WO2014132021A1 - Capteur de couple de manivelle pour une bicyclette - Google Patents

Capteur de couple de manivelle pour une bicyclette Download PDF

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Publication number
WO2014132021A1
WO2014132021A1 PCT/GB2014/000070 GB2014000070W WO2014132021A1 WO 2014132021 A1 WO2014132021 A1 WO 2014132021A1 GB 2014000070 W GB2014000070 W GB 2014000070W WO 2014132021 A1 WO2014132021 A1 WO 2014132021A1
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WO
WIPO (PCT)
Prior art keywords
torque
sprocket
pedal
encoder
pedal shaft
Prior art date
Application number
PCT/GB2014/000070
Other languages
English (en)
Inventor
Richard Thorpe
Lawrence LUKIS
Original Assignee
Karbon Kinetics Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Karbon Kinetics Limited filed Critical Karbon Kinetics Limited
Publication of WO2014132021A1 publication Critical patent/WO2014132021A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62M—RIDER PROPULSION OF WHEELED VEHICLES OR SLEDGES; POWERED PROPULSION OF SLEDGES OR SINGLE-TRACK CYCLES; TRANSMISSIONS SPECIALLY ADAPTED FOR SUCH VEHICLES
    • B62M3/00—Construction of cranks operated by hand or foot
    • B62M3/003—Combination of crank axles and bearings housed in the bottom bracket
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62M—RIDER PROPULSION OF WHEELED VEHICLES OR SLEDGES; POWERED PROPULSION OF SLEDGES OR SINGLE-TRACK CYCLES; TRANSMISSIONS SPECIALLY ADAPTED FOR SUCH VEHICLES
    • B62M6/00—Rider propulsion of wheeled vehicles with additional source of power, e.g. combustion engine or electric motor
    • B62M6/40—Rider propelled cycles with auxiliary electric motor
    • B62M6/45—Control or actuating devices therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62M—RIDER PROPULSION OF WHEELED VEHICLES OR SLEDGES; POWERED PROPULSION OF SLEDGES OR SINGLE-TRACK CYCLES; TRANSMISSIONS SPECIALLY ADAPTED FOR SUCH VEHICLES
    • B62M6/00—Rider propulsion of wheeled vehicles with additional source of power, e.g. combustion engine or electric motor
    • B62M6/40—Rider propelled cycles with auxiliary electric motor
    • B62M6/45—Control or actuating devices therefor
    • B62M6/50—Control or actuating devices therefor characterised by detectors or sensors, or arrangement thereof
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L3/00—Measuring torque, work, mechanical power, or mechanical efficiency, in general
    • G01L3/02—Rotary-transmission dynamometers
    • G01L3/14—Rotary-transmission dynamometers wherein the torque-transmitting element is other than a torsionally-flexible shaft
    • G01L3/1407—Rotary-transmission dynamometers wherein the torque-transmitting element is other than a torsionally-flexible shaft involving springs
    • G01L3/1428—Rotary-transmission dynamometers wherein the torque-transmitting element is other than a torsionally-flexible shaft involving springs using electrical transducers
    • G01L3/1435—Rotary-transmission dynamometers wherein the torque-transmitting element is other than a torsionally-flexible shaft involving springs using electrical transducers involving magnetic or electromagnetic means

