DRIVE SYSTEM

Disclosed is a drive system. The drive system comprises a first and a second electrical motor respectively provided with a first rotor and a second rotor. The first rotor presents a first rotor shaft and the second rotor presents a second rotor shaft which is aligned and distal from the first rotor shaft. Furthermore, the system comprises an interface configured to interface the first electrical motor and the second electrical motor through a first and a second element coupled to respective rotor and developing outside of the rotation axis toward each other overlapping in an overlapping area wherein at least one interfacing bearing is inserted.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to European Patent Application No. 22162739.1, filed Mar. 17, 2022, the entire disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention pertains to the technical field of devices for handling mechanical energy. In particular, the present invention relates to a drive system that could be advantageously implemented as a drive system for a vehicle.

BACKGROUND OF THE INVENTION

In a drive system which comprises/connects a motor with a gearbox in order to increase the efficiency of the motor-gearbox assembly it is necessary to eliminate as much loss-generating elements as possible from the power flow.

To achieve this goal, it is known to implement bearings that couple the moving portions of the assembly with the static ones to reduce to a minimum the mechanical losses between the various components involved and the consequent power loss.

However, said bearings are usually subject to the full rotational speed of the motors to which they are coupled, which would imply considerable losses that are proportional to the rotational speed of the rotating part of the motor.

Furthermore, specifically, when more than one motor is present, the need may arise to provide a connection between their respective rotor shafts to interface them and provide stability to the resulting device.

Said connection, of which a possible example is shown in document US2021/381587A1, may be mediated by the aforementioned bearings which are implemented in specific interfacing means that have a crucial role in the efficiency of the resulting device, insofar as they contribute significantly to the stability of the overall structure and consequently to the consistency of the provided output.

In view of the above it is evident how in the field there is a great need for novel solution providing new configuration aimed at increasing the power transmission efficiency by reducing the loss correlated to the interaction between the various components of the drive system and improving the structure of the interfacing means.

SUMMARY OF THE INVENTION

In view of the foregoing disadvantages inherent in the prior art, the general purpose of the present invention is to provide a drive system to include all advantages of the prior art, and to overcome the drawbacks inherent in the prior art.

In particular, the aim of the invention is to provide a drive system with an increased efficiency deriving from a reduction in the power-flow loss due to a corresponding reduction in bearing churning and load losses.

The technical purpose indicated and the aims specified are substantially achieved by a drive system comprising the technical features described in one or more of the appended claims.

The invention describes a drive system which comprises a first electrical motor, a second electrical motor, and an interface.

The first electrical motor comprises a first rotor provided with a first rotor shaft developing along a rotation axis.

The second electrical motor flanks the first electrical motor and comprises a second rotor provided with a second rotor shaft coaxial and distal to the first rotor shaft.

The interface is configured to interface the first electrical motor and the second electrical motor and comprise a first element, a second element and at least one interfacing bearing.

The first element is coupled to the first rotor and develops outside of the rotation axis towards the second rotor.

The second element is coupled to the second rotor and develops outside of the rotation axis towards the first rotor so as to overlap the first element in an overlapping area.

At least one interfacing bearing is radially interposed between the first element and the second element at the overlapping area.

Advantageously, the specific configuration provided by the interface of the present invention allows to reduce the power loss due to the relative motion of the component of the drive system, in particular by reducing the speed difference that the component configured to couple the motors have to withstand.

This together with the other aspects of the present invention, along with the various features of novelty that characterize the present invention, is pointed out with particularity in the claims annexed hereto and forms a part of the present invention. For a better understanding of the present invention, its operating advantages, and the specified object attained by its uses, reference should be made to the accompanying drawings and descriptive matter in which there are illustrated exemplary embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

For a thorough understanding of the present invention, reference is to be made to the following detailed description, including the appended claims, in connection with the above-described drawings. Although the present invention is described in connection with exemplary embodiments, the present invention is not intended to be limited to the specific forms set forth herein. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but these are intended to cover the application or implementation without departing from the spirit or scope of the claims of the present invention. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.

The terms, “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.

In the accompanying figures with the reference numeral1is indicated in general a drive system, which could be advantageously implemented as a drive system1for a vehicle.

In other words, the drive system1of the present invention, henceforth referred to as system1, can be used to generate/transfer mechanical power to any kind of device, but is particularly apt to operate in the automotive field.

From a structural point of view, the drive system1essentially comprises a first electrical motor2, a second electrical motor3, and interface4.

In particular, the first electrical motor2comprises a first rotor5equipped with a respective first rotor shaft5awhich develops along a rotation axis X.

Correspondingly, the second electrical motor3comprises a second rotor6with a respective second rotor shaft6awhich develops along the same rotation axis X.

In other words, the first and second electrical motor2,3are coupled in such a way that the respective rotor shafts5a,6aare aligned along the rotation axis X.

