ELECTRIC VEHICLE TRACTION GEAR REDUCER WITH LUBRICATION FLUID PUMP

Abstract

A motor vehicle electric traction motor speed reducer comprising gears carried by a primary shaft connected to the electric motor (6) and a secondary shaft driven by it (10), an upper receptacle (20) receiving a lubricating fluid by spraying during gear rotation, and comprising a pump (48) drawing this fluid from a reservoir (46) to ensure cooling of the electric motor (4), this reducer having a passage (28) for the fluid to descend from the receptacle (20) to the reservoir (46), which is separated from the volume containing the gears. Figure 1

Description

Title of the invention: SPEED REDUCER FOR ELECTRIC VEHICLE TRACTION MACHINE WITH LUBRICATION FLUID PUMP

[0001] The present invention relates to a speed reducer for an electric traction machine of a motor vehicle, comprising a lubrication and cooling fluid circuit equipped with a pump, as well as a motor vehicle having such a speed reducer.

[0002] A type of speed reducer known for an electric traction machine of a motor vehicle, described in particular by document WO-A1-2020157004, comprises, within a transmission housing, a first pinion fixed at the end of the machine which drives a secondary shaft, forming a first speed reduction. This secondary shaft, with a second reduction, drives the ring gear of a differential, which transmits the motion to the two drive wheels of the vehicle. The pinions of the two speed reductions are arranged in two parallel transverse planes.

[0003] The differential ring, coming into the lowest position of the housing, carries with its teeth during its rotation a lubricating fluid, in particular an oil, to raise it and project it towards a pinion of the secondary shaft which then projects it in turn into an upper receptacle located at the top of the housing.

[0004] This is achieved through a pumping effect with the rotating gears, resulting in oil being drawn up from the bottom of the crankcase to the upper receptacle, which then distributes it through gravity outlets to various locations for lubrication and cooling. In particular, the gears and bearings must receive a constant flow of oil to ensure lubrication and dissipate the heat generated by friction.

[0005] The upper oil receptacle has a transverse wall arranged between the two parallel planes of the gears of the two reductions to limit disturbances in the circulation of the oil by the gears of these two planes rotating in opposite directions, and to reduce excessive mixing of the fluid which slows the rotation of the elements with losses in efficiency.

[0006] Furthermore, a known type of electrical machine, presented in particular by document EP-A1-4270733, includes in the rotor shaft and in the stator axial bores receiving lubricating oil from the reducer, in order to improve cooling as close as possible to their active elements releasing heat to optimize the power and efficiency of the machine, and to reduce its mass and size.

[0007] In this case, an oil pump is provided in the gearbox housing, drawing the fluid from a lower reservoir located at the bottom of this housing, which receives the oil flowing down by gravity, coming in particular from the upper receptacle after its distribution to particular points.

[0008] However, under certain operating conditions of the vehicle, depending in particular on the rotational speed of the machine, the temperature of the fluid, and other parameters such as the movements of the vehicle, it is possible to obtain a mixing of the oil by the different rotating components in the reducer which prevents a sufficiently rapid descent of the fluid into the lower reservoir.

[0009] This creates a temporary risk of insufficient fluid level in the reservoir and pump failure, resulting in an interruption of flow to the components requiring cooling and lubrication. This can lead to performance losses in the machine, or even failure of components that continue to generate traction power for the vehicle despite no longer being under optimal cooling or lubrication conditions.

[0010] The present invention aims in particular to avoid these problems of the prior art.

[0011] To this end, it proposes a speed reducer for an electric traction machine of a motor vehicle, comprising gears carried by a primary shaft linked to the electric machine and by a secondary shaft which it drives, an upper receptacle receiving a lubricating fluid by projection during the rotation of the gears, and comprising a pump taking this fluid from a reservoir to ensure cooling of the electric machine, this reducer being characterized in that it includes a passage for the fluid to descend from the receptacle to the reservoir which is separated from the volume containing the gears.

[0012] One advantage of this speed reducer is that by simply providing a protected fluid descent from the upper receptacle, which is separated from the volume of the gears in order to reach the reservoir, interference with the flows projected by the rotating pinions of these gears is avoided, and a rapid and continuous flow of fluid is allowed towards the lower reservoir which is protected from their movements.

[0013] This avoids the risk of insufficiently rapid descent resulting in a fluid level that is too low in the reservoir, with disturbances in the flow delivered by the pump which would no longer be supplied, particularly for specific driving conditions including machine rotation speeds or lateral accelerations of the vehicle which modify the fluid movements.

[0014] The speed reducer according to the invention may further comprise one or more of the following characteristics, which may be combined with each other.

[0015] Advantageously, the fluid passage is separated from the volume of the gears by a wall arranged in a plane transverse to the axes of the primary and secondary shafts.

[0016] Moreover, advantageously the bearings at the ends of the shafts are in the passage which recovers the lubricating fluid from these bearings.

[0017] Advantageously, the wall has axial edges formed on the sides of the passage, which come close to an inner face of the housing arranged opposite this wall.

[0018] In this case, the wall may include intermediate axial edges formed between the side edges, which guide the fluid flow.

[0019] Advantageously, the wall with its side edges bypasses the primary and secondary trees.

[0020] Advantageously, the wall is formed in one piece with the upper receptacle.

[0021] Advantageously, the upper receptacle and the separate passage are formed by a plastic molding.

[0022] The invention also relates to an electric motor vehicle equipped with a speed reducer comprising any one of the preceding characteristics, remarkable in that the electric machine includes internal channels for circulating the fluid coming from the pump for its cooling.