Definitions

  • Torque is related to the force applied on the pedal by the rider and the distance and angle that the force is applied relative to the central rotational axis of the pedal crank shaft.
  • rotational speed usually measured in revolutions per minute (rpm) of the pedal crank arm assembly (which typically vary between 40 and 120 rpm, depending on the rider), then the power produced by the rider can be calculated as well.
  • the rider input measured in torque and power may be used as a means to control rider assistance levels provided by the electric motor.
  • This method of controlling power to the electric motor allows for a smooth and natural speed control whereby power can be increased to the electric motor when the rider needs assistance. For example, when the rider exerts additional pressure on the pedals (detected by an increase in torque) to pedal up a hill, the bicycle's electric motor may be automatically turned on, or motor power increased, to provide assistance to the rider.
  • strain gauge is sensitive to damage during production and requires specialist skills and techniques to mount on to the material component where strain is being measured. Calibration is also an issue in that strain gauges are sensitive to changes in temperature and other atmospheric conditions.
  • strain gauge requires a physical wired connection to a power source, and electronic circuits are required to interpret the signal from the strain gauge itself. Varying degrees of strain will alter the resistance to electrical flow in the strain gauge and this signal requires amplification and manipulation in order to convert it into a usable form. So the power supply and electronics to power, amplify, and rectify the strain gauge output must be placed with the strain gauge and therefore because the component that is measured is rotating, the pedal crank assembly in this case, there must also be an onboard wireless transmitter to send the signal to another computer on the main frame of the cycle. This is usually a handlebar-mounted device that can give the rider a numeric display of the torque and/or power that he or she is inputting to the pedal crank assembly. Typically these athlete-oriented devices have the strain gauge fitted to the chain ring, which has the advantage of enabling torque to be measured from input on both left and right side pedal crank arms.
  • Some other torque sensing devices fit the strain gauge in the pedal spindle. However these suffer from the same disadvantages of high cost of the strain gauge and requiring supporting power and wireless transmission electronics on the rotating components.
  • a ring of magnetoelastic material is pressed and fixed onto the rotating pedal crank shaft and a non-contacting magnetic field sensor transducer sleeve device is fixed to the bicycle frame and surrounds the rotating shaft and ring.
  • a significant disadvantage to this type of torque sensor is extremely high cost, due to the highly specialised processing and production and quality control techniques required to manufacture and to attach the magnetoelastic ring onto the pedal crank shaft. There are also specialist techniques required to orientate and calibrate the magnetic properties of the magnetoelastic material.
  • Another drawback to the system is that it is most easily and primarily produced in a form that only enables measurement of torque from only the pedal crank arm on the side of the bicycle remote from the chain ring sprocket. This is because the magnetoelastic ring is usually mounted at the midpoint on the pedal crank shaft , and the chain ring sprocket is mounted at one end of the pedal crank shaft adjacent one of the pedal cranks.
  • the present invention seeks to provide a low cost pedal crank torque sensor for a bicycle comprising a plurality of optical sensors cooperating with a multiplicity of optically detectable features, for example mechanical formations, on two different portions of the rotating pedal crank assembly that are separated by a rotationally compliant section.
  • the effect of torque on the assembly induced by the rider's force on the pedals is to cause a relative angular deflection between the two portions of the pedal crank assembly, and thus a change in the relative timing of the pulses produced by the optical sensors associated with the respective portions.
  • This change in timing can be detected with high accuracy and low cost using well known digital logic and microprocessor circuits.
  • the relative timing change can be converted into a measure of the torque on the pedal crank assembly.
  • the optical sensors may be amounted to the bicycle frame, and cooperate with mechanical formations on the rotating pedal crank assembly to detect the angular positions of the two portions of the crank assembly rel tive to the bicycle frame.
  • a first aspect of the present invention provides torque sensing system for a bicycle having a pair of pedals mounted at respective ends of a pedal shaft , and a drive sprocket mounted to the pedal shaft adjacent one end thereof, comprising, first and second encoders mounted at spaced locations for rotation with the pedal shaft and sprocket, respective first and second detectors for sensing angularly spaced points on the said first and second encoders, and control circuitry for receiving input signals from said first and second detectors, the control circuitry being operable to determine the relative angular positions of the first and second encoders; and to determine a torque value based on the determined relative angular positions of the first and second encoders.
