CONTINUOUSLY VARIABLE TRANSMISSION POWERTRAIN WITH EPICYCLOIDAL AND CYCLOIDAL REDUCERS

Abstract

The invention relates to a powertrain (4) for an electrically assisted bicycle. The powertrain (4) comprises a first electric motor (M1), a second electric motor (M2), and a gearbox (5). The gearbox (5) includes an epicyclic transmission device (8) and a cycloidal transmission device (6) which is mechanically connected to the epicyclic transmission device (8) and the second electric motor (M2). The first electric motor (M1) is configured to drive an output transmission element (88) of the gearbox. The second electric motor (M2) is configured to drive the epicyclic transmission device (8) via the cycloidal transmission device (6). (See Figure 2 for abbreviations.)

Description

Title of the invention: POWERTRAIN WITH CONTINUOUSLY VARIABLE TRANSMISSION AND EPICYCLOIDAL AND CYCLOIDAL REDUCER TECHNICAL FIELD OF THE INVENTION

[0001] The invention relates to the general technical field of electrically assisted cycles. More specifically, the invention relates to a powertrain for an electrically assisted bicycle. STATE OF THE ART

[0002] An electrically assisted bicycle comprises a powertrain that provides assistance to a user, enabling the user to travel on steep terrain and / or over long distances, which would for example be inaccessible with a conventional bicycle without assistance. Electrical assistance also makes it easier for a large number of people to practice cycling, particularly as an alternative to using a car.

[0003] Patent application FR2202477 discloses a powertrain comprising a first electric motor, a second electric motor and an epicyclic reducer whose transmission elements are driven by the first electric motor and by the second electric motor.

[0004] The space available for the powertrain on the bicycle or in the bicycle is small. In particular, the space available for the reducer is small due to the size of the electric motor. The reduction ratio of the reducer is generally high, in order to be able to use a powerful electric motor and so that the powertrain can provide efficient electric assistance. The reduction ratio in a reduced size is likely to be improved.

[0005] There is also a powertrain for an electrically assisted bicycle which comprises a single electric motor and a cycloidal reducer. However, such a powertrain is likely to generate torque breaks during an automatic gear change. These unexpected torque breaks are very badly perceived by a user, who may believe that there is a malfunction of the powertrain. The reduction ratio in a reduced size is still likely to be improved.

[0006] There is therefore a need to improve the electrical assistance of a cycle, while limiting the mass and size of the powertrain for an electrically assisted cycle, and while facilitating automatic gear changes and improving the comfort of use of the cycle. Statement of the invention

[0007] The present invention aims to remedy all or part of the drawbacks of the state of the art cited above.

[0008] To this end, the invention relates to a powertrain for an electrically assisted cycle. The powertrain comprises a first electric motor, a second electric motor separate from the first electric motor, and a reducer which comprises an epicyclic transmission device.

[0009] According to the invention, the reducer comprises a cycloidal transmission device which is mechanically connected to the epicyclic transmission device and to the second electric motor. The first electric motor is configured to drive an output transmission element of the reducer. The second electric motor is configured to drive the epicyclic transmission device via the cycloidal transmission device.

[0010] Thanks to the powertrain according to the invention, the electric assistance of the cycle is improved, while limiting the mass and size of the powertrain. In particular, automatic gear changing tends to be facilitated, the comfort of use of the cycle to be improved, the maximum power delivered to increase, the efficiency of the reduction gear of the powertrain to increase, while limiting the mass and size of the powertrain, and while having a powertrain that is relatively simple to manufacture.

