WO2024105254A1

WO2024105254A1 - Reduction gear system having hybrid assembly

Info

Publication number: WO2024105254A1
Application number: PCT/EP2023/082258
Authority: WO
Inventors: Benoit Jourdain; Cédric LALOS; Alexandre LE GALL; Patrice Mercay
Original assignee: New H Powertrain Holding, S.L.U
Priority date: 2022-11-17
Filing date: 2023-11-17
Publication date: 2024-05-23
Also published as: FR3142229A1

Abstract

The present invention relates to a reduction gear system (1) for an electric vehicle, characterised in that it comprises at least one motor output shaft (2) and a fixed pinion (4) which is attached to said motor output shaft (2), the system having means for assembling the fixed pinion (4) to the motor output shaft (2), the assembly means comprising splines (42) and at least one smooth bearing surface (36, 37), which are arranged successively along the motor output shaft (2), the fixed pinion (4) being braced onto at least one smooth bearing surface (36, 37) of the motor output shaft (2).

Description

DESCRIPTION

Title: Hybrid assembly geared motor assembly

The present invention relates to the field of gearboxes, in particular electric vehicles, and more particularly geared motor assemblies associated with these gearboxes and comprising at least one shaft and one pinion, intended to participate in the transmission of power aimed at to regulate the speed of a vehicle.

Currently, most electric vehicles include a geared motor assembly comprising an electric motor, a plurality of shafts parallel to the rotor shaft secured to the electric motor, and pinions respectively attached to one or the other of the shafts.

The pinions, once mounted on the shafts, cooperate with each other to form a gear train and allow power transmission from the engine to the vehicle drive means according to a gear ratio given according to the size of the gears in mesh. , and more particularly depending on the dimension of a driving pinion and the dimension of a driven pinion.

The cooperation of the driven and driving gears takes place over all or part of their respective toothed surfaces, a functional zone being defined by the axial extent in which the teeth of the driving gear are in contact with the teeth of the driven gear. It is important to ensure that the machining of the gears in this functional area is very precise and that the dimensions are respected so that power transmission is as efficient as possible. However, the assembly of the gears on their shaft can involve a deformation of the toothed surfaces in their functional zone and requires a re-machining operation once the gears are assembled on the shaft.

More particularly, it is known to attach pinions to their respective shaft via two different assembly techniques, both of which implement long centering of the pinion on the shaft, over the entire axial dimension of the pinion.

A first assembly technique consists of implementing smooth bearing surfaces on the shaft and on the pinion. Once in position, the pinion is shrink-fitted, that is to say mounted by force, on the shaft and the contact between the two components is defined by these smooth surfaces all around the shaft, over the entire axial dimension of the pinion. The rotational drive, and therefore the transmission of power, takes place between the shaft and the corresponding pinion by these worn smooth so the fit is very tight. A second assembly technique consists of implementing splines, both on the internal surface of the pinion and on the shaft, at least on the pinion receiving area. The splines interacting with each other participate in the transmission of power and the shrinking, or force mounting, is done on the top of the splines of one or the other of the pinion or the shaft. The shrinking on the splines is done continuously over the entire axial dimension of the pinion.

As mentioned previously, one or other of the assembly operations requires an additional machining operation to grind the pinion, so as to prevent shrink fit from having a detrimental impact on the quality of the pinion teeth. . Indeed, the precision of the machining of the pinions and the respect of the theoretical dimensions in the gearing has a direct impact on the acoustic and mechanical performances of the vehicle.

Grinding the pinion teeth generates chips. When the gears are assembled on the primary and secondary shafts housed in a transmission housing, which is then connected to the rotor shaft, it is easy, to prevent these chips subsequently having an impact on the mechanical operation of the vehicle, to clean the casing before connection to the rotor shaft. The chips can be cleaned and are not likely to lodge in the electric motor and in particular in the bearings which guide the rotor shaft attached to the electric motor.

However, the present invention is part of a context of reducing the bulk of the geared motor assembly, with a pinion which is directly fixed on the rotor shaft, as close as possible to the bearings arranged around the rotor shaft in the vicinity of the electric motor. In this way, grinding the pinion once it is assembled on the shaft risks generating chips in the bearings of the electric motor directly nearby.