  • a second aspect of the present invention provides a pedal crank assembly for a bicycle, comprising a pedal shaft, a drive sprocket mounted to the pedal shaft adjacent one end thereof, and first and second encoders mounted at spaced locations for rotation with the pedal shaft and sprocket.
  • a third aspect of the present invention provides a chain sprocket for a bicycle, comprising an inner substantially rigid zone mountable to a pedal shaf, an outer substantially rigid zone engageable with a flexible tension element, a resiliently deformable intermediate zone between the inner and outer zones, a first sensor ring associated with the inner substantially rigid zone, and a second sensor ring associated with the outer substantially rigid zone.
  • a fourth aspect of the invention provides a bicycle, having a frame, a pedal shaft mounted to the frame for rotation relative thereto, a pair of pedals mounted at respective ends of the pedal shaft, a drive sprocket mounted to the pedal shaft adjacent one end thereof, first and second encoders mounted at spaced locations for rotation with the pedal shaft and drive sprocket, respective first and second detectors mounted to the frame for sensing angularly spaced points on the said first and second encoders, control circuitry for receiving input signals from said first and second detectors, the control circuitry being operable to determine the relative angular positions of the first and second encoders and to determine a torque value based on the determined relative angular positions of the first and second encoders.
  • a fifth aspect of the invention provides a cartridge-type pedal axle assembly for a bicycle, comprising, a cylindrical housing receivable within a bicycle frame, a pedal axle mounted coaxially with the housing for rotation relative thereto and formed at its ends with pedal-receiving formations extending beyond the housing, a pair of encoder wheels mounted to the pedal axle at spaced locations, and a pair of detectors co-operable with respective ones of the pair of encoder wheels.
  • the cartridge-type pedal axle assembly further comprises a control unit mounted within the cartridge and arranged to receive signals from said pair of detectors, the control unit including a processor adapted to calculate, on the basis of signals received from the detectors, an amount of torque being transmitted by the pedal axle, and to provide an output to a display device indicative of the calculated amount of torque.
  • the output signal may be provided wirelessly to a remote display unit, or through a wired connection.
  • the same sensing apparatus which may be optical, may also be used to detect the rotational speed of the pedal crank assembly, and thus the processor may also produce an output indicative of the power being applied by the rider by combining the torque and rotational speed data.
  • a first encoder in the form of a wheel having 32 substantially equally spaced teeth, is formed on a drive sprocket positioned substantially adjacent the rotational axis and a second encoder, also in the form of a wheel having 32 substantially equally spaced teeth, is formed onto the same sprocket, at a larger radius so that the second output encoder is positioned adjacent the outer diameter of the sprocket.
  • One or more light sources provide respective light beams which pass through the first and second encoder wheels to impinge on respective first and second photosensitive detectors, so that as the drive sprocket rotates the alternating teeth and gaps of the encoder wheels provide intervals of light and darkness at the photosensitive detectors.
  • the sprocket is rigidly connected to the pedal crank shaft.
  • the sprocket has a torsional compliant region between the input and output encoder wheels such that, when torque is applied to the sprocket in one direction by the pedal crank shaft and an opposing torque is applied to the sprocket by the chain engaging the sprocket teeth, said torsional compliant area will elastically deform and there will be a measurable change in the relative angular positions of the encoder wheels.
  • This change in relative angular position of the encoder wheel teeth is detected by the inner and outer photo sensors as a change in the relative timing of the intervals of light and darkness at the first and second photosensitive detectors.
  • the nature of the torsional compliance region of the sprocket between the two encoder wheels can be that of a single homogenous sprocket design made of one material such as steel, aluminium, or titanium. Materials and geometry selection can be widely varied and are readily determinable to those skilled in the art of bicycle design and Finite Element Analysis (FEA) in order to enable appropriate stiffness, strength, ductility and fatigue resistance in the homogenous structure.
  • the torsional compliance region may, for example, comprise a number of radially extending spokes strong enough to transmit the required torque from the crankshaft to the chain, but flexible enough to provide relative angular movement between the encoders.
  • a non homogenous construction using a flexible medium such as polyurethane bushing or metal springs acting in a spring link manner and substantially between an input side of the sprocket and an output side of the sprocket could be used.
