WO2019238588A1 - An electrical bicycle with an electrical transmission chain parallel to that for peddling and comprising a dual control for starting up the motor - Google Patents

Abstract

The invention essentially consists in installing two independent controls (HMI and intentional triggering sensor) of the electrical motor in a bicycle comprising two independent transmissions (electric motor and peddling system) according to patent application FR1755510.

Description

 ELECTRIC BIKE WITH ELECTRIC TRANSMISSION CHAIN PARALLEL TO THE PEDAL AND WITH DOUBLE CONTROL

STARTING THE ENGINE

 Technical area

 The present invention relates to the field of electric bicycles, that is to say those which carry an electric motor and a battery supplying the motor.

 It relates more particularly to electric bikes, intended for a sporting use, in particular the mountain bikes (VTT) with which one wishes punctually to cross very steep slopes or to cross natural obstacles.

 The invention aims to exceed the limits of the operating modes of current electric bikes, and therefore to offer a wider range of riding modes, in particular direct / instant riding by the user.

 Prior art

 A so-called electrically assisted bicycle, as it currently exists, is a bicycle with a conventional pedaling mechanism to which the following components have been added:

 - an electric motor arranged in the front wheel, the rear wheel, or near the bottom bracket, usually qualified as “central motor” in this case;

 - an electric motor supply battery;

 - an electronic control-command unit which regulates the control (operation) of the various electrical components;

 - if necessary, a control unit, generally arranged at the level of the handlebars, and which allows the user to define a mode of assistance, to modulate the level of his assistance, to know his mileage ...

 It is the European directive 2002/24 / EC which fixes in Europe, the criteria so that an electrically assisted bicycle can circulate on the public road. In particular, it is specified that assistance should only be done if the cyclist pedals, and cut himself when pedaling stops (but that) it is however authorized to set up a starting assistance without having recourse pedaling but which must not exceed 6 km / h.

In practice, all electrically assisted bikes with a central motor and rear wheel drive, which exist to date, are designed with a transmission of the engine torque which is in series with that of the pedaling torque, so that the addition of engine torque to pedaling torque and transmission to the rear wheel hub is by through a single chain or belt. Thus, the motor necessarily adds a torque to that of pedaling.

 This design has several major drawbacks.

 A first major difficulty comes from the fact that the optimal speed of rotation of electric motors, although operational with a high torque as soon as they start from a standstill, is in a range of 300 to 2,000 or even 3,000 rpm, while the pedaling rotation speed that a cyclist can exercise durably is between 20 and 80 rpm, while avoiding discontinuous variations in frequency. In order to match these rotational speeds, it is therefore necessary to insert a speed reducer, after the output of the motor since the latter is in series with the crankset. The addition of a speed reducer leads to overweight, a geometric constraint for the layout of the engine and additional mechanical complexity.

 A second recurring point which generates debates, both for users and for legislators, is crystallized around the factors and control laws to manage the operation of the engine, by enslaving it to the user's pedaling action. .

 Several solutions exist to detect when and how to achieve this excess torque by the electric motor.

 First of all, assistance can be obtained by detecting the rotation of the bottom bracket. A sensor arranged at the pedal level detects the rotation of the pedal and therefore pedaling, which then allows the electric motor to provide sound in addition to pedaling.

 Assistance can also be done by means of a pressure sensor fitted on the pedal: the engine can start as soon as it feels the pressure exerted on the pedal. In general, the more the user presses the pedals, the more the motor helps him, even if his pedaling rate is low.

 In place of a pressure sensor, detection can be done by a torque or effort sensor: it is often a combination of effort and cadence that controls the power of the motor. The more the cyclist pedals at a high rate and / or the more his effort increases by exerting a high torque, the more he receives assistance, this in order to stay within a range of rotational speed and a value of torque to provide comfortable for the cyclist.

Finally, there are assistances in which the engine torque is evaluated from knowledge of the chain tension. This system is very responsive since the chain is tightened as soon as the foot is placed on the pedal, this will therefore start the engine as soon as the crankset begins to turn.

