Electric motor

Abstract

The invention relates to an electric motor, having a rotor shaft (4), a floating bearing (1) and an end shield (3), wherein the floating bearing (1) is provided for rotatably mounting the rotor shaft (4), wherein the floating bearing (1) has an inner ring and an outer ring, wherein the outer ring of the floating bearing is received in a bearing seat formed in the end shield (3), wherein the inner ring is fitted onto the rotor shaft (4), wherein a spring disc (2) is arranged in the axial direction between the outer ring and the end shield, wherein the spring disc (2) has a coating at least on first and second surface regions.

Description

[0001] electric motor

[0002] Description:

[0003] The invention relates to an electric motor.

[0004] It is generally known that at least two bearings, in particular rolling bearings, are used to support a shaft.

[0005] From DE 20 2007 009 954 U1, an electric motor is known as the closest state of the art.

[0006] EP 2 902 648 A1 discloses a bearing arrangement for an electric motor with an axially preloaded ball bearing.

[0007] An electric motor is known from DE 10 2011 119 603 A1.

[0008] A torsional vibration damper with friction coefficient adjustment is known from DE 10 2020 120 389 A1.

[0009] From DE 10 2019 207 290 A1 a friction brake body for a friction brake of a motor vehicle is known.

[0010] EP 1 711 642 B1 discloses an iron-containing layer of a sliding surface applied by thermal spraying.

[0011] A regulated powder welding process is known from DE 10 2018 130 798 A1.

[0012] From DE 10 2020 006 831 A1 an electric motor with fan cover and relative to the

[0013] Fan cover with rotatably mounted rotor shaft and angle sensor known.

[0014] An electric motor is known from DE 10 2008 028 607 A1. The invention is therefore based on the object of further developing an electric motor, whereby the operation of the electric motor is to be carried out as safely as possible.

[0015] According to the invention, the object is achieved in the electric motor according to the features specified in claim 1.

[0016] Important features of the invention in the electric motor are that the electric motor has a rotor shaft, a floating bearing and a bearing shield, wherein the floating bearing is provided for the rotatable mounting of the rotor shaft, wherein the floating bearing has an inner ring and an outer ring, in particular wherein rolling elements are arranged between the inner ring and the outer ring, wherein the outer ring of the floating bearing is received in a bearing receptacle formed, in particular molded, in the bearing shield, in particular a cup-shaped bearing receptacle and / or blind hole, wherein the inner ring is placed on the rotor shaft, wherein a spring washer is arranged in the axial direction between the outer ring and the bearing shield, in particular the bottom of the bearing receptacle, wherein the spring washer has a coating at least on first and second surface areas or is roughened by sandblasting or laser-structured,in particular with elevations that extend further in the radial direction than in the circumferential direction.

[0017] The advantage of this design is that safe operation is ensured because the outer ring of the floating bearing is prevented from rotating or slipping. On the one hand, the outer ring of the floating bearing is arranged so that it can be axially displaced, so that thermally induced axial length changes of the shaft are tolerable. On the other hand, circumferential rotation of the outer ring is prevented by the rotationally fixed connection of the outer ring to the bearing support of the bearing shield. Although the spring washer is axially deflected by the thermally induced axial length changes, the spring washer prevents the outer ring from rotating in the circumferential direction.This is achieved through the increased adhesion or friction that can be brought about by means of the coatings and / or roughening, particularly in comparison to an uncoated spring washer made from sheet steel and housed in the steel bearing seat, with the outer ring also being made of steel. Thus, even a simple rubber coating of the spring washer can achieve high adhesion between the spring washer and bearing shield, as well as between the spring washer and outer ring. However, if adhesive is used as a coating at the contact points between the spring washer and bearing shield, and between the spring washer and outer ring, a particularly rotationally rigid connection can be achieved, thus preventing the outer ring from spinning or rotating.

[0018] In particular, the first surface regions are spaced apart from one another in the circumferential direction, and the second surface regions are spaced apart from one another in the circumferential direction. The first surface regions are arranged axially on the front side of the spring washer, and the second surface regions are arranged axially on the rear side of the spring washer. This is advantageous because the spring washer achieves increased static friction at its contact areas in the front and rear axial directions.

[0019] In particular, the spring washer can also be described as a spring wave washer because it is designed as an annular perforated washer whose peripheral edge runs in a wave-like manner in the axial direction. As the circumferential angle increases, the axial position of the spring washer fluctuates. This means that the axial position of the spring washer is a periodic function of the circumferential angle.

