gear ratio Gr(stage) are both excluded (step St1225), the provisionally determined gear ratio Gr(stage) is determined as the gear ratio (step St1226). In this way, according to the electric assist bicycle 1 of this embodiment, by using a Hall sensor or the like to detect the rotational speed Nm (rpm) of the motor 40, the fourth calculation unit 1540 can determine the current stage with higher accuracy.

[0121] Figure 10(a) is a diagram illustrating gear shift detection and motor control in electric assist bicycle 1. In Figure 10(a), the vertical axis represents the status of gear determination in the software. The voltage output represents the gear ratio, and the horizontal axis represents time. "Unconnected" indicates cases where the assist output is suppressed at the start of pedaling or where the assist output is suppressed after detecting a gear change. As shown in Figure 10(a), the time ta from changing from gear G9 (9th gear) to gear G8 (8th gear) and then confirming gear G8 (8th gear) after the gear ratio state determination process shown in Figure 9 above is longer than the time tb from changing from gear G8 (8th gear) to gear G7 (7th gear) and confirming gear G7 (7th gear). A similar relationship holds true, with the shortest time tc being the time from changing from gear G2 (2nd gear) to gear G1 (1st gear) and confirming gear G1 (1st gear). This is because heavier gears have a smaller difference in the number of teeth between the upper and lower gears, so it takes longer for the gear to be confirmed compared to lighter gears. For example, as shown in Table 1, gear G9 (9th stage) has 11 teeth and gear G8 (8th stage) has 13 teeth, so the difference in the number of teeth between gears G9 and G8 is 2. On the other hand, gear G2 (2nd stage) has 30 teeth and gear G1 (1st stage) has 36 teeth, so the difference in the number of teeth between gears G2 and G1 is 6. Note that the time it takes to change from gear G9 (9th stage) to gear G8 (8th stage) and to become fixed as gear G8 (8th stage) is the same as the time it takes to change from gear G8 (8th stage) to gear G9 (9th stage) and to become fixed as gear G9 (9th stage).

[0122] Figure 10(b) is an enlarged view of the portion of Figure 10(a) from the change from gear G9 (9th gear) to gear G8 (8th gear), and from the gear ratio state determination process shown in Figure 9 until it is determined to be gear G8 (8th gear). Immediately after the change from gear G9 (9th gear) to gear G8 (8th gear), the assist output is suppressed. Next, gear G8 (8th gear) is tentatively determined, and the voltage output becomes the voltage level of gear G8 (8th gear). Next, gear G8 and gear G7 are tentatively determined, and the voltage output becomes the voltage level between gear G8 (8th gear) and gear G7 (7th gear). Next, gear G7 (7th gear) is excluded, and since only gear G8 (8th gear) is tentatively determined, the voltage output becomes the voltage level of gear G8 (8th gear). Next, gear G9 (9th stage) is also tentatively identified, and since both gear G8 (8th stage) and gear G9 (9th stage) are tentatively identified, the voltage output will be at a voltage level between gear G8 (8th stage) and gear G9 (9th stage). Finally, gear G9 (9th stage) is excluded, gear G8 (8th stage) is confirmed, and the voltage output becomes the voltage level of gear G8 (8th stage).

[0123] Figure 10(c) is an enlarged view of the portion of Figure 10(a) from the change from gear G2 (2nd gear) to gear G1 (1st gear), through the gear ratio state determination process shown in Figure 9, until it is determined to be gear G1 (1st gear). Immediately after the change from gear G2 (2nd gear) to gear G1 (1st gear), the assist output is suppressed. Next, gear G1 (1st gear) is provisionally determined, and the voltage output becomes the voltage level of gear G1 (1st gear). As mentioned above, because the difference in the number of teeth between gears G2 and G1 is large, the determination is not ambiguous.

[0124] Now, let's return to Figure 4 and explain the control steps from step St3 onward.

[0125] (Step St3) Based on the wheel rotation speed Nw (rpm) calculated by the first calculation unit 51, the table T stored in the storage unit 58, and the "data indicating the current stage" updated in step St2, the control device 50 calculates the first target rotation speed Npg1 (rpm) of the pedal 4 in the determination unit 56 using the above-described formula (C). The control device 50 stores this data of the first target rotation speed Npg1 (rpm) in the storage unit 58. Then, the control device 50 advances the control steps to step St4.