 Regarding the assistance modes that are applied, the control laws or assistance program are preprogrammed by the bicycle manufacturer or the engine block supplier. The user chooses a level of assistance from a number generally from 3 to 5 levels, i.e. a value of the motor torque proportional to that of pedaling developed by the user.

 We can say that the current laws or programs, which therefore systematically add an additional torque to the pedaling torque, are well suited when the user defines a type of effort over a relatively long period, for example by attacking a climb or a section quite "rolling". They are therefore well suited to regular terrain profiles.

 On the other hand, each control law is frozen since it is preprogrammed and therefore controls the electric motor to the pedaling provided as long as the user does not change the law himself.

 During tests carried out by the applicant on existing electrically assisted mountain bikes, with sports users, both in search of pleasure, of sensations but also of challenges (including) of endurance efforts, it was found that they had, during ad hoc technical passages, a very strong tendency to want to increase the level of assistance to the maximum. In reality, these users occasionally used the switch to a program with more assistance (normally dedicated to a more restrictive use) as an indirect accelerator.

 And even if they use this maximum assistance program, sports users have found themselves in situations in which the assistance of the electric motor does not fully satisfy them.

 This is particularly important when they suddenly face an obstacle or very steep slope or when they want to start instantly in extreme slope configurations. The obligation to pedal for assistance was also not compatible with slopes, on tree roots or on hollowed out paths in which the pedals regularly catch a higher edge.

On the contrary, during the many less demanding passages, they wanted to be able to pedal without any assistance, which is not provided for in the modes offered. Of more, the weight of the bikes offered does not always allow to do it in practice and very rarely over a significant distance.

 In addition, the serial design of the electric motor with the transmission by pedaling induces major drawbacks which can be listed as follows.

 First of all, there may be premature breaks or wear on the transmission (chain, sprockets, freewheel, etc.), as it was not originally designed to transmit significant engine torques , which is particularly true in the situations described above.

 Then, a user can experience significant difficulties in changing the gear ratios when the electric motor is running and provides torque, since it applies a significant tension to the chain. A known solution consists in providing power cuts to achieve these speed changes, but this is neither efficient nor comfortable to use, since this induces discontinuities in the speed and in the effort of the user. , without forgetting the shocks created between the mobile elements of the transmission chain (chain, sprockets, derailleur, ...).

 To best satisfy users, in particular sportspeople, certain models of electrically assisted bicycles or mopeds offer a throttle system by handle or trigger which makes it possible to provide the rear wheel with engine torque, without it being necessary for the user to pedal.

 These models always using either a motor at the rear wheel which, due to its large eccentric weight, proves to be very unsuitable for use on all terrain, or a transmission of engine torque necessarily in series with pedaling, the same drawbacks and limitations as mentioned above remain.

Wheel motors have been proposed for electric assistance for bicycles, that is to say assemblies with an electric motor incorporated in the generally rear wheel of bicycles. The use of wheel motors is an interesting solution which makes it possible to have a transmission of the torque from the engine in parallel with the torque from the pedaling. The transmission mechanism of the wheel motor is by design very simplified since directly grafted into the hub of the rear wheel. It often includes the motor and a reduction gear, which already constitutes a significant weight and also a very high inertia in rotation. This significant weight and inertia have a negative influence on the handling of the bike, especially when riding must be precise and fast. The weight of several kilos added to the rear wheel is felt even more when the bike is not on the ground, when carrying it for example, but also in crossings where it is necessary to take off the rear wheel and also in the show jumping very present in the mountain biking. Finally, it is a major drawback when you want to pedal as a dancer during demanding climbs, since a low inertia of the bike under the cyclist is a very important factor of efficiency.

 This is how for the majority of practices, apart from use at moderate speed on the road or in town where you can pedal without forcing and sitting on the saddle, the installation of electric motors in the central part of the bikes is widespread.

 He has already proposed an electrically assisted bicycle design according to which the driving torque is brought to the rear wheel in parallel with the pedaling torque: see for example the utility model DE20 2016104737. But in this design, there is always provided a speed reducer between the motor and the crankset, which brings the same drawbacks as those previously mentioned of weight of increased mechanical complexity and also of loss of output. In addition, the motor is installed on the rear of the bicycle in overhang.

