JP2004099019A - Power-assisted bicycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide power assisted bicycle capable of generating assist force corresponding to pedal stepping force, reducing wearing and detecting pedal stepping force by a miniaturized and simple detection means. <P>SOLUTION: An output rotor 12 fixed to a chain driving sprocket 6 is rotatably arranged relatively to a crank shaft 10 in which pedal stepping force is input, and a twist coil spring 17 connected to the crank shaft 10 at one end and connected to the output rotor 12 at the other end is fitted to the outer periphery of the crank shaft 10. A lift member 22 is provided rotatably integral with the crank shaft 10 and movable axially, and a pin 12d fixed to the output rotor 12 is engaged with the cam face 22d of the lift member 22, and the relative rotational difference between the crank shaft 10 and the output rotor 12 is converted into the axial movement of the lift member 22. The axial moving quantity of the lift member 22 according to pedal stepping force is detected by a pedal stepping force detecting sensor 23 to assist pedal stepping force by driving an electric motor 8. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electric assist bicycle, and more particularly to a bicycle that generates an assist force corresponding to a pedaling force.
[0002]
[Prior art]
[Patent Document 1] JP-A-11-248566
[Patent Document 2] JP-A-2001-151184
[Patent Document 3] JP-A-8-156870
[Patent Document 4] JP-A-9-193875
2. Description of the Related Art In recent years, an electric assist bicycle that can run lightly even on a slope by attracting a human pedaling force with an electric motor has attracted attention. The electrically assisted bicycle includes an electric motor that generates an assist force in accordance with a pedal depression force input to a crankshaft, and combines the assist force and the depression force and transmits the resultant to a driving wheel.
[0003]
As a conventional electric assist bicycle, a driving side cam connected to a crankshaft and a driven side cam connected to a chain driving sprocket are used, and the driven side cam is pressed against the driving side cam by a compression spring, and the driven side cam is driven. Patent Documents 1 and 2 propose a technique in which a pedal depression force is detected based on an axial displacement amount of a cam, and an assist force is controlled in accordance with the pedal depression force.
[0004]
However, in this case, there is a problem that it is difficult to control the assist control to an assist force corresponding to the pedal depressing force because the assist control is influenced by an unstable element such as a frictional force between the driving cam and the driven cam. That is, when the pedaling force is increased, the frictional force acting between the drive side cam and the driven side cam is overcome, and a slip is generated between both cams, and the driven side cam is displaced in the axial direction, and the assist force is applied. . However, since the pedaling force when slippage occurs between both cams is not constant, there occurs a phenomenon that the assisting force works when the pedaling force is the same, and the working does not work at some time. Further, in order to transmit a predetermined pedaling force between the drive side cam and the driven side cam, it is necessary to increase the spring pressure or the inclination angle of the cam surface. There is a problem that it becomes severe and shortens the life. Further, there is a problem that the device becomes large due to an increase in the spring pressure.
[0005]
On the other hand, as another type of electric assist bicycle, a torsion coil spring is connected between the input side member and the output side member, and the pedal depression force is transmitted to the output side member via the torsion coil spring, and the input side member and the output side are connected. Patent Literatures 3 and 4 disclose a technique for detecting a pedaling force based on a relative rotation difference with respect to a member. In this case, since the torsion coil spring is twisted in proportion to the pedal depression force, it is easy to control the assist force to match the pedal depression force, and there is little problem of wear.
[0006]
[Problems to be solved by the invention]
However, this method has a problem that the treading force detecting device is complicated and large, and is difficult to be mounted on a bicycle that requires small size and light weight.
For example, in the case of Patent Document 3, a light-transmitting hole having a predetermined phase difference is provided between an input-side member and an output-side member, and a light-emitting element and a light-receiving element are provided on both sides of the input-side member and the output-side member. When the pedaling force exceeds a predetermined value, light from the light emitting element reaches the light receiving element via the light transmitting hole and drives the electric motor. However, since the input-side member and the output-side member are rotating, the light passing through the light-transmitting hole becomes blinking light, which is likely to cause malfunction, and the input-side member and the output-side member have a predetermined diameter. Since it is necessary to be configured with a disk having the same, there is a disadvantage that the treading force detecting device becomes large.
[0007]
On the other hand, in the case of Patent Document 4, a differential gear mechanism is used to detect a rotation difference between the input side member and the output side member. Since the rotation angle of the shaft is detected by a sensor such as a potentiometer, there is a disadvantage that the detection circuit becomes complicated. In an ordinary electrically assisted bicycle, it is not necessary to continuously detect the pedaling force, and it is sufficient to detect at least two levels, that is, at least a certain value or less, or more than two levels. Continuous rotation angle detection devices, such as potentiometers, result in over-installation and increased costs.
