FR3157498A1 - Arrangement for a geared motor comprising an element stiffening the rotor shaft of such a geared motor. - Google Patents

Abstract

Arrangement for a geared motor comprising an element stiffening the rotor shaft of such a geared motor. The invention relates to an arrangement (2) for a geared motor, comprising a housing (4), a shaft (10) arranged at least partially within the housing (4), a bearing (5) arranged between the housing (4) and the shaft (10), the bearing (5) at least partially supporting the shaft (10) in rotation, a rotor (6) of such a geared motor, the rotor (6) being fixed on the shaft (10) and extending within the housing (4), a space (E) extending around the shaft (10) between the bearing (5) and the rotor (6), the arrangement (2) comprising an element (20) fixed on the shaft (10) within the space (E) so as to stiffen the shaft (10), in particular in terms of bending. Figure for abstract: Figure 3

Description

Arrangement for a geared motor comprising an element stiffening the rotor shaft of such a geared motor. Technical field of the invention

The invention relates to an arrangement for a geared motor comprising an element stiffening the shaft supporting the rotor of the geared motor. The invention also relates to a geared motor comprising such an arrangement. The invention also relates to a vehicle, in particular a motor vehicle, comprising such a geared motor or such an arrangement.

State of the prior art

A vehicle with a hybrid or electric motor generally comprises a geared motor generating torque for traction and/or propulsion of such a vehicle. Such a geared motor generally comprises a shaft supporting a rotor. Such a shaft comprises an output pinion for transmitting such torque. Such a pinion is generally arranged at the end of the shaft, the shaft being held in rotation by two bearings relative to a housing. Such an output pinion generally has helical teeth.

Only such helical teeth generate a force that causes such a shaft to bend, particularly between the two bearings. Such shaft bending affects the quality of the meshing on the output pinion. This results in premature deterioration of the helical teeth. In addition, this wear affects the transmission efficiency and/or generates noise, which is prohibitive for a vehicle with an electric or hybrid engine.

This situation is not acceptable.

Presentation of the invention

The object of the invention is to provide an arrangement for a geared motor which overcomes the above drawbacks.

More specifically, an object of the invention is to provide a geared motor offering excellent efficiency and a long service life, while being silent.

To achieve this objective, the invention relates to an arrangement for a geared motor, in particular a geared motor for towing and/or propelling a vehicle, comprising:
- a casing,
- a shaft arranged at least partially within the casing,
- a bearing arranged between the housing and the shaft, the bearing at least partially supporting the rotating shaft,
- a rotor of such a geared motor, the rotor being fixed on the shaft and extending within the casing,
- a space extending around the shaft between the bearing and the rotor,
the arrangement comprising an element fixed to the shaft within the space so as to stiffen the shaft, in particular in terms of bending.

The element may be cylindrical or substantially cylindrical.

The member may include a first bore arranged adjacent the bearing and the shaft may include a first portion, the first bore of the member being able to contact the first portion of the shaft.

The first bore of the element can be shrunk onto the first portion of the shaft.

The first bore of the member may include internal splines and the first portion of the shaft may include external splines, the internal splines cooperating with the external splines.

The element may include a second bore arranged adjacent the rotor, the second bore being of larger diameter than the first bore,
and the shaft may comprise a second portion for mounting the rotor, in particular a second portion comprising external grooves parallel to the axis of the shaft, the second bore being able to be shrunk at least over a part of the axial length of the second portion.

The second portion of the shaft may include a truncated portion to facilitate mounting of the rotor.

The element may include radial extensions.

The invention also relates to a geared motor, in particular intended for towing and/or propelling a vehicle, comprising an arrangement as defined previously.

The invention also relates to a vehicle, in particular a motor vehicle, comprising an arrangement as defined previously, or a geared motor as defined previously.

Presentation of figures

These objects, characteristics and advantages of the present invention will be explained in detail in the following description of a particular embodiment made without limitation in relation to the attached figures among which:

There FIG. 1 is a schematic profile view of a motor vehicle according to one embodiment of the invention.

There FIG. 2 is a partial sectional view of a geared motor according to one embodiment of the invention, the sectional plane passing through the axis of the shaft of the geared motor.

There FIG. 3 is a detailed sectional view of the geared motor comprising a stiffening element for the shaft of the geared motor according to a first embodiment of the invention, the sectional plane passing through the axis of the shaft of the geared motor.

There FIG. 4 is a detailed sectional view of the geared motor comprising a stiffening element for the shaft of the geared motor according to a second embodiment of the invention, the sectional plane passing through the axis of the shaft of the geared motor.

