Hybrid assembly type gear motor assembly

Abstract

The invention relates to a reduction gear system (1) for an electric vehicle, characterized in that it comprises at least one motor output shaft (2) and a stationary pinion (4) attached to said motor output shaft (2), the system having means for fitting the stationary pinion (4) onto the motor output shaft (2), the assembly device comprises a spline (42) and at least one smooth bearing surface (36, 37) arranged in succession along the motor output shaft (2), onto which the fixed pinion (4) is supported.

Description

[0001] The present invention relates to the field of gearboxes, in particular gearboxes for electric vehicles, and more particularly to gearmotor assemblies associated with these gearboxes, comprising at least a shaft and a pinion, intended to participate in the transmission of power for the purpose of regulating the speed of the vehicle.

[0002] Currently, most electric vehicles include a gear motor assembly that includes an electric motor, a plurality of shafts parallel to a rotor shaft integral with the electric motor, and pinions each attached to one or the other of the shafts.

[0003] Once mounted on the shaft, the pinions interact to form a gear train and allow power to be transmitted from the electric motor to the vehicle drive according to the pinion ratio (which is determined by the size of the meshing pinions, more specifically, the size of the driving pinion and the size of the driven pinion).

[0004] The interaction between the driven and driving pinions occurs over all or part of their respective tooth surfaces. The functional area is defined by the axial extent in which the teeth of the driving and driven pinions come into contact. Extremely precise machining of the pinion in this functional area, with strict adherence to dimensions, is essential for ensuring the most efficient power transmission. However, assembly of the pinion on its shaft can involve deformation of the tooth surfaces in this functional area, necessitating remachining operations once the pinion is assembled on the shaft.

[0005] More specifically, it is known to attach the pinions to their respective shafts by means of two different assembly techniques, both of which achieve a long centring of the pinion on the shaft over the entire axial dimension of the pinion.

[0006] The first assembly technique consists in realizing smooth bearing surfaces on the shaft and the pinion. Once in place, the pinion is shrunk, that is to say, press-fitted onto the shaft, the contact between the two components being defined by these smooth bearing surfaces over the entire periphery of the shaft and over the entire axial dimension of the pinion. The rotational drive and thus the power transmission takes place between the shaft and the corresponding pinion via these smooth bearing surfaces, resulting in a very tight fit. The second assembly technique consists in using splines both on the inner surface of the pinion and on the shaft (at least on the pinion receiving area). The splines, which interact with each other, participate in the transmission of power, and the shrink fit or press fit is carried out on top of the splines of the pinion or the shaft. The shrink fit on the splines is carried out continuously over the entire axial dimension of the pinion.

[0007] As mentioned above, any assembly operation requires an additional machining operation to grind the pinion in order to avoid shrink fit that adversely affects the quality of the pinion teeth. In fact, the machining accuracy of the pinion and the theoretical size of the gear have a direct impact on the acoustic and mechanical performance of the vehicle.

[0008] Grinding the pinion teeth generates debris. When the pinion is assembled on the main and countershafts housed in the transmission housing, which is then connected to the rotor shaft, it is easier to clean the housing before it is connected to the rotor shaft to prevent this debris from subsequently affecting the vehicle's mechanical operation. This debris can be cleaned without the risk of becoming lodged in the electric motor, particularly in the bearings that guide the rotor shaft, which is integral to the electric motor.

[0009] However, the present invention aims to reduce the size of the gear motor assembly by attaching the pinion gear directly to the rotor shaft, as close as possible to the bearings arranged around the rotor shaft near the motor. Thus, grinding the pinion gear once it is assembled on the shaft could potentially generate debris in the adjacent motor bearings.

[0010] The object of the present invention is to provide a solution with a compact gear motor assembly having a fixed pinion mounted directly on the motor output shaft and wherein the quality of the tooth surfaces of the fixed pinion is at a quality level obtainable after a machining grinding operation.

[0011] Therefore, the main object of the present invention is a gear motor assembly for an electric vehicle, characterized in that the gear motor assembly comprises at least one motor output shaft and a fixed pinion attached to the motor output shaft, the assembly having a device for assembling the fixed pinion to the motor output shaft, the assembly device comprising splines arranged in sequence along the motor output shaft and at least one smooth bearing surface, the fixed pinion shrinking onto the at least one smooth bearing surface of the motor output shaft.

