Electric vehicle traction machine cooled by oil circulation generated by rotor rotation

Abstract

An electric traction machine for an electric or hybrid vehicle comprising a rotor shaft (12) having an axial bore connected upstream to an oil reservoir (4), and connected downstream to axial channels (20) formed in a stack of sheet metal fixed to this shaft, which form an oil cooling circuit opening through outlets (14) arranged radially outside the rotor (12), this machine comprising at the end of the shaft forming the inlet of the axial bore a rotating seal (18). Figure 1

Description

Title of the invention: ELECTRIC VEHICLE TRACTION MACHINE COOLED BY OIL CIRCULATION GENERATED BY ROTOR ROTATION

[0001] The present invention relates to an electric motor vehicle traction machine cooled by an internal circulation of oil generated by the rotation of the rotor, as well as an electric or hybrid motor vehicle equipped with such a machine.

[0002] A known type of electric machine for traction of an electric or hybrid vehicle, presented in particular by document US-A1-2021351664, comprises an oil projection system contained in the casing of the powertrain, using for example gears of the transmission, in order to fill a reservoir arranged at a level higher than the rotor shaft of this machine. The oil contained in the reservoir then flows by gravity to enter an axial bore of the rotor shaft, then circulates in axial channels of stacking of sheets surrounding the shaft in order to cool these sheets as well as permanent magnets fixed around.

[0003] The rotation of the rotor creates a centrifugal force which increases the pressure of the fluid depending on the radius of positioning of the conduit relative to the axis, this effect results in forced circulation in the rotor channels which goes from the central axis to the radially outer points, where it opens into the casing of the machine.

[0004] In particular for electric traction machines of electric or hybrid vehicles, it is generally desired to obtain a high power density with reduced mass and volume, so as to obtain more power while housing the powertrain in the engine compartment, which often offers limited space. In addition, the best efficiency of electric machines is sought in motor vehicles in order to reduce energy consumption to increase the autonomy of these vehicles, giving more flexibility for its use, and reducing operating costs.

[0005] However, this arrangement presented by the prior art document requires a pumping system to project the oil into the reservoir arranged above the axis of the shaft, which adds drag slowing down rotation with losses of efficiency, and a space to house this reservoir taking up space in the powertrain.

[0006] Furthermore, it is known to add an autonomous pump in the powertrain, in particular a mechanically or electrically driven pump, which generates pressure to supply the drilling of the rotor shaft. This type of pump with its control has an energy consumption, has a bulk and adds costs.

[0007] The present invention aims in particular to avoid these problems of the prior art.

[0008] To this end, it proposes an electric traction machine for an electric or hybrid vehicle comprising a rotor shaft having an axial bore connected upstream to an oil reserve, and connected downstream to axial channels made in a stack of sheets fixed to this shaft, which form an oil cooling circuit opening out via outlets arranged radially outside the rotor, this electric machine being remarkable in that it comprises at the end of the shaft forming the inlet of the axial bore a rotating seal.

[0009] An advantage of this electrical machine is that the rotation of the rotor causes centrifugation of the oil contained in the channels of the sheets which tends to flow radially outwards, generating a depression at the axial bore of the shaft. Thanks to the rotating joint ensuring a seal between the bore of the shaft and the oil reserve, this depression is communicated to the reserve which sucks the oil up, making it rise, then circulate in the channels towards the outlet.

[0010] The oil in the reserve, which may be at a lower level than the shaft, thus rises towards this shaft to supply the rotor cooling circuit without using a pumping system, in particular an electric or mechanical pump. Losses are reduced by avoiding the energy consumption of a pumping system, the number of parts in the powertrain is reduced, its size is minimal and costs are limited.

[0011] The electric traction machine according to the invention may further comprise one or more of the following characteristics, which may be combined with each other.

[0012] Advantageously, the rotor comprises at each end a clamping plate for stacking the sheets, comprising cutouts forming oil passages towards the axial channels.

[0013] Advantageously, each plate has angular sectors each comprising identical cutouts.

[0014] In this case, advantageously the two end plates have between them an angular offset equal to half an angular sector.

[0015] Advantageously, each plate comprises three angular sectors.

[0016] In this case, advantageously the sheets have six identical drilling patterns, two patterns covering a sector of the plate.

[0017] In addition, certain cutouts can feed two axial channels arranged in parallel.

[0018] Advantageously, the axial channels form two symmetrical sets with respect to a transverse median plane, each comprising an inlet on one side of the rotor.

[0019] Advantageously, the flow of oil passes through channels of the stator before arriving at the rotor via the rotating seal.

[0020] The invention also relates to an electric or hybrid motor vehicle equipped with an electric traction powertrain, remarkable in that this powertrain comprises an oil reserve which is arranged at a lower level than the axis of the rotor of this machine.

[0021] The invention will be better understood and other characteristics and advantages will appear more clearly on reading the description below given by way of example, with reference to the appended drawings in which:

[0022] [Fig.l] shows a diagram of an electrical machine circuit of a vehicle according to the invention;

[0023] [Fig.2] shows the two clamping plates of the ends of the stack of sheets of its rotor, showing the oil flows between them;

[0024] [Fig.3] shows a standard sheet of this stack.

[0025] [Fig.l] shows an electric traction machine for a motor vehicle 2, contained in a casing having in the lower part a tank for receiving a lubricating and cooling oil.