Furthermore, the second rotor shaft6ais distal from the first rotor shaft5a,meaning that the two are not in direct contact with each other.

The drive system1may further comprise or be connected to one or more gearboxes through which the drive system1itself may be coupled to one or more elements that need to receive mechanical power from it, i.e., the wheels of a vehicle if the drive system1is implemented in the automotive field.

More in detail, the drive system1may comprise or be connected to a first gearbox (not illustrated in the accompanying figures) coupled to the first rotor shaft5aand a second gearbox (also not illustrated) coupled to the second rotor shaft6a.

By way of an example, one or both of said gearboxes may be a planetary gearbox or a spur/helical gearbox or any analogous/equivalent type of transmission.

The interaction and coupling between the two electrical motors2,3is mediated by the interface4which are configured to interface the first electrical motor2with the second electrical motor3, in particular by coupling the respective rotor5,6.

Structurally, the interface4comprises a first element7and a second element8.

The first element7is coupled to the first rotor5, preferably to the first rotor shaft5a,and develops outside of the rotation axis X towards the second rotor6.

Correspondingly, the second element8is coupled to the second rotor6, preferably to the second rotor shaft6a,and develops outside of the rotation axis X towards the first rotor5.

In other words, the interface4comprises a couple of elements7,8that are linked to respective rotors5,6and develop toward each other extending outside of the rotation axis X.

In particular, the second element8presents such a structure so as to overlap the first element7in an overlapping area, which is preferably midway between the first electrical motor2and the second electrical motor3.

In the overlapping area the interface4comprises at least one interfacing bearing B, e.g., a roller bearing, which is interposed between the first and second element7,8allowing a reciprocal rotation

In other words, the first and second electrical motor2,3are interfaced through the interface4that provides a coupling via the interfacing bearing B.

When both the first and second electrical motor2,3provide the same torque (e.g., to move a vehicle along a straight forward/backward trajectory) both rotor5,6will experience the same loading in terms of torque applied and will then experience the same amount of axial force (generated by the gearboxes as a consequence of the torque being applied) in opposite directions and thus the system1will be self-balanced.

Since in this situation both motors2,3are substantially spinning at the same speed no losses are generated at the interface between the motors2,3because there would be no relative motion between the first and second element7,8that the interfacing bearing B needs to withstand.

Instead, when the first and second electrical motor2,3are required to provide different amounts of torque/speed (e.g., while moving a vehicle on a turn) thus spinning at different speeds and consequently losses are experienced in the drive system1.

In this case losses are generated in particular at the interface between the motor2,3but thanks to the specific configuration of the interface, the losses generated in this situation will be reduced since the difference in rotational speed between the inner and outer race on the at least one interfacing bearing B is equal to the speed difference between the first and second rotor5,6.

Thus, the interfacing bearing B will need to withstand a much smaller speed difference than in conventional designs where the outer race, which is coupled to a housing of the system, is static and consequently at almost any given automotive applicable condition the present solution will guarantee a lower difference in rotational speed at this interface than the known solutions which require to install bearings connected to the housing.

Advantageously, since mechanical losses on bearings correlate linearly with rotational speed, the present system1allows to significantly reduce losses thus providing for an improved efficiency, since the interfacing bearing B will experience a lower difference in rotational speed in the overlapping area between the two elements7,8than would a bearing coupled to the housing as is provided for in a conventional drive system.

Furthermore, the above-mentioned rotational speed difference between the motors that the interfacing bearing B needs to deal with will be present only while the output of the two motors2,3is different, e.g., while cornering.

Instead, during straight forward or backward driving, the speed difference between the first motor2and the second motor3, and hence the losses experienced by the interfacing bearing B, are zero.

According to a possible embodiment, which is showed inFIG.1, the interface4comprises two interfacing bearings B aligned along the rotation axis.

Preferably the interface4comprises exactly two interfacing bearings, allowing for optimal stability and stiffness of the system1, while at the same time maintaining a simple structure.

According to an aspect of the present invention, which again is shown in the exemplary embodiment displayed inFIG.1, the first element7and the second element8are defined by respective peripheric portions of a couple of pressure plates coupled to the rotors5a,6a.

In particular, the system1can comprise a first pressure plate9and a second pressure plate10, wherein the first pressure plate9is coupled to the first rotor5in such a way as to maintain first rotor shaft5ain a fixed position and to help coupling it to a first rotor stack R1, while the second pressure plate10is coupled to the second rotor6in such a way as to maintain the second rotor shaft6ain a fixed position and coupled to the corresponding second rotor stack R2.

In this context the peripheric portion of the pressure plates9,10develops around the rotation axis X and toward each other defining respective annular structure (with one structure presenting a radius bigger than the other) that overlap in the overlapping area interposed between the two motors2,3and thus provide for the first and second element7,8.

Alternatively, the element7,8can develop directly from the respective rotor shaft5a,6a.

