Differential transmission method and power train for electrically-assisted bicycle

Abstract

To provide a differential transmission method and a power train for an electrically-assisted bicycle.SOLUTION: The invention relates to a method of assisted differential transmission assisted for an electric bicycle including two motors articulated around of a differential system including a ring gear having an inner surface and an element cooperating with the inner surface, the periphery of the element containing, al all times, the geometric center of the ring gear, and a power train associated with the method.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a new type of auxiliary powertrain for bicycles. [Background technology]

[0002] The development of electric mobility has prompted an increase in electric assist systems for bicycles. Most systems work on the principle of a simple torque assistance provided by a motor at the crankset level. The motor provides the power. The speed is transmitted to the rear wheel by a chain or belt. The gear ratio is managed by the rider through a system of sprockets on the rear wheel (derailer gear) or through a gearbox integrated in the rear hub of the rear wheel.

[0003] A differential system is described in which an epicycloidal gear train ensures both torque assistance and gear ratio management in the same box. Similarly, improvements are described, firstly to allow the use of the bike even when the battery is dead, and secondly, to adapt the speed and / or torque assistance to the force applied by the rider, mainly to facilitate the management of relaxation and to prevent transmission slippage.

[0004] Such systems are described, for example, in WO2016 / 034574, WO2019158503A1, WO2019043123, and WO2021032548. In these systems, an epicycloidal gear train including a ring gear, a sun gear, and a planetary carrier, possibly a double planetary carrier, is utilized in combination with a reduction stage to obtain the required reduction ratio. However, these systems lack compactness and the multiplicity of parts leads to low yields, large clearances, high noise levels, and high costs. Therefore, the main challenge of electric assist is to obtain a system that is very compact, lightweight, and at the same time robust over time.

[0005] To address these challenges, various approaches have been taken. For example, DE202017007569U1 describes a system including two motors associated with a Harmonic Drive®, each with a separate shaft, one associated with an output that defines the speed of the assistance and the other that regulates the cadence. The two Harmonic Drives® have non-overlapping parallel shafts and cooperate through intermediate gears or by direct engagement of the outer surfaces of the Harmonic Drives®. The result is a significant obstacle that complicates the creation and running of this system. In particular, the volume of the tulips of the flex gears of the Harmonic system, associated with the fatigue and losses they generate, has discouraged those skilled in the art from utilizing them in electric assisted powertrains. The applicant therefore considered it necessary to address the shortcomings and weaknesses of existing systems. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] WO2016 / 034574 [Patent Document 2] WO2019158503A1 [Patent Document 3] WO2019043123 [Patent Document 4] WO2021032548 [Patent Document 5] DE202017007569U1 [Patent Document 6] U.S. Patent No. 4,969,376A [Patent Document 7] WO2023 / 042167A1 Summary of the Invention [Means for solving the problem]

[0007] The subject of the present invention is a method of assisted differential transmission for an electric bicycle, comprising: - an angular velocity ω1 is applied to a first input of the differential system by the action of a first motor; - an angular velocity ω2 is applied to a second input of the differential system by an input transmitting at least the action of the cyclist on the crankset; - the angular velocities ω1 and ω2 are combined in a differential system including a ring gear having an inner surface and an element cooperating with said inner surface, the periphery of which always includes the geometric center of the ring gear, and transmitted to an output body as an angular velocity ω3; Including, a second motor for adjusting the assistance to the driver in combination with the driver's action, connected to the second input through the input body or connected to the output; The axis of the output body, the main axis of the differential system, the axis of the first motor and the axis of the second motor are coincident and / or concentric with the axis of the input body.

[0008] The angular velocities ω1 and ω2 are combined in a differential system and transmitted to an output means, and the angular velocities ω1 and ω2 are combined in a differential system to give an angular velocity ω3 at a differential output which is then transmitted to the output.

[0009] The invention also relates to a powertrain making it possible to carry out the method of the invention.

[0010] The powertrain for electric bicycles is - a differential system including a ring gear having an inner surface and an element cooperating with said inner surface, the periphery of the element defining a plane that contains a geometric centre of the ring gear; - a first motor configured to impart an angular velocity to a first input of the differential system; an input configured to provide an angular velocity to a second input of the differential system; - an output body; - a second motor for adjusting the assistance to the driver, the second motor being connected to a second input in combination with the input body or connected to an output body; Equipped with The axis of the output body, the main axis of the differential system, the axis of the first motor and the axis of the second motor are coincident and / or concentric with the axis of the input body.

[0011] The input is an element known to those skilled in the art. It constitutes the interface between the interior and the exterior of the housing or box in which the powertrain is housed. It may be an interface with an upstream transmission. Alternatively, it may be directly connected to or coincident with the crankset.

[0012] The output is an element known to those skilled in the art. It constitutes the interface between the interior and the exterior of the housing or box in which the powertrain is housed. It may be an interface with a downstream transmission. Alternatively, it may be directly connected to one of the wheel rims or coincide with one of the wheel rims.

[0013] Preferably, the input is directly or indirectly (via the transmission) linked to at least the action of the cyclist on the crankset, i.e. to the axis of the crankset.

[0014] In some cases, the input may coincide with the crankset, in which case the powertrain is located at crankset level, i.e. concentric with the crankset axis, and the transmission is located at output level.

[0015] In other cases, the powertrain may include an upstream transmission of the chain or belt type, for example connecting the crankset to the input of the powertrain (in a differential system). In this case, the powertrain is not concentric with the crankset. It may be concentric with the axis of the drive wheels, in which case no downstream transmission is provided at the output. It may also be located neither concentric with the crankset axis nor with the wheel axis, in which case an upstream transmission and a downstream transmission may be provided.

[0016] Hereinafter, in this application, the term "connected" or "coupled" refers loosely to either a direct or indirect (via transmission) connection.

[0017] In order to obtain maximum compactness, the axis of the output body, the main axis of the differential system, the axis of the first motor and the axis of the second motor coincide and / or are concentric with the axis of the input body.

[0018] By aligning / integrating these shafts a very compact system is obtained. With two motors on either side of the differential system, heat dissipation is optimally managed.