The present invention aims to propose a solution making it possible to have a compact geared motor assembly, with a fixed gear directly assembled on the motor output shaft, and in which the quality of the toothed surface of the fixed gear is at the level of the quality that can be obtained after a machining grinding operation.

The main object of the present invention is thus a geared motor assembly for an electric vehicle characterized in that it comprises at least one motor output shaft and a fixed pinion attached to said motor output shaft, the assembly having means of assembly of the fixed pinion to the motor output shaft, the assembly means comprise splines and at least one smooth surface arranged successively along the motor output shaft, the fixed gear being fitted onto at least one smooth surface of the motor output shaft.

The geared motor assembly according to the invention is intended to equip a vehicle, for example an electric vehicle and it has the particularity of having a fixed pinion directly mounted on the rotor shaft at the motor output, the assembly means being particular to avoid having to carry out a machining grinding operation after assembly. The fixed gear directly mounted on the motor output shaft makes it possible to merge the function of the motor shaft and the primary shaft, and thus generate a more compact assembly than usual. Furthermore, the assembly means allow the implementation of a hybrid assembly mode alternating smooth bearings and splines which contribute to generating an assembly by long centering without having significant shrinkage zones allowing the centering of the pinion around of the motor output shaft, while ensuring good power transmission through the cooperation of the splines. In this way, we can reduce the constraints on the materials that this force assembly generates, and the centering being short, it is possible to locate these constraints on the axial dimension of the pinion, for example in areas that do not impact the quality of the toothing of the pinion is fixed and therefore non-impacting for the efficiency and quality, sound for example, of the power transmission.

More particularly, such a hybrid assembly, namely a combination of assembly means with smooth surfaces and assembly means with splines, makes it possible to adjust and define the position of the zones in which the pinion is fitted onto the shaft. , for example by shifting them axially relative to the toothing areas of the fixed gear intended to be in contact with a driven gear participating in power transmission. This ensures that the shrink fit has no or very little impact on the structure of the fixed gear in the toothing areas intended to cooperate with a driven gear and therefore that the grinding step can be avoided. of the pinion, responsible for the creation of chips and risking hindering the mechanical operation of the gear motor assembly.

According to an optional characteristic of the invention, the motor output shaft has two smooth surfaces arranged on either side of the splines.

The presence of two plain bearings has the advantage of increasing the surface covered by the plain bearings, and therefore of increasing the extent of centering to ensure that the coaxial position of the fixed gear relative to the motor shaft is correct , and the arrangement of these two smooth surfaces on either side of the splines makes it possible to maintain a spline zone in which the fixed gear is not clamped onto the shaft and therefore in which the assembly operation does not generate forces on the pinion.

According to an optional characteristic of the invention, the motor output shaft comprises a first smooth bearing having a first external diameter and a second smooth bearing having a second external diameter whose value is different from the value of the first external diameter. This results in a staggering, or radial offset, of the two smooth surfaces offset axially relative to each other, which ensures that the fixed pinion can cooperate simultaneously with each of the smooth surfaces of the shaft. motor output during its axial fitting around the shaft.

According to an optional characteristic of the invention, the motor output shaft has a free end opposite the motor, the first smooth bearing is located on the side of the motor while the second smooth bearing is located in the vicinity of the end free. The different external diameters of these smooth bearings on the shaft are such that the first external diameter has a value greater than the value of the second external diameter. These differences in dimensions of the smooth bearing surfaces, depending on their position relative to the free end of the motor output shaft, make it possible to ensure the assembly of the fixed gear on the motor output shaft, the fixed gear having correspondingly at least two zones whose internal diameter is different.

According to an optional characteristic of the invention, the fixed gear is an annular part whose internal surface has grooves and whose external surface forms teeth.

