Torque measurement sensor for electrically assisted bicycle

Abstract

The invention relates to an electrical 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) for detecting deformations of the casing, fixed on the latter and capable of measuring deformations due to the pedalling efforts of a cyclist; means (40, 50, 52), programmed or specially adapted, for evaluating or calculating a pedalling torque, separately from an assistance torque or without the latter, and for calculating a new electrical assistance torque.

Description

[0001] DESCRIPTION

[0002] Title: TORQUE MEASURING SENSOR FOR ELECTRIC BICYCLE

[0003] TECHNICAL FIELD AND PRIOR ART

[0004] The invention relates to the field of electric assistance units for electrically assisted bicycles and to that of electrically assisted bicycles.

[0005] In order to provide the power or torque needed for assistance, we seek to have a measurement of the effort applied by the cyclist when pedaling.

[0006] Generally, solutions using sensors operating on the basis of inverse magnetostriction are implemented: these sensors are placed on the crank axle, the deformation of the latter inducing modifications of the magnetic field seen by the sensor; the latter can therefore generate a signal which is sent to the bicycle control unit. Other solutions exist, based on strain gauges, or optical or magnetic sensors.

[0007] Reverse magnetostriction sensors cooperate with the moving ferromagnetic hub of the crankset, which complicates their implementation, particularly with regard to data transmission to the electric assistance control means. In addition, these sensors are usually installed to capture the forces coming from the two pedals, which requires positioning them in areas where other mechanical or electrical parts are already located. For strain gauges, the gauge and part of the circuit are on the hub, therefore rotating with it. Wireless communication, or with a brush, is carried out between the moving part and the fixed part.

[0008] 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 using techniques such as magnetostrictive techniques. DISCLOSURE OF THE INVENTION

[0009] The invention firstly relates to an electric assistance unit for an electrically assisted bicycle comprising:

[0010] - an electric motor in a casing;

[0011] - a crankshaft axle which passes through the crankcase;

[0012] - at least one casing deformation sensor, fixed on and / or against the casing and / or arranged near the shaft, capable of measuring the deformations due to the pedaling efforts of a cyclist.

[0013] The housing may include or possibly contain a transmission and / or gearbox system.

[0014] The invention makes it possible to measure the forces applied by the cyclist to the pedals. Preferably, the sensor(s) can be arranged close to the axis of the crankset, for example less than 5 cm from this axis.

[0015] These alternating forces are transmitted by the pedals to the crankcase, in which they create stresses or deformations, which directly reflect the cyclist's effort.

[0016] By measuring the stress, using one or more sensors, for example one or more strain gauges, mounted in or on the crankcase, the cyclist's effort can be calculated. The invention therefore makes it possible to measure the deformation of the crankcase directly due to the force applied by the cyclist to the pedal. According to an exemplary embodiment, a correlation is established between the pedaling efforts and the deformation on the crankcase. 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. 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 crankcase. 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.

[0017] Compared to existing solutions: - the invention does not require additional components, in particular no expensive, bulky gears that cause a loss of efficiency;

[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.

[0019] In the context of the present invention, at least one deformation sensor or gauge may comprise an electrical resistor which may for example have a resistance value of between 100 ohms and 1000 ohms or even 5000 ohms, but preferably between 120 and 500 ohms, for example 350 ohms. These values ​​make it possible to have a good compromise between the management of energy consumption and the sensitivity of the sensor or gauge.

[0020] An electrical assistance unit according to the invention may further comprise, or be associated or coupled with, means, for example digital means (for example at least one processor), which are, or may be, programmed or specially adapted, to evaluate or calculate the pedaling torque, separately from the assistance torque or without it, and for example to calculate a new assistance torque, preferably as a function of the pedaling torque.

[0021] An electric assistance unit according to the invention may comprise, for example, between 2 and 6 casing deformation sensors, fixed to the casing. A reduced number of deformation sensors, for example less than or equal to 3, allows for savings in equipment and simplified maintenance.

[0022] The sensor(s), or at least part of them, is / are preferably arranged close to the axis, for example less than 5 cm from it.

