INTERNALLY LUBRICATED TRANSMISSION MECHANISM, ELECTRIC PROPULSION ASSEMBLY AND ASSOCIATED VEHICLE

Abstract

A transmission mechanism (10) with internal lubrication comprises, housed in a casing (12), a drive shaft (16) guided in rotation about a drive axis (38) and integral in rotation with at least one drive pinion (17), and a receiving member (18) guided in rotation about a receiving axis (40) and integral in rotation with at least one receiving pinion (20). The drive axis (38) and the receiving axis (40) are contained in a reference plane (42). A portion of the receiving pinion (20) and a portion of the drive pinion (17) is located below an oil level plane at rest (14) when the transmission mechanism (10) is in a reference operational position. The transmission mechanism (10) comprises an oil collecting tank (22) housed in the casing (12), the oil collecting tank (22) delimiting a collecting volume (24). (Fig. 2)

Description

Title of the invention: INTERNALLY LUBRICATED TRANSMISSION MECHANISM, ASSOCIATED ELECTRIC PROPULSION ASSEMBLY AND VEHICLE TECHNICAL FIELD OF THE INVENTION

[0001] The invention relates to the internal lubrication, for example by splashing, of the components of a transmission mechanism, and in particular of a speed reduction mechanism. STATE OF THE PRIOR ART

[0002] To lubricate the components of a transmission mechanism, and in particular the rotating guide bearings and gears of such a mechanism, it is known to arrange the moving components of the mechanism inside a casing containing oil, but without the moving components being completely immersed in the oil. It is then the movement of the transmission mechanism which, by splashing, stirs the oil and projects it throughout the entire interior volume of the casing, to ensure the desired lubrication of the entire mechanism, including the non-immersed parts.

[0003] A compromise must be found between the requirement for sufficient lubrication, including at low speed, which encourages increasing the oil level in the crankcase, and the desire to minimize the energy consumption caused by mixing the oil, which encourages lowering the oil level instead.

[0004] To reconcile these requirements, it is possible, for example, to ensure, in a transmission mechanism comprising several parallel shafts rotating at different speeds, that only one shaft, for example the shaft rotating the slowest, splashes in the oil, the other shafts being located above the oil level at rest, as illustrated for example in document US2008076616. However, such an arrangement only allows good lubrication above a certain speed. In addition, energy losses due to mixing remain significant when the speed increases. Finally, the resulting arrangement induces a high positioning of the center of gravity of the mechanism.

[0005] For a better compromise, it has been proposed to provide, inside the casing, devices such as intermediate reservoirs, which delay the fall of the sprayed oil, and thus reduce the effective level of the oil when the rotation speed increases. Various embodiments of such reservoirs, often combined with deflectors to direct the oil flows in a preferential manner towards certain components such as the bearings, are illustrated in documents JP2012137126, JP2010223376 and JP2012233495. In the configurations proposed in these documents, the oil level at rest is such that only the largest gear of the slowest rotating shaft is immersed in the oil at rest. This leads to the other shaft(s) of the transmission mechanism being positioned higher, with the disadvantages previously mentioned, namely a lack of lubrication at low speed and a high level of the center of gravity of the mechanism. Statement of the invention

[0006] The invention aims to remedy the drawbacks of the state of the art and to propose a transmission mechanism combining good lubrication at low speed, low energy consumption at high speed, and a low center of gravity of the mechanism.

[0007] To this end, according to a first aspect of the invention, a splash lubrication transmission mechanism is proposed, comprising a casing, the casing defining an oil level plane at rest when the transmission mechanism is in a reference operational position, the transmission mechanism further comprising, housed in the casing, a motor shaft guided in rotation about a motor axis and integral in rotation with at least one motor pinion, and a receiving member guided in rotation about a receiving axis and integral in rotation with at least one receiving pinion, the motor axis and the receiving axis being contained in a reference plane of the transmission mechanism, a portion of the receiving pinion being located below the oil level plane at rest when the transmission mechanism is in the reference operational position, the transmission mechanism comprising an oil collecting tank housed in the casing,the oil collecting tank delimiting a collecting volume, characterized in that a part of the motor pinion and / or of an external guide track of a bearing for guiding the rotation of the motor shaft is located below the oil level plane at rest when the transmission mechanism is in the reference operational position, and a portion of the reference plane located between the motor axis and the receiving axis passes through the collecting volume.