According to an optional characteristic of the invention, the grooves of the internal surface of the fixed gear extend over the entire axial dimension of the fixed gear and are configured to cooperate with each of the assembly means formed on the motor output shaft. In other words, the splines of the fixed gear are on the one hand configured, in shape and dimensions, to interact with the splines formed on the motor output shaft, by interposing between each other. In this way, the rotation of the motor output shaft can be transmitted to the fixed gear, by tangential cooperation of the splines of the two components. On the other hand, the splines of the fixed gear are dimensioned to be in tight contact, that is to say mounted by force, in relation to the smooth surfaces of the motor output shaft. According to an optional characteristic of the invention, the cooperation of the grooves of the internal surface of the fixed gear with the assembly means formed on the motor output shaft defines a zone for receiving the fixed gear on the motor output shaft. The receiving zone has an axial dimension substantially equal to the axial dimension of the fixed gear and substantially equal to the sum of the axial dimensions of the smooth surfaces and the splines formed on the motor output shaft.

According to an optional characteristic of the invention, the internal surface of the fixed gear is configured to form stepped splines. In other words, along the axial dimension of the fixed gear, the internal diameter of the internal surface, that is to say the internal diameter measured between two diametrically opposed spline vertices, takes on at least two different values.

According to an optional characteristic of the invention, the fixed gear comprises, successively considering an axial direction of the fixed gear, a first lateral part, intended to be in the vicinity of a free end of the motor output shaft when the fixed gear is assembled on the motor output shaft and having a first internal diameter, a central part, as well as a second side part having a second internal diameter, the value of which is different from the value of the first internal diameter.

These different internal diameters are respectively values slightly lower than the corresponding value of the external diameter of the smooth seat of the motor output shaft. In other words, when the fixed gear is assembled on the motor output shaft, the first lateral part of the fixed gear, of a first internal diameter, faces the first smooth surface of the motor output shaft , whose first external diameter is slightly greater than the first internal diameter so as to generate shrinkage during assembly. And similarly, when the fixed gear is assembled on the motor output shaft, the second lateral part of the fixed gear, of a second internal diameter, faces the second smooth surface of the motor output shaft, whose second external diameter is slightly greater than the second internal diameter so as to also generate shrinkage during assembly, thus increasing the extent of centering of the fixed gear.

According to an optional characteristic of the invention, the internal diameter of the central part of the fixed gear is of a value equal to the value of the first diameter or of a value equal to the value of the second diameter. We thus see a continuity between the central part and one of the lateral parts at the level of the internal diameter of the fixed gear, the staggering of the splines, that is to say the change in internal diameter, taking place at the junction of the central part with one of the lateral parts.

According to one characteristic of the invention, the fixed gear is arranged axially on the motor output shaft between an axial stop wall located between the motor and the fixed gear and a stopping means arranged in the vicinity of the free end of the motor output shaft.

The axial stop wall and the stopping means are intended to precisely center the fixed gear on the motor output shaft, and to ensure that the receiving zone is positioned axially on the motor output shaft in accordance with to what is planned. The fixed gear being fitted onto the motor output shaft, it is difficult to ensure the correct axial positioning of the fixed gear and the axial thrust wall presents this technical effect. The axial thrust wall can be formed by a shoulder of the motor output shaft and/or by a face of a bearing facing the fixed gear. The stopping means may comprise an elastic ring disposed in a groove formed for this purpose in the motor output shaft, and being sufficiently thick to axially block the fixed gear in a direction opposite to the axial stop wall.

According to an optional characteristic of the invention, the external surface of the fixed gear forming a toothing is intended to engage with the external surface of corresponding shape of a driven gear to be able to transmit the rotation of the motor output shaft, c i.e. the primary shaft, to a secondary shaft with a defined gear ratio. As a non-limiting example, the fixed gear has helical teeth of a given pitch and depth and the driven gear has corresponding helical teeth.

According to an optional characteristic of the invention, the axial dimension of the teeth of the fixed gear is greater than the axial dimension of the teeth of the driven gear so that only part of the teeth of the fixed gear is engaged with the driven gear, the zone of cooperation of the teeth defining a functional zone.

We understand that the teeth of the fixed driving pinion and the driven pinion make it possible to form a gear train, generating the reduction in the speed of rotation of the motor output shaft. This gear train is formed in a functional zone which is only an axial portion of the teeth of the fixed driving gear. In other words, Portions of the teeth are not active, in the sense that they do not cooperate with another pinion.

