JP2008254592A - Power-assisted bicycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power-assisted bicycle for performing a motor assisting control under an assisting ratio suitable for a crank angle. <P>SOLUTION: A motor assisted bicycle runs with an auxiliary power together with a treading power. The treading power is detected, the number of hole element outputted pulses is counted and a bicycle speed V is detected (300, 302, and 304). After a treading state is detected in response to a variation in treading operation, the crank angle at the time of detection is set to a starting angle θs (308), a maximum treading power angle θm0 from the starting angle θs and a finishing angle θe0 are determined (310), and an assisting ratio pattern Ar acting as a function between a bicycle speed V and a crank angle θ (312). An actual crank angle θ is detected with the number of pulse count from the starting angle θs (314), the assisting ratio corresponding to the detected crank angle is calculated from the determined assisting ratio, an auxiliary power is calculated in reference to the assisting ratio and the detected treading power and a motor means is controlled in such a way that the auxiliary power may be outputted (316). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrically assisted bicycle capable of changing an assist ratio.

  Conventionally, the assist ratio of the electrically assisted bicycle (ratio of the output of the electric motor to the pedaling force) is set within the legal range in consideration of fuel consumption, assist feeling, etc. according to the vehicle speed.

  For example, in Patent Document 1 below, in an electrically assisted bicycle, the assist ratio becomes a substantially constant value in a low and medium vehicle speed range, gradually decreases in a high vehicle speed region, and is substantially 0 or in a low and medium vehicle speed region. A technique is disclosed that includes a controller that controls the driving force of an electric motor so that the driving force is reduced to a substantially constant value smaller than the assist ratio.

In the above technique, the assist ratio is changed for each vehicle speed range, as shown in FIGS. 7A, 7B, and 7C of Patent Document 1. FIG. 7 shows temporal changes in the driving force FM and the pedaling force FL, and a wave corresponding to one cycle of this change corresponds to half a pedal crank rotation. It can be understood from the figure that the assist ratio (F _M / F _L ) within the same vehicle speed per half rotation of the pedal crank is maintained constant.

However, in the above prior art, since the assist ratio is constant regardless of the crank angle, the auxiliary power becomes too large when the vehicle body is started by sudden start, etc. At the crank angle at the time of pedaling, the auxiliary power tends to be smaller than necessary.
JP-A-6-107266 (Japanese Patent No. 2623419)

  The present invention has been made in view of the above-described facts, and an object thereof is to provide an electric assist bicycle capable of executing electric assist control with an assist ratio suitable for a crank angle.

  In order to solve the above problems, the present invention is an electrically assisted bicycle that travels by the rotation of a pedal crank by a pedaling force, and includes an electric means for generating auxiliary power, and for adding the auxiliary power to the pedaling force in parallel. Resultant force means, pedal force detecting means for detecting pedal force, crank angle detecting means for detecting a crank angle that is an angle of the pedal crank with respect to the vehicle body, and an assist ratio for determining an assist ratio pattern at least as a function of the crank angle The assist means corresponding to the detected crank angle is determined from the determined assist ratio pattern, the assist power is calculated from the assist ratio and the detected pedaling force, and the assist power is output. And a control means for controlling the electric means.

  According to the present invention, an assist ratio corresponding to the detected crank angle is obtained from at least an assist ratio pattern as a function of the crank angle, and the auxiliary power is calculated from the assist ratio and the detected pedaling force. Since the electric assist control is performed by adding to the pedaling force, an appropriate auxiliary power suitable for the crank angle can be achieved.

  Preferably, the assist ratio pattern determined by the assist ratio determining means is a function of the crank angle and the vehicle speed of the electrically assisted bicycle.

  In the pedal half-turn cycle, when the depression angle is defined as the depression angle, the crank angle when the depression force is maximum is defined as the maximum depression force angle, and the crank angle when the depression is completed is defined as the depression angle. The assist ratio pattern determined by the assist ratio determining means is defined from the start angle to the end angle.

  Preferably, in the assist ratio pattern determined by the assist ratio determining means, the assist ratio is gradually increased when the crank angle changes from the start angle to the maximum pedaling force angle, and the assist ratio is maximized at the maximum pedaling force angle. When the angle changes from the maximum pedaling force angle to the end angle, the assist ratio is gradually reduced. Accordingly, the auxiliary power can be kept relatively small as long as the crank angle is small, for example, when the vehicle body is started by sudden start. Furthermore, the auxiliary power can be made relatively large at the crank angle at the maximum pedaling force that requires the most auxiliary power.

  In one aspect of the assist ratio determining means, when the depression start angle is detected, an assist ratio pattern having the maximum depression force angle and the depression end angle as typical fixed values is determined.

  In another aspect of the assist ratio determining means, a pedal force pattern for monitoring a pedal force pattern as a function of a crank angle based on a pedal force detected by the pedal force detector and a crank angle detected by the crank angle detector. Monitoring means is further provided, and the assist ratio determining means determines the assist ratio pattern based on the pedaling force pattern monitored by the pedaling force pattern monitoring means. Therefore, according to this aspect, it is possible to travel at an assist ratio suitable for a pedaling force pattern that varies according to individual differences, road surface conditions, and the like.

  In this aspect, as an example, the pedaling force pattern monitoring unit monitors the pedaling force pattern by extracting at least the maximum pedaling force angle and the pedaling end angle as parameters characterizing the pedaling force pattern, and the assist ratio determining unit Determines an assist ratio pattern having the characteristic parameter of the pedaling force pattern. The characteristic parameter may include a maximum pedaling force value of the pedaling force pattern.

  Preferably, the pedaling force pattern monitoring unit may obtain respective average calculation values of a maximum pedaling force angle and a pedaling end angle of a plurality of past pedaling force patterns as the characteristic parameter. The plurality of past pedaling force patterns may be any of a plurality of pedaling force patterns immediately before being sequentially detected while the electric assist bicycle is running or a plurality of pedaling force patterns detected within a certain learning period. Good.

