JP2006143216A - Power-assisted bicycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power-assisted bicycle capable of minimizing the modification of a conventional bicycle body frame, and realizing easy installation, space saving and weight reduction of a vehicle speed detection mechanism and a torque detection mechanism. <P>SOLUTION: The power-assisted bicycle 1 comprises a gear to be rotated as a bicycle travels, a flexible ring magnet formed in a sheet shape of the predetermined thickness, a rotational speed detection means which detects the magnetic field at the fixed position adjacent to the surface of the ring magnet and obtains the rotational speed of the gear based on the magnetic field, a one-way clutch having two components and an elastic means in order to transfer only the one-way rotation of a drive shaft to a sprocket, a stepping force detection means which detects the distortion of the elastic means and obtains the pedal stepping force based on the distortion, a power unit 13 to output the assist power, and a control means to control the assist power based on the obtained rotational speed of the gear and the obtained pedal stepping force. A plurality of magnet sections are formed on the surface of the ring magnet. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power-assisted bicycle that adds auxiliary power to pedal effort.

  Some normal bicycles are equipped with a meter for displaying the vehicle speed to improve driving safety. In particular, in an electrically assisted bicycle that assists human power by adding assist torque from an electric motor to the pedaling force according to the magnitude of the detected pedaling force, it is essential to detect both the vehicle speed and the pedaling force for safe assist. Become.

  In general, a rotation speed sensor for detecting the vehicle speed of a bicycle is attached so as to detect the rotation speed of a rotating body such as a rotating disk / gear that rotates as the bicycle runs and the pedal rotates.

  Conventionally, for example, a metal rotor having a plurality of irregularities formed at equal intervals on the outer peripheral surface is used as the rotating body, and a sensor that generates a high-frequency magnetic field toward these irregular surfaces is attached close to the rotor. On one concave surface or convex surface facing the sensor, an eddy current is generated by a high-frequency magnetic field from the sensor. Therefore, this sensor detects a change in the magnetic field generated by the eddy current or the inductance of the detection coil. Since the distance between the rotor outer peripheral surface and the sensor changes with the rotation of the rotating body due to the uneven surface, the strength of the magnetic field generated by the eddy current or the inductance of the detection coil also varies. Since this fluctuation cycle is inversely proportional to the rotation speed of the rotator, the rotation speed of the rotator and therefore the bicycle speed can be detected by extracting the fluctuation period of the intensity signal detected by the sensor.

  In another prior art, as shown in FIG. 17, a rotating magnet having convex magnets attached to the band surface of the torus at equal intervals is used, and a Hall element is provided adjacent to the torus. Deploy. Similar to the above prior art, the rotational speed of the torus can be obtained by detecting the fluctuation period of the magnetic field strength signal detected by the Hall element.

  However, in any of the above prior arts, since a large rotating body with unevenness is used, not only can it not be easily manufactured, but it is also necessary to take up space in the bicycle frame and to increase rigidity for forming unevenness. The problem is that the weight also increases. Therefore, it is difficult to attach the vehicle speed detection means as in the prior art to a bicycle having a conventional body structure without changing the body frame. In particular, the vehicle speed detection means having the above-mentioned problem is not preferable for a power-assisted bicycle that must be newly provided with a torque detection means, an electric motor, or the like.

  Also, with regard to the treading force detection sensor, since a new treading force detection member such as a torsion bar is incorporated into the bicycle frame, crankshaft, etc., the space and weight occupied by the torque detection mechanism is increased, and the conventional body frame is greatly increased. The problem of having to change arises.

  The present invention has been made in view of the above-described facts, and has achieved the ease of installation, space saving, and weight reduction of the vehicle speed detection mechanism and the torque detection mechanism while minimizing changes in the conventional body frame. The purpose is to provide an assist bicycle.

  The present invention relates to a power assist bicycle that travels by adding auxiliary power corresponding to a pedal depression force acting on a drive shaft in parallel to the pedal depression force, a gear that rotates as the power assist bicycle travels, and a substantially flat surface. A flexible ring magnet formed in a sheet shape with a substantially constant thickness over the entire area, the ring magnet having a surface arranged perpendicular to the rotation axis of the gear. The ring magnet is attached to the gear so that a plurality of magnet sections are formed on the surface so as to generate a magnetic field spatially changing on the surface at a constant angular period along a circumferential direction. And a rotational speed detecting means for detecting a magnetic field at a fixed position adjacent to the surface of the ring magnet and obtaining the rotational speed of the gear based on the magnetic field, and scanning only in one direction of the drive shaft. One-way clutch means for connecting a drive shaft and a sprocket so as to transmit to a rocket, the one-way clutch means comprising two parts and an elastic means arranged adjacent to each other along the axial direction of the drive shaft The two parts engage with each other when rotating in the one direction and increase the distance between the parts in the axial direction while being countered by the elastic force of the elastic means, and engage when rotating in the direction opposite to the one direction. The one-way clutch means, the pedaling force detection means for detecting the pedal depression force based on the distortion, the gear rotation speed and the pedaling force obtained by the rotation speed detection means Control means for controlling auxiliary power based on the pedal effort determined by the detection means.

  On the substantially flat surface of the ring magnet, a plurality of magnet sections are formed on the surface to generate a magnetic field that varies spatially at a constant angular period along the circumferential direction. The detected magnetic field fluctuates at a period according to the constant angular period and the rotation speed of the ring magnet. Therefore, the rotation speed detecting means can determine the rotation speed of the ring magnet and hence the rotation speed of the gear from the detected period of the magnetic field signal.

  Since a plurality of magnet sections are provided on a substantially flat surface having no irregularities of the ring magnet and the magnetic field detecting means is disposed adjacent to the surface, either the radial direction or the axial direction of the ring magnet is compared with the conventional technique. In addition, space saving can be achieved.

  In addition, since the ring magnet is formed in a sheet shape having a substantially constant thickness over the entire region, it is possible to further promote the ease of assembly to the gear and the reduction in weight. Furthermore, since the ring magnet is flexible, it can be easily assembled to the gear.

  Here, any form and arrangement of the magnet sections can be adopted as long as a magnetic field that changes spatially at a constant angular period along the circumferential direction is generated. Preferably, the angle between two adjacent magnet sections is changed to a sine wave with a constant angular period. For example, a plurality of magnet sections may take a form in which magnetic poles alternately reversed along the circumferential direction are respectively directed to a substantially flat surface of the ring magnet. That is, it is preferable that any two adjacent magnet sections among a plurality of magnet sections arranged in a ring shape in the circumferential direction are always composed of an N pole and an S pole having the same magnitude of the magnetic field. Here, if each angle formed by the plurality of magnet sections is substantially equal, one spatial period can be made equal to each other.