 We can also cite the old patents BE 661118A, and US 2331976 which disclose a design of a bicycle assisted by a thermal engine with a driving torque brought to the rear wheel in parallel with the pedaling torque, with the same disadvantages even more accentuated since a clutch must be integrated to allow the vehicle to start without stalling the engine. In addition, these days it is no longer reasonable to design bikes powered by an internal combustion engine.

 Also, in order to improve current electrically assisted bikes, the Applicant has proposed in patent application No. FR 17555 lO filed on June 16, 2017, a bicycle design according to which the conventional pedal transmission is combined with an additional transmission by electric motor which is in parallel and completely decoupled from the pedaling transmission. The mechanical decoupling between the two transmission mechanisms is ensured by two free wheels, one dedicated to the pedaling mechanism as usual which can be integrated in a pinion cassette, the other dedicated to the mechanism of the electric motor, and which can be introduced either near the engine outlet, directly on the rear wheel axle.

This design significantly improves assistance bikes electric vehicles especially for sports users, because the punctual and intense assistance of the electric motor allows the instantaneous crossing of an obstacle or a steep slope, even without pedaling and from the stop, and this without harming the 'autonomy, that is to say the ability of the engine to significantly increase performance or relieve users, very punctually.

 Thus, with this design, the user can instantly control the electric motor to start and adjust the desired speed of the bicycle, with or without simultaneous pedaling contribution. The application of the engine torque can be limited to relatively short periods of time, and in the absence of this torque, the bicycle behaves identical to that of a conventional bicycle without electric assistance.

 For starting and piloting the engine, it is necessary to provide a man-machine piloting interface (HMI), connected to the electronic engine control unit. The inventors of the aforementioned application FR1755510 provide that the HMI is in the form of an acceleration trigger or an accelerator handle, ergonomic and intuitive control and which can bring feelings of control and reactivity to the user as well as providing a callback function as soon as it is released.

 This being the case, since the engine can potentially make its contribution since stopping, it must not be carried out unintentionally by an inappropriate or involuntary action by the user or the external environment on the HMI .

 In other words, there is a need to guarantee the safety of a user of the bicycle designed according to the aforementioned patent application FR1755510, or that of individuals nearby, by guaranteeing that when the bicycle is stopped, or even at n Regardless of the speed of the bicycle, the electric motor cannot start without the assurance of intentional action by the user.

 The object of the invention is to meet this need at least in part.

Statement of the invention

 To do this, the invention relates, in one of its aspects, to an electric bicycle, comprising:

a rear wheel; - A crankset, intended to be actuated by the muscular force of a user to transform it into a pedaling torque, comprising two cranks of crankset rotating around a crankset axle and two pedals each fixed to a crank;

 - an electric bike speed sensor;

 - an electric drive motor, comprising a stator and a rotor which can rotate around a rotor axis, the rotor axis being spaced apart while being close to the crankset axis;

 - an electronic engine control unit;

 a first torque transmission mechanism, the first mechanism comprising a first input wheel, which can be driven in rotation about the axis of the crankset, a first flexible transmission element, at least one first output wheel, which can be driven by the first input wheel via the first flexible element, a first free wheel device, adapted to transmit the pedaling torque to the rear wheel via the first output wheel;

 - a second torque transmission mechanism, distinct from the first mechanism, the second mechanism comprising a second input wheel, which can be driven in rotation about the axis of the rotor, a second flexible transmission element, at least a second wheel output, can be driven by the second input wheel via the second flexible element, a second freewheel device, adapted to transmit the driving torque from the motor to the rear wheel via the second output wheel;

 - a man-machine control interface (HMI), connected to the electronic engine control unit, adapted so that the user can start and control the engine independently of the torque and / or pedaling movement;

 - at least one trigger sensor, connected to the electronic engine control unit, adapted to detect an intentional action by the user independent of the intentional action on GIHM;

the electronic control unit being adapted for, when the speed of the bicycle detected by the speed sensor is zero up to a threshold value, authorize at least the starting of the motor and its control up to a duration and / or a torque of rotation and / or a predetermined speed of rotation (s), if and only if the user activates GIHM and simultaneously the trigger sensor detects an intentional action of the user independent of the intentional action on the HMI.