  • Embodiments of the invention may comprise non-contact photo sensors fitted to detect light passing through gaps between the teeth of the respective input and output encoder wheels such that a signal is produced as the encoder teeth pass by the sensors when the sprocket is rotating about the pedal shaft axis.
  • the output encoder wheel may be fitted with two non-contact photo sensors such that a signal is produced at each sensor as the teeth of the encoder wheel pass by the sensor.
  • the photo sensors on the output encoder wheel may be spaced such that the phasing of teeth passing through these sensors is nominally one quarter of a tooth out of phase based on a complete phase being detection of the leading edge of a solid tooth to the leading edge of the next solid tooth for example.
  • This preferred embodiment with two photo sensors on the output encoder wheel allows for calculation of direction of rotation. Such a determination may be important, for example when the torque detection is used to control an electric motor for a bicycle, where application of drive to the motor is to be prevented when the rider is turning the pedals backwards.
  • rotation direction detection can be effected by using just a single inner sensor and a single outer sensor, the phasing of the two sensors being, for example, 1 ⁇ 4 tooth (or some other predetermined interval) when under no torsional load. Under load, the relative angular displacement is changed so as to be less or more than the predetermined interval of 14 tooth (or other predetermined interval).
  • measurements can be made at each of the 32 points during a complete revolution of the sprocket. The reaction of the force of the rider's input into the pedal crank arm and the chain input to the sprocket will effect a deflection of the torsionally compliant region of the sprocket between the inner encoder wheel and the outer encoder wheel.
  • the deflection can be designed to be from about 0.1 to about 10 degrees, preferably in the order of 2 degrees.
  • the change in relative angular displacement between the inner and outer encoder wheels between the unstressed condition and the maximum torque condition is preferably not more than the angle subtended by one half of a tooth.
  • the relative angular positions of the inner and outer encoder wheels can then be detected at 32 discreet points during each rotation of the crank, and the torque being applied to the sprocket at each of those 32 points can be derived.
  • B. By comparing the relative anger displacement of the input encoder sensor and the output encoder sensor and taking into account rotational speed of the crank assembly, calculated from the number and frequency of the teeth passing the encoder sensors, the power developed by the rider can be calculated.
  • the discreet data measured at each point can be averaged to produce a smooth, continuous and natural signal of torque, and in combination with the measured speed in rpm can give a smoothed indication of power output.
  • each encoder wheel has 32 teeth and 32 spaces, it is foreseen that each encoder wheel may have more or fewer than 32 teeth and spaces.
  • the first and second encoder wheels have the same number of teeth and spaces as each other.
  • one encoder wheel may have a number of teeth which is an integral multiple of the number of teeth on the other encoder wheel.
  • the encoder wheel with the larger number of teeth may be used to provide a measurement of the rotation speed, while torque is measured only at points corresponding to teeth on the encoder wheel with the smaller number of teeth.
  • a distinct advantage of the preferred embodiment of the present invention is that twist or flex is being measured within the chain ring sprocket itself and therefore torque derived from input from both the right and left hand pedal crank arms can be measured.
  • the encoder wheel teeth can be formed as part of the chain ring sprocket with negligible increase in the cost of the sprocket.
  • the sensors required to detect the teeth on the encoder wheels are readily available, low cost, and robust and since they are mounted on the bicycle frame, the system does not require a power supply, wireless transmitter, or electronics on the rotating components of the pedal crank assembly.
  • a cartridge-type pedal axle in which the axle is rotatably mounted in bearings within a housing which is adapted to be fitted into the frame of the bicycle.
  • the axle has formations at its ends for mounting pedals to the axle, and is provided with two encoder wheels mounted to the axle at spaced locations along its length.
  • the cartridge further includes detectors mounted to its housing and co-operable with the encoder wheels to provide outputs to a control unit which calculates torque and optionally also rotation speed of the pedal axle.
  • the control unit may be integrated into the cartridge, and may also include a wireless transmitter for sending torque and speed information to a remote display device. Alternatively, the detectors within the housing may be connected by wires to an external control unit, optionally integrated with a display.
  • the control unit and/or display may be mounted to the bicycle handlebar.
  • Hall effect sensors may be used instead of optical sensors.
  • the encoder wheels may be replaced by a sequence of magnets, or the Hall effect sensors may operate in combination with encoder wheel teeth formed from ferrous materials.
  • the number of teeth on the input and output encoder wheels could be different from each other, and the teeth could also be unevenly spaced around the circumference of their respective encoder wheels.