[0023] For example :

[0024] - one of the sensors can be placed under the bottom bracket axle, another being behind this axle (relative to the direction of movement of the bicycle);

[0025] - and / or one of the sensors can be placed above the bottom bracket axle.

[0026] The sensor(s) may be arranged on only one side of the housing, or at least one sensor may be arranged on each side of the housing.

[0027] 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 local thinning of the wall of the casing, or even by an area of ​​the wall of the casing, this area being made of a material different from the wall.

[0028] 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 pedal 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.

[0029] 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.

[0030] An electric assistance unit according to the invention may further comprise means adapted or programmed for:

[0031] - correct or compensate the signal or signals from the sensor(s) as a function of temperature, for example to correct a gain value applied to the signal(s); this is the case, for example, 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;

[0032] - and / or carry out one or more windowing steps of the signal, this windowing being temporal and / or amplitude; windowing makes it possible to select a portion of interest of the signal;

[0033] - and / or correct the signal from the sensor(s) for possible hysteresis of the sensor(s);

[0034] - and / or correct the signal with a self-adaptation function, for example to take into account the different biases of the terrain;

[0035] - and / or linearize the signal from the sensor(s) in at least one zone of a signal delivered by at least one sensor or at least one of the sensor(s).

[0036] - and / or carry out one or more steps of filtering the signal or signals from the sensor(s). The invention also relates to an electrically assisted bicycle comprising an electrically assisted unit according to the invention.

[0037] Such a bicycle may also have a temperature sensor.

[0038] 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:

[0039] - the identification of one or more areas of the casing in which the deformations of the casing are mainly or solely due to the pedaling efforts of a cyclist;

[0040] - the positioning of one or more deformation sensors, for example between 2 and 6 sensors, in said areas of the casing identified in the previous step; a reduced number of deformation sensors, for example less than or equal to 3, allows for savings on equipment and simplified maintenance;

[0041] - the positioning of the electric motor on and / or against the casing in one or more of said zone(s).

[0042] It is also possible to position in the housing 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 and possibly for calculating a new electric assistance torque as a function of the pedaling torque.

[0043] At least one strain sensor or gauge may include an electrical resistor which may, for example, have a resistance value between 100 ohms and 1000 ohms or even 5000 ohms, but preferably between 120 and 500 ohms, for example 350 ohms. These values ​​provide a good compromise between energy consumption management and the sensitivity of the sensor or gauge.

[0044] At least one crankcase deformation sensor can be positioned less than 5 cm from the crankshaft axle.

[0045] 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:

[0046] - one or more sensors may be glued or fixed, for example by their 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;

[0047] - 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, a gauge, located on and / or against this intermediate part.

[0048] 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'i) less than the thickness e of the casing.

[0049] 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:

[0050] - to calculate or estimate, from the signals of the sensor(s), the cyclist's effort only;

[0051] - and / or to calculate and inject electrical assistance into the motor;

[0052] - and / or to calculate or estimate, from the signals of the sensor(s), the new torque level, but with known assistance, then possibly to deduce the value of the new electric assistance torque to be applied;

[0053] - and / or to isolate, by processing the signal or signals coming from the sensor(s), what comes mainly or only from the cyclist.

[0054] - and / or correct the signal with a self-adaptation function, for example to take into account the different biases of the terrain;

[0055] BRIEF DESCRIPTION OF THE DRAWINGS

[0056] An exemplary embodiment of the invention will now be described with reference to the accompanying drawings in which; [FIG 1A] and [FIG 1B] represent an example of an embodiment of a bicycle and a casing to which the invention can be applied,

[0057] [FIG 2] represents a particular embodiment of a bicycle casing according to the invention.

[0058] [FIG 3A], [FIG 3B] and [FIG 3C] show an embodiment of a bicycle casing according to the invention and the detection of forces applied in various directions;

[0059] 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;

[0060] [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 housing.

[0061] [FIG 6A] and [FIG 6B] represent a measuring system according to the invention.

[0062] In the figures, similar or identical technical elements are designated by the same reference numbers.

[0063] DETAILED DESCRIPTION OF EMBODIMENTS

[0064] Figure 1A shows an example of an embodiment of a bicycle to which the invention can be applied.