[0011] Automatic gear shifting is smooth due to the continuously variable transmission which is possible due to the two electric motors, and torque breaks are for example avoided during automatic variation of the transmission ratios. The powertrain is in particular compact due to the cycloidal reduction gear which replaces cylindrical gears with external teeth and / or epicyclic gears. The arrangement of the cycloidal transmission device between the second electric motor and the epicyclic transmission device, in particular around a pedal shaft, tends to facilitate the manufacture of the powertrain and to make the powertrain compact. The manufacture of the powertrain, in particular the assembly of the transmission elements of the reduction gear, is facilitated by the limited number of gears in the powertrain.The epicyclic transmission device and the cycloidal transmission device limit in particular the number of gears of the powertrain, and the mass of the powertrain is reduced. The efficiency of the powertrain reducer tends to increase, by limiting the number of gears and due to the continuously variable transmission. The high compactness and efficiency of the reducer make it possible to use at least one particularly powerful electric motor.

[0012] According to a particular embodiment, the second electric motor is centered around a first shaft of the powertrain. The first electric motor is centered around a second shaft of the powertrain which is strictly parallel to the first shaft.

[0013] According to another particular embodiment, the epicyclic transmission device comprises a first input transmission element and the output transmission element, the first input transmission element being fixed relative to a crankshaft, the output transmission element being fixed relative to an output shaft of the powertrain. The crankshaft and the output shaft are concentric.

[0014] According to a particular embodiment, the epicyclic transmission device comprises an epicyclic train which comprises an outer ring gear, a sun gear, a planet carrier and planet gears. The planet carrier is the first input transmission element of the epicyclic transmission device. The outer ring gear is a second input transmission element of the epicyclic transmission device. The outer ring gear is connected to the cycloidal transmission device. The sun gear is the output transmission element.

[0015] According to a particular embodiment, the reducer comprises a freewheel between the crankshaft and the output shaft of the reducer, when the freewheel is engaged. The freewheel is used in particular to use the cycle without electrical assistance by directly connecting the crankshaft to the output shaft when the freewheel is engaged.

[0016] According to a particular embodiment, the first electric motor is mechanically connected to the output transmission element via a cylindrical gear train with external teeth.

[0017] According to a particular embodiment, the cycloidal transmission device comprises an input shaft, an eccentric ring, a first lobed crown and a concentric ring. The eccentric ring is configured to mechanically engage the input shaft, the first lobed crown and the concentric ring.

[0018] According to a particular embodiment, the eccentric ring comprises a first ring which is configured to mechanically engage an eccentricity of the input shaft. The input shaft is in particular to be centered around a first longitudinal axis of the reducer.

[0019] According to a particular embodiment, the eccentric ring comprises a second lobed ring which has internal lobes and external lobes. The second lobed ring is configured to mechanically engage the first lobed crown and the concentric ring.

[0020] According to a particular embodiment, the outer lobes are configured to mechanically engage inner lobes of the first lobed crown. The outer lobes are in particular configured to each have a relative epitrochoidal trajectory. tively to a first longitudinal axis of the reducer.

[0021] According to a particular embodiment, the internal lobes are configured to mechanically engage external lobes of the concentric ring. The internal lobes are in particular configured to each have an epitrochoidal trajectory relative to a first longitudinal axis of the reducer.

[0022] According to a particular embodiment, the first lobed crown is fixed relative to a first longitudinal axis of the reducer.

[0023] According to a particular embodiment, an output transmission element of the cycloidal transmission device is fixed relative to an input transmission element of the epicyclic transmission device.

[0024] According to a particular embodiment, the concentric ring comprises a second lobed crown and an outer crown which is in one piece with the second lobed crown. The second lobed crown mechanically engages the eccentric ring. The outer crown is the second input transmission element of the epicyclic transmission device.

[0025] According to a particular embodiment, the cycloidal transmission device and the epicyclic transmission device extend around a first longitudinal axis of the reducer. Preferably, the first longitudinal axis of the reducer is a longitudinal axis of a pedal shaft.

[0026] The invention also relates to an electrically assisted cycle which comprises a powertrain as defined above. Preferably, the cycle is a bicycle or a cargo bicycle.

