JP2000053071A - Motor-driven bicycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately supply auxiliary driving force on the basis of motor torque high in detecting accuracy and to compute the residual quantity of battery power by computing motor driving force from a battery current sensor, and controlling a switching element on the basis of the motor driving force and the output of a manual force detecting means. SOLUTION: A motor driving means comprises a DC motor 14, a battery 13 and a switching element 21, and a battery current sensor 22 is provided between the switching element 21 and the battery 13. A motor current Ia has a different value from a battery current Ib. The battery current Ib is expressed by the product of the motor current Ia and the duty ratio of the switching element 21, and the motor current Ia is computed from the battery current Ib through an integrater and a divider. The residual quantity of battery power can also be computed from the motor current Ia and battery voltage. Motor driving force can be computed only by providing one battery current sensor, and motor torque can be accurately detected, so that auxiliary power can be accurately controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric bicycle, and more particularly to an electric bicycle which assists human power by an auxiliary driving force of an electric motor.

[0002]

2. Description of the Related Art A conventional electric bicycle includes (1) a pedaling force sensor for detecting a main driving force by human power and a battery current sensor for detecting a motor torque based on a battery current supplied from a battery to the motor. An apparatus that controls the auxiliary driving force of the electric motor based on the output of the sensor (for example, see Japanese Patent Application Laid-Open No. H4-100790), and (2) detecting the remaining power of the battery and detecting it. One that is displayed (for example,
-144343), and the like.

[0003]

In the above (1),
When a DC motor is used as a motor and the output of a battery is intermittently supplied to the motor via a switching element to control the output of the motor, a high voltage is generated by an induction component of the motor when the switching element is turned off. So to protect the switching element from its high voltage, usually
A flywheel diode is connected to both ends of the motor.

However, since the current flows through the motor (armature) even when the switching element is off due to the action of the flywheel diode, the current that actually flows through the motor differs from the battery current that the battery outputs to the motor.
Since the battery current sensor cannot correctly detect the motor torque, that is, the auxiliary driving force, there is a problem that a separate motor current sensor is required.

In the above (2), the remaining power of the battery is calculated based on both the output voltage and the output current of the battery. Therefore, the battery current sensor for detecting the battery current is replaced with a motor current sensor. Must be provided separately.

The present invention has been made in view of such circumstances, and it is possible to appropriately provide an auxiliary driving force based on a precisely detected motor torque and calculate the remaining power of a battery. It is intended to provide a simple electric bicycle.

[0007]

As shown in FIG. 14, the present invention comprises a manual driving means for driving wheels by human power, a DC motor 14, a battery 13 and a switching element 21, and the DC motor 14 Drive means for driving the motor, the switching element 21 and the battery 1
3, a battery current sensor 22 for detecting the battery current, a human power detecting means for detecting the driving force of the manual driving means, and an electric driving force calculated from the battery current sensor 22. And control means for controlling the switching element 21 based on the output of the electric bicycle.

[0008] The main driving force by human power in the present invention is a force that a person depresses a pedal and transmits to driving wheels as seen in a normal bicycle. Can be used.

The auxiliary driving force by the electric motor 14 is as follows.
When the main driving force by human power operates on the bicycle,
The driving force is an auxiliary driving force applied from the electric motor 14.

By controlling the ratio of the auxiliary driving force to the main driving force (referred to as an auxiliary ratio) to 1 or less, the electric bicycle of the present invention is handled as a bicycle (ordinary bicycle) according to the Road Traffic Law.

Further, as a configuration for transmitting the auxiliary driving force from the electric motor to the driving wheels of the bicycle, means for transmitting the output of the electric motor to the rotating shaft of the driving wheels via several stages of gears, belts or chains, After the output shaft is decelerated by a gear, means for transmitting the output shaft to the tire or rim of the drive wheel is used.

When the rotation speed of the drive wheel is higher than the drive rotation speed of the motor, the motor and the drive wheel are connected via a one-way clutch so that the motor does not apply a braking force to the drive wheel. Is preferred.

As the electric motor 14, for example, a DC brush motor of a permanent magnet excitation type can be used.

