CN116783112A

CN116783112A - External force measuring system, measuring method and electric auxiliary bicycle

Info

Publication number: CN116783112A
Application number: CN202180087368.4A
Authority: CN
Inventors: 海恩斯·霍农
Original assignee: TQ Systems GmbH
Current assignee: TQ Systems GmbH
Priority date: 2020-12-24
Filing date: 2021-12-24
Publication date: 2023-09-19

Abstract

The external force measurement unit comprises a load cell having a support ring, wherein a first tab and a second tab are arranged on the support ring, wherein the second tab is arranged on the support ring opposite to the first tab, wherein each tab is arranged to the outside of the outer ring in a radial direction, and a first tab end and a second tab end are arranged at respective ends of the first tab and the second tab. A second aspect relates to a measurement method for measuring an external force with an external force measurement unit including a load cell, the external force measurement unit housing a spindle. A third aspect relates to an electric assist bicycle that includes an external force measurement unit.

Description

External force measuring system, measuring method and electric auxiliary bicycle

The application relates to an external force measuring system, a measuring method and an electric auxiliary bicycle.

It is an object of the present application to provide an improved external force measuring unit and measuring method.

The present application provides an external force measuring unit for measuring an external force applied to a main shaft or a lower bracket of an electric assist bicycle. The external force measurement unit includes a load cell having a support ring, wherein a first tab and a second tab are disposed on the support ring, wherein the second tab is disposed on the support ring opposite the first tab.

Unlike other designs, the present application provides a device for measuring the force applied to a spindle by a rider of a bicycle. This will determine the amount of additional power or torque applied to the main shaft by the electric motor of the bicycle. Conventional designs provide a device that measures the moment applied to the main shaft by the rider of the bicycle by pushing a crank with a pedal, the crank being attached to the main shaft. The present application provides a way to determine the amount of additional power or torque by essentially measuring the vertical force acting on the spindle in the vertical direction.

In one embodiment, even the horizontal forces acting on the spindle are not considered in determining the amount of additional power or torque. This is done in order to determine the amount of additional power or torque by measuring only the vertical force acting on the main shaft in the vertical direction.

Excluding the horizontal force acting on the main shaft from the measurement means that the force transmitted to the bicycle chain of the main shaft by means of the front sprocket is excluded, which in turn provides a simplified way of determining said additional power or torque quantity.

The design according to the application provides each tab in a radial direction towards the outside of the outer ring, which tab can later be arranged in a vertical direction with respect to the ground on which the electric assist bicycle is intended to operate.

The first strain gauge is disposed on the first airfoil and the second strain gauge is disposed on the second airfoil. When the first and/or second fins are compressed or expanded by a force acting on the spindle, the first and/or second strain gauges will change their respective resistances depending on the length change of the fins.

According to the application, an evaluation unit is provided for measuring the resistances of the first strain gauge and the second strain gauge. This is a reliable way of converting the vertical force acting on the spindle into two measured values. According to the present application, the two resistance values of the first strain gauge and the second strain gauge may be used separately and not combined as conventionally known from the prior art. In the design of the present application, two strain gauges supply two separate measurements, which are evaluated separately. This makes it possible to determine further operating states, for example when the upper first tab is vertically disengaged from the adjacent surface of the load cell carrier while the lower first tab still contacts its corresponding adjacent surface of the load cell carrier, or for adjusting the zero point of the spindle within the motor housing.

In practice, the resistance of the first strain gauge is measured using two electrical paths or connecting wires to the control and evaluation unit. The resistance of the second strain gauge is measured using two electrical paths or connecting wires to the control and evaluation unit, wherein the first strain gauge and the second strain gauge may share one conductive path, for example by a common ground connection with the evaluation unit.

The load cell also has a first bearing support for supporting a first bearing in a first bearing housing, wherein the first bearing is provided with a first outer ring mounted to the first bearing housing for transmitting a first force, wherein the external force comprises a first force transmitted from the spindle to the first bearing to the first inner ring and a second force received by the adapted second bearing. The first inner ring is connected to the first outer rolling ring by a first bearing element to transmit a first force from the adapted spindle.

If the first and second tab ends are arranged at the respective ends of the first and second tabs, a secure placement of the external force measuring unit in the motor housing is facilitated by supporting the first and second tabs in a load cell carrier in the motor housing.

The evaluation unit is further adapted to determine an offset of the external force (e.g. the weight of the spindle), the position of the lever arm of the spindle, and to determine the external force applied to the adapted spindle based on the measured resistance and the determined offset of the first force.

The evaluation unit smoothes the measured resistance of the strain gauge over time by means of a low-pass filter and can determine the drift of the measured resistances of the first strain gauge and the second strain gauge over time. This enables recalibration of the first and second strain gauge measurements by applying drift compensation after a predefined time.

According to the application, the freewheel is connected integrally or in a form-fitting manner with the main shaft. The freewheel is part of a freewheel device that prevents the main shaft from being connected with the sprocket and/or the electric motor when needed for a predetermined operating state of the electric bicycle.

The application also provides an angular encoder to determine the radial or angular position of the spindle. The spindle position is needed in order to determine when and what additional power or torque the electric motor is providing to the spindle. This enables fine tuning of the applied power. The angle decoder may be a conventional hall sensor mounted at the load cell, while the magnetic flux through the hall sensor may be a series of magnets arranged in a ring at adjacent sections of the spindle. Alternatively, the magnetic flux through the hall sensor may be a series of short flux slots in the spindle, arranged in a ring directly below the hall sensor element.

Each of these flux slots extends longitudinally parallel to the axis of symmetry of the spindle, and the slots are arranged on a circumference in the outer cylindrical surface of the spindle. For example, 36 flux slots are arranged at every 10 degrees of angular position on the circumference in the outer cylindrical surface of the spindle, and each flux slot may have a circumferential width corresponding to a 5 degree section of the outer cylindrical surface of the spindle. One of the 36 slots may have a width greater or less than the other 35 slots, or the reference slot may have a depth greater or less than the other slots. When the spindle rotates while the hall sensor remains stationary with the motor housing, the hall sensor may detect changes in the magnetic flux caused by a series of flux slots as they move under the hall sensor, and the changing values of the hall sensor signal provide the angular position of the spindle relative to the hall sensor and motor housing. The reference flux slots cause a change in the hall sensor signal that is different from the change in the hall sensor signal caused by the conventional flux slots and is used to detect the absolute angular position of the spindle relative to the hall sensor. In other words, the width of one of the reference flux grooves in the circumferential direction may be different from the other flux grooves and/or the depth of the reference flux groove may be different from the depth of the other flux grooves.

It is also possible to provide a reference flux shoulder between the flux grooves, the width of the reference flux shoulder in the circumferential direction being different from the flux shoulders between the other flux grooves. The wider or narrower reference flux shoulder causes a change in the hall sensor signal that is different from the change in the hall sensor signal caused by the conventional flux shoulder and is used to detect the absolute angular position of the spindle relative to the hall sensor. In other words, the width of one of the reference flux shoulders in the circumferential direction may be different from the other flux slots.

The accuracy of the device can be increased by using two hall sensors and by biasing the spindle with a permanent magnet placed near the hall sensors, for example, at a position directly above the hall sensors and above the spindle.

According to the present application, the external force measuring unit accommodates the main shaft inside the first bearing ring of the first bearing and inside the second bearing ring of the second bearing. This is how the spindle applies a first force to the first inner bearing ring and a second force to the second inner bearing ring, wherein the first force and the second force are part of an external force applied to at least one end of the spindle by means of a lever arm. The lever arm may be, for example, a crank with a pedal.

The evaluation unit calculates a calculated force-dependent moment applied by the rider of the bicycle and an effective lever arm length of each lever arm, said effective lever arm length being dependent on the current angular position of the main shaft.

The present application provides a method for measuring an external force that measures a change in resistance of a first strain gauge. The first strain gauge is disposed on the first tab due to the change in length of the first tab, and this changes the resistance of the second strain gauge disposed on the second tab due to the change in length of the second tab. The method includes determining an offset of an external force induced by the external force (e.g., by a weight of the spindle), determining an angular or rotational position of a lever arm of the spindle, determining the external force applied to the spindle based on the measured resistance and the determined offset of the first force.

A vertical guide assembly may be provided to the load cell.

In one embodiment of the vertical guide assembly, the load cell has an anchor tab that protrudes from the axis of symmetry of the support ring at an angle of about 90 °. A fixation pin hole is provided in the anchor tab, the axis of symmetry of the fixation pin hole being substantially parallel to the axis of symmetry of the support ring.

In the mounted state of the load cell in the motor housing, the fixing pin is inserted into the fixing pin hole and into the corresponding anchoring hole in the motor housing. The fixing pin transmits the horizontal force of the load cell to the motor housing, thereby preventing the spindle from moving horizontally due to the horizontal force acting on the spindle, for example, caused by a bicycle chain.

The vertical guide assembly with the horizontal arrangement of the anchor tabs provides for the first and second strain gauges to remain outside of the deformation zone caused by these horizontal forces in the load cell, as compared to the vertical arrangement of the first and second tabs carrying the first and second strain gauges. This arrangement improves the accuracy of measurement of the vertical force transmitted to the load cell by the spindle. The design of the anchor tab and the fixation pin in the fixation pin hole provides a better measurement of the vertical force and reduces the number of parts needed to achieve a separation of the horizontal force acting on the main shaft from the vertical force in the area of the external force measuring unit.

In other embodiments of the vertical guide assembly, the assembly provides a slot to a fixation pin hole or to a corresponding hole in the motor housing. The slit provides vertical movement of the load cell in the motor housing while preventing horizontal movement of the load cell in the motor housing. For example, the fixing pin may be provided in a fixed position in the fixing pin hole while it is vertically movable in a slit in the motor housing. Alternatively, the fixing pin may be provided in a fixed position in the motor housing while it is vertically movable in a slit in the fixing pin hole.

