INTERNALLY LUBRICATED TRANSMISSION MECHANISM

Abstract

The invention relates to an internally lubricated transmission mechanism (1) comprising a housing (40a, 40b) that defines a lubricant level plane at rest (14) when the transmission mechanism (1) is in a reference operating position. The transmission mechanism (1) comprises a first transmission shaft (10) guided in rotation about a first axis of rotation (X1), a second transmission shaft (20) guided in rotation about a second axis of rotation (X2), and a third transmission shaft (30) guided in rotation about a third axis of rotation (X3) and rotationally fixed to at least one torque output gear (31). A portion of the torque output gear (31) is located below the lubricant level plane at rest (14). The transmission mechanism (1) comprises a lubricant guide device (50) housed within the housing (40a, 40b). (Fig. 1)

Description

Title of the invention: INTERNALLY LUBRICATED TRANSMISSION MECHANISM Technical field of the invention

[0001] The invention relates to the internal lubrication, for example by splash lubrication, of the components of a transmission mechanism, and in particular of a transmission mechanism comprising a speed reduction device. Prior art

[0002] To lubricate a speed reduction device, in particular bearings, gears, etc., the transmission mechanism can be equipped with a pump that circulates a lubricant such as oil in a lubrication circuit configured to reach different specific areas requiring lubrication. These lubrication devices are called "active." Such a device is described, for example, in document FR2982003, in which a pump supplies oil to a gearbox via a trough acting as a reservoir within the gearbox casing. The trough supplies oil to the rotating shafts of the gearbox via a plurality of orifices.This device has the disadvantage of being energy-intensive to operate the pump and bulky along a vertical axis since the single reservoir of the chute is positioned above the transmission shafts, specifically between a secondary shaft and the upper wall of the casing.

[0003] There are also so-called "passive" lubrication devices, i.e., those without a pump, in which the moving components of the transmission mechanism are known to be placed inside a housing containing oil, but without the moving components being completely immersed in the oil. It is then the movement of the transmission mechanism that, by splashing, mixes the oil and projects it throughout the entire internal volume of the housing, to ensure the desired lubrication of the entire mechanism, including the non-immersed parts.

[0004] However, these passive lubrication solutions do not give complete satisfaction and the upward movement of lubricant from the bottom to the top of the crankcase is sometimes insufficient, particularly when elements of the speed reduction device, for example a transmission shaft carrying gears, obstruct the upward movement of the lubricant.

[0005] This problem is all the more important when the architecture of the speed reduction device is oriented vertically, that is to say when the transmission mechanism is placed in a reference operational position, the shaft of The transmission supporting the differential is located at the bottom of the housing. In this configuration, two other drive shafts for the speed reduction mechanism are situated above the differential's axis of rotation. For this type of design, the upward flow of lubricant from the bottom to the top of the speed reduction mechanism is insufficient. Description of the invention

[0006] The invention aims to remedy the drawbacks of the prior art and to propose a transmission mechanism combining good lubrication of the guide bearings located at the top of the speed reduction device and low energy consumption.

[0007] To this end, according to a first aspect of the invention, an internally lubricated transmission mechanism is proposed, comprising a housing, the housing defining a lubricant level plane at rest when the transmission mechanism is in a reference operational position, the transmission mechanism further comprising, housed in the housing, a first transmission shaft guided in rotation about a first axis of rotation XI and fixed in rotation to at least one torque input pinion, a second transmission shaft guided in rotation about a second axis of rotation X2 and a third transmission shaft guided in rotation about a third axis of rotation X3 and fixed in rotation to at least one torque output gear, the first transmission shaft and the third transmission shaft overlapping at least partially in a vertical direction with respect to the reference operational position,a portion of the torque output gear located below the lubricant level plane at rest when the transmission mechanism is in the reference operating position, the transmission mechanism comprising a lubricant guide device housed in the casing and disposed between the casing and the torque output gear, ,

[0008] the lubricant guide device comprising an upper channel whose internal surface is oriented towards the torque output gear, the first end of the upper channel covers the torque output gear and the second end of the upper channel covers the torque input pinion.

[0009] This transmission mechanism with its lubricant guide device has the advantage of recovering and distributing a significant quantity of lubricant present within the speed reduction device from the bottom to the top of the housing. The internal surface of the upper trough receives the lubricant spray generated by the splashing of the helical teeth of the torque output gear immersed in oil. The lubricant is then channeled to the second end of the upper channel. This promotes the upward flow of lubricant from the bottom of the casing, thus dispersing the lubricant in different areas located at the top of the transmission mechanism.

