Transmission shaft for a transmission system for an electric or hybrid vehicle

Abstract

The invention relates to a transmission shaft (10) for a transmission system of an electric or hybrid vehicle, comprising: - a main body (13) having a main axis of revolution (X) and which has an outer surface (14) and a first end wall (11) and a second end wall (12) which are substantially perpendicular to the main axis of revolution (X); - at least one toothed pinion (30), which can be constrained to rotate with the transmission shaft or rotate freely about the transmission shaft; - a hole (20) extending longitudinally along the main axis of revolution (X), starting from the first end wall (11) and extending into the main body (13); and - a passive or active damping device (50) inserted into the hole, the damping device being pressed against the inner periphery of the hole (20) in a contact region (17) that runs through the middle of the transmission shaft.

Description

DESCRIPTION TITLE: DRIVE SHAFT FOR TRANSMISSION SYSTEM FOR ELECTRIC OR HYBRID VEHICLES TECHNICAL FIELD OF THE INVENTION

[0001] The invention relates to a driveshaft for an electric or hybrid vehicle transmission system. This transmission system includes, in particular, an electric motor providing torque and at least one series of gear trains intended to be connected to the vehicle's wheels. When the vehicle also includes an internal combustion engine coupled to the electric motor, the vehicle is said to be "hybrid" because the vehicle's propulsion can be achieved either purely electrically, purely thermally, or in a hybrid manner using both types of energy simultaneously.

[0002] In the case of a purely electric vehicle, meaning one without an internal combustion engine, electricity can be supplied by a battery or by means of a fuel cell using hydrogen as a reducing fuel. The electric vehicle can be a passenger car or an industrial vehicle, such as a truck, bus, or tractor. PREVIOUS STATE OF THE ART

[0003] The transmission system typically comprises a housing and drive shafts equipped with gears supported by the housing via guide bearings. The drive shafts carry gears and pinions that generate vibrations through meshing. These vibrations are then transmitted through the drive shafts and the guide bearings to the housing walls. The vibrations cause the drive shaft to excite according to its natural modes. One of these natural modes of the drive shaft corresponds to a deflection along its axis of rotation with deflection values ​​on the order of 0.1 to 0.3 pm. These vibrations ultimately create a noise that the driver of the purely electric vehicle can perceive.

[0004] There is a need to improve the acoustic vibration level of this type of transmission system, particularly by developing solutions that address vibrations within the transmission shaft.

[0005] One such transmission system is described, for example, in US patent application 2022128141AA. In this patent application, the hollow transmission shaft incorporates a dynamic damper of the "beater" type, consisting of a suspended mass made of a high-density material (lead or cast iron) housed in the central bore of the transmission shaft. The suspended mass is mounted on a rubber component with appropriate stiffness. The damping is determined by the chemical composition of the rubber, with the aim of "damping" resonance caused by the bending of the transmission shaft.

[0006] This type of solution is bulky, adds weight to the transmission shaft and increases the overall inertia of the transmission system so that there is always a need to improve the acoustic vibration level of this type of transmission system. DESCRIPTION OF THE INVENTION

[0007] The invention relates to a drive shaft for an electric or hybrid vehicle transmission system, comprising: - a principal body having a principal axis of revolution which has an external surface, a first end wall and a second end wall substantially perpendicular to the principal axis of revolution; - at least one toothed pinion, which can be fixed in rotation with the transmission shaft or rotate freely around the transmission shaft; - a hole extending longitudinally along the main axis of revolution, formed from the first end wall and extending into the main body; and - a passive or active damping device inserted into the hole; The damping device covers the inner perimeter of the hole at a contact area that is continuous over 360° and passes through the middle of the transmission shaft in the axial direction.

[0008] This driveshaft offers the advantage, thanks to its continuous 360° contact area, of increasing the heat exchange surface with the main body of the driveshaft. This increased exchange surface allows the passive or active damping device to limit the driveshaft's deflection along its axis of rotation. The objective is to dissipate vibrational energy by absorbing it directly within the driveshaft.

