Geared motor and associated assembly process

Abstract

Geared motor and associated assembly method. The present invention relates to a geared motor (1), particularly for a vehicle wiper device, comprising: - an electric motor (3) configured to drive a transmission shaft (4) of the geared motor (1), - a reducer (5) comprising: - a worm gear (7) rotationally fixed to the transmission shaft (4), - a toothed wheel (9) configured to mesh with the worm gear (7), wherein the geared motor (1) also comprises a guide bearing (110, 111) for the transmission shaft (4) and a frame (1a) receiving the reducer (5), said frame (1a) comprising a housing (20) receiving said guide bearing (110, 111), said guide bearing (110, 111) comprising an outer ring (110b, 111b) contacting a wall of the housing (20), said housing (20) comprising a bead of retention (22) of said outer ring (110b, 111b) of the guide bearing (110, 111),said retaining bead (22) being obtained by laser melting of the wall of the housing of the frame (1a). Figure for the abbreviation: Figure 8,

Description

Title of the invention: Geared motor and associated assembly method

[0001] The present invention falls within the field of geared motors combining an electric motor and a reducer and in particular geared motors used in wiping devices of motor vehicles to drive the wiper blades.

[0002] The present invention relates more particularly to geared motors whose reducer is provided with a worm screw arranged on a transmission shaft driven by the electric motor and a toothed wheel meshing with the worm screw.

[0003] Such geared motors comprise a stator, which in some versions is made from a stack of blades, sometimes called sheets. These blades are necessarily made from a specific steel, in order to obtain the magnetic properties necessary for the proper functioning of the electric motor.

[0004] It is known to mount the stator of the electric motor by force in the motor casing, or to fix it by gluing, because it is necessary to fix the stator in its housing in a solid and consistent manner. These fixing methods are not ideal: the first can lead to the formation of metal shavings which require a cleaning operation, and the second can reduce the thermal conductivity between the stator and the casing.

[0005] Such geared motors also comprise transmission shaft guide bearings for radially guiding the transmission shaft. Such guide bearings are, for example, made of ball bearings.

[0006] However, the gearing of the toothed wheel on the worm screw also causes high axial stresses on the transmission shaft and therefore on the bearings, for example axial forces greater than 1000N, so that the ball bearings must be held axially in position to allow the reducer to withstand such forces.

[0007] For this, the internal part of the bearing must be held axially relative to the transmission shaft on the one hand and the external part of the bearing must be held axially relative to a fixed element of the reducer such as a frame on the other hand.

[0008] Furthermore, in order to obtain good axial guidance, it is necessary to limit as much as possible the deformation of the bearings which would lead to an imbalance of the transmission shaft which could create an unbalance and therefore be detrimental to the operation of the geared motor. To this end, it is necessary to limit the thermal stresses which could produce a deformation of the bearing such as the stresses induced by arc welding (the melting temperature of the steel being 1700°C).

[0009] To overcome this problem and avoid thermal stresses on the bearings, it is known to use retaining rings, also called circlips, arranged in grooves provided on the transmission shaft to axially maintain the bearing relative to the transmission shaft. The axial maintenance of the external part of the bearing can be achieved by a cover of the frame comprising shims coming into axial contact with the periphery of the external part of the bearing.

[0010] However, these solutions can be difficult or expensive to implement (need to bore the transmission shaft and reduced tolerances on the frame to obtain good positioning of the shims) and also tend to increase the axial size of the geared motor.

[0011] Furthermore, whether it is the stator or the rolling bearings, it is impossible to fix them in their respective housings by a conventional welding process, given the difference in composition (steel versus aluminum) between these two components and the motor casing.

[0012] It is therefore appropriate to resolve these problems at least partially and provide a simple and space-saving solution making it possible to obtain axial support of the bearings relative to the transmission shaft on the one hand and relative to the frame on the other hand.

[0013] Similarly, it is also an object of the present invention to provide a simple and space-saving solution for obtaining axial support of the stator in its housing in the electric motor.