According to an optional characteristic of the invention, the functional zone is formed by the central part of the fixed gear, the lateral parts of the fixed gear forming parts arranged on either side of this functional zone. It is notable that these two lateral parts of the fixed gear are intended to cooperate, at the level of the internal surface of the fixed gear, respectively with one of the two smooth bearing surfaces of the motor output shaft. In this way, the mechanical stresses during assembly by shrink fit are located on the lateral parts of the fixed gear and therefore in areas of the teeth which do not participate in defining the functional zone.

According to an optional characteristic of the invention, the first side part and the second side part of the fixed gear have an external diameter equal to the external diameter of the central part. In other words, the teeth of the fixed gear have a uniform thickness over the entire axial dimension of the fixed gear, both for the central part defining the functional zone in engagement with the driven gear and for the lateral parts. The uniform thickness of the fixed gear allows in particular a simplified execution of the heat treatment of the fixed gear, for example by quenching, before its assembly on the motor output shaft.

According to an optional characteristic of the invention, the geared motor assembly comprises a lubrication circuit comprising at least one axial conduit formed by an internal bore of the motor output shaft and a radial conduit formed in the thickness of the motor output shaft, said radial conduit opening at one end onto the axial conduit and at its other end onto the external surface of the motor output shaft, in the portion having the splines. The lubrication circuit further comprises axial channels, formed between the external surface of the motor output shaft, whether this has splines or smooth surfaces, and the internal splined surface of the fixed gear. These axial channels extend to the axial ends of the fixed gear. The fixed pinion has at least on its axial end face facing away from the motor, that is to say on the side of the free end of the motor output shaft, notches allowing evacuation of a lubricant circulating in the axial channels, while this axial end face abuts against an axial stopping means which also prevents the flow of the lubricant. Such a lubrication circuit initially allows the evacuation of the lubricant present in the engine. It is configured, by the arrangement of the axial and radial conduits within the shaft and by the presence of notches on the fixed gear at the end of the axial channels, to use the lubricant to be evacuated and pass it to the interface between fixed gear and motor output shaft, in particular to evacuate any dirt which may have slipped into it.

Other characteristics, details and advantages of the invention will emerge more clearly on reading the description of a detailed embodiment which follows, given for informational and non-limiting purposes with reference to the appended schematic drawings, in which:

[Fig.l] schematically and partially illustrates a geared motor assembly according to the invention, this figure notably making visible a fixed pinion assembled on a motor output shaft and its cooperation with a driven pinion of this geared motor assembly;

[Fig.2] illustrates, in perspective and partially, a geared motor assembly according to one embodiment of the invention, this figure making visible in particular the fixed gear and the motor output shaft;

[Fig.3] illustrates, in perspective, the pinion of Figure 2;

[Fig.4] is a sectional view of the pinion of Figure 3, making visible in particular two portions of grooves of different diameters;

[Fig.5] illustrates, in perspective, the motor output shaft of Figure 2;

[Fig.6] is a sectional view of the motor output shaft of Figure 5, making visible in particular hybrid assembly means with two smooth surfaces of different diameters arranged on either side of the splines;

[Fig.7] illustrates, schematically in section, the geared motor assembly of Figure 2 to make particularly visible the means of assembly between the motor output shaft and the pinion.

The characteristics, variants and different embodiments of the invention can be associated with each other, in various combinations, to the extent that they are not incompatible or exclusive with respect to each other. In particular, it will be possible to imagine variants of the invention comprising only a selection of characteristics described subsequently in isolation from the other characteristics described, if this selection of characteristics is sufficient to confer a technical advantage and/or to differentiate the invention. compared to the state of the prior art. In the figures, elements common to several figures retain the same reference.

In the above and in the detailed description which follows, the terms “axial” and “radial” refer to the axis of rotation of the motor output shaft. An axial direction is parallel to the direction defined by this axis of rotation and a radial direction is parallel to a straight line perpendicular and secant to this axis of rotation.

As a reminder, the invention relates to a geared motor assembly 1 which comprises a motor output shaft 2 and a fixed gear 4 directly fixed to the motor output shaft 2 according to a hybrid assembly mode, with assembly means which include both means of transmitting rotational torque by splines and means of fixing and centering by shrinking on a smooth surface.