[0027] According to a particular embodiment, the electrically assisted cycle comprises a front wheel, a rear wheel and a transmission system which comprises a chain, sprockets and at least one chainring. The powertrain is configured to drive the chainring which is fixed relative to an output shaft of the powertrain. BRIEF DESCRIPTION OF THE FIGURES

[0028] Other advantages, aims and particular characteristics of the present invention will emerge from the following non-limiting description of at least one particular embodiment of the devices and methods which are the subject of the present invention, with reference to the appended drawings, in which: • [Fig.l] is a schematic representation of an electrically assisted cycle, comprising a powertrain according to a first embodiment of the invention; • [Fig.2] is a partial kinematic representation of a powertrain for an electrically assisted cycle, according to the first mode of realization ; • [Fig.3] is an exploded schematic representation of a cycloidal transmission device of the powertrain according to the first embodiment; • [Fig.4] is a partial schematic cross-sectional representation of the cycloidal transmission device of the powertrain according to the first embodiment, illustrating the operation of the cycloidal transmission device of the powertrain. DETAILED DESCRIPTION OF THE INVENTION

[0029] The present description is given as a non-limiting example of embodiment.

[0030] [Fig.l] is a schematic representation of an electrically assisted cycle 1 according to a first embodiment shown. In the first embodiment shown, the electrically assisted cycle is a bicycle. The electrically assisted cycle 1 comprises a frame 2, a front wheel 10F, a rear wheel 10R, pedals 11 and a transmission and drive system 3.

[0031] The transmission and drive system 3 comprises a battery B, a powertrain 4 and a transmission system 30. In the embodiment shown, the battery B is assembled in a removable manner to the frame 12 of the bicycle, for example on a down tube 22 of the frame. The transmission and drive system 3 is configured to drive the wheels 10F, 10R from the movement of the pedals 11, with possible electric assistance.

[0032] The transmission system 30 comprises a chain 31, sprockets 34 and at least one chainring 32. The cycle 1 preferably comprises at least two chainrings 32, preferably three chainrings 32. The chain 31 mechanically connects at least one chainring 32 to one of the sprockets 34. The transmission system 30 drives, for example, the rear wheel 10R from the crankset.

[0033] With joint reference to Figures 2 to 4, the powertrain 4 comprises a first electric motor M1, a second electric motor M2, a reduction gear 5 which comprises a cycloidal transmission device 6 and an epicycloidal transmission device 8, a drive device, a control system, a monitoring system, a crankshaft 41, a traction motor shaft 42 and an output shaft 49 of the powertrain. The powertrain 4 is configured to electrically assist the pedaling of a user of the cycle. In the embodiment shown, the powertrain 4 is designed to drive each chainring 32.

[0034] The crankshaft 41 forms a first shaft of the powertrain. The crankshaft 41 is centered around a first longitudinal axis XI of the reducer which is also called longitudinal axis XI of the crankshaft. The shaft 42 of the traction motor is strictly parallel to the crankshaft 41 extending around a second longitudinal axis X2 of the reducer. The output shaft 49 is concentric with the crankshaft 41. In the embodiment shown, the output shaft 49 is a hollow shaft which is located radially outside the crankshaft 41 and which is fixed relative to each chainring 32.

[0035] In the present document, a direction parallel to the first longitudinal axis XI is a transverse direction of the cycle and a longitudinal direction of the reducer 5. The direction Y which is represented in [Fig.l] is orthogonal to the direction of the first longitudinal axis XI and it corresponds to the longitudinal direction of the cycle.

[0036] The first electric motor M1 is centered around the second longitudinal axis X2 of the reducer, being located around the traction motor shaft 42. The first electric motor M1 is called the traction motor. It is configured to drive the output shaft 49 via the drive device by assisting the user's pedaling.

