Electric drive system

Abstract

The invention relates to an electric drive system (1) for a motor vehicle comprising: - at least one first casing element (10) and a second casing element (11) which define an internal space (9), the first casing element (10; 46) and the second casing element (11) being fixed to each other by fixing members (20) regularly distributed around the X axis; - an electric machine (2) housed in the internal space and comprising a stator (7) which is fixed inside the first casing element (10; 46) and a rotor (6) mounted to rotate freely around the X axis inside the first casing element; - an annular damping seal (19) which is disposed around the X axis and is interposed axially between the first casing element (10) and the second casing element (11) so as to filter the vibrations likely to be generated by the electric machine (2) in operation. Figure for the abbreviation: 1

Description

Title of the invention: Electric drive system technical field

[0001] The invention relates to the field of electric drive systems, in particular for motor vehicles. Technological background

[0002] In the prior art, electric drive systems comprising an electric machine, a reduction device, and an electric machine control module are known. The electric machine comprises a rotor, a stator, and housing elements defining, in particular, an internal space in which the rotor and stator are housed.

[0003] Prior art electric drive systems are not entirely satisfactory, particularly in that the electromagnetic forces present in the stator when the rotating electric machine is operating, as well as the rotational movement of the rotor, result in strong vibrational excitation of the housing components. Consequently, high levels of noise and vibration are measured outside the housing. Summary of the invention

[0004] One idea underlying the invention is to propose an electrical drive system generating vibrations of lower intensity.

[0005] According to one embodiment, the invention provides an electric drive system for a motor vehicle comprising: - a housing comprising at least a first housing element and a second housing element which define an internal space, the first housing element and the second housing element being fixed to each other by fixing members distributed around the X axis; - an electrical machine housed within the internal space and comprising a stator fixed inside the first casing element and a rotor mounted to rotate freely around the X-axis inside the first casing element; and - a first annular damping seal which is arranged around the X axis and is interposed axially between the first housing element and the second housing element so as to filter the vibrations likely to be generated by the electrical machine in operation.

[0006] The transmission of vibrations towards the second housing element is thus reduced by the interposition of the damping seal between the first and the second crankcase elements. The inventors thus found that such a damping seal made it possible to significantly reduce the intensity of noise and vibration.

[0007] According to embodiments, such an electric drive system may include one or more of the following characteristics.

[0008] According to one embodiment, the fastening members are configured to exert on the first housing element and the second housing element an axially directed fastening force, i.e. parallel to the X axis. Thus, the fastening force exerted by the fastening members has the effect of axially compressing the annular damping seal between the first and second housing elements.

[0009] According to one embodiment, one of the first housing element and the second housing element has an opening through which the rotor shaft passes and furthermore forms part of a housing of a reduction device.

[0010] According to one embodiment, the other of the first housing element and the second housing element has an opening through which the rotor shaft passes, the electric drive system further comprising a cover which is fixed to said housing element so as to define a second space receiving an angular position sensor which is configured to deliver a signal representative of the angular position of the rotor shaft.

[0011] According to one embodiment, the first housing element carries one or more annular sealing gaskets, each of which is mounted in a groove formed on a radially external surface of a cylindrical skirt of the first housing element, the annular sealing gasket or gaskets being radially in contact against an internal surface of a cylindrical skirt of the second housing element.

[0012] According to one embodiment, the electric drive system includes a third housing element which is fixed to the first housing element and a second annular damping seal which is arranged around the X axis, is interposed axially between the first housing element and the third housing element so as to filter the vibrations likely to be generated by the electric machine in operation.

[0013] According to one embodiment, the electric drive system further comprises an electric machine control module comprising a housing, the housing being at least fixed to the second housing element by fastening members, said fastening members each comprising a head and a threaded rod which passes through a bore formed in the housing and is screwed into a tapped bore formed in the second housing element, an annular damping pad being positioned around the threaded rod of each of the fastening members, said annular damping pad being interposed between the head of said fastening member and a bearing surface opposite the housing or between the housing and the second housing element. Annular damping pads thus allow vibrations to be reduced even further.

[0014] According to one embodiment, the first annular damping seal has damping zones distributed around the X-axis and separated from each other by connecting zones, the damping zones having a thickness in the axial direction greater than the thickness of the connecting zones. This makes it possible to limit the amount of material required to manufacture the first annular seal.