[0019] Here, the differential system is a system with a ring gear having an inner surface. An element cooperating with this inner surface encompasses the geometric center of the ring gear, i.e. the element has a periphery that progresses in contact with the ring gear at least at one point, and the geometric center of the ring gear is always contained within the plane defined by the periphery. This definition extends to the context of a perpendicular section to the main axis of the differential. Thus, the differential system cannot be an epicycloidal gear train, and indeed the planetary gears of such a train do not meet this definition. However, there are several other types of differential systems that meet this definition, such as simple or complex harmonic or cycloidal systems, possibly including intermediate transmission gears, such as those described in US Pat. No. 4,969,376 A and reproduced in WO 2023 / 042167 A1.

[0020] The ring gear has an inner surface which may, for example, carry internal teeth, and the element cooperating with this inner surface is therefore an element adapted to engage with said teeth, in which case the element presents peripheral teeth which tend to engage with the teeth of the ring gear, the geometric centre of the ring gear always being contained within a plane defined by the engagement circle of this element within the ring gear (the circumference or periphery of the teeth).

[0021] The term teeth is not limited in any precise manner and generally refers to projections that can engage with complementary projections. A person skilled in the art knows how to select the shape of the teeth depending on the application, size, applied forces, etc.

[0022] The invention is not necessarily limited to toothed engagement: the ring gear may also cooperate with the inner element by adhesion. The invention therefore also encompasses rolling systems that are in particular based on adhesion.

[0023] For the following description, the engagement option will be used for clarity, but it is interchangeable with the rolling system.

[0024] In general, a differential system applies a reduction ratio R which is determined according to the following equation:

number

[0025] where ωα, ωβ, and ωγ are the angular velocities of the differential connection.

[0026] The differential has two so-called "low speed" connections and one so-called "high speed" connection. Preferably, the first motor is associated with the high speed connection in order to efficiently influence the speed of the output body.

[0027] The powertrain reduction ratio RDU is defined as follows:

number

[0028] where ωO is the angular velocity of the output body and ωI is the angular velocity of the input body.

[0029] The reduction ratio RDU is adjusted either naturally and continuously or artificially and discretely by the first motor, the second motor being dedicated to adjusting the assistance in torque.

[0030] In some cases, the powertrain provides motion to at least one of the two wheels of the bicycle without the rider pedaling, particularly in a "walk assist" mode where this mode is limited to low speeds.

[0031] In some cases, the powertrain can operate in a non-assisted mode. This mode may be entered automatically when the rider applies sufficient or excessive force, for example, especially in relation to legal regulations (above a threshold speed). This mode may also be useful for bicycles, since it can operate even when the battery is nearly dead. In this mode, motors M1 and M2 may be controlled such that only the constraint of zero net assistance is respected.

[0032] In some cases, ω may be negative. This is the reverse gear mode.

[0033] In some cases, the velocity ωI of the input body or the velocity ωO of the output body are blocked to zero. This is especially the case in anti-theft modes.

[0034] In some cases, the first motor and / or the second motor act as generators. When the cumulative power of the two motors is negative, this is the case in "regenerative braking" mode.

[0035] Furthermore, the powertrain may include a reduction gear system configured to combine the action of the second motor with the action of the output or to combine the action of the second motor with the action of the input body. Preferably, the shaft of the reduction gear associated with the second motor may coincide with the input and output shafts.

[0036] The powertrain of the present invention is compact enough to be installed at crankset level or wheel level.

[0037] Preferably, to maintain balance while optimizing heat dissipation of the motors, the first motor and the second motor are located on either side of an element to which the bicycle powertrain is fixed, for example, a motor is located on either side of the wheel or on either side of the crankset.

[0038] The differential system may be a cycloidal transmission system (or gear train).

[0039] This type of system allows high reduction ratios for a particularly compact volume. In this case, the element engaging the ring gear is a gear with a diameter smaller than the inner diameter of the ring gear and with a number of teeth less than that of the ring gear. The eccentric motion is imparted by an eccentric exciter on which the gear is mounted. Due to the engagement of the ring gear with the eccentric exciter, the gear follows a cycloidal motion. The gear is associated with one or more conducting eccentrics associated with an eccentric carrier.

[0040] The ring gear, eccentric exciter and eccentric carrier can each act as an input or output of the system. The eccentric exciter is the so-called "fast" connection and the ring gear and eccentric carrier are the so-called slow speed connections.

[0041] In a cycloidal transmission, one or several cycloidal gears are engaged inside a cycloidal ring gear, the number of teeth of which, Zc, is slightly greater than the number of teeth of the gear, Zr. <Zcである。

[0042] For clarity and for purposes of explanation, and without loss of generality, it will be assumed that the transmission has only one cycloidal gear.

[0043] The eccentric exciter constitutes the first connection of the transmission. Its main shaft is concentric with the ring gear. The second shaft is slightly eccentric and concentric with the gear.

[0044] Also, for the purposes of explanation only and without loss of generality, the ring gear is considered to be immobile. The rotation of the eccentric exciter causes the gear to roll within the ring gear while engaging with it. For each revolution of the eccentric exciter, the effective engagement point between the deformable gear and the ring gear completes one revolution. At the end of this displacement, the gear has rotated an angle corresponding to the difference in the number of teeth between the ring gear and the gear. It is therefore possible to obtain very small angular displacements of the gear by choosing a difference of only one tooth.

[0045] Note that the gear displacement is cycloidal, not purely circular.

[0046] The cycloidal transmission system includes at least one transmission eccentric, preferably at least two transmission eccentrics for greater robustness, configured to transmit the cycloidal motion of the gears to an eccentric carrier whose axis of rotation coincides with the axis of rotation of the ring gear.

[0047] In order to be able to transmit this small displacement to the required pure circular motion, it is necessary to utilize a transmission eccentric which ensures the connection between the gear and the eccentric carrier.

[0048] The eccentric carrier moves concentrically with the main transmission axis in a pure circular motion. The conducting eccentric has a main axis concentric with the axis fixed to the eccentric carrier and a second axis concentric with the axis fixed to the gear. To ensure the operation of the system, the eccentricity of the eccentric exciter and the conducting eccentric are identical. Technically a single conducting eccentric is sufficient, but to improve the robustness of the system it is possible to use two or more.

