FR2617970A1 - Method and device for measuring a drive torque and/or an associated magnitude, and cycle thus equipped - Google Patents

Abstract

The hub M is composed of a torsion shaft 9 which is fitted at one end into the body 11 of the hub M, and joined at its other end to the free wheel. This shaft 9 deforms under the effect of the transmission torque C, the angular displacement theta being produced by a helical potentiometer whose pitch is very large. The information is transmitted to a processing and display unit via a rotary collector 24, 25, 26. The processing unit determines the speed V and calculates the power P and the energy expended W. Use for training sportsmen and rehabilitation of heart patients.

Description

 The present invention relates to a method for measuring the torque transmitted by a drive wheel and in particular the drive wheel of a bicycle.

 The present invention also relates to a device for implementing this method.

 The present invention also relates to a cycle thus equipped.

 The bicycle is becoming increasingly important in the field of sports and also as a special training device for improving physical capacities. It is also used more and more for the treatment and readaptation of patients with circulation diseases and of accident victims, cardiac patients. In the execution of such training or treatment programs, it would be interesting to have information on the developed power and the energy expended by the subject, because these ineormations allow to draw results on the training or the treatment. Many home appliances already provide these items.

 but by their principle they transform by measuring the mechanical yes of the cyclist into thermal or electric power.

 The object of the invention is, on the contrary, to produce a measuring device which can be adapted to autonomous cycles and which makes it possible to measure the transmitted power, without transforming or affecting its transmitted value.

 we know from FR-A-2 394 790 a device of the kind indicated at the start in which a roller is applied under the pressure of a spring against the motor strand of the transmission chain of the bi-debt. The greater the force transmitted by the chain, the more the n motor of the latter tends to straighten by compressing the spring. There is therefore a rule of correspondence between the deflection of the spring and the force transmitted by the motor strand of the chain.

 This device has multiple drawbacks.

He's heavy. Its indications are imprecise taking into account the parasites corresponding to the operating vibrations of the chain. The measured force is the force transmitted by the chain which, for equal value, can correspond to different torques on the driving wheel if the bicycle is equipped with a speed change device. In addition, the known device introduces friction on the chain.

 We also know from FR-A 2 546 297 a device of the kind indicated at the start in which the transmitted force is determined indirectly by the measurement of the magnitudes which oppose the displacement such as, the slope of the dimension, the speed frontal of the wind, I acceleration. rolling friction. This device also has multiple drawbacks. Its indications are imprecise because your values are calculated from coefficients taken as being constant, and not being in reality.

 The object of the invention is thus to remedy these drawbacks by proposing a method, a device and a free cycle in which the measurement of the torque, or of a quantity which is linked to it, is carried out in a simple manner, largely insensitive to parasites, independent of the transmission ratio determined by the mechanism driving the wheel, and not causing additional friction.

 According to the invention, the method for measuring the torque transmitted by a driving wheel, in particular the driving wheel of a cycle, or a mechanical quantity which is a function of said torque, is characterized in that it is measured, with respect to a reference position corresponding to zero torque, the angular displacement, around the axis of the wheel, of a piece of the hub subjected to the transmission torque. The torque is deduced using a rule of correspondence between this displacement and the transmitted torque. For example, if it is a piece of material with elastic linear behavior, the torque will be proportional to the angular location.

 If a static torque is easy to measure, it is much more difficult to measure a torque on a rotating shaft without affecting the transmitted torque. Indeed, the systems of gauge of elasticimetry, very widespread, are ill suited to: rotating shafts: they require a connection by rotating collector, they are special, very expensive, bulky, not very stable and introduce strands. On the contrary, we are looking here for a reliable, stable system which introduces little hysteresis and does not require complicated equipment for data processing. Rour measure this couple, let's go. as we have seen previously, sol t i to cite a place which will deform, the problem will then be to measure this deformation or the (angular) displacement of the part.

To introduce this measurement technique, we will make a preliminary mathematical remark illustrated by the figure (1/5). Let us choose 2 curves (# 1) and (# 2) included in the same envelope of revolution (#) of axis Suppose (# 1) f fixed with respect to sun orthonormal reference (0, x, y1, z1) O being a point of the axis of revolution and # 1 materializing an at: e passing through O and cutting (# 1 in
Call ## the normalized vector materializing the orthogonal axis a ## passing through O. Let us call # the angle (0, # 1, # 2).

Let us suppose that these two curves were chosen such that, whatever is e belonging to a continuous interval, they have only one common point B.

