WO2022111747A1

WO2022111747A1 - Rolling bearing

Info

Publication number: WO2022111747A1
Application number: PCT/DE2021/100802
Authority: WO
Inventors: Manfred Tietz; Norbert Metten; Paul WITTMANN; Eckhard RUSCHITZKA; Klaus PICHL
Original assignee: Schaeffler Technologies AG & Co. KG
Priority date: 2020-11-24
Filing date: 2021-10-06
Publication date: 2022-06-02
Also published as: DE102020131018A1

Abstract

The invention relates to a rolling bearing comprising an outer ring (2), an inner ring (4) and rolling elements (7) rolling on raceways (3, 5) provided on the outer and inner rings (2, 4), wherein the outer circumference of the outer ring (2) or the inner circumference of the inner ring (4) is coated with an insulating layer (8) made of a thermosetting resin (9) is provided on, the surface (11) of which is machined by grinding in order to adjust the roundness of the outer or inner ring (2, 4) and a predetermined diameter of the outer or inner ring (2, 4).

Description

roller bearing

The invention relates to a roller bearing, comprising an outer ring, an inner ring and rolling elements arranged in between and rolling on raceways provided on the outer and inner rings.

Such rolling bearings are used in a wide variety of areas. One example is the use in electric motors, which are also used in a wide variety of cases, increasingly in the automotive sector, for example, as drives for partially electric or fully electric ferry operations. Among other things, roller bearings are used for the rotary bearing of the rotor, which usually rotates at a high speed, which is why high-speed bearings are usually used, so-called high-speed motor bearings (HSMB). When operating electric motors, bearing damage can sometimes occur due to current flowing through the roller bearing. Such a passage of current results, for example, from circular currents in the electric motor. As a result of the passage of current, lightning discharges can occur within the rolling bearing, which can damage the raceways on which the rolling elements, which can be balls or rollers or similar, roll. In extreme cases, the damage can be so serious that the bearing fails. In order to avoid the passage of current, it is known to equip the roller bearing with an insulation level, so that no current passage is possible due to this electrical insulation. It is known to design the rolling bearings as ceramic bodies, mostly ceramic balls, which means that the rolling bodies themselves form the insulation level. Alternatively, it is also known to cover one of the rings with an oxide ceramic layer, which also has an insulating effect. These Lageraus guides are very complex and expensive to manufacture.

The invention is therefore based on the problem of specifying a roller bearing that is improved in comparison.

To solve this problem, a roller bearing of the type mentioned is characterized in that the outer ring on the outer circumference or the inner ring on the inner circumference is covered with an insulating layer made of a thermoset, the surface of which Setting the roundness of the outer or inner ring and a predetermined diameter of the outer or inner ring is machined by grinding.

In the roller bearing according to the invention, an insulating layer made of a duroplast, ie a plastic, is used, which is applied, preferably sprayed, either to the outer circumference of the outer ring or to the inner circumference of the inner ring. This insulating layer has sufficient electrical insulating properties so that it can reliably prevent the passage of current through the roller bearing. A suitable resin can be used as the thermoset, for example an epoxy resin or a formaldehyde resin or materials based on this.

The surface of the applied insulating layer is machined or machined by grinding. The insulating layer is processed in such a way that the outer circumference or the inner circumference of the insulating layer and thus the outer circumference of the bearing or the inner circumference of the bearing has the best possible roundness, apart from minimal tolerances. The outer or inner diameter of the applied insulating layer and thus of the outer or inner ring or the outer or inner bearing diameter is also set with high precision by grinding.

According to the invention, roundness is defined as a deviation of the shape of the mechanically machined surface from an ideal cylindrical shape in any radial planes perpendicular to the axis of rotation of the roller bearing. The roundness therefore stands for the deviation of the outer contour (in the case of an outer ring) and the inner contour (in the case of an inner ring) from an ideal cylindrical shape. From the cylindrical shape deviating geometries are considered polyhedron-shaped, oval or wave-shaped geometries in cross-section in any perpendicular pierced by the axis of rotation of the Wälzla gers radial planes of the rolling bearing.