There FIG. 5 is a perspective view of the stiffening element of the geared motor shaft according to one embodiment of the invention.

There FIG. 6 is a partial perspective view of the geared motor according to the embodiment of the invention, without a shaft stiffening element.

There FIG. 7 is another partial perspective view of the geared motor according to the embodiment of the invention, with the shaft stiffening element.

Detailed description

There FIG. 1 schematically illustrates a vehicle 1, preferably a motor vehicle. The vehicle 1 may be a private vehicle or a utility vehicle. Alternatively, it could be a truck, a bus, a lifting machine, an agricultural machine or even any other type of land vehicle, such as a two-wheeler. The vehicle 1 is advantageously hybrid or electric powered. The vehicle 1 comprises a geared motor 3. By geared motor, we mean in particular an electric machine powered by an electric current and capable of providing a torque intended to move the vehicle 1. The torque output from the geared motor 3 is preferably intended to drive at least one front wheel (traction) and/or at least one rear wheel (propulsion).

The vehicle 1, or the geared motor 3, comprises at least one arrangement 2.

As illustrated on the FIG. 2 , the arrangement 2 comprises a casing or housing 4. The arrangement 2 further comprises a shaft 10 arranged at least partially within the casing 4. Preferably, the shaft 10 passes through the casing 4, protruding on either side of the casing 4 as illustrated in the FIG. 2 . The arrangement 2 further comprises a bearing 5 arranged between the casing 4 and the shaft 10. The bearing 5 at least partially supports the shaft 10 in rotation. Advantageously, the casing 4 comprises another bearing 7 so as to place the shaft 10 in pivot connection with respect to the casing 4 while being held by the two bearings 5, 7. Preferably, the two bearings 5, 7 are arranged near the two ends of the shaft 10.

The arrangement 2 also comprises a rotor 6 for the geared motor 3. The rotor 6 is fixed on the shaft 10 and extends within the casing 4 between the two bearings 5, 7. Advantageously, the rotor 6 comprises stacks and the method of fixing the rotor 6 on the shaft 10 is hooping.

For example, at least one bearing, or even both bearings 5, 7, are ball, roller, or needle bearings so as to limit the friction linked to the rotation of the shaft 10.

The arrangement 2 further comprises a space E extending around the shaft 10. More precisely, the space E extends in the axial direction of the shaft 10 between the bearing 5 and the rotor 6, as illustrated in FIGS. 2, 3 and 4.

The arrangement 2 further comprises a stiffening element 20 fixed to the shaft 10 and extending in the space E. Advantageously, the installation of the element 20 on the shaft 10 only serves to stiffen the shaft 10, to increase the stiffness of the shaft, in particular to limit the bending of the shaft 10 due to the meshing of a drive pinion 8, preferably helical, arranged at the end of the shaft. Preferably, in particular for balancing purposes, the element 20 is cylindrical or substantially cylindrical.

According to a first embodiment, as illustrated in the FIG. 3 , the element 20 comprises a first bore 21 arranged so as to be found next to, close to the bearing 5 after assembly. The shaft 10 comprises a first cylindrical or substantially cylindrical portion 11. The first bore 21 of the element 20 comes into contact with the first portion 11 of the shaft 10. Preferably, the first bore 21 of the element 20 is shrunk, that is to say force-fitted, onto the first portion 11 of the shaft 10.

Advantageously again, as illustrated in Figures 3 and 5, the first bore 21 of the element 20 comprises internal splines 25. The first portion 11 of the shaft 10 then comprises external splines 15. Thus, the internal splines 25 formed in the first bore 21 of the element 20 cooperate with the external splines 15 formed at the level of the first cylindrical portion 11 of the shaft 10. Advantageously, the splines 15, 25 are associated with the hooping, complete the hooping, to ensure reliable and durable retention of the element 20 on the shaft 10.

The element 20 comprises a second bore 22 arranged so as to be located next to, in proximity to, the rotor 6 of the geared motor 3 after assembly. The second bore 22 preferably has a larger diameter than the diameter of the first bore 21. The shaft 10 comprises a second cylindrical portion 12 for mounting the rotor 6. Advantageously, as illustrated in FIGS. 6 and 7, the second portion 12 comprises external grooves 13 parallel to the axis A of the shaft 10. The second bore 22 is mounted by shrink-fitting on at least a portion L12 of the axial length of the second cylindrical or substantially cylindrical portion 12. Advantageously, the portion having an axial length L12 of the shaft 10 extends outside an internal volume V of the rotor 6, as illustrated in FIGS. FIG. 3 .

