Hybrid geared motor assembly

Abstract

Title: Hybrid Motor-Reducer Assembly The present invention relates to a motor-reducer assembly (1) for an electric vehicle, characterized in that it comprises at least one motor output shaft (2) and a fixed pinion (4) mounted on said motor output shaft (2). The assembly includes means for mounting the fixed pinion (4) to the motor output shaft (2). These mounting means include splines (42) and at least one smooth bearing surface (36, 37) arranged successively along the motor output shaft (2). The fixed pinion (4) is press-fitted onto at least one smooth bearing surface (36, 37) of the motor output shaft (2). Abstract Figure: Figure 7

Description

Description Title of the invention: Motor-reducer assembly with assembly hybrid

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

[0002] — Currently, most electric vehicles include a motor- reducer comprising an electric motor, a plurality of shafts parallel to the shaft rotor attached to the electric motor, and pinions respectively attached to one or the other of the trees.

[0003] — The pinions, once mounted on the shafts, cooperate with each other to form a train gears and allow power transmission from the engine to the means vehicle drive according to a given gear ratio depending on the size of the gears in mesh, and more particularly as a function of the size of a driving pinion and the size of a driven pinion.

[0004] — The cooperation of the driven and driving gears is done on all or part of their surface respective toothed, a functional zone being defined by the axial extent in which the teeth of the driving pinion are in contact with the teeth of the driven pinion. It is suitable to ensure that the machining of the gears in this functional area is very precise and that the dimensions are respected so that the power transmission is as efficient as possible possible. However, the assembly of the pinions on their shaft can involve deformation toothed surfaces in their functional area and requires a reworking operation machining once the gears are assembled on the shaft.

[0005] — More particularly, it is known to attach pinions to their respective shafts via two different assembly techniques, both of which implement a long centering of the pinion on the shaft, over the entire axial dimension of the pinion.