 According to an advantageous embodiment, the electronic control unit is further adapted for, when the speed of the bicycle is above the threshold value, continue to authorize the piloting of the started engine or not, either if the user operates the HMI without the need for detection on the part of the trigger sensor, ie if the user actuates the HMI and simultaneously the trigger sensor still detects an intentional action by the user.

 Thus, the invention essentially consists of installing two independent controls (HMI and voluntary trigger sensor) of the electric motor in a bicycle with two independent transmissions (electric motor and pedaling system) according to patent application FR1755510.

 This independent double control will be activated by two distinct, voluntary and simultaneous actions of the user of the bicycle when the latter is stationary and at least until he has reached a speed threshold value, which can typically be of the order of 10 to 15 km / h.

 The need to have two separate, voluntary and simultaneous actions by the user thus makes it possible to guarantee his safety as well as that of third parties, that is to say prevent any inadvertent starting of the electric motor in an undesired, suffered or unintentionally activated by the user.

 This could for example happen when an external object or body, such as a branch, a physical obstacle, a garment or any product transported on the handlebars of the bicycle accidentally activates GIHM, that is to say say the basic command dedicated to driving the engine.

 Thus, the operation of the bicycle according to the invention provided with its independent double control is as follows.

In current use, that is to say when the bicycle has a speed above the threshold speed, the user can control the electric motor at any time and instantly by its basic control, the HMI, preferably consisting of a trigger or an accelerator handle with automatic return, pivotally mounted on the handlebars of the bicycle. By design and function, the trigger or throttle handle can normally only be actuated intentionally during use. This basic command or trigger therefore allows the user to dose the engine speed exactly as necessary. When the user fully releases the acceleration trigger, the engine is instantly shut down thanks to the automatic mechanical return of the trigger to its initial cut-off position. This automatic return of the acceleration trigger thus achieves the rolling safety function.

 When the bicycle is stopped and also when the bicycle is advancing by applying a pedaling torque or due to the downhill relief to a speed threshold value, the user must simultaneously actuate the trigger. acceleration and perform another voluntary action detected by a trigger sensor.

 These two distinct, voluntary and simultaneous actions are detected / analyzed in the form of signals by the electronic engine control-command unit which then triggers the starting and the possibility of piloting the latter.

 The processing of these signals can be done either directly in the sensor, or in the processor of the electronic engine control and command unit.

 Several types of algorithms applied by the processor may be necessary, depending on the definition of the conditional law of control by the trigger sensor.

 These can be algorithms suitable for:

 - direct measurement of the target quantity with binary processing depending on whether or not a threshold is exceeded;

 - a measurement of an indirect quantity then calculation of the target quantity, for example of a force by means of a displacement, or of a couple by means of a rotation,

 - a measurement of parameters that are highly variable over time and that we will take care to filter in order to clearly differentiate from the current values, that is to say, not corresponding to an intentional action, the values characteristic of voluntary action;

 - detection of a characteristic curve over the variable variable over time, for example:

 • double pressing on at least one of the two pedals,

 • a succession of short and long presses on at least one of the two pedals

• a combination of large amplitude displacements, then a smaller amplitude, then a very small displacement characteristic of an effort / pressing on the pedal. Thus, according to a first advantageous embodiment, the trigger sensor is adapted to detect an intentional action by the user on at least one of the two pedals.

 This mode is advantageous because this type of action is very natural for a cyclist with his pedals, and in addition is similar to what is already done for the approval of conventional electric assistance bikes. It differs from it, however, in the detection technology necessary to measure this intentional action.

 According to this mode, the trigger sensor can be either a force sensor arranged in one of the pedals, or a torque sensor arranged in the axis of the crankset.