[0009] The contact area of ​​the passive or active damping device is located within the maximum deformation zone of the transmission shaft. Since this is bending deformation, the maximum deformation zone of the transmission shaft passes through the midpoint of the transmission shaft in the axial direction.

[0010] The midpoint of the transmission shaft in the axial direction corresponds to an area located halfway between the first end wall and the second end wall along the main axis of revolution.

[0011] Preferably, the damping device adheres to the inner perimeter of the hole at the contact area, which helps reduce noise from the drive shaft.

[0012] Advantageously, the damping device has a cylindrical profile stopped by two end surfaces and the damping device is pressed onto the entire contact area, the cylindrical profile of the damping device being complementary to the profile of the hole.

[0013] According to one variant of the invention, the cylindrical profile of the damping device is circular and concentric with the main axis of revolution.

[0014] According to another variant of the invention, the cylindrical profile of the damping device is polygonal and surrounds the main axis of revolution.

[0015] For example, the hole includes grooves extending longitudinally along the main axis of revolution, cut from a central circular bore. In this way, the exchange surface of the passive or active damping device with the transmission shaft is increased.

[0016] According to one aspect of the invention, the hole in the main body extends to the second end wall, and the damping device has at least one orifice passing through it, arranged to allow lubricating fluid to pass through the transmission shaft. In this configuration, the flow rate of the lubricating fluid at the second end wall is adjusted according to the diameter of the orifice. The orifice is, for example, centrally located.

[0017] In one example, the contact area can extend along the entire length of the hole.

[0018] According to one aspect of the invention, the damping device is passive and comprises a central insert made of a viscoelastic damping material. The use of this central insert, with its increased contact area with the drive shaft, allows for the dissipation of vibrational energy through shear in the damping material. The objective is to dissipate the vibrational energy resulting from the bending of the drive shaft by absorbing the energy directly within the central insert using a shear-acting damping material. To enhance damping, the damping material adheres to the inner circumference of the hole.

[0019] Viscoelastic damping materials possess both elastic (like springs) and viscous (like fluids) properties. When the damping material is deformed by vibrations, some of the energy is reversibly stored (elastic) and some is dissipated as heat (viscous). Thus, the damping material can exhibit hyperelastic behavior with hysteresis as it deforms. This behavior can be nonlinear.

[0020] The cushioning material is, for example, an adhesive foam that sticks to the inner perimeter of the hole.

[0021] The cushioning material is, for example, polyurethane foam.

[0022] The cushioning material is, for example, a synthetic foam.

[0023] The cushioning material is, for example, silicone.

[0024] The damping material is, for example, an elastomer.

[0025] The damping material includes, for example, sand and cement bonded together in a hydraulic binder.

[0026] According to one variant of the invention, the passive type damping device is pre-stressed and assembled inside the hole, the outside diameter of the passive type damping device being less than the diameter of the hole.

[0027] According to one embodiment of the invention, the central insert is divided into different sections by adhesion walls that extend longitudinally along the hole. For example, the adhesion walls are distributed angularly around the principal axis of revolution. The adhesion walls increase the surface area of ​​contact with the damping material of the central insert, which operates in shear.

[0028] The adhesion walls can be in contact with the inner perimeter of the hole. This allows the passive damping device to be centered within the hole.

[0029] The adhesion walls can be made of steel. This increases the exchange surface between the transmission shaft and the central insert in order to dissipate energy as heat, given that the damping material works in shear.

[0030] The adhesion walls can be arranged in a cross shape.

[0031] According to another aspect of the invention, the passive damping device comprises an inner tube extending along the main axis of revolution which is attached to the central insert, the central insert being interposed between the inner rim of the hole and the inner tube. This increases the exchange surface between the transmission shaft, the inner tube, and the central insert in order to dissipate energy as heat, since the damping material works in shear.

[0032] Preferably, the inner tube is made from a sheet of metal wrapped around the main axis of revolution. The inner tube is, for example, longitudinally split.