  • the encoder wheels may provide a single measurement point (tooth) per revolution, the measurement point preferably being arranged so that the measurement is taken when the pedal crank position is near the rider's point of peak force on one of the pedals. A minimum of two measurement points could be useful for measuring both pedals.
  • One or more of the encoder wheels may have the same number of teeth as the number of chain-engaging teeth on the drive sprocket. Such an arrangement gives a very adequate measure of the rider's input while still keeping the implementation cost very low.
  • the sprocket teeth of the chain wheel may be used as the teeth of one of the encoder wheels.
  • the encoder may be a series of light and dark areas drawn onto the sprocket in an annular formation, so that light directed onto the light and dark areas may be reflected and detected, to determine the angular orientation and rotation speed of the sprocket.
  • FIGURE 1 is a side view of a first embodiment of the invention mounted to a bicycle
  • FIGURE 2 is a perspective exploded view showing the various parts of the first embodiment of the invention.
  • FIGURE 3 is a side view showing the orientation of the encoder wheels and the photo sensors of the first embodiment
  • FIGURE 4 is a perspective exploded view showing an alternative embodiment of the invention.
  • FIGURE 5 is a side view of a bicycle fitted with a transmission cover of well known construction for protecting the invention from adverse effects of weather, water, or debris;
  • FIGURE 7 is a cutaway sectional view schematically illustrating a third embodiment of the torque sensor of the present invention.
  • FIGURE 8 cutaway sectional view schematically illustrating a cartridge- type pedal axle embodiment of the torque sensor of the present invention.
  • FIGURE 1 there is shown a sprocket torque sensor assembly 2 attached to a bicycle 1.
  • FIGURE 2 shows the sprocket tcrque sensor assembly 2 in detail.
  • the assembly comprises a sprocket-side pedal 8 fitted to a sprocket side crank arm 7 which is rigidly coupled to a sprocket end of a pedal crank shaft 18 rotatable about pedal crank axis 21.
  • a non sprocket side crank arm 15 is rigidly coupled to the other end of pedal crank shaft 18.
  • Pedal crank shaft 18 is rotatably mounted to a bicycle frame 17 by means of rotatable bearings 14 which are rigidly housed within bicycle frame 17.
  • a sprocket 12 is rigidly mounted to the pedal crank shaft 18 by means well known such as spline fitting, welding, or bolting.
  • Sprocket 12 comprises an outer toothed encoder wheel 9 and an inner toothed encoder wheel 5.
  • Outer toothed encoder wheel 9 and inner toothed encoder wheel 5 each comprise a number of teeth extending from the plane of sprocket 12 in the direction of the rotation axis 21, so that the teeth extend laterally from the sprocket 12. Adjacent pairs of teeth are separated by respective gaps.
  • the outer encoder wheel 5 has the same number of teeth as the inner encoder wheel 9. The teeth and gaps of encoder wheel 5 are thus wider (in the circumferential direction) than those of the inner encoder wheel
  • Both encoder wheels have a similar profile 22 which is well known and understood and suited for detection by respective sensors.
  • An inner sensor 16 is arranged to detect the teeth and gaps of the inner encoder wheel 9 , while an outer sensor 4 and a rotational direction sensor 6 are arranged to detect the teeth and gaps of the outer encoder wheel five at two circumferentially-spaced locations .
  • the sensors 4, 6 and 16 are connected to an electronic control module 3.
  • the sensors in this embodiment are of the photo interrupt type such as those using for example infrared light wavelength detection. Alternat ively, sensors of the Hall effect type such as are well known in the art of encoding wheel sensing technology may be used.
  • inner sensor 16 comprises a light emitter and a photodetector mounted so that light passes from the emitter to the photodetector through the gaps between the teeth of the inner encoder wheel 9.
  • the photodetector produces a series of output pulses.
  • the outer sensor 4 comprises a light emitter and a photodetector mounted so that light passes from the emitter to the photodetector through the gaps between the teeth of the outer encoder wheel 5.
  • the inner and outer sensors are mounted to the bicycle frame such that when the inner sensor 16 detects the leading edge of a tooth of the inner encoder wheel 9, the outer sensor 4 is positioned centrally with respect to a tooth of the outer encoder wheel.
  • the series of output pulses from the outer sensor is out of phase by a predetermined amount with the series of pulses from the inner detector 16.
  • the two sensors 4 and 16 are so positioned that this phase offset is approximately one quarter or 90 degrees.
  • Figure 6 schematically illustrates the output pulses from the inner and outer encoder wheels.
  • the upper trace 61 represents the output pulses from the sensor 16, which detects the teeth of the inner sensor wheel 9
  • the lower trace 62 represents the output pulses from the sensor 4 which detects the teeth of the outer sensor wheel 5.
  • the processing circuitry detects the rising edges 65 of the traces, and compares rising edges of the two traces to calculate the time interval To between the arrival of rising edges in the two traces.
