ELECTRIC POWERTRAIN FOR AUTOMOTIVE TRACTION WITH ASSEMBLED CRANKCASE

Abstract

Electric traction powertrain of a motor vehicle comprising an electric machine and a speed reducer including motion transmission shafts (14, 22, 52), arranged in a housing system, and comprising at least two housings (2) which are joined by a parting line (P1) passing through a first axis (A1) of the electric machine, and through at least one axis (A2) of another parallel transmission shaft (22). Figure 1

Description

Title of the invention: ELECTRIC MOTOR VEHICLE TRACTION POWERTRAIN WITH ASSEMBLED HOUSINGS

[0001] The present invention relates to an electric traction powertrain for a motor vehicle comprising assembled housings, as well as a method for assembling this powertrain and a motor vehicle equipped with such a powertrain.

[0002] A type of electric machine known for use in motor vehicle powertrains, notably described in document FR-A1-3135364, comprises a main housing with a generally cylindrical recess closed on one rear axial side, which houses the electric machine, and then, on the front face of this housing, a cover clamping a sealing ring. This type of design imposes specific constraints on the design and manufacture of the housing components, as well as on the assembly of the whole.

[0003] In particular, for the main housing obtained by injection molding of an aluminum alloy, its recess receiving the machine's stator must have a slightly conical shape that provides a draft angle to the core of the mold forming this recess, to allow the mold to open along the axial direction of the rotor. The shapes of the main housing, especially the external ribs, must be oriented along the opening direction of the two mold halves if additional slots in the mold that would provide other opening directions are to be avoided, thus limiting the design possibilities of this housing.

[0004] General architectural constraints are obtained for the elements of the casing which in some cases do not allow their shapes to be optimized to achieve better compactness, a reduction in mass and significant integration of components into the powertrain.

[0005] In addition, the two support bearings of the electric machine rotor are held in two different elements, the main casing and the cover, which leads to dispersions in the alignment of the housings of these bearings because of the machining and assembly tolerances of the complementary centering shapes of the two elements.

[0006] Moreover, this type of design requires a method of assembling the electrical machine in the casing comprising successively the axial insertion of the stator and rotor, the sealing ring and then the cover, with few possibilities for pre-equipping each casing element to create sub-assemblies including a maximum number of components to facilitate the final assembly of the powertrain.

[0007] In particular, the speed reducer, which includes a differential for distributing motion on the vehicle's wheel shafts, cannot be integrated into the electric machine's housing. Independent sub-assemblies, each with its own housing, must be produced, thus multiplying the total number of housing components and the required seals between them.

[0008] The present invention is specifically intended to avoid these problems of the prior art.

[0009] To this end, it proposes an electric traction powertrain for a vehicle automobile comprising an electric machine and a speed reducer including motion transmission shafts, arranged in a casing system, this group being remarkable in that it comprises at least two casings which are joined by a joint plane passing through a first axis of the electric machine, and by at least a second axis of another transmission shaft which is parallel.

[0010] An advantage of this powertrain is that by arranging the axis of the electric machine and another axis in the parting plane, the shapes of the two housings can be designed with surfaces perpendicular to the parting plane, allowing the opening of parts of the mold in this direction, in particular thin reinforcing ribs, or housings for complementary components on the external surfaces of this group.

[0011] Furthermore, the two bearings of each shaft can have, for each housing, housings machined directly into the same piece, without intermediate connections between these housings, which ensures their alignment with greater precision. This reduces the stresses that can be applied to these bearings, thereby decreasing losses due to internal friction.

[0012] Furthermore, a sub-assembly can be prepared in a housing comprising the elements arranged along the axes of the joint plane, in particular the stator and the rotor of the electric machine, the first shaft aligned on this rotor and at least one other complete transmission shaft, which are only placed in their respective housing before closing by the second housing.

[0013] The powertrain according to the invention may further comprise one or more of the following characteristics, which may be combined with each other.

[0014] Advantageously, the same housing has two housings which position two bearings of the same shaft.

[0015] In this case, the housing may include flanges fixing each bearing of a shaft onto the same housing.

[0016] Advantageously, the housings are made by injection molding in molds comprising an opening of the mold parts in a direction perpendicular to the parting planes.

[0017] Advantageously, the housings have ribs having an orientation that is perpendicular to the joint planes.

[0018] According to one embodiment, the shaft comprising the second axis is the shaft of an output differential of the transmission movement.