[0065] 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.

[0066] A pedal set comprises two pedals 22, 24, connected by cranks 22', 24' to an axle which enters a housing. Figure 2 shows the hole 21 (or hub hole) on one side of this housing. The action of the cyclist on the pedal set drives a chain 28. In the case of an electrically assisted bicycle, an electric motor is housed in a casing 20 which is crossed by the casing which houses the axle of the pedal set. The casing 20 may also contain a control system 40 (in broken lines in Figures 1 and 2), which makes it possible to control the assistance provided to the cyclist by the electric motor. Reference 32 designates an electric battery.The force Fl applied by a cyclist on the pedal 22 results in corresponding forces F2 and F'2 applied to the casing 20: as can be seen in figure 1A, and in more detail in figure 1B, 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.

[0067] Figure 1B shows the casing of Figure 1A in more detail. Numerical references identical to those in Figure 1A represent the same technical elements. The cyclist's force Fl is transmitted by a force path between the pedaling axle 21' (or hub) and the attachment points 20i, 20? to the frame. This force path passes largely through the hub and the area surrounding it; it is therefore this area, the hub and its periphery, which undergoes the greatest deformation. The attachment points also see this force, but to a lesser extent.

[0068] Figure 2 shows a side view of the housing 20, from which the axle and its pedals have been removed.

[0069] In this figure, as in the following ones, the references 23, 25, T1 represent three sensors, for example strain gauges, for example electrical resistors and / or rosette type. In the context of the present invention, a gauge formed from an electrical resistor may for example have a resistance of between 100 ohms and 1000 ohms or even 5000 ohms, but preferably between 120 and 500 ohms, for example 350 ohms. A gauge with too high a resistance will consume little energy but will not have the desired sensitivity; a gauge with too low a resistance will have too high a sensitivity. Care will also be taken to orient the gauge so that it is oriented or glued in the correct direction of deformation. Alternatively, a gauge may be fixed by its ends to an area intended to deform.

[0070] Each gauge has specific coordinates in the 2D plane to pass or apply maximum deformation to it. In addition, any interference from the stressed body can be compensated if the gauge is applied in the correct orientation.

[0071] 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 T1 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 Figure 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.

[0072] Figures 3A-3C represent the case of only 2 sensors 23, 25, but arranged as described above in connection with Figure 2 (sensor 23 is arranged behind the crank axle, and sensor 25 is arranged below). Sensor 25 detects the force applied by a vertical force, as illustrated in Figure 3A; the two sensors 23, 25 each detect a portion of the force applied by a force F which has the diagonal direction shown in Figure 3B and sensor 23 detects the force applied by a horizontal force, as illustrated in Figure 3C.

[0073] Another arrangement of 3 sensors or gauges 23, 25, Tl is shown in figure 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, Tl, arranged on either side of the central gauge 25 (for example oriented horizontally), can be arranged at an angle P relative to the vertical axis AA'.

[0074] 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 control to provide temperature compensation.

[0075] As seen in these figures, the sensor(s) 23-27 is / are arranged near the crankshaft.

[0076] More generally, we seek to position 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 translates into, 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.

[0077] For example, at least one sensor or gauge placed a few centimeters, 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 allows the deformations of the crankcase resulting from the cyclist's effort to be properly measured.

[0078] According to another example, one or more local stress wells can be identified or created to allow good reading of the deformations resulting 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 ei < e (for example ei = 2 mm 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.

[0079] When manufacturing such a casing, it is possible to identify in advance, by mechanical stress tests (or a 3D computer simulation), the areas most likely to concentrate the deformations resulting from the cyclist's effort: these are the areas that will be sought to be thinned, as illustrated in FIG. 4A, in order to position gauges there. As a variant, illustrated in FIG. 4B, the wall 30 has an area 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 area 30a forms a stress well. The gauge 23b is for example fixed by its ends 23bi, 23b?. For example, generally speaking, the casing 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.As a further variant, illustrated in Figure 4C, the wall 30 has a hole or orifice or recess 30o above which, preferably on the inside 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 30bi, 30bz. For example, this test body has a thickness e'i 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.

