Power-assisted bicycle

Abstract

To provide a control device capable of suppressing occurrence of an abnormal sound in a power-assisted bicycle.SOLUTION: A control device 50 increases a degree of assisting rotation of a pedal 4 when a ratio R between a rotational speed Nw (rpm) of a wheel and a rotational speed Nm (rpm) of a motor 40 is within a prescribed range Ra, in comparison with a degree of assisting the rotation of the pedal 4 when the ratio R between the rotational speed Nw (rpm) of the wheel and the rotational speed Nm (rpm) of the motor 40 is outside the prescribed range Ra.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to an electric assist bicycle.

Background Art

[0002] An electric assist bicycle configured to determine the necessity of assist based on the pedaling force applied to the pedals and, when assist is necessary, rotate a motor to provide assist to the electric assist bicycle is known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a bicycle including an electric assist bicycle, for example, when traveling downhill or when the pedal rotation speed is slow with respect to the vehicle speed, the pedals spin and the rotation of the pedals does not become a driving force. In such a case, in an electric assist bicycle, since the force (pedaling force) applied by the driver to pedal the bicycle does not become a driving force, it is preferable that assist by the motor is not provided. However, when a strain type torque sensor is used as a sensor for detecting the pedaling force, the pedaling force is detected even when pedaling downhill or the like, so assist may occur when the pedal rotation speed is slow with respect to the vehicle speed.

[0005] Therefore, one of the problems of the present invention is to provide an electric assist bicycle capable of more reliably canceling the assist of the motor when the pedal rotation speed is slow with respect to the vehicle speed.

Means for Solving the Problems

[0006] (1) In the electric assist bicycle according to the present invention, when the rotation speed of the pedal decreases and falls below the first rotation speed, the assist of the pedal is released, and when the rotation speed of the pedal increases and exceeds the second rotation speed, the assist to the pedal is started.

[0007] (2) In (1), the second rotation speed may be greater than the first rotation speed.

[0008] (3) In (1) or (2), the first rotation speed and the second rotation speed are collectively referred to as the target rotation speed Npg. When the number of teeth of the sprocket of the electric assist bicycle 1 is n s i and the number of teeth of the chainring of the electric assist bicycle 1 is n c and the rotation speed of the wheel of the electric assist bicycle is Nw, it may be obtained by the following formula (1). Npg = k(n s i / n c )Nw ··· (1) (k = k1 (in the case of the first rotation speed Npg1)) (k = k2(> k1) (in the case of the second rotation speed Npg2))

[0009] (4) In any one of (1) to (3), the time from when the first gear ratio is changed to the second gear ratio until the assist of the pedal corresponding to the second gear ratio is started may be different from the time from when the third gear ratio is changed to the fourth gear ratio until the assist of the pedal corresponding to the fourth gear ratio is started.

[0010] (5) In (4), the time until the assist of the pedal corresponding to the second gear ratio is started may be within the time required for one rotation of the wheel.

[0011] (6): In any one of (1) to (5), the electrically assisted bicycle is provided with a wheel, a control device, a rotation device having a reducer and a motor that assists the pedals, 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 pedals, and Nw is the rotation speed (rpm) of the wheel, Nm is the rotation speed (rpm) of the motor, and gr MDU is the reduction ratio of the rotation device, the control device may determine whether the magnitude of the following equation (E) is included within a predetermined range corresponding to the gear ratio of the power-assisted bicycle. Nm / (gr MDU Nw) Equation (E) [Brief explanation of the drawings]

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7(a)

Figure 7(b)

Figure 8

Figure 9

Figure 10

Figure 11(a)

Figure 11(b)

Figure 11(c)

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments for carrying out the electric assist bicycle according to the present invention are illustrated together with the accompanying drawings. The embodiments illustrated below are for facilitating the understanding of the present invention and are not for limiting and interpreting the present invention. The present invention can be changed and improved from the following embodiments without departing from its gist. Also, in the above accompanying drawings, the dimensions of each member may be exaggerated or reduced for easy understanding, or hatching may be omitted.

[0014] (First Embodiment) FIG. 1 is a side view showing an electric assist bicycle according to the first embodiment. As shown in FIG. 1, the electric assist bicycle 1 includes a frame F, a handle H, a saddle S, a transmission body C, a chain ring CR, a sprocket SP, a battery B, and a motor drive unit (MDU) 100 as a rotating device (hereinafter referred to as "MDU 100"), wheels (front wheel 2 and rear wheel 3), and pedals 4. The chain ring CR is a gear that rotates together with the pedals 4 under predetermined conditions (for example, when the driving force of the MDU 100 is transmitted to the pedals 4). In this embodiment, it includes a single-stage gear. The sprocket SP is attached to the rear wheel 3 and is configured as a multi-stage gear in which a plurality of gears are stacked. That is, the sprocket SP has i-stage (i is a natural number of 2 or more) gears. 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 body C is bridged between the gear of the chain ring CR and the gear of the sprocket SP. The MDU 100 includes a motor 40 and a control device 50 that controls the drive of the motor 40 to provide assistance to the electric assist bicycle 1.

[0015] When the driver sits on the saddle S of the electric assist bicycle 1 and paddles the pedals 4 to rotate the pedals 4, under predetermined conditions, the driving force is transmitted to the wheels (typically the rear wheel 3) via the chain ring CR, the sprocket SP, and the transmission body C, enabling forward travel. 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 with which the driver paddles the pedals 4 is reduced (assisted) by the assistance caused by the rotation of this motor 40. The transmission body C may be a chain or a belt.

[0016] In the vicinity of the rotation axis of, for example, the front wheel 2 or the rear wheel 3, a first sensor 5 for detecting 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 is arranged. In this specification, "detecting the rotational speed Nw (rpm) of the wheels and the vehicle speed Vb (km / h) of the electric assist bicycle 1" may mean that the first sensor 5 itself calculates the rotational speed Nw (rpm) of the wheels and the vehicle speed Vb (km / h) of the electric assist bicycle 1, or the first sensor 5 outputs signals necessary for calculating the rotational speed Nw (rpm) of the wheels and the vehicle speed Vb (km / h) of the electric assist bicycle 1 to the control device 50, and the control device 50 calculates the rotational speed Nw (rpm) of the wheels and the vehicle speed Vb (km / h) of the electric assist bicycle 1, or the first sensor 5 outputs signals necessary for calculating the rotational speed Nw (rpm) of the wheels and the vehicle speed Vb (km / h) of the electric assist bicycle 1 to another arithmetic unit (not shown), and the arithmetic unit that receives the output signal calculates the rotational speed Nw (rpm) of the wheels and the vehicle speed Vb (km / h) of the electric assist bicycle 1 and outputs the result to the control device 50. Fig. 1 shows an example in which the first sensor 5 is arranged in the vicinity of the rotation axis of the rear wheel 3. As the first sensor 5, a known sensor capable of detecting the rotational speed Nw (rpm) of the wheels and the vehicle speed Vb (km / h) of the electric assist bicycle 1, or capable of outputting signals necessary for calculating the rotational speed Nw (rpm) of the wheels 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 a hall sensor capable of detecting the rotational speed Nw (rpm) of the wheels and the vehicle speed Vb (km / h) of the electric assist bicycle 1, or an optical sensor capable of detecting the rotational speed Nw (rpm) of the wheels and the vehicle speed Vb (km / h) of the electric assist bicycle 1. Also, the position where the first sensor 5 is arranged may be any position where the rotational speed Nw (rpm) of the wheels and the vehicle speed Vb (km / h) of the electric assist bicycle 1 can be detected. For example, it may be arranged at a position away from the rotation axis of the front wheel 2 or the rear wheel 3.

[0017] In addition, a fourth sensor 8 for detecting a predetermined rotation angle An (deg) of the wheel is disposed, for example, near the rotation axis of the front wheel 2 or the rear wheel 3. 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 the fourth sensor 8 outputs a signal necessary for calculating 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 the fourth sensor 8 outputs a signal necessary for calculating the predetermined rotation angle An (deg) of the wheel to another arithmetic device (not shown), and the arithmetic device that receives the output signal calculates the predetermined rotation angle An (deg) of the wheel and outputs it to the control device 50. FIG. 1 shows an example in which the fourth sensor 8 is disposed 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 or outputting a signal necessary for calculating the predetermined rotation angle An (deg) of the wheel can be used. The fourth sensor 8 may be, for example, a magnetic sensor or a 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. Further, the position where the fourth sensor 8 is disposed may be a position where the predetermined rotation angle An (deg) of the wheel or the predetermined rotation angle An (deg) of the wheel can be detected. For example, it may be disposed at a position away from the rotation axis of the front wheel 2 or the rear wheel 3.

[0018] In the present embodiment, the fourth sensor 8 outputs a signal Sa to a fourth calculation unit 54 (described later) of the control device 50 every time the wheel (for example, the rear wheel 3) rotates by a predetermined rotation angle An (deg). That is, the fourth sensor 8 outputs a signal Sa indicating that the wheel has rotated by a predetermined rotation angle An (deg) to the fourth calculation unit 54 (described later) of the control device 50. The predetermined rotation angle An (deg) is not particularly limited. For example, it may be 30°, 120°, 90°, 60°, 45°, 15°, 10°, or any predetermined angle selected from the range of 1° to 360°.

[0019] Note that the first sensor 5 and the fourth sensor 8 may be the same sensor.

[0020] Also, in the present embodiment, the electric assist bicycle 1 includes a fifth sensor 9 that detects the rotation speed Np (rpm) of the pedal 4. The fifth sensor 9 is not particularly limited as long as it can detect the rotation speed Np (rpm) of the pedal 4. In the present embodiment, a cadence sensor is used as the fifth sensor 9. For example, the fifth sensor 9 may have a magnet attached to a crank arm that connects the pedal 4 and the crankshaft 23, and a sensor attached to the frame F. The sensor attached to the frame F may detect the magnetic force from the magnet attached to the crank arm to detect the rotation speed Np (rpm) of the pedal 4. In this specification, "detecting the rotation speed Np (rpm) of the pedal 4" may mean that the fifth sensor 9 itself calculates the rotation speed Np (rpm) of the pedal 4, or the fifth sensor 9 outputs a signal necessary for calculating the rotation speed Np (rpm) of the pedal 4 to the control device 50, and the control device 50 calculates the rotation speed Np (rpm) of the pedal 4, or the fifth sensor 9 outputs a signal necessary for calculating the rotation speed Np (rpm) of the pedal 4 to another arithmetic device (not shown), and the arithmetic device that receives the output signal calculates the rotation speed Np (rpm) of the pedal 4 and outputs it to the control device 50. In the present embodiment, the fifth sensor 9 outputs a signal indicating the rotation speed Np (rpm) of the pedal 4 to a determination unit 56 (described later) of the control device 50.