 According to an advantageous variant, the trigger sensor is a rotation sensor comprising:

 - a read head fixed near the bottom bracket axle and connected to the electronic control unit;

 - a coding wheel fixed on the axle of the crankset so that its radius coincides comes opposite the read head,

 the read head and the coding wheel being adapted to measure very small variations in the angle of rotation of the crankset, preferably between 0.1 and 2 °, correlated with values of the force of pressing on the pedals and / or torque applied to the crankset.

 According to this variant, the read head is preferably integrated either in the external casing of the electric motor, or in one of the parts of the frame of the bicycle.

 More preferably, the coding wheel integral with the crankset axle is integrated in the external crankcase.

 According to a second advantageous embodiment, the trigger sensor is a touch sensor fixed on the handlebars of the bicycle, suitable for detecting an intentional touch / dexter support of the user. The choice of a touch sensor can be made in particular according to the typology of the cyclists.

 According to a third advantageous embodiment, the trigger sensor is adapted to detect an intentional pressing of the user on the saddle of the bicycle.

The sensor is then either a force sensor fixed on the saddle or on the seat tube, or a pressure sensor adapted to measure the pressure in the seatpost. Here, when the user is seated on the saddle, there is normal support. The voluntary action cannot therefore be proven by the presence of a support and therefore be limited to its simple detection by the sensor.

 To authorize triggering by the motor control and command unit, a combination and / or sequence with other parameters is required. Thus, it can be a choice:

 - a combination of pressing on the saddle and pressing on a pedal, which therefore by definition requires the presence of a torque / force sensor on at least one pedal,

 - a sequence of presses on the saddle interspersed with one or more presses on the command GIHM,

 - variable support on the saddle, such as the fact that after being seated, the user gradually rises from the saddle by resting on his pedals, while operating GIHM.

 The invention also relates in another of its aspects to a method of operating an electric bicycle described above, comprising the following steps:

 a / when the bicycle is stopped and up to a bicycle speed lower than or equal to the threshold value, application of a pedaling torque and / or actuation of the HMI by the user and simultaneously carrying out an intentional user action detected by the trigger sensor so as to apply a motor torque to the rear wheel;

 b / when the speed of the bicycle is greater than the threshold value, then application of a pedaling torque and / or control of the motor started or not, either only by actuation of the HMI by the user, or by l actuation of the HMI by the user and simultaneously carrying out an intentional action of the user detected by the trigger sensor.

 The invention brings many advantages, among which:

 - any involuntary or accidental starting of the electric motor is avoided;

- possibility of applying a pedaling torque without having to apply the simultaneous and voluntary dual control according to the invention;

- possibility of starting and piloting the almost instantaneous electric motor even though the double control according to the invention must be actuated; - possibility of installing the simultaneous and voluntary dual control according to the invention on any type of electric bicycle with two independent transmissions (pedaling in parallel of a transmission by electric motor).

 detailed description

 Other advantages and characteristics of the invention will emerge more clearly on reading the detailed description of examples of implementation of the invention made by way of illustration and not limitation, with reference to the following figures among which:

 - Figure 1 is a partial schematic view of a prototype electric bicycle according to the invention;

 - Figure 2 is a side view of the rear of the electric bike according to Figure 1;

- Figure 3 is a schematic perspective view of the arrangement of a rotation sensor constituting a trigger sensor of a dual control of the electric motor of the bicycle according to the invention;

 - Figure 4 illustrates in the form of curves the values of angle of rotation measured by the sensor of Figure 3, correlated to the values of force applied to the pedals by a user.

 For the sake of clarity, the same references designating the same system elements according to the invention are used for all of FIGS. 1 to 3.

 Figures 1 and 2 show an electric bicycle 1 according to the invention.

The electric bicycle 1 comprises a frame 2 with a rear wheel 3 arranged between the two rear shrouds 20, 21 of the bicycle.

 The mechanism for transmitting the pedaling torque is conventional: it includes, from the crankset 4 which can rotate around the axis 40, a plate 41, a roller chain 12, a cassette of sprockets around the axis 11 of the rear wheel as well that a first freewheel device, not shown, making it possible to drive the rear wheel only clockwise when pedaling.

 As visible in FIG. 2, this mechanism is installed as usual, that is to say on the side of the rear shroud on the right 21.

