Electric powertrain having two axial-flux electric machines
The electric powertrain design with dual axial flux machines in a single casing and opposing axial force absorption reduces mass and size by eliminating splined couplings and bearings, maintaining consistent air gaps and mechanical performance.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- AMPERE SAS
- Filing Date
- 2025-12-11
- Publication Date
- 2026-06-25
Smart Images
Figure EP2025086672_25062026_PF_FP_ABST
Abstract
Description
Description Title of the invention: Electric powertrain with two axial flux electric machines
[0001] The present invention relates to the fields of electrotechnics and mechanics, and more specifically concerns an electric powertrain.
[0002] Currently, electric or hybrid electric vehicles use electric traction or propulsion motors, which are often radial flux electric machines, meaning that the stator windings of such a machine generate a magnetic flux in a radial direction relative to an axial direction corresponding to the axis of rotation of the machine.
[0003] To reduce the size of an electric powertrain in such a vehicle and optimize its efficiency, the use of axial flux electric machines, coupled to gearboxes directly connected to the vehicle's front or rear wheels, is being considered instead of radial flux electric machines. Axial flux electric machines are generally more compact than radial flux electric machines, at least in the axial direction.
[0004] However, a challenge with such a powertrain, comprising an axial flux machine coupled to a gearbox, is maintaining the smallest possible air gap between the magnetic poles of a rotor and the magnetic poles of a stator, without this air gap being eliminated or increased by mechanical stresses generated in the axial direction by the gearbox operation. Indeed, the gearbox typically uses helical gears, which generate axial stresses that can affect the air gap.
[0005] This difficulty is even greater when the axial flux machine has two stators on either side of the rotor, because it is then necessary to maintain air gaps of the same values on either side of the rotor, so as not to impact the performance of the axial flux machine.
[0006] It is known to overcome the constraints generated by the gears of the reducer, by using a coupling between a shaft of the rotor of the electric machine and a primary shaft of the reducer, using splines, which allows the primary shaft to slide relative to the shaft of the rotor of the electric machine.
[0007] However, this solution goes against the objective of reducing the mass and complexity of the powertrain.
[0008] The present invention aims to remedy, at least in part, the aforementioned drawbacks by providing an electric powertrain in which the axial forces generated by the gears of a reduction gear of the electric powertrain do not influence not on an air gap of an electric machine of this powertrain group, without using a splined coupling system between an output shaft of the electric machine and a primary shaft of the reducer.
[0009] To this end, the invention proposes an electric powertrain comprising: - a first axial flux electric machine and a first reducer comprising at least one toothed wheel, called a left-hand electric machine and left-hand reducer, capable of turning a first wheel of a vehicle, - a second axial flux electric machine and a second gearbox comprising at least one toothed wheel, referred to as a right-hand electric machine and right-hand gearbox, capable of turning a second wheel of a vehicle, each of the left and right-hand electric machines comprising, on the one hand, at least one stator having stator magnetic poles, and on the other hand, a rotor having rotor magnetic poles, separated from the stator magnetic poles by an air gap, the rotor further comprising a rotating shaft mounted rotatably, on the one hand, at one of its ends, in a first bearing, and on the other hand, between the first bearing and a second of its ends, in a second bearing, the electric powertrain being characterized in that: - The right and left electrical machines are arranged in the same casing, - at least one of the rotating shafts of the left or right electrical machine forms a single primary drive shaft for the left or right reducer respectively, the second end of the rotating shaft being fitted with teeth suitable for cooperating with the gear of one of the left or right reducers respectively, and - the toothed wheel of the left reducer being capable of generating by its rotation an axial force on the first or second bearing of the left electric machine, in the opposite direction to an axial force capable of being generated by a rotation of the toothed wheel of the right reducer on the first or respectively the second bearing of the right electric machine, the casing includes at least one reinforcement structure capable of receiving the first or respectively the second bearings, and of taking at least part of the axial forces in the opposite direction.
[0010] It should be noted that in this patent application, the terms "axial / e / ment" (or "axials") refer, unless otherwise stated, to a direction parallel to the axes of rotation of the rotors of the right or left-hand electric machines.
[0011] The invention utilizes the presence of two electrical machines, right and left, subjected to axial forces in opposite directions, to merge the output shaft of at least one of the electrical machines with the primary shaft of the corresponding gearbox, into a single primary drive shaft for the gearbox. Thus, The invention allows for a reduction in the mass and size of the powertrain, as the presence of splines is no longer necessary. In particular, having a single shaft rather than two connected by splines eliminates the need for one of the bearings used in the prior art to guide the rotation of the two shafts.
[0012] The casing's reinforcement structure(s) are either fixed together or formed as a single unit. The casing allows opposing axial forces to be absorbed by one or more of these reinforcement structures and partially canceled out, because the reinforcement structures, being fixed together, transmit these opposing axial forces. For example, the axial forces due to the gear teeth are directed towards the stiffest casing, which is the machine casing.
