NL2009766A

NL2009766A - Torque detection device and bicycle including the same.

Info

Publication number: NL2009766A
Application number: NL2009766A
Authority: NL
Inventors: Masato Iwase; Haruo Yo; Takayuki Hosoda; Tatsutoshi Shinjo; Hiroyasu Noguchi; Yoshinori Fukasaku
Original assignee: Nidec Copal Corp
Priority date: 2011-11-07
Filing date: 2012-11-06
Publication date: 2013-05-08
Also published as: TW201319536A; JP2013100999A; JP5479436B2; CN103091017A; DE102012110617A1; NL2009766C2

Description

TORQUE DETECTION DEVICE AND BICYCLE INCLUDING THE SAME

The present invention relates to a torque detection device used to detect a pedaling force of an electric assisted bicycle or the like.

Japanese Unexamined Patent Application Publication No. 10-232175 describes a technology in this technical field. This Publication describes an electric assisted bicycle including a front wheel, handle bars, a main frame, and a rear wheel. The front wheel and the handlebars are attached to a front portion of the main frame. The rear wheel, which is a driving wheel, is attached to a rear portion of the main frame. A seat tube is disposed at substantially the center of the main frame, and a saddle is mounted on an upper end of the seat tube. A pedal mechanism is rotatably supported by a cylindrical frame, which is disposed at a lower end of the seat tube. A crank of the pedal mechanism is connected to a sprocket through compression springs. The sprocket is connected to a sprocket of a rear wheel, which is driven by a motor, through a chain. To be specific, the compression springs are inserted into openings formed in the sprocket. First ends of the compression springs are supported by pressing tabs of an engagement plate, which is fixed to a shaft portion of the crank. Second ends of the compression springs are supported by edges of the openings. Thus, when a pedal mounted on the crank is pressed, the pedaling force is transmitted to the sprocket through the compression springs. The pedal mechanism further includes a torque detection device. The torque detection device includes an outer wheel, an inner wheel, a magnet, an inner Hall element, and an outer Hall element. The outer wheel is disposed on the sprocket and has outer detection windows that are arranged in the circumferential direction at a regular pitch. The inner wheel is disposed on the engagement plate and has inner detection windows arranged in the circumferential direction at a regular pitch. The magnet is disposed between the outer and inner wheels, which are disposed so as to face each other. The inner Hall element is disposed so as to face the magnet with the inner wheel therebetween. The outer Hall element is disposed so as to face the magnet with the outer wheel therebetween. If there occurs a phase shift between the inner wheel and the outer wheel, a phase shift also occurs between the output waveforms of the two (inner and outer) Hall elements. The torque detection device detects the phase shift between the output waveforms and sends a signal corresponding to the phase shift to a control unit of a motor, which is an auxiliary power source.

However, a technical problem is that it is difficult to reduce the size of the existing torque detection device described above, because the torque detection device, which requires two (inner and outer) Hall elements and inner and outer detection windows, has a complex structure.

An object of the present invention is to provide a torque detection device that has a simple structure. An object of the invention is to provide a torque detection device that can be easily reduced in size.

According to the present invention, there is provided a torque detection device for detecting a torque applied to a primary rotation member of a rotor that includes the primary rotation member and a secondary rotation member that is connected to the primary rotation member through an elastic member, the torque detection device including an annular magnet that is magnetized such that S-poles and N-poles are alternately arranged in a circumferential direction; a first yoke including first magnetized portions and a first annular plate, the first magnetized portions being arranged in an annular shape such that each of the first magnetized portions faces a corresponding one of the S-poles of the magnet, the first annular plate being formed in an annular shape so as to connect the first magnetized portions to each other; a second yoke including second magnetized portions and a second annular plate, the second magnetized portions being arranged in an annular shape such that each of the second magnetized portions faces a corresponding one of the N-poles of the magnet, the second annular plate being formed in an annular shape so as to connect the second magnetized portions to each other and being disposed so as to face the first annular plate; and a magnetic sensor that is disposed between the first annular plate and the second annular plate and that detects quantity of magnetism. The magnet is fixed to one of the primary rotation member and the secondary rotation member of the rotor, the first and second yokes are fixed to the other of the primary rotation member and the secondary rotation member of the rotor, and the magnetic sensor is fixed to a non-rotating member.

