TORQUE MEASURING SENSOR FOR ELECTRIC BICYCLE

Abstract

The invention relates to an electric assistance unit for an electrically assisted bicycle comprising: - an electric motor in a casing (2); - a bottom bracket axle which passes through the casing; - at least one sensor (23, 25, 27) of deformations of the casing, fixed thereon and capable of measuring the deformations due to the pedaling efforts of a cyclist; - means (40, 50, 52), programmed or specially adapted, for evaluating or calculating a pedaling torque, separately from an assistance torque or without it, and for calculating a new electric assistance torque. Figure 2

Description

Title of the invention: TORQUE MEASURING SENSOR FOR ELECTRICALLY ASSISTED BICYCLE TECHNICAL FIELD AND PRIOR ART

[0001] The invention relates to the field of electric assistance units for electrically assisted bicycles and to that of electrically assisted bicycles.

[0002] In order to provide the power or torque necessary for assistance, we seek to have a measurement of the effort applied by the cyclist when pedaling.

[0003] generally, solutions using sensors operating based on opposite magnetostrication are implemented: these sensors are arranged on the axis of the crankset, the deformation of the latter inducing magnetic field modifications seen by the sensor; The latter can therefore generate a signal which is sent to the bicycle control unit. Other solutions exist, based on deformation gauges, or optical or magnetic sensors.

[0004] The reverse magnetostrication sensors cooperate with the mobile ferromagnetic hub of the crankset, which complicates its implementation, in particular with regard to the transmission of data to the control means of electrical assistance. In addition, these sensors are usually installed to capture efforts from the two pedals, which requires positioning them in areas where other mechanical or electric parts are already arranged. For the deformation gauges, the gauge and part of the circuit are on the hub, therefore turn with it. Wireless communication, or with a broom, is carried out between the mobile part and the fixed part.

[0005] The problem therefore arises of finding a simpler and less cumbersome system for capturing the cyclist's efforts. Preferably, such a system can detect these efforts, but not the torque provided by the electric assistance. Also preferably, such a system is less expensive than those implementing techniques, for example of the magnetostrictive type. Statement of the invention

[0006] The invention firstly relates to an electric assistance unit for an electrically assisted bicycle comprising:

[0007] - an electric motor in a housing;

[0008] - a pedal axle which passes through the casing;

[0009] - at least one casing deformation sensor, fixed on and / or against the casing and placed near the tree, capable of measuring the deformations due to the pedaling efforts of a cyclist.

[0010] The casing may include or possibly contain a transmission and / or gearbox system.

[0011] The invention makes it possible to measure the forces applied by the cyclist to the pedals. Preferably, the sensor(s) is / are arranged close to the axis of the crankset, for example less than 5 cm from this axis.

[0012] These alternating forces are transmitted by the pedals to the casing, in which they create stresses or deformations, which directly reflect the effort of the cyclist.

[0013] By measuring the stress, using one or more sensors, for example one or more strain gauges, mounted in or on the casing, the cyclist's effort can be calculated. The invention therefore makes it possible to measure the deformation of the casing directly due to the force applied by the cyclist on the pedal. According to an exemplary embodiment, a correlation is established between the pedaling forces and the deformation on the casing. This correlation can then be used or projected to calculate the cyclists' efforts. The appropriate electrical assistance can then be calculated or estimated and applied.

[0014] The sensor(s) is / are not connected to the pedals, the crankset, or the derailleur or any moving part of the bicycle. It is / are fixed relative to the casing.

[0015] The invention makes it possible to measure a signal associated with the pedaling torque, different from the assistance torque, whereas known systems always measure the sum of the pedaling and assistance torques.

[0016] Compared to existing solutions:

[0017] - the invention does not require additional components, in particular no expensive, bulky and yield-reducing sprockets;

[0018] - it allows the effort to be measured as close as possible to the cyclist, without the measurement being polluted by friction induced by the installation. An electrical assistance unit according to the invention may also include, or be associated or coupled with, means, for example digital means (for example at least one processor), which are, or can be, programmed or specially adapted, to assess or calculate the pedaling torque, separately from the assistance torque or without it, and for example to calculate a new assistance torque, preferably depending on the pedaling torque.