The battery 13 may be, for example, a rechargeable nickel-cadmium battery.

As the switching element 21, a switching transistor or a thyristor can be used.

The diode 20 is used as a flywheel diode of the electric motor 14, and includes a switching element 21.
To prevent the high induced voltage generated in the electric motor 14 from being applied to the switching element 21 when the switching element 21 is turned off.

The battery current sensor 22 may be any element that converts a current into a voltage. For example, a shunt resistor of several mΩ, a Hall element, or the like is used.

The pedaling force sensor is a sensor for detecting a main driving force due to human power, and includes a main driving force transmission system from a pedal to a driving wheel. A combination of an element that causes deformation and a sensor (for example, a strain gauge, a potentiometer, or a differential transformer) that converts the distortion or the amount of deformation into an electric signal is used.

The control means is, for example, 100 to 1000 Hz
The switching element 21 is turned on / off by outputting a pulse signal having a constant frequency of about 1 to 10 ms, and the duty ratio (on pulse width) of the switching element 21 is changed to perform PWM control of the motor 14. This includes C
A microcomputer consisting of PU, ROM and RAM can be used.

Preferably, the control means controls the duty ratio of the switching element 21 so that the ratio of the auxiliary driving force to the main driving force increases as the main driving force increases, from the viewpoint of improving ride comfort.

Note that the duty ratio of the switching element 21 is the ratio of the ON time to the cycle when the switching element 21 is turned on and off at a predetermined cycle.

Further, the present invention provides a battery current sensor 2
There is provided a calculating means for calculating the motor current based on the battery current detected by the second and the duty ratio of the switching element 21.

The calculation means and the calculation means also include a CPU,
It can be constituted by a microcomputer including a ROM and a RAM.

Further, according to the present invention, as shown in FIG.
A human driving means for driving wheels by human power; an electric driving means comprising a DC motor 14, a battery 13 and a switching element 21 for driving wheels by the DC motor 14, and a human power detecting means for detecting a driving force of the human driving means A motor current sensor 22 connected in series with the DC motor 14; and a flywheel diode 20 connected in parallel to the series circuit. An electric driving force is calculated from the electric motor current sensor 22, and the electric driving force and the human power are calculated. The switching element is controlled based on the output from the detecting means, the signal detected by the motor current sensor 22 is calculated to calculate the battery current, and the remaining power of the battery 13 is calculated based on the battery current and the battery voltage. The present invention provides an electric bicycle characterized by including calculation means for calculating the electric bicycle.

The battery current is calculated by calculating the motor current input via the integrator and a signal for controlling the switching element by a multiplier.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. Thus, the present invention is not limited.

FIG. 3 is a side view of the electric bicycle of the embodiment, and FIG. 4 is an explanatory view of a drive system of the electric bicycle.

In these figures, the electric bicycle main body 1
Has a driving wheel 2 driven by a human-powered driving means 9 and an electric driving means 12, and a front wheel 3 for determining a traveling direction. Further, the main body 1 includes a frame constituted by a standing pipe 4, an upper pipe 5, and a lower pipe 6, and a saddle 7 is provided at an upper end of the standing pipe 4. A handle 8 for determining the direction of the front wheel 3 is provided above a portion where the upper pipe 5 and the lower pipe 6 intersect.

The human-powered driving means 9 for driving the driving wheels 2 has a pedal 10 like a general bicycle,
The driving force (also referred to as the pedaling force) is transmitted to the chain 11 by stepping and rotating the 0 with the foot, and the driving force is further transmitted to the driving wheels 2 via the sprocket 11a, the one-way clutch 11b, and the pedaling force sensor 11c. And drive wheel 2
Are driven.

The treading force sensor 11c has a structure in which the rotating shaft of the sprocket 11a and the rotating shaft of the driving wheel 2 are connected by an elastic body, and a magnet displaced by the distortion of the elastic body is detected by a detecting coil. are doing.

Further, the one-way clutch 11b operates the driving wheel 2 more than the rotational speed at which the pedaling force is applied to the driving wheel 2.
When the rotation speed is high, the driving force is prevented from being transmitted reversely from the driving wheels 2 to the chain 11.