The geared motor assembly 1 is intended to equip a motorized vehicle, for example an electric vehicle comprising an electric motor 6, as detailed in Figure 1, the operation of which generates the rotation of a motor output shaft 2, and this geared motor assembly comprises a set of pinions mounted on shafts parallel to each other and whose interaction contributes to the transmission of power. In Figure 1, the geared motor assembly 1 is only partially shown with a fixed pinion 4 forming a driving pinion which cooperates with a driven pinion 8 integral in rotation with a secondary shaft 10. It is understood that other shafts and other gears may be present without departing from the context of the invention.

The geared motor assembly 1 according to the invention has a reduced size insofar as the fixed pinion which transmits the output torque of the motor to all of the pinions is directly fixed on the motor output shaft, such that is visible in Figure 1 in particular, being in direct abutment against a wall of the motor or as illustrated in direct abutment against a bearing 12 of the motor facilitating the rotation of the motor output shaft. In this geared motor assembly 1, the fixed gear 4 and the motor output shaft 2 are assembled so as to form an integral assembly rotating around a common axis, directly at the motor output.

The fixed gear 4 extends between a free end 14 of the motor output shaft 2 and a component of the motor, here the bearing 12, defining in the present invention an end of the output shaft called motor end 16, such that this is particularly visible in Figures 2 and 7. More particularly, the axial position of the fixed gear 4 on the motor output shaft 2 is defined by an axial stop 18 located on the side of the motor end 16, here formed by the bearing 12, and by a stopping means 20 which is attached to the motor output shaft once the pinion is mounted on the motor output shaft and which is arranged on the side of the free end 14.

The stopping means 20 is here formed by an elastic ring 22 sufficiently thick to absorb the axial forces generated by the axial micro-displacements of the fixed gear during power transmission, the elastic ring 22 being mounted in a groove 24 formed for this purpose in the motor output shaft 2. The axial stop 18 and the stopping means 20 are thus two elements which participate in forming a device for positioning the fixed gear, having the objective of positioning the fixed gear 4 so precisely on the motor output shaft 2, in a so-called reception zone visible in Figure 7.

We will now describe the structure of the fixed gear in more detail, in particular with reference to Figures 2 to 4.

The fixed gear 4 is an annular part, around an axis of revolution, of which an internal surface has grooves 26 and whose external surface forms a toothing 28, here helical. It is desired to assemble the fixed gear on the motor output shaft in such a way that the axis of revolution coincides with the axis of revolution of the motor output shaft.

Considering the axial direction of the fixed pinion, it is notable that it successively comprises a first lateral part 30, a central part 32 and a second lateral part 34. These different parts are distinguished by their function once the pinion is assembled fixed on the motor output shaft made.

The first lateral part 30, intended to be in the vicinity of the motor end of the motor output shaft when the fixed gear is assembled on the motor output shaft, has the function of cooperating with a first smooth surface 36 formed on the motor output shaft 2 in the vicinity of this motor end 16 to participate in the centering by shrinking the fixed gear on the motor shaft.

The second lateral part 34, axially opposite the pinion and therefore intended to be in the vicinity of the free end of the motor output shaft when the fixed pinion is assembled on the motor output shaft, has the function of cooperate with a second smooth span 37 formed on the motor output shaft 2 in the vicinity of this free end 14, also to participate in the centering by shrinking of the fixed gear on the motor shaft.

We understand that it is the internal surfaces of these lateral parts 30, 34 of the fixed gear which are operational and which cooperate with other elements, here the smooth surfaces of the motor output shaft.

Finally, the central part 32 placed between the two lateral parts 30, 34 has a dual function. At the level of the internal surface of the fixed gear 4, its function is to cooperate with splines present on the motor output shaft, in particular to transmit the rotational torques and ensure that the fixed gear is integral in rotation with the motor output shaft. At the level of the external surface of the fixed gear 4, and therefore of the teeth 28, its function is to cooperate with the teeth of the driven gear 8 secured to the secondary shaft 10, so that the transmission of power from the fixed gear to the driven gear is made at the level of the central part 32 in a zone defined as a functional zone 38. It is notable in Figure 1 and in Figure 7 that the axial dimension of the driven gear 8 is less than that of the teeth 28 of the fixed gear 4, so that the functional zone defined by the central part 32 of the fixed gear 4 does not extend over the entire axial dimension of the fixed gear 4.