[0010] The lubricant guidance device allows the flow of lubricant brought to the top of the crankcase to be controlled reliably and regardless of the rotation speed of the third transmission shaft.

[0011] According to one embodiment of the invention, the first transmission shaft, the second transmission shaft, and the third transmission shaft overlap at least partially in a vertical direction relative to the reference operating position. In this embodiment, the second transmission shaft is interposed between the first and third transmission shafts in the vertical direction, but this does not necessarily imply that the first, second, and third axes of rotation are aligned.

[0012] Preferably, the second transmission shaft is rotationally fixed to an intermediate gear and an intermediate pinion axially offset from each other along the second axis of rotation X2, the torque input pinion of the first transmission shaft meshes with the intermediate gear and the torque output pinion of the third transmission shaft meshes with the intermediate pinion, the upper channel of the lubricant guide device has a profile which deviates axially from the median plane of the torque output pinion to the median plane of the torque input pinion.

[0013] Advantageously, the upper channel of the lubricant guide device has a curved profile, for example in the shape of an S, so that the internal surface of the upper channel covers the torque output gear and the torque input pinion.

[0014] According to one aspect of the invention, the upper channel is elongated with two ends, a first end being arranged to receive lubricant projected into the housing by the torque output gear and the second end being arranged to evacuate the lubricant channeled through the upper channel.

[0015] Preferably, the upper chute has a bottom and two lateral edges to form, at the inlet of the lubricant guide device, a channel having an open cross-sectional profile, the bottom supporting the internal surface arranged to receive the lubricant. The two lateral edges extend from the internal surface towards the torque output gear.

[0016] According to one aspect of the invention, the lubricant guide device comprises a lower trough fixed to the second end of the upper trough to form, at the outlet of the lubricant guide device, a channel having in cross-section transverse closed profile. Advantageously, the lubricant is channeled in a desired direction into an upper part of the transmission mechanism.

[0017] Preferably, the lower channel has a rounded lubricant receiving plate that covers the torque input gear. In this way, the lubricant continues to be channeled to the outlet of the lubricant guide device. Indeed, the lubricant has a high velocity at the outlet of the torque output gear. The lubricant is pressed against the inner surface of the upper channel at the inlet of the lubricant guide device. As it travels upwards within the upper channel, the lubricant loses velocity. The lubricant is then collected by the lower channel with the help of the receiving plate.

[0018] For example, the lower chute may include the lubricant receiving plate and two edges that merge with the two lateral edges of the upper chute. The receiving plate includes a receiving surface that faces the inner surface of the upper chute. According to this design, the receiving surface of the lower chute and the inner surface of the upper chute face each other and have complementary shapes.

[0019] Advantageously, the bottom of the upper channel, the two lateral edges, and the lubricant receiving plate of the lower channel form a funnel that channels the lubricant towards the second end of the lower channel. According to this design, the lower and upper channels face each other and have complementary shapes.

[0020] According to one aspect of the invention, the upper channel has a long length of conduit Ls and the lower channel has a short length of conduit Li. The overlap ratio of the lower channel to the upper channel Li / Ls is between 15 and 50%. The length of the lower channel depends on the angle of inclination α of the internal surface at the inlet of the upper channel relative to the lubricant level plane at rest when the transmission mechanism is in a reference operating position. The greater the angle of inclination, the closer the overlap ratio is to 50%.

[0021] According to one aspect of the invention, the second end of the lower chute comprises at least one lubricant outlet chute oriented perpendicularly to the lateral edges of the upper chute.

[0022] Preferably, the lubricant outlet gutter is contiguous with the lubricant receiving plate of the lower gutter.

[0023] According to a variant of the invention, the lubricant outlet gutter may include a first spout oriented towards a first guide bearing of the first transmission shaft.

[0024] According to a variant of the invention, the lubricant outlet gutter may include a first spout directed towards a first guide bearing of the first transmission shaft and a second spout directed towards a second guide bearing of the first transmission shaft.

[0025] The transmission mechanism according to the invention may have one or more of the characteristics described below, either combined or taken independently of each other:

[0026] - the two lateral edges cover the sides of the torque output gear.

