System for transmitting a driving torque

Abstract

The invention relates to a system for transmitting a driving torque, comprising a rotor (1) driven in rotation with respect to a stator (2) housed in a casing (3) by way of a rear bearing (4) and a front bearing (5), each of the bearings having an internal member (4i, 5i) mounted on the rotor (1) and an external member (4e, 5e) secured to the casing (3), the rotor having a torque transmission mechanism (6) which is arranged at the front of the front bearing (5), the members (5i, 5e) of the front bearing (5) each having two runway tracks forming two raceways in which is respectively arranged a row of spherical rolling bodies (14), the rows of rolling bodies (14) being in angular contact with the raceways in an X setup.

Description

[0001] ENGINE TORQUE TRANSMISSION SYSTEM

[0002] The invention relates to a system for transmitting an engine torque comprising a rotor driven in rotation relative to a stator housed in a casing.

[0003] The invention relates in particular to an electrical machine of the motor and / or generator type in which the casing integrates means of electromagnetic coupling with the rotor so as to transform electrical energy into mechanical energy transmitted by said rotor and / or such mechanical energy into electrical energy.

[0004] It applies in particular to such machines for the propulsion of a motor vehicle with an electric motor, in which the rotor comprises a mechanism for transmitting a motor torque to the wheels, said mechanism also making it possible to transmit a motor torque from said wheels to generate an electric current for recharging a battery.

[0005] Conventionally, the rotor is rotatably mounted in the casing by means of a rear bearing and a front bearing which are axially spaced between said rotor and said casing, each of said bearings having an inner member mounted on the rotor and an outer member secured to the casing.

[0006] In addition to their function of guiding the rotation of the rotor, the bearings must maintain the rotor axially and radially in the casing in order to guarantee optimal transmission of the engine torque, as well as the reliability of the cooperation between the rotor and the stator.

[0007] To satisfy these constraints, the use of bearings is known, the members of which each have a rolling track forming between said members a raceway in which is arranged a row of spherical rolling bodies which are mounted in radial contact in said raceway to allow rotation of the inner member relative to the outer member around the axis of the rotor.

[0008] This type of bearing has a radial clearance between the components which is necessary to be able to absorb the dimensional variations of its mounting at the interface between the rotor and the casing, said clearance also making it possible to reduce the drag torque of the bearing and therefore the energy dissipated by its rotation.

[0009] However, the oscillation of this type of bearing induces axial play between the components, which goes against the axial stability of the rotor when it transmits engine torque.

[0010] In particular, since the front bearing is arranged on the side of the torque transmission mechanism, the latter absorbs high mechanical stresses, in particular axial forces, which can induce significant movements, in particular axial, of the rotor in the casing.

[0011] The absorption of such axial forces could be achieved by increasing the contact angles of the rolling bodies in the raceway. However, this solution requires an increase in the radial clearance between the components, which is detrimental to the efficiency of the transmission system.

[0012] The invention aims to improve the prior art by proposing in particular a system for transmitting an engine torque in which the bearings ensure an optimal compromise between their functions of guiding and holding the rotor in the casing, and this 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.

[0013] To this end, the invention proposes a system for transmitting an engine torque comprising a rotor driven in rotation relative to a stator housed in a casing, said rotor being mounted in rotation in the casing by means of a rear bearing and a front bearing which are axially spaced between said rotor and said casing, each of said bearings having an inner member mounted on the rotor and an outer member secured to the casing, said rotor having a torque transmission mechanism which is arranged in front of the front bearing, the members of the front bearing each having two raceways which are axially spaced so as to form between said members two raceways in which is respectively arranged a row of spherical rolling bodies to allow rotation of the inner member relative to the outer member around the axis of the rotor,the rows of rolling bodies being in oblique contact in the raceways following an X-shaped assembly.,

[0014] Other objects and advantages of the invention will appear in the following description, made with reference to the appended figures, in which:

[0015] - figures 1a, 1b and 1c represent a transmission system according to an embodiment of the invention, respectively partially in perspective (figure 1a), in longitudinal half-section (figure 1b) and in enlargement of figure 1b (figure 1c);

[0016] - figure 2 is a view similar to figure 1c showing an alternative embodiment;

[0017] - Figure 3 is a view similar to Figure 1c showing another embodiment of the invention, Figure 3a being an enlargement of Figure 3.