[0020] Instead of coating, roughening the surface is also possible, particularly by sandblasting or laser structuring. With the latter, it is advantageous to create elongated structures in the microscale in the radial direction so that static friction prevents the spring washer or the outer ring of the floating bearing from rotating as effectively as possible. In an advantageous design, the spring washer rests against both the bearing plate, particularly the base of the bearing housing, and the outer ring. This provides increased adhesion and thus resistance to rotation.

[0021] In an advantageous embodiment, the axial position of the spring washer, in particular the axial position of the mean value of the area covered by the spring washer in the axial direction, is a periodic, in particular non-vanishing, function of the circumferential angular position. Advantageously, the spring washer periodically oscillates back and forth in the circumferential direction as the circumferential angle increases in the axial direction. Thus, the installation of the spring washer between the outer ring and the bearing mount causes an elastic deflection of the spring washer, which thus sets or generates the bearing tension. The ring axis, in particular the central axis of the spring washer, is aligned parallel to the axial direction.

[0022] In an advantageous embodiment, the outer ring is accommodated in the bearing mount with an interference fit. The advantage here is that in the event of thermally induced length changes of the rotor shaft, the floating bearing, in particular the outer ring of the floating bearing, can be moved in the axial direction. It is important that the static friction is kept correspondingly low. This can be achieved by designing the bearing mount with a sufficiently widened design so that the outer ring can be accommodated with a transition fit, with the transition fit being tolerated in such a way that the floating bearing can be moved axially in the event of thermally induced length changes. However, in order to prevent the outer ring from rotating in the circumferential direction relative to the axis of rotation of the rotor shaft with this widened bearing mount, the coatings of the spring washer are selected such that the outer ring is connected in a rotationally fixed manner to the bearing shield via the spring washer, particularly in the bearing mount.

[0023] In an advantageous embodiment, the outer ring is accommodated in the bearing mount with such a precise fit that the static friction moment generated by the operative connection of the outer ring accommodated in the bearing mount with the bearing shield is smaller than any static friction moment generated by the operative connection of the spring washer with the outer ring and than any static friction moment generated by the operative connection of the spring washer with the bearing shield. The advantage here is that, on the one hand, a rotationally fixed, materially connected and / or force-fit connection between the outer ring and the bearing shield is achieved by means of the spring washer, but, on the other hand, axial displacement of the floating bearing is possible without force or with only minimal force.

[0024] In an advantageous embodiment, the coating is an adhesive, a rubber coating, and / or a plastic layer. The advantage here is that a force-locking and / or material-locking, non-rotatable connection between the outer ring and the bearing plate can be achieved by means of the spring washer.

[0025] In an advantageous embodiment, the first surface areas coated are those areas of the spring washer that are the farthest from the outer ring. This is advantageous because only minimal material expenditure is required, since only the contact areas between the spring washer and the outer ring and between the spring washer and the bearing plate need to be coated.

[0026] In an advantageous embodiment, the second surface areas coated are those areas of the spring washer that are closest to the outer ring, in particular those that contact the outer ring. This is advantageous because only minimal material expenditure is required, since only the contact areas between the spring washer and the outer ring and between the spring washer and the bearing plate need to be coated.

[0027] In an advantageous embodiment, the spring washer is made of a steel sheet to which the coatings are applied. This is advantageous because it provides a high modulus of elasticity. This allows the spring washer to be manufactured cost-effectively and generates a high spring force even with a small axial deflection.

[0028] In an advantageous embodiment, the outer ring is arranged so as to be axially displaceable, in particular in the bearing mount, and / or the outer ring is connected to the bearing shield in a rotationally fixed manner by means of the spring washer. The advantage here is that, in the event of thermally induced length changes of the rotor shaft, the floating bearing is arranged so as to be axially displaceable, although it is connected to the bearing shield in a rotationally fixed manner, in particular by a material fit and / or force fit. In an advantageous embodiment, the spring washer contacts both the outer ring and the bearing shield. The advantage here is that the bearing tension is provided by means of the spring washer, and in addition, the coating provides the rotationally fixed connection between the outer ring and the bearing shield.

[0029] In an advantageous embodiment, the bearing shield is connected to a stator housing of the electric motor, wherein a bearing flange is connected to the stator housing on the side of the stator housing axially facing away from the bearing shield, wherein an outer ring of a fixed bearing is received in the bearing flange, the inner ring of which is placed on the rotor shaft, in particular wherein the inner ring of the fixed bearing is positioned against a shaft step and is axially delimited by a retaining ring which is arranged in an annular groove of the rotor shaft, in particular wherein the outer ring of the fixed bearing axially bears on the one hand against the base of the bearing receptacle of the bearing flange and axially is positioned against a retaining ring arranged in an annular groove of the rotor shaft. The advantage here is that the stator housing causes thermally induced length changes, in particular in the axial direction, by means of power loss of the stator winding.Depending on the material and geometry, these can vary depending on the length change of the rotor shaft. To compensate, the floating bearing is arranged so that it can be moved axially.

