JP2000203484A - Motor assist bicycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify a resultant force mechanism of the pedaling force and the electric motor force of a motor assist bicycle and to reduce size. SOLUTION: This bicycle comprises a sprocket 2 rotated by a pedal pedaling force; an electric motor 37; a sprocket drive gear 11 connected to the electric motor through a deceleration mechanism 35 with a one-way clutch and fitted in the tooth part of the sprocket 2; a detecting sensor 34 to detect an axial displacement amount of a protuberant part 27; and a controller 14 to compute torque based on the pedal pedaling force from an output from the sensor and control the electric motor based on the torque value. A sprocket drive gear 11 is formed that a plurality of rollers have their roller axes arrayed at the same pitch at two parallel plates along the periphery thereof. Since electric motor torque is directly transmitted to the sprocket 2, having a comparatively large diameter, through a sprocket drive gear 11, compared with structure where electric motor torque is added from a drive shaft, a deceleration ratio is set to a higher value and a resultant force mechanism is decreased in size and weight and simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric assist bicycle equipped with an electric motor for assisting the pedaling force of a rider, and more particularly, to a mechanism for directly transmitting the torque of the electric motor to a sprocket. The present invention relates to an electrically assisted bicycle provided with.

[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.

[0003] In general, such an electric assist bicycle combines a pedal pressing force applied to a crankshaft and an auxiliary power by an electric motor, and transmits a resultant force to driving wheels via a rotating shaft of a sprocket. Is provided. Conventionally, a planetary gear device, a differential device, or the like has been used as the resultant device.

Further, the conventional electric assist bicycle is provided with a torque detecting mechanism for detecting a stepping torque acting on the rotating mechanism in accordance with the pedaling force in order to maintain the pedaling force and the auxiliary power at a predetermined assist ratio in the resultant force. Things are common. Conventionally, the following measures have been taken as such a torque detecting mechanism. (1) A torsion bar is provided in the crankshaft or on the rear wheel axle, which is torsionally deformed according to the pedaling force, and the torsion deformation of the torsion bar is converted into a linear motion by a cam or the like connected to the torsion bar. The change in the resistance of the potentiometer linked to the is detected as the input torque. Alternatively, the torsional rotation angle of the torsion bar is directly detected (JP-A-9-207868). (2) A coil spring is connected to one end of the rear wheel gear holder so that the pedaling force transmitted to the rear wheel free gear via the chain is transmitted to the pulley integrated with the rear wheel via the coil spring. The amount of deflection of the coil spring is detected as input torque. (3) A disk member that receives an input to the pedal from the crankshaft side and transmits it to another mechanism is supported on the frame so as to be rotatable and axially movable in a state of being coaxial with the crankshaft. A coil spring having one end fixed to the crankshaft and the other end fixed to the disk member is provided in a state of being inserted inside, and a change in distance of the disk member from the frame is detected as a driving torque (Japanese Patent Laid-Open No. Hei 8 −230
756). (4) The axle support portion is constituted by a long hole formed long in the front and rear, the axle is supported in the long hole, and the axle and the sprocket are fixed by a compression coil spring disposed between a movable core integral with the axle and the main frame. The axle and the sprocket are held at the rear end position of the long hole by elastically urging backward, and the displacement of the sprocket in the front-rear direction with respect to the main frame, that is, the winding tension of the endless rotating chain is detected as the driving torque (Japanese Patent Laid-Open No. No. 9-301263). (5) an input plate connected to the crankshaft and rotating together with the shaft; an output plate connected to the input plate via a spring biasing the input plate in the rotation direction; and an output shaft fixed to the output plate. 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). . (6) A first slit plate which is attached to a rotation center of a crank to which a pedal is attached and in which a large 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).

[0005]

However, the above-described conventional force-assisting device for an electrically assisted bicycle has a structure in which a resultant force is applied to the drive shaft by using a planetary gear device or a differential device, so that it is complicated, large, and heavy. There was a problem of becoming. Further, in order to mount such a resultant force mechanism, the frame structure of the conventional bicycle has to be changed, which has further complicated and increased the size of the bicycle structure.

[0006] In addition, in the conventional torque detecting mechanism, an elastic member that is deformed in accordance with the pedal depressing force is provided in a power transmission mechanism in a path where the depressing force is transmitted from the pedal to the rear wheel sprocket, such as a sprocket or the like. It is newly added separately from the configuration requirements. 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.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances. An electric assist bicycle which realizes light driving by simplifying a resultant force mechanism and a torque detecting mechanism and greatly reducing the space and weight occupied by these mechanisms. The purpose is to provide.

[0008]

In order to solve the above-mentioned problems, a first aspect of the present invention provides a sprocket which is rotated by a pedal depressing force, an electric motor, and a sprocket which is connected to a rotating shaft of the electric motor. A sprocket drive gear fitted to the tooth portion, torque detecting means for detecting a torque based on the pedal depression force or a physical quantity related to the torque, and controlling the electric motor based on the torque detected by the torque detecting means And control means.

According to the present invention, the control means controls the electric motor based on the torque detected by the torque detection means. The electric torque generated by the electric motor is transmitted to a sprocket drive gear connected to the rotation shaft, acts on a sprocket fitted with the gear, and is combined with a stepping torque to assist human power. As described above, in the present invention, since the electric torque is directly transmitted to the sprocket having a relatively large diameter via the sprocket drive gear, the speed is reduced as compared with the structure in which the electric torque is applied from the drive shaft as in the above-described prior art. The ratio can be increased, and the frame structure of the vehicle does not need to be changed. This makes it possible to reduce the size and weight and simplify the resultant force mechanism. Further, since the sprocket has high rigidity, the sprocket can reliably transmit the electric torque.

As the sprocket drive gear, any gear can be used as long as it can fit the sprocket and transmit torque.
A plurality of rollers are arranged at the same pitch on two opposing parallel plates along the circumference thereof so that their roller axes intersect substantially perpendicularly to the parallel plates, and are arranged in gaps formed between adjacent rollers. Preferably, the teeth of each of the sprockets are formed to fit sequentially.

As described above, according to the second aspect of the present invention, since the structure of the sprocket drive gear is similar to the chain structure,
The engagement between the sprocket and the sprocket drive gear is improved, and the electric torque can be reliably transmitted to the sprocket.

Also, as in the invention of claim 3, claim 2
It is preferable that a concave portion is formed in the outer peripheral portion between adjacent rollers in the two parallel plates. This makes it easier for the teeth of the sprocket to enter the gap between the adjacent rollers, thereby further improving the fit between the sprocket and the sprocket drive gear.