The grooves 26 of the internal surface of the fixed gear 4 extend over substantially the entire axial dimension of the fixed gear 4 and as is visible in Figures 3 and 4, on each of the lateral and central parts previously defined. In order to allow the mounting of the fixed pinion along the motor output shaft and to ensure centering by shrinking simultaneously on the two smooth surfaces via the side part of the corresponding pinion, the internal surface of each side part 30, 34 is configured such that these side parts have internal diameters of different values, with the first side part 30 which has a first internal diameter Dil and the second side part 34 which has a second internal diameter Di2, the first internal diameter Dil having a value greater than the value of the second internal diameter Di2.

The grooves 26 present in the internal surface of the central part 32 have the same dimension as those present in the internal surface of one of the lateral parts, here the first lateral part. In other words, the grooves present in the central part have an internal diameter of value equal to that of the first internal diameter Dil. This results in an internal surface comprising stepped grooves 26, with a shoulder 40 which is created on the internal surface of the fixed gear between the central part 32 and one of the side parts, here the second side part 34. It should be noted that the difference between the values of two internal diameters is minimal, of of the order of a tenth of a millimeter, but that this is sufficient to allow passage of the first lateral part and the central part opposite the second smooth surface during assembly without shrinking being carried out, in order to to be able to position the first lateral part facing the first smooth span and the second lateral part facing the second smooth span.

The teeth 28 of the fixed gear have a substantially uniform thickness, from one axial end to the other. In other words, the central part 32 and the lateral parts 30, 34 all three form a part of the teeth 28 whose radial dimension, defined by the external diameter of each of the parts, is the same as the other parts of the teeth. The lateral parts of the teeth thus have a thickness identical to that of the central part of the teeth, even if these lateral parts are not intended to engage with the driven pinion 8 and do not participate in forming the functional zone 38 previously mentioned. . This homogeneous thickness is interesting in that it facilitates the heat treatment operations of the fixed gear, for example by quenching.

The two lateral parts 30, 34 of the fixed gear, which each have a portion of teeth not included in the functional zone 38 and therefore exempt from the constraints generated by the contact of the driven gear during torque transmission, are located to the right of the bearing surfaces smooth 36, 37 of the motor output shaft 2 as they will be described in more detail below in particular with reference to Figures 5 and 6.

In a complementary manner, the central part 32 of the fixed gear, which forms the functional zone 38 for the transmission of torque with the driven gear and which must therefore precisely respect the theoretical dimensions of the teeth, here helical, is located to the right of the splines 42 of the motor output shaft as they will be described in more detail below, in particular with reference to Figures 5 and 6.

The deformations suffered by the fixed gear during shrinking are thus concentrated on the lateral parts 30, 34 of the fixed gear and the portion of teeth located in the central part 32 is not or only slightly impacted by this shrinking operation so that it is not necessary to plan an operation to grind the teeth after assembly. The fixed gear 4 also includes several lubrication notches 44, participating in a lubrication circuit formed in the motor output shaft and between it and the fixed gear. The notches 44 make it possible to release the oil playing the role of the lubricant circulating within the lubrication circuit and thus to provide for the renewal of the oil despite the presence of the stopping means 20 against the fixed gear, which could prevent the oil flow.

We will now describe, in particular with reference to Figures 5 and 6, the motor output shaft 2.

As has been mentioned, the geared motor assembly 1 is particular in that the fixed gear is mounted on the motor output shaft via a hybrid assembly mode. In this context of the invention, the motor output shaft comprises assembly means comprising at least one smooth bearing and splines 42. The at least one smooth bearing allows the force mounting of the pinion and makes it possible to locate the stress zones due to this force assembly and the presence of the splines makes it possible to distribute the torque transmission efforts over the entire axial dimension of the fixed gear which includes splines of complementary shapes and dimensions.