[0030] In an advantageous embodiment, the rotor shaft extends through a recess in the bearing plate, and a fan is connected to the rotor shaft in a rotationally fixed manner on the side of the bearing plate axially remote from the floating bearing. To seal the recess, a shaft seal is accommodated in the bearing plate, in particular in the recess of the bearing plate, and seals against the rotor shaft, in particular by a sealing lip of the shaft seal contacting the rotor shaft. This is advantageous because the bearing plate can be cooled by the air flow conveyed by the fan, thus reducing length changes.

[0031] In an advantageous embodiment, the rotor shaft protrudes through a bore extending through the bearing flange, with an additional shaft seal being accommodated in the bore on the side of the fixed bearing axially remote from the floating bearing and sealing against the rotor shaft, in particular by a sealing lip of the additional shaft seal contacting the rotor shaft. The advantage here is that the shaft seal accommodated in the bearing shield and the shaft seal accommodated in the bearing flange together seal the interior of the electric motor from the environment, thus preventing dirt or dust from penetrating the bearing mount, which could impede or prevent the floating bearing from moving.

[0032] In an advantageous embodiment, a stator core with a stator winding is housed in the stator housing, and a squirrel cage is mounted on the rotor shaft and connected in a rotationally fixed manner. This is advantageous because the stator housing and the rotor shaft can be exposed to varying degrees of heat loss depending on the operating state of the motor. The resulting length changes can be compensated for by the spring washer according to the invention.

[0033] Further advantages emerge from the dependent claims. The invention is not limited to the combination of features in the claims. Further possible combinations of claims and / or individual claim features and / or features of the description and / or the figures will become apparent to those skilled in the art, particularly from the problem and / or the problem posed by comparison with the prior art. The invention will now be explained in more detail with reference to schematic illustrations:

[0034] Figure 1 shows an electric motor according to the invention in a sectional view.

[0035] Figure 2 shows an exploded oblique view of a bearing plate 3 with a spring washer 2 and a loose bearing 1 of the electric motor.

[0036] Figure 3 shows an oblique view of the spring washer 2.

[0037] Figure 4 shows a side view of the spring washer 2.

[0038] As shown in the figures, the electric motor has a stator housing 9, which is connected at its first axial end region to a bearing plate 3 and at its other axial end region to a bearing flange 8. The stator housing 9 is thus arranged axially between the bearing flange 8 and the bearing plate 3.

[0039] A fixed bearing 7 is housed in the bearing shield 3, the inner ring of which is mounted on a rotor shaft 4 of the electric motor and positioned against a shaft stage of the rotor shaft 4. The outer ring of the fixed bearing 7 is housed in a bearing recess formed on the bearing flange 8 and is axially limited by a retaining ring arranged in an annular groove of the bearing flange 8. A further retaining ring arranged in an annular groove of the rotor shaft 4 limits the inner ring of the fixed bearing. The fixed bearing is thus axially fixed. Thermally induced expansion of the rotor shaft 4 must therefore be compensated by a floating bearing 1.

[0040] The outer ring of the floating bearing 1 is accommodated in the bearing shield 3. The inner ring of the floating bearing 1 is placed on the rotor shaft 4 and, on its side facing the fixed bearing, is positioned against a shaft step formed on the rotor shaft 4.

[0041] A spring washer 2 is arranged on the side of the floating bearing 1 facing away from the fixed bearing 7. In particular, the spring washer 2 is arranged axially between the bottom of the bearing seat and the outer ring of the floating bearing 1. The spring washer 2, in particular a wave washer or even an elastically deformable and / or resilient wave washer, is designed as an annular perforated washer whose ring axis is aligned coaxially with the axis of rotation of the rotor shaft 4 and whose edge region runs in a wave-like manner in the circumferential direction, in particular with the wave amplitude varying in the axial direction. In particular, the wave amplitude or the axial position of the spring washer 2 fluctuates with increasing circumferential angle. This means in particular that the axial position of the spring washer 2 runs as a periodic function of the circumferential angle.

[0042] When installed in the electric motor, the spring washer 2 generates the bearing tension and is elastically deformed, in particular pre-tensioned.