Also, as in the invention of claim 4, claim 2
Alternatively, it is further preferable that the plurality of rollers according to claim 3 are arranged in substantially the same shape, the same size, and the same pitch as the rollers constituting the chain stretched on the sprocket.

The sprocket drive gear according to any one of the first to fourth aspects is preferably arranged such that the sprocket drive gear is provided on a tooth of the sprocket portion which is not fitted with a chain stretched over the sprocket. Mated.

[0015] Also, as in the invention of claim 6, claim 1
In the invention according to any one of claims 5 to 5, a speed reduction mechanism may be interposed between the sprocket drive gear and a rotation shaft of the electric motor. As a result, a desired reduction ratio is obtained. In the present invention, even if the speed reduction mechanism is provided, since the electric torque is directly transmitted to the sprocket having a relatively large diameter, the size of the speed reduction mechanism can be reduced and simplified as compared with the above-described conventional technology.

The invention according to claim 7 is the invention according to claims 1 to 6.
In the invention according to any one of the above, a clutch mechanism is interposed between the sprocket drive gear and a rotating shaft of the electric motor.

According to the seventh aspect of the present invention, only the power of the electric motor can be transmitted to the sprocket drive gear by the clutch mechanism, and the power in the opposite direction can not be transmitted to the electric motor. Is not performed, a light operation can be realized without applying a load of the electric motor to the sprocket. As this clutch mechanism, a so-called one-way clutch that transmits torque in only one direction is most preferable. Note that other types of clutches, such as connecting and disconnecting the sprocket drive gear and the rotating shaft of the electric motor when not operating the electric motor, and connecting the sprocket drive gear and electric motor when operating the electric motor. A controlled, electric clutch may be used.

[0018] The invention according to claim 8 is the invention according to claims 1 to 7.
Wherein the torque detecting means detects a torque based on the pedaling force or a physical quantity related to the torque, based on a displacement amount generated on the sprocket itself by the action of the pedaling force. And

According to the invention of claim 8, when torque acts on the sprocket, the sprocket itself having elasticity undergoes stress deformation. The amount of displacement varies depending on the magnitude of the applied torque. The present invention focuses on this point, and detects torque based on the amount of displacement generated on the sprocket itself due to the action of torque. As described above, in the present invention, it is not necessary to add a large elastic body separately from components such as sprockets and the like, so that not only can the detection mechanism be configured very simply, but also the space and weight occupied by this mechanism are greatly reduced. Can be reduced. Therefore, coupled with the simplification of the resultant force mechanism, there is almost no need to change the frame structure of the bicycle, so that it is possible to realize a light-weight, simplified electric-assisted bicycle with a light driving.

According to a ninth aspect of the present invention, there is provided the sprocket according to the eighth aspect of the present invention, wherein the amount of displacement generated on the sprocket itself is such that a tooth portion formed on an outer periphery of the sprocket for fitting with a chain, and the pedal is provided on the sprocket. The rotational phase difference between the shaft portion for fixedly supporting the drive shaft for transmitting the treading force.

According to the ninth aspect of the present invention, the rotational phase difference between the tooth portion and the shaft portion increases as the pedaling force increases. Therefore, it is possible to detect the torque applied to the sprocket based on the rotational phase difference. it can. This rotational phase difference is
It can be detected using an encoder or the like. Since the electric torque is transmitted to the teeth of the sprocket via the sprocket drive gear, this rotational phase difference purely reflects the depression torque based on the pedal effort. Therefore, the calculation of the stepping torque can be performed with high accuracy.

On the other hand, according to a tenth aspect of the present invention, the amount of displacement generated in the sprocket itself according to the eighth aspect is such that the sprocket surface is deformed by the stress deformation generated in the sprocket itself due to the action of the pedal depression force. It is characterized by a displacement amount when displaced.

According to the tenth aspect of the present invention, in order to detect the amount of displacement of the sprocket surface, for example, a means for detecting the distance to the displaced sprocket surface can determine the amount of displacement reflecting the stepping torque. As described above, in the present invention, a means for detecting a distance or the like may be added, and the torque detecting means can be further simplified and downsized as compared with the case of detecting a rotational phase difference.

In order to improve the torque detection accuracy by increasing the displacement caused by the stress deformation, it is necessary to provide a portion for detecting the displacement of the sprocket with elasticity. Then, the invention of claim 11 is that the sprocket of claim 10 is
A rigid tooth portion formed on the outer periphery of the sprocket for fitting with a chain; a rigid shaft portion for fixedly supporting a drive shaft for transmitting the pedal depression force to the sprocket; the tooth portion and the shaft portion And a stress deforming portion having elasticity formed between the stress deforming portion, and detecting a torque based on the pedal depression force or a physical amount related to the torque based on a displacement amount of a sprocket surface of the stress deforming portion. Features.

According to the eleventh aspect of the present invention, when torque from the drive shaft is transmitted to the shaft portion, the entire sprocket tends to rotate by this torque. At this time, the applied torque is transmitted to the tooth portion via the stress deforming portion. When the chain is fitted to the tooth portion, the tensile force of the chain acts as a load opposing the torque. Therefore, since the stress deforming portion formed between the shaft portion and the tooth portion has elasticity, the stress deforming portion is elastically deformed by the opposing stress, and the sprocket surface is greatly displaced accordingly. Therefore, detection accuracy can be improved. At this time, since the shaft and the teeth have rigidity, the torque applied to the sprocket via the shaft is reliably transmitted to the chain.

In order to further increase the detection accuracy by further increasing the amount of displacement due to stress, the invention according to claim 12 is characterized in that the sprocket surface of the stress deforming portion is mainly subjected to the stress deformation due to the action of the pedal depression force in the axial direction of the sprocket. Characterized by being formed into a specific shape that appears as a displacement amount.

[0027] For example, as in the thirteenth aspect of the present invention, the plurality of raised portions formed so that the specific shape of the stress deforming portion of the twelfth shape is raised with respect to a surrounding sprocket surface, and the sprocket. A plurality of holes penetrating through;
Are alternately formed along the circumferential direction, and the raised portion is recessed on the sprocket surface opposite to the raised side, and has surface portions on both sides facing the adjacent hole. Preferably not.

According to the thirteenth aspect of the present invention, when the raised portion is pulled from both sides of the skirt portion by the opposing stress generated in the stress deforming portion, the height of the raised portion is reduced. The displacement can be detected very efficiently. Further, since the holes are formed in the adjacent portions, the degree of freedom of the raised portions is increased, the elasticity is greatly improved, and the amount of stress deformation is increased. Also, the presence of the hole facilitates the formation of the raised portion. Further, in the present invention, since the surface portion is not provided in the direction in which the stress is less likely to be received, and the opposite side of the ridge is concave, the reduction of the ridge due to the opposing stress appears more remarkably.