[0008]
Accordingly, it is an object of the present invention to provide an electric assist bicycle that can generate an assisting force corresponding to the pedaling force, reduce wear, and detect the pedaling force with a small and simple detecting means.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides an electric assist that includes an electric motor that generates an assisting force in accordance with a pedaling force input to a crankshaft, and that combines the assisting force and the pedaling force and transmits the combined force to driving wheels. In a bicycle, an output rotator that is disposed so as to be rotatable relative to the crankshaft and fixed to a chain drive sprocket, is inserted through the outer periphery of the crankshaft, one end is connected to the crankshaft, and the other end is output. A torsion coil spring connected to the rotating body, and a cam surface provided so as to be integrally rotatable with respect to one of the crankshaft and the output rotating body and movable in the axial direction, and having a predetermined inclination angle with respect to the axial direction. Is formed, and is fixed to the other of the crankshaft and the output rotating body, and comes into contact with a cam surface of the lifting member to determine a relative rotation difference between the crankshaft and the output rotating body. Providing a conversion member for converting the axial movement of the shift member, a pedal pressure detecting means for detecting the pedaling force in response to axial movement of the lifting member, a motor-assisted bicycle characterized by comprising a.
[0010]
The pedal depression force input to the crankshaft is transmitted to the output rotary body by the torsion coil spring, and further transmitted from the chain driving sprocket to the rear wheel (drive wheel) via the chain. When the load on the rear wheel is large, a relative rotation difference occurs between the crankshaft and the output rotating body, and the torsion coil spring is twisted according to the rotation difference. The relative rotation difference between the crankshaft and the output rotating body is converted into the axial displacement of the lift member by the action of the cam surface and the conversion member. The assisting force of the electric motor can be generated by detecting the amount of movement of the lift member in the axial direction by the pedaling force detecting means. The torsion coil spring is twisted in proportion to the pedal depression force, and the lift member moves in the axial direction according to the torsion amount of the torsion coil spring.Therefore, the pedal depression force can be accurately detected based on the axial movement amount of the lift member, and the pedal depression force is It can be controlled to the appropriate assist force.
In the case of the present invention, the pedal effort is transmitted to the crankshaft, the torsion coil spring, the output rotating body, and the sprocket, and no torque is transmitted to the lift member. That is, no pedaling force acts on the lift member for controlling the assist amount. Therefore, wear of the cam surface of the lift member and the conversion member engaged with the cam surface can be ignored.
Further, the lift member moves in the axial direction while rotating, but the treading force detecting means only needs to detect the axial movement of the lift member, so that the output signal is stable and erroneous operation is small. In addition, a complicated detection mechanism such as a gear mechanism is not required, and the apparatus can be made compact.
[0011]
It is preferable that the torsion coil spring be covered with a cylindrical lift member.
That is, since the lift member covers the periphery of the torsion coil spring, the connection between the torsion coil spring and the crankshaft or the output rotating body is disconnected, or even if the torsion coil spring is broken, it is possible to prevent the torsion coil spring from coming apart, It is possible to prevent adverse effects on other parts.
[0012]
According to a third aspect of the present invention, the torsion coil spring may be mounted in a direction in which the number of turns increases as the pedaling force input to the crankshaft increases. It may be mounted in a direction in which the number of windings decreases as the pedaling force increases.
If the torsion coil spring is mounted in a direction in which the number of turns increases as the pedaling force increases, the outer diameter of the torsion coil spring decreases as the pedaling force increases, so that the storage space can be reduced. When the periphery is covered with the lift member as in claim 2, it is possible to prevent the torsion coil spring from interfering with the lift member.
On the other hand, in the case of mounting in a direction in which the number of windings decreases as the pedaling force increases, there is no need to form a hook at the end of the torsion coil spring, and the end face only comes into contact with the output rotating body or the spring receiving member. This is advantageous in that processing is easy and the axial dimension can be reduced.
[0013]
According to a fifth aspect, between the crankshaft and the output rotating body, the output rotating body can be relatively rotated with respect to the crankshaft by a predetermined angle range that is equal to or less than a rotating angle range in which the conversion member can contact the cam surface. It is preferable to provide an angle limiting unit that performs the operation.
The relative rotational difference between the crankshaft and the output rotating body may be limited by a torsion coil spring.However, if the relative rotational difference between the two is too large, the pedal stroke will be longer when the pedal is depressed. It may not be transmitted directly to the chain, which may cause discomfort.
Therefore, by providing an angle limiter that limits the relative rotation difference between the crankshaft and the output rotary body, it is possible to reduce a sense of discomfort. Further, by providing the angle limiting portion, the amount of movement of the lift member in the axial direction is also limited, so that positioning with the treading force detecting means is facilitated.
Further, even if the torsion coil spring is broken, the pedaling force of the crankshaft can be transmitted to the output rotating body via the angle limiting section, so that the bicycle can be used as a normal bicycle.
[0014]
According to a sixth aspect of the present invention, a torsion coil spring may be attached to apply an initial torsion torque in a direction opposite to the pedal depression force to the crankshaft in a state where the pedal depression force is not input to the crankshaft.
