JP2014198505A - Power-assisted bicycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power-assisted bicycle in which simplification of a structure can be achieved, while pedaling force is accurately detected with a non-contact type magnetostrictive sensor.SOLUTION: A pedaling force sensor SE3 is a non-contact type magnetostrictive sensor 37 including two magnetostrictive films 101, 102 formed on a hollow shaft 42 and two coils 39, 40. The two magnetostrictive films 101, 102 are formed by arranging belt-like bodies each having a predetermined width and wound around an outer peripheral surface of the hollow shaft 42 so as to be adjacent to each other in an axial direction and so as not to overlap each other. The two magnetostrictive films 101, 102 include a first magnetostrictive film 101 in which the impedance output of the coil 39 decreases as input torque increases from zero, and a second magnetostrictive film 102 in which the impedance output of the coil 40 increases as the input torque increases from the zero. The first magnetostrictive film 101 is disposed at a side adjacent to a clutch outer 42c, and the second magnetostrictive film 102 is disposed at a side separated from the clutch outer 42c.

Description

  The present invention relates to an electrically assisted bicycle, and more particularly to an electrically assisted bicycle in which a driving force is assisted by a motor in accordance with a pedaling force detected by a magnetostrictive sensor.

  2. Description of the Related Art Conventionally, an electrically assisted bicycle that assists a driving force by a motor in accordance with a pedaling force by human power is known. In such an electrically assisted bicycle, usually, a motor driving force is applied to a drive chain or a pedal crankshaft that transmits a driving force to the rear wheels. This is done by a well-known torque sensor on the shaft. For this torque sensor, a non-contact type magnetostrictive sensor using a magnetostrictive element that converts a change in strain generated by applying torque into a change in magnetic field is often applied.

  Japanese Patent Application Laid-Open No. 2004-133867 discloses an electrically assisted bicycle that applies a motor driving force to a pedal crankshaft, and has a dual-structure pedal crankshaft composed of an inner shaft and an outer hollow shaft. A structure in which the magnetostrictive element is arranged is disclosed.

  In the electrically assisted bicycle described in Patent Document 1, the hollow shaft is fixed to the pedal crankshaft by a spline formed on the inner peripheral portion on one end side of the hollow shaft, and the other end side of the hollow shaft is connected via a one-way clutch. A motor driving force input gear is attached. A drive sprocket around which a drive chain that transmits driving force to the rear wheels is wound is fixed to the input gear.

JP 2008-114851 A

  However, in the technique described in Patent Document 1, the structure is likely to be complicated because three elements of the hollow shaft, the one-way clutch, and the input gear are interposed between the pedal crankshaft and the drive sprocket. In addition, an increase in the number of parts may cause backlash due to gaps between parts.

  Further, SNCM (nickel molybdenum steel) and Ni-Fe (permalloy) are known as typical magnetostrictive elements used for non-contact type magnetostrictive sensors. Of these, when SNCM is used, the change in the magnetic field with respect to the change in torque is small, in other words, the change in impedance of the coil that detects the change in magnetic field due to the magnetostrictive element is small. In the case where they are arranged close to each other, there is a problem that a complicated amplifier circuit for increasing the S / N ratio of the output signal is required.

  On the other hand, when Ni—Fe is used, there is an advantage that a complicated amplification circuit is not required because the impedance change of the coil with respect to the torque change is large, but the maximum pedal depression force is the torque generated by Ni—Fe. Since it exceeds the region suitable for detection, there is a problem that it is difficult to detect the correct pedal effort in the region beyond the region.

  An object of the present invention is to solve the above-described problems of the prior art and to provide an electric assist bicycle capable of simplifying the structure while accurately detecting the pedaling force with a non-contact type magnetostrictive sensor.