[0008] The fact that the driving pinion and the receiving pinion both splash in the oil at rest ensures good lubrication at low speed. It results from this arrangement that the distance measured in projection on the oil level plane at rest, between the driving axis and the receiving axis, is significant, greater than when the driving pinion is far from the oil level plane at rest. There is therefore an available volume between the driving axis and the receiving axis which is used to position an oil collecting tank whose volume can be significant without harming the compactness of the casing. Only the internal volume of the casing is used to install the oil collecting tank.

[0009] According to one embodiment, the collector volume crosses the oil level plane at rest.

[0010] According to one embodiment, the oil level plane at rest is located above a guide track of a rotating guide bearing of the receiving member, when the transmission mechanism is in the reference operational position.

[0011] By guide track, we mean here a raceway if the bearing is a rolling bearing, or a sliding track for a plain bearing. The outer guide track is the one that is turned radially inwards opposite another guide track, called the inner one, which it surrounds. The fact that the outer guide track is at least partially immersed in oil at rest ensures perfect lubrication of the bearing at low speed. In the event that the casing contains more than one bearing for guiding the rotation of the motor shaft, the oil level plane at rest is preferably above the outer guide tracks of each of the bearings for guiding the rotation of the motor shaft.

[0012] According to one embodiment, the oil level plane at rest is determined by an oil injection orifice in the casing: it may be prescribed to fill the casing with oil up to the oil level plane at rest when the casing is in a reference position. It is then the orifice which determines the oil level plane at rest and therefore the prescribed volume of oil in the casing, the oil level plane at rest being tangent to the thread of the orifice allowing a plug to be associated with it.

[0013] According to one embodiment, the motor shaft and the receiving shaft are located above the oil level plane at rest when the transmission mechanism is in the reference operational position, which ensures perfect lubrication of the bearing at low speed. In the event that the casing contains more than one rotational guide bearing of the receiving member, the oil level plane at rest is preferably located above the outer guide tracks of each of the rotational guide bearings of the receiving member.

[0014] To limit energy consumption, it is preferable that the motor shaft and the receiving member are not completely immersed in oil at low speed. Thus, preferably, the motor shaft is closer to the oil level plane at rest than the receiving shaft, when the transmission mechanism is in a reference operational position.

[0015] According to one embodiment, the oil collecting tank has at least one upper opening located on the top of the oil collecting tank and one or more lower openings, located below the oil level plane at rest when the transmission mechanism is in the reference operational position.

[0016] According to one embodiment, the oil collecting tank has one or more intermediate openings located below the opening(s) on lower and above the oil level plane at rest when the transmission mechanism is in the reference operating position. The lower opening(s) allow controlled flow of oil. Preferably, the upper opening has an area greater than the sum of the areas of the lower opening(s) and / or the intermediate opening(s). If necessary, several openings may be provided at different levels, so as to vary the flow rate depending on the oil level in the crankcase.

[0017] According to one embodiment, when the transmission mechanism is in the reference operational position: a collector volume of the oil reservoir located above the oil level plane at rest is at least equal to, and preferably greater than: a volume available outside the oil collector reservoir, inside the casing, between the oil level plane at rest and a low receiving plane tangent to an outer guide track of a rotational guide bearing of the receiving member and parallel to the oil level plane at rest; and / or a low driving plane tangent to an outer guide track of a rotational guide bearing of the driving shaft and parallel to the oil level plane at rest. It is indeed desired to be able to collect the oil in the reservoir, therefore to ensure an incoming flow rate greater than the outgoing flow rate.

[0018] It is also desired that the capacity of the collector tank be sufficient to allow a significant drop in the oil level in the casing under certain operating conditions, and in particular when the speed increases. It is particularly desired that under certain operating conditions, the bearing of the receiving member no longer splashes in the oil and is no longer lubricated except by spraying. It is therefore preferentially provided that the oil collector tank is configured to contain at least 10% of a total volume of oil contained in the casing. Similarly, it is particularly desired that under certain operating conditions, the bearing of the receiving shaft no longer splashes in the oil and is no longer lubricated except by spraying. It is therefore preferentially provided at least 15% of a total volume of oil contained in the casing, and preferably at most 70%, for example at most 60%.