[0043] For this purpose, the spring washer 2 is produced as a deformed stamped sheet metal part, in particular as an annular sheet steel body, in particular wherein the perforated disk punched out of sheet metal is bent in such a wavy manner as a bent part that, with reference to the axis of rotation of the rotor shaft 4, the axial position of the spring washer 2 is a periodic function as a function of the circumferential angular position. The period length in the circumferential direction is preferably 360° / N, where N is a natural number, in particular greater than two. The spring washer therefore has N maxima in the axial direction and N minima in the axial direction on the circumference, in particular wherein the maxima press against the outer ring of the loose bearing 1 in an elastically preloaded manner and touch this, and wherein the minima press against the bearing plate 3 in an elastically preloaded manner and touch this.

[0044] The axis of rotation of the rotor shaft 4 is thus aligned coaxially with the ring axis of the spring washer 2, which is designed as a wavy perforated disc.

[0045] The sheet thickness, especially the wall thickness, of the spring washer 2 is constant everywhere.

[0046] At those points of the spring washer 2 which have the greatest distance from the outer ring of the floating bearing 1, in particular at the minima, the spring washer 2 has adhesive 30 on its side facing away from the floating bearing 1. At those points of the spring washer 2 which have the smallest distance from the outer ring of the floating bearing 1, in particular at the maxima, the spring washer 2 has adhesive 40 on its side facing the floating bearing 1.

[0047] In this way, a material connection is created between the spring washer 2 and the outer ring of the floating bearing 1 and between the spring washer 2 and the bearing plate 3. This prevents the spring washer 2 from rotating or the outer ring of the floating bearing 1 from rotating.

[0048] In this case, the bearing mount is also designed with a transition fit, so that the outer ring is accommodated in the bearing mount with only minimal static friction. This allows for axial displacement of the outer ring of the floating bearing 1 during thermal expansion of the rotor shaft 4 without the outer ring being dragged along. This is because, although the elastic preload changes during axial displacement, bearing tension is still provided by the spring washer 2.

[0049] The static friction torque, which is provided by means of the transition fit in the bearing seat for the outer ring of the floating bearing 1 to prevent co-rotation in the circumferential direction, is smaller than the critical torque, at the exceedance of which the adhesive connection between the spring washer 2 and the bearing plate 3 and / or the adhesive connection between the spring washer 2 and the outer ring of the floating bearing 1 fails.

[0050] A fan 5 is non-rotatably connected to the rotor shaft 4 on the side of the bearing plate 3 axially facing away from the fixed bearing 7. This enables efficient passive cooling.

[0051] A fan cover 6 surrounds the fan 5 and is connected to the bearing plate 3.

[0052] A stator 10, in particular a stator laminated core with stator winding, is accommodated in the stator housing 9.

[0053] In further embodiments according to the invention, a rubber coating or another coating is used instead of the adhesive, which generates sufficient static friction in operative connection with the material of the bearing plate or with the material of the outer ring of the floating bearing 1. The static friction moment, which is provided by means of the transition fit in the bearing holder for the outer ring of the floating bearing 1 to prevent co-rotation in the circumferential direction, is smaller than the maximum static friction moment that can be provided by the friction partners, i.e. spring washer 2, bearing plate 3 and / or outer ring of the floating bearing 1, in particular in the circumferential direction.

[0054] In further embodiments of the invention, a carbide layer applied by means of HS-LMD is used instead of the adhesive.

[0055] In further embodiments according to the invention, the surface is roughened instead of the coating or adhesive. Either sandblasting or laser structuring can be used for this. While sandblasting can be carried out cost-effectively, laser structuring also enables the creation of depressions and elevations that extend further in the radial direction than in the circumferential direction, instead of isotropic elevations in the micro range to increase static friction. Since the depressions and elevations created by the laser extend further in the radial direction than in the circumferential direction, a high static friction moment can be generated, i.e., a relative rotational movement of the spring washer 2 relative to the respective friction partner, in particular the bearing plate 3 or the outer ring of the floating bearing 1.

[0056] In further development, one of the above-mentioned coatings can be applied to the roughened surface.

[0057] List of reference symbols

[0058] 1 Floating bearing 2 Spring washer

[0059] 3 bearing plate

[0060] 4 Rotor shaft

[0061] 5 fans

[0062] 6 Fan cover 7 Fixed bearing

[0063] 8 Bearing flange

[0064] 9 Stator housing

[0065] 10 Stator, in particular stator core with stator winding

[0066] 30 Adhesive 40 Adhesive

Claims

Patent claims:

