Patent Description:
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.

For example, <CIT> 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.

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. A vehicle according to the preamble of claim <NUM> is disclosed in <CIT>.

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

A saddle-type vehicle according to the invention is defined in claim <NUM>. The dependent claims relate to preferred additional features and embodiments. Specifically, the vehicle described herein comprises 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 <NUM>°-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.

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.

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.

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.

The pinion of the bevel gear drive transmitting motion from the electric motor to the housing of the differential are 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.

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.

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.

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> and <FIG> schematically show a three-wheel saddle-type vehicle <NUM>, comprising a propulsion unit, according to the present invention. The saddle-type vehicle <NUM> 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 <NUM> has a tilting or rolling frame <NUM>, to which a steered front wheel <NUM> is connected. The frame <NUM> is connected to a non-tilting rear part of the vehicle <NUM>, as described below. The non-tilting rear part comprises a left rear driving wheel 7a and a right rear driving wheel 7b. In <FIG>, the left rear driving wheel has been omitted better to view the propulsion unit <NUM>, with which the vehicle <NUM> is provided and which will be described in greater detail below.

The frame <NUM> comprises a steering sleeve <NUM>, where a steering column, integral with a handlebar <NUM>, is housed. The front steered wheel <NUM> is connected to the steering column <NUM>, through the interposition of a suitable suspension <NUM>. In the embodiment illustrated in the figures, the suspension <NUM> comprises two spring-shock absorber units 15a e 15b, respectively. The number <NUM> indicates a saddle of the saddle-type vehicle <NUM>.

The propulsion unit <NUM> is connected to the frame <NUM> 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 <NUM> and the front steered wheel <NUM>, form the unsprung mass of the vehicle <NUM>. In the embodiment illustrated in <FIG> and <FIG>, the propulsion unit <NUM> is connected to the frame <NUM> through a connecting element <NUM> that is rigidly coupled to a casing <NUM> of the propulsion unit <NUM>. The connecting element <NUM> is coupled to the frame <NUM> through a roll joint <NUM> defining a roll axis X-X (<FIG>), around which the frame <NUM> can rotate relative to the connecting element <NUM>.

In this way, the frame <NUM>, the front steered wheel <NUM> with the corresponding suspension <NUM>, the handlebar <NUM>, the steering column <NUM>, the steering sleeve <NUM> and the saddle <NUM> can perform a rolling movement around the axis X-X with respect to the propulsion unit <NUM> and the rear wheels 7a, 7b, that are non-tilting, i.e. that do not lean when the vehicle turns, for example.

As shown for example in <FIG>, the roll joint <NUM> is arranged approximately aligned with the propulsion unit <NUM> and ahead thereof relative to the forward moving direction of the vehicle.

The roll joint <NUM> and the connecting element <NUM> can rotate relative to the frame <NUM> thanks to a pitching joint <NUM> having a pitching transverse axis Y-Y, i.e. an axis directed in right-left direction (arrow L-R in <FIG>), orthogonal to the forward direction (arrow F, <FIG>) of the vehicle <NUM>. A rear suspension <NUM> is provided to damp the springing movement between the roll joint <NUM> and the frame <NUM>. The transverse axis Y-Y may intersect the roll axis X-X. The transverse axis Y-Y is arranged ahead of the roll joint <NUM> relative to the forward moving direction of the vehicle <NUM>.

The details of the propulsion unit <NUM> are shown in <FIG> and following, and will be described in greater detail below.

In the illustrated embodiment, the propulsion unit <NUM> comprises the casing <NUM>, to which the connecting element <NUM> is rigidly coupled (not shown in <FIG> and following), and an electric motor <NUM>, flanged to the casing <NUM>. The axis of the electric motor <NUM> 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.

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

Therefore, in practical embodiments the roll joint <NUM> may be aligned with the electric motor <NUM>.

In the illustrated embodiment, the casing <NUM> 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 <NUM>.

A differential <NUM> is provided inside the casing <NUM>; reference number <NUM> indicates the housing or planetary carrier thereof, see in particular <FIG>. A crown gear <NUM> is integral with the housing <NUM>. In a known manner, inside the housing <NUM> of the differential <NUM> one or more planet gears <NUM> are arranged, typically constituted by bevel gears, mounted idle on respective shafts radial relative to the rotation axis of the crown gear <NUM>. 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>) 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.