In other words, the first element and the second element7,8can be directly coupled and in contact with the first rotor shaft5aand the second rotor shaft6aor develop from elements (i.e., the corresponding pressure plate9,10) that link them with the corresponding rotor shaft5a,6a.

Even when the elements7,8are in direct contact with the rotor shafts5a,6a,they still develop outside the rotation axis X, it is to say that starting from the respective rotor shaft5a,6aeach element7,8develop for a first portion away from the rotation axis X (i.e., they form with the rotation axis an angle greater than 0 degrees) and then for a second portion towards each other.

Specifically, the second portion occupies at least a portion of the overlapping area wherein the interfacing bearing B is installed.

In general, the elements7,8, whether they are coupled directly to the rotor shafts5a,6aor through the pressure plate9,10or any structurally/functionally analogous component of the system1, may present in the overlapping area a continuous profile which provides for a contact surface with the entire inner/outer race of the interfacing bearing B.

Alternatively, the first element7comprises a first plurality of protrusions, developing along a direction substantially parallel to the rotation axis X, engaging a first side (i.e., the inner race) of the interfacing bearing B and the second element comprises a second plurality of protrusions, also developing along a direction parallel to the rotation axis X, engaging a second side (i.e., the outer race) of the interfacing bearing B opposite to the first side.

In other words, each element7,8presents a claw-like structure that engages either the inner or outer race of the interfacing bearing B thus defining a succession of distinct contact points between the elements7,8and the interfacing bearing B.

Further to the above, the system1may also comprise a single housing configured to lodge both the first electrical motor2and the second electrical motor3.

In particular, the first and second electrical motor2,3are placed inside the housing in such a way that the first rotor shaft5aand the second rotor shaft6aprotrudes from opposite sides of the single housing.

In other words, the two motors2,3are placed side by side with the respective rotor shaft5a,6aaligned and extending in opposite direction with a terminal portion protruding outside the housing.

Preferably, the housing defines an internal chamber and the first rotor shaft5aand the second rotor shaft6aextend only in a peripheric portion of said internal chamber.

Consequently, each rotor shaft5a,6adevelop from a first extremity which is placed ideally at a midway section of the respective motor2,3and is distal from the first extremity of the other rotor shaft6a,5a,to a second extremity which passes through a wall of the housing and protrudes outside of the same to link the rotor3,4with further components like the above-mentioned gearboxes.

Furthermore, as discussed above, the interfacing bearing B and also the first and second element7,8present a substantially annular conformation so that a central portion of the internal chamber, which is interposed between the first rotor shaft5aand the second rotor shaft6aremains unoccupied.

In view of the above, as could be seen inFIG.1, it follows that in the system1, the space between the rotor5,6remains substantially empty.

The above is allowed thanks to the specific structure of the interface4that allow to couple the electrical motor2,3without the need to directly connect/couple the rotor shaft5a,6awhich are encumbering, heavy and usually require complex structures and design to be interfaced with a reciprocal direct contact.

In this way it is possible to improve the performances of the system1at least by reducing its weight and the complexity of the device interfacing its two motors2,3.

More in detail, the system1comprises no bearings interposed between the interface4and the housing so that the coupling of the electrical motors2,3is completely managed by the interfacing bearing B and the mechanical losses are reduced insofar there is no absorption/dissipation of mechanical energy between the housing and the interface4.

To improve the overall stability while in use, the system1may instead comprise a couple of outer bearings interposed directly between the rotor shafts5a,6aand the housing.

In particular, the system1may comprise a first outer bearing11interposed between the first rotor shaft5aand the housing and a second outer bearing12interposed between the second rotor shaft6aand the housing.

Furthermore, the outer bearing11can be coupled to respective elastic device14, which may comprise for example a wave springs, that allow to preload the outer bearing11.

Alternatively or additionally, the same arrangement may also be implemented for the outer bearing12which may also be coupled to respective elastic device14.

In other words, the system1comprises elastic device14which are configured to exercise an elastic force against the first and/or second outer bearing11,12in such a way as to maintain them in a preloaded state.

The presence of the elastic device14prevents the system1from producing noise caused by rotor assembly axial shifting due to changes in resultant axial force or inertial forces.

Alternatively, or additionally, the elastic device14may also be coupled and/or active on the interfacing bearing B to keep them in a preloaded state

The system1may further comprise a cooling system configured to absorb thermal energy from the first electrical motor2and the second electrical motor3.

In particular, the cooling system may be lodged at least partially inside the housing and in thermal contact with both the first electrical motor2and the second electrical motor3.

In other words, there may be just one cooling system that operates on both electrical motors2,3without the need for a duplication of the same, thus simplifying the overall structure of the system1.

For example, the cooling system may comprise a conduit developing around or in proximity of the two motors2,3and configured to channel a heat transfer fluid to absorb heat from both motors2,3.