UNIT

DESCRIPTION TECHNICAL FIELD

[0001] The present invention relates to an electric saddle-type vehicle and a propulsion unit for a saddle-type vehicle. Embodiments described herein relate, in particular, to an electric propulsion unit provided with a differential and two axle- shafts for actuating two rear driving wheels, and to a saddle-type vehicle having two rear driving wheels and a tilting frame, to which one or more front steered wheels are connected.

BACKGROUND ART

[0002] Electric-drive vehicles are increasingly used in order to reduce emissions of polluting gases from internal-combustion engines. Electrically propelled vehicles of small sizes have been especially developed, in particular saddle-type vehicles.

[0003] For example, US8789639 discloses a saddle-type vehicle having an electric motor that actuates a pair of rear driving wheels. The vehicle has also a front axle with only one steered front wheel. For transmitting power to the two rear driving wheels, a differential with two axle-shafts is provided, in particular a left axle-shaft for actuating the left rear driving wheel, and a right axle-shaft for actuating the right rear driving wheel. An electric motor transmits motion to the housing of the differential through a complex and bulky gear transmission.

[0004] In these known vehicles, the transmission from the electric motor to the differential constitutes an expensive and bulky component, adversely affecting the overall cost, the weight and the fuel consumption of the vehicle, also due to non- negligible power losses in the transmission.

[0005] There is therefore a need for providing electric propulsion units and saddle- type vehicles that fully or partially overcome the drawbacks of the prior art propulsion units and vehicles. SUMMARY

[0006] According to a first aspect, a saddle-type vehicle is described comprising a tilting frame, at least one steered front wheel supported by the frame, and a propulsion unit. The propulsion unit comprises a casing; inside the casing, a differential is provided, connected to a left transmission axle-shaft and to a right transmission axle- shaft that are coaxial with each other and both rotating around a rotation axis. An electric motor is provided, integral with the casing and having a drive shaft with a rotation axis. The drive shaft is 90°-oriented with respect to the left axle-shaft and to the right axle-shaft. The propulsion unit is connected to a left rear driving wheel and to a right rear driving wheel through the left axle-shaft and the right axle-shaft, respectively. The left rear driving wheel, the right rear driving wheel and the propulsion unit are non-tilting relative.

[0007] As used herein, the terms “right” and “left” are merely conventional and have only descriptive purpose. They refer to the position relative to the driver, sitting on the saddle and facing the forward direction of the vehicle.

[0008] Thanks to the arrangement described above, a vehicle can be provided with a compact and efficient arrangement of the propulsion unit, with a limited number of mechanical members and therefore with less losses and high mechanical yield. The lower bulk allows not only lower costs but also reduced inertia.

[0009] In some embodiments, a flexible coupling is provided between the drive shaft and the bevel gear drive which transmits the motion to the housing of the differential. The flexible coupling protects the bevel gear drive against peaks. Moreover, thanks to the flexible coupling there is no need for very precise tolerances for the coupling between motor and transmission. Small errors in parallelism and orthogonality are balanced by the deformable elements, typically made of rubber, thus making the production of the parts of the propulsion unit easier and less expensive, and the installation thereof simpler.

[0010] In embodiments disclosed herein, the pinion of the bevel gear drive transmitting motion from the electric motor to the housing of the differential may be supported by support members installed in the casing and axially arranged in an intermediate position between the pinion and the first rotating member of the flexible coupling, with a particularly compact arrangement of small axial length. In particularly advantageous embodiments, the members supporting the pinion of the bevel gear drive are constituted by only one double-row bearing.

[0011] The casing of the propulsion unit may be constituted by two equal bodies coupled to each other along a median plane. This allows reducing the number of different parts to be manufactured for assembling the propulsion unit.