[0027] - the two lateral edges border the inner surface along the entire length of the upper chute.

[0028] - the lower chute includes a lubricant receiving plate and two separate guide edges from the two lateral edges of the upper chute.

[0029] - the lower chute is elongated in shape with two ends, a first lubricant receiving end being arranged to receive lubricant channeled through the upper channel and a second lubricant discharge end being arranged to discharge the lubricant channeled through the upper channel.

[0030] - the lubricant receiving plate of the lower chute includes a spoiler receiving end located on the first lubricant receiving end.

[0031] - the torque input pinion is located above the lubricant level plane at rest when the transmission mechanism is in the reference operational position.

[0032] - the intermediate gear is located above the lubricant level plane at rest when the transmission mechanism is in the reference operational position.

[0033] - a closing cover is attached to the main cover so as to form an enclosed chamber around the transmission mechanism, the lubricant guide device being held in position partly by the main casing and partly by the closing casing.

[0034] - the lubricant guide device is partially formed from material in the crankcase main or in the closing casing.

[0035] - the peripheral wall of the main housing comprises a coaxial cylindrical surface to the third axis of rotation X3 which partially surrounds the outer periphery of the torque output gear.

[0036] - the crankcase contains a lubricant, for example oil, reaching a plane of oil level at rest when the transmission mechanism is in a reference operating position.

[0037] The invention also relates to a propulsion assembly comprising an electric motor and a transmission mechanism incorporating all or part of the Characteristics mentioned previously, the first transmission shaft constituting an output shaft of the electric motor or being rotationally fixed to a drive shaft of the electric motor. Where applicable, the electric machine includes a rotor shaft which may be coaxial and rotationally fixed to the input shaft of the speed reducer.

[0038] Other features and advantages of the invention are highlighted by the following description of non-limiting examples of implementation of the different aspects of the invention. brief description of the figures

[0039] Other features and advantages of the invention will become apparent from the following description, with reference to the accompanying figures, which illustrate: [Fig.1]: [Fig.1] is a front view of the inside of a transmission mechanism according to a first embodiment of the invention.

[0040] [Fig.2]: [Fig.2] is an isometric view of the transmission mechanism of [Fig.1].

[0041] [Fig.3] : [Fig.3] is a simplified view of the transmission mechanism of [Fig.1].

[0042] [Fig.4]: [Fig.4] is a detailed view of the lubricant guide device of the transmission mechanism of the [Fig.1]. DETAILED description of a method of implementation

[0043] Figures 1 to 4 show a transmission mechanism 1 of a motor vehicle according to a first embodiment of the invention. This transmission mechanism 1 is generally integrated within a main drive system of a vehicle, in particular an electric motor vehicle, or a secondary drive system. For example, it may be a secondary electric drive system of a hybrid vehicle, in particular intended for the rear axle of the vehicle.

[0044] The transmission mechanism 1 includes, in particular in an orthogonal frame XYZ, a first transmission shaft 1 0 extending along a first axis of rotation X 1 and coaxially carrying a torque input pinion 11. In the orthogonal frame XYZ, the planes XY, YZ and XZ are perpendicular to each other.

[0045] In the description and claims, the terms "external" and "internal," as well as the orientations "axial" and "radial," shall be used to designate, according to the definitions given in the description, elements of the transmission system. By convention, the "axial" orientation relates to the reference axes X, Y, or Z or to directions parallel to these axes, and the "radial" orientation is directed orthogonally to the reference axes X, Y, and Z. A "radially internal" element is located closer to the reference axis than a "radially external" element.

[0046] The terms "upper", "lower", "top", "bottom", and "bottom" should be taken into consideration when viewing the transmission mechanism in a position / incline similar to its position when mounted on a vehicle parked horizontally; this position is referred to in the following description as the "reference operating position".

[0047] Figure 3 illustrates an electric propulsion assembly 100, comprising an electric motor 70 and the transmission mechanism 10.

[0048] The electric motor 70 can be, for example, an induction electric motor, comprising a rotor and a stator, electrically powered by three-phase alternating current from accumulator batteries via a current converter (not shown in [Fig.3]).

[0049] The electric motor 70 is held on a housing 40a, 40b which is an element of the transmission mechanism 10. The housing generally consists of a main housing 40a supporting the electric motor 70 and a closing housing 40b bearing against the main housing 40a, at a joint 48, to seal a cavity delimited by the main housing 40a and the closing housing 40b. The main housing 40a and the closing housing 40b may be composed of several attached parts or of a single part, the part(s) being cast and / or machined.

