JP2000272575A - Electric-power assisted bicycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify and miniaturize the torque detecting mechanism of an electric-power assisted bicycle. SOLUTION: A sprocket 2 is provided with a shaft portion 2b attached to a drive shaft 4, a gear portion 2a fitted in concentric-circularly to the outer periphery of the shaft portion 2b, and a spring 44 for pressing the shaft and gear portions 2b and 2a. In the shaft and gear portions 2b and 2a, eight magnets 40 and 42 are respectively buried at equal intervals in a circumferential direction. Magnetic sensors 60 and 62 are provided, 60 being fixed in a position for detecting the magnetic field of each magnet 40, and 62 being fixed in a position for detecting the magnetic field of each magnet 42, and these sensors are connected to a controller 14 for performing power assisting control. The controller computes a difference in rotational phases between the shaft and gear portions 2b and 2a based on the detecting time of the magnets 40 and 42. Thus, by detecting the rotational deformation of the sprocket 2 itself with a simple mechanism, a torque detecting mechanism is simplified and miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrically assisted bicycle that detects a torque due to a pedaling force of an occupant and assists the pedaling force using auxiliary power when the torque satisfies a predetermined condition. The present invention relates to an electric assist bicycle that detects torque based on a rotational phase difference between a shaft portion and a tooth portion of a sprocket.

[0002]

2. Description of the Related Art Conventionally, an electric drive system is added in parallel to a bicycle driven by manpower, and the output of the electric drive system is controlled based on a change in the treading force by manpower, thereby assisting the pedaling force by manpower. Electric assisted bicycles have been implemented.

A conventional electric assist bicycle includes a torque detecting mechanism for detecting a stepping torque acting on a rotating mechanism in accordance with a pedaling force, and adds an auxiliary power when the detected torque reaches a predetermined condition. are doing. Among such torque detection mechanisms, there is the following method for detecting, as a stepping torque, a rotational phase difference between a rotating body linked to the drive shaft and a rotating body linked to the teeth of the sprocket. (1) An input plate that is connected to a crankshaft and rotates together with the shaft, an output plate that is connected to the input plate via a spring that urges the input plate in the rotation direction, and is fixed to the output plate via an outer shaft. And a sprocket connected thereto, and the amount of compression deformation of the spring, that is, the relative amount of rotation between the input plate and the output plate, is detected as a stepping torque on the pedal using a rotary encoder or the like (Japanese Patent Laid-Open No. 8-169385). . (2) A first slit plate which is attached to a rotation center of a crank to which a pedal is attached and in which a number of first slits are formed in a circular shape, has the same shape and the same pitch as the first slits. The same number of second slits are formed, and the chain sprocket is substantially parallel to the first slit plate so that the second slit faces the first slit with a predetermined phase difference. Fixed second
An elastic member disposed between the rotation center of the crank and the chain sprocket;
Detecting means for calculating a phase difference between a crank rotation center portion and a chain sprocket by detecting a time when light passes through the slit and the second slit, and calculating the phase difference as a torque generated by depressing a pedal. (Japanese Patent Application Laid-Open No. 6-111179). (3) a first rotating body including a first rotating body in which a sprocket is fitted on a drive shaft, and a second rotating body concentrically rotatably fitted on the outside of the first rotating body; A leaf spring as an elastic body is fitted between the first rotating body and the second rotating body, and biases both rotating bodies so as to be able to rotate integrally. And
Spur teeth are provided on the outer periphery of both the first rotating body and the second rotating body, and the first and second rotating driven wheels that rotate together with them are fitted respectively, and further fitted between these rotating driven wheels. The swinging body is fitted to the driven wheel via a measuring arm, and the angle formed by the two measuring arms is measured by a potentiometer to detect the stepping torque (see Japanese Unexamined Patent Application Publication No.
-257605).

[0004]

However, in the torque detecting mechanisms disclosed in JP-A-8-169385 and JP-A-6-21179, the torque transmitting mechanism is provided in a power transmission mechanism on a path in which the pedaling force is transmitted from the pedal to the rear wheel sprocket. An elastic member that is deformed according to the pedaling force is newly added separately from components such as sprockets. Such an elastic member has a high rigidity and a large elastic modulus to resist the pedaling force directly applied thereto. For this reason, not only does the space and weight occupied by the power transmission mechanism increase due to the new addition of the elastic member, but another transmission mechanism for deforming the elastic member according to the treading force is further required, There is a problem that the torque detecting mechanism is further complicated and large.

In Japanese Patent Application Laid-Open No. 9-257605, the sprocket itself is composed of two rotating bodies. However, in order to detect a phase difference between these rotating bodies, another gear mechanism is required. Complicated torque detection mechanism,
It is getting larger. In addition, since the first and second rotating bodies are arranged in an overlapping manner, there is a disadvantage that the thickness of the sprocket increases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and provides an electric assist bicycle that realizes light driving by greatly reducing and simplifying the space and weight occupied by a torque detecting mechanism. With the goal.