  In order to achieve the above object, the present invention provides a pedal effort sensor (SE3) for detecting an input torque to the pedal crankshaft (14) and assisting the driving force according to the output of the pedal effort sensor (SE3). In an electrically assisted bicycle (1) having a motor (17) for performing, the rotational drive force of the pedal crankshaft (14) is disposed on the outer peripheral side of the pedal crankshaft (14) via a one-way clutch (78). The pedal depression force sensor (SE3) includes two magnetostrictive films (101, 102) formed on the hollow shaft (42) and the two magnetostrictive films (101, 102). 102) is a non-contact type magnetostrictive sensor (37) including two coils (39, 40) respectively corresponding to the two magnetostrictive films (101, 102) of the hollow shaft (42). The strips of a predetermined width wound around the circumferential surface are arranged close to each other in the axial direction so as not to overlap each other, and the two magnetostrictive films (101, 102) are arranged so that the coil (39 ) And a second magnetostrictive film (102) that decreases with an extreme value after the impedance output of the coil (40) increases as the input torque increases from zero. The one-way clutch (78) has a clutch outer (42c) formed integrally with the hollow shaft (42), and the first magnetostrictive film (42c) is disposed on the side close to the clutch outer (42c). 101), and the second magnetostrictive film (102) is disposed on the side away from the clutch outer (42c).

  Further, the two magnetic films (101, 102) are given different magnetic anisotropies, and the input torque is detected as a difference between impedance outputs detected by the two coils (39, 40), respectively. The point calculated based on this is the second feature.

  The one-way clutch (78) includes a clutch inner (14a) provided integrally with the pedal crankshaft (14), a clutch outer (42c) provided integrally with the hollow shaft (42), and the clutch inner A third feature is that the mechanism includes a claw (78a) that transmits a driving force from (14a) to the clutch outer (42c).

  Further, the driving force is transmitted to the rear wheel (WR) via the input gear (27) to which the driving force of the motor (17) is applied and the drive chain (22) to the hollow shaft (42). There is a fourth feature in that the drive sprocket (15) is directly fixed.

  The magnetostrictive film (101, 102) has a fifth feature made of Ni-Fe attached to the surface of the hollow shaft (42) by plating or sputtering.

  The clutch outer (42c) is formed at the left end of the hollow shaft (42) in the vehicle width direction, and the drive sprocket (15) is fixed to the right end of the hollow shaft (42) in the vehicle width direction. The spline (42a) is formed, and the magnetostrictive film (101, 102) is provided between the clutch outer (42c) and the spline (42a).

  Furthermore, an input gear (27) to which the driving force of the motor (17) is applied is disposed between the magnetostrictive films (101, 102) and the drive sprocket (15) on the hollow shaft (42). There is a seventh feature in this point.

  According to a first feature, the apparatus includes a hollow shaft that is disposed on an outer peripheral side of the pedal crankshaft and transmits a rotational driving force of the pedal crankshaft via a one-way clutch, and the pedal treading force sensor is the hollow A non-contact type magnetostrictive sensor including two magnetostrictive films formed on a shaft and two coils respectively corresponding to the two magnetostrictive films, wherein the two magnetostrictive films are wound around an outer peripheral surface of the hollow shaft. The two magnetostrictive films are arranged close to each other in the axial direction so as not to overlap each other, and the two magnetostrictive films rotate with a first magnetostrictive film in which the impedance output of the coil decreases as the input torque increases from zero. A second magnetostrictive film that decreases with an extremum after the impedance output of the coil increases as the input torque increases from zero, and the one-way clutch includes the hollow shaft and Since the first magnetostrictive film is disposed on the side close to the clutch outer and the second magnetostrictive film is disposed on the side away from the clutch outer, the pedal has a clutch outer formed on the body. By integrally forming the clutch outer on the hollow shaft that transmits the rotational driving force of the crankshaft, it is possible to reduce the number of parts of the power transmission system and to prevent rattling due to gaps between the parts.

  Further, even when a large pedal depression force is input and stress concentrates on the one-way clutch, and the effect reaches the magnetostrictive film of the hollow shaft, the accuracy of torque detection can be maintained.

  According to the second feature, the two magnetic films are given different magnetic anisotropies, and the input torque is calculated based on a difference between impedance outputs respectively detected by the two coils. Therefore, the structure of the assist drive unit of the electrically assisted bicycle can be simplified using a general magnetostrictive sensor.

  According to a third feature, the one-way clutch transmits a driving force from the clutch inner to the clutch outer, a clutch inner provided integrally with the pedal crankshaft, a clutch outer provided integrally with the hollow shaft, and the clutch outer. Since the mechanism includes a claw, the number of parts and the cost can be reduced with a simple structure.