[0023] The invention will be better understood and other features and advantages will become more apparent upon reading the following description given by way of example, with reference to the accompanying drawings in which:

[0024] [Fig-1] is a perspective view of a speed reducer according to the invention with its fluid downflow passage and its upper receptacle, shown without the front casing and the differential;

[0025] [Fig.2] is a side view of this reducer;

[0026] [Fig.3] is a front view of this reducer without its front casing; and

[0027] [Fig.4] is a view of a fluid downflow passage with its upper receptacle according to one variant.

[0028] Figures 1, 2, 3 and 4 show an electric vehicle powertrain comprising a main housing 2 containing an electric machine 4 arranged along a main axis, which drives a speed reducer fixed to the end of a front axial direction AV.

[0029] A primary shaft 6, driven directly by the electric machine 4, comprises successively, starting from this machine, a driving pinion 40 which meshes with a driven pinion 42 fixed on a secondary shaft 10 to form the first reduction, then a first end bearing 8. The secondary shaft 10 comprises successively, starting from the electric machine 4, a second driving pinion 44 which meshes with the crown of a differential not shown to form the second reduction, the driven pinion 42, then a second end bearing 12.

[0030] The reducer has in front of the transverse sealing front face 14 of the main housing 2, two parallel gear planes comprising first the second reduction and then the first reduction.

[0031] A front housing 32 comprising a rear face bearing on the sealing face of the main housing 14, has a transverse inner face 34 receiving the front end bearings 8, 12 of the shafts 6, 10.

[0032] The primary shafts 6 and secondary shaft 8 are superimposed, the differential axis being offset to the side of the powertrain to drive the vehicle's drive wheels by shafts which pass to the side of the electric machine 4.

[0033] The reducer includes a lower reservoir 46 of a lubricating and cooling fluid, an oil in particular, which supplies a pump 48 distributing the fluid to internal cooling channels of the electrical machine 4, and to various specific lubrication points of the rotating shafts of the reducer.

[0034] The rotation of the gears of the reducer also generates a mixing of oil sprayed on the faces of the casing, which falls back partly into an upper receptacle 20 arranged above the driving pinion 40 of the primary shaft 6. The upper receptacle 20 has two slopes surrounded by rims 24, distributing received oil on two sides, the larger slope 22 ending with a lower flow point 26 feeding a substantially vertical passage 28.

[0035] A wall 30, located below the upper receptacle 20 in a plane transverse to the axes of the shafts 6, 10, is positioned axially between the gears 40, 42, 44 and the end bearings 8, 12 of these shafts. The vertical passage 28 is defined between the wall 30, axial side edges of the passage 36 fixed to this wall, facing forward and approaching the transverse inner face 34 of the front housing 32, and this inner face, which substantially closes the passage. The lower end of the passage 28 extends above the reservoir 46 to supply it directly with fluid.

[0036] The wall 30 has intermediate edges 40 formed between the side edges 36, which guide the fluid flow.

[0037] The wall 30 with its edges 36 goes around the primary 6 and secondary 10 shafts by fitting below them to recover the fluid coming from the end bearings 8, 12.

[0038] The oil is recovered from the mixing in the upper receptacle 20, which extends across the width of the reducer, above all the gears. The oil then flows down the steep slope 22 through the vertical passage 28, framed by the transverse wall 30, the edges 28, and the inner face of the housing 34, which is protected from the rotation of the gears located behind this wall. The fluid flow... made freely in a calm volume, regardless of its viscosity, without disturbance by the movements of the gears and by the projections of oil directly sent by these gears in all directions.

[0039] The oil sprayed into the gearbox and collected in the upper receptacle 20 ensures good conduction to the reservoir 46, preventing supply failures to the pump 48. Lubrication of the various gearbox components and cooling of the electric machine are also guaranteed. This allows for optimization, in particular, of the sizing of the active components of the electric machine 4, resulting in maximum efficiency and power output within a reduced volume.

[0040] Advantageously the upper receptacle with the transverse wall 30 and its edges 24, 36 are formed in one piece by a plastic molding, making it possible to obtain economically all the shapes which can be complex to optimize the flows.

Claims

Demands

1. A motor vehicle electric traction motor speed reducer comprising gears (40, 42, 44) carried by a primary shaft connected to the electric motor (6) and by a secondary shaft (10) which it drives, an upper receptacle (20) receiving a lubricating fluid by spraying during the rotation of the gears (40, 42, 44), and comprising a pump (48) drawing this fluid from a reservoir (46) to ensure cooling of the electric motor (4), characterized in that it comprises a fluid passage (28) for the descent of the fluid from the receptacle (20) to the reservoir (46) which is separated from the volume containing the gears (40, 42, 44), this fluid passage (28) being separated from the volume of the gears (40, 42, 44) by a wall (30) disposed in a plane transverse to the axes of the primary (6) and secondary (10) shafts, this wall (30) comprising axial edges (36) formed on the sides of the passage (28),which come close to an inner face of the casing (34) arranged opposite this wall (30).

2. Reducer according to claim 1, characterized in that the bearings (8, 12) of the ends of the shafts (6, 10) are in the passage (28) which recovers the lubricating fluid from these bearings (8, 12).

3. Reducer according to any one of the preceding claims, characterized in that the wall (30) has intermediate axial rims (40) formed between the side rims (36), which guide the fluid flow.

4. Reducer according to any one of the preceding claims, characterized in that the wall (30) with its side edges (36) bypasses the primary (6) and secondary (10) shafts.

5. Reducer according to any one of the preceding claims, characterized in that the wall (30) is formed in one piece with the upper receptacle (20).

6. Reducer according to any one of the preceding claims, characterized in that the upper receptacle (20) and the separate passage (28) are formed by a plastic molding.

7. An electric motor vehicle equipped with a speed reducer according to any one of the preceding claims, characterized in that the stator of the electric machine (4) comprises channels internal circulation of the fluid coming from the pump (48) for its cooling.

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