For example, the initial torsional torque from the torsion coil spring to the crankshaft may be set to 0 (free state) in a state where the pedal effort is not input to the crankshaft. It may rotate relative to the body, causing a sense of incongruity such as rattling. Therefore, if an initial torsional torque in the opposite direction to the pedaling torque is applied to the crankshaft from the torsion coil spring, the crankshaft and the output rotating body rotate relatively when a small pedaling force less than the initial torsional torque acts. However, the relative rotation is performed only when a further depressing force is applied, so that an uncomfortable feeling can be eliminated.
As a method of applying the initial torsion torque, for example, the initial torsion torque can be easily applied by fixing the spring support supporting one end of the torsion coil spring to the crankshaft in a state of being twisted in the pedal pressing force direction.
[0015]
8. A non-contact type sensor, wherein a treading force detecting means is fixed to a detecting portion provided on an outer peripheral portion of a lift member and a vehicle body stationary member, and detects the detecting portion and outputs a plurality of output signals. It is good to be composed with.
As the treading force detecting means, it is possible to use a contact-type sensor that contacts the lift member and detects its axial movement, but since the lift member rotates together with the crankshaft, it is severely worn and easily breaks down. On the other hand, when a non-contact type sensor is used, wear and failure can be reduced, and stable pedaling force detection can be performed.
[0016]
A reed switch may be used as the non-contact type sensor, and a permanent magnet attached in a ring shape to the outer periphery of the lift member may be used as the detection unit. The number of reed switches is not limited to one, and a plurality of reed switches may be provided in the crankshaft direction so that the assist torque can be controlled in a plurality of stages.
In addition, the non-contact type sensor is not limited to a reed switch, and various non-contact type sensors such as a photo sensor, a magnetic sensitive sensor such as a magnetoresistive element, a Hall element, a coil, a capacitance type proximity sensor, and an inductance type displacement sensor. Sensors can be used.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
-1st Example-
FIG. 1 shows an example of an electric assist bicycle according to the present invention.
The bicycle frame 1 includes a head pipe 1a for supporting the front wheel 2, a seat pipe 1b, a main pipe 1c, a rear stay 1d for supporting the rear wheel 3, and the like. The seat pipe 1b, the main pipe 1c, and the rear stay 1d Are connected by a bottom pipe 1e. A crank shaft 10 shown in FIG. 2 is rotatably supported on the bottom pipe 1 e, and a pedal 5 is attached to the crank shaft 10 via a crank 4. When the pedal 5 is depressed, the chain drive sprocket 6 rotates, and the rear wheel 3 is driven via the chain 7. The rear wheel 3 is equipped with an electric motor 8 for generating an assist force, and behind the seat pipe 1b is equipped with a battery unit 9 containing a power supply, a controller and the like.
[0018]
Next, a transmission mechanism that is a main part of the present invention will be described with reference to FIGS.
As shown in FIG. 2, a wheel base 12, which is an output rotating body, is rotatably supported inside the bottom pipe 1 e via a first bearing 11, and inside the wheel base 12 via a second bearing 13. One end of the crankshaft 10 is rotatably supported. Further, the other end of the crankshaft 10 is rotatably supported inside the bottom pipe 1e via a third bearing 14. Left and right cranks 4 are non-rotatably fitted to both axial ends (left and right ends) of the crankshaft 10 and fastened with bolts 15. The wheel base 12 also serves as an outer ring of the second bearing 13, and the chain drive sprocket 6 is fixed to one end in the axial direction by welding or the like.
[0019]
As shown in FIG. 5, an angle limiter 16 is provided between the crankshaft 10 and the wheelbase 12 so as to allow the wheelbase 12 to rotate relative to the crankshaft 10 by a predetermined angle. In this embodiment, the angle limiting portion 16 is composed of a key portion 10a protruding from the outer peripheral surface of the crankshaft 10 and a fan-shaped groove 12a formed on the inner peripheral surface of the wheel base 12. The rotation angle is limited to °. The maximum rotation angle of the angle limiter 16 is not limited to 45 °, but may be set to an angle smaller than 45 °. When the vehicle is not running, the key portion 10a is in contact with one end surface of the groove 12a as shown by the solid line position in FIG. 5, and when a pedal pressing force exceeding a predetermined value acts, the key portion 10a is Abuts the other end face of
[0020]
A torsion coil spring 17 is inserted into the outer periphery of the crankshaft 10, and one end 17 a of the torsion coil spring 17 has an edge of a cylindrical boss 12 b which is the other end in the axial direction of the wheel base 12 as shown in FIG. It is locked in a locking groove 12c formed in the portion. On the outer peripheral surface of the boss portion 12b of the wheel base 12, a knock pin 12d as a conversion member that is engaged with a cam surface 22d of the lift member 22, which will be described later, protrudes. The other end 17b of the torsion coil spring 17 is inserted into the crankshaft 10 and is locked in a locking groove 19a of a spring holder 19 fixed by a set bolt 18. The torsion coil spring 17 is attached in a direction in which the number of turns increases as the pedaling force input to the crankshaft 10 increases. The fixed position of the spring holder 19 is set such that the torsion coil spring 17 applies an initial torsion torque to the crankshaft 10 in a direction opposite to the pedal depression force even when the pedal depression force is zero.