[0013] These reinforcement structures have a very high stiffness coefficient, for example on the order of two million Newtons per millimeter, so as to withstand significant axial forces, on the order of several thousand Newtons. In particular, they have a stiffness coefficient strictly greater than that of the first or second bearings, for example at least four to five times greater than that of the first or second bearings.
[0014] In one embodiment of the invention, the two rotating shafts each form, for example, a single primary drive shaft for either the left or right gearbox. In this embodiment, the right electric motor has a structure symmetrical to that of the left electric motor with respect to a plane orthogonal to the axial direction and passing between the two electric motors, and the right gearbox has a structure symmetrical to that of the left gearbox with respect to this orthogonal plane. Thus, the axial forces generated by the gears of the gearboxes are almost entirely canceled out at the level of the casing reinforcement structure(s), which limits deformation of the powertrain components and results in a negligible impact on the air gaps of the right and left electric motors.
[0015] Furthermore, according to an optional and advantageous feature of the invention, each rotating shaft has at least one recess extending axially within the shaft. Each end of the rotating shaft is, for example, hollowed out at its center, with the recesses extending axially in depth to a solid portion of the rotating shaft, the axial dimension of which is less than one-tenth of the axial dimension of the rotating shaft. These recesses make it possible to considerably reduce the mass of the powertrain while maintaining its mechanical performance.
[0016] Furthermore, each right-hand or left-hand electrical machine includes, for example, two stators. In this optional embodiment, said at least one stator is therefore a first stator, and each right-hand or left-hand electrical machine includes a second stator, the rotor of the right-hand or left-hand electrical machine being axially arranged between the first stator of the right or respectively left electric machine and the second stator of the right or respectively left electric machine.
[0017] According to an optional feature of the invention, the stator magnetic poles of said at least one stator of the left electric machine and the stator magnetic poles of said at least one stator of the right electric machine are fixed axially on either side of the reinforcement structure, in which are arranged first bearings suitable for receiving the first bearings, the reinforcement structure extending mainly orthogonally to the axes of rotation of the rotating shafts.
[0018] In other words, the reinforcement structure extends mainly in a plane orthogonal to the axes of rotation. The first bearings undergo axial forces in opposite directions generated by the gears of the reducers; these axial forces are absorbed by this reinforcement structure common to the first bearings and are canceled out there, without deformation of this reinforcement structure, due to its central location in an axial direction, between the first two bearings.
[0019] In one embodiment of the invention, the teeth on each rotating shaft are, for example, helical teeth oriented such that the rotation of each gear cooperating with the helical teeth of the rotating shaft generates an axial force directed towards the first end of the rotating shaft. In other words, the axial forces exerted by the gears are directed towards the interior of the powertrain and tend to push the first bearings against the reinforcement structure. Their actions are therefore canceled out at the reinforcement structure located between the two electric machines on the right and left.
[0020] The reinforcement structure includes, for example, a central wall orthogonal to the axes of rotation of the rotating shafts, an annular support plate for the stator magnetic poles of said at least one stator of the right-hand electric machine and an annular support plate for the stator magnetic poles of said at least one stator of the left-hand electric machine, the annular support plates being fixed on either side of the central wall, each annular support plate having an internal rim projecting axially from the annular support plate and forming the first bearing for the first bearing of the right-hand or left-hand electric machine, the first bearing having a stop capable of retaining the first bearing when it is subjected to an axial force directed towards the first end of the rotating shaft carrying the first bearing.The central wall and the annular support plates each have a generally discoidal shape with a hole in the center to allow the first ends of the rotating shafts to pass through, and also to allow air to circulate for cooling the air gaps. Alternatively, the reinforcement structure is a single piece.
[0021] Thus, for example, in a first embodiment of the invention with two stators per right-hand or left-handed electric machine: - the annular support plates are the first annular plates, - the casing comprises a cylindrical wall surrounding the central wall and delimiting on the one hand a left volume occupied by the rotor and stator magnetic poles of the left-hand electric machine, on a so-called left side of the central wall, and on the other hand a right volume occupied by the rotor and stator magnetic poles of the right-hand electric machine, on a so-called right side of the central wall, the right side being opposite the left side with respect to the central wall, - the electric powertrain comprises, for each left or right reduction gear, a housing including a reinforcing section extending mainly orthogonally to the axes of rotation of the rotating shafts, and - the casing further comprises for each second stator of the right or left electric machine, a second annular support plate, positioned against one of the ends of the cylindrical wall, and fixed to the reinforcement portion of the housing of the right or respectively left reducer, each second annular support plate having an internal rim projecting axially from the second annular support plate and forming a second bearing for the second bearing of the right or left electric machine.
[0022] The cylindrical wall is another reinforcing structure, for example, made of a material with the central wall extending primarily orthogonally to the axes of rotation of the right and left electrical machines and separating them. This cylindrical wall effectively absorbs the axial forces that may be exerted on the second bearings mounted in the second housings of the second annular support plates, which are integral with this cylindrical wall. Each second housing includes, in particular, a thrust bearing capable of retaining the second bearing when it is subjected to an axial force directed towards the second end of the rotating shaft carrying this second bearing.