[0049] With the use of a transmission eccentric, the eccentric carrier, which forms the second connection of the transmission, is rotated concentrically to the main axis of the system by a small angle corresponding to the difference in the number of teeth between the ring gear and the toothed wheel, so that the transmission ratio is:

number

[0050] ωp is the angular velocity of the eccentric carrier [rad / s], and ωe is the angular velocity of the eccentric exciter [rad / s].

[0051] The use of a conductive eccentric is one method of restoring circular motion, but not the only method. It is not considered limiting.

[0052] Generally speaking, if the ring gear is not fixed and constitutes the third connection point of the system, the transmission is transformed into a differential system and the equations of motion can be generalized as follows:

number

[0053] ωc is the angular velocity of the ring gear (rad / s).

[0054] Generally speaking, the eccentric exciter, the ring gear and the eccentric carrier are the three connections of the differential, which can act as the input or output of the system respectively. The eccentric exciter is the so-called "fast" connection, and the ring gear and the eccentric carrier are the so-called "slow" connections.

[0055] In one embodiment, a first motor is connected to an eccentric exciter, ω1=ωe, an input body is connected to a ring gear, ω2=ωc, and an output is via an eccentric carrier, ω3=ωp. A second motor may be connected to the ring gear in combination with the input body, possibly via a reducer, or to an output body which is connected to the eccentric carrier at the output.

[0056] In another embodiment, the input body is connected to an eccentric exciter, ω2=ωe, the first motor is connected to a ring gear, ω1=ωc, and the output is via an eccentric carrier, ω3=ωp. A second motor, possibly via a gear reducer, may be connected to the eccentric exciter in combination with the input body, or to an output body connected to the eccentric carrier at the output.

[0057] In another embodiment, a first motor is connected to the eccentric exciter, ω1=ωe, an input body is connected to the eccentric carrier, ω2=ωp, and the output is via a ring gear, ω3=ωc. A second motor may be connected in combination with the input body to the eccentric carrier, possibly via a reducer, or connected to the ring gear at the output.

[0058] In another embodiment, the input body is connected to an eccentric exciter, ω2=ωe, a first motor is connected to an eccentric carrier, ω1=ωp, and the output is via a ring gear, ω3=ωc. A second motor, possibly via a reducer, may be connected to the eccentric exciter in combination with the input body or to the ring gear at the output.

[0059] In another embodiment, a first motor is connected to the eccentric carrier, ω1=ωp, an input body is connected to a ring gear, ω2=ωc, and the output is via an eccentric exciter, ω3=ωe. A second motor may be connected to the ring gear in combination with the input body, possibly via a reducer, or to an eccentric exciter at the output.

[0060] In another embodiment, a first motor is connected to the ring gear, ω1=ωc, an input body is connected to the eccentric carrier, ω2=ωp, and the output is via an eccentric exciter, ω3=ωe. A second motor may be connected to the eccentric carrier in combination with the input body, possibly via a reducer, or to an eccentric exciter at the output.

[0061] The advantage of the cycloidal transmission is that it allows for large reduction ratios while reducing size and complexity.

[0062] Preferably, the cycloidal transmission of the invention comprises at least two gears. In fact, the main drawback in the case of a cycloidal transmission utilizing a transmission eccentric with a single cycloidal gear is that the movement of the cycloidal gear produces a rather large unbalance. The most common solution to this problem is to stack several identical transmission units with phasing. In that case the excitation eccentric and the transmission eccentric can be coupled, respectively. The use of a single ring gear and a single eccentric carrier is also possible.

[0063] In one variation of the described system, the ring gear may be replaced by a set of Zc cylindrical shafts arranged parallel and regularly spaced around the periphery of the shaft carrier.

[0064] In another variation, the transmission eccentric is not implemented, and the shaft of the eccentric carrier rubs directly in the bore of the gear. Depending on the desired geometry, this configuration results in the same kinematics as a system utilizing a transmission eccentric.

[0065] These two variants are known in the state of the art.

[0066] A variation of the cycloid transmission system, a double cycloid engagement system.

[0067] In a second embodiment of the cycloidal transmission technique, two engagements or gear meshes may be used, possibly concentric. As in the cycloidal transmission system described above, an eccentric exciter, constituting the first connection of the differential system, supports a gear on an eccentric shaft, rotatably along the eccentric shaft. Any type of connection with at least one rotational degree of freedom may be used. However, a low-friction connection is preferred. This gear, by its shape (preferably external teeth), engages with an outer ring gear (internal teeth) by the kinematics given by the eccentric exciter. This constitutes the first engagement. Furthermore, the gear is also provided with internal teeth axially juxtaposed adjacent to the connection with the eccentric exciter. Furthermore, a sprocket, constituting the second connection of the cycloidal system, is rotatably articulated on the main shaft of the cycloidal module. The sprocket is provided with external teeth matching the internal teeth of the gear and is involved in the second engagement.

[0068] This "intermediate" gear is thus a cylinder which presents, on its outer surface, means of adhesion (engagement) for the inner surface of the ring gear in which it progresses, and on its inner surface, means of adhesion (engagement) for the sprocket around which it progresses. The gear thus presents an evenly toothed inner surface adapted to engage with a sprocket articulated for rotation about an axis coincident with the axis of the ring gear.

[0069] A ring gear, rotatable along the main axis of the cycloid module, constitutes the third and final connection to the differential system.

[0070] When certain geometric conditions are considered, the cycloidal motion of the intermediate gears and their engagement with the sprocket imparts a simple rotation to the sprocket.

[0071] To ensure operation of the system, the eccentricities of the two cycloidal engagements must be equal (unless flexibility is introduced into the system).