[0007]

In order to solve the above-mentioned problems, a first aspect of the present invention is an electric assist bicycle having an electric motor for assisting pedal depression force, wherein a shaft attached to a drive shaft and the shaft are provided. A sprocket having teeth that are rotatably fitted to the outer periphery of the shaft and have teeth for fitting with the chain, and an elastic portion that connects the shaft to the teeth; and a predetermined position of the shaft. A shaft phase display member, a tooth phase display member disposed at a predetermined position of the tooth portion, and a shaft phase detecting that the shaft phase display member has passed a first predetermined position. Detecting means, tooth part phase detecting means for detecting that the tooth part phase display member has passed a second predetermined position, and time based on the detection of the shaft part phase display member and the tooth part phase display member. Between the shaft portion and the tooth portion. Calculates a rotational phase difference caused in,
Torque detecting means for detecting a stepping torque based on the pedaling force from the rotational phase difference; andcontrolling means for controlling the electric motor to assist the pedaling force based on the detected stepping torque. Features.

When the pedaling force acts on the drive shaft, a stepping torque acts on the shaft, so that the teeth try to rotate together with the shaft. At this time, the tooth portion also receives a pulling force from the chain from the opposite direction, so that the tooth portion rotates in the opposite direction relative to the shaft portion until it balances with the elasticity of the elastic body connecting the shaft portion and the tooth portion. . Thus, a rotation phase difference occurs between the shaft portion and the tooth portion according to the stepping torque.

The shaft phase detecting means and the tooth detecting phase means sequentially detect the shaft phase displaying member provided on the shaft and the tooth phase displaying member provided on the tooth. The rotational phase difference between the shaft portion and the tooth portion is immediately obtained based on the rotational speed difference, and the stepping torque is detected from the rotational phase difference. Then, the control means controls the electric motor based on the detected stepping torque to assist the pedaling force.

The torque detecting means according to the first aspect of the present invention may be configured such that at least one of a detection cycle of the shaft phase display member and a detection cycle of the tooth phase display member is provided, The rotational phase difference is calculated based on a detection time difference between the phase display member and the tooth portion phase display member.

Further, the shaft phase display member and the tooth phase display member are provided in a plurality and in the same number, and each is arranged at substantially the same pitch. Is preferred. This facilitates the calculation of the rotational phase difference from the detection time-series data of the shaft portion phase display member and the tooth portion phase display member, and the calculation accuracy can be improved by providing a plurality of rotation phase differences.

The shaft phase display member and the tooth phase display member are constituted by magnets, for example, as in the invention of claim 4, and the shaft phase detection means and the tooth phase detection means are magnetic sensors. It can be.

In another example, the shaft phase display member and the tooth phase display member may have protrusions protruding from the surfaces of the shaft portion and the tooth portion to predetermined heights, respectively, as in the invention of claim 5. Wherein the shaft part phase detecting means and the tooth part phase detecting means are position sensors for respectively detecting the distance to the shaft part and the tooth part when passing through the first and second predetermined positions. be able to.

[0014] The elastic portion may connect between a bridge extending outward from the shaft portion and a bridge extending inward from the tooth portion, for example, as in the invention of claim 6. A spring that expands and contracts in the circumferential direction may be used.

In another embodiment, the elastic portion may be a member that connects the shaft portion and the tooth portion from one side of the sprocket and has elasticity in a main stress direction. Good.

Here, as in the invention of claim 8, the shaft portion and the tooth portion are provided with locking portions each defining an angle range in which the tooth portion can rotate with respect to the shaft portion. Is preferred. As a result, it is possible to prevent a rotation phase difference from occurring beyond the elastic limit of the elastic portion, and to avoid deterioration of the elastic portion.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an electric assist bicycle according to each embodiment of the present invention will be described with reference to the drawings. (First Embodiment) FIG. 1 schematically shows an electric assist bicycle 1 according to a first embodiment of the present invention. As shown in the figure, a main skeleton portion of the electric assist bicycle 1 is constituted by a body frame 3 made of a metal tube.
A front wheel 20, a handle 16 for steering the front wheel, a rear wheel 22, a saddle 18, and the like are attached to the vehicle body frame 3 in a known manner.

A sprocket 2 is rotatably supported at the center lower portion of the vehicle body frame 3. The sprocket 2 is integrated with the sprocket 2 on both left and right sides via a drive shaft 4 having the same axis 5 as the sprocket. Rotating crank rods 6L, 6R are respectively attached, and pedals 8L, 8R are provided at the tips of these crank rods, respectively.
Further, a rear wheel power mechanism 10 for applying the transmitted pedaling force to the rear wheel is provided at a central portion of the rear wheel 22, and a free wheel (not shown) provided inside the rear wheel power mechanism is provided. Endlessly rotating chain 1 between sprocket 2
2 is stretched.

