DE102012008476A1 - Crank for determining pedaling power with resilient executed pedal mount, has pedal mount that is connected over spring bars, so that measurable rotating movements are limited during pedaling on movement toward propulsion force vector - Google Patents

Abstract

The crank (1) has a pedal mount (2) that is connected with the crank over circular arranged spring bars, such that measurable rotating movements are limited during pedaling only on the movement approximately in the direction of propulsion force vector. The rotating movement against the spring action is limited by a stop between the pedal mount and resilient handle. The rotating movement is measured by using a Hall sensor magnet assembly.

Description

The invention relates to a device for selectively determining the pedaling force on a crank with a spring running pedal receptacle for measuring the propulsion force vector and optionally the power loss vector for the left and right crank side separately. For the transmission of the measuring signals a telemetric transmission or a slip ring is provided. The convertible into a movement of the bicycle torque is determined solely by the proportion of pedaling force, each of which acts tangentially on the circularly rotating about the pedal crank pedals. A deflection of the pedal effected against the spring force exclusively in this direction can therefore be used directly to determine that portion of the treading force which generates a torque which can be converted into a movement of the bicycle (driving force). Another important factor is the pedal movement, which is possible against the action of the spring, on movements approximately in the direction of the crank. This force direction causes only a compression of the crank and is converted into no usable torque (power loss). This information enables a cyclist to specifically improve the movement sequences as well as the optimal implementation of the work he puts into speed.

State of the art

From the DD294673 For the first time, a system has been described which divides the forces created during pedaling into vertical and horizontal components, taking the angular position into account.

The DE1015860 and DE10158600 describes a device for force and power measurement on a bicycle crank. The force is determined by means of several strain gauges on the crank pin. This makes it possible to determine the tangential to the crank axis forces. The disadvantage is that the crank pin deformation is still very indirectly closed to the relevant forces.

From the DE10044701 a device for determining the treading force is known, which allows easy mounting to existing crank systems. The tangential forces acting on the pedal crank axle are measured. It can be measured both the train introduced by the cyclist and the compressive forces. The known device is characterized in that a pedal is mounted resiliently mounted on a pedal crank and a tangential to the pedal crank axis against a spring effect occurring pedal movement is measurable. In particular, the device should be able to be used without a costly change or a complete replacement of the pedal crank assembly. The disadvantage is the offset between the pedal and crank and the additional resulting weight of the crank system.

In the WO 2010/088888 the invention is achieved in that the magnitude of force is determined by measuring the deformation of a deformation body, which is rotatably mounted on the pedal axle and within the pedal body and relative to the pedal body and are arranged on the four DMS strips at different angles, in particular by a measurement of the single normal strain of the strain gauges. The power flow from the pedal body via joints to the deformation body up to the screw thread of the pedal axle takes place completely via these strain gauges. The disadvantage is that the pedal is tied to a specific pedal system and that the conversion into the propulsion-effecting force vectors is very expensive.

Disadvantages state of the art

All measuring devices that can not clearly conclude on the propulsive forces via a suitable load cell, and optionally also on the loss forces, require complex algorithms for conversion into the desired forces of the respective force directions. In the case of an indirect measurement, not all unwanted deformations can usually be clearly assigned by means of the algorithms. The selected deformation bodies provide an indirect measurement.

task

The object of the invention is therefore to design a pedal crank for determining the treading force so that a precise measurement of the propulsion-acting forces can take place independently on both sides of the crank. Optionally, it is also desirable to be able to measure the radial forces acting on the crank circle. The force distribution for both legs separated and divided into the force vectors tangentially and radially to the crank circle, as a function of the crank angle determined. Suitable contours are to be created which allow almost only measurable movements in the force directions to be measured when pedaling.

