Patent Description:
This invention relates to a driving axle for a hybrid heavy vehicle.

As is well known, heavy vehicles such as trucks, lorries, buses and similar vehicles are equipped with a front driver's cab and one or more rear compartments for transporting goods or passengers, depending on their use.

Normally, the rear compartments are supported by a lower portion of the body shell, also called the floor of the vehicle.

In turn, the floor is supported by a set of suspensions with a plurality of axles, which each carry two or more aligned wheels and have the function of transmitting the load of the compartments and of the bottom to the wheels.

In some cases, at least one of the axles is a driving axle, i.e. it contributes to the traction of the vehicle and is therefore equipped with an automotive differential.

This differential typically has one input connected to a power take-off of the vehicle and two outputs connected to the wheels via two respective semi-axles forming part of the axle.

Each of the driving axles extends between the wheels below the floor of the vehicle, so that it is possible to follow the movements of the suspensions without interfering with the floor itself.

Thus, the dimensions of the driving axles means that the floor of the vehicle has to be lifted off the ground.

In contrast, it is generally known that lowering the ground clearance of the vehicle floor results in better suspension performance.

In addition, a reduced ground clearance enables a reduction in the overall dimensions of the vehicle and, therefore, the possibility of increasing the transport capacity of the vehicle itself, for example by increasing the capacity of the compartments.

There is a need, therefore, to lower the ground clearance of the vehicle floor, without causing interference of any kind between the semi-axles and the floor itself.

More generally, there is also a need to reduce the overall dimensions of known axles and to simplify the vehicle architecture while maintaining robustness and reliability. Meeting these requirements is of particular importance in hybrid vehicles, as the latter have a significantly more complex architecture than purely thermal-powered vehicles.

For example, <CIT> discloses a complex and cumbersome drive device with plural suspension links.

<CIT> and <CIT> disclose different examples of drive devices.

<CIT> discloses another cumbersome drive device including a drive axle with a pair of wheels being each driven by an associated electric motor.

A similar drive device is disclosed also in W2013173915A1.

The preamble of claim <NUM> is disclosed by <CIT>, which concerns different axle arrangements for a hybrid vehicle.

<CIT> discloses an axle assembly where an electric machine is positioned within an axle housing of the axle assembly.

The purpose of the invention is to satisfy at least one of the above needs in a simple and economical way.

The above-mentioned purpose is achieved with a driving axle for a hybrid heavy vehicle, as claimed in the attached claims.

In order to better understand this invention, nonlimiting embodiments thereof will now be described by way of example with reference to the accompanying drawings, in which:.

In <FIG>, the reference number <NUM> indicates a hybrid heavy vehicle, in particular a freight truck.

The vehicle <NUM> comprises a frame <NUM> that has, according to the forward direction of the vehicle <NUM> in use, a front portion <NUM> defining a driver's cab and a rear portion <NUM>.

The rear portion <NUM> extends along a straight axis A, which is direct along the forward direction of the vehicle <NUM>. The rear portion <NUM> supports, in addition, from below a cargo compartment <NUM> of the vehicle <NUM> for containing freight.

The cargo compartment <NUM> has a horizontal floor that extends along the axis A above the rear portion <NUM> and is coupled to the latter, especially directly.

In addition, the vehicle <NUM> comprises a front axle (not illustrated) of a known type and not described in detail, which is arranged beneath the front portion <NUM> and is coupled to the latter by means of a suspension of a known type (not illustrated).

The vehicle <NUM> also comprises two pairs of front wheels (not illustrated) that are coaxial to each other and, respectively, arranged on opposite sides of the front portion <NUM> in relation to the axis A.

The pairs of front wheels are aligned with each other along one axis B, which is orthogonal to another axis A, and fixed to the front axle. Together with the front axle, the pairs of front wheels support the front portion <NUM>.

The vehicle <NUM> also comprises two pairs of rear wheels <NUM> and a driving axle <NUM> that couples the two pairs of wheels <NUM> to the rear portion <NUM>.

More specifically, as can be seen in <FIG>, the rear portion <NUM> comprises a central structure 4a along the axis A and a plurality of structural appendages 4b that extend transversely to the axis A, i.e. to the opposite sides of the central structure 4a.

