JPH0858671A - Power assist device for bicycle - Google Patents

Abstract

PURPOSE: To allow easy installation on each type of a bicycle, and ensure a compact and lightweight structure. CONSTITUTION: This device is constituted of a battery case 16 to house a battery, an electric motor 21 to generate driving force, using the battery in the case 16 as a power supply, a gear case 15 to house a reduction gear for transmitting the rotation of the motor 21 via a reduction gear, a circuit box 22 to house a control circuit for controlling the drive of the electric motor 21, a torque detection connecting shaft jointed to a crank connecting shaft fixed to a pedal crank, and a torque detection means mounted on the torque detection connecting shaft for detecting torque due to the rotation of the pedal crank. Also, the last stage gear of the reduction gear has one end of a center shaft coupled and fixed to the pedal crankshaft of a bicycle, and the other end connected to the crank connecting shaft via the torque detection connecting shaft. In addition, the control circuit controls the drive of the motor 21 on the basis of torque detected with the torque detection means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power assist device for a bicycle, which is mounted on a bicycle and is capable of both pedal driving and electric motor driving.

[0002]

2. Description of the Related Art Conventionally, many electric bicycles have been developed, and these bicycles can be roughly classified into two types. One is a bicycle type with a prime mover that has a drive switch or control accelerator on the handle, and can drive the electric motor regardless of running conditions such as running on flat ground or on slopes. It is a type that detects the pedal rotation force, such as one that assists power when the load becomes heavier and a load torque greater than a set value is detected by the torque detection device, or one that constantly assists power commensurate with the power of human power.

In the case of a bicycle type with a prime mover, when an auxiliary power unit is attached to a bicycle, a roller is pressed against the tire portions of the front and rear wheels, or an electric motor with a reduction gear is attached to the central axle hub portion of the rear tires. Are known.

[0004]

However, in the conventional auxiliary power unit, the types of bicycles that can be mounted are limited due to the restriction of the bicycle frame structure, and the bicycle body must have a special dedicated structure. It was

Therefore, the present invention provides a power assist device for a bicycle, which can be mounted on various types of bicycles, and which is small, lightweight and easy to mount.

[0006]

The invention according to claim 1 is
A battery case containing a battery, an electric motor driven by the battery of the battery case as a power source, a speed reducer for transmitting the rotation of the electric motor through a plurality of reduction gears, a control circuit for driving and controlling the electric motor, and a bicycle. Connecting shaft for torque detection connected to the crank connecting shaft fixed to the petal crank of
Attached to this torque detection connecting shaft, it consists of torque detection means for detecting the torque associated with the rotation of the petal crank,
The final stage gear of the speed reducer has one end of the center shaft engaged and fixed to the petal crank shaft of the bicycle, and the other end thereof connected to the crank connecting shaft of the bicycle through the torque detecting connecting shaft, and detected by the torque detecting means. The control circuit drives and controls the electric motor based on the torque.

According to a second aspect of the invention, in the power assist device for a bicycle according to the first aspect, the reduction gear is housed in a gear case, the gear case is fixed in parallel with the body frame of the bicycle, and the electric motor is a petal crankshaft. And the center axis of rotation is located below the center of the petal crankshaft so as to be orthogonal to the gear case.

According to a third aspect of the invention, in the power assist device for a bicycle according to the second aspect, the battery case is arranged at an upper side portion or an upper portion of the gear case such that an outer surface of the case does not protrude from an outer surface of the gear case. It is arranged parallel to the body frame of the bicycle.

According to a fourth aspect of the invention, in the power assist device for a bicycle according to the first aspect, the torque detecting means connects the final stage gear of the reduction gear and the torque detecting connecting shaft with an elastic member, and the final stage. The pedaling force is detected by detecting the displacement between the gear and the torque detecting connecting shaft.

According to a fifth aspect of the present invention, in the bicycle power assisting device according to the first aspect, a one-way clutch for transmitting the rotational force to the speed reducer in only one direction is provided, and the no-load rotational speed of the electric motor is pedaled. When converted by the crankshaft, it is set so as to be slower than the rotation speed of the pedal crankshaft due to human power.