The electric driving means 12 for driving the driving wheels 2 in combination with the manual driving means 9 uses a rechargeable battery 13 provided above the driving wheels 2 as a power source, and is provided from the battery 13 to a hub of the driving wheels 2. Electric power is supplied to the electric motor 14.

In the electric drive means 12, the output from the electric motor 14 is decelerated by a speed reduction mechanism 14a consisting of a gear and a belt, and transmitted to the drive wheels 2 via a one-way clutch 14b. The one-way clutch 14b is configured such that the electric motor 14
When the actual rotational speed of the drive wheel 2 is higher than the rotational speed to be applied to the motor 14, the driving force is prevented from being transmitted back from the drive wheel 2 to the electric motor 14.

FIG. 5 is a top view of the handle of the electric bicycle. A grip 15 is provided at both ends of the handle 8 and a brake lever 16a for operating brake shoes (not shown) of the front wheel 3 and the drive wheel 2 respectively. ,
16b is provided.

Reference numeral 25 denotes a remaining battery level display unit, which includes LEDs 26 and 27 for displaying the remaining power level of the battery 13.

Next, a control circuit of the electric bicycle will be described with reference to FIG.

As shown in FIG. 6, a voltage of a battery 13 is applied to a series circuit of a motor 14 and a motor current sensor (hereinafter referred to as a current sensor) 22 via a switching element 21 and a power switch 19. Is connected to a flywheel diode 20.

Reference numeral 17 denotes a microcomputer (hereinafter referred to as a microcomputer) including a CPU, a ROM, and a RAM. The microcomputer 17 includes a voltage detection circuit 24 for detecting a voltage Vb of the battery 13, a current sensor 22, and a pedaling force sensor 11.
Upon receiving the output from c, it performs signal processing and outputs it to the switching element 21 and the remaining battery level display unit 25. The LEDs 26 and 27 indicate the remaining battery power.

In this embodiment, the motor 14 has a permanent magnet excitation type DC brush motor (maximum output 300).
W), a 24 V, 5 Ah nickel-cadmium battery is used for the battery, and a shunt resistor of 2.25 mΩ is used for the current sensor 22.

The microcomputer 17 turns on and off the switching element 21 at a frequency of 244 Hz, and
4 is PWM-controlled.

In such a configuration, the power switch 1
9 is turned on, and when the pedal 10 of the electric bicycle is depressed by the user, the depressing force is transmitted to the driving wheel 2 via the chain 11 and the magnitude of the pedaling is transmitted to the driving force sensor 11c.
And is input to the microcomputer 17. The microcomputer 17 performs PWM control on the motor 14 to balance the motor current (motor torque) detected by the current sensor 22 with the pedaling force.

Here, the fact that the output torque T of the electric motor 14 is accurately detected by the current Ia obtained from the current sensor 22 will be described.

FIG. 7 is a timing chart showing voltage / current waveforms at various parts of the circuit shown in FIG. 6. The battery voltage Vb shown in FIG. Is applied to a series circuit composed of the electric motor 14 and the switching element 21, and when the switching element 21 is repeatedly turned on and off with the duty of the period t and the _ON period t _ON as shown in FIG. Thus, a battery current Ib as shown in FIG. On the other hand, the motor current Ia flows continuously through the armature of the motor 14 by the action of the flywheel diode 20 as shown in FIG.

At this time, the armature voltage Va of the motor 14 is as shown in FIG. 3C, and the terminal voltage Vs of the switching element 21 is as shown in FIG.

In FIGS. 7 (c) and 7 (d),
Flywheel diode 20 and switching element 2
1 is ignored because it is sufficiently smaller than the voltage Vb (24 V).

Here, the motor current Ia and the battery current I
Find the relationship with b.