[0023] It is further understood that at least one reinforcing portion of the housing of each right and left gearbox closes, at each of its bases, the cylindrical wall housing the right and left electrical machines. This reinforcing portion is, however, perforated to allow the passage of the rotating shaft extending within the right or left gearbox, respectively. The housing also includes a cover to protect the right or left gearbox once the powertrain is assembled. Compared to the prior art, which comprises a primary gearbox shaft separate from an output shaft of the electrical machine coupled to this gearbox, the invention eliminates the need for a bearing mounted in the cover to support the free end of the shaft. primary of the reducer, and therefore to further reduce the mass of the electric powertrain.
[0024] Since the rotating shaft of the right or left electric machine is longer than in the prior art, in this first variant of the invention, a third bearing is used near the second end of the rotating shaft, in the reduction housing that accommodates it.
[0025] More specifically, the reinforcement portion of each right or left gearbox has, for example, a central opening and forms a third bearing around this central opening, extending axially into the inside of the gearbox. Since the rotating shaft of the right or left electric machine extends into the gearbox through this central opening, the electric drive unit includes two third bearings. Each third bearing is mounted on one of the rotating shafts and also in the third bearing housing that receives this rotating shaft. The third bearing is designed to withstand radial forces exerted on the rotating shaft. It is understood that this third bearing is solely intended to prevent the rotating shaft from moving radially relative to the axial direction. Therefore, the third bearing housing does not necessarily include a thrust bearing to axially restrain the third bearing.
[0026] Once the right or left-handed electric machine is assembled, and the third bearing is mounted on the rotating shaft, the corresponding reinforcing portion of the gearbox housing is attached to the cylindrical wall, leaving the second end of the rotating shaft protruding from the third bearing. A lip seal is then positioned radially between the rotating shaft and the third bearing, and axially between the third bearing and the second end of the rotating shaft, to prevent gearbox lubricating oil from entering the electric machine.
[0027] Then, the free end of the third bearing is fitted with a fixed part of an angular position sensor for the electric machine's rotor, positioned opposite a rotating part of the sensor, which is mounted on the rotating shaft. The second end of the rotating shaft, extending from the third bearing, then receives a pinion with helical teeth. Using a pinion insert simplifies the assembly of the electric machine and the gearbox. Indeed, choosing a tooth diameter directly machined on the shaft that is smaller than the inner diameter of the sensor's target would be too restrictive an architectural constraint, preventing the desired tooth configuration. Using a pinion insert eliminates this constraint.
[0028] In a second embodiment of the invention with two stators per right- or left-handed electric machine, a third bearing is not used, but the second bearing is arranged closer to the second end of the rotating shaft. which saves another bearing and reduces the mass of the powertrain. More specifically, for example in this second variant:
[0029] - the annular support plates are the first annular support plates, - the casing comprises a cylindrical wall surrounding the central wall and delimiting on the one hand a left volume occupied by the rotor and stator magnetic poles of the left-hand electric machine, on a so-called left side of the central wall, and on the other hand a right volume occupied by the rotor and stator magnetic poles of the right-hand electric machine, on a so-called right side of the central wall, the right side being opposite the left side with respect to the central wall, -the electric powertrain comprises, for each left or right reduction gear, a housing including a reinforcing section extending mainly orthogonally to the axes of rotation of the rotating shafts, and - the casing also includes, for each second stator of the right or left electric machine, a second annular support plate, positioned against one end of the cylindrical wall, and fixed to the reinforcing portion of the right or left gearbox housing respectively, - the reinforcement portion of each right or left reducer housing has a central orifice and forms around the central orifice, a second bearing extending axially towards the inside of the right or left reducer housing, and in which, the rotating shaft of the right or left electric machine extending into the right or left reducer housing respectively through the central orifice, each second bearing is mounted on one side on one of the rotating shafts and on the other side in the second bearing receiving this rotating shaft, the second bearing having a stop capable of retaining the second bearing when it is subjected to an axial force directed outwards from the right or left electric machine.
[0030] Compared to the first embodiment, in the second embodiment, the second bearing therefore plays the role of the third bearing and the second bearing plays the role of the third bearing.
[0031] This second embodiment includes an assembly of the electric drive unit similar to that of the first embodiment of the invention. In particular, in this second embodiment, the electric drive unit also includes an added pinion, a lip seal, and an angular position sensor for the rotor of the right or left-hand electric machine in question.
[0032] Other features and advantages of the invention will become apparent from the following description on the one hand, and from several illustrative and non-limiting examples of embodiments given with reference to the attached schematic drawings on the other hand, in which:
[0033] [Fig. 1] illustrates an electric powertrain according to the invention, in a first variant of an embodiment of the invention, and
[0034] [Fig.2] illustrates an electric powertrain according to the invention, in a second variant of the embodiment of the invention of [Fig.1].