[0126] (Step St4) The control device 50 reads the data of the first rotational speed Npg1 (rpm) calculated in step St3 from the storage unit 58, and the determination unit 56 determines whether the first rotational speed Npg1 (rpm) is greater than or equal to the rotational speed Np (rpm) of the pedal 4 input from the fifth sensor 9. The control device 50 determines if the rotational speed Np (rpm) of the pedal 4 input from the fifth sensor 9 is greater than the first rotational speed If the rotational speed of pedal 4 is Np(rpm) or higher, the control step is returned to step St1. On the other hand, if the rotational speed Np(rpm) of pedal 4 input from the fifth sensor 9 falls below the first rotational speed Npg1(rpm) (or is less than or equal to the first rotational speed Npg1(rpm)), the control device 50 advances the control step to step St5. Specifically, the control device 50 outputs the first signal S1 from the determination unit 56 to the output adjustment unit 55 and advances the control step to step St5. Note that if the rotational speed Np(rpm) of pedal 4 falls below the first rotational speed Npg1(rpm), as will be explained again later, it means that the rotation of pedal 4 (crankshaft 23) is not transmitted to the chainring CR, and pedal 4 is spinning freely.

[0127] (Step St5) When the first signal S1 is input to the output adjustment unit 55 (i.e., when pedal 4 is detected to be slipping), the control device 50 outputs a third signal S3 to the drive signal generation unit 59, which indicates the suppression torque command value RTm(Nm) calculated by the third calculation unit 53. As described above, this suppression torque command value RTm may be the first suppression torque command value RTm1 or the second suppression torque command value RTm2. When the third signal S3 is input to the drive signal generation unit 59, the control device 50 generates a drive signal Sd in the drive signal generation unit 59 to cause the motor 40 to exert a torque of the suppression torque command value RTm(Nm) indicated by the third signal S3, and controls the drive of the motor 40 based on this drive signal Sd. In other words, in this step, if the first suppression torque command value RTm1 is output, the motor 40 stops driving, and if the second suppression torque command value RTm2 is output, the motor 40 continues to drive, but the driver does not feel the assistance from the motor 40. Thus, in this step, the electric assist bicycle 1 enters an assist-off state. The control device 50 then proceeds to step St6 in the control process.

[0128] (Step St6) The control device 50 again determines whether a signal Sa indicating that the wheel has rotated by a predetermined rotation angle An(deg) has been input to the fourth calculation unit 1540. If the control device 50 determines that a signal Sa has been input to the fourth calculation unit 1540 (i.e., if a second signal Sa has been input to the fourth calculation unit 1540 in one cycle of the steps in this control), it advances the control steps to step St7. If it determines that a signal Sa has not been input to the fourth calculation unit 1540, it repeats this step.

[0129] (Step St7) Based on the wheel rotation speed Nw (rpm) calculated by the first calculation unit 51, the table T stored in the storage unit 58, and the data indicating the "current stage" determined in step St2 and stored in the storage unit 58, the control device 50 calculates the second target rotation speed Npg2 (rpm) of the pedal 4 using the above-described formula (D) in the determination unit 56. The control device 50 stores this data of the second target rotation speed Npg2 (rpm) in the storage unit 58. Then, the control device 50 advances the control steps to step St8.

[0130] (Step St8) The control device 50 reads the data of the second rotational speed Npg2 (rpm) calculated in step St7 from the storage unit 58, and the determination unit 56 determines whether the second rotational speed Npg2 (rpm) is greater than or equal to the rotational speed Np (rpm) of the pedal 4 input from the fifth sensor 9. If the rotational speed Np (rpm) of the pedal 4 input from the fifth sensor 9 exceeds the second rotational speed Npg2 (rpm) (or is greater than or equal to the second rotational speed Npg2 (rpm)), the control device 50 advances the control step to step St9. Specifically, the control device 50 outputs the second signal S2 from the determination unit 56 to the output adjustment unit 55 and advances the control step to step St9. On the other hand, if the rotational speed Np (rpm) of the pedal 4 input from the fifth sensor 9 is less than or equal to the second rotational speed Npg2 (rpm) (or is greater than or equal to the second rotational speed Npg If the speed is below 2 (rpm), the control step is advanced to step St10.

[0131] The control device 50 may proceed to step St9 if the rotational speed Np (rpm) of the pedal 4 input from the fifth sensor 9 is equal to or greater than the second rotational speed Npg2 (rpm), and to step St10 if the rotational speed Np (rpm) of the pedal 4 input from the fifth sensor 9 is less than the second rotational speed Npg2 (rpm).