[0019] Preferably, the casing comprises one or more deflectors configured to guide the oil towards at least one gear between the drive shaft and the receiving member and / or a guide bearing of the drive shaft and / or a guide bearing of the receiving member and / or the oil collecting tank and / or the upper opening(s).

[0020] According to various embodiments, the drive pinion has an outside diameter and a number of teeth smaller than the outside diameter and the number of teeth of the driven pinion.

[0021] The invention is more particularly applicable to a mechanism of reducer transmission, and in particular to a fixed-ratio speed reducer. The invention also applies to dual-ratio reducers.

[0022] According to one embodiment, the transmission mechanism comprises one or more gears establishing at least one fixed speed ratio between the driving pinion and the receiving pinion, this speed ratio being greater than one.

[0023] According to one embodiment, the transmission mechanism further comprises at least one intermediate shaft between the drive shaft and the receiving member, a first speed reduction gear comprising the drive pinion between the drive shaft and the intermediate shaft, and a second speed reduction gear comprising the receiving pinion between the intermediate shaft and the receiving member. In particular, the transmission mechanism further comprises a differential housed in the casing, the receiving member constituting an input member of the differential.

[0024] According to a particular embodiment, the casing contains oil reaching without exceeding the oil level plane at rest when the transmission mechanism is in a reference operational position.

[0025] According to another aspect of the invention, the invention relates to the motor shaft constituting an output shaft of the electric motor or being rotationally integral with an output shaft of the electric motor. Preferably, the electric motor is fixed to the casing.

[0026] According to another aspect of the invention, it relates to a motorized vehicle comprising a transmission mechanism according to the preceding characteristics, and the oil level plane at rest being horizontal when the vehicle is resting on a horizontal plane.

[0027] Advantageously, the oil collecting tank can extend axially along the intermediate shaft. BRIEF DESCRIPTION OF THE FIGURES

[0028] Other characteristics and advantages of the invention will emerge on reading the description which follows, with reference to the appended figures.

[0029] [Fig.l] [Fig.l] schematically illustrates an electric propulsion assembly including a transmission mechanism according to an embodiment of the invention.

[0030] [Fig.2] [Fig.2] illustrates a section of the transmission mechanism of [Fig.l] along a transverse section plane, in a reference operational position.

[0031] [Fig.3] [Fig.3] illustrates an isometric view of the transmission mechanism of the [Fig.2],

[0032] [Fig.4] [Fig.4] illustrates an isometric view of another embodiment of the transmission mechanism of [Fig.2].

[0033] For clarity, identical or similar elements are identified by identical reference signs throughout the figures. DETAILED description of embodiments

[0034] In [Fig. 1] an electric propulsion assembly 56 is illustrated, comprising an electric motor 54 and a transmission mechanism 10.

[0035] The electric motor 54 may be, for example, an induction electric motor, comprising a rotor and a stator, electrically powered with three-phase alternating current by storage batteries via a current converter (not shown in [Fig.l]).

[0036] The electric motor 54 is held on a casing 12, an element of a transmission mechanism 10. The casing 12 is generally composed of a main body 60 supporting the electric motor 54 and a closing cover 62 bearing on the main body 60, at a joint plane 58, to seal a cavity delimited by the main body 60 and the cover 62 of the casing 12. The body of the casing 12 may be composed of several added parts or a single part, the part(s) being molded and / or machined.

[0037] The electric motor 54 rotates a motor shaft 16 which penetrates into the casing 12. The motor shaft 16 constitutes an input shaft of the transmission mechanism 10, which comprises an intermediate shaft 46, and a receiving member 18.

[0038] The motor shaft 16 is aligned on a motor axis 38 fixed relative to the casing 12, and carries at least one toothed wheel in joint rotation, here called motor pinion 17. The motor shaft 16 is guided by one or more rotation guide bearings 26. These rotation guide bearings 26 allow the motor shaft 16 to be held in its motor axis 38.

[0039] The receiving member 18 is guided by one or more rotational guide bearings 28 so as to rotate about a receiving axis 40 fixed relative to the casing 12. The receiving member 18 carries in joint rotation at least one receiving pinion 20. The receiving member 18 further comprises a fixed rotational connection with a planet carrier of a differential 52, or constitutes the planet carrier of the differential 52. The differential 52 can be open or limited slip, depending on the desired properties.