[0050] The electric motor 70 drives a drive shaft which enters the housing 40a, 40b. The electric motor 70 drives the first transmission shaft 10 which constitutes an input shaft of the transmission mechanism 1. The speed reduction device of the transmission mechanism 1 also includes a second transmission shaft 20, and a third transmission shaft 30 which constitutes an output shaft of the transmission mechanism 1.

[0051] The second transmission shaft 20, which constitutes an intermediate shaft of the transmission mechanism 1, is parallel to the first transmission shaft 10 and the third transmission shaft 30 of the transmission mechanism 1. At the output of the speed reduction device, the third transmission shaft 30 is a differential which is used to transmit and distribute torque from the electric motor 70 to two wheel shafts of an axle of a motor vehicle.

[0052] The third transmission shaft 30 includes a torque output gear 31 but also a fixed rotational link with a planet carrier of a differential 32, or constitutes the planet carrier of the differential 32. The differential 32 can be open or limited slip, depending on the properties required.

[0053] The second transmission shaft 20 is rotationally fixed to an intermediate gear 21 and an intermediate pinion 22, which are axially offset from each other along the second axis of rotation X2. The intermediate gear 21 forms a first reduction stage with the torque input pinion 11 of the first transmission shaft 10, and the intermediate pinion 22 forms a second reduction stage with the torque output gear 31 of the third transmission shaft 30.

[0054] The first, second and third axes of rotation XI, X2, X3 are parallel to each other.

[0055] The first transmission shaft 10 is guided in rotation relative to the housing 40a, 40b by one or more guide bearings 100a, 100b.

[0056] The second transmission shaft 20 is guided in rotation relative to the housing 40a, 40b by one or more guide bearings 200a, 200b.

[0057] The third transmission shaft 30 is guided in rotation relative to the housing 40a, 40b by one or more guide bearings 300a, 300b.

[0058] These different rotational guide bearings allow the transmission shafts to be held within the housing 40a, 40b according to their respective axis of rotation.

[0059] The hollow-shaped main housing 40a comprises a base 45 and a peripheral wall 46 formed from the same material as the base, the peripheral wall partially surrounding the speed reduction device. The peripheral wall 46 partially surrounds the torque output gear 31 of the third transmission shaft 30. In this example, the speed reduction device comprises a single speed ratio.

[0060] In operation, the housing 40a, 40b is filled with lubricant, for example, lubricating oil, up to a prescribed limit corresponding to a resting oil level plane 14. This resting lubricant level plane 14 is horizontal when the transmission mechanism is in its reference operating position. Each housing model 40a, 40b has its own specific oil level limit depending on its characteristics. Where applicable, this oil level limit and the resting lubricant level plane 14 may be defined by an oil injection port 15, in the sense that, in the reference operating position, the housing 40a, 40b is filled only until the oil level reaches the port 15, and not beyond. The oil level plane at rest is then tangent to the thread of the orifice 15 allowing a plug 2 5 to be associated with it.

[0061] For the remainder of this description, a reference operating position of the housing 40a, 40b is defined as the three-dimensional orientation in which the housing 40a, 40b is installed in a horizontal vehicle. In this reference operating position, the third axis of rotation X3 is located above the resting lubricant level plane 14. In the remainder of this description, unless otherwise stated, the invention will be described in a reference operating position.

[0062] Figure 1 illustrates the transmission mechanism 1 in a cutting plane orthogonal to the first, second and third axes of rotation XI, X2, X3, and in Reference operational position. The transmission mechanism 1 is shown in a static position, i.e., the torque output gear 31 of the third transmission shaft 30 is not rotated. The transmission mechanism 1 has a relatively low part and a relatively high part.

[0063] In this reference operating position, the first transmission shaft 10 and the third transmission shaft 30 overlap at least partially in a vertical direction with respect to the reference operating position. That is to say, there is a plane normal to the reference axis Z which simultaneously intersects the first transmission shaft 10 and the third transmission shaft 30.

[0064] The guide bearings 300a, 300b and a portion of the torque output gear 31 are immersed in oil at rest. Thus, a portion of the torque output gear 31 is located below the lubricant level plane 14 at rest when the transmission mechanism 1 is in the reference operating position.