  According to the fourth feature, the input gear to which the driving force of the motor is applied and the drive sprocket for transmitting the driving force to the rear wheel via the drive chain are directly fixed to the hollow shaft. Therefore, by providing the hollow shaft with a function of supporting a plurality of components, it is possible to reduce the number of components and prevent backlash due to a gap between the components.

  According to a fifth feature, since the magnetostrictive film is made of Ni—Fe deposited on the surface of the hollow shaft by plating or sputtering, a large impedance change is caused as compared with an SNCM known as a general magnetostrictive element. Since it can be detected, a complicated amplifier circuit is not required, and the configuration can be simplified.

  According to the sixth feature, the clutch outer is formed at the left end of the hollow shaft in the vehicle width direction, and a spline for fixing the drive sprocket is formed at the right end of the hollow shaft in the vehicle width direction. Since the magnetostrictive film is provided between the clutch outer and the spline, a space between the clutch outer and the drive sprocket can be obtained while obtaining an appearance in which the drive sprocket is exposed on the right side in the vehicle width direction as in a normal bicycle. It is possible to dispose a coil for detecting a change in the magnetic field of the magnetostrictive film by effectively utilizing. Thereby, size reduction of an assist drive unit can be achieved.

  According to the seventh feature, since the input gear to which the driving force of the motor is applied is disposed between the magnetostrictive film and the drive sprocket on the hollow shaft, the magnetostriction in the driving force transmission path is provided. By providing the input gear on the downstream side of the sensor, it is possible to prevent the magnetostrictive sensor output from being affected due to the auxiliary force of the motor. Further, the assist drive unit can be miniaturized by using the space to attach the input gear.

1 is a left side view of an electrically assisted bicycle according to an embodiment of the present invention. It is a left view which shows the principal part of an electrically assisted bicycle. It is a right view which shows the principal part of an electrically assisted bicycle. FIG. 4 is a sectional view taken along line AA in FIG. 3. It is a block diagram which shows the motor control part which performs assist / regenerative control, and its periphery structure. It is a left view of a hollow shaft. It is the BB sectional view taken on the line of FIG. It is a stress analysis figure of a hollow shaft when a crew member steps on a pedal and makes a crankshaft rotate forward. It is an output conceptual diagram of a magnetostriction sensor. FIG. 6 is a relationship diagram between impedance output and distortion (the present invention). FIG. 6 is a relationship diagram between impedance output and distortion (arrangement different from the present invention).

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a left side view of an electrically assisted bicycle 1 according to an embodiment of the present invention. 2 is a left side view showing a main part of the electrically assisted bicycle 1 in FIG. 1, FIG. 3 is a right side view thereof, and FIG. 4 is a sectional view taken along line AA in FIG.

  The electric assist bicycle 1 includes a head pipe 3 positioned in front of the vehicle body, a down frame 2 extending rearward and downward from the head pipe 3, and a seat pipe 6 rising upward from a rear end of the down frame 2. A front fork 5 extending downward is steerably connected to the head pipe 3, and a front wheel WF is pivotally supported at the lower end of the front fork 5. A handle 4 is provided at the upper end of the head pipe 3, and a pair of left and right brake levers 44 are attached to both ends of the handle 4. The support portion of the brake lever 44 is provided with a brake switch SW for detecting a brake operation.

  A rear fork 11 extending rearward is disposed at the rear end of the down frame 2, and a rear wheel WR is pivotally supported at the rear end of the rear fork 11. A pair of left and right stays 10 are disposed between the upper portion of the seat pipe 6 and the rear portion of the rear fork 11.

  The down frame 2 and the rear fork 11 support the assist drive unit 24. A seat post 8 is supported on the seat pipe 6 so that the vertical position of the seat 7 can be adjusted. A battery 9 for supplying electric power to the assist drive unit 24 is detachably attached to the stay 20 of the seat pipe 6 behind the seat pipe 6.