Another way to provide a vertical guide assembly is to provide a vertical protrusion in the motor housing, against which the load cell abuts in a horizontal direction. The load cell can still slide up and down along the vertical protrusion, while the vertical protrusion provides the load cell with a horizontal guide that prevents horizontal movement of the spindle.

The present application also provides an electric assist bicycle having an external force measuring unit as described herein.

According to a first aspect, an external force measurement unit for measuring an external force applied to a spindle is provided.

The external force measuring unit includes a load cell having a support ring, wherein a first fin and a second fin are arranged on the support ring, wherein the second fin is arranged on the support ring opposite to the first fin, and wherein each fin is arranged to the outside of the outer ring in a radial direction. The unit further includes first and second tab ends disposed at respective ends of the first and second tabs.

The external force measuring unit further comprises a first strain gauge arranged on the first wing and a second strain gauge arranged on the second wing, wherein the first strain gauge and/or the second strain gauge is adapted to change its respective resistance depending on a change in the length of the first wing or the second wing due to expansion of the material.

The external force measurement unit further comprises an evaluation unit adapted to measure the resistances of the first and second strain gauges, the evaluation unit further being adapted to determine an offset of the external force induced by the weight of the spindle, and the evaluation unit further being adapted to determine the position of the lever arm of the spindle and to determine the external force applied to the adapted spindle based on the measured resistance and the determined offset of the first force.

The external force measurement unit further comprises a first bearing support to support the first bearing in the first bearing housing, a first bearing having a first outer ring, wherein the first outer ring is mounted to the first bearing housing to transmit a first force, wherein the external force comprises a first force transmitted from the spindle to the first bearing to the first inner ring and a second force absorbed by the adapted second bearing, and the first inner ring is connected to the first outer rolling ring through the first bearing element to transmit the first force from the adapted spindle.

The external force measuring unit may be a system to measure a force applied from the outside. The external force measuring unit measures the change in resistance. The external force is calculated depending on the measured resistance.

External force is applied to the external force measurement from outside the cell. Mainly, people can apply external force. For example, an external force is applied to the pedals of a bicycle by a person's foot.

The pedal may be part of a bicycle and rotatable. Therefore, the external force is mainly applied perpendicular to the pedal.

The spindle may be a shaft, a hollow shaft or a cylinder. The first bearing and the second bearing receive the spindle. Bearings are machine elements that limit relative motion to only the desired motion, and reduce friction between moving parts. The bearing may be, for example, a rolling element bearing, a planar bearing, a ball bearing, a rolling bearing, a jewel bearing, a fluid bearing, a magnetic bearing or a flexible bearing.

A load cell with a support ring is a device used to house a bearing, for example, by engineering fit. The load cell may be made of aluminum or steel or any other suitable material. Engineering works as part of geometric dimensioning and tolerance dimensioning when designing parts or assemblies. A fit is a gap between two mating parts, and the size of this gap determines whether the parts can move or rotate independently of each other at one end of the spectrum, or be temporarily or permanently joined at the other end. The bearing may be supported in the first bearing seat of the support ring by a set bearing arrangement, wherein one of the bearings is movable and the other is fixed.

The fixed bearing is mounted on the element and is supported in such a way that it cannot move in the axial direction. The positioning bearing thus absorbs both radial and axial forces. The fit may also be a load bearing support bearing, with axial force being split between the two bearings. Each of the two bearings absorbs axial forces in one direction, so that the two bearings together can absorb all axial forces.

The first tab and the second tab are elements disposed on the load cell. Each tab may also be named a tongue or a bracket. At least the fins may transfer forces in a predefined direction. The radial direction of the deployment tabs points outwardly from the center of the load cell. Both tabs may be arranged on each side of the two ends of the line through the centre. Thus, the fins are on opposite sides of the load cell. The fins may partially surround the load cells. The fins may have a gap therebetween.

The tab ends may also be arranged on a line through the center. The tab end is disposed on the proximal end of the load cell. A tab end is disposed on each proximal end of each tab. Each tab end may form an angle with the corresponding tab. In an exemplary embodiment, the angle is 90 °.

Strain gauges are devices used to measure strain on an object. In this case, the object is each tab. The strain gage may be comprised of an insulating flexible backing supporting a metal foil pattern. When the fins are deformed, the foil is also deformed so that its resistance changes. This change in resistance, typically measured using a wheatstone bridge, is related to strain by an amount known as the strain coefficient. In an exemplary embodiment, the strain gauge measures primarily changes in length along the radial direction.

The evaluation unit may be, for example, a microprocessor or a logic chip. The evaluation unit may be connected to each strain gauge. As described above, the evaluation unit may measure the resistance of each strain gauge. The evaluation unit may also have an output to transmit the calculated result. The output may be connected to an engine control unit to control the motor.

With this solution it is possible to provide a simple force measuring unit. The measuring unit has few components and can be easily adapted. The compactness and accuracy of the measuring unit can be improved. The measuring unit allows to construct a more compact motor unit with a higher durability.

The external force measuring unit may be further improved by including a motor housing, wherein the first tab end and the second tab end are adapted to mount the load cell to a load cell carrier on the motor housing of the spindle, and the second outer ring is mounted to a second rolling support of the motor housing.

The motor housing supports the external force measuring unit. The measuring unit is mounted to the motor housing. The load cell is mounted to the motor housing by a tab end. The second bearing may be mounted to the housing by a bearing support, as described above.

The motor housing may be part of the motor unit. The motor unit may include a motor, a battery holder, and an external force measuring unit. The external force measuring unit may be mainly enclosed by the motor housing. The load cell may also be mounted to the outer wall of the motor housing. Specifically, the end of the spindle is disposed on the exterior of the motor housing. The motor housing may include at least two openings to mount the spindle. The motor housing may further comprise fastening elements to mount the motor housing to the rail. The track may be part of a bicycle.

With this solution it is possible to protect the load cell from environmental influences and mount it to the bicycle track. Housing the external force measuring unit in the motor housing also improves durability and can attenuate impact.

The external force measurement unit may be further improved in that the evaluation unit smoothes the measured resistance of the strain gauge over time by means of a low-pass filter.

The low pass filter may be analog. The analog filter may be an electronic circuit that operates on a continuous-time analog signal. In an exemplary embodiment, the low pass filter is a digital filter. A digital filter is a system that performs mathematical operations on a sampled discrete-time signal to reduce or enhance certain aspects of the signal. The digital filter may be part of the evaluation unit.

With this solution it is possible to improve the reliability of the measured resistance and fit the measured resistance into the measurement series. Depending on the quality of the measured resistance, the accuracy of the calculation can be improved.

The external force measurement unit may be further improved in that the evaluation unit determines a drift of the measured resistances of the first strain gauge and the second strain gauge over time and recalibrates the first strain gauge and the second strain gauge by applying a drift compensation after a predefined time span.

The drift is the shift of the measured value (in particular the measured resistance) over time. The drift may be affected by the following factors: strain gauges heat up, signs of fatigue due to deflection, material creep under continuous loads on the order of magnitude of the measurement range in one direction, or sensitivity drift due to aging and hardening processes of various materials, and therefore recalibration is often required.

The predefined time span may also be a single event. For example, if the resistance changes from the previous resistance by more than a predefined threshold. The time span may also be defined as a number of rotations of the spindle.

With this solution it is possible to improve the uniformity and comparability of the measured resistances. This allows the external force to be calculated more accurately. This improves the overall quality of the external force measuring unit.

The external force measuring unit can be further improved by including a freewheel, which is positively connected to the spindle.

The freewheel may be an overrunning clutch. The freewheel allows the drive shaft to disengage from the driven shaft (especially the main shaft) when the driven shaft rotates faster than the drive shaft. The freewheel may be a pinch roller freewheel, a pinch body freewheel, a pawl freewheel, a claw ring freewheel, or a wrap spring freewheel. The freewheel comprises an inner part, also called star, and an outer part. The inner part is positively connected to the spindle. The inner portion may transfer force from the outer portion to the spindle.

With this solution, it is possible to separate the motor from the spindle when the spindle is turned faster than the motor can or is allowed to turn to support the external force.

The external force measuring unit may be further improved by including an angle encoder to determine the radial position of the spindle.

Angular encoders, also known as rotary encoders or shaft encoders, are electromechanical devices that convert the angular position or motion of a shaft or shaft into an analog or digital output signal.

The angle encoder may be an absolute encoder. The absolute encoder indicates the current spindle position. In an exemplary embodiment, the angular encoder is an incremental encoder. The output of the incremental encoder provides information about the movement of the spindle or the change in position of the spindle. In particular, the angular encoder may be an off-axis magnetic encoder.

With this solution it is possible to improve the position recognition of the spindle. The use of an angular encoder provides more detailed information about the position of the spindle and thus the pedal and pedal crank. Thus, more detailed information corresponding to the riding situation and force management may be provided.

The external force measuring unit may be further improved in that the main shaft is received inside the first bearing ring of the first bearing and inside the second bearing ring of the second bearing, wherein the main shaft applies a first force to the first bearing ring and a second force to the second inner bearing ring, wherein the first force and the second force are parts of an external force, which is applied to at least one end of the main shaft through the lever arm.

The spindle may include a spindle end at each side. The spindle end may be external to the motor housing. Each spindle end may support a lever arm. The lever arm may be a pedal crank. The pedal crank may have a predefined length. On one side of the pedal crank, the pedal crank may be mounted to the spindle end. On the other side of the pedal crank, a pedal may be received. External force acts on the pedal. The pedal crank transmits force to the spindle. The transmitted force may be a moment.

