Arrangement of a shaft and a casing

Abstract

The invention relates to an arrangement (1) which comprises a casing (5), a shaft (3) rotatably mounted inside the casing (5), and a first electrically conductive element (7) rigidly connected to the casing (5) extending along the axis of rotation (A) of the shaft (3). The arrangement comprises a second electrically conductive element (9) of conical shape with an axis (A), a first end (9a) of which has a cross-section of smaller diameter than a second end (9b) and is in sliding contact with one end (7a) of the first conductive element (7). An oil-guiding element (11) is located above the shaft (3) radially, and defines with an inner wall (51) of the casing (5) a funnel, a lower opening of which opens radially above the first end (9a) of the second conductive element (9). The second conductive element is accommodated inside a recess (30) of the shaft and at least one channel (36) connects the recess to the outer surface of the shaft.

Description

[0001] Title of the invention: Arrangement of a shaft and a casing

[0002] The invention relates to an arrangement of a shaft and a housing, comprising a housing, in particular a mechanical reducer housing, and a shaft, in particular a rotating electrical machine shaft, rotatably mounted inside the housing.

[0003] As is known per se, rotating electrical machines comprise a stator, secured to a casing, and a rotor, secured to a shaft. The rotor may be secured to a driving and / or driven shaft and may belong to a rotating electrical machine in the form of an alternator or an electric motor. The casing of the electrical machine is configured to rotate the rotor shaft by means of ball bearings, for example made of steel.

[0004] During operation, the rotor is charged with static electricity like a capacitor and discharges, generating electric arcs on the rotor teeth and the bearing balls, which deteriorates their surface and, ultimately, leads to their destruction. It is therefore necessary to be able to connect the rotor to ground in order to avoid the generation of these electric arcs.

[0005] One solution is to use a conductive felt, as described in document US20160010750. This felt extends radially from the shaft to the housing and ensures electrical contact between the shaft and the housing, the latter being connected to ground. However, felt is an expensive, fragile material, which degrades over time and therefore loses efficiency. Another solution is to use brushes extending radially between the shaft and the gearbox housing, the latter being connected to ground. However, the friction generated by the brushes leads to a reduction in the machine's efficiency. In order to reduce friction, a single brush has also been arranged axially, in the extension of the shaft, this brush, integral with the gearbox housing, having one end in sliding contact with the shaft.

[0006] Furthermore, an electric powertrain of a motor vehicle comprises a rotating electrical machine and various mechanical parts, such as the mechanical reducer for modifying the speed ratio or the torque between the input shaft and the output shaft of the motor. These mechanical parts need to be lubricated by a lubricating oil forming a thin film between the mechanical parts to limit friction between them and thus reduce their wear. The reducer is typically housed inside a casing, this casing being able to also receive the rotating electrical machine to form a geared motor. Alternatively, the reducer casing may not include the rotating electrical machine and receive only one end of the shaft of the rotating electrical machine.In all cases, the shaft of the rotating electrical machine has splines cooperating with at least one pinion forming part of the reducer and requiring the supply of lubricating oil. This lubrication of the spline-pinion interface is carried out by supplying oil circulating inside the reducer housing and penetrating into the space between the splines and the pinion from the axial ends of the latter, which does not allow good lubrication of this interface.

[0007] There is therefore a need for an arrangement between a shaft and a housing that improves lubrication of the shaft while allowing electrical discharge of the shaft.

[0008] For this purpose, an arrangement of a shaft and a housing is provided, comprising a housing, a shaft rotatably mounted inside the housing about an axis of rotation and a first electrically conductive element integral with the housing extending along the axis of rotation of the shaft. The arrangement further comprises:

[0009] - a second electrically conductive element of conical shape with an axis coincident with the axis of rotation of the shaft and having a first end and a second end, the first end having a cross-section of smaller diameter than the second end and being in sliding contact with one end of the first conductive element, the second end being integral in rotation with the shaft,

[0010] - an oil guide element located radially above the shaft, and defining with an internal wall of the casing a funnel, a lower opening of which opens radially above the first end of the second conductive element.

