Gearbox, powertrain for a vehicle including the gearbox, and vehicle including the gearbox

Abstract

The gearbox (29) includes an annular support (31) on which gear pairs (33A-33J) for inputting motion to the gearbox (29) are rotatably supported. Each of the gear pairs includes a first gear (35) adapted to receive the input motion and a second gear (37). The first gear (35) and the second gear (37) are coaxial and angularly coupled to each other for rotation as a unit. Each of the gear pairs defines a transmission ratio different from the transmission ratio defined by the other gear pairs. The annular support is angularly movable about a selected axis, whereby one of the gear pairs can be selectively placed in an angular motion disengagement position relative to the gearbox. The gearbox further includes a mechanical connection between a second gear of the gear pair in an angular motion disengagement position to the gearbox and an output shaft having an axis of rotation (AA) parallel to or coincident with the selected axis, where the output shaft passes through the annular support.

Description

[Technical field]

[0001] The present invention relates to gearboxes, and more particularly to gearboxes for applications including, but not limited to, human powered vehicles, such as pedal assist bicycles.

[0002] According to a particular aspect, the present invention relates to vehicles such as various types of bicycles, bicycle taxis, three-wheelers, four-wheelers, torpedoes, urban rickshaws, and two-seater bicycles, including a propulsion-assist system, i.e. a drive-assist. In this specification and the appended claims, the terms drive-assist or propulsion-assist are used synonymously, unless otherwise stated. By a propulsion-assist or drive-assist vehicle is meant a vehicle that can be propelled by the use of muscle power in combination with a torque generated by a motor, such as an electric motor in particular. As described herein, a typical example of a drive-assist or propulsion-assist vehicle is a pedal-assist bicycle. [Background technology]

[0003] A device for changing the gear ratio of a human powered vehicle such as a bicycle is known. The device includes a plurality of pinions coaxially mounted on the hub of a drive wheel, each pinion having a different diameter to define a different gear ratio. The device also includes a transmission for disengaging the drive chain from one pinion and engaging another pinion to change gears, and a control (usually a manual cable control) for operating the transmission.

[0004] In such devices, the various pinions are arranged in separate planes perpendicular to the hub of the drive wheel. Therefore, as a rule, there is a maximum of one pinion that is arranged in the same plane with the crown. Therefore, as a rule, the links of the drive chain are not arranged in the same plane, but at an angle to each other. The ideal operating condition of the drive chain is for the links to be aligned in the same plane. In the above-mentioned arrangement, the friction between the links is large. As a result, the deterioration of the transmission performance in the various gears is more or less emphasized, noise is generated, they are prone to wear, they lose lateral rigidity, which requires frequent maintenance and impairs the functioning of the gearbox.

[0005] Another drawback of transmission gears is the inability to quickly and / or directly change between non-consecutive gear ratios, which reduces vehicle performance, especially when road gradients change suddenly and significantly.

[0006] Furthermore, the transmission gearing does not allow the gear ratio to be changed when the vehicle is stationary and cannot tackle a hill with the appropriate gear ratio already set.

[0007] To solve these problems, gearings have been developed, consisting of a box containing gears, integrated into the hub of the driving wheel, typically the rear wheel hub, or into the central shaft. These devices include a number of toothed wheels, each of which corresponds to a given transmission ratio and is arranged along its own axis, so that it has a particularly elongated shape along the direction of its axis. However, these devices have various drawbacks.

[0008] Devices integrated into the hubs of the drive wheels are not suitable for retrofitting, i.e. they generally cannot be easily retrofitted to modernize existing vehicles, especially those based on older technology. In fact, their installation requires the wheels to be replaced or adapted to be suitable for assembly, which is very difficult for the user to carry out. Furthermore, since the gearbox-integrated hub replaces the normal hub and becomes part of the wheel, in case of wheel damage, a quick recovery of the wheel and gearbox is only possible if the second wheel is also equipped with a gearbox, which significantly increases costs.

[0009] Furthermore, devices built into the drive wheel hubs reduce the dynamic balance of the vehicle by placing the entire weight on the rear wheels.

[0010] On the other hand, the devices integrated into the central shaft require a specially shaped frame for their installation, so that they can only be replaced by identical devices, limiting the user's freedom of choice. Moreover, for the same reason, these devices do not offer the possibility of retrofitting.

[0011] Furthermore, devices integrated into the wheel hub and into the central shaft of the type described above make the introduction of a pedal-assist motor disadvantageous or impossible, in particular due to the axial size of the gear change device due to its arrangement along the axis of the toothed wheel corresponding to the various gear ratios.

[0012] In fact, known types of gearbox arrangements for installation on the hubs of the driving wheels completely occupy the space normally used for installing the motor, forcing the use of unconventional and expensive motors for installation on the central axle or on separate wheels (usually the front wheels). On the other hand, an arrangement integrated on the central axle would not be possible to integrate with a coaxial motor, since the integrated arrangement would be too long to be placed between the cranks. For this reason, the motor must be installed separately on the hubs of the driving wheels (typically the rear wheels), creating similar problems for the weight distribution of the vehicle. This is even worse if the electric battery is mounted above the driving wheels.

[0013] German patent application 740086 describes a gearbox for vehicles having a central driven shaft on which are keyed several central driven gears with variable diameters. A drive shaft, which is coaxial with the driven shaft, transmits the motion to the drive gears. Auxiliary shafts are arranged around the driven shaft. Each auxiliary shaft is keyed with a first toothed wheel adapted to mesh with the drive gears and a second toothed wheel adapted to mesh with one of the central gears. The number of driven shafts is equal to the number of central driven gears. One or the other of the auxiliary shafts is selected to transmit motion from the drive shaft to the driven shafts. Each auxiliary shaft provides a different gear ratio between the drive shaft and the central driven shaft, since the second pinion of each auxiliary shaft meshes with a different central driven gear. To bring the auxiliary shafts into an operating position corresponding to the desired transmission ratio, the auxiliary shafts are imposed with a radial movement towards the drive shaft and the central driven shaft. To this end, each auxiliary shaft is supported by pads which are radially movable relative to the axes of the drive shaft and the central driven shaft, the radial movement being effected by translation of the support pads of the auxiliary shafts and controlled by cams mounted on rings which rotate about the axes of the drive shaft and the central driven shaft.