[0033] Advantageously, the inner tube is made of sheet steel.

[0034] Preferably, the thickness of the central insert is less than the thickness of the inner tube.

[0035] Advantageously, the central insert longitudinally covers the inner tube along its entire length.

[0036] Preferably, the thickness of the inner tube is less than the thickness of the main body of the transmission shaft.

[0037] Advantageously, the mass of the inner tube is less than 3% of the mass of the transmission shaft. This avoids any dynamic vibration. For example, the mass of the inner tube is approximately equal to 1% of the mass of the transmission shaft.

[0038] According to one aspect of the invention, the damping device is of the active type and comprises a piezoelectric subassembly inserted in a protective envelope, the protective envelope being pressed against the inner perimeter of the hole at the contact area.

[0039] The use of a piezoelectric sub-assembly with an increased contact area with the transmission shaft makes it possible to couple the mechanical structure of the transmission shaft to an electrical circuit intended to modify its vibration dynamics.

[0040] In terms of damping, piezoelectric components enable the conversion of vibrational energy into electrical energy. The presence of an inductor in the circuit creates an electrical resonance due to the exchange of charge with the piezoelectric capacitance. Thus, tuning the natural frequency of this resonant system to that of the mechanical structure of the transmission shaft is equivalent to implementing a tuned mass damper. The vibrational amplitude generated within the transmission shaft is reduced through the electromechanical coupling of the piezoelectric sub-assembly, which is controlled by an electronic circuit.

[0041] The protective casing is, for example, an epoxy resin that adheres to the inner rim of the hole. The aim is to dissipate the vibrational energy from the bending of the drive shaft by absorbing the energy directly within the piezoelectric sub-assembly. Therefore, a direct connection to the inner rim of the hole is important.

[0042] The transmission shaft according to the invention may have one or more of the characteristics described below, either combined or taken independently of each other: - the main body may include at least one additional fluid flow conduit arranged perpendicular to the main axis of revolution; - the main body is partially cylindrical, the external surface may include for example splines, gear teeth, a groove, a cylindrical bearing centering surface; - the transmission shaft includes raw machining surfaces and machined surfaces suitable for contacting a guide bearing and / or splined surfaces suitable for contacting a toothed pinion; - the transmission shaft has one or more gears, these can be fixed in rotation with the transmission shaft or rotate freely around the transmission shaft; - the first end wall and a second end wall are distinct from the external surface.

[0043] The invention also relates, according to another aspect, to a transmission system for an electric or hybrid vehicle comprising: - a crankcase; - a transmission shaft incorporating all or part of the characteristics mentioned above, which is free to rotate relative to the casing around its main axis of revolution; - a guide bearing supporting the transmission shaft relative to the casing which includes bearing elements, the guide bearing being inserted into a cylindrical housing made in the casing.

[0044] Preferably, the transmission system for electric or hybrid vehicles may also include: - a collector ring with electrical connections attached to the housing; in which the collector ring comprises a rotor and a fixed base rotating relative to the cylindrical housing, the rotor being inserted into the hole of the transmission shaft and electrically connected to the active type damping device.

[0045] The vibration amplitude generated within the transmission shaft is reduced thanks to the electromechanical coupling of the piezoelectric sub-assembly controlled by an electronic circuit.

[0046] Preferably, the base of the slip ring is electrically connected to an inverter of the electrical transmission system.