  A crankshaft (pedal crankshaft) 14 extending in the vehicle width direction is disposed through the assist drive unit 24 and a sprocket (drive sprocket) 15. A crank 12L having a pedal 13L and a crank 12R having a pedal 13R are fixed on both sides of the crankshaft 14, and a torque is applied to the crankshaft 14 by a driver rowing the pedals 13L and 13R. .

  The crankshaft 14 is rotatably supported inside a cylindrical hollow shaft 42 via a one-way clutch 78 (see FIG. 3), and the sprocket 15 is fixed to the outer peripheral side of the hollow shaft 42 by spline engagement. Has been. The rotation of the sprocket 15 is transmitted via a drive chain 22 to a sprocket (driven sprocket) 23 on the rear wheel WR side.

  The assist drive unit 24 includes a brushless motor (hereinafter also simply referred to as a motor) 17, a drive driver 25 for driving the motor 17, and an output of a pedal depression force sensor, which will be described later, inside a case 26 as a housing. The controller 16 that performs PWM control of the drive driver 25 based on the values, the drive gear 35 that rotates in mesh with the drive shaft 18 of the motor 17, the output shaft 33 that rotates together with the drive gear 35, and the output shaft 33 And an input gear 27 that meshes with and rotates. Similarly to the sprocket 15, the input gear 27 is fixed to the hollow shaft 42 of the crankshaft 14 by spline engagement. The output shaft 33 is rotatably supported by a bearing 48 fixed to the left case half 28 and a bearing 49 fixed to the right case half 29.

  The drive shaft 18 of the motor 17 is provided with a motor rotation speed sensor SE1 that detects the rotation speed of the motor 17. A vehicle speed sensor SE2 is provided on the axle of the front wheel WF, and a pedal depression sensor SE3 for detecting a pedal depression force by the driver is provided on the crankshaft 14. The motor rotation speed sensor SE1 includes a magnet provided on the outer peripheral portion of the drive shaft 18 of the motor 17 and a Hall IC that detects passage of the magnet. The pedal depression force sensor SE3 includes a non-contact type magnetostrictive sensor 37 (see FIG. 4) disposed on the outer peripheral portion of the hollow shaft 42. The vehicle speed sensor SE1 may be provided on the rear wheel WR or the like.

  The controller 16 serving as a motor control unit calculates the force by which the driver steps on the pedals 13L and 13R in the vertical direction based on the rotational torque value detected by the magnetostrictive sensor 37, and determines the stepping force and the vehicle speed of the electrically assisted bicycle 1. The drive driver 25 of the motor 17 is PWM controlled so that an assist torque determined by the corresponding assist ratio is generated.

  The drive driver 25 has a three-phase switching element composed of a U phase, a V phase, and a W phase. The controller 16 performs PWM control of the drive driver 25 by performing on / off control of each UVW-phase switching element with a predetermined duty ratio. The drive driver 25 converts the DC power of the battery 9 into three-phase AC power by this PWM control, and energizes the U-phase, V-phase, and W-phase stator coils of the motor 17.

  The assist torque generated by the motor 17 is transmitted to the output shaft 33 via the drive shaft 18 and the drive gear 48. The assist torque transmitted to the output shaft 33 is transmitted to the hollow shaft 42 of the crankshaft 14 via the input gear 27. As a result, the resultant force of the rotational torque applied by the driver to the crankshaft 14 and the assist torque provided by the motor 17 is transmitted to the rear wheel-side sprocket 23 via the chain 22.

  The magnetostrictive sensor 37 is composed of magnetostrictive films 101 and 102 made of magnetostrictive elements provided on the outer peripheral surface of the hollow shaft 42, and annular coils 39 and 40 disposed outside the magnetostrictive films 101 and 102. The coils 39 and 40 are fixed to the case 26 by the support member 36 so as to have a predetermined gap with respect to the magnetostrictive films 101 and 102, respectively.

  When a torsional torque is applied to the hollow shaft 42 by the occupant's pedaling force, the magnetostrictive films 101 and 102 are distorted to change the magnetic permeability, which is detected as an impedance change of the coils 39 and 40. Output signals from the coils 39 and 40 are transmitted to the controller 16, and a torque value due to the pedal effort is calculated from the difference between the output signals of both coils.