 By rotation of angle e around the axis O of the coordinate system (O, @, @@, @@) of (r =) compared to the coordinate system (O, Z, @@) of (Ta), the abscissa curvilinear @@ will be a function of e and if these two curves are judiciously chosen, the function A @ ef (e) can be a bijection on the previous continuous interval. If this is the case, we can find a reciprocal function over the interval and express the relative angular displacement e as a function of the curvilinear abscissa @@.

 Thus, by taking a part subjected to a couple of axis @ angularly deforming along the axis @ and by fixing each of its ends respectively to (@@) and (T2), we will be able, if we know how to measure l 'curvilinear abscissa, deduce the angular displacement of the ends of the part and draw the transmitted torque thanks to a rule of behavior between the previous displacement of the two extremities of the part and the couple requesting it.

 According to a second aspect of the invention, the device for implementing the above method is characterized in that it has a hub making it possible to measure the curvilinear abscissa and means for indicating the torque transmitted or a quantity which it is linked by the use of the rule of behavior between the curvilinear abscissa and the transmitted couple.

 The abscissa. curvilinear can be easily measured, as we will see later, with. for example, an electrical resistance materializing (Ir) and a metallic cursor materializing (T2). Thus, the resistance between an end of the resistance and the metallic cursor will be a function of the angular displacement e.

According to a third aspect of the invention, the cycle equipped with the above device is characterized in that the part requested by a torque is a torsion shaft
Other features and advantages of
The invention will further emerge from the description below:
FIG. 1 is an illustration of the principle of
measurement of the angular displacement relative to the
previous description.

FIG. 2 is a side elevation view
of a bicycle according to the invention.

the figure is a sectional view with a view in
SS section of the drive wheel hub of the
Figure 1 bicycle (the connections
are not shown, the item
is brought back into the section plane).

FIG. 4 is a perspective view of the
device for measuring displacement
angle of the figure (to facilitate
reading, some parts are truncated).

FIG. 5 is a partial section of the system of
Figure 4.

FIG. 6 is a view of the block diagram of the circuit
of evaluation provided on the bicy debt of figure i.

FIG. 7 represents the appearance of the transmitted signals
through the hub, through the tracks,
time function.

 As shown in Figure 2, the bicycle has a frame 1 which is articulated a fork 2 rotatably supporting a front wheel. @ The frame 1 itself supports in rotation about a horizontal axis 4 a driving rear wheel 6 driven in rotation by means of a transmission chain 7 from a crankset 8.

 As shown in Figure 3, the hub of the rear wheel is radiated to the rim by means of ravons 10.

This hub M is composed of an If shaft fixed relative to the frame materializing the axis 4. This shaft comprises nuts, a spacer and ball bearing flanges 13 and 14. This hub M also comprises a shaft twist 9 rotating around the shaft 12 through 1 intermediate of the ball bearing 1. At the end: on the side of the bearing 13, the shaft 9 has a threaded seat thus rigidly fixing the wheel 9 to the shaft free driven by chain 7. The second end of the tree is cinnamon. fit in the body 11 of the hub M. This same body ll of the hub M can rotate around the shaft 12 by means of the ball bearing 14. The body ll of the hub M can also rotate around the shaft 9 by relative to its threaded end fixing the freewheel, via the 15 'ball bearing
As shown in your figure and Figure 4, two half-cylinders 17 and the plastic one are assembled to the moveu M of screw 27 around the central part of the torsion shaft 9 (see Figure 5). between the torsion shaft 9 and the two half-cylinders 17 and 1a, so that they can rotate freely around the torsion shaft 9 and of axis 4. These two half-cylinders 17 and 18 have a inner annular recess of axis 4 in which is housed a rubber O-ring 19, rubbing on the torsion shaft 9 at its end comprising the bearings 13 and 15. This O-ring 19 frictionally drives the two half-cylinders 17 and 15 rotating around the axis 4 with the freewheel end of the torsion shaft 9.The two half-cylinders 17 and 18 each have a very large pitch axis 4 propeller made on the outside diameter of the two half-cylinders 17 and 13 in which is housed a metal slider 29 which is connected to a conducting wire Ca. Two rings 16 and 22 are tied in the body 11 of the hub M. These two rings 16 and 22 are connected by threaded rods 20, parallel to the axis 4 and distributed on the rings there and -2, comprising nuts 21.