With this solution it is possible to calculate the external force and lever arm length depending on the measured resistance and to output a more detailed position of the pedal relative to the spindle.

The external force measuring unit may be further improved in that the evaluation unit calculates a moment that depends on the calculated force and an effective lever arm length of each lever arm, which effective lever arm length depends on the position of the spindle.

The length of the lever arm that contributes to the moment may vary depending on the position of the lever arm and pedal. For example, if the lever arm on each end is in a vertical position, the horizontal distance between the pedal and the spindle may be zero. Thus, the lever arm contributes little to the torque applied to the spindle.

As the spindle rotates, the pedal and pedal crank also rotate. Thus, the position of the lever arm changes over time. Depending on this change, the lever arm length contributing to the starting torque also changes over time. The horizontal distance between the pedal and the spindle is equal to the effective lever arm length. Thus, depending on pedal position, the effective lever arm length may change over time.

In this regard, the evaluation unit calculates a moment, which is applied to the spindle via the lever arm, as a function of the measured resistance and the determined first force.

In the case of forces acting on two pedals displaced 180 ° on each end of the spindle, external forces acting mainly in the tangential direction of the spindle rotation contribute to the moment.

With this solution it is possible to calculate a more accurate moment. Accurate measurement of torque is important for transmitting improved torque information to the engine control unit. The motor control unit can control the motor more precisely, and the motor can provide the spindle with a moment more suitable for the riding situation to support the external force applied to the spindle of the electric bicycle by a person.

According to another aspect, there is provided a measuring method for measuring an external force with an external force measuring unit including a load cell, the external force measuring unit housing a spindle.

The method comprises the steps of changing the resistance of a first strain gauge arranged on a first tab due to a change in length of the first tab and changing the resistance of a second strain gauge arranged on a second tab due to a change in length of the second tab, wherein each tab is arranged to a load cell.

The method further includes the step of measuring each resistance of the first strain gauge and the second strain gauge with an evaluation unit.

The method further comprises the step of determining, with the evaluation unit, a deflection of the external force induced by the weight of the spindle.

The method further comprises the step of determining the position of the lever arm of the spindle with an evaluation unit.

The method further comprises the step of determining, with the evaluation unit, an external force applied to the adapted spindle based on the measured resistance and the determined offset of the first force.

By this method, a more accurate and cost effective measurement method to determine the external force acting on the spindle is provided.

According to another aspect, there is provided an electric assist bicycle including an external force measuring unit.

For example, an electric assist bicycle is a bicycle that includes an electric motor to support or assist a rider and an energy store that stores energy to be provided to the electric motor in the form of electrical energy.

The electric motor may be, for example, a hub electric motor or a chain electric motor, which comprises at least one DC or AC powered electric motor. The energy store may be, for example, a battery or accumulator, such as a lead-based or lithium-based battery or accumulator. Alternatively or additionally, the energy store may be a fuel cell store. The electric motor provides energy in addition to the human muscle power of the rider pedaling the bicycle with the aid of the auxiliary factor. Examples of such electric assist bicycles are electric bicycles, such as electric bicycles or electric power assisted vehicles.

With this solution it is possible to provide an electric auxiliary bicycle with a motor unit having a load cell for measuring the resistance of the strain gauge. The load cell provides an improved external force measurement unit which is enhanced in terms of simplicity. Therefore, accuracy is improved, and manufacturing cost is reduced.

Regarding the advantages of the method and the electric assist bicycle, reference is made to the external force measuring unit and the embodiments described above.

It will be readily understood that individual or all steps of the method may be performed by the external force measurement unit, and vice versa.

According to another aspect, there is provided a motor unit for an electric assist bicycle comprising a freewheel, an outer ring, an inner ring and a sprocket carrier.

The freewheel is adapted to separate the sprocket carrier from the outer ring. Separation means that the inner ring can rotate at a different speed than the sprocket carrier.

With this solution, in a situation where the rotational speed generated by the external force is faster than the speed of the inner ring, the external force applied to the sprocket carrier is not transmitted to the inner ring. This results in reduced friction losses.

The motor unit may be further improved by including a freewheel.

The motor unit comprises no more than one freewheel. Specifically, the motor unit includes not less than one freewheel. The number of freewheel may be equal to one.

A motor unit with only one freewheel makes it possible to construct a more compact and smaller motor unit.

Furthermore, the motor unit comprises a motor housing which supports the freewheel, the outer ring, the inner ring and the sprocket carrier.

The motor housing may be made of plastic or metal. The motor housing may be vibration-proof and/or waterproof. The motor housing may protect the freewheel, outer ring, inner ring and sprocket carrier from environmental influences.

In another embodiment, the electric motor includes a rotor, wherein the rotor is mounted to a harmonic pin ring drive.

The harmonic pin ring drive provides a pinion gear between the electric motor and the spindle. Minimizing the size of the gears enables the drive unit to be minimized.

The motor housing may include a first motor housing portion, a second motor housing portion, and a third motor housing portion.

The first motor housing portion may be a gear box and an outer rim. The second motor housing portion is adapted to support a load cell. The third motor housing portion is adapted to support a sprocket carrier.

With this solution, the motor housing can be fitted to the frame of the bicycle. In addition, the size of the motor housing can be reduced.

In another aspect, an electric assist bicycle includes a motor unit, as described above.

The electric assist bicycle may include a frame. The housing of the motor unit may be mounted to the frame. The motor housing may also be integrated into the frame. The motor housing may support the motor unit.

Reducing the size of the motor housing results in improved drive characteristics.

In another aspect, a driving method is adapted to control an electric motor of a motor unit, the driving method comprising the steps of:

determining a second moment with the external force measuring unit, wherein the second moment is applied to the spindle via the crank,

-calculating a first moment based on the second moment, and

-controlling the electric motor based on the calculated second torque.

For example, the driving method may be applied to a driving unit, as described above. In particular, the drive unit may be built into the electric assist bicycle. The electric assist bicycle is ridden by a user. The user applies force to the pedal crank through the pedal. With respect to the measurement method described above, the second moment is detected. The second moment may be applied by a user.

Depending on the gain factor, a first moment is calculated. The first torque is provided by an electric motor. A first moment is applied to the main shaft by the freewheel.

Furthermore, the driving method includes a step in which a rotational direction of the spindle is determined.

Determining the direction of rotation enables control of the direction of rotation of the motor. By controlling the motor in both rotational directions, support can be provided for each rotational direction of the spindle.

For advantages of the method, the electric assist bicycle and the external force measuring unit, reference is made to a motor unit and a driving method.

The application also provides an electric auxiliary bicycle with the electric driving device, which comprises an external force measuring unit.

The application provides a stable electric auxiliary driving device. No long factory recalibration is required. The sensitivity of the sensor remains stable over a long period of time. The signal of the empty strain gauge is negative and it has low saturation. A small offset value is required and the conversion from the measurement signal to the control signal of the electric motor is linear. There is less hysteresis than other designs.

Embodiments of the present application will now be described with reference to the accompanying drawings, in which:

figure 1 shows a motor unit 1 comprising an external force measuring unit,

Figure 2 shows a schematic side view of the motor unit of figure 1,

figure 3 shows a perspective view of the motor unit of figure 1 with a freewheel on the front side of the first end,

figure 4 shows a view of the motor unit of figure 3 with a freewheel on the back side of the second end,

fig. 5 shows the motor unit of fig. 4 with a motor housing, which supports an external force measuring unit with a load cell and a spindle,

figure 6 shows a front perspective view of the load cell from the first end of the spindle as shown in figure 3,

figure 7 shows a rear perspective view of the load cell from the second end of the spindle as shown in figure 4,

fig. 8 shows a motor unit as shown in fig. 5 having a motor housing with a first fastening element and a second fastening element,

figure 9 shows an angle encoder with a hall sensor and a magnetic ring,

figure 10 shows the strain gauge of figure 1 in more detail,

figure 11 shows a front view of an external force measuring unit of the hall sensor assembled with the angle detector,

figure 12 shows a rear view of another embodiment of an external force measuring unit of the hall sensor assembled with the angle detector,

fig. 13 shows schematically a side view of the spindle with the pedal and pedal crank in vertical position and an external force f _e Acts on the pedal to make the pedal move,

fig. 14 shows schematically a side view of the spindle with the pedal and pedal crank in horizontal position and an external force f _e Acts on the pedal to make the pedal move,

figure 15 shows a graph of typical signals of measured resistance for each strain gauge mapped to the rotation angle of each pedal crank,

fig. 16 shows a graph of measured resistance of each strain gauge mapped to each pedal crank for low cadence without motor support,

fig. 17 shows a graph of typical signals of measured resistance of each strain gauge mapped to each pedal crank for high cadence, without motor support,

fig. 18 shows a cross section along the intersection line "AA" of fig. 8 through a load cell having a spindle, the load cell and spindle being mounted in a motor housing,

figure 19 shows a perspective view of another external force measuring unit,

fig. 20 shows a front view of the external force measuring unit of fig. 20, and

fig. 21 shows a detailed view of the area labeled "CC" in fig. 20.

In the drawings, the same or similar features are referred to by the same reference numerals and/or terms.

Fig. 1 shows a motor unit 1 or an electric drive device, which comprises an external force measuring unit 4.

The external force measuring unit 4 comprises a load cell 5 with a first bearing support 6. The first bearing support 6 comprises a support ring 61. The first tab 62 is integrally arranged on the support ring 61. The support ring 61 is also part of the load cell 5. The first tab 62 partially encircles the support ring 61. The first tab 62 is disposed on the opposite side from the second tab 65. The second tab 65 is also integrally arranged on the support ring 61 and partially surrounds the support ring 61. The first tab 62 and the second tab 65 are of the same size. The first tab 62 and the second tab 65 are arranged on the outside of the load cell 5 in a radial direction with respect to the support ring 61.