Furthermore, the deviation of the shape in any given radial plane should be within the limits of a defined ring surface, the outside and inside diameter of which are the permissible limits within which a permissible shape deviation may be due. The permissible deviations from the cylindrical or circular Round shape are therefore based on the outer diameter (outer ring with coating on the outside) or inner diameter (inner ring with coating on the inside) in any radial plane within the limits of a ring surface. The inner diameter of this ring surface specifies the inner tolerance limit for roundness and corresponds to the smallest permissible outer diameter tolerance of the outer ring with coating. The outer diameter of this ring surface is determined by the maximum permissible value of the diameter tolerance of the outer ring with the outer coating. Within these limits, the outer contour of the outer ring with the insulating layer may deviate from the purely cylindrical or circular shape. The same applies to an insulating layer on the inner ring, in which case the values are based on the smallest and largest inner diameter of the inner coating of the inner ring. The roundness should be less than or equal to 0.006 mm.

Ultimately, this mechanical grinding process means that the finished roller bearing on the side provided with the insulating layer has a roundness and diameter accuracy like a normal bearing of this size, for example a bearing that has been used up to now and has, for example, ceramic rolling elements or the oxide ceramic coating. This means that the rolling bearing according to the invention or the duroplastic insulating layer is processed in such a way that the bearing dimensions correspond exactly to those of the bearing used previously, so that easy replacement is possible and no adjustments need to be made to the end shield or the bearing mount on the component to be stored. With the dimensions defined by the machined insulating layer, the roller bearing according to the invention is therefore exactly the same as the dimensions of the bearing used previously and has tolerances in terms of roundness and diameter that correspond to those of the original bearing.

Compared to insulating roller bearings, such as those previously used for such applications, for example in particular within an electric motor and there in particular for rotor mounting, the roller bearing according to the invention is significantly simpler to manufacture, since no insulating ceramic means have to be provided to form the insulation level. Instead, an insulating duroplastic material is used, which can be applied in a simple manner, for example by spraying that can be suitably machined to produce the required dimensions and that exhibits the required mechanical properties.

It is conceivable to apply the insulating layer only to the outer circumference of the outer ring or the inner circumference of the inner ring. However, it is also expedient to apply the insulating layer to both end faces of the outer or inner ring at least in sections, with the coated outer or inner ring being narrower than the uncoated inner or outer ring, but not necessarily so. The insulating layer on the end faces can be mechanically processed by grinding in such a way that the width of the coated outer or inner ring essentially corresponds to that of the uncoated inner or outer ring, but this is not mandatory, especially if a different width is required due to the space available . The coated outer or inner ring, based on its outer or inner diameter, must be designed differently compared to another uncoated ring, since the insulating layer is applied as described, which has a thickness in the range of 0.5-1.5 mm, for example having. In order to avoid current passage via the end faces, this variant of the invention now provides for the insulating layer to also extend to the two end faces. In this case, the width of the respective outer or inner ring can then also be reduced in comparison to an uncoated ring, in order to then also machine the width of the coated outer or inner ring by grinding in accordance with the uncoated ring, if this is required is. However, the ring widths including the coating can also differ in width.

As described, the grinding is carried out in such a way that the corresponding dimensions correspond to those of a comparison bearing with uncoated rings, also with regard to the tolerance range. In the bearing according to the invention, the tolerance of the diameter of the insulating layer of the coated outer or inner ring should be between -0.005 mm and -0.015 mm, in particular -0.01 mm, based on a predetermined target diameter. With regard to the fact that the bearing has the best possible roundness and a diameter that is as exact as possible, minimum tolerances are defined here, since this also means that the running accuracy of the bearing raceway of the coated outer ring to the outer diameter of the outer ring or the bearing raceway of the coated inner ring to the inner diameter of the inner - is defined around. The high-precision grinding according to the invention makes it possible, please include the tolerances of the dimensions in relation to the outer or inner diameter and the roundness to be realized in such a way as they are given in a comparable, but for example non-insulated bearing or high-speed bearing.