[0037] In the embodiment shown, the drive device is a train 44 of cylindrical gears with external teeth which is made up of cylindrical gear wheels with straight teeth. The train 44 of cylindrical gears comprises in this order from the first electric motor M1 to the output shaft 49, a first pinion P11, a second pinion P1.2 mechanically engaging the first pinion P11, a third pinion P1.3 which is fixed relative to the second pinion P1.2, a fourth pinion P1.4 which mechanically engages the third pinion, a fifth pinion P1.5 which is fixed relative to the fourth pinion P1.4 and which mechanically engages a sixth pinion P1.6. The sixth pinion P1.6 is fixed relative to the output shaft 49 and is called the motor pinion.

[0038] The second electric motor M2 is centered around the first longitudinal axis XI of the reducer. The second electric motor M2 is configured to drive the epicyclic transmission device 8 via the cycloidal transmission device 6. The second electric motor M2 is configured to vary the ratio of the reducer 5, for example so that the user can pedal at a constant speed. The second motor M2 is called a variable speed motor.

[0039] The control system comprises at least one sensor. It is configured to directly or indirectly detect the rotation speed of the first electric motor M1, of the second electric motor M2 and the force exerted by the user on the pedals 11. In the embodiment shown, the control system comprises a torque sensor 45 which detects the torque exerted by the user on the pedals 11.

[0040] The control system comprises at least one control unit 43. The control unit 43 is configured to control the first electric motor M1, in particular in torque, and the second electric motor M2, in particular in speed, to assist pedaling based on data detected by the control system. The control unit 43 takes, for example, the form of an electronic control card for the powertrain 4.

[0041] The reducer 5 comprises the cycloidal transmission device 6, the epicyclic transmission device 8 and a freewheel 51. The longitudinal axis of the reducer 5 is the first longitudinal axis XL. The reducer 5 is configured to increase the torque of the output shaft 49 from the rotational speed of the second electric motor M2.

[0042] The freewheel 51 is located between the crankshaft 41 and the output shaft 49 of the reducer. When the freewheel 51 is engaged, the output shaft 49 rotates at the same speed as the crankshaft 41. The crankshaft 41 and the output shaft 49 then drive, for example, the second electric motor M2 via the epicyclic transmission device 8 and the cycloidal transmission device 6, in particular via the outer ring gear 84. The freewheel 51 allows in particular the direct drive of the output shaft 49 by the crankshaft 41, when the second electric motor M2 is no longer able to control the speed of the outer ring gear 84 to maintain it at a sufficient speed. In practice, such a situation occurs for example when the rotation speed of the crankshaft 41 around the first longitudinal axis XI is greater than a maximum assistance speed of the powertrain 4.Freewheel 51 is used in particular to use cycle 1 without electrical assistance. . .

[0043] The epicyclic transmission device 8 is an epicyclic gear train. The epicyclic gear train comprises an outer ring gear 84, a sun gear 88, a planet carrier 82 and planet gears 86. The epicyclic gear train of the powertrain 4 may be of type I, II, III or IV. In the embodiment shown, the planet carrier 82 is the first input transmission element of the epicyclic transmission device. The outer ring gear 84 is a second input transmission element of the epicyclic transmission device which is connected to the cycloidal transmission device 6. The planet carrier 82 is fixed relative to the crankshaft 41 which forms a first input shaft of the epicyclic reduction gear. The outer ring gear 84 is movable relative to the first longitudinal axis XL. The sun gear 88 is the output transmission element. The sun gear 88 is fixed relative to the output shaft 49.The epicyclic transmission device 8 is configured to drive the output shaft 49 from the crankshaft 41 and the drive by the second electric motor M2 via the cycloidal drive device 6. In the embodiment shown, the ratio of the epicyclic gear train is for example 0.33.

[0044] With joint reference to Figures 2 to 4, the cycloidal transmission device 6 comprises an input shaft 61, an eccentric ring 64, a first lobed crown 67 and a concentric ring 70 which comprises a second lobed crown 72. The cycloidal transmission device 6 is mechanically connected to the epicyclic transmission device 8 and to the second electric motor M2, being kinetically between the second electric motor M2 and a second input transmission element of the epicyclic transmission device 8.