[0047] The invention also relates to a motorized vehicle, for example a hybrid or electric motor vehicle comprising a transmission system as described above. The motorized vehicle could be an industrial vehicle. BRIEF DESCRIPTION OF THE FIGURES

[0048] Other features and advantages of the invention will become apparent from the following description, with reference to the attached figures. [Fig. 1] Figure 1 is a simplified cross-sectional view of a transmission system for an electric or hybrid vehicle comprising a drive shaft according to a first embodiment of the invention; [Fig. 2] Figure 2 is a simplified cross-sectional view of a transmission system for an electric or hybrid vehicle comprising a drive shaft according to a second embodiment of the invention; [Fig. 3] Figure 3 is a cross-sectional view perpendicular to the main axis of revolution of the transmission shaft according to a third embodiment of the invention; [Fig. 4] Figure 4 is a cross-sectional view perpendicular to the main axis of revolution of the transmission shaft according to a fourth embodiment of the invention; [Fig. 5] Figure 5 is a cross-sectional view perpendicular to the main axis of revolution of the transmission shaft according to a fifth embodiment of the invention; [Fig. 6] Figure 6 is a simplified cross-sectional view of a transmission system for an electric or hybrid vehicle comprising a drive shaft according to a sixth embodiment of the invention; [Fig. 7] Figure 7 is a perspective view of a damping device according to the sixth embodiment of the invention of Figure 6. For clarity, identical or similar elements are identified by identical reference symbols across all figures. DETAILED DESCRIPTION OF IMPLEMENTATION METHODS

[0049] In the description and claims, the terms "external" and "internal," as well as the orientations "axial" and "radial," will be used to designate, according to the definitions given in the description, elements of the transmission shaft. By convention, the "radial" orientation is directed orthogonally to the axis of revolution. principal X of the transmission shaft determining the "axial" orientation and, from the inside out away from said axis, the "circumferential" orientation is directed orthogonally to the principal axis of revolution X and orthogonally to the radial direction.

[0050] Figure 1 illustrates a transmission system 1 for an electric or hybrid vehicle, comprising an electric machine (not shown) and a speed reduction device 2 kinematically linked to this electric machine. The speed reduction device 2 transmits the torque from the electric machine to the wheels of the electric or hybrid vehicle.

[0051] The electric machine can be, for example, an induction electric motor, comprising a rotor and a stator, electrically powered by three-phase alternating current from accumulator batteries via a current converter (not shown in Figure 1).

[0052] The electric machine is held on a housing 40a, 40b of the transmission system 1. The housing generally consists of a main housing 40a supporting the electric machine and a closing housing 40b bearing against the main housing 40a at a joint 48, to seal a cavity defined by the main housing 40a and the closing housing 40b. The cavity notably receives a transmission shaft 10 manufactured according to a first embodiment of the invention. The transmission shaft 10 includes at least one toothed pinion contributing to the reduction of the rotational speed of the electric machine.

[0053] In the transmission system 1 shown in Figure 1, the transmission shaft 10 is mobile in rotation relative to the housings 40a, 40b around its main axis of revolution X. Two guide bearings 100a, 100b support the transmission shaft relative to the housing at its two ends, each guide bearing being inserted into a cylindrical housing 41a, 41b provided in the main housing 40a and the closing housing 40b.

[0054] To lubricate the various components of the transmission system 1, the casing 40a, 40b contains lubricating fluid F, for example The oil. The guide bearings 100a, 100b and the transmission shaft pinion are partially immersed in the oil. It is then the activation of the speed reduction device 2 which, by splashing, mixes the oil and projects it throughout the entire internal volume of the casing, to ensure the desired lubrication of the entire system, including the non-immersed parts.

[0055] For the remainder of this description, a reference operational position of the transmission system 1 is defined as the three-dimensional orientation in which the transmission system 1 is installed in a horizontal vehicle. In this reference operational position, the transmission shaft 10 is located above the lubricating oil level. In the remainder of this description, unless otherwise stated, the invention will be described in a reference operational position.

[0056] The transmission shaft 10 carries a toothed pinion 30 which meshes with a gear of the speed reduction device 2. The meshing of the toothed surfaces generates vibrations that propagate through the body 13 of the transmission shaft. These vibrations generate excitation of the transmission shaft according to its natural modes.

[0057] To limit the impact of these vibrations and to limit the natural mode of the transmission shaft corresponding to bending along its axis of rotation, a passive damping element 50 is inserted into a hole provided in the main body 13 of the transmission shaft. The main body 13 has a principal axis of revolution X which has an external surface 14, a first end wall 11 and a second end wall 12 substantially perpendicular to the principal axis of revolution X.