[0020] An electric assistance unit according to the invention may comprise, for example, between 2 and 6 casing deformation sensors, fixed thereto and preferably arranged close to the axis, for example less than 5 cm from it.

[0021] For example:

[0022] - one of the sensors can be arranged under the pedal axle, another being behind this axis (relative to the direction of movement of the bicycle);

[0023] - and / or one of the sensors can be arranged above the pedal axle.

[0024] The sensor(s) may be arranged on only one side of the casing, or on the at least one sensor can be placed on each side of the housing.

[0025] According to a particular embodiment, at least one casing deformation sensor is arranged in or on, and / or so as to measure the stresses in, at least one stress well; a stress well captures the stresses applied to the casing when the cyclist pedals or these pass through him; one or more wells can be made in the wall of the casing, for example by a local thinning of the wall of the casing, or even by a zone of the wall of the casing, this zone being made of a material different from the wall.

[0026] According to yet another particular embodiment, an intermediate part, or "test body", can serve as a stress path between the bearing of the shaft or the pedaling axle and the casing, in order to transmit the forces measured by the gauge(s) or sensor(s), located on and / or against this intermediate part.

[0027] For example, at least one stress well is produced by an orifice or a recess on and / or against which a test body is positioned; this test body preferably has a thickness (e'i) less than the thickness e of the casing.

[0028] An electric assistance unit according to the invention may further comprise means adapted or programmed for:

[0029] - correct or compensate the signal or signals from the sensor(s) in temperature function, for example to correct a gain value applied to the signal(s); this is for example the case if several sensors or strain gauges are used to form a Wheatstone bridge, one of these sensors being used as a control to provide temperature compensation;

[0030] - and / or carry out one or more signal windowing steps, this windowing being temporal and / or amplitude; windowing allows you to select a portion of the signal of interest;

[0031] - and / or correct the signal from the sensor(s) for possible hysteresis of the / sensor(s);

[0032] - and / or linearize the signal from the sensor(s) in at least one area of ​​a signal delivered by at least one sensor or at least one of the sensor(s).

[0033] - and / or carry out one or more steps of filtering the signal or signals from the or sensor(s).

[0034] The invention also relates to an electrically assisted bicycle comprising an electrically assisted unit according to the invention.

[0035] Such a bicycle may further include a temperature sensor.

[0036] The invention also relates to a method for producing an electric assistance unit for an electrically assisted bicycle, this unit comprising an electric motor in a casing, said method comprising:

[0037] - the identification of one or more zone(s) of the casing in which the crankcase deformations are mainly or solely due to the pedaling efforts of a cyclist;

[0038] - the positioning of one or more deformation sensors in said zones of the crankcase identified in the previous step;

[0039] - the positioning of the electric motor on and / or against the casing in one or several of said zone(s). It is also possible to position in the housing of the means, for example digital means (for example at least one processor), programmed or specially adapted, to assess or calculate the pedaling torque, separately from the assistance torque or without it and possibly to calculate a new electric assistance torque as a function of the pedaling torque.

[0041] At least one crankcase deformation sensor can be positioned less than 5 cm from the crankshaft axis.

[0042] A method according to the invention may further comprise the formation of at least one stress well (in the sense already explained above) in the wall of the casing, and the positioning of at least one sensor in and / or on and / or against said stress well. For example, at least one stress well may be produced by local thinning of the wall of the casing, and / or:

[0043] - one or more sensors may be glued or fixed, for example by their ex ends, above or in the vicinity of an area of ​​the wall of the casing, this area being made of a material different from the wall and forming a stress well;

[0044] - and / or an intermediate part, or "test body", serves as a stress path between the pedal shaft bearing and the casing, in order to transmit the forces measured by at least one sensor to a gauge, located on and / or against this intermediate part.

[0045] For example, at least one stress well is produced by forming a recess on which a test body is positioned, said test body possibly having a thickness (e') less than the thickness e of the casing.