First, since the power taken out of the battery 13 and the power received by the motor 14 are equal, Vb · Ib = Va · Ia (1) Further, from FIGS. 7 (a), (c) and (d), Va = Vb−Vs (2) Substituting (2) into (1), Ib = Ia (Vb−Vs) / Vb (3) By the way, the voltage Vs is obtained by changing the waveform of FIG. Vs = Vb (1−t _ON ) / t (4) When (4) is substituted into (3), Ib = Ia · t _ON / t (5), and the battery current Ib is the motor current Ia And the duty ratio of the switching element 21.

That is, the motor current Ia has a value different from the battery current Ib, and the current sensor 22 inserted in the closed circuit of the motor 14 and the flywheel diode 20
, It can be understood that it is correctly detected for the first time.

It should be noted that Vb,
Ib, Va, Ia, and Vs all represent average values, and the relationship of Expression (5) can be similarly obtained from the ratio of the areas of the waveforms of (e) and (f) in FIG.

When the motor current Ia is correctly detected, the output torque T of the DC motor is generally represented by T = K · Ia (K is a constant) (6) if the excitation is constant. Thus, the auxiliary driving force of the electric bicycle is correctly calculated from the electric motor current Ia.

Next, control characteristics of the electric bicycle will be described.

[0052] In the electric bicycle, the main driving force due to the inherent human power, as is well known, that is, those that drive the bicycle by applying the auxiliary driving force T _M by the electric motor to the depression force T _L. Treading force T _L
Is substantially maximum when the two pedals 10 are located horizontally with respect to each other, and substantially minimizes when the two pedals 10 are located vertically with respect to each other, so that the pedaling force _TL is given an auxiliary driving force T _M. The timing and the applied ratio (assistance ratio) T _M / T _L determine the riding comfort of the electric bicycle.

Therefore, in the electric bicycle of the present invention, the microcomputer 17 amplifies the output signal a of the treading force sensor 11c and the output signal b of the current sensor 22 at amplification factors A and B, respectively, and calculates the difference (A · a− B · b), the duty ratio of the switching element 21 is changed, and A · a = B · b
The output of the electric motor 14 is controlled so as to satisfy the following condition, and the amplification factor A or B is changed according to the output signal a of the pedaling force sensor 11c.

As a result, the pedaling force-auxiliary ratio characteristic as shown in FIG. 8 (a), (b) or (c) is obtained.

FIG. 8A shows the case where the assisting ratio is changed in direct proportion to the pedaling force, and FIG. 8B shows the case where the assisting ratio is made constant when the pedaling force exceeds a predetermined value in FIG. FIG. 7C shows a case where the assist ratio is changed exponentially with respect to the pedaling force.

FIGS. 9 and 10 show equivalent circuits of the control circuit having such control characteristics (FIG. 6). In these figures, A1, A2 and A3 are amplifiers, D is an integrator, G is a pulse generator, F is a subtractor, and the amplifiers A1 and A2 have A and B gains, respectively.

In these figures, the amplifier A1 or A1
The gain A or B of 2 changes according to the output a of the pedaling force sensor 11c, and (A-a-b-b) is integrated (delayed) by the integrator D and amplified by the amplifier A3. The pulse is converted into a pulse having a corresponding on-duty and supplied to the switching element 21 and A
The PWM control of the electric motor 22 is performed so that a = B · b.

In FIG. 9, the gain B of the amplifier A2 is shown, and in FIG.
Each is controlled according to the magnitude of the output a of the treading force sensor 11c. Thus, the ratio of the auxiliary driving force F _M relative to the pedal effort F _L, i.e. subsidy rate will vary as (a) ~ (c) of FIG.

[0059] The timing of imparting the auxiliary driving force T _M in pedaling force T _L is the degree of the delay of the integrator D, it can be set appropriately.

[0060] By controlling in accordance with this auxiliary rate depression force, pedal force when the low subsidy rate low, the auxiliary rate increases as the pedal effort is increased, relative to periodic changes in the pedal force F _L smoothly auxiliary driving force F _M increases or decreases, it is possible to provide a pleasant ride to the driver.