[0072] The number of teeth of the ring gear (Zc), the number of teeth of the gear (external teeth Zre and internal teeth Zri), and the number of teeth of the sprocket Zp satisfy the following ratio. Zc>Zre Zri>Zp

[0073] The ratio R of this system is defined as

number

[0074] The special case is given as Zre = Zri = Zc-1 = Zp+1, and the formula simplifies to:

number

[0075] The combination of two cycloidal engagements is advantageous as it makes it possible to eliminate the need for conversion of cycloidal motion into circular motion by using a transmission eccentric. There are therefore fewer mechanical joints, thereby reducing cost, weight, bulk, complexity and play. There are fewer moving parts, reducing the inertia of the transmission. Furthermore, there is less mass to move eccentrically, thereby reducing parasitic vibrations. This solution is therefore more advantageous.

[0076] Generally speaking, the eccentric exciter, the ring gear, and the sprocket are the three connections of the differential, each of which can act as an input or output of the system. The eccentric exciter is the so-called "fast" connection, and the ring gear and sprocket are the so-called "slow" connections.

[0077] The differential system may be a harmonic transmission system.

[0078] In a harmonic transmission, the element that engages with the internal teeth of the ring gear is the deformable gear. The number of teeth of the ring gear, Zc, is slightly greater than the number of teeth of the deformable gear, Zr. <Zcである。

[0079] The wave generator is guided in rotation around the main axis of the gear train. It has a certain number Zl of lobes, in the most frequent case it is two, but one configuration based on one lobe is envisaged. However, the number of lobes must be sufficiently less than the number of teeth of the ring gear and the deformable gear, Zl << Zr <Zcである。

[0080] For purposes of illustration only and without loss of generality, the ring gear is considered to be immobile. The rotation of the wave generator causes the deformable gear to roll within the ring gear, engaging each end of the lobes. For each revolution of the wave generator, the effective engagement point between the deformable gear and the ring gear completes one revolution. At the end of this displacement, the deformable gear has rotated concentrically with the main axis of the system by a small angle corresponding to the difference in the number of teeth between the ring gear and the deformable gear, resulting in a transmission ratio of:

number

[0081] ωr is the angular velocity of the flexible gear [rad / s], and ωg is the angular velocity of the wave generator [rad / s].

[0082] If the ring gear is not fixed and constitutes the third connection point of the system, the transmission is transformed into a differential system and the equations of motion can be generalized as follows:

number

[0083] ωc is the angular velocity of the ring gear [rad / s].

[0084] Generally speaking, the wave generator, the ring gear and the gear wheel are the three connections of the differential, which can act as the input or output of the system respectively. The wave generator is the so-called "fast" connection, and the ring gear and the deformable gear are the so-called "slow" connections.

[0085] In one embodiment, a first motor is connected to a wave generator, ω1 = ωg, an input is connected to a ring gear, ω2 = ωc, and the output is via a flex gear, ω3 = ωr. A second motor may be connected to the ring gear in combination with the input, possibly via a reducer, or connected to the flex gear at the output.

[0086] In this embodiment, when a second motor is coupled to the ring gear in combination with the input, it is preferred that this coupling not occur via harmonic transmission.

[0087] This particular embodiment may possibly be excluded from the invention if a second motor is associated or connected to the input body, in which case the combination is made with the aid of, for example, a cycloidal or epicycloidal reducer.

[0088] In another embodiment, the input is connected to a wave generator, ω2=ωg, a first motor is connected to a ring gear, ω1=ωc, and the output is via a flex gear, ω3=ωr. A second motor, possibly via a reducer, may be connected to the wave generator in combination with the input, or to the flex gear at the output.

[0089] In another embodiment, a first motor is connected to a wave generator, ω1 = ωg, an input is connected to a flex gear, ω2 = ωr, and the output is via a ring gear, ω3 = ωc. A second motor may be connected to the flex gear in combination with the input, possibly via a reducer, or to the ring gear at the output.

[0090] In this embodiment, if a second motor is connected to the output ring gear, this connection is preferably not made via a harmonic transmission. If a second motor is associated or connected to the output, this particular embodiment may possibly be excluded from the invention. In this case, the combination is made with the aid of, for example, a cycloidal or epicycloidal reducer.

[0091] In another embodiment, the input is connected to a wave generator, ω2=ωg, a first motor is connected to a flex gear, ω1=ωr, and the output is via a ring gear, ω3=ωc. A second motor, possibly via a reducer, may be connected to the wave generator in combination with the input or to the ring gear at the output.

[0092] In another embodiment, a first motor is connected to a flex gear, ω1=ωr, an input is connected to a ring gear, ω2=ωc, and the output is via a wave generator, ω3=ωg. A second motor may be connected to the ring gear in combination with the input, possibly via a reducer, or connected to a wave generator at the output.

[0093] In another embodiment, a first motor is connected to the ring gear, ω1=ωc, the input is connected to a flex gear, ω2=ωr, and the output is via a wave generator, ω3=ωg. A second motor, possibly via a reducer, may be connected to the flex gear in combination with the input or to a wave generator at the output.

[0094] The advantage of the harmonic transmission is that it allows for large reduction ratios while reducing size and complexity compared to known epicycloidal gear trains.

[0095] In harmonic transmissions, the deformable gear undergoes a very large number of significant deformation cycles. This can lead to the need for long tulips and therefore increased overall bulk and fatigue resistance issues. The contact between the deformable gear and the wave generator can introduce significant friction. One solution to this problem is the use of balls or rollers between the two bodies, as illustrated for example in https: / / commons.wikimedia.org / wiki / File:Harmonic-drive-explanation-contrast.gif.

[0096] Like the gears in a cycloidal gear train, the deformable gears in a harmonic transmission contain a surface on the inside of their teeth that contains the geometric center of the ring gear.

[0097] The movement of the deformable gears of the harmonic transmission is a rotational movement around the main axis of the gear train, given by the deformation of the tulip and the toothed part at the level of the pressure area exerted by the lobes of the wave generator.

[0098] Other equivalent transmission systems, particularly variations of cycloidal and harmonic systems, may also be utilized within the scope of the present invention.

[0099] It may be, for example, a transmission system similar to that described in WO2023 / 042167A1, in which an intermediate transmission gear, preferably flexible as in a harmonic transmission, is housed between a ring gear and a gear of a cycloidal system and driven by a cycloidal motion. This transmission gear presents, on its outer surface, teeth that engage with the ring gear and, on its inner surface, teeth that engage with the gear. The number of teeth of the gear transmission can be adjusted to improve the reduction ratio.