[0040] Like the receiving member 18 and the motor shaft 16, the intermediate shaft 46 is guided by one or more guide bearings in rotation around an intermediate axis 47 fixed in rotation relative to the casing 12, and carries at least two pinions in joint rotation, one forming a first speed reduction gear 48 with the motor pinion 17 of the motor shaft 16, and the second pinion forming a second speed reduction gear 50 with the receiving pinion 20 of the receiving member 18

[0041] The motor axis 38, the intermediate axis 47 and the receiving axis 40 are parallel to each other, parallel to the oil level plane at rest 14, and preferably perpendicular to the joint plane 58. The motor axis 38 and the receiving axis 40 are located in a reference plane 42 of the transmission mechanism 10. The intermediate axis 47 is located outside the reference plane 42.

[0042] The driving pinion 17 has a diameter and a number of teeth smaller than the diameter and the number of teeth of the first pinion 46A of the intermediate shaft 46 forming the first speed reduction gear 48. Similarly, the second pinion 46B of the intermediate shaft 46 forming the first speed reduction gear 48 has a diameter and a number of teeth smaller than the diameter and the number of teeth of the receiving pinion 20 of the receiving member 18. The transmission mechanism 10 is therefore reducing and without changing ratio.

[0043] For the remainder of the description, a reference operational position of the casing 12 is defined as being the three-dimensional orientation in which the casing 12 is installed in a vehicle horizontally. In this reference operational position, the intermediate axis 47 is located above the reference plane 42. In the remainder of this description, unless otherwise stated, the invention will be described in a reference operational position.

[0044] In [Fig.2] the transmission mechanism 10 is illustrated in a section plane orthogonal to the motor axis 38, the receiving axis 40 and the intermediate axis 47, and in the reference operational position.

[0045] In service, the casing 12 is filled with lubricating oil up to a prescribed limit which corresponds to an oil level plane at rest 14, this oil level plane at rest 14 being horizontal when the transmission mechanism is in the reference operational position. Each model of casing 12 has an oil level limit which is specific to it depending on the characteristics of the latter. Where appropriate, this oil level limit and the oil level plane at rest 14 may be materialized by an oil injection orifice 15, in the sense that it is prescribed, in the reference operational position, to fill the casing 12 until the oil level reaches the orifice 15, and not beyond. The oil level plane at rest is then tangent to the thread 19 of the orifice 15 allowing a plug 21 to be associated therewith.

[0046] A portion of the reference plane 42 of the transmission mechanism 10, delimited by the motor axis 38 as well as the receiving axis 40, is located above the oil level plane at rest 14. In the example illustrated, the orientation of the reference plane 42 is such that the motor axis 38 is closer to the oil level plane at rest 14 than the receiving axis 40. However, the reverse is also possible.

[0047] [Fig. 2] shows a low engine plane 37 tangent to the lowest point of an outer guide track of one of the guide bearings 26 and parallel to the oil level plane at rest 14. [Fig. 2] also shows a low receiving plane 36 tangent to the lowest point of an outer guide track of one of the guide bearings 28 and parallel to the oil level plane at rest 14. Depending on the inclination of the reference plane relative to the oil level plane at rest, and depending on the diameter of the guide bearings 26 and 28, the low engine plane 37 can be located under the low receiving plane 36 or vice versa. Remarkably, at least one of the two planes 36, 37, and preferably both planes 36, 37 are located under the oil level plane at rest 14. This means that in practice, at least one of the guide bearings 26 and 28, and preferably at least one guide bearing 26 of the engine shaft 16 and one guide bearing 28 of the receiving member 18, and preferably both guide bearings 26 of the engine shaft 16 and both guide bearings 28 of the receiving member 18, splash in the oil at rest.

[0048] The driving pinion 17, whose diameter is smaller than the receiving pinion 20, splashes in the oil when the transmission mechanism 10 is at rest.