  In this way, it is possible to generate a magnetic field that changes spatially with the period occupied by the two magnet sections as a period. At this time, since the magnetic pole strength changes from N pole to S pole within one spatial period, the magnetic field waveform becomes sharp, and the rotation speed can be detected by the signal processing means with high accuracy. Further, since the N pole and the S pole are adjacent to each other, it is preferable from the viewpoint of maintaining magnetism in the magnet section. Adjacent magnet sections are in contact with each other, i.e., the area efficiency of the ring magnet can be increased by eliminating a region that is not magnetized at the boundary.

  Each of the plurality of magnet sections preferably has one magnetic pole facing the surface and the other magnetic pole facing the surface opposite to the surface. More preferably, the direction connecting both magnetic poles of each magnet section is preferably aligned substantially parallel to the axial direction of the ring magnet. Thereby, the magnetic field on a ring magnet can be strengthened and detection accuracy can be improved, and magnetism can also be maintained satisfactorily.

  A ring magnet can be made by, for example, magnetizing each section of a ring-shaped ferromagnetic material. Moreover, you may make by connecting the magnet corresponded to a magnet division. Therefore, manufacturing is very easy.

  The ring magnet can adopt an arbitrary shape as long as it is topologically ring-shaped. For example, in the case of having N magnet sections, it can be formed as a regular N-gon figure having a hole in the center. Moreover, it is preferable that the ring magnet has an annular shape with a hole formed in the center from the viewpoints of the symmetry of the magnetic field and the ease of assembly to the part to be inspected.

  In a preferred embodiment, the ring magnet is accommodated in a groove formed in the detected part. As a result, the space occupied by the rotation speed sensor can be reduced. Furthermore, if the surface of the ring magnet housed in the groove is flush with the surface of the detected portion outside the groove, it is not necessary to provide irregularities in the conventional inspected portion. There are advantages. The ring magnet can be assembled more easily if it can be fixed in the groove with an adhesive.

  As the magnetic field detection means, a Hall element is preferable in terms of magnetic field detection accuracy and space saving.

  When the driver steps on the pedal, the two components housed in the one-way clutch engage with each other to increase the axial component interval. This increase in spacing is countered by elastic means. Since the elastic means is elastically distorted according to the pedal effort, the distortion of the elastic means reflects the pedal effort. The pedaling force detection means detects the distortion of the elastic means and obtains the pedaling force based on the distortion. When the driver does not apply the pedaling force, the two parts are disengaged and the interval increased by the elastic force of the elastic means is restored.

  According to the present invention, the control means controls the auxiliary power based on the rotation speed of the gear (corresponding to the vehicle speed of the bicycle) obtained by the rotation speed detection means and the pedal depression force obtained by the pedaling force detection means. For example, when traveling at high speed, the assist ratio (auxiliary power / stepping force) is decreased to increase safety, and during traveling at low speed, the assist ratio is increased to enable light driving.

  According to the present invention, a means for detecting the pedaling force is provided inside the one-way clutch means, which is an essential component of the bicycle, and is formed in a sheet shape having a substantially constant thickness over the entire area in order to detect the vehicle speed. Since the ring magnet is used, the pedal force detection means and the vehicle speed detection means can be easily installed on the vehicle body with little space. Thus, it is unnecessary to change the frame structure of the bicycle, and it is possible to achieve an extremely advantageous effect that it is possible to realize an electric assist bicycle with a light feeling driving that realizes ease of manufacture and weight reduction at a high level. It is done.

BEST MODE FOR CARRYING OUT THE INVENTION

(First embodiment; rotational speed sensor)
FIG. 2 shows an NS polarization ring magnet 200 constituting the rotational speed sensor according to the first embodiment of the present invention. The ring magnet 200 is formed in a substantially flat ring having an opening 205 at the center thereof. The ring magnet 200 includes a plurality of magnet sections that divide the ring into equal angles. In these magnet sections, the N pole section 202 facing the N pole side as viewed from the front and the S pole side facing. The S pole sections 204 are alternately arranged. In this case, as shown in the side view, the opposite side of the N pole section 202 is the S pole, and the opposite side of the S pole section 204 is the N pole so that the direction of the magnetic field lines is approximately perpendicular to the ring surface. It is preferable to orient the south pole. In the example of the figure, twelve magnet sections are formed, but the number may be more or less than this, and can be arbitrarily and suitably changed according to the rotation speed of the detected portion and the required detection accuracy. .

  In addition, if the perpendicular component of a magnetic field exists with respect to a ring surface, the method of the orientation of NS pole of each magnet division can be changed arbitrarily suitably. For example, adjacent N pole sections and S pole sections may be arranged in the circumferential direction as both poles of one magnet. In this case, the opposite side of the N-pole section 202 is also the N-pole, and the opposite side of the S-pole section 204 is also the S-pole. However, the example of FIG.

  FIG. 3 shows a gear 210 as a detected part of the rotational speed. The gear 210 is rotated by the torque transmitted by the shaft 214, and a ring groove 208 having a size and shape capable of accommodating the ring magnet 200 is formed on one surface thereof. The ring magnet 200 is accommodated in the ring groove 208 and attached with an adhesive or the like. At this time, as shown in the figure, it is preferable that the ring magnet 200 and the surface of the gear 210 are flush with each other. As a result, the ring magnet does not protrude from the gear surface, and the space reduction due to the installation of the rotation speed sensor can be minimized.

  A hall element 212 for detecting a magnetic field is disposed adjacent to the ring magnet 208 installed on the gear 210. This Hall element is an existing magnetic field detection element that generates an electromotive force proportional to the current and the magnetic field in the direction perpendicular to the current and the magnetic field by the Hall effect when a magnetic field is perpendicular to the direction of current flow in the semiconductor. Of course, as long as the magnetic field can be detected, a magnetic field detection sensor other than the Hall element, such as a coil, may be used. The output terminal of the hall element 212 is connected to the controller 14. If the rotational speed sensor 220 of FIG. 3 is represented with a perspective view, it will become as shown in FIG.

  The controller 14 detects the rotational speed of the gear 210 by analyzing the magnetic field detection signal from the Hall element 212 by any suitable method. Here, an example of the waveform of the magnetic field signal output from the Hall element 212 to the controller 14 is shown in FIG. For example, the controller 14 has a function of detecting a zero crossing point (time at a point where the magnetic field intensity is zero), an N-pole side peak, or an S-pole side peak of a magnetic field signal, and obtaining those times. Since the N pole side peak 222 and the S pole side peak 224 shown in FIG. 5 indicate the time points when the maximum magnetic poles of the N pole section and the S pole section pass through the detection region of the Hall element 212, the number of appearance of each peak The time T required for the gear 210 to make one rotation can be detected based on the time. Thus, the rotational speed (2π / T) of the gear 210 can be obtained immediately. Of course, the rotation speed of the gear may be obtained when the gear 210 is rotated by a predetermined angle without waiting for one rotation of the gear 210.

  Since the NS polarization ring magnet 200 has a flat ring shape, the rotation speed sensor of this embodiment can achieve space saving and weight reduction without being bulky. Further, since the structure is very simple, the manufacture is easy, and therefore the cost can be reduced.