[0014] To this end, the present invention relates to a geared motor, in particular for a motor vehicle wiping device, comprising: - an electric motor comprising a stator, a stator housing receiving said stator, and a rotor, the electric motor being configured to rotate a transmission shaft secured to the rotor of the geared motor, and a reducer comprising: - a worm screw rotating with the transmission shaft, -a toothed wheel configured to mesh with the worm screw, at least one guide bearing of the transmission shaft, said at least one guide bearing comprising an outer ring coming into contact with a wall of a bearing housing, and a frame receiving the reducer, said frame comprising a housing receiving said guide bearing, said guide bearing comprising an outer ring coming into contact with a wall of the housing.

[0015] According to the invention, at least one of said housings comprises a retaining bead retaining the corresponding guide bearing or stator in its housing and being obtained by laser melting of the wall of the housing of the frame.

[0016] The use of a retaining bead obtained by laser fusion makes it possible to maintain the bearing axially relative to the frame without the need for additional part(s) or adaptation of the frame.

[0017] According to another aspect of the present invention, the stator and / or the outer ring of the guide bearing is made of steel and the wall of the housing of the frame and / or the housing of the stator is made of aluminum.

[0018] According to another aspect of the present invention, the retaining bead is continuous around the circumference of the stator and / or the outer ring of the guide bearing.

[0019] According to another aspect of the present invention, the retaining bead is produced only on portions of the circumference of the stator of the outer ring of the guide bearing.

[0020] According to another aspect of the present invention, the geared motor comprises a plurality of guide bearings and the frame comprises a plurality of housings respectively receiving the plurality of guide bearings and in which said guide bearings comprise an outer ring coming into contact with a wall of their respective housings, said respective housings comprising a retaining bead for said outer ring of the guide bearing, said retaining bead being obtained by laser melting of the wall of the housing of the frame.

[0021] According to another aspect of the present invention, the guide bearing also comprises an inner ring welded to the transmission shaft by laser fusion located at the interface between the inner ring and the transmission shaft.

[0022] According to another aspect of the present invention, the inner ring and the transmission shaft are made of steel.

[0023] According to another aspect of the present invention, the weld is continuous around the circumference of the transmission shaft.

[0024] According to another aspect of the present invention, the welding is carried out only on portions of the circumference of the transmission shaft.

[0025] The present invention also relates to a method of assembling a geared motor as described above, comprising a step of positioning the stator and / or the guide bearing in a respective housing provided in the geared motor, and a step of forming a retaining bead for the stator and / or an outer ring of the bearing by laser melting the wall of the respective housing.

[0026] According to another aspect of the present invention, the retaining bead is continuous around the periphery of the stator and / or the outer ring of the bearing.

[0027] According to another aspect of the present invention, the laser is a continuous wave diode laser.

[0028] According to another aspect of the present invention, the laser has a power of between 200W and 500W.

[0029] Other characteristics and advantages of the invention will appear more clearly on reading the following description, given by way of illustrative and non-limiting example, and the appended drawings among which:

[0030] [Fig-1] represents a schematic view of a geared motor;

[0031] [Fig.2] represents a schematic view of a wiping device for a vehicle at car;

[0032] [Fig.3] represents a partial schematic perspective view of a ball bearing;

[0033] [Fig.4] represents a partial schematic perspective view of a roller bearing

[0034] [Fig.5] represents a schematic perspective view of a transmission shaft and a bearing;

[0035] [Fig.6] represents a flowchart of the steps of a method of assembling a bearing on a transmission shaft;

[0036] [Fig.7] represents a schematic perspective view of a frame of a geared motor;

[0037] [Fig.8] represents a schematic view of a housing of the frame of [Fig.6] and of a rolling;

[0038] [Fig.9] represents a flowchart of the steps of a method of assembling a bearing in a housing of a frame of a geared motor;

[0039] In these figures, identical elements bear the same references.

[0040] The following embodiments are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment, or that the features apply only to a single embodiment. Single features of different embodiments may also be combined or interchanged to provide other embodiments.

[0041] In particular, although the embodiments described below are oriented towards the installation and fixing of one or more bearings of a brushless direct current electric motor, the application of the invention to the installation and fixing of a stator of an electric motor has also been envisaged in the same way, and without starting from the principle of the invention.