[0049] In Figures 2 and 3 an oil collecting tank 22 is illustrated, arranged between the shafts 16, 46 and the receiving member 18 contained in the casing 12. The oil collecting tank 22 has an upper opening 32, located above the oil level plane at rest 14. According to another embodiment illustrated in [Fig. 4], the oil collecting tank 22 has several upper openings 32. These upper openings 32 are substantial since their purpose is to collect the oil projected into the interior cavity of the casing 12.

[0050] In the embodiment of [Fig.4], the two upper openings 32 are distributed on either side of the motor shaft 16.

[0051] The oil collecting tank 22 also comprises one or more lower openings 34 located below the resting oil level plane 12.

[0052] The oil collecting reservoir 22 may further comprise one or more intermediate openings 35 located below the upper opening 32 and above the resting oil level plane 12. The oil collecting reservoir 22 has one or more tubular branches with an intermediate opening 35 at each end, in order to precisely control the lubrication of one or more regions of the transmission mechanism 10.

[0053] The upper opening 32 has an opening area greater than the sum of the opening area(s) of the lower openings 34 and the intermediate openings 35. This characteristic makes it possible to have a potential oil inlet into the oil collecting tank 22 through the upper opening(s) 32 greater than a potential oil outlet through the lower opening(s) 34 and the intermediate opening(s) 35, and thus create oil retention in the casing 12 and therefore a reduction in the oil level in the casing 12 outside the oil collecting tank 22.

[0054] The volume of the oil collecting tank 22 is designed to contain at least 10% of the total volume of oil contained in the crankcase 12, and can contain up to 70% of the total volume of oil contained in the crankcase 12.

[0055] The oil collecting tank 22 is embedded between the drive shaft 16, the intermediate shaft 46 and the receiving member 18. The volume of the oil collecting tank 22 is in particular cut by the reference plane portion 42 of the transmission mechanism 10.

[0056] The oil collecting tank 22 preferably covers without contact at least a portion of the drive shaft 16 and / or the receiving member 18. The oil collecting tank 22 preferably envelops, over at least a portion, the receiving pinion 20. Where appropriate, the oil collecting tank 22 has curved walls which follow without contact the outer envelope of the trajectory of any of the pinions over at least a portion of its surface of revolution, this outer envelope being defined by the surface of revolution formed by the revolution of a set of points of the pinion, furthest from the axis of rotation, around this same axis of rotation.

[0057] The casing 12 comprises deflectors 44. These deflectors 44 may be directly molded into the shell of the casing 12 or may be added parts. The deflectors 44 have the purpose of directing the oil at least towards one gear and / or towards the oil collecting tank 22.

[0058] The oil collecting tank 22 makes it possible to provide a dynamic oil level depending on the rotation speed of the drive shaft 16, and more precisely, to reduce the oil level when the speed increases, by retaining a portion of the oil sprayed by the elements of the transmission mechanism which splash in the oil.

[0059] At rest, that is to say when stopped, the part of the oil collecting tank 22 located above the rest oil level plane 14 is empty, and the oil level corresponds to the rest oil level plane 14. The maximum oil level varies only slightly when the transmission mechanism 10 operates at very low speed. This is explained by a low-speed rotation of the driven pinion 20, the driven pinion 20 being the largest toothed wheel of the transmission mechanism 10 and therefore the wheel most capable of projecting the oil into the cavity formed by the casing 12.

[0060] The higher the rotation of the shafts 16, 46 and / or the receiving member 18, the more the oil will be projected through the casing 12 by the rotation of the pinions. When the oil is projected into the casing 12, it falls back • on a mechanical part such as a pinion or a bearing; and / or • in the bottom of the crankcase 12 where the oil rests; and / or • in the oil collecting tank 22.

[0061] The oil collected by the oil collecting tank 22 is continuously discharged through the lower openings 34, but the areas of the lower openings 34 are sized so that the amount of oil retained by the collecting tank 22 increases as the speed increases. As the oil collecting tank 22 fills, the quantity of oil present in the volume of the crankcase 12 but outside the oil collecting tank 22 decreases.

[0062] Thus, the oil level in the casing 12, outside the oil collecting tank 22, varies between a maximum level corresponding to the oil level plane at rest 14 and a minimum level. The minimum oil level is preferably such that the driving pinion 17 and the guide bearings 26, 28 no longer splash in the oil. The driving pinion 17 continues to be lubricated by the continuous projections of oil by the receiving pinion 20, which remains the only pinion in the casing 12 to splash in the oil. This level is reached when the rotation speed of the receiving pinion 20 is very high, and consequently, the oil collecting tank 22 is full.