Optionally, the second portion 12 comprises a frustoconical portion 17, in particular extending over the axial length L12 of the shaft 10. Thus, the passage of the rotor over the start of this second portion 12 is facilitated before shrinking the rotor 6 further onto the shaft 10. Thus, the rotor is first inserted around the first portion 11 of the shaft 10 before being translated onto the frustoconical portion 17 if applicable, then onto the remainder of the second portion 12. In this case, the small diameter of the frustoconical portion 17 is on the side of the bearing 5 and the large diameter of the frustoconical portion 17 is on the side of the rotor 6. Preferably, the large diameter of the frustoconical portion 17 is equal, or substantially equal, to the diameter of a receiving part 16 of the rotor. As illustrated in the FIG. 3 , the rotor 6 is fixed, preferably by shrinking, on the receiving part 16 of the shaft 10.

Note that the shaft 10 includes a shoulder 14 at the level of the difference in diameters between the first portion 11 and the second portion 12, as illustrated in figures 3 and 6.

According to a second embodiment illustrated on the FIG. 4 , the element 20 also comprises the first bore 21 arranged so as to be found next to, close to the bearing 5 after assembly. The first bore 21 of the element 20 comes into contact with the first portion 11 of the shaft 10. Preferably, the first bore 21 of the element 20 is shrunk, that is to say force-fitted, onto the first portion 11 of the shaft 10.

Advantageously again, as illustrated in Figures 4 and 5, the first bore 21 of the element 20 comprises the internal splines 25. The first portion 11 of the shaft 10 comprises the external splines 15. Thus, the internal splines 25 formed in the first bore 21 of the element 20 cooperate with the external splines 15 formed at the level of the first cylindrical portion 11 of the shaft 10. Advantageously, the splines 15, 25 are associated with the hooping, complete the hooping, to ensure reliable and durable retention of the element 20 on the shaft 10.

The element 20 of the second embodiment also comprises the second bore 22 arranged so as to be located next to, in proximity to, the rotor 6 of the geared motor 3 after assembly. The second bore 22 preferably has a larger diameter than the diameter of the first bore 21. The second bore 22 is mounted by shrink-fitting on at least the part L12 of the axial length of the second cylindrical or substantially cylindrical portion 12. Advantageously, the part having an axial length L12 of the shaft 10 extends outside the internal volume V of the rotor 6, as illustrated in the FIG. 4 .

Especially, according to the second embodiment of element 20, illustrated in the FIG. 4 , the element 20 comprises a third bore 26, of the counterbore, recess, or groove type between the first and second bores 21, 22. The third bore 26 is preferably of larger diameter than each of the first and second bores 21, 22. In particular, the third bore 26 facilitates the manufacture of the reinforcing element 20 by allowing tool clearances, for example useful for obtaining the internal grooves 25. The axial lengths L21 and L22, respectively of the first bore 21 and of the second bore 22, present at each end of the element 20 or hoop, allow the work, the function of the element 20, namely to avoid the bending of the shaft 10. These lengths L21, L22, locally reduced compared to the first embodiment without the counterbore 26, also allow the limitation of the fitting force without reducing the stiffness objective of the shaft. For example, the length L21 of the first bore 21, advantageously splined, is between 5 mm and 15 mm, or even between 8 mm and 12 mm. This length is sufficient, even if it is necessary to transmit a torque by teeth 23.

Indeed, possibly, as illustrated in figures 3 and 4, the element 20 comprises external teeth or radial extensions 23, for example at the level of the first bore in the axial direction.

The solution makes it possible to increase the rigidity and stiffness of the shaft 10 of the geared motor without modifying the bearings 5, 7 and the casing 4.

Indeed, the reinforcing element 20 limits the deflection of the shaft 10, in particular in the case of a powertrain comprising the geared motor 3 equipped with the output pinion 8 at the end of the shaft 10. This deflection is in particular reduced or even eliminated, between the two bearings 5, 7. In the case of a helical pinion 8 generating significant forces at the end of the shaft, the stiffening element 20 prevents bending, also called “biasing” resulting from such forces. Note that these forces are, for example, simultaneously radial and axial. The solution does not generate any additional friction so that the efficiency of the geared motor is not impaired.

By avoiding such bending of the shaft 10, any damage to the pinion 8 and/or the toothed wheel cooperating with this pinion 8 and any resulting noise are avoided. In other words, the teeth of this gear are preserved over time, which extends the service life and/or limits the maintenance required.

The solution does not impact the rotor, the casing, or the bearings. Regarding the shaft, only 15 splines, if applicable, and/or differences in diameter between portion 11 and portion 12, are required in terms of modifications. Thus, the usual components are compatible with the solution, which makes it very economical.