Incidentally, the stress generated in the stress deforming portion is as follows.
Since the torque transmitted from the shaft portion and the tensile force of the chain are opposed to each other, the direction oblique to the radial direction is the maximum stress direction. That is, the stress distribution has a spiral shape.
Therefore, the direction in which the bulge is stretched by the stress is preferably along the maximum stress direction in order to increase the displacement.

Therefore, the invention of claim 14 is based on claim 13
Extends so as to obliquely intersect the radial direction of the sprocket in the plane of the sprocket, and the shape of the raised portion and the hole as viewed from the axial direction of the sprocket is the same as that of the sprocket. It is characterized in that it is formed in a shape that swirls in the direction of rotation.

According to the fourteenth aspect, the plurality of raised portions are
Since it extends in a spiral shape along the direction in which it is stretched by stress, stress deformation due to the action of torque can be efficiently extracted as the amount of displacement of the sprocket surface,
The detection accuracy can be improved.

According to a fifteenth aspect of the present invention, in any one of the eleventh to fourteenth aspects, the tooth portion, the stress deforming portion, and the shaft portion are separately formed. It is formed as a part, and the sprocket is characterized by connecting these components.

According to the fifteenth aspect of the present invention, since each of the sprockets is formed of a separate component, it is extremely easy to form the stress deforming portion so as to have elasticity. In other words, it can be easily formed so as to increase the elasticity of the stress deformation portion. For example, the stress-deformed portion is made of a material having a large elastic modulus, or is formed of the same metal material having a small plate thickness in order to reduce rigidity as compared with the tooth portion and the shaft portion. Alternatively, it may be formed into a shape having a large elastic modulus.

Preferably, as in the invention of claim 16,
The invention according to claim 15, wherein the shaft portion is formed in a disk, is rotatable while being fitted in a central hole of the tooth portion, and has a certain range within the shaft portion and the tooth portion. Locking means for locking the rotation beyond the above angle may be provided respectively.

According to the sixteenth aspect, when torque is transmitted from the drive shaft to the shaft portion, the shaft portion is rotated to the rotation angle corresponding to the magnitude of the torque while being fitted in the central hole of the tooth portion. I do. When a limit torque exceeding a certain level acts, the locking means locks the rotation of the shaft. With this lock,
It is possible to prevent the stress deformation portion from being deformed beyond its elastic limit.

As described above, it is preferable that the sprocket is composed of a plurality of constituent parts. However, when only the stress deforming portion can be formed to have elasticity, the sprocket can be formed as described in claim 17 through claim 21. In the invention according to any one of the fourteenth aspects, it is a matter of course that the sprocket may be formed by integral molding.

By the way, when detecting the axial displacement of the stress-deformed portion, the axial position of the raised portion which has been turned to a specific detection position by rotation is sequentially detected, and the detected axial position is determined from the detected axial position. It is preferable to determine the axial displacement of the ridge. At this time, since the plurality of ridges are discretely arranged and only a hole exists between each adjacent ridge, a certain ridge separates from the above-mentioned detection position by rotation, and the next ridge becomes this detection position. A certain period of time elapses before reaching. For this reason, it is impossible to detect the axial displacement during this fixed time, and it is difficult to perform continuous and smooth detection.

Therefore, the invention of claim 18 is based on claim 13
In the invention according to any one of claims 17 to 17,
The apparatus further comprises a detection member having a substantially flat detection surface and capable of being elastically displaced in the axial direction, wherein the detection member is arranged in contact with the plurality of raised portions.

According to the eighteenth aspect of the present invention, since the detected member having the substantially flat detection surface is disposed in contact with the plurality of raised portions, the detection surface also extends to the gap between the adjacent raised portions.
Moreover, since the detected member can be elastically displaced in the axial direction, its detection surface is displaced in the axial direction in accordance with the axial displacement of each raised portion, and even on the detection surface between the adjacent raised portions, A highly reliable axial position can be indicated. As a result, the discrete displacement of each raised portion is converted into a continuous amount on the detection surface, and highly accurate detection can be performed very easily.

According to a nineteenth aspect, in the eighteenth aspect, the detection sensor for detecting a distance from the fixed position to a specific position on the detection surface where the amount of axial displacement due to the stress deformation of the sprocket is maximum is provided. It is characterized by being attached.

Here, the fixed position means a position outside the sprocket and stationary with respect to the sprocket. For example, when this torque detection device is applied to an electrically assisted bicycle, it is a position attached to a vehicle body frame.

According to the nineteenth aspect, the detection sensor is
The distance from the fixed position to the detection surface that is displaced in the axial direction in accordance with the displacement of each raised portion due to the stress deformation due to the torque action is detected. The detected distance can be converted into an axial displacement that reflects the magnitude of the applied torque by calculating the difference from the distance when no torque is applied. Furthermore, in the invention of claim 19, the detection sensor can detect the distance to the specific position where the amount of displacement in the axial direction is maximum, so that the detection accuracy can be improved. Here, this specific position is where the teeth of the sprocket have turned to the tight side of the chain (the maximum stress deformation position M described later).

[0043]

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 body frame 3, and the sprocket 2 rotates integrally with the sprocket 2 on both left and right sides via a drive shaft 4 coaxial with the sprocket. The crank rods 6L and 6R are respectively attached, and pedals 8L and 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 12 between sprocket 2
Is stretched.

Although not shown, the chain 12 has a pin link formed by press-fitting two pins into two cocoon-shaped link plates and two bushings press-fitted into two ring plates. Roller links around which rollers are rotatably fitted are alternately combined. The pitch and the diameter of each roller constituting the pin link and the roller link of the chain 12 are determined so as to fit with each tooth of the sprocket 2.

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.

A sprocket driving gear 11 is fitted to the sprocket 2, and the sprocket driving gear 11 is connected to driving means 13 described later.
FIG. 4 shows a top view and a side view of the sprocket drive gear 11. As shown in FIG.
1, two roller plates 17a opposed in parallel,
17b and a plurality (six in the example in the figure) of cylinders press-fitted substantially perpendicularly to the plates at the same pitch as the rollers of the chain 12 along the peripheral region of the plates so as to connect the plates. Bushings (roller shafts) 15, a plurality of (six in the example in the figure) cylindrical rollers 21 rotatably fitted over the outer periphery of these bushings,
It has. The roller plates 17a and 17b have a mounting hole 19 formed at the center thereof for mounting to the driving means 13, and a concave portion 33 recessed inward at an outer peripheral portion between the adjacent rollers 21.