[0012] The gear motor assembly according to the present invention is intended to equip a vehicle (e.g. an electric vehicle) and has the characteristic of a fixed pinion mounted directly on the rotor shaft at the output of the motor, the assembly device being special so as to avoid the need for machining correction operations after assembly. The fixed pinion mounted directly on the motor output shaft allows the functions of the motor shaft and the main shaft to be merged, thereby producing a more compact assembly than usual. In addition, the assembly device allows the implementation of a mixed assembly mode of alternating smooth spans and splines, which produces an assembly through long centering participation without a significant shrink fit area for centering the pinion around the motor output shaft, while ensuring good power transmission through the interaction of the splines. In this way, the stresses caused to the material by the press-fit assembly can be reduced. Due to the short centering, these stresses can be located along the axial dimension of the pinion, for example, in an area that does not affect the quality of the tooth portion of the fixed pinion and therefore does not affect the efficiency or quality of power transmission (such as the noise level).

[0013] More specifically, this hybrid assembly, i.e., the combination of an assembly with a smooth bearing surface and an assembly with splines, makes it possible to adjust and define the position of the area where the pinion is contracted onto the shaft, for example by axially offsetting it relative to the tooth area of ​​the fixed pinion intended to come into contact with the driven pinion involved in the power transmission. This makes it possible to ensure that the shrink fit has little or no effect on the structure of the fixed pinion in the tooth area intended to mate with the driven pinion, thus avoiding the pinion grinding step, which would generate debris and risk hindering the mechanical operation of the gearmotor assembly.

[0014] According to an optional feature of the invention, the motor output shaft comprises two smooth bearing surfaces arranged on either side of the spline.

[0015] The presence of two smooth bearing surfaces has the advantage of increasing the area covered by the smooth bearing surfaces, thereby increasing the scope for centering to ensure that the coaxial position of the fixed pinion relative to the drive shaft is correct, and the arrangement of these two smooth bearing surfaces on both sides of the spline makes it possible to maintain a spline area in which the fixed pinion does not shrink onto the shaft, and therefore in which the assembly operation does not generate forces on the pinion.

[0016] According to an optional feature of the invention, the motor output shaft comprises a first smooth bearing surface having a first outer diameter and a second smooth bearing surface having a second outer diameter, the value of the second outer diameter being different from the value of the first outer diameter. This results in a staggered or radial offset of the two smooth bearing surfaces axially offset relative to one another, which makes it possible to ensure that the fixed pinion can interact simultaneously with each smooth bearing surface of the motor output shaft during its axial assembly around the shaft.

[0017] According to an optional feature of the present invention, the motor output shaft has a free end opposite the motor, a first smooth bearing surface being located on the motor side, and a second smooth bearing surface being located near the free end. The different outer diameters of these smooth bearing surfaces on the shaft are such that the first outer diameter has a greater value than the second outer diameter. These dimensional differences in 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 pinion on the motor output shaft, the fixed pinion accordingly having at least two regions with different inner diameters.

[0018] According to an optional feature of the invention, the fixed pinion is an annular component, the inner surface of which is provided with splines and the outer surface of which forms the teeth.

[0019] According to an optional feature of the present invention, the splines on the inner surface of the fixed pinion extend over the entire axial dimension of the fixed pinion and are configured to cooperate with each assembly device formed on the motor output shaft. In other words, the splines of the fixed pinion are configured in shape and size on the one hand to interact with the splines formed on the motor output shaft by inserting into each other. In this way, the rotation of the motor output shaft can be transmitted to the fixed pinion through the tangential interaction of the splines of the two components. On the other hand, the spline size of the fixed pinion is designed to be in close contact with the smooth bearing surface of the motor output shaft (i.e., press fit).

[0020] According to an optional feature of the invention, the splines on the inner surface of the fixed pinion cooperate with the mounting means formed on the motor output shaft to define an area for receiving the fixed pinion on the motor output shaft. The axial dimension of the receiving area is substantially equal to the axial dimension of the fixed pinion and substantially equal to the sum of the axial dimensions of the smooth bearing surface and the splines formed on the motor output shaft.