  In still another aspect of the assist ratio determining means, a storage means storing a plurality of assist ratio patterns, a pedaling force detected by the pedaling force detecting means, and a crank angle detected by the crank angle detecting means, Pedal force pattern monitoring means for monitoring a pedal force pattern as a function of an angle, and the assist ratio determining means receives an assist ratio pattern corresponding to the pedal force pattern monitored by the pedal force pattern monitoring means from the storage means. Search and decide. Therefore, according to this aspect, it is possible to travel at an assist ratio suitable for a pedaling force pattern that varies according to individual differences, road surface conditions, and the like.

  One aspect of the crank angle detection means includes a disk fixed coaxially to the sprocket, a plurality of permanent magnets equally arranged on one plate surface side of the disk, and the one plate of the disk. A magnetic field detection means fixed to the vehicle body adjacent to the surface side, and a counting means for counting a magnetic field pulse signal from the magnetic field detection means, and when the start of depression is detected by the pedaling force detection means The crank angle is detected based on the count value of the magnetic field pulse signal counted by the counting means. The vehicle speed can also be detected from the count value of the magnetic field pulse signal.

  Preferably, the disk is configured as a gear having a plurality of teeth on the outer periphery, and the resultant force means is configured by meshing the disk gear with the output gear of the electric means.

  More preferably, it further includes a one-way clutch that connects the drive shaft and the sprocket so as to transmit only one-way rotation corresponding to the vehicle body forward direction of the drive shaft to which the pedal crank is connected, to the sprocket, The one-way clutch includes a piece portion on which a plurality of front pieces are formed, and a tooth portion on which a plurality of teeth that respectively engage with the plurality of pieces are formed, and any one of the piece portion and the tooth portion One of them is formed on the plate surface of the disk.

  More preferably, the other of the piece portion and the tooth portion that is not formed on the disk is attached to the drive shaft so as not to rotate relative to the drive shaft and to be slidable in the axial direction. When rotating, the piece and the tooth engage so as to lock the relative rotation between the piece and the tooth, and the other of the piece and the tooth is the elastic force of the elastic means. When the drive shaft is rotated in a direction opposite to the one direction at an axial distance corresponding to a pedaling force against one of the piece parts and the tooth parts, the space between the piece parts and the tooth parts is So that the relative rotation of the elastic means is released, the axial distance is reduced by the elastic force of the elastic means, and the treading force detecting means detects the elastic strain of the elastic means. By Determining the pedal force Te. In this aspect, the disk functions as an integral component of the one-way clutch constituting the pedal force detection means, the resultant force means, and the pedal detection means. As a result, the number of parts can be reduced and the axial space can be saved in the electrically assisted bicycle. Further, the gear of the disk can function as a reduction gear at the time of resultant force by adjusting the gear ratio, and further as a vehicle speed detection means that also serves as a pedal detection means.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows an outline of the electrically assisted bicycle 1. As shown in the figure, the main skeleton portion of the electrically assisted bicycle 1 is composed of a body frame 3 made of metal pipe, as in a normal bicycle. The body frame 3 includes a front wheel 20 and a rear wheel 22. , Handle 16 and saddle 18 are attached in a known manner.

  A drive shaft 4 is rotatably supported at the lower center of the vehicle body frame 3, and pedals 8L and 8R are attached to left and right ends thereof via pedal cranks 6L and 6R, respectively. A sprocket 2 is coaxially attached to the drive shaft 4 via a one-way clutch (99 in FIG. 3 described later) for transmitting only rotation in the R direction corresponding to the forward direction of the vehicle body. An endless rotating chain 12 is stretched between the sprocket 2 and a rear wheel power mechanism 10 provided at the center of the rear wheel 22.

  An electric assist unit 11 that generates an auxiliary electric force is attached to the electric assist bicycle 1. The generated auxiliary electric force is transmitted to the drive wheels 22 using a resultant force mechanism described later.

  An outline of the control system of the electric assist bicycle 1 housed in the electric assist unit 11 is shown in FIG. The control system of the electric assist bicycle 1 is directly connected to one microcomputer 14 that collectively controls electronic processing of the entire bicycle, an electric motor 37 capable of PWM control, and the microcomputer 14, and its control signal And an amplifier circuit 15 for amplifying the power of A battery 17 (external to the unit 11) for supplying power to the electric motor 37 is connected to the amplifier circuit 15. Further, the electric assist unit 11 accommodates a reduction gear for reducing the rotational speed of the motor.

  The microcomputer 14 receives magnetic field pulse signals for detecting a crank angle formed by the pedal crank 6R (6L) with respect to the vehicle body frame, and magnetic field signals 1, 2, and 3 for calculating the pedaling force. Means for generating these input signals will be described later. A signal for designating a mode of electric assist (for example, normal mode, turbo mode, eco mode, etc.) may also be input. The microcomputer 14 calculates the traveling speed, crank angle, and pedaling force from these input signals, and performs electronic processing for determining the assist ratio (auxiliary power / treading force) based on a predetermined algorithm. Next, in order to instruct the electric motor 37 to generate auxiliary power corresponding to the determined assist ratio, the microcomputer 14 sequentially outputs PWM commands corresponding to the auxiliary power.

Hereinafter, a pedaling force detection mechanism, a resultant force mechanism, and a crank angle and vehicle speed detection mechanism of an electrically assisted bicycle according to an embodiment of the present invention will be described.
(Treading force detection mechanism)
A pedal force detection mechanism that outputs magnetic field signals 1, 2, and 3 input to the microcomputer 14 will be described with reference to FIGS. The pedaling force detection mechanism detects a magnetic field that changes due to the deformation of the one-way clutch 99 according to the pedaling force.

  As shown in FIG. 3, the one-way clutch 99 includes a piece part 100 and a tooth part 112.

  As shown in FIG. 4A, the piece portion 100 has a substantially disk shape in which a piece portion bore 106 for receiving the drive shaft 4 is formed in the center portion, and is equiangular along the circumferential direction. Three rigid ratchet pieces 102 are arranged on the second engagement surface 110 side facing the tooth portion 112. Since the piece part 100 accommodates each ratchet piece 102, as shown in FIG.4 (b), the three recessed parts 170 are formed along the circumferential direction. Thus, the ratchet piece 102 is rotated in a state where the rotation shaft portion is accommodated in the recess 170, and the ratchet piece 102 changes an angle with respect to the second engagement surface 110 in accordance with the rotation.