[0014] US Patent Application No. 2019 / 0368579 (WO 2018095910) describes a gearbox that is particularly suitable for bicycles. This gearbox is, in some versions, integrated with an electric motor to form a pedal-assisted vehicle. Although this device overcomes many of the shortcomings of the prior art devices, there are still some limitations and room for improvement. In particular, the device described in this prior art publication, especially in its pedal-assisted version, cannot be freely inserted into an existing vehicle, for example an existing bicycle, but requires the creation of an ad-hoc frame. Summary of the Invention [Problem to be solved by the invention]

[0015] It would therefore be desirable to provide a gearbox with an integral motor that completely or partially overcomes the shortcomings of the prior art devices. [Means for solving the problem]

[0016] According to one aspect, described herein is a gearbox including an annular support on which gear pairs are rotatably supported for inputting motion to the gearbox. Each of the gear pairs includes a first gear adapted to receive the input motion and a second gear. The first gear and the second gear are coaxial and angularly coupled to each other for rotation in unison.

[0017] In fact, each of the gear pairs is rotatably supported on the annular support in the sense that it rotates about an axis common to the two coaxial gears, the axis being integral with the annular support, in other words, the annular support rotatably supports each gear pair.

[0018] Each of the gear pairs defines a transmission ratio different from the transmission ratios defined by the other gear pairs. The annular support is angularly movable about a selected axis, so that one gear pair can be selectively placed in an angular motion disengagement position relative to the gearbox. The gearbox further includes a mechanical connection between a second gear of the gear pair in an angular motion disengagement position to the gearbox and an output shaft passing through the annular support and having an axis of rotation parallel to or coinciding with the selected axis, i.e. an arrangement in which the output shaft and the annular bearing are coaxial. In fact, the output shaft also extends into the annular support. Essentially, in the gearbox of the invention, motion is introduced from the periphery through one of the gears carried by the annular support and transmitted towards the gearbox and up to the shaft passing through the annular support. For this purpose, advantageously, the first gear of each of the gear pairs and the annular support are positioned such that the first gear in an angular motion disengagement position receives an input motion peripherally from a pinion of a drive member, where the pinion is outside the annular support. In fact, in this way the input torque to the gearbox can be reduced, making it possible, for example, to use a lower torque motor, and the mechanical stresses on the annular support which, together with each gear pair, constitutes the input member of the gearbox are also reduced.

[0019] This can create a particularly compact and efficient drive system for some of the applications described herein, which can be easily retrofitted to existing vehicle frames if required.

[0020] In a practical embodiment, the mechanical connection comprises a gear train, which may typically constitute a reduction gear.

[0021] In some embodiments, the mechanical connection includes a first ring gear meshing with a second gear of the gear pair in an angular disengagement position at the input to the gearbox. Preferably, the ring gear is a ring gear having a plurality of external teeth and has an axis of rotation passing through the annular support, e.g., coincident with or parallel to a selected axis about which the annular support rotates.

[0022] The first ring gear may be part of a reduction gear train or a speed-up gear train depending on the torque required at the output and the torque available by the source of motion to transfer motion to the gearbox.

[0023] If the mechanical connection comprises a reduction unit, this may comprise a first ring gear and may have the form of a planetary gear mechanism. In a practical embodiment, the first ring gear constitutes the planet carrier of the planetary gear.

[0024] The possibility of using a gearbox with a lower reduction ratio or (depending on the circumstances) a gearbox is not excluded.

[0025] In an advantageous embodiment, the annular support and the first ring gear are coaxial or parallel and closely spaced apart, such that the first ring gear can mesh with the respective second gear of the gear pair at any angular position of the annular support.

[0026] Further advantageous features and embodiments of the gearbox are described below with reference to the accompanying drawings and the appended claims.

[0027] According to a further aspect, the subject matter of the invention also includes a powertrain for a vehicle, comprising a motor having a drive shaft with a pinion, and a gearbox as described above and in more detail below. Advantageously, in the embodiments described herein, the pinion has an axis of rotation external to the annular support, whereby motion is input to the periphery of the gearbox via a first gear of the gear pair in a motion disengagement position.

[0028] Advantageously, the annular support of the gearbox may be arranged to selectively bring a first gear of one of the gear pairs into mesh with the pinion depending on the required transmission ratio by rotation of the annular support about a selected axis, the selective rotation being free in the sense that it is not limited to a single circumferential angle (360°).

[0029] Further advantageous features and embodiments of the powertrain are described below with reference to the accompanying drawings and the appended claims.

[0030] The invention also relates to a vehicle including a powertrain as described above.

[0031] In particular, the vehicle may be a traction-assisted vehicle, i.e. a propulsion-assisted vehicle, for example a pedal-assisted bicycle.

[0032] Specifically, according to some embodiments, the invention relates to a vehicle including a frame, at least one driving wheel, at least one operating wheel, a motor including a drive shaft and a pinion rotated by the drive shaft, and a gearbox interposed between the motor and the driving wheel. The gearbox includes an annular support on which an input gear pair is rotatably supported. Each of the gear pairs includes a coaxial first gear and a second gear that are angularly coupled to each other for rotation together. Each of the gear pairs defines a transmission ratio that is different from the transmission ratios defined by the other gear pairs. The annular support is angularly movable about a selection axis to selectively place one gear pair in an active position such that a first gear of the gear pair in the active position meshes with a pinion of the drive shaft. Additionally, the vehicle includes a mechanical connection between a second gear of the gear pair in the active position and an output shaft having an axis of rotation that passes through the annular support and is parallel to the selection axis. A device for rotating the annular support to effect a shift, i.e., a change in the transmission ratio, may be provided. This allows the annular support to be selectively positioned in a plurality of angular positions. At each angular position, a respective gear pair is in an active position with the respective first gear meshing with the pinion of the drive shaft. The control device can be automatic, semi-automatic, servo-assisted, or fully manual. Preferred embodiments provide an automatic or semi-automatic gear change system.

[0033] Further features and embodiments of the vehicle are described below with reference to the accompanying drawings and the appended claims.