[0021] The MDU100 and the battery B are typically arranged around the crankshaft 23 connected to the pedal 4. As shown in FIG. 1, the MDU100 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. inside. The rotating device 70 has a motor 40, a speed reducer 10, and a third sensor 7 as a torque sensor. In FIG. 1, since the rotating device 70 and the control device 50 are housed inside the housing 60 and not visible, they are shown by dashed lines. Note that part or all of the control device 50 may be arranged outside the housing 60. The battery B supplies power to the motor 40 and the control device 50, and the motor 40 and the control device 50 operate with this power.

[0022] The motor 40 of the rotating device 70 is driven under the control of the control device 50 to assist the rotation of the pedal 4 via the speed reducer 10. In this specification, "rotation of the pedal 4" refers to the rotation (revolution) of the pedal 4 around the crankshaft 23. Also, in this specification, "assist" includes reducing the force (pedaling force) for rotating the pedal 4 manually (pedaling the pedal 4). The motor 40 is not particularly limited, and for example, it may be a brushless DC motor having coils corresponding to three phases (U phase, V phase, and W phase).

[0023] As shown in FIG. 1, a second sensor 6 for detecting the rotational speed Nm (rpm) of the rotor of the motor 40 (hereinafter simply referred to as "the rotational speed Nm (rpm) of the motor 40") is arranged on the motor 40. In this specification, "detecting the rotational speed Nm (rpm) of the motor 40" may mean that the second sensor 6 itself calculates the rotational speed Nm (rpm) of the motor 40, or the second sensor 6 outputs a signal necessary for calculating the rotational speed Nm (rpm) of the motor 40 to the control device 50, and the control device 50 calculates the rotational speed Nm (rpm) of the motor 40, or the second sensor 6 outputs a signal necessary for calculating the rotational speed Nm (rpm) of the motor 40 to another arithmetic device (not shown), and the arithmetic device that receives the output signal calculates the rotational speed Nm (rpm) of the motor 40 and outputs it to the control device 50. FIG. 1 shows an example in which the second sensor 6 is mounted on the motor 40. However, the position where the second sensor 6 is arranged is not particularly limited as long as it is a position where the rotational speed Nm (rpm) of the motor 40 can be detected. As the second sensor 6, a known sensor capable of detecting the rotational speed Nm (rpm) of the motor 40 or outputting a signal necessary for calculating the rotational speed Nm (rpm) of the motor 40 can be used. The second sensor 6 may be, for example, a magnetic sensor or a hall sensor capable of detecting the rotational speed Nm (rpm) of the motor 40, or an optical sensor or the like capable of detecting the rotational speed Nm (rpm) of the motor 40.

[0024] Note that in this embodiment, the second sensor 6 does not have to be a sensor for detecting the rotational speed Nm (rpm) of the motor 40. The second sensor 6 may be, for example, a sensor capable of directly calculating the rotational speed Nc (rpm) of the chain ring CR. For example, by attaching a magnet to the chain ring CR and attaching a magnetic sensor near the chain ring CR, it is possible to directly detect the rotational speed Nc (rpm) of the chain ring CR.

[0025] As shown in FIG. 1, the crankshaft 23 passes through 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 extending direction (axial direction or longitudinal direction) of the crankshaft 23. When the pedal 4 is pulled and rotated, the crankshaft 23 rotates. The above-described third sensor 7 is a strain type torque sensor that detects the pedal force Tf (N) applied to the pedal 4 by detecting the strain of the crankshaft 23 deformed due to the pedal force applied to the pedal 4. Therefore, by the third sensor 7 detecting the strain of the crankshaft 23, the pedal force applied to the pedal 4 is detected, and based on this pedal force and the like, the control device 50 controls the driving of the motor 40.

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

[0027] The speed reducer 10 of the rotating device 70 includes a plurality of gears, a plurality of shafts, and a plurality of clutches (one-way clutches), etc. With such a configuration, the speed reducer 10 has a predetermined reduction ratio gr MDU and has this reduction ratio gr MDUBased on this, the rotation of the motor 40 can be decelerated. A chain ring CR is fixed to one of the plurality of gears in the speed reducer 10. The plurality of clutches of the speed reducer 10 include a gear fixed to the chain ring (hereinafter referred to as the "output gear"). The plurality of clutches of the speed reducer 10 are configured to transmit the rotation of the pedal 4 (crankshaft 23) in one direction (forward direction) and not to transmit the rotation in the other direction (reverse direction).

[0028] For example, when the pedal 4 is rotated in the reverse direction (the direction opposite to the direction in which the pedal 4 is rotated to move the electric assist bicycle 1 forward), the crankshaft 23 rotates in the reverse direction relative to the output gear. In this case, the rotation of the pedal 4 (crankshaft 23) is not transmitted to the output gear. That is, since the rotation of the pedal 4 (crankshaft 23) is not transmitted to the chain ring CR fixed to the output gear, the rotation of the wheels according to the pedaling of the pedal 4 is prevented, and the force (pedaling force) applied by the driver to pedal the pedal 4 is prevented from becoming the driving force of the electric assist bicycle 1. In this way, when the pedal 4 (crankshaft 23) rotates in the reverse direction, the assist of the motor 40 is prevented from being transmitted to the pedal 4 by the clutch (one-way clutch) or the like of the speed reducer 10. Hereinafter, the "rotation in the relative reverse direction" may be simply referred to as the "rotation in the reverse direction".

[0029] On the one hand, when the rotational speed of the pedal 4 (crankshaft 23) in the forward direction reaches a certain rotational speed, the clutch connects the crankshaft 23 and the output gear, and the crankshaft 23 and the output gear rotate integrally in the forward direction in synchronization (hereinafter, may be described as "rotation in the synchronized forward direction"). In this way, the rotation of the pedal 4 (crankshaft 23) is transmitted to the output gear. Then, thereby, the chain ring CR fixed to the output gear rotates, and the sprocket SP and the rotation axis of the rear wheel 3 are connected via the transmission body C spanned between the gear of the chain ring CR and the gear of the sprocket SP, and thereby, the driving force due to the rotation of the pedal 4 is transmitted to the rear wheel 3. In other words, when the rotational speed of the pedal 4 (crankshaft 23) in the forward direction reaches a certain rotational speed, the rotational force of the motor 40 can be transmitted to the pedal 4 by the clutch or the like of the speed reducer 10, and the force required to step on the pedal 4 is reduced (assisted) under a predetermined condition. In such a case where rotation in the synchronized forward direction occurs, typically, the rotational speed Np (rpm) of the pedal 4 becomes a value obtained by multiplying the rotational speed Nw (rpm) of the wheel by the gear ratio Gr corresponding to the current gear stage of the sprocket SP.

[0030] Also, as shown in FIG. 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 positive direction with respect to the rotation direction of the rear wheel 3 to the rear wheel 3, and not to transmit the rotation of the sprocket SP that rotates in the reverse direction with respect to the rotation direction of the rear wheel 3. Thereby, when the rotational speed Nw (rpm) of the wheels increases, for example, when driving downhill, the clutch RC disengages, preventing the pedal 4 from rotating quickly following the rapid rotation of the wheels. Also, when the rotational speed Nw (rpm) of the wheels increases, for example, when driving downhill, the clutch RC of the rear wheel 3 described later disengages, preventing the pedal 4 from rotating quickly following the rapid rotation of the wheels. As a result, the crankshaft 23 rotates in the opposite direction relative to the output gear. Also in this case, the rotation of the pedal 4 (crankshaft 23) is not transmitted to the output gear. Therefore, at the timing when the rotation of the sprocket SP that rotates in the positive direction with respect to the rotation direction of the rear wheel 3 is transmitted to the rear wheel 3, as a result of the metal members constituting the clutch RC of the rear wheel 3 coming into contact with each other, the rotational force of the pedal 4 and the rotational force of the motor 40 are transmitted to the rear wheel 3 via the chain ring CR, the sprocket SP, the transmission body C, and the clutch RC of the rear wheel 3.

[0031] Next, the control device 50 will be described in detail. FIG. 2 is a block diagram showing the configurations 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 FIG. 2, the control device 50 includes a control circuit 50a and a drive circuit 50b. Note that the functions and configurations of the control device 50 shown in FIG. 2 may be part of the overall functions and configurations of the control device 50. That is, the control device 50 may include configurations or components other than those shown in FIG. 2.

[0032] The control circuit 50a is realized by a program processing device (e.g., a microcontroller) having a configuration in which a processor such as a CPU, various storage devices such as a RAM and a ROM, and peripheral circuits such as a counter (timer), an A / D conversion circuit, a D / A conversion circuit, a clock generation circuit, and an input / output I / F circuit are connected to each other via a bus or a dedicated line.

[0033] As shown in FIG. 2, in the present embodiment, the control circuit 50a includes, as functional blocks, a first calculation unit 51, a second calculation unit 52, a third calculation unit 53, a fourth calculation unit 54, an output adjustment unit 55, a determination unit 56, a storage unit (memory) 58, and a drive signal generation unit 59. The storage unit 58 may be all or part of the above-described various storage devices such as the RAM and the ROM. The first calculation unit 51, the second calculation unit 52, the third calculation unit 53, the fourth calculation unit 54, the determination unit 56, the output adjustment unit 55, and the drive signal generation unit 59 are realized, for example, in the program processing device as the control circuit 50a, by the processor executing various arithmetic processes according to various programs stored in the above-described various storage devices including the storage unit 58 and controlling peripheral circuits such as a counter and an A / D conversion circuit. In the present embodiment, the above-described various programs include a program (hereinafter sometimes referred to as a "gear stage determination program") for determining the current gear stage (hereinafter sometimes referred to as the "current stage") of the sprocket SP based on the rotational speed Nc (rpm) of the chain ring CR and the rotational speed Nw (rpm) of the wheel.