As is well known, the pedaling force applied to the pedal 8 in the forward direction acts on the sprocket 2 via the crank rod 6 as a stepping torque in the R direction in the figure, and the stepping torque is transmitted through the chain 12 to the rear. The power is transmitted to the wheel power mechanism 10, and as a result, the rear wheel 22 is rotated to cause the bicycle 1 to run forward.

FIGS. 2A and 2B show a detailed front view of the vicinity of the sprocket 2 and a cross-sectional view taken along a plane including the drive center shaft 5. As shown in the front view, the chain 12 stretched over the sprocket 2 includes a pin link in which two pins are press-fitted into two cocoon-shaped link plates, and two bushes into two ring plates. It is formed by alternately combining a press-fitted roller link with a roller rotatably fitted around the outer periphery of the bush. Chain 1
The pitch and diameter of the rollers constituting the two pin links and the roller links are determined so as to be fitted to the respective teeth of the sprocket 2.

A sprocket driving gear 11 is fitted to the sprocket 2, and the sprocket driving gear 11 is connected to a driving means 13 for supplying auxiliary power when predetermined conditions are satisfied.

This sprocket 2 has at least the structure shown in FIG.
It can be disassembled into a tooth portion 2a and a shaft portion 2b shown in FIGS. 4A and 4B show a front view and a side view of the tooth portion and the shaft portion.

As shown in the front view of FIG. 4A, the tooth portion 2a has a plurality of teeth 2 for fitting with the chain 12.
A recess 25 is formed on the outer periphery between the teeth 4 and adjacent teeth, and a hole 46 for receiving the shaft 2b is perforated in the central region. Also, four first locking portions 48 are provided at regular intervals along the circumferential direction so as to protrude into the region of the hole portion 46.
a and the second locking portion 48b are respectively formed. The first holding portion 52a further extends from the side of the second locking portion 48b. Eight cylindrical magnets 42 are embedded in the teeth 2a at equal distances from the center at equal intervals along the circumferential direction. These magnets 4
2 is preferably arranged such that a straight line connecting the N pole and the S pole is substantially perpendicular to the flat surface of the tooth portion 2a (ie, substantially parallel to the drive center axis 5).

As shown in the front view of FIG. 4 (b), the shaft portions 2b are provided with three third locking portions 48c at regular intervals along the circumferential direction so as to protrude outward. And the fourth locking portion 48d are formed respectively. The second holding portion 52b further extends from the side of the fourth locking portion 48d. As shown in the side view, a cylindrical portion 54 is formed at the center of the shaft portion 2b to receive the drive shaft 4, and a hole 56 is formed in the cylindrical portion 54. Eight cylindrical magnets 40 are embedded around the outer periphery of the cylindrical portion 54 at equal distances from the center at equal intervals along the circumferential direction. These magnets 40
Is preferably arranged such that a straight line connecting the N pole and the S pole is substantially perpendicular to the flat surface of the shaft portion 2b (that is, substantially parallel to the drive center axis 5).

FIG. 3A is a front view of the sprocket 2 in a state where the teeth 2a and the shaft 2b are assembled. As shown in the figure, the third locking portion 48c of the shaft portion 2b is
a first locking portion 48a and second locking portion 48b in FIG.
It is received with a space left in the recessed region 51 formed between them. This figure shows the drive shaft 4
In this case, the third locking portion 48 is engaged with the second locking portion 48b as shown in the figure, and the shaft portion 2b
The eight magnets 40 are arranged in a state in which the eight magnets 42 of the tooth portion 2a are in phase with each other (for example, the angle with respect to the line SS ′ can be selected).

A spring 44 is provided between the second locking portion 48b of the tooth portion 2a and the fourth locking portion 48d of the shaft portion 2b.
Are attached via the holding section 52a and the holding section 52b. A total of four springs 44
Is attached. These springs 44 are provided so that the third locking portion 48 is engaged with the second locking portion 48b as shown in the drawing when the stepping torque is not applied from the drive shaft 4, so that the teeth 2a and the An elastic force acts on the shaft portion 2b.

FIG. 2B shows a means for detecting the magnetic field exerted by the magnet 42 of the tooth 2a and the magnet 40 of the shaft 2b. The mounting stage 58 is supported so as to be fixed to the vehicle body frame so that the mounting surface is substantially parallel to the surface of the sprocket 2. On the mounting stage 58, one first magnetic sensor 60 is disposed at a position where the distance from the drive center axis 5 is substantially equal to the distance of the magnet 40, and the distance from the drive center axis 5 is substantially equal to the distance of the magnet 42. One second magnetic sensor 62 is arranged at the same position. First and second magnetic sensors 6
Reference numerals 0 and 62 are arranged so as to mainly detect a magnetic field of a component substantially parallel to the drive center axis 5, and a Hall element or the like is used as an example. With such an arrangement, the magnet 40 and the magnet 42 move within the sensitivity range of the first and second magnetic sensors 60 and 62 with the rotation of the sprocket 2, respectively.
Passing sequentially. First and second magnetic sensors 60,
The detection signal output by 62 is transmitted to a controller described later.