[0046] In an electric assistance unit according to the invention or in a method according to the invention, the means, for example digital means (for example at least one processor), programmed or specially adapted, for evaluating or calculating the pedaling torque, separately from the assistance torque or without it, can allow:

[0047] - to calculate or estimate, from the signals of the sensor(s), the effort of the cyclist uniquely ;

[0048] - and / or to calculate and inject electrical assistance into the motor;

[0049] - and / or to calculate or estimate, from the signals of the sensor(s), the new torque level, but with known assistance, then possibly deduce the value of the new electric assistance torque to be applied;

[0050] - and / or to isolate, by processing the signal or signals coming from the sensor(s), which comes mainly or only from the cyclist. Brief description of the drawings

[0051] An exemplary embodiment of the invention will now be described with reference to the accompanying drawings in which;

[0052] [Fig.lA] and [Fig.lB] show an example of an embodiment of a bicycle and a casing to which the invention can be applied,

[0053] [Fig.2] represents a particular embodiment of a bicycle casing according to the invention.

[0054] [Fig.3A], [Fig.3B] and [Fig.3C] represent an embodiment of a bicycle casing according to the invention and the detection of forces applied in various directions;

[0055] Figures [Fig.4A], [Fig.4B] and [Fig.4C] each represent a wall of a casing according to the invention provided with one or more stress wells or one or more stress capture zones;

[0056] [Fig.5] shows an example of an embodiment of a bicycle to which the invention can be applied, one or more sensors being arranged on only one side of the casing.

[0057] [Fig.6A] and [Fig.6B] represent a measuring system according to the invention.

[0058] In the figures, similar or identical technical elements are designated by the same reference numbers. DETAILED DESCRIPTION OF EMBODIMENTS

[0059] [Fig.1A] shows an example of an embodiment of a bicycle to which the invention can be applied.

[0060] This bicycle 10 comprises, in a known manner, a frame 16 (composed of several assembled tubes), a front wheel 4, a rear wheel 6, a handlebar 8 connected to the front wheel by a fork 12, a saddle 14. A pedals have two pedals 22, 24, connected by 22 'cranks, 24' to an axis which enters a box. We see, in [fig.2], the orifice 21 (or hub orifice) on one side of this case. The cyclist's action on the crankset leads to a chain 28. As a result of an electric assistance bicycle, an electric motor is hosted in a Carter 20 which is crossed by the case that hosts the axis of the crankset. The Carter 20 can also contain a 40 -de control system (in interrupted features in Figures 1 and 2), which allows you to control the assistance provided to the cyclist by the electric motor. Reference 32 designates an electric battery.

[0062] The force Fl applied by a cyclist on the pedal 22 results in cor forces corresponding F2 and F'2 applied to the casing 20: as seen in [Fig.lA], and in more detail in [Fig.lB], the force F2 applied to the front part of the casing is greater than that (F'2) which is applied, in the opposite direction, to the rear part.

[0063] The [Fig.lb] represents the Carter of the [Fig.la] in more detail. Digital references identical to those of the [Fig.la] represent the same technical elements. The strength FL of the cyclist is transmitted by an effort path between the 21 'axis (or hub) of pedaling and the hanging points 20i, 202au frame. This effort path goes largely through the hub and the area which is peripheral; It is therefore this area, the hub and its periphery, which undergoes the greatest deformation. The attachment points also see this effort, but less importantly.

[0064] [Fig.2] shows a side view of the casing 20, from which the axle and its pedals have been removed. On this figure, as on the following figures, references 23, 25, 27 represent three sensors, for example deformation gauges, for example electrical resistance and / or rosette type. As part of this invention, a gauge made up of an electrical resistance can for example have resistance between 100 ohms and 1000 ohms or even 5000 ohms, but preferably between 120 and 500 ohms, for example 350 ohms. A too strong resistance gauge will consume little energy but will not have the desired sensitivity; A too low resistance gauge will have too much sensitivity. We will also ensure the orientation of the gauge, so that it is oriented or glued in the right direction of deformation. As a variant, a gauge can be fixed by its ends on an area provided to deform.

[0066] Each gauge has specific coordinates in the 2D plane to make it pass or apply a maximum deformation. In addition, any interference from the stressed body can be compensated if the gauge is applied in the correct orientation.