[0034] When the second sensor 6 is, for example, a hall sensor that detects the rotational speed Nm (rpm) of the motor 40, the gear stage determination program divides the rotational speed Nm (rpm) of the motor 40 by the reduction ratio gr of the reduction gear 10 MDUAfter multiplying by the reciprocal of [the value], the rotational speed Nc (rpm) of the chain ring CR (i.e., the rotational speed Np (rpm) of the pedal 4) is calculated, and based on the calculated rotational speed Nc (rpm) of the chain ring CR and the rotational speed Nw (rpm) of the wheel, the current gear may be determined. Further, when the second sensor 6 is a sensor that directly detects the rotational speed Nc (rpm) of the chain ring CR described above, the gear determination program may determine the current gear based on the rotational speed Nc (rpm) of the chain ring CR detected by the second sensor 6 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 on the reduction ratio gr MDU of the speed reducer 10 (hereinafter, may be referred to as "reduction ratio data"), a table T of the gear ratio Gr of the electric assist bicycle 1, and data indicating the current gear, etc. Note that the control circuit 50a may have other functional blocks.

[0036] Here, the table T of the gear ratio Gr will be described. FIG. 3 is a diagram showing an example of the table T. As described above, in the present embodiment, the chain ring CR includes a single-stage gear, and the sprocket SP has an i-stage gear. Therefore, the number of teeth n c of the chain ring CR is a constant, and the number of teeth n s i of the sprocket SP differs depending on the gear stage (1st stage to i-th stage) of the sprocket SP. Here, the number of teeth of the sprocket SP when the sprocket SP is in the 1st stage is denoted as n s 1 and the number of teeth of the sprocket SP when the sprocket SP is in the 2nd stage is denoted as n s 2 and the number of teeth of the sprocket SP when the sprocket SP is in the 3rd stage is denoted as n s 3 and the number of teeth of the sprocket SP when the sprocket SP is in the i-th stage is denoted as n s i In the present embodiment, the gear ratio Gr of the electric assist bicycle 1 is defined by the following formula (A). Gr = ns i / n c ···(A) As shown in FIG. 3, in the table T, data of the gear ratio Gr based on the formula (A) is associated with each of the gear steps (1st to i-th steps) of the sprocket SP.

[0037] As shown in FIG. 2, the control circuit 50a receives signals output from a first sensor 5 that detects the rotational speed Nw of the wheel and the vehicle speed Vb of the electric assist bicycle 1 described above, a second sensor 6 that detects the rotational speed Nm of the rotor of the motor 40 described above, a third sensor 7 as the torque sensor described above, a fourth sensor 8 that detects a predetermined rotational angle An of the wheel described above, and a fifth sensor 9 that detects the rotational speed Np of the pedal 4 described above. The first calculation unit 51 calculates the rotational speed Nw (rpm) of the wheel based on the signal input from the first sensor 5.

[0038] 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 gauge torque sensor, and further calculates a torque command value Tm (Nm) which is a target value for causing the motor 40 to exert a predetermined torque based on the rotational speed Nw (rpm) of the wheel and the vehicle speed Vb (km / h) calculated by the first calculation unit 51.

[0039] When the second sensor 6 is, for example, a hall sensor that detects the rotational speed Nm (rpm) of the motor 40, 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, and based on the calculated rotational speed Nm (rpm) of the motor 40 and the reduction ratio data (the reduction ratio gr of the speed reducer 10 MDU stored in the storage unit 58), calculates the rotational speed Nc (rpm) of the chain ring CR. The rotational speed Nc (rpm) of the chain ring 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 gr of the speed reducer 10 MDU of. Therefore, the second calculation unit 52 calculates the rotational speed Nc (rpm) of the chain ring CR based on the following formula (B). Nc = Nm / gr MDU ···Formula (B)

[0040] In addition, when the second sensor 6 is a sensor that directly detects the rotational speed Nc (rpm) of the chain ring CR, the value detected by the second sensor 6 directly becomes the value of the rotational speed Nc (rpm) of the chain ring CR.

[0041] By the way, since a sensor (typically, a hall sensor) that detects the rotational speed Nm (rpm) of the motor 40 may be able to detect the rotational angle with higher accuracy than a sensor that directly detects the rotational speed Np (rpm) of the pedal (crankshaft), by calculating the rotational speed Np (rpm) of the pedal 4 using the formula (B), it is possible to obtain more accurate data on the rotational speed Np (rpm) of the pedal 4 (for example, at the time intervals desired for software use). As a first case where the rotational speed can be obtained more accurately by using a sensor that detects the rotational speed Nm (rpm) of the motor 40, in the case of a sensor that directly detects the rotational speed Np (rpm) of the pedal, there is a case where the distance between the magnet on the shaft connecting both pedals 4 and the magnetic sensor slightly changes due to the influence 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 so as to always be in the same position with respect to the rotor of the motor 40, the sensor that detects the rotational speed Nm (rpm) of the motor 40 can substantially always obtain accurate magnetism. Further, as a second case, there is the influence of the power of the rotating body to be detected. That is, in the sensor that detects the rotational speed Nm (rpm) of the motor 40, the power of the rotating body (motor 40) to be detected is electricity, whereas in the sensor that directly detects the rotational speed Np (rpm) of the pedal, the power of the rotating body to be detected is human power. For example, when the detection period is 1 ms, the variation per detection period is smaller for electricity than for human power, and it becomes possible to use it as data in software.

[0042] When the second sensor 6 is a sensor (for example, a Hall sensor) that detects the rotational speed Nm (rpm) of the motor 40, the fourth calculation unit 54 may determine the current gear stage using a gear stage determination program based on the rotational speed Nc (rpm) of the chain ring CR calculated by the second calculation unit 52 according to formula (B) and the rotational speed Nw (rpm) of the wheel calculated by the first calculation unit 51. Further, when the second sensor 6 is a sensor that directly detects the rotational speed Nc (rpm) of the chain ring CR, the fourth calculation unit 54 may determine the current gear stage using a gear stage determination program based on the rotational speed Nc (rpm) of the chain ring CR detected by the second sensor 6 and the rotational speed Nw (rpm) of the wheel calculated by the first calculation unit 51. The fourth calculation unit 54 stores the data indicating the determined current gear stage in the storage unit 58, thereby overwriting (updating) the data indicating the currently stored current gear stage.

[0043] Note that, in order to determine the current gear stage, a gear position sensor (not shown) or the like capable of detecting the gear stage of the sprocket SP may be arranged. When arranging the gear position sensor, the fourth calculation unit 54 may determine the current gear stage based on the signal from the gear position sensor.

[0044] When the signal Sa is input to the fourth calculation unit 54 from the fourth sensor 8 for the first time during one cycle of the steps in the control described later and the current gear stage is calculated, the determination unit 56 reads out the table T and the data indicating the calculated current gear stage from the storage unit 58 to specify the gear ratio Gr of the current gear stage. For example, as shown in FIG. 3, when the current gear stage is the i-th gear stage, the gear ratio Gr is n s i / n c is. Then, when the signal Sa is input to the fourth calculation unit 54 from the fourth sensor 8 for the first time during one cycle of the steps in the control described later and the current gear stage is calculated, the gear ratio Gr (n of the calculated current gear stage s i / n cBased on the vehicle speed V (km / h) calculated by the first calculation unit 51 and the rotational speed Nw (rpm) of the wheel calculated by the first calculation unit 51, the first target rotational speed Npg1 (rpm) of the pedal 4 (hereinafter, may be simply referred to as "the first rotational speed Npg1") is calculated using the following formula (C). Npg1 = k1(n s i / n c )Nw ···(C) In formula (C), k1 is a positive constant smaller than 1. The numerical value of k1 is not particularly limited. For example, it may be 0.70 or more and 0.80 or less, and more specifically, it may be 0.75. Then, the determination unit 56 determines the magnitude relationship between the first rotational speed Npg1 (rpm) and the rotational speed Np (rpm) of the pedal 4 detected by the fifth sensor 9. Here, in formula (C), a positive constant k1 smaller than 1 is multiplied to calculate the first rotational speed Npg1 (rpm). This suppresses the accidental cancellation of assistance due to the influence of the sensor accuracy during normal driving. Specifically, due to the influence of the sensor accuracy, there may be a deviation (error) between the detected rotational speed of the pedal and the actual rotational speed of the pedal during normal driving, and this deviation may cause the cancellation of assistance. By multiplying by a positive constant k1 smaller than 1, the threshold value (that is, the first rotational speed Npg1) decreases, so it becomes possible to eliminate the influence of such an error.

[0045] In this way, when the determination unit 56 uses Nw as the rotational speed of the wheel, Nm as the rotational speed of the motor 40, Np as the rotational speed of the pedal 4, and gr MDU as the reduction ratio of the reduction gear 10, it is determined whether the magnitude of the above formula (B) (that is, the rotational speed Np (rpm) of the pedal 4) is included within a predetermined range (Npg1 > Np) corresponding to the transmission ratio Gr(n s i / n c ).

[0046] In this embodiment, when the rotation speed Np (rpm) of the pedal 4 is less than the first rotation speed Npg1 (rpm), the determination unit 56 outputs the first signal S1 to the output adjustment unit 55. Note that the determination unit 56 may output the first signal S1 to the output adjustment unit 55 when the rotation speed Np (rpm) of the pedal 4 is less than or equal to the first rotation speed Npg1 (rpm).

[0047] Further, when the signal Sa is input to the fourth calculation unit 54 from the fourth sensor 8 for the second time during one cycle of the steps in the control described later, the determination unit 56 reads the table T and the data indicating the current stage from the storage unit 58, and based on the current stage Gr(n s i / n c ) and the rotation speed Nw (rpm) of the wheel 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, may be simply described as "the second rotation speed Npg2"). Npg2 = k2(n s i / n c )Nw ··· (D) In formula (D), k2 is a positive constant that is less than 1 and greater than k1. Note that the value of k2 is not particularly limited, and for example, it may be 0.80 or more and 0.90 or less, and more specifically, it may be 0.85. And the determination unit 56 determines the magnitude relationship between the second rotational speed Npg2 (rpm) and the rotational speed Np (rpm) of the pedal 4 detected by the fifth sensor 9. Here, in formula (D), a positive constant k2 that is less than 1 is multiplied to calculate the second rotational speed Npg2 (rpm). Thereby, it is possible to suppress the occurrence of a phenomenon in which, even though the pedal 4 is not idling due to the assist being released and being in the normal running state, the assist is not started (resumed) at a desired timing due to the influence of the sensor accuracy. Further, in formula (D), a constant k2 that is greater than k1 is multiplied to calculate the second rotational speed Npg2 (rpm). Thereby, a difference is generated between the second rotational speed Npg2 and the first rotational speed Npg1, and it is possible to suppress the cycle in which the assist is started (resumed) after the assist is released from being repeated during an undesired short period.