[0034] The present invention also relates to a method of converting a human-powered vehicle, such as a bicycle, into a power-assisted or propulsion-assisted vehicle, comprising replacing the muscle force application mechanism to at least one drive wheel of the vehicle with a power train as described above and in more detail in the various embodiments below.

[0035] In this specification and the appended claims, a pedal-assist, traction-assist, or propulsion-assist vehicle generally refers to a vehicle having a motor, e.g., an electric motor, coupled via a suitable coupling mechanism with a mechanism that allows torque generated by the muscular force of a user of the vehicle or multiple users of the vehicle to be applied simultaneously to the drive wheel or wheels of the vehicle.

[0036] Torque may be generated by the user's lower or upper limbs, typically by rotating or swinging a pedal crank, lever, arm, handlebar, or other member to apply muscular force.

[0037] Thus, a vehicle with "pedal assist" or traction or propulsion assist, as understood in this specification, also includes vehicles in which muscle forces are generated by the user's upper extremities (arms) and not necessarily the lower extremities (legs). [Brief description of the drawings]

[0038] The invention will become clearer from the following description and the accompanying drawings, which show, by way of example, non-limiting embodiments of the invention. [Figure 1] FIG. 1 is a side view of a bicycle including a gearbox according to a first embodiment of the present invention integrated with a pedal-assist motor. [Diagram 2] FIG. 2 is a plan view taken along line II-II in FIG. [Diagram 3] FIG. 3 is a partial side view taken along line III-III in FIG. 2. [Figure 4] FIG. 6 is a cross-sectional view taken along line IV-IV in FIG. 5. [Diagram 5] FIG. 5 is a cross-sectional view taken along line VV in FIG. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. [Figure 7] FIG. 1 is a functional block diagram of a control system for a vehicle having a shift and pedal assist system. [Figure 8]8 is a plan view similar to FIG. 2 of the second embodiment taken along line VIII-VIII in FIG. 2; [Figure 9] IX-IX of the second embodiment of FIG. 4, taken along line IX-IX; FIG. [Figure 10] 5 is a cross-sectional view similar to that of FIG. 6 of the second embodiment taken along line XX of FIG. 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] In the following, the gearbox is described as being applied to a pedal-assisted bicycle. It is noted that, although this application is particularly advantageous, the gearbox described herein may have other applications. For example, the gearbox may be used in vehicles other than two-wheeled bicycles, such as three-wheeled or four-wheeled vehicles, or in hand-push vehicles. Furthermore, the gearbox may also find advantageous application in vehicles that are driven only by a motor associated with the gearbox, i.e. that do not have pedal cranks or other members for applying muscle power.

[0040] In figures 1 to 7 a first embodiment of a gearbox for a pedal-assisted bicycle according to the invention is shown. Figure 1 shows a side view of the bicycle 1, and figure 2 shows a top view thereof. The bicycle 1 comprises a frame 3, a rear drive wheel 5, a front operating wheel 7 and a handlebar 9. In the example shown in the figures, the bicycle 1 is a pedal-assisted bicycle. Reference number 11 indicates as a whole an actuation device, here indicated as a power train. The actuation device comprises a motor, typically an electric motor 12, which will be described later, is driven by a battery or storage unit 13 and is controlled by a central control unit, which will be described later. Reference number 15 indicates a pedal crank with respective pedals 16 for applying the muscular force exerted by the user to the power train 11. The drive unit 11 comprises a toothed wheel for a chain, a so-called chain ring 19. Around this chain ring 19 a transmission chain 17 is threaded. This transmission chain 17 transmits the motion to a pinion 21, which is keyed to the rear drive wheel 5.

[0041] The powertrain 11 also includes a gearbox between the electric motor 12 and the chain ring 19. The powertrain 11 further includes a mechanism that allows combining the drive torque generated by the electric motor 12 with a drive torque generated by muscle force applied via the pedal crank 15. The gearbox and the drive torque combining mechanism will be described below with reference to Figures 3 to 7.

[0042] As shown particularly in Figures 3-6, the powertrain includes a housing generally indicated by reference numeral 23. This housing may consist of several parts assembled together. Inside it are housed the motor 12, the gearbox and the combination of the drive torque generated by the motor 12 and the pedal crank 15 with the opposing pedal 16. The housing 23 is integral with the frame 3.

[0043] In the embodiment shown, the housing 23 comprises a bushing 23A housed in a cylindrical part 3A of the frame 3. The bushing 23A forms the seat of the bottom bracket of the bicycle 1, i.e. the assembly including the pedal crank 15, the pedals 16 and the shaft or pin joining the pedal crank 15, as will be explained below.

[0044] The motor 12 has an output shaft 25 to which a pinion 27 is keyed. The pinion 27 may be fixed to the shaft 25 by a keyway or other type of coupling. Alternatively, the pinion 27 may be formed integrally with the shaft 25. The line XX indicates the axis of rotation of the motor 12 and the relative shaft 25.

[0045] The pinion 27 transmits the torque, and therefore the motion, generated by the motor 12 to the chain rings 19 via a gearbox, generally designated by the reference number 29. The gearbox 29 comprises an annular support 31, which is supported in the housing 23 so as to be rotatable about an axis AA, which in the example shown coincides with the axis of rotation of the pedal crank 15 and constitutes a selection axis for selecting the transmission ratio, as will be described below. In the embodiment shown, the annular support 31 comprises two rings integral with one another. A number of gear pairs 33 are rotatably supported on the annular support 31, more particularly between the two rings which form its main part. In the example shown, the gearbox 29 has ten different transmission ratios, so that ten gear pairs are provided, designated successively from 33A to 33J. In the following, the reference number 33 denotes a general gear pair.

[0046] Each of the gear pairs 33 includes a first gear 35 and a second gear 37 (see in particular Figures 5 and 6). The two gears 35 and 37 of each gear pair are coaxial, integral with each other and may be made as a single member. Each of the gear pairs 33 is supported in a freely movable manner on the annular support 31. In this way, each of the gear pairs 33 is rotatably supported on the annular support 31. As shown in the figures, in fact, each of the gear pairs 33 has a shaft and is associated with a support bearing for rotatably supporting the gear pair on the annular support 31. The axis of each of the gear pairs 33 is stationary with respect to the annular support 31.