  In addition, since the plurality of magnet sections are combined into one flat ring, it is very easy to assemble the apparatus. For example, as shown in FIG. 3, a ring-shaped groove is dug in the surface of the gear 210, and a ring magnet is embedded therein and fixed with an adhesive or the like. Compared with the work of embedding individual magnets corresponding to polarization in gears, the work efficiency can be improved at each stage. In addition, if the groove depth and the height of the ring magnet are aligned, it does not protrude at all and contributes to space saving.

  Moreover, the time resolution of the rotational speed can be improved by reducing the angle range occupied by each magnet section.

Hereinafter, a bicycle according to another embodiment incorporating the rotation speed sensor according to the first embodiment of the present invention will be described with reference to the drawings. The bicycle described below will be described as an electrically assisted bicycle that gives an auxiliary torque by an electric motor as an example.
(Second embodiment; electric assist bicycle)
FIG. 1 shows an outline of an electrically assisted bicycle 1 according to a second embodiment of the present invention. In addition, the same code | symbol shall be used about the component similar to 1st Embodiment.

  As shown in the figure, the main skeleton part of the electrically assisted bicycle 1 is composed of a body frame 3 made of a metal tube, and the body frame 3 includes a front wheel 20 and a handle for steering the front wheel. 16, rear wheel 22 and saddle 18 are attached in a known manner.

  Further, a drive shaft 4 is pivotally supported at the center lower portion of the vehicle body frame 3 so as to be rotatable with respect to the vehicle body frame 3, and pedals 8L and 6L are connected to left and right ends of the drive shaft via crank rods 6L and 6R, respectively. 8R is attached to each. A sprocket 2 as a driven side is coaxially attached to the drive shaft 4 as a driving side via a ratchet gear, which will be described later, and this ratchet gear rotates in one direction (R direction) to advance the bicycle 1. It is constructed and arranged so that only torque is transmitted from the drive side to the driven side.

  Further, a rear wheel power mechanism 10 is provided at the central portion of the rear wheel 22 to give the transmitted pedal force to the rear wheel. A free wheel (not shown) provided inside the rear wheel power mechanism and An endlessly rotating chain 12 is stretched between the sprocket 2.

  As is well known, the forward pedaling force applied to the pedal 8 rotates the drive shaft 4 via the crank rod 6, and this rotational force rotates the sprocket 2 as a stepping torque in the R direction in the figure. Torque is transmitted to the rear wheel power mechanism 10 via the chain 12, and as a result, the rear wheel 22 is rotated to run the bicycle 1 forward.

  The rotation speed sensor 220 can be attached to any detected part that rotates to reflect the traveling speed. Examples of the detected portion include a gear (not shown) arranged in the rear wheel power transmission mechanism 10, a sprocket 2, a sprocket drive gear 11 described later, and a rotating portion of a front wheel axle. The controller 14 has a reference table for converting the rotational speed of these parts to be inspected into the traveling speed of the vehicle body.

  Next, the configuration of the torque detection mechanism according to the present embodiment will be described with reference to FIGS.

  First, FIG. 7 shows a front view of the sprocket 2 and the ratchet gear 39 connected to the sprocket 2, and a cross-sectional side view of the sprocket 2 and the ratchet gear 39 taken along the line SS ′ of the front view. The figure is shown. As shown in the front view, the sprocket 2 has a plurality of teeth 24 for fitting with the chain 12 over the outer periphery of the rigid body portion 38 and recesses 25 formed between adjacent teeth. A hole 41 for allowing the drive shaft 4 to pass therethrough and a cylindrical stopper 46 surrounding the periphery of the hole 41 are formed in the central portion of 38.

  The ratchet gear 39 includes three ratchet pieces 40 fixedly arranged on the body portion 38 of the sprocket 2 at equal angles at equal distances from the sprocket center (in the figure, coincident with the drive axis 5), and the ratchet pieces 39 And ratchet teeth 43 arranged on one side of the sprocket 2 so as to be fitted.

  7 shows a state in which the sprocket 2 and the ratchet gear 39 are attached to the drive shaft 4. According to the figure, a drive shaft 42 is provided around the drive shaft 4 so as to be concentric with the drive shaft so as not to move relative to the shaft. The drive shaft 42 is formed with a pedestal 45 having a cylindrical shaft surface substantially parallel to the axis 5 on the outer periphery thereof. The pedestal 45 is disposed in a state where the sprocket 2 and the ratchet teeth portion 43 are engaged. The sprocket 2 can rotate independently of the drive shaft 42 in the pedestal 45 in the direction in which the clutch of the ratchet gear 39 does not act, and the ratchet tooth portion 43 is fixed to the drive shaft 42 as described later. Yes.

  Here, the engagement state and the clutch function of the sprocket 2 and the ratchet tooth portion 43 will be conceptually described with reference to FIGS. 8 and 9.

  FIG. 8 shows a schematic perspective view of the sprocket 2 and the ratchet tooth portion 43 in an exploded state. As shown in the figure, the ratchet piece 40 is formed as a claw-like member obtained by bending a long and thin metal flat plate having elasticity, and a tip end portion 40a of the claw-like member is fixed to the body portion 38 of the sprocket 2. The rear portion 40b is fixed to the body portion 38 by welding or the like so as to form an inclination angle of.

  Further, the ratchet tooth portion 43 includes a disc portion 60 having a flat surface. On the surface of the disc portion 60 on the side facing the sprocket surface, the ratchet piece 40 and the ratchet piece 40 are provided along the outer circumference. A plurality of teeth 44 for engagement are formed. Each tooth 44 has a gentler slope 44a and a steeper slope 44b, respectively. Furthermore, a cylindrical center shaft 54 extending in the axial direction is provided at the center of the disc portion 60 so as to protrude outward from the plane of the disc portion, and the center shaft has a drive shaft. An opening 57 for receiving a drive shaft 42 provided around 4 passes therethrough. Further, in the center shaft 54 on the side opposite to the side facing the sprocket surface of the disc portion 60, a flat plate-like detent 52 is fixedly connected to the inner wall of the shaft so as to bridge over the diameter of the opening 57. Has been. Further, a coil spring 50 is inserted into the center shaft 54, one end portion of the coil spring 50 abuts against the rotation preventing portion 52, and the other end portion is fixed to the drive shaft 42 (not shown).

  In the engaged state of the sprocket 2 and the ratchet tooth portion 43, as shown in FIG. 9, the tip end portion 40a of the ratchet piece 40 enters into the recess defined by the adjacent slope 44a and slope 44b, and its most advanced portion is , Abuts against a steeper slope 44b. The opening 57 of the center shaft 54 receives the drive shaft 42. At this time, although not shown, the rotation preventing portion 52 is inserted into a longer slot 58 formed so as to penetrate the shaft portion along the axial direction of the drive shaft 42. As a result, the ratchet teeth 43 do not rotate with respect to the drive shaft 42 but rotate together with the drive shaft 4 that rotates by the stepping torque. Further, since the axial width of the anti-rotation portion 52 is smaller than the length of the slot 58, the anti-rotation portion 52 can slide in the axial direction along the slot 58. At this time, since the rotation preventing portion 52 is urged in the direction toward the sprocket 2 by the coil spring 50, the leading end portion of the ratchet piece 40 is locked at the height where the ratchet tooth portion 43 is engaged. .