[0132] (Step St9) When the second signal S2 is input to the output adjustment unit 55, the control device 50 outputs a fourth signal S4 to the drive signal generation unit 59, which indicates the first torque command value Tm (Nm) calculated by the third calculation unit 53. The control device 50 then generates a drive signal Sd in the drive signal generation unit 59 to cause the motor 40 to exert a torque of the first torque command value Tm (Nm) indicated by the fourth signal S4, and controls (starts) the drive of the motor 40 based on this drive signal Sd. In other words, in this step, the motor 40 starts driving with the second driving force, and the assistance to the pedal 4 starts (resumes). In this step, the control device 50 controls the motor 40 so that it drives to the stage determined in step St10, which will be described later, based on the first torque command value Tm (Nm). The control device 50 then returns the control steps to step St1.

[0133] (Step St10) The control device 50 determines whether the pedal 4 is rotating for a specified time, in other words, whether the rotation of the pedal 4 has not stopped for a specified time. In this embodiment, if the signal input from the fifth sensor 9 (cadence sensor) to the determination unit 56 changes during the specified time, the determination unit 56 determines that the pedal 4 is rotating for the specified time (in other words, the rotation of the pedal 4 has not stopped for a specified time). On the other hand, if the signal input from the fifth sensor 9 (cadence sensor) to the determination unit 56 does not change during the specified time, the determination unit 56 determines that the pedal 4 is not rotating for the specified time. If the control device 50 determines that the pedal 4 is not rotating for the specified time, it returns the control step to step St6. On the other hand, if the control device 50 determines that the pedal 4 is rotating for the specified time (in other words, the rotation of the pedal 4 has not stopped for a specified time), it executes the gear update flow GRF. That is, the control device 50 executes the gear update flow GRF when it determines that the pedal 4 is free-spinning.

[0134] Furthermore, the method for determining whether or not pedal 4 has stopped rotating for a specified period of time is not limited to the method described above.

[0135] The following describes the gear replacement flow GRF. Figure 11 is a flowchart of the gear replacement flow GRF.

[0136] As shown in Figure 11, the gear update flow GRF includes steps St101, St102, and St103.

[0137] (Step St101) The control device 50 may use the second sensor 6 to determine whether or not the motor 40 is being driven (rotating). For example, the determination unit 56 may read the motor 40 rotation speed Nm data calculated by the second calculation unit 52 based on the signal input from the second sensor 6 from the storage unit 58, and the determination unit 56 may determine that the motor 40 is rotating if the motor 40 rotation speed Nm is greater than (or above) a predetermined threshold, and determine that the motor 40 is not rotating if the motor 40 rotation speed Nm is below (or below) a predetermined threshold. In this step, if the motor 40 is not rotating, it means that the motor 40 is stopped based on the first suppression torque command value RTm1. The control device 50 determines if the motor 40 is rotating. If it is determined that this is not the case, the control process proceeds to step St102.

[0138] On the other hand, if the control device 50 determines that the motor 40 is rotating, it advances the control step to step St103. In this step, if the motor 40 is rotating, it means that the motor 40 is rotating based on the second suppression torque command value RTm2. That is, in this case, during the period from the release of the assist (step St5) to the start (restart) (step St9), while the pedal 4 is rotating (free-spinning), the motor 40 is driven (rotating) with the fifth driving force based on the second suppression torque command value RTm2.

[0139] (Step St102) The determination unit 56 outputs the fifth signal S5 to the output adjustment unit 55. When the output adjustment unit 55 receives the fifth signal S5, it outputs the seventh signal S7, indicating the second torque command value Tm2, ​​to the drive signal generation unit 59. As a result, the stopped motor 40 starts up with the third driving force (starting torque). Next, the determination unit 56 outputs the sixth signal S6 to the output adjustment unit 55. When the output adjustment unit 55 receives the sixth signal S6, it outputs the eighth signal S8, indicating the third torque command value Tm3, to the drive signal generation unit 59. As a result, the motor 40 is driven (rotates) with the first driving force (inertia torque). In other words, the motor 40 is driven while the pedal 4 is rotating (free-spinning) during the period from the release of the assist (step St5) to the start (restart) (step St9). Furthermore, during the period from the release of the assist (step St5) to the start (restart) (step St9), the motor 40 starts with a third driving force (starting torque), and the motor 40, having started with the third driving force, rotates with a first driving force (inertia torque) which is smaller than the third driving force. In this way, through this step, during the period from the release of the assist (step St5) to the start (restart) (step St9), while the pedal 4 is rotating (free-spinning), the motor 40 is driven (starts and then rotates) with a torque so weak that the assist from the motor 40 is not felt. Then, the control device 50 advances the control steps to step St103.