[0065] In the example of [Fig. 1], the second transmission shaft 20 and the first transmission shaft 10 do not splash around since the first transmission shaft 10, the second transmission shaft 20, and the third transmission shaft 30 overlap at least partially in a vertical direction with respect to the reference operating position. Thus, there is a plane normal to the reference axis Z that simultaneously intersects the first transmission shaft 10, the second transmission shaft 20, and the third transmission shaft 30.

[0066] Figures 1 to 4 illustrate a lubricant guide device 50 whose function is to bring the lubricating oil from the bottom to the top of the crankcase and distribute it to different points of the speed reduction device.

[0067] To improve lubrication within the transmission mechanism 1, the lubricant guide device 50 includes an upper channel 51 whose internal surface 5la is oriented towards the torque output gear 31. The orientation of the teeth of the torque output gear 31 prevents the lubricating oil from being projected directly towards the torque input pinion 21. The shape of the upper channel has the effect of channeling the lubricating oil towards the teeth of the torque input pinion 21. For this purpose, the first end 53 of the upper channel 51 covers the torque output gear 31 and the second end 54 of the upper channel covers the torque input pinion 21.

[0068] The upper channel 51 has a profile that deviates axially from the median plane PI of the torque output gear to the median plane P2 of the torque input pinion. More specifically, the upper channel 52 of the lubricant guide device has a curved profile, for example S-shaped, such that the internal surface 5la of the upper channel covers the output gear of torque and the torque input pinion. The lubricant flow is thus directed to the desired area of ​​the housing.

[0069] The upper chute 5 1 could have another type of profile but in all cases the first end 53 of the upper chute 51 would cover the torque output gear 31 and the second end 54 of the upper chute would cover the torque input pinion 21.

[0070] The upper chute 51 is inclined relative to the resting lubricant level plane 14 when the transmission mechanism is in a reference operating position. The angle of inclination α of the internal surface 51a at the inlet of the upper chute 51 relative to the resting lubricant level plane 14 is generally between 30° and 70°, for example 60° as illustrated in [Fig. 1]. The angle of inclination α is a consequence of the vertical architecture of the transmission mechanism 1 as described above.

[0071] The upper chute 5 1 is elongated with two ends, the first end 53 being arranged to receive lubricant projected into the housing by the torque output gear 31 and the second end 54 being arranged to evacuate the lubricant channeled through the upper chute.

[0072] As illustrated in [Fig. 3], the upper chute 51 has a bottom 56 and two lateral edges 57 to form, at the inlet of the lubricant guide device 50, a channel having an open cross-sectional profile, the bottom 56 supporting the internal surface 51a arranged to receive the lubricant. The two lateral edges 57 cover the flanks of the torque output gear 31.

[0073] For example, the two lateral edges 57 border the internal surface 51a along the entire length of the upper chute.

[0074] The lubricant guide device 50 also includes a lower channel 60 fixed to the second end 54 of the upper channel 51 to form, at the outlet of the lubricant guide device, a channel having a closed cross-sectional profile. The lower channel 60 has a rounded lubricant receiving plate 61 that covers the torque input pinion 21. The curvature of the lubricant receiving plate 61 is substantially concentric with the torque input pinion 21. A clearance exists between these two components.

[0075] According to one example, the lower chute 60 can be attached to the upper chute 51 and held in place by gluing, welding, riveting.

[0076] According to another example, the lower chute 60 and the upper chute 51 can be obtained directly from material by plastic injection.

[0077] The lower chute 60 is elongated with two ends, the first end 63 being designed to receive lubricant projected into the housing by the torque output gear 31 and the second The lubricant outlet 64 is arranged to discharge lubricant towards the gear pinion 21. The lower channel 60 includes the lubricant receiving plate 61 and two flanges that merge with the two lateral flanges 57 of the upper channel. The receiving plate 61 includes a receiving surface 61a that faces the inner surface 51ade of the upper channel 51.

[0078] The bottom 56 of the upper chute, the two lateral edges 57, and the lubricant receiving plate 61 of the lower chute 60 form a funnel that channels the lubricant towards the second lubricant discharge end 64 of the lower chute. According to this design, the receiving surface 61a of the lower chute 60 and the internal surface 51a of the upper chute 51 face each other and have complementary shapes.