[0058] The transmission shaft has a non-through hole 20 concentric with the main axis of revolution X. The hole 20 is formed from the first end wall 11 and extends inside the main body 13.

[0059] The damping device 50 covers the inner perimeter of the hole 20 at a contact zone 17 which is continuous over 360° and passes through the middle of the transmission shaft in the axial direction. The midpoint of the transmission shaft is illustrated in Figure 1 by a geometric plane M located midway between the first end wall 11 and the second end wall 12 along the principal axis of revolution X.

[0060] The damping device 50 has a cylindrical profile 51 stopped by two end surfaces 52. The cylindrical profile 51 of the damping device is circular and concentric to the main axis of revolution and the cylindrical profile 51 of the damping device is complementary to the profile of the hole 20.

[0061] The passive damping device 50 is affixed to the entire contact area 17. The passive damping device 50 comprises a central insert 53 made of a viscoelastic damping material. In this example, the damping material is an adhesive polyurethane foam that adheres to the inner perimeter of the hole 20. The adhesion of the damping device 50 to the inner perimeter of the hole 20 at the contact area 17 helps reduce noise from the drive shaft.

[0062] We will now describe, with reference to figure 2, a transmission shaft 10 according to a second embodiment of the invention which differs from the first embodiment in that the hole 20a is through.

[0063] The two guide bearings 100a, 100b, which include rolling elements 103, require continuous lubrication with lubricating oil. To lubricate the first guide bearing inserted in the main housing 40a, an oil supply channel F opens into the housing 41a.

[0064] Through the outlet of the open hole 20a, the drive shaft supplies various lubrication points within the transmission system 1, for example the second guide bearing 100b located opposite the first end wall 11. The transport of fluid F takes place from the first end wall 11 of the shaft to the second end wall 12.

[0065] In this second mode, the damping device 50 is pressed against the inner perimeter of the hole 20 at a continuous 360° contact zone 17 passing through the middle of the transmission shaft. The middle of the transmission shaft is shown in Figure 2 by a geometric plane M.

[0066] The damping device 50 has a cylindrical profile 51 stopped by two end surfaces 52. The cylindrical profile 51 of the damping device is circular and concentric to the main axis of revolution and the cylindrical profile 51 of the damping device is complementary to the profile of the through hole 20a.

[0067] The damping device 50 is pressed against the entire contact area 17. In this case, the contact area 17 extends over the entire through hole 20a. The damping device 50 passes through the middle of the transmission shaft.

[0068] The damping device 50 has an orifice 55 passing through it and arranged to allow the lubricating fluid to pass through the transmission shaft. The oil F is thus conveyed to the second guide bearing 100b by passing through the orifice 55.

[0069] A lubrication fluid diffuser 80 inserted in the cylindrical housing 41a of the main housing 40a allows the fluid to be injected directly into the hole 20a. The lubrication fluid diffuser 80 includes, in particular, a nozzle which is inserted into an inlet portion 26 of the hole 20a of the transmission shaft at the first end wall 11.

[0070] The inlet portion 26 is made by drilling from the first end wall 11. The inlet portion 26 is concentric with the main axis of revolution X.

[0071] The passive damping device 50 comprises a central insert 53 made of viscoelastic synthetic foam. The central insert 53, made of damping material, is fitted inside the transmission shaft and bonded to the inner perimeter of the through hole 20a. The central insert 53 is pre-stressed inside hole 20a, the outer diameter of the damping device 50 before assembly being smaller than the diameter of the hole. The positioning of the damping device 50 against the inner circumference of hole 20 at the contact area 17 helps reduce transmission shaft noise.

[0072] We will now describe, with reference to Figure 3, a transmission shaft 10 according to a third embodiment of the invention which differs from the first embodiment in that the hole 20a includes grooves Tl extending longitudinally along the main axis of revolution X to increase the exchange surface between the passive type damping device 50 and the transmission shaft 10.