[0140] (Step St103) If the control device 50 determines in step St101 that the motor 40 is rotating, the fourth calculation unit 1540 determines the current stage in the same manner as in step St2, based on the rotational speed Nm of the motor 40 rotating with the fifth driving force based on the second suppression torque command value RTm2.

[0141] On the other hand, if the control device 50 determines in step St101 that the motor 40 is not rotating, it proceeds through step St102 and determines the current stage in the fourth calculation unit 1540 in the same manner as in step St2. That is, if the control device 50 determines in step St101 that the motor 40 is not rotating, it determines the current stage in the fourth calculation unit 1540 in the same manner as in step St2, based on the rotational speed Nm of the motor 40 rotating with the first driving force (inertia torque) based on the third torque command value Tm3.

[0142] Then, the control device 50 updates the data for the current stage stored in the memory unit 58 with the data for the current stage determined in step St103. Then, as shown in Figure 4, the control device 50 returns the control step to step St6. Thus, the gear update flow GRF is completed. Note that if the control adopted in step St5 is such that the motor 40 is stopped based on the first suppression torque command value RTm1, the control steps in this embodiment return to step St6 via the gear update flow GRF, so the drive of the motor 40 is released after the determination by the control device 50 (i.e., after step St103).

[0143] After the gear update flow GRF, the control unit 50 executes step St8 again. If the answer in step 8 is YES, then step St9 is executed, and assistance by motor 40 (i.e., driving by the second driving force of motor 40) is started (restarted).

[0144] Therefore, in the electric assist bicycle 1, assistance is initiated based on the changed gear ratio (step St103) between the time assistance is deactivated (step St5) and restarted (step St9). In other words, according to the electric assist bicycle 1, after the pedal 4 reaches a predetermined rotational speed (after the pedal 4 is no longer free-spinning), the motor 40 assists the pedal 4 with a second driving force based on the gear ratio Gr determined by the gear update flow GRF.

[0145] In particular, if it is determined that the motor 40 is not rotating in step St101, according to the electric assist bicycle 1, during the period from the release of the assist (step St5) to the start (restart) (step St9), while the pedal 4 is rotating (free-spinning), the motor 40 is started by a third driving force (starting torque) provided by the second torque command value Tm2, ​​and then rotates with a first driving force (inertia torque) provided by the third torque command value Tm3. The first and third driving forces of the motor 40 are smaller than the second driving force of the motor 40 (driving force in the assist state).

[0146] As explained above, in the electric assist bicycle 1, when the rotation speed of pedal 4 decreases and falls below the first rotation speed Npg1, the assist to pedal 4 is released, and when the rotation speed of pedal 4 increases and exceeds the second rotation speed Npg2, the assist to pedal 4 is started. The first rotation speed Npg1 and the second rotation speed Npg2 are collectively referred to as the target rotation speed Npg, the number of teeth of the sprocket Sp of the electric assist bicycle 1 is nsi, the number of teeth of the chainring CR of the electric assist bicycle 1 is nc, and the rotation speed of the wheels 2 and 3 of the electric assist bicycle 1 is Nw, and are obtained by the following equation (1). Npg=k(n s i / n c )Nw···(1) (k=k1 (when the first rotational speed Npg1)) (k=k2(>k1)(in the case of the second rotational speed Npg2))

[0147] Here, the first target rotational speed Npg1 is a value obtained by multiplying the current gear ratio Gr(nsi / nc) by the current wheel rotational speed Nw(rpm) and a constant k1 less than 1. Therefore, if the rotational speed Np(rpm) of pedal 4 is equal to or greater than the first target rotational speed Npg1, it can be estimated that the rotational speed Np(rpm) of pedal 4 is synchronized with the wheel rotational speed Nw(rpm), and that the pedal 4 (chainring CR) and crankshaft 23 rotate in the forward direction in synchronization with the output gear of the reduction gear 10, thereby transmitting the driving force of the MDU 100 to pedal 4. Conversely, if the rotational speed Np (rpm) of pedal 4 is lower than the first target rotational speed Npg1, it can be inferred that the rotational speed Np (rpm) of pedal 4 is lower than the rotational speed Nw (rpm) of the wheel, and that the pedal 4 (chainring CR) and crankshaft 23 are rotating in the opposite direction, and the driving force of MDU 100 is not transmitted to pedal 4 (pedal 4 is spinning freely).