Preferably, the material used for the stiffening element 20 is steel in order to provide maximum stiffness and to be compatible with hooping.

For example, the thickness E20 of the element 20, in the radial direction, illustrated in Figures 3 and 4, is between 1 mm and 5 mm, or even between 2 mm and 4 mm, preferably of the order of 3 mm in order to provide substantial stiffness without, however, requiring too much force for the hooping. Although the thickness E20 is illustrated at the level of the second bore 22, this thickness E20 can also be substantially valid at the level of the first bore 21. Indeed, the difference in diameter between the first bore and the second bore can be small. This resulting increase in thickness of the shaft makes it possible to achieve the desired limitation of the deflection. The length L20, in the axial direction, of the hoop 20 is for example between 20 mm and 80 mm, for example of the order of 50 mm. Advantageously, the length of the hoop 20 is maximized in relation to the space E available between the bearing 5 and the rotor 6.

The stiffening element 20 of the shaft 10, in particular its thickness E20 in the radial direction, therefore contributes to the stiffness of the part of the shaft 10 supporting the rotor 6. Note that the shaft 10 is cantilevered between the bearing 5 and the active parts of the rotor 6.

As a reminder, so that the element 20 contributes as much as possible to increasing the stiffness of the shaft 10, the second bore 22 is shrunk onto the motor shaft 10.

As seen previously, the rotor shaft 10 has external grooves 13 extending parallel to the axis A of the shaft, for example four in number. These grooves 13 allow the hooping and fitting of the active parts of the rotor 6, preferably active parts of the stacking type. The solution is compatible with these grooves 13 which preferably extend beyond the axial length L17 of the frustoconical portion 17 intended to facilitate the fitting of the rotor 6. More precisely, these grooves extend at least partly within the volume V of the rotor 6.

In particular, in order to be able to transmit a torque with possible radial projections 23 of the hoop 20, a bearing surface at the level of the first bore 21 is provided to come and fret on the external diameter of the external splines 15 of the shaft. In other words, the teeth of the splines allow the torque to be transmitted and the tops of the teeth of the splines are fretted into the sleeve 20 in order to increase the stiffness of the shaft. For example, the hooping is carried out with a relatively low fitting force so as to eliminate any risk of damage to the shaft 10 and/or the active parts of the rotor 6 and/or the element 20, while allowing the sleeve 20 to take up the mainly bending forces of the rotor shaft 10 at the two bores 21, 22. For example, the difference in diameters between the diameter of the hoop and the diameter of the shaft at this/these hooping(s) is between 5 microns and 60 microns, or even between 10 microns and 54 microns in the case of a smooth shaft, and between 5 microns and 85 microns, or even between 10 microns and 80 microns in the case of splined or grooved shafts. Such example values are given for a shaft of approximately 50 mm in diameter and are to be adapted for a shaft of smaller diameter or larger diameter.

Thus, the hoops do not require significant effort, which facilitates assembly in terms of the arrangement assembly process.

In terms of the assembly method, the components are simply fitted axially, one behind the other, along the length of the rotor shaft 10. As mentioned, the element 20 is shrunk on the one hand on a part of the side of the bearing 5, at the level of its splines 25 while being guided by these teeth cooperating with the splines 15, and on the other hand on a part of the side of the rotor 6, at the level of its second bore 22 over the length L12. During assembly, the insertion of the element 20 onto the shaft 10 continues until contact is made between an internal shoulder 24 of the sleeve 20 and a shoulder 14 provided on the shaft 10. More precisely, the shoulder 24 of the stiffening ring 20 results from the difference between the second bore 22 and the first bore 21, the second bore being of larger diameter than the first bore. The shoulder 14 of the shaft 10 is at the junction between the first portion 11 and the frustoconical portion 17 preferably.

Advantageously, the bearing 5 comprises a bearing, for example a ball bearing, the inner ring 51 of which is shrunk onto a bearing surface 18 of the shaft. For example, the inner ring 51 of the bearing bears axially against the element 20. Alternatively, the inner ring 51 of the bearing bears axially against a shoulder extending between the bearing surface 18 and the first portion 11 of the shaft 10. The output pinion 8 is advantageously mounted on splines 30, for example by being centered or substantially centered. For example, an axial stop of the pinion 8 is ensured against the inner ring 51 of the bearing 5 via a shoulder 53 provided on the pinion ( FIG. 2 ). Preferably, an axial locking means 9, for example of the split elastic clip type, or snap ring, cooperating with a groove provided on the shaft 10, is mounted at the end of the shaft on the side of the output pinion 8. This locking means 9 ensures an axial stop of the stack on the shaft 10. This locking means 9 and/or the groove in which it is inserted, are preferably adjusted to the stack on the shaft 10 comprising the inserted and shrink-fitted element 20, the bearing whose inner ring 51 is preferably shrink-fitted, and the pinion 8. In practice, after this assembly, an axial measurement is carried out of the stack obtained from these three components 20, 51, 8 and the thickness in the axial direction of the locking means 9 is deduced, for example, in order to adjust, possibly with a desired level of tightening. In other words, the axial thickness of the locking means 9 plays the role of a shim for adjusting the stacking obtained. Optionally, an axial hole communicating with a radial lubrication hole is made at the end of the shaft in order to lubricate the contact of the teeth of the splines 30 of the pinion 8.