  Referring to FIG. 4B again, the piece portion 100 is formed with linear grooves 171 that can accommodate the spring bars 104 adjacent to the respective concave portions 170, and both end portions of the three linear grooves 171. Extends to the outer peripheral edge of the piece 100. As shown in FIG. 4C, the spring bar 104 has one end A bent substantially vertically and the other end B bent in a U shape. When the spring bar 104 is mounted in the straight groove 171 of the piece part 100, as shown in FIG. 4 (b), the U-shaped B part ties the piece part 100 while sliding the spring bar 104 in the straight groove. The spring bar 104 can be easily attached to the piece part 100 simply by being clamped. However, if this is left, the spring bar 104 may fall off due to the pulling force from the B part. Therefore, the A part bent vertically is engaged with the side wall of the piece part to prevent the spring bar from falling off. . Therefore, the spring bar 104 of this embodiment is compatible with both ease of attachment and prevention of disconnection.

  When the spring bar 104 is attached to the straight groove 171 of the piece part 100, the length direction of the ratchet piece 102 makes a predetermined angle with respect to the second engagement surface 110 when no external force is applied ( It rises in the direction of equilibrium 160) in FIG. As shown in FIG. 5, when the ratchet piece 102 is biased from the equilibrium direction 160 in the upward direction a or the downward direction b, the spring bar 104 has a slight elastic force applied to the ratchet piece 102 so as to return the bias to the equilibrium direction 160. Effect.

  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 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. 6A, 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.

  Further, as a method of attaching the piece portion 100 to the drive shaft 4, it is possible to use means other than the ball spline of FIG. For example, as shown in FIG. 6B, 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. 6B, 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. 6C, a fourth rotation prevention groove 108b extending in the axial direction and a fifth rotation prevention groove 140b facing the groove 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.

  As shown in FIG. 3, a disc spring 137 is interposed between the piece portion 100 and a support disk 151 fixed to the drive shaft 4. Both end portions of the disc spring 137 are in contact with the back surface of the piece portion 100 and the support disk 151, respectively. Therefore, the disc spring 137 opposes the sliding of the piece portion 100 in the axial direction with an elastic force.

  On the other hand, as shown in FIG. 7, the tooth portion 112 is formed on a first engagement surface 121 that is a surface of the power transmission gear 200. A plurality of ratchet teeth 114 for engaging with the ratchet piece 102 are formed on the first engagement surface 121. As shown in FIG. 5, the ratchet teeth 114 are formed in a staggered manner along the circumferential direction of the tooth portion periodically and with a steeper slope 118 with respect to the first engagement surface 121 and a gentler And a slope 116. The tooth portion 112 is driven in a state where the first engagement surface 121 faces the second engagement surface 110 of the piece portion 100 and the ratchet piece 102 and the ratchet teeth 112 are engaged (FIG. 5). The shaft 4 is pivotally supported so as to be slidable. That is, the drive shaft 4 is operatively connected to the tooth portion 112 only through the engagement portion between the ratchet piece 102 and the ratchet tooth 112.

  As shown in FIG. 3, the power transmission gear 200 including the tooth portion 112 is fixed coaxially with the sprocket 2 using a fixing pin 206, and a pedal shaft is attached to the tip of the drive shaft 4. Thus, the ratchet gear 99 for connecting the drive shaft 4 and the sprocket 2 so as to transmit only the rotation by the pedal depression force in the vehicle body forward direction to the sprocket 2 is completed.

  Further, a permanent magnet 161 formed in a ring shape is attached to the piece portion 100 of the ratchet gear 99 concentrically with the drive shaft 4 and the piece portion 100. The ring-shaped permanent magnet 161 is preferably configured so that one surface of the ring is N-pole and the opposite surface is S-pole, and the ring axial direction of the permanent magnet 161 and the axial direction of the ratchet gear 99 are Arranged to align.

  In addition, a plurality (three in this embodiment) of hall elements 162 for detecting the magnetic field are respectively arranged at three predetermined positions in a plane perpendicular to the axis of the drive shaft 4. Preferably, the three predetermined positions at which the Hall elements are arranged are positions substantially equidistant in the radial direction and approximately equiangular in the circumferential direction around the axis. Further, the predetermined position where the hall element 162 is disposed corresponds to a fixed position of the vehicle body frame in the vicinity of the ring-shaped permanent magnet 161. These Hall elements 162 are connected to the microcomputer 14 (FIG. 2). The magnetic field detection signals 1, 2, and 3 output from the three Hall elements 162 are input to the microcomputer 14 (FIG. 2) as described above.

  As an alternative embodiment, a ring member 163 made of a magnetic material such as iron can be used instead of the ring-shaped permanent magnet 161. In this case, the magnet 164 is fixed at a predetermined position where the piece portion 100 moves relatively, for example, a position close to the Hall element 162. The material of the ring member 163 can also be made of any material that can change the magnetic field of the magnet 164, for example, a diamagnetic material.

  Next, the operation of this pedal effort detection mechanism will be described.

  When the rider applies a pedaling force to the pedals 8R and 8L (FIG. 1) and rotates the drive shaft 4 in the vehicle body forward direction, the rotational force is pivotally supported with respect to the drive shaft 4 so that it cannot rotate and can slide. Is transmitted to the frame unit 100. At this time, as shown in FIG. 5, the ratchet piece 102 is given a force Fd corresponding to the pedal depression force from the piece portion 100, so that its tip portion 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. At this time, the piece part 100 moves inward in the axial direction by the rising of the ratchet piece 102 and pushes the disc spring 137 interposed between the piece part 100 and the support disk 151. The disc spring 137 counteracts this and applies an elastic force Fr to the piece portion 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 axial position of the piece 100 is a physical quantity that reflects the pedal effort.

  In the case of the embodiment using the ring-shaped permanent magnet, the magnetic field intensity detected by the Hall element 162 differs depending on the axial position of the piece part 100. That is, when the pedal depression force increases, the piece portion 100 slides inward in the axial direction, and the permanent magnet 161 approaches the Hall element 162, so that the magnetic field strength detected by the Hall element increases. Conversely, when the pedal effort is reduced, the piece 100 slides outward in the axial direction, and the permanent magnet 161 moves away from the Hall element 162, so that the magnetic field strength detected by the Hall element decreases.