[0006] A first assembly technique consists of implementing smooth bearing surfaces on the shaft and on the pinion. Once in position, the pinion is shrunk, that is to say mounted by force, on the shaft and the contact between the two components is defined by these bearing surfaces smooth around the entire circumference of the shaft, over the entire axial dimension of the pinion. The rotational drive, and therefore the power transmission, takes place between the shaft and the corresponding pinion by these smooth bearings so that the fit is very tight. A second assembly technique consists of using grooves, both on the internal surface of the pinion and on the shaft, at least on the area of reception of the pinion. The splines interacting with each other participate in the power transmission and the shrink fit, or force fit, is done on the top of the splines of either the pinion or the shaft. The shrink fit on the splines is done continuously over the entire axial dimension of the pinion. As mentioned above, either assembly operation requires an additional machining operation to grind the pinion, so as to prevent the shrink fit from having a detrimental impact on the quality of the pinion teeth. Indeed, the precision of the machining of the pinions and compliance with the theoretical dimensions in the gear has a direct impact on the acoustic and mechanical performance of the vehicle. Grinding the pinion teeth generates chips. When the pinions 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 from subsequently affecting the mechanical operation of the vehicle, to clean the housing before connecting it to the rotor shaft. The chips can be cleaned and do not risk getting lodged in the electric motor and in particular in the bearings that guide the rotor shaft attached to the electric motor. However, the present invention is part of a context of reducing the size of the motor-reducer 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 motor-reducer assembly, with a fixed pinion directly assembled on the motor output shaft, and in which the quality of the toothed surface of the fixed pinion is of the level of quality which can be obtained after a machining grinding operation. The main subject of the present invention is therefore 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 for assembling the fixed pinion to the motor output shaft, the assembly means comprising splines and at least one smooth bearing surface arranged successively along the motor output shaft, the fixed pinion being shrunk onto at least one smooth bearing surface of the motor output shaft. The motor-reducer 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 output of the motor, the assembly means being particular to avoid having to carry out a grinding operation. machining after assembly. The fixed pinion directly mounted on the engine output shaft allows the function of the engine shaft and the primary shaft to be merged, thus generating 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 large shrinking areas allowing the centering of the pinion around the engine output shaft, while ensuring good power transmission through the cooperation of the splines.In this way, the stresses on the materials generated by this force assembly can be reduced, and since the centering is short, it is possible to locate these stresses on the axial dimension of the pinion, for example in areas which do not impact the quality of the teeth of the fixed pinion and therefore do not impact the efficiency and quality, for example sound, 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 shrunk onto the shaft, for example by offsetting them axially relative to the toothing zones of the fixed pinion intended to be in contact with a driven pinion participating in the power transmission. This makes it possible to ensure that the shrunk has little or no impact on the structure of the fixed pinion in the toothing zones intended to cooperate with a driven pinion and therefore that the step of grinding the pinion, responsible for the creation of chips and risking hindering the mechanical operation of the motor-reducer assembly, can be avoided. According to an optional characteristic of the invention, the engine output shaft comprises two smooth bearing surfaces arranged on either side of the splines. The presence of two smooth bearings has the advantage of increasing the surface area covered by the smooth bearings, and therefore of increasing the extent of the centering to ensure that the coaxial position of the fixed pinion relative to the motor shaft is correct, and the arrangement of these two smooth bearings on either side of the splines makes it possible to maintain a spline zone in which the fixed pinion is not shrunk onto the shaft and therefore in which the assembly operation does not generate forces on the pinion. According to an optional feature of the invention, the motor output shaft comprises a first smooth bearing surface having a first external diameter and a second smooth bearing surface 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 bearing surfaces offset axially relative to each other, which makes it possible to ensure that the fixed pinion can cooperate simultaneously with each of the smooth bearing surfaces of the motor output shaft during its axial fitting around the shaft. According to an optional feature of the invention, the motor output shaft has a free end opposite the motor, the first smooth bearing surface is located on the motor side while the second smooth bearing surface is located in the vicinity of the free end. The different external diameters of these smooth bearing surfaces 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 pinion on the motor output shaft, the fixed pinion correspondingly having at least two zones whose internal diameter is different. According to an optional characteristic of the invention, the fixed pinion is an annular part of which an internal surface has grooves and an external surface of which forms a toothing. According to an optional feature of the invention, the splines of the internal surface of the fixed pinion extend over the entire axial dimension of the fixed pinion 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 pinion are on the one hand configured, in shapes and dimensions, to interact with the splines formed on the motor output shaft, by