[0015] According to one embodiment, each damping zone is arranged radially between one of the fixing members and the X axis. Thus, the damping zones are positioned in the areas in which the connecting members exert their fixing force, which makes it possible to further improve the efficiency of vibration filtering.

[0016] According to one embodiment, the first annular damping seal is made of an elastomeric material.

[0017] According to one embodiment, the fastening members are screws each having a head and a threaded shank which passes through a first bore formed in one of the first and second housing elements and which is screwed into a second tapped bore of the other of the first and second housing elements, the head being supported by means of an annular damping pad against a bearing surface, opposite, of the housing, the annular damping pad being fitted onto the threaded shank.

[0018] According to one embodiment, the annular damping pads are made of an elastomeric material. Brief description of the figures

[0019] The invention will be better understood, and other objects, details, features and advantages thereof will become more apparent from the following description of several particular embodiments of the invention, given solely by way of illustration and not limitation, with reference to the accompanying drawings.

[0020] [Fig-1] Fig. 1 is an exploded perspective view of a drive system electric according to a first embodiment.

[0021] [Fig.2] The [Fig.2] is an exploded side view of the electric drive system of the [Fig.1].

[0022] [Fig.3] The [Fig.3] includes a cross-sectional view of the electric drive system of the [Fig.1] as well as detail views illustrating the positioning of an annular damping seal and that of an annular damping buffer.

[0023] [Fig.4] Fig.4 includes another cross-sectional view of the drive system electrical diagrams of figures 1 to 3 and a detailed view of another annular damping buffer.

[0024] [Fig.5] Fig.5 is a perspective view representing the annular joint visible damping in figures 1, 2 and 3.

[0025] [Fig.6] Fig.6 is an exploded view of an electric drive system according to a second mode of implementation.

[0026] [Fig.7] Fig.7 is a cross-sectional view of the electric drive system of the [Fig.6]. Description of the implementation methods

[0027] 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 electric drive system. By convention, the X-axis of rotation of the rotor defines the "axial" orientation. The terms "external" and "internal" are used to define the relative position of one element with respect to another, with reference to the X-axis; an element close to the X-axis is thus described as internal, as opposed to an external element located radially at the periphery.

[0028] The electric drive system 1, shown in figures 1 to 4, is intended to equip an electric or hybrid vehicle.

[0029] The electric drive system 1 comprises an electric machine 2, a reduction device 3, of which only a part of the housing 4 is shown in Figures 1 to 3, and an electric machine control module 5.

[0030] The electric machine 2 is, for example, a permanent magnet synchronous electric machine or an alternating current asynchronous electric machine. The electric machine 2 comprises a rotor 6 and a stator 7. In the illustrated embodiment, the stator 7 radially surrounds the rotor 6, and the electric machine 2 is a radial flux rotating electric machine. However, in unillustrated embodiments, the electric machine 2 is an axial flux rotating electric machine, meaning that it has at least one stator 7 axially opposed to at least one rotor 6, so that the gap between the rotor 6 and the stator 7, and therefore the direction of the magnetic flux between the two, is aligned parallel to the axis of rotation, rather than radially.

[0031] The stator 7 comprises an iron core that carries windings. The iron core is formed by a plurality of grooves into which the windings are inserted. The iron core comprises, for example, several plates, such as electrical steel plates, which are stacked one on top of the other to form a laminate.

[0032] According to an embodiment in which the electric machine 2 is a permanent magnet synchronous electric machine, the rotor 6 comprises permanent magnets which create a magnetic field synchronized with the rotating magnetic field produced by the stator windings 7.

[0033] The rotor 6 is mounted to rotate about the axis of rotation X. More particularly, the rotor 6 is connected, in a non-rotating manner, to a rotor shaft 8 which is mounted to rotate along the axis X.

[0034] The rotor 6 and the stator 7 of the electric machine 2 are housed in an internal space 9 which is defined here by two housing elements, namely a first housing element 10 and a second housing element 11. The first housing element 10 also forms part of the housing 4 of the reduction device 3. It has a cylindrical skirt 12 which projects axially from a bottom wall 13 and within which the stator 7 and the rotor 6 of the electric machine 2 are housed.

[0035] The bottom wall 13 has an opening 14 allowing the passage of the rotor shaft 8 so that it can couple with an input shaft, not shown, of the reduction device 3.