[0011] Furthermore, according to the invention, the tree has:

[0012] - an axis housing merged with the axis of rotation of the shaft, having an opening located axially opposite the first conductive element and receiving the second conductive element,

[0013] - at least one channel connecting the housing to an external surface of the shaft and opening inside the housing between the second end of the second conductive element and the opening of the housing.

[0014] Thus, a characteristic of the invention lies in the implementation of a second electrically conductive element placed inside a housing made in the shaft to lubricate the external surface of the latter and serve as an electrical contactor between the shaft and the casing via the first electrically conductive element.

[0015] The second conductive element thus allows the electricity accumulated by the shaft to be transmitted to the first conductive element, which is an element electrically connected to the casing and to ground. Typically, the second conductive element may be made of an electrically conductive metallic material. The second conductive element may thus be aluminum, copper, or any other conductive metal or alloy. Preferably, it is made of aluminum.

[0016] In addition, the second conductive element also makes it possible to conduct the oil to at least one channel to lubricate the shaft. The guide element makes it possible to recover the oil flowing at the casing to direct it towards the second conductive element. The oil, guided by the guide element, thus falls onto the first end of the second conductive element and, since the second conductive element is integral in rotation with the shaft, this rotation will drive the oil towards the second end of the second conductive element and then into at least one channel.

[0017] Advantageously, at least one channel can open into the interior of the housing near the second end of the second conductive element. This makes it possible to position the channel as close as possible to or at the level of an area in which the oil will accumulate due to the conical shape of the second conductive element, making it possible to send a maximum of oil into the channel. This area corresponds to the contact area between the housing and the second end of the second conductive element.

[0018] Advantageously, at least one channel may extend radially, which may facilitate the flow of oil from the housing to the outer surface of the shaft.

[0019] Advantageously, the second conductive element can be force-mounted inside the shaft housing. This ensures good electrical contact between the shaft and the second conductive element.

[0020] The housing typically has a symmetry of revolution. It is advantageous to produce a cylindrical housing, simple to produce and ensuring good contact between the second end of the second conductive element and the shaft. Although this is not preferred, a housing of conical or truncated shape, with a reduction in the diameter of the opening of the housing towards the bottom of the housing, is possible, this housing having for example advantageously a small apex angle, for example less than 8°.

[0021] Advantageously, the second conductive element may have a wall extending radially on the side of its first end, in sliding contact against the first conductive element, in particular the end thereof. This wall allows better electrical contact between the first end of the second conductive element and the first conductive element. It also makes it possible to limit the passage of oil towards the contact zone between the first conductive element and the second conductive element. Finally, this wall may make it possible to promote the guiding of the oil from the internal wall of the casing defining a funnel with the guiding element towards the first end of the second conductive element, in particular when the wall extends in the extension of the internal wall of the casing, and in particular of a radial lower part of this internal wall.

[0022] Advantageously, the external surface of the shaft may have at least one groove into which the at least one channel opens. This may make it possible to constitute an oil reserve on the external surface of the shaft to improve lubrication. In particular, the external surface of the shaft may have grooves, in particular intended to cooperate with a reduction gear pinion, and the at least one groove may be located, and / or the at least one channel may open, at the level of the grooves, to ensure good lubrication of the surface of the grooves. In particular, the at least one groove may be located, and / or the at least one channel may open, at mid-axial length of the grooves. The at least one groove may further extend over all or part of the periphery of the external surface and thus form an annular groove in an axial plane.

[0023] One, two or more channels connecting the housing to the external surface of the shaft may be provided. When two or more channels are present, they may be axially spaced, in particular regularly spaced, or located in the same radial plane and / or regularly distributed around the axis of rotation of the shaft. In particular, a regular axial and radial distribution ensures balance of the shaft by distributing its mass around its axis of rotation, thus limiting the generation of vibrations during its rotation.

[0024] Advantageously, the external surface of the shaft may have grooves and the at least one channel may open at the grooves, for optimal lubrication of the interface between the grooves and a pinion intended to cooperate with the grooves of the shaft. Thus, in one embodiment, the arrangement also comprises a pinion cooperating with said grooves.