[0100] In a preferred embodiment, the differential system is a cycloidal gear train (or transmission).

[0101] A second input of the differential system receives torque from the rider through the input body and via the crankset, which includes the crankset shaft.

[0102] The first and second motors are powered by a battery with the aid of suitable control electronics.

[0103] The first motor M1 can be speed controlled to control the transmission ratio of the motor reducer to a desired ratio.

[0104] The second motor M2 may be torque controlled to reduce driver effort according to a selected level of assistance.

[0105] In a first variant of the invention, a second motor M2 adjusts the assistance to the driver relative to the input of the differential system. A reducer is used to match the operating speed / torque of the driver and the electric motor to:

number

[0106] ωM2 is the angular velocity of motor M2 [rad / s], ωI is the angular velocity of the input body [rad / s], and RRM2 is the ratio of the reducer associated with motor M2.

[0107] A second motor, which thus regulates the assistance to the driver, is connected to a second input in combination with the driver's action. The combination is preferably performed with the aid of a reducer, the rotation of which is linked to its input and the input body is linked to its output, the output having an angular velocity ω2. This refers for example to an epicycloid, cycloid or harmonic reducer, or any other suitable reducer.

[0108] Preferably, the second motor is not associated with a harmonic transmission wave generator coupled to the action of the driver.

[0109] Preferably, the reducer at the output of motor M2 is a cycloidal gear train, with either the eccentric carrier (or sprocket depending on the type of cycloidal gear train used) or the ring gear fixed to downgrade the differential system to a simple reducer, but any other reducer system may also be used.

[0110] In one preferred embodiment according to this first variant, the differential system is a cycloidal transmission, where a first motor applies an angular velocity ω1 to a first input, an eccentric exciter, and a second motor and input body provides an angular velocity ω2 to a second input, a ring gear, and the output is therefore an eccentric carrier which transmits an angular velocity ω3 to the output body.

[0111] In another preferred embodiment according to this first variant, the differential system is a cycloidal transmission, where a first motor applies an angular velocity ω1 to a first input, an eccentric exciter, and a second motor and input body applies an angular velocity ω2 to a second input, an eccentric carrier, and the output is therefore a ring gear transmitting an angular velocity ω3 to the output body.

[0112] In a second variant of the invention, a second motor, which regulates the assistance to the driver, is connected to the output of the differential transmission. A reduction gear system can be used to combine the action of the second motor with that of the output.

[0113] The possible variants described with respect to the method of the invention also apply to the construction of the powertrain.

[0114] Regardless of the variants and embodiments, anti-reverse means, such as, for example, one or several free wheels, may also optionally be provided.

[0115] For example, a freewheel is an associated input that prevents the system from driving the crankset while allowing the crankset to drive the system. This function is essentially dictated by rider safety considerations. However, the freewheel is optional.

[0116] For example, a freewheel may also (or alternatively) connect the input and output. Thus, the speed of the output cannot be lower than the speed of the input, ωO ≥ ωI. The aim is to ensure drivability of the bike even in case of a system failure (dead battery, or to a lesser extent any malfunction).

[0117] Other freewheel configurations are also envisioned, and one skilled in the art would know how to successfully implement the required freewheel.

[0118] The invention will now be explained in more detail with the aid of the accompanying drawings. [Brief description of the drawings]

[0119] [Figure 1] FIG. 2 is a schematic diagram of the transmission between the powertrain of the present invention and elements external to this group. [Diagram 2] FIG. 1 is a block diagram illustrating the method of the present invention in which a second motor is placed at the input of a differential. [Diagram 3] FIG. 3 is a simplified version of the block diagram of FIG. 2. [Figure 4] FIG. 11 is a block diagram showing the method of the present invention in which a second motor is placed at the output of a differential. [Diagram 5] FIG. 5 is a simplified version of the block diagram of FIG. [Figure 6] FIG. 4 shows the architecture of the powertrain of the present invention implementing a cycloidal differential, operating according to the principles of FIG. [Figure 7]FIG. 4 illustrates another powertrain architecture of the present invention implementing a cycloidal differential, operating according to the principles of FIG. [Figure 8] FIG. 4 illustrates another powertrain architecture of the present invention implementing a cycloidal differential, operating according to the principles of FIG. [Figure 9] FIG. 4 illustrates another powertrain architecture of the present invention implementing a cycloidal differential, operating according to the principles of FIG. [Figure 10] FIG. 4 illustrates the architecture of the powertrain of the present invention implementing a double-engagement cycloidal differential operating according to the principles of FIG. [Figure 11] FIG. 4 illustrates another powertrain architecture of the present invention implementing a double-engagement cycloidal differential operating according to the principles of FIG. [Figure 12] FIG. 4 illustrates another powertrain architecture of the present invention implementing a double-engagement cycloidal differential operating according to the principles of FIG. [Figure 13] FIG. 4 illustrates another powertrain architecture of the present invention implementing a double-engagement cycloidal differential operating according to the principles of FIG. [Figure 14] FIG. 1 is a side view of a dual engagement cycloidal differential system. [Figure 15] FIG. 15 is a cross-sectional view of the device of FIG. 14 along plane B. [Figure 16] FIG. 15 is a cross-sectional view of the device of FIG. 14 along plane C. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0120] In different figures, identical elements are identified by the same reference numbers without limitation to the use of a single part, i.e., for example, a ring gear referenced in a figure may have a different shape, size, material than a ring gear shown in another figure.

[0121] The various embodiment variations described below are not mutually exclusive unless they are technically inconsistent.

[0122] 1 shows roughly the transmission ratios between the powertrain DU according to the invention and elements outside this group. The elements shown in dotted lines are optional depending on the position of the powertrain in the bicycle.

[0123] The powertrain DU comprises an input I associated with a crankset P that can be acted upon by a driver C, and an output O associated with wheels W. The term "associated" indicates that a direct or indirect ratio via a transmission T may be provided as the case may be.

[0124] When the power train DU is located at the crankset P (i.e. concentric with the axis of the crankset), the output body O is advantageously connected to transmission means Tout to at least one wheel of the vehicle. These transmission means are, for example, a chain or a belt.