The bicycle 1 also includes an electric battery 5, of the Li-polymer type which supplies, by means of control electronics, an electric motor 6, of the brush type, the battery and the motor being integrated and fixed to the inside the central mast 5 of the frame 2. As can be seen in FIGS. 1 and 2, the electric motor 6 is intended to drive the rear wheel 3 directly via a transmission mechanism which is arranged on the side of the rear shroud 20 to the left of the frame 2.

 More specifically, the output shaft of the electric motor 6 is provided with a toothed wheel 7 which constitutes the input wheel which directly drives, via a roller chain 8, the output toothed wheel 9, in the form of a crown, mounted on the rear wheel 3 around the rear wheel axle 11.

 A second freewheel device, not shown, makes it possible to drive the rear wheel 3 by means of the ring gear 9 only when it is driven in one direction by the electric motor.

 The engine torque transmission mechanism is therefore simple and direct since it is produced without any speed reducer which would add weight to the bicycle, as in electric bikes according to the state of the art.

 For example, the input gear wheel 7 may have between 8 and 12 teeth and the output gear 9 between 60 and 120 teeth.

 The operation of an electric bike 1 according to the invention allows, unlike electric bikes according to the state of the art, instantaneous control completely hybrid and this when the bike stops.

 Thus, the operating modes of the electric bike while driving can be as follows:

 - a classic pedaling mode without any action of the electric motor and its transmission mechanism on the rear wheel;

 - a unique mode of action of the electric motor on the rear wheel, without any pedaling action. This mode can be activated at start-up, or in the event of an obstacle and / or very steep slope that cannot be crossed by pedaling force alone;

 - a combined mode of pedaling and electric motor actions in which the torque of the electric motor complements that of pedaling or vice-versa.

Another operating mode made possible by the transmission mechanism is, during braking or downhill phases, the use of the engine as a brake by blocking the dedicated freewheel mechanism, this engine brake also advantageously achieves a recovery of energy by recharging the motor supply battery and / or a super capacitor. The man-machine interface connected to the electronic engine control unit, which allows the user to control the engine, is in the form of an accelerator trigger pivotally mounted on the handlebars of the bicycle. This trigger is with automatic return, that is to say that in the absence of pressing on it, it returns to its inactive position in which the electric motor cannot bring torque to the rear wheel.

 The inventors have thought of implementing an additional safety function on the bicycle which has just been described.

 Indeed, due to the independence between the transmission by pedaling and that by motor in parallel, in the absence of security, any action on the trigger would result in a starting of the electric motor and therefore a brought engine torque directly to the rear wheel of the bike.

 However, this could include involuntary or accidental actions on the part of the user. For example, the user walking next to their bicycle by pushing it may unintentionally operate the throttle trigger. For example, an external body, such as a tree branch, clothing or other product placed on the handlebars can accidentally rotate the trigger.

 If, while riding, the user can react quickly in most of these situations without this having harmful consequences, by again mastering the action on the trigger, this can be more annoying or even dangerous when the bicycle is at stopping and more generally at low speed in situations of starting the bike.

 Also, according to the invention, a double control of the electric motor is provided, that is to say in addition to the control by the trigger, another voluntary and simultaneous action on the part of the user detected by a sensor. additional whose function is to trigger the possibility of piloting the engine by the trigger control.

 Thus, when the speed of the bicycle detected by a bicycle speed sensor is zero up to a threshold value, the control unit will authorize at least the starting of the motor and its control up to a duration and / or a torque and / or a predetermined speed (s), if and only if the user actuates the HMI and simultaneously the trigger sensor detects an intentional action of the user.

An advantageous embodiment of the trigger sensor is a rotation sensor which acts as a pedaling force sensor. The arrangement of such a sensor 13 at the level of the pedal 4 of the bicycle is mounted in FIG. 3.

 The sensor 13 comprises a read head 15 fixed close to the pedal axis 40 and connected to the electronic motor control unit, as well as a coding wheel 16 secured to the pedal axis 40 so that that its radius comes opposite from the read head 15.