[0025] Advantageously, the first conductive element may comprise a body secured to the casing and provided with a housing, an electrically conductive brush extending in the direction of rotation of the shaft and received inside the housing, and a spring exerting an axial force on the brush in the direction of the shaft. The spring makes it possible to exert sufficient force on the brush to maintain contact between the brush and the second conductive element. Typically, the brush may be made of a conductive material different from the second conductive element. Preferably, the brush is made of a carbon-based material, such as graphite or a composite containing carbon.

[0026] To facilitate maintenance and the production of the funnel shape, the casing may have a removable part forming a cover to which the first conductive element is secured, and the internal wall of the casing defining a funnel with the guide element may be an internal wall of this removable casing part. This makes it possible in particular to implement the invention without having to modify the casing, but only its removable part.

[0027] The arrangement according to the invention thus makes it possible to lubricate and ground a shaft mounted to rotate in a casing.

[0028] Advantageously, the shaft of the arrangement according to the invention may be a shaft of a rotating electrical machine and have splines on its external face, the arrangement may comprise at least one pinion located inside the casing and cooperating with the splines of the shaft, and at least one channel of the shaft may open at the splines. The electrical machine may be a rotating electrical machine with axial or radial flux, advantageously with axial flux. The at least one pinion may be part of a reducer and the casing may be a reducer casing.

[0029] The arrangement according to the invention is however not limited to this application and can be implemented whenever a rotating shaft must be electrically connected to a casing and be lubricated by oil present inside the casing.

[0030] Other features and advantages of the invention will emerge from reading the description given below of several particular embodiments of the invention, given for informational purposes but not as a limitation, with reference to the appended drawings in which:

[0031] [Fig. 1] is a side sectional view of a shaft and housing arrangement according to one embodiment of the invention.

[0032] [Fig. 2] is a partial perspective view of the arrangement of Fig. 2 showing the oil guide member.

[0033] In the present description the terms "above", "upper", "below", "lower" relate to a vertical direction corresponding to the direction of gravity, the arrangement according to the invention being in a position of use. The term "axial" corresponds to a direction coincident with the axis of rotation A of the shaft, the term "radial" corresponding to a direction perpendicular to the axis of rotation A of the shaft.

[0034] Figure 1 represents an arrangement 1 according to an embodiment of the invention of a shaft 3 and a casing 5. This arrangement 1 therefore comprises a casing 5 and a shaft 3 rotatably mounted inside the casing 5.

[0035] The shaft 3 is here a shaft of a rotating electrical machine 2 partially shown in Figure 1. The rotating electrical machine 2 comprises in particular a casing 20 (partially shown) rotatably mounted on the shaft 3 via bearings 22, here ball bearings. The rotating electrical machine 2 further comprises in the usual manner at least one rotor (not shown) integral in rotation with the shaft 3 and at least one stator (not shown) movable in rotation. These elements are well known and will not be described in more detail. The rotating electrical machine 2 may be axial flux or radial flux, preferably axial flux.

[0036] Usually, the shaft 3 of the rotating electrical machine is connected to a reducer 4 comprising at least one pinion 40. For this purpose, the shaft 3 has on its external face 32 splines 34 cooperating with the pinion 40, and located at the interface between the shaft 3 and the pinion 40. The reducer 4 is here housed inside the casing 5, like the shaft 3. The casing 5 may or may not be integral with the casing 20 of the rotating electrical machine 2.

[0037] The housing 5 and the shaft 3 are typically metal parts and may be made of any metal or alloy commonly used to manufacture housings and shafts, such as aluminum. Typically, the housing 5 is connected to ground.

[0038] The arrangement 1 also comprises, inside the casing 5, a first electrically conductive element 7 secured to the casing 5 extending along the axis of rotation A of the shaft 3.