FIG. 5 (a) is a front view showing 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 one tooth 24 of the sprocket 2 enters the gap between these rollers. Here, a cross-sectional view taken along the line SS ′ is shown in FIG. As is apparent from the figure, in the fitted state, the teeth 24 of the sprocket 2 are sandwiched between the plates 17a and 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. For example, a constricted portion at the center of the chain-shaped link plate of the chain 12 is used. Preferably, it is formed in substantially the same shape.

When the sprocket drive gear 11 rotates in the direction K in the drawing around the drive center axis 9 in the fitted state as shown in FIGS. 5 (a) and 5 (b), 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, since the electric torque from the electric motor 37 is transmitted to the highly rigid teeth 23 of the sprocket 2 via the sprocket drive gear 11, the sprocket 2
The pedaling force can be assisted without bending the shaft and without shifting the rotation center.

FIG. 2 shows a schematic configuration of a torque detecting device applied to the electric assist bicycle 1 according to the first embodiment, and electric assist means including the sprocket drive gear 11 described above. The figure is shown as an upper view of a horizontal section taken through the center axis 5 of the drive shaft 4, and for simplification, only the left crank rod 6L and the pedal 8L are shown. I have.

First, the torque detecting device according to the present embodiment will be described with reference to FIG. As shown in the figure, the torque detecting device is configured to detect an axial displacement (a direction parallel to the axis 5) due to stress deformation of the sprocket 2 itself. One surface side of sprocket 2 (left side in the figure) for easy detection
And a detection sensor 34 used to detect the axial displacement amount.

The sprocket 2 is integrally formed from a predetermined metal material, and has a center hole 30 through which the drive shaft 4 passes as shown in FIG. 3 (top view and conceptual side view). Center portion 29, a plurality of raised portions 27 and a plurality of holes 28 are alternately formed along the circumferential direction in a stress deforming portion 26, and a plurality of teeth 24 formed on the outermost peripheral portion of the sprocket 2, And the above-described tooth portion 23 including the concave portion 25 formed between adjacent teeth.

FIG. 8A is a side view of the raised portion 27 of the stress deforming portion 26 when viewed along the line BB '(top view in FIG. 3). As shown in the figure, the protruding portion 27 protrudes on one surface side of the sprocket 2 and is recessed on the other surface side in order to convert deformation due to stress into an axial displacement. In the illustrated example, the sprocket 2 has an inclined portion 27a inclined with respect to the flat surface, and a flat top 27b. Further, it can be seen that the protruding portion 27 has no surface portion on the side surface facing the adjacent hole portion 28.

FIG. 8B is a front view of the raised portion 27 as viewed from the line AA ′. As shown in the figure, it can be seen that the inclined portion 27a is an inclined flat surface portion.

Note that, as shown in FIG.
7 'may be configured in a completely convex or semi-circular shape without the top 27b. The line A-
The appearance viewed from A ′ is similar to that of FIG.

The raised portion 27 formed as described above is similar to that shown in FIG.
As shown in FIG. 7, the stresses F and −F generated from the antagonism between the chain pulling force and the stepping torque cause the stresses F and −F to be applied from both sides (that is, from the teeth 23 and the center 29: see FIG. 7).
When pulled, the inclination of the inclined portion 27a becomes gentle and the height of the top decreases. The amount of decrease in the height is the amount of axial displacement ΔL, which reflects the stepping torque that is the source of the chain pulling force.

The hole 28 is formed through the thickness of the sprocket 2 so as to reduce the rigidity of the stress deformation portion 26 and increase the amount of stress deformation of the raised portion 27.
The central portion 29 and the tooth portion 26 are formed so as to have a sufficient rigidity. It is preferable to form the thinner than 29 or the like.

Further, the stress deformation section 26 converts the deformation due to the stress into an axial displacement more efficiently, as shown in FIG.
As shown in (top view), the protruding portion 27 and the hole portion 28 are each formed to have a spiral shape in the forward rotation direction R for running the bicycle 1 forward. Thereby, the raised portion 27 is simply moved in the radial direction (the direction extending radially from the center of the circle).
As compared with the case where the protrusions are formed radially, the direction of the pulling force from both sides of the protrusion 27 is closer to the direction of the maximum stress, and the protrusion can be deformed more greatly.

In the top view of FIG. 3, if the center O of the sprocket 2 is the origin, the traveling direction of the bicycle 1 is the positive direction of the X axis, and the direction perpendicular to the X axis is the positive direction of the Y axis. The sprocket 2 can be conveniently divided into four sections, i.e., quadrants I, II, III, and IV, according to the X and Y axes. At this time, the chain 12
In the section where is wound, the first quadrant on the tight side of the chain 12 receives the largest tensile force, and the amount of stress deformation generated thereby becomes the maximum. It is also said that, in the quadrant I, the point where the maximum stress deformation is caused (the maximum stress deformation position M) is a point advanced by about two or three teeth in the R direction from the intersection with the positive direction of the Y axis. However, the maximum stress deformation position M varies depending on various conditions.

The position detecting disk 32 is shown in FIG.
As shown in the figure, a central hole 40 formed in the center portion, a plurality of non-stretchable flat portions 38 formed over the entire outer peripheral portion of the central hole 40, and a portion between adjacent flat portions 38 And a plurality of elastic folds 39 formed respectively.

As shown in FIG. 6B, the elastic folds 39 can be formed, for example, by bending a sheet metal at least in a triangular shape to form a groove. Therefore, the expansion and contraction folds 39 have elasticity and can expand and contract in the P and Q directions. Thus, each flat portion 38 is not only able to move up and down with respect to the adjacent flat portion in the U direction, but is also returned to the original position by the elasticity of the elastic fold portion 39.

As shown in FIG. 2, each flat portion 38 of the position detecting disk 32 is
Are fixedly supported by the drive shaft 4 in a state of contact with the sprocket 2 and rotate together with the sprocket 2. Each ridge 27
As the plate moves up and down in the axial direction due to the stress deformation, each flat portion 38 of the position detecting disk 32 also moves up and down while being in contact with the raised portion. By contacting the position detecting disk 32 with the sprocket 2, it is possible to detect the amount of displacement of each of the discretely arranged flat portions 38 as a continuous amount of displacement.