[0021] According to an optional feature of the invention, the inner surface of the fixed pinion is configured to form a stepped spline. In other words, along the axial dimension of the fixed pinion, the inner diameter of the inner surface (for example, the inner diameter measured between two diametrically opposite spline vertices) takes at least two different values.

[0022] According to an optional feature of the present invention, considering the axial direction of the fixed pinion in sequence, the fixed pinion includes a first transverse portion, a central portion and a second transverse portion. When the fixed pinion is assembled on the motor output shaft, the first transverse portion is intended to be located near the free end of the motor output shaft and has a first inner diameter, and the second transverse portion has a second inner diameter, and the value of the second inner diameter is different from the value of the first inner diameter.

[0023] These different inner diameters are each slightly smaller than the corresponding values ​​of the outer diameters of the smooth bearing surface of the motor output shaft. In other words, when the fixed pinion is assembled on the motor output shaft, the first transverse portion of the fixed pinion having the first inner diameter is opposite the first smooth bearing surface of the motor output shaft, and the first outer diameter of the first smooth bearing surface is slightly larger than the first inner diameter to allow for contraction during assembly. Similarly, when the fixed pinion is assembled on the motor output shaft, the second transverse portion of the fixed pinion having the second inner diameter is opposite the second smooth bearing surface of the motor output shaft, and the second outer diameter of the second smooth bearing surface is slightly larger than the second inner diameter to allow for contraction during assembly, thereby increasing the degree of centering of the fixed pinion.

[0024] According to an optional feature of the invention, the value of the inner diameter of the central portion of the fixed pinion is equal to the value of the first diameter or equal to the value of the second diameter. Thus, at the level of the inner diameter of the fixed pinion, there is continuity between the central portion and one of the transverse portions, the stepping of the spline (that is to say the change in the inner diameter) occurring at the junction of the central portion with one of the transverse portions.

[0025] According to a feature of the invention, the fixed pinion is arranged axially on the motor output shaft between an axial stop wall (located between the motor and the fixed pinion) and a stop device (arranged near the free end of the motor output shaft).

[0026] The axial stop wall and the stop device are intended to precisely center the fixed pinion on the motor output shaft and ensure that the receiving area is axially positioned in the motor output shaft direction according to the provided content. Since the fixed pinion is shrunk onto the motor output shaft, it is difficult to ensure the correct axial positioning of the fixed pinion, and the axial stop wall has this technical effect. The axial stop wall can be formed by a shoulder of the motor output shaft and / or by the surface of the bearing facing the fixed pinion. The stop device can include an elastic ring that is arranged in a groove formed for this purpose in the motor output shaft and is thick enough to axially lock the fixed pinion in the direction opposite to the axial stop wall.

[0027] According to an optional feature of the present invention, the outer surface of the fixed pinion, which forms a toothing, is intended to engage with the correspondingly shaped outer surface of the driven pinion, so as to be able to transmit the rotation of the motor output shaft (i.e., the main shaft) to the secondary shaft at a defined gear ratio. As a non-limiting example, the fixed pinion has a helical toothing with a given pitch and depth, and the driven pinion has a corresponding helical toothing.

[0028] According to an optional feature of the invention, the axial dimension of the teeth of the fixed pinion is greater than the axial dimension of the teeth of the driven pinion, so that only a part of the teeth of the fixed pinion meshes with the driven pinion, and the interaction area of ​​the teeth defines the functional area.

[0029] It should be understood that the teeth of the active fixed pinion and the driven pinion form a gear train that reduces the rotational speed of the motor output shaft. This gear train is formed within the functional area of ​​only the axial portion of the active fixed pinion's teeth. In other words, some of the teeth are inactive because they do not interact with the other pinions.

[0030] According to an optional feature of the invention, the functional area is formed by the central portion of the fixed pinion, with the fixed pinion transverse portions forming the elements arranged on either side of this functional area. Notably, the two transverse portions of the fixed pinion are designed to interact with one of the two smooth bearing surfaces of the motor output shaft, respectively, at the level of the fixed pinion's inner surface. This way, mechanical stresses during shrink-fit assembly are localized on the transverse portions of the fixed pinion and, therefore, in areas of the toothing that do not contribute to defining the functional area.