being interposed between each other. In this way, the rotation of the motor output shaft can be transmitted to the fixed pinion, by tangential cooperation of the splines of the two components. On the other hand, the splines of the fixed pinion are dimensioned to be in tight contact, that is to say force-fitted, with respect to the smooth surfaces of the motor output shaft. According to an optional feature of the invention, the cooperation of the splines of the internal surface of the fixed pinion with the assembly means formed on the motor output shaft defines a receiving zone of the fixed pinion on the motor output shaft. The receiving zone has an axial dimension substantially equal to the axial dimension of the fixed pinion and substantially equal to the sum of the axial dimensions of the smooth bearing surfaces and the splines formed on the motor output shaft. According to an optional feature of the invention, the inner surface of the fixed pinion is configured to form stepped splines. In other words, along the axial dimension of the fixed pinion, the inner diameter of the inner surface, i.e. the inner diameter measured between two diametrically opposite spline peaks, takes at least two different values. According to an optional characteristic of the invention, the fixed pinion comprises, successively considering an axial direction of the fixed pinion, a first lateral part, intended to be in the vicinity of a free end of the motor output shaft when the fixed pinion is assembled on the motor output shaft and having a first internal diameter, a central part, as well as a second lateral 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 of values ​​slightly smaller than the corresponding value of the external diameter 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 lateral part of the fixed pinion, of a first internal diameter, is opposite the first smooth bearing surface of the motor output shaft, the first external diameter of which is slightly larger than the first internal diameter so as to generate a shrink fit during assembly. And similarly, when the fixed pinion is assembled on the motor output shaft, the second lateral part of the fixed pinion, of a second internal diameter, is opposite the second smooth bearing surface of the motor output shaft, the second external diameter of which is slightly larger than the second internal diameter so as to also generate a shrink fit during assembly, thus increasing the extent of centering of the fixed pinion.. According to an optional feature of the invention, the internal diameter of the central part of the fixed pinion is of a value equal to the value of the first diameter or of a value equal to the value of the second diameter. There is thus continuity between the central part and one of the lateral parts at the level of the internal diameter of the fixed pinion, 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 a characteristic 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 means arranged in the vicinity of the free end of the motor output shaft. The axial stop wall and the stop means are intended to precisely center the fixed pinion on the motor output shaft, and to ensure that the receiving zone is axially positioned on the motor output shaft as intended. 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 may be formed by a shoulder of the motor output shaft and / or by a face of a bearing opposite the fixed pinion. The stop means may comprise an elastic ring arranged in a groove formed for this purpose in the motor output shaft, and being sufficiently thick to axially block the fixed pinion in a direction opposite the axial stop wall. According to an optional characteristic of the invention, the external surface of the fixed pinion forming a toothing is intended to be engaged with the external surface of cor- corresponding to a driven pinion to be able to transmit the rotation of the engine output shaft, i.e. the primary shaft, to a secondary shaft with a defined gear ratio. As a non-limiting example, the fixed pinion has helical teeth of a given pitch and depth and the driven pinion has corresponding helical teeth. According to an optional characteristic 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 is engaged with the driven pinion, the zone of cooperation of the teeth defining a functional zone. It is understood that the teeth of the fixed driving pinion and the driven pinion make it possible to form a gear train, generating the reduction of the rotational speed 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 pinion. 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 feature of the invention, the functional zone is formed by the central part of the fixed pinion, the lateral parts of the fixed pinion forming parts arranged on either side of this functional zone. It is notable that these two lateral parts of the fixed pinion are intended to cooperate, at the level of the internal surface of the fixed pinion, respectively with one of the two smooth bearing surfaces of the motor output shaft. In this way, the mechanical stresses during assembly by shrink fitting are localized on the lateral parts of the fixed pinion and therefore in areas of the teeth which do not participate in defining the functional zone. According to an optional feature of the invention, the first lateral part and the second lateral part of the fixed pinion have an external diameter equal to the external diameter of the central part. In other words, the teeth of the fixed pinion have a uniform thickness over the entire axial dimension of the fixed pinion, both for the central part defining the functional zone in engagement with the driven pinion and for the lateral parts. The uniform thickness of the fixed pinion allows in particular simplified heat treatment of the fixed pinion, for example by quenching, before its assembly on the motor output shaft. According to an optional feature of the invention, the motor-reducer assembly comprises a lubrication circuit comprising at least one axial duct formed by an internal bore of the motor output shaft and a radial duct formed in the thickness of the motor output shaft, said radial duct opening at one end onto the axial duct 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, that it has grooves or smooth bearing surfaces, and the grooved internal surface of the