[0125] If the power train DU is located at the wheel W (i.e. concentric with the wheel), the axis of the crankset is advantageously connected to transmission means Tin upstream from the power train DU. These transmission means are for example chains or belts.

[0126] If the powertrain is located neither concentric with nor at the wheel W, nor concentric with nor at the crankset axis, it may have an upstream Tin and downstream Tout transmission at the same time.

[0127] In a first variant of the invention shown in FIG. 2, a second motor M2 assists the driver at the entry into the differential system.

[0128] With reference to FIG. 2, the method of assisted differential transmission for electric bicycle is as follows: - an angular velocity ω1 is applied to a first input of the differential system D by the action of a first motor M1, a reducer RM1 optionally being inserted between them; - the angular velocity ω2 resulting from the action of the driver C on the crankset CK combined with the action of the second motor M2 with the aid of the reducer RM2 is applied to a second input of the differential system D, the axis of which gives an angular velocity ωCK to the input I of the powertrain DU, possibly via a transmission Tin (optional depending on the position of the DU group on the bicycle); Includes.

[0129] The angular velocities ω1 and ω2 are combined in the differential system D and transmitted to the output body O as angular velocity ω3. Optionally, a reducer RO is installed between the output of the differential system D and the output body. An optional freewheel F1 is installed between the input body I and a second input of the differential system D, optionally via a reducer system RI1. The angular velocity at the output of the freewheel F1 is denoted as ωF1. The function of this freewheel is to prevent the system from driving the input body while allowing the input body to drive the system. This function is essentially dictated by driver safety considerations. However, this freewheel is optional.

[0130] Here another optional freewheel F2 is shown between the input body I and the output O, possibly with a reducer RI2 in between. The angular velocity at the output of the freewheel F2 is denoted ωF2, and the function of this freewheel is to make it impossible for the speed of the output sprocket to be lower than the speed of the input body, ωO ≥ ωI. The objective is to ensure drivability of the bicycle even in case of a system failure (dead battery, or to a lesser extent any malfunction).

[0131] Motors M1 and M2 are powered by a battery B (which may be a single battery or separate batteries).

[0132] The motors M1 and M2 are controlled by a control unit E.

[0133] A reducer RM2 is utilized to match the operating speed / torque of the driver and electric motor to:

number

[0134] where ωM2 is the angular velocity of motor M2 [rad / s], ωF1 is the angular velocity of the input body (possibly after passing the freewheel F1) and RRM2 is the ratio of the reducer associated with motor M2.

[0135] The angular velocity ωO at the output of the output body O is transmitted to the wheel W. Depending on the position of the powertrain on the bicycle, a transmission Tout may be provided downstream of the output O (ωTO), possibly finally by a freewheel F3, which transmits the angular velocity ωW to the wheel W.

[0136] Elements F1, RM1, RI1, RI2, RO, Tin, Tout, F3 are replaced by connections if they are not needed. In particular, if F2 is not present, all branches containing RI2 are omitted.

[0137] All elements contained within the powertrain DU are shown within the dotted box, other elements are located outside the powertrain.

[0138] FIG. 3 shows a simplified implementation of the embodiment described in FIG. 2, in which the optional reducers RM1, RI1, RI2, and RO are omitted.

[0139] In a second variant of the invention shown in FIG. 4, a second motor M2 regulates the assistance at the output of the differential system.

[0140] In this embodiment, unlike the embodiment of Fig. 2, the angular velocity ω2 resulting from the action of the rider C on the crankset CK is not combined with the angular velocity of the second motor M2. The angular velocity ωM2 is combined with the angular velocity ω3 at the output of the differential D via the reducer R'M2. The other elements are identical to the embodiment of Fig. 2.

[0141] Here an optional freewheel F1 is installed between the input and the second input of the differential system D (optionally together with a reducer RI1). Its function is to prevent the system from driving the crankset while allowing the crankset to drive the system. This function is essentially dictated by rider safety considerations. However, this freewheel is strictly optional.

[0142] Here another optional freewheel F2 as mentioned above is present between the input body and the output body O (through an optional reducer RI2). Its function is to ensure that the speed of the output sprocket cannot be lower than the speed of the input body (associated with the crankset), ωO ≥ ωI. The purpose is to ensure the drivability of the bicycle even in case of a system failure (dead battery, or to a lesser extent any malfunction).

[0143] Motors M1 and M2 are again powered by a battery B (which may be a single battery or separate batteries).

[0144] The motors M1 and M2 are controlled by a control unit E.

[0145] A reducer R'M2 is utilized to match the differential and the speed / output torque of the electric motor M2 to:

number

[0146] ωM2 is the angular velocity [rad / s] of the motor M2, and RR'M2 is the ratio of the reducer R'M2 associated with the motor M2.

[0147] In order for the motor M2 to adjust the input or output assist of the differential D, the system applies a reduction ratio Rm determined according to the following formula:

number

[0148] FIG. 5 shows a simplified implementation of the embodiment described in FIG. 4, in which the optional reducers RM1, RI1, RI2, and RO are omitted.

[0149] These two general operating aspects being established, structural examples based on the architecture aspects are now described. The following figures (FIGS. 6-9) are based on the principle of FIG. 1 (M2 at the input).

[0150] With reference to FIG. 6, the powertrain for an electric bicycle is integrated in a box 1 fixed to the frame of the bicycle, here at crankset P level.

[0151] The (mechanical) input is realised by the axis 2 of the crankset, which receives energy from the rider via the pedals. The (mechanical) output of the system is an output body 3, which supports for example a toothed sprocket in case of transmission by chain or a toothed pulley in case of transmission by belt, these two solutions being fully compatible with the power train. Other transmission systems (cardan, drive shaft, etc.) are also possible and compatible. The transmission here is to one wheel of the bicycle, preferably the rear wheel.

[0152] The powertrain is electrically powered by a battery consisting of accumulators placed anywhere on the bike. Generally speaking, the powertrain, and in particular the motors, exchange (send and receive) information with other electric and / or electronic elements of the bike, such as displays, command modules, battery management systems, sensors, etc. The CAN exchange protocol is one possible solution.