[0042] [Fig.l] represents a diagram of a geared motor 1 comprising an electric motor 3, in particular a brushless direct current motor comprising a stator 3a and a rotor 3b and configured to rotate a transmission shaft 4, also called an intermediate shaft or armature shaft. The transmission shaft 4 is integral in rotation with the rotor 3b of the electric motor 3.

[0043] The geared motor 1 also comprises a reducer 5 produced by a worm screw 7 integral in rotation with the transmission shaft 4. The worm screw 7 is for example provided directly on the transmission shaft 4, for example via a boring process.

[0044] The reducer 5 also comprises a toothed wheel 9 configured to mesh with the worm screw 7. The assembly comprising the worm screw 7 and the toothed wheel 9 is configured to produce a predetermined reduction ratio. An output shaft of the reducer 5 is for example integral in rotation with the toothed wheel 9.

[0045] The geared motor 1 also comprises guide bearings 11 for the transmission shaft 4, made for example by ball bearings. In [Fig.l], the guide bearings 11 are two in number and are arranged on either side of the worm screw 7, but a different number of guide bearings 11 and / or a different positioning of the guide bearings 11 is also possible. The different guide bearings 11 may also have different technologies. For example, one of the guide bearings 11 may be made by a ball bearing, while the other guide bearing 11 may be made by a sleeve-shaped plain bearing.

[0046] The geared motor 1 is for example part of a motor vehicle wiping device 10. [Fig. 2] represents a diagram of such a wiping device 10. The wiping device 10 comprises in particular a linkage 11 connected to the output of the geared motor 1 and configured to drive the wiping arms 13 carrying the wiping blades 15 in a back-and-forth movement.

[0047] The geared motor 1 is for example arranged in a frame or casing ensuring the protection of the reducer 5.

[0048] The guide bearings 11 are configured to ensure the axial guidance of the transmission shaft 4 relative to the frame 1a but also to absorb the axial forces produced by the gearing between the toothed wheel 9 and the worm screw 7.

[0049] [Fig. 3] represents an exemplary embodiment of a ball bearing 110 comprising an inner ring 110a configured to be positioned around the transmission shaft 4, an outer ring 110b configured to be arranged in a housing of the frame 1a and a plurality of balls 110c interposed between the inner ring 110a and the outer ring 110b.

[0050] In the same way, [Fig. 4] represents an exemplary embodiment of a roller bearing 111 comprising an inner ring 111a configured to be positioned around the transmission shaft 4, an outer ring 111b configured to be arranged in a housing of the frame 1a and a plurality of rollers 111e, for example cylindrical rollers, interposed between the inner ring 11a and the outer ring 111b.

[0051] These two types of bearings can be used as guide bearings 11 within the framework of the present invention.

[0052] [Fig.5] shows a ball bearing 110 arranged around the transmission shaft 4.

[0053] According to one embodiment, the inner ring 110a of the bearing is welded to the transmission shaft 4 by laser fusion located at the interface between the inner ring 110a and the transmission shaft 4. Indeed, the use of a laser fusion method makes it possible to precisely locate the weld at the interface between the inner ring 110a and the transmission shaft 4 and thus limit heating to a reduced area around this interface. Such a method therefore significantly limits the thermal stresses undergone by the inner ring 110a and consequently any deformations of the inner ring 110a or the ball bearing 110, which makes it possible to limit the risks of radial guidance defects of the ball bearing 110 while obtaining a fixing of the inner ring 110a of the bearing 110 on the transmission shaft 4 sufficient to withstand forces greater than 1000N, in particular 3000N.These effects are achieved in the same way with other types of bearings such as 111 roller bearings.

[0054] The welding can be carried out around the entire circumference of the transmission shaft 4 (i.e., around the entire circumference of the inner ring 110a) or only on angular portions of the circumference of the interface between the inner ring 110a and the transmission shaft 4. The laser used is, for example, a continuous laser diode laser and has, for example, a power of between 700W and 1300W, but other types of laser, for example, a fiber pulse laser, and other powers can be used. Furthermore, the welding can be carried out under a nitrogen atmosphere. The welding can be carried out on one side of the inner ring or on both sides.