  As shown in the lower part of FIG. 9, when the drive shaft 42 rotates in the R direction corresponding to the advancing direction of the bicycle 1, the most advanced portion of the ratchet piece 40 comes into contact with the slope 44 b with the steeper slope 44 b of the tooth 44. Since it does not slide along, the ratchet teeth 43 and the sprocket 2 together with the drive shaft 42 rotate in the R direction. On the other hand, when the drive shaft 42 rotates in the direction opposite to the R direction, the back surface of the tip end portion 40a comes into contact with the gentler slope 44a, so that the drive shaft 42 starts to slide along the slope without being locked. The rotation is not transmitted to the sprocket 2. This is the principle of the one-way clutch of the ratchet gear 39.

  When the rotation of the drive shaft 42 in the R direction is transmitted to the sprocket 2 via the ratchet teeth 43, as shown in the lower diagram of FIG. 9, the ratchet has elasticity against the rotational force received from the steeper slope 44b. The piece 40 stands up. For this reason, the ratchet teeth 43 are displaced in the axial direction from the normal axial position (position 48a in FIGS. 6 and 7) so as to be further away from the sprocket 2 while resisting the biasing force of the coil spring 50, and the pedal depression force It stops at a position where the rotational force and the elastic force of the ratchet piece 40 are balanced (position 48b in FIGS. 6 and 7). When the stepping torque is reduced, the rotational force received from the steeper slope 44b is weakened. Therefore, the ratchet piece 40 tries to return to its original height due to its elasticity, and the ratchet tooth portion urged downward by the coil spring 50 together with this. 43 is displaced in the axial direction so as to approach the sprocket 2. Thus, the axial displacement amount ΔL (FIG. 7) of the ratchet tooth portion 43 reflects the magnitude of the depression torque.

  In order to detect the axial displacement of the ratchet teeth 43, as shown in FIG. 6, a position sensor 34 for detecting the axial distance from a predetermined position to the disc 60 of the ratchet teeth 43 is arranged on the vehicle body frame. Set up. The position sensor 34 is disposed, for example, in the vicinity of a detection body made of a magnetic material such as ferrite attached so as to move in the axial direction in accordance with the axial displacement of the disc portion 60. And a detection circuit capable of electrically detecting a change in inductance of the coil as a change in impedance. In the case of this configuration, the detection body approaches or moves away from the coil according to the axial displacement amount of the ratchet teeth 43, but the inductance of the coil changes according to the distance between the detection body and the coil. By detecting with the detection circuit, the axial distance L1 to the ratchet tooth portion 43 can be calculated. Of course, any other type of sensor may be used as long as the axial distance of the ratchet tooth portion 43 or its displacement ΔL can be detected, and depending on the sensor, it may be arranged in the ratchet gear 39. .

  A controller 14 that receives a detection signal from the sensor is connected to an output terminal of the position sensor 34. The controller 14 can be realized by a so-called microcomputer or the like, and has a calculation function for calculating a stepping torque value based on the received detection signal regarding the axial distance.

  Next, the electric assist means of this embodiment will be described. As shown in FIG. 6, the electric assist means includes a sprocket drive gear 11 that is directly fitted to the sprocket 2, an electric motor 37 that is rotationally driven by a battery (not shown), and transmits the auxiliary torque via a rotating shaft 37a. The speed reduction mechanism 35 that reduces the rotational speed of the electric motor 37 around the rotation shaft 37a and transmits it to the sprocket drive gear 11 via the gear shaft 35a, and the electric motor 37 is controlled based on the calculated stepping torque value. And the controller 14.

  Of these, the speed reduction mechanism 35 is configured by combining a plurality of gears, for example, and is a so-called one-way clutch that transmits power in only one direction in the middle of an auxiliary torque transmission path constituted by these gears. (Not shown) is provided. The one-way clutch is configured and connected so as to transmit the auxiliary torque from the electric motor 37 to the sprocket drive gear 11 but not in the opposite direction, that is, from the sprocket drive gear to the speed reduction mechanism 35. As a result, the load of the electric motor 37 when not driven is not transmitted to the sprocket 2, and a light operation is always possible.

  A front view of the sprocket drive gear 11 and the sprocket 2 in a fitted state is shown in FIG. 10 (the crank rod is not shown). Here, the chain 12 stretched on the sprocket 2 has a pin link in which two pins are press-fitted into two eyebrows-type link plates, and two bushes are press-fitted into two ring plates. A roller link in which a roller is rotatably fitted around the outer periphery of the roller is alternately combined. Each roller constituting the pin link and the roller link of the chain 12 has a pitch and a diameter so as to be fitted to each tooth of the sprocket 2.

  For example, the sprocket drive gear 11 is configured as shown in FIG. 11 so as to be fitted to the sprocket 2 in the same manner as the fitting of the chain 12. The sprocket drive gear 11 has two roller plates 17a and 17b arranged in parallel to each other, and the plate 12 along the peripheral region of the plate so as to connect the plates to each other at the same pitch as the rollers of the chain 12. A plurality (six in the illustrated example) of cylindrical bushes (roller shafts) 15 press-fitted substantially vertically, and a plurality (six in the illustrated example) that are rotatably fitted around the outer periphery of these bushes. ) Cylindrical rollers 21. The roller plates 17a and 17b are formed with an attachment hole 19 for attachment to the driving means 13 in the center thereof, and an indented recess 33 is formed in the outer peripheral portion between the adjacent rollers 21.

  Two adjacent rollers 21 of the sprocket drive gear 11 engage with the recess 25 of the sprocket 2, and one tooth 24 of the sprocket 2 enters the gap between these rollers (see FIG. 10). The above-described recess 33 of the sprocket drive gear 11 is preferably formed so that the teeth of the chain 12 can be easily fitted between the rollers 21. For example, the constricted portion at the center of the eyebrow-shaped link plate of the chain 12 It is preferable to be formed into substantially the same shape as the above.

  Next, the operation of the second embodiment of the present invention will be described with reference to the drawings.

  When the rider applies a pedaling force to the pedals 8R and 8L and rotates the drive shaft 4 in the R direction, the ratchet tooth portion 43 fixed to the drive shaft 4 so as not to rotate by the rotation preventing portion 52 rotates together with the drive shaft 4. The stepping torque is applied to the sprocket 2 on which the tensile force from the chain 12 acts as a load via the ratchet piece 40 engaged with the teeth 44. At this time, the elastic ratchet piece 40 stands up against the rotational force received from the steep slope 44b of the ratchet teeth, and therefore the ratchet tooth portion 43 has a normal axial position (position 48a in FIG. 7). Is displaced axially away from the sprocket 2 while resisting the biasing force of the coil spring 50, and stops at a position (position 48b in FIG. 7) where the rotational force of the pedal depression force and the elastic force of the ratchet piece 40 are balanced. .