The first tab 62 protrudes from the symmetry axis 100 of the support ring 61 at an angle of about 90 °. And, the second tab 62 protrudes from the symmetry axis 100 of the support ring 61 at an angle of about 90 °.

The first tab end 63 is disposed on the outer end of the first tab 62 and the second tab end 66 is disposed on the outer end of the second tab 65.

The first tab 62 comprises a first strain gauge 64 in the area between the first tab 63 and the support ring 61, and the second tab 65 comprises a second strain gauge 67 in the area between the second tab 65 and the support ring 61.

The first bearing support 6 further comprises a first bearing seat 68, which supports the first bearing 7. The first bearing 7 comprises a first outer ring 71 and a first inner ring 72. At least one first bearing element 73 is arranged between the first outer ring 71 and the first inner ring 72.

The evaluation unit 8 is arranged on the load cell 5.

The motor unit 1 further comprises a second bearing 9. The second bearing 9 comprises a second outer ring 91. The second outer ring 91 is supported in a support bearing housing, not shown here, and the second inner ring 92. At least one second bearing element 93 is arranged between the second outer ring 91 and the second inner ring 92.

The first inner ring 72 and the second inner ring 92 of the first bearing 7 support the spindle 10 having a spindle symmetry axis 100, as shown in fig. 1. The spindle 10 includes a first end 103 and a second end 107.

The motor unit 1 also comprises an angular encoder, not shown here, for detecting a change in the angular position of the spindle 10. In an embodiment not shown here, the angular encoder detects the absolute angular position of the spindle 10.

The load cell 5 also includes a mechanical guide 69. The mechanical guide 69 locks the movement of the load cell 5 in the x-direction and the z-direction.

In one embodiment, the mechanical guide 69 is on the exterior of the load cell 5, immediately adjacent each tab at a 90 ° angle. The mechanical guide 69 comprises a plastic pin, not shown here, which locks the movement of the load cell 5 in the x-direction and in the z-direction. The plastic pins are arranged on and run along mechanical guides, which are arranged on the load cell carrier 51.

In another embodiment, a plastic pin is on each end along the z-axis for each tab end 63, 66. The plastic pin runs in the guide. The mechanical guide also locks the movement of the load cell in at least the x-direction.

Fig. 2 shows a schematic side view of the motor unit 1 of fig. 1.

The first end 103 of the spindle 10 is provided with a first crank 101 connected to a first pedal 102 by a first pedal spindle 130 having a first axis of symmetry 104 as shown in fig. 2. The first pedal 102 is rotatable about a first axis of symmetry 104 and transmits the rider's force to the first crank 101. Likewise, the second crank 105 is connected to the second pedal 106 by a second pedal spindle 131 having a first axis of symmetry 109 as shown in fig. 2. The second pedal 106 is rotatable about a second axis of symmetry 109 as shown in fig. 2 and transfers the rider's force to the first crank 101.

Fig. 2 also shows an angle encoder 11. The angular encoder 11 is mounted to the load cell 5, which also supports a first bearing 7 (not seen here). The angle encoder 11 is arranged between the first bearing 7 and the second bearing 9. The angle encoder 11 is arranged on the load cell 5 such that it remains stationary together with the motor housing 3.

The first pedal 102 applies an external force f _e To the spindle 10. In addition, the spindle 10 applies a first force f ₁ And a second force f ₂ To the second bearing 9 and the first bearing 7. And a first horizontal force f _x1 And a second horizontal force f _x2 From chain 114 to deflector blades 110, which act asA toothed front wheel for a bicycle is arranged on the main shaft 10.

The deflector blades 110 are mounted to the main shaft 10. First force f _x1 And a second force f _x2 Substantially perpendicular to external force f _e First force f ₁ And a second force f ₂ . External force f _e First force f ₁ And a second force f ₂ Acting along the y-axis. The forces acting along the y-axis are here vertical forces.

First horizontal force f _x1 And a second horizontal force f _x2 Acting along the x-axis. First horizontal force f _x1 And a second horizontal force f _x2 Acting in the horizontal direction.

Fig. 3 shows a motor unit 1' as shown in fig. 1 but with a freewheel 108.

On one side of the first bearing 7, the spindle 10 comprises a first end 103. On the other side of the first bearing 7, the main shaft 10 comprises a freewheel 108 and a second end 107. Freewheel 108 is a roller freewheel. The star of the freewheel 108 is arranged as a form-locking connection with the main shaft 10. It is also possible to arrange the star integrally on the main shaft, forming a single piece with the main shaft.

Fig. 4 shows a view of the motor unit 1' of fig. 3 with the freewheel 108 from the rear side of the second end 107.

Freewheel 108 includes a freewheel clutch not shown here. The freewheel clutch has a spring-loaded roller inside the slave cylinder. At least one of the parts of the star has a bevel on one side. On the opposite side, the star has edges in the radial direction of the spindle 10. The edge is immediately adjacent the spindle 10. The proximal edge is arranged tangentially to the spindle 10. The cover covers the front side of freewheel 108. Each portion of the star includes a recess immediately adjacent the radial side. The recess is arranged on the side opposite to the bevel.

In another embodiment not shown here, the freewheel is a clamping freewheel. The clamping freewheel comprises at least two zigzag spring-loaded disks which rest against one another with the tooth flanks together, like a ratchet. Rotating in one direction, the teeth of the driving disk lock with the teeth of the driven disk, causing them to rotate at the same speed.

Fig. 5 shows a motor unit 1 with a motor housing 3 supporting an external force measuring unit 4 with a load cell 5 and a spindle 10.

The motor housing 3 supports the motor unit 1. The motor unit 1 is mounted to the motor housing 3 by a holding plate 31 having four screws 32. The holding plate 31 holds the first tab end 63 and the second tab end 66. The first tab end 63 and the second tab end 66 are clamped between the motor housing 3 and the holding disk 31 by the screw 32. Each tab 62, 65 is also stationary due to the clamping of the first tab end 63 and the second tab end 66.

Thanks to the fixation of each tab 62, 65, the load cell 5 with the first bearing support 6 and the support ring 61 is fixed in the load cell carrier 51 of the motor housing 3, not shown here. The motor housing 3 also comprises a support bearing housing, not shown here, for mounting a second bearing, also not shown here.

The spindle comprises a first end 103 which faces the outside of the motor housing 3.

As can best be seen in fig. 5, in the mounted state of the load cell 5 in the motor housing 3, a spacer (not shown here) made of plastic or aluminum can be inserted between the lateral side of the first tab 62 and the adjacent screw 32 and between the lateral side of the second tab 65 and the adjacent screw 32. These distance members transmit the horizontal force of the load cell 5 to the motor housing 3, thereby preventing the spindle 10 from moving horizontally due to the horizontal force acting on the spindle 10, e.g. caused by a bicycle chain.

Fig. 6 shows a front view of the load cell 5 from the first end 103 of the spindle 10 as shown in fig. 3.

The edge between the support ring 61 and the first bearing housing 68 is ground smooth.

Each tab 62, 65 has less than half the size of the support ring 61 in the direction of the principal axis of symmetry 100. One side in the direction of the principal axis of symmetry 100 of each tab 62, 65 is arranged on the same plane as the support ring 61. The opposite side is connected to the support ring by a smooth connection.

Each tab end 63, 66 is disposed on the proximal end of the support ring 61. The tab ends 63, 66 are bent in almost the same shape as the support ring 61. The edges of each tab end 63, 66 are ground smooth. The tab ends 63, 66 are directed to the front side of the load cell 5. The tab ends 63, 65 have nearly the same width as each tab 62, 64.

Fig. 7 shows a rear view of the load cell 5 from the second end 107 of the spindle 10 as shown in fig. 4.

The support ring 61 is associated with the front edge of the first bearing seat 68. The front edge is disposed inside the first bearing seat 68.

Fig. 8 shows a motor unit 1 as shown in fig. 5 with a motor housing 3 having a first fastening element 33 and a second fastening element 34.

The first fastening element 33 and the second fastening element 34 are arranged on the outside of the motor housing 3. The first fastening element 33 and the second fastening element 34 are used for mounting the motor housing 3 to a bicycle frame, which is not shown here.

The first two fastening elements 33 are arranged on opposite sides of the motor housing 3. One of the two first fastening elements is arranged immediately outside the battery holder 12 of the motor housing 3.

The second fastening elements 34 are arranged in a rectangular shape. One of the four second fastening elements 34 is arranged next to the first fastening element 33, said second fastening element being positioned on the opposite side from the first fastening element 33 next to the battery holder 12.

The first fastening element 33 has a larger diameter than the second fastening element 34.

The battery holder 12 is also part of the motor housing 3. The battery holder 12 is arranged on the periphery of the motor housing 3 between two first fastening elements 33.

Fig. 9 shows an angle encoder 11 comprising a hall sensor 111 and a magnetic ring 112.

The magnetic ring includes 72 north magnetic poles and 72 south magnetic poles. North and south magnetic poles alternate on the magnetic ring 112. The change from one pole to one pole is equal to a 2.5 change in the position of the magnetic ring.

When the magnetic ring 112 rotates and the hall sensor 111 is in a fixed position, the magnetic poles are alternating. The hall sensor 111 measures a magnetic field. The hall sensor 111 detects a change in the magnetic field. Thus, each switching from the south pole to the north pole and vice versa is detected. A magnetic ring 122 is arranged to the spindle 10. The change in the position of the spindle 10 is detected depending on the change in the position of the magnetic ring 112 relative to the hall sensor 111.