[0055] The geared motor 1 may comprise a plurality of guide bearings 11 of the transmission shaft 4 and each guide bearing 11 may comprise a bearing 110, 111 whose inner ring 110a, 111a is welded to the transmission shaft 4 by laser fusion. Alternatively, only one or some of the guide bearings 11 may be made by a bearing 110, 111 whose inner ring 110a, 111a is welded to the transmission shaft 4 by laser fusion.

[0056] The present invention also relates to a method of assembling a guide bearing 110, 111 on a transmission shaft 4 of a geared motor 1 in which the transmission shaft 4 is configured to be driven in rotation by an electric motor 3 and comprises a worm screw 7 integral in rotation with the transmission shaft 4 and configured to mesh with a toothed wheel 9 as described previously.

[0057] [Fig.6] represents the different steps of the method of assembling a bearing 110, 111 on a transmission shaft 4. The order of the steps may be different from the proposed order and some of these steps may be optional.

[0058] The first step 101 concerns the positioning of a bearing 110 around the transmission shaft 4. The positioning of the bearing 110, 111 is for example ensured by a radial protrusion of the transmission shaft 4 or a partial bore of the transmission shaft 4 or via external holding means such as a support configured to hold the bearing in position around the transmission shaft. If the manufacturing tolerances of the transmission shaft 4 and the bearing 110, 111 are small, the bearing 110 can also be force-mounted around the transmission shaft 4 and held in position by friction.

[0059] The second step 102 concerns the application of a laser beam to the interface between the inner ring 110a, 111a of the bearing 110, 111 and the transmission shaft 4. The laser beam is for example applied over the entire circumference of the transmission shaft 4 (also corresponding to the circumference of the inner ring 110a, 111a). Alternatively, the beam can be applied only to certain angular portions of the circumference of the transmission shaft, preferably distributed in a balanced manner around the transmission axis (for example three portions whose center is separated by 120° from the centers of the other two portions). The power and speed of movement of the laser beam are chosen so as to obtain a fusion of the adjacent parts of the inner ring 110a, 11a and of the transmission shaft 4 to obtain a weld while limiting as much as possible the heating of the other parts of the inner ring 110a, 11a.The chosen laser is for example a continuous diode laser with a power between 700W and 1300W but other types of laser and / or other powers are also possible. Welding can also be carried out in a nitrogen atmosphere to avoid cracks.

[0060] The third step 103 is an optional step and concerns the polishing of the weld obtained in step 102 in order to obtain a smooth weld.

[0061] Also optionally, steps 102 and 103 may be repeated on the second side of the inner ring 110a, 11a so as to weld the two sides of the inner ring 110a, 11a and obtain an even stronger axial fixing of the bearing 110, 111.

[0062] Thus, the use of laser fusion welding to ensure the axial fixing of the inner ring 110a, 11a of the bearing 110, 111 on the transmission shaft 4 makes it possible to obtain, in a simple manner, a fixing capable of withstanding axial forces greater than 1000N, for example 3000N, while limiting the risk of damage to the bearing 110, 111 due to thermal stresses, unlike arc welding, for example.

[0063] In order to ensure the guidance of the transmission shaft 4, it is also appropriate to ensure the maintenance of the external ring 110b, 111b of the bearings 110, 111 relative to the frame 1a which is a fixed part (relative to the stator 3a of the electric motor 3). For this purpose, the frame 1a comprises a housing 20 configured to receive the bearing 110, 111. The frame 1a is for example made of aluminum. The outer ring 110b, 111b of the bearing 110, 111 is for example made of steel.

[0064] Depending on the configuration of the motor, the stator 3a may be housed in a similar housing (not shown), substantially cylindrical and also included in and forming part of the frame 1a. Alternatively, the housing of the stator 3a may be part of a separate part of the motor housing, subsequently assembled on the frame. In all cases, the stator 3a is inserted into a housing and is fixed in a manner substantially identical to that which will be described subsequently.