 Two rectilinear electrical residues 23a and 23b are fixed parallel to the axis 4 on the inside diameter of the rings lj and 22 and stretched along the axis 4 by means of the nuts 21 and the threaded rods 20. A nylon thread 28 is stretched in accordance in Figure 4 and in Figure 5 between two :: twisted rods 20 and a resistor so that the stretch of the nylon til 28 lying between the two twisted rods 20 and in contact with the resistor 2, is curved by the reaction of the resistance 23. The preceding assembly (16, 20, 21, 22, 23, 28) is housed around the axis 9 provided with its two half-cylinders 17 and 18 and with its resistors 23a and - Zb. These two subassemblies are angularly relative to each other so that each metal slider 29 is in good contact with a rectilinear electrical resistance 2Z. This contact is well ensured by means of the nylon thread 28 which, by its reaction, plates the electrical resistance on the helical cursor.

Thus dodging the description of the angular displacement measurement technique seen previously), the electrical resistance between C1 and C2 will be a function of this angular displacement of the two half-cylinders 17 and 18 relative to the body Il of the hub M. The pitch of the 'helix of these two half-cylinders 17 and 18 being constant, the relation linking the electrical resistance between C, and C2 and the angular displacement, will be linear, the torsion shaft 9 having a linear behavior reversible in torsion: the electrical resistance between C and C = will therefore be a linear function of the torque transmitted by the torsion shaft 9. It is then easy, for example, thanks to a potentiometric assembly, to convert the information
in the form of voltage or intensity It was arranged on
the body 11 of the hub four metallic circular tracks
4a and 24b, 25 and 26, connected respectively to the two ends of the rectilinear resistances and to the metal cursor, 1 set being fixed to the body 11 of the hub M by means of resin 30. The two tracks 24a and
24b torment only one piece 24 but one of the two tracks is grooved (see Figure 2 section SS), to allow, as we will see later, to determine the
speed. These four tracks 24a, 24b, 25 and "s, rotate
so around the axis 4 with the body 11 of the hub M: four
sliders (not shown), fixed relative to axis 12,
therefore fixed with respect to box 1, trot on each of the tracks 24a, 24b, 25 and to and transmit the
electrical information via a cable
electric quadrifilar 31 (represents
schematic in Figure 2) to the treatment system, (of
storage) and display of information 2, fixed by
example on handlebar J. This treatment cysteme, (of
storage) and display of information 32, receives
information via circular tracks
24a and 24b and quadrifilar link 31. These
information can be perceived through a simple potentiometric assembly with a zero-setting system (34) which transmits its information via a signal 38 to an analog / digital converter 35 which is interfaced to a microprocessor â fitted with its auxiliary circuits, which will process the information to display the results.

The results can be as follows:
The author torque C transmitted by the drive wheel to can be directly given after adjustment of sero 44 achieved at zero engine torque and a proportional coefficient, depending on the pitch of the propeller of the dew half-cylinders 17 and 18, as well as of the geometric dimensions of the torsion shaft 9 and of the torsional elasticity modulus of the material composing it.

déformation angulaire
(radians)
L longeur de l'arbre (m)
C couple de torsion (N.m)
G module d'élasticité en
torsion (N.m-2.rad-1) lo moment quadratique de
l'arbre par rapport a' son
axe (m2)
D diamètre extérieur de la
section Cm >
diamètre intérieur creux. Recall that the angular deformation e of a torsion shaft made of reversible linear material, verifies the following relation:

angular deformation
(radians)
L length of tree (m)
C torque (Nm)
G modulus of elasticity in
torsion (Nm-2.rad-1) lo quadratic moment of
the tree in relation to its
axis (m2)
D outer diameter of the
Cm section>
hollow inside diameter.

of section (m)
abscissa on the tree 4 of
rotation (ml
The displacement speed V of the cycle eu and "" - obtained by analyzing the frequency of the signal transmitted by the cannellated track 24a, connected to ground via a resistor 7 thus giving a signal analogous to FIG. 7, curve 24a. It is necessary to enter by the keyboard 40 a constant representing the circumference of the wheel to obtain a fair value of the speed. The average speed and the maximum speed can be read from a reference instant, which was ordered on the keyboard 40 of the case
The distance parcc> urue can be obtained by integrating the speed from the reference instant ordered on the keyboard 40 of the case 32; it therefore suffices for the microprocessor to count the number of slots re-represented in FIG. 7 curve 24a and to deduce therefrom the distance traveled, knowing the circumference of the wheel.

 the developed power P can be obtained by multiplying the value of the engine torque transmitted by the drive wheel 6, by the speed of rotation of this same wheel z. Immediate power can thus be displayed.

The average power and the manimal power since the reference time can also be memorized and displayed.