[0048] In the present embodiment, when the rotational speed Np (rpm) of the pedal 4 is greater than the second rotational speed Npg2 (rpm), the determination unit 56 outputs the second signal S2 to the output adjustment unit 55. Note that the determination unit 56 may output the second signal S2 to the drive signal generation unit 59 when the rotational speed Np (rpm) of the pedal 4 is equal to or greater than the second rotational speed Npg2 (rpm).

[0049] Here, if the first rotational speed Npg1 (rpm) in formula (C) and the second rotational speed Npg2 (rpm) in formula (D) are collectively referred to as the target rotational speed Npg, the target rotational speed Npg is obtained by the following formula (1). Npg = k(n s i / n c )Nw ··· (1) (k = k1 (in the case of the first rotational speed Npg1)) (k = k2 (in the case of the second rotational speed Npg2)) Note that in the present embodiment, k1 < k2.

[0050] Note that, as described above, in the present embodiment, the constant k2 in the formula (D) is larger than the constant k1 in the formula (C). Therefore, in the present embodiment, the second rotational speed Npg2 (rpm) obtained using the formula (D) tends to be larger than the first rotational speed Npg1 (rpm) obtained using the formula (C), and when the gear ratio Gr (n s i / n c ) and the rotational speed Nw (rpm) of the wheel are the same, the second rotational speed Npg2 (rpm) is larger than the first rotational speed Npg1 (rpm).

[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 to the drive signal generation unit 59. The control mode for driving the motor 40 based on the torque command value Tm (Nm) is the normal output mode. 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 (hereinafter, may be referred to as "suppressed torque command value RTm (Nm)") obtained by suppressing the torque command value Tm (Nm) calculated by the third calculation unit 53 to the drive signal generation unit 59.

[0052] Here, the suppressed torque command value RTm (Nm) may be, for example, a value that does not drive the motor 40 (for example, zero), or may be a value indicating the torque of the motor 40 such that the drive of the motor 40 is not transmitted to the output gear. For example, it may be a torque obtained by multiplying the torque (Nm) of the smallest motor 40 in the normal output mode by a number M (0 < M < 1) smaller than 1 (that is, a torque smaller than the torque in the normal output mode).

[0053] The drive signal generation unit 59 generates a drive signal Sd for driving 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 for causing the motor 40 to exhibit the torque of the torque command value Tm (Nm) indicated by the fourth signal S4, and when the third signal S3 is input, the drive signal generation unit 59 outputs a drive signal Sd for causing the motor 40 to exhibit the torque of the suppression torque command value RTm (Nm) indicated by the third signal S3 to the drive circuit 50b. The drive signal Sd is, for example, a PWM (Pulse Width Modulation) signal.

[0054] Based on the drive signal Sd, the drive circuit 50b drives the motor 40, for example, when the motor 40 is a brushless DC motor having coils corresponding to three phases (U phase, V phase, and W phase), by exciting the coils corresponding to the three phases (U phase, V phase, and W phase) of the motor 40. The drive circuit 50b may include, for example, an inverter circuit for driving each coil, a pre-drive circuit for driving the inverter circuit according to the drive signal Sd, and a current detection circuit for detecting the current flowing through each coil.

[0055] Note that the control device 50 as 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 one integrated circuit device (IC), or the control circuit 50a and the drive circuit 50b may be packaged as individual integrated circuit devices, respectively.

[0056] Next, an example of the steps in the control by the control device 50 will be described. FIG. 4 is a flowchart showing an example of the steps in the control by the control device 50. Note that the steps in the control by the control device 50 are not limited to the steps in the control shown in FIG. 4. As shown in FIG. 4, the steps in the control according to the present embodiment include steps St1 to St9.

[0057] In this embodiment, for example, when the driving of the motor 40 is started, the step of starting the control may be started (START). Specifically, the step of starting the control may be started at the timing when the drive signal generation unit 59 generates a drive signal Sd for driving the motor 40 and outputs it to the drive circuit 50b. At this time, in the storage unit 58, the gear stage of the sprocket SP set immediately before the start (START) of the step in the control is stored as data indicating the current stage.

[0058] (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 54. When the control device 50 determines that the signal Sa has been input to the fourth calculation unit 54, the control step proceeds to step St2, and when it determines that the signal Sa has not been input to the fourth calculation unit 54, the control step returns to step St1. Note that the signal Sa does not necessarily have to be a signal indicating that the wheel has rotated by a predetermined rotation angle An (deg), and may be, for example, a signal transmitted from a predetermined timer at regular intervals.

[0059] (Step St2) When the second sensor 6 is a sensor (for example, a hall sensor) that detects the rotational speed Nm (rpm) of the motor 40, in the fourth calculation unit 54, the rotational speed Nm (rpm) of the motor 40 calculated by the second calculation unit 52, the rotational speed Nw (rpm) of the wheel calculated by the first calculation unit 51, and the reduction ratio data (reduction ratio gr of the speed reducer 10) stored in the storage unit 58 MDUBased on the data of ( ) and the above-mentioned gear stage determination program, the current gear stage is determined (calculated). Also, when the second sensor 6 is a sensor that directly detects the rotational speed Nc (rpm) of the chain ring CR, the control device 50, in the fourth calculation unit 54, based on the rotational speed Nc (rpm) of the chain ring CR detected by the second sensor 6, the rotational speed Nw (rpm) of the wheel calculated by the first calculation unit 51, and the above-mentioned gear stage determination program, determines (calculates) the current gear stage. Further, when the electric assist bicycle 1 is equipped with a gear position sensor, the control device 50 may determine (calculate) the current gear stage based on the signal from the gear position sensor. The control device 50 overwrites (updates) the data indicating the current gear stage determined in this step on the "data indicating the current gear stage" stored in the storage unit 58 until now (i.e., at the time of START), and advances the step in the control to step St3.

[0060] (Step St3) Based on the rotational speed Nw (rpm) of the wheel calculated by the first calculation unit 51, the table T stored in the storage unit 58, and the "data indicating the current gear stage" updated in step St2, the control device 50 calculates, in the determination unit 56, the first target rotational speed Npg1 (rpm) of the pedal 4 using the above formula (C). The control device 50 stores the data of this first target rotational speed Npg1 (rpm) in the storage unit 58. Then, the control device 50 advances the step in the control to step St4.

[0061] (Step St4) The control device 50 reads out the data of the first rotational speed Npg1 (rpm) calculated in step St3 from the storage unit 58, and in the determination unit 56, determines the magnitude relationship between the first rotational speed Npg1 (rpm) and the rotational speed Np (rpm) of the pedal 4 input from the fifth sensor 9. When the rotational speed Np (rpm) of the pedal 4 input from the fifth sensor 9 is equal to or higher than the first rotational speed Npg1 (rpm), the control device 50 returns the control step to step St1. On the other hand, when the rotational speed Np (rpm) of the pedal 4 input from the fifth sensor 9 is lower than the first rotational speed Npg1 (rpm) (or equal to or lower than the first rotational speed Npg1 (rpm)), the control device 50 advances the control step to step St5. Specifically, the control device 50 outputs a first signal S1 from the determination unit 56 to the output adjustment unit 55 to advance the control step to step St5.

[0062] (Step St5) When the first signal S1 is input to the output adjustment unit 55, the control device 50 outputs a third signal S3 indicating a suppressed torque command value RTm (Nm) obtained by suppressing the torque command value Tm (Nm) calculated by the third calculation unit 53 to the drive signal generation unit 59 in the output adjustment unit 55. Then, when the third signal S3 is input to the drive signal generation unit 59, the drive signal generation unit 59 generates a drive signal Sd for causing the motor 40 to exert the torque of the suppressed 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. That is, in this step, the drive of the motor 40 stops (or the electric assist bicycle does not accelerate due to the drive of the motor 40), and the assist of the motor 40 to the electric assist bicycle 1 is released. Then, the control device 50 advances the control step to step St6.

[0063] (Step St6) The control device 50 determines again 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 54. When the control device 50 determines that the signal Sa has been input to the fourth calculation unit 54 (that is, when the signal Sa is input to the fourth calculation unit 54 for the second time in one cycle of the steps in this control), the control advances to step St7. When it is determined that the signal Sa has not been input to the fourth calculation unit 54, this step is repeated.

[0064] (Step St7) Based on the rotational speed Nw (rpm) of the wheel 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 determination unit 56 calculates the second target rotational speed Npg2 (rpm) of the pedal 4 using the above formula (D). The control device 50 stores the data of this second target rotational speed Npg2 (rpm) in the storage unit 58. Then, the control device 50 advances the step in the control to step St8.

[0065] (Step St8) The control device 50 reads out the data of the second rotational speed Npg2 (rpm) calculated in step St7 from the storage unit 58, and the determination unit 56 determines the magnitude relationship between the second rotational speed Npg2 (rpm) and the rotational speed Np (rpm) of the pedal 4 input from the fifth sensor 9. When 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), the control device 50 returns the step in the control to step St6. On the other hand, when the rotational speed Np (rpm) of the pedal 4 input from the fifth sensor 9 exceeds the second rotational speed Npg2 (rpm), the control device 50 advances the step in the control 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 step in the control to step St9.

[0066] (Step St9) When the second signal S2 is input 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 to the drive signal generation unit 59. Then, the control device 50 generates a drive signal Sd for causing the motor 40 to exert the torque of the torque command value Tm (Nm) indicated by the fourth signal S4 in the drive signal generation unit 59, and controls (starts) the drive of the motor 40 based on this drive signal Sd. That is, in this step, the drive of the motor 40 is started, and the assist to the pedal 4 is started (resumed). In this step, the control device 50 controls the motor 40 to drive according to the stage determined in step St2 based on the torque command value Tm (Nm). Then, the control device 50 returns the step in the control to step St1.