[0063] The oil volume between the maximum oil level, the minimum oil level and the interior of the crankcase 12 is less than or equal to the collector volume 24 of the oil collector reservoir 22 above the resting oil level plane 14.

[0064] The collector volume 24 of the oil collector tank 22, depending on the embodiment, may vary. The collector volume 24 may collect up to 70% of the total oil volume in the crankcase 12. Beyond this threshold value, there is a risk of no longer having enough oil projected into the internal cavity of the crankcase 12.

[0065] An oil collecting tank 22 whose collecting volume 24 is capable of collecting 10% of the total oil volume in the casing 12 represents a collecting volume 24 of minimum configuration. In other words, below this threshold value of 10%, the volume of oil collected by the oil collecting tank 22 is too low and has little impact on the lubrication or not of the mechanical parts in the casing 12.

[0066] The position of the oil collecting tank 22 in the center of the transmission mechanism 10 makes it possible to keep a compact casing 12 unlike a tank which would be peripheral, for example along an interior wall of the casing 12. Also, the oil collecting tank 22 fills and empties by exploiting the transmission mechanism 10 to its advantage. Apart from the oil collecting tank 22, there is no need to add an additional mechanical part to the transmission mechanism 10, nor a motor such as a pump.

[0067] The collecting volume 24 of the oil collecting tank 22 is cut by the joint plane 58.

[0068] Preferably, at least some of the walls of the oil collecting tank 22 are fitted into the casing 12. The oil collecting tank 22 may be made from a part, preferably made of plastic, molded and / or machined and / or from two assembled half-shells.

[0069] The oil collecting tank 22 may comprise support legs and feet, of the same material as the oil collecting tank 22 and made on the part(s) made to produce the oil collecting tank 22 or added to posteriori. If necessary, the oil collecting tank 22 can be supported by the tabs which fit into the inner wall of the housing 12 and / or the closing cover. The oil collecting tank 22 can be placed on its feet at the bottom of the housing 12 or supported by one of the shafts in order to be held in position.

[0070] The oil collecting tank 22 extends axially along the intermediate shaft 46.

[0071] Naturally, the examples shown in the figures and discussed above are given for illustrative purposes only and are not limiting. It is explicitly provided that the different embodiments illustrated can be combined with each other to propose others.

[0072] According to a variant not illustrated, the oil collecting reservoir 22 has one or more tubular branches with an intermediate opening 35 at each end, in order to precisely control the lubrication of one or more regions of the transmission mechanism 10.

[0073] The transmission mechanism described above is a reduction mechanism with a constant speed ratio to an intermediate shaft 46, but the invention is also intended to be applied to mechanisms with several intermediate shafts, or without an intermediate shaft 46, to mechanisms with several speed ratios, and / or to mechanisms whose ratio of the input speed to the output speed is less than 1

[0074] The transmission mechanism 10 described above is a speed reducer mechanism with internal splash lubrication, but the invention is also intended to be applied to a speed reducer mechanism with internal lubrication under pressure in which the oil is directed via pipes or hoses to the main points of the reducer to be lubricated. The oil then falls by gravity into the bottom of the casing. In this other example, a mechanical or electric pump can be used to bring the pressurized fluid into the pipes or hoses.

Claims

Claims

1. Internally lubricated transmission mechanism (10), comprising a casing (12), the casing (12) defining an oil level plane at rest (14) when the transmission mechanism (10) is in a reference operational position, the transmission mechanism (10) further comprising, housed in the casing (12), a drive shaft (16) guided in rotation about a drive axis (38) and integral in rotation with at least one drive pinion (17), and a receiving member (18) guided in rotation about a receiving axis (40) and integral in rotation with at least one receiving pinion (20), the drive axis (38) and the receiving axis (40) being contained in a reference plane (42) of the transmission mechanism (10), a portion of the receiving pinion (20) being located below the oil level plane at rest (14) when the transmission mechanism (10) is in the reference operational position reference,the transmission mechanism (10) comprising an oil collecting tank (22) housed in the casing (12), the oil collecting tank (22) delimiting a collecting volume (24), characterized in that: - a part of the drive pinion (17) and / or of an outer guide track of a bearing for guiding the rotation of the drive shaft (26) is located below the oil level plane at rest (14) when the transmission mechanism (10) is in the reference operational position, and - a portion of the reference plane (42) located between the drive axis (38) and the receiving axis (40) passes through the collecting volume (24).,

2. Transmission mechanism (10) according to any one of the preceding claims, characterized in that the resting oil level plane (14) is located above a guide track of a rotational guide bearing of the receiving member (28), when the transmission mechanism (10) is in the reference operational position.