[0047] The first gears 35 of all the gear pairs 33 are coplanar with each other. Similarly, the second gears 37 of all the gear pairs 33 are coplanar with each other. More specifically, the first gears 35 are arranged on a plane perpendicular to the axis of rotation AA of the annular support 31 such that each first gear 35 can selectively mesh with a pinion 27 keyed to the shaft 25 of the motor 12. In the position shown in FIG. 4, the first gear 35 of the gear pair 33A meshes with the pinion 27. By rotating the annular support 31 about the axis AA, the first gear 35 of any one of the gear pairs 33 can be selectively meshed with the pinion 27.

[0048] The plane on which the second gears 37 are disposed is arranged so that the second gears 37 mesh with a first ring gear 41 that rotates about an axis AA. In the illustrated embodiment, the positions of the annular support 31, the gear pairs 33, and the first ring gear 41 are such that the second gears 37 of all gear pairs 33A-33J mesh with the first ring gear 41 simultaneously, as shown in particular in FIG.

[0049] The first ring gear 41 is supported by bearings 43 for free rotation about axis AA. The latter is arranged between the first ring gear 41 and a hollow shaft 45 constituting the output shaft of the gearbox 29 and the powertrain 11, as will be described later. The output shaft 45 rotates about axis AA and transmits motion to the chain 17 in unison with the chainring 19. The first ring gear 41 constitutes an element of a planetary gear mechanism, generally designated by reference number 47. It receives motion from the pinion 27, via one of the gear pairs 33A-33J, and transmits it, with an appropriate reduction ratio, via the output shaft 45 to the chainring 19. The axis AA constitutes the axis of the planetary gear mechanism about which the components rotate, as will be described later.

[0050] The first ring gear 41 forms the planet carrier of the planetary gear mechanism 47. Two planetary units 51 are supported in a freely floating manner on the planet carrier consisting of the first ring gear 41. The number of planetary units 51 may differ from that shown in the figures. In a simplified embodiment, a single planetary unit 51 is sufficient. The use of two or more planetary units allows a better distribution of the forces involved.

[0051] Each planetary unit 51 includes a first toothed wheel 53 and a second toothed wheel 55 (see FIG. 5). The two toothed wheels 53 and 55 of each planetary unit 51 are coaxial and angularly interlocked with each other so as to rotate together about their respective axes. Each planetary unit 51 is supported by a bearing 71 so as to be freely movable on a planetary carrier constituted by a first ring gear 41. The first toothed wheel 53 of each planetary unit 51 meshes with a second ring gear 59 that is coaxial with the first ring gear 41. The second ring gear 59 constitutes the sun gear of the planetary gear mechanism 47 and is fixed with respect to the housing 23 and thus the frame 3 of the bicycle 1. A bearing 60 is arranged coaxially with the second ring gear 59 and forms a radial bearing for the hollow output shaft 45.

[0052] Therefore, when the first ring gear 41 constituting the planetary carrier of the planetary gear mechanism 47 rotates about the axis AA, the axis of the planetary unit 51 rotates about the axis AA, and the first toothed wheel 53 of the planetary unit 51 rolls on the second ring gear 59.

[0053] The second toothed wheel 55 of each planetary unit 51 meshes with a third ring gear 61 that is coaxial with the first ring gear 41 and the second ring gear 59. The third ring gear 61 constitutes the sun gear of the planetary gear set 47 and is coaxial with the axis AA. While the second ring gear 59 is fixed with respect to the housing 23, the third ring gear 61 is supported rotatably about the axis AA.

[0054] Generally, the third ring gear 61 is mechanically connected to the hollow output shaft 45 and transmits the rotational motion generated by the motor 12 thereto. In some embodiments (not shown), the third ring gear 61 may be keyed to the output shaft 45. In contrast, in the illustrated embodiment, the mechanical connection between the third ring gear 61 and the output shaft is achieved through the interposition of a freewheel 62 (see FIGS. 5, 6) for purposes described below.

[0055] When the planet carrier constituted by the first ring gear 41 rotates about the axis AA of the planetary gear set 47, the second toothed wheel 55 transmits the rotational motion with a reduction defined by the planetary gear set 47 and the third ring gear 61 to the third ring gear 61. This motion is transmitted via the hollow output shaft 45 to the gearbox 19 and from there via the chain 17 to the rear drive wheels 5.

[0056] In general, the vehicle 1 may be an electric motor vehicle that moves by power provided by the motor 12. In this case, the freewheel 62 may be replaced by a fixed torsional connection between the output shaft 54 ​​and the third ring gear 61. Also, the output shaft 45 may be solid rather than hollow.

[0057] On the other hand, in the embodiment shown in the figures, the vehicle 1 is a pedal-assisted bicycle in which forward motion is also obtained by the user's muscular force, via the pedal cranks 15 and the pedals 16. The two pedal cranks 15 are fixed to the ends 63A of a pin 63. Its axis coincides with the axis of rotation AA of the components of the planetary gear mechanism 47 and the annular support 31. The pin 63 constitutes a transmission shaft for the drive torque generated by the muscular force, which can be utilized in addition to or instead of the drive torque transmitted by the drive shaft 25 to move the vehicle 1 forward, and is therefore referred to below as the auxiliary shaft. The auxiliary shaft or journal 63 is rotatably supported in the bush 23A by a bearing 65. It passes through the hollow output shaft 45, which is supported there by a bearing 67, such as a needle roller bearing. In this way, the auxiliary shaft 63 and the output shaft 45 can rotate relative to each other about a common axis AA.

[0058] However, the auxiliary shaft 63 and the hollow output shaft 45 are connected to each other by a second freewheel 69 so that under certain conditions the hollow shaft 45 can rotate freely around the auxiliary shaft 63 and under other conditions the auxiliary shaft 63 can rotate the hollow output shaft 45.