In other words, the structural appendages 4b protrude laterally in relation to the central structure 4a, i.e. according to a direction transverse, more precisely orthogonal, to the axis A.

In particular, the structural appendages 4b comprise a plurality of plates connected to each other. The central structure 4a supports the cargo compartment <NUM> and the floor thereof.

The driving axle <NUM> is coupled to the frame <NUM>, in particular to the rear portion <NUM>, and, more in particular, to the structural appendages 4b, specifically directly; as can be seen in <FIG> and <FIG>, the driving axle <NUM> extends at least in part below the central structure 4a.

In other words, the driving axle <NUM> includes at least one portion arranged at least at the same height level as the central structure 4a or at a higher height level.

Thus, the pairs of wheels <NUM> and the driving axle <NUM> support the rear portion <NUM> and the cargo compartment <NUM>.

The pairs of wheels <NUM> comprise respective wheel-hubs <NUM> (<FIG>) that are coupled, respectively, to ends of the axle <NUM> and each of which carries, coaxially, two tyres <NUM>.

The wheel-hubs <NUM> are of a known type and, therefore, are not described in further detail. Possibly, each wheel-hub <NUM> can introduce a fixed or variable transmission ratio between the driving axle <NUM> and the corresponding tyres <NUM>. An example of a wheel-hub that introduces a variable transmission ratio is described, in particular, in <CIT>.

In <FIG>, the pairs of wheels <NUM> are aligned with each other along an axis C parallel to the axis B.

As shown in <FIG>, the driving axle <NUM> comprises:.

The ends <NUM>, the power take-off <NUM>, and the differential <NUM> are arranged below the central structure 4a.

On the other hand, the driving groups <NUM> and the ends <NUM> are arranged spaced apart from the central structure 4a in a direction that is transverse to the axis A.

In other words, the driving assemblies <NUM> and the ends <NUM> are arranged laterally in relation to the central structure 4a, i.e. the central structure 4a extends between the driving assemblies <NUM>.

The driving assemblies <NUM> are fixed with respect to the power take-off <NUM> and to the differential <NUM>.

For the sake of clarity, as can also be understood directly and unequivocally from <FIG>, the expression "carried in a fixed position" means "stiffly coupled", i.e. that the whole pose, that is the position and orientation, of the stator <NUM> is fixed with respect to the suspension arm <NUM>. In other words, it means that the stator <NUM> moves entirely in a way stiffly integral with the suspension arm <NUM>. This means that the expression "carried in a fixed position" excludes relative translations and rotations between the stator <NUM> and the suspension arm <NUM>.

Each driving assembly <NUM> is coupled to a corresponding axle shaft <NUM>; more in detail, the end <NUM> of the corresponding axle shaft <NUM> is coupled to the corresponding shaft <NUM> so that the rotation of the axle shaft <NUM> is conveyed to the shaft <NUM>.

In other words, the axle <NUM> comprises, in addition, two transmissions <NUM>, in particular two equal to each other, that connect each of the ends <NUM> to each corresponding shaft <NUM>. Specifically, each transmission <NUM> introduces a fixed transmission ratio between the corresponding end <NUM> and the corresponding shaft <NUM>. In particular, each transmission <NUM> comprises a pair of gears <NUM>, <NUM> engaging each other and respectively fitted to the corresponding end <NUM> and to the corresponding shaft <NUM>.

According to the embodiment illustrated in <FIG>, the axle shafts <NUM> extend on opposite sides of the differential <NUM> and along corresponding axis E, F, which are parallel to the axis C and lie on the same plane of the axis C, in particular vertically, above the latter. The two axle shafts <NUM> have different lengths and the differential <NUM> along with the power take-off <NUM> are near to one of the driving assemblies <NUM>.

In the variant in <FIG>, on the other hand, the axle shafts <NUM> have the same length, and the differential <NUM> and the power take-off <NUM> are arranged centrally between the driving assemblies <NUM>.

As shown in <FIG>, the driving assemblies <NUM> are preferably identical to each other. Therefore, only one of the driving assemblies <NUM> will be described in greater detail below.