3. Transmission mechanism (10) according to any one of the preceding claims, characterized in that the driving axis (38) and the receiving axis (40) are located above the resting oil level plane (14) when the transmission mechanism (10) is in the reference operational position.

4. Transmission mechanism (10) according to any one of the claims- preceding indications, characterized in that the motor axis (38) is closer to the oil level plane at rest (14) than the receiving axis (40), when the transmission mechanism (10) is in a reference operational position.

5. A transmission mechanism (10) according to any preceding claim, characterized in that the oil collecting tank (22) has at least one upper opening (32) located on the top of the oil collecting tank (22) and one or more lower openings (34), located below the rest oil level plane (14) when the transmission mechanism (10) is in the reference operational position.

6. Transmission mechanism (10) according to claim 5, characterized in that the oil collecting tank (22) has one or more intermediate openings (35) located below the upper opening(s) (32) and above the rest oil level plane (14) when the transmission mechanism (10) is in the reference operational position.

7. Transmission mechanism (10) according to claim 6, characterized in that the upper opening (32) has an area greater than the sum of the areas of the lower opening(s) (34) and / or the intermediate opening(s) (35).

8. Transmission mechanism (10) according to any one of the preceding claims, characterized in that when the transmission mechanism (10) is in the reference operational position: a collector volume (24) of the oil reservoir (22) located above the rest oil level plane (14) is at least equal to, and preferably greater than: a volume available outside the oil collector reservoir (22), inside the casing, between the rest oil level plane (14) and - a low receiving plane (36) tangent to an outer guide track of a rotational guide bearing of the receiving member (28) and parallel to the rest oil level plane (14); and / or - a low driving plane (37) tangent to an outer guide track of a rotational guide bearing of the driving shaft (26) and parallel to the rest oil level plane (14).

9. Transmission mechanism (10) according to any one of the preceding claims, characterized in that the oil collecting tank (22) is configured to contain at least 10% of a total volume of oil contained in the casing (12), preferably at least 15%, and preferably at most 70%, for example at most 60%.

10. Transmission mechanism (10) according to any one of the preceding claims, characterized in that the casing (12) comprises one or more deflectors (44) configured to guide the oil towards at least one gear between the drive shaft (16) and the receiving member (18) and / or a guide bearing of the drive shaft (26) and / or a guide bearing of the receiving member (28) and / or the oil collecting tank (22) and / or the upper opening(s) (32).

11. Transmission mechanism (10) according to any one of the preceding claims, characterized in that the transmission mechanism comprises one or more gears establishing at least one fixed speed ratio between the driving pinion (17) and the receiving pinion (20), this speed ratio being greater than one.

12. Transmission mechanism (10) according to claim 11, characterized in that it further comprises at least one intermediate shaft (46) between the motor shaft (16) and the receiving member (18), a first speed reduction gear (48) comprising the motor pinion (17) between the motor shaft (16) and the intermediate shaft (46), and a second speed reduction gear (50) comprising the receiving pinion (20) between the intermediate shaft (46) and the receiving member (18).

13. Transmission mechanism (10) according to any one of the preceding claims, characterized in that it further comprises a differential (52) housed in the casing (12), the receiving member (18) constituting an input member of the differential (52).

14. A transmission mechanism (10) according to any preceding claim, characterized in that the casing (12) contains oil reaching but not exceeding the resting oil level plane (14) when the transmission mechanism (10) is in a reference operational position.

15. An electric propulsion assembly comprising an electric motor (54) and a transmission mechanism (10) according to any one of the preceding claims, the motor shaft (16) constituting an output shaft of the electric motor (54) or being rotationally integral with an output shaft of the electric motor.

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