[0018] In connection with these figures, a system for transmitting engine torque is described below, for example in the form of an electric machine of the motor and / or generator type which can be used for the propulsion of a motor vehicle with an electric motor.

[0019] The transmission system comprises a rotor 1 driven in rotation about an axis A relative to a stator 2 housed in a casing 3 integrating means for electromagnetic coupling with said rotor so as to transform electrical energy into mechanical energy transmitted by said rotor and / or such mechanical energy into electrical energy. The rotor 1 is mounted in rotation in the casing 3 by means of a rear bearing 4 and a front bearing 5 which are axially spaced between said rotor and said casing, in particular by each being arranged in an interface formed between a rear wall - respectively front - of the casing 3 and a rear portion - respectively front - of the rotor 1.

[0020] In the description, the terms "front" and "rear" are defined in relation to the direction of use of the system for a location respectively on the left and on the right, in particular in figure 1 b. The terms "outside" and "inside" are defined in relation to the axis A of rotation of the rotor 1, respectively for a location far and close to said axis.

[0021] The rotor 1 has a torque transmission mechanism 6 which is arranged in front of the front bearing 5. In relation to Figure 1a, the torque transmission mechanism 6 comprises at least one gear 6a which is mounted around the rotor 1 in front of the front bearing 5.

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

[0023] Each of the bearings 4, 5 has an inner member 4i, 5i mounted on the rotor 1 and an outer member 4e, 5e secured to the casing 3. In particular, the inner members 4i, 5i each have a bore, the rotor 1 having a front bearing surface 7a - respectively rear 7b - on which a complementary bearing surface 9a, 9b of said bore is radially shrunk.

[0024] In the figures, the bearing surfaces 7a, 7b extend axially and have a shoulder 8a, 8b on which the inner member 4i, 5i comes into axial abutment at the end of shrinking. In the embodiment of figures 1 and 2, the system comprises a nut 10 mounted at the front of the front bearing 5, said nut being tightened on the front inner member 5i to retain it axially on the front bearing surface 7a, in particular in axial abutment on the shoulder 8a. In particular, the nut 10 is interposed between the front bearing 5 and the transmission mechanism 6.

[0025] In Figure 3, the front bearing surface 7a is bordered by a front groove 11 in which a ring 30 is arranged, said ring being in axial interference with the front inner member 5i to retain it axially on the front bearing surface 7a.

[0026] The members 5i, 5e of the front bearing 5 each have two rolling tracks 12i, 13i, 12e, 13e which are axially spaced so as to form between said members two rolling tracks in which a row of rolling bodies 14 is respectively arranged to allow the rotation of the inner member 5i relative to the outer member 5e around the axis A of the rotor 1.

[0027] In particular, the rolling bodies 14 are spherical insofar as this configuration has a lower rotational torque than a solution for absorbing axial forces with conical rolling bodies.

[0028] In particular, the raceways have substantially the same diameter, the same number of rolling bodies 14 being provided for each row, in particular by holding said rolling bodies in their row by means of a retention cage.

[0029] The rows of rolling bodies 14 are in oblique contact in the raceways according to an X-shaped arrangement, that is to say that the load lines La, Lb which connect the contact surfaces between the rolling bodies 14 of a row and the tracks 12i, 13i; 12e, 13e intersect according to an X. In particular, an X-shaped arrangement is distinguished from an O-shaped arrangement, as for example presented in the Wikipedia page generally presenting the technical field of mechanical bearings: https: / / fr.wikipedia.orq / wiki / Roulement m%C3%A9canique#Roule ment %C3%A0 rouleaus coniques. These two rows of rolling bodies 14 make it possible, in particular in the front bearing 5 which is the most mechanically stressed, to be able to finely adjust the axial and radial clearance between the members 5i, 5e, the X-shaped arrangement making it possible to limit the possibilities of relative axial displacement of said members.

