Drive Torque Transmission System

Abstract

The present disclosure relates to a drive torque transmission system comprising a rotor (1) which is driven in rotation relative to a stator (2) housed in a casing (3) via a rear bearing (4) and a front bearing (5), each of said bearings having an inner member (4i, 5i) attached to the rotor (1) and an outer member (4e, 5e) fixed to the casing (3), said rotor having a torque transmission mechanism (6) arranged forward of the front bearing (5), the members (5i, 5e) of the front bearing (5) having two running raceways each forming two raceways in which rows of spherical rolling elements (14) are arranged, the rows of rolling elements (14) being in angular contact within the raceways in an X arrangement.

Description

Detailed Description of the Invention

[0001] The present disclosure relates to a system for transmitting a driving torque, comprising a rotor rotatably driven relative to a stator housed within a casing.

[0002] The present disclosure relates in particular to electric machines of motor and / or generator type incorporating means for electromagnetic coupling with a rotor, the casing being adapted to convert electrical energy into mechanical energy transmitted by said rotor and / or to convert such mechanical energy into electrical energy.

[0003] It applies in particular to such machines for the propulsion of vehicles equipped with an electric motor, the rotor of which comprises a mechanism for transmitting a drive torque to the wheels, said mechanism also capable of transmitting the drive torque from said wheels and generating an electric current for charging the battery.

[0004] Conventionally, a rotor is rotatably mounted within a casing by means of rear and front bearings spaced axially between the rotor and the casing, each bearing having an inner member attached to the rotor and an outer member fixed to the casing.

[0005] In addition to guiding the rotation of the rotor, the bearings must retain the rotor axially and radially within the casing to ensure optimum transmission of torque and reliable interlocking between the rotor and stator.

[0006] To meet these constraints, it is known to use bearings, each having a running track forming a raceway between said members, in which a row of spherical rolling elements are arranged in radial contact to enable rotation of the inner member relative to the outer member about the rotor axis.

[0007] This type of bearing has the radial clearance between the parts necessary to accommodate the dimensional changes of the mounting at the interface between the rotor and the casing, which clearance also makes it possible to reduce the drag torque of the bearing and therefore the energy dissipated by the rotation of the bearing.

[0008] However, this type of bearing wobble induces axial clearances between the members and is detrimental to the axial stability of the rotor when transmitting drive torque.

[0009] In particular, the front bearing is located on the side of the torque transmission mechanism and is therefore subjected to high mechanical stresses, in particular axial stresses, which can lead to large displacements, in particular axial displacements, of the rotor within the casing.

[0010] Such axial forces can be absorbed by increasing the contact angle of the rolling elements in the raceways, but this solution requires large radial clearances between the components, which negatively impacts the efficiency of the transmission system.

[0011] The aim of the present disclosure is in particular to improve upon the prior art by proposing a system for transmitting driving torque, which offers an optimal compromise between the functions of the bearings to guide and retain the rotor in the casing, in particular with regard to the axial stability of the rotor and the limitation of the drag torque induced by the rotation of the bearings.

[0012] To this end, the present disclosure proposes a system for transmitting a driving torque comprising a rotor driven in rotation relative to a stator housed in a casing, said rotor being rotatably mounted in the casing by rear and front bearings, the rear and front bearings being axially spaced between the rotor and the casing, each of the bearings having an inner member attached to the rotor and an outer member fixed to the casing, the rotor having a torque transmission mechanism arranged in front of the front bearing, the front bearing members each having two running tracks (12i, 13i, 12e, 13e) spaced axially such that two tracks are formed between the members, and each arranged with a row of spherical rolling elements enabling the rotation of the inner member relative to the outer member about the rotor axis, the rows of rolling elements being in angular contact in the tracks in an X arrangement.

[0013] Further objects and advantages of the present disclosure will become apparent from the following description taken in conjunction with the accompanying drawings.

[0014] 1a, 1b and 1c show a transmission system according to one embodiment of the present disclosure, respectively showing a partially projected view (FIG. 1a), a longitudinal cross-sectional view (FIG. 1b) and an enlarged view (FIG. 1c) of FIG. 1b.

[0015] FIG. 2 is a view similar to FIG. 1c showing a variant.

[0016] FIG. 3 is a view similar to FIG. 1c showing another embodiment of the present disclosure, with FIG. 3a being an enlarged view of FIG.