[0012] Further advantageous features and embodiments of the invention will be described in greater detail below with reference to the accompanying drawings and are defined in the attached claims, that form an integral part of the present description. BRIEF DESCRIPTION OF THE DRAWING

[0013] The invention will be better understood by following the description below and the attached drawing, showing a non-limiting embodiment of the invention. More specifically, in the drawing:

Fig. 1 is an axonometric view of a three-wheel vehicle with a propulsion unit according to the present description;

Fig. 2 is a side view of the vehicle of Fig. 1;

Fig. 3 is an axonometric view of propulsion unit of the vehicle of Figs. 1 and 2;

Fig. 4 is an axonometric view of the propulsion unit of Fig. 3, with a portion of the casing removed; Fig. 5 shows an enlarged detail from Fig. 4;

Fig.6 is a cross-section of the propulsion unit according to a plane containing the axis of the electric motor;

Fig. 7 is an axonometric view of a flexible coupling interposed between the electric motor and the differential of the propulsion unit; and Fig. 8 shows a cross-section of the propulsion unit and the rear driving wheels according to a plane containing the two axle-shafts of the wheels and the drive shaft.

DETAILED DESCRIPTION

[0014] Figs. 1 and 2 schematically show a three-wheel saddle-type vehicle 1, comprising a propulsion unit, according to the present invention. The saddle-type vehicle l is a so-called tilting or rolling vehicle, i.e. a vehicle that can lean to the right and to the left around a roll axis, for example while moving along a curved trajectory. More specifically, the saddle-type vehicle 1 has a tilting or rolling frame 3, to which a steered front wheel 5 is connected. The frame 3 is connected to a non-tilting rear part of the vehicle 1, as described below. The non-tilting rear part comprises a left rear driving wheel 7a and a right rear driving wheel 7b. In Fig. 1, the left rear driving wheel has been omitted better to view the propulsion unit 9, with which the vehicle 1 is provided and which will be described in greater detail below.

[0015] The frame 3 comprises a steering sleeve 11, where a steering column, integral with a handlebar 13, is housed. The front steered wheel 5 is connected to the steering column 12, through the interposition of a suitable suspension 15. In the embodiment illustrated in the figures, the suspension 15 comprises two spring-shock absorber units 15a e 15b, respectively. The number 17 indicates a saddle of the saddle-type vehicle 1 [0016] The propulsion unit 9 is connected to the frame 3 so that the frame can perform rolling movements, for example when turning, and springing movements relative to the rear driving wheels 7a, 7b that, together with the propulsion unit 9 and the front steered wheel 5, form the unsprung mass of the vehicle 1. In the embodiment illustrated in Figs. 1 and 2, the propulsion unit 9 is connected to the frame 3 through a connecting element 21 that is rigidly coupled to a casing 23 of the propulsion unit 9.

The connecting element 21 is coupled to the frame 3 through a roll joint 25 defining a roll axis X-X (Fig. 2), around which the frame 3 can rotate relative to the connecting element 21.

[0017] In this way, the frame 3, the front steered wheel 5 with the corresponding suspension 15, the handlebar 13, the steering column 12, the steering sleeve 11 and the saddle 17 can perform a rolling movement around the axis X-X with respect to the propulsion unit 9 and the rear wheels 7a, 7b, that are non-tilting, i.e. that do not lean when the vehicle turns, for example.

[0018] As shown for example in Fig. 2, the roll joint 25 is arranged approximately aligned with the propulsion unit 9 and ahead thereof relative to the forward moving direction of the vehicle. [0019] The roll j oint 25 and the connecting element 21 can rotate relative to the frame 3 thanks to a pitching joint 26 having a pitching transverse axis Y-Y, i.e. an axis directed in right-left direction (arrow L-R in Fig. 1), orthogonal to the forward direction (arrow F, Fig. 2) of the vehicle 1. A rear suspension 27 is provided to damp the springing movement between the roll j oint 25 and the frame 3. The transverse axis

Y-Y may intersect the roll axis X-X. The transverse axis Y-Y is arranged ahead of the roll joint 25 relative to the forward moving direction of the vehicle 1.

[0020] The details of the propulsion unit 9 are shown in Figs. 3 and following, and will be described in greater detail below. [0021] In the illustrated embodiment, the propulsion unit 9 comprises the casing 23, to which the connecting element 21 is rigidly coupled (not shown in Figs. 3 and following), and an electric motor 31, flanged to the casing 23. The axis of the electric motor 31 is indicated with A-A. The axis A-A is orthogonal to an axis B-B representing the common rotation axis of the left rear driving wheel 7a and of the right rear driving wheel 7b.