[0067] Here, the first target rotational speed Npg1 is a value obtained by multiplying the current gear ratio Gr (n s i / nc) by the current rotational speed Nw (rpm) of the wheel and a constant k1 less than 1. Therefore, when the rotational speed Np (rpm) of the pedal 4 is equal to or higher than the first target rotational speed Npg1, it can be estimated that the rotational speed Np (rpm) of the pedal 4 is synchronized with the rotational speed Nw (rpm) of the wheel, and it can be estimated that the pedal 4 (chain ring CR) and the crankshaft 23 rotate forward in synchronization with the output gear of the speed reducer 10 and the driving force of the MDU1*** is transmitted to the pedal 4. Conversely, when the rotational speed Np (rpm) of the pedal 4 is lower than the first target rotational speed Npg1, it is the case where the rotational speed Np (rpm) of the pedal 4 is lower than the rotational speed Nw (rpm) of the wheel, and it can be estimated that the pedal 4 (chain ring CR) and the crankshaft 23 rotate reversely and the driving force of the MDU1*** is not transmitted to the pedal 4 (the pedal 4 idles).

[0068] As described in the steps in the control of FIG. 4 above, in the electric assist bicycle 1, when the rotational speed Np (rpm) of the pedal 4 decreases and falls below the first rotational speed Npg1 calculated by the formula (C), the drive of the motor 40 is stopped (the assist to the pedal 4 is released). On the other hand, when the rotational speed Np (rpm) of the pedal 4 increases and exceeds the second rotational speed Npg2, the drive of the motor 40 is started (the assist to the pedal 4 is started). That is, in the electric assist bicycle 1, when the reverse rotation of the pedal 4 can be estimated, the assist to the pedal 4 is released, and when the synchronized forward rotation of the pedal 4 can be estimated, the assist to the pedal 4 is started.

[0069] Therefore, according to the electric assist bicycle 1, when the rotational speed of the pedal 4 is slower than the vehicle speed (the rotational speed Nw (rpm) of the wheels) (when the pedal 4 idles), it is possible to more surely release the assist by the motor. Furthermore, even when a strain type torque sensor is used as a sensor for detecting the pedaling force Tf (N), it is possible to more surely release the motor assist when the rotational speed of the pedal 4 is slower than the vehicle speed.

[0070] Here, consider the case where the rotational speed Np (rpm) of the pedal 4 drops to (n s i / n c )×Nw´ (Nw´ < Nw) while the rotational speed Nw (rpm) of the wheels remains when the pedal 4 is not idling, and the pedal 4 starts to idle. At this time, if the motor 40 is driving, the chain ring CR continues to rotate at a rotational speed of (n s i / n c )×Nw (rpm), just as when the pedal 4 is not idling. The reason for this is as follows.

[0071] If the motor 40 were to decelerate in the same way as the pedals 4, the chainring CR and sprocket SP would also decelerate, resulting in the clutch RC of the rear wheel 3 being disengaged (disconnected). In this case, the load seen by the motor 40 would consist only of the chainring CR, transmission body C, and sprocket SP, so the motor 40 would be in a substantially no-load state. When the torque of the motor 40 acts in this no-load state, the chainring CR and sprocket SP would accelerate to a rotational speed at which a large load would be applied, that is, the wheel, vehicle body, and rider (i.e., the rotational speed at which the clutch RC of the rear wheel 3 would engage). As a result, the chainring CR would rotate (n s i / n c ) × Nw (rpm).

[0072] In this case, because the rotation speed Np (rpm) of the pedals 4 is slower than that of the chain ring CR, the clutch of the reducer 10 disengages, and the pedals 4 (crankshaft 23) are disconnected from the output gear of the reducer 10, resulting in all parts of the drive system moving in tandem except for the pedals 4. In other words, in this case, even though the force exerted by the pedals 4 is not contributing to the propulsion force of the electrically assisted bicycle 1, the motor 40 still moves the electrically assisted bicycle 1.

[0073] As described above, with the electric assist bicycle 1, it is possible to more reliably cancel the motor assist when the rotation speed of the pedal 4 is slow compared to the vehicle speed (wheel rotation speed Nw (rpm)) (when the pedal 4 spins freely), thereby effectively preventing the motor 40 from moving the electric assist bicycle 1 even though the force of pedaling the pedal 4 is not contributing to the propulsion force of the electric assist bicycle 1.

[0074] (Second embodiment) Next, the electric assist bicycle according to the second embodiment will be described. The electric assist bicycle of this embodiment mainly differs from the electric assist bicycle 1 of the first embodiment in that the method for determining the current gear (step St2 shown in FIG. 4) is different from step St2 of the electric assist bicycle according to the first embodiment.

[0075] More specifically, as shown in FIG. 5, the electric assist bicycle 200 of this embodiment includes a fourth calculation unit 1540 different from the fourth calculation unit 54 of the electric assist bicycle 1 according to the first embodiment, determines the current gear by performing a gear ratio state determination process described later in step St2 shown in FIG. 4, and in the electric assist bicycle 1 of the first embodiment, either a sensor (for example, a hall sensor) that detects the rotation speed Nm (rpm) of the motor 40 and a sensor that directly detects the rotation speed Nc (rpm) of the chain ring CR can be used as the second sensor 6. In contrast, in the electric assist bicycle 200 of this embodiment, the former (the sensor that detects the rotation speed Nm (rpm) of the motor 40) is used. It is different from the electric assist bicycle 1 according to the first embodiment, and in other respects, it is generally common with the electric assist bicycle 1. Therefore, for this embodiment, these differences will be mainly described, and for other configurations, the same reference numerals as those in the first embodiment will be used and the description will be omitted.

[0076] In this embodiment, in order to determine the current gear ratio (current gear) of the electric assist bicycle, the rotation speed of the motor and the rotation speed of the wheel are measured. However, due to problems with the accuracy of the sensor, a state may occur where "it is not known which of the adjacent gear ratios is correct". For example, even when set to gear 3 (third gear), it may not be possible to tell from the results of measuring the rotation speed of the motor and the rotation speed of the wheel whether it is set to gear 2 (second gear) or gear 3 (third gear). In this state, if it is erroneously determined that it is set to gear 2, the electric assist bicycle may behave unexpectedly. However, according to this embodiment, it is possible to accurately determine the state where "it is not known which of the adjacent gear ratios (gears) is correct". This will be described below.

[0077] As an example of the gear position of the sprocket SP of the electric assist bicycle 200 of the present embodiment, the position where the number of teeth of the gear is 36 may be the first stage, the position where the number of teeth of the gear is 30 may be the second stage, and the position where the number of teeth of the gear is 26 may be the third stage. Gear 1 (first stage) is the lightest, and gear 9 (ninth stage) is the heaviest. Table 1 shows the set values of the gears (stages) of the present embodiment. The table (table) shown below, including Table 1, may be stored in the storage unit 58 of the control circuit 50a (see FIG. 2), for example. The ratio of the number of teeth of the rear (sprocket SP) to the number of teeth of the front (chain ring CR) (rear tooth number / front tooth number) corresponds to the ratio of the rotational speeds of the rear and the front (theoretical value), and such a theoretical value (that is, the gear ratio Gr) is based on the above formula (A), and the gear tooth number (n s i ) of the rear (sprocket SP) / the gear tooth number (n c ) of the front (chain ring CR) can be calculated. In Table 1, only up to the third decimal place is described, but in actual calculations, the fourth decimal place and below are also used. In the present embodiment, the lower limit of the threshold value used for determination is 90% of the theoretical value of the rotational speed ratio, and the upper limit of the threshold value is 110% of the theoretical value of the rotational speed ratio, but the upper and lower limits of the threshold value can be arbitrarily set.

[0078]

Table 1

[0079] On the other hand, the actual rotational speed ratio R is represented by formula (E). R = Nm / (gr MDU ·Nw) ··· Formula (E) Note that the meanings of Nm, Nw, and gr MDU are the same as those in the first embodiment. In the gear ratio state determination process described later, the control device 50 determines whether the ratio R, that is, the magnitude of formula (E), is included within a predetermined range (the threshold range in Table 1) corresponding to each gear ratio Gr.

[0080] As shown in FIG. 5, the electric assist bicycle 200 has a similar configuration except for the configuration of the fourth calculation unit 1540. Therefore, hereinafter, the fourth calculation unit 1540 will be described, and detailed descriptions of other configurations will be omitted.

[0081] FIG. 6 is a block diagram showing the functional configuration of the fourth calculation unit 1540. As shown in FIG. 6, the fourth calculation unit 1540 includes, as functional blocks, for example, a rotation 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 rotation speed calculation unit 1541, the i comparison unit 1542, the threshold comparison unit 1543, the gear ratio setting unit 1544, the i setting unit 1545, the C setting unit 1546, and the count threshold comparison unit 1547 are realized, for example, in a program processing device as the control circuit 50a, when the processor executes various arithmetic processes according to various programs stored in the above-described respective storage devices including the storage unit 58 and controls peripheral circuits such as a counter and an A / D conversion circuit. Note that the fourth calculation unit 1540 may have other functional blocks. The functions and operations of the rotation speed calculation unit 1541, the i comparison unit 1542, the threshold comparison unit 1543, the gear ratio setting unit 1544, the i setting unit 1545, the C setting unit 1546, and the count threshold comparison unit 1547 will be described using the flowchart of the gear ratio state determination process described later.

[0082] In the electric assist bicycle 200 of the present embodiment, the flowcharts of steps St3 and St9 for determining the current gear are different from those of steps St3 and St9 of the electric assist bicycle 1 of the first embodiment. FIG. 7(a) is a flowchart for explaining a part of the steps in the control of the electric assist bicycle 200 of the present embodiment, specifically, a flowchart for explaining the control performed in step St2 in the electric assist bicycle 200. FIG. 7(b) is a timing diagram for explaining the control shown in FIG. 7(a).