[0045] In the embodiment shown, the ratio of the cycloidal transmission device 6 is for example 0.05. Generally, the reduction ratio of the cycloidal transmission device 6 is particularly high, with a reduced number of gears and with limited bulk.

[0046] The input shaft 61 is concentric and centered around the first longitudinal axis XI of the reducer. The input shaft 61 comprises at least one eccentricity 62 which has an eccentric trajectory relative to the first longitudinal axis XL. The eccentricity 62 is configured to drive the eccentric ring 64.

[0047] The first lobed crown 67 is fixed relative to the first longitudinal axis XI of the reducer. The first lobed crown 67 is centered around the first longitudinal axis XL. The first lobed crown 67 is an outer lobed crown which delimits in particular the cycloidal reduction device 6 radially outwards. The first lobed crown 67 comprises inner lobes 67a which are regularly spaced on the inner circumference of the first lobed crown 67. The outer contour 67b of the first lobed crown 67 is for example smooth or it comprises shapes arranged to ensure the rotational locking of the first lobed crown 67.

[0048] The eccentric ring 64 comprises a first ring 65 and a second lobed ring 68 which is integral with the first ring 65. In particular, thanks to the eccentric ring 64, the second lobed ring 68 is fixed relative to the first ring 65. The eccentric ring 64 is configured to mechanically engage the input shaft 61, the first lobed ring 67 and the concentric ring 70.

[0049] The eccentric ring 64 forms a particularly compact transmission element of the cycloidal transmission device 6 in view of the number of gears of which it is a part, by mechanically engaging the input shaft 61, the first lobed crown 67 and the concentric ring 70. The second lobed ring 68 being fixed relative to the first ring 65, the manufacture of the reducer 5 is also facilitated.

[0050] The first ring 65 is configured to mechanically engage the eccentricity 62 of the input shaft. It is located around the input shaft 61. The first ring 65 is configured to have an eccentric displacement around the first longitudinal axis XL

[0051] The second lobed ring 68 has inner lobes 68a and outer lobes 66a. The second lobed ring 68 is configured to mechanically engage the first lobed crown 67 and the concentric ring 70. The outer lobes 66a are configured to mechanically engage inner lobes 67a of the first lobed crown 67, each having an epitrochoidal trajectory relative to a first longitudinal axis XI of the reducer. The inner lobes 68a are configured to mechanically engage outer lobes 72a of the concentric ring 70, each having an epitrochoidal trajectory relative to a first longitudinal axis XI of the reducer.

[0052] The concentric ring 70 comprises the second lobed crown 72 and the outer crown 84 which is in one piece with the second lobed crown 72. In particular, thanks to the eccentric ring 70, an output transmission element of the cycloidal transmission device 6 is fixed relative to a second input transmission element of the epicyclic transmission device 8. The concentric ring 70 forms both an output transmission element of the cycloidal transmission device 6 and a second input transmission element of the epicyclic transmission device 8. The concentric ring 70 is configured to have a concentric movement centered on the first longitudinal axis XI, when it is mechanically driven by the eccentric ring 64.

[0053] The concentric ring 70 forms a particularly compact transmission element of the reducer 5, by integrating the second lobed crown 72 and the outer crown 84. The outer crown 84 being fixed relative to the second lobed crown 72, the manufacture of the reducer 5 is also facilitated.

[0054] The second lobed ring 72 is cylindrical. The second lobed ring 72 comprises outer lobes 72a which mechanically engage the inner lobes 68a of the second lobed ring 68. The outer lobes 72a engage by shape cooperation the inner lobes 68a and they are preferably of a shape complementary to that of the inner lobes 68a. The second lobed ring 72 forms the output transmission element of the cycloidal transmission device 6.