  The position sensor 34 in FIG. 6 constantly detects the axial distance from the fixed position to the disc portion 60 of the ratchet tooth portion 43, and transmits the detection signal (corresponding to the position 48 b) to the controller 14. The controller 14 calculates the difference between the position 48a of the ratchet tooth 43 when the stepping torque stored in the internal memory is not acting and the position 48b indicated by the received detection signal, and calculates the axial direction. A displacement amount ΔL is obtained. Since this axial displacement amount ΔL increases as the stepping torque increases, the controller 14 can calculate the stepping torque value from the correspondence between the two. This can be achieved, for example, by experimentally obtaining a relationship between the axial displacement amount ΔL and the stepping torque in advance and storing a reference table representing this relationship in the internal memory of the controller 14.

  Next, the controller 14 calculates an assisting auxiliary torque Te to be applied based on at least the calculated stepping torque T, and outputs a control signal for instructing the electric motor 37 to be driven to rotate with the auxiliary torque. To do. Preferably, the controller 14 converts the rotational speed detected by the rotational speed sensor 220 into a vehicle speed, and calculates the auxiliary torque Te based on both the stepping torque T and the rotational speed sensor vehicle speed.

  For example, in the simplest electric assist control, when the calculated stepping torque T is equal to or greater than a predetermined value, the motor that instructs the auxiliary torque to turn on the electric motor 37 and maintain a predetermined ratio with respect to the stepping torque. A control signal is output, otherwise a motor control signal for turning off the electric motor is output. In this case, the electric motor 37 may be turned on only when the axial displacement amount ΔL itself is directly used and this value becomes a certain value or more.

  When the electric motor 37 is turned on and rotated, this rotational force is transmitted to the sprocket drive gear 11 via the speed reduction mechanism 35, and the sprocket drive gear 11 is rotated around the drive center shaft 9 in the K direction shown in FIG. Rotate to. At this time, the respective rollers 21 are sequentially engaged with the respective concave portions 25 of the sprocket 2, and at the same time, the sprocket 2 is given a driving torque in the R direction around the central axis 5 of the drive shaft 4. Thus, in this embodiment, since the auxiliary torque from the electric motor 37 is transmitted to the region of the sprocket 2 where the highly rigid teeth 24 are formed via the sprocket drive gear 11, the sprocket 2 is not bent. In addition, it is possible to assist the pedaling force without shifting the center of rotation. As described above, the assisting auxiliary torque is applied under such a condition that the depression torque is considered to be a certain level or more, so that the pedal operation can be easily performed.

  As described above, in the present embodiment, the shaft inside the ratchet gear that is also required for a general bicycle without adding an elastic member, a transmission mechanism, etc. having high rigidity and large volume and weight separately to an existing electric assist bicycle. Since the torque is calculated based on the amount of directional displacement, the space and weight of the torque detection mechanism can be greatly reduced and the mechanism can be simplified.

  Further, in the present embodiment, since the auxiliary torque from the electric motor 37 is transmitted to the outer peripheral portion of the sprocket 2 having a large diameter via the sprocket drive gear 11, the auxiliary torque is applied from the drive shaft 4. There is an advantage that a large reduction ratio can be obtained. As a result, the resultant force mechanism can be reduced in size and weight and simplified.

Furthermore, in the present embodiment, the elastic displacement portion of the torque detection mechanism is integrally included in the ratchet gear, and the electric assist means is configured only by providing the sprocket drive gear 11 and the drive means 13. There is almost no need to change the frame structure, and the electric assist bicycle can be further reduced in size and weight, simplified, and reduced in cost.
(Third embodiment)
FIGS. 12A and 12B show a torque detection mechanism according to the third embodiment of the present invention. In addition, since it is the same as that of 2nd Embodiment except a torque detection mechanism, detailed description is abbreviate | omitted and it attaches | subjects the same code | symbol about the same component.

  As shown in FIGS. 12A and 12B, the torque detection mechanism according to the third embodiment includes a sprocket 70 having a cylindrical housing portion 82 at the center thereof. The cylindrical housing portion 82 projects cylindrically on one plate surface side of the sprocket 70 and is recessed on the other plate surface side. The sprocket 70 is disposed so that the recessed portion of the cylindrical housing portion 82 faces the pedal side, and the recessed portion transmits only one direction of rotation from the driving side portion to the driven side portion. A clutch 72 is housed. This one-way clutch 72 is fixedly connected at its driven side portion at the engaging portion with the recessed portion of the cylindrical housing portion 82 so as to transmit the rotation only in the R direction to the sprocket 70. Is fixedly connected to the drive shaft 4. Note that the sprocket 70 has a plurality of holes 84 (FIG. 12A) formed around the cylindrical housing portion 82 for weight reduction.

  As the one-way clutch 72, when the drive shaft 4 rotates in the R direction and the rotational force is transmitted to the sprocket 70, the driven side portion of the one-way clutch 72 has an amount of displacement corresponding to the magnitude of the stepping torque. A type of clutch that is displaced toward the sprocket along the direction is selected. An example is the ratchet gear type one-way clutch of the second embodiment.

  On the other hand, a bearing 74 is arranged around the protruding portion of the cylindrical accommodating portion 82 on the inner surface of the sprocket 70 on the opposite side, and holds the cylindrical accommodating portion from the periphery of the side surface. This bearing 74 preferably accommodates both axial and radial loads. Further, a disc-shaped conical disc spring 76 having elasticity holds the bearing 74 so as to cover the outer periphery of the bearing 74, and the disc spring 76 is fixed to the vehicle body via a rigid support base 78. ing. That is, the sprocket 70 is elastically held on the side opposite to the one-way clutch 72 so as to be rotatable with respect to the vehicle body. As apparent from FIG. 12B, when the axial width of the one-way clutch 72 and the axial width of the disc spring 76 are projected onto the central axis of the drive shaft 4, there is an overlapping region at the axial position. I understand that.

  Further, a strain gauge 80 for detecting the strain of the disc spring due to the applied stress is attached to the disc spring 76, and the strain gauge 80 is connected to the controller 14 (see FIG. 6). The strain gauge 80 can be formed of, for example, a thin film metal resistance element. In the case of this thin-film metal resistance element, a thin oxide film insulating layer is provided on the surface of the mirror-polished disc spring 76, and a resistor composed of a plurality of elements is formed in a bridge shape by a technique such as sputtering. The controller 14 can detect the magnitude of the stress by detecting the change in the resistance of the bridge element due to the stress strain applied to the disc spring 76. In order to improve the detection accuracy, it is preferable that the strain gauge 80 is installed at a place where the disk spring 76 is most susceptible to stress deformation so that the change in resistance value due to the amount of stress deformation is as large as possible.