The detection sensor 34 arranged toward the position detection disk 32 is provided with a sprocket 2
Is fixed to the body frame 3 so as to detect a distance to a detection point on the position detection disk 32 at which the axial displacement amount becomes relatively large. This detection sensor 34
Detects an axial distance from the fixed position attached to the vehicle body frame 3 (FIG. 1) to the position detecting disc 32, and outputs a detection signal indicating the distance. Preferably, the detection sensor 34 is attached so that the axial distance L1 to the maximum stress deformation point M in FIG. 3 can be detected.

The detection sensor 34 is, for example,
A detection body made of a magnetic material such as ferrite attached so as to move in the axial direction according to an axial displacement of the position detection disk 32, and a coil arranged near the detection body;
And a detection circuit capable of detecting a change in inductance of the coil by converting the change into an electric signal. In the case of this configuration, although the detection object approaches or moves away from the coil according to the axial displacement amount of the sprocket 2,
Since the inductance of the coil changes depending on the distance between the detection object and the coil, the axial distance L1 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 L1 can be detected.

The output terminal of the detection sensor 34 is connected to the controller 14 for receiving a detection signal from the sensor. The controller 14 can be realized by a so-called microcomputer or the like, and has a calculation function for calculating the value of the torque applied to the sprocket 2 based on the received detection signal.

Next, the electric assist means of this embodiment will be described. This electric assist means, as shown in FIG.
The above-described sprocket drive gear 11 fitted to the sprocket 2 and the electric motor 3 which is driven to rotate by a battery (not shown) and transmits the electric torque via a rotating shaft 37a.
7, the rotation speed of the electric motor 37 around the rotation shaft 37a is reduced, and the sprocket driving gear 1 is reduced via the gear shaft 35a.
1 and the controller 14 described above.
And is comprised. The driving means 13 described above is used.
Comprises an electric motor 37 and a speed reduction mechanism 35.

The speed reduction mechanism 35 includes, for example, a combination of a plurality of gears, and transmits power in only one direction along the transmission path of the electric torque formed by the gears. A so-called one-way clutch (not shown) is provided. 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.

Further, the controller 14 determines whether or not the electric assist is necessary based on the detection signal from the detection sensor 34.
And outputs a motor control signal for controlling the rotation of the motor.

Next, the operation of the first embodiment of the present invention will be described. When the rider steps on the pedals 8R and 8L and runs the bicycle 1 forward, the sprocket 2 rotates in the R direction. At this time, the sprocket 2 transmits the driving force to the chain 12 fitted thereto, and at the same time, at each point of the sprocket due to the tensile force from the chain 12, which is the load.
Stress is distributed according to the antagonism of these forces. Due to this stress, the sprocket 2 undergoes the greatest stress deformation at the stress deformation portion 26 thereof. This stress acts most strongly in the section of the stress deforming portion 26 while passing through the quadrant I of FIG. 3 on the tight side of the chain 12, and as shown in FIG. Are applied so as to pull. In accordance with the magnitude of the stress F, the height of the raised portion 27 in the axial direction decreases as compared with the case where no stress is applied. This decrease increases as the pedal depression torque increases and the stress F increases.

With the rotation of the sprocket 2, each raised portion 2
7 moves up and down in the axial direction by the action of stress generated according to its rotational position and stepping torque, respectively.
Each flat portion 38 of the elastic position detecting disk 32 in contact with this also moves up and down completely following the fluctuation of each raised portion 27.

The detection sensor 34 constantly determines the distance from the mounting position fixed to the vehicle body frame 3 to the sprocket portion passing through a specific detection position (for example, the maximum stress deformation position M) in the quadrant I. Measurement is performed, and the measurement result is output to the controller 14 as a detection signal.
Since the detection sensor 34 detects the distance to the detection position via the position detection disk 32, the detection signal is a signal that fluctuates continuously.
4 makes it possible to very easily perform the torque calculation and the assist determination based on the torque.

When the controller 14 receives the detection signal,
The axial distance L0 when no stress is applied, which is stored in advance in memory, and the axial distance L1 indicated by this detection signal.
And the axial displacement ΔL of the sprocket 2 as the difference between
(L0-L1; FIG. 7), and the torque T applied to the sprocket 2 is calculated from the axial displacement ΔL according to a predetermined conversion.

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

In the simplest electric assist control, for example, when the calculated torque T becomes equal to or more than a predetermined value, the electric motor 37 is turned on, and an electric torque such as to maintain a predetermined ratio with respect to the stepping torque is instructed. A motor control signal for turning off the electric motor is output otherwise. In this case, the electric motor 37 may be turned on only when the axial distance L1 detected by the detection sensor 34 exceeds a certain value.

When the electric motor 37 is turned on and rotated, this 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, in the first embodiment of the present invention,
The electric torque from the electric motor 37 is transmitted through the sprocket drive gear 11 to the teeth 2 of the sprocket 2 having a large diameter.
3 is directly transmitted to the drive shaft 3, so that there is an advantage that a large reduction ratio can be obtained as compared with the structure in which the electric torque is added from the drive shaft 4 as in the above-described conventional technology. This makes it possible to reduce the size and weight and simplify the resultant force mechanism. Further, the sprocket driving gear 11 and the driving means 1
Since the electric assist means can be configured only by providing the third and third components, 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 transmitted to the tooth portion 23 which is the outer peripheral portion of the sprocket, the torque measured by the tooth portion 23 and the torque detecting device of this embodiment reflects only the stepping torque, and And the stepping torque can be clearly separated, and the stepping torque can be accurately calculated.

Further, in this embodiment, the torque based on the amount of stress deformation of the sprocket itself can be obtained without separately adding an elastic member having a high rigidity and a large volume and weight, a transmission mechanism, and the like to an existing electric assist bicycle. , So that the space and weight of the torque detection mechanism can be reduced and the mechanism greatly simplified, while enjoying the effect that the pedal can be easily depressed even on a steep slope as in the past. Second Embodiment) A torque detecting device for an electrically assisted bicycle according to a second embodiment will be described. This torque detecting device is characterized in that the sprocket is not integrally formed as in the first embodiment, but is constituted by a plurality of parts. The sprocket according to the present embodiment also has the first
The sprocket drive gear 11 is fitted in the same manner as in the embodiment. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted.

FIG. 9 shows components (top view and conceptual side view) of a sprocket to be detected by the torque detecting device according to the second embodiment. As shown in the figure, the sprocket of this embodiment has three sprocket teeth 50A, an elastically deformable portion 50B, and a disk portion 50C.
Consists of two components.

The sprocket tooth portion 50A has an outer peripheral portion 53 in which a plurality of teeth 51 and concave portions 52 are alternately formed over the outermost periphery, a perforation 56 opening at the center portion, and a perforation 56 from the outer peripheral portion 53. , And three protrusions 54 formed at equal angles in the circumferential direction. The sprocket teeth 50A are connected to the chain 1
2 is integrally molded from a metal material so as to have rigidity so as to ensure the fitting with the metal material.