[0017] In connection with these figures, a system for transmitting a drive torque is described below in the form of an electric machine, for example of the motor and / or generator type, which can be used to propel an electrically powered vehicle.

[0018] The transmission system consists of a rotor 1 and a stator 2. The rotor 1 is driven in rotation about an axis A and the stator 2 is housed in a casing 3 associated with the axis A and incorporating means for electromagnetically coupling with said rotor, for converting electrical energy into mechanical energy transmitted by the rotor and / or for converting such mechanical energy into electrical energy.

[0019] The rotor 1 is rotatably mounted within the casing 3 by means of a rear bearing 4 and a front bearing 5 which are axially spaced apart between the rotor and the casing, and in particular each is located at the interface formed between the rear wall (respectively the front wall) of the casing 3 and the rear part (respectively the front wall) of the rotor 1.

[0020] In this specification, the terms "forward" and "aft" are defined relative to the orientation of use of the system, which is respectively to the left and right, particularly in Fig. 1b. The terms "outer" and "inner" are defined relative to the axis of rotation A of the rotor 1, and are defined relative to positions away from and closer to said axis, respectively.

[0021] The rotor 1 has a torque transmission mechanism 6 located forward of the front bearing 5. Referring to Figure 1a, the torque transmission mechanism 6 comprises at least one gear 6a mounted on the periphery of the rotor 1 forward of the front bearing 5.

[0022] In particular, the gear 6a may be of the helical type which meshes with a complementary gear of the driven element, the cooperation of said gears producing in particular axial force variations on the rotor 1 during the transmission of the driving torque.

[0023] Each bearing 4, 5 has an inner member 4i, 5i attached to the rotor 1 and an outer member 4e, 5e fixed to the casing 3. In particular, the inner members 4i, 5i each have a bore and the rotor 1 has a front bearing surface 7a and a rear bearing surface 7b on which respectively the complementary bearing surfaces 9a, 9b of said bore are radially constricted.

[0024] In the figure, the bearing surfaces 7a, 7b extend axially and the inner members 4i, 5i have shoulders 8a, 8b which abut axially against the ends of the constrictions.

[0025] In the embodiment shown in Figures 1 and 2, the system comprises a nut 10 mounted in front of the front bearing 5, said nut being tightened on the front inner member 5i in order to hold the front inner member 5i axially biased against the front bearing surface 7a, in particular against the shoulder 8a. In particular, the nut 10 is interposed between the front bearing 5 and the transmission mechanism 6.

[0026] In FIG. 3, the front bearing surface 7a adjoins a front groove 11 in which a ring 30 is located, said ring being axially retained at the front bearing surface 7a in axial interference with the front inner member 5i.

[0027] The members 5i, 5e of the front bearing 5 each have two running tracks 12i, 13i, 12e, 13e, spaced axially apart to form two tracks between said members, in which rows of rolling elements 14 are arranged respectively, enabling rotation of the inner member 5i relative to the outer member 5e about the axis A of the rotor 1.

[0028] In particular, the rolling elements 14 are spherical, since this configuration results in a lower torque than axial force absorbing solutions with conical rolling elements.

[0029] In particular, the raceways have substantially the same diameter and the same number of rolling elements 14 are provided in each row, said rolling elements being retained in their row in particular by a retaining cage.

[0030] The rows of rolling elements 14 are in angular contact in the raceways in an X arrangement, i.e. the load lines La, Lb connecting the contact surfaces of the rolling elements 14 of a row with the raceways 12i, 13i; 12e, 13e cross in an X pattern. In particular, the X arrangement is distinct from the 0 arrangement, as presented for example in the Wikipedia page (https: / / fr.wikipedia.org / wiki / Roulement_m%C3%A9canique#Roulement_%C3%A0_rouleaux_coniques) providing an overview of the technical field of mechanical bearings.

[0031] These two rows of rolling elements 14 allow fine adjustment of the axial and radial clearance between the members 5i, 5e and are subject to the greatest mechanical stresses, especially in the front bearing (5), since the X arrangement limits the possible relative axial displacements of said members.

[0032] With reference to the figure, the outer member 5e of the front bearing 5 is made in one piece in which two running tracks 12e, 13e are formed, said running tracks being connected by a central area 15 formed in the piece. In particular, the central area 15 extends axially between the running tracks 12e, 13e.