  The microcomputer 14 calculates the average magnetic field strength by performing an average operation (including a simple addition operation) on the magnetic field detection signals detected by the three Hall elements 162. The microcomputer 14 stores a look-up table representing a functional relationship between the magnetic field strength and the axial position of the permanent magnet 161 reflecting the pedaling force in the memory, and calculates an average magnetic field calculated by referring to the table. The pedal depression force T is obtained from the strength.

  As described above, since the microcomputer 14 averages the magnetic fields in the axial direction at a plurality of locations, the microcomputer 14 can not only improve the SN ratio but also cancel out variations in the magnetic field strength caused by the shake of the piece portion 100. Thus, the pedal depression force T can be obtained more accurately.

  In the case of an alternative embodiment using a magnetic or diamagnetic ring member 163, the magnetic field distribution of the magnet 164 changes depending on the influence of the magnetic body or diamagnetic body depending on the axial position of the ring member 163. To do. Accordingly, in the alternative embodiment, the pedal depression force T can be obtained as described above based on the detected magnetic field strength.

The pedaling force detection mechanism described above has the following excellent effects.
(1) Since the disc spring 137 is in contact with the piece portion 100 and the support disk 151 that do not rotate relative to the drive shaft 4, the disc spring 137 also has the drive shaft 4, the piece portion 100, and the support disc 151. ,Rotate. Therefore, no friction is generated between the disc spring 137 and the piece 100, and no rotation resistance is generated.
(2) Since the one-way clutch and the pedaling force detection mechanism are realized by one mechanism, the number of parts can be reduced, and a reduction in size, weight and cost can be achieved.
(3) Since the magnetic force detection unit is provided close to the disc spring for detecting the treading force, there is no disc spring wear or rotational resistance, and the accuracy of the torque detector is improved. And durability can be improved.
(4) As shown in items (2) and (3) above, the pedal force detection mechanism has been reduced in size, weight and simplification to a higher level. Sex has further expanded.
(5) Due to the reasons described in the above items (2) and (3), a non-contact type treading force detection mechanism using a magnetic field strength is used compared to the conventional mechanism, thus realizing an assist feeling with good control responsiveness. it can.
(6) For the reasons shown in items (2) and (3) above, there is no unnecessary movement (until the sensor senses) the pedal compared to the conventional mechanism (using a coil spring), and the feeling when the pedal is depressed The conventional mechanism had a feeling of elasticity when depressed, whereas in the above example, it was the same as the feeling of a normal bicycle.
(Force mechanism)
A resultant force mechanism of the electrically assisted bicycle 1 will be described with reference to FIGS. 3 and 7.

  FIG. 3 shows the power transmission gear 200 fixed coaxially to the sprocket 2 using the fixing pin 206 as described above. As shown in FIG. 7, the power transmission gear 200 has a plurality of teeth 204 formed on the outer periphery.

As shown in FIG. 3, the teeth 204 of the power transmission gear 200 are engaged with a gear 220 provided at the tip of the auxiliary power output shaft 222 of the electric assist unit 11. Therefore, the auxiliary power output from the electric assist unit 11 is transmitted to the power transmission gear 200 via the shaft 222 and the gear 220, and is transmitted from the power transmission gear 200 to the driving wheel via the sprocket 2 and the chain 12. . Thus, the resultant force of the pedaling force and the auxiliary power is achieved. Since the number of teeth 204 of the power transmission gear 200 is larger than the number of teeth of the gear 220, the power transmission gear 200 also functions as a reduction gear.
(Crank angle and vehicle speed detection mechanism)
A crank angle detection mechanism of the electrically assisted bicycle 1 will be described with reference to FIGS. 3 and 7 to 8.

  As shown in FIG. 7, twelve permanent magnets 202 are equally divided into a circumference 12 on one plate surface side of the power transmission gear 200. These permanent magnets 202 emit one magnetic pole (N pole or S pole) to the surface of the plate surface, the other magnetic pole is directed to the opposite side of the surface, and the direction connecting both magnetic poles is the axis of the drive shaft 4. It is arranged to align in the direction. It is preferable that all the magnetic poles appearing on the surface of the plate surface are the same, but the magnetic poles of adjacent magnets 202 may be arranged alternately.

  Referring to FIG. 3, the hall element 210 is disposed at a position fixed to the body frame adjacent to the plate surface of the power transmission gear 200 on which the magnet 202 is disposed. The radial distance of the hall element 210 from the drive shaft 4 is set to be substantially the same as the radial distance of the permanent magnet 202 from the drive shaft 4. The power transmission gear 200 rotates with the rotation of the pedal, while the hall element 210 is stationary with respect to the vehicle body, so that the magnetic field of the permanent magnet 202 crosses the detection range of the hall element 210 one after another by the pedal crank rotation. Go. Accordingly, the Hall element 210 outputs a detection signal having a pulse number corresponding to the pedal crank rotation speed. This magnetic field pulse signal is input to the microcomputer 14 (FIG. 2).

  Since the power transmission gear 200 rotates together with the pedal crank and the sprocket 2, the rotational speed of the power transmission gear 200 reflects the vehicle speed and the crank angular speed. Thus, the microcomputer 14 can calculate the vehicle speed and the increment of the crank angle from the number of magnetic field pulse signals counted per unit time.

  Here, with reference to FIG. 8, a method of obtaining an (absolute) crank angle with respect to the vehicle body from the count number of the magnetic field pulse signal will be described. As shown in FIG. 8, the pedal 8R (8L) is typically started to be depressed at a crank angle of “starting angle”. Accordingly, when the pedaling force detected by the pedaling force detection mechanism described above exceeds a predetermined threshold, the crank angle can be regarded as a depression “starting angle”. The magnetic field pulse signal of the hall element 210 is counted from the time when the depression start angle is detected, and the crank angle with respect to the vehicle body on which the current pedal crank 6R (6L) is located is obtained from the count value (an increase in crank angle). Can do. Also, when the detected pedal force becomes smaller than a predetermined threshold and / or when the detected crank angle exceeds a predetermined angle, it is considered that the crank angle has exceeded the depression end angle, and the increment of the crank angle is reset. The above-described detection of the start of depression is executed again. Also, if the detected pedaling force is less than the predetermined threshold for more than the predetermined time, it is considered that the pedal is not depressed, such as when it is going down a slope, and the increment of the crank angle is reset. Then, the above-described detection of the start of depression is executed again.