[0055] The outer ring gear 84 is for example of a diameter greater than that of the second lobed ring gear 72. It is cylindrical and it has internal teeth. By being fixed relative to the second lobed ring gear 72, the outer ring gear 84 is intended to be driven by the cycloidal transmission device 6 and the outer ring gear 84 forms the second input transmission element of the epicyclic transmission device 8.

[0056] The operation of the powertrain 4 is described below with joint reference to Figures 1 to 4. The pedals 11 drive the crankshaft 41 and the planet carrier 82 which forms the first input transmission element of the epicyclic transmission device 8. The control unit 43 controls the first motor electric motor M1 which drives the output shaft 49 via the cylindrical gear train 44, based on the data from the sensor 45. The control unit 43 controls the second electric motor M2 so that it modifies the rotation speed of the outer ring 84, based on the data from the sensor 45. The control of the second electric motor M2 aims, for example, to maintain a similar pedaling cadence regardless of the distance traveled and the slope, taking into account the physical condition of the user. When no electric assistance is required, the freewheel 51 allows the direct drive of the output shaft 49 by the crankshaft 41.

[0057] Thanks to the powertrain 4 according to the invention, the electric assistance of cycle 1 is improved, while limiting the mass and size of the powertrain 4.

[0058] Automatic gear shifting is smooth due to the continuously variable transmission which is possible due to the two electric motors M1, M2. Torque breaks are for example avoided during the automatic variation of the transmission ratios of cycle 1. The electric assistance of cycle 1 is improved.

[0059] The freewheel 51 improves pedaling comfort when no electrical assistance is required. In particular, the freewheel 51 improves pedaling comfort by directly connecting the crankshaft 41 to the output shaft 49 in order to ensure transmission of the cyclist's torque to the wheel of the cycle 1 when the second electric motor M2 is not able to control the speed of the outer ring 84.

[0060] The powertrain 4 is compact due to the cycloidal reduction gear 6 which replaces cylindrical gears with external teeth and / or epicyclic gears. The arrangement of the cycloidal transmission device 6 between the second electric motor M2 and the epicyclic transmission device 8 tends to make the powertrain 4 compact. The powertrain 4 is made particularly compact by the arrangement of the epicyclic transmission device, the cycloidal transmission device 6 and the second electric motor M2 around the crankshaft 41. The integration of the epicyclic transmission device 8 and the epicyclic transmission device 6, in particular the outer ring 84 and the second lobed ring 72 within the concentric ring 70, also makes the powertrain 4 particularly compact.The eccentric ring 64 also tends to make the cycloidal transmission device particularly compact.

[0061] The cycloidal transmission device 6 on the one hand and the at least partial integration of the epicyclic transmission device 8 and the cycloidal transmission device 6 on the other hand tend to increase the reduction ratio of the powertrain 4.

[0062] The manufacture of the powertrain group 4, in particular the assembly of the transmission elements of the reducer, is facilitated by the low number of gears in the group. powertrain 4. The manufacture of the powertrain 4 is facilitated by the at least partial integration of the cycloidal transmission device 6 and the epicyclic transmission device 8, which tends in particular to further reduce the number of gears of the reducer 5. The arrangement of the epicyclic transmission device 8 and that of the cycloidal transmission device 6 around the crankshaft 41 also facilitates the manufacture of the powertrain 4.

[0063] The low number of gears of the powertrain 4 tends to reduce the mass of the powertrain 4.

[0064] The efficiency of the reducer 5 of the powertrain 4 is high, due to the small number of gears of the reducer 5 and due to the continuously variable transmission. The planet carrier 82, which forms the first input element of the epicyclic transmission device 8, being fixed relative to the pedal shaft 41, the energy losses are reduced between the pedals 11 and the input of the epicyclic reducer 8, and the efficiency of the reducer 5 tends to increase. The efficiency of the reducer 5 is particularly high with the epicyclic train of the reducer 5 according to the first embodiment compared to that of a reducer 5 which would comprise another type of cycloidal reducer.