[0035] According to an embodiment of the invention shown in [Fig. 1], an electric powertrain 1 according to the invention comprises a first axial flux electric machine, hereafter referred to as left-hand electric machine 2g, coupled to a first reduction gear, hereafter referred to as left-hand reduction gear 3g. Similarly, the electric powertrain 1 comprises a second axial flux electric machine, hereafter referred to as right-hand electric machine 2d, coupled to a second reduction gear, hereafter referred to as right-hand reduction gear 3d. Of course, the right-hand and left-hand electric machines are distinct, and the right-hand and left-hand reduction gears are distinct.
[0036] Each electric machine and gearbox assembly, to which the electric machine is coupled, is mechanically coupled to a separate wheel of an electric or hybrid vehicle. For example, the vehicle has an electric powertrain 1 according to the invention on its rear axle, to turn the rear wheels of the vehicle, and an electric powertrain 1 according to the invention on its front axle, to turn the front wheels of the vehicle.
[0037] Each right-hand 2d or left-hand 2g electric machine comprises a rotor respectively 25d, 25g, arranged axially each between on the one hand a first stator respectively 22d, 22g and on the other hand a second stator respectively 24d, 24g.
[0038] To simplify reading, in this main embodiment of the invention, it is understood that references ending with the letter "d" relate only to the right-hand electric machine 2d or the right-hand reducer 2d, while references ending with the letter "g" relate only to the left-hand electric machine 2g or the left-hand reducer 2g.
[0039] A first air gap is therefore present between the first stator 22d, 22g of each electric machine 2d, 2g and the rotor 25d, 25g of the latter, and a second air gap is present between the second stator 24d, 24g of each electric machine 2d, 2g and the rotor 25d, 25g of the latter.
[0040] Each rotor 25d, 25g is discoidal in type. It comprises a body 25Id, 251g made of composite material, for example, synthetic polymer and glass or carbon fibers. This body 25Id, 251g forms a star shape, a central portion of which is fixed, here screwed, to a hub of a rotating shaft 27d, 27g of the electrical machine 2d, 2g, which includes the rotor 25d, 25g. The rotating shafts 27d, 27g are mounted to rotate about the same axial direction X.
[0041] The 25 Id, 251g star-shaped body has radii regularly distributed around its central part, between which rotor magnetic poles are inserted, Each magnet is composed of segmented magnets 253d, 253g, or bonded magnets (i.e., magnetic powder consolidated in resin), or a mixture of segmented and bonded magnets. A ring 255d, 255g surrounds the star-shaped body 25 Id, 251g to constrain the rotor magnetic poles to remain within the star-shaped body 25 Id, 251g despite the centrifugal force.
[0042] The first stator 22d, 22g of each electrical machine 2d, 2g comprises a first annular support plate 221d, 221g, in the general shape of a disc with a hole in its center to allow passage of the rotating shaft 27d, 27g. The first annular support plate 22d, 221g has around this central hole an internal rim projecting axially from the first annular support plate 22d, 221g and forming a first bearing 71d, 71g, housing a first bearing 81d, 81g in which the rotating shaft 27d, 27g is mounted.
[0043] On the first annular support plate 221d, 221g is fixed a magnetic steel structure 223d, 223g, forming a stator yoke in the shape of a circular crown from which trapezoidal stator teeth project axially, regularly spaced angularly, each stator tooth being surrounded by a coil holder carrying a winding 225d, 225g of conductive wire. Each stator tooth with its winding 225d, 225g forms a stator magnetic pole of the first stator 22d, 22g.
[0044] In this embodiment of the invention, the first stator 22d, 22g further comprises an annular cooling chamber, enveloping its stator magnetic poles, and in which a dielectric heat transfer fluid circulates. Other types of cooling are nevertheless conceivable.
[0045] Similarly, the second stator 24d, 24g of each electric machine 2d, 2g has a second annular support plate 24Id, 241g, in the overall shape of a disc with a hole in its center to allow passage of the rotating shaft 27d, 27g. The second annular support plate 24Id, 241g has around this central hole an internal rim projecting axially from the second annular support plate 241d, 241g and forming a second bearing 72d, 72g, housing a second bearing 82d, 82g in which the rotating shaft 27d, 27g is mounted.
[0046] On the second annular support plate 24Id, 241g is fixed a magnetic steel structure 243d, 243g, forming a stator yoke in the shape of a circular crown from which trapezoidal stator teeth project axially, regularly spaced angularly, each stator tooth being surrounded by a coil holder carrying a winding 245d, 245g of conductive wire. Each stator tooth with its winding 245d, 245g forms a stator magnetic pole of the second stator 24d, 24g.
[0047] The second stator 24d, 24g also has an annular cooling chamber, enveloping its stator magnetic poles, and in which a dielectric heat transfer fluid circulates.
[0048] The right-hand (2d) and left-hand (2g) electrical machines are housed in a single casing 4, comprising a cylindrical wall 44, with its axis of revolution along the axial direction X, and a central wall 42 extending primarily orthogonally to the axial direction X, and having an overall disc shape with a hole in its center. The central wall 42 and the cylindrical wall 44 form a single piece, for example, made of steel, in one piece, with a stiffness coefficient on the order of 2 million Newtons per millimeter. The cylindrical wall 44 is, of course, only globally cylindrical since it includes passages for the dielectric coolant.