fixed pinion. These axial channels extend to the axial ends of the fixed pinion. The fixed pinion has at least on its axial end face facing away from the motor, i.e. on the side of the free end of the motor output shaft, notches allowing the evacuation of a lubricant circulating in the axial channels, while this axial end face is in abutment against an axial stop means which also prevents the flow of the lubricant. Such a lubrication circuit initially allows the lubricant present in the engine to be evacuated. It is configured, by the arrangement of the axial and radial ducts within the shaft and by the presence of the notches on the fixed pinion at the end of the axial channels, to use the lubricant to be evacuated and pass it to the interface between the fixed pinion and the engine output shaft, in particular to evacuate any dirt that may have slipped in there, 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.1] schematically and partially illustrates a motor-reducer assembly according to the invention, this figure notably showing a fixed pinion assembled on a motor output shaft and its cooperation with a driven pinion of this motor-reducer assembly; [Fig.2] illustrates, in perspective and partially, a motor-reducer assembly according to an embodiment of the invention, this figure notably making visible the fixed pinion and the motor output shaft; [Fig.3] illustrates, in perspective, the gable of [Fig.2]; [Fig.4] is a sectional view of the pinion of [Fig.3], showing in particular two portions of splines of different diameters; [Fig.5] illustrates, in perspective, the engine output shaft of [Fig.2]; [Fig.6] is a sectional view of the engine output shaft of [Fig.5], notably showing hybrid assembly means with two smooth bearing surfaces of different diameters arranged on either side of splines; [Fig.7] illustrates, schematically in section, the motor-reducer assembly of [Fig.2] to make the assembly means between the motor output shaft and the pinion particularly visible. The features, variants and different embodiments of the invention may be combined with each other, in various combinations, provided that they are not incompatible or mutually exclusive. In particular, variants of the invention may be imagined which do not include than a selection of features described subsequently in isolation from the other features described, if this selection of features is sufficient to confer a technical advantage and / or to differentiate the invention from the state of the prior art. In the figures, elements common to several figures retain the same reference. In the foregoing and in the detailed description that 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 to and intersecting this axis of rotation. As a reminder, the invention relates to a motor-reducer assembly 1 which comprises a motor output shaft 2 and a fixed pinion 4 directly fixed to the motor output shaft 2 according to a hybrid assembly method, with assembly means which comprise both means for transmitting rotational torque by splines and means for fixing and centering by shrinking on a smooth bearing 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 [Fig. 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 mutually parallel shafts and the interaction of which participates in the transmission of power. In [Fig. 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 pinions may be present without departing from the context of the invention. The motor-reducer assembly 1 according to the invention has a reduced size insofar as the fixed pinion which transmits the output torque of the motor to the set of pinions is directly fixed on the motor output shaft, as can be seen in [Fig. 1] in particular, by 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 motor-reducer assembly 1, the fixed pinion 4 and the motor output shaft 2 are assembled so as to form a unitary assembly in rotation around a common axis, directly at the output of the motor. The fixed pinion 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 one end of the output shaft called the motor end 16, as can be seen in particular in Figures 2 and 7. 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 the side of the motor end 16, here formed by the bearing 12, and by a stop 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 stop 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 pinion during the transmission of power, the elastic ring 22 being mounted in a groove 24 formed for this purpose in the engine output shaft 2. The axial stop 18 and the stop means 20 are thus two elements which participate in forming a device for positioning the fixed pinion, the objective of which is to position the fixed pinion 4 precisely on the engine output shaft 2, in a so-called receiving zone visible in [Fig.7]. We will now describe the structure of the fixed pinion in more detail, particularly with reference to figures 2 to 4. The fixed pinion 4 is an annular part, around an axis of revolution, an internal surface of which has grooves 26 and the external surface of which forms a toothing 28, here helical. It is sought to assemble the fixed pinion on the engine output shaft in such a way that the axis of revolution coincides with the axis of revolution of the engine 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 assembly of the fixed pinion on the engine output shaft has been carried out. The first lateral part 30, intended to be in the vicinity of the motor end of the motor output shaft when the fixed pinion is assembled on the motor output shaft, has the function of cooperating with a first smooth bearing surface 36 formed on the motor output shaft 2 in the vicinity of this motor end 16 to participate in the centering by shrinking of the fixed pinion 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 cooperating with a second smooth bearing surface 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 pinion on the motor shaft. It is understood that it is the internal surfaces of these lateral parts 30, 34 of the fixed pinion which are operational and which cooperate with other elements, here the smooth bearing surfaces of the engine output shaft. Finally, the central part 32 arranged between the two lateral parts 30, 34 has a dual function. At the level of the internal surface of the fixed pinion 4, its function is to cooperate with splines