[0022] In some embodiments, the axis A-A of the electric motor is parallel to the roll axis X-X and, if necessary, coincident therewith.

[0023] Therefore, in practical embodiments the roll joint 25 may be aligned with the electric motor 31. [0024] In the illustrated embodiment, the casing 23 is formed by two components, respectively a left component 23a and a right component 23b, substantially equal to one another and coupled along a median plane of the vehicle 1.

[0025] A differential 33 is provided inside the casing 23; reference number 35 indicates the housing or planetary carrier thereof, see in particular Fig. 8. A crown gear 37 is integral with the housing 35. In a known manner, inside the housing 35 of the differential 33 one or more planet gears 36 are arranged, typically constituted by bevel gears, mounted idle on respective shafts radial relative to the rotation axis of the crown gear 37. The planet gears engage a left crown wheel 38a and a right crown wheel 38b. The crown wheels 38a, 38b are constituted by bevel gears, respectively integral with a left axle-shaft 39a (see Fig. 1) and a right axle-shaft 39b, whose common rotation axis is the axis B-B. The left axle-shaft 39a transmits the rotary motion to the left rear driving wheel 7a, and the right axle-shaft 39b transmits the rotary motion to the right rear driving wheel 7b.

[0026] The rotary motion is transmitted to the housing 35 of the differential 33 by a pinion 41 that is coaxial with the electric motor 31, and whose rotation axis is therefore the axis A-A. In advantageous embodiments, the axis A-A lies on a median plane of the vehicle 1.

[0027] A flexible coupling 43, shown in isolation in Fig. 7, may be provided along the line shaft connecting the electric motor 31 and the pinion 41. In advantageous embodiments, the flexible coupling 43 comprises a first rotating member 45 rotatingly coupled to a drive shaft (output shaft) 47 of the electric motor 31 , and a second rotating member 49 rotating around the axis of the drive shaft 47. The first rotating member 45 and the second rotating member 49 are joined by members adapted to damp torsional vibrations. In the illustrated embodiment, the mutual connection between the first rotating member 45 and the second rotating member 49 is provided by dumping members interposed between the first rotating member 45 and the second rotating member 49. Just by way of example, the dumping members are formed like elastic cylinders 51, inside which pins 53 are fastened, integral with the first rotating member 45 and housed in seats 55 integral to the second rotating member 49. The pins 53 are parallel to the rotation axis A-A of the electric motor 31. [0028] The second rotating member 49 is torsionally coupled to a shaft 59 integral with the pinion 41, for example through a profile provided in a hollow shaft 49a of the second rotating member 49 (see Figs. 6 and 7). Reference number 61 indicates the support members supporting the second rotating member 49 and the shaft 59 of the pinion 41. The support members 61 may be mounted in a sleeve 63 integral with a flange 65 formed by the central body 23 c, 23 d of the casing 23. In some embodiments, the support members 61 are constituted by only one double-row bearing, for example a double-row ball bearing or preferably a double-row roller bearing, to support bidirectional radial and axial loads.

[0029] In advantageous embodiments, a seal 62 is provided between the support members 61 of the rotating member 49 and the bevel gear drive formed by the pinion 41 and by the crown gear 37. Providing the seal 62 in this position is beneficial since the support members 61 are not immersed in lubricant bath. [0030] In this embodiment, the support members 61 of the pinion 41 are therefore arranged along the axis A-A in an intermediate position between the pinion 41 and the first rotating member 45 of the flexible coupling 43. The dumping members 53 and the seats 55 thereof are arranged around the support members 61, so as to reduce the axial bulk of the line shaft connecting the electric motor 31 and the pinion 41, to have a compact arrangement of the propulsion unit 9.

[0031] The propulsion unit 9, configured in this way, is particularly compact and has a reduced number of components. This results in cost reduction and increased efficiency of the propulsion unit of the invention with respect to prior art electric propulsion units.