[0079] The upper trough 51 has a long channel length Ls and the lower trough 60 has a short channel length Li. The overlap ratio of the lower trough to the upper trough, Li / Ls, is between 15 and 50%. The value of the channel length of the lower trough depends on the angle of inclination α of the internal surface at the inlet of the upper trough relative to the lubricant level plane at rest when the transmission mechanism is in a reference operating position. The greater the angle of inclination α, the closer the overlap ratio Li / Ls is to 50%. The length Li,Ls can be curved if the trough is curved. The length Li,Ls is measured between the two ends of the trough.

[0080] The second lubricant outlet end 64 of the lower channel includes at least one lubricant outlet channel 66 oriented perpendicularly to the lateral edges 57 of the upper channel. The lubricant outlet channel 66 is contiguous with the lubricant receiving plate 61 of the lower channel.

[0081] In this example of an implementation of the invention, the lubricant outlet gutter 66 includes a first spout 67 directed towards a first guide bearing 100a of the first transmission shaft 10 and a second spout 68 directed towards a second guide bearing 100b of the first transmission shaft.

[0082] At rest, i.e., when stopped, the lubricant guide device 50 located above the oil level plane at rest is empty, and the oil level corresponds to the lubricant level plane at rest 14. The maximum oil level varies only slightly when the transmission mechanism 1 operates at very low speed. This is due to the low-speed rotation of the torque output gear 31, which is the largest gear in the transmission mechanism 1 and therefore the gear best suited to project oil through the housing 40a, 40b.

[0083] The higher the rotation of the transmission shafts, the more oil will be projected through the housing 40a, 40b by the rotation of the torque output gear 31. When the oil is projected into the housing, it is pressed against the inner surface 51a of the upper channel which covers the torque output gear 31.

[0084] The oil captured by the lubricant guide device 50 is then channeled within the upper trough 51, from the first end 53 to the second end 54. Under the effect of gravity, the oil captured by the inner surface 51a falls back onto the receiving surface 61a of the lower trough 60. The funnel shape of the lubricant guide device 50 channels the lubricant towards the second end 64 of the lower trough. Finally, the oil flows through the lubricant outlet trough 66, which is oriented perpendicularly to the lateral edges 57 of the upper trough. Part of the oil flows into the first spout 67 directed towards a first guide bearing 100a of the first transmission shaft 10 and part of the oil flows into the second spout 68 directed towards a second guide bearing 100b of the first transmission shaft.

[0085] Each of the spouts 67, 68 directs the oil into a groove 45 formed in the housing 40a, 40b so that it is conveyed to the guide bearings 100a, 100b as illustrated by the arrows in [Fig. 3]. The groove 45 opens into the upper part of a cylindrical housing 41 for receiving the second guide bearing 100b. A flow of lubricating oil is thus conveyed from the bottom of the main housing 40a to be directed subsequently to the second guide bearing 100b located at the top of the closing housing 40b.

[0086] Naturally, the invention is described above by way of example. It is understood that a person skilled in the art is able to carry out different embodiments of the invention without departing from its scope. For example, the invention described here in the context of a single-speed reducer can also be applied to a two-speed reducer or even a reducer with more than two speeds. The invention can also be applied to gearboxes. The transmission mechanism may include a fourth transmission shaft kinematically interposed between the first and third transmission shafts.

[0087] For example, the lubricant guide device could be partially formed from material in the main housing or in the closing housing. That is to say, part of the upper channel could be made from the same material as one of the housings. In this case, one of the lateral edges and / or the inner face of the upper channel would be formed partly by the housing and partly by an added component.

[0088] It is emphasized that all features, as they are apparent to a person skilled in the art from the present description, drawings and attached claims, even if in practice they have only been described in relation to other specific features, both individually and in any combinations, can be combined with other features or groups of features disclosed herein, provided that this has not been expressly excluded or that technical circumstances make such combinations impossible or meaningless.