[0039] In the example shown, the first conductive element 7 comprises a body 70 secured to the casing 5 and provided with a housing 72, and a conductive brush 74 extending in the direction of the axis of rotation A of the shaft 3 and received inside the housing 72. The first conductive element 7 also comprises a spring 76 exerting an axial force on the brush 74 in the direction of the shaft 3.

[0040] The body 70 and the brush 74 of the first element 7 are made of an electrically conductive material. The body 70 may be made of any conductive metal or alloy, such as aluminum. Preferably, it is made of the same material as the casing 5. The brush 74, for its part, may be a highly conductive and low-abrasive compound, generally carbon-based, such as graphite or a composite containing carbon.

[0041] Thus, the first conductive element 7 makes it possible to ground the shaft 3 by electrically connecting the shaft 3 and the casing 5, via the second conductive element 9 as described below, thus allowing the electrical discharge of the shaft 3 without generating electric arcs with the metallic elements surrounding the shaft.

[0042] The first conductive element 7, and in particular its body 70, may have a polygonal shape, preferably rectangular or square, cooperating with a complementary shape of the casing 5, thus preventing it from being driven in rotation when the shaft 3 is rotated. The first conductive element 7, and in particular its body 70, may be secured to the casing 5 by any appropriate means ensuring electrical contact, for example by simple interlocking or by force-fitting, by screwing, gluing with a conductive glue or other.

[0043] The invention is of course not limited by a shape and / or a structure of the first conductive element 7 provided that it is electrically conductive. Thus, the brush 74 could be received directly in a housing of the casing provided for this purpose.

[0044] According to the invention, the arrangement 1 further comprises, inside the casing 5, a second conductive element 9 and a guide element 11. These elements, in cooperation with the particular structure of the shaft 3 according to the invention, participate in the lubrication of the external surface 32 of the shaft 3.

[0045] The shaft 3 thus has a housing 30 with an axis coincident with the axis of rotation A of the shaft 3. The housing 30 has an opening 30a located axially opposite the first conductive element 7. The housing 30 makes it possible to receive the second electrically conductive element 9. This housing 30 advantageously has a cylindrical shape that is simple to produce. A conical or truncated cone shape as described above is however conceivable although not preferred.

[0046] The second electrically conductive element 9 is conical in shape with an axis coincident with the axis of rotation A of the shaft 3. The second conductive element 9 has a first end 9a and a second end 9b. The first end 9a has a cross-section of smaller diameter than the second end 9b and is in sliding contact with an end 7a of the first conductive element 7. The second end 9b is integral in rotation with the shaft 3. In particular, this second end 9b may be located near, or against, the bottom 30b of the housing 30 of the shaft 3, as shown in FIG. 1.

[0047] The second conductive element 9 makes it possible in particular to ensure electrical conduction between the shaft 3 and the first element 7. For this purpose, the second conductive element 9 is made of an electrically conductive material. It can be composed of any electrically conductive metal or alloy, such as aluminum, copper or other. However, the choice of its material will advantageously be made according to the material of the first electrically conductive element 7, and in particular of the brush 74, with which it is in contact to avoid and / or limit corrosion at the interface between these two elements.

[0048] To ensure better contact between the first element 7 and the second element 9, the latter may have a wall 90 extending radially on the side of its first end 9a, in sliding support against the end 7a of the first conductive element 7, here against the brush 74.

[0049] The second conductive element 9 is preferably force-mounted, for example by shrinking, inside the housing 30 of the shaft 3. However, it can also be secured to the shaft by any means usually used ensuring electrical contact with the shaft, for example by welding or the use of a conductive glue, or other.

[0050] According to the invention, the shaft 3 also has at least one channel 36 connecting the housing 30 to its external surface 32 and opening inside the housing 30 between the second end 9b of the second conductive element 9 and the opening 30a of the housing 30.

[0051] To facilitate its production and the flow of the oil, the at least one channel 36 advantageously extends radially. The at least one channel 36 may further have a cylindrical shape which can be easily produced by drilling into the shaft 3. The invention is however not limited to a particular shape of a channel and / or to a particular orientation of a channel provided that the channel allows the oil to be conveyed from the housing to the external face of the shaft.