 More specifically, the read head 15 is housed in a specific housing provided in the closure cover 60 of the housing of the electric motor 6, the head being held by the closure part 14.

 The coding wheel 16 forms a protrusion of a ring on the outside of the bottom bracket 41 4, as shown in FIG. 3. Thus, the coding wheel 16 can have a large diameter which makes it possible to envisage there code a lot of information.

 This annular coding wheel 16 can advantageously comprise at least one main track comprising an integer number N of marks positioned so as to have a symmetry of revolution of order N, N being greater than or equal to 8, preferably greater than or equal to 36 , around the axle of the crankset. These marks can be constituted in particular by magnetic poles, optical marks or mechanical marks in the form of protrusions, hollows or recesses.

 Preferably, the read head 15 includes a plurality of sensitive elements suitable for reading a track of the annular coding wheel, and grouped into at least two sub-assemblies to deliver at least two phase-shifted electrical signals, preferably in quadrature.

 To increase the spatial resolution, it can advantageously be provided that the read head is linked to a spatial interpolator adapted to multiply the number of pulses coming from a track of the annular coding wheel by a coefficient greater than or equal to 2, preferably greater to 4. Reference may be made, where appropriate, to patent applications FR2792403 or FR2754063 or WO98 / 14756 for descriptions of various types of read heads known to those skilled in the art, and of their implementation.

If the coding wheel 16 is magnetic, the sensitive elements can be chosen, for example, from a group comprising Hall effect probes, magnetoresistors, giant magnetoresistors. The inventors have carried out experimental measurements to correlate the values of rotation of the crankset in transmission stop with the values of support forces exerted on the pedals and, in order to calibrate a minimum value which corresponds to a voluntary / intentional support that the motor control unit recognizes as such.

 The experimental measurements were carried out in three consecutive phases which can be distinguished, as below.

 It is specified here that the tests were carried out with a user of 65 kg.

 Phase 1: Initially, the play in the torque transmission mechanism is maximum. To make up for this play, the crank is brought into transmission abutment, in an angular position at approximately 45 ° relative to the vertical, which corresponds to a natural position in which a user brings his initial support pedal when he wishes start.

 The user therefore provides a relatively small effort on the pedal to reach the transmission stop. The bike speed is zero.

 Phase 2: The user continues to gradually press the pedal, which allows him to catch the elasticity of the cranks and the crankset. The effort provided is greater. The bike speed is zero.

 Phase 3: The bike begins to move forward. The user begins to pedal. The effort is slightly higher than the previous effort. The angle traveled increases quite quickly. The speed is not zero and the acceleration is positive.

 Thus, during these phases 1 to 3, different force values are applied to the pedal and the corresponding rotation values are measured using the rotation sensor described above.

The table below gives the measured values.

 The results of these measurements are illustrated on the form of a curve in FIG. 4. It appears that:

 - during phase 1: G user must provide a pedaling effort of 1N, for an angle traveled by the crankset between 6.5 and 7 °;

- during phase 2, which is the phase used in the context of the invention, the pedaling effort is of the order of 30 to 33 N for an angle traversed by the crankset between 7 and 8 ° , or an additional angle between 1 and 2 °; during phase 3 of starting the bike, the effort is around 35N.

The calculation of the slope of the curve from the measurements during the transition from phase 1 to phase 2, gives a value between 50 and 75daN / °. In other words, with a sensor sensitivity of 0.1 °, a variation between 5 and 7.5N is detected.

 Thus, with a rotation sensor as described above, it is entirely possible to detect with very high sensitivity, a consequent variation in force which corresponds to an intentional support of a user of the bicycle according to the invention.

 Other variants and embodiments can be envisaged without departing from the scope of the invention which has just been described.

 The expression "comprising a" or "comprising a" should be understood as being synonymous with "comprising at least one", unless otherwise specified.