[0059] The assembly including the motor 12, the gearbox 29, the bottom bracket including the auxiliary shaft 63, and the pedal crank 15 with the pedals 16 works as follows: The desired transmission ratio can be set manually or automatically by rotating the annular support 31 and selecting the gear pairs 33 required to obtain the transmission ratio. The drive torque generated by the motor 12 is transmitted to the gearbox 19 and from there to the rear drive wheel 5 via preselected gear pairs 35, 37. These gears 35, 37 are in an angular disengaged or active position with the respective first gears 35 meshing with the pinions 27. The torque is transmitted via the second gear 37 to the first ring gear 41 (constituting the planet carrier of the planetary gear set 47) and from there to the third ring gear 61 via toothed wheels 53, 55. When the auxiliary shaft 63 is stationary or rotates at an angular velocity lower than that of the third toothed wheel 61, the motion is transmitted by the auxiliary shaft 63 via the first freewheel 62 to the output shaft 45 and thus to the gearbox 19.

[0060] The second freewheel 69 enables the output shaft 45 to rotate relative to the auxiliary shaft 63 and exceed it in angular velocity.

[0061] When the user, by means of the pedal crank 15 and pedals 16, rotates the auxiliary shaft 63 at an angular velocity greater than the angular velocity of the third ring gear 61, the auxiliary shaft 63 is torsionally coupled to the output shaft 45 by the second freewheel 69, causing the two shafts 63, 45 to rotate together, while the first freewheel 62 torsionally releases the auxiliary output shaft 45 relative to the third ring gear 61, allowing the shaft 45 to rotate faster than the third ring gear 61.

[0062] The gear ratio between the electric motor 12 and the output shaft 45 can be changed by gradually rotating the annular support 31 and positioning one of the multiple gear pairs 33A-33J supported freely by the annular support 31 in an active position, i.e., a motion disengagement position (the position where the gear pair 33A is located in the figure).

[0063] The powertrain 11 described above can be easily integrated into newly built bicycles and can also be used as a retrofit to upgrade existing bicycles. In fact, the complete set of components (motor, gearbox including planetary gear mechanism) can be accommodated in a normal existing bicycle frame without modification. The seat 3A, which is normally provided in the frame 3 to accommodate a conventional bottom bracket of a bicycle, can accommodate the bushing 23A of the seat 23 without modification.

[0064] Thus, the powertrain 11 can be used to convert a conventional bicycle into a pedal-assisted bicycle, with an automatic or manual gear change system. In particular, as will be described below, the powertrain 11 can be provided with a control unit and suitable sensors, via which the drive mode can be set so that the control unit controls the gearbox and appropriately manages the power flow.

[0065] Rotation of the annular support 31 to set the desired transmission ratio can be performed manually using a suitable mechanism for transmitting movement from a lever or control knob located on the handlebar to the annular support 31. However, in a preferred embodiment, to facilitate the operation of changing the transmission ratio, and possibly automatically by a control unit, the gearbox can include a device for rotating the annular support 31, generally designated by reference numeral 71. This rotation device can be as described in U.S. Patent Application Publication No. 2019 / 0368579 (WO 2018095910), the entire contents of which are incorporated herein by reference.

[0066] In the embodiment shown in the figures, the rotating device 71 comprises an actuator, for example an electric motor 73. It rotates a shaft 75, on which an axle 80, integral with the molded disk 77, is keyed about the axis YY. The latter cooperates with the annular support 31 through a pin 79 and two crescent or semicircular cams 81. The pin 79 is adapted to fit into a radial groove 83 of the annular support 31, the semicircular portion 81 being adapted to cooperate with a complementary shaped recess 31A provided on the ring forming the annular support 31. The annular support 31 has, on the two rings which compose it, a number of recesses 31A equal to the number of gear pairs 33A-33J and a number of radial grooves 83 equal to the number of gear pairs 33A-33J. Each rotation of the molded disk 77 rotates the annular support 31 of the gear box 29 by one pitch. Thus, at the meshing position of the gear pair 33 with the pinion 27, a displacement of the adjacent gear pair is performed. An absolute encoder 85, mechanically connected to the shaft 75 via a gear chain 87 with the appropriate transmission ratio, stores the angular position of the disk 77 and thus of the annular support 31, even in the event of a power failure. In this way, the central control unit 89 can always have information about which transmission ratio is engaged, i.e. which of the various gear pairs 33 are in the active position meshing with the pinion 27.

[0067] Since the gear changing operation requires a complete rotation of the disc 77 about the axis YY, in some embodiments a sensor 91, for example a Hall sensor, cooperating with a magnet 93 integral with the disc 77 is provided. Via this sensor the central control unit 89 can verify that the gear changing operation is complete.

[0068] 7 shows diagrammatically the sensors and central control unit 89 for managing the vehicle 1. It shows an absolute encoder 85 identifying the engaged gear wheel, a sensor 91, the gear-changing actuator 73, a force sensor 95 detecting the force exerted by the user on the pedal crank 15, an angular velocity sensor 97 detecting the angular velocity of the auxiliary shaft 63 and the pedal crank 15, a speed sensor 99 detecting the speed of the vehicle 1, and an electrical energy store 13.

[0069] Components including a monitor or display 101, a button set or other interface 103 for setting the vehicle advancement system management mode, and a second interface 105 for non-automatically setting the transmission ratio if desired, may be located on the handlebar 9.

[0070] The arrangement of the electrical and electronic components described above allows a series of management methods of the electric motor 12 and the gearbox 29 to be realized. The management of the performance and type of operation of the powertrain 11 may be carried out by a central control unit 89 constituting the central node of the connection network between the various electrical devices described above, as shown in Figure 7. It is noted that the performance may be managed through various command and control modes, some examples of which are given below, but are not limited to them.

[0071] According to a possible manual management method, the transmission ratio is selected manually by acting on the gearbox 29, with the possibility of freely selecting the available transmission ratios. The set transmission ratio is detected by the absolute encoder 85 and displayed on the display 101. This manual control can be associated with the possibility of manually selecting from several constant performance levels of the motor 12. These performance levels can also be displayed on the display 101. In this type of manual management of the motor 12 and the gearbox 29, the energy input to the device via the auxiliary shaft 63 is added to the energy input from the electric motor 12. Together they contribute to determining the forward speed of the vehicle 1 up to the achievement of the maximum permissible speed. For this, a constant torque selected by the user and generated by the motor 12 is utilized. The power supply to the motor 12 is gradually reduced and is finally cut off when the vehicle reaches the maximum permissible speed detected by the speed sensor 99.