As described above, the power transmission gear 200 is a means in which the tooth portion 112 of the one-way clutch 99 constituting the pedaling force detection means, the resultant force mechanism, the reduction gear at the time of the resultant force, the vehicle speed detection mechanism, and the pedal detection mechanism are integrated. Is functioning as Thereby, in the electrically assisted bicycle 1, the number of parts can be reduced and the space in the axial direction can be saved.
(Operation of the embodiment of the present invention)
As shown in FIG. 8, the depression of the right pedal crank 6R with respect to the pedal 8R is started at the depression start angle, and as the crank angle θ increases, the depression force gradually increases, the depression force becomes maximum at the maximum depression force angle, and then the depression force gradually increases. Decreases, the pedaling force becomes substantially zero at the depression end angle, and the pedal half rotation cycle in the right pedal crank 6R is completed. When the crank angle further increases by a certain angle from the end angle, the left pedal crank 6L starts to be depressed with respect to the pedal 8L, and similarly, the pedal half rotation cycle in the left pedal crank 6L is executed.

  FIG. 9 shows a graph of pedal effort and auxiliary power that varies as a function of crank angle. In FIG. 9, θs (k), θm (k), and θe (k) respectively indicate the depression start angle and the depression force in the k-th pedal half rotation cycle (cycle number k = 1, 2, 3,...). The maximum angle and the depression end angle. For example, if the pedal half-rotation cycle at k = 1 is related to the right pedal crank 6R, the pedal half-rotation cycle at k = 2 is related to the left pedal crank 6L, and so on. Appear.

  Note that θs (k), θm (k), and θe (k) increase on the graph as the number of cycles k increases, but hereinafter, when simply referred to as “crank angle”, θs Assume that (k) = 0 is reset. That is, the maximum pedaling force angle and the pedaling end angle, which will be described later, are crank angles when the start angle is 0, respectively.

As shown in FIG. 9, the pedaling force F _L (θ, k) gradually increases from the crank angle θs (k), becomes maximum at θm (k), and gradually decreases from there, and becomes substantially 0 at θe (k). Become. fm (θ, k) indicates a change in auxiliary power when the assist ratio when the vehicle speed is constant in the pedal half-rotation cycle is constant regardless of the crank angle in the cycle (conventional technology). FIG. 9 shows the auxiliary power added when the hatched portion has a constant assist ratio. It can be understood that fm (θ, k) also increases or decreases according to the change in the pedaling force F _L (θ, k).

On the other hand, F _M (θ, k) indicates auxiliary power based on assist ratio control depending on the crank angle according to the embodiment of the present invention. Here, the flow of the electric assist process of the electric assist bicycle 1 using the assist ratio control according to the present embodiment will be described with reference to the flowcharts of FIGS. 10 to 13.

  As shown in FIG. 10, the pedaling force FL detection process is executed by the pedaling force detection mechanism described above (step 300), and the output pulse number count process of the hall element 210 is executed (step 302). In steps 302 and 304, the microcomputer 14 determines whether the hall element 162 and the hall element 210 are independent of the situation where the pedal is actually depressed or the situation where the pedal force is not detected (for example, a situation where the pedal is downhill). The output signal from is constantly monitored. When the number of output pulses is counted in step 302, the vehicle speed V is detected from the number of pulses counted (step 304). Note that these steps 300, 302, and 304 are always executed by the microcomputer 14 even after shifting to the next step.

  Next, it is determined whether or not depression is detected by the detected change in the depression force FL (step 306). For example, when the detected pedaling force FL exceeds a predetermined threshold value, it is determined that the depression is started. When depression is detected (Yes in step 306), the crank angle at the time of depression detection is set to the start angle θs (step 308), and the maximum pedaling force angle θm0 and the end angle θe0 from the start angle θs are determined. In one embodiment, the maximum pedaling force angle θm0 and the end angle θe0 can be set to typical fixed values obtained in advance by experience.

  Next, an assist ratio pattern Ar (θ, V) as a function of the vehicle speed V and the crank angle θ is determined (step 312). When the maximum pedaling force angle θm0 and the end angle θe0 are always determined as fixed values in step 310, the assist ratio pattern Ar can always use the same change pattern for each speed range of the vehicle speed V. According to the assist ratio pattern Ar, for example, when the crank angle changes from the start angle θs to the maximum pedaling force angle θm0, the assist ratio is gradually increased, and the maximum assisting ratio is achieved at the maximum pedaling force angle θm0. When the pedaling force angle θm0 changes to the end angle θe0, the assist ratio is gradually decreased.

  When the assist ratio pattern Ar is determined, the crank angle θ is actually detected in real time from the pulse count from the start angle θs (step 314), and the assist ratio pattern Ar determined in step 312 is detected at the detected crank angle θ. The electric motor is controlled to realize the assist ratio. That is, the electric assist control is executed with the auxiliary power FM determined based on the assist ratio pattern Ar, the crank angle θ, the vehicle speed V, and the pedaling force FL (step 316). After the stepping end angle θe0, the process returns to step 306 and the same control is repeated from the stepping detection.