Next, means related to the electric assist drive of the present embodiment will be described. First, a top view and a side view of the sprocket drive gear 11 are shown in FIG. As shown in the figure, the sprocket drive gear 11 has two roller plates 17a, 17b opposed in parallel, and the same roller as the chain 12 along the peripheral region of the plate so as to connect the plates. A plurality (six in the example in the figure) of cylindrical bushings (roller shafts) 15 which are press-fitted substantially perpendicularly to the plate for each pitch, and are rotatably fitted so as to cover the outer periphery of these bushings. And a plurality (six in the example in the figure) of cylindrical rollers 21. Roller plates 17a and 17b are provided with driving means 1 at the center thereof.
A mounting hole 19 for mounting on the roller 3 is formed.
3 are formed.

FIG. 3A shows a state where the sprocket drive gear 11 is fitted to the sprocket 2. In this state, two adjacent rollers 21 of the sprocket drive gear 11 are engaged with the concave portions 25 of the sprocket 2, and the gap between these rollers is one tooth 2 of the sprocket 2.
4 enter each. Here, a cross-sectional view taken along the line SS ′ is shown in FIG. As is clear from the figure,
In the fitted state, the teeth 24 of the sprocket 2 are held between the plates 17a, 17b of the sprocket drive gear 11. The recess 33 of the sprocket drive gear 11 is preferably formed so that the teeth of the chain 12 can easily fit between the rollers 21.
It is preferable that the link is formed in substantially the same shape as the constricted portion at the center of the cocoon-shaped link plate.

3 (a) and 3 (b), when the sprocket drive gear 11 rotates around its drive center axis 9 in the direction K in the figure, each roller 21 The sprockets 2 are successively engaged with the respective recesses 25, and the driving torque in the R direction about the central axis 5 of the drive 4 is given to the sprocket 2. As described above, in the present embodiment, the electric torque from the electric motor 37 is applied to the teeth 24 having high rigidity via the sprocket drive gear 11.
Is transmitted to the area of the sprocket 2 where
The pedaling force can be assisted without bending the sprocket 2 and without shifting the rotation center.

The sprocket drive gear 11 is shown in FIG.
As shown in (b), the reduction mechanism 35 of the driving means 13 is rotatably supported via a gear shaft 35a. The reduction mechanism 35 is driven to rotate by a battery (not shown), and the electric torque is transmitted via a rotation shaft 37a. It is connected to an electric motor 37 for transmission. The reduction mechanism 35 is configured by, for example, combining a plurality of gears and the like, and a so-called one-way clutch that transmits power only in one direction is provided in the middle of the electric torque transmission path configured by these gears. (Not shown). The one-way clutch is configured and connected so as to transmit the electric torque from the electric motor 37 to the sprocket drive gear 11 but not in the reverse direction, that is, to transmit the torque from the sprocket drive gear to the reduction mechanism 35. As a result, the load of the electric motor 37 at the time of non-drive is not transmitted to the sprocket 2, and light driving is always possible.

The electric motor 37 is connected to the controller 14. The controller 14 calculates the rotational phase difference between the shaft 2b and the tooth 2a from the detection signals from the first and second magnetic sensors 60 and 62 shown in FIG.
A stepping torque is calculated from the rotation phase difference, and it is determined whether or not electric assist is necessary based on the stepping torque. A motor control signal for controlling the rotation of the electric motor 37 is output based on the result of the determination. I do. This controller 14 can be realized by a so-called microcomputer or the like.

Next, the operation of the first embodiment of the present invention will be described with reference to the drawings. When the occupant passes through the drive shaft 4 from the pedals 8R and 8L, the shaft portion 2b of the sprocket 2
When the stepping torque is given to the shaft 2, the shaft 2b rotates in the R direction in the sprocket 2, while the tooth 2a
It receives a pulling force from the chain in the direction opposite to the R direction.
Therefore, four springs 44 connecting the shaft portion 2b and the tooth portion 2a are provided.
Are further contracted and energized. At this time, the third locking portion 48c moves in the concave region 51 apart from the second locking portion 48b. The second locking portion 48b in the concave area 51
Is determined according to the magnitude of the stepping torque balanced with the urging forces of the four springs 44, and when a stepping torque exceeding a certain limit acts, the first engaging portion 48a is engaged to move. limit. This prevents elastic fatigue due to stepping torque exceeding the elastic limit of the spring 44.

Thus, a rotational phase difference is determined between the tooth portion 2a and the shaft portion 2b in accordance with the magnitude of the stepping torque, and the rotational phase difference is the phase difference between the magnet 40 and the magnet 42. Appear as.

The first and second magnetic sensors 60, 62
Mounting stage 5 fixed to body frame 3
8, the magnetic field B of the magnet 40 and the magnet 42 passing through each sensitivity region one after another is constantly measured, and these measurement results are used as detection signals as the controller 1.
4 is output. The waveform of this detection signal (the horizontal axis is time,
FIG. 6 shows an example of the vertical axis (the measured value of the magnetic field B).