[0153] Within the box 1, the mechanical combination is organised concentrically around the axis 2 of the crankset here.

[0154] The transmission is collected between two motors M1 and M2, which include a rotor, 11 and 21 respectively, and a stator, 12 and 22 respectively. This configuration allows the motors to be flanked on both sides of the box, allowing maximum cooling. As elements that release a lot of energy through losses, this arrangement of the motors is optimal from a thermal point of view.

[0155] The rotor 21 of M2 is the input of the reducer A, shown here with fine dotted lines, which is for example a cycloidal gear train with a ring gear A1 fixed to the box 1. The ring gear A1 presents teeth on its inner surface, inside which the gear A2 engages with a cycloidal movement (represented here by a closer or less close wave depending on the position of the contact point with the ring gear, which is the upper part of the diagram), driving a conductive eccentric A3 associated with an eccentric carrier A4. The eccentric carrier is connected to the axis 2 of the crankset, at the level of the freewheel F1, in order to combine the movement of the crankset with that of the second motor, at the input of the differential D, shown with fine dotted lines to the right of the reducer A. The eccentric carrier is at the output of the reducer.

[0156] The differential D here is similar to a cycloid train and has a ring gear D1, the input of which is connected to the output of the reducer A described above. The rotor 11 of the first motor is connected to an eccentric exciter D2, which supports a gear D3. The output of the differential D is an eccentric carrier D4, which is connected to the output body 3.

[0157] Here, the optional freewheel F2 described in connection with FIG. 1 is arranged between the eccentric carrier D4 and the axis 2 of the crankset.

[0158] For this embodiment, as for the following embodiment and all other possible embodiments, abutments, rollers, and friction bearings of various types are used to guide the assembly. Several variations of these elements are possible, but the effect is similar to the extent that the inventive character of the present invention does not depend thereon.

[0159] Motors M1 and M2 may independently be radial or axial flux motors.

[0160] The embodiment shown in Fig. 7 differs from the embodiment of Fig. 6 in the embodiment of the reducer A. Here, the reducer A' is still a cycloid train, but now the output is a ring gear A1 and the eccentric carrier is fixed to the box 1.

[0161] The embodiment shown in Fig. 8 differs from the embodiment of Fig. 6 in the implementation of the differential D. Here, the ring gear D'1 is the output of the differential D', and the eccentric carrier D'3 and the rotor 11 of the first motor M1 are arranged at the input of the differential, via an eccentric exciter.

[0162] FIG. 9 illustrates an embodiment in which the reducer A' shown in FIG. 7 is combined with the differential D' shown in FIG.

[0163] 6 to 9 have been described as having a cycloid train, but the cycloid train may be replaced by any other type of reducer, for example an epicycloid reducer, a harmonic reducer, etc.

[0164] Furthermore, the cycloidal transmission used for the differential may be replaced by any other differential which satisfies the condition that the periphery of the elements progressing in the ring gear always contains the geometric center of the ring gear. This ensures the compactness of the system, unlike the use of, for example, epicycloidal gear trains.

[0165] FIG. 10 shows the embodiment of FIG. 6 in which both the reducer A and the differential D are replaced by a double cycloidal engagement system.

[0166] In particular, the reducer A'' includes a ring gear A1 having teeth on its inner surface, inside which an intermediate gear A''2, which engages with a cycloidal motion on its outer surface (represented by closer or less closely spaced waves depending on the position of the contact point with the ring gear), and its evenly toothed inner surface A''3, an output sprocket A''4.

[0167] Here the differential D'' is similar to the double engagement system and has a ring gear D1, the input of which is connected to the output of the reducer A'' described above. The rotor 11 of the first motor is connected to an eccentric exciter D''2 which drives an intermediate gear D''3 which moves in a cycloidal motion between the ring gear D1 and a sprocket D''4, the output of the differential D, which is connected to the output body 3.

[0168] Here, the optional freewheel F2 described in connection with FIG. 2 is arranged between the gear D''4 and the axis 2 of the crankset.

[0169] The embodiment shown in FIG. 11 differs from that of FIG. 10 in the implementation of the reducer A″. Here, the reducer A″ is still a double-engage cycloidal train, but now the input is the ring gear A1 and the sprocket A″4 is fixed to the box.

[0170] The embodiment shown in FIG. 12 differs from the embodiment of FIG. 10 in the implementation of the differential D″. Here, the ring gear D″1 is the output of the differential D″, while the sprocket D″4 and the rotor 11 of the first motor M1 are arranged at the input of the differential, via an intermediate gear.

[0171] FIG. 13 describes an embodiment that combines the reducer A'' shown in FIG. 11 with the differential D'''' shown in FIG.

[0172] All elements of the powertrain may be located about a single axis.

[0173] In Figures 6 to 13, the axial centre is the axis of the crankset, which coincides with the axis of the output body, i.e. with the axis of the sprocket associated with the transmission allowing to drive one wheel of the bicycle.

[0174] According to a similar embodiment, the axis centre may be the output shaft, for example advantageously the axis of the wheel, and the input shaft of the sprocket to which the action of the crankset is transmitted.

[0175] The method and associated powertrain of the present invention therefore offers great flexibility in implementation.

[0176] Figures 14 to 16 describe a, here concentric, cycloidal double engagement transmission 140. Figure 14 is a side view, while Figures 15 and 16 are cross-sectional views along planes B and C, respectively.

[0177] As in the cycloidal transmission system described above, the eccentric exciter 141, constituting the first connection of the differential system, supports on its eccentric axis a gear 142 rotatable along the eccentric second axis of the eccentric exciter. Any type of connection having at least one rotational degree of freedom may be used. This gear 142 is provided with external teeth and engages in an external ring gear 143 (with internal teeth). This constitutes the first engagement. Furthermore, the gear is evenly provided with internal teeth juxtaposed in the axial direction adjacent to the connection with the eccentric exciter 141. Furthermore, a sprocket 144, constituting the second input of the cycloidal system, is articulated rotatably on the main axis AA of the cycloidal module. The sprocket is provided with external teeth 145 that match the internal teeth of the gear 142 and is involved in the second engagement.