Auxiliary power controlled by the step 316 is illustrated in FIG. 9 as an auxiliary power F _{M (θ,} k). As shown in the figure, auxiliary power F _{M (θ,} k), when changing from the crank angle start angle θs to a predetermined angle to the maximum pedaling force angle Shitaemu0, the same assist ratio in the pedal half-cycle of the same vehicle It is controlled to be smaller than the auxiliary power f _M (θ, k) of the prior art that achieves the above. When the crank angle approaches the maximum pedaling force angle θm0 within a predetermined angle range, the auxiliary power F _M (θ, k) becomes larger than the auxiliary power f _M (θ, k), and the difference between the two at the maximum pedaling force angle θm0. Is controlled to be maximum. The auxiliary power F _M (θ, k) is controlled to be larger than the auxiliary power f _M (θ, k) even when the crank angle is after the maximum pedaling force angle θm0 and within the predetermined angle range from the angle. . When the crank angle exceeds a predetermined angle range from the maximum pedaling force angle θm0, the auxiliary power F _M (θ, k) is again controlled to be smaller than the auxiliary power f _M (θ, k). As a result, the resultant force of pedaling force FL (theta, k) and auxiliary power F _{M (θ,} k) is, in FIG. 9, S (θ, k) is expressed as the contour lines of the prior art force by (hatched portion ) Is slightly sharper than

  Therefore, according to the control for changing the assist ratio according to the crank angle according to the embodiment of the present invention, the auxiliary power can be kept relatively small as long as the crank angle is small, such as when the vehicle body is started by sudden start. it can. Furthermore, the auxiliary power can be made relatively large at the crank angle at the maximum pedaling force that requires the most auxiliary power.

  In step 310 of FIG. 10, the maximum pedaling force angle θm0 and the ending angle θe0 are always determined as fixed values. Is not limited. Considering this point, a method of changing the maximum pedaling force angle θm0 and the end angle θe0 depending on the situation will be described with reference to FIG. The control in FIG. 11 is implemented as a subroutine called in step 310 in FIG.

  As shown in FIG. 11, the pedaling force FL detected in step 300 of FIG. 10 and the count value of the Hall element output pulse counted in step 302 are delivered to this subroutine program (step 330, step 332). Next, the characteristic parameter of the change pattern of the treading force FL is extracted for each pedal half rotation cycle (step 334). As this characteristic parameter, for example, the maximum depression force angle θm (k) and the depression end angle θe (k) are extracted in each pedal half-rotation cycle k. As these extraction methods, regarding the depression end angle θe, as a crank angle when a crank angle of a certain level or more increases after the depression start angle θs is detected and the depression force FL starts to become a predetermined threshold value or less. Can be extracted. For the maximum pedaling force angle θm (k), the maximum pedaling force FLmax (k) is searched by a known maximum value search algorithm or the like when the crank angle is between the pedaling start angle θs and the pedaling end angle θe. The given crank angle is extracted as the maximum pedaling force angle θm (k).

  Next, the previous n pieces of data just before the data extracted in step 334 are averaged (step 336). For example, if the current pedal half-rotation cycle number is p, the past n maximum pedaling force angle data is θm (p−n), θm (p−n + 1),. . θm (p−1), and the average maximum pedaling force angle Avθm is calculated from these data as follows.

Av.theta.m = (. Theta.m (pn) +. Theta.m (pn-1) + .. theta.m (p-1)) / n
In addition, the past n stepping end angle data θe (p−n), θe (p−n + 1),. . The average maximum pedaling force angle Avθe is calculated from θe (p−1) as follows.

Avθe = (θe (p−n) + θe (p−n + 1) +... Θe (p−1)) / n
Further, the past n maximum pedaling force data FLmax (p−n), FLmax (p−n + 1),. . The average maximum pedaling force AvFLmax can be calculated from FLmax (p-1) as follows.

AvFLmax = (FLmax (pn) +. FLmax (p-1)) / n
When the average value is calculated in step 336, the process returns to step 310 of FIG. At this time, Avθm and Avθe obtained in step 336 are substituted for the maximum pedaling force angle θm0 and the end angle θe0, respectively, and the process proceeds to step 312. As described above, in this subroutine, the maximum pedaling force angle θm0 and the ending angle θe0 are obtained by averaging the past n pieces of data, so parameters applied to pedaling force patterns that vary according to individual differences, road surface conditions, etc. Can be set. In step 336, the average calculation is performed based on the past n pieces of data. For example, Avθm and Avθe are obtained based on the n pieces of data acquired during the travel of the specified constant learning period, and the learning period ends. After that, those average values can also be used as fixed values in step 310. In addition, n = 1 may be sufficient.

  Next, the method of step 312 in FIG. 10 for determining the assist ratio pattern Ar using Avθm and Avθe obtained in step 336 will be described with reference to FIG. The control in FIG. 12 is implemented as a subroutine called in step 312 in FIG.

  As shown in FIG. 12, the vehicle speed V, the average maximum pedaling force angle Avθm, and the average end angle Avθe are handed over to this subroutine (steps 350 and 352). The average maximum pedaling force AvFLmax may also be delivered. Next, a typical assist ratio pattern Ar at the vehicle speed V is changed based on the average maximum pedaling force angle Avθm and the average end angle Avθe. For example, a typical assist ratio pattern Ar as a function of the vehicle speed V and the crank angle θ is stored in the memory of the microcomputer 14. This typical assist ratio pattern Ar is stored as a symmetrical change pattern, for example, so that θm / (θe−θm) = 1 (assuming θs = 0), that is, centering on the maximum pedaling force angle. Yes. However, in practice, the ratio Avθm / (Avθe−Avθm) using the data delivered in step 352 is not always 1. Therefore, a typical assist ratio pattern Ar is changed according to the ratio Avθm / (Avθe−Avθm). For example, when θs ≦ crank angle θ ≦ Avθm, the typical pattern Ar is used as it is, and when Avθm <crank angle θ ≦ Avθm, the typical assist ratio pattern Ar is set in the X direction (the crank angle axis in FIG. 8). ) In a direction of Avθm / (Avθe−Avθm). In this manner, the assist ratio pattern Ar defined in the entire definition region of θs ≦ crank angle θ ≦ Avθe can be obtained. Furthermore, the maximum assist ratio of the typical assist ratio pattern Ar can be changed in accordance with the average maximum pedaling force AvFLmax delivered in step 352. For example, the average maximum pedaling force AvFLmax is classified into a plurality of stages according to the magnitude, and gains are associated with each stage. Then, the typical pattern Ar is increased or decreased in the Y direction (the direction of the force axis in FIG. 8) with the gain corresponding to the delivered AvFLmax.