[0033] The inner member 5i of the front bearing 5 is made from a single piece in which two running tracks 12i, 13i are formed, said running tracks being separated by a collar 16 formed as a radial projection on the piece.

[0034] Advantageously, the members 4i, 4e of the rear bearing 4 have running tracks 17i, 17e, respectively, in which are arranged rows of rolling bodies 18 enabling rotation of the inner member 4i relative to the outer member 4e around the axis A of the rotor 1.

[0035] In particular, the rolling elements 18 of the rear bearing 4 may be spherical and mounted in radical contact in the raceway, when the rocking motion of the bearings can be increased without affecting the axial clearance.

[0036] In one embodiment, an axial preload spring washer may be used on the outer member 4 e to induce a contact angle due to the presence of radial clearance in the rear bearing 4 .

[0037] Advantageously, the use of an X-configuration for the front bearing 5 makes it possible to form complementary bearing surfaces 9a having a central recess 19 forming a constriction on either side of the front bearing surface 7a of the rotor 1.

[0038] In this way, the effect of the radial stresses of the shrink fit on the raceway diameter can be reduced, thereby limiting the load on the front bearing 5 and therefore the drag torque.

[0039] Likewise, the use of an X arrangement makes it possible to envisage a front bearing 5 equipped with at least one sealing device fixed to the outer member 5e and equipped with an element 20 which rubs against the inner member 5i and / or the rotor 1.

[0040] In particular, in this embodiment, the friction diameter of the sealing element 20 is reduced, so that the reaction torque of the front bearing 5 is limited.

[0041] 3a, each side of the front bearing 5 is provided with an element 20 having one end fixed in a groove in the running tracks 12e, 13e of the outer member 5e and a free lip which rubs in a groove in the running tracks 12i, 13i of the inner member 5i. Alternatively, the lip can be located close to the inner member 5i to form a chicane.

[0042] In particular, the sealing element 20 limits the leakage of lubricating oil present in the raceways and limits the contamination of said raceways by external contaminants.

[0043] According to the embodiment shown in FIGS. 1 and 2, the front outer member 5 e has a flange 21 extending radially outwardly therefrom, said flange being associated with the casing 3 .

[0044] In particular, this embodiment makes it possible to limit the variations in the diameter of the bottom of the planing tracks 12e, 13e, which may be caused by thermal gradients between the casing 3 and the outer member 5e, which may increase the drag torque of the front bearing 5 and / or limit the axial strength of the rotor 1.

[0045] In the embodiment shown, the flange 21 has a rear face 21a axially facing the front wall 3a of the casing 3, said flange and said casing being provided with means for clamping said face to said front wall in the form of a screw 22 passing through said flange for fixing it to said front wall.

[0046] In this way, the radial stiffness of the front external member 5e is increased, limiting its influence on the bottom diameter of the shrink-fit raceways 12e, 13e in the casing 3, i.e. the drag torque of the front bearing 5 and / or the axial strength of the rotor 1.

[0047] 1a to 1c, the casing 3 has a forward bearing surface 3b onto which the forward external member 5e is radially compressed by a complementary bearing surface 23. In particular, the flange 21 extends around the periphery of the forward external member 5e and defines a complementary rear bearing surface 23a which is radially compressed against the forward bearing surface 3b, while at the same time bringing the bearing surface 21a of the flange 21 into substantial axial contact with the forward wall 3a of the casing 3.

[0048] Alternatively, as shown in FIG. 2, the complementary rear bearing surface 23a is spaced radially from the forward bearing surface 3b and the forward bearing 5 is centred by a flange 21 having a peripheral bearing surface 21b which is radially compressed onto the complementary bearing surface 3c of the casing 3, with the bearing surface 21a of the flange 21 generally coinciding axially on the forward wall 3a of the casing 3.

[0049] As shown in Figure 3, the front bearing surface 3b is axially supported on a front groove 24 in which a ring 25 is disposed, said ring being axially supported on the front bearing surface 3b by axial interference with the front outer member 5e. Furthermore, the front bearing surface 3b is adjacent a rear shoulder 26 against which the outer member 5e axially abuts. [Brief description of the drawings]

[0050] [Figure 1a] FIG. 2 is a perspective view of a delivery system according to an embodiment of the present disclosure. [Figure 1b] FIG. 1 is a longitudinal cross-sectional view of a transmission system according to an embodiment of the present disclosure. [Figure 1c] This is an enlarged view of FIG. [Diagram 2] FIG. 1c is a view similar to FIG. [Diagram 3] FIG. 1c is a view similar to FIG. 1c showing another embodiment of the present disclosure. [Figure 3a] FIG. 4 is an enlarged view of FIG.