[0073] The Tl grooves are machined from a central circular bore. For manufacturing reasons, the hole 20 is through. The Tl grooves are produced, for example, by broaching.

[0074] The grooves Tl are distributed angularly around the main axis of revolution X.

[0075] The transmission shaft 10 includes raw machined surfaces and machined surfaces suitable for contacting a guide bearing and / or splined surfaces suitable for contacting a toothed pinion.

[0076] The passive type damping device 50 includes a central insert 53 made of a damping material having viscoelastic behavior comprising sand and cement agglomerated in a hydraulic binder.

[0077] We will now describe, with reference to Figure 4, a transmission shaft 10 according to a fourth embodiment of the invention which differs from the first embodiment in that the passive type damping device 50 comprises a central insert 53 compartmentalized into different sections by adhesion walls 54 which extend longitudinally along the hole 20. The adhesion walls 54 make it possible to increase the exchange surface with the damping material of the central insert 53 which works in shear.

[0078] The adhesion walls 54 are distributed angularly around the principal axis of revolution X, for example every 60°. In the present case, some adhesion walls 54 are in contact with the inner perimeter of the hole and other adhesion walls 54 are not.

[0079] The adhesion walls 54 are made of steel. The adhesion of the damping device 50 to the inner perimeter of the hole 20 at the contact area 17 and to the adhesion walls 54 promotes the reduction of noise from the transmission shaft.

[0080] We will now describe, with reference to Figure 5, a transmission shaft 10 according to a fifth embodiment of the invention, which differs from the previous embodiment in that the passive damping device 50 comprises a central insert 53 and an inner tube 70 extending along the main axis of revolution, which is pressed against the central insert. The central insert 53 is interposed between the inner circumference of the hole 20 and the inner tube 70. This increases the exchange surface area between the transmission shaft, the inner tube, and the central insert in order to dissipate energy as heat, given that the damping material operates in shear.

[0081] The inner tube 70 is made from a sheet of steel wound around the main axis of revolution. The inner tube 70 is split longitudinally.

[0082] The thickness Ep2 of the central insert 53 is less than the thickness Ep3 of the inner tube 70, and the thickness Ep3 of the inner tube is less than the thickness Epi of the main body 13 of the transmission shaft. The thickness Ep2 of the central insert 53 is between 0.2 and 2 mm.

[0083] In this example, the mass of the inner tube 70 is less than 3% of the mass of the transmission shaft.

[0084] The damping device 50 also has an orifice through said device and arranged to allow the lubricating fluid to pass through the transmission shaft.

[0085] The passive damping device 50 comprises a central insert 53 made of silicone. This damping material exhibits viscoelastic properties. The central insert 53 of the damping device adheres to the inner circumference of the hole 20 at the contact area 17. The adhesion of the damping device 50 to the inner circumference of the hole 20 at the contact area 17, as well as to the inner tube 70, contributes to reducing transmission shaft noise.

[0086] We will now describe, with reference to figures 6 and 7, a transmission shaft 10 according to a sixth embodiment of the invention which differs from the first embodiment in that the damping device 60 is of the active type and includes a piezoelectric sub-assembly 61 inserted in a protective envelope 62, the protective envelope 62 being pressed against the inner perimeter of the hole 20b at the level of the contact area 17.

[0087] The transmission shaft 10 carries a toothed pinion 30 which meshes with a gear of the speed reduction device 2. The meshing of the toothed surfaces generates vibrations that propagate through the body 13 of the transmission shaft. These vibrations generate excitation of the transmission shaft according to its natural modes.

[0088] To limit the impact of these vibrations and to limit the natural mode of the transmission shaft corresponding to bending along its axis of rotation, an active damping element 60 is inserted into a hole 20b in the main body 13 of the transmission shaft. The main body 13 has a principal axis of revolution X which has an external surface 14, a first end wall 11 and a second end wall 12 substantially perpendicular to the principal axis of revolution X.