[0036] The second housing element 11 also includes a bottom wall 15 and a cylindrical skirt 16 which extends axially from said bottom wall 15. The cylindrical skirt 16 is positioned radially outside a portion of the cylindrical skirt 12 of the first housing element 10.

[0037] As illustrated in [Fig.3], the cylindrical skirt 16 has a free end 17 which is axially abutted against a shoulder 18 formed on the outer periphery of the cylindrical skirt 12 of the first housing element 10. An annular damping seal 19, which will be described in more detail later, is further interposed axially between the free end 17 of the cylindrical skirt 16 of the second housing element 11 and the shoulder 18 of the first housing element 10 in order to limit the propagation of vibrations produced by the electrical machine 2 to the second housing element 11.

[0038] Furthermore, the first housing element 10 and the second housing element 11 are fastened to each other by a plurality of fasteners 20, visible in Figures 1 to 3. The fasteners 20 are evenly distributed around the X-axis. In the embodiment shown, the fasteners 20 are fasteners, each having a head 21 and a threaded shank 22. As illustrated in [Fig. 3], the threaded shank 22 passes through a bore 23 in the second housing element 11 and is screwed into a tapped bore 24 in the first housing element 10. The bores 23 and 24 are respectively formed in lugs 25 and 26 that project radially outwards from the cylindrical skirt 12 of the first housing element 10 and from the cylindrical skirt 16 of the second housing element 11. The fastening members 20 exert axially directed fastening forces.

[0039] The annular damping seal 19 will now be described in relation to [Fig. 4]. The annular damping seal 19 is made of a material having a Young's modulus between 0.001 and 0.1 GPa. This material is advantageously an elastomer.

[0040] In the embodiment of [Fig. 4], the annular damping joint 19 has axially thicker areas, hereafter referred to as damping areas 27, and axially thinner areas, hereafter referred to as connecting areas 28. The damping areas 27 serve to dampen vibrations, while the connecting areas 28 serve to ensure the relative positioning of the damping areas 27 with respect to each other.

[0041] The damping zones 27 and the connecting zones 28 are regularly and alternately distributed around the X axis. In other words, the damping zones 27 are circumferentially separated from each other by connecting zones 28.

[0042] The damping zones 27 are each arranged in the same angular sector as one of the connecting members 20 described above. Thus, each damping zone 27 is arranged radially between one of the fixing members 20 and the X-axis.

[0043] Furthermore, advantageously, as shown in [Fig. 3], an annular damping pad 29 is positioned around the threaded rod 23 of the fasteners 20. Each annular damping pad 29 is interposed between the head 21 of one of the fasteners 20 and a bearing surface of the second housing element 11 bordering the corresponding bore 23 of the second housing element 11. This further limits the transmission of vibrations from the first housing element 10 to the second housing element 11. The annular damping pads 29 are advantageously made of the same material as the annular damping seal 19, i.e. having a Young's modulus between 0.001 and 0.1 GPa and which is advantageously an elastomer.

[0044] Furthermore, as shown in [Fig. 3], the first housing element 10 carries two annular sealing rings 30, 31, each of which is mounted in a groove formed on the radially external surface of the cylindrical skirt 12 of the first housing element 10. The two annular sealing rings 30, 31 come into radial contact against the internal surface of the cylindrical skirt 16 of the second housing element 11. The annular sealing rings 30, 31 thus ensure the sealing of the internal space 9, which is intended to receive a cooling fluid and is defined by the first and second housing elements 11. The aforementioned coolant is a dielectric fluid, such as oil for example.

[0045] The rotor shaft 8 is guided in rotation by means of a pair of bearings, not illustrated, which are respectively housed in housings 32, 33, illustrated on [Fig.3], provided in the first housing element 10 and in the second housing element 11.

[0046] The bottom wall 15 of the second housing element 11 also has an opening 34 through which the rotor shaft 8 passes. The bottom wall 15 defines, with a cover 35, a second space 36 in which one of the ends of the rotor shaft 8 is positioned. This second space 36 forms, in particular, a housing for an angular position sensor, not shown, which delivers a signal representative of the angular position of the rotor shaft 8.

[0047] The cover 35 is attached to the second housing element 11 by fasteners 37, visible in [Fig. 3]. The fasteners 37 are, for example, fixing screws, each of which passes through a bore formed on the periphery of the cover 35 and is screwed into a threaded bore of the second housing element 11. An annular sealing gasket 38, visible in [Fig. 3], is received in a groove formed in the second housing element 11 or in the cover 35 and is interposed between the cover 35 and the second housing element 11 in order to seal the second space 36.