  • the sensors 16 and 4 are mounted to the bicycle frame such that a rising edge 65 of the signal trace from sensor 16 occurs roughly at the midpoint of a high part of the signal from the sensor 4, when the sprocket is not transmitting any torque and thus the interval T 0 corresponds to about a quarter of the period of the signal trace.
  • Sprocket 12 has a torsionally compliant region 13 extending radially between the inner toothed encoder wheel 9 and the outer toothed encoder wheel 5, such that force applied to pedal 8 will transfer to sprocket-side crank arm 7 and transfer to pedal crank shaft 18 and transfer to sprocket 12 through rigid mounted connection and transfer through torsionally compliant area 13 and be reacted finally through sprocket teeth 10 at the perimeter of sprocket 12 by power transfer device 1 1 which in this embodiment is a roller chain.
  • Rotational direction sensor 6 is positioned such that when sprocket 12 rotates about pedal shaft axis 21 , passing toothed profile 22 of outer toothed encoder wheel 5 will also give rise to a one quarter out of phase detection of toothed profile 22 relative to output sensor 4.
  • Figure 6B illustrates, similarly to Figure 6A, the signal traces from the sensors 16 and 4 when torque is applied to the sprocket 12. Deflection of the torsionally compliant region 13 alters the angular position of the outer encoder wheel relative to the inner encoder wheel, so as to increase the detected interval between rising edges 65 from To to Ti , the amount of this alteration corresponding to the amount of torque applied.
  • Electronic control module 3 comprises a printed circuit board containing a digital power and signal interface and microprocessor to capture with high resolution and accuracy, the timing of each of the signals from inner sensor 16, outer sensor 4 and direction sensor 6.
  • the control module 3 is preferably able to capture the pulse trains output from the three sensors 4, 6 and 16, and accurately time the rising and/or falling edges of the pulses.
  • Toothed profile 22 provides 32 discreet detectable points within a single complete revolution of sprocket 12 about pedal shaft axis 21 , corresponding to the rising edges or the falling edges of the pulses output by one of the sensors.
  • the rotational speed of the crank assembly can thus be derived by simply timing the interval V (seen in Figure 6A) between the rising edges of pulses in the pulse train from one of the detectors 4 6 or 16, corresponding to the detection of a successive teeth of the corresponding encoder wheel. Since the number of teeth of the encoder wheel is known, the rotational speed of the crank assembly can be determined from interval V.
  • rotational direction can be derived by comparing the signals output from outer sensor 4 and rotational direction sensor 6. Since the degree of offset about pedal shaft axis 21 between output sensor 4 and rotational direction sensor 6 is known, conventional quadrature encoder logic can provide output indicating the direction of rotation.
  • Sprocket 12 rotational speed about pedal shaft axis 21 can also be determined by measuring the time V between two or more successive pulses from output sensor 4. Two successive pulses are sufficient if said rotational speed is relatively constant within nominal interval of toothed profile 22. A minimum of three discreetly detected points on toothed profile 22 could be used to compensate for varying speed due to constant acceleration.
  • Calibration of the system can be achieved by rotating sprocket 12 at a constant speed and without any opposing forces reacting through torsional compliant area 13 at input toothed encoder wheel 9 and output toothed encoder wheel 5 while noting the time of the arrival of a signal from input sensor 16 relative to the time between 2 successive signals from output sensor 4 or 6.
  • Calibration may be performed using a calibration mode of the control circuitry, by simply spinning the crank assembly in a predetermined direction with the chain removed from the sprocket 12.
  • the control circuitry will capture the interval V to determine the rotational speed of the crank assembly, and the interval To, and from these two values determine the initial angular offset between the encoder wheels 5 and 9 under no torque.
  • This relative time is a measure of the zero torque angular positioning of the input and output portions of the rotating sprocket and is used as the zero torque calibration point. Note that these relative times may vary slightly due to manufacturing variations of toothed profile 22 and these slight variations can also be compensated for within well known microprocessor processing logic to further improve accuracy.
  • Toothed profile 22 can be made such that a singular point per complete rotation of sprocket 12 about pedal axis 21 can be detected by output sensor 4 or output sensor 6 or input sensor 16, or by an additional separate sensor for detecting each complete rotation of sprocket 12.
  • the torsional displacement may be converted to a torque value even when the torsional compliance is non-linear.
  • the control unit may and capture values of V and Tl from the detectors 4 and 16, and process the signals to determine the instantaneous angular offset between the encoder wheels. This angular offset may then be compared with angular offset values for the different torque levels, with interpolation as required, in order to output a value for the instantaneous torque level at the sprocket.
  • the torque level may be displayed to the rider on a handlebar display, and the control unit may also calculate instantaneous power values, from the torque level and the angular velocity of the crank.