The solution is particularly compact, and offers a gain in mass and therefore in cost concerning the raw material of the shaft 10 of the geared motor.

In summary, despite the forces applied to the pinion 8, preferably helical (motor torque output) at the end of the geared motor shaft supporting the rotor 6, the shaft 10 does not bend, it does not flex. The solution prevents the degradation of the teeth of the helical pinion and avoids the creation of an unbalance linked to the bending of the shaft. This results in an increased service life of the bearings 5, 7 of the assembly.

The solution allows the shaft stiffness to be increased without increasing the volume of material in the shaft, in particular without increasing its diameter. The inner diameter of the rotor is not changed and therefore the entire rotor is not affected. The part furthest from the rotor's rotational axis, which is subject to a very high tangential speed, is therefore not affected.

Optionally, although the sleeve 20 has been described only on the output pinion side, it could be arranged between the rotor 6 and the bearing 7, i.e. on the other side of the rotor. Alternatively, a second sleeve could be arranged between the rotor 6 and the bearing 7, in addition to the sleeve 20 arranged between the rotor 6 and the bearing 5.

The invention is particularly suitable for a vehicle, in particular a motor vehicle, and can be used for a truck, a bus, a coach, an agricultural machine, a lifting machine and any other motorized machine such as a motorcycle for example. In addition, it can be adapted to any engine comprising a space between a rotor and at least one of these bearings.

Claims (10)

Arrangement (2) for a geared motor (3), in particular a geared motor (3) for towing and/or propelling a vehicle (1), comprising:
- a casing (4),
- a shaft (10) arranged at least partially within the casing (4),
- a bearing (5) arranged between the casing (4) and the shaft (10), the bearing (5) at least partially supporting the shaft (10) in rotation,
- a rotor (6) of such a geared motor (3), the rotor (6) being fixed on the shaft (10) and extending within the casing (4),
- a space (E) extending around the shaft (10) between the bearing (5) and the rotor (6),
characterized in that the arrangement (2) comprises an element (20) fixed to the shaft (10) within the space (E) so as to stiffen the shaft (10), in particular in terms of bending. Arrangement (2) according to the preceding claim, characterized in that the element (20) is cylindrical or substantially cylindrical. Arrangement (2) according to one of the preceding claims, characterized in that the element (20) comprises a first bore (21) arranged next to the bearing (5) and in that the shaft (10) comprises a first portion (11), the first bore (21) of the element (20) coming into contact with the first portion (11) of the shaft (10). Arrangement (2) according to the preceding claim, characterized in that the first bore (21) of the element (20) is shrunk onto the first portion (11) of the shaft (10). Arrangement (2) according to the preceding claim, characterized in that the first bore (21) of the element (20) comprises internal splines (25) and in that the first portion (11) of the shaft (10) comprises external splines (15), the internal splines (25) cooperating with the external splines (15). Arrangement (2) according to one of claims 3 to 5, characterized in that the element (20) comprises a second bore (22) arranged next to the rotor (6), the second bore (22) being of larger diameter than the first bore (21),
and in that the shaft (10) comprises a second portion (12) for mounting the rotor (6), in particular a second portion (12) comprising external grooves (13) parallel to the axis of the shaft (10), the second bore (22) being shrunk at least over a part (L12) of the axial length of the second portion (12). Arrangement (2) according to the preceding claim, characterized in that the second portion (12) of the shaft (10) comprises a frustoconical portion (17) so as to facilitate the mounting of the rotor (6). Arrangement (2) according to one of the preceding claims, characterized in that the element (20) comprises radial extensions (23). Geared motor (3), in particular intended for towing and/or propelling a vehicle, characterized in that it comprises an arrangement (2) according to one of the preceding claims. Vehicle, in particular a motor vehicle (1), characterized in that it comprises an arrangement (2) according to one of claims 1 to 8, or a geared motor (3) according to claim 9.