[0065] Figures 7 and 8 represent schematic perspective views of a bearing 110 positioned in a housing 20 of the frame 1a of the geared motor 1. The housing 20 has, for example, a cylindrical shape whose internal diameter corresponds (within manufacturing tolerances) to the external diameter of the bearing 110. The bottom of the housing 20 makes it possible to block the external ring 110b of the bearing 110 in a first axial direction.

[0066] The frame 1a also comprises a retaining bead or rim 22 obtained by laser fusion and making it possible to block the axial displacement of the outer ring 110b of the bearing 110 in the second direction (opposite to the first). The retaining bead 22 is obtained by fusion of the wall of the housing 20 adjacent to the outer ring 110b of the bearing 110. This fusion is obtained by laser radiation so as to be localized on the portion of the housing 20 adjacent to the outer ring 110b of the bearing 110. The use of laser fusion makes it possible to limit the heating of the outer ring 110b of the bearing 110 and therefore to limit the thermal stresses on the bearing 110 which could harm its operation.

[0067] The retaining bead 22 is configured to partially cover the lateral part of the outer ring 110b of the bearing 110 and is therefore produced when the bearing 110 is positioned in the housing 20. The thickness of the retaining bead 22 is for example between 1 mm and 3 mm.

[0068] The retaining bead 22 extends for example over the entire periphery of the outer ring 110b as shown in the example of FIGS. 7 and 8. Alternatively, the retaining bead 22 may be provided only on certain angular portions of the circumference of the outer ring 110b. Preferably, the different portions are then distributed regularly over the circumference of the outer ring 110b.

[0069] Such a retaining bead 22 can be produced to ensure the axial retention of the external ring 110b of several bearings 110 ensuring the guidance of the transmission shaft 4.

[0070] The use of a retaining bead 22 obtained by laser fusion thus makes it possible to ensure axial retention of the outer ring 110b of the bearing 110 which can withstand axial forces greater than 1000N, for example 3000N in a simple manner and by limiting the risks of damage to the bearing 110 due to thermal stresses since heating is limited to a restricted zone at the interface between the housing 20 and the outer ring 110b.

[0071] The above discussion focuses on the mounting of one or more guide bearings for a transmission shaft of a geared motor. However, it will soon be recognized that these teachings also apply to the mounting of the stator 3a in its housing (not shown). More specifically, since the stator 3a is conventionally mounted in a housing of generally cylindrical shape, the principle of fixing by the formation of a retaining bead also applies to the retention of the stator 3a in its housing.

[0072] In such a configuration, the retention bead forms an axial stop against which the last blade of the stator. The stator is therefore locked in the mounted position, securely retained in the motor.

[0073] The present invention also relates to a method of assembling a guide bearing 110, 111 of a transmission shaft 4 of a geared motor 1 in a frame 1a of the geared motor 1 as described previously.

[0074] [Fig.9] shows the different steps of this assembly process. The order of the steps may be different from the proposed order and some of these steps may be optional.

[0075] The first step 201 concerns the positioning of the guide bearing 110, 111 in the housing 20 of the frame 1a. The bearing 110, 111 is for example forcibly inserted into the housing 20.

[0076] The second step 202 concerns the production of a retaining bead 22. The retaining bead 22 is obtained by laser melting of the portion of the wall of the housing 20 adjacent to the outer ring 1110b, 111b of the bearing 110, 111.

[0077] The laser used to produce the retaining bead 22 is for example a continuous diode laser whose power is between 200W and 500W, in particular 300W, but other types of laser and / or other powers can be used.

[0078] The retaining bead 22 may be produced over the entire periphery of the outer ring 110b, 111b or only over certain angular portions (in this case, the angular portions are preferably distributed around the circumference of the outer ring 110b, 111b). The laser melting may be accompanied by an application of mechanical stress, for example via an external tool, to obtain the retaining bead 22.

[0079] The present invention also relates to a method of assembling a geared motor comprising the steps of the method of assembling a bearing 110, 111 on a transmission shaft 4 described from [Fig.6] for at least one of the guide bearings 110, 111 and the steps of the method of assembling a bearing guide 110, 111 of a transmission shaft 4 of a geared motor 1 in a frame 1a of the geared motor 1 described from [Fig.9] for at least one of the bearings 110, 111.