  As an alternative to the strain gauge 80, there is a piezo-piezoresistive element that detects a change in resistance due to pressure applied to the disc spring 76, or a position sensor that detects the amount of displacement of the disc spring 76 surface.

  Next, the operation of the third embodiment will be described.

  When the rider applies a pedal depression force to the pedals 8R and 8L and rotates the drive shaft 4 in the R direction, this rotational force is transmitted to the sprocket 70 via the drive side portion of the one-way clutch 72. At this time, the driven side portion of the one-way clutch 72 tries to displace the sprocket 70 along the axial direction by a displacement corresponding to the stepping torque, so that the sprocket 70 is pushed further inward along the axial direction. Force acts. This pushing force is applied to the disc spring 76 that holds the sprocket 70 via the bearing 74, and causes a strain on the disc spring 76. This stress strain reflects the amount of movement of the sprocket 70 in the axial direction by the one-way clutch 72, that is, the magnitude of the stepping torque.

  The resistance value of the strain gauge 80 changes due to the stress strain of the disc spring 76. This changed resistance value is detected by the controller 14. The controller 14 stores a reference table indicating the correspondence between the resistance value of the strain gauge 80 and the depression torque in advance in its internal memory, and the depression is performed by comparing the detected resistance value of the strain gauge with the reference table. Torque T is obtained. As in the second embodiment, the controller 14 controls the electric motor 37 so as to be rotationally driven by the auxiliary torque Te calculated based on the stepping torque T, and the auxiliary torque is transmitted via the sprocket drive gear 11 to the sprocket. 70 is transmitted directly.

  As described above, also in the third embodiment, a one-way clutch that is necessary even for a general bicycle without adding an elastic member, a transmission mechanism, or the like having high rigidity and large volume and weight to an existing electric assist bicycle. Since the torque is calculated based on the stress distortion of the disc spring 76 due to the pushing force of 72, the space and weight of the torque detection mechanism can be greatly reduced and the mechanism can be simplified.

Further, in the third embodiment, the one-way clutch 72 is housed in the cylindrical housing portion 82 of the sprocket 70, and both the disc springs 76 are indirectly held from the outer periphery of the housing portion within the same width. Therefore, the axial stroke is shorter. This advantage is further advanced by adopting a means for detecting the amount corresponding to the stepping torque by the strain gauge 80 formed thin on the surface of the disc spring 76. Thus, the third embodiment has an effect that is further superior to the second embodiment in terms of space saving.
(Fourth embodiment)
A torque detection mechanism according to a fourth embodiment of the present invention will be described with reference to FIGS. In addition, since it is the same as that of 2nd and 3rd Embodiment except a torque detection mechanism, detailed description is abbreviate | omitted and it attaches | subjects the same code | symbol about the same component.

  As shown in FIG. 13, the sprocket 2 is pivotally supported on the drive shaft 4 via a ratchet gear. As shown in FIG. 14, the ratchet gear includes a piece part 100 and a tooth part 112.

  In the piece part 100, three ratchet pieces 102 are arranged on the second engagement surface 110 at equal angles along the circumferential direction. The ratchet piece 102 is made of a rigid body and is rotatable around an axis that is close to the second engagement surface 110 and substantially along the radial direction of the engagement surface. When the ratchet piece 102 is not acting on the ratchet piece 102, the piece rises so that the length direction forms a predetermined angle with respect to the second engagement surface 110 (equilibrium direction 160 in FIG. 15). The spring 104 is biased. As shown in FIG. 15, when the ratchet piece 102 is biased from the equilibrium direction 160 in the ascending direction a or the descending direction b, the piece raising spring 104 is slightly in the ratchet piece 102 so as to return the bias to the equilibrium direction 160. Exerts an elastic force.

  In addition, a piece portion bore 106 for receiving the drive shaft 4 is formed at the center portion of the piece portion 100, and this piece portion bore 106 also penetrates the cylindrical portion 103 protruding from the back surface 101 of the piece portion 100. . A circular groove 155 (FIG. 13) is formed on the outer periphery of the cylindrical portion 103 on the back surface 101, and a large number of steel balls 152 are rotatably fitted in the circular groove 155. As a result, a bearing for an axial load bearing and sliding bearing is formed on the back surface 101.

  The disc spring 124 is brought into contact with the back surface 101 of the piece portion 100 through the cylindrical portion 103 in the center hole 127. At this time, the disc spring 124 is slidably in contact with the back surface 101 via the steel ball 152, that is, the load receiving bearing, in a direction that opposes the pressure from the piece portion 100 with elasticity. On the surface of the disc spring 124, strain gauges 126 are installed at two locations facing each other with a positional relationship of 180 degrees. These strain gauges 126 are electrically connected to the controller 14 via lead wires 128. More preferably, three or more strain gauges may be installed on the disc spring 124. At this time, it is preferable that the plurality of strain gauges are installed on the surface of the disc spring 124 so as to be in rotationally symmetric positions.

  The disc spring 124 is accommodated in the inner bottom portion 132 of the bowl-shaped supporter 130. The supporter 130 is formed with a support bore 133 that passes through the center portion for receiving the drive shaft 4 and a support cylindrical portion 134 that protrudes from the rear surface. A bearing 138 corresponding to both axial and radial loads is engaged with the inner wall of the support cylindrical portion 134 (see FIG. 13). The bearing 138 is locked by a stopper inclined surface 144 formed on the drive shaft 4.

  Four first anti-rotation grooves 108 extending in the axial direction 5 are formed in the inner wall of the piece bore 106. Four second anti-rotation grooves 140 extending in the axial direction 5 so as to face the first anti-rotation groove 108 are also formed at four locations on the outer wall portion of the drive shaft 4 that is in sliding contact with the inner wall of the piece bore 106. ing. As shown in FIG. 16A, the first antirotation groove 108 and the second antirotation groove 140 facing the first antirotation groove form a cylindrical groove extending along the axial direction. Inside, a large number of steel balls 150 are accommodated so as to fill them. Thereby, the piece part 100 can move along the axial direction 5 with the minimum frictional resistance, and the relative rotation with respect to the drive shaft 4 is prevented. This is a kind of ball spline, but other types of ball splines, such as an endless rotating ball spline, can be applied as such a slidable rotation preventing means.

  It is also possible to use means other than the ball spline. For example, as shown in FIG. 16B, a protrusion 140a extending in the axial direction is provided on the drive shaft 4, and a third anti-rotation groove 108a that accommodates the protrusion 140a is formed in the piece 100. A key spline type is also applicable as a rotation prevention means. In FIG. 16B, the protrusion 140a may be provided on the piece 100 side and the third rotation prevention groove 108a may be provided on the drive shaft 4 side. Further, as shown in FIG. 16 (c), a fourth rotation prevention groove 108b extending in the axial direction and a fifth rotation prevention groove 140b facing this are provided in the piece portion 100 and the drive shaft 4, respectively. A so-called key groove type in which the key plate is accommodated in a rectangular parallelepiped groove formed by the groove is also applicable as the rotation preventing means. Note that the detent 52 shown in the second embodiment can also be employed in the fourth embodiment.