[0072] According to another semi-automatic management method, the gearbox 29 can operate automatically. This can be combined with a manual selection of a constant torque level delivered by the electric motor 12, with the possibility of selecting several motor performance levels displayed on the display 101. In this semi-automatic command and control mode, the automatic management of the gearbox 29 relies on the result of an algorithm that tends to reach the maximum permissible speed of the vehicle 1, within the range allowed by the drive torque limit set by the user for the electric motor 12, and processes the data flowing to the central control unit 89, in particular the rotational speed of the electric motor 12, the speed of the vehicle 1, the current absorption of the electric motor 12. For this purpose, the electric motor 12 can be associated with respective sensors, in particular a speed sensor, interfaced with the central control unit 89.

[0073] In some embodiments, the electric motor 12 may be a brushless motor. In an embodiment, the motor 12 may already be provided with all the necessary sensors, in particular a speed sensor. In Fig. 7, the motor speed sensor is not shown, but is integrated into the motor itself, i.e. forms an integral part of the motor 12 instrumentation.

[0074] A further semi-automatic management method allows the opposite case to be provided in the same automated application as described above, i.e. automatic management of the level of torque provided by the electric motor 12 and manual control of the gearbox 29.

[0075] According to yet another automatic management mode, an automatic control of the gearbox 29 and the electric motor 12 can be provided via algorithms executed on the central control unit 89. This can for example be advantageous in saving electrical energy. In this fully automated command and control mode, certain algorithms process the data flowing to the central control unit 89 via the aforementioned sensors and return information useful for the command of the gearbox and the control of the electric motor 12. Now, a compensation management mode of mechanical energy is supplied to the device via two different input paths: the pedal 16 and the motor 12. This mode complements the energy values ​​supplied to the device via the auxiliary shaft 63 and the pedal crank 15 and the energy values ​​introduced via the electric motor 12, giving priority to the energy from the auxiliary shaft and keeping the sum of the two energies always equal to the sum of the energy supplied to the device, set by the user via the selection of the desired energy level selected on a predefined scale.

[0076] The energy, and therefore the power, of the motor 12 has a maximum value allowed by standards or the equipment manufacturer, and the motor management operates within this value, with further limits set via the operating modes set by the user, as described above.

[0077] That is, in a manual or semi-automatic management method, the user or central control unit applies a constant torque level to the motor 12 and the maximum allowable power limit that may be reached is controlled by the central control unit 89, whereas in a fully automatic mode the performance of the motor 12 varies between zero and the maximum possible or allowed values, in both torque and power, depending on the performance level selected by the user and the muscle force torque applied.

[0078] In this last fully automatic mode, a larger amount of energy from the pedal crank 15 corresponds to a smaller amount of energy from the electric motor 12, up to the limit condition of the energy being introduced entirely via pedal actuation.

[0079] In addition to balancing the energy sources described above, the fully autonomous management mode pursues the objective of maximizing vehicle autonomy through the selection of gear ratios, which are appropriately selected to keep the motor 12 in a rotational regime close to maximum efficiency and minimum energy consumption.

[0080] As mentioned above, in the automatic command and control mode, data is required regarding the energy input via the auxiliary shaft 63. For this purpose, a force sensor 95 is provided which detects the force acting on the auxiliary shaft 63 via the pedal crank 15. The output data from the force sensor 95, together with the value of the rotational speed of the auxiliary shaft 63 detected by the speed sensor 97, make it possible to calculate the value of the energy supplied by the muscle force path.

[0081] A further embodiment of a gearbox according to the invention is shown in figures 8, 9 and 10. Figures 4 and 7 show parts which are the same in the further embodiment. Like reference numbers indicate parts which are identical or equivalent to those described with reference to figures 1 to 7 and which will not be described in detail again.

[0082] The embodiment of Figures 8-10 differs from the embodiment of Figures 1-7 mainly in the way in which the muscle forces generated by the user via the pedal crank 15 and pedals 16 are introduced into the powertrain.

[0083] In the embodiment of Figures 8 to 10, the auxiliary shaft 63 is supported in the hollow output shaft 45 and in the bush 23A by means of bearings 65 and 67, but no connection by means of a second freewheel 69 is provided. Furthermore, the third ring gear 61 is keyed directly to the hollow output shaft 45 and rotates integrally therewith, regardless of the rotational speed of the motor 12 and the pedal crank 15. Indeed, for example in the embodiment of Figures 8 to 10, the third ring gear 61 is formed integrally with the hollow output shaft 45.

[0084] The transmission of torque generated by the muscular force exerted by the user via the pedal crank 15 is carried out via the motor 12. Indeed, in this embodiment, a first freewheel / bearing 162 is keyed to the drive shaft 25 and is interposed between the drive shaft 25 and the rotor 12R of the electric motor 12. The reference 12S indicates, in a schematic manner, the stator of the electric motor 12. A second freewheel / bearing 169 is keyed to the shaft 25 and is interposed between the drive shaft 25 and an auxiliary gear 171, which is coaxial with the drive shaft 25. The auxiliary gear 171 meshes with an auxiliary ring gear 173, which is keyed to the auxiliary shaft or pin 63 that receives the motion from the pedal crank 15. The auxiliary ring gear 173 is housed in a protective casing 175.

[0085] The above-mentioned components combine the motion of the pedal crank 15 and the motion of the auxiliary pin or shaft 63 with the motion imparted by the motor 12 in the following way: When the pedal crank 15 rotates due to the thrust exerted by the user's muscles, the auxiliary shaft 63 rotates about the axis AA. This rotation is transmitted to the freewheel / bearing 169 via the auxiliary ring gear 173 and the auxiliary gear 171. This transmits the motion from the auxiliary gear 171 to the drive shaft 25 when the angular velocity imparted to the auxiliary gear 171 is greater than the angular velocity of the rotor 12R of the motor 12. In this condition, the torque is transmitted to the pinion 27 via the second freewheel / bearing 169 and the shaft 25, and the first freewheel / bearing 162 releases the rotation of the rotor 12R.

[0086] On the other hand, if the angular velocity of the rotor 12R of the motor 12 is higher than the angular velocity applied to the auxiliary gear 171 by the pedal crank 15, the second freewheel / bearing 169 angularly decouples the auxiliary gear 171 from the drive shaft 25 and the first freewheel / bearing 162 transmits the torque from the rotor 12R to the drive shaft 25 and from there to the pinion 27.