[0067] These gauges will make it possible to measure the deformations of the casing 20 during the cyclist's effort. In the example illustrated, the sensor 27 is arranged above the position of the axis, the sensor 23 is arranged behind it (relative to the direction of travel of the bicycle), and the sensor 25 is arranged below. In [Fig.2], the gauges are shown outside the casing, but it will be preferable, subsequently, to arrange them against the inner wall of the casing for protection reasons. Whether they are arranged inside or outside, they are preferably in areas of high stress levels.

[0068] Figures 3A-3C represent the case of only 2 sensors 23, 25, but arranged as described above in connection with [Fig.2] (sensor 23 is arranged behind the crank axle, and sensor 25 is arranged below). Sensor 25 clearly detects the force applied by a vertical force, as illustrated in [Fig.3A]; the two sensors 23, 25 each detect a part of the force applied by a force F which has the diagonal direction shown in [Fig.3B] and the sensor 23 detects the force applied by a horizontal force, as illustrated in [Fig.3C].

[0069] Another arrangement of 3 sensors or gauges 23, 25, 27 is shown in [Fig.6A]: they are all 3 oriented in the direction of the axis of the pedal assembly; they can form between them 2 equal angles a and the gauges 23, 27, arranged on either side of the central gauge 25 (for example oriented horizontally), can be arranged at an angle [3 relative to the vertical axis AA'.

[0070] At least one temperature sensor may be provided on or in the casing 20 or elsewhere on the bicycle: such a sensor may provide information on temperature variations, which may be integrated into the processing of the signals from the sensors 23-27 in order to correct them for any drifts due to these temperature variations. According to an exemplary embodiment, the sensors or strain gauges form a Wheatstone bridge, one of these sensors being used as a witness to provide temperature compensation.

[0071] As seen in these figures, the sensor(s) 23-27 is / are arranged close to the crankshaft.

[0072] More generally, we seek to place the sensor(s) or gauge(s) in areas in which the constraints linked to the pedaling effort will be most measurable by the sensor(s) or gauge(s). In fact, the torque created by the assistance motor is a torque, so the sum of the forces is zero. The cyclist's effort results in, or is, a torque, but generated by an asymmetrical effort, the cancellation of which comes from the reaction of the casing: we therefore capture the reaction forces which pass through the casing, to go into the motor's hooks, into the frame, and, finally, through the wheels to compensate for the vertical and downward force of the cyclist. Signal processing makes it possible to recognize this effort as opposed to an assistance torque.

[0073] For example, at least one sensor or gauge placed a few centimeters away, for example less than 1 cm, for example 5 mm, or even less than 4 cm, for example 10 mm or 20 mm, or even less than 5 cm or even 10 cm, from the hub of the crankset makes it possible to properly measure the deformations of the casing which result from the cyclist's effort.

[0074] According to another example, one or more local stress wells can be identified or created to allow a good reading of the deformations which result from the cyclist's effort with sensors or gauges located on and / or against or in these wells. For example, the wall of the casing 20 can be locally thinner as illustrated in [Fig.4A], which represents the wall 30 of the casing, wall of thickness e, in which one or more zones 34, 36, of thickness el < e (for example el = 2mm and e = 3 mm) is / are thinned to position there (or to position against the thinned zone(s)) sensors or gauges 23a, 25' for measuring stresses, which are mainly due to the cyclist's efforts, as explained above.

[0075] When manufacturing such a casing, it is possible to identify beforehand, by mechanical stress tests (or a 3D computer simulation) the zones most likely to concentrate the deformations resulting from the cyclist's effort: these are the zones that one will seek to thin, as illustrated in [Fig.4A], to position gauges there.

[0076] As a variant, illustrated in [Fig.4B], the wall 30 has a zone 30a of different configuration (for example thinner) and / or of different material from the other parts of the wall 30 and against which a gauge 23b is positioned; this zone 30a forms a stress well. The gauge 23b is for example fixed by its ends 23bb 23b2.For example, generally speaking, the housing 30 may be made of aluminum or magnesium or steel, or any other metallic material. A different material for the area 30a is, for example, a plastic material.

[0077] As a further variant, illustrated in [Fig.4C], the wall 30 has a hole or orifice or recess 30o above which, preferably on the inner side of the casing, a test body 30b, for example made of plastic material, is positioned and is fixed to the edges of the hole 30o for example by its lateral ends 30b 1, 30b2. For example, this test body has a thickness e' 1 less than the thickness e of the casing. On or against this test body 30b is fixed a gauge 23c, which will detect the deformations of the body 30b.

