DE102016202108A1 - Rolling bearings for an electric machine - Google Patents

Abstract

The invention relates to a rolling bearing (1) for an electric machine, comprising an inner ring (2), an outer ring (3) and rolling elements (4) arranged radially between the inner ring (2) and the outer ring (3). According to the invention, a burnishing layer (5) for reducing wear and an insulating layer (6) for current insulation are arranged at least partially on the inner ring (2) and / or on the outer ring (3).

Description

The invention relates to a rolling bearing for an electrical machine, comprising an inner ring, an outer ring and arranged radially between the inner ring and the outer ring rolling elements. Thus, the field of application of the invention extends primarily to electrical machines, in particular generators for wind turbines.

The growth of wind turbines to multi-megawatt power plants leads to higher forces and moments, which burden in particular the rolling bearing components more and more. At the same time, downtimes and maintenance work, especially for offshore installations, cause ever higher costs. A phenomenon that adversely affects the reliability of rolling bearings, even outside the wind industry, are the so-called White Etching Cracks (WEC). In addition to bearings for wind turbines, white etching cracks are also found in bearings of other industrial applications, such as electric motors, paper machines, industrial gearboxes for large hydraulic excavators, pump systems or marine propulsion, as well as in the automotive sector.

White etching cracks are structural changes in the material that form below the bearing surface. As a result, cracks develop under the influence of various external stresses, which spread to the surface under stress. This can eventually lead to a rupture of the inner or outer ring and thus to a premature failure of the affected bearing. These cracks occur in both through hardened and case hardened bearings. The causes for the formation of white etching cracks is not yet fully understood. However, according to the current state of knowledge, additional stresses in the form of dynamics, mixed friction and / or electrics form the precondition for the formation of white etching cracks.

The DE 10 2011 006 296 A1 discloses a rolling bearing comprising an outer race, an inner race and rolling elements rolling on raceways of the races. The raceway of the inner and / or outer ring and / or the surface of the rolling elements has a burnishing layer. Further, the inner and / or the outer ring and / or the rolling elements of a steel which has a hardness of at least 58 HRC at least below the burnishing layer. To further reduce cracking, especially to further increase resistance to white etching cracks, alloying elements below the burnishing layer are set as follows. A nitrogen content is at least in the boundary layer 0.03-0.8%, wherein the nitrogen is at least partially dissolved. A carbon content is 0.1-1.2% at least in the surface layer, a nickel content is less than or equal to 0.4%, a silicon content is 0.2-1.0%, a chromium content is less than or equal to 1.0%, a sulfur content is less than or equal to 0.008%, an oxygen content is less than or equal to 15 ppm and a titanium content is less than or equal to 50 ppm.

The object of the invention is to develop a rolling bearing for an electric machine, and in particular to increase the resistance of the rolling bearing against white etching cracks.

According to the invention, a burnishing layer for reducing wear and an insulation layer for current insulation are arranged at least partially on the inner ring and / or on the outer ring. In other words, both layers are respectively arranged on the inner ring or respectively on the outer ring or in each case on the inner and outer ring. The insulating layer is essentially intended to protect the inner ring and / or outer ring from a passage of electricity and additives from the lubricant. Thus, the insulation layer allows not only electrical insulation but also corrosion protection. The burnishing layer, on the other hand, is essentially intended to minimize friction and wear on the inner ring and / or outer ring. Furthermore, the burnishing layer also allows weak corrosion protection.

Preferably, the burnishing layer is formed on an inner peripheral surface of the outer ring and / or on an outer circumferential surface of the inner ring. In particular, the burnishing layer is arranged on a respective raceway of the rolling element on the respective inner ring and / or outer ring. In contrast, the insulating layer is preferably formed on an inner peripheral surface of the inner ring and / or on an outer peripheral surface of the outer ring. In this case, the inner peripheral surface of the inner ring is provided to come to rest on a shaft, wherein the outer peripheral surface of the outer ring is provided to come to a housing to the plant.