present on the engine output shaft, in particular to transmit the rotational torques and ensure that the fixed pinion is integral in rotation with the engine output shaft. At the level of the external surface of the fixed pinion 4, and therefore of the toothing 28, its function is to cooperate with the toothing of the driven pinion 8 integral with the secondary shaft 10, so that the transmission of power from the fixed pinion to the driven pinion takes place at the level of the central part 32 in an area defined as a functional area 38. It is notable in [Fig. 1] and in [Fig. 7] that the axial dimension of the driven pinion 8 is smaller than that of the toothing 28 of the fixed pinion 4, so that the functional area defined by the central part 32 of the fixed pinion 4 does not extend over the entire axial dimension of the fixed pinion 4. The grooves 26 of the internal surface of the fixed pinion 4 extend over substantially the entire axial dimension of the fixed pinion 4 and as can be seen in Figures 3 and 4, on each of the lateral and central parts previously defined. In order to allow the fixed pinion to be mounted along the motor output shaft and to ensure centering by shrinking simultaneously on the two smooth bearing surfaces via the corresponding lateral part of the pinion, the internal surface of each lateral part 30, 34 is configured such that these lateral parts have internal diameters of different values, with the first lateral part 30 having a first internal diameter Di1 and the second lateral part 34 having a second internal diameter Di2, the first internal diameter Di1 having a value greater than the value of the second internal diameter Di2. The splines 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 splines 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 splines 26, with a shoulder 40 which is created on the internal surface of the fixed pinion between the central part 32 and one of the lateral parts, here the second lateral part 34.It should be noted that the difference between the values ​​of two internal diameters is minimal, 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 hooping being carried out, in order to be able to position the first lateral part opposite the first smooth surface and the second lateral part opposite the second smooth surface. The toothing 28 of the fixed pinion has 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 toothing 28 whose dimension radial, defined by the outer diameter of each of the parts, is the same as the other parts of the toothing. The lateral parts of the toothing thus have a thickness identical to that of the central part of the toothing, even if these lateral parts are not intended to be engaged with the driven pinion 8 and do not participate in forming the functional zone 38 previously mentioned. This homogeneous thickness is interesting insofar as it makes it possible to facilitate the heat treatment operations of the fixed pinion, for example by quenching. The two lateral parts 30, 34 of the fixed pinion, which each have a toothing part not included in the functional zone 38 and therefore exempt from the stresses generated by the contact of the driven pinion during the transmission of torque, are located at right angles to the smooth bearing surfaces 36, 37 of the motor output shaft 2 as they will be described in more detail below, in particular with reference to FIGS. 5 and 6. In a complementary manner, the central part 32 of the fixed pinion, which forms the functional zone 38 for the transmission of torque with the driven pinion and which must in fact precisely respect the theoretical dimensions of the teeth, here helical, is located in line with the splines 42 of the engine output shaft as they will be described in more detail below, in particular with reference to figures 5 and 6. The deformations undergone by the fixed pinion during shrinking are thus concentrated on the lateral parts 30, 34 of the fixed pinion 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 provide an operation for grinding the teeth after assembly. The fixed pinion 4 also comprises several lubrication notches 44, participating in a lubrication circuit formed in the engine output shaft and between the latter and the fixed pinion. 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 stop means 20 against the fixed pinion, which could prevent the flow of the oil. We will now describe, in particular with reference to figures 5 and 6, the engine output shaft 2. As mentioned, the motor-reducer assembly 1 is particular in that the fixed pinion is mounted on the motor output shaft by means of a hybrid assembly method. In this context of the invention, the motor output shaft comprises assembly means comprising at least one smooth bearing surface and splines 42. The at least one smooth bearing surface allows the pinion to be force-fitted and makes it possible to locate the stress zones due to this force-fitting and the presence of the splines makes it possible to distribute the torque transmission forces over the entire axial dimension of the fixed pinion which comprises splines of complementary shapes and dimensions. In the example illustrated, the assembly means comprise two smooth bearing surfaces 36, 37, arranged on either side of the splines 42. This increases the axial dimension on which the fixed pinion is centered by shrinking on the motor output shaft and thus ensures long centering, without generating stresses due to shrinking over the entire axial dimension of the fixed pinion. As mentioned previously, this makes it possible to provide a zone, here central, in which the stresses 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 fixed pinion arranged at right angles to this zone. It is notable in the figures that each of the smooth bearing surfaces is distant from the grooves 42, separated by a clearance portion 45. A first smooth bearing surface 36 of the motor output shaft 2 is located on the motor side, and more particularly in the vicinity of the motor end 16 of the motor output shaft 2. This first smooth bearing surface 36 has a first external diameter Del. A second smooth bearing surface 37 is located in the vicinity of the free end 14 of the motor output shaft. This second smooth bearing surface 37 has a second external diameter De2, of a 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, the