[0078] For example, several casings can be tested, with different sensors or gauges, different angular rotations of the sensors or gauges and at different proximities of the axes, with calibrated instruments and compare the results with another torque sensor. Different casings will have different moduli of elasticity and / or different imperfections of symmetry, which makes it possible to compensate for imperfections in the measurement and signal processing chain.

[0079] Depending on the exact shape and material of each casing, the position and / or orientation of the sensors or gauges and / or the position of the stress wells may be adapted by applying the above indications to best capture the stresses resulting from the cyclist's efforts. For example, in practice:

[0080] - tests can be carried out with one or more gauges placed in different locations of the casing and / or following different orientations to test the deformations;

[0081] - and / or tests at three different proximity points give indications on the how the deformation is a function of the proximity to the crank axis;

[0082] - and / or 3 gauges at the same point, which makes it possible to determine the gauge which, for a given point, which will be the most suitable.

[0083] From these tests we can deduce a better mapping of the intensity of de- formation on the crankcase and the contribution of the cyclist's efforts to these deformations.

[0084] To produce an electrically assisted unit according to the invention, for an electrically assisted bicycle, a casing is first produced, then:

[0085] - one or more zones of the wall 30 of the casing 20 can be identified in which the deformations of the latter are mainly or solely due to the pedaling efforts of a cyclist;

[0086] - one or more constraint wells can be produced, such as explained above in said areas;

[0087] - one or more sensors 23, 25, 27 can be positioned at 90° to each other, or distributed with angles different from 90° between them, of deformations in said areas of the casing, identified in the 1st step above, and / or possibly in or on or against one or more stress wells, made in the previous step.

[0088] Finally, the electric motor can be introduced or positioned in the casing, as can one or more electronic card(s).

[0089] To prevent any residual interference on the measurements that would come from the effects of the motor or the electric assistance, a preliminary calibration can be carried out in the factory. Once the effects of the motor on the deformations of the casing are known, the influence of these effects can be subtracted from the measurements made by the gauges according to the invention. It should be noted that we know how to recognize the cyclist's effort just before applying assistance, we also know the electric assistance therefore, for example by mapping the different cases of cyclist effort and engine torque, we know how to go back to the cyclist's torque.

[0090] Laboratory tests, on the one hand by fixing the casing on a bench mount which is without external noise and on the other hand on a real bicycle, can make it possible to deduce the impact of the disturbances on the casing coming from the internal motor (therefore from the electric assistance) but also from the external environment. It is then possible to subtract these disturbances to check the real deformation of the casing due to the pedaling efforts of the cyclist. In addition, more in-depth measurements of the deformation of the casing around the pedaling axis give more information to better choose the coordinates where the deformation is maximum. For example, the distribution of the disturbances can depend on the properties of the material (for example: aluminum, or magnesium, or steel, or plastic); it may not be equally and / or progressively distributed: one can therefore for example seek to make the maximum then select the zone(s) capturing the maximum deformation.

[0091] To eliminate other parasitic deformations, for example due to the presence of stones on a road, an average of the measurements can be carried out. Such an average makes it possible to reduce the influence of the parasites over a short period. For example, if a cyclist steps off a sidewalk, there will be a peak of deformation. The average makes it possible to reduce the influence of this peak.

[0092] It is also possible to implement a self-adaptation function in the signal processing chain, this function taking into account the different biases of the terrain and correcting them. The bias coefficient(s) can be found in the laboratory, and for example then be corrected progressively once the cyclist starts to use the bicycle in different conditions each day.

[0093] [Fig. 5] represents an application of the invention in which several sensors (only sensor 23 is shown in this figure) are distributed on a single side of the casing, for example on the right side 10d of the bicycle 10. These sensors provide different measurements depending on the leg which produces the force. It is therefore possible to detect which leg produces the force on the corresponding pedal and to adjust the assistance of the electric motor. For example, in the case of a person with reduced mobility with a prosthesis on the left leg, the motor can increase the driving power (or the electrical assistance) when the left leg with the prosthesis produces the force on the pedal and conversely, the driving power (or the electrical assistance) is reduced when the right leg produces the force on the pedal.If gauges are present on both sides of the casing, it is also possible to identify the forces supplied by one leg and those produced by the other leg and adapt the electrical assistance accordingly.