  FIG. 5 is a block diagram illustrating a configuration of a motor control unit that performs assist / regenerative control and its surroundings. Sensor information from the motor speed sensor SE1 (Hall IC and magnet), vehicle speed sensor SE2, pedal depression force sensor SE3 (magnetostriction sensor 37) and information from the brake switch SW are input to the motor control unit (controller) 16, respectively. The Based on these information, the motor control unit 16 drives the motor 17 as a motor to give assist torque, while driving the motor 17 as a generator to generate regenerative power and charge the battery 9 by this power generation. Is configured to run.

  The motor control unit 16 includes a gradient estimation unit 80, a state determination unit 81, and a timer 82. The gradient estimation means 80 has a function of estimating the degree of gradient of the road surface on which the electrically assisted bicycle 1 is traveling based on each sensor information. Further, the state determination unit 81 has a function of determining the control state of the motor 17 based on each sensor information and brake information. The timer 82 measures various times. For example, the timer 82 obtains time information for calculating the rotation speed of the motor 17 based on pulsar signal information output from the Hall IC constituting the motor rotation speed sensor SE1. Can do.

  Referring to the sectional view of the assist drive unit in FIG. 4, the motor 17 includes a rotor 32 having, for example, eight N-pole and S-pole permanent magnets alternately arranged in the circumferential direction, and an outer periphery of the rotor 32. For example, twelve stators 30 having three-phase stator windings that generate a rotating magnetic field that rotates the rotor 32 and that are opposed to each other in the radial direction so as to cover the part. The drive shaft 18 is fixed to the rotor 32 and rotates integrally therewith.

  The assist drive unit 24 rotates the sprocket 15 when the pedals 13L and 13R are moved forward by the action of the one-way clutch 78, and does not rotate the sprocket 15 when the pedals 13L and 13R are pressed in the reverse direction. It has a mechanism.

  The one-way clutch 78 is provided between the crankshaft 14 and the hollow shaft 42 that is fitted on the outer periphery of the crankshaft 14. The right end of the crankshaft 14 in the figure is pivotally supported on the right case half 29 of the case 26 by a bearing 38. The illustrated left end side of the hollow shaft 42 is pivotally supported on the left case half 28 of the case 26 by a bearing 43. A spline for fixing the sprocket 15 is formed on the outer peripheral portion on the right end side of the hollow shaft 42.

  When the pedals 13L and 13R are turned in the forward direction (forward direction), the crankshaft 14 rotates and the one-way clutch 78 is engaged to rotate the crankshaft 14 and the hollow shaft 42 integrally. On the other hand, when the pedals 13L and 13R are turned in the reverse direction, the crankshaft 14 rotates, but the one-way clutch 78 is idled and the hollow shaft 42 does not rotate.

  Further, power is constantly transmitted between the drive shaft 18 and the output shaft 33 of the motor 17, and when the sprocket 15 is driven to rotate by the rotation of the rear wheel WR, the motor 17 is driven. Although it rotates, the power by this driven rotation is not transmitted to the pedals 13L and 13R. This makes it possible to perform regenerative power generation by operating the motor 17 as a generator during braking, when traveling downhill and on a flat road surface, and the like.

  If regenerative power generation by the motor 17 is not performed, a one-way clutch may be provided on the driven sprocket 23 side so that the driven rotational force is not transmitted to the drive chain 22.

  The motor rotation speed sensor SE1 that detects the rotation speed of the motor 17 is composed of a magnet fixed to the drive shaft 18 of the motor 17 and a Hall IC that detects the passage state of the magnet. The cover 60 that protects the motor 17 is attached to the case 26 by a plurality of bolts 34 disposed along the outer periphery of the motor 17. The drive shaft 18 of the motor 17 is rotatably supported by a bearing 57 fixed to the motor cover 60 and a bearing 50 fixed to the right case half 29 at the left and right positions of the rotor 32.

  The motor 17 is housed and disposed in a space partitioned from the magnetostrictive sensor 37 in front of and below the vehicle body of the crankshaft 14. The driving driver 25 and the controller 16 are fixed to the wall surface of the case 26 below the vehicle body of the magnetostrictive sensor 37.