As shown in FIG. 6, it can be seen that a magnetic field that fluctuates while periodically forming a peak is detected. In the waveform example shown in the figure, the detection signals of the magnetic sensor 62 indicate the times t _a1 , t
The peak of the detected magnetic field is observed at _a2 and _ta3.
In the detection signal of ( ₁₎ , peaks of the detection magnetic field are observed at times t _b1 , t _b2 , and t _b3 . It can be seen that the magnetic field is hardly detected outside the region of a certain time width sandwiching these peaks. That is, these peak times are determined by the magnets 40 and 42.
Are just passing through the sensitivity region of the magnetic sensors 60 and 62.

When the stepping torque is not applied, the rotational phase difference between the tooth portion 2a and the shaft portion 2b is zero, so that the magnetic field peak times of the two coincide with each other. However, when the stepping torque acts, the phase of the tooth portion 2a is delayed with respect to the shaft portion 2b as described above, and therefore, as shown in FIG.
The magnetic field peak time a is detected later than the magnetic field peak time of the shaft portion 2b. The time difference Δt between the two magnetic field peaks reflects the rotational phase difference between the two. The rotation phase (angle) difference Δθ is expressed by the following equation, where the rotation cycle of the sprocket 2 is ΔT.

Δθ = Δt / ΔT (1) Here, the time difference Δt at the time of the magnetic field peak is determined by
The peak time of the magnetic field _b2, Detected shortly after that
The magnetic field peak time of the tooth portion 2a is represented by t_a2Then, Δt = t_a2-T_b2 (2) The rotation cycle of the sprocket 2 was calculated by Δt.
Considering that it is expressed by the rotation period of the tooth portion 2a at the time,
ΔT = (t)_a2-T_a1) · 2π / ΔA (3) Here, ΔA indicates that two adjacent magnets 42
In this embodiment, the angle is π / 4 (45 degrees).
is there. On the other hand, the rotation cycle of the sprocket 2
Considering that the rotation speed is represented by a rotation cycle, ΔT = (t_b2-T_b1) · 2π / ΔA (4)

In any case, the rotational phase difference Δ
θ can be arbitrarily and suitably represented by time-series data of the magnetic field peak detection time in the tooth portion 2a and the shaft portion 2b,
The present invention can include all such methods.

Since the biasing force of the spring 44, which balances with the stepping torque, is substantially proportional to the rotational phase difference Δθ, the controller 14 calculates the rotational phase difference Δθ obtained sequentially from the magnetic field peak detection time series data from the equation (1). The stepping torque T can be calculated in real time from the series data.

Further, the controller 14 calculates an assist electric torque Te to be applied based on the calculated stepping torque T, and calculates a control signal for instructing the electric motor 37 to rotate by the electric torque. Output.

For example, in the case of the simplest electric assist control, when the calculated stepping torque T becomes a predetermined value or more, the electric motor 37 is turned on to generate an electric torque that maintains a predetermined ratio with respect to the stepping torque. It outputs a motor control signal for commanding, and otherwise outputs a motor control signal for turning off the electric motor. In this case, the rotation phase difference Δ
The electric motor 37 may be turned on only when this value becomes a certain value or more by directly using θ.

When the electric motor 37 is turned on and rotated, the rotation is transmitted to the vicinity of the highly rigid tooth portion of the sprocket 2 via the speed reduction mechanism 35 and the sprocket drive gear 11, and the assist electric power is transmitted to the sprocket 2. Apply torque. As described above, the assisting electric torque is applied under such a condition that the stepping torque is considered to be equal to or more than a certain value, so that the pedal operation can be performed easily.

As described above, according to the present embodiment, the elastic member having a high rigidity and a large volume and weight, a transmission mechanism, and the like are not separately added to the existing electric assist bicycle, but are based on the rotational phase difference of the sprocket itself. The torque is calculated using the torque detection mechanism, which reduces the space and weight of the torque detection mechanism, greatly simplifies the mechanism, and offers the advantage that the pedal can be easily depressed even on steep hills as before. In addition, it can be driven very lightly.

Further, as shown in FIG. 2 (b), the rotation phase difference can be detected only by disposing a magnetic sensor such as a Hall element on only one side of the sprocket 2, so that the conventional method can be used. As described above, in order to connect mechanical means to both of the two rotating bodies or to measure the amount of light passing through the slot, compared to a torque detecting mechanism in which a light emitting element and a light receiving element detecting means are respectively disposed on both sides of the rotating body. Thus, further simplification of the mechanism and space saving can be achieved.