[0094] Preferably, the sensors of a bicycle according to the invention are arranged inside the casing, which allows them to be protected.

[0095] The sensors are fixed relative to the casing, their assembly and use therefore do not require a complex part. For example, the gauges can be glued against the casing, by cold glue, but preferably by hot glue which will better withstand temperature variations.

[0096] The transmission of the signal produced by the sensor(s) to the control system 40 can be carried out by wire or wirelessly. This control system 40 is itself preferably arranged in the casing. It comprises programmed elements to implement electrical assistance to the pedaling of a cyclist, for example according to one of the methods described in the present application. It also makes it possible to process the measurement data provided by the sensor(s) 23-27.

[0097] According to one example, for a deformation measurement of 20mV given by a gauge, the associated torque can be, for example, 23Nm. At rest, the gauge gives a voltage of 8mV for a torque of 0 (therefore without electrical assistance).

[0098] If the system is linear, then we can deduce a mathematical formula of Nm as a function of the measured voltage, for example Nm = 1.9166xmV-15.33, which will allow for any measurement given by the gauge to calculate the corresponding torque. This formula can be programmed, for example in unit 50 (see [Fig.6A], description below) to convert the measured voltage, for example into a torque value.

[0099] If the system is not linear, it is still possible to deduce the torque by associating the values ​​given by the sensor with the corresponding torques applied by the cyclist. For example, we can have the following correspondence table:

[0100] 8mV for ONm

[0101] 8.2mV for O.INm

[0102] 8.4mV for 0.36Nm.

[0103] Etc

[0104] This correspondence table can be stored in storage means, for example in unit 50 (see [Fig.6A], description below).

[0105] The values ​​may be read, for example in real time and / or with a delay, for example 10 ms, from one or more lists and a moving average may be calculated to eliminate jolts or noise peaks. If, in any way, this system fails, a pre-recorded table may be used as a reference until the system is corrected or replaced. Alternatively, if the deformation of the casing 20 is the same or close to the applied torque, but on a different scale, the deformation may be converted using a gain coefficient to derive the torque. Again, the conversion may be performed by electronic means or circuit specifically programmed for this purpose, for example a processor, for example contained in the unit 50 described later in connection with [Fig.6A],

[0106] According to an example of embodiment or operation of an electric assistance unit, or more generally of a bicycle, according to the invention:

[0107] In a 1st state: there is no pedaling, and no assistance;

[0108] In a 2nd state: the cyclist applies an effort, which is not yet processed: the sensor(s) measure pedaling effort only;

[0109] In a 3rd state: the processing means, for example the processor, calculate and inject electrical assistance into the motor;

[0110] In a 4th state: the sensor(s) measure(s) the new torque level, but with known assistance; the processing means, for example the processor, can deduce the value of the new electric assistance torque to be applied.

[0111] Signal processing makes it possible to isolate what comes from the cyclist.

[0112] Whatever the embodiment of the invention, the processor of the means 40 can implement digitization and / or calculation steps which make it possible to convert the measurements made by the gauge(s) into calculated or estimated values ​​of the torques applied by the cyclist, either by a calculation (linear law or gain) or by a correspondence table.

[0113] Various stages of processing the signal from the sensors can be implemented artwork.

[0114] For example, it is possible to carry out one or more of the following steps, before estimating the torque and / or the effort (or force) applied by the cyclist:

[0115] - correct the signal or signals from the sensor(s) according to the temperature temperature, for example to correct a gain value applied to the signal(s)

[0116] - and / or carry out one or more signal windowing (or “trimming”) steps in Anglo-Saxon terminology) around the region of interest of the signal; this windowing can be temporal (we select a part of the signal in a time window) and / or in amplitude (we select a part of the signal between a maximum intensity value and a minimum intensity value);

[0117] - and / or correct the signal from the sensor(s) for any hysteresis of the sensor(s) sensors;

[0118] - and / or linearize the signal from the sensor(s) around the measuring point;

[0119] - and / or carry out one or more steps of filtering the signal or signals from the or sensors.