With greater detail, the stator <NUM> and the rotor <NUM> are coaxial to each other around an axis D, preferably parallel to the axis C and, specifically, aligned with the latter. Clearly, the axis D is completely fixed with respect to the suspension arm <NUM>.

More precisely, the rotor <NUM> is directly coupled to the shaft <NUM>, for example by means of a keyed connection. Alternatively, the driving assembly <NUM> could comprise any transmission to couple the shaft <NUM> to the rotor <NUM> and to transmit the rotation motion of the latter to the shaft <NUM>.

According to the invention, the suspension arm <NUM> comprises a hollow portion <NUM> (<FIG>) that at least partially houses the motor <NUM>. Specifically, the hollow portion <NUM> completely houses the rotor <NUM> and, conveniently, the stator <NUM> too. In particular, the motor <NUM> comprises a connection portion <NUM>, particularly of the flange type, which is fixed in relation to the stator <NUM>, for example since it is made of a single piece with the stator <NUM>, protrudes along the axis D with respect to the hollow portion <NUM>, and is stiffly fixed to the latter, for example by means of threaded elements (not illustrated).

As shown in <FIG>, the hollow portion <NUM> is cylindrical in shape and is arranged around the axis D.

In addition, the suspension arm <NUM> comprises an additional hollow portion <NUM> arranged between the wheel-hub <NUM> and the hollow portion <NUM>, fixed with respect to the hollow portion <NUM> and housing the corresponding transmission <NUM>. In particular, the hollow portion <NUM> houses, at least partially, the corresponding end <NUM>.

The hollow portions <NUM>, <NUM> respectively define internal volumes that communicate with each other and, preferably, are made of a single piece, so as to define a single hollow portion.

As shown in <FIG>, the hollow portion <NUM> has an oval shape and is, ideally, traversed by axes C, D, E, F.

In addition, the suspension arm <NUM> comprises two arm portions <NUM>, <NUM> that extend from the hollow portion <NUM> in a transverse manner to the axis D, in particular according to corresponding directions aligned and opposite to each other, so that the one hollow portion <NUM> and, where present, the other hollow portion <NUM> define an intermediate portion of the suspension arm <NUM>.

More specifically, the extension directions of the arm portions <NUM>, <NUM> lie, ideally, on a plane that is perpendicular to that on which the axes C, D ideally lie. In practice, the extension directions of the arm portions <NUM>, <NUM> are aligned with each other and, substantially, horizontal.

The arm portions <NUM>, <NUM> have respective ends <NUM>, <NUM> opposite with respect to the hollow portion <NUM> and, respectively, coupled to the rear portion <NUM>, specifically to two of the structural appendages 4b.

In particular, the driving assembly <NUM> comprises at least one elastically deformable element <NUM>, for example an air spring, as in <FIG>, that couples the end <NUM> to the rear portion <NUM> in an elastically yielding manner. More specifically, the elastically deformable element <NUM> is fixed to the end <NUM> and to a corresponding appendage 4b.

In addition, the driving assembly <NUM> comprises another elastically deformable element <NUM>, for example one that is the same as the elastically deformable element <NUM>, which couples the end <NUM> to the rear portion <NUM> in an elastically yielding manner. More specifically, the elastically deformable element <NUM> is fixed to the end <NUM> and to the other of the two appendages 4b (<FIG>).

Alternatively, one of the ends <NUM>, <NUM> could extend along a hinge axis and be hinged, potentially virtually like a torsion bar, to the corresponding appendage 4b.

Conveniently, the suspension arm <NUM> could be made of a single piece and/or comprise metal, for example steel or aluminium.

As schematically illustrated in <FIG>, the driving assembly <NUM> preferably comprises, in addition, a brake caliper device <NUM>, for example of a known type, and an attachment member <NUM> (<FIG>) for attaching a damper device (not illustrated), for example of a known type. The brake caliper device <NUM> and the attachment member <NUM> are carried in a fixed position by the hollow portion <NUM>.

The brake caliper device <NUM> is configured to operatively cooperate with a brake disc <NUM>, which is part of the corresponding wheel-hub <NUM>.