Solution:

The object is achieved in that a circularly arranged spring contour is connected via a lever arm with the pedal receptacle and allows for any force introduction into the pedal only movements tangential to the crank circle. The rotational movement is approximately proportional to the propulsion force vector. Optionally, a further contour is provided which, in conjunction with the first spring contour, additionally forms a parallelogram, which, with any desired force introduction, only Movements radially to the crank circle allows. The parallel shift is approximately proportional to the power loss vector.

The deflections resulting from the introduction of force against the spring action are converted by means of suitable displacement, pressure or strain-measuring methods into parameters which are proportional to the force. The raw data of the sensors or the already converted measured quantities can be transmitted telemetrically or by slip ring to an evaluation station.

It is also possible to deduce the force vector resulting from pedaling from the power loss vector and the propulsion force vector.

Advantages of the solution

The advantages are a contour that allows almost only tangential or radial movements to the crank circle. A clear assignment of the force sizes and directions is possible. A larger biomechanics negatively influencing axle width is avoided. The device is fully integrated in the crank. The system is independent of the pedal systems used. The output loss and propulsive power can be determined separately for both sides of the crank. The cadence necessary for the power calculation can be calculated on the basis of the periodic tread pattern from the propulsion power and / or the power loss function. It is also possible to use a commercially available rotary encoder or step sensor.

Advantageous embodiments or developments of the invention will become apparent from the features of the subclaims.

Surprisingly, it had been shown that the spring contour arranged in a circle around a center point, connected to the pedal receptacle on the outer circumference with the crank and spaced from the center, most clearly permits movements only tangential to the crank circle with any introduction of force into the pedal against the spring effect. The spring bars are connected at their ends to the outside with the crank and to the center with a lever arm, which in turn receives the pedal via the threaded bore (pedal receptacle) connected. A one-piece design of the spring contour to the crank and the lever arm, with radii provided to reduce the voltage spikes, has been found to be particularly suitable. A minimal hysteresis is so accessible. There are at least three spring bars provided as a spring contour to achieve a stable rotational movement. The spring bars may have differently adapted to the voltages applied during stress web widths and connection radii. The axis of rotation of the crank, the center of the pedal receptacle and the pivot point of the spring contour are approximately in line. With this arrangement it is ensured that almost only movements tangential to the crank circle are possible. The rotational movement is so small that the angular error due to the deviating pivot point of the spring contour to the crank axis is negligible. If one lets a weight hang freely on the pedal, if possible at the point where the force is usually applied when pedaling, and if one turns the crank by 360 ° when taking the measured values, a function arises over the rotation angle. This sinusoidal function should provide a measured value at 0 ° and 180 ° crank position, which is also measured without weight, furthermore at the crank angles 90 ° and 270 ° the measured value should be maximum. It has been shown that the position of the pivot points to each other as described for optimizing the 0-passages at 0 ° and 180 ° crank position and the maximum measured values at 90 ° and 270 °, must be adjusted. This means then that the described pivot points could not be exactly on a line. The optimization of the position of the spring contours and their lever arm to the crank is iterated using different weights. By means of factors, the measured sinusoidal actual curve can then be adapted to the theoretically determined desired curve in the software depending on the angle. For measuring the rotation of the spring contour, with force introduction, opposite the crank, different measuring methods can be used. By means of a Hall effect sensor applied to the crank and aligned with a magnet starting from the center of the spring contour towards the sensor, the rotation can be measured via the displacement of the magnet and, associated therewith, the change in the magnetic field. It is also possible to apply the sensor to the rotating part and the magnet to the stationary part. Basically, a shield against external magnetic fields is provided in the Hall sensor magnet assembly. It could also be a stationary coil with a movable core used as an inductive measuring method. A capacitive path / angle measurement method can also be used. It is also possible by means of at least one strain gauge strip applied to one or more spring bars to measure the applied tangential force approximately proportional elongation. As an alternative, at least one piezocrystal can measure the change in pressure loads as a stop to the movement. Optionally, the forces should be measured perpendicular to the crank circle. An additional slot, below the spring contour contour for measuring the tangential force, creates two further spring bars, which in conjunction with the spring bars ( 3 ) and ( 4 ) form a parallelogram and allow only radial movements on the crank circle. This additional spring contour, which correlates with the first spring contour, serves the measurement of the loss forces. Such forces, which only compress the crank, twist, bend and generate no propulsion. The measurement of the deflections of the parallelogram or the expansions of the associated spring bars is analogous to the measuring methods already described. The spring contour for propulsion force measurement consists of the spring bars ( 3 . 4 ) and ( 5 ). The spring contour for loss force measurement consists of the spring bars ( 3 . 4 ) and ( 12 . 13 ). The correlation of the two spring bar contours must be taken into account when placing the measuring systems. Clear measurement results provide strain measurements on the spring bars ( 1 ) and ( 12 ) and or ( 13 ). At these webs a clear assignment of the forces tangentially or radially to the crank circle is possible. The spring bars ( 2 ) and ( 3 ) belong simultaneously to the spring contour for measuring the propulsion and loss forces, so that no clear assignment to these spring bars in the two directions of force is possible. You can nevertheless provide important information in combination with the marginal fiber tensions of the spring bars ( 1 . 12 ) and or ( 13 ) deliver. It is also possible to use the other measuring methods already described or to combine different measuring methods, such as strain measurement and Hall effect sensor arrangement. The correlation of the movements of the two spring contours is to be particularly noted in the path and angle measuring methods. Piezocrystals can measure as a further possible training the change of the pressure loads as a stop against the respective movement. Advantageously, it is provided that the pedal movements possible against the spring effects are limited by end stops. By such stops too large deflections of the movably mounted pedal and the associated spring are prevented. Damage to the springs due to excessive force and a misalignment of the measuring system can be avoided with simple means. An overload of the spring bars can be prevented for example by a mechanical stop in the pedal receiving. The upper part of the crank encloses the spring-loaded pedal. The gap between the pedal receptacle and the upper portion of the crank determines the maximum deflection of the pedal receptacle and prevents the plastic deformation of one or more spring bars. An additional gap-reducing component between the crank and the pedal receptacle may be required due to the production.