  The front view of the hollow shaft 42 in FIG. 6 is also referred to. The hollow shaft 42 according to the present embodiment functions not only as a torque detection body on which the magnetostrictive films 101 and 102 are formed, but also has a function of fixing the drive sprocket 15 by having an integral shape that is long in the axial direction, and an input gear. 27 as well as a function as an outer case of the one-way clutch 78. This reduces the number of parts and simplifies the structure compared to the structure in which the hollow shaft, the one-way clutch and the input gear are connected in series between the crankshaft and the drive sprocket as in the prior art described above. Is possible.

  More specifically, the magnetostrictive films 101 and 102 made of Ni—Fe formed by plating or sputtering are formed on the cylindrical main body portion 42b in a band shape having a predetermined width. The two adjacent magnetostrictive films 101 and 102 are given different anisotropies, and the controller 16 calculates torque based on the difference value of the impedance output of the coils 39 and 40. A spline 42a with which the sprocket 15 is engaged is formed on the right end side of the main body 42b in the figure, and a clutch outer 42c of the one-way clutch 78 is formed on the left end of the main body 42b in the figure.

  7 is a cross-sectional view taken along line BB in FIG. In the present embodiment, a two-claw ratchet mechanism is applied as the one-way clutch 78. The one-way clutch 78 as a ratchet mechanism is integrally molded on the hollow shaft 42 and a clutch inner 14a integrally formed on the crankshaft 14, two ratchet claws 78a supported so as to be swingable with respect to the clutch inner 14a. Clutch outer 42c. Each of the two ratchet claws 78a is urged so as to swing outward in the radial direction by a resilient member (not shown) such as a coil spring, and is formed in a groove formed in the inner peripheral portion of the clutch outer 42c. It is configured to engage with 78b.

  FIG. 8 is a stress analysis diagram of the hollow shaft 42 when the occupant of the electrically assisted bicycle 1 steps on the pedal to rotate the crankshaft 14 in the forward direction (the forward direction of the electrically assisted bicycle 1). This figure shows that the larger the color, the greater the distortion.

  When the occupant steps on the pedal to rotate the crankshaft 14 in the normal direction, the ratchet mechanism is engaged and the hollow shaft 42 is rotated. Since the driving force transmitted from the clutch inner 14a to the clutch outer 42c is performed by the two ratchet claws 78a engaged with the groove 78b, stress concentrates at two locations on the side wall of the clutch outer 42c. At this time, in the example of the present embodiment, the influence of the distortion generated in the clutch outer 42c extends not only to the wall portion of the clutch inner storage portion 42d but also to the magnetostrictive film 101 of the main body portion 42b (B arrow portion). . That is, although this degree of distortion does not affect the operating state of the parts, the effect of reducing the number of parts can be obtained by integrating the clutch outer 42c with the end of the hollow shaft 42, while magnetostriction is achieved. The output value of the sensor 37 may be affected.

  Incidentally, the magnetostrictive sensor converts the amount of change in strain generated in the magnetostrictive film by the input torque into the amount of change in impedance. Ideally, this strain is uniform at any location in a single magnetostrictive film. However, as described with reference to FIG. 8, when the magnetostrictive film is formed on the hollow shaft in which the clutch outer is integrally formed, and the pedal depression force is large, of the two magnetostrictive films 101 and 102, Due to the influence of the ratchet pawl of the clutch inner on the magnetostrictive film 101 on the side close to the clutch outer 42c, the generated distortion is greatly uneven. When a location where a strain larger than the average of the generated strains (the dark-colored portion shown in FIG. 8) is on the magnetostrictive film having an extreme value, the impedance change corresponding to that location is linear. Therefore, the reliability of the impedance output value is expected to be lacking.

  FIG. 9 is an output conceptual diagram of the magnetostrictive sensor 37. A magnetostrictive sensor using Ni—Fe magnetostrictive films having different magnetic anisotropies is suitable for detecting a relatively low torque generated from the neutral position on both the forward rotation side and the reverse rotation side. As a typical application, in a power steering device for a four-wheeled vehicle, there is a case where a passenger detects torque generated on a rotating shaft of the steering wheel by rotating the steering wheel.