[0120] The torque and / or effort (or force) applied by the cyclist can be estimated or calculated as a function of the measured signal(s) and possibly one or more of the steps described above. Thus, at least one filtering and / or gain adjustment, and / or the elimination of one or more point error(s) can be carried out. The processing may be more or less easy to do depending on the quality of positioning of the gauges as described above.

[0121] After having estimated or calculated the torque and / or the effort (or the force) applied by the cyclist, it is possible, for example:

[0122] - to calculate the angle of a pedal as a function of the calculated or estimated torque signal;

[0123] - and / or to calculate the electric assistance torque to be applied to the electric motor; This torque is transmitted to the transmission chain.

[0124] Figures 6A and 6B represent a functional diagram of a measurement implementing steps as described above. These steps can be implemented by electronic components, for example comprising one or more processors, specifically adapted or programmed to implement said processing steps, all of these components being for example integrated in the form of a printed circuit (PCB) 50.

[0125] In step S1, the signal from the sensor(s) 23-27 is digitized. It can then be filtered (step S2 and / or S6), then corrected (step S3, which concerns for example a correction of the gain applied to the signal and a possible time windowing thereof), as a function of a temperature measurement (step S4) and windowing (step S5).

[0126] The steps of temperature measurement (step S4) and signal windowing can condition a step of selection and / or calculation of the gain applied to the signal.

[0127] S8 represents the storage in memory of coefficient(s) and / or software parameters, with a view to processing the signal by these coefficient(s) and / or parameters. Processing can be carried out with hardware and / or software components and / or with parameters specified by the users.

[0128] S7 represents the grouping (in a central unit) of the software parameters, the filtered signal and possibly the temperature compensation(s) (after windowing).

[0129] A hysteresis compensation step (S9) of the sensor(s) is then applied.

[0130] We can then apply:

[0131] - a step (S 10) of linearizing the part of the signal which has been selected by windowing;

[0132] - and / or a windowing step (SI 1) in amplitude (a value is selected maximum and minimum value of the signal);

[0133] - and / or a compensation step (S 12) for a possible drift, for example in temperature, of the signal, with a view to converting the digital signal into an analog signal.

[0134] Finally, the torque or effort (step S13) of the cyclist may be calculated or estimated, for example based on values ​​given above or previously estimated or measured. At least part of the calculated or estimated values ​​may be stored, for example to calculate a moving average. A calculation of the electric assistance torque to be applied may also be carried out at this step S13. The signal obtained in S12 therefore makes it possible to carry out, in S13, a calculation of the electric assistance torque to be applied.

[0135] The steps and / or means described above make it possible to know the cyclist's effort just before applying the electric assistance: we know the electric assistance applied at time t, therefore, for example by mapping or localizing the different cases of cyclist effort and engine torque, we know how to go back to the cyclist's torque at this same time t.

[0136] Optionally (step S14), the angle a of the pedal can be calculated, from the information on the torque or the force estimated or calculated during step S13 and for example as a function of the orientation of the sensors / gauges.

[0137] Depending on the torque signal Sc to be applied and possibly the pedal angle signal Sa, the electric assistance torque to be applied to the motor can then be transmitted to the motor.

[0138] This can be achieved by the reducer control module 52, for example produced in the form of a PCB, again for example as illustrated in [Fig.6B]. The data is processed to be transmitted to an inverter (step S16), then to the motor (step S17), to a reducer (step S18) and finally an electric assistance torque is transmitted to the axle (step S19).

[0139] The means, or electronic components, for implementing the steps mentioned above in connection with Figures 6A and 6B are preferably located (see the means 40 of Figures 1A-2) inside the casing 20.

Claims

Claims

1. Electrical assistance unit for an electrically assisted bicycle comprising: - an electric motor in a casing (20); - a crankset axle which passes through the casing; - at least one sensor (23, 23a-23c, 25, 27) of deformations of the casing, comprising an electrical resistance of between 120 and 500 ohms, fixed thereon and capable of measuring at least the deformations due to the pedaling efforts of a cyclist; - means (40, 50, 52), programmed or specially adapted, for evaluating or calculating a pedaling torque, separately from an assistance torque or without it, and for calculating a new electrical assistance torque as a function of the pedaling torque.