The tolerance of the width of the coated outer or inner ring should be between -0.05 mm and -0.15 mm, in particular -0.12 mm, in relation to a predetermined target width. Here, too, grinding is carried out with sufficient accuracy, but the tolerance requirements are not as strict as with regard to the diameter and thus the roundness.

Furthermore, it is expedient to provide at least one circumferential annular groove, which is filled with the insulating layer, on the coated outer circumference or on the coated inner circumference of the outer or inner ring. The insulating layer therefore engages in the ring groove, which is also used to anchor it to the respective bearing ring, on the one hand by enlarging the interface between the ring and the insulating layer and on the other hand by the fact that there is a form-fitting bond.

The insulating layer is expediently sprayed on, so it can be easily applied with a suitable spray tool and, after curing, can be sanded accordingly. A fiber-reinforced thermoset, in particular a glass-fiber-reinforced thermoset, is preferably used in order to adjust the mechanical properties of the insulating layer or to adapt it to the requirements.

The roller bearing itself is expediently a high-speed bearing, as is used in electric motors. However, it can also be a standard bearing, since it is used in a flow-critical area but is exposed to lower speeds.

In addition to the roller bearing itself, the invention relates to the use of a roller bearing of the type described above. Such a roller bearing can preferably be used as a bearing for a rotating component of an electric motor, in particular as a rotor bearing. In this case, it serves as a high-speed bearing or HSMB bearing. but Another use, such as use as a bearing for a rotating construction part of a transmission, is also conceivable.

The invention also relates to a method for producing an outer or inner ring covered with an insulating layer for a roller bearing of the type described above. Accordingly, an insulating layer made of a possibly fiber-reinforced thermoset is applied to the outer circumference of the outer ring or the inner circumference of the inner ring applied, in particular sprayed on, which is mechanically processed by grinding on the surface to set the roundness of the outer or inner ring and a predetermined diam sers of the outer or inner ring.

It is conceivable to also apply the insulating layer to the two end faces of the outer or inner ring at least in sections, the insulating layer also being ground to a predetermined value on the end faces to adjust the width of the outer or inner ring.

The surface is expediently ground in such a way that the tolerance of the diameter of the coated outer or inner ring is between -0.005 mm and -0.015 mm, in particular -0.01 mm, based on a predetermined target diameter. This means that there is almost complete roundness, since the diameter tolerance is extremely small. The tolerance of the width of the coated outer or inner ring should be between -0.05 mm and -0.15 mm, in particular - 0.12 mm in relation to a predetermined target width.

The invention is explained below using exemplary embodiments with reference to the drawings. The drawings are schematic representations and show:

Figure 1 is a schematic representation of a roller bearing according to the invention of a first embodiment, in section,

Figure 2 is a schematic representation of a rolling bearing according to the invention of a second embodiment, in a sectional partial view, and FIG. 3 shows a schematic diagram of a third embodiment of a roller bearing according to the invention, in a sectional partial view.

Figure 1 shows a rolling bearing 1 according to the invention, comprising an outer ring 2 with a raceway 3 and an inner ring 4 with a raceway 5, and with a rim comprising a plurality of rolling elements 7 held in a cage 6, here in the form of balls, which are on the raceways 3, 5 roll. The roller bearing 1 is, for example, a high-speed bearing, as can be used, for example, to mount a rotor of an electric machine. Such a bearing can be made without seals, as shown, in the case of an oil-lubricated application. Alternatively, the bearing can also be filled with grease and also closed axially on both sides via seals, for which purpose corresponding measurements on the rings are provided for the annular seals.

On the inner circumference of the inner ring 4, an insulating layer 8 made of a thermoset 9, preferably reinforced with glass fibers, is applied, preferably sprayed on. The inner diameter of the inner ring 4 is slightly increased for this purpose compared to a bearing or inner ring that can be used for the same purpose. The insulating layer 8 it stretches not only over the inner lateral surface, but also over the two end faces 10 and overlaps them partially.