Conveniently, the driving assembly <NUM> also comprises the above-mentioned damper device attached to the attachment member <NUM> and coupled to the rear portion <NUM> in order to dampen, in use, the vibrations owing to the contact between the pairs of wheels <NUM> and the road.

The driving assembly comprises, in addition, a base, carried by the hollow portion <NUM> and to which the brake caliper device <NUM> and the attachment member <NUM> are both coupled in a fixed position.

In addition, the vehicle <NUM> comprises a control unit ECU (<FIG>) electrically coupled to each motor <NUM> of each driving assembly <NUM> and configured to independently control the rotations of the corresponding rotors <NUM> and, consequently, the rotations of the wheel-hubs <NUM>.

The control unit ECU is also electrically coupled to the power take-off <NUM> and is configured to activate and deactivate the connection between the power take-off <NUM> and the internal combustion engine.

When the power take-off <NUM> is connected to the internal combustion engine, the control unit ECU drives the motors <NUM> so that the angular velocity transmitted by each of the motors <NUM> to the corresponding shaft <NUM> is the same angular velocity that is transmitted to the same shaft <NUM> by the corresponding axle shaft <NUM> to which it is coupled. In this way, the torque transmitted to the shaft <NUM> by the motor <NUM> and by the axle shaft <NUM> are combined and the vehicle <NUM> moves regularly.

The operation of the embodiment of the vehicle <NUM> described above is the following.

When the vehicle <NUM> moves forward, each pair of wheels <NUM> is rotated by means of the corresponding driving assembly <NUM> that supplies the rotation of the wheel-hub <NUM>. The motor <NUM> exerts a torque that is directly transmitted to the shaft <NUM>, while the internal combustion engine can contribute to the vehicle <NUM> traction when the control unit ECU connects the power take-off <NUM> to the same internal combustion engine.

Here, the torque distributed by the internal combustion engine is transmitted to the corresponding axle shaft <NUM> by means of the differential <NUM> and, thus, to the shaft <NUM> through the transmission <NUM>.

In particular, the torque distributed by the thermal engine is transmitted to the shaft <NUM> according to a fixed and constant transmission ratio, imposed by the engagement of the gears <NUM>, <NUM>.

When the vehicle <NUM> rounds a curve, the control unit ECU commands each motor <NUM>, so that each distributes a different torque. More specifically, the torque supplied are such that the angular velocities are different for each shaft <NUM> and suitable for keeping the pairs of wheels <NUM> optimally adhering to the road.

If the power take-off <NUM> is connected to the internal combustion engine, each motor <NUM> is controlled by the control unit ECU so that the angular velocity transmitted to each shaft <NUM> by the corresponding motor <NUM> is equal to the angular velocity transmitted to the same shaft <NUM> by the corresponding axle shaft <NUM>.

In addition, when the vehicle <NUM> moves forward, each pair of wheels <NUM> follows the conformation of the road and the corresponding suspension arm <NUM> moves as a result; in particular, the ends <NUM>, <NUM> move by respectively deforming the elastically deformable elements <NUM>, <NUM>. At the same time, the damper device attached to the attachment member <NUM> dissipates the kinetic energy transferred by the pair of wheels <NUM> to the driving assembly <NUM>.

The advantages of an axle <NUM> according to the invention are apparent from the above description.

Unlike known axles, the axle <NUM> comprises two more driving assemblies <NUM> that are independent and that are able, in themselves, to rotate the corresponding wheel-hubs <NUM> with a minimal number of components.

The same components also enable the transmission of the operating loads of the vehicle <NUM> between the frame <NUM> and the corresponding pairs of wheels <NUM>.

The driving assemblies <NUM>, adapted to make the vehicle <NUM> hybrid, have a minimal overall size, so that it is possible to reduce the ground clearance of the vehicle floor <NUM>.

In fact, each driving assembly <NUM> is laterally spaced apart from the central structure 4a that supports the floor of the cargo compartment <NUM>. In this way, the floor itself, like the whole rear portion <NUM>, can have a minimum ground clearance.

This entails a corresponding increase in the load capacity of the vehicle <NUM> and in the overall performance of its suspensions, without interference between the driving assemblies <NUM> and the frame <NUM>.