Application:

The necessary electronics for telemetric data transmission and, for example, a battery for powering the sensors can be accommodated directly in the crank. When using a slip ring, the power supply of the sensors from the stationary bicycle frame to the rotating crank can be done in addition to the signal transmission. The data may be displayed graphically or as pure values by means of a bicycle computer, navigation device or a smartphone. It makes sense to determine values such as the power, force or torque in connection with the angular position of the crank for each crank side separately in real time and to present it in a simple and clear way. A feedback on the tensile and compressive force distribution when pedaling with click pedals is just as important as a feedback on the shares of loss forces, ie forces whose force vector are radially on the crank axis and generate no propulsion and the shares of propulsive forces whose direction of force tangential to the crank circle. From all this information is the biomechanical efficiency (ratio of propulsive forces to loss forces) and the size and direction of the resulting force vector ( 8th ) calculable. Through the real-time feedback, the pedal can steadily improve his tread pattern. The application described above is particularly suitable for training with racing bike mountain bikes and other bicycles without and with auxiliary drive as well as the system can be used during training on an exercise bike (home trainer). The measuring signals can also be used to control the drive motor in pedelecs (pedal-assisted electric bicycles) for pedaling-dependent motor assistance. The stronger the propulsive force, the more Elekromotorleistung is fed. In this area, there are no measuring systems that can measure the left and right sides of the crank separately in this way. Another area is in medicine for electro-stimulation of muscles at z. B. paraplegic persons. With the help of electrostimulation and such a measuring system, this group of people is again able to drive a tricycle with their own paralyzed legs. For optimal stimulation of the respective muscles usually both force components (propulsion and loss) are needed.

Embodiments of the invention will be explained in more detail, which are illustrated in the drawing.