Claims

Demands

1. Internally lubricated transmission mechanism (1) comprising a housing (40a, 40b), the housing (40a, 40b) defining a lubricant level plane at rest (14) when the transmission mechanism (1) is in a reference operating position, the transmission mechanism (1) further comprising, housed in the housing (40a, 40b), a first transmission shaft (10) guided in rotation about a first axis of rotation (XI) and rotationally fixed to at least one torque input pinion (11), a second transmission shaft guided in rotation about a second axis of rotation (X2) and a third transmission shaft (18) guided in rotation about a third axis of rotation (X3) and rotationally fixed to at least one torque output gear (31),the first transmission shaft (10) and the third transmission shaft (30) overlapping at least partially in a vertical direction with respect to the reference operating position, a portion of the torque output gear (31) being located below the lubricant level plane at rest (14) when the transmission mechanism (1) is in the reference operating position, the transmission mechanism (1) comprising a lubricant guide device (50) housed in the casing (40a, 40b) and disposed between the casing and the torque output gear (31), characterized in that the lubricant guide device (50) comprises an upper channel (51) whose internal surface (51a) is oriented in the direction of the torque output gear (31),The first end (53) of the upper channel covers the torque output gear (31) and the second end (54) of the upper channel covers the torque input pinion (11).

2. Transmission mechanism (1) according to claim 1, wherein the second transmission shaft (20) is rotationally fixed to an intermediate gear (21) and an intermediate pinion (22) axially offset from each other about the second axis of rotation (X2), the torque input pinion (11) of the first transmission shaft (10) meshes with the intermediate gear (21) and the torque output pinion (31) of the third transmission shaft (30) meshes with the intermediate pinion (22), the upper chute of the lubricant guide device (50) presents a profile which deviates axially from the median plane of the torque output gear (31) to the median plane of the torque input pinion (11).

3. Transmission mechanism (1) according to the preceding claim, wherein the upper channel (51) of the lubricant guide device (50) has a curved profile, for example in the shape of an S, such that the internal surface (51a) of the upper channel covers the torque output gear (31) and the torque input pinion (11).

4. Transmission mechanism (1) according to any one of the preceding claims, wherein the upper chute (51) has a bottom (55) and two lateral rims (57) to form, at the inlet of the lubricant guide device (50), a channel having in cross-section an open profile, the bottom supporting the internal surface arranged to receive the lubricant.

5. Transmission mechanism (1) according to the preceding claim, wherein the two lateral rims (57) cover the flanks of the torque output gear (31).

6. Transmission mechanism (1) according to any one of the preceding claims, wherein the lubricant guide device (50) comprises a lower chute (60) fixed on the second end (54) of the upper chute to form, at the outlet of the lubricant guide device (50), a channel having a closed cross-sectional profile.

7. Transmission mechanism (1) according to the preceding claim, wherein the lower chute (60) has a rounded lubricant receiving plate (61) which covers the torque input pinion (11).

8. Transmission mechanism (1) according to the preceding claim, wherein the lower chute (60) includes the lubricant receiving plate (61) and two rims which merge with the two lateral rims (57) of the upper chute, the receiving plate (61) includes a receiving surface (61a) which faces the internal surface (51a) of the upper chute (51).

9. Transmission mechanism (1) according to the preceding claim, wherein the lubricant receiving plate (61) of the lower chute includes a receiving spoiler located on a first lubricant receiving end (63).

10. Transmission mechanism (1) according to any one of claims 6 to 9, wherein the upper chute (51) has a large length of conduit (Ls) and the lower chute (60) has a small length of conduit (Li), the overlap ratio of the lower chute to the upper chute Li / Ls is between 15 and 50%.

11. Transmission mechanism (1) according to any one of claims 6 to 10, wherein a bottom (55) of the upper chute, two lateral rims (57) of the upper chute and the lubricant receiving plate (61) of the lower chute (60) form a funnel which channels the lubricant towards a second lubricant discharge end (64) of the lower chute.

12. Transmission mechanism (1) according to the preceding claim, wherein the second end (64) of the lower chute (60) comprises at least one lubricant outlet chute (66) oriented perpendicularly with respect to the lateral edges (57) of the upper chute (51).

13. Transmission mechanism (1) according to the preceding claim, wherein the lubricant outlet trough (66) is contiguous with the lubricant receiving plate (61) of the lower trough.

14. Transmission mechanism (1) according to claim 12 or 13, wherein the lubricant outlet trough (66) comprises a first spout (67) oriented towards a first guide bearing (100a) of the first transmission shaft (10) and a second spout (68) oriented towards a second guide bearing (100b) of the first transmission shaft.

15. Transmission mechanism (1) one of the preceding claims, wherein the housing (40a, 40b) is composed of a main housing (40a) and a closing housing (40b) connected together via a joint plane (48) to form a sealed cavity, the lubricant guide device (50) being disposed between the main housing and the closing housing.

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