[0083] As shown in FIG. 7(a), in step St2, step St1100, step St1200, and step St1300 are performed. In step St1100, the control device 50 detects whether the gear ratio (the stage of the sprocket SP) has been changed from the first gear ratio (the first stage) to the second gear ratio (the second stage). Let the time point when the gear ratio is changed from the first gear ratio to the second gear ratio be t = t10 (see FIG. 7(b)). In step St1200, the control device 50 performs a gear ratio state determination process described later. In step St1300, the control device 50 controls to start the assist of the pedal corresponding to the second gear ratio. Let the time point when the assist of the pedal corresponding to the second gear ratio is started be t = t11 (see FIG. 7(b)). The time from when the gear ratio is changed from the first gear ratio to the second gear ratio until the assist of the pedal corresponding to the second gear ratio is started is (t11 - t10). Here, the process of step St2 in the present embodiment ends, but in the present embodiment, this process is performed every time the gear ratio (stage) is changed.

[0084] For example, if the time point when the gear ratio is changed from the third gear ratio to the fourth gear ratio is set as t = t12 (see FIG. 7(b)) and the time point when the assist of the pedal corresponding to the fourth gear ratio is started is set as t = t13 (see FIG. 7(b)), then the time from when the gear ratio is changed from the third gear ratio to the fourth gear ratio until the assist of the pedal corresponding to the fourth gear ratio is started is (t13 - t12). In the present invention, due to the gear ratio state determination process described later, the time (t11 - t10) from when the gear ratio is changed from the first gear ratio to the second gear ratio until the assist of the pedal corresponding to the second gear ratio is started is different from the time (t13 - t12) from when the gear ratio is changed from the third gear ratio to the fourth gear ratio until the assist of the pedal corresponding to the fourth gear ratio is started.

[0085] FIG. 8 is a timing chart for explaining other control in the present embodiment. Consider the case where the control device 50 starts at time t = t20 from a stopped state. The pedal assist does not start simultaneously with the start, but starts after a predetermined time. For example, assume that at time t = t21 shown in FIG. 8, the pedal assist corresponding to the gear ratio set at startup starts. Consider the case where the gear ratio is changed at time t = t22 after a predetermined time has elapsed since the control device 50 started. Similar to when the control device 50 starts, the pedal assist at the changed gear ratio is not applied simultaneously with the change in the gear ratio, but is applied after a predetermined time. For example, assume that at time t = t23, the pedal assist corresponding to the changed gear ratio starts. In the present embodiment, due to the gear ratio state determination process described later, the time (t21 - t20) from the start of the stopped control device 50 until the pedal assist corresponding to the gear ratio starts is longer than the time (t23 - t22) from the change in the gear ratio until the pedal assist corresponding to the changed gear ratio starts.

[0086] Here, the time until the pedal assist corresponding to the gear ratio starts may be, for example, within the time taken for one rotation of the wheel. Specifically, the times (t11 - t10), (t13 - t12), (t21 - t20), and (t23 - t22) may be within the time taken for one rotation of the rear wheel 3.

[0087] FIG. 9 is a timing chart for explaining other control in the present embodiment. Assume that at time t = t30 shown in FIG. 9, a predetermined gear ratio is changed. At time t = 31 before the elapse of the first period p1 after the change to the predetermined gear ratio, the control device 50 determines (temporarily determines) a candidate for the predetermined gear ratio by a gear ratio state determination process described later. For example, gears 2 and 3 (second and third gears) are determined (temporarily determined) as candidates. At time t = 32 after the elapse of the first period p1 and before the elapse of the second period p2, 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 is determined that gear 3 (third gear) is the current gear ratio (current gear) from the two candidates (gears 2 and 3).

[0088] Here, the period including the first period p1 and the second period p2 is preferably within the time taken for one rotation of the wheel (rear wheel 3), for example.

[0089] In addition, as a method for checking whether a certain electric assist bicycle has the magnitude relationship of time (time lag), which is a characteristic feature of the present invention, checking a display (display device) that displays the gear position, checking that the assist output is suppressed until the gear position is determined, checking that a time lag occurs in the output of the assist due to the motor current, etc. can be considered.

[0090] FIG. 10 is a flowchart for explaining the gear ratio state determination process (step St1200 shown in FIG. 7). In the following description, it is assumed that the current gear ratio (current stage) is set to gear 3 (third gear). However, as described above, from the results of measuring the rotational speed of the motor and the rotational speed of the wheels, there may be cases where it is not known whether the current stage is set to gear 2 (second gear) or gear 3 (third gear). The state of "not knowing which of the adjacent gear ratios is correct" can occur, for example, when changing the gear ratio and when starting to pedal after starting the system (control device 50) from a stopped state. According to the electric assist bicycle 200 of the present embodiment, the gear ratio state determination process shown in FIG. 10 can preliminarily determine or confirm which gear (stage) the current stage is. As Example 1, the case where the ratio of the rotational speeds does not change at R = 0.63 is shown. As Example 2, the case where the ratio of the rotational speeds changes from R = 0.63 to R = 0.55 is shown. As Example 3, the case where the ratio of the rotational speeds changes from R = 0.55 to R = 0.63 is shown.

[0091] In Example 1, the ratio of the rotational speeds does not change at R = 0.63. Each time a signal (vehicle speed pulse) indicating the vehicle speed of the electric assist bicycle 200 comes, the count values C of gear 2 (second gear) and gear 3 (third gear) increase. When the count value C exceeds the count threshold value, gear 2 (second gear) and gear 3 (third gear) are "preliminarily determined". Hereinafter, a detailed description will be given along the flowchart of FIG. 10. In the present embodiment, as the first sensor 5, a sensor that outputs 12 pulses (hereinafter referred to as vehicle speed pulses) per one rotation of the wheel is used.

[0092] In step St1211, the rotation speed calculation unit 1541 receives a signal indicating the rotation speed Nw (rpm) of the wheel from the first calculation unit 51, and detects the timing (whether the 1 / 12 vehicle speed pulse has arrived) at which the vehicle speed is changed. Hereinafter, the timing at which the vehicle speed is changed is referred to as the vehicle speed change timing. When the vehicle speed change timing occurs (when the 1 / 12 vehicle speed pulse arrives), in step S1212, the rotation speed calculation unit 1541, based on the signal from the first calculation unit 51 and the signal indicating the rotation speed Nm (rpm) of the motor 40 from the second calculation unit 52, calculates the rotation speed ratio R (the actual rotation speed ratio) according to the above-described formula (E). In the first embodiment, it is assumed that the ratio R = 0.63.

[0093] In step St1213, the i comparison unit 1542 compares i with Ngear. The initial value of i is 1, Ngear is the number of gear ratios (the number of steps of the sprocket SP), and in this embodiment, it is 9. Here, since i ≠ 9, 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 to 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 1 is "temporary determination" or "confirmation". As shown in Table 2, the initial value of the gear ratio state of all gears 1 to 9 is "undetermined", and the gear ratio state of gear 1 is also "undetermined", so the process proceeds to step St1221.

Table 2

[0094] In step St1213, the i comparison unit 1542 compares i with Ngear. Since i = 2, it 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 to 0.750, and since the ratio R = 0.63 is within the threshold range, it proceeds to step St1216. In step St1216, the C setting unit 1546 counts up the count value C of gear 2 (2nd stage). Specifically, it changes the count value C of gear 2 (2nd stage) in Table 3 from 0 to 1. In the tables shown below, including Table 3, the changed locations in this step are marked with an asterisk.

Table 3

[0095] In step St1213, the i comparison unit 1542 compares i with Ngear. Since i = 3, it 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 to 0.650, and since the ratio R = 0.63 is within the threshold range, it proceeds to step St1216. In step St1216, the C setting unit 1546 increments the count value C of gear 3 (3rd gear). Specifically, it changes the count value C of gear 3 in Table 4 from 0 to 1.

Table 4

[0096] In step S13, the i comparison unit 1542 compares i with Ngear. Since i = 4, it 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 to 0.535, and since the ratio R = 0.63 is not within the threshold range, it proceeds to step St1215. In step St1215, the gear ratio setting unit 1544 checks whether the gear ratio state of gear 4 is "temporary determination" or "confirmed". As shown in Table 4, the gear ratio state of gear 4 is "undetermined", so it proceeds to step St1221. In step St1221, the i setting unit 1545 increments i and returns to step St1213.

[0097] Since i = 5 to 9 is the same as the case of i = 4 described above, in step St1221, the i setting unit 1545 counts up i and skips until i = 10.

[0098] In step St1213, the i comparison unit 1542 compares i with Ngear. Since i = 9, it 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 one or more gear ratio states of "temporary determination" or "confirmation" among the gear ratio states of all gears (stages). As shown in Table 4, since the gear ratio states of all gears (stages) are "undetermined", it proceeds to step St1224. In step St1224, the gear ratio setting unit 1544 sets the gear ratio states of all gears (stages) to "undetermined". In the first embodiment, since the gear ratio states of all gears (stages) are already "undetermined", it does nothing and returns to step St1211.

[0099] In step St1211, the rotation speed calculation unit 1541 receives a signal indicating the rotation speed Nw (rpm) of the wheels from the first calculation unit 51 and detects the vehicle speed change timing (whether the 2 / 12 vehicle speed pulse has come). At the vehicle speed change timing (when the 2 / 12 vehicle speed pulse comes), 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 indicating the rotation speed Nm (rpm) of the motor 40 from the second calculation unit 52. In the first embodiment, since it is assumed that the ratio R = 0.63 remains unchanged, 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.

[0100] In step St1213, the i comparison unit 1542 compares i with Ngear. Since i = 2, it 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 to 0.750, and since the ratio R = 0.63 is within the threshold range, it proceeds to step St1216. In step St1216, the C setting unit 1546 increments the count value C of gear 2 (2nd stage). Specifically, the count value C of gear 2 (2nd stage) in Table 5 is changed from 1 to 2.

Table 5

[0101] In step St1213, the i comparison unit 1542 compares i with Ngear. Since i = 3, it 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 to 0.650, and since the ratio R = 0.63 is within the threshold range, it proceeds to step St1216. In step St1216, the C setting unit 1546 increments the count value C of gear 3 (3rd stage). Specifically, the count value C of gear 3 (3rd stage) in Table 6 is changed from 1 to 2.

Table 6

[0102] Similarly, at subsequent vehicle speed change timings (when the 3 / 12, 4 / 12, 5 / 12 vehicle speed pulses come), as shown in Table 7, the C setting unit increments the count values C of gears 2 and 3.