[0031] According to an optional feature of the present invention, the outer diameters of the first and second transverse sections of the fixed pinion are equal to the outer diameter of the central section. In other words, the toothing of the fixed pinion has a uniform thickness over the entire axial dimension of the fixed pinion, both in the central section defining the functional area for engagement with the driven pinion and in the transverse sections. This uniform thickness of the fixed pinion makes it possible, in particular, to simplify heat treatment (e.g., by quenching) of the fixed pinion before assembly to the motor output shaft.

[0032] According to an optional feature of the invention, the gear motor assembly includes a lubrication circuit comprising at least one axial duct formed by the inner bore of the motor output shaft and radial ducts formed in the thickness of the motor output shaft, one end of each radial duct opening into the axial duct and the other end of each radial duct opening into the outer surface of the motor output shaft in a splined portion. The lubrication circuit also includes axial channels formed between the outer surface of the motor output shaft (regardless of whether the motor output shaft has a splined or smooth bearing surface) and the splined inner surface of the fixed pinion. These axial channels extend to the axial ends of the fixed pinion. The fixed pinion has a recess on at least its axial end face facing away from the motor (that is, on the side of the free end of the motor output shaft), which allows the lubricant circulating in the axial channel to be discharged, while this axial end face abuts against an axial stop that also prevents the lubricant from flowing.

[0033] Such a lubrication circuit initially allows the lubricant present in the motor to be drained. By means of the arrangement of the axial and radial ducts in the shaft and the presence of a recess on the fixed pinion at the end of the axial channel, the lubrication circuit is configured to drain the lubricant and pass it through the interface between the fixed pinion and the motor output shaft, in particular to dislodge any dirt that may have slipped into it.

[0034] Other features, details and advantages of the present invention will become more apparent from the following description of detailed embodiments provided by way of example and not limitation with reference to the accompanying drawings, in which:

[0035] Figure 1A schematic and partial illustration of a gear motor assembly according to the invention, the figure showing in particular a fixed pinion mounted on the motor output shaft and its interaction with a driven pinion of the gear motor assembly;

[0036] Figure 2 A gear motor assembly according to an embodiment of the present invention is partially illustrated in perspective view, showing a fixed pinion and a motor output shaft;

[0037] Figure 3 Shown in perspective Figure 2 The pinion;

[0038] Figure 4 yes Figure 3 a cross-section of a pinion showing two spline sections of different diameters;

[0039] Figure 5 Shown in perspective Figure 2 The motor output shaft;

[0040] Figure 6 yes Figure 5 A cross-sectional view of a motor output shaft, particularly showing a hybrid assembly having two smooth bearing surfaces of different diameters arranged on both sides of the spline;

[0041] Figure 7 Schematically shows Figure 2 The gear motor assembly is shown in cross section, in particular making visible the connection between the motor output shaft and the pinion.

[0042] The features, variations and different embodiments of the present invention may be associated with one another in various combinations, provided they are not incompatible or exclusive of one another. In particular, it is conceivable that a variant of the present invention comprises only a selection of the features described below, separated from the other features described, if this selection is sufficient to confer a technical advantage on the present invention and / or to distinguish the present invention from the prior art.

[0043] In the figures, elements common to several figures retain the same reference numerals.

[0044] In the above and following detailed descriptions, the terms "axial" and "radial" refer to the rotation axis of the motor output shaft. The axial direction is parallel to the direction defined by the rotation axis, and the radial direction is parallel to a line perpendicular to and tangential to the rotation axis.

[0045] As a reminder, the present invention relates to a gear motor assembly 1 comprising a motor output shaft 2 and a fixed pinion 4 fixed directly to the motor output shaft 2 according to a mixed assembly mode using an assembly device comprising means for transmitting rotational torque by splines and means for fixing and centering by shrink fit on a smooth surface.

[0046] The gear motor assembly 1 is intended to equip a motor vehicle (for example an electric vehicle) comprising an electric motor 6, such as Figure 1 As shown, the motor 6 is operated to generate the rotation of the motor output shaft 2, and the gear motor assembly includes a set of pinions mounted on shafts parallel to each other, and the interaction of the pinions participates in the transmission of power. Figure 1 In the figure, the gear motor assembly 1 is only partially shown, wherein the fixed pinion 4 forms the driving pinion which interacts with the driven pinion 8 rotating integrally with the layshaft 10. It will be understood that other shafts and other sprockets may be present without departing from the context of the invention.