[0052] It is preferable for the at least one channel 36 to open into the interior of the housing 30 near the second end 9b of the second conductive element 9, in particular as close as possible to the contact zone between this second end 9b and the housing 30. This second end 9b obstructing the housing 30, the oil will tend to accumulate along the contact zone between the second end 9b and the housing 30, ensuring an oil reserve allowing a continuous supply of oil to the channel(s) 36 opening into this zone.

[0053] In the embodiment shown, the at least one channel 36 opens at the level of the splines 34 of the external surface 32 of the shaft 3, advantageously at mid-distance axially of the length of the splines 34 for better lubrication of the splines over their entire length (measured axially).

[0054] The shaft 3 may have two or more channels 36 distributed regularly around its periphery and / or spaced axially, preferably regularly spaced. Preferably, the shaft 3 has two or three, advantageously arranged in the same axial plane, and distributed regularly around the axis A to maintain a balance of the inertia of the shaft. They are thus distributed angularly regularly around the second conductive element 9.

[0055] The oil is supplied to the second conductive element 9 via the guide element 11, which is located above the shaft 3 radially (i.e. vertically), so that the oil falls onto the second conductive element under the effect of gravity.

[0056] As seen in Figures 1 and 2, the guide element 11 defines with an internal wall 51 of the casing 5 a funnel 13 of which a lower opening 13a opens radially above the first end 9a of the second conductive element 9. In the example shown, the guide element 11 thus has two side walls 110, 111 facing each other, these walls being, on one side, connected to each other by a partly inclined side wall 112, and, on the other side, secured to the internal wall 51 of the casing. The partly inclined side wall 112 is inclined towards the internal wall 51 in order to form the funnel shape 13 therewith. Finally, the guide element 11 can be fixed to the internal wall 51 of the casing 5 by interlocking, welding or other means. Of course, the invention is not limited to a specific shape of the guide element 11 provided that it defines a general funnel shape 13 with the internal wall 51 of the casing.The guide element 11 could thus have a more rounded shape.

[0057] During rotation of the shaft 3, the oil present inside the casing 5 (and used for lubricating the mechanical parts present inside the casing) is projected against the internal wall of the casing 5, and in particular against the internal wall 50 located above the shaft 3, flows under the effect of gravity and its viscosity along this internal wall 50 and also along the internal wall 51 defining the funnel 13 with the guide element 11. The oil is thus collected by the guide element 11 and then flows from the opening 13a of the funnel 13 onto the first end 9a of the second conductive element 9. In order to promote this flow of the oil, the internal wall 51 of the casing 5 may advantageously have a radial lower part 51a located radially above this first end 9a, in particular immediately above.This arrangement of the internal wall 51 can be provided regardless of the embodiment of the guide element 11 and / or the number, arrangement and shape of the channel(s). Furthermore, the second conductive element 9 can advantageously be dimensioned so that its wall 90 extends in the extension of the part 51a, regardless of the embodiment of the arrangement according to the invention. Thus, the oil flowing through the opening 13a is not projected towards the first conductive element 7 and is guided towards the first end 9a of the second conductive element 9.

[0058] The conical shape of the second conductive element 9 then makes it possible to convey the oil from the first end 9a to the second end 9b. Indeed, the second conductive element 9 being rotated, the oil will move along the surface of this second element 9 thanks to the centrifugal force and the viscosity of the oil from the first end 9a to the second end 9b. The angle at the apex of the conical shape of the second conductive element 9 may be chosen so as to optimize the path of the oil along the surface and according to the dimensions of the housing. For example, a conical shape with an apex angle of 10° to 40°, preferably 20° to 30°, may be produced. The oil accumulated at this second end 9b is then evacuated through the channel(s) 36 towards the external surface 32 of the shaft 3, ensuring the lubrication of this surface.