[0011]

In the present invention having such a structure, the control circuit drives and controls the electric motor based on the torque detected by the torque detecting means. As a result, the electric motor rotates, and this rotational force is transmitted to the petal crankshaft via the reduction gear, and auxiliary power is transmitted to the rotation of the petal crankshaft.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

The pedal crank shafts of general-purpose bicycles are standardized into two types: a square cut shaft with a screw boss, and a shaft with a chrysanthemum groove in which a screw hole is provided at the center to mount the pedal crank. A chain wheel is attached to the right side of the vehicle body, but there is a space on the left side. Furthermore, there is a space between the chain wheel and the front wheels. From this point of view, in the present embodiment, the device of the present invention is mounted using the space of a general-purpose bicycle.

FIG. 1 is a view showing the entire structure of a bicycle, and 1 is a body frame. The body frame 1 includes a head pipe 2, a top tube 3 extending rearward from the head pipe 2, a seat tube 5 extending from the top tube 3 to a bottom bracket 4, and a head tube 2 extending from the head pipe 2 to the bottom bracket 4. Down tube 6
And a pair of left and right rear stays 7 extending rearward from the bottom bracket 4, and a pair of left and right seat stays 8 connecting the upper end of the seat tube 5 and the rear end of the rear stay 7.

A front fork 9 and a handle bar 10 are held on the head pipe 2 so as to be rotatable left and right, and a front wheel 11 is rotatably attached to the front fork 9, and the handle bar 1
The handle 12 is fixed to 0. A rear wheel 13 is rotatably attached to the rear end of the rear stay 7. A saddle 14 is attached to the upper end of the seat tube 5 so as to be vertically movable.

2 is a view of the bottom bracket 4 from the left side, FIG. 3 is a view of the bottom bracket 4 from the right side, and FIG. 4 is a view of the bottom bracket 4 from the top and FIGS. [FIG. 3] is a front view of the portion of the bottom bracket 4.

As shown in FIGS. 2 to 5, a gear case 15 is attached to the left side of the portion of the bottom bracket 4,
A battery case 16 is detachably attached to the upper inner side of the gear case 15. A left pedal crank 17a and a pedal 18a are provided outside the gear case 15.

A chain wheel 19 is attached to the right side of the bottom bracket 4, and the chain wheel 19 is covered with a chain wheel cover 20. A right pedal crank 17b and a pedal 18b are provided outside the chain wheel cover 20.

One end of the electric motor 21 is fixed to the inner surface of the lower end of the gear case 15 and the other end is passed under the down tube 6 and extended to the opposite side (right side). The electric motor 2 is provided below the battery case 16.
A circuit box 22 accommodating a control circuit for driving and controlling the electric motor 21 is arranged in the rear of 1.

As shown in FIG. 6, the battery case 16 includes a plurality of batteries, for example, three 12V sealed lead acid batteries 2.
3,23,23 are connected in series and stored, and each battery 2
Driving power is supplied from 3 to the electric motor 21.

As shown in FIG. 7, the gear case 15 includes a reduction gear 25 including a plurality of reduction gears 24, 24, ....
Is stored. Each of the reduction gears 24 is an outer ring of a needle bearing 27 of a shell type configuration shown in FIG. 8, which is rotatably attached to a shaft 26 fixed in the case 15.
The gear hub 28 is press-fitted and fixed to be rotatable.

Reference numeral 29 denotes a gear output shaft fixed to a petal crank shaft 30 of the bicycle. The gear output shaft 29 and the reduction gear 2
The outer peripheral portion 24a of No. 4 is connected by a one-way clutch 31.

In the one-way clutch 31, as shown in FIG. 9, a ratchet plate 33 is rotatably attached to a pin 32 fixed to the gear outer peripheral portion 24a, and the ratchet plate 33 is biased toward the center by a spring 34. are doing.

The one-way clutch 31 includes a gear outer peripheral portion 2
When 4a rotates in the direction of the arrow in the figure, that is, counterclockwise, torque is transmitted to the gear output shaft 29, and conversely, the gear outer peripheral portion 2
When 4a rotates clockwise, it is in a free state. In addition, the pedals 18a, 18
When the rotation speed of b is faster than the rotation speed of the electric motor 21 reduced by the speed reducer 25, the one-way clutch 31 prevents the electric motor 21 side from being a load against human power.