[0021]
FIG. 6 shows the relationship between the relative rotation angle between the crankshaft 10 and the wheel base 12 and the spring reaction force of the torsion coil spring 17, and the torsion corresponding to the initial torsion torque even when the relative rotation angle is 0 °. The spring reaction force of the coil spring 17 acts. Therefore, when a small pedaling force equal to or less than the initial torsional torque is applied, the wheel base 12 rotates integrally with the crankshaft 10, and the sense of discomfort can be eliminated.
[0022]
A guide plate 20 having a projection 20a on the outer peripheral portion is arranged behind the spring receiving member 19, and a nut 21 is screwed onto the male screw portion 10b of the crankshaft 10 from behind the guide plate 20, so that the guide plate 20 becomes a spring receiving member. It is fixed to the crankshaft 10 by 19 and a nut 21. In this embodiment, the projection 20a is formed by the guide plate 20, but it may be formed by fixing a pin directly to the crankshaft 10 instead of the guide plate.
[0023]
The outer periphery of the torsion coil spring 17 is covered by a cylindrical lift member 22. As shown in FIGS. 2 and 3, a large-diameter portion 22a is provided at one axial end of the lift member 22, a small-diameter portion 22b is provided at the other end, and a step 22c is formed therebetween. The large-diameter portion 22a forms a first reflecting portion that reflects light well, and the small-diameter portion 22b forms a second reflecting portion that does not reflect light or has little reflection. As the second reflection portion 22b, for example, a paint such as black may be applied, or a process for scattering light may be performed. The second reflecting portion 22b reflects light, but may have a reflecting direction different from that of the light receiving element 23b of the photo sensor 23 described later. A cam surface 22d having a predetermined inclination angle with respect to the axial direction is formed on the large diameter portion 22a of the lift member 22, and a knock pin 12d protruding from the outer peripheral surface of the wheel base 12 is formed on the cam surface 22d. Are engaged. The cam surface 22d in this embodiment is an inclined cam groove opened at one axial end, but may be an inclined elongated hole. The small diameter portion 22b of the lift member 22 is formed with a guide hole 22e which is axially engaged with the guide projection 20a of the guide plate 20. Therefore, the lift member 22 can rotate integrally with the crankshaft 10 and can move in the axial direction. One end of the lift member 22 is fitted to the boss portion 12b of the wheel base 12, the central portion covers the torsion coil spring 17, and the other end covers the outer peripheral portions of the spring receiver 19, the guide plate 20, and the nut 21. . That is, since the lift member 22 always covers the torsion coil spring 17, both ends 17a and 17b of the torsion coil spring 17 are prevented from coming off the locking grooves 12c and 19a, and even if the torsion coil spring 17 is broken. , Can be prevented from falling apart. Further, since the inner surfaces of both ends of the lift member 22 are slidably supported by the boss portion 12b of the wheel base 12 and the spring receiving member 19, there is little backlash in the radial direction, and a malfunction of the photo sensor 23 described later. Can be prevented.
[0024]
A plurality of reflective photosensors 23 are attached to the bottom pipe 1e such that the sensing surface faces the lift member 22. Each photo sensor 23 includes a light emitting element 23a and a light receiving element 23b as shown in FIG. 4, and a plurality (two in this case) is arranged in the axial direction of the crankshaft 10. While all the photosensors 23 face the small-diameter portion (second reflecting portion) 22b of the lift member 22, the light of the light emitting element 23a does not reach the light receiving element 23b, so that all the photosensors 23 are turned off. I have. When the pedaling force increases and a relative rotation difference occurs between the crankshaft 10 and the wheel base 12, the lift member 22 moves in the axial direction, and one of the photo sensors 23 or all the photo sensors 23 The photosensor 23 facing the large-diameter portion (first reflection portion) 22a is turned ON. The photo sensor 23 is connected to the controller housed in the battery unit 9 described above, controls the driving force of the electric motor 8 based on the detection signal of the photo sensor 23, and controls the assist force. Since this control is already known, the description is omitted.
[0025]
FIG. 7 shows an example of the relationship between the relative rotation angle between the crankshaft 10 and the wheel base 12 and the assisting force of the electric motor 8.
Relative rotation angle is 0 to θ ₁ , The assist force is 0 and θ ₁ ~ Θ ₂ , Θ ₂ The setting is such that the assist force increases stepwise as the angle becomes 45 °. Note that the three-stage switching as shown in FIG. 7 is merely an example, and when a single photosensor 23 is used, only two-stage switching of assist OFF and ON is performed, and three or more photosensors 23 are used. Switching of four or more stages is possible.