After application, the insulating layer 8 is machined on its surface 11, 12 on the inner circumference and on the end faces by grinding. The surface 11 on the inner circumference is processed in such a way that the insulating layer 8 has the best possible roundness (preferably less than or equal to 0.006 mm), which means that the inner diameter has a minimum tolerance in the range between -0.005 mm and -0.015 mm be around -0.01 mm. The machining is extremely precise, so that it is ensured that the inner diameter of this roller bearing 1 according to the invention, provided with the insulating layer 8, corresponds to the inner diameter of a comparable high-speed bearing that can be replaced identically for the intended purpose and has an uncoated inner ring, so that the roller bearing according to the invention 1 can be used in exchange for the previously used roller bearing that has no or an integrated insulating level of whatever type. The surface 12 on the end faces is also ground accordingly in order to adapt the width of the inner ring 4 together with the insulating layer 8 to the width of the outer ring 2, as is clearly shown in FIG. There are no extremely tight tolerances to be observed here, as with the processing of the surface 11, but the tolerance in relation to the width should be between -0.05 mm and -0.15 mm in relation to a predetermined target width, which ultimately depends on the width of the Outer ring 2 is specified amount.

The thickness of the insulating layer 8 is dimensioned in such a way that the roller bearing is given the best possible current insulation against the passage of current, while at the same time the inner diameter of the metal inner ring 10 or its width is increased as little as possible. At the same time, the high-precision grinding with the lowest possible roughness, in particular of the inner peripheral surface 11 as a whole, serves to ensure the high running accuracy of the raceway 5 of the inner ring 4 with respect to the inner diameter of the inner ring.

The thermoset is one with sufficient electrical insulation properties. It can be, for example, an epoxy resin or a formaldehyde resin, for example phenol-formaldehyde resin or melamine-formaldehyde resin. The duroplast is preferably fiber-reinforced, for which glass fibers are suitable, but carbon fibers are also possible.

FIG. 2 shows a sectional partial view of a roller bearing 1 according to the invention in a second embodiment, with comparable components having the same reference numbers. An outer ring 2 , an inner ring 4 and rolling elements 7 , which are guided in a cage 6 , are also provided here.

Here, too, an insulating layer 8 made of a duroplastic 9 is applied to the inner circumference of the inner ring 4 . This insulating layer 8 extends from the inner circumference to the end faces 10 of the inner ring 4 and occupies them in sections. In the same way as in the similar embodiment according to FIG. 1, the surface of the insulating layer 8 is also ground accordingly to set the required dimensions in connection with the given tolerances. In contrast to the configuration according to FIG. 1, the inner ring 4 has an annular groove 13 on its inner circumference, which is filled with the insulating layer 8 or the thermoplast 9 . This achieves an even better anchoring of the insulating layer 8 on the one hand due to the larger contact surface and on the other hand due to the shape circuit.

The configuration according to FIG. 3 shows a roller bearing 1 according to the invention, again with an outer ring 2, an inner ring 4 and rolling elements 7 rolling in between and guided in a cage 6. In this configuration, the insulating layer 8 is made of the preferably fiber-reinforced duroplast 9 on the outer circumference of the outer ring 2 brought up. This is slightly reduced in its outer diameter, as well as in width, so that the insulating layer 8 can be applied. The insulating layer 8 again stretches slightly over the end faces 14 of the outer ring 1.

A circumferential annular groove 15 is also formed on the outer ring 1, which, similar to the exemplary embodiment according to FIG.

Here, too, the surface 16 on the outer circumference of the insulating layer 8 and the surface 17 on the end faces are mechanically reworked by grinding. The surface 16 on the outer circumference is in turn ground with high precision in order to ensure the best possible roundness of the outer circumference or of the coated outer ring 2, while at the same time having a minimum tolerance in the outer diameter. The surfaces 17 are ground in such a way that the width of the coated outer ring 2 also corresponds to the width of the inner ring 3 here.