  A plurality of ratchet teeth 114 for engaging with the ratchet piece 102 are formed on the first engagement surface 121 of the tooth portion 112. The ratchet teeth 114 are configured by steep slopes 118 and gentler slopes 116 with respect to the first engagement surface 121, which are alternately and periodically formed along the circumferential direction of the tooth portion. .

  The tooth portion 112 is pivotally supported by the drive shaft 4 so that the first engagement surface 121 thereof faces the second engagement surface 110 of the piece portion 100, and the ratchet piece 102 and the ratchet teeth 112 are engaged. (FIG. 15). At this time, the drive shaft 4 passes through the tooth bore 120 formed at the center of the tooth portion 112 via the collar 111 and is fixed from the end portion 142 via the washer 122 (FIG. 13). Further, the tooth portion 112 is connected to a support 130 that is rotatable with respect to the sprocket 2 and the drive shaft 4. Thus, the ratchet gear for connecting the drive shaft 4 and the sprocket 2 so as to transmit only the rotation of the drive shaft 4 in the vehicle body forward direction to the sprocket 2 is completed.

  Preferably, the offset spring 136 is interposed between the stopper inclined surface 144 of the drive shaft 4 and the back surface 101 of the piece portion 100. The offset spring 136 is configured to generate a clearance between the steel ball 152 accommodated on the back surface 101 and the disc spring 124 when the pedal depression force is equal to or less than a predetermined value (for example, substantially close to zero). 100 is biased axially.

  Next, the operation of the fourth embodiment will be described.

  When the rider applies a pedal depression force to the pedals 8R and 8L and rotates the drive shaft 4 in the vehicle body forward direction, this rotational force is transmitted to the piece portion 100 that is pivotally supported with respect to the drive shaft 4. . At this time, as shown in FIG. 15, the ratchet piece 102 is given a force Fd corresponding to the pedal depression force from the piece portion 100, so that the tip end portion thereof comes into contact with the steep slope 118 of the ratchet teeth of the tooth portion 112. Try to transmit this force to the ratchet teeth. Since the ratchet teeth 112 are connected to the sprocket 2, the tip of the ratchet piece 102 receives a force Fp due to a load for driving from a steeper slope 118. The ratchet piece 102 to which opposite forces Fp and Fd are applied from both ends thereof rotates in the direction a and rises. The piece part 100 moves inward in the axial direction when the ratchet piece 102 rises, and pushes the disc spring 124 interposed between the piece part 100 and the supporter 130. The disc spring 124 opposes this and acts the elastic force Fr on the piece part 100. This force Fr and the force reflecting the pedal depression force that moves the piece part 100 in the axial direction are balanced in a short time. Thus, the stress strain of the disc spring 124, the clearance between the piece portion 100 and the tooth portion 112, the angle of the ratchet piece 102 with respect to the second engagement surface 110, the position of the piece portion 100 with respect to the vehicle body frame, and the disc spring 124 are pushed in. The applied pressure is a physical quantity that reflects the pedal effort. Therefore, it is possible to estimate the depression torque by detecting at least one of these.

  In the present embodiment, as an example, the stress strain of the disc spring 124 is detected. The controller 14 adds at least the signals from the two strain gauges 126 provided on the disc spring 124 (including an average calculation). By averaging and measuring the stress strain amounts at a plurality of locations in this way, the output change can be increased and the noise component can be smoothed even with the same stepping torque, so the SN ratio is improved and the torque estimation accuracy is further improved. Can be improved. This effect increases as the number of strain gauges increases.

  Further, when the pedal depression force is less than a predetermined value, the offset spring 136 creates a clearance between the back surface 101 of the piece 100 and the disc spring 124, so that the steel ball 152 is frequently applied to the disc spring 124. Less impact. Thereby, the noise component of the strain gauge signal can be reduced, and the stability of torque detection and electric assist control can be improved.

  The flow of the electric assist control of the present embodiment is the same as that of the second and third embodiments.

The fourth embodiment has the following more excellent effects.
1. Since the ratchet gear and the torque detection mechanism are realized by a single mechanism, the number of parts can be reduced, and a reduction in size, weight, and cost can be achieved.
2. The disc spring that integrates the load receiving unit and the load detection sensor is used in the part that detects the depression torque, and two functions are realized in one unit, so in addition to the above effects, further miniaturization, weight reduction and low cost can be achieved. Can be achieved.
3. As shown in the above items 1 and 2, since the torque detection mechanism has been reduced in size, weight and simplification at a higher level, the possibility of attaching the torque detection mechanism has been further expanded even for a normal bicycle.
4). For the reasons described in items 1 and 2 above, the load transmission loss is reduced as compared with the conventional mechanism, and an assist feeling with good control responsiveness can be realized.
5. Due to the reasons shown in items 1 and 2 above, there is no useless movement (until the sensor senses) the pedal compared to the conventional mechanism (using a coil spring), and the feeling when the pedal is depressed is While there was a feeling of elasticity, in this embodiment, it was the same as the feeling of a normal bicycle.

  Although the above is each embodiment of the present invention, the present invention is not limited to the above example, and can be arbitrarily and suitably changed within the scope of the gist of the present invention.

  For example, in each of the above embodiments, the electric motor is exemplified as the means for providing the auxiliary torque. However, the present invention is not limited to this, and any other power means such as a gasoline engine can be used. is there.

  Moreover, in each embodiment, it can change arbitrarily suitably whether any one of the piece and teeth of a ratchet gear is attached to a sprocket, and the other is attached to a drive shaft. For example, in the case of the fourth embodiment, the piece part 100 may be attached to the sprocket side, the tooth part 112 may be slidably attached to the drive shaft 4 and cannot be rotated, and the disc spring 124 may be pushed by the tooth part 112.

  In the second and fourth embodiments, an example in which there are three ratchet pieces has been described, but it is needless to say that there may be two or more ratchet pieces. The number of grooves and the number of protrusions of the rotation preventing means shown in FIGS. 16A, 16B, and 16C may be other than those described above.

  The configuration requirements described in the above-described one or two embodiments but not described in other embodiments can be applied to the other embodiments within the scope of not changing the gist thereof. For example, the rotation preventing means shown in FIGS. 16A, 16B, and 16C can be applied to both the second and third embodiments. Further, the ratchet gears of the second and fourth embodiments can be applied to the one-way clutch of the third embodiment. Further, a plurality of strain gauges according to the third embodiment may be provided in the same manner as in the fourth embodiment, and the output signals may be averaged.

  In addition, the type and shape of the elastic body arranged against the deformation of the ratchet gear can be arbitrarily and suitably changed. For example, a rubber elastic body can be used in addition to the disc spring and the coil spring.