[0049] The central wall 42 is arranged axially halfway between the axial ends of the cylindrical wall 44. Thus, the casing 4 delimits on the one hand a left volume occupied by the rotor and stator magnetic poles of the left electric machine 2g, on a so-called left side of the central wall 42, and on the other hand a right volume occupied by the rotor and stator magnetic poles of the right electric machine 2d, on a so-called right side of the central wall 42, the right side being opposite to the left side with respect to the central wall 42.
[0050] The first annular support plates 221d, 221g are fixed, here by screwing, on either side of the central wall 42.
[0051] The second annular support plates 241d, 241g are each positioned against a distinct axial end of the cylindrical wall 44, and each is screwed, on the side opposite the right or left volume, to the bottom of a first part of a housing for the right or left gearbox, respectively. This first housing part is a steel reinforcement section 33d, 33g, extending primarily orthogonally to the axial direction X. The reinforcement section 33d, 33g has a central opening for the rotating shaft 27d, 27g. Around this central opening, it forms a third bearing in which a third bearing 83d, 83g is mounted, the rotating part of which is fixed to the rotating shaft 27d, 27g.
[0052] The first and second annular support plates 221d, 221g, 241d, 241g as well as the reinforcement portions 33d, 33g are for example made of steel with a stiffness coefficient of the same order of magnitude as the crankcase 4 of the powertrain group 1.
[0053] The housings of the right reducer 3d and left reducer 3g each also include a cover 35d, 35g, the edges of which are screwed to the external edges of the reinforcement portion 33d, 33g, located on the opposite side to the bottom of this reinforcement portion 33d, 33g.
[0054] Each rotating shaft 27d, 27g therefore extends from a first end which stops axially in the central opening of the central wall 42, to a second end which extends into the right or left reduction housing respectively, the second end extending axially from the third bearing, and receiving a pinion 31d, 31g having helical teeth.
[0055] Each rotating shaft 27d, 27g forms a single primary drive shaft of the right-hand reducer 3d or left-hand reducer 3g, meaning that the primary line of the right-hand reducer 3d or left-hand reducer 3g consists of only one shaft, which is the rotating shaft 27d, 27g of the right-hand electric machine 2d or left-hand reducer 2g. The secondary line of each right-hand reducer 3d or left-hand reducer 3g is formed by a secondary shaft 32d, 32g mounted at one end in a bearing housed in the reinforcing portion 33d, 33g and at the other end in a bearing housed in the cover 35d, 35g. A toothed wheel 34d, 34g mounted on each secondary shaft 32d, 32g cooperates with the pinion 31d, 31g to transmit the rotation from the rotating shaft 27d, 27g to the secondary shaft 32d, 32g.
[0056] Each gear 34d, 34g therefore has a helical tooth profile complementary to that of the pinion 31d, 31g. During the rotation of the gear 34d, 34g, it transmits axial forces to the rotating shaft 27d, 27g.
[0057] In this embodiment of the invention, the helical gears on each rotating shaft 27g, 27d are oriented such that the rotation of the gear 34d, 34g with which they cooperate generates an axial force Fd, Fg, directed towards the first end of the rotating shaft 27d, 27g, i.e., towards the interior of the electric drive unit. This axial force Fd, Fg is transmitted through the rotating shaft 27d, 27g to the first bearing 81d, 81g. The first bearing housings 71d, 71g each have a thrust bearing 712d, 712g capable of retaining the first bearing 81d, 81g when it is subjected to this axial force Fd, Fg. The axial force Fd generated by the gear 32d of the right reducer 3d is substantially identical in absolute value to the axial force Fg generated by the gear 32g of the left reducer 3g, because the right 2d and left 2g electrical machines are configured to work approximately at the same operating point.However, the axial forces Fd and Fg are in opposite directions.
[0058] The first bearings 81d, 81g have a much lower stiffness coefficient than that of the first annular support plates 22 Id, 221g and the central wall 42, which form a reinforcement structure of the casing 4.
[0059] As for the rotating shafts 27d, 27g, these have a very high stiffness coefficient, being, for example, made of steel with a stiffness coefficient of the same order of magnitude as the casing 4 of the powertrain 1, although each of their first or second ends is hollowed out to limit their mass. They may each include through-holes extending radially from each of their hollows into the interior of the electrical machine to which They belong, in order to promote air cooling of the rotor of this electric machine.
[0060] Each axial force Fd, Fg exerted by one of the gears 32d, 32g being very significant, it could, if acting alone on the rotating shaft 27d, 27g, the first bearing 81d, 81g, and the reinforcing structure, deform the latter and eliminate the first air gap. However, by acting together with the same magnitude and in opposite directions, they symmetrically compress the rotating shaft 27d, 27g and the first bearing 81d, 81g against the reinforcing structure, which is therefore not deformed.