In the example illustrated, the assembly means comprise two smooth surfaces 36, 37, arranged on either side of the grooves 42. This increases the axial dimension on which the fixed gear is centered by shrinking on the shaft. motor output and thus ensures long centering, without generating stresses due to shrinking over the entire axial dimension of the fixed gear. As was mentioned previously, this makes it possible to provide a zone, here central, in which the constraints due to shrinking are zero or negligible on the fixed pinion, which makes it possible not to impact the functional zone of the teeth of the pinion. fixed located to the right of this zone.

It is notable in the figures that each of the smooth surfaces is distant from the grooves 42, separated by a clearance portion 45.

A first smooth surface 36 of the motor output shaft 2 is located on the side of the motor, and more particularly in the vicinity of the motor end 16 of the motor output shaft 2. This first smooth surface 36 has a first external diameter Of the. A second smooth surface 37 is located near the free end 14 of the motor output shaft. This second smooth surface 37 has a second external diameter De2, of value different from that of the first external diameter. More particularly, the second external diameter De2 has a value less than the value of the first external diameter Del.

In order to allow, during the assembly which will be described below, to slide the fixed gear 4 along the motor output shaft 2 to the area receiving the pinion, with the first lateral part 30 of the fixed gear which is facing the first smooth bearing 36 and the second lateral part 34 of the fixed gear which is facing the second smooth bearing 37, the second external diameter De2 of the second smooth bearing 37 is of a value slightly less than the value of the first internal diameter Dil of the first lateral part 30.

In order to allow shrinking in this position, the first external diameter Del of the first smooth surface 36 is also of a value slightly greater than the value of the first internal diameter Dil of the first lateral part 30 and the second external diameter De2 of the second smooth surface 37 has a value slightly greater than the value of the second internal diameter Di2 of the second lateral part 34.

The motor output shaft 2 includes elements participating in forming the lubrication circuit previously mentioned. The lubrication circuit thus comprises an axial conduit 46 defined by a bore within the motor output shaft and through which lubricant arrives from the motor. It also includes a radial conduit 48, formed by a bore passing through the motor output shaft from the axial conduit 46 to the external surface of the motor pinion. In the example illustrated, the axial conduit 46 opens substantially in the center of the portion presenting the grooves, here in a lubricant distribution groove 50 forming an interruption in the grooves.

The lubrication circuit also includes axial channels formed by the fixed gear 4 and the motor output shaft, between the splines of each of these elements, which allow the lubricant to be guided towards the notches 44 of the fixed gear 4 previously mentioned.

We will now describe the mounting of the fixed gear on the engine output shaft, in particular to illustrate the advantage of the presence of hybrid assembly means such as they have just been presented, with splines and smooth surfaces present. on the motor output shaft 2 and stepped splines present on the fixed gear, of different diameters.

The fixed gear 4 is brought opposite the free end 14 of the motor output shaft 2, on which the stopping means 40 are not yet mounted. The fixed gear is then pushed so as to slide around the motor output shaft, with the first lateral part 30 of the fixed gear 4 which engages opposite the second smooth bearing surface 37. As previously specified, the first lateral part 30 of the fixed gear 4 has a first internal diameter Dil of a value greater than the value of the second external diameter De2 of the second smooth bearing 37 which makes it possible to avoid causing the fixed gear to rub on the second smooth bearing. The splines 26 present on the internal surface of the fixed gear then engage between the splines 42 present on the motor output shaft and the movement of the fixed gear takes place without friction until the second lateral part 34 of the fixed gear arrives opposite the second smooth part 37 of the motor output shaft 2. Simultaneously, the first lateral part 30 of the fixed gear 4 arrives opposite the first smooth surface 36 of the motor output shaft 2, located on the side from the motor end 16. The arrangement of the splines on the internal surface of the fixed gear is such that the pinion must be mounted by force so that the first lateral part 30 of first internal diameter Dil slides along the first smooth bearing surface. of first external diameter Del, with the first internal diameter Dil which has a value slightly lower than the value of the first external diameter Del, and so that at the same time the second lateral part 34 of second internal diameter Di2 slides along the second smooth bearing of second external diameter De2, with the second internal diameter Di2 which has a value slightly lower than the value of the second external diameter De2. This force assembly continues until the fixed gear reaches the position illustrated in Figure 7 abutting on the axial abutment wall 18, and it generates shrinking and two centering zones of the fixed gear on the shaft. motor output 2. These two centering zones being arranged at each end of the pinion receiving zone as defined previously, a long centering of the fixed pinion is thus achieved.