  The physical quantity detected in each embodiment can be arbitrarily selected as long as it is based on the deformation of the ratchet gear as in the example given in the description of the fourth embodiment. For example, in the second embodiment, a piezoelectric sensor that detects a change in the extrusion pressure due to the axial displacement of the ratchet tooth portion may be used. It is also possible to attach a strain gauge to the ratchet piece and calculate the depression torque based on the stress strain amount of the ratchet piece. In the fourth embodiment, a piezoelectric sensor may be disposed on the inner bottom of the support. Further, the rotation angle of the ratchet piece may be detected by an encoder provided on the rotation shaft. Furthermore, a position sensor that detects the position of the piece portion with respect to the tooth portion may be provided.

  In addition, as a means for detecting stress strain, a strain gauge is taken as an example, but the present invention is not limited to this as long as a physical quantity related to stress strain can be detected.

FIG. 1 is a schematic view of a power-assisted bicycle according to the present invention. FIG. 2 is a top view and a side view of the NS polarization ring magnet constituting the rotational speed sensor according to the first embodiment of the present invention. FIG. 3 is a front view showing a state in which the rotational speed sensor according to the first embodiment is configured by assembling the NS polarization ring magnet of FIG. 2 on the gear surface, and a sectional side view taken along a vertical line. FIG. 4 is a perspective view of the rotation speed sensor according to the first embodiment. FIG. 5 is a waveform showing a temporal change of the magnetic field signal detected by the Hall element arranged adjacent to the NS polarization ring magnet. FIG. 6 is a view showing a torque detection mechanism of a power-assisted bicycle according to a second embodiment in which the rotational speed sensor of the present invention is assembled. FIG. 7 is a front view and a side view of a state in which a sprocket and a ratchet gear used in the power-assisted bicycle according to the second embodiment of the present invention are fitted. FIG. 8 is a schematic perspective view of a state in which the sprocket and the ratchet teeth are disassembled. FIG. 9 is a schematic perspective view showing a state in which a sprocket and a ratchet gear are fitted in order to explain the axial displacement of the ratchet tooth portion. FIG. 10 is a front view of the sprocket and the sprocket drive gear of the power-assisted bicycle according to the second embodiment. FIG. 11 is a front view and a side view of the sprocket drive gear. 12A and 12B are diagrams related to the third embodiment of the present invention, in which FIG. 12A is a front view of a sprocket according to the third embodiment, and FIG. 12B is a side cross-sectional view of a torque detection mechanism according to the third embodiment. FIG. FIG. 13 is a side sectional view of a torque detection mechanism according to the fourth embodiment of the present invention. FIG. 14 is an exploded perspective view of the ratchet gear constituting the torque detection mechanism shown in FIG. FIG. 15 is a diagram showing a fitting state of the teeth and pieces of the ratchet gear. FIG. 16 is a diagram showing an example of rotation preventing means for preventing relative rotation of the frame portion with respect to the drive shaft, (a) is a ball spline, (b) is a spline key, and (c) is a schematic configuration of a keyway. FIG. FIG. 17 is a perspective view of a conventional rotational speed sensor.

Claims (17)

A power-assisted bicycle that travels by adding auxiliary power corresponding to the pedal depression force acting on the drive shaft in parallel to the pedal depression force,
A gear that rotates as the power-assisted bicycle travels;
A ring magnet having flexibility that is formed in a sheet shape having a substantially flat surface and having a substantially constant thickness over the entire area, and the ring magnet has a surface on the rotating shaft of the gear. Attached to the gear to be vertically arranged, the surface was formed with a plurality of magnet sections so as to generate a magnetic field on the surface that varied spatially with a constant angular period along the circumferential direction. The ring magnet;
Rotational speed detection means for detecting a magnetic field at a fixed position adjacent to the surface of the ring magnet and obtaining the rotational speed of the gear based on the magnetic field;
One-way clutch means for connecting the drive shaft and the sprocket so as to transmit only rotation in one direction of the drive shaft to the sprocket, the one-way clutch means extending along the axial direction of the drive shaft Two parts arranged adjacent to each other and elastic means are arranged, and the two parts engage with each other during rotation in the one direction and are opposed to each other by the elastic force of the elastic means, thereby maintaining an axial part interval. The one-way clutch means to be increased and disengaged when rotating in a direction opposite to the one direction;
Treading force detecting means for detecting distortion of the elastic means and obtaining the pedal depression force based on the distortion;
Control means for controlling the auxiliary power based on the rotation speed of the gear obtained by the rotation speed detection means and the pedal depression force obtained by the pedal effort detection means;
Power assisted bicycle with 2. The power assist bicycle according to claim 1, wherein the plurality of magnet sections of the ring magnet respectively have magnetic poles alternately reversed along the circumferential direction facing the surface. The power-assisted bicycle according to claim 2, wherein each magnet section of the ring magnet has one magnetic pole facing the surface and the other magnetic pole facing the surface opposite to the surface. The power assist bicycle according to claim 3, wherein a direction connecting both magnetic poles of each magnet section of the ring magnet is aligned substantially parallel to an axial direction of the ring magnet. The power-assisted bicycle according to claim 2, wherein each angle formed by the plurality of magnet sections of the ring magnet is substantially equal. The power-assisted bicycle according to claim 2, wherein adjacent magnet sections of the ring magnet are in contact with each other. The power-assisted bicycle according to claim 1, wherein the magnetic field generated on the surface of the ring magnet of the ring magnet changes in a sine wave shape with an angle between two adjacent magnet sections as a constant angular period. The rotational speed detection sensor according to claim 1, wherein the ring magnet has an annular shape with a hole formed in the center. The power assist bicycle according to claim 1, wherein the ring magnet is housed in a groove formed in the gear. The power assist bicycle according to claim 9, wherein the ring magnet is fixed in the groove with an adhesive. The power-assisted bicycle according to claim 9, wherein a surface of the ring magnet housed in the groove is flush with a surface outside the groove of the detected portion. The power-assisted bicycle according to claim 1, wherein the rotation speed detection means detects a magnetic field of the ring magnet using a Hall element. Either one of the two parts is slidable along the axial direction and is attached to the drive shaft via an anti-rotation means so as to prevent relative rotation with respect to the drive shaft, and the other is The power-assisted bicycle according to any one of claims 1 to 12, wherein the power-assisted bicycle is connected to a sprocket. Any one of the two parts slidably attached in the axial direction via the rotation preventing means is supported so that the elastic means can come into contact with the back surface opposite to the engagement surface. The power-assisted bicycle according to claim 13. The power-assisted bicycle according to claim 14, wherein the elastic means is a disc spring. The power-assisted bicycle according to claim 15, wherein the disc spring is provided with one or more strain gauges for detecting strain of the elastic means. The power assisted bicycle according to claim 14 , wherein the auxiliary power is supplied by an electric motor.

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