In the case where the assist force is set to increase stepwise with the increase of the relative rotation angle as shown in FIG. 7, in view of the correlation with the spring characteristic shown in FIG. Therefore, it is possible to realize a comfortable running.
[0026]
Next, the operation of the electric assist bicycle having the above configuration will be described with reference to FIG.
When the pedaling force is small, the torsion coil spring 17 is hardly twisted, so the relative rotation difference between the crankshaft 10 and the wheel base 12 is small, and the knock pin 12d is located near the bottom of the cam surface 22d. The axial movement amount of the member 22 is also small. Therefore, as shown in FIG. 8A, all the photosensors 23 face the small-diameter portion (second reflecting portion) 22b of the lift member 22, and all the photosensors 23 are turned off. In this range, 0 to θ in FIG. ₁ As shown by, the assist force is zero. That is, the vehicle runs only with human power.
When the pedaling force increases, the torsion coil spring 17 is twisted, and a relative rotation difference occurs between the crankshaft 10 and the wheel base 12. The lift member 22 rotates integrally with the crankshaft 10 by the engagement between the guide hole 22e and the guide protrusion 20a, and the knock pin 12d rotates integrally with the wheel base 12, so that the knock pin 12d rides on the cam surface 22d of the lift member 22 and lifts. The member 22 is moved to the left as shown in FIG. The movement of the lift member 22 causes the right photosensor 23 to face the large-diameter portion (first reflection portion) 22a of the lift member 22, and the photosensor 23 facing the photosensor 23 to turn ON. Therefore, in FIG. ₁ ~ Θ ₂ As shown by, a relatively small assist force is generated, and the burden on human power is reduced.
When the pedal effort further increases, the torsion coil spring 17 is further twisted, and the key portion 10a of the crankshaft 10 comes into contact with the end face of the fan-shaped groove 12a of the wheel base 12, thereby limiting the rotation angle. This angle is, for example, about 45 °. The knock pin 12d further rides on the cam surface 22d of the lift member 22 due to the relative rotation difference between the crankshaft 10 and the wheel base 12, and moves the lift member 22 to the left as much as shown in FIG. 8C. . By the movement of the lift member 22, both the left and right photo sensors 23 face the large-diameter portion (first reflection portion) 22a of the lift member 22, and both photo sensors 23 are turned on. Therefore, in FIG. ₂ As shown by ４５45 °, a large assist force is generated, and the burden on human power can be reduced.
Even if the pedal effort is further increased, the relative rotation difference between the crankshaft 10 and the wheel base 12 is limited to about 45 ° by the angle limiting unit 16, so that the axial movement of the lift member 22 is also limited, and the knock pin 12d does not come off the cam surface 22d. Also, the assist force does not increase any more.
[0027]
-2nd Example-
FIG. 9 shows a second embodiment of the present invention, in which a magnetoresistive element 24 is used as a pedaling force detecting means. Also in this embodiment, two magnetoresistive elements 24 are arranged in the crankshaft direction.
On the other hand, the lift member 22 is formed of a magnetic material, and has a large-diameter portion 22a at one axial end and a small-diameter portion 22b at the other end. In this embodiment, the cam surface 22d of the lift member 22 is formed by a long hole.
The principle by which the magnetoresistive element 24 detects the axial movement of the lift member 22 is the same as in FIG. That is, when the magnetoresistive element 24 facing the small-diameter portion 22b faces the large-diameter portion 22a as the lift member 22 moves in the axial direction, the magnetic resistance decreases and the output signal changes. Using the change in the output signal, the axial displacement of the lift member 22 can be detected.
[0028]
-Third embodiment-
10 to 13 show a third embodiment of the present invention.
This embodiment is an example in which the torsion coil spring 17 is mounted in a direction in which the number of turns decreases as the pedaling force input to the crankshaft 10 increases, and the reed switch 25 and the permanent magnet 26 are used as the pedaling force detecting means. . The same components as those in the first embodiment are denoted by the same reference numerals, and redundant description will be omitted.
[0029]
The torsion coil spring 17 of this embodiment is wound in the opposite direction (left-handed direction) to the torsion coil spring 17 of the first embodiment, and both end portions 17a and 17b are cut substantially vertically. One end 17a is in contact with an end face of a spiral locking groove 12c formed on the edge of the cylindrical boss 12b of the wheel base 12, and the other end 17b is a spiral locking groove 19a of the spring receiving member 19. Is in contact with the end face of By forming the grooves 12c and 19a along the spiral of the coil spring 17 in this manner, both ends of the coil spring 17 are locked, so that there is no need to bend both ends of the coil spring 17 as in the first embodiment. In addition, the processing is facilitated, and the space for disposing the coil spring 17 in the axial direction can be reduced.