The elastically deforming portion 50B is integrally formed of an elastic body in order to increase the amount of stress deformation, and has an annular outer peripheral portion 58 and a central hole 64 at the same center as the outer peripheral portion 58, through which the drive shaft 4 passes. A central inner circular portion 62, and a plurality of elongated (six in the figure) connecting portions 61 connecting the outer peripheral portion 58 and the central inner circular portion 62 at predetermined angles. Are formed with raised portions 60, respectively, and holes 65 are formed between adjacent connecting portions 61, respectively. The elastically deformable portion 50B can be made of a material having a large elastic modulus or the same metal material having a smaller thickness than the sprocket teeth 50A.

The connecting portion 61 bridges the outer peripheral portion 58 and the central inner circular portion 62 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 direction of the connecting portion 61, and the axial displacement of the raised portion 60 can be increased. In addition, the raised portion 60 is formed as shown in FIG.
The shape is the same as that of the raised portion 27 'in (c).

The disk portion 50C is integrally formed of a metal material so as to have rigidity.
And a cylindrical portion 70 having a central hole 74 for receiving the drive shaft 4. A plurality of radially concave notches 68 are provided on the outer periphery of the outer peripheral disk portion 66 at equal angles ( In the figure, three teeth are formed, and internal teeth 72 for fitting and fixing to the drive shaft 4 are formed on the inner wall of the center hole 74 of the cylindrical portion 70.

The disc 50C is inserted into the hole 56 of the sprocket tooth 50A so that the disc 50C can be fitted.
Has an outer diameter substantially equal to the inner diameter of the perforation 56 of the sprocket tooth portion 50A, and the cutout portion 68 has a length in the radial direction substantially equal to that of the projection portion 54 and a length in the circumferential direction. Formed longer. For this reason, the disk part 50C is
When fitted to the sprocket teeth 50A, the disk 50C can be rotated within a range in which the protrusion 54 engages from one inner wall of the notch 68 to the other.

FIG. 10A shows a sprocket 77 completed by combining the components shown in FIG. As shown in the figure, each projection 54 is formed on the inner wall 68 of each notch 68 on the forward side with respect to the rotation direction R ′ of the sprocket 77.
The disc portion 50C is fitted into the sprocket tooth portion 50A in a state in which the disc portion 50a is in contact with each other. Further, the cylindrical portion 70 of the disk portion 50C is further inserted into the central hole 64 of the elastic deformation portion 50B.
Is inserted, the elastically deforming portion 50B connects the sprocket teeth 50A and the disc 50C to each other. These components can be connected, such as by welding or rippling, as is well known to those skilled in the art.

As shown in FIG. 10 (a) (side view), a disc 80 is in contact with the sprocket 77 so as to abut against each raised portion 60 of the elastically deformable portion 50B. Is in contact with a wavy washer 84. Further, the wavy washer 84 is pressed from the other end by a spring holding plate 90 fixed to the drive shaft 4 (FIG. 2).

The disk 80 is, as shown in FIG.
It has a rigid outer peripheral disc portion 81 and a central hole 82 formed at the center portion for penetrating the drive shaft 4 and functions as a position detection surface for a detection sensor. Further, the wavy washer 84 has a wavy disk portion 88 that can be elastically expanded and contracted in the axial direction, and a central hole 82 formed at a central portion for penetrating the drive shaft 4. The wavy disk portion 88 is simply formed by bending a sheet metal so that a wavy portion is formed periodically in the circumferential direction, whereby the wavy washer 88 applies a force applied in the axial direction. It is possible to expand and contract elastically according to.

The sprocket 77 shown in FIG.
As shown in (1), it is fitted to the drive shaft 4 instead of the splat 2 of the first embodiment. At this time, FIG.
As shown in (a), the connecting portion 61 extending obliquely to the radial direction is attached so as to be inclined obliquely to the rotation direction R ′ of the sprocket 77. Thereby, since the connecting portion 61 and the hole 65 have a spiral shape in the rotation direction R ′, the amount of stress deformation can be efficiently reflected in the axial direction as in the first embodiment. The holder 33 of the electric assist device is attached to the rigid sprocket tooth 50A by welding or the like.

The disk 80, the wavy washer 84, and the spring pressing plate 90 constitute a flexible position detecting disk as a whole, and the position detecting disk 32 of the first embodiment.
Instead, it is mounted in contact with the sprocket 77. At this time, the detection sensor 34 is attached to the vehicle body frame 3 so that the distance from the fixed position to the disk 80 can be detected. Thus, the discrete axial displacement of each raised portion 60 of the sprocket 77 can be detected as a continuous amount.

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 50C tries to rotate in the R ′ direction as a whole as shown in FIG. At this time,
Since a pulling force from the chain 12 against the stepping torque acts on the sprocket teeth 50A connected to the disc 50C via the elastically deforming portions 50B, the sprocket teeth 50A are relatively positioned with respect to the disc 50C. The protrusion 54 moves in the R ″ direction while moving away from the inner wall 68a of the cutout 68 in the R ″ direction.

Therefore, as shown in FIG. 9, the stress G mainly acts on the connecting portion 61 on the elastically deforming portion 50B which mediates the sprocket tooth portion 50A and the disc portion 50C which are in opposition to each other as described above. Each of the raised portions 60 extends in the direction of the stress G according to the size thereof, and
When the elasticity of B and the stress G are balanced, the extension stops. Along with this elongation, each ridge 60 has a reduced axial height and maintains its height when balanced. Conversely, if the stepping torque becomes small, the elastic deformation portion 5
The raised portion 60 contracts due to the elasticity of 0B, and its height increases.

However, when a stepping torque exceeding a certain level acts, the projection 54 rotating in the R ″ direction is
As shown in the top view of (b), since the notch 68 is locked in contact with the inner wall 68b on the other side, even if a torque larger than that is applied, the elastic deformation portion 50B extends beyond the elastic limit. Is prevented, and deterioration of the elastically deformable portion 50B can be prevented.

Thus, as shown in the side view of FIG. 10B, the raised portion 60 moves up and down within a predetermined range in the axial direction H so as to have a height corresponding to the stepping torque. At the same time, the disk 80 arranged between the raised portion 60 and the wavy washer 84 takes a configuration corresponding to the height of each raised portion 60. Then, similarly to the first embodiment, the detection sensor 3
4 detects the axial distance from the fixed position to the disk 80, the controller 14 calculates the stepping torque based on the detected axial distance, and controls the electric motor 37. The electric torque generated by the electric motor 37 is transmitted to the teeth 50 of the sprocket 77 via the sprocket drive gear 11.
A is transmitted directly to A to assist the pedaling force.