[0030] In relation to the figures, the outer member 5e of the front bearing 5 is formed from a single piece on which the two raceways 12e, 13e are formed, said raceways being connected by a central zone 15 formed on the piece. In particular, the central zone 15 extends axially between the raceways 12e, 13e.

[0031] The inner member 5i of the front bearing 5 is formed from a single piece on which the two bearing tracks 12i, 13i are formed, said bearing tracks being separated by a collar 16 formed in radial projection on the piece.

[0032] Advantageously, the members 4i, 4e of the rear bearing 4 each have a rolling track 1Zi, 17e forming between said members a rolling path in which a row of rolling bodies 18 is arranged to allow the rotation of the inner member 4i relative to the outer member 4e around the axis A of the rotor 1.

[0033] In particular, the rolling bodies 18 of the rear bearing 4 can be spherical while being mounted in radial contact in the raceway, insofar as the oscillation of such a bearing can be increased without impact on the axial play.

[0034] According to one embodiment, an axial preload elastic washer can be used on the outer member 4e to induce a contact angle due to the presence of radial play in the rear bearing 4.

[0035] Advantageously, the use of an X-shaped assembly in the front bearing 5 makes it possible to produce a complementary bearing surface 9a having a central recess 19 forming on either side a fretted section on the front bearing surface 7a of the rotor 1.

[0036] Thus, the impact of the radial stress of the hooping on the diameter of the bearing races can be reduced, which makes it possible to limit the load and therefore the drag torque of the front bearing 5.

[0037] Likewise, the use of an X-shaped assembly makes it possible to envisage a front bearing 5 equipped with at least one sealing device comprising an element 20 which is fixed to the outer member 5e to rub against the inner member 5i and / or against the rotor 1.

[0038] In particular, this embodiment makes it possible to reduce the friction diameter of the sealing element 20, and therefore to limit the drag torque of the front bearing 5.

[0039] In relation to Figure 3a, each of the sides of the front bearing 5 is equipped with an element 20 having one end fixed in a groove bordering a raceway 12e, 13e of the outer member 5e, and a free lip rubbing in a groove bordering the raceway 12i, 13i of the inner member 5i. Alternatively, the lip can be positioned close to the inner member 5i to form a chicane.

[0040] In particular, the sealing elements 20 make it possible to limit leaks of lubricant present in the raceways, as well as the contamination of said raceways with external pollutants.

[0041] According to an embodiment shown in Figures 1 and 2, the front external member 5e has a flange 21 extending radially outside said member, said flange being associated with the casing 3.

[0042] This embodiment makes it possible in particular to limit the variations in the diameter of the bottom of the track 12th, 13th which could be induced by a thermal gradient between the casing 3 and the external member 5th which could increase the drag torque of the front bearing 5 and / or limit the axial strength of the rotor 1.

[0043] In the embodiment shown, the flange 21 has a rear face 21a which is axially supported on a front wall 3a of the casing 3, said flange and said casing being equipped with means for clamping said face on said wall, in particular in the form of screws 22 passing through said flange to be fixed in said front wall.

[0044] Thus, the radial stiffness of the front outer member 5th is increased, which limits the impact on the bottom diameter of the tracks 12th, 13th of its shrinkage in the casing 3, and therefore the drag torque of the front bearing 5 and / or the axial strength of the rotor 1.

[0045] In relation to figures 1a-1c, the casing 3 has a front bearing surface 3b on which the front outer member 5e is radially shrunk by means of a complementary bearing surface 23. In particular, the flange 21 extends around the front outer member 5e, delimiting a rear complementary bearing surface 23a which is radially shrunk into the front bearing surface 3b, placing the bearing surface 21a of the flange 21 in axial abutment on the front wall 3a of the casing 3.

[0046] In the variant shown in Figure 2, the rear complementary bearing surface 23a is arranged at a radial distance from the front bearing surface 3b, the centering of the front bearing 5 being achieved by means of a flange 21 having a peripheral bearing surface 21b which is radially shrunk onto a complementary bearing surface 3c of the casing 3, by placing the bearing surface 21a of the flange 21 in axial abutment on the front wall 3a of the casing 3.