[0087] That is, the embodiment shown in Figures 8-10 operates similarly to the embodiment shown in Figures 1-7 when the angular velocity of the motor 12 exceeds the angular velocity of the auxiliary gear 171. Also, when the velocity applied by the user via the pedal crank 15 is such that the angular velocity of the auxiliary gear 171 exceeds the angular velocity of the motor, muscle force no longer passes directly from the pin or auxiliary axle 63 to the hollow shaft output gear 45, but rather through the kinetic chain of the auxiliary ring gear 173, the auxiliary gear 171, the drive shaft 25, the pinion 27, and the gearbox 29 to the output shaft 45 and thence to the chainring 19.

[0088] From the viewpoint of mechanical efficiency, the embodiment shown in Figures 8 to 10 is disadvantageous compared to the embodiment shown in Figures 1 to 7. This is because part of the muscle force is dissipated in the above-mentioned kinetic chain from the pin or auxiliary shaft 63 through the drive shaft 25 and the gear box 29 having the relative reducer consisting of the planetary gear mechanism 47 to the output shaft 45. On the other hand, the embodiment shown in Figures 8 to 10 has the advantage that the user can change the gear ratio by the gear box 29 even when using the vehicle 1 only by pedal operation without using the power of the motor 12.

[0089] In both of the above-mentioned embodiments, the annular support 31 with the gear pairs which constitute the moving elements with respect to the change of the transmission ratio is placed upstream of the reducer and not downstream, and therefore at low torque, unlike other transmissions in similar applications, which reduces the stresses applied to the moving components of the transmission.

[0090] The device provided with the electric motor 12 can be used both as an OEM device for vehicles and as a retrofit upgrade for vehicles that already have or do not have a conventional gearbox device with multiple chainrings and pinions. In fact, the device described herein can be configured to be mounted on a standard frame and replace other possible components of the motion transmission to the wheels. In this way, it becomes possible to convert these vehicles into pedal-assisted vehicles, or more generally into propulsion-assisted or traction-assisted vehicles.

[0091] The device described herein, unlike conventional gearboxes, does not require any adjustments during installation on the vehicle or during use and therefore does not require any special skills from the installer, particularly the user.

[0092] Maintenance requirements are very limited to regular checking of the oil level in the gearbox (but no oil is consumed) and cleaning and lubricating the chain 17.

[0093] In some embodiments, the chain 17 may advantageously be replaced by a toothed belt or other continuous flexible member, which allows further reduction in vehicle maintenance. The possibility of transmitting motion to the shaft transmission member using possible suitable transmission joints is not excluded.

[0094] By maximizing the attributes of duration and reliability, the system is suitable for use in vehicles with intensive use that require functional safety of the entire motion transmission. Consider for example vehicles such as bicycle taxis, three-wheelers, four-wheelers, torpedoes, urban rickshaws, cargo bikes, etc. These vehicles require high reliability and do not allow easy access to repair or intervene in the mechanical transmission during use, for example if the chain simply breaks off, as occurs with conventional transmission systems.

[0095] Furthermore, since the chain 17 always runs in alignment, i.e. with the driving wheel pinion and the chain ring 19 always in the same plane, it is not subject to the premature wear problems typical of systems with variable speed gears. The chain 17 can therefore be wider than the chains conventionally used in vehicles with variable speed gears, which further extends the operating period and minimizes the need for interventions to replace worn parts.

[0096] As a result, the chain drive (chain rings 19, chain 17, sprockets 21) typically wears out over a much longer period of time. Furthermore, this wear in the transmission does not affect the proper functioning of gear changes, as occurs in conventional derailleur systems.

[0097] The system described herein has a minimal weight due to the presence of the gearbox and in particular the use of a small electric motor, yet there is sufficient power generated at relatively low speeds, which has further beneficial effects on the complexity, weight and performance of the gearbox / reduction gear system.

[0098] An additional advantage is that by locating the motor 12 below the bottom bracket of the vehicle (i.e., below axis AA), the center of gravity of the entire vehicle is lowered, thereby significantly improving the dynamic characteristics and handling of the vehicle 1.

[0099] In order to maximize the dynamic characteristics of the vehicle, it is advantageous to position the central control unit 89, and in particular the battery 13, below the diagonal tube 3B (FIG. 1) of the frame 3, so that the center of gravity is located at the minimum possible height.

[0100] The gearbox and relative reducer assembly is particularly advantageous, but not exclusively, when used for propulsion of bicycles or other saddle-mounted vehicles. In the advantageous embodiment described above, the gearbox and the respective reducer can be used particularly advantageously in the case of traction-assisted or propulsion-assisted vehicles, since the gearbox reduction system in vehicles with a pedal crank bottom bracket for muscular traction can be easily integrated. However, the possibility of using the gearbox with a relative reducer for other applications is not excluded. Here, a combination of a motion provided by a first power source, such as the motor 12 which transmits the motion to the gear pair 33, and a motion provided by an auxiliary power source via the auxiliary shaft 63 can be envisaged.

Claims

1. A gearbox (29), (a) an annular support (31) on which gear pairs (33A-33J) for inputting motion to said gearbox (29) are rotatably supported, each of said gear pairs (33A-33J) includes a first gear (35) adapted to receive an input motion and a second gear (37), said first gear (35) and said second gear (37) being coaxial and angularly coupled to each other for unitary rotation; each of said gear pairs (33A-33J) defines a gear ratio different from the gear ratios defined by the other gear pairs; said annular support (31) being angularly movable about a selected axis to selectively position one of said gear pairs (33A-33J) in an angular disengagement position relative to said gearbox (29); An annular support (31); (b) a mechanical connection between the second gear (37) of the gear pair (33A-33J) in the angularly disengaged position to the gearbox (29) and an output shaft (45) having an axis of rotation (A-A) parallel to or coinciding with the selected axis, the output shaft (45) passing through the annular support (31); A gear box (29).

2. 2. A gearbox (29) according to claim 1, wherein the first gear (35) of the gear pair (33A-33J) and the annular support (31) are arranged in a position such that the first gear (35) in the angular motion disengagement position peripherally receives an input motion from a pinion (27) of a drive member (12), the pinion (27) being external to the annular support (31).