[0061] Under these conditions, only the compressions of the rotating shafts 27d, 27g, the first bearings 81d, 81g, and the reinforcement structure need to be considered to keep the first and second air gaps substantially constant. However, only the first bearings 81d, 81g have a stiffness coefficient low enough to require consideration of their compression, which nevertheless remains negligible, here on the order of 60 micrometers at maximum torque. Therefore, the invention makes it possible to avoid significantly altering the first or second air gap during the operation of the electric drive unit 1, particularly because the reinforcement structure, due to its stiffness and arrangement, is not deformed during the rotations of the gears 34d, 34g.
[0062] It should be noted that this result remains valid whether the reinforcement structure comprises only the central wall 42 or the central wall and the first annular support plates, as in this embodiment. Indeed, the compression of the first bearings 81d, 81g against the thrust bearings 712d, 712g, due to the axial forces generated by the gears 34d, 34g, is exerted symmetrically on both sides of the central wall 42, being partially absorbed by each first annular support plate 22d, 22g. Consequently, at the central wall 42, these axial forces cancel each other out and are not likely to deform this reinforcement structure.
[0063] The structure of the electric powertrain 1 also allows for a simple assembly of its elements. In particular, the first stators 22d, 22g are first fixed to the central wall 42, then each rotor 25d, 25g with its rotating shaft 27d, 27g on which the first, second and third bearings 81d, 82d, 83d or 81g, 82g, 83g are mounted, is positioned with its rotor magnetic poles opposite the stator magnetic poles of the first stator 22d, 22g, the first bearing 81d, 81g being mounted in the first bearing 71d, 71g.
[0064] Each second stator 24d, 24g is then fixed to the reinforcing portion 33d, 33g of the right or left reduction housing, then the corresponding second annular support plate 24Id, 241g is positioned against one of the axial ends of the cylindrical wall 44 to adjust the air gap between the second stator 24d, 24g and the rotor 25d, 25g by acting on the screws connecting the second stator 24d, 24g and the reinforcement portion 33d, 33g.
[0065] When the air gap is adjusted, the reinforcing portion 33d, 33g is screwed to the corresponding axial end of the cylindrical wall 44. When positioning the second annular support plate 24 Id, 241g against the cylindrical wall 44, the second bearing 82d, 82g is inserted into the bearing 72d, 72g formed by the second annular support plate 24 Id, 241g, the bearing 72d, 72g having a stop 722d, 722g coming against the second bearing 82d, 82g.
[0066] When attaching the reinforcement section 33d, 33g, the third bearing 83d, 83g is inserted into the third housing, which does not have a thrust bearing. This third bearing 83d, 83g is positioned close to the second end of the rotating shaft 27d, 27g, so that the shaft does not move radially and is therefore designed to withstand only radial forces. It thus prevents the first or second air gap from being deformed by a radial movement of the rotating shaft 27d, 27g, which would cause it to tilt. As explained below, the third bearing is not, however, fixed to the free edge of the third housing, in order to allow for the insertion of a lip seal 10d, 10g into the housing.
[0067] Following the fixing of the reinforcement portion 33d, 33g, the lip seal lOd, 10g is inserted around each rotating shaft 27d, 27g, from its second end. This lip seal lOd, 10g is positioned radially between the rotating shaft 27d, 27g and the third bearing it passes through, and axially between the third bearing 83d, 83g and the second end of the rotating shaft 27d, 27g, to prevent the lubricating oil of the right-hand gearbox 3d or left-hand gearbox 3g from passing into the right-hand electric machine 2d or left-hand electric machine 2g, respectively.
[0068] A 9d, 9g angular positioning sensor is then positioned in each right 3d or left 3g reducer, to know the angular position of the 25d, 25g rotor.
[0069] The fixed part of each angular position sensor 9d, 9g is fixed on the free end of a third bearing, opposite the rotating part of the angular position sensor 9d, 9g, which is mounted on the rotating shaft 27d, 27g.
[0070] Finally, the second end of each rotating shaft 27d, 27g, protruding from the third bearing which it passes through, receives the pinion 31d, 31g, the latter being held in place by a ring.
[0071] Of course each rotating shaft 27d, 27g has shoulders, each shoulder allowing the positioning of an element mounted around the rotating shaft 27d, 27g, such as one of the first, second or third bearings, the lip seal, the rotating part of the angular positioning sensor or the pinion.
[0072] We now describe, in relation to [Fig.2], an electric powertrain 1b according to the invention, in a variant of the embodiment of [Fig.1]. Only the right part of the electric powertrain 1b is shown, the left part of the electric powertrain 1b being of symmetrical design to this right part with respect to a central wall 42, which is identical to the central wall 42 of the powertrain 1 of the main embodiment of the invention.
[0073] In this variant, only two bearings are used to support the rotating shaft 27d, 27g of each electric machine of the powertrain 1b. Since many elements are identical between the two embodiment variants, these identical elements are referenced in the same way.