We then mount the elastic ring 22 participating in forming the stopping means 20 in the groove 24 in order to block axially the fixed pinion 4 between the two stopping points forming the centering system which are the axial stop 18 and the means stop 20.

As could be specified previously, it is notable that during this assembly operation, the two lateral parts 30, 34 of the fixed gear 4 support forces in contact with the smooth bearing surfaces 36, 37 of the motor output shaft 2 , but that these lateral parts have portions of the teeth 28 which are not in the functional zone 38 of the teeth. As it has just been described, the present invention achieves the goals it has set for itself, namely ensuring that it is not necessary to rework machining on a fixed gear tooth. force-mounted directly on a motor output shaft, providing a hybrid assembly system of the fixed pinion on the motor output shaft which implements both centering means by shrink fit and means of torque transmission by splines . The geared motor assembly according to the invention thus allows a saving of mechanical parts and makes it possible to meet the need for durability and acoustics required for an electric vehicle.

The present invention cannot, however, be limited to the means and configurations described and illustrated here and it also extends to any equivalent means and configuration as well as to any technically effective combination of such means.

Claims

1. Geared motor assembly (1) for an electric vehicle characterized in that it comprises at least one motor output shaft (2) and a fixed pinion (4) attached to said motor output shaft (2), the assembly having means for assembling the fixed gear (4) to the motor output shaft (2), the assembly means comprising splines (42) and at least one smooth surface (36, 37), arranged successively along of the motor output shaft (2), the fixed gear (4) being fitted onto at least one smooth surface (36, 37) of the motor output shaft (2).

2. Geared motor assembly (1) according to the preceding claim, in which the motor output shaft (2) has two smooth surfaces (36, 37) arranged on either side of the splines (42).

3. geared motor assembly (1) according to any one of the preceding claims, in which the motor output shaft (2) comprises a first smooth surface (36) having a first external diameter (Del) and a second smooth surface (37) having a second external diameter (De2) whose value is different from the value of the first external diameter (Del).

4. geared motor assembly (1) according to any one of the preceding claims, in which the fixed gear (4) successively comprises, considering an axial direction of the fixed gear (4), a first lateral part (30) intended to be in the vicinity of a free end (14) of the motor output shaft (2) when the fixed gear (4) is assembled on the motor output shaft (2) and having a first internal diameter (Dil), a central part (32), as well as a second lateral part (34) having a second internal diameter (Di2), the value of which is different from the value of the first internal diameter (Dil).

5. Geared motor assembly (1) according to one of the preceding claims, in which the fixed pinion (4) is an annular part whose internal surface has grooves (26) and whose external surface forms teeth (28) .

6. Geared motor assembly (1) according to the preceding claim, wherein the internal surface of the fixed gear (4) is configured to form stepped splines (26).

7. geared motor assembly (1) according to claim 5 or 6, in which the cooperation of the splines (26) of the internal surface of the fixed gear (4) with the means assembly formed on the motor output shaft (2) defines a receiving area of the fixed gear (4) on the motor output shaft (2).

8. Geared motor assembly according to any one of claims 5 to 7, in which the external surface of the fixed gear (4) forming the teeth (28) is intended to engage with the external surface of corresponding shape of a driven gear (8), the axial dimension of the teeth (28) of the fixed gear (4) being greater than the axial dimension of the teeth of the driven gear so that only part of the teeth (28) of the fixed gear (4) ) is engaged with the driven pinion, the cooperation zone of the teeth defining a functional zone (38).

9. Geared motor assembly according to the preceding claim, in combination with claim 4, in which the functional zone (38) is formed by the central part (32) of the fixed gear (4), the lateral parts (30, 34) of the fixed gear (4) forming parts arranged on either side of this functional zone (38).

10. Geared motor assembly according to one of the preceding claims, in combination with claim 4, in which the first lateral part (30) and the second lateral part (34) of the fixed gear (4) have an external diameter equal to the external diameter of the central part (32).