What all the configurations have in common is that the geometry and dimensions of the coated outer ring 2 or the coated inner ring 3 correspond exactly to an uncoated outer or inner ring of a roller bearing, which can be used in the same place, i.e. for the same purpose, and that has no insulating coating on any of its rings. Because the roller bearing according to the invention makes it possible to be able to be mounted instead of a previously installed roller bearing, ie instead of a roller bearing whose outer ring has no outer coating or whose inner ring has no inner coating. That is, a simpler Exchange is possible without having to make any changes either to the bearing plate on which the roller bearing 1 is mounted with its outer ring or on the rotatably mounted construction, for example the rotor on which the roller bearing 1 is mounted via its inner ring. Instead, there is a high degree of accuracy of fit due to the high-precision grinding provided according to the invention.

List of reference symbols Roller bearing Outer ring Raceway Inner ring Raceway Cage Rolling body Insulating layer Duroplast Face surface Surface Ring groove Face surface Ring groove surface Surface

Claims

patent claims

1. Rolling bearing comprising an outer ring (2), an inner ring (4) and rolling elements (7) arranged therebetween and rolling on the outer and inner rings (2, 4) provided raceways (3, 5), characterized in that the The outer ring (2) on the outer circumference or the inner ring (4) on the inner circumference is covered with an insulating layer (8) made of a duroplast (9), the surface (11) of which is used to adjust the roundness of the outer or inner ring (2, 4) and a predetermined diameter of the outer or inner ring (2, 4) is machined mechanically by grinding.

2. Rolling bearing according to claim 1, characterized in that the roundness is defined as a deviation of the shape of the machined surface from an ideal cylindrical shape in any radial planes perpendicular to the axis of rotation of the rolling bearing.

3. Rolling bearing according to claim 2, characterized in that the deviation of the form in any radial plane within the limits of a defined annular surface, the outer and inner diameter of which are the permissible limits within which a permissible form deviation may move, is.

4. Rolling bearing according to one of the preceding claims, characterized in that the tolerance of the diameter of the coated outer or inner ring (2, 4) is between - 0.005 mm and - 0.015 mm, in particular - 0.01 mm, based on a predetermined target diameter, amounts to.

5. Rolling bearing according to one of the preceding claims, characterized in that the insulating layer (8) also overlaps the two end faces (10, 14) of the outer or inner ring (2, 4) at least in sections.

6. Rolling bearing according to one of the preceding claims, characterized in that the insulating layer (8) is sprayed on and/or consists of a fiber-reinforced, in particular glass-fiber-reinforced, duroplast (9).

7. Rolling bearing according to one of the preceding claims, characterized in that at least one circumferential annular groove (13, 15) which is filled with the insulating layer (8) is provided on the coated outer circumference or on the coated inner circumference.

8. A method for producing an outer or inner ring covered with an insulating layer (2, 4) for a roller bearing (1) according to any one of claims 1 to 6, characterized in that on the outer circumference of the outer ring (2) or the inner circumference of the inner ring (4), an insulating layer (8) made of an optionally fibre-reinforced duroplastic (9) is applied, in particular sprayed on, which is applied on the surface to adjust the roundness of the outer or inner ring (2, 4) and a predetermined diameter of the outer or inner ring (2, 4) is mechanically processed by grinding.

9. The method according to claim 8, characterized in that the insulating layer (8) and the two end faces (10, 14) of the outer or inner ring (2, 4) is applied at least in sections across, the insulating layer (8) also on the end faces (101, 14) to adjust the width of the outer or inner ring (2, 4) is ground to a predetermined value.

10. The method according to claim 8 or 9, characterized in that the Oberflä surface (11, 12, 16, 17) is ground in such a way that the tolerance of the diameter of the coated outer or inner ring (2, 4) is between - 0.005 mm and - 0.015 mm, in particular - 0.01 mm, based on a predetermined target diameter, and if necessary the tolerance of the width of the coated outer or inner ring (2, 4) between - 0.05 mm and - 0.15 mm, in particular - 0 .12 mm, with respect to a predetermined target width.