[0080] For example, one can test several casings, 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.

[0081] 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 can be adapted by applying the above indications to best capture the stresses resulting from the cyclist's efforts. For example, practically:

[0082] - tests can be carried out with one or more gauges placed at different locations on the casing and / or in different orientations to test for deformations;

[0083] - and / or tests at three different proximity points give indications on how the deformation is a function of the proximity to the crank axle;

[0084] - and / or 3 gauges at the same point, which makes it possible to determine the gauge which, for a given point, will be the most suitable.

[0085] From these tests, we can deduce a better mapping of the intensity of deformation on the casing and the contribution of the cyclist's efforts to these deformations.

[0086] To produce an electrically assisted unit according to the invention, for an electrically assisted bicycle, a casing is first produced, then:

[0087] - one or more zones of the wall 30 of the casing 20 can be identified in which the deformations thereof are mainly or solely due to the pedaling efforts of a cyclist; - one or more stress wells can possibly be produced, as explained above in said zones;

[0088] - one or more sensors 23, 25, Tl, can be positioned at 90° to each other, or distributed with angles different from 90° between them, of deformations in said zones 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. Finally, the electric motor can be introduced or positioned in the casing, as well as 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 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 cyclist's pedaling efforts. 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 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: we can therefore, for example, look for the maximum area and then select the zone(s) capturing the maximum deformation.

[0091] To eliminate other unwanted distortions, for example due to the presence of stones on a road, an average of the measurements can be taken. Such an average helps reduce the influence of interference over a short period. For example, if a cyclist steps off a sidewalk, there will be a peak in distortion. The average helps 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 using the bike in different conditions each day.

[0093] Figure 5 shows 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 that produces the force. It is therefore possible to detect which leg produces the force on the corresponding pedal and 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, so their installation and use do not require any complex parts. For example, the gauges can be glued to the casing using cold glue, but preferably 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] For example, for a strain 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 a mathematical formula of Nm as a function of the measured voltage can be deduced, 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 figure 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: 8mV for ONm 8.2mV for O.INm

[0100] 8.4mV for 0.36Nm.

[0101] Etc

[0102] This correspondence table can be stored in storage means, for example in unit 50 (see Figure 6A, description below).

[0103] 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 some 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 circuitry specifically programmed for this purpose, for example a processor, for example contained in the unit 50 described later in connection with the figure

[0104] 6A. According to an example of embodiment or operation of an electric assistance unit, or more generally of a bicycle, according to the invention: In a 1 er state: there is no pedaling, and no assistance;

[0105] In a 2 ème state: the cyclist applies an effort, which is not yet processed: the sensor(s) measure(s) the pedaling effort only;

[0106] In a 3 ème state: the processing means, for example the processor, calculate and inject electrical assistance into the motor;

[0107] In a 4 ème 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.

[0108] Signal processing allows us to isolate what is coming from the cyclist.

[0109] 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.

[0110] Various steps can be implemented to process the signal from the sensors. For example, one or more of the following steps can be performed before estimating the torque and / or effort (or force) applied by the cyclist:

[0111] - correct the signal(s) from the sensor(s) as a function of temperature, for example to correct a gain value applied to the signal(s);

[0112] - and / or carry out one or more signal windowing steps (or “trimming”) around the region of interest of the signal; this windowing can be temporal (a part of the signal is selected in a time window) and / or amplitude (a part of the signal is selected between a maximum intensity value and a minimum intensity value);

[0113] - and / or correct the signal from the sensor(s) for any hysteresis of the sensor(s);

[0114] - and / or linearize the signal from the sensor(s) around the measurement point; - and / or carry out one or more filtering steps of the signal(s) from the sensor(s).

[0115] The torque and / or effort (or force) applied by the cyclist can be estimated or calculated based on the measured signal(s) and possibly one or more of the steps described above. This will allow at least one filtering and / or gain adjustment, and / or the elimination of one or more point errors. The processing may be more or less easy to do depending on the quality of positioning of the gauges as described above.