[0178] A ring gear 143, which is rotatably movable along the main axis AA of the cycloid module, constitutes the third and final connection of the differential system.

[0179] The cycloidal motion of the intermediate gear 142 and its engagement with the sprocket 144 imparts simple rotation to the sprocket 144 .

[0180] To ensure the operation of the system, the eccentricities of the two cycloidal engagements (ring gear-intermediate gear and intermediate gear-sprocket) must be equal (unless flexibility is introduced into the system).

Claims

1. A method of assisted differential transmission for an electric bicycle, comprising: an angular velocity ω1 is applied to a first input of a differential system by action of a first motor; an angular velocity ω2 is applied to a second input of the differential system by an input transmitting at least the action of the cyclist on the crankset; said angular velocities ω1 and ω2 being combined in said differential system, comprising a ring gear having an inner surface and an element cooperating with said inner surface, the periphery of said element always including the geometric centre of said ring gear, and transmitted to an output of said differential as an angular velocity ω3; a step of transmitting the velocity ω3 to an output body; Including, a second motor for adjusting the assistance to the driver in combination with the action of the driver, the second motor being connected to the second input through the input body or to the output; the axis of the output body, the main axis of the differential system, the axis of the first motor and the axis of the second motor are coincident and / or concentric with the axis of the input body; method.

2. The method of claim 1 , wherein the input is indirectly related to an axis of the crankset.

3. the inner surface of the ring gear exhibits internal teeth; the element cooperating with the inner surface is configured to engage the teeth; The method according to claim 1 or 2.

4. 4. The method according to claim 1, wherein the differential system is a cycloidal transmission system.

5. the ring gear having an inner toothed surface; the element cooperating with the inner surface is a gear wheel movable according to a cycloidal motion, the teeth of the ring gear have a number of teeth Zc greater than a number of teeth Zr of the gear; The method according to claim 4.

6. 6. The method according to claim 4 or 5, wherein the cycloidal transmission system includes at least one transmitting eccentric associated with an eccentric carrier and configured to transmit the cycloidal motion of the gears to the output, the output having an axis of rotation coinciding with an axis of rotation of the ring gear.

7. 7. A method according to claim 5 or 6, wherein the gear also presents a uniformly toothed inner surface adapted to engage a sprocket articulated for rotation about an axis coincident with the axis of the ring gear.

8. 8. The method according to claim 4, wherein the cycloidal transmission comprises at least two gears.

9. the differential system is a cycloidal transmission; The first motor applies an angular velocity ω1 to the first input, an eccentric exciter; The second motor and the input body provide an angular velocity ω2 to the ring gear, which is the second input; The output is an eccentric carrier or sprocket that transmits the angular velocity ω3.

9. The method according to any one of claims 1 to 8.

10. the differential system is a cycloidal transmission; The first motor applies an angular velocity ω1 to the first input, an eccentric exciter; The second motor and the input body impart an angular velocity ω2 to the eccentric reducer or the sprocket, which is the second input; The output is the ring gear transmitting the angular velocity ω3.

9. The method according to any one of claims 1 to 8.

11. 4. The method according to claim 1, wherein the differential system is a harmonic transmission system, the ring gear of which has a toothed inner surface and the element cooperating with said inner surface is a deformable gear surrounding a wave generator, the number of teeth Zc of the ring gear being greater than the number of teeth Zr of the deformable gear.

12. 12. The method of claim 1, wherein a torque control is applied to the second motor.

13. A powertrain for an electric bicycle, comprising: a differential system including a ring gear having an inner surface and an element cooperating with said inner surface, the periphery of said element defining a plane that contains a geometric center of said ring gear; a first motor configured to provide an angular velocity to a first input of the differential system; an input configured to provide an angular velocity to a second input of the differential system; an output of the differential system configured to impart a velocity to an output body; a second motor connected to the second input in combination with the input body or connected to the output for adjusting the assistance to the driver; Equipped with the axis of the output body, the main axis of the differential system, the axis of the first motor and the axis of the second motor are coincident and / or concentric with the axis of the input body; Powertrain.

14. The powertrain of claim 13 , wherein the input is directly or indirectly associated with an axis of a crankset.

15. 15. A powertrain as claimed in claim 13 or 14, wherein the output is coupled to at least one wheel of the bicycle via a transmission means.

16. 16. A powertrain as claimed in any one of claims 12 to 15, wherein the input is connected to the shaft of the crankset via a transmission means.

17. the inner surface of the ring gear exhibits internal teeth; the element cooperating with the inner surface is configured to engage the teeth; A powertrain according to any one of claims 13 to 16.

18. 18. The powertrain of claim 13, wherein the differential system is a cycloidal transmission system, in which the inner surface of the ring gear presents internal teeth, the elements engaging the internal teeth of the ring gear are gears, and the teeth of the cycloidal ring gear have a number of teeth Zc that is greater than a number of teeth Zr of the gears.

19. 20. The powertrain of claim 18, wherein said gear also presents a uniformly toothed inner surface configured to engage a sprocket articulated for rotation about an axis coincident with an axis of said ring gear.

20. 18. The powertrain according to claim 13, wherein the differential system is a harmonic transmission system, in which the inner surface of the ring gear presents internal teeth, the element engaging with the internal teeth of the ring gear is a deformable gear surrounding a wave generator, and the number of teeth Zc of the ring gear is greater than the number of teeth Zr of the deformable gear.

21. 21. A powertrain as claimed in any one of claims 13 to 20, further comprising a non-reversing means.

22. 22. The powertrain of claim 13, further comprising a system reducer configured to allow combination of the action of the second motor with the action of the output or combination of the action of the second motor with the action of the input.

23. 23. A powertrain as claimed in any one of claims 13 to 22, wherein the axis of the output body coincides with and / or is concentric with an axis of a reducer associated with the second motor M2.

24. 24. A powertrain as claimed in any one of claims 13 to 23, wherein the two motors are mounted on either side of the differential system.

25. An electric bicycle comprising a powertrain according to any one of claims 13 to 24, the axis of the ring gear is coincident with and / or concentric with the axis of the bicycle wheel; Electric bicycle.

Images