In the torque detection device, the magnet, the first yoke, and the second yoke are fixed to the rotor; the rotor includes the primary rotation member and the secondary rotation member, which are connected to each other through the elastic member. The magnetic sensor detects the phase difference between the primary rotation member and the secondary rotation member. In detecting variation in the torque applied to a rotor, the more complex the structure of a torque detection device, the easier it is for the torque detection device to become broken. Therefore, it is important that a torque detection device have a simple structure. In particular, because reduction in size and weight are required for a bicycle, it is desirable that a torque detection device be reduced in size and weight. To achieve such an object, the torque detection device according to the present invention includes an annular magnet, a first yoke, a second yoke, and a magnetic sensor. The annular magnet is magnetized such that S-poles and N-poles are alternately arranged in a circumferential direction. The first yoke includes first magnetized portions and a first annular plate, the first magnetized portions being arranged in an annular shape such that each of the first magnetized portions faces a corresponding one of the S-poles of the magnet, the first annular plate being formed in an annular shape so as to connect the first magnetized portions to each other. The second yoke includes second magnetized portions and a second annular plate, the second magnetized portions being arranged in an annular shape such that each of the second magnetized portions faces a corresponding one of the N-poles of the magnet, the second annular plate being formed in an annular shape so as to connect the second magnetized portions to each other and being disposed so as to face the first annular plate. The magnetic sensor is disposed between the first annular plate and the second annular plate and detects quantity of magnetism. Therefore, with the torque detection device according to the present invention, variation in the torque applied to the primary rotation member can be reliably detected even if the torque detection device includes only one magnetic sensor and only one magnet. Thus, the structure of the torque detection device can be simplified and the size of the torque detection device can be easily reduced. Moreover, variation in the torque can be reliably detected for any rotation speed of the rotor.

The torque detection device may further include a nonmagnetic annular spacer that is disposed so as to surround the magnet and so as to be in contact with the first and second magnetized portions and that serves as a base for the first and second magnetized portions.

In this case, the first and second yokes can be stably fixed in place due to the presence of the spacer. Moreover, a small gap can be easily and precisely created between a surface of the magnet and each of the first and second magnetized portions.

The first magnetized portions and the second magnetized portions may be arranged in a single plane extending perpendicular to a rotation axis of the rotor.

In this case, the magnetized portions can be made flat, and thereby the magnet can be spaced apart from the magnetized portions with a uniform distance therebetween. As a result, a uniform magnetic field can be created on the first and second annular plates. Therefore, torque variation at any position on the rotor can be reliably and precisely measured by the detection sensor, which is disposed between the first annular plate and the second annular plate.

Each of the first and second magnetized portions may have a tooth-like shape oriented in a direction substantially perpendicular to a rotation axis of the rotor, and each of the first and second annular plates may have a surface disposed at substantially a right angle to the first and second magnetized portions.

In this case, the first and second yokes can be reduced in size.

Each of the first and second magnetized portions may have a tooth-like shape oriented in a direction substantially perpendicular to a rotation axis of the rotor, and each of the first and second annular plates may have a planar surface disposed at substantially a right angle to the rotation axis.

In this case, the first and second yokes can be made flatter and thinner.

With the present invention, a torque detection device is provided that has a simple structure. With the present invention, a torque detection device is provided that can be easily reduced in size.

Hereinafter, a torque detection device according to an embodiment of the present invention will be described in detail with reference to the drawings.

Fig. 1 is an exploded perspective view illustrating a torque detection device according to an embodiment of the present invention.

Fig. 2 is a plan view illustrating the torque detection device mounted in a bicycle.

Fig. 3 is a sectional view of the torque detection device illustrated in Fig. 2.

Fig. 4 is a plan view of a first yoke.

Fig. 5 is a sectional view of the first yoke illustrated in Fig. 4.

Fig. 6 is a plan view of a second yoke.

Fig. 7 is a sectional view of the second yoke illustrated in Fig. 6.