[0047] The gear motor assembly 1 according to the present invention has a reduced size because the fixed pinion that transmits the output torque of the motor to the pinion gear set is directly fixed to the motor output shaft, such as Figure 1 This facilitates the rotation of the motor output shaft, in particular by abutting directly against the wall of the motor or, as shown, against the bearing 12 of the motor. In this gear motor assembly 1, the fixed pinion 4 and the motor output shaft 2 are assembled so as to form an assembly rotating integrally about a common axis directly at the output of the motor.

[0048] The fixed pinion 4 extends between the free end 14 of the motor output shaft 2 and a component of the motor, here a bearing 12, which in the present invention defines one end of the output shaft (called the motor end 16), in particular as Figure 2 and Figure 7 shown.

[0049] More specifically, the axial position of the fixed pinion 4 on the motor output shaft 2 is defined by an axial stop 18 located on one side of the motor end 16 (here formed by the bearing 12) and a stop 20 attached to the motor output shaft after the pinion is mounted on the motor output shaft and arranged on the side of the free end 14.

[0050] The stop 20 is here formed by an elastic ring 22 of sufficient thickness to absorb the axial forces generated by the slight axial displacement of the fixed pinion during the 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 stop 20 are therefore two elements that participate in forming the device for positioning the fixed pinion, the purpose of which is to position the fixed pinion 4 in the Figure 7 The so-called receiving area visible in the figure is positioned precisely on the motor output shaft 2.

[0051] The structure of the fixed pinion will now be described in more detail, with particular reference to Figures 2 to 4 .

[0052] The fixed pinion 4 is an annular portion around the axis of rotation, its inner surface having splines 26 and its outer surface forming teeth 28 (in this case helical). It is desirable to fit the fixed pinion on the motor output shaft so that the axis of rotation coincides with the axis of rotation of the motor output shaft.

[0053] Considering the axial direction of the fixed pinion, it is worth noting that the fixed pinion comprises, in order, a first transverse portion 30, a central portion 32 and a second transverse portion 34. Once the fixed pinion has been assembled on the motor output shaft, these different portions are distinguished according to their function.

[0054] When the fixed pinion is assembled on the motor output shaft, the function of the first transverse portion 30 (which is intended to be located near the end of the motor of the motor output shaft) is to interact with a first smooth bearing surface 36 formed on the motor output shaft 2 near this motor end 16 to participate in centering by retraction of the fixed pinion on the motor shaft.

[0055] The second transverse portion 34 is axially opposite to the pinion, so when the fixed pinion is assembled on the motor output shaft, the second transverse portion 34 is intended to be located near the free end of the motor output shaft. The function of the second transverse portion 34 is to interact with a second smooth bearing surface 37 formed on the motor output shaft 2 near the free end 14, and also to participate in centering by retracting the fixed pinion on the motor shaft.

[0056] It will be appreciated that the inner surfaces of these transverse portions 30, 34 of the fixed pinion are operable to cooperate with other elements, in this case the smooth bearing surfaces of the motor output shaft.

[0057] Finally, the central portion 32 arranged between the two transverse portions 30, 34 has a dual function. At the inner surface of the fixed pinion 4, its function is to cooperate with the splines present on the motor output shaft, in order in particular to transmit the rotational torque and to ensure that the fixed pinion rotates integrally with the motor output shaft. At the outer surface of the fixed pinion 4 (that is to say the toothing 28), its function is to interact with the toothing of the driven pinion 8 integral with the secondary shaft 10, so that the power transmission from the fixed pinion to the driven pinion takes place in the central portion 32 in the area defined as the functional area 38. It is worth noting that in Figure 1 and Figure 7 In the embodiment, the axial dimension of the driven pinion 8 is smaller than the axial dimension of the tooth portion 28 of the fixed pinion 4 , so that the functional area defined by the central portion 32 of the fixed pinion 4 does not extend over the entire axial dimension of the fixed pinion 4 .