[0116] After estimating or calculating the torque and / or effort (or force) applied by the cyclist, it is possible, for example:

[0117] - to calculate the angle of a pedal based on the calculated or estimated torque signal;

[0118] - and / or to calculate the electric assistance torque to be applied to the electric motor; this torque is transmitted to the transmission chain.

[0119] 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.

[0120] 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 of the latter), as a function of a temperature measurement (step S4) and windowing (step S5).

[0121] The temperature measurement steps (step S4) and signal windowing steps can condition a step of selection and / or calculation of the gain applied to the signal.

[0122] S8 represents the storage in memory of the coefficient(s) and / or software parameters, with a view to signal processing 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. S7 represents the grouping (in a central unit) of the software parameters, the filtered signal and possibly the temperature compensation(s) (after windowing).

[0123] A hysteresis compensation step (S9) of the sensor(s) is then applied.

[0124] We can then apply:

[0125] - a step (S10) of linearizing the part of the signal which has been selected by windowing;

[0126] - and / or a windowing step (SU) in amplitude (a maximum value and a minimum value of the signal are selected);

[0127] - and / or a step (S12) of compensating for any drift, for example in temperature, of the signal, with a view to converting the digital signal into an analog signal.

[0128] Finally, the torque or effort (step S13) of the cyclist can 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 ​​can be stored, for example to calculate a moving average. A calculation of the electric assistance torque to be applied can also be carried out at this step S13. The signal obtained at S12 therefore makes it possible to carry out, at S13, a calculation of the electric assistance torque to be applied.

[0129] 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.

[0130] 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 according to the orientation of the sensors / gauges.

[0131] 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. This can be achieved by the gearbox control module 52, for example produced in the form of a PCB, again for example as illustrated in Figure 6B. The data are processed to be transmitted to an inverter (step S16), then to the motor (step S17), to a gearbox (step S18) and finally an electric assistance torque is transmitted to the axle (step S19).

[0132] 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 housing 20.

Claims

CLAIMS 1. Electrical assistance unit for an electrically assisted bicycle comprising: an electric motor in a casing (20); a crankshaft which passes through the casing; at least one sensor (23, 23a-23c, 25, 27) of deformations of the casing, 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. Electric 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. Electrical assistance unit according to claim 3, one (27) of the sensors being arranged above the axis.

5. Electrical assistance unit according to one of claims 1 to 4, comprising a number of deformation sensors less than or equal to 3.

6. Electrical assistance unit according to one of claims 1 to 5, at least one deformation sensor comprising at least one resistor having a value between 120 ohms and 500 ohms.

7. Electric assistance unit according to one of claims 1 to 6, the sensor(s) being arranged on only one side of the casing.

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

9. Electric assistance unit according to one of claims 1 to 8, 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.

10. Electric assistance unit according to one of claims 1 to 9, 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, 30 o ) in the wall (30) of the casing.

11. Electrical assistance unit according to claim 10, at least one stress well being produced by a local thinning (34, 36) of the wall (30) of the casing.

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

13. Electrical assistance unit according to claim 10, said test body (30b) having a thickness (e'i) less than the thickness e of the casing (30).

14. Electrical assistance unit according to claim 10, 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. Electrical assistance unit according to one of claims 1 to 14, 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 the possible hysteresis of the sensor(s); and / or correct the signal with a self-adaptation function; 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). Electrically assisted bicycle comprising an electrical assistance unit according to one of claims 1 to 15.Electrically assisted bicycle according to claim 16, further comprising at least one temperature sensor. Method for producing an electrically assisted unit for an electrically assisted bicycle, this unit comprising an electric motor in a casing (20), crossed by a bottom bracket axle, said method comprising: identifying 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; positioning one or more deformation sensors (23, 25, 27) in said zones of the casing identified in the previous step; 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.

19. 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.

20. A method according to claim 18 or 19, 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.

21. Method according to claim 20, at least one stress well being produced by local thinning (34, 36) of the wall of the casing.

22. Method according to one of claims 18 to 21, 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.

23. Method according to claim 22, at least one stress well being produced by forming a recess (30 o ) on which a test body (30b) is positioned.

24. The method of claim 23, said test body (30b) having a thickness (e'i) less than the thickness e of the casing (30).

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