  At this time, if the distortion generated on the rotating shaft of the steering wheel, which is the basis of torque detection, falls within the range D of minus T1 to plus T1, the difference value d1 is set within a range in which the impedance outputs of the two coils both maintain linearity. Can be calculated. More specifically, when the right rotation side of the steering wheel is set to forward rotation, the output of the first coil decreases substantially linearly as the input torque increases in the right direction and the second coil as long as the distortion T1 is reached. Since the output increases substantially linearly, the difference value d1 is accurately obtained.

  On the other hand, when a magnetostrictive sensor using the same Ni—Fe magnetostrictive film is used for pedal depression force detection of an electrically assisted bicycle, the assumed width of the distortion is in a range E of zero to plus T2. This is because in an electrically assisted bicycle, no driving force is applied in the reverse direction, and it is necessary to detect a large pedal depression force due to foot movement on the forward side.

  Therefore, in the present invention, of the two magnetostrictive films adjacent on the same axis, the first magnetostrictive film 101 in which the impedance output of the coil decreases as the strain increases from zero is disposed at a position close to the clutch outer 42c. Thus, accurate torque detection can be performed even when the pedal effort is large. Details will be described with reference to FIGS.

  10 and 11 are relationship diagrams between impedance output and distortion. The curve in the figure shows the impedance output, and the bar graph shows the distribution of strain generated in the magnetostrictive film. FIG. 10 shows a case where two magnetostrictive films are arranged according to the present invention, and FIG. 11 shows a case where they are arranged oppositely.

  As described above, of the two magnetostrictive films, the distortion is generated in the magnetostrictive film on the side close to the clutch outer due to the effect of the ratchet pawl. The bar graph in the figure shows the strain distribution, and it can be seen that the strain distribution is broadened to the left and right on the close side compared to the separated side. The hatching process (color density) indicating the magnitude of strain corresponds to the stress analysis diagram of FIG.

  At this time, as shown in FIG. 11, when the second magnetostrictive film 102 in which the impedance output of the coil increases as the input torque increases from zero is arranged on the proximity side of the clutch outer, the impedance output of the second coil Where the value decreases through an extreme value, the impedance cannot be kept linear due to the influence of distortion, and accurate torque detection becomes difficult.

  On the other hand, as shown in FIG. 10 corresponding to the present invention, when the first magnetostrictive film 101 in which the impedance output of the coil decreases as the input torque increases from zero is arranged on the proximity side of the clutch outer, Since there is no extreme value in the impedance output, the linearity of the impedance output is maintained. On the other hand, since the second magnetostrictive film 102 on the separated side is in a region where the strain distribution maintains the linearity of the impedance, no problem occurs.

  Therefore, in addition to the setting of the magnetostrictive film described above, by setting the coil 39 shown in FIG. 6 as the first coil and the coil 40 as the second coil, as shown in FIG. 9, only the region where the difference d2 is calculated can be obtained. In addition, accurate torque detection is possible even in the region of the difference d3 where the impedance output of the second coil exceeds the extreme value.

  As described above, according to the electrically assisted bicycle according to the present invention, the hollow shaft provided with the magnetostrictive film of the magnetostrictive sensor is an integral part that is long in the axial direction, and the clutch outer of the ratchet mechanism is formed at one end thereof, and the other end The drive sprocket and the motor drive force input gear are directly mounted on the side, and the first magnetostrictive film on the side where the impedance output of the coil decreases as the input torque increases from zero is disposed on the side closer to the clutch outer. In addition, since the second magnetostrictive film on the side where the impedance output of the coil increases as the input torque increases from zero is arranged on the side far from the clutch outer, even when the clutch outer is distorted by a large pedal effort, Unaffected, thereby integrating the hollow shaft while maintaining the accuracy of torque detection It is possible to simplify the by structure.

  In addition, the form of the electric assist bicycle, the structure of the assist drive unit, the location of the magnetostrictive film of the magnetostrictive sensor, the material and forming method, the structure and arrangement of the coil, the shape and material of the hollow shaft, the shape and material of the crankshaft, the one-way clutch The structure and the like are not limited to the above embodiment, and various changes can be made. The electric assist bicycle according to the present invention may be configured as a three-wheel bicycle or a four-wheel bicycle having an assist drive unit.