[0148] As explained in the control steps in Figure 4 above, in the electric assist bicycle 1, when the rotational speed Np (rpm) of pedal 4 decreases and falls below the first rotational speed Npg1 calculated by equation (C), the motor 40 is stopped (assistance to pedal 4 is released), while when the rotational speed Np (rpm) of pedal 4 increases and exceeds the second rotational speed Npg2, the motor 40 is started (assistance to pedal 4 is started). In other words, in the electric assist bicycle 1, assistance to pedal 4 is released when the reverse rotation of pedal 4 can be estimated, and assistance to pedal 4 is started when the synchronized forward rotation of pedal 4 can be estimated.

[0149] Therefore, according to the electrically power-assisted bicycle 1, when the rotational speed of the pedal 4 is lower than the vehicle speed (the wheel rotation speed Nw (rpm)) (when the pedal 4 idles), the assistance by the motor can be more reliably canceled. Furthermore, even when a strain-type torque sensor is used as a sensor for detecting the pedaling force Tf (N), the assistance by the motor can be more reliably canceled when the rotational speed of the pedal 4 is lower than the vehicle speed. Therefore, according to the electrically power-assisted bicycle 1, appropriate assistance can be implemented.

[0150] Here, consider a case where the rotation speed Np (rpm) of the pedal 4 drops to (n s i / n c )×Nw´ (Nw´<Nw) while the rotation speed Nw (rpm) of the wheel remains unchanged from when the pedal 4 is not idling, and the pedal 4 starts idling. In this case, if the motor 40 is being driven, the chain ring CR continues to rotate at a rotation speed of (n s i / n c )×Nw (rpm) in the same manner as when the pedal 4 is not idling. The reason for this is as follows.

[0151] Assuming that the motor 40 decelerates in the same manner as the pedal 4, the chain ring CR and the sprocket SP also decelerate, and as a result, the clutch RC of the rear wheel 3 is disengaged (becomes uncoupled). In this case, the load seen from the motor 40 is only on the chain ring CR, the transmission member TC, and the sprocket SP, so the motor 40 is substantially in a no-load state. If the torque of the motor 40 acts in such a no-load state, the chain ring CR and the sprocket SP accelerate up to the rotation speed at which a large load including the wheel, the vehicle body, and the driver is applied (that is, the rotation speed at which the clutch RC of the rear wheel 3 engages). As a result, the chain ring CR rotates at a rotation speed of (n s i / n c )×Nw (rpm) in accordance with the wheel rotation speed Nw (rpm).

[0152] In this case, because the rotational speed Np (rpm) of pedal 4 is slower than that of chainring CR, the clutch of the reduction gear 10 disengages, and pedal 4 (crankshaft 23) and the output gear of the reduction gear 10 become disconnected. As a result, all drive systems except pedal 4 move in conjunction. In other words, in this case, even though the force applied to pedal 4 is not contributing to the propulsion of the electric assist bicycle 1, the motor 40 moves the electric assist bicycle 1.

[0153] As described above, with the electric assist bicycle 1, when the rotation speed of the pedal 4 is slower than the vehicle speed (wheel rotation speed Nw (rpm)) (when the pedal 4 is free-spinning), the motor assist can be more reliably released. Therefore, it is possible to effectively suppress the situation in which the motor 40 moves the electric assist bicycle 1 even though the force being applied to the pedal 4 is not contributing to the propulsion of the electric assist bicycle 1.

[0154] Furthermore, in the electric assist bicycle 1, the current gear is determined based on the rotational speed Nm of the rotating motor 40, thus improving the accuracy of gear determination as described above. Therefore, the electric assist bicycle 1 makes it possible to provide more appropriate assistance.