In the present embodiment, the electric torque from the electric motor 37 is transmitted through the sprocket drive gear 11 to
Since the power is transmitted to the outer peripheral portion of the sprocket 2 having a large diameter, there is an advantage that a large reduction ratio can be obtained as compared with a structure in which electric torque is applied from the drive shaft 4. This makes it possible to reduce the size and weight and simplify the resultant force mechanism. Further, the sprocket drive gear 11
Since the electric assist means can be configured only by providing the motor and the driving means 13, it is not necessary to change the frame structure of the conventional vehicle body, and the bicycle structure can be further reduced in size and weight, simplified, and reduced in cost. .

Further, since the electric torque is directly transmitted to the outer periphery of the sprocket, the torque measured by the torque detecting device of the present embodiment reflects only the stepping torque, and the electric torque and the stepping torque are clearly separated. Thus, the depression torque can be accurately calculated.

(Second Embodiment) Next, a second embodiment will be described. Since the main difference from the first embodiment is the sprocket, only the configuration of the sprocket will be described in detail, and the same components as those in the first embodiment will be denoted by the same reference numerals and detailed description thereof will be omitted. .

FIG. 7 shows the components (top view and conceptual side view) of the sprocket used in the torque detecting device according to the second embodiment. As shown in the figure, the sprocket includes three components: a sprocket tooth portion 70a, an elastic portion 70b, and a disk portion 70c.

The sprocket tooth portion 70a has an outer peripheral portion in which a plurality of teeth 71 and concave portions 72 are alternately formed over the outermost periphery, a perforation 76 opening at a central portion, and a hole from the outer peripheral portion toward the perforation 76. And three locking portions 74 protruding in the radial direction and formed at equal angles in the circumferential direction. The sprocket teeth 70a are integrally formed of a metal material so as to have rigidity in order to ensure the engagement with the chain 12. Further, a plurality of projections 100 are formed on the sprocket teeth 70a at equal distances from the center around the perforations 76 at equal intervals along the circumferential direction. As shown in the side view, these projections 100 are raised higher in the axial direction than the surrounding sprocket surfaces.

The elastic portion 70b is integrally formed of an elastic body in order to increase the amount of stress deformation, and has an annular outer peripheral portion 78 and a central hole 74 which passes through the drive shaft 4 at the same center as the outer peripheral portion 78. Central inner circle portion 82 and outer peripheral portion 7
And a plurality of (six in the figure) connecting portions 81 connecting the inner portion 8 and the center inner circle portion 82 at predetermined angles in the radial direction. A raised portion 80 is provided at the center of each connecting portion 81. Holes 85 are respectively formed between adjacent connecting portions 81. The elastic portion 70b can be made of a material having a large elastic modulus or the same metal material having a smaller thickness than the sprocket tooth portion 70a.

The connecting portion 81 bridges the outer peripheral portion 78 and the central inner circular portion 82 in a state inclined with respect to the radial direction.
Thus, the stress G generated by the antagonism between the pulling force of the chain 12 and the stepping torque acts efficiently along the length direction of the connecting portion 81.

The disk portion 70c is integrally formed of a metal material so as to have rigidity, and has an outer peripheral disk portion 86.
And a cylindrical portion 90 having a central hole 94 for receiving the drive shaft 4. On the outer periphery of the outer peripheral disk portion 86, a plurality of radially concave notched portions 88 are provided at equal angles ( In the figure, three teeth are formed, and internal teeth 92 for fitting and fixing to the drive shaft 4 are formed on the inner wall of the central hole 94 of the cylindrical portion 90. Also in the disk portion 70c, a plurality of projections 102 are formed around the cylindrical portion 90 at equal distances from the center at equal intervals along the circumferential direction. These projections 102 are provided on the sprocket teeth 70.
The protrusions 100 are arranged in the same number as the protrusions 100a, and as shown in the side view, protrude higher in the axial direction than the surface of the surrounding disk. It is preferable that the height of the raised portion 100 and the height of the raised portion 102 be the same.

The disk portion 70c is inserted into the hole 76 of the sprocket tooth portion 70a so that the disk portion 70c can be fitted.
Has an outer diameter substantially equal to the inner diameter of the hole 76 of the sprocket tooth portion 70A, and the cutout portion 88 has a radial length substantially equal to that of the locking portion 74, and a circumferential length thereof. Are formed longer. For this reason, the disk part 70c
When fitted to the sprocket teeth 70a, the disk portion 70c can be rotated within a range where the locking portion 74 engages from one inner wall of the notch 88 to the other inner wall.

FIG. 8A shows a sprocket 77 completed by combining the components shown in FIG. As shown in the figure, each locking portion 74 is rotated in the rotation direction R ′ of the sprocket 77.
The disc portion 70c is fitted into the sprocket tooth portion 70a in a state in which the disc portion 70c is in contact with one inner wall of each notch portion 88 on the front side. And furthermore, the elastic part 7
The elastic part 70b connects the sprocket tooth part 70a and the disk part 70c to each other with the cylindrical part 90 of the disk part 70c inserted into the central hole 84 of the disk 0b. These components can be connected, such as by welding or riveting, as is well known to those skilled in the art.