As shown in FIG. 10, the gear output shaft 29 is fixed to the petal crank shaft 30 with a bayonet nut 40, and a torque detecting connecting shaft 36 and a crank connecting shaft 35 are screwed to the gear output shaft 29. The right screw 35a prevents loosening, and the left pedal crank 17a is fixed to the crank connecting shaft 35 by a nut 41.

As shown in FIG. 7, a part of the weight of the gear case 15 and the reaction force of the shaft due to the torque transmission are supported by the pedal crank shaft 30 via a bearing 42.

Then, as shown in FIG. 11, one end of a spring 38 is locked to a projection 37 provided integrally with the torque detecting connecting shaft 36, and the other end of the spring 38 is fixed by a stopper 39 to detect the torque. Constitutes a means. 11 shows the pedal crank 17a, the crank connecting shaft 35, the reduction gear 2
4 is omitted.

In the torque detecting means, when the torque detecting connecting shaft 36 rotates in the direction of the arrow in the figure, the spring 38 locked to the protrusion 37 causes the rotating force to be applied to the gear output shaft 29 while the torque detecting connecting shaft 36 winds. introduce. At this time, the protrusion 37
The distance between the stopper 39 and the stopper 39 approaches in proportion to the applied torque. The same effect can be obtained by integrating the torque detecting connecting shaft 36 and the crank connecting shaft 35 with rubber.

The close distance between the protrusion 37 and the stopper 39 can be detected as a change in magnetic flux density by using a magnet and a Hall element. Thus, the magnitude of the torque applied to the torque detecting connecting shaft 36 can be detected.

FIG. 12 is a diagram showing the structure of the speed reducer 25. The rotation of the rotary shaft 21a of the electric motor 21 is controlled by the first speed reduction gear 241.
To the rotary shaft 241a of the first reduction gear 241.
Is transmitted to the second reduction gear 242, rotation of the rotation shaft 242a of the second reduction gear 242 is transmitted to the third reduction gear 243, and rotation of the rotation shaft 2 of the third reduction gear 243 is transmitted.
The rotation of 43a is transmitted to the fourth reduction gear 244, and the rotation shaft of the fourth reduction gear 244 is the gear output shaft 29.

For example, the rotation speed of the electric motor 21 is 7,000.
rpm and this is 1,500 with the first reduction gear 241.
The speed is reduced to rpm and this is reduced to 460 by the second reduction gear 242.
The speed is reduced to rpm, and this is reduced to 200 by the third reduction gear 243.
The speed is reduced to 5 rpm by the fourth reduction gear 244.
The speed is reduced to 8 rpm and output to the gear output shaft 29.

As shown in FIG. 13, the control circuit box 22 includes a CPU 51 constituting a control unit main body, a motor control circuit 52 for driving and controlling the electric motor 21,
A circuit such as an I / O port 53 for outputting data from the CPU 51 to the motor control circuit 52 as a signal is arranged and accommodated in, for example, a circuit board.

FIG. 14 shows the motor control circuit 52.
In the concrete circuit diagram of, the resistor R1 is connected between the + e1 terminal and ground.
An NPN-type transistor Tr1 is connected via the resistor, and the collector of the transistor Tr1 is connected to the inverting input terminal of the differential amplifier AM via the resistor R2. The differential amplifier A
The non-inverting input terminal of M is grounded through the resistors R3 and R4 in series and the resistors R5 and R6 are grounded in series. Connect the connection point of the resistors R3 and R4 to the resistor R
It is connected to the + e2 terminal via 7.

The output terminal of the differential amplifier AM is a resistor R8.
Is connected to the base of the NPN type transistor Tr2 via the resistor R9 and is also connected to its own non-inverting input terminal via the resistor R9.

The transistor Tr2 has a collector connected to the + E terminal via the electric motor 21, an emitter grounded via the resistor R10, and an inverting input terminal of the comparator CM via the resistor R11.