[0059] In order to allow an oil reserve to be formed on the external surface 32 of the shaft (and thus at the shaft-pinion interface) and thus improve the lubrication of this external surface, one or more grooves 38 may be made on the external surface of the shaft 3 inside which the at least one channel 36 opens. The groove(s) 38 may be axial, or not, for example helical or other, and / or extend over all or part of the periphery of the shaft. This embodiment may be combined with all the embodiments described.

[0060] In the example shown, and as seen more particularly in Figure 2, the part of the casing 5 which receives the first conductive element 7 and to which the guide element 11 is fixed forms a removable cover 52, which can be fixed to the rest of the casing by screws (not shown). This cover 52 thus extends axially opposite the end of the shaft 3 comprising the housing 30. This arrangement allows simple and rapid assembly / disassembly of the first conductive element 7, and also facilitates the replacement of the brush 74, the guide element or another element, if necessary. This arrangement can be combined with all the embodiments previously described.

Claims

Claims

1. Arrangement (1) of a shaft (3) and a casing (5), comprising a casing (5), a shaft (3) rotatably mounted inside the casing (5) around an axis of rotation (A) and a first electrically conductive element (7) integral with the casing (5) extending along the axis of rotation (A) of the shaft (3), characterized in that it comprises: - a second electrically conductive element (9) of conical shape with an axis coincident with the axis of rotation (A) of the shaft (3) and having a first end (9a) and a second end (9b), the first end (9a) having a cross-section of smaller diameter than the second end (9b) and being in sliding contact with one end (7a) of the first conductive element (7), the second end (9b) being integral in rotation with the shaft (3), - an oil guide element (11) located radially above the shaft (3), and defining with an internal wall (51) of the casing (5) a funnel (13) of which a lower opening (13a) opens radially above the first end (9a) of the second conductive element (9), and in that the shaft (3) has: - a housing (30) with an axis coincident with the axis of rotation (A) of the shaft (3), having an opening (30a) located axially opposite the first conductive element (7) and receiving the second conductive element (9), - at least one channel (36) connecting the housing (30) to an external surface (32) of the shaft (3) and opening inside the housing (30) between the second end (9b) of the second conductive element (9) and the opening (30a) of the housing (30).

2. Arrangement (1) according to claim 1, characterized in that the at least one channel (36) opens into the interior of the housing (30) near the second end (9b) of the second conductive element (9).

3. Arrangement (1) according to claim 1 or 2, characterized in that the at least one channel (36) extends radially.

4. Arrangement (1) according to any one of claims 1 to 3, characterized in that the second conductive element (9) is force-mounted inside the housing (30) of the shaft (3).

5. Arrangement (1) according to any one of claims 1 to 4, characterized in that the second conductive element (9) has a wall (90) extending radially on the side of its first end (9a), in sliding support against the first conductive element (7).

6. Arrangement (1) according to any one of claims 1 to 5, characterized in that the external surface (32) of the shaft (3) has at least one groove (38) inside which the at least one channel (36) opens.

7. Arrangement (1) according to any one of claims 1 to 6, characterized in that the shaft (3) has at least one of the following characteristics: - two or more channels (36) regularly distributed around the axis of rotation of the shaft, - two or more channels (36) spaced axially apart or located in the same radial plane.

8. Arrangement (1) according to any one of claims 1 to 7, characterized in that the first conductive element (7) comprises a body (70) integral with the casing (5) and provided with a housing (72), an electrically conductive brush (74) extending in the direction of rotation (A) of the shaft (3) and received inside the housing (72), and a spring (76) exerting an axial force on the brush (74) in the direction of the shaft (3).

9. Arrangement (1) according to any one of claims 1 to 8, characterized in that the casing (5) has a removable part (52) forming a cover to which the first conductive element (7) is secured, and the internal wall (51) of the casing defining a funnel with the guide element (11) is an internal wall of this removable casing part.

10. Arrangement (1) according to any one of claims 1 to 9, the shaft (3) being a shaft of a rotating electrical machine (2) and having splines (34) on its external face, and the arrangement further comprising at least one pinion (40) located inside the casing and cooperating with the splines (34) of the shaft and the at least one channel (36) of the shaft opening at the splines.

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