Fig. 8 is a plan view of a spacer.

Fig. 9 is a sectional view of the spacer illustrated in Fig. 8.

Fig. 10 is a plan view illustrating the relationship between a magnet and the yokes.

Fig. 11 is a schematic view illustrating the relationship among the magnet, a first magnetized portion, and a second magnetized portion.

Fig. 12 is a perspective view illustrating first and second yokes according to a modification.

Fig. 13 is a sectional view illustrating the first and second yokes illustrated in Fig. 12 that are joined to each other.

Fig. 14 is an exploded perspective view illustrating a torque detection device according to another embodiment of the present invention.

Fig. 15 is a side view illustrating an electric assisted bicycle including a torque detection device.

Fig. 16 is block diagram illustrating the system configuration of the electric assisted bicycle.

Fig. 1 illustrates a torque detection device 1 used in an electric bicycle or an electric assisted bicycle. As illustrated in Fig. 15, an electric assisted bicycle 50 includes a main frame 51, to which a saddle 52 is attached. A front wheel 54, which is provided with a motor 53, and handlebars 56 are attached to a front portion of the main frame 51.

A rear wheel 55 is attached to a rear portion of the main frame 51. A sprocket 11 of the torque detection device 1 is rotatably mounted on a substantially central portion of the main frame 51. The sprocket 11 is connected to a sprocket of the rear wheel 55 through a chain. The motor 53 drives the front wheel 54 so as to assist a pedaling force applied to pedals 2.

The sprocket 11, which is rotated via the pedals 2, is included in a rotor 10 and is connected to a crank 4. The rotor 10 includes the sprocket 11 (secondary rotation member), a disk 12 (primary rotation member), and compression coil springs 13. The sprocket 11 meshes with a chain. The disk 12, to which the crank 4 is fixed, includes a cylindrical boss portion 12a that is inserted into a central opening 11a in the sprocket 11. The compression coil springs 13, which serve as an elastic member, connect the sprocket 11 and the disk 12 to each other.

Four spring insertion holes 11b are formed in the sprocket 11 so as to surround the central opening 11a. The disk 12 includes a flange portion 12b that slidably contacts a flat surface of the sprocket 11. The flange portion 12b includes spring receiving portions 12c, which are inserted into the spring insertion holes 11b. Protrusions 11c, which are formed at edges of the spring insertion holes 11b, are inserted into first ends of the compression coil springs 13. Protrusions 12d, which are formed on the spring receiving portions 12c, are inserted into second ends of the compression coil springs 13. Thus, the compression coil springs 13 are prevented from coming off the spring insertion holes 11b.

With the rotor 10 having such a structure, the disk 12 is rotated by a pedaling force applied to the pedals 2, and the rotational force of the disk 12 is transmitted to the sprocket 11 through the compression coil springs 13. The torque detection device 1 is attached to the rotor 10 in order to detect a torque variation in the pedaling force transmitted to the disk 12.

The torque detection device 1 includes an annular magnet 21, a first yoke 22, a second yoke 23, and a Hall element 24. The annular magnet 21 is magnetized such that S-poles and N-poles are alternately arranged in the circumferential direction (see Fig.

10). The first yoke 22 includes tooth-like first magnetized portions 22a and a first annular plate 22b. The first magnetized portions 22a are arranged in an annular shape such that each of the first magnetized portions 22a faces a corresponding one of the S-poles of the magnet 21 with a gap therebetween. The first annular plate 22b is formed in an annular shape so as to connect the first magnetized portions 22a to each other. The second yoke 23 includes tooth-like second magnetized portions 23a and a second annular plate 23b. The second magnetized portions 23a are arranged in an annular shape such that each of the second magnetized portions 23a faces a corresponding one of the N-poles of the magnet 21 with a gap therebetween. The second annular plate 23b is formed in an annular shape so as to connect the second magnetized portions 23a to each other and is disposed so as to face the first annular plate 22b. The Hall element 24, which serves as a magnetic sensor, is disposed between the first annular plate 22b and the second annular plate 23b and detects the quantity of magnetism.