[0089] The transmission shaft has a hole 20b concentric with the main axis of revolution X. The hole 20b is formed from the first end wall 11 and extends inside the main body 13 to the second end wall 12.

[0090] The damping device 60 covers the inner circumference of the hole 20b at a contact zone 17 which is continuous over 360° and passes through the middle of the transmission shaft in the axial direction. The middle of the transmission shaft is shown in Figure 6 by a geometric plane M located midway between the first end wall 11 and the second end wall 12 along the principal axis of revolution X.

[0091] The damping device 60 has a cylindrical profile 63 stopped by two end surfaces 64. The cylindrical profile 63 of the damping device is circular and concentric to the main axis of revolution and the cylindrical profile 63 of the damping device is complementary to the profile of the hole 20b.

[0092] A second guide bearing 100b supports the transmission shaft 10 relative to the housing 40a, 40b of the transmission system 1 which includes bearing elements 103, the second guide bearing 100b being inserted into a cylindrical housing 41b provided in the housing.

[0093] At the second end wall 12, a slip ring 80 with electrical connections is fitted into the transmission shaft. The slip ring 80 with electrical connections is attached to the housing 40a, 40b.

[0094] The slip ring 80 comprises a rotor 81 and a fixed base 82 that rotates relative to the cylindrical housing 41b. The rotor 81 is inserted into the hole 20b of the transmission shaft and electrically connected to the active damping device 60. The base 82 of the slip ring is electrically connected to an inverter 90 of the transmission system. The slip ring 80 transmits electrical current within a pivot joint and ensures electrical contact between the rotating transmission shaft 10 and the fixed housing 40a, 40b.

[0095] The transmission shaft 10 also includes an accelerometer 70 coupled to the piezoelectric sub-assembly 61. However, the invention can operate without an accelerometer.

[0096] The vibration amplitude generated within the transmission shaft is reduced thanks to the electromechanical coupling of the piezoelectric sub-assembly 61 controlled by an electronic circuit contained in the electrical inverter 90.

[0097] The accelerometer 70 detects vibrations of the transmission shaft 10. The signal is transmitted to the inverter's electronic circuit 90 via the slip ring 80 with electrical connections. The inverter's electronic circuit 90 calculates a counter-vibration and sends this signal to the piezoelectric sub-assembly 61, which then generates a counter-vibration.

[0098] As illustrated in Figure 7, the piezoelectric subassembly 61 consists of an axial stack of piezoelectric cells to generate an excitation force Fx and a displacement within the active damping device 60. The construction of a piezoelectric cell comprises a piezo-ceramic layer axially separated by two electrodes (+ and -) which generates an excitation force Fx along the principal axis of revolution X when an electric current is applied. The piezoelectric subassembly 61 also includes two end plates and a protective casing 62. Each electrode (+ and -) is connected according to its polarity to a connecting bar 69, which is itself connected to the rotor 81 of the electrically connected slip ring 80.

[0099] The piezoelectric subassembly 61 is fixed inside the drive shaft 10 using an epoxy resin that adheres to the inner rim of the hole 20b. The epoxy resin forms the protective casing 62. The piezoelectric subassembly 61 must be fixed to transfer the axial force within the drive shaft. The adhesion of the damping device 60 to the inner rim of the hole 20b at the contact area 17 thus contributes to reducing noise from the drive shaft.

[0100] Alternatively, the piezoelectric sub-assembly 61 can be fixed inside the drive shaft using a protective cover made of injection-molded plastic. The plastic cylinder is, for example, fixed on one side by a shoulder formed in the shaft and on the other by a fixing screw.

[0101] The invention is not limited to the examples just described. For example, the invention can be applied to a drive shaft directly connected to an output shaft of an electric machine rotor.