[0048] Furthermore, the electric machine control module 5 comprises a housing 39 which is here fixed above the second casing element 11 by fasteners 40, one of which is illustrated in [Fig. 3]. The fasteners 40 are screws, each having a threaded shank 41 which passes through a bore 42 formed in the housing 39 of the electric machine control module 5 and is screwed into a tapped bore 43 formed in the second casing element 11. In addition, an annular damping pad 44 is positioned around the threaded shank 41 of each of the fasteners 40. Each annular damping pad 44 is interposed between the head 45 of one of the fasteners 40 and a bearing surface of the housing 39. This further limits the transmission of vibrations through the various elements of the electric drive system 1.

[0049] The control module of the electric machine 5 is advantageously an inverter configured to convert direct current (DC) into alternating current (AC) to power the electric machine 2. The inverter is also configured to control and regulate the output frequency and voltage.

[0050] The control module of the electric machine 5 is connected to an interconnector, not shown, of the electric machine 2 via an electrical connection assembly, also not shown. The electrical connection assembly passes through a dedicated opening made in the bottom wall of the second casing element 11 then passes through openings 60, 61, illustrated on the [Fig.3], which are made in the cover 35 and in the housing 39 of the control module of the electric machine 5.

[0051] Figures 5 and 6 illustrate an electric drive system 1 according to a second embodiment. This electric drive system 1 differs in particular from that described above in relation to Figures 1 to 4 by the structure of the housing. In this embodiment, the internal space 9 in which the rotor 6 and the stator 7 of the electric machine 2 are housed is defined by three housing elements, namely a first housing element 46, a second housing element 47 and a third housing element 48.

[0052] The first housing element 46 has a cylindrical skirt 49 which has an opening at each of its ends and inside which are housed the rotor 6 and the stator 7 of the electric machine 2.

[0053] The second housing element 47 further forms part of the housing 4 of the reduction device 3. It has a cylindrical skirt 50 that projects axially from a bottom wall 51 of the second housing element 47 that separates the electric machine 2 from the reduction device 3. The cylindrical skirt 50 of the second housing element 47 is positioned radially outside the cylindrical skirt 49 of the first housing element 46, while the bottom wall 51 of the second housing element 47 closes one side of the internal space 9. The third housing element 48 has a bottom wall 52 that closes the other side of the internal space 9.

[0054] In [Fig. 6], it can be seen that the first housing element 46 has a flange 53 that projects radially outwards from one end of the cylindrical skirt 49. The flange 53 is sandwiched between the end of the cylindrical skirt 49 of the second housing element 47 and the bottom wall 52 of the third housing element 48. In addition, a first annular damping seal 54 is interposed axially between the end of the cylindrical skirt 49 of the second housing element 47 and the flange 53, while a second annular damping seal 55 is interposed axially between the flange 53 and the bottom wall 52 of the third housing element 48. The first and second annular damping seals 54, 55 thus limit the transmission of vibrations generated by the electrical machine 2 from the first housing element 46 to the second housing element 47 and the third crankcase element 48.In this embodiment, the annular damping seals 54, 55 also serve to ensure the sealing of the internal space 9.

[0055] The first, second, and third housing elements 46, 47, 48 are fastened to each other by fasteners, not shown. The fasteners are screws comprising a threaded shank, each passing through bores formed in ears projecting radially outwards from the first, second, and third housing elements 46, 47, 48. One of the bores formed in the second or third housing element is a tapped bore into which the threaded rod is screwed, while the other is bordered by a bearing surface against which the head of the fastener makes contact. Advantageously, annular damping pads, as described previously in connection with the first embodiment, are advantageously mounted on the rod of the fasteners and are interposed between their head and a respective bearing surface.

[0056] Furthermore, the housing 39 of the control module of the electric machine 5 is fixed to the second housing element 47 and to the third housing element 48 by fastening members 56, one of which is shown in [Fig.7]. As in the previous embodiment, the fasteners 56 are advantageously screws, each comprising a threaded shank that passes through a bore formed in the housing 39 and is screwed into a tapped bore formed in the second or third housing element 47, 48. In addition, an annular damping pad 57 is positioned around each threaded shank and positioned between the housing 39 of the control module of the electric machine 5 and the second or third housing element 47, 48. Alternatively, the annular damping pad 57 is interposed between the head of each of the fasteners 56 and a bearing surface opposite the housing 39.