Table 7

[0103] The flow for each vehicle speed change timing (3 / 12, 4 / 12, 5 / 12 vehicle speed pulses) is the same as the above - described case. 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 those for each vehicle speed change timing (1 / 12, 2 / 12, 3 / 12, 4 / 12, 5 / 12 vehicle speed pulses) described above. So, in step St1221, the i setting unit 1545 increments i and skips until i = 2.

[0104] In step St1213, the i comparison unit 1542 compares i with Ngear. Since i = 2, it 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 the ratio R = 0.63 is within the threshold range, so it proceeds to step St1216. In step St1216, the C setting unit 1546 increments the count value C of gear 2 (2 - speed). Specifically, it changes the count value C of gear 2 in Table 8 from 5 to 6.

Table 8

Table 9

[0105] Similarly, in the loop of the vehicle speed change timing (6 / 12 vehicle speed pulses), since the count value C of gear 3 also becomes 6, as shown in Table 10, the gear ratio setting unit 1544 also changes the gear ratio state of gear 3 (third gear) to "provisional determination".

Table 10

[0106] For i = 4 to 8, it is the same as the cases of the above-described vehicle speed change timings (1 / 12, 2 / 12, 3 / 12, 4 / 12, 5 / 12 vehicle speed pulses). Therefore, in step St1221, the i setting unit 1545 counts up i and skips until i = 9.

[0107] In step St1213, the i comparison unit 1542 compares i with Ngear. Since i = 9, it 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 one or more "temporary determination" or "confirmed" gear ratio states among the gear ratio states of all gears (stages). As shown in Table 10, since the gear ratio states of gears 2 and 3 are "temporary determination", it proceeds to step St1225. In step St1225, the gear ratio setting unit 1544 checks whether the number of "temporary determination" gear ratio states is one and whether the upper and lower gear ratio states are "excluded". As shown in Table 10, since there are two gears, gears 2 and 3, in the "temporary determination" gear ratio state, it returns to step St1211.

[0108] 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 values C of gears 2 and 3. In Example 1, since the ratio R = 0.63 is assumed to remain unchanged, there is no change in the gear ratio state and the loop continues. Therefore, the gear ratio state is not confirmed, and both gears 2 and 3 are in the temporary determination state. As a result, by tentatively determining both adjacent gear ratios (gears 2 and 3) as candidates, the risk of misjudgment can be reduced. However, when the count value C reaches the count threshold, it is not necessary to increment the count further. That is, in Table 11, the count values C of gears 2 and 3 may be stopped at 6.

Table 11

[0109] In Example 1, as shown in Table 1, the control device 50 determines one or more numerical ranges including the gear ratio calculated by formula (1) among the numerical ranges corresponding to a plurality of gear ratios (gears 1 to 9) (step St1214), and one or more gear ratios (gears 2, 3) corresponding to the one or more numerical ranges are candidates for a predetermined gear ratio.

[0110] In the second embodiment, the rotation speed ratio changes from the state of the first embodiment (R = 0.63) to R = 0.55. When the first vehicle speed pulse comes after the change, the gear 2 (second gear) deviates from the threshold value (NO in step St1214). Since the gear 2 (second gear) was in a preliminary determination (YES in step St1215), the gear 2 (second gear) is "excluded" (step St1220). Since R = 0.55 is included in the threshold values of both the gear 3 (third gear) and the gear 4 (fourth gear) (step St1214), the count values C of the gear 3 (third gear) and the gear 4 (fourth gear) increase (step St1216) and exceed the count threshold value (YES in step St1217). As a result, the gear 3 (third gear) and the gear 4 (fourth gear) become "preliminary determination" (step St1219). Hereinafter, a detailed description will be given along the flowchart.

[0111] In step St1211, the rotation speed calculation unit 1541 receives a signal indicating the rotation speed of the wheel (rear wheel 3) from the first sensor 5 and detects the vehicle speed change timing (whether the 10 / 12 vehicle speed pulse has come). At the vehicle speed change timing (when the 10 / 12 vehicle speed pulse comes), 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 indicating the rotation speed Nm (rpm) of the motor 40 from the second calculation unit 52. In the second embodiment, it is assumed that the ratio R = 0.55.

[0112] In step St1213, the i comparison unit 1542 compares i with Ngear. 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 value for i = 1 is from 0.736 to 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 1 is "preliminary determination" or "confirmed". As shown in Table 11, the gear ratio state of gear 1 is "undetermined", so the process proceeds to step St1221. In step St1221, the i setting unit 1545 increments i and returns to step St1213.

[0113] In step St1213, the i comparison unit 1542 compares i with Ngear. Since i = 2, it 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 to 0.750, and since the ratio R = 0.55 is not within the threshold range, it proceeds to step St1215. In step St1215, the gear ratio setting unit 1544 checks whether the gear ratio state of gear 2 is "temporary determination" or "confirmed". As shown in Table 11, the gear ratio state of gear 2 is "temporary determination", so it 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 2 from "temporary determination" to "excluded", and the C setting unit 1546 resets (to zero) the count value C.

Table 12

[0114] In step St1213, the i comparison unit 1542 compares i with Ngear. Since i = 3, it 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 to 0.650, and since the ratio R = 0.55 is within the threshold range, it proceeds to step St1216. In step St1216, the C setting unit 1546 increments the count value C for gear 3 (3rd gear). Specifically, it changes the count value C for gear 3 (3rd gear) in Table 13 from 9 to 10.

Table 13

[0115] In step St1213, the i comparison unit 1542 compares i with Ngear. 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 to 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 4 (fourth gear). Specifically, the count value C of gear 4 in Table 14 is changed from 0 to 1.

Table 14

[0116] When i = 5 to 9, it is the same as the case of i = 1 described above. Therefore, in step St1221, the i setting unit 1545 increments i and skips until i = 10.

[0117] In step St1213, the i comparison unit 1542 compares i with Ngear. Since i = 10, it 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 one or more "temporary determination" or "confirmed" gear ratio states among the gear ratio states of all gears (steps). As shown in Table 14, since the gear ratio state of gear 3 is "temporary determination", it proceeds to step St1225. In step St1225, the gear ratio setting unit 1544 checks whether the number of "temporary determination" gear ratio states is one and whether the upper and lower gear ratio states are "excluded". As shown in Table 14, the gear with the gear ratio state of "temporary determination" is only gear 3, the gear ratio state of gear 2 above gear 3 is "excluded", and the gear ratio state of gear 4 below gear 3 is "undetermined". Therefore, it returns to step St1211.

[0118] Similarly, at subsequent vehicle speed change timings (when the 11 / 12, 12 / 12, 1 / 12, 2 / 12 vehicle speed pulses come), as shown in Table 15, the C setting unit 1546 increments the count values C of gears 3 and 4.

Table 15

[0119] Since the flow of each vehicle speed change timing (11 / 12, 12 / 12, 1 / 12, 2 / 12 vehicle speed pulses) is the same as the above-described case, in step St1216 of the loop at the vehicle speed change timing (3 / 12 vehicle speed pulse), as shown in Table 16, it skips until the count value C of gear 4 becomes 6.

Table 16

[0120] In step St1217, the count threshold comparison unit 1547 compares the count value C of gear 4 (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 4 is "excluded". As shown in Table 16, the gear ratio state of gear 4 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 4 (4th gear) from "undetermined" to "temporary determination".

Table 17

[0121] Since i = 5 to 9 is the same as the case of i = 4 in Embodiment 1, in step St1221, the i setting unit 1545 increments i and skips until i = 10.

[0122] In step St1213, the i comparison unit 1542 compares i with Ngear. Since i = 10, it proceeds to step St1222. In step St1222, after the i setting unit 1545 resets i to 1, it proceeds to step St1223. In step St1223, the gear ratio setting unit 1544 checks whether there is one or more gear ratio states of "temporary determination" or "confirmation" among the gear ratio states of all gears (stages). As shown in Table 17, since the gear ratio states of gears 3 and 4 are "temporary determination", it proceeds to step St1225. In step St1225, the gear ratio setting unit 1544 checks whether the number of gear ratio states of "temporary determination" is one, and whether the upper and lower gear ratio states are "excluded". As shown in Table 17, since there are two gears, gears 3 and 4, in the gear ratio state of "temporary determination", it returns to step St1211. In the second embodiment, the gear ratio state is not determined, and both gears 3 and 4 are in the state of temporary determination. As a result, by tentatively determining both adjacent gear ratios (gears 3 and 4) as candidates, the risk of misjudgment can be reduced.

[0123] In the third embodiment, when the rotation speed ratio changes from the state of the second embodiment (R = 0.55) to R = 0.63, and when the first vehicle speed pulse comes after the change, gear 4 (4th gear) deviates from the threshold value (NO in step St1214). Since gear 4 (4th gear) was in a tentative determination state (YES in step St1215), gear 4 (4th gear) is "excluded" (step St1220). At this time, gear 3 (3rd gear) has not been "excluded" yet, and the gear ratio that has been tentatively determined or confirmed is only gear 3 (3rd gear) (YES in step St1223). Since the upper and lower gears, gear 2 and gear 4, of gear 3 (3rd gear) are "excluded", gear 3 (3rd gear) becomes "confirmed" (YES in step St1225). Hereinafter, it will be described in detail along the flowchart.

[0124] In step St1211, the rotation speed calculation unit 1541 receives a signal indicating the rotation speed of the wheel (rear wheel 3) from the first sensor 5, and detects the vehicle speed change timing (whether the 4 / 12 vehicle speed pulse has arrived). At the vehicle speed change timing (when the 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 indicating the rotation speed Nm (rpm) of the motor 40 from the second calculation unit 52. In the third embodiment, it is assumed that the ratio R = 0.63.

[0125] In step St1213, the i comparison unit 1542 compares i with Ngear. Since i = 1, it 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 to 0.900, and since the ratio R = 0.63 is not within the threshold range, it proceeds to step St1215. In step St1215, the gear ratio setting unit 1544 checks whether the gear ratio state of gear 1 is "temporary determination" or "confirmation". As shown in Table 17, the gear ratio state of gear 1 is "undetermined", so it proceeds to step St1221. In step St1221, the i setting unit 1545 increments i and returns to step St1213.