Claims

DEMANDS 1. Drive shaft (10) for electric or hybrid vehicle transmission system, comprising: - a main body (13) having a main axis of revolution (X) which has an external surface (14), a first end wall (11) and a second end wall (12) substantially perpendicular to the main axis of revolution (X); - at least one toothed pinion (30), which can be fixed in rotation with the transmission shaft or rotate freely around the transmission shaft; - a hole (20, 20a, 20b) extending longitudinally along the main axis of revolution (X), formed from the first end wall (11) and extending into the main body (13); and - a damping device (50, 60) of passive or active type inserted in the hole; the damping device (50, 60) covers the inner perimeter of the hole (20, 20a, 20b) at the level of a contact area (17) which is continuous over 360° and passes through the middle of the transmission shaft in the axial direction.

2. Transmission shaft (10) according to the preceding claim, wherein the damping device (50, 60) has a cylindrical profile (51, 63) stopped by two end surfaces (52, 64) and the damping device is pressed onto the entire contact area (17), the cylindrical profile of the damping device being complementary to the profile of the hole (20, 20a, 20b).

3. Transmission shaft (10) according to claim 1 or 2, wherein the cylindrical profile (51, 63) of the damping device (50, 60) is circular and concentric with the main axis of revolution (X).

4. Transmission shaft (10) according to the preceding claim, in which the damping device (50, 60) is pre-stressed assembled inside the hole (20, 20a, 20b), the outside diameter of the damping device being less than the diameter of the hole.

5. Transmission shaft (10) according to claim 1 or 2, wherein the cylindrical profile (51, 63) of the damping device (50, 60) is polygonal and surrounds the main axis of revolution (X).

6. Transmission shaft (10) according to the preceding claim, in which the hole (20) includes grooves (27) extending longitudinally along the main axis of revolution (X), cut from a central circular bore.

7. Transmission shaft (10) according to any one of the preceding claims, wherein the hole (20, 20a, 20b) provided in the main body (13) is open to the second end wall (12), and the damping device (50, 60) has at least one orifice (55) passing through it and arranged to allow a lubricating fluid to pass through the transmission shaft.

8. Transmission shaft (10) according to any one of claims 1 to 7, wherein the damping device (50) is of the passive type and comprises a central insert (53) made of damping material having viscoelastic behavior, for example silicone or polyurethane foam.

9. Transmission shaft (10) according to claim 8, in which the central insert (53) is compartmentalized into different sections by adhesion walls (54) which extend longitudinally along the hole (20, 20a).

10. Transmission shaft (10) according to the preceding claim, in which the adhesion walls (54) are distributed angularly around the main axis of revolution (X).

11. Transmission shaft (10) according to claim 8, wherein the passive type damping device (50) comprises an inner tube (70) extending along the main axis of revolution (X) which is pressed against the central insert (53), the central insert (53) being interposed between the inner perimeter of the hole (20, 20a) and the inner tube (70).

12. Transmission shaft (10) according to the preceding claim, in which the inner tube (70) is made from a sheet of metal wrapped around the main axis of revolution (X).

13. Transmission shaft (10) according to any one of claims 1 to 7, wherein the damping device (60) is of the active type and comprises a piezoelectric subassembly (61) inserted in a protective envelope (62), the protective envelope (62) being pressed against the inner perimeter of the hole (20b) at the level of the contact area (17).

14. Transmission system (1) for electric or hybrid vehicles comprising: - a housing (40a, 40b); - a transmission shaft (10) according to claim 13, movable in rotation relative to the casing around its main axis of revolution (X); - a guide bearing (100) supporting the transmission shaft relative to the housing which includes bearing elements (103), the guide bearing being inserted in a cylindrical housing (41a, 41b) provided in the housing; - a collector ring (80) with electrical connections attached to the housing; in which the collector ring comprises a rotor (81) and a base (82) fixed in rotation relative to the cylindrical housing (41a, 41b), the rotor being inserted into the hole (20b) of the transmission shaft (10) and electrically connected to the active type damping device (60).

15. Transmission system (1) according to the preceding claim, in which the base (82) of the slip ring (80) is electrically connected to an electric inverter (90).

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