[0047] According to the embodiment of Figure 3, the front bearing surface 3b is bordered by a front groove 24 in which a ring 25 is arranged, said ring being in axial interference with the front outer member 5e to retain it axially on the front bearing surface 3b. Furthermore, the front bearing surface 3b is bordered by a rear shoulder 26 on which the outer member 5e is in axial abutment.

Claims

DEMANDS 1. A motor torque transmission system comprising a rotor (1) driven in rotation relative to a stator (2) housed in a casing (3), said rotor being mounted in rotation in the casing (3) by means of a rear bearing (4) and a front bearing (5) which are axially spaced between said rotor and said casing, each of said bearings having an inner element (4i, 5i) mounted on the rotor (1) and an outer element (4e, 5e) integral with the casing (3), said rotor having a torque transmission mechanism (6) which is disposed in front of the front bearing (5), said system being characterized in that the elements (5i, 5e) of the front bearing (5) each have two bearing tracks (12i, 13i;12e, 13e) which are axially spaced so as to form between said organs two rolling paths in which is respectively arranged a row of spherical rolling bodies (14) to allow the rotation of the inner organ (5i) relative to the outer organ (5e) around the axis (A) of the rotor (1), the rows of rolling bodies (14) being in oblique contact in the rolling paths according to an X-shaped arrangement.; 2. Transmission system according to claim 1, characterized in that the outer element (5e) of the front bearing (5) is formed of a single piece on which the two bearing tracks (12e, 13e) are formed.

3. Transmission system according to claim 2, characterized in that the two bearing tracks (12e, 13e) are connected by a central area (15) formed on the part.

4. Transmission system according to any one of claims 1 to 3, characterized in that the inner element (5i) of the front bearing (5) is formed of a single piece on which the two raceways (12i, 13i) are formed.

5. Transmission system according to claim 4, characterized in that the two bearing tracks (12i, 13i) are separated by a collar (16) formed in radial projection on the part.

6. Transmission system according to any one of claims 1 to 5, characterized in that the elements (4i, 4e) of the rear bearing (4) each have a rolling track (1 Zi, 17e) forming between said elements a rolling track in which is arranged a row of rolling bodies (18) to allow the rotation of the inner element (4i) relative to the outer element (4e) around the axis (A) of the rotor (1), said rolling bodies being spherical by being mounted in radial contact in the rolling track.

7. Transmission system according to any one of claims 1 to 6, characterized in that the rotor (1) has a front bearing surface (7a) on which the front inner member (5i) is radially shrunk via a complementary bearing surface (9a).

8. Transmission system according to claim 7, characterized in that the complementary bearing (9a) has a central recess (19) forming on either side a section pressed onto the front bearing (7a) of the rotor (1).

9. 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 the front outer member (5e) is radially clamped by means of a complementary bearing surface (23).

10. Transmission system according to claim 9, characterized in that the front bearing (3b) is bordered by a front groove (24) in which a ring (25) is disposed, said ring being in axial interference with the front external member (5e) to retain it axially on the front bearing (3b).

11. A transmission system according to any one of claims 1 to 8, characterized in that the front external member (5e) has a flange (21) extending radially outward from said member, said flange being associated with the housing (3) by having a rear face (21a) which bears axially against a wall before (3a) of the housing (3), said flange and said housing being equipped with means for clamping said face on said wall.

12. Transmission system according to claim 11, characterized in that the flange (21) has a peripheral bearing surface (21b) which is radially shrink-fitted onto a complementary bearing surface (3c) of the housing (3).

13. Transmission system according to claim 11, characterized in that the flange (21) delimits a complementary rear bearing surface (23a) on the front outer member (5e), ​​said bearing surface being radially shrunk into a front bearing surface (3b) of the housing (3).

14. 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 comprising an element (20) which is fixed to the outer member (5e) to rub against the inner member (5i) and / or against the rotor (1).

15. 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 around the rotor (1) in front of the front bearing (5), in particular a helical gear.

Images