In the second embodiment, as described above, the magnets are not used as the members for displaying the rotational phase, and the protrusions 100 and 102 are used instead. Correspondingly, at the positions of the magnetic sensors 60 and 62 shown in FIG. 2B, position sensors 110 and 112 for detecting the distance from the mounting position to the sprocket surface are respectively arranged.

When the projections 100 and 102 are made of a magnetic material such as ferrite, for example, the position sensors 110 and 112 use a coil aligned in the axial direction of the sprocket and a change in the inductance of the coil as an electric signal. And a detection circuit that can detect the conversion. In the case of this configuration, the inductance of the coil changes depending on the distance between the protrusions 100 and 102 and the coil. Therefore, the axial distance to the sprocket 2 can be calculated by detecting the change in the inductance of the coil by the detection circuit. . Of course, any other type of detection sensor may be used as long as the axial distance can be detected.

Next, the operation of the second embodiment will be described.
The sprocket 77 to which the depressing torque for traveling forward is transmitted to the disk portion 70c tries to rotate in the R 'direction as a whole as shown in FIG. 8A. At this time, a sprocket tooth portion 70a connected to the disk portion 70c via the elastic portion 70b has a chain 1 against the stepping torque.
2, the sprocket teeth 70
a tends to rotate relative to the disc portion 70c in the direction opposite to the R ′ direction, and the locking portion 74 moves away from the inner wall of the notch portion 88 and moves inside the notch portion 88 in the opposite direction. I do.

Therefore, the stress G acts on the connecting portion 81 on the elastic portion 70b connecting the sprocket tooth portion 70a and the disc portion 70c which are in opposition to each other as described above.
Each raised portion 80 expands and contracts in the direction of the stress G according to its magnitude, and stops expanding and contracting when the elasticity of the elastic portion 70b and the stress G are balanced (see FIG. 8B). In this way, the sprocket tooth portion 7 is changed according to the magnitude of the stepping torque.
A rotational phase difference is generated between Oa and the disk portion 70c.

The detection signals from the position sensors 110 and 112 for detecting the projections 100 and 102 indicate that the projections 100 and
When the top of 2 passes through the sensitivity area of the position sensor, a curve with the minimum detection distance is obtained. When the stepping torque is applied, the minimum distance point detected by the sprocket teeth 70a is delayed from the minimum distance point detected by the disk part 70c according to the rotational phase difference. Therefore, as described in the first embodiment, the depression torque is calculated based on the equations (1) to (4) and the like.

As described above, in the second embodiment, the sprocket 77 combining the three components is made to have substantially the same volume and weight as the integrally formed sprocket, and the stepping torque is calculated based on the elastic deformation of the sprocket 77 itself. Therefore, as in the first embodiment, excellent effects such as space saving, light weight, and a simple mechanism can be achieved as compared with the related art.

Further, since the disk portion 70c fixed to the drive shaft 4 and the sprocket teeth 70a fitted to the chain 12 are connected via the elastic portion 70b, a large force is suddenly applied to the chain 12. In this case, the elastic portion 70a functions as a shock absorber. This protects not only the teeth 70a but also, for example, a ratchet gear (not shown) arranged around the drive shaft 4, and extends the life of these gears.

In the second embodiment, the disk portion 70c can be cut out from the metal material in which only the outer periphery of the sprocket tooth portion 70a is formed, so that the cost and labor can be reduced in the forming process.

The embodiments of the torque detecting device according to the present invention have been described above. However, the present invention is not limited to the above example, and can be arbitrarily and suitably changed within the scope of the present invention.

For example, the elastic portion 70b of the second embodiment may be replaced with an elastic portion 104 shown in FIG. The elastic portion 104 shown in FIG.
Is formed. In the torsion portion 106, a metal portion connecting the outer peripheral portion 103 and the central inner circular bridge portion 105 is formed by twisting the metal portion by half a turn to have elasticity.

Further, the magnets 40 and 42 and the projections 100,
When the stepping torque is not applied, the elements 102 are arranged so as to have the same phase, but may be arranged so as to be shifted by a predetermined phase. In this case, needless to say, the rotational phase difference is calculated in consideration of the initial phase difference.

[0067]

As described above in detail, according to the first to eighth aspects of the present invention, the sprocket itself is to be detected, and the sprocket phase display member provided on the shaft and the teeth are provided on the teeth. Since the rotational phase difference can be obtained by directly detecting the tooth phase display member provided, the need for separately provided gears, a rotating body, a disk with a slit, etc. is unnecessary, and the torque detecting mechanism is greatly increased. It can be simplified and lightened. Further, the elastic portion connecting the shaft portion and the tooth portion is provided integrally with the sprocket, and
Since the teeth are fitted on the outer periphery of the shaft, the thickness of the sprocket can be suppressed, and the space and weight of the torque detection mechanism can be reduced. As described above, since there is almost no need to change the frame structure of the bicycle, there is obtained an excellent effect that a light-weight and simplified electric-assisted bicycle that is lightly driven can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic view of an electric assist bicycle according to the present invention.