[0026] The oil circuit comprises successively in the direction of circulation starting from the tank 4, a suction filter 6, a heat exchanger 8 receiving the cooling fluid from the vehicle 10 in order to regulate its temperature, then the active parts of the machine 2 comprising the stack of sheets of the stator 10, then that of the rotor 12 ending in several outlets 14 with the fluid returning to the lower tank.

[0027] The stator 10 comprises a succession of axial channels 16 arranged in parallel, through which the oil flow passes to achieve as uniform a cooling as possible of these sheets receiving the copper wire windings which generate calories.

[0028] The oil circuit comprises at the outlet of the channels 16 of the stator 10, a grouping of these flows to supply an axial bore of the shaft of the machine formed along its length, by means of a rotating seal 18 arranged at the end of this shaft.

[0029] The rotor 12 comprises a stack of sheets comprising several particular oil passage circuits using axial channels 20, which allow for each circuit several passages in one axial direction then in the other in order to increase the passage time and the duration of the heat exchange.

[0030] In particular, half of the internal circuits of the rotor 12 start from a first end of the shaft and end with an outlet 14 on the second end, the other half making a reverse path which makes it possible to homogenize as much as possible the temperature of the rotor 12 receiving the calories symmetrically.

[0031] The rotation of the rotor 12 causes centrifugation of the oil generating a force radial extraction which creates a depression in the axial bore of the shaft, transmitted via the rotating seal 18 to the upstream circuit. The oil is automatically sucked into the recovery tank 4 via the filter 6 and the cooler 8, to pass through the stator 10 and then supply the rotor 12 without using a pumping system.

[0032] [Fig. 2] shows a first plate 30A on a first side of the rotor 12 and a second distribution plate 30B on the second side, which are identical, mounted at the ends of the stack of sheets of this rotor. Each plate 30 has cutouts forming three identical patterns each arranged on a sector of 120°, the arrows showing the oil passages in these cutouts. The two distribution plates 30 clamping the stack of sheets of the rotor 12, are mounted with an offset of 60° between them.

[0033] [Fig. 3] shows a sheet 40 of the stack of sheets of the rotor 12, comprising holes 42 which are aligned on the complete stack of sheets so as to form the axial channels of the rotor 20. The holes of each sheet 42 form six identical patterns 50 each arranged at an angle of 60°, two patterns covering a plate sector 30.

[0034] Each pattern 50 comprises a first batch of two close holes 44 on a small radius, in alignment with this first batch a second batch of two close holes 46 on a medium radius, and on a large radius a third batch of four holes 48 distributed on the outer edge.

[0035] Coming from the rotor shaft 12, the first plate 30A on the first side has a first radial cutout forming a passage 32 towards the first set of two holes 44 forming two grouped parallel channels. The second plate on the other side of the rotor 30B transfers the oil flow via a second cutout 34 to the second set of two holes 46 forming two grouped parallel channels.

[0036] The first plate on the first side of the rotor 30A then transfers the flow through two cutouts 36, each taking the flow rate from a channel to send it to a first bore 52 of the third batch 48 forming a channel arranged near the outer contour of the rotor 12. The second plate on the second side 30B then transfers through a fourth cutout 38 oriented in the circular direction, the flow to a second bore 54 of the third batch 48 forming another channel arranged near the outer contour, which ends on the first side of the rotor 12 by a radially outer outlet 14 of this rotor.

[0037] This operation comprising the channels 20 of three patterns 50 of the discs 40, is reproduced symmetrically by reversing the direction of the rotor 12 on three other sectors alternating with these first three. An identical operation is obtained for the six sectors of the rotor 12, with a reversal of the direction each time which gives a good homogeneity of the exchange of calories, in particular just below the magnets fixed on the external contour of this rotor.

Claims

Claims

1. Electric traction machine for an electric or hybrid vehicle comprising a rotor shaft (12) having an axial bore connected upstream to an oil reserve (4), and connected downstream to axial channels (20) made in a stack of sheets (40) fixed on this shaft, which form an oil cooling circuit opening through outlets (14) arranged radially outside the rotor (12), characterized in that it comprises at the end of the shaft forming the inlet of the axial bore a rotating seal (18).

2. Electrical machine according to claim 1, characterized in that the rotor (12) comprises at each end a clamping plate (30) for the stack of sheets (40), comprising cutouts (32, 34, 36, 38) forming oil passages towards the axial channels (20).

3. Electrical machine according to claim 2, characterized in that each plate (30) has angular sectors each comprising identical cutouts (32, 34, 36, 38).

4. Electrical machine according to claim 3, characterized in that the two end plates (30) have between them an angular offset equal to half an angular sector.

5. Electrical machine according to claim 3 or 4, characterized in that each plate (30) comprises three angular sectors.

6. Electrical machine according to claim 5, characterized in that the sheets (40) comprise six identical patterns (50) of holes (42), two patterns covering a plate sector (30).

7. Electrical machine according to any one of claims 2 to 6, characterized in that certain cutouts (32, 34) supply two axial channels (20) arranged in parallel.

8. Electrical machine according to any one of the preceding claims, characterized in that the axial channels (20) form two symmetrical sets with respect to a transverse median plane, each comprising an inlet on one side of the rotor (12).

9. An electrical machine according to any preceding claim, characterized in that the oil flow passes through channels of the stator (16) before reaching the rotor (12) via the rotating seal (18).

10. Electric or hybrid motor vehicle equipped with an electric traction powertrain (2), characterized in that this powertrain The power unit comprises an oil reserve (4) which is arranged at a lower level than the rotor axis (12) of this machine (2).

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