In another embodiment, the angular encoder is an on-axis magnetic encoder. The on-shaft magnetic encoder uses specially magnetized 2-pole neodymium magnets attached to the motor shaft. Because it can be fixed to the end of the shaft, it can work with a motor having only 1 shaft extending out of the motor body.

In another embodiment, the housing of the spindle 10 comprises (in cross-section) a tooth form. The hall sensor 111 may be arranged directly above the tooth profile. As the spindle 10 rotates, the castellated hills and valleys alternate below the hall sensor 111. The change from hills to valleys and vice versa changes the magnetic field.

Fig. 10 shows the strain gauges 64, 67 of fig. 1 in more detail.

The first strain gauge 64 and the second strain gauge 67 are designed as dual-axis strain gauges. The two-axis strain gauge measures the change in length in one first direction with the second portion 642 of the two-axis strain gauges 64, 67. The dual-axis strain gauge also measures the change in length in a second direction, perpendicular to the first direction, with a first portion of the dual-axis strain gauge 64, 67.

In one embodiment, using the first strain gauge 64 as shown in fig. 1, only the first portion 641 is used to measure the change in length of the first tab 62 between the support ring 61 and the first tab end 63.

When the second strain gauge 67 is used, as shown in fig. 1, only the first portion 642 is used to measure the change in length of the second tab 65 between the support ring 61 and the second tab end 66.

The first portion 641 of the first strain gauge 64 and the first portion 642 of the second strain gauge 67 measure the vertical change in length in the y-direction as shown in fig. 10.

Fig. 11 shows a front view of the external force measurement unit 4 of the hall sensor 111 assembled with the angle detector 11.

The magnetic ring 112 and the hall sensor 111 of the angle detector 11 are arranged on the front side, as shown in fig. 6. The magnetic ring 112 is rotatably arranged on the support ring 61 of the bearing support 6. The magnetic ring 112 is rotatably arranged, while the hall sensor 111 is fixed. The hall sensor 111 is arranged to detect a change in the magnetic field from the magnetic loop 112.

A plastic cover 113 covers the magnet ring 111. The plastic cover 113 has a recess, and the hall sensor 112 is arranged in the recess.

The angle decoder may be a conventional hall sensor 111 mounted at the load cell, while the magnetic flux through the hall sensor 111 may be a series of magnets in the form of magnetic rings 112 arranged in a ring at adjacent sections of the spindle directly below the hall sensor 111.

As an alternative to the magnetic ring 112, the magnetic flux through the hall sensor 11 may also be a series of short flux slots arranged in years in the spindle 10 directly below the hall sensor element 111, but is not shown in fig. 9. The spindle 10 must then be provided with a magnetic material which causes the hall sensor 111 to signal when the spindle 10 rotates. Each of these flux slots extends longitudinally in the z-direction parallel to the axis of symmetry of the spindle 10, and is arranged on a circumference in the outer cylindrical surface of the spindle 10. For example, 36 flux slots are arranged at every 10 degrees of angular position on a 360 degree circumference in the outer cylindrical surface of the spindle 10, and each flux slot may have a circumferential width corresponding to a 5 degree section of the outer cylindrical surface of the spindle 10. One of the 36 slots may have a width in the circumferential direction that is greater than the other 35 slots, or the reference slot may have a depth that is greater than the other slots. When the spindle 10 rotates while the hall sensor 111 remains stationary with the motor housing 3, the hall sensor 111 may detect changes in the magnetic flux caused by a series of flux slots as they move under the hall sensor 111, and the changing values of the hall sensor signals provide the angular position of the spindle relative to the hall sensor 111 and the motor housing 3. The reference flux slots cause a change in hall sensor signal that is different from the change in hall sensor signal caused by the conventional flux slots and is used to detect the absolute angular position of the spindle 10 relative to the hall sensor 111.

Fig. 12 shows a rear view of another embodiment of the external force measurement unit 4 of the hall sensor 111 assembled with the angle detector 11.

The magnetic ring 112 and the hall sensor 111 of the angle detector 11 are arranged on the back side, as shown in fig. 7. Also, a first strain gauge 64 and a second strain gauge 67 are arranged on each back side of the fins 62, 65.

An evaluation unit 8 is attached to the load cell 5. The evaluation unit 8 is connected to the first strain gauge 64, the second strain gauge 67 and the hall sensor 111.

A magnetic ring 112 is arranged on the back side of the support ring 61. The hall sensor 111 is fixed. The hall sensor 111 is arranged to detect a change in the magnetic field from the magnetic loop 112.

A plastic cover 113 covers the magnet ring 111. The plastic cover 113 has a recess. A hall sensor 112 is arranged in the recess.

Fig. 13 shows a schematic side view of the spindle 10, wherein pedals 102, 106 and pedal cranks 101, 105, while a first external force f _e1 Acting on the first pedal 102 and a second external force f _e2 Acting on the second pedal 106. The load cell 5 with the first ball bearing 7 is not shown here.

In this view, the pedal cranks 101, 105 are in a vertical position along the y-axis. The first pedal 102 applies a first external force f through the first pedal crank 101 _e1 Is provided to the spindle 10. The second pedal 106 applies a second external force f via the second pedal crank 105 _e2 To the spindle 10.

First external force f _e1 And a second external force f _e2 Is an external force f _e The external force acts on the spindle 10. Each external force f _e1 、f _e2 Acting in the same vertical direction.

Fig. 14 shows a schematic side view of the spindle 10 with the pedals 102, 106 and pedal cranks 101, 105 in a horizontal position. The load cell 5 with the first ball bearing 7 is not shown here.

In this view, the pedal cranks 101, 105 are in a horizontal position. First external force f _e1 Acting on the first pedal 102 and a second external force f _e2 Acting on the second pedal 106. Each pedal applies an external force f through each corresponding pedal crank 101, 105 _e1 And f _e2 To the spindle 10. Each external force f _e Acting in the same vertical direction. First external force f _e1 And a second external force f _e2 Is an external force f _e The external force acts on the spindle 10.

Fig. 15 shows a graph of typical signals of measured resistance of each strain gauge 54, 67 mapped to each pedal 102, 106 at the angular position of the spindle 100.

The graph is a single line graph. The y-axis represents the corresponding resistance and the x-axis represents time.

The first signal 201 shows the course of the resistance mapped to the first pedal 102. Two periods p1 of the first signal are plotted. The first signal has a first period p1 and a first amplitude a1. The first signal 201 is almost a sine function. The first signal is shifted almost in the negative y-direction by a first amplitude a1.

The second signal 202 shows the course of the resistance mapped to the second pedal 106. Two periods p2 of the first signal are plotted. The second signal 202 has a second period p2 and a second amplitude a2. The second signal 202 is almost a sine function. The second signal is shifted almost in the negative y-direction by a second amplitude a2. The second signal 202 has a plateau at its maximum value. The length of the plateau is almost half of the second period p2.

The first signal 201 is shifted by almost half of the period p1, p2 to the second signal 202. The second amplitude p2 is almost half of the first amplitude p 1. The first period p1 and the second period p2 are almost the same.

The maximum value of each signal 201, 202 is disposed on the baseline 210. In addition to the shift in the y-direction, each signal 201, 202 has an offset o1. The offset ol corresponds to the shift between the baseline 210 and zero.

Fig. 16 shows a graph of typical signals mapped to the resistance of each pedal 102, 106 for a low cadence of a pushing rider without motor support.

The hall sensor signal 205 shows the change in magnetic field measured with the angle detector 11. Each change in the hall sensor signal 205 corresponds to a change in the magnetic field due to a change in the detected magnetic pole of the magnetic loop 112.

The ramp function 206 shows the calculated relative position of the spindle 10. A ramp function 206 is calculated based on the hall sensor signal 205. The middle m3 of the ramp period p3 is arranged at almost the same x position as the middle m1 of the first period p 1. Also, the minimum value of the second signal 202 is almost at the same x position as the middle m1 of the first period p 1.

Each signal 201, 201 has a plateau at its maximum value. The magnitude of the maximum value is almost half of the first period p 1. The first signal 201 is shifted to the second signal in the y-direction.

Fig. 17 shows a graph of typical signals mapped to the resistance of each pedal 102, 106 for a high cadence pushing the rider without motor support.

The procedure of the first period p1 and the second period p2 and their positions with respect to each of them are almost the same as those illustrated in fig. 16. The first signal 201 has a shorter plateau at its maximum point compared to fig. 16. Which is almost a quarter of the period m1.

The middle m3 of the ramp period p3 of the ramp function 206 is shifted in the negative x direction with respect to the middle m1 of the first period p 1. The minimum value of the second signal 202 is shifted by a quarter of the first period to the middle m1 of the first period p 1.

The first signal 201 and the second signal 202 are delayed more relative to the ramp function 206 as shown in fig. 16.

At each intersection 207 of the first plot 201 and the second plot 202, the left pedal is in its highest y position. The first pedal is a pedal, which is arranged on the left side of the spindle 10. The left side is a side on the left side of the main shaft 10 when the main shaft 10 moves in the total moving direction.

The evaluation unit determines a control signal to the electric motor driving the spindle 10 on the freewheel device 108 based on the signals of the angular encoder and the first and second strain gauges shown above.

Fig. 18 shows a cross-sectional view along the intersection line AA of the load cell 5 as shown in fig. 8, with the spindle 10 mounted in the motor housing 3.

The motor housing 3 is cut along the intersecting line AA as shown in fig. 5 and 8.

The load cell 5 is arranged on the motor housing 3. Between each tab 62, 65 with each tab end 63, 66 and the motor housing 3 is a gap in the y-direction. In the z-direction, the load cell 5 is fixed with a holding plate 31. The holding plate 31 is fixed to the motor housing by screws 32. The holding plate 31 includes a central hole, and the spindle 10 is fitted through this hole. The aperture includes a sealing lip on an inner edge thereof. The sealing lip protects the load cell 5 from the environment.