  • FIGURE 3 shows a side view of the sprocket 12 containing sprocket teeth 10 with input toothed encoder wheel 9 and output toothed encoder wheel 5 having both a toothed profile 22 allowing for 32 discreet detectable points within a single complete revolution of sprocket 12.
  • the encoder wheels 9 and 5 are positioned respectively inboard and outboard of the torsionally compliant area 13, which in this embodiment is formed by a number of elastic re-deformable radial spokes.
  • Input sensors 4 and 16 are placed in a radial plane 20 passing through the rotatable centre of sprocket 12.
  • Rotational direction sensor 6 is positioned to detect the teeth of the outer encoder wheel 5 in a radial plane 19 circumferentially offset relative to output sensor 4.
  • Torsionally compliant area 13 is shown in plan view to have a nominally webbed or spoke form suitable to allow rotational displacement between input toothed encoder wheel 9 and output toothed encoder wheel 5 whilst minimising displacement outside of the plane normal to the axis of rotation of the sprocket 12.
  • FIGURE 4 shows a perspective exploded view of an alternative embodiment of the invention having the inner encoder wheel 16 mounted to the pedal shaft 18.
  • angular offset between outer encoder wheel 5 and inner encoder wheel 9 is induced from an input force at crank arm 15 through rigid mounted input encoder wheel 9, through pedal shaft 18, and through rigid mounted sprocket 12 and through torsionally compliant area 13 to outer encoder wheel 5 whereby said input force is reacted finally at power transfer device 1 1.
  • this embodiment cannot measure torque from force input at crank arm 7 since the force load path reacted by power transfer device 1 1 does not pass through input encoder wheel 16.
  • the varying angular offset between inner encoder wheel nine and outer encoder wheel 5 thus includes not only the deflection of the torsionally compliant region 13, but also twisting of the crankshaft 18 between the sprocket 12 and the inner encoder wheel 9.
  • the calibration and operation of the torque sensor in this embodiment substantially corresponds to that described in relation to the previous embodiment.
  • FIGURE 5 shows a bicycle 1 fitted with a transmission cover structure 23 enclosing the torque-sensing components and the drivetrain, to provide protection from weather, water, or debris that could inhibit the function said invention in part or on the whole.
  • FIGURE 7 illustrates a third embodiment of the torque-sensor, in which both encoder wheels 5 and 9 are mounted to the crank shaft 18 within the frame 17. In this way, the encoder wheels, detectors and control circuitry are protected from the elements.
  • Inner and outer encoder wheels 9 and 5 are mounted to crankshaft 18 at two spaced locations between the sprocket 12 and the pedal crank 15.
  • Detectors 16 and 4 are mounted within the frame 17 to detect rotation of the encoder wheels 9 and 5. Operation of the torque sensor is substantially as described in relation to previous embodiments.
  • torque applied by the rider to pedal crank 15 is transmitted to the sprocket 12 via the part of the crankshaft 18 between the sensor wheels 9 and 5, and the sensors 16 and 4 enable the control circuitry to determine the angular displacement between encoder wheels 16 and 4 and thus to calculate the amount of twist in the crankshaft 18, to determine the torque applied by the crank 15.
  • Force applied by the rider to the sprocket-side crank 7 s not transmitted by the part of the crankshaft 18 between the sensor wheels 9 and 5, and thus is not measured.
  • the torque sensing device may be provided in the form of a cartridge-type pedal axle, comprising a generally tubular housing 80 which is receivable in the lower part of the bicycle frame. Mounted to the housing by a pair of ball bearings 81 is the pedal axle 18, the ends 82 of the pedal axle extending beyond the housing and being formed to accept pedals. In this embodiment, the ends 82 are formed as tapered square- section elements to which hurdles are attachable.
  • a pair of encoder wheels 5 and 9 are mounted to the pedal axle 18 at spaced locations, and a pair of detectors 4 and 16 are mounted to the housing 80 to cooperate with the encoder wheels 5 and 9, respectively.
  • a control unit 83 is mounted within the housing 80 to receive signals from the detectors 4 and 16 and process them to produce an output signal representing measured torque and/or rotation speed of the pedal axle 18.
  • the output signal may be transmitted by wires or wirelessly to a remote display device (not shown) mounted, for example, on the handlebar of the bicycle.
  • the detectors 4 and 16 may provide outputs to a remote control unit by means of wires extending through the housing 80.
  • the remote control unit may be integrated into a display unit mounted to the bicycle.
  • the invention can be implemented with any identifiable and detectable formations or marks in place of the above-described encoder teeth disposed on the sprocket 12 or, in the alternative embodiment, disposed on the pedal shaft 18.
  • the teeth and gaps of the encoder wheels may be replaced by a ring of alternate light and dark regions on the sprocket 12, or alternative and dark regions on the pedal crankshaft, such that light from a light source may be reflected from the light regions and detected, to generate a signal indicative of angular position.