 The energy consumed W from the same reference instant commanded on the keyboard 40 of the housing -.-, is obtained by integrating the developed power, from the reference instant until the reading time.

 The pedaling rhythm N can be determined, noticing from FIG. 7 that the torque C transmitted by the driving rear wheel b, has a sinusoidal shape which is caused by the alternating movement generated by the pedaling transmitted by the pedal 8. The pedaling rhythm N is therefore obtained by analyzing the frequency of irregularity of the motor torque C.

 All these results can be displayed on the screen 41 in a parallel manner (all together) or in a multiple manner (l (one after the other) or else at the request of the user via the keyboard 40 or The power supply 39 of the box 2 may in between be effected by means of a battery, solar collectors or an electric generator driven by the cyclist.

We will now describe the operation of the bicycle, including the description of the process of the invention. At rest, in the absence of transmitted torque C, the torsion shaft 9 is not deformed; the setting of the zero setting (.4) makes it possible to zero the torque C. When the chain 7 transmits a torque C of rotation to the wheel S, the shaft 9 is deformed, carrying with it both half-cylinders 17 and 18, in rotation of axis 4 with respect to the body il of the hub M: the two points of contact respectively between the metal cursor 29a and the resistance Ta -t between the metal cursor -? b and the resistance - = b, move along the helix and the resistance, thus causing a variation e the voltage of the signal 26 and therefore of the signal 7.8
corrected by resetting), depending on the torque C transmitted. As we have seen above, the speed V is deduced from the frequency of the signal from the fluted circular track 24a. The quantities such as, the power P, the energy expended W, the distance traveled or the pedaling rhythm N, can also be calculated.

 The invention is applicable to other wheels and other types of vehicles, in particular self-propelled cycles.

Claims (3)

- CLAIMS -  1. Proceeds to measure the neck transmitted (C) by a driving wheel (6L in particular the driving wheel of a cycle, or an associated mechanical quantity (PW N) which is a function of said torque, characterized in that one detects l angular deviation (#) around the axis (4) of the wheel (6) between a region of the hub (M) driven and constrained in rotation by the transmission system (7,8) considered as upstream to the driving wheel (to) and another region of the hub (M), driven and constrained by the previous region and driving the downstream part of the drive wheel (6). These two regions of the hub (M) are therefore considered relative to the hub (M ) as  "leading" for the first and "led" for the second.  This angular deviation (#) is measured relative to a relative angular position of reference, corresponding to a zero torque. and we determine the couple (C) or the quantity  P, W. N) which is linked to it, by exploiting a rule of predetermined correspondence between the angular difference (#) detected and the couple (C) which generates it.  Method according to claim 1. characterized in  that, to detect the angular deviation (#), the displacement (s) (s) (ee) is detected relative to a reference position of the contact point (s) (B) between two curves (# )  r =), belonging to the same envelope of revolution (fi) of axis (4), one (#) belonging to a "minus" region (#) of the hub (M) and the other, (#), belonging to the "leading" region of the hub (M) (according to the terms of claim 1). The angular deviation (#) is detected by the use of a correspondence rule between the displacement (s) (ee)  contact point (s) and angular deviation (#).  r. Device ocar la mie -n oeuvre ou orocede According to. ce claims 1 and 2, characterized in that the displacement of the contact point (ee) is carried out electrically by materializing (#) and / or (#) by an electrically resistive material and deducing the displacement (ee), relative to the position of reference, from the point of contact (B) by the operation. of a rule this correspondence with the electrical resistance between åeu: fixed points, one belonging to the first curve (#) the other belonging to the second curve (#). 4. Device according to claims I, 2 characterized in that the curves (rX and r => set out in claim 2, are at least one cylindrical helix (#) 3 and a straight line (r =) parallel to the axis t4) of the wheel (6).  5. Device according to claims 1, 2, ~ and 4 characterized in that the hub (M) comprises a torsion shaft.  Device according to claims 1 and 2 characterized in that it comprises means (36) for deducing, from the irregularities of the torque (C), the pedaling rhythm (N) or cyclist. Device according to one of the preceding claims, characterized in that it has means (36) for determining from a substantially binary signal, smis by a rotary collector (24, 25, 26), the speed (v) d advancement of the cycle and / or a quantity linked to it. 8. Dispositi + according to the preceding claims taken as a whole, characterized in that it comprises a battery-powered power supply.  9. Device according to the preceding claims taken as a whole, characterized in that the unit d of has a keyboard (40) intended to select and display the various output signals of the analysis circuit (36).