As illustrated in Figs. 1 to 5, the first magnetized portions 22a of the first yoke 22 are arranged at a regular pitch and each have a trapezoidal tooth-like shape oriented in a direction substantially perpendicular to a rotation axis L of the rotor 10. The first annular plate 22b is formed in an annular shape so as to connect base ends of the first magnetized portions 22a, and the first annular plate 22b has a surface that is disposed at substantially a right angle to the first magnetized portions 22a. At a base end of the first annular plate 22b, cutout portions 22c are formed between the first magnetized portions 22a. The second magnetized portions 23a of the second yoke 23 are inserted into the cutout portions 22c with gaps therebetween.

As illustrated in Figs. 1, 2, 3, 6, and 7, the second magnetized portions 23a of the second yoke 23 are arranged at a regular pitch and each have a trapezoidal tooth-like shape oriented in a direction substantially perpendicular to the rotation axis L of the rotor 10. The second annular plate 23b is joined to an annular expansion portion 23c that is formed in an annular shape so as to connect base ends of the second magnetized portions 23a to each other. The second annular plate 23b has a surface that is disposed outside of the first annular plate 22b at substantially a right angle to the second magnetized portions 23a.

The first and second magnetized portions 22a and 23a are arranged on an annular spacer 27 illustrated in Figs. 8 and 9, which is made of a non-magnetic material (such as aluminum). The annular spacer 27 is disposed so as to surround the annular magnet 21 and so as to be in contact with the first and second magnetized portions 22a and 23a. The annular spacer 27 serves as a base for the first and second magnetized portions 22a and 23a. By using the spacer 27, the first and second yokes 22 and 23 can be stably fixed in place. The spacer 27 has a thickness slightly larger than that of the magnet 21. Due to the difference in thickness between the spacer 27 and the magnet 21, a small gap can be easily and precisely created between a surface of the magnet 21 and each of the first and second magnetized portions 22a and 23a.

Moreover, as illustrated in Fig. 10, due to the presence of the spacer 27, the first magnetized portions 22a and the second magnetized portions 23a are arranged in a single plane extending perpendicular to the rotation axis L of the rotor 10. Each of the first magnetized portions 22a faces a corresponding one of the S-poles of the magnet 21 with a gap therebetween. Each of the second magnetized portions 23a faces a corresponding one of the N-poles of the magnet 21 with a gap therebetween. Thus, the first annular plate 22b becomes an S-pole over the entire circumference thereof, and the second annular plate 23b becomes an N-pole over the entire circumference thereof.

By using the spacer 27, the magnetized portions 22a and 23a can be easily made flat, and thereby the magnet 21 can be spaced apart from the magnetized portions 22a and 23a with a uniform distance therebetween. As a result, a uniform magnetic field can be created on the first and second annular plates 22b and 23b. Therefore, torque variation at any position on the rotor 10 can be reliably and precisely measured by the Hall element 24, which is disposed between the first annular plate 22b and the second annular plate 23b.

As illustrated in Figs. 1 to 3, the magnet 21 is fixed to the boss portion 12a of the disk 12 using an adhesive. The first and second yokes 22 and 23 are fixed to the spacer 27, which is nonmagnetic, using screws 25 and 26. The screws 25 and 26 extend through screw insertion holes 22d and 23d (see Figs. 4 and 6) formed in the first and second magnetized portions 22a and 23a. The spacer 27 is fixed to the sprocket 11 using an adhesive. The spacer 27, which is made of a non-magnetic material such as aluminium, includes positioning protrusions 27a (see Figs. 8 and 9). The spacer 27 can be efficiently attached to the sprocket 11 by inserting the positioning protrusions 27a into positioning recesses 11d formed in the sprocket 11.

The Hall element 24, which is disposed between the first annular plate 22b and the second annular plate 23b, is fixed to a circuit board 28. The circuit board 28 is fixed to a non-rotating member (not shown), such as a chain cover or the main frame. The circuit board 28 is connected to a control unit 57 through a wire.