fixed pinion 4 to slide along the motor output shaft 2 to the pinion receiving zone, with the first lateral part 30 of the fixed pinion which is opposite the first smooth bearing surface 36 and the second lateral part 34 of the fixed pinion which is opposite the second smooth bearing surface 37, the second external diameter De2 of the second smooth bearing surface 37 is of a value slightly lower than the value of the first internal diameter Dil of the first lateral part 30. In order to allow hooping in this position, the first external diameter Del of the first smooth bearing surface 36 is also of a value slightly greater than the value of the first internal diameter Di1 of the first lateral part 30 and the second external diameter De2 of the second smooth bearing surface 37 is of a value slightly greater than the value of the second internal diameter Di2 of the second lateral part 34. The engine output shaft 2 comprises elements participating in forming the lubrication circuit previously mentioned. The lubrication circuit thus comprises an axial duct 46 defined by a bore within the engine output shaft and through which lubricant arrives from the engine. It also comprises a radial duct 48, formed by a bore passing through the engine output shaft from the axial duct 46 to the external surface of the engine pinion. In the example illustrated, the axial duct 46 opens substantially in the center of the portion having 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 pinion 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 pinion 4 previously mentioned. We will now describe the mounting of the fixed pinion on the engine output shaft, in particular to illustrate the advantage of the presence of hybrid assembly means such as those just presented, with splines and smooth bearing surfaces present on the engine output shaft 2 and stepped splines present on the fixed pinion, of different diameters. The fixed pinion 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 pinion is then pushed so as to slide around the motor output shaft, with the first lateral part 30 of the fixed pinion 4 which engages opposite the second smooth bearing surface 37. As previously specified, the first lateral part 30 of the fixed pinion 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 surface 37, which makes it possible not to cause the fixed pinion to rub against the second smooth bearing surface.The splines 26 present on the internal surface of the fixed pinion then engage between the splines 42 present on the motor output shaft and the movement of the fixed pinion is done without friction until the second lateral part 34 of the fixed pinion arrives opposite the second smooth part 37 of the motor output shaft 2. Simultaneously, the first lateral part 30 of the fixed pinion 4 arrives opposite the first smooth bearing surface 36 of the motor output shaft 2, located on the side of the motor end 16.The staggering of the splines on the internal surface of the fixed pinion is such that the pinion must be force-fitted 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 having a value slightly less 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 surface of second external diameter De2, with the second internal diameter Di2 having a value slightly less than the value of the second external diameter De2. This force-fitting continues until the fixed pinion reaches the position illustrated in [Fig.7] in abutment on the axial abutment wall 18, and it generates a shrink fit and two centering zones of the fixed pinion on the motor output shaft 2.These two centering zones being arranged at each end of the pinion reception zone as defined previously, a long centering of the fixed pinion is thus achieved. The elastic ring 22 participating in forming the stop means 20 is then mounted in the groove 24 in order to axially block the fixed pinion 4 between the two stop points forming the centering system which are the axial stop 18 and the stop means 20. As has been previously specified, it is notable that during this assembly operation, the two lateral parts 30, 34 of the fixed pinion 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 just described, the present invention achieves the aims it has set itself, namely to ensure that it is not necessary to carry out machining rework on a fixed pinion toothing force-mounted directly on a motor output shaft, by providing a hybrid assembly system for the fixed pinion on the motor output shaft which implements both centering means by shrinking and torque transmission means by splines. The motor-reducer assembly according to the invention thus allows a saving in 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

Claims

1. Geared motor assembly (1) for electric vehicle characterized in cc that it comprises at least one motor output shaft (2) and a fixed pinion (4) reported on said engine output shaft (2), the assembly having means for assembling the fixed pinion (4) to the motor output shaft (2), the assembly means comprising grooves (42) and at less a smooth span (36, 37), arranged successively along the motor output shaft (2), the fixed pinion (4) being shrunk on at least a smooth bearing (36, 37) of the motor output shaft (2).

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

3. Geared motor assembly (1) according to any one of the claims previous, in which the motor output shaft (2) comprises a first smooth bearing (36) having a first external diameter (Del) and a second smooth bearing (37) having a second diameter external (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 claims previous, in which the fixed pinion (4) successively comprises in considering an axial direction of the fixed pinion (4), a first part lateral (30) intended to be in the vicinity of a free end (14) of the motor output shaft (2) when the fixed pinion (4) is assembled on the engine 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 (Di1).

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

6. Geared motor assembly (1) according to the preceding claim, in which the inner surface of the fixed pinion (4) is configured to form stepped grooves (26).

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

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

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

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