[0155] Furthermore, the electric assist bicycle 1 is equipped with wheels 2 and 3, a control device 50, pedals 4, a rotating device 70 having a reduction gear 10 and a motor 40 that assists pedals 4, a first sensor 5 (sensor) that detects the rotational speed of wheels 2 and 3, a second sensor 6 (sensor) that detects the rotational speed of motor 40, and a fifth sensor 9 (sensor) that detects the rotational speed of pedals 4. The control device 50 determines the gear ratio Gr of wheels 2 and 3 based on the rotational speed Nw of wheels 2 and 3, the rotational speed Nm of motor 40, and the reduction ratio grMDU of the rotating device 70. When the rotational speed Np of pedals 4 decreases and falls below the first rotational speed Npg1, the assist to pedals 4 is released, and when the rotational speed Np of pedals 4 increases and exceeds the second rotational speed Npg2, the assist to pedals 4 is started, and based on the changed gear ratio Gr between the release and start of the assist... Then the assistance begins.

[0156] With this configuration, the gear update flow GRF is executed between the release and start of the assist (between step St5 and step St9 shown in Figure 4). Therefore, even if the gear (stage) is changed while pedal 4 is spinning freely, the changed gear (stage) can be accurately determined based on the gear ratio state determination (see Figures 6(a) and 9). Consequently, the electric assist bicycle 1 can suppress unintended assist operation caused by a discrepancy between the "current stage information stored in the memory unit 58" and the "actual stage" after pedal 4 has finished spinning freely (for example, after step St9). Consequently, the electric assist bicycle 1 can provide more appropriate assist.

[0157] Although the present invention has been described above using an electric assist bicycle 1 as an example, the present invention is not limited thereto, and those skilled in the art can appropriately modify the electric assist bicycle 1 according to the embodiment in accordance with conventionally known knowledge. As long as such modifications still possess the configuration of the present invention, they are of course included within the scope of the present invention. [Explanation of symbols]

[0158] 1...Electric-assist bicycle, 2,3...Wheels, 4...Pedals, 5,6,9...Sensors, 10...Gear reducer, 50...Control device, 70...Rotation device, Gr...Gear ratio

Claims

1. Wheels and, Control device and Pedals and, A rotating device having a reduction gear and a motor that assists the pedal, A sensor for detecting the rotation speed of the wheel, A sensor for detecting the rotational speed of the motor, A sensor for detecting the rotation speed of the pedal, Equipped with, The control device determines the gear ratio of the wheel based on the rotational speed of the wheel, the rotational speed of the motor, and the reduction ratio of the rotating device. When the rotational speed of the pedal decreases and falls below the first rotational speed, the assist for the pedal is released. When the rotational speed of the pedal increases and exceeds the second rotational speed, assistance to the pedal is initiated. An electric assist bicycle in which the assist is started based on the changed gear ratio between the time the assist is deactivated and the time it is activated.

2. The electric assist bicycle according to claim 1, wherein the motor is driven while the pedals are rotating during the period from the release to the start of the assist.

3. The electric assist bicycle according to claim 2, wherein the motor is deactivated after determination by the control device.

4. During the period from the release to the start of the assist, while the pedal is rotating, the motor rotates with the first driving force. After the pedal reaches a predetermined rotational speed, the motor assists the pedal with a second driving force. The electric assist bicycle according to claim 3, wherein the first driving force of the motor is less than the second driving force of the motor.

5. During the period from the release of the assist to its start, the motor is started with a third driving force. The motor, which was started by the third driving force, rotates with the first driving force. The electric assist bicycle according to claim 4, wherein the first driving force and the second driving force are smaller than the third driving force.

6. When the rotational speed of the pedal decreases and falls below the first rotational speed, the assist for the pedal is released. When the rotational speed of the pedal increases and exceeds the second rotational speed, assistance to the pedal is initiated. The electric assist bicycle according to any one of claims 1 to 5, obtained by the following formula (1), where the first rotational speed and the second rotational speed are collectively referred to as the target rotational speed Npg, the number of teeth of the sprocket of the electric assist bicycle 1 is nsi, the number of teeth of the chainring of the electric assist bicycle 1 is nc, and the rotational speed of the wheel of the electric assist bicycle is Nw. Npg=k(n ｓ ｉ / n ｃ )Nw・・・(1) (k = k1 (in the case of the first rotational speed Npg1)) (k = k² (>k1) (in the case of the second rotational speed Npg²))

7. The aforementioned wheel is designated as the first wheel, and a second wheel is provided. The gear ratio of the wheels is the ratio of the rotational speed of the second wheel to the rotational speed of the first wheel. An electric assist bicycle according to any one of claims 1 to 6.

Images