[0065] The high compactness and efficiency of the reducer 5 make it possible to use at least one particularly powerful electric motor M1, M2. More precisely, it is possible to use at least one larger and more powerful electric motor M1, M2 for an equivalent volume of geared motor, due to the greater compactness of the reducer 5.

[0066] The engagement of the outer lobes 66a and the inner lobes 68a of the eccentric ring with the first lobed crown 67 on the one hand and with the second lobed crown 72 on the other hand tends to limit the vibrations of the eccentric ring 64 and the noise generated by the cycloidal transmission device 6. By reducing the number of gears of the reducer 5, the noise during use of the powertrain 4 is reduced.

[0067] Of course, various modifications can be made by those skilled in the art to the invention which has just been described without departing from the scope of the disclosure of the invention.

[0068] Alternatively, the electrically assisted cycle 1 is a cargo bike. Alternatively, the electrically assisted cycle 1 is, for example, a monowheel or a tricycle.

[0069] Alternatively, battery B is housed inside the frame 12. Alternatively, battery B is attached to the rear of the bicycle, for example on a luggage rack.

[0070] Alternatively, the powertrain 4 is connected directly to the hub of a wheel 10F, 10R of the electrically assisted cycle, instead of being integrated at least partially into the crankset of the cycle.

[0071] Alternatively, the crankshaft 41 is hollow.

[0072] Alternatively, the drive device may comprise transmission elements other than straight toothed wheels, for example a flat wheel. The number of gears in the drive device may vary.

[0073] Additionally or alternatively, the control system comprises at least one relative and / or absolute sensor for detecting the rotational speed of the first electric motor M1 and / or the second electric motor M2. This sensor is for example a Hall effect sensor.

[0074] As a variant, the reducer 5 comprises a freewheel 51 between the second electric motor M2 and the crankshaft 41, which in particular makes it easier to reposition the pedals 11 at the start of cycle 1.

[0075] As a variant, the sun gear 88 is for example a first input transmission element of the epicyclic transmission device 8, the planet carrier 82 is an output transmission element of the epicyclic transmission device 8, the outer ring gear 84 is a second input transmission element of the epicyclic transmission device 8.

[0076] Alternatively, the first lobed crown 67 is a crown that is movable relative to the longitudinal axis XI of the crankshaft. In addition or as an alternative, the first lobed crown 67 is an inner lobed crown that mechanically engages inner lobes of the second lobed ring 68, the second lobed crown 72 is then an outer lobed crown that mechanically engages outer lobes of the second lobed ring 68.

[0077] Alternatively, the first ring 65 is attached to the second lobed ring 68. Alternatively, the eccentric ring 64 comprises a third lobed ring. Alternatively, the outer ring 84 is attached to the second lobed ring 72.

[0078] Alternatively, the epicyclic transmission device 8 and / or the cycloidal transmission device 6 comprises at least one cylindrical gear.

[0079] The shape and arrangement of the teeth and / or lobes of the transmission elements of the reducer 5 may vary.

Claims

Claims

1. Powertrain (4) for an electrically assisted cycle (1) comprising: a first electric motor (Ml), a second electric motor (M2) separate from the first electric motor (Ml), and a reducer (5) which comprises an epicyclic transmission device (8), characterized in that the reducer (5) comprises a cycloidal transmission device (6) which is mechanically connected to the epicyclic transmission device (8) and to the second electric motor (M2), the first electric motor (Ml) is configured to drive an output transmission element (88) of the reducer, the second electric motor (M2) is configured to drive the epicyclic transmission device (8) via the cycloidal transmission device (6).

2. Powertrain (4) according to the preceding claim, wherein the second electric motor (M2) is centered around a first shaft (41) of the powertrain, the first electric motor (M1) being centered around a second shaft (42) of the powertrain which is strictly parallel to the first shaft (41).