As shown in fig. 2, an external force f _e Acting on the first pedal 102. External force f _e Is a force acting along the y-direction and mainly in the negative y-direction. The first pedal crank 101 applies an external force f through the first pedal spindle 104 _e From the first pedal 102 to the first pedal crank 101. The first pedal 102 is rotatable about a first spindle symmetry axis 104, as shown in fig. 2. Thus, the first pedal 102 is maintained in a horizontal position.

The first crank 101 is rotatable about an axis of symmetry 100. The first pedal crank 101 is mounted to the first spindle end 103 to apply an external force f _e To the spindle 10.

The main shaft 10 applies an external force f _e To the first bearing 7 and the second bearing 9. The first inner bearing ring 72 of the first bearing 7 is subjected to a first force f _l The first force is an external force f _e Is a part of the same. The second inner bearing 92 of the second bearing 9 is subjected to a second force f ₂ The second force is also an external force f _e Is a part of the same. First force f ₁ With a second force f ₂ Is equal to the sum of the external forces f _e . The first inner bearing ring 72 and the second inner bearing ring 92 will each force f ₁ 、f ₂ To each roller 73, 93 of each bearing 7, 9. Each rollThe rollers 73, 93 arrange each inner bearing ring 72, 92 rotatable to each outer bearing ring 71, 91.

The support ring 61 supports the first bearing 7. The first bearing 7 applies a first force f ₁ To the support ring 61. The support ring 61 applies a first force f ₁ To the first tab 63 and the second tab 66.

External force f _e First force f ₁ And a second force f ₂ Is a vertical force. The vertical force acts in the y-direction.

In an embodiment not shown here, the external force f _e Acting on the second pedal 106. As explained above, the second pedal 106 applies the external force f through the second pedal spindle 109 _e To the second pedal crank 105. The second pedal is rotatable about a second spindle 109 having a second spindle symmetry axis 131, as shown in fig. 2.

The second crank 105 applies an external force f _e Is transferred to the spindle 10 and is rotatable about a spindle symmetry axis 100, as shown in fig. 2. The second crank 105 is mounted to the second end 107 of the spindle 10. An external force f transmitted to the spindle in the same manner as explained above _e Is transmitted to the motor housing 3 through the first bearing 7, the second bearing 9 and the load cell 5.

Chain 114, not shown here, will exert a horizontal force f _x1 、f _x2 To the deflector vane 110. First horizontal force f _x1 The deflector blades 110 are pulled in the horizontal x-direction. Second horizontal force f _x2 Pushing the deflector blades in the horizontal x-direction.

The deflector blades 110 will exert a horizontal force f _x1 、f _x2 To the spindle 10. The spindle 10 also applies a horizontal force f via the ball bearings 7, 9 as explained above _x1 、f _x2 To each ball bearing housing. Horizontal force f _x1 、f _x2 Independent of force f _e 、f ₁ 、f ₂ And are not further considered herein.

The second ball bearing 9 applies a second force f _x2 To the motor housing 3.

Due to the transmitted first force f ₁ The first strain gauge 64 measures a first airfoil62. The second strain gauge 67 also measures a force f dependent on the first force ₁ A change in the length of the second tab 65. Each strain gauge 64, 67 changes its resistance due to the change in length.

The evaluation unit 8 shown in fig. 1 determines the resistance of each strain gauge 64, 67. Due to the predefined material expansion coefficient, the evaluation unit 8 calculates the force measured with each strain gauge 64, 67 depending on the change in the resistance of each strain gauge 64, 67, and calculates the first force f ₁ 。

The strain gauges 64, 67 are arranged to measure primarily the change in length in the radial airfoil direction, as shown in fig. 1.

As shown in fig. 10, each strain gauge 64, 67 includes a vertical strain gauge and a horizontal strain gauge. To measure the change in length of each tab 62, 65, only the vertical portion 641 of each strain gauge 64, 67 is used. The first horizontal portion of each strain gauge 64, 67 is used to measure the change in length due to the change in temperature. This determined temperature change is later used to calculate drift compensation.

Each strain gauge 64, 67 may be part of a half-bridge circuit. For example, a voltage of 36 volts is connected to each outer end of the strain gauge. As each resistance changes, the relationship between the pressures decreases in the first portion 641 and the second portion 642. Depending on this relationship, the resistance of each portion 641, 642 is calculated.

Furthermore, each airfoil 62, 65 will apply a first force f ₁ To each tab end 63, 66. The tab end 63, 66 will apply a first force f ₁ Is transferred to a load cell seat 68 of the motor housing 3 in which the load cell 5 is supported.

In addition to the first strain gauge 64 and the second strain gauge 67, the motor unit 1 includes an angle detector 11. An angle detector 11 is attached to the load cell 5 to detect a change in the position of the spindle 10 relative to the spindle symmetry axis 100. The hall sensor 111 of the angle detector 11 has a fixed position with respect to the magnetic ring 112, and detects a change in the magnetic field from the magnetic ring 112, which is connected to the spindle 10. The change in position of the magnetic ring 112 indicates a change in position of the spindle 10. In addition, the magnetic ring 112 includes a first marker and the spindle includes a second marker. In the case of an angular encoder detecting an absolute position, it is necessary to match the first mark with the second mark at the time of assembly.

The relative position of the first pedal crank 101 is determined by the evaluation unit 8 depending on the change in position of the spindle 10. The absolute position of the spindle 10 is determined depending on the positional calibration of the spindle 10. The absolute position of the first pedal crank 101 is determined due to the absolute position of the spindle 10. The position of the pedal 102 relative to the spindle 10 is calculated depending on the absolute position of the first pedal crank 101.

Taking into account the external force f _e Mainly acts on the pedal 102 when the first pedal 102 is more in the positive x direction than the spindle 10, determining the external force f _e Acting on which pedal.

Dependent on the first force f ₁ With a second force f ₂ The evaluation unit 8 determines the external force f _e 。

The external force f is alternately applied between each pedal 102, 106 _e . Force f _e Mainly to pedals 102, 106, which move downwards in the negative y-direction.

As shown in fig. 13, a first external force f _e1 Acts on the first pedal 102 and the second force f _e2 Acting on the second pedal 106. External force f applied to the downwardly moving pedals 102, 106 _e1 、f _e2 Greater than the force acting on the other pedal 102, 106. For example, if the first pedal 102 is traveling downward, a first external force f _e1 Is greater than the second external force f _e2 。

As shown in fig. 13, the first pedal 104 is in a higher position relative to the y-position than the second pedal 106. Thus, a first external force f _e1 Is greater than the second external force f _e2 . Even in this position, the second external force f _e2 For total external force f _e With the contribution that the total external force acts on the spindle 10.

Providing an external force f _e1 、f _e2 Is required to be balanced so that the second external force f _e2 Greater than zero.

As shown in fig. 14, step onThe plates 102, 106 are at approximately the same height relative to the y-position. In this case, an external force f acting in the pedal direction _e1 、f _e2 Larger. For example, if the pedal rotates counterclockwise about the spindle symmetry axis 100, the first external force is greater than the second external force f _e2 . Providing a first external force f _e2 Must maintain its balance, a second external force f _e2 Greater than zero, as explained above.

Fig. 15 shows a graph with two lines. The first graph 201 shows the resistance of the second strain gauge 65. The first graph 201 has several minima and maxima. At each minimum of the first graph 201, a first force f _e1 And begins to act on the first pedal 102. As the first pedal 102 travels downward, the resistance changes from its maximum value to its minimum value. With each repetition of the rotation of the first pedal 102, the first graph 201 repeats.

As explained above, the second graph 202 shows the resistance of the first strain gauge 62. At each minimum, the second pedal 106 is in its lowest x position.

The change in each graph 201, 202 is equal to a half turn of the pedals 102, 106 about the spindle symmetry axis 100, as shown in fig. 2.

Due to the small external force f at all times _e For example, gravity, acts on the spindle 10, so each graph 201, 202 has an offset o1 between the baseline 210 and zero.

Due to the ball bearing clearance of the first bearing 7 and for other reasons, the change in resistance of one strain gauge 62, 64 is delayed relative to the change in resistance of the other strain gauge 62, 64. Thus, the maximum value of one graph 201, 202 and the minimum value of the other graph 201, 202 do not have the same x position. Graphs 201, 202 are respectively delayed. And there is a gap between the first tab, not shown here, having the first tab end and the load cell carrier, also not shown here. Because of these gaps, the maximum value of the second graph 202 has a plateau.

Taking into account the offset o1 and the delay, the evaluation unit 8 determines a zero calibration, which is applied to the determined first force f ₁ . Taking outIn this case, the external force f is calculated _e 。

As shown in fig. 16 and 17, the hall sensor signal 205 is used to calculate a ramp function 206. The ramp function 206 is calculated by summing each absolute value of the hall sensor signal 205 and counting the number of signals. After one revolution of the spindle 10 equal to 144 hall sensor signal changes, the ramp function 206 is set to zero. This operation is repeated for each turn.

Fig. 16 shows a graph at a low tempo, and fig. 17 shows a graph at a high tempo. Comparing the two graphs, in the graph showing the high tempo shift, the ramp function is shifted more in the negative x-direction than in fig. 16 with respect to the first graph 201 and the second graph 202. This means that the relation between the ramp function 206 and the graphs 201, 202 depends on the tempo. When the spindle 10 has a high cadence, centrifugal force acts on the spindle 10. Centrifugal force is also measured with each strain gauge 64, 67. Thus, the centrifugal force is also the determined first force f _l But not an external force f _e Is a part of the same. Determining the actual external force means compensating the centrifugal force. This is done by the evaluation unit 8.