[0080] Thus, the use of a retaining bead 22 makes it possible to obtain axial retention of the bearing 110, 111 in its housing and makes it possible to withstand axial forces greater than 1000N, for example 3000N, in a simple manner and by limiting the risks of damage to the bearing 110 due to thermal stresses since heating of the bearing 110, 111 is reduced. In addition, this makes it possible to avoid the use of retaining rings or circlips and therefore to obtain a geared motor 1 having a reduced axial dimension.

[0081] Thus, the axial retention of the inner ring 110a, 111a of the bearing on the transmission shaft 4 via laser fusion welding on the one hand and the axial retention of the outer ring 110b, 111b in a housing 20 of the frame 1a via a retaining bead 22 obtained by laser fusion on the other hand make it possible to obtain a compact geared motor 1 (particularly in its axial dimension) and the assembly process of which is simple with a reduced number of steps and requiring a reduced number of parts (and therefore references) as well.

[0082] Such a geared motor 1, due to its reduced size and its low manufacturing cost, is particularly suitable for use in motor vehicle equipment and in particular in a wiping device for producing, via a linkage, the back-and-forth movement of the wiping arms carrying the wiping blades of the motor vehicle.

Claims

Claims

1. Geared motor (1), in particular for a motor vehicle wiping device, comprising: an electric motor (3) comprising a stator (3a), a stator housing receiving said stator (3b), and a rotor (3b), the electric motor being configured to rotate a transmission shaft (4) secured to the rotor (3b) of the geared motor (1), and a reducer (5) comprising - a worm screw (7) secured in rotation to the transmission shaft (4), - a toothed wheel (9) configured to mesh with the worm screw (7), - at least one guide bearing (110, 111) of the transmission shaft (4), said at least one guide bearing (110, 111) comprising an outer ring (110b, 111b) coming into contact with a wall of a bearing housing (20), and - a frame (la) receiving the reducer (5), said frame (la) comprising a bearing housing (20) receiving said guide bearing (110, 111),characterized in that at least one of said bearing housing (20) and stator housing comprises a retaining bead (22) retaining the corresponding guide bearing or stator in its housing and being obtained by laser melting of the wall of the housing of the frame (la).,

2. Geared motor (1) according to claim 1 wherein the stator (3b) and / or the outer ring (110b, 111b) of the guide bearing (110, 111) is made of steel and the wall of the housing of the frame (la) and / or the housing of the stator (3a) is made of aluminum.

3. Geared motor (1) according to claim 1 or 2 wherein the retaining bead (22) is continuous around the circumference of the stator and / or the outer ring (110b, 111b) of the guide bearing (110, 111).

4. Geared motor (1) according to claim 1 or 2 wherein the retaining bead (22) is produced only on portions of the circumference of the stator and / or of the outer ring (110b, 11a) of the guide bearing (110, 111).

5. Geared motor (1) according to one of the preceding claims comprising a plurality of guide bearings (110, 111) and in which the frame (la) comprises a plurality of housings (20) respectively receiving the plurality of guide bearings (110, 111) and in which said guide bearings (110, 111) comprise a ring external (110b, 111b) coming into contact with a wall of their respective housings (20), each of said respective housings (20) comprising a retaining bead (22) of said external ring (110b, 111b) of the guide bearing (110, 111).

6. A method of assembling a geared motor (1) according to any one of the preceding claims, comprising a step (201) of positioning the stator (3a) and / or the guide bearing (110, 111) in a respective housing (20) provided in the geared motor (1), and a step (202) of forming a retaining bead (22) of the stator and / or an outer ring (110b, 111b) of the bearing (110, 111) by laser melting the wall of the respective housing (20).

7. Assembly method according to the preceding claim in which the retaining bead (22) is formed continuously on the periphery of the stator (3a) and / or of the outer ring (110b, 111b).

8. An assembly method according to claim 10 or 11 wherein the laser is a continuous wave diode laser.

9. An assembly method according to claim 11 wherein the laser has a power of between 200W and 500W.

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