[0074] The right-hand side of the electric powertrain 1b comprises an electric machine 2e coupled to a reduction gear 3e. The only difference between the electric machine 2e and the right-hand electric machine 2d of [Fig. 1] is that the second stator 24e of the electric machine 2e has a second annular support plate 241e which does not form a second bearing.
[0075] Indeed, the rotating shaft 27d is mounted to rotate only on one side in the first bearing 81d housed in the first bearing 7 Id formed by the first annular support plate 22 Id, and on the other side in a second bearing 82e housed in a second bearing formed by the gearbox housing 2e. More precisely, this housing has a first part called the reinforcement portion 33e and identical to the reinforcement portion 33d of [Fig. 1], except that the bearing 72e formed around the central opening of the reinforcement portion 33e, which is here a second bearing, has a stop 722e allowing the second bearing 82e to be retained when it is subjected to an axial force directed outwards from the electrical machine 2e.Indeed, in this embodiment of the invention, the second bearing is intended to resist radial forces but also axial forces directed towards the second end of the rotating shaft 27d, since this embodiment no longer includes an intermediate bearing between the first bearing 81d and the second bearing 82e to play this role.
[0076] This alternative embodiment saves a second bearing and therefore reduces the mass of the electric powertrain compared to the main embodiment of the invention.
[0077] Of course, the invention is not limited to the examples just described and many modifications can be made to these examples without departing from the scope of the invention.
Claims
Demands
1. Electric powertrain (1, 1b) comprising: - a first axial flux electric machine and a first reducer comprising at least one toothed wheel (34g), called left-hand electric machine (2g) and left-hand reducer (3g), capable of turning a first wheel of a vehicle, - a second axial flux electric machine and a second gearbox comprising at least one toothed wheel (34d), referred to as the right electric machine (2d, 2e) and right gearbox (3d, 3e), capable of turning a second wheel of a vehicle, each of the left (2g) and right (2d, 2e) electric machines comprising, on the one hand, at least one stator (22g, 24g, 22d, 24d, 24e) comprising stator magnetic poles, and on the other hand, a rotor (25g, 25d) comprising rotor magnetic poles (253g, 253d), separated from the stator magnetic poles by an air gap, the rotor (25g, 25d) further comprising a rotating shaft (27g, 27d) mounted rotatably, on the one hand, at one of its ends, in a first bearing (81g, 81d), and on the other hand, between the first bearing and a second of its ends, in a second bearing (82g, 82d, 82e), the electric powertrain (1, 1b) being characterized in that: - the right (2d, 2e) and left (2g) electrical machines are arranged in the same casing (4), - at least one of the rotating shafts (27g, 27d) of the left (2g) or right (2d, 2e) electrical machine forms a single primary drive shaft of the left reducer (3g) or respectively of the right reducer (3d, 3e), the second end of the rotating shaft (27g, 27d) being provided with teeth adapted to cooperate with the gear (34g, 34d) of one of the left or respectively right reducers (3g, 3d, 3e), and - the toothed wheel of the left-hand reducer (3g) being capable of generating, by its rotation, an axial force (Fg) on the first (81g) or the second bearing (82g) of the left-hand electrical machine (2g), in the opposite direction to an axial force (Fd) capable of being generated by a rotation of the toothed wheel of the right-hand reducer (3d, 3e) on the first (81d) or respectively the second bearing (82d, 82e) of the machine electric right (2d, 2e), the housing (4) includes at least one reinforcement structure suitable for receiving the first (81g, 81d) or respectively the second bearings (82g, 82d, 82e), and for taking up at least part of the axial forces (Fg, Fd) in opposite directions.
2. Electric powertrain (1, 1b) according to claim 1, wherein the two rotating shafts (27g, 27d) each form a single primary drive shaft of the left reducer (3g) or the right reducer (3d, 3e).
3. Electric powertrain (1, 1b) according to claim 1 or 2, wherein each rotating shaft (27g, 27d) has at least one recess extending axially in the rotating shaft (27g, 27d).
4. Electric powertrain (1, 1b) according to any one of claims 1 to 3, wherein said at least one stator is a first stator (22g, 22d), and wherein each right (2d, 2e) or left (2g) electric machine comprises a second stator (24g, 24d, 24e), the rotor (25d, 25g) of the right (2d, 2e) or left (2g) electric machine being arranged axially between the first stator (22d, 22g) of the right (2d, 2e) or left (2g) electric machine and the second stator (24d, 24e, 24g) of the right (2d, 2e) or left (2g) electric machine.
5. Electric powertrain (1, 1b) according to any one of claims 1 to 4, wherein the stator magnetic poles of said at least one stator of the left electric machine (2g) and the stator magnetic poles of said at least one stator of the right electric machine (2d, 2e) are fixed axially on either side of the reinforcement structure, in which are arranged first bearings (71g, 71d) suitable for receiving the first bearings (81g, 81d), the reinforcement structure extending mainly orthogonally to the axes of rotation of the rotating shafts (27g, 27d).