In one embodiment, the evaluation unit 8 considers the ramp function 206 and the graphs 201, 202 and calculates the absolute pedal position. With the knowledge according to which the first pedal 102 is at its lowest position at each minimum of each graph 201, the ramp function is calibrated to this position. Calibration for the second graph 202 and the second pedal 106 functions in a similar manner.

In another embodiment, the evaluation unit 8 smoothes the measured resistances of the first strain gauge 64 and the second strain gauge 67. Smoothing is performed with a low pass filter. The signal from each strain gauge 62, 66 passes through a low pass filter. If the signal frequency is less than the selected cutoff frequency, the signal passes through a low pass filter.

If the signal frequency of the signal is above the selected cutoff frequency, the low pass filter attenuates the frequency at a frequency above the cutoff frequency. The measurement error and noise of the resistance signal are smoothed in this way.

In another embodiment, the evaluation unit 8 applies leveling to the measured resistance of each strain gauge 64, 67. The leveling compensates for errors in the measurement corresponding to the heating of the strain gauges 64, 67. If the strain gauges 64, 67 become hot, the relationship between resistance and length change will change. This means that the predefined relationship between resistance and length change is inaccurate.

Thus, the evaluation unit 8 calculates a leveling compensation and applies this compensation to the measured resistance. This leveling compensation is an offset that is applied to each strain gauge 64, 67. Leveling compensation is applied to the measured value of each resistance of the strain gauges 64, 67 after a predefined span.

In another embodiment, the absolute position of the pedal cranks 101, 105 and the external force f are dependent _e The moment is determined. Depending on the position of the pedals 102, 106, the position of the pedal cranks 101, 105 and the position of the spindle 10, the effective lever arm length of the pedal is calculated.

The lever arm length of the pedal cranks 101, 106 is predefined and saved to the evaluation unit 8. When the position of the pedals 102, 106 is changed, the vertical distance between the pedals 102, 106, together with the pedal cranks 101, 105, and the spindle symmetry axis 100 is also changed. The effective lever arm length is equal to the distance between the pedals 102, 106 and the spindle symmetry axis 100. The evaluation unit 8 depends on the calculated external force f, taking into account the effective lever arm length _e The moment is determined.

In another embodiment, the signal of the torque provided by the electric motor to the spindle 10 is determined according to the following hierarchical calculations.

Level 1: screening of strain gauge signals

Level 2: zero adjustment of spindle 10

Level 3: zero adjustment of electrical signals

Level 4: calculation of the resulting force acting on the spindle

Level 5: calculation of equilibrium forces

Level 6: evaluation of pedal position

Level 6: calculation of spindle torque/electric motor control signals

Although the calculation of the spindle torque/electric motor control signal may be performed using only the level 1 information, the calculation accuracy improves as the information level increases. The design of the present application provides a system that permits individual levels of information to be tested and adjusted at the same electrical drive.

In practice, the zero point of the strain gauge signal may be calculated only after 2 pedal rotations. The zero point is continuously adjusted.

The resulting force may be calculated by the difference of the forces of the two strain gauges. The two strain gauge signal amplifiers may be tuned by HPF. The amplifier of the right pedal should be adjusted to be higher than the amplifier of the right pedal.

The equalization force is the force exerted by the pushing rider also using the passive legs. After having a reliable signal offset, the equalization force is calculated after about two pedal rotations. Due to practical considerations, the equalization forces are limited to between 10N and 200N.

It is also possible to readjust the equalization force after one pedal rotation or after half pedal rotation.

If the right pedal is located behind the actual right line through the center of the spindle, then the upper strain gauge will never be present.

Fig. 19 shows a front perspective view of another embodiment of a load cell 5' from a first end of a spindle not shown herein.

The load cell 5' has an anchor tab 250 that protrudes from the axis of symmetry 100 of the support ring 61 at an angle of about 90 °. A fixation pin hole 251 is provided in the anchor tab 250, the symmetry axis of the fixation pin hole 251 being substantially parallel to the symmetry axis 100 of the support ring 61.

In the mounted state of the load cell 5' in the motor housing 3, a fixing pin (not shown here) is inserted into the fixing pin hole 251 and into a corresponding anchoring hole in the motor housing 3. The fixing pin transmits the horizontal force of the load cell 5' to the motor housing 3, thereby preventing the spindle from moving horizontally due to the horizontal force acting on the spindle, for example, caused by a bicycle chain.

The horizontal arrangement of the anchor tab 250 provides for the first and second strain gauges 64 and 67 to remain outside of the deformation zone caused in the load cell 5' by these horizontal forces, as compared to the vertical arrangement of the first and second tabs 62 and 65 carrying the first and second strain gauges 64 and 67. This differs from the solution presented in fig. 5 in that the accuracy of the measurement of the vertical force transmitted by the spindle to the load cell 5' is improved, the distance piece being located between the lateral side of the first tab 62 and the adjacent screw 32 and between the lateral side of the second tab 65 and the adjacent screw 32. The design of the anchor tab 250 and the fixation pin in the fixation pin hole 251 not only provides a better measurement of the vertical force, but also the distance piece is not worn out since it is no longer needed.

Fig. 20 shows a front view of the external force measuring unit of fig. 20.

The angle decoder in fig. 21 is a pair of conventional hall sensors 255, 256 mounted at the load cell directly above the spindle 10 provided with a flux slot ring 280.

The accuracy of the device is improved by using two hall sensors 255, 256 and by biasing the spindle 10 with a permanent magnet 265 placed near the hall sensors 255, 256, at a position directly above the hall sensors 255, 256 and above the spindle 10.

Fig. 21 shows a detailed view of the area labeled "CC" in fig. 20.

The magnetic flux through the hall sensors 255, 256 is provided by a series of short flux slots 282, 283 in the spindle 10, which are arranged in year directly below the hall sensors 255, 256.

Each of these flux grooves 282, 283 extends longitudinally parallel to the axis of symmetry of the spindle 10, and these grooves 282, 283 are arranged on a circumference in the outer cylindrical surface of the spindle 10. The width of the reference flux slot 282 in these slots is smaller than the other flux slots 283. When the spindle 10 rotates while the hall sensors 255, 256 remain stationary with the motor housing 3, the hall sensors can detect changes in the magnetic flux caused by the series of flux slots 282, 283 as these flux slots 282, 283 move under the hall sensors 255, 256, and the constantly changing values of the hall sensor signals provide the angular position of the spindle 10' relative to the hall sensors 255, 256 and the motor housing 3. The reference flux slot 282 causes a change in the hall sensor signal that is different from the change in the hall sensor signal caused by the conventional flux slot 283 and is used to detect the absolute angular position of the spindle 10 relative to the hall sensors 255, 256.

There is also a reference flux shoulder 281 between the flux grooves 282, 283 that is wider in the circumferential direction than the flux shoulders between the other flux grooves 282, 283. The wider reference flux shoulder 281 causes a change in the hall sensor signal that is different from the change in the hall sensor signal caused by a conventional flux shoulder and is used to detect the absolute angular position of the spindle 10 relative to the hall sensors 255, 256.

Example 1

For measuring external force (f _e ) An external force measuring unit (4) of the above, the external force measuring unit (4) comprising a first strain gauge (64) and an evaluation unit (8), the evaluation unit being further adapted to determine the external force (f) _e )。

Example 2

The external force measurement unit (4) according to example 1, wherein the external force measurement unit (4) is applied to a spindle (10).

Example 3

The external force measurement unit (4) according to any of the previous examples, comprising a load cell (5) having a support ring (61), wherein a first tab (62) and a second tab (65) are arranged on the support ring (61), wherein the second tab (65) is arranged on the support ring (61) opposite to the first tab (62), wherein each tab (62, 65) is arranged to the outside of the outer ring (61) in a radial direction, and a first tab end (63) and a second tab end (66) are arranged at respective ends of the first tab (62) and the second tab (64).

Example 4

The external force measurement unit (4) according to any of the previous examples, wherein the first strain gauge (64) is arranged on the first tab (62), wherein the first strain gauge (64) is adapted to change its respective resistance depending on a change in length of the first tab (62) due to material expansion.

Example 5

The external force measurement unit (4) according to any of the previous examples, comprising a second strain gauge (67) arranged on the second wing (65), wherein the second strain gauge (67) is adapted to change its respective resistance depending on a change in the length of the second wing (65) due to material expansion.

Example 6

The external force measurement unit (4) according to any of the previous examples, comprising a first bearing support (6) to support a first bearing (7) in a first bearing seat (68).

Example 7

The external force measuring unit (4) according to any of the previous examples, comprising the first bearing (7) having a first outer ring (71), wherein the first outer ring (71) is mounted to the first bearing seat (68) for transmitting a first force (f ₁ ) Wherein the external force (f _e ) Comprises said first force (f ₁ ) And a second force (f ₂ ) The first force is transmitted from the spindle (10) to the first bearing (7) to a first inner ring (72), the second force is absorbed by an adapted second bearing (9), and the first inner ring (72) is connected to a first outer rolling ring (71) by a first bearing element (73) to transmit the first force (f) from the adapted spindle (10) ₁ )。

Example 8

The external force measurement unit (4) according to any of the previous examples, wherein the evaluation unit (8) is adapted to measure the resistance of the second strain gauge (67) to determine the external force (f _e )。

Example 9

The external force measurement unit (4) according to any of the previous examples, wherein the evaluation unit (8) is further adapted to determine the external force (f) induced by the weight of the spindle (10) _e ) And the evaluation unit is further adapted to determine the position of the lever arm of the spindle (10) and to determine the external force (f _e ) The external force is based on the measured resistance and the first force (f ₁ ) Applied to the adapted spindle by a determined offset of (a)(10)。

Example 9

The external force measurement unit (4) according to any of the previous examples, further comprising a motor housing (3).