The comparator CM has a non-inverting input terminal grounded via a resistor R12 and a resistor R13 in series.
The connecting point of the resistors R12 and R13 is + e2 via the resistor R14.
It is connected to the terminal.

The comparator CM has its output terminal connected to its own inverting input terminal via a resistor R15 and a resistor R16 in series, and at the connection point of the resistors R5 and R6 via a resistor R15 and a resistor R17 in series. Connected.

The electric motor 21 is, for example, a series motor having a maximum speed without load when the speed of the bicycle is 25 km / h, and is designed so that maximum power assistance is possible at 15 km / h.

The resistor R10 and the comparator CM connected in series with the transistor Tr2 control the current so that an overcurrent does not flow at the time of starting. That is, if the terminal voltage of the resistor R10 rises too much due to the increase in current, the comparator C
The output of M becomes low level, which causes the differential amplifier A
When the output of M becomes low level, the transistor Tr2 turns off, and the terminal voltage of the resistor R10 drops, the comparator CM
Output becomes high level, which causes the differential amplifier AM
Output becomes high level and the transistor Tr2 is turned on. This prevents an excessive acceleration from being applied at the time of startup and an overcurrent from flowing to the battery 23.

The current of the electric motor 21 decreases as the speed increases, and the torque also decreases accordingly, but the output of the electric motor 21 proportional to the product of the torque and the speed is designed to have a small decrease rate.

In the motor control circuit 52, when the transistor Tr1 is turned on, the output level of the differential amplifier AM becomes high level, the transistor Tr2 is turned on, and when the transistor Tr1 is turned off, the differential amplifier A is turned on.
The output level of M becomes low level and the transistor Tr2
Works off.

The CPU 51 is adapted to perform the control shown in FIG. That is, when human power is applied to the pedals 18a and 18b and the detected torque T of the torque sensor as the torque detecting means exceeds a preset constant value T0, a signal for turning on the transistor Tr1 is output to the control circuit 52.

Then, the control circuit outputs a signal for keeping the ON state for a fixed time corresponding to one rotation of the pedal crankshaft 30 and for turning off the transistor Tr1 when the detected torque T becomes a fixed value T0 or less after the lapse of the fixed time. 52 to output. If the detected torque T exceeds the constant value T0 even after the lapse of a fixed time, the ON operation of the transistor Tr1 is continued.

Further, the speed or position is detected, and arithmetic processing is performed or direct acceleration is detected. When the acceleration α becomes negative, it is judged that the brake is applied and the transistor T
A signal for turning off r1 is output to the control circuit 52. That is, the electric motor 21 is controlled so that the power assistance is not differential.
Shut off the current.

In the power assist system of this embodiment, the gear case 15 is connected to the left pedal crankshaft 30. That is, the pedal crank 17a on the left side of the existing bicycle is removed, and the pedal crank shaft 30 is attached to the gear output shaft 29 of the speed reducer.
Are fixed with screws 40. As a result, the flat gear case 15 is arranged parallel to the vehicle body.

Then, the electric motor 21 is arranged so as to project inwardly of the vehicle body at a lower front portion orthogonal to the gear case 15.
The battery case 16 and the circuit box 22 are arranged between the gear case 15 and the vehicle body frame (seat tube 5, down tube 6).

By arranging the electric motor 21 in the lower front portion of the vehicle body in this way, the electric motor 21 can be used regardless of the structure of the vehicle body frame that supports the front wheels 11, the rear wheels 13, the handle 12, and the saddle 14. It can be installed without any trouble. Further, the battery 23 can be easily attached and detached, and therefore, the battery 23 can be easily charged at home.

Part of the load of the gear case 15 is the bearing 4
It is structured so as to be supported by the pedal crankshaft 30 via the shaft 2. The gear output shaft 29 attached to the pedal crankshaft 30 is meshed with a gear 24a held via a one-way clutch 31, and the outer shape of a cylindrical member integral with the preceding gear 24 is the one-way clutch 31. An outer diameter housing of the needle bearing 27 is press-fitted and fixed to the inner diameter of the sliding shaft.