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, similar to the first embodiment, excellent effects such as space saving, light weight, and a simple mechanism can be obtained as compared with the related art in which an elastic body is provided outside the sprocket.

Further, in the sprocket 77, the sprocket teeth 50A and the disk 50C having rigidity and the elastically deforming portion 50B having elasticity are formed as separate parts, so that a part having elasticity is formed by integral molding. In comparison with the case, the formation of the elastically deformable portion is extremely easy. In other words, since the elastically deformable portion 50B having a large elastic modulus can be easily formed, the displacement amount in the axial direction can be set to a larger amplitude, so that the detection accuracy of the stepping torque can be further improved. .

Further, since the disk portion 50C fixed to the drive shaft 4 and the sprocket tooth portion 50A fitted to the chain 12 are connected via the elastically deformable portion 50B, a large force is suddenly applied to the chain 12. Even if it is added, the elastically deformable portion 50A plays a role of a shock absorber. This protects not only the teeth 50A but also, for example, a ratchet gear (not shown) disposed around the drive shaft 4, and extends the life of these gears.

Further, in the second embodiment, since the disk portion 50C can be cut out by cutting the metal material in which only the outer periphery of the sprocket tooth portion 50A is formed, the cost and labor can be reduced in the forming process.

Although the embodiments of the torque detecting device of the present invention have been described above, the present invention is not limited to the above-described example. For example, if only the simplification of the resultant force mechanism is intended, another torque detecting device may be used. In this case, any suitable torque detecting device other than the above embodiment can be used as long as the sprocket driving gear 11 is fitted to the sprocket and the electric torque is directly transmitted.
As a preferable example of another torque detecting device, for example, FIG.
In the sprocket 2 described above, when the stepping torque acts instead of the axial displacement amount of the sprocket, the stress deformation portion 2
The rotational phase difference between the central portion 29 and the tooth portion 23 generated by the extension of the gear 6 may be detected as an amount reflecting the stepping torque. Further, in the case of the sprocket 77 of FIG.
The rotational phase difference between the disk portion 50C and the sprocket tooth portion 50A generated by the extension of B is detected as an amount reflecting the stepping torque. As means for detecting the rotational phase difference, for example, there is a potentiometer.

The sprocket drive gear 11 can take a form other than that shown in FIG. 4 as long as the sprocket can be fitted to the sprocket to transmit electric torque. For example, the number of the rollers 21 and the shape of the concave portion 33 can be arbitrarily and suitably changed.

Further, in the second embodiment, the third embodiment shown in FIG.
Although the sprocket 77 is composed of two components, the present invention is not limited to this. For example, as shown in FIG. 12, a boss portion 91 which penetrates the drive shaft 4 and is fixed thereto, a sprocket gear 92 The sprocket 89 may be formed by connecting the two members by welding or the like with a plurality of spring members 94 having a raised portion 93.

The position detecting disk is also described in the first embodiment (FIGS. 6A and 6B) and the second embodiment (FIG. 11).
Embodiments other than (a) and (b)) are possible. For example, as shown in FIG. 13, a disk 95 is brought into contact with a spring member 94 of a sprocket 89, and a telescopic spring 96 that presses the disk 94 from above the disk 94 is disposed through the drive shaft 4. By pressing the other end of the expansion spring 96 with a spring pressing plate 97 fixed to the drive shaft 4, the disk 95 can be used as a position detecting surface that moves up and down in accordance with the axial displacement of the raised portion 93. it can. These position detecting disks (FIGS. 6, 11, and 12)
Are the sprockets of each embodiment (FIG. 3, FIG. 10 (a),
It can be arbitrarily applied to any of the sprockets in FIG.

In each embodiment, the detection sensor 34
Although an example in which only one is attached has been shown, it is also possible to provide a detection sensor at each of a plurality of locations and calculate the torque based on a plurality of detection signals detected by these detection sensors. Regarding the mounting position of the detection sensor 34, if the axial displacement amount of the sprocket can be detected, it may be mounted on the sprocket instead of the vehicle body frame 3.

Further, in each of the embodiments, the displacement in the axial direction perpendicular to the sprocket surface is detected, but the displacement in the sprocket surface oblique to the axial direction is detected. Can also.

[0104]

As described above in detail, according to the first to seventh aspects of the present invention, the electric torque from the electric motor is directly transmitted to the sprocket having a relatively large diameter via the sprocket driving gear. Therefore, as compared with the structure in which the electric torque is applied from the drive shaft as in the prior art, a large reduction ratio can be obtained, and there is no need to change the frame structure of the vehicle body. Can be achieved,
The effect is obtained.

Further, according to the invention of claims 8 to 19, the torque based on the pedal depression force is detected based on the displacement amount generated on the sprocket itself by the action of the pedal depression force. Since there is no need to add a large elastic body separately from the constituent requirements such as etc., not only can the detection mechanism be configured very simply,
The space and weight occupied by this mechanism can be greatly reduced. Therefore, coupled with the simplification of the resultant force mechanism, there is almost no need to change the frame structure of the bicycle, so that it is possible to realize a light-weight, simplified, and lightly driven electric assist bicycle. can get.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an electric assist bicycle to which a torque detection device according to the present invention is applied.

FIG. 2 is a sectional view showing a schematic configuration of a torque detection device and an electric assist unit according to the first embodiment of the present invention.

FIG. 3 is a top view and a side view of a sprocket of the electric assist bicycle to which the torque detection device according to the first embodiment is applied.

FIG. 4 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.

FIGS. 5A and 5B are diagrams showing a state in which the sprocket of FIG. 4 is fitted to the sprocket of the electric assist bicycle according to the first embodiment, wherein FIG.
FIG. 5B is a cross-sectional view taken along the line SS ′ in FIG.

6A and 6B are schematic diagrams of a position detecting disk which makes contact with the sprocket of FIG. 3 to facilitate measurement of the amount of deformation of the sprocket, and FIG. 6A is a top view of the position detecting disk. FIG. 2B is a perspective view showing the shape of the elastic fold of the position detecting disk.

FIG. 7 is a diagram illustrating how stress deformation causes an axial displacement when a ridge formed on a sprocket receives stress and when it does not.

FIGS. 8A and 8B are schematic external views of a raised portion formed on the sprocket, where FIG. 8A is a side view when the BB ′ line in FIG. 3 is viewed as a line of sight, and FIG. FIG. 9C is a front view of the raised portion when the line −A ′ is viewed as the line of sight, and FIG. 10C is a side view of the raised portion according to another embodiment.