[0019] In this case, advantageously the group includes a second joint plane parallel to the first joint plane receiving a lower housing of the powertrain group, passing through a third axis of a shaft which is intermediate between a first shaft fixed at the end of the electric machine and a ring of the differential shaft.

[0020] Advantageously, each joint plane has a closed sealing contour that surrounds all the components placed in that plane.

[0021] The invention also relates to a method of assembling a powertrain comprising any one of the preceding characteristics, remarkable in that it involves removing all rotating components with positions in the same joint plane onto a housing, and then removing another housing closing this joint plane.

[0022] The invention further relates to a motor vehicle equipped with an electric traction powertrain comprising any one of the preceding characteristics, remarkable in that this powertrain has axes which are arranged transversely in the vehicle.

[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] presents in perspective the lower casing of a powertrain according to the invention receiving part of the equipment;

[0025] [Fig.2] shows a top view of this lower casing;

[0026] [Fig.3] shows the two lower and upper housings assembled; and

[0027] [Fig.4] shows in side view the three housings of this powertrain which are separated.

[0028] Throughout the document, the upper or top direction is relative to a powertrain mounted in a vehicle placed on a horizontal surface, and the transverse direction is perpendicular to the longitudinal axis of the vehicle.

[0029] Figures 1, 2, 3 and 4 show a powertrain comprising a housing system including a main housing 2 assembled above with an upper housing 4 along a first parting line PI passing through a first axis Al of a machine electrical and a second axis A2 of a differential shaft 22, and below with a lower casing 50 following a second joint plane P2 parallel to the first joint plane, passing through the axis A3 of an intermediate shaft 52.

[0030] The main housing 2 has on its top a machine recess 8 receiving the electric machine 10 comprising the stator aligned along the first axis Al, which is positioned and clamped in this recess. Along the axial direction, each side of this machine recess 8 has a bearing housing 12 forming a semicircle, which receives a bearing for the rotor shaft 6.

[0031] By convention the side of the rotor transmitting the movement is called the front axial side AV.

[0032] A primary shaft 14 connected to the end of the rotor shaft 8 supports a first pinion 32 which is framed by two bearings 18 positioned and clamped each in a bearing housing 12 of the main housing 2 forming a semicircle.

[0033] Each primary shaft bearing 18 is held in its housing 12 by a flange 16 forming a semicircle complementary to this housing, covering the bearing, which has at each end a hole receiving a clamping screw perpendicular to the first joint plane PI. In this way, each primary shaft bearing 18 is positioned and fixed solely on the main housing 2, with machining carried out on the same part, thus allowing for high alignment accuracy of these bearings.

[0034] The main housing 2 has a recess for the differential with its ring gear 22 aligned along a second axis A2, comprising on each side a semicircular recess for a differential bearing 24, which also allows for precise positioning of the differential. The main housing 2 has, at the rear of the differential, a recess for receiving the end of a wheel shaft 26, and at the front, a recess for a pivot joint 28 located at the end of the other wheel shaft.

[0035] The upper housing 4 has bosses that surround the components deposited in the main housing 2, including an electrical machine boss 40, a primary shaft boss 42 and a differential boss 44, so as to cover these components as closely as possible in order to limit wasted space, materials used and total mass.

[0036] The outer face of the upper casing 4 has in the same molding mounting tabs 46 having axial holes for fixing the powertrain in the vehicle.

[0037] The second joint plane P2 connecting the lower casing 50 to the main casing 2 passes through the third axis A3 of an intermediate shaft 52 having a pinion in contact with the first pinion 32 of the primary shaft 14, and a second pinion in contact with the differential ring 22 to achieve a speed reduction.

[0038] The lower casing 50 includes a lower reservoir 54 forming an oil reservoir which is collected below the various gears to limit the hydrodynamic braking of the moving parts.

[0039] For each joint plane PI, P2, all the component housings located in the casings 2, 4, 50, in particular the electric motor 10 and the shafts, are surrounded by a closed sealing contour 34 formed in the two casings of this joint plane, which receives a seal between them. In this way, the internal volume of the powertrain containing a lubricating and cooling oil is sealed.

[0040] The main housing 2 has ribs 30 surrounding the sealing contour 34, which are arranged perpendicular to this plane, allowing for a shell molding between two main parts of a mold that opens along this perpendicular direction. The arrangement and thickness of the ribs 30 arranged along this orientation are not limited by the molding; in particular, thin ribs with a reduced mass can be provided.