As illustrated in part (a) of Fig. 11, when the bicycle is moving at a constant speed, each of the first magnetized portions 22a faces a corresponding one of the S-poles of the magnet 21, and each of the second magnetized portions 23a faces a corresponding one of the N-poles of the magnet 21. As illustrated in part (b) of Fig. 11, when a rider accelerates the bicycle from this state by pressing the pedals 2, the magnet 21 moves in the direction of arrow A. At this time, a change occurs in the direction of a magnetic field and the quantity of magnetic flux that passes through the Hall element 24. The Hall element 24 converts this change into an electric signal. This electric signal is sent to the control unit 57, which increases the output power of the motor 53 in accordance with the electric signal. The same applies to the case where the bicycle starts moving.

As illustrated in Figs. 15 and 16, the torque detection device 1, which includes the Hall element 24, is connected to the control unit 57. In addition, the motor 53, a battery 58, a controller 59, and a light 61 are connected to the control unit 57 through connectors. The battery 58 is disposed at substantially the center of the main frame 51. The controller 59 is disposed on the handlebars 56 and a rider performs operations such as a power-on/off operation using the controller 59. The light 61 is disposed on a front portion of the bicycle. A brake switch 60 is connected to the controller 59. The control unit 57 includes a central processing unit (CPU) and stores a program for controlling the electric assisted bicycle 50. The control unit 57 controls the output power of the motor 53 on the basis of information about a pedaling force applied to the pedals 2, which is detected by the torque detection device 1, information about a braking operation performed on the brake switch 60, and the like.

In the torque detection device 1, the magnet 21, the first yoke 22, and the second yoke 23 are fixed to the rotor 10. The rotor 10 includes the disk 12 (primary rotation member) and the sprocket 11 (secondary rotation member), which are connected to each other through the compression coil springs 13. The Hall element 24, which serves as a magnetic sensor, detects the phase difference between the disk 12 (primary rotation member) and the sprocket 11 (secondary rotation member). In detecting variation in the torque applied to the rotor 10, the more complex the structure of the torque detection device 1, the more easily the torque detection device 1 may become broken. Therefore, it is important that the torque detection device 1 have a simple structure. Moreover, because reduction in size and weight are required for a bicycle, it is desirable that the torque detection device 1 be reduced in size and weight.

To achieve such an object, the torque detection device 1 includes the annular magnet 21, the first yoke 22, the second yoke 23, and the Hall element 24. The annular magnet 21 is magnetized such that S-poles and N-poles are alternately arranged in the circumferential direction. The first yoke 22 includes the tooth-like first magnetized portions 22a and the first annular plate 22b. The first magnetized portions 22a are arranged in an annular shape such that each of the first magnetized portions 22a faces a corresponding one of the S-poles of the magnet 21. The first annular plate 22b is formed in an annular shape so as to connect the first magnetized portions 22a to each other.

The second yoke 23 includes the tooth-like second magnetized portions 23a and the second annular plate 23b. The second magnetized portions 23a are arranged in an annular shape so that each of the second magnetized portions 23a faces a corresponding one of the N-poles of the magnet 21. The second annular plate 23b is formed in an annular shape so as to connect the second magnetized portions 23a to each other and is disposed so as to face the first annular plate 22b. The Hall element 24 is disposed between the first annular plate 22b and the second annular plate 23b and detects the quantity of magnetism.

Therefore, with the torque detection device 1, variation in the torque applied to the disk 12 (primary rotation member) can be reliably detected even if the torque detection device 1 includes only one Hall element 24 and only one magnet 21. Thus, the structure of the torque detection device 1 can be simplified and the size of the torque detection device 1 can be easily reduced. Moreover, variation in the torque can be reliably detected at any rotation speed of the rotor 10.

The present invention is not limited to the embodiment described above.

For example, as illustrated in Figs. 12 and 13, first magnetized portions 32a of a first yoke 32 each have a trapezoidal tooth-like shape oriented in a direction substantially perpendicular to the rotation axis L of the rotor 10. The first magnetized portions 32a are joined to one end of an annular connection plate 32c, and the connection plate 32c is disposed at substantially a right angle to the first magnetized portions 32a. A first annular plate 32b, which has a planar surface disposed at substantially a right angle to the rotation axis L, is joined to the other end of the connection plate 32c.