The rotary motion is transmitted to the housing <NUM> of the differential <NUM> by a pinion <NUM> that is coaxial with the electric motor <NUM>, 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 <NUM>.

A flexible coupling <NUM>, shown in isolation in <FIG>, may be provided along the line shaft connecting the electric motor <NUM> and the pinion <NUM>. In advantageous embodiments, the flexible coupling <NUM> comprises a first rotating member <NUM> rotatingly coupled to a drive shaft (output shaft) <NUM> of the electric motor <NUM>, and a second rotating member <NUM> rotating around the axis of the drive shaft <NUM>. The first rotating member <NUM> and the second rotating member <NUM> are joined by members adapted to damp torsional vibrations. In the illustrated embodiment, the mutual connection between the first rotating member <NUM> and the second rotating member <NUM> is provided by damping members interposed between the first rotating member <NUM> and the second rotating member <NUM>. Just by way of example, the damping members are formed like elastic cylinders <NUM>, inside which pins <NUM> are fastened, integral with the first rotating member <NUM> and housed in seats <NUM> integral to the second rotating member <NUM>. The pins <NUM> are parallel to the rotation axis A-A of the electric motor <NUM>.

The second rotating member <NUM> is torsionally coupled to a shaft <NUM> integral with the pinion <NUM>, for example through a profile provided in a hollow shaft 49a of the second rotating member <NUM> (see <FIG> and <FIG>). Reference number <NUM> indicates the support members supporting the second rotating member <NUM> and the shaft <NUM> of the pinion <NUM>. The support members <NUM> may be mounted in a sleeve <NUM> integral with a flange <NUM> formed by the central body 23c, 23d of the casing <NUM>. In some embodiments, the support members <NUM> 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.

In advantageous embodiments, a seal <NUM> is provided between the support members <NUM> of the rotating member <NUM> and the bevel gear drive formed by the pinion <NUM> and by the crown gear <NUM>. Providing the seal <NUM> in this position is beneficial since the support members <NUM> are not immersed in lubricant bath.

In this embodiment, the support members <NUM> of the pinion <NUM> are therefore arranged along the axis A-A in an intermediate position between the pinion <NUM> and the first rotating member <NUM> of the flexible coupling <NUM>. The damping members <NUM> and the seats <NUM> thereof are arranged around the support members <NUM>, so as to reduce the axial bulk of the line shaft connecting the electric motor <NUM> and the pinion <NUM>, to have a compact arrangement of the propulsion unit <NUM>.

The propulsion unit <NUM>, 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.

Claim 1:
A saddle-type vehicle (<NUM>) comprising:
- a tilting frame (<NUM>);
- at least one steered front wheel (<NUM>) supported by the frame (<NUM>);
- a propulsion unit (<NUM>) comprising:
∘ a casing (<NUM>);
∘ inside the casing (<NUM>), a differential (<NUM>) 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 (<NUM>), an electric motor (<NUM>) with a drive shaft (<NUM>) with rotation axis (A-A);
wherein: the drive shaft (<NUM>) is <NUM>°-oriented with respect to the left axle-shaft (39a) and to the right axle-shaft (39b); the propulsion unit (<NUM>) is connected to a left rear driving wheel (7a) through the left axle-shaft (39a) and to a right rear driving wheel (7b) through the right axle-shaft (39b); and the left rear driving wheel (7a), the right rear driving wheel (7b) and the propulsion unit (<NUM>) are non-tilting;
characterized in that:
the drive shaft (<NUM>) is connected to the differential (<NUM>) through a shaft line comprising a flexible coupling (<NUM>);
the flexible coupling (<NUM>) comprises a first rotating member (<NUM>) torsionally coupled to the drive shaft (<NUM>) and connected, through the interposition of a plurality of damping members (<NUM>), to a second rotating member (<NUM>) rotatable around the axis (A-A) of the drive shaft (<NUM>);
the second rotating member (<NUM>) is torsionally coupled to a pinion (<NUM>) engaging a crown gear (<NUM>) integral with a housing (<NUM>) of the differential (<NUM>);
the pinion (<NUM>) is supported by support members (<NUM>) that are installed in the casing (<NUM>) and are axially arranged in an intermediate position between the pinion (<NUM>) and the first rotating member (<NUM>) of the flexible coupling (<NUM>); and
the damping members (<NUM>) are arranged around the support members (<NUM>) of the pinion (<NUM>).