The needle bearing 27 is fixed to the gear case 15 and slides on the shaft, and realizes a flat structure by a method different from the normal gear train in which the shaft is fixed by the upper and lower bearings, thereby realizing a flat structure between the gear case 15 and the body frame. A space for accommodating the battery case 16 is secured therebetween. Further, since the thickness of the gear case 15 can be minimized by using the needle bearing 27, there is no discomfort as a bicycle, the number of bearings used can be reduced, and an inexpensive and strong gear case 15 can be configured.

Further, the clutch and the electric motor 21 are projected toward the vehicle body, and the central axis position of the clutch and the electric motor 21 is the pedal crankshaft 30.
Since the battery case 16 is placed below the crankshaft hub, the heavy battery case 16 can be sufficiently supported by the upper part of the crankshaft hub. The center of gravity is also in a low position, and the running stability is excellent. Therefore, even if this device is attached, it is easy to drive as a bicycle.

Further, the gear output shaft 2 in the gear case 15
9, a torque detecting connecting shaft 36 integrated via a spring 38 is provided coaxially with the gear output shaft 29, and an inner diameter of the connecting shaft 36 is left-threaded on the axial side of the vehicle body, and a right-hand screw is provided on the outer side thereof. It is provided. A left screw of the torque detecting connecting shaft 36 integrated with the gear output shaft 29 is engaged with a crank connecting shaft 35 having the same shape as the pedal crank shaft 30 to which the pedal crank 17a of the existing bicycle is attached. A right-hand screw nut is attached to prevent loosening during reverse rotation. Then, the pedal crank 17a is connected to the crank connecting shaft 35.
It is fixed with a nut 41.

With this structure, the pedals 18a, 1
The stepping force of 8b can be easily detected by the torque detecting means,
The electric motor 21 can be drive-controlled by the detection signal. That is, it is not necessary to provide a switch on the handle 12 or the like and wire the battery, the control circuit, and the electric motor.

Shaft 2 with needle bearing 27 attached
Since 6 does not rotate, it has the effect of increasing the strength as a support for supporting the gear case 15, and the effect of significantly reducing the thickness of the gear case 15. That is, in the present embodiment, the thickness of the gear case 15 can be set to 25 mm or less, whereby a gap of about 45 mm can be secured between the body frame and the gear case 15, and the battery case 16 can be easily stored in this gap. .

By mounting a one-way clutch between the pedal crank 17b on the right side and the crankshaft, the inertial energy of the electric motor 21 prevents the pedal from rotating regardless of the position where the pedal is stopped. be able to.

Further, the circuit box 22 is attached to the battery case 1
Since it is arranged below 6, the battery case 16 serves as a seal for the circuit box 22, and there is no risk of rainwater entering the inside.

Further, the gear case 15 and the battery case 1
6. Since the circuit box 22 and the electric motor 21 are arranged adjacent to each other, the covers can be integrated with each other, and the size can be reduced.

A one-way clutch may be provided integrally with the torque detecting connecting shaft 36, and the same structure as the free hub used for the chain connecting portion of the rear wheel of the bicycle may be incorporated in this portion.

[0058]

As described above, according to the present invention, a battery case accommodating a battery, an electric motor driven by the battery of the battery case as a power source, and a speed reducer for transmitting the rotation of the electric motor through a plurality of reduction gears. And a control circuit for driving and controlling the electric motor, a torque detecting connecting shaft connected to a crank connecting shaft fixed to a bicycle petal crank, and a torque detecting connecting shaft attached to the torque detecting connecting shaft to detect torque associated with rotation of the petal crank. The final stage gear of the speed reducer has one end of the center shaft engaged and fixed to the bicycle petal crank shaft and the other end connected to the bicycle crank connecting shaft through the torque detecting connecting shaft. Since the control circuit is configured to drive and control the electric motor based on the torque detected by the torque detecting means, this device can be easily attached to a general-purpose bicycle, and The torque applied to the more the pedal can be easily detected.