Next, the control for displaying the remaining battery capacity of the electric bicycle will be described. First, when the signal b detected by the current sensor 22 and the signal c detected by the voltage detection circuit 24 are input to the microcomputer 17,
Calculates the battery current Ib based on the equation (5), that is, Ib = Ia · t _ON / t, using the signal b representing the motor current Ia, and calculates the battery current Ib and the battery obtained from the signal c. By calculating the voltage Vb, the remaining power of the battery 13 is obtained, and the remaining power display 25
To be displayed.

At this time, the remaining battery power is calculated by combining the battery voltage Vb and the battery current Ib.
This is because the voltage value of the battery 13 changes according to the battery current Ib.

That is, even if the remaining amount of the battery 13 is large, the voltage drops when a large amount of the battery current Ib flows.
In the present embodiment, the battery 13 having a rated voltage of 24 V is used. For example, when the current of only 3 A flows and the voltage of the battery 13 is 20 V, it is determined that the remaining amount of the battery 13 is 5% or less. Then, the power supply to the electric motor 14 is stopped.

However, a high load is applied to the battery 13,
When the battery current Ib is 24 A, even if the voltage value drops to 20 V, the remaining amount is determined to be 50% or more, and energization is continued. This is because when the battery current value is different even if the voltage value of the battery 13 is the same, the remaining amount of the battery 13 is different, so that the remaining amount of the battery 13 is calculated by comprehensive judgment of the current value and the voltage value. I have.

In the present embodiment, as shown in FIG. 5, the battery remaining amount display section 25 displays an LED, but the LED 26 uses green and the LED 27 uses red. LED2 up to 50%
6 is always turned on, LED 26 is turned off at 50% or less and LE
D27 blinks. Further, when the remaining amount of the battery 13 becomes 10%, the LED 27 is constantly turned on, and when it is 5% or less, the LED 27 is turned off.

In this way, the battery current Ib can be easily calculated from the motor current Ia by the equation (5).
It is not necessary to newly provide a battery current detection sensor to calculate the remaining power (or power consumption) of the battery 13.

Conversely, in FIG. 6, a battery current sensor for detecting the battery current Ib may be provided between the switching element 21 and the battery 13 without providing the motor current sensor 22.

In this case, the motor current Ia is calculated from the following equation (3): Ia = Ib · Vb / (Vb−Vs) (7) or from the equation (5), Ia = Ib · t / t _ON .. (8)

FIGS. 11 to 14 are equivalent circuits showing equivalently the functions of the microcomputer 17 for performing the above calculations. In these figures, P _{1 to} P ₄ are integrators, Q is a multiplier, and R is It is a divider.

FIG. 11 shows the relationship between the battery current I using the equation (3).
FIG. 12 is an equivalent circuit for calculating the motor current Ia using equation (7). In FIG. 12, the current sensor 22 detects the battery current Ib
The switching element 21 and the battery 13
Has been inserted between.

FIG. 13 is an equivalent circuit for calculating the battery current Ib using equation (5), and FIG.
Is an equivalent circuit for calculating the motor current Ia using the following equation. In FIG. 14, the current sensor 22 is inserted between the switching element 21 and the battery 13 to detect the battery current Ib.

Further, as shown in FIG.
If a gate H that opens and closes by a pulse signal for controlling the on / off of the motor 1 is used, a current sensor 2 that detects the motor current
When 2 outputs the instantaneous value I _A, it is possible to detect the instantaneous value I _B of the battery current.

Therefore, as shown in FIG. 6, when a flywheel diode is connected to the motor, the motor current and the battery current are different. However, if one is detected, the other is calculated. If one current sensor is installed according to the above circumstances and the convenience of assembly and maintenance, any current can be arbitrarily detected.

[0074]

According to the first aspect of the present invention, since the electric driving force is calculated from the battery current sensor and the switching element is controlled based on the output of the electric driving force and the output of the human power detecting means, the battery current sensor 1 Thus, the electric driving force is calculated, the electric motor torque is accurately detected, and the control of the auxiliary power in the electric bicycle is accurately performed.

According to the second aspect of the present invention, the switching element is controlled such that the ratio of the electric driving force to the manual driving force increases in accordance with the increase in the manual driving force. It runs smoothly and improves ride comfort.