[0057] Furthermore, the electric drive system 1 includes a fourth housing element 58 which together with the second housing element 47 forms the housing 4 of the reduction device 3. The second housing element 47 and the fourth housing element 58 are also fixed to each other by fasteners, such as screws.

[0058] Furthermore, as shown in [Fig.6], a damping joint 59 is interposed axially between the second housing element 47 and the fourth housing element 58, which makes it possible to limit the transmission of vibrations produced by the electrical machine 2 towards the fourth housing element 58.

[0059] The damping joints 54, 55, 59 and the damping pads 57 described above in relation to the second embodiment of Figures 5 and 6 are made of materials having characteristics similar to those described in relation to the first embodiment of Figures 1 to 4, i.e. having a Young's modulus which is between 0.001 and 0.1 GPa and which is advantageously an elastomer.

[0060] Although the invention has been described in connection with several particular embodiments, it is clearly evident that it is by no means limited to them and that it includes all technical equivalents of the means described as well as their combinations if these fall within the scope of the invention, as defined by the claims.

[0061] The use of the verb "comprise", "comprendre" or "include" and its conjugated forms does not exclude the presence of other elements or other steps than those stated in a claim.

[0062] In the claims, any reference sign in parentheses shall not be interpreted as a limitation of the claim.

Claims

Demands

1. Electric drive system (1) for a motor vehicle comprising: - a casing comprising at least a first casing element (10; 46) and a second casing element (11; 47) which define an internal space (9), the first casing element (10; 46) and the second casing element (11; 47) being fixed to each other by fastening members (20) distributed around the X axis; - an electrical machine (2) housed in the internal space and comprising a stator (7) which is fixed inside the first housing element (10; 46) and a rotor (6) mounted to rotate freely about the X axis inside the first housing element (10; 46); and - a first annular damping seal (19, 54) which is disposed around the X axis and is interposed axially between the first housing element (10; 46) and the second housing element (11;47) so as to filter out vibrations that may be generated by the electrical machine (2) in operation.;

2. Electric drive system (1) according to claim 1, wherein one of the first housing element (10; 46) and the second housing element (11; 47) has an opening (14) through which the rotor shaft (8) passes and further forms part of a housing (4) of a reduction device (3).

3. Electric drive system (1) according to claim 1 or 2, further comprising a third housing element (48) which is fixed to the first housing element (46) and a second annular damping seal (55) which is arranged around the X axis, is interposed axially between the first housing element (46) and the third housing element (48) so as to filter the vibrations likely to be generated by the electric machine (2) in operation.

4. An electric drive system (1) according to any one of claims 1 to 3, further comprising an electric machine control module (5) having a housing (39), the housing (39) being at least fixed to the second casing element (11; 47) by fastening members (40; 56), said fastening members (40; 56) each having a head (45) and a threaded rod (41) passing through a bore (42) formed in the housing (39) and screwed into a tapped bore (43) formed in the second element of housing (11), an annular damping pad (44; 57) being positioned around the threaded rod (41) of each of the fastener members (40; 56), said annular damping pad (44; 57) being interposed between the head (45) of said fastener member (40) and a bearing surface opposite the housing (39) or between the housing (39) and the second housing element (11; 47).

5. Electric drive system (1) according to any one of claims 1 to 4, wherein the first annular damping joint (19) has damping zones (27) distributed around the X axis and separated from each other by connecting zones (28), the damping zones (27) having a thickness in the axial direction greater than a thickness of the connecting zones (28).

6. Electric drive system (1) according to claim 5, wherein each damping zone (27) is arranged radially between one of the fastening members (20) and the X axis.

7. Electric drive system (1) according to any one of claims 1 to 6, wherein the first annular damping seal (19) is made of an elastomeric material.

8. Electric drive system (1) according to any one of claims 1 to 7, wherein the fasteners (20) are screws each having a head (21) and a threaded shank (22) which passes through a first bore (23) formed in one of the first and second housing elements and which is screwed into a second bore (24), tapped, of the other of the first and second housing elements, the head (21) being supported by means of an annular damping pad (29) against a bearing surface, opposite, of the housing, the annular damping pad (29) being fitted onto the threaded shank (22).

9. Electric drive system (1) according to claim 8, wherein the annular damping pads (29) are made of an elastomeric material.

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