2. Electrical assistance unit according to claim 1, comprising between 2 and 6 sensors (23, 23a-23c, 25, 27) of deformations of the casing, fixed thereon and arranged close to the axis.

3. Electrical assistance unit according to claim 2, one (25) of the sensors being arranged under the axle, another (23) being behind the axle.

4. An electric assistance unit according to claim 3, one (27) of the sensors being arranged above the axis.

5. Electric assistance unit according to one of claims 1 to 4, the sensor(s) being arranged on only one side of the casing.

6. Electric assistance unit according to one of claims 1 to 4, at least one sensor being arranged on each side of the housing.

7. Electric assistance unit according to one of claims 1 to 6, at least one sensor (23, 23a-23c, 25, 27) of deformations of the casing being arranged less than 5 cm from the axis of the pedal crank.

8. Electric assistance unit according to one of claims 1 to 7, at least one sensor (23, 23a-23c, 25, 27) of deformations of the casing being arranged in or against at least one stress well (34, 36, 30o) in the wall (30) of the casing.

9. Electrical assistance unit according to claim 8, at least one stress well being produced by a local thinning (34, 36) of the wall (30) of the casing.

10. An electrical assistance unit according to claim 8, at least one stress well being provided by a recess (30o) on which a test body (30b) is positioned.

11. An electrical assistance unit according to claim 8, said test body (30b) having a thickness (e'i) less than the thickness e of the casing (30).

12. Electrical assistance unit according to claim 8, at least one stress well being produced by an area (30') of the wall (30) of the casing, this area (30') being made of a material different from the wall.

13. Electrical assistance unit according to one of claims 1 to 12, further comprising means (40, 50, 52) adapted or programmed to: - correct the signal or signals from the sensor(s) as a function of the temperature, for example to correct a gain value applied to the signal(s); - and / or carry out one or more steps of windowing the signal, this windowing being temporal and / or amplitude; - and / or correct the signal from the sensor(s) for any hysteresis of the sensor(s); - and / or linearize the signal from the sensor(s) in at least one zone of a signal delivered by at least one of the sensors. - and / or carry out one or more steps of filtering the signal or signals from the sensor(s).

14. Electrically assisted bicycle comprising an electrically assisted unit according to one of claims 1 to 13.

15. An electrically assisted bicycle according to claim 14, further comprising at least one temperature sensor.

16. Method for producing an electric assistance unit for an electrically assisted bicycle, this unit comprising an electric motor in a casing (20), crossed by a pedal axle, said method comprising - the identification of the zones (34, 36, 30') of the wall (30) of the casing (20) in which the deformations of the casing (20) are mainly or solely due to the pedaling efforts of a cyclist; - the positioning, in said identified zones of the casing in the previous step, one or more deformation sensors (23, 25, 27), comprising an electrical resistance of between 120 and 500 ohms; - the positioning of an electric motor in the casing (20) and means (40, 50, 52), programmed or specially adapted, for evaluating or calculating the pedaling torque, separately from the assistance torque or without it and for calculating a new electric assistance torque as a function of the pedaling torque.

17. Method for producing an electric assistance unit according to the preceding claim, comprising the positioning of at least one sensor (23, 25, 27) of deformations of the casing less than 5 cm from the axis of the pedal crank.

18. A method according to claim 16 or 17, comprising forming at least one stress well (30', 34, 36) in the wall of the housing, and positioning at least one sensor (23, 25, 27) in or against said stress well.

19. Method according to claim 18, at least one stress well being produced by local thinning (34, 36) of the wall of the casing.

20. Method according to one of claims 16 to 19, one or more sensors being glued or fixed by their ends above or in the vicinity of an area (30') of the wall (30) of the casing, this area (30') being made of a material different from the wall.

21. A method according to claim 20, at least one stress well being provided by forming a recess (30o) on which a test body (30b) is positioned.

22. A method according to claim 21, said test body (30b) having a thickness (e'i) less than the thickness e of the casing (30).

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