1. An electric motor comprising a rotor shaft, a floating bearing, and a bearing shield, the floating bearing being provided for rotatably supporting the rotor shaft, the floating bearing having an inner ring and an outer ring, in particular rolling elements being arranged between the inner ring and the outer ring, the outer ring of the floating bearing being received in a bearing receptacle formed, in particular molded, in the bearing shield, in particular a cup-shaped bearing receptacle and / or blind hole, the inner ring being placed onto the rotor shaft, characterized in that a spring washer, in particular a resilient wave washer, is arranged in the axial direction between the outer ring and the bearing shield, in particular the bottom of the bearing receptacle, the spring washer having a coating at least on the first and second surface areas, or being roughened by sandblasting or laser-structured,in particular with elevations that extend further in the radial direction than in the circumferential direction, in particular wherein the first surface regions are spaced apart from one another in the circumferential direction and wherein the second surface regions are spaced apart from one another in the circumferential direction., 2. Electric motor according to claim 1, characterized in that the spring washer rests both on the bearing plate, in particular on the bottom of the bearing holder, and on the outer ring.

3. Electric motor according to one of the preceding claims, characterized in that the axial position of the spring washer, in particular the axial position of the mean value of the area covered by the spring washer in the axial direction, is a periodic, in particular non-vanishing, function of the circumferential angular position.

4. Electric motor according to one of the preceding claims, characterized in that the outer ring is received in the bearing holder with an overfit.

5. Electric motor according to one of the preceding claims, characterized in that the outer ring is accommodated in the bearing receptacle with such a precise fit that the static friction moment which is generated in the operative connection of the outer ring accommodated in the bearing receptacle with the bearing plate is smaller than any static friction moment or the static friction moment which can be generated by means of the operative connection of the spring washer with the outer ring and than any static friction moment or the static friction moment which can be generated by means of the operative connection of the spring washer with the bearing plate.

6. Electric motor according to one of the preceding claims, characterized in that the coating is an adhesive, a rubber coating and / or a plastic layer or that the coating has a metallic layer or that the coating has a carbide layer, in particular a metal-carbide layer, in particular wherein the carbide layer, in particular a metal-carbide layer, is applied to a surface of the spring washer that is roughened in particular by means of a laser and / or wherein the carbide layer, in particular a metal-carbide layer, is applied to the spring washer by means of a high-speed laser deposition welding process (HS-LMD).

7. Electric motor according to one of the preceding claims, characterized in that the first surface areas provided with the coating are those areas of the spring washer which have the greatest distance from the outer ring.

8. Electric motor according to one of the preceding claims, characterized in that the second surface areas provided with the coating are those areas of the spring washer which have the smallest distance from the outer ring, in particular which touch the outer ring.

9. Electric motor according to one of the preceding claims, characterized in that the spring washer is made of a steel sheet to which the coatings are applied.

10. Electric motor according to one of the preceding claims, characterized in that the outer ring is arranged to be displaceable in the axial direction, in particular in the bearing receptacle, and / or that the outer ring is connected to the bearing plate by means of the spring washer in a rotationally fixed manner.

11. Electric motor according to one of the preceding claims, characterized in that the spring washer contacts both the outer ring and the bearing plate.

12. Electric motor according to one of the preceding claims, characterized in that the bearing shield is connected to a stator housing of the electric motor, wherein on the side of the stator housing axially facing away from the bearing shield, a bearing flange is connected to the stator housing, wherein an outer ring of a fixed bearing is received in the bearing flange, the inner ring of which is placed on the rotor shaft, in particular wherein the inner ring of the fixed bearing is positioned against a shaft step and is axially delimited by a retaining ring which is arranged in an annular groove of the rotor shaft, in particular wherein the outer ring of the fixed bearing axially bears on the one hand against the base of the bearing receptacle of the bearing flange and axially on the other hand is positioned against a retaining ring arranged in an annular groove of the rotor shaft.

13. Electric motor according to one of the preceding claims, characterized in that the rotor shaft projects through a recess in the bearing plate and a fan is connected in a rotationally fixed manner to the rotor shaft on the side of the bearing plate axially remote from the floating bearing, wherein, for sealing the recess, a shaft sealing ring is accommodated in the bearing plate, in particular in the recess of the bearing plate, and seals towards the rotor shaft, in particular in that a sealing lip of the shaft sealing ring touches the rotor shaft.

14. Electric motor according to one of the preceding claims, characterized in that the rotor shaft projects through a bore through the bearing flange, wherein a further shaft sealing ring is received in the bore on the side of the fixed bearing axially facing away from the movable bearing and seals towards the rotor shaft, in particular in that a sealing lip of the further shaft sealing ring touches the rotor shaft.

15. Electric motor according to one of the preceding claims, characterized in that a stator core with stator winding is accommodated in the stator housing and a squirrel cage is plugged onto the rotor shaft and connected in a rotationally fixed manner.

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