3. 3. A gearbox (29) as claimed in claim 1 or 2, wherein the annular support is adapted to rotate about the selected axis without rotational angle restriction.

4. The gearbox (29) according to any one of claims 1 to 3, wherein the mechanical connection includes a first ring gear (41) meshing with at least the second gear (37) of the gear pair (33A-33J) in the angular motion disengagement position at the input to the gearbox (19).

5. 5. The gearbox (29) of claim 4, wherein the first ring gear (41) has external teeth and a rotation axis passing through the annular support (31), the rotation axis being parallel to or coincident with the selected axis.

6. The gearbox (29) according to claim 4 or 5, wherein the mechanical connection comprises a reducer (47), the reducer (47) comprising the first ring gear (41).

7. The gearbox (29) according to claim 5 or 6, wherein the annular support (31) and the first ring gear (41) have parallel or same axes, and the first ring gear (41) meshes with the second gears (37) of each of the gear pairs (33A to 33J) at any angular position of the annular support (31).

8. 8. The gearbox (29) according to claim 6 or 7, wherein the reducer (47) comprises a planetary gear set, the first ring gear (41) constituting a planet carrier of the planetary gear set (47) which rotates about a central axis of the planetary gear set (47) coinciding with the axis of the output shaft (45), and at least one of the planet carriers comprises first and second toothed wheels which are freely movable supported on the planet carrier and are coaxially connected angularly to one another.

9. 9. A gearbox (29) according to claim 8, wherein the first toothed wheel (53) of the planetary set (51) meshes with a second ring gear (5) coaxial with the first ring gear (41) fixed relative to a bearing structure, and the second toothed wheel (55) of the planetary set (51) meshes with a third ring gear (61) rotatable about the axis of the output shaft (45), a mechanical coupling being arranged to transmit motion from the third ring gear (61) to the output shaft (45).

10. 10. A gearbox (29) according to claim 9, wherein the mechanical coupling between the third toothed ring gear (61) and the output shaft (45) comprises a first freewheel (62), preferably the output shaft (45) being a hollow shaft, an auxiliary shaft (63) for input of motion from an auxiliary motion source extends coaxially with the output shaft (45), and a second freewheel (69) is arranged between the hollow output shaft (45) and the auxiliary shaft (63).

11. 11. A gearbox (29) according to any one of claims 1 to 10, further comprising a device (71) for rotating the annular support (31), the device (71) being adapted to selectively position the annular support (31) in a plurality of angular positions, in each of which one of the gear pairs is in an active position.

12. A powertrain (11) for a vehicle, comprising: a motor (12) having a drive shaft (25) with a pinion (27); A gearbox (29) according to any one of claims 1 to 11, Including, the annular support (31) of the gearbox (29) is arranged such that rotation of the annular support (31) about a selected axis selectively brings a first gear (35) of one of the gear pairs (33A-33J) into mesh with the pinion (27) according to the required transmission ratio, the pinion having an axis of rotation outside the annular support (31), whereby motion is input to the periphery of the gearbox via the first gear (35) of the gear pair (33A-33J) in a motion disengagement position, Powertrain (11).

13. 13. The powertrain (11) of claim 12, wherein the motor (12) is an electric motor including a stator (12S) and a rotor (12R), a first freewheel (162) is interposed between the rotor (12R) and the drive shaft (25), and a second freewheel (169) is interposed between the drive shaft (25) and an auxiliary gear (171) coaxial with the drive shaft (25) and adapted to receive torque from an auxiliary power source, the second freewheel (169) being keyed to the drive shaft (25).

14. 13. The powertrain (11) according to claim 12, wherein the auxiliary gear (171) meshes with an auxiliary ring gear (173) keyed to an auxiliary shaft (63), preferably coaxial with the axis of the output shaft, preferably the auxiliary shaft (63) being rotatably supported within the output shaft (45), and at both ends of the auxiliary shaft (63) members (15, 16) for applying muscular forces to the auxiliary shaft (63) are preferably keyed.

15. A vehicle (1), Frame (3); At least one drive wheel (5); At least one operating wheel (7); a motor (12) including a drive shaft (25) and a pinion (27) rotated by said drive shaft; a gear box (29) interposed between the motor (25) and the drive wheel (5); Including, The gearbox is configured as claimed in any one of claims 1 to 10, wherein the pinion (27) of the drive shaft (25) is arranged outside an annular support (31) of the gearbox, the annular support (31) being adapted to be arranged in a plurality of angular positions, whereby in each of the angular positions the gear pairs (33A-33J) are in an active position with a respective first gear (35) of the gear pairs (33A-33J) disengaged from the pinion (27) of the drive shaft, Vehicle (1).

16. 16. A vehicle (1) as claimed in claim 15, wherein the vehicle is a power assisted vehicle and includes an auxiliary shaft (63) to which a member (15, 16) for applying muscular force to the auxiliary shaft (63) is keyed, the auxiliary shaft being connected to an output shaft (45) via a system including a freewheel.

17. The motor (12) is an electric motor including a stator (12S) and a rotor (12R), The system including the freewheel comprises: a first freewheel (162) interposed between the rotor (12R) and the drive shaft (25); a second freewheel (169) keyed to the drive shaft (25) and interposed between the drive shaft (25) and an auxiliary gear (171) coaxial with the drive shaft (25), meshing with an auxiliary toothed wheel (173) keyed to the auxiliary shaft (63); Including, The auxiliary shaft (63) is coaxial with the axis of the output shaft (45) and is rotatably supported within the output shaft (45).

17. A vehicle (1) according to claim 16.

18. The vehicle (1) according to any one of claims 15 to 17, wherein the vehicle is a bicycle including a bottom bracket, and the output shaft (45) is coaxial with the bottom bracket.

19. A method for converting a human-powered vehicle (1) into a power-assisted vehicle, comprising the step of inserting a powertrain according to any one of claims 11 to 13 into a torque transmission line of driving wheels (5) of the vehicle (1).

20. 20. The method of claim 19, wherein the vehicle (1) is a bicycle and the powertrain is used in place of a bottom bracket of the bicycle.

Images