[0030]
The spring receiver 19 of this embodiment has a female screw 19b on the inner peripheral surface, and the female screw 19b is screwed with a male screw 10b provided on the crankshaft 10. The external thread 10b of the crankshaft 10 is a left-hand thread, and the spring receiver 19 is screwed counterclockwise. The reason is that the end face of the locking groove 19a is brought into contact with the end 17b of the torsion coil spring 17 while the spring receiver 19 is screwed to the crankshaft 10 because the coil spring 17 is wound left. is there. Even when the pedaling force is zero, the torsion coil spring 17 applies an initial torsional torque to the crankshaft 10 in a direction opposite to the pedaling force, and the spring receiving member 19 holds the hexagon socket head cap screw 27 screwed in its radial direction. Is fixed to the crankshaft 10. The hexagon socket head cap screw 27 is engaged with a guide hole 22 e provided in the lift member 22, and guides the lift member 22 in the axial direction of the crankshaft 10. Note that, instead of the hexagon socket head bolt 27, a fixing pin, a set bolt, or the like may be used.
[0031]
The lift member 22 covers the outer periphery of the torsion coil spring 17, and has an oblong cam surface 22 d having a long hole shape at one axial end thereof, and a guide hole 22 e having an open end at the other end. ing. A hexagon socket head cap screw 28 screwed to the outer peripheral surface of the cylindrical boss portion 12b of the wheel base 12 is engaged with the cam surface 22d, so that the relative position between the crankshaft 10 (lift member 22) and the wheel base 12 is increased. The rotation allows the lift member 22 to move in the axial direction. A knock pin may be used instead of the hexagon socket head cap screw 28. The lift member 22 is formed of a non-magnetic material, and a ring-shaped permanent magnet 26 is fixed to an outer peripheral surface at a central portion thereof. As the permanent magnet 26 of this embodiment, magnets having different polarities on the inner and outer peripheral sides are used, but magnets having different polarities on both ends in the axial direction may be used.
[0032]
Two reed switches 25 (25a, 25b) are attached to the bottom pipe 1e side by side in the crankshaft direction such that the sensing surface faces the lift member 22. The reed switch 25 is turned on when the permanent magnet 26 attached to the outer periphery of the lift member 22 approaches, and drives the electric motor 8 to generate an assist force as in the first embodiment, thereby reducing the burden on human power. it can. In particular, by arranging a plurality of reed switches 25 in the crankshaft direction, the assist force can be controlled in a plurality of stages as shown in FIG.
[0033]
As shown in FIG. 11, the angle limiting portion 16 of this embodiment has only one key portion 10 a protruding from the outer peripheral surface of the crankshaft 10 and only one fan-shaped groove 12 a of the wheel base 12. ing. The key portion 10a is rotatable relative to the groove 12a within a range of 0 to 45 °.
[0034]
The operation of the third embodiment will be described with reference to FIG.
FIG. 13A shows a state in which the pedal effort is small and the torsion coil spring 17 is hardly twisted, so that the relative rotation difference between the crankshaft 10 and the wheel base 12 is small, and the bolt 28 is located at the bottom of the cam surface 22d. It is located in the vicinity, and the axial movement amount of the lift member 22 is also small. Therefore, the distance L1 between the right reed switch 25a and the permanent magnet 26 is longer than the sensing distance, and all the reed switches 25 are off. In this range, the assist force of the motor is 0, and the vehicle travels only with human power.
When the pedal effort transmitted to the crankshaft 10 increases, the torsion coil spring 17 is twisted in the opening direction, and a relative rotation difference occurs between the crankshaft 10 and the wheel base 12. The lift member 22 rotates integrally with the crankshaft 10 by the engagement of the guide hole 22e and the bolt 27, and the bolt 28 rides on the cam surface 22d of the lift member 22, as shown in FIG. 13B. Move to the left. Since the distance L2 between the right reed switch 25a and the permanent magnet 26 is shorter than the sensing distance by the movement of the lift member 22, only the right reed switch 25a is turned on. Since the distance L2 between the left reed switch 25b and the permanent magnet 26 is longer than the sensing distance, the left reed switch 25b remains OFF. Therefore, a relatively small assist force is generated, and the burden on human power is reduced.
When the pedaling force further increases, the torsion coil spring 17 is further twisted in the opening direction, and the rotation angle is limited by the key portion 10a of the crankshaft 10 abutting on the end face of the fan-shaped groove 12a of the wheel base 12. Due to the relative rotation difference between the crankshaft 10 and the wheel base 12, the bolt 28 further rides on the cam surface 22d of the lift member 22, and moves the lift member 22 to the left as shown in FIG. 13C. . By the movement of the lift member 22, the distance L2 between the left reed switch 25b and the permanent magnet 26 becomes shorter than the sensing distance, and both reed switches 25a and 25b are turned on. Therefore, the maximum assist force is generated, and the burden on human power can be reduced.
Even if the pedal effort is further increased, the relative rotation difference between the crankshaft 10 and the wheel base 12 is limited to about 45 ° by the angle limiter 16, so that the axial movement of the lift member 22 is also limited, and There is no further increase in power.