According to the third aspect of the present invention, the calculating means for calculating the motor current from the battery current detected by the battery current sensor, and the remaining power of the battery is calculated based on the calculated motor current and battery voltage. Calculation means for controlling the motor power and calculating the remaining power with one current sensor.

According to the fourth and fifth aspects of the present invention,
Since the battery current detected by the battery current sensor is calculated by the motor current via the integrator and the divider, and the motor current is determined by the battery current and the signal for controlling the switching element,
The motor current can be calculated with a simple configuration.

According to the sixth aspect of the present invention, there is provided a calculating means for calculating a battery current by calculating a signal detected by a motor current sensor and calculating a remaining power of the battery based on the battery current and the battery voltage. Since it is provided, it is possible to control the motor power and calculate the remaining power with one current sensor.

According to the seventh aspect of the present invention, the battery current is calculated by inputting the motor current input via the integrator and the signal for controlling the switching element to the multiplier. The motor current can be calculated with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a basic configuration of the present invention.

FIG. 2 is a time chart showing waveforms of main parts in FIG.

FIG. 3 is a side view of the electric bicycle of the embodiment.

FIG. 4 is a configuration explanatory view showing a drive system of the embodiment.

FIG. 5 is a top view of a main part of FIG. 3;

FIG. 6 is a control circuit diagram of the embodiment.

FIG. 7 is a time chart showing waveforms at various parts in FIG. 6;

FIG. 8 is a graph showing the relationship between the pedaling force and the assist ratio according to the embodiment.

FIG. 9 is an equivalent circuit diagram of FIG. 6;

FIG. 10 is an equivalent circuit diagram of FIG. 6;

FIG. 11 is an equivalent circuit diagram showing functions of main parts of the embodiment.

FIG. 12 is an equivalent circuit diagram showing functions of main parts of the embodiment.

FIG. 13 is an equivalent circuit diagram showing functions of main parts of the embodiment.

FIG. 14 is an equivalent circuit diagram showing functions of main parts of the embodiment.

FIG. 15 is an equivalent circuit diagram showing functions of main parts of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main body 2 Drive wheel 3 Front wheel 4 Standing pipe 5 Upper pipe 6 Lower pipe 7 Saddle 8 Handle 9 Human power driving means 10 Pedal 11 Chain 12 Electric driving means 13 Battery 14 Electric motor

Claims (7)

[Claims] 1. A human-powered driving means for driving wheels by human power, an electric driving means comprising a DC motor, a battery and a switching element, and driving the wheels by a DC motor; and a battery current provided between the switching element and the battery. A battery current sensor for detecting, a human power detecting means for detecting a driving force of the human driving means, and an electric driving force calculated from the battery current sensor, and controlling the switching element based on the outputs of the electric driving force and the human power detecting means An electric bicycle comprising control means. 2. The electric bicycle according to claim 1, wherein the control means controls the switching element such that a ratio of the electric driving force to the human driving force increases in accordance with the increase in the human driving force. 3. The electric bicycle according to claim 1, further comprising calculating means for calculating a remaining power of the battery based on the battery current and the battery voltage detected by the battery current sensor. 4. The electric bicycle according to claim 1, wherein the motor current is calculated from the battery current detected by the battery current sensor via an integrator and a divider. 5. The electric bicycle according to claim 4, wherein the motor current is obtained from the battery current and a signal for controlling a switching element. 6. A human power driving means for driving wheels by human power, an electric driving means comprising a DC motor, a battery and a switching element, for driving wheels by a DC motor, and a human power detecting means for detecting a driving force of the human driving means. Means, a motor current sensor connected in series with the DC motor, a flywheel diode connected in parallel to the series circuit is provided, an electric driving force is calculated from the electric motor current sensor, and the electric driving force and human power detecting means are provided. Calculating means for controlling a switching element based on the output of the motor, calculating a signal detected by the motor current sensor to calculate a battery current, and calculating a remaining power of the battery based on the battery current and the battery voltage. An electric bicycle characterized by the following. 7. The battery according to claim 6, wherein the battery current is calculated by inputting a motor current input via an integrator and a signal for controlling a switching element to a multiplier. Electric bicycle.