[0058] The splines 26 of the inner surface of the fixed pinion 4 extend substantially over the entire axial dimension of the fixed pinion and are Figure 3 and Figure 4As shown, it extends over each of the previously defined transverse sections and the central section. In order to allow the fixed pinion to be mounted along the motor output shaft and to ensure centering by the simultaneous contraction of the corresponding transverse section of the pinion on two smooth bearing surfaces, the inner surface of each transverse section 30, 34 is configured so that these transverse sections have internal diameters of different values, wherein the first transverse section 30 has a first internal diameter Di1 and the second transverse section 34 has a second internal diameter Di2, the value of the first internal diameter Di1 being greater than the value of the second internal diameter Di2.

[0059] The splines 26 present in the inner surface of the central portion 32 have the same dimensions as the splines present in the inner surface of one of the transverse portions (here, the first transverse portion). In other words, the inner diameter of the splines present in the central portion is equal to the value of the first inner diameter Di1. The result is an inner surface with stepped splines 26, forming a shoulder 40 on the inner surface of the fixed pinion between the central portion 32 and one of the transverse portions (here, the second transverse portion 34). It should be noted that the difference between the values ​​of the two inner diameters is very small, approximately one tenth of a millimeter, but it is sufficient to allow the first transverse portion and the central portion to pass relative to the second smooth bearing surface without shrinking during assembly, so that the first transverse portion can be positioned opposite the first smooth bearing surface, and the second transverse portion can be positioned opposite the second smooth bearing surface.

[0060] The fixed pinion toothing 28 has a substantially uniform thickness from one axial end to the other. In other words, the central portion 32 and the transverse portions 30 and 34 all form part of the toothing 28, and the radial dimensions of the toothing 28, as defined by the outer diameter of each portion, are the same as those of the rest of the toothing. Thus, even though these transverse portions are not intended to mesh with the driven pinion 8 and do not contribute to the formation of the functional region 38 described above, the transverse portions of the toothing have the same thickness as the central portion of the toothing. This uniform thickness is advantageous because it facilitates heat treatment operations (e.g., quenching) on ​​the fixed pinion.

[0061] The two transverse portions 30, 34 of the fixed pinion, each of which has a portion of its toothing which is not included in the functional area 38 and which is therefore not subject to the stresses arising from the contact with the driven pinion during the transmission of torque, are located in alignment with the smooth bearing surfaces 36, 37 of the motor output shaft 2, as will be described in more detail below, in particular with reference to Figure 5 and Figure 6 .

[0062] Furthermore, the central portion 32 of the fixed pinion (which forms the functional area 38 for transmitting torque with the driven pinion and which in practice must precisely adhere to the theoretical dimensions of the toothing (here helical)) is located in alignment with the splines 42 of the motor output shaft, as will be described in more detail below, in particular with reference to Figure 5 and Figure 6 .

[0063] Therefore, the deformations experienced by the fixed pinion during the shrinking process are concentrated on the lateral portions 30 , 34 of the fixed pinion, and the toothing portion located in the central portion 32 is not or hardly affected by the shrinking operation, so there is no need to provide an operation of grinding the toothing after assembly.

[0064] The fixed pinion 4 also comprises a plurality of lubrication recesses 44 which participate in the lubrication circuit formed in the motor output shaft and between the motor output shaft and the fixed pinion. The recesses 44 make it possible to release the oil acting as lubricant circulating in the lubrication circuit, thus providing a renewal of the oil despite the presence of the stop 20 against the fixed pinion which could otherwise prevent the flow of oil.

[0065] We will now refer specifically to Figure 5 and Figure 6 Describe the motor output shaft 2.

[0066] As mentioned above, the unique feature of the gear motor assembly 1 is that the fixed pinion is mounted on the motor output shaft using a mixed assembly method. In the context of the present invention, the motor output shaft includes an assembly device comprising at least one smooth bearing surface and splines 42. The at least one smooth bearing surface allows the pinion to be press-fitted, and due to this press-fit, stress areas can be localized. The presence of the splines makes it possible to distribute the torque transmission forces over the entire axial dimension of the fixed pinion, which includes splines of complementary shape and size.

[0067] In the example shown, the assembly device includes two smooth bearing surfaces 36, 37, which are arranged on either side of the spline 42. This increases the axial dimension of the fixed pinion for centering the fixed pinion on the motor output shaft via the shrink fit, thereby ensuring long-range centering without stresses due to the shrink fit over the entire axial length of the fixed pinion. As mentioned above, this makes it possible to provide a region (here, the central region) in which the stresses on the fixed pinion due to the shrink fit are zero or negligible, making it possible to avoid affecting the functional area of ​​the fixed pinion toothing aligned with this region.