FIG. 9 is a top view and a side view of each component of a sprocket according to a second embodiment of the present invention.

10A and 10B are a top view of the sprocket when the sprocket components according to the second embodiment shown in FIG. 9 are assembled and a side view when the sprocket is attached to a drive shaft. FIG. In the case where no torque is applied, (b) shows the sprocket when the stepping torque is applied to the maximum.

11A and 11B are a top view and a side view of components of a position detection disk according to a second embodiment, wherein FIG. 11A shows a disk functioning as a position detection surface, and FIG. 3 shows a wavy washer for imparting elasticity.

FIG. 12 shows a second example in which the sprocket is composed of a plurality of parts
FIG. 10 is a perspective view of a sprocket according to another embodiment other than the embodiment, in which the elastically deformable portion is configured by a plurality of spring members.

FIG. 13 is a perspective view showing a position detecting disk according to another embodiment other than the first and second embodiments.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric assist bicycle 2 Sprocket 3 Body frame 4 Drive shaft 5 Axis line 11 Sprocket drive gear 12 Chain 13 Drive means 14 Controller 15 Bush (roller shaft) 17a, 17b Roller plate 21 Roller 23 Tooth part 26 Stress deformation part 27 Projection 27a Slope Part 27b Top 28 Hole 29 Central part 32 Position detecting disk 33 Concave part 34 Detection sensor 35 Reduction mechanism 37 Electric motor 37a Motor rotation shaft 38 Flat part 39 Telescopic fold 50A Sprocket tooth 50B Elastic deformation part 50C Disk part 54 Projection part 60 Protrusion part 61 Connection part 64 Notch part 65 Hole part 80 Disk (Position detection surface) 84 Wavy washer 93 Spring member

Claims (19)

[Claims] A sprocket rotating by a pedaling force; an electric motor; a sprocket driving gear connected to a rotating shaft of the electric motor and fitted to a tooth portion of the sprocket; and a torque or a torque based on the pedaling force. An electrically assisted bicycle comprising: torque detection means for detecting a physical quantity related to the torque; and control means for controlling the electric motor based on the torque detected by the torque detection means. 2. The sprocket drive gear according to claim 1, wherein a plurality of rollers are arranged on two opposing parallel plates along the circumference thereof at the same pitch so that the roller shafts intersect substantially perpendicularly with the parallel plates. The electric assist bicycle according to claim 1, wherein each tooth of the sprocket is formed so as to sequentially fit in a gap formed between the rollers. 3. The electric assist bicycle according to claim 2, wherein the two parallel plates have a concave portion formed in an outer peripheral portion between adjacent rollers. 4. The roller according to claim 2, wherein the plurality of rollers are arranged with substantially the same shape, the same size, and the same pitch as the rollers constituting the chain stretched on the sprocket. The electric assist bicycle according to claim 3. 5. The sprocket drive gear is fitted to teeth of the sprocket portion that is not fitted to a chain stretched over the sprocket.
The electric assist bicycle according to any one of claims 1 to 4. 6. The apparatus according to claim 1, wherein a speed reduction mechanism is interposed between the sprocket drive gear and a rotation shaft of the electric motor. Electric assist bicycle. 7. The electric assist according to claim 1, wherein a clutch mechanism is interposed between the sprocket drive gear and a rotation shaft of the electric motor. bicycle. 8. The torque detecting means detects a torque based on the pedaling force or a physical quantity related to the torque, based on a displacement amount generated on the sprocket itself by the action of the pedaling force. The electric assist bicycle according to any one of claims 1 to 7, which performs the operation. 9. The amount of displacement generated on the sprocket itself is for fixing and supporting a tooth portion formed on an outer periphery of the sprocket for fitting with a chain and a drive shaft for transmitting the pedal depression force to the sprocket. Of the shaft,
The electrically assisted bicycle according to claim 8, wherein the rotational phase difference is between: 10. The displacement amount generated in the sprocket itself is a displacement amount when a sprocket surface is displaced due to stress deformation generated in the sprocket itself due to the action of the pedal depression force. , Claim 8
The electric assisted bicycle according to 1. 11. The sprocket has a rigid tooth portion formed on an outer periphery of the sprocket for fitting with a chain, and a rigid shaft portion for fixedly supporting a drive shaft transmitting the pedaling force to the sprocket. And a stress deforming portion having elasticity formed between the tooth portion and the shaft portion. The torque or the torque based on the pedal depression force based on the amount of displacement of the sprocket surface of the stress deforming portion. The electric assist bicycle according to claim 10, wherein a physical quantity related to the bicycle is detected. 12. The sprocket surface of the stress deforming portion,
The electric assist bicycle according to claim 11, wherein the bicycle is formed in a specific shape such that stress deformation due to the action of the pedaling force mainly appears as an axial displacement amount of the sprocket. 13. The specific shape of the stress deforming portion includes a plurality of raised portions formed so as to protrude with respect to a surrounding sprocket surface, and a plurality of holes penetrating the sprocket. Are alternately formed along with each other, wherein the raised portion is concave on a sprocket surface opposite to the raised side, and has no surface portion on both sides facing the adjacent hole. The electric assist bicycle according to claim 12, wherein the bicycle is an electric assist bicycle. 14. The protruding portion extends so as to obliquely intersect the radial direction of the sprocket in the plane of the sprocket, and the protruding portion and the hole have a shape viewed from the axial direction of the sprocket. 14. The electric assist bicycle according to claim 13, wherein the bicycle is formed into a shape that spirals in a rotation direction of the sprocket. 15. The tooth portion, the stress deforming portion, and the shaft portion are formed as separate components, respectively, and the sprocket is formed by connecting these components. The electric assist bicycle according to any one of claims 11 to 14. 16. The shaft portion is formed in a disk, and is rotatable while being fitted in a central hole of the tooth portion, and the shaft portion and the tooth portion have an angle exceeding a certain range. The electric assist bicycle according to claim 15, wherein a locking means for locking the rotation is provided. 17. The electric assist bicycle according to claim 1, wherein the sprocket is formed integrally. 18. The apparatus according to claim 18, further comprising a detected member having a substantially flat detection surface and being elastically displaceable in the axial direction, wherein the detected member is arranged in contact with the plurality of raised portions. The electric assist bicycle according to any one of claims 13 to 17, characterized in that: 19. A detection sensor for detecting a distance from a fixed position to a specific position on a detection surface where the amount of axial displacement due to stress deformation of the sprocket is maximum is attached. The electric assisted bicycle according to 1.