The suspension arm <NUM> has particularly advantageous construction features, from the point of view of compactness, simplicity of construction, and strength. The motor <NUM> is optimally supported by the corresponding suspension arm <NUM>, which houses at least one rotor <NUM> thereof. The suspension arm <NUM> also houses the corresponding transmission <NUM>.

In addition, the suspension arm <NUM> can effectively carry components such as the brake caliper device <NUM> or the attachment member <NUM>, thus facilitating a better organisation of the overall dimensions of the vehicle <NUM>.

Thanks to the control unit ECU, it is possible to independently control the motors <NUM>.

Finally, it is clear that the axle <NUM> according to this invention can be modified and variations can be made without departing from the scope of protection, as set forth in the claims.

In particular, the pairs of wheels <NUM> and/or the other pairs of wheels <NUM> could be, respectively, replaced with single wheels, each having its own wheel-hub.

The geometry of the transmission arm <NUM> could be different to that described and illustrated. For example, just one of the two arm portions <NUM>, <NUM> could be provided, or there could be additional arm portions as well as the arm portions <NUM>, <NUM>.

In addition, the elastically deformable element <NUM> could be arranged in a different position in relation to the suspension arm <NUM>. Similarly, the brake caliper device <NUM> and the attachment member <NUM> could be carried by different portions of the suspension arm <NUM>, for example by the hollow portion <NUM>.

In addition, the driving assemblies <NUM> could be applied to the front traction of the vehicle <NUM>, i.e. to support the front portion <NUM>.

Between the shaft <NUM> and the rotor <NUM>, there could be a transmission, in particular to multiply the torque distributed by the motor <NUM> in the transmission of the same torque to the shaft <NUM>.

The axes C, D may not be aligned with each other. Each transmission <NUM> could introduce variable transmission ratios and/or enable the temporary decoupling between the corresponding axle shaft <NUM> and the corresponding shaft <NUM>.

The differential input <NUM> could be detachable from the corresponding outlets, so that it is possible to prevent the transfer of power from the internal combustion engine to the wheel-hubs <NUM>. In this case, the power take-off <NUM> could also be permanently connected to the internal combustion engine.

Claim 1:
A driving axle (<NUM>) for a hybrid heavy vehicle (<NUM>), the axle comprising:
- a power take-off (<NUM>) configured to receive power from an internal combustion engine of said heavy vehicle (<NUM>);
- power distribution means (<NUM>) comprising two power outlets and configured to distribute the power received from said power take-off (<NUM>) to said power outlets;
- two axle shafts (<NUM>) having respective first portions (<NUM>) coupled to said power outlets to receive power from said power distribution means (<NUM>) and respective second portions (<NUM>) arranged to be coupled to respective wheel-hubs (<NUM>) of said heavy vehicle (<NUM>) and supply power to said wheel-hubs (<NUM>);
characterized in that the axle further comprises:
- two suspension arms (<NUM>) for being coupled to a frame (<NUM>) of said heavy vehicle (<NUM>);
- two shafts (<NUM>) carried by said suspension arm (<NUM>, <NUM>') in a rotatable manner around an axis (C) and having relative axial ends (<NUM>) to be respectively connected to said wheel-hubs (<NUM>); and
- two electric motors (<NUM>) each having a stator portion (<NUM>), which is carried by one of said suspension arms (<NUM>) in a fixed position with respect to the same one of said suspension arms (<NUM>), and a rotor portion (<NUM>), which is coupled to one of said shafts (<NUM>) to drive the same one of said shafts (<NUM>) in rotation around said axis (C);
wherein said second portions (<NUM>) are respectively coupled to said shafts (<NUM>) to drive said shafts (<NUM>) in rotation around said axis (C), the driving axle further comprising a transmission (<NUM>) that couples one of said second portions (<NUM>) to one of the corresponding said shafts (<NUM>),
wherein one of said suspension arms (<NUM>) comprises a first hollow portion (<NUM>) that houses said transmission (<NUM>), and
wherein at least a first arm of said suspension arms (<NUM>) comprises a second hollow portion (<NUM>) that houses, at least partially, a first motor of said motors (<NUM>).