[0068] It is noteworthy in the Figures that each smooth bearing surface is spaced apart from the splines 42 by a gap portion 45 .

[0069] A first smooth bearing surface 36 of the motor output shaft 2 is located on the motor side, more specifically, near the motor end 16 of the motor output shaft 2. This first smooth bearing surface 36 has a first outer diameter De1. A second smooth bearing surface 37 is located near the free end 14 of the motor output shaft. This second smooth bearing surface 37 has a second outer diameter De2, which is different from the first outer diameter. More specifically, the second outer diameter De2 is smaller than the first outer diameter De1.

[0070] In the assembly process to be described below, in order to enable the fixed pinion 4 to slide along the motor output shaft 2 all the way to the pinion receiving area (where the first lateral portion 30 of the fixed pinion is opposite to the first smooth supporting surface 36, and the second lateral portion 34 of the fixed pinion is opposite to the second smooth supporting surface 37), the value of the second outer diameter De2 of the second smooth supporting surface 37 is slightly smaller than the value of the first inner diameter Di1 of the first lateral portion 30.

[0071] To allow for contraction at this position, the first outer diameter De1 of the first smooth supporting surface 36 is slightly larger than the first inner diameter Di1 of the first transverse portion 30 , and the second outer diameter De2 of the second smooth supporting surface 37 is slightly larger than the second inner diameter Di2 of the second transverse portion 34 .

[0072] The motor output shaft 2 includes elements that participate in forming the aforementioned lubrication circuit. Thus, the lubrication circuit comprises an axial duct 46, defined by a hole in the motor output shaft, through which lubricant is discharged from the motor. It also comprises radial ducts 48, formed by holes extending from the axial duct 46 through the motor output shaft to the outer surface of the motor pinion. In the example shown, the axial duct 46 emerges substantially in the center of the splined portion (here, in a lubricant distribution groove 50 formed as an interruption in the spline).

[0073] The lubrication circuit also comprises an axial channel formed by the fixed pinion 4 and the motor output shaft, between the splines of each of these elements, which allows the lubricant to be directed towards the notches 44 of the aforementioned fixed pinion 4 .

[0074] The mounting of the fixed pinion on the motor output shaft will now be described, in particular in order to illustrate the advantages of the hybrid assembly arrangement just proposed, in which the splines and smooth surfaces present on the motor output shaft 2 and the stepped splines present on the fixed pinion have different diameters.

[0075] The fixed pinion 4 is positioned opposite the free end 14 of the motor output shaft 2, with the stopper 40 not yet installed on the fixed pinion 4. The fixed pinion is then pushed so as to slide around the motor output shaft, with the first transverse portion 30 of the fixed pinion 4 engaging the second smooth bearing surface 37. As described above, the first transverse portion 30 of the fixed pinion 4 has a first inner diameter Di1 that is greater than the second outer diameter De2 of the second smooth bearing surface 37. This prevents the fixed pinion from rubbing against the second smooth bearing surface. The splines 26 on the inner surface of the fixed pinion then engage between the splines 42 on the motor output shaft, and the fixed pinion moves frictionlessly until the second transverse portion 34 of the fixed pinion reaches and faces the second smooth portion 37 of the motor output shaft 2. Simultaneously, the first transverse portion 30 of the fixed pinion 4 reaches and faces the first smooth bearing surface 36 of the motor output shaft 2 located on the motor end 16 side. The step of the spline on the inner surface of the fixed pinion makes it necessary to force the pinion to be mounted so that the first transverse portion 30 of the first inner diameter Di1 slides along the first smooth bearing surface of the first outer diameter De1 (where the value of the first inner diameter Di1 is slightly smaller than the value of the first outer diameter Del), and at the same time the second transverse portion 34 of the second inner diameter Di2 slides along the second smooth bearing surface of the second outer diameter De2 (where the value of the second inner diameter Di2 is slightly smaller than the value of the second outer diameter De2). This press fit continues until the fixed pinion reaches Figure 7 The position shown abuts against the axial stop wall 18 and produces a shrink fit and two centering areas for the fixed pinion on the motor output shaft 2. These two centering areas are arranged at each end of the area for receiving the pinion as defined above, thus achieving long centering of the fixed pinion.