It shows:

1 a side view of a crank for measuring the propulsive pedaling force.

2 a side view of a crank for measuring the propulsive pedaling force and the power loss.

1 shows a side view of a crank with a crank circle ( 16 ) for measuring the propulsive pedaling force ( 6 ) (Driving force vector), as a fulcrum arrangement. The pedal ( 1 ) a standardized, largely identically designed by all manufacturers tapped hole as a pedal ( 2 ) on. The pedal recording ( 2 ) is pivotable about the axis ( 9 ) arranged. The extensions of the center lines of the spring bar arrangements ( 3 . 4 . 5 ) form the center of the axis ( 9 ) around which the pedal receptacle ( 2 ) against the spring action against the rigid part of the crank ( 1 ) twisted when force. By means of a sensor arrangement, the rotation is measurable. The sensor arrangement consists of a directly to the crank 1 mounted Hall effect sensor ( 15 ) and one around the center of the axis ( 9 ) rotatable magnets ( 17 ). The magnet ( 17 ) is located at the outer end of the shaft ( 14 ), the other end of the wave ( 14 ) is at the contour of the axial center ( 9 ) fixed. The shielding ( 19 ) protects the device from external magnetic fields. By means of a mounted on the circumference of the crank holder stop sleeve ( 20 ) creates a wegbegrenzender gap, which protects the spring bars from overloading. The sensors are connected to the evaluation unit ( 11 ) within the pedal and send the data to a display and evaluation unit.

2 shows a side view of a crank for measuring the propulsive pedaling force ( 6 ) and the loss power ( 7 ). One on the crank circle ( 16 ) shows the propulsion force vector ( 6 ), the loss force vector ( 7 ) and the resulting force vector ( 8th ). In addition to the above described measuring arrangement for propulsion force measurement ( 6 ) with a spring bar arrangement ( 3 . 4 . 5 ) and the axis of rotation ( 9 ) this version has a further measurement arrangement for loss force measurement with a spring bar arrangement ( 3 . 4 . 12 . 13 ). The result is a parallelogram which preferably only allows movements approximately radially to the crank circle. By means of strain gauges on the spring bars ( 5 . 12 . 13 ) both directions of movement can be measured via the marginal fiber voltages. Between the pedal recording ( 2 ) and the rigid part of the crank ( 1 ) is a gap, which serves as an end stop and limits both movements.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DD 294673 [0002]
• DE 1015860 [0003]
• DE 10158600 [0003]
• DE 10044701 [0004]
• WO 2010/088888 [0005]

Claims (7)

Pedal crank for determining the pedaling force with a spring-running pedal receptacle for measuring the propulsion component, characterized in that the pedal receptacle is connected via at least three circularly arranged spring bars with the crank in such a way that measurable rotational movements during pedaling are limited only to movements approximately in the direction of Vortriebkraftvektors , Pedal crank according to claim 1, characterized in that the spring web contours resulting from the theoretically determined voltage curve and can vary individually in their thickness and the connection radii. Pedal crank according to claim 1, characterized in that the possible against the spring action rotational movement is limited by a stop between the resilient pedal receptacle and the crank. Pedal crank according to claim 1, characterized in that the rotational movement is measured by means of a Hall sensor magnet arrangement Tretkurbel for determining the pedaling force with a spring running pedal recording for measuring the propulsive force and the loss component characterized in that in addition to the contour for the measurement of Vortriebskraftkomponente by means of another contour a parallelogram is formed, in addition to movement in Vortriebskraftrichtung, movements in the direction of the power loss vector limited. Pedal crank according to claim 1 and 2, characterized in that the movements by means of the edge fiber tension of the spring bars and at least one strain gauge is measured. Pedal crank according to claim 1 and 2, characterized in that the movements by means of at least one strain gauge and by means of at least one Hall-effect sensor arrangement is measured in combination.

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