[0035]
-Fourth embodiment-
FIGS. 14 and 15 show a fourth embodiment of the present invention, in which a reed switch 25 similar to that of the third embodiment is used as a pedaling force detecting means, and a permanent magnet 30 for operating the reed switch 25 is separate from the lift member 22. It is an example of attaching to a. Also in this embodiment, two reed switches 25a and 25b are arranged in the crankshaft direction.
The holder 31 holding the reed switch 25 also serves as a fixture for the bottom pipe 1e. An operation shaft 32 extending in the crankshaft direction is supported on the holder 31 so as to be slidable in the axial direction, and the permanent magnet 30 is fixed to the operation shaft 32. The permanent magnet 30 is constantly urged rightward in FIG. 14 by a spring 33 inserted through the operation shaft 32. Therefore, the permanent magnet 30 is normally at a position away from the reed switch 25, and the reed switch 25 is in the OFF state. An abrasion-resistant contact plate 34 made of fluororesin or the like is attached to the operation shaft 32 on the right side of the permanent magnet 30.
[0036]
When the pedaling force applied to the crankshaft 10 increases and a relative rotation difference occurs between the crankshaft 10 and the wheel base 12, the lift member 22 moves in the axial direction (leftward in FIG. 14) according to the same principle as in the above embodiment. Go to A step portion or a flange portion 22f is formed on the outer peripheral surface of the lift member 22. When the lift member 22 moves to the left in FIG. 14, the flange portion 22f hits the contact plate 34 to move the operation shaft 32 in FIG. Press to the left. As a result, the permanent magnet 30 fixed to the operation shaft 32 approaches the reed switch 25, and can operate the reed switch 25.
[0037]
This embodiment has an advantage that the permanent magnet 30 for operating the reed switch 25 can be made small.
In addition, since components such as the reed switch 25, the operating shaft 32, the permanent magnet 30, the spring 33, and the contact plate 34 are integrally assembled to the holder 31 and assembled, defects in the reed switch 25 and the permanent magnet 30 may occur. If there is, as shown in FIG. 15, the entire holder 31 can be replaced, and there is an advantage that repair and replacement are facilitated.
In the fourth embodiment, the permanent magnet 30 is always urged rightward in FIG. 14 by the spring 33. However, instead of this, for example, a circumferential groove engaged with the contact plate 34 is formed on the outer circumferential surface of the lift member 22. , The movement of the lift member 22 in the axial direction may be transmitted to the contact plate 34.
[0038]
As the non-contact type sensor, various known sensors such as a Hall element, a coil, an inductance type displacement sensor, and a capacitance type proximity sensor can be used in addition to a photo sensor, a magnetic resistance element, and a reed switch. Correspondingly, a part or the whole of the lift member 22 may be formed of a magnetic material or a magnet, or may be formed of a dielectric material or a conductor.
Further, it is also possible to use not only a non-contact type sensor but also a contact type detection unit.
[0039]
The present invention is not limited to the above embodiment.
As an example of the conversion member, the knock pin 12d is fixed to the outer peripheral surface of the wheel base 12. However, in order to reduce wear caused by sliding with the cam surface 22d, a bearing is provided at a contact portion of the knock pin 12 with the cam surface. You may.
Further, the cam surface provided on the lift member is not limited to the inclined groove or the elongated hole having one end opened as in the embodiment, but may be provided with a mountain-shaped cam surface. However, in this case, it is necessary to provide a spring that urges the lift member in the cam follower direction so that the cam surface and the cam follower (conversion member) can always contact.
When an inclined groove or a long hole as in the embodiment is provided as the cam surface 22d, even when the crankshaft 10 is relatively rotated not only in the pedal pressing force direction with respect to the wheel base 12 but also in the opposite direction, the conversion member 12d is formed. Has the advantage that the lift member 22 does not rattle in the axial direction and erroneous detection by the sensor 23 can be prevented.
[0040]
In the above embodiment, the lift member 22 is provided so as to be rotatable integrally with the crankshaft and movable in the axial direction, and the conversion member (knock pin) 12d is fixed to the wheel base. May be provided so as to be integrally rotatable with respect to the wheel base and movable in the axial direction, and the conversion member (knock pin) 12d may be fixed to the crankshaft.
The electric motor 8 is not limited to the example provided on the rear wheel as in the embodiment, and may be provided at any part.
[0041]
【The invention's effect】
As is apparent from the above description, according to the present invention, the pedal depression force input to the crankshaft is transmitted to the output rotating body via the torsion coil spring, and further transmitted to the chain drive sprocket, and the pedal depression force is also reduced. The assisting force of the electric motor is generated by converting the relative rotation difference generated between the crankshaft and the output rotating body with the increase into the axial displacement of the lift member and detecting this by the pedaling force detecting means. . That is, the amount of torsion of the torsion coil spring is proportional to the pedaling force, and the amount of axial movement of the lift member corresponds to the amount of torsion of the torsion coil spring. Can be generated.