  When the assist ratio is calculated in step 354, the subroutine is returned to step 312 in FIG. 10, and the electric assist control is executed with the calculated assist ratio. Therefore, it is possible to travel at an assist ratio suitable for a pedaling force pattern that varies according to individual differences, road surface conditions, and the like.

  Next, a method for determining the assist ratio pattern Ar by a method different from FIG. 12 will be described with reference to FIG. Note that the control shown in FIG. 13 is also implemented as a subroutine called in step 312 of FIG.

  As shown in FIG. 13, the vehicle speed V, the average maximum pedaling force angle Avθm, and the average end angle Avθe are handed over to this subroutine (steps 360, 362). At this time, the average maximum pedaling force AvFLmax may also be delivered.

  Next, one of a plurality of assist ratio patterns Ar at the vehicle speed V suitable for the average maximum pedaling force angle Avθm and the average end angle Avθe (or AvFLmax in addition thereto) is selected (step 364). In the present embodiment, the microcomputer 14 stores a plurality of assist ratio patterns in the memory, and each of these patterns is determined to be empirically suitable for each of various road surface conditions, for example. This is a typical pattern. Furthermore, feature parameter values associated with each typical pattern are stored in the memory. Examples of the characteristic parameter value include a ratio of maximum pedaling force angle θm / (end angle θe−maximum pedaling force angle θm), maximum pedaling force FLmax / crank angle θe for half pedal rotation cycle, and the like. Accordingly, in step 364, a feature parameter value is calculated based on Avθm, Avθe and / or AvFLmax delivered in step 362, and an assist ratio pattern corresponding to the feature parameter closest to the calculated feature parameter is retrieved from the memory. Thus, it is possible to select an assist ratio pattern that is most suitable for the current running state. If the crank angle definition area of the selected assist ratio pattern is different from the crank angle definition area of the average pedal effort FL delivered at step 362, the definition area as implemented at step 354 of FIG. Processing may be performed.

  When an assist ratio pattern is selected in step 364, the present subroutine is returned to, and the process returns to step 312 in FIG. 10, and electric assist control is executed with the selected assist ratio pattern. Therefore, also in the present embodiment, it is possible to travel with an assist ratio pattern suitable for a pedaling force pattern that varies according to individual differences, road surface conditions, and the like.

  In the assist ratio pattern selection process in step 364, a step of selecting one from a plurality of assist ratio patterns in accordance with a mode signal (for example, normal mode, turbo mode, eco mode, etc.) input to the microcomputer 14 is performed. May be added. The selection of the assist ratio pattern by the mode signal may be performed independently from step 364, and the typical assist ratio pattern used in step 354 of FIG. 12 may also be selected by the mode signal. it can.

  The above is the embodiment of the present invention, but the present invention is not limited to the above-described example, and can be arbitrarily modified within the scope of the gist of the present invention.

  For example, whether one of the piece 100 and the tooth 112 of the one-way clutch 99 is formed in the power transmission gear 200 and the other is attached to the drive shaft can be arbitrarily and suitably changed. For example, the piece part 100 may be formed on the power transmission gear 200 side, the tooth part 112 may be slidably and non-rotatably attached to the drive shaft 4, and the disc spring 137 may be pushed by the tooth part 112.

  Furthermore, the type and shape of the elastic body arranged to oppose the deformation of the one-way clutch 99 can be arbitrarily changed. Other than the disc spring, for example, an elastic body such as a coil spring or rubber may be used. In addition, although the Hall element is taken as an example of the means for detecting the magnetic field, it is not limited to this as long as the magnetic field can be detected.

  In addition, regarding the crank detection means and the pedaling force detection means, the position of the magnetic field detection means, the shape of the magnet and its mounting position, and the shape of the magnetic body or diamagnetic body and the mounting position thereof are also determined by the magnetic field pulse signal As long as it can detect a change in the magnetic field caused by the deformation, it can be suitably changed. Further, the number of magnetic field detection means, magnets, and magnetic bodies or diamagnetic bodies is not limited to the above example, and can be arbitrarily changed.

FIG. 1 is a schematic view of an electrically assisted bicycle according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing a control system of the electrically assisted bicycle shown in FIG. FIG. 3 is a side view of a one-way clutch used in the electrically assisted bicycle shown in FIG. 1 and incorporating a torque detection mechanism according to an embodiment of the present invention. FIG. 4 is a view showing the configuration of the one-way clutch piece and the spring bar used in the piece part, wherein (a) is a perspective view of the piece part with the spring bar attached, ) Is a perspective view of the piece part with the spring bar removed, and FIG. 5C is a side view of the spring bar. FIG. 5 is a diagram showing a fitting state of teeth and pieces of a one-way clutch (ratchet gear) in order to explain the principle of pedaling force detection of the electrically assisted bicycle shown in FIG. FIG. 6 is a view showing an example of rotation preventing means for preventing relative rotation of the piece 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 key groove. FIG. FIG. 7 is a front view and a side view of a power transmission gear used in the resultant force mechanism according to the embodiment of the present invention. FIG. 8 is an explanatory diagram showing a state in which the crank angle of the electrically assisted bicycle according to the embodiment of the present invention is in the stepping start angle, the maximum stepping force angle, and the stepping end angle. FIG. 9 shows the assisting power when the pedal effort, the assist power applied in the present embodiment, the resultant force of the pedal effort and the assist power, and the assist ratio is 1: 1 in the electrically assisted bicycle according to the embodiment of the present invention. It is a graph which shows a time change. FIG. 10 is a main flowchart showing a flow of control for changing the assist ratio according to the crank angle of the electrically assisted bicycle according to the embodiment of the present invention. FIG. 11 is a subroutine flowchart showing a flow of determining the maximum pedaling force angle and the end angle in the assist ratio change control shown in FIG. FIG. 12 is a subroutine flowchart showing a flow of determining the assist ratio as an example in the control of changing the assist ratio shown in FIG. FIG. 13 is a subroutine flowchart showing a flow of assist ratio determination as another example in the assist ratio change control shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric assist bicycle 2 Sprocket 3 Frame 4 Drive shaft 11 Electric assist unit 12 Chain 14 Microcomputer 15 Amplifier circuit 17 Battery 22 Drive wheel (rear wheel)
37 electric motor 37a output shaft of electric motor 99 one-way clutch 100 piece part 102 ratchet piece 108 first rotation prevention groove 112 tooth part 114 ratchet tooth 137 disc spring 140 second rotation prevention groove 150 steel ball 151 support disk 161 Ring-shaped permanent magnet 162 Hall element 163 Ring member (made of magnetic or diamagnetic material) 164 Permanent magnet 200 Auxiliary power transmission gear 202 Permanent magnet for crank angle detection 204 Tooth portion 206 of power transmission gear 206 Fixing pin 210 Hall element for detecting crank angle 220 Gear 222 Output shaft of auxiliary power