[0032] In the illustrated embodiment, the vehicle 1 has only one front steered wheel 5. However, it is also possible to provide, with a similar configuration of the propulsion unit 9, a vehicle with two front steered wheels, connected to the frame 3 through a four-bar linkage system allowing the tilting movements of the frame 3.

[0033] The elements identified by the following clauses form specific object of the present invention:

Clause 1. An electric propulsion unit (9) for a saddle-type vehicle (1), comprising: a casing (23); inside the casing (23), a differential (33) connected to a left transmission axle- shaft (39a) and to a right transmission axle-shaft (39b), coaxial with each other and both rotating around a rotation axis (B-B); and integral with the casing (23), an electric motor (31) with a drive shaft (47) with a rotation axis (A-A); wherein the drive shaft (47) is 90°-oriented with respect to the left axle-shaft (39a) and to the right axle-shaft (39b).

Clause 2. The propulsion unit (9) of clause 1, wherein the drive shaft (47) is connected to the differential (33) through a shaft line comprising a flexible coupling (45).

Clause 3. The propulsion unit (9) of clause 2, wherein the flexible coupling (45) comprises a first rotating member (45) torsionally coupled to the drive shaft (47) and connected, through the interposition of a plurality of dumping members (51), to a second rotating member (49) rotatable around the axis (A- A) of the drive shaft (47).

Clause 4. The propulsion unit (9) of clause 3, wherein the second rotating member (49) is torsionally coupled to a pinion (41) engaging a crown gear (37) integral with a housing (35) of the differential (33).

Clause 5. The propulsion unit (9) of clause 4, wherein the pinion (41) is supported by support members (61) that are installed in the casing (23) and are axially arranged in an intermediate position between the pinion (41) and the first rotating member (45) of the flexible coupling (43).

Clause 6. The propulsion unit of clause 5, wherein the support members (61) are constituted by only one double-row bearing.

Clause 7. The propulsion unit of clause 5 or 6, comprising a seal (62) between the support members and a bevel gear drive (61) formed by the pinion (41) and the crown gear (37).

Clause 8. The propulsion unit (9) of clause 5, 6 or 7 wherein the dumping members (51) are arranged around the support members (61) of the pinion (41).

Clause 9. The propulsion unit (9) of one or more of the previous clauses, wherein the casing (23) is constituted by two equal bodies (23a, 23b) coupled to each other along a median plane.

Clause 10. A saddle-type vehicle (1) comprising: a frame (3); a left rear driving wheel (7a); a right rear driving wheel (7b); at least one steered front wheel (5); the propulsion unit (9) of one or more of the previous clauses, connected to the left rear driving wheel (7a) and to the right rear driving wheel (7b) through the left axle-shaft (39a) and the right axle-shaft (39b).

Clause 11. The vehicle (1) of clause 10, wherein the electric motor (31) is arranged ahead of the left axle-shaft(39a) and the right axle-shaft (3 lb) with respect to the forwards moving direction (F) of the vehicle (1).

Clause 12. The vehicle (1) of clause 10 or 11, wherein the casing (23) of the propulsion unit (9) is connected to the frame (3) of the vehicle (1) by means of a roll joint (25), adapted to allow a tilting movement of the frame (3) with respect to the left rear driving wheel (7a) and to the right rear driving wheel (7b); and wherein the left rear driving wheel (7a), the right rear driving wheel (7b) and the propulsion unit (9) are non-tilting.

Clause 13. The vehicle (1) of one or more of clauses 10 to 12, wherein the casing (23) of the propulsion unit (9) is connected to the frame (3) of the vehicle (1) by means of a pitching joint (26), adapted to allow a pitching movement of the propulsion unit (9) with respect to frame (3) around a transverse axis (Y-Y).

Clause 14. The vehicle (1) of clause 13, comprising a rear suspension (27) connected at the top to the frame (3) and at the bottom to the roll joint (25). Clause 15. The vehicle of one or more of clause 10 to 14, wherein the rotation axis (A-A) of the drive shaft (47) lies on, or is parallel to, a vertical median plane of the vehicle (1).