3. A powertrain (4) according to claim 1 or 2, wherein the epicyclic transmission device (8) comprises a first input transmission element (82) and the output transmission element (88), the first input transmission element (82) being fixed relative to a crankshaft (41), the output transmission element (88) being fixed relative to an output shaft (49) of the powertrain, the crankshaft (41) and the output shaft (49) being concentric.

4. Powertrain (4) according to claim 3, wherein the epicyclic transmission device (8) comprises an epicyclic gear train which comprises an outer ring gear (84), a sun gear (88), a planet carrier (82) and planet gears (86), the planet carrier (82) being the first input transmission element of the epicyclic transmission device, the outer ring gear (84) being a second input transmission element of the epicyclic transmission device which is connected to the cycloidal transmission device (6), the sun gear (88) being the output transmission element.

5. Powertrain (4) according to any one of claims 3 or 4, wherein the reduction gear (5) comprises a freewheel (51) between the crankshaft (41) and the output shaft (49) of the reducer, in particular for using the cycle (1) without electrical assistance by directly connecting the crankshaft (41) to the output shaft (49), when the freewheel (51) is engaged.

6. A powertrain (4) according to any preceding claim, wherein the first electric motor (Ml) is mechanically connected to the output transmission element (88) via a cylindrical gear train with external teeth.

7. A powertrain (4) according to any preceding claim, wherein the cycloidal transmission device (6) comprises an input shaft (61), an eccentric ring (64), a first lobed crown (67) and a concentric ring (70), the eccentric ring (64) being configured to mechanically engage the input shaft (61), the first lobed crown (67) and the concentric ring (70).

8. Powertrain (4) according to the preceding claim, wherein the eccentric ring (64) comprises a first ring (65) which is configured to mechanically engage an eccentricity (62) of the input shaft, the input shaft (61) being in particular to be centered around a first longitudinal axis (XI) of the reducer, and / or wherein the eccentric ring (64) comprises a second lobed ring (68) which comprises internal lobes (68a) and external lobes (66a), the second lobed ring (68) being configured to mechanically engage the first lobed ring (67) and the concentric ring (70).

9. Powertrain (4) according to the preceding claim, in which the outer lobes (66a) are configured to mechanically engage inner lobes (67a) of the first lobed ring (67), in particular by each having an epitrochoidal trajectory relative to a first longitudinal axis (XI) of the reducer, and / or in which the inner lobes (68a) are configured to mechanically engage outer lobes (72a) of the concentric ring (70), in particular by each having an epitrochoidal trajectory relative to a first longitudinal axis (XI) of the reducer.

10. Powertrain (4) according to any one of the preceding claims 7 to 9, in which the first lobed crown (67) is fixed relative to a first longitudinal axis (XI) of the reducer.

11. A powertrain (4) according to any one of the preceding claims 7 to 10, wherein an output transmission element (70) of the cycloidal transmission device is fixed relative to an input transmission element (84) of the epi-cycloidal transmission device.

12. Powertrain (4) according to the preceding claim, wherein the concentric ring (70) comprises a second lobed crown (72) and an outer crown (84) which is in one piece with the second lobed crown (72), the second lobed crown (72) mechanically engaging the eccentric ring (64), the outer crown (84) being the second input transmission element of the epicyclic transmission device.

13. Powertrain (4) according to any one of the preceding claims 7 to 12, wherein the cycloidal transmission device (6) and the epicyclic transmission device (8) extend around a first longitudinal axis (XI) of the reducer which is preferably a longitudinal axis of a crankshaft (41).

14. An electrically assisted cycle (1) comprising a powertrain (4) according to any one of the preceding claims, wherein the cycle (1) is preferably a bicycle or a cargo bicycle.

15. Electrically assisted cycle (1) according to the preceding claim, comprising a front wheel (10F), a rear wheel (10R), a transmission system (30) comprising a chain (31), sprockets (34) and at least one chainring (32), the powertrain (4) being configured to drive the chainring (32) which is fixed relative to an output shaft (49) of the powertrain.

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