6. Electric powertrain (1, 1b) according to any one of claims 1 to 5, wherein the teeth on each rotating shaft (27g, 27d) are helical teeth, oriented such that the rotation of each gear (34g, 34d) cooperating with the helical teeth of the rotating shaft (27g, 27d) generates an axial force (Fg, Fd) directed towards the first end of the rotating shaft (27g, 27d).
7. Electric powertrain (1, 1b) according to claims 5 and 6, wherein the reinforcement structure comprises a central wall (42) orthogonal to the axes of rotation of the rotating shafts (27g, 27d), an annular support plate (221d) for the stator magnetic poles of said at least one stator (22d, 22e) of the right-hand electric machine (2d, 2e) and an annular support plate (221g) for the stator magnetic poles of said at least one stator (22g) of the left-hand electric machine (2g), the annular support plates (221d, 221g) being fixed on either side of the central wall (42), each annular support plate (221d, 221g) having an internal rim projecting axially from the annular support plate (221d, 221g) and forming the first bearing (71d, 71g) for the first bearing (81d, 81g) of the right (2d, 2e) or left (2g) electric machine, the first bearing (71d, 71g) having a thrust bearing (712d,712g) capable of retaining the first bearing (81d, 81g) when the latter is subjected to an axial force (Fd, Fg) directed towards the first end of the rotating shaft (27d, 27g) carrying the first bearing (81d, 81g).
8. Electric powertrain (1) according to claims 4 and 7, wherein: - the annular support plates are the first annular plates (22 Id, 221g), - the casing (4) comprises a cylindrical wall (44) surrounding the central wall (42) and delimiting on the one hand a left volume occupied by the rotor and stator magnetic poles of the left electric machine (2g), on a so-called left side of the central wall (42), and on the other hand a right volume occupied by the rotor and stator magnetic poles of the right electric machine (2d), on a so-called right side of the central wall (42), the right side being opposite to the left side with respect to the central wall (42), - the electric powertrain (1) comprises, for each left (3g) or right (3d) reduction gear, a housing including a reinforcing portion (33g, 33d) extending mainly orthogonally to the axes of rotation of the rotating shafts (27g, 27d), and - the casing (4) further comprises, for each second stator (24g, 24d) of the right (2d) or left (2g) electric machine, a second annular support plate (241d, 241g), positioned against one end of the cylindrical wall (44), and fixed to the reinforcement portion (33g, 33d) of the housing of the right (3d) or respectively left (3g) reducer, each second annular support plate (24 Id, 241g) having an internal rim projecting axially from the second annular support plate (24 Id, 241g) and forming a second bearing (72d, 72g) for the second bearing (82d, 82g) of the right (2d) or left (2g) electric machine.
9. An electric drive unit (1) according to claim 8, wherein the reinforcing portion (33g, 33d) of each right (3d) or left (3g) reduction housing has a central opening and forms, around the central opening, a third bearing extending axially inward from the right (3d) or left (3g) reduction housing, and wherein, the rotating shaft (27d, 27g) of the right (2d) or left (2g) electric machine extending into the right (3d) or left (3g) reduction housing respectively through the central opening, the electric drive unit (1) comprises two third bearings (83d, 83g), each third bearing (83d, 83g) being mounted on one side on one of the rotating shafts (27d, 27g) and on the other side in the third bearing receiving this rotating shaft (27d, 27g). (83d, 83g) being able to withstand radial forces exerted on the rotating shaft (27d, 27g).
10. Electric powertrain (1b) according to claims 4 and 7, wherein: - the annular support plates are the first annular support plates (22 Id), - the casing (4) comprises a cylindrical wall (44) surrounding the central wall (42) and delimiting, on the one hand, a left-hand volume occupied by the rotor and stator magnetic poles of the left-hand electric machine, on the left side of the central wall (42), and on the other hand, a right-hand volume occupied by the rotor and stator magnetic poles of the right-hand electric machine (2e), on the right side of the central wall (42), the right side being opposite the left side with respect to the central wall (42), - the electric powertrain (1b) comprises, for each left-hand or right-hand reduction gear (3e), a housing including a reinforcing portion (33e) extending mainly orthogonally to the axes of rotation of the rotating shafts (27g, 27d), and - the casing (4) further comprises, for each second stator (24e) of the right (2e) or left electric machine, a second annular support plate (241e), positioned against one of the ends of the cylindrical wall (44), and fixed to the reinforcing portion (33e) of the right (3e) or respectively left gearbox housing, - the reinforcing portion (33e) of each right (3e) or left reducer housing has a central orifice and forms around the central orifice, a second bearing (72e) extending axially towards the inside of the right (3e) or left reducer housing, and in which, the rotating shaft (27d) of the right (3e) or left electric machine extending into the right (3e) or respectively left reducer housing through the central orifice, each second bearing (82e) is mounted on one side on one of the rotating shafts (27d) and on the other side in the second bearing (72e) receiving this rotating shaft (27d), the second bearing (72e) having a stop (722e) capable of retaining the second bearing (82e) when it is subjected to an axial force directed outwards from the right (2e) or left electric machine.