Second magnetized portions 33a of a second yoke 33 each have a trapezoidal tooth-like shape oriented in a direction substantially perpendicular to the rotation axis L of the rotor 10. The base ends of the second magnetized portions 33a are joined to a second annular plate 33b, which has a planar surface disposed at substantially a right angle to the rotation axis L. By using the first and second yokes 32 and 33 having such shapes, The first and second yokes 32 and 33 can be made flatter and thinner.

In the rotor 10, the magnet 21 may be fixed to the sprocket 11 (secondary rotation member), and the first and second yokes 22, 32, 23, and 33 may be fixed to the disk 12 (primary rotation member). Also in this case, an intended object can be achieved.

The torque detection device 1 may include a plurality of Hall elements 24. For example, as illustrated in Fig. 14, two Hall elements 24 may be disposed so as to face each other with the rotation axis L therebetween, i.e., at positions separated from each other by 180 degrees around the rotation axis L.

Instead of a Hall element, an MR sensor may be used as a magnetic sensor.

A torque detection device according to the present invention can be used in devices other than electric or electric assisted bicycles.

In the electric or electric assisted bicycle according to the embodiment described above, the front wheel is driven by a motor. Alternatively, the rear wheel may be driven by a motor.

Reference Signs List 1: torque detection device 10: rotor 11: sprocket (secondary rotation member) 12: disk (primary rotation member) 13: compression coil spring (elastic member) 21: magnet 22, 32: first yoke 22a, 32a: first magnetized portion 22b, 32b: first annular plate 23, 33: second yoke 23a, 33a: second magnetized portion 23b, 33b: second annular plate 24: Hall element (magnetic sensor) 27: spacer L: rotation axis

Claims

A torque detection device for detecting a torque applied to a primary rotation member of a rotor comprising the primary rotation member and a secondary rotation member connected to the primary rotation member via an elastic member, the torque detection device comprising: an annular magnet that is magnetized that the Z poles and N poles are arranged alternately in a circumferential direction; a first yoke comprising first magnetized parts and a first annular plate, the first magnetized parts being arranged in an annular shape such that each of the first magnetized parts faces a corresponding Z-pole of the magnet, the first annular plate having an annular shape has to connect the first magnetized parts together; a second yoke comprising second magnetized parts and a second annular plate, the second magnetized parts being arranged in an annular shape such that each of the second magnetized parts faces a corresponding N-pole of the magnet, the second annular plate having an annular shape has to connect the second magnetized portions to each other and is arranged to face the first annular plate; and a magnetic sensor disposed between the first annular plate and the second annular plate and detecting an amount of magnetism, the magnet being attached to one of the primary rotary member and the secondary rotary member of the rotor, the first and second yokes being mounted to the other of the primary rotary member and the secondary rotary member of the rotor, and wherein the magnetic sensor is attached to a non-rotating member.

The couple detection device according to claim 1, further comprising: a non-magnetic annular spacer arranged to surround the magnet and to be in contact with the first and second magnetized parts, and which serves as the basis for the first and second magnetized parts.

A torque detection device according to claim 1 or 2, wherein the first and second magnetized parts are arranged in a single plane that extends perpendicular to an axis of rotation of the rotor.

A torque detection device according to any one of claims 1-3, wherein each of the first and second magnetized parts has a tooth-like shape, directed substantially perpendicular to an axis of rotation of the rotor, and wherein each first and second annular plate has a surface which is is substantially perpendicular to the first and second magnetized parts.

A torque detection device according to any one of claims 1-3, wherein each of the first and second magnetized parts has a tooth-like shape, directed substantially perpendicular to an axis of rotation of the rotor, and wherein a flat surface of each first and second annular plate in is substantially perpendicular to the axis of rotation.

A torque detection device according to any of claims 1-5, wherein a crankshaft to which a pedal can be attached is attached to the primary rotary member.

A bicycle, comprising: a torque detection device according to any of claims 1-6; a motor that drives a wheel; and a control unit which controls the motor on the basis of a detection signal from the torque detection device.