[0076] The elastic ring 22 which participates in forming the stop means 20 is then mounted in the groove 24 in order to axially lock the fixed pinion 4 between the two stop points forming the centering system, namely the axial stop 18 and the stop 20 .

[0077] As mentioned above, it is worth noting that during this assembly operation, the two transverse portions 30 , 34 of the fixed pinion 4 are subjected to forces in contact with the smooth bearing surfaces 36 , 37 of the motor output shaft 2 , but these transverse portions have a portion of the toothing 28 that is not in the functional area 38 of this toothing.

[0078] As described above, the present invention achieves its stated goal by providing a hybrid assembly system for a fixed pinion on a motor output shaft that utilizes both shrinkage for centering and splined torque transmission, eliminating the need for re-machining the teeth of the fixed pinion directly press-fitted onto the motor output shaft. Consequently, the geared motor assembly according to the present invention saves on mechanical components and meets the durability and acoustic requirements of electric vehicles.

[0079] However, the present invention is not limited to the devices and configurations described and illustrated herein, but extends to any equivalent devices and configurations and any technically operational combination of these devices.

Claims

1. A gear motor assembly (1) for an electric vehicle, characterized in that The assembly comprises at least one motor output shaft (2) and a fixed pinion (4) attached to the motor output shaft (2), the assembly having a device for assembling the fixed pinion (4) to the motor output shaft (2), the assembling device comprising splines (42) and at least one smooth bearing surface (36, 37) arranged in sequence along the motor output shaft (2), the fixed pinion (4) being shrunk onto the at least one smooth bearing surface (36, 37) of the motor output shaft (2).

2. The gear motor assembly (1) according to the preceding claim, wherein The motor output shaft (2) comprises two smooth bearing surfaces (36, 37) arranged on either side of the spline (42).

3. The gear motor assembly (1) according to any one of the preceding claims, wherein The motor output shaft (2) comprises a first smooth bearing surface (36) having a first outer diameter (De1) and a second smooth bearing surface (37) having a second outer diameter (De2), the value of the second outer diameter (De2) being different from the value of the first outer diameter (De1).

4. The gear motor assembly (1) according to any one of the preceding claims, wherein Taking into account the axial direction of the fixed pinion (4), the fixed pinion (4) comprises, in sequence: a first transverse portion (30), which is used to be located near the free end (14) of the motor output shaft (2) when the fixed pinion (4) is assembled on the motor output shaft (2) and has a first inner diameter (Di1); a central portion (32); and a second transverse portion (34), which has a second inner diameter (Di2), the value of the second inner diameter (Di2) being different from the value of the first inner diameter (Di1).

5. The gear motor assembly (1) according to any one of the preceding claims, wherein The fixed pinion (4) is an annular member having splines (26) on its inner surface and teeth (28) formed on its outer surface.

6. Gear motor assembly (1) according to the preceding claim, wherein The inner surface of the fixed pinion (4) is configured to form a stepped spline (26).

7. The gear motor assembly (1) according to claim 5 or 6, wherein: The interaction of the splines (26) on the inner surface of the fixed pinion (4) and the assembly means formed on the motor output shaft (2) defines a receiving area for the fixed pinion (4) on the motor output shaft (2).

8. The gear motor assembly according to any one of claims 5 to 7, wherein: The outer surface of the fixed pinion (4) forming the tooth portion (28) is intended to engage with the outer surface of the corresponding shape of the driven pinion (8), the axial dimension of the tooth portion (28) of the fixed pinion (4) being greater than the axial dimension of the tooth portion of the driven pinion, so that only a portion of the tooth portion (28) of the fixed pinion (4) meshes with the driven pinion, and the mating area of ​​the tooth portion defines a functional area (38).

9. A gear motor assembly according to the preceding claim in combination with claim 4, wherein: The functional area (38) is formed by the central portion (32) of the fixed pinion (4), and the lateral portions (30, 34) of the fixed pinion (4) form portions arranged on both sides of the functional area (38).

10. A gear motor assembly according to any one of the preceding claims in combination with claim 4, wherein: The outer diameters of the first transverse portion (30) and the second transverse portion (34) of the fixed pinion (4) are equal to the outer diameter of the central portion (32).

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