In addition, since the torsion coil spring bears the pedaling force and no pedaling force acts on the lift member for controlling the assist amount, wear of the cam surface of the lift member and the conversion member engaged with the cam surface is reduced. It can be reduced and a durable electric assist bicycle can be realized.
Furthermore, since the torsion coil spring is inserted around the outer periphery of the crankshaft, it can be made compact without protruding greatly in the radial and axial directions.
In addition, since the treading force detecting means only needs to detect the movement of the lift member in the axial direction, it does not require a complicated mechanism such as a gear mechanism, can be made compact, and has few malfunctions.
[Brief description of the drawings]
FIG. 1 is a side view of an example of an electric assist bicycle according to the present invention.
FIG. 2 is a sectional view taken along line AA of FIG.
FIG. 3 is an exploded perspective view of a main part of the present invention.
FIG. 4 is a sectional view taken along line BB of FIG. 2;
FIG. 5 is a sectional view taken along line CC of FIG. 2;
FIG. 6 is a characteristic diagram showing a relationship between a relative rotation angle between a crankshaft and a wheel base and a spring reaction force of a torsion coil spring.
FIG. 7 is a characteristic diagram illustrating a relationship between a relative rotation angle between a crankshaft and a wheel base and an assist force.
FIG. 8 is an operation explanatory diagram showing a positional relationship between a lift member and a photo sensor in the first embodiment.
FIG. 9 is a sectional view of a second embodiment using a non-contact type detecting means as a pedaling force detecting means.
FIG. 10 is a sectional view of a crankshaft portion of a third embodiment of the electrically assisted bicycle according to the present invention.
FIG. 11 is a sectional view taken along line DD of FIG. 10;
FIG. 12 is an exploded perspective view of a main part shown in FIG.
FIG. 13 is an operation explanatory diagram showing a positional relationship between a lift member and a reed switch in a third embodiment.
FIG. 14 is a sectional view of a main part in a fourth embodiment.
FIG. 15 is a diagram illustrating an operation of attaching and detaching the holder according to the fourth embodiment to and from a vehicle body.
[Explanation of symbols]
One frame
5 pedals
6 Chain drive sprocket
8 Electric motor
9 Battery unit
10 Crankshaft
12 Wheel base (output rotator)
12d knock pin (conversion member)
17 Torsion coil spring
22 Lifting member
22a Large diameter part (first reflection part)
22b Small diameter part (second reflection part)
22d cam surface
23 Photo sensor (pedal force detection sensor)
25 Reed switch (pedal force detection sensor)
26 permanent magnet

Claims (8)

An electric assist bicycle that includes an electric motor that generates an assist force in accordance with a pedal depression force input to a crankshaft, and that synthesizes the assist force and the depression force and transmits the resultant to drive wheels.
An output rotator disposed rotatably relative to the crankshaft and fixed to a chain drive sprocket;
A torsion coil spring inserted through the outer periphery of the crankshaft, one end connected to the crankshaft, and the other end connected to the output rotating body;
A lift member provided integrally rotatably with respect to one of the crankshaft and the output rotating body, and movable in the axial direction, and having a cam surface having a predetermined inclination angle with respect to the axial direction;
A conversion member that is fixed to the other of the crankshaft and the output rotary body, and that contacts a cam surface of the lift member to convert a relative rotation difference between the crankshaft and the output rotary body into an axial movement of the lift member;
An electric assist bicycle comprising: a pedaling force detecting unit configured to detect a pedaling force according to an axial movement amount of the lift member. The lift member is formed in a cylindrical shape,
The electric assist bicycle according to claim 1, wherein the periphery of the torsion coil spring is covered with the lift member. 3. The electric assist bicycle according to claim 1, wherein the torsion coil spring is attached in a direction in which the number of turns increases as a pedaling force input to a crankshaft increases. 4. 3. The electric assist bicycle according to claim 1, wherein the torsion coil spring is mounted in a direction in which the number of windings decreases as a pedaling force input to a crankshaft increases. 4. An angle limiter is provided between the crankshaft and the output rotary body, the output rotary body being relatively rotatable with respect to the crankshaft within a predetermined angle range equal to or less than a rotation angle range in which the conversion member can contact the cam surface. The electric assist bicycle according to any one of claims 1 to 4, wherein: The torsion coil spring is mounted to apply an initial torsion torque to the crankshaft in a direction opposite to the pedal depression force in a state where the pedal depression force is not input to the crankshaft. 5. The electric assist bicycle according to any one of 5. The treading force detecting means includes a detecting unit provided on an outer peripheral portion of the lift member, and a non-contact type sensor fixed to the vehicle body stationary member and detecting the detecting unit and outputting a plurality of output signals. The electric assist bicycle according to any one of claims 1 to 6, wherein The electric assist bicycle according to claim 7, wherein the non-contact type sensor is a reed switch, and the detection unit is a permanent magnet attached in a ring shape to an outer peripheral portion of a lift member.

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