Further, according to the present invention, the speed reducer is housed in the gear case, the gear case is fixed in parallel to the body frame of the bicycle, and the electric motor is located in front of the petal crankshaft and the rotation center axis is the petal crankshaft. Since it is located below the center and orthogonal to the gear case,
The center of gravity is in a low position, which is excellent in driving stability and easy to drive.

Further, according to the present invention, the battery case is arranged on the upper side or upper part of the gear case so that the outer surface of the case does not protrude from the outer surface of the gear case and is arranged parallel to the body frame of the bicycle. The battery can be easily attached and detached. In addition, the wiring between the battery, the control circuit, and the electric motor need not be routed along the vehicle body frame, and can be shortened.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of a bicycle showing an embodiment of the present invention.

FIG. 2 is a side view of a main part of the same embodiment as seen from the left side.

FIG. 3 is a side view of the main part of the same embodiment as seen from the right side.

FIG. 4 is a plan view of a main part of the same embodiment as seen from above.

FIG. 5 is a front view of a main part of the same embodiment as seen from the front.

FIG. 6 is a plan view showing the internal structure of the battery case of the embodiment.

FIG. 7 is a plan view showing a partial configuration inside the gear case of the embodiment.

FIG. 8 is a view showing a configuration of a needle bearing of the same embodiment.

FIG. 9 is a diagram showing a configuration of a one-way clutch used in the speed reducer of the embodiment.

FIG. 10 is a partial cross-sectional view showing the configuration in the vicinity of the pedal crank shaft of the embodiment.

FIG. 11 is a diagram showing a configuration of a torque detection unit of the embodiment.

FIG. 12 is a diagram showing a configuration of a speed reducer of the embodiment.

FIG. 13 is a block diagram showing a control circuit of the embodiment.

FIG. 14 is a circuit diagram showing a specific circuit configuration of a motor control circuit of the control circuit.

FIG. 15 is a flowchart showing main part control of a CPU of the control circuit.

[Explanation of symbols]

 15 ... Gear case 16 ... Battery case 17a, 17b ... Pedal crank 21 ... Electric motor 22 ... Circuit box 29 ... Gear output shaft 30 ... Pedal crank shaft 31 ... One-way clutch 35 ... Crank connecting shaft 36 ... Torque detecting connecting shaft 38 ... Spring

Claims (5)

[Claims] 1. A battery case accommodating a battery, an electric motor driven by the battery in the battery case as a power source, and a speed reducer for transmitting the rotation of the electric motor through a plurality of reduction gears.
A control circuit for driving and controlling the electric motor, a torque detecting connecting shaft connected to a crank connecting shaft fixed to a petal crank of a bicycle, and a torque detecting connecting shaft attached to the torque detecting connecting shaft to detect torque accompanying rotation of the petal crank. The final stage gear of the speed reducer has one end of a central shaft engaged and fixed to a petal crank shaft of the bicycle, and the other end of the gear connected to the crank connecting shaft of the bicycle via the torque detecting connecting shaft. A power assist device for a bicycle, characterized in that the control circuit drives and controls the electric motor based on the torque detected by the torque detecting means. 2. A speed reducer is housed in a gear case, the gear case is fixed in parallel to the body frame of the bicycle, and the electric motor is located in front of the petal crankshaft and the rotation center axis is below the center of the petal crankshaft. The power assist device for a bicycle according to claim 1, wherein the power assist device for a bicycle is positioned so as to be orthogonal to the gear case. 3. The battery case is arranged on the upper side or upper part of the gear case so that the outer surface of the case does not protrude from the outer surface of the gear case and is arranged parallel to the body frame of the bicycle. Item 2. A bicycle power assist device according to item 2. 4. The torque detecting means connects the final stage gear of the speed reducer and the torque detecting connecting shaft with an elastic member, detects displacement between the final stage gear and the torque detecting connecting shaft, and depresses the pedal. The power assist device for a bicycle according to claim 1, wherein force is detected. 5. The speed reducer is provided with a one-way clutch for transmitting the rotational force in only one direction, and when the no-load rotational speed of the electric motor is converted by the pedal crankshaft, it is slower than the rotational speed of the pedal crankshaft due to human power. The power assist device for a bicycle according to claim 1, wherein the power assist device for a bicycle is set as follows.