Claims

1. Electric bike (1), comprising:  - a rear wheel (3);  - a crankset (4), intended to be actuated by the muscular force of a user to transform it into a pedaling torque, comprising two cranks crankset rotating around a crankset shaft (40) and two pedals each fixed to a crank;  - an electric bike speed sensor;  - an electric drive motor, comprising a stator and a rotor which can rotate around a rotor axis, the rotor axis being spaced apart while being close to the crankset axis;  - an electronic engine control unit;  - a first torque transmission mechanism, the first mechanism comprising a first input wheel, which can be driven in rotation about the axis of the crankset, a first flexible transmission element (12), at least a first output wheel , being able to be driven by the first input wheel via the first flexible element, a first freewheel device, adapted to transmit the pedaling torque to the rear wheel via the first output wheel;  - a second torque transmission mechanism, distinct from the first mechanism, the second mechanism comprising a second input wheel (7), which can be driven in rotation about the axis of the rotor, a second flexible transmission element (8) , at least a second output wheel (9), which can be driven by the second input wheel via the second flexible element, a second freewheel device (14), adapted to transmit the drive torque from the motor to the rear wheel via the second output wheel;  - a man-machine control interface (HMI), connected to the electronic engine control unit, adapted so that the user can start and control the engine independently of the torque and / or pedaling movement;  - at least one trigger sensor, connected to the electronic engine control unit, adapted to detect an intentional action by the user independent of the intentional action on GIHM; the electronic control unit being adapted for, when the bicycle speed detected by the speed sensor is zero up to a threshold value, authorize at least the starting the engine and controlling it up to a predetermined duration and / or a torque and / or a rotational speed (s), if and only if G user activates GIHM and simultaneously the trigger sensor detects an intentional action of G user independent of intentional action on GIHM.  2. Electric bike according to claim 1, GIHM being constituted by a trigger or an acceleration handle with automatic return, pivotally mounted on the handlebars of the bicycle.  3. Electric bicycle according to claim 1 or 2, the electronic control unit being further adapted for, when the speed of the bicycle is above the threshold value, continue to authorize the control of the engine started or not, either if the user activates GIHM without the need for detection on the part of the trigger sensor, ie if the user actuates GIHM and simultaneously the trigger sensor still detects an intentional action by the user.  4. Electric bike according to one of claims 1 to 3, the trigger sensor being adapted to detect an intentional action of the user on at least one of the two pedals.  5. Electric bike according to claim 4, the trigger sensor being either a force sensor arranged in one of the pedals, or a torque sensor arranged in the axis of the crankset.  6. Electric bike according to claim 5, the trigger sensor being a rotation sensor comprising:  - a read head fixed near the bottom bracket axle and connected to the electronic control unit;  - a coding wheel fixed on the axle of the crankset so that its radius comes opposite the read head,  the read head and the coding wheel being adapted to measure very small variations in the angle of rotation of the crankset relative to a position of the latter as a transmission stop, preferably between 0.1 and 2 °, correlated with force values on the pedals and / or torque applied to the pedal. 7. An electric bicycle according to claim 6, the reading head being integrated either in the external casing of the electric motor, or in one of the parts of the frame of the bicycle. 8. An electric bike according to claim 6 or 7, the coding wheel integral with the crankset shaft being integrated in the external crankcase.  9. Electric bicycle according to one of claims 1 to 3, the trigger sensor being a tactile sensor fixed on the handlebars of the bicycle, adapted to detect an intentional tactile support of the user.  10. Electric bike according to one of claims 1 to 3, the trigger sensor being adapted to detect an intentional support of P user on the saddle of the bike.  11. Electric bike according to claim 10, the sensor being either a force sensor fixed on the saddle or on the seat tube, or a pressure sensor adapted to measure the pressure in the seatpost.  12. Method of operating an electric bicycle according to one of claims 1 to 11, comprising the following steps:  a / when the bicycle is stopped and up to a bicycle speed lower than or equal to the threshold value, application of a pedaling torque and / or actuation of the HMI by the user and simultaneously realization of an intentional user action detected by the trigger sensor so as to apply a motor torque to the rear wheel;  b / when the speed of the bicycle is greater than the threshold value, then application of a pedaling torque and / or control of the motor started or not, either only by G actuation of GIHM by the user, or by G actuation of GIHM by the user and simultaneously carrying out an intentional action of the user detected by the trigger sensor.