FIG. 2 is a diagram showing a torque detection mechanism of the electric assist bicycle according to the present invention, wherein (a) is a front view showing a state in which a sprocket to be detected is arranged on the electric assist bicycle;
(B) is a side sectional view showing an arrangement of a magnetic sensor (position sensor).

3A and 3B are views showing a fitted state of a sprocket and a sprocket driving gear after assembly, wherein FIG. 3A is a front view of the fitted state, and FIG. It is a sectional side view of the fitting state.

FIG. 4 is an exploded view of the sprocket according to the first embodiment of the present invention, wherein (a) is a front view and a side view of a tooth portion,
(B) is the front view and side view of a shaft part.

FIG. 5 is a front view and a side view of a sprocket drive gear used in the electric assist bicycle according to the first embodiment of the present invention.

FIG. 6 is a graph showing a change over time of a detection signal of a magnetic sensor when a shaft magnet and a tooth magnet are detected in the sprocket of the electrically assisted bicycle according to the first embodiment.

FIG. 7 is a front view and a side view of respective components of a sprocket according to a second embodiment of the present invention, ie, a sprocket tooth portion, an elastic portion, and a disk portion.

8A and 8B are a front view and a side view of the sprocket when the sprocket components according to the second embodiment shown in FIG. 7 are assembled. FIG. 8A shows a case where no stepping torque is applied, and FIG. The parentheses indicate sprockets when the maximum stepping torque is applied.

FIG. 9 is a front view and a side view showing another embodiment of the elastic portion of the sprocket according to the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric assist bicycle 2 Sprocket 2a Tooth part 2b Shaft part 3 Body frame 4 Drive shaft 5 Center axis 11 Sprocket drive gear 12 Chain 13 Drive means 14 Controller 35 Reduction mechanism 37 Electric motor 40 Magnet (shaft) 42 Magnet (tooth) 44 Spring 48a First locking part 48b Second locking part 48c Third locking part 48d Fourth locking part 60 Magnetic sensor 62 Magnetic sensor 70a Sprocket tooth part 70b Elastic part 70c Disk part 74 Locking part Reference Signs List 80 raised portion 81 connecting portion 84 cutout portion 100 projecting portion 102 projecting portion 103 elastic portion 106 torsion portion 110 position sensor 112 position sensor

Claims (8)

[Claims] 1. An electric assisted bicycle provided with an electric motor for assisting pedaling force, comprising: a shaft mounted on a drive shaft, rotatably fitted on an outer periphery of the shaft, and fitted to a chain. A sprocket having a tooth portion provided with teeth, and an elastic portion connecting the shaft portion and the tooth portion; a shaft portion phase display member disposed at a predetermined position on the shaft portion; A tooth phase display member disposed at a position; a shaft phase detection means for detecting that the shaft phase display member has passed a first predetermined position; and a tooth phase display member at a second predetermined position. Tooth phase detecting means for detecting that the tooth has passed, and rotation generated between the shaft and the tooth based on the time when the shaft phase display member and the tooth phase display member are detected. A phase difference is calculated, and the pedal An electric assist bicycle comprising: torque detecting means for detecting a stepping torque based on the pedaling force; and control means for controlling the electric motor to assist the pedaling force based on the detected stepping torque. 2. The method according to claim 1, wherein the torque detecting unit detects at least one of a detection cycle of the shaft phase display member and a detection cycle of the tooth phase display member, and detects the shaft phase display member and the tooth phase display member. The electric assist bicycle according to claim 1, wherein the rotational phase difference is calculated based on a time difference. 3. The plurality of shaft phase display members and the plurality of tooth phase display members are provided in the same number, and each is arranged at substantially the same pitch. Electric assist bicycle. 4. The shaft phase display member and the tooth phase display member are constituted by magnets, and the shaft phase detection means and the tooth phase detection means are magnetic sensors.
The electric assist bicycle according to any one of claims 1 to 3. 5. The shaft part phase display member and the tooth part phase display member are projections projecting from a surface of the shaft part and the tooth part to a predetermined height, respectively, and the shaft part phase detecting means and the tooth are provided. 2. The partial phase detecting means is a position sensor for detecting a distance to the shaft portion and the tooth portion when passing through the first and second predetermined positions, respectively. 3.
The electric assist bicycle according to any one of claims 1 to 3. 6. The elastic portion is a spring that expands and contracts in a circumferential direction, which connects between a bridge portion extending outward from the shaft portion and a bridge portion extending inward from the tooth portion. The electric assist bicycle according to any one of claims 1 to 5. 7. The elastic member according to claim 1, wherein the elastic portion is a member that connects the shaft portion and the tooth portion from one side of a sprocket and has elasticity in a main stress direction. The electric assist bicycle described. 8. The shaft portion and the tooth portion are provided with locking portions each defining a rotatable angle range of the tooth portion with respect to the shaft portion. 2. The electric assist bicycle according to claim 1.