Claims (15)

An electrically assisted bicycle that runs with the rotation of a pedal crank by a pedaling force,
Electric means for generating auxiliary power;
Resultant force means for adding the auxiliary power in parallel to the pedal force;
Treading force detecting means for detecting treading force;
Crank angle detecting means for detecting a crank angle that is an angle of the pedal crank with respect to the vehicle body;
Assist ratio determining means for determining an assist ratio pattern as a function of at least a crank angle;
An assist ratio corresponding to the detected crank angle is obtained from the determined assist ratio pattern, an auxiliary power is calculated from the assist ratio and the detected pedaling force, and the electric means is controlled to output the auxiliary power Control means,
An electrically assisted bicycle.   The electrically assisted bicycle according to claim 1, wherein the assist ratio pattern determined by the assist ratio determining means is a function of the crank angle and a vehicle speed of the electrically assisted bicycle. In the pedal half rotation cycle, when the depression is started, the depression angle is defined as the depression angle, the maximum depression angle is defined as the maximum depression force angle, and the depression angle when the depression is completed is defined as the depression angle. ,
The power-assisted bicycle according to claim 1 or 2, wherein the assist ratio pattern determined by the assist ratio determining means is defined from the start angle to the end angle.   In the assist ratio pattern determined by the assist ratio determining means, the assist ratio is gradually increased when the crank angle changes from the start angle to the maximum pedaling force angle, and the assist ratio is maximized at the maximum pedaling force angle. The electrically assisted bicycle according to claim 3, wherein the assist ratio is gradually reduced when changing from a maximum pedaling force angle to the end angle.   5. The electric motor according to claim 3, wherein the assist ratio determining unit determines an assist ratio pattern having a maximum pedaling force angle and a pedaling end angle as typical fixed values when the stepping start angle is detected. Assist bicycle. Further comprising pedal force pattern monitoring means for monitoring the pedal force pattern as a function of the crank angle based on the pedal force detected by the pedal force detecting means and the crank angle detected by the crank angle detecting means;
The electric assist bicycle according to claim 3 or 4, wherein the assist ratio determining means determines the assist ratio pattern based on a pedaling force pattern monitored by the pedaling force pattern monitoring means. The pedaling force pattern monitoring means monitors the pedaling force pattern by extracting at least the maximum pedaling force angle and the pedaling end angle as parameters characterizing the pedaling force pattern,
The electrically assisted bicycle according to claim 6, wherein the assist ratio determining unit determines an assist ratio pattern having the characteristic parameter of the pedaling force pattern.   The electrically assisted bicycle according to claim 7, wherein the pedal force pattern monitoring unit obtains respective average calculation values of a maximum pedaling force angle and a pedaling end angle of a plurality of past pedaling force patterns as the characteristic parameter.   The plurality of past pedaling force patterns are any of a plurality of pedaling force patterns immediately before being sequentially detected while the electric assist bicycle is running, or a plurality of pedaling force patterns detected within a certain learning period. The electrically assisted bicycle according to claim 8.   The electrically assisted bicycle according to any one of claims 7 to 9, wherein the characteristic parameter includes a maximum pedaling force value of the pedaling force pattern. Storage means for storing a plurality of assist ratio patterns;
Pedal force pattern monitoring means for monitoring a pedal force pattern as a function of the crank angle based on the pedal force detected by the pedal force detection means and the crank angle detected by the crank angle detection means;
5. The electrically assisted bicycle according to claim 3, wherein the assist ratio determining unit searches and determines an assist ratio pattern corresponding to the pedaling force pattern monitored by the pedaling force pattern monitoring unit from the storage unit. The crank angle detection means includes
A disk fixed coaxially to the sprocket;
A plurality of permanent magnets equally spaced on one plate surface side of the disk;
Magnetic field detection means fixed to the vehicle body adjacent to the one plate surface side of the disk;
Counting means for counting magnetic field pulse signals from the magnetic field detection means;
With
The electric motor according to any one of claims 1 to 11, wherein the crank angle is detected based on a count value of a magnetic field pulse signal counted by the counting means from when the depression start is detected by the pedaling force detection means. Assist bicycle. The disc is configured as a gear having a plurality of teeth around the outside;
The electrically assisted bicycle according to claim 12, wherein the resultant force means is configured by meshing a gear of the disk and an output gear of the electric means. A one-way clutch that connects the drive shaft and the sprocket so as to transmit to the sprocket only rotation in one direction corresponding to the vehicle body forward direction of the drive shaft to which the pedal crank is connected;
The one-way clutch is
A piece part formed with a plurality of pieces in front,
A tooth portion formed with a plurality of teeth each engaging with the plurality of pieces;
With
The electrically assisted bicycle according to claim 12 or 13, wherein one of the piece part and the tooth part is formed on a plate surface of the disk. The other of the piece part and the tooth part that is not formed on the disk is attached to the drive shaft so as not to rotate relative to the drive shaft and to be slidable in the axial direction.
When the drive shaft rotates in the one direction, the piece and the tooth are engaged so as to lock the relative rotation between the piece and the tooth, and the piece and the tooth The other is separated from one of the piece part and the tooth part at an axial distance corresponding to the pedaling force against the elastic force of the elastic means,
When the drive shaft rotates in a direction opposite to the one direction, the locking by the teeth and the pieces is released so as to enable relative rotation between the pieces and the teeth, and the elasticity of the elastic means Force reduces the axial distance,
The electrically assisted bicycle according to claim 14, wherein the pedaling force detecting means obtains the pedaling force by detecting an elastic strain of the elastic means.

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