[0126] In step St1213, the i comparison unit 1542 compares i with Ngear. Since i = 2, it 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 to 0.750, and since the ratio R = 0.63 is within the threshold range, it proceeds to step St1216. In step St1216, the C setting unit 1546 increments the count value C of gear 2 (second gear). Specifically, the count value C of gear 2 in Table 18 is changed from 0 to 1.

Table 18

[0127] In step St1213, the i comparison unit 1542 compares i with Ngear. Since i = 3, it 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, it proceeds to step St1216. In step St1216, the C setting unit 1546 increments the count value C of gear 3 (third gear). Specifically, it changes the count value C of gear 3 in Table 19 from 15 to 16.

Table 19

[0128] In step St1213, the i comparison unit 1542 compares i with Ngear. Since i = 4, it 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 to 0.575, and since the ratio R = 0.63 is not within the threshold range, it proceeds to step St1215. In step St1215, the gear ratio setting unit 1544 checks whether the gear ratio state of gear 4 (4th gear) is "temporary determination" or "confirmed". As shown in Table 19, the gear ratio state of gear 4 (4th gear) is "temporary determination", so it 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 4 (4th gear) from "temporary determination" to "excluded", and the C setting unit 1546 resets (to zero) the count value C.

Table 20

[0129] For i = 5 to 9, it is the same as the case of i = 1 described above. So, in step St1221, the i setting unit 1545 counts up i and skips until i = 10.

[0130] In step St1213, the i comparison unit 1542 compares i with Ngear. Since i = 10, it proceeds to step St1222. In step St1222, after the i setting unit 1545 resets i to 1, it proceeds to step St1223. In step St1223, the gear ratio setting unit 1544 checks whether there is one or more gear ratio states of "temporary determination" or "confirmation" among the gear ratio states of all gears (steps). As shown in Table 20, since the gear ratio state of gear 3 is "temporary determination", it proceeds to step St1225. In step St1225, the gear ratio setting unit 1544 checks whether the number of gear ratio states of "temporary determination" is one, and whether the upper and lower gear ratio states are "excluded". As shown in Table 20, there is one gear with a gear ratio state of "temporary determination", which is gear 3. Also, the gear ratio state of gear 2 above gear 3 is "excluded", and the gear ratio state of gear 4 below gear 3 is also "excluded". So, it 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 3 (3rd step) from "temporary determination" to "confirmation".

Table 21

[0131] In this embodiment, in steps St3 and St9 of FIG. 4, when the ratio R of the rotational speeds (the actual ratio of the rotational speeds) of the control device 50 is within the threshold range of Table 1 during a predetermined period (for example, the time while the wheel (rear wheel 3) makes one rotation), it is determined that the gear ratio Gr (step) is in that state. However, even after the determination, the gear ratio state determination process continues. When the driver changes the gear ratio Gr (step), the previously determined gear (step) ratio no longer satisfies Equation (1). At this time, the control device 50 detects that the gear ratio Gr has been changed.

[0132] Summarizing Examples 1 to 3, the fourth calculation unit 1540 is configured as follows. Based on the signal indicating the rotational speed Nw (rpm) of the wheel from the first calculation unit 51 and the signal indicating the rotational speed Nm (rpm) of the motor 40 from the second calculation unit 52, the ratio R (actual rotational speed ratio) of the rotational speeds is calculated according to formula (E) (steps St1211 and S12). For one or more of all the gear ratios Gr (gears 1 to 9), when the ratio R is within the threshold range for a predetermined number of times (count threshold, 6 in this example) or more (step St1217), one or more gear ratios Gr (stages) are tentatively determined (step St1219). For a gear ratio Gr (stage) that has been tentatively determined, when the ratio R goes out of the threshold range (step St1215), that gear ratio Gr (stage) is excluded (step St1220). When both of the two gear ratios Gr (stages) adjacent to the tentatively determined one gear ratio Gr (stage) are excluded (step St1225), the tentatively determined one gear ratio Gr (stage) is determined as the gear ratio (step St1226). In this way, according to the electric assist bicycle 200 of the present embodiment, by using a hall sensor or the like that detects the rotational speed Nm (rpm) of the motor 40, the fourth calculation unit 1540 can determine the current gear more accurately.

[0133] FIG. 11(a) is a simulation diagram for explaining detection and motor control during gear shifting in an electric assist bicycle. In FIG. 11(a), the vertical axis represents the status of gear determination in software by voltage output, and the horizontal axis represents time. "Unconnected" means a case where assist output is suppressed at the start of pedaling or a case where assist output is suppressed when gear change is detected. As shown in FIG. 11(a), the time ta from when the gear changes from gear 9 (9th gear) to gear 8 (8th gear) until it is confirmed as gear 8 (8th gear) through the gear ratio state determination process shown in FIG. 10 described above is longer than the time tb from when the gear changes from gear 8 (8th gear) to gear 7 (7th gear) until it is confirmed as gear 7 (7th gear). The same magnitude relationship holds, and the time tc from when the gear changes from gear 2 (2nd gear) to gear 1 (1st gear) until it is confirmed as gear 1 (1st gear) is the shortest. This is because the heavier the gear, the smaller the difference in the number of teeth between the upper and lower gears, so the time it takes for the gear to be confirmed is longer compared to a lighter gear. For example, as shown in Table 1, the number of teeth of gear 9 (9th gear) is 11, and the number of teeth of gear 8 (8th gear) is 13, so the difference in the number of teeth between gears 9 and 8 is 2. On the other hand, the number of teeth of gear 2 (2nd gear) is 30, and the number of teeth of gear 1 (1st gear) is 36, so the difference in the number of teeth between gears 2 and 1 is 6. Note that the time from when the gear changes from gear 9 (9th gear) to gear 8 (8th gear) until it is confirmed as gear 8 (8th gear) is the same as the time from when the gear changes from gear 8 (8th gear) to gear 9 (9th gear) until it is confirmed as gear 9 (9th gear).

[0134] Figure 11(b) is an enlarged simulation diagram of the portion from gear 9 (9th gear) to gear 8 (8th gear) in Figure 11(a) until it is determined to be gear 8 (8th gear) through the gear ratio state determination process shown in Figure 10. Immediately after the change from gear 9 (9th gear) to gear 8 (8th gear), the assist output is suppressed. Next, gear 8 (8th gear) is tentatively determined, and the voltage output becomes the voltage level of gear 8 (8th gear). Next, gears 8 and 7 are tentatively determined once, and the voltage output becomes the voltage level between gear 8 (8th gear) and gear 7 (7th gear). Next, gear 7 (7th gear) is excluded, and since only gear 8 (8th gear) is tentatively determined, the voltage output becomes the voltage level of gear 8 (8th gear). Next, gear 9 (9th gear) is also tentatively determined, and since gears 8 (8th gear) and 9 (9th gear) are tentatively determined, the voltage output becomes the voltage level between gear 8 (8th gear) and gear 9 (8th gear). Finally, gear 9 (9th gear) is excluded, gear 8 (8th gear) is determined, and the voltage output becomes the voltage level of gear 8 (8th gear).

[0135] Figure 11(c) is an enlarged simulation diagram of the portion from gear 2 (2nd gear) to gear 1 (1st gear) in Figure 11(a) until it is determined to be gear 1 (1st gear) through the gear ratio state determination process shown in Figure 10. Immediately after the change from gear 2 (2nd gear) to gear 1 (1st gear), the assist output is suppressed. Next, gear 1 (1st gear) is tentatively determined, and the voltage output becomes the voltage level of gear 1 (1st gear). As described above, since the difference in the number of teeth between gears 2 and 1 is large, there is no ambiguous determination.

[0136] As described above, according to the electric assist bicycle 200 of the present embodiment, in addition to the effects described in the first embodiment, in step St2 shown in Figure 4, the current gear can be determined with higher accuracy.

[0137] As described above, the present invention has been described by taking the above first embodiment and the above second embodiment as examples, but the present invention is not limited to this, and those skilled in the art can appropriately modify the electric assist bicycle of the present invention according to conventionally known knowledge. As long as the configuration of the present invention is still provided by such modifications, of course, it is included in the scope of the present invention.

Explanation of Signs

[0138] 1,200…Electrically assisted bicycle, 4…Pedal, 10…Reducer, 50…Control device, Gr…Gear ratio

Claims

1. When the rotation speed of the pedal decreases and falls below the first rotation speed, the assist for the pedal is released, and when the rotation speed of the pedal increases and exceeds the second rotation speed, the assist to the pedal is started. An electric assist bicycle.

2. The electric assist bicycle according to Claim 1, wherein the second rotation speed is greater than the first rotation speed.

3. The first rotational speed and the second rotational speed are collectively referred to as a target rotational speed Npg, and the number of teeth n of the sprocket of the electric assist bicycle 1 ｓ ｉ is used, and when the number of teeth of the chain ring of the electric assist bicycle 1 is n ｃ is used, and when the rotational speed of the wheel of the electric assist bicycle is Nw, the electric assist bicycle according to claim 1 or 2, which is obtained by the following formula (1). Npg = k(n ｓ ｉ / n ｃ )Nw...(1) (k = k1 (in the case of the first rotation speed Npg1)) (k = k2 (> k1) (in the case of the second rotation speed Npg2))

4. The time from when the gear ratio is changed from the first gear ratio to the second gear ratio until the assist for the pedal corresponding to the second gear ratio is started is different from the time from when the gear ratio is changed from the third gear ratio to the fourth gear ratio until the assist for the pedal corresponding to the fourth gear ratio is started. The electric assist bicycle according to any one of Claims 1 to 3.

5. The electric assist bicycle according to Claim 4, wherein the time until the assist for the pedal corresponding to the second gear ratio is started is within the time taken for one rotation of the wheel.

6. A wheel, a control device, a reduction gear and a rotating device having a motor for assisting the pedal, a sensor for detecting the rotation speed of the wheel, a sensor for detecting the rotation speed of the motor, a sensor for detecting the rotation speed of the pedal, and comprising Let Nw be the rotational speed (rpm) of the wheel, Nm be the rotational speed (rpm) of the motor, and gr ＭＤＵ be the reduction ratio of the rotating device. The control device determines whether the magnitude of the following formula (E) is included within a predetermined range corresponding to the gear ratio of the electric assist bicycle. The electric assist bicycle according to any one of claims 1 to 5. Nm / (gr ＭＤＵ ·Nw)···Formula (E)

Images