Claims

1. A torque transmission system comprising a rotor (1) rotatably driven relative to a stator (2) housed in a casing (3), the rotor is rotatably mounted within the casing (3) by rear and front bearings (4, 5), the rear and front bearings (4, 5) being axially spaced apart between the rotor and the casing; Each of the bearings has an inner member (4i, 5i) attached to the rotor (1) and an outer member (4e, 5e) fixed to the casing (3), The rotor has a torque transmission mechanism (6) disposed in front of the front bearing (5), The system comprises: said members (5i, 5e) of said front bearing (5) each have two running tracks (12i, 13i, 12e, 13e) spaced apart in the axial direction to form two tracks between said members; a row of spherical rolling elements (14) arranged in each of the raceways, which enable the rotation of the inner member (5i) relative to the outer member (5e) about the axis (A) of the rotor (1); A torque transmission system, characterized in that the rows of rolling elements (14) are arranged in an X-arrangement and in angular contact within the raceways.

2. 2. A transmission system according to claim 1, characterized in that the outer member (5e) of the front bearing (5) is made in one piece, in which the two running tracks (12e, 13e) are formed.

3. 3. A transmission system according to claim 2, characterized in that the two running tracks (12e, 13e) are connected by a central area (15) formed in the piece.

4. 4. A transmission system according to claim 1, wherein the inner member (5i) of the front bearing (5) is made in one piece, in which the two running tracks (12i, 13i) are formed.

5. 5. A transmission system according to claim 4, characterized in that the two running tracks (12i, 13i) are separated by a collar (16) formed as a radial projection on the piece.

6. the members (4i, 4e) of the rear bearing (4) each have a running track (17i, 17e) forming a running line between them, on which a row of rolling elements (18) is arranged which allows the rotation of the inner member (4i) relative to the outer member (4e) about the axis (A) of the rotor (1); 6. A transmission system according to claim 1, wherein the rolling elements are spherical and are mounted in radial contact within the raceways.

7. 7. A transmission system according to claim 1, characterized in that the rotor (1) has a front bearing surface (7a) on which the front inner member (5i) is radially compressed via a complementary bearing surface (9a).

8. 8. A transmission system according to claim 7, characterized in that the complementary bearing surface (9a) has a central recess (19) on either side of which are formed constrictions in the front bearing surface (7a) of the rotor (1).

9. 9. A transmission system according to any one of claims 1 to 8, characterized in that the casing (3) has a front bearing surface (3b) on which a front external member (5e) is radially contracted via a complementary bearing surface (23).

10. said front bearing surface (3b) being adjacent to a front groove (24) in which a ring (25) is located; 10. A transmission system according to claim 9, characterized in that the ring is in axial interference with the front external member (5e) so as to be axially retained on the front bearing surface (3b).

11. The front outer member (5e) has a flange (21) extending radially outwardly therefrom; the flange is associated with the casing (3) by having a rear face (21a) which axially retains the front wall (3a) of the casing (3); 9. A transmission system according to any one of claims 1 to 8, characterized in that the flange and the casing are provided with means for clamping the rear face to the wall.

12. 12. Transmission system according to claim 11, characterized in that the flange (21) has a peripheral bearing surface (21b) and is radially constricted at a complementary bearing surface (3c) of the casing (3).

13. The flange (21) defines a rear complementary bearing surface (23a) on the front outer member (5e); 12. Transmission system according to claim 11, characterized in that the bearing surface is radially constricted into a front bearing surface (3b) of the casing (3).

14. 14. A transmission system according to any one of claims 1 to 13, characterized in that the front bearing (5) is equipped with at least one sealing device, which includes an element (20) fixed to the outer member (5e) for friction against the inner member (5i) and / or the rotor (1).

15. 15. A transmission system according to any one of claims 1 to 14, characterized in that the torque transmission mechanism (6) comprises at least one gear (6a), which is mounted on the periphery of the rotor (1) in front of the front bearing (5), and in particular comprises a helical gear.

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