  DESCRIPTION OF SYMBOLS 1 ... Electric assist bicycle, 9 ... Battery, 13L, 13R ... Pedal, 14 ... Crankshaft (pedal crankshaft), 14a ... Clutch inner, 16 ... Controller (motor control part), 17 ... Motor, 24 ... Assist drive unit, 26 ... Case, 39 ... First coil, 40 ... Second coil, 42 ... Hollow shaft, 42a ... Spline, 42c ... Clutch outer, 78 ... One-way clutch (ratchet mechanism), 78a ... Ratchet pawl, 80 ... Gradient estimation means, DESCRIPTION OF SYMBOLS 81 ... State determination means, 82 ... Timer, 101 ... 1st magnetic film, 102 ... 2nd magnetic film, SE1 ... Motor rotational speed sensor, SE2 ... Vehicle speed sensor, SE3 ... Pedal pedal force sensor (magnetostriction sensor 37), SW ... Brake Switch, WF ... Front wheel, WR ... Rear wheel

Claims (7)

Electric assist bicycle having a pedal depression force sensor (SE3) for detecting an input torque to the pedal crankshaft (14) and a motor (17) for assisting a driving force in accordance with an output of the pedal depression force sensor (SE3) In 1)
A hollow shaft (42) disposed on the outer peripheral side of the pedal crankshaft (14) for transmitting the rotational driving force of the pedal crankshaft (14) via a one-way clutch (78);
The pedal depression force sensor (SE3) includes two magnetostrictive films (101, 102) formed on the hollow shaft (42), and two coils (39, 39) respectively corresponding to the two magnetostrictive films (101, 102). 40) and a non-contact magnetostrictive sensor (37),
The two magnetostrictive films (101, 102) are arranged close to each other in the axial direction so as not to overlap each other with a band having a predetermined width wound around the outer peripheral surface of the hollow shaft (42),
The two magnetostrictive films (101, 102) include a first magnetostrictive film (101) in which the impedance output of the coil (39) decreases as the input torque increases from zero, and the coil as the input torque increases from zero. A second magnetostrictive film (102) that decreases with an extreme value after the impedance output of (40) increases,
The one-way clutch (78) has a clutch outer (42c) formed integrally with the hollow shaft (42),
The first magnetostrictive film (101) is disposed on the side close to the clutch outer (42c), and the second magnetostrictive film (102) is disposed on the side away from the clutch outer (42c). The featured electric assist bicycle. The two magnetic films (101, 102) are given different magnetic anisotropies,
The electrically assisted bicycle according to claim 1, wherein the input torque is calculated based on a difference between impedance outputs respectively detected by the two coils (39, 40).   The one-way clutch (78) includes a clutch inner (14a) provided integrally with the pedal crankshaft (14), a clutch outer (42c) provided integrally with the hollow shaft (42), and the clutch inner (14a). 3. The electrically assisted bicycle according to claim 1, further comprising a claw (78 a) that transmits a driving force to the clutch outer (42 c).   An input gear (27) to which the driving force of the motor (17) is applied to the hollow shaft (42) and a driving force for transmitting the driving force to the rear wheel (WR) via the drive chain (22). The power-assisted bicycle according to any one of claims 1 to 3, wherein the drive sprocket (15) is directly fixed.   The electrically assisted bicycle according to any one of claims 1 to 4, wherein the magnetostrictive film (101, 102) is made of Ni-Fe attached to the surface of the hollow shaft (42) by plating or sputtering. . The clutch outer (42c) is formed at the left end in the vehicle width direction of the hollow shaft (42), and the spline for fixing the drive sprocket (15) at the right end in the vehicle width direction of the hollow shaft (42). (42a) is formed,
The electrically assisted bicycle according to any one of claims 1 to 5, wherein the magnetostrictive film (101, 102) is provided between the clutch outer (42c) and the spline (42a).   On the hollow shaft (42), an input gear (27) to which a driving force of the motor (17) is applied is disposed between the magnetostrictive films (101, 102) and the drive sprocket (15). The electrically assisted bicycle according to claim 6.