[0041] Screws perpendicular to the joint plane PI, clamping together the two housings 2, 4, are arranged in particular near the bearings 18, 24 to lock them and to reinforce the housings at these locations subjected to mechanical stresses, and around the sealing contour 34 to ensure this sealing.

[0042] Furthermore, the external faces of the housings 2, 4, 50 can receive any shape produced during the molding, in particular respecting the direction of opening of the molds to avoid additional cores, in order to receive components fixed to the outside of the powertrain.

[0043] Figure 4 shows, as an alternative, a second possible formation of the parting planes of the housings 2, 5, 50 of the powertrain, comprising a third plane P3 passing through the first axis Al of the electric machine 10 and the third axis A3 of the intermediate shaft 52, and a fourth parallel plane P4 passing through the second axis A2 of the differential 22. A third possible formation of the parting planes comprises a fifth plane P5 passing through the third axis A3 of the intermediate shaft 52 and the second axis A2 of the differential 22, and a sixth parallel plane P6 passing through the first axis Al of the electric machine 10.

[0044] Several housing design possibilities are obtained which must be taken into account in order to obtain a simplification of the parts produced, an optimization of the rigidity of the housings, a good alignment accuracy of the shafts, a better integration of the components, an improvement in mass and volume, and a reduction in costs.

[0045] It should be noted that electric traction powertrains generate more bothersome noise than those equipped with a combustion engine, which largely masks transmission noise, thus requiring particular attention to be paid to them. on the alignment of the shafts and the rigidity of the housings in order to limit noise emissions, particularly from the gears.

[0046] The design of the powertrain housings 2, 4, 50 allows for the easy assembly of a large number of components within the housings before they are closed. In particular, the main housing 2 receives, as shown in the figures, the electric machine 10, the primary shaft 14, and the differential 22 with their bearings, which are simply placed on top of it to form a sub-assembly that then receives the upper housing 4. Similarly, the main housing 2 or the lower housing 50 can receive the intermediate shaft 52 before their assembly.

[0047] It should be noted that this type of assembly is done by simply placing it on a superior surface, without having to perform axial sliding of sub-assemblies including bearing fittings in housings which are necessary for powertrains according to the prior art.

Claims

Demands

1. Motor vehicle electric traction powertrain comprising an electric machine (10) and a speed reducer including motion transmission shafts (14, 22, 52), arranged in a housing system, characterized in that it comprises at least two housings (2, 4, 50) which are assembled by a parting plane (PI, P2) passing through a first axis (Al) of the electric machine (10), and by at least one axis (A2, A3) of another transmission shaft (22, 52) which is parallel.

2. Powertrain according to claim 1, characterized in that the same casing (2, 4, 50) has two housings (12) which position two bearings (18, 24) of the same shaft (14, 22, 52).

3. Powertrain according to claim 2, characterized in that it comprises flanges (16) fixing each bearing (18) of a shaft (14) on the same housing (2).

4. Powertrain according to any one of the preceding claims, characterized in that the crankcases (2, 4, 50) are made by shell injection in molds comprising an opening of the mold parts along a direction perpendicular to the parting planes (PI, P2).

5. Powertrain according to any one of the preceding claims, characterized in that the casings (2, 4, 50) have ribs (30) having an orientation that is perpendicular to the joint planes (PI, P2).

6. Powertrain according to any one of the preceding claims, characterized in that the shaft comprising the second axis (A2) is the shaft of a differential (22) output of the transmission motion.

7. Powertrain according to claim 6, characterized in that it comprises a second joint plane (P2) parallel to the first joint plane (PI) receiving a lower housing of the powertrain (50), passing through a third axis (A3) of a shaft (52) which is intermediate between a first shaft (14) fixed at the end of the electric machine (10) and a ring of the differential shaft (22).

8. Powertrain according to any one of the preceding claims, characterized in that each joint plane (PI, P2) includes a closed sealing contour (34) which surrounds all the components placed in this plane (PI, P2).

9. Method of assembling a powertrain according to any one of the preceding claims, characterized in that it comprises removing onto a housing (2, 4, 50) all the rotating components having positions in the same joint plane (PI, P2), then removing another housing (2, 4, 50) closing this joint plane.

10. Motor vehicle equipped with an electric traction powertrain according to any one of claims 1 to 8, characterized in that this powertrain has axes (A1, A2, A3) which are arranged transversely in the vehicle.

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