Example 10

The external force measurement unit (4) according to any of the previous examples, wherein the first tab end (63) and the second tab end (66) are adapted to mount the load cell (5) to a load cell carrier (51) on the motor housing (3) of the spindle (10).

Example 11

The external force measurement unit (4) according to any of the previous examples, wherein a second outer ring (91) is mounted to a second rolling support of the motor housing (3).

Example 12

The external force measurement unit (4) according to any of the previous examples, wherein the evaluation unit (8) smoothes the measured resistance of the strain gauge (64, 67) over time by a low pass filter.

Example 13

The external force measurement unit (4) according to any of the previous examples, wherein the evaluation unit (8) determines a drift of the measured resistance of the first strain gauge (64) and the second strain gauge (67) over time.

Example 13

The external force measurement unit (4) according to any of the previous examples, wherein the evaluation unit (8) recalibrates the first strain gauge (64) and the second strain gauge (67) by applying drift compensation after a predefined time span.

Example 14

The external force measuring unit (4) according to any of the previous examples, further comprising a freewheel (108) which is positively connected with the main shaft (10).

Example 15

The external force measurement unit (4) according to any of the previous examples, further comprising an angular encoder (11) to determine the radial position of the spindle (10).

Example 16

The external force measurement unit (4) according to any of the previous examples, further comprising the spindle (10) received inside a first bearing ring (72) of a first bearing (7) and inside a second bearing ring (92) of a second bearing (7), wherein the spindle (10) couples the first force (f) ₁ ) Is applied to the first bearing ring (72) and a second force (f ₂ ) Is applied to a second inner bearing ring (92), wherein the first force (f ₁ ) And the second force (f ₂ ) For the external force (f _e ) Is a part of the same.

Example 17

The external force measurement unit (4) according to any of the preceding examples, wherein the external force (f _e ) Is applied to at least one end (103, 107) of the spindle (10) by means of a lever arm (101, 105).

Example 18

The external force measurement unit (4) according to any of the previous examples, wherein the evaluation unit (8) calculates a value dependent on the calculated force (f _e ) And an effective lever arm length of each of the lever arms (101, 105), the effective lever arm length being dependent on the position of the spindle (10).

Example 18

An electric assist bicycle having an external force measuring unit (4) according to any one of the previous examples 1 to 17.

Example 19

For measuring an external force (f) applied to a spindle (10) _e ) An external force measurement unit (4), the external force measurement unit (4) comprising:

a load cell (5) having a support ring (61),

-wherein a first tab (62) and a second tab (65) are arranged on the support ring (61), wherein the second tab (65) is arranged on the support ring (61) opposite to the first tab (62),

Wherein each tab (62, 65) is arranged in a radial direction towards the outside of the support ring (61),

a first strain gauge (64) arranged on the first wing (62) and a second strain gauge (67) arranged on the second wing (65),

-an evaluation unit (8) for measuring the resistance of the first strain gauge (64) and the resistance of the second strain gauge (67)

-a first bearing support (6) for supporting a first bearing (7) in a first bearing seat (68), wherein the first bearing (7) is adapted to support a rotating spindle (10).

Example 20

The external force measurement unit (4) according to example 19, wherein the resistance of the first strain gauge (64) is measured separately from the resistance of the second strain gauge (67).

Example 21

The external force measurement unit (4) according to example 19 or example 20, wherein there are exactly two tabs provided with strain gauges, namely a first tab (62) and a second tab (65).

Example 22

A magnetic angular position encoder for a rotating spindle (10) in the vicinity of an external force measuring unit (4), wherein the spindle (10) is provided with a magnetic material that causes a hall sensor to signal when the spindle (10) rotates, a plurality of magnetic flux slots extending longitudinally parallel to the axis of symmetry of the spindle (10), the magnetic flux slots being arranged on a circumference in an outer cylindrical surface of the spindle (10).

EXAMPLE 23

The magnetic angular position encoder for a rotating main shaft of example 22, wherein at least one of the reference flux slots has a width in a circumferential direction that is different from some or all of the other flux slots, and/or a depth that is different from the depth of some or all of the other flux slots.

EXAMPLE 24

A magnetic angular position encoder for a rotating spindle according to example 22 or 23, wherein at least one reference flux shoulder between the flux slots is different in width in the circumferential direction than the flux shoulders between some or all of the other flux slots.

List of reference numerals

1. Motor unit

La motor

2. Electric motor

3. Motor casing

4. External force measuring unit

5. Force transducer

6. First bearing support

7. First bearing

8. Evaluation unit

9. Second bearing

10. Main shaft

11. Angle encoder

12. Battery holder

31. Holding plate

32. Screw bolt

33. First fastening element

34. Second fastening element

35. Sealing lip

51. Load cell bearing seat

61. Support ring

62. First wing

63. First airfoil end

64. First strain gauge

65. Second wing

66. Second airfoil end

67. Second strain gauge

68. First bearing seat

69. Mechanical guide

71. First outer ring

72. First inner ring

73. First bearing element

91. Second outer ring

92. Second inner ring

93. Second bearing element

100. Principal axis symmetry axis

101. First crank

102. First pedal

103. First end portion

104. First symmetry axis

105. Second crank

106. Second pedal

107. Second end portion

108. Freewheel

109. Second symmetry axis

110. Deflector blade

111. Hall sensor

112. Magnetic ring

113. Plastic cover

114. Chain

130. First pedal spindle

131. Second pedal spindle

201. First graph of

202. Second graph

205. Hall sensor signal

206. Ramp function

207. Intersection point

210. Base line

250. Anchor tab

251. Fixing pin hole

255. First Hall sensor

256. Second Hall sensor

257 PCB

258 PCB mounting screw

259. Anchor tab

260. Fixing pin

265. Permanent magnet

280. Magnetic flux slot ring

281. Reference shoulder

282. Reference flux slot

283. Magnetic flux slot

fe external force meter

f1 First force

f2 Second force

o1 offset

P1 first period of time

p2 second period of time

m1 center of first period

m3 center of third period

a1 First amplitude

a2 Second amplitude

a3 Third amplitude

fx1 first horizontal force

fx2 second horizontal force

first external force of fe1

fe 2.

Claims

1. For measuring an external force (f) applied to a spindle (10) _e ) An external force measurement unit (4), the external force measurement unit (4) comprising:

a load cell (5) having a support ring (61),

an evaluation unit (8) for measuring the resistance of the first strain gauge (64) and the resistance of the second strain gauge (67), wherein the resistance of the first strain gauge (64) is measured separately from the resistance of the second strain gauge (67),

2. External force measuring unit (4) according to claim 1, wherein a first tab end (63) and a second tab end (66) are arranged at respective ends of the first tab (62) and the second tab (64).

3. According to claim 1 or claimThe external force measurement unit (4) of claim 2, wherein the evaluation unit (8) is further adapted to determine the external force (f _e ) And the evaluation unit is further adapted to determine the position of the lever arm of the spindle (10) and to determine the external force (f _e ) The external force is based on the measured resistance and the first force (f ₁ ) Is applied to the adapted spindle (10).

4. An external force measurement unit (4) according to any of claims 1 to 3, further comprising a motor housing (3), wherein the first tab (62) and the second tab (64) are supported in a load cell carrier (51) in the motor housing (3).

5. The external force measurement unit (4) according to any of the preceding claims, wherein the evaluation unit (8) smoothes the measured resistance of the strain gauge (64, 67) over time by a low pass filter.

6. The external force measurement unit (4) according to any of the preceding claims, wherein the evaluation unit (8) determines a drift of the measured resistances of the first strain gauge (64) and the second strain gauge (67) over time and recalibrates the first strain gauge (64) and the second strain gauge (67) by applying drift compensation (after a predefined time).

7. External force measurement unit (4) according to any of the preceding claims, further comprising a freewheel (108) connected with the main shaft (10).

8. External force measurement unit (4) according to any of the preceding claims, further comprising an angular encoder (11) to determine the radial position of the spindle (10).

9. The external force measurement unit (4) according to any of the preceding claims, wherein the spindle (10) is received inside a first bearing ring (72) of a first bearing (7) and inside a second bearing ring (92) of a second bearing (7).

10. External force measurement unit according to any of the preceding claims, wherein the load cell (5') is provided with a vertical guide assembly interacting with the motor housing 3.

11. External force measurement unit according to claim 10, wherein the vertical guide assembly is provided as an anchor tab (250) with a fixation pin hole (251), the symmetry axis of the fixation pin hole 251 being substantially parallel to the symmetry axis 100 of the support ring 61.

12. The external force measurement unit according to claim 11, wherein in the mounted state of the load cell (5') in a motor housing (3) a fixing pin is inserted into the fixing pin hole (251) and into a corresponding anchoring hole in the motor housing 3.

13. An electric drive device having a motor housing (3) for an electric auxiliary bicycle, an electric motor and an external force measuring unit (4) according to claims 1 to 12.

14. An electric drive according to claim 13, wherein a spindle (10) is arranged in the vicinity of the external force measuring unit (4), wherein the spindle (10) is provided with a magnetic material which causes the hall sensor to signal when the spindle 10 rotates, a plurality of magnetic flux slots extending longitudinally parallel to the symmetry axis of the spindle (10), the magnetic flux slots being arranged on a circumference in the outer cylindrical surface of the spindle (10).

15. An electric drive according to claim 14, wherein one of the reference flux slots has a width in the circumferential direction that is different from the other flux slots and/or the reference flux slot has a depth that is different from the depth of the other flux slots.

16. An electric drive according to claim 14 or claim 15, wherein the width of one reference flux shoulder between the flux slots in the circumferential direction is different from the flux shoulders between the other flux slots.

17. An electric assist bicycle having an electric drive according to any one of claims 13 to 15.