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  • Force Measurement Appropriate To Specific Purposes (AREA)

Abstract

L'invention concerne un système de détection de couple pour une bicyclette (1) qui présente une paire de pédales (8) montées sur des extrémités respectives d'un arbre (18) de pédalier, ainsi qu'un pignon (12) d'entraînement, monté sur l'arbre de pédalier adjacent à une de ses extrémités, le système de détection de couple comprenant des premier et second encodeurs (5, 9) montés en des emplacements espacés pour rotation avec l'arbre de pédalier et le pignon, des premier et second détecteurs (4, 16) respectifs, afin de détecter des points espacés au plan angulaire sur lesdits premier et second encodeurs, ainsi qu'un ensemble de circuits de commande, afin de recevoir des signaux d'entrée provenant des premier et second détecteurs, l'ensemble de circuits de commande étant fonctionnel pour déterminer les positions angulaires relatives des premier et second encodeurs et pour déterminer une valeur de couple, sur la base des positions angulaires relatives déterminées des premier et second encodeurs.
PCT/GB2014/000070 2013-03-01 2014-02-28 Capteur de couple de manivelle pour une bicyclette WO2014132021A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB1303776.7 2013-03-01
GB201303776A GB201303776D0 (en) 2013-03-01 2013-03-01 Non contact pedal crank torque for a bicycle

Publications (1)

Publication Number Publication Date
WO2014132021A1 true WO2014132021A1 (fr) 2014-09-04

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PCT/GB2014/000070 WO2014132021A1 (fr) 2013-03-01 2014-02-28 Capteur de couple de manivelle pour une bicyclette

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GB (1) GB201303776D0 (fr)
WO (1) WO2014132021A1 (fr)

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WO2016078981A1 (fr) * 2014-11-21 2016-05-26 Siemens Aktiengesellschaft Détection de forces et de couples dans un dispositif d'entraînement
EP3029442A1 (fr) * 2014-12-01 2016-06-08 Höganäs AB (publ) Moteur de bicyclette électrique
WO2017097833A1 (fr) * 2015-12-09 2017-06-15 Robert Bosch Gmbh Dispositif pour calculer une vitesse de roue d'un véhicule
CN108407960A (zh) * 2017-02-10 2018-08-17 李森墉 电助自行车的后车架扭矩感测装置
CN109572913A (zh) * 2018-12-26 2019-04-05 重庆理工大学 一种悬挂式电动自行车力矩测量装置
WO2020071913A1 (fr) 2018-10-02 2020-04-09 Truekinetix B.V. Système de détection de couple
NL2021908B1 (en) 2018-10-31 2020-05-14 Truekinetix B V A torque sensing system
TWI834435B (zh) 2022-12-15 2024-03-01 搏盟科技股份有限公司 自行車用之光電光柵穿透式速度感測器及其測速方法
FR3139111A1 (fr) * 2022-08-29 2024-03-01 Ntn-Snr Roulements Système de détermination d’un couple appliqué entre deux organes tournants

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JPH09290795A (ja) * 1996-04-25 1997-11-11 Yamaha Motor Co Ltd 電動モータ付き乗り物
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CN202414079U (zh) * 2011-12-29 2012-09-05 苏州博菲利电动科技有限公司 一种磁控式力矩感应传动系统

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2016078981A1 (fr) * 2014-11-21 2016-05-26 Siemens Aktiengesellschaft Détection de forces et de couples dans un dispositif d'entraînement
EP3029442A1 (fr) * 2014-12-01 2016-06-08 Höganäs AB (publ) Moteur de bicyclette électrique
WO2017097833A1 (fr) * 2015-12-09 2017-06-15 Robert Bosch Gmbh Dispositif pour calculer une vitesse de roue d'un véhicule
CN108369241A (zh) * 2015-12-09 2018-08-03 罗伯特·博世有限公司 用于计算车辆的轮速的装置
CN108407960A (zh) * 2017-02-10 2018-08-17 李森墉 电助自行车的后车架扭矩感测装置
WO2020071913A1 (fr) 2018-10-02 2020-04-09 Truekinetix B.V. Système de détection de couple
NL2021908B1 (en) 2018-10-31 2020-05-14 Truekinetix B V A torque sensing system
CN109572913A (zh) * 2018-12-26 2019-04-05 重庆理工大学 一种悬挂式电动自行车力矩测量装置
CN109572913B (zh) * 2018-12-26 2020-06-30 重庆理工大学 一种悬挂式电动自行车力矩测量装置
FR3139111A1 (fr) * 2022-08-29 2024-03-01 Ntn-Snr Roulements Système de détermination d’un couple appliqué entre deux organes tournants
TWI834435B (zh) 2022-12-15 2024-03-01 搏盟科技股份有限公司 自行車用之光電光柵穿透式速度感測器及其測速方法

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