According to a preferred embodiment, the inner ring and / or outer ring is completely coated, wherein the inner peripheral surface of the outer ring and / or the outer peripheral surface of the inner ring comprises the burnishing layer, wherein the remaining surface of the inner ring and / or outer ring further comprises the insulating layer. In other words, the entire surface of the inner ring and / or outer ring is completely coated, wherein a part of the surface of the inner ring and / or outer ring is coated with the burnishing layer and the other part of the surface of the inner ring and / or outer ring is coated with the insulating layer. The two layers are not arranged one above the other. The substrate is always the inner ring and / or outer ring.

Preferably, the burnishing layer is formed from iron mixed oxides. In particular, the burnishing layer is a so-called Durotect B mixed iron oxide layer. The name Durotect B is protected by trademark. In contrast, the insulating layer is preferably formed of aluminum oxide. In particular, the insulating layer is a so-called Insutect A ceramic layer of Al ₂ O ₃ . The name Insutect A is protected by trademark.

The burnishing layer is preferably formed by immersing the component in a bath provided for this purpose, the burnishing layer having a layer thickness of 0.5 to 2 μm. Furthermore, the insulation layer is preferably formed by flame spraying, wherein the insulation layer has a layer thickness of 50 to 300 μm.

Furthermore, the invention relates to an electrical machine with a rolling bearing described above. In particular, the electric machine is an electric motor or a generator.

Furthermore, the invention also relates to a method for coating a component, in particular a bearing ring for a previously mentioned rolling bearing, wherein first a burnishing layer and then an insulating layer or first the insulating layer and then the burnishing layer are formed on a surface of the component. Consequently, the two layers are successively applied to the respective component. Advantageously, the layer applied first is protected during the application of the second layer by a protective lacquer or a masking.

Further measures improving the invention will be described in more detail below together with the description of two preferred embodiments of the invention with reference to the two figures, wherein the same or similar elements are provided with the same reference numerals. Show it

1 a schematic sectional view of a component according to the invention, and

2 a schematic sectional view of a rolling bearing according to the invention for an electrical machine.

According to 1 a component according to the invention, which was produced by a method according to the invention, has a burnishing layer 5 and an insulation layer 6 on. The component according to the invention is, for example, an outer ring 3 a - not shown here - rolling bearing. The burnishing layer 5 is formed on an inner peripheral surface, in particular a raceway for - not shown here - rolling elements. The remaining surface, namely an outer peripheral surface and the two end faces of the outer ring 3 are with the insulation layer 6 coated.

To 2 has an inventive rolling bearing 1 for an - not shown here - electric machine an inner ring 2 , an outer ring 3 as well as radially between the inner ring 2 and the outer ring 3 arranged rolling elements 4 on. The rolling bearing 1 is meant to be a wave 7 opposite a stationary fixed housing 8th rotatably store. Both the inner ring 2 as well as the outer ring 3 have a burnishing layer 5 for wear reduction and an insulation layer 6 for electricity insulation. The inner ring 2 and outer ring 3 are fully coated, with the inner peripheral surface of the outer ring 3 and the outer peripheral surface of the inner ring 2 the burnishing layer 5 and wherein the remaining surface of the inner ring 2 and outer ring 3 the insulation layer 6 having.

In both figures is the burnishing layer 5 formed from iron mixed oxides and has a layer thickness of 2 microns. In contrast, the insulation layer 6 formed of aluminum oxide and has a layer thickness of 200 microns. The two layers lead to an increase in the resistance of the rolling bearing 1 towards White Etching Cracks.

LIST OF REFERENCE NUMBERS

1

 roller bearing

2

 inner ring

3

 outer ring

4

 rolling elements

5

 Brünierschicht

6

 insulation layer

7

 wave

8th

 casing

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102011006296 A1 [0004]

Claims (10)

Roller bearing ( 1 ) for an electrical machine, comprising an inner ring ( 2 ), an outer ring ( 3 ) and radially between the inner ring ( 2 ) and the outer ring ( 3 ) arranged rolling elements ( 4 ), characterized in that at least partially on the inner ring ( 2 ) and / or on the outer ring ( 3 ) a burnishing layer ( 5 ) for reducing wear and an insulating layer ( 6 ) are arranged for current isolation. Roller bearing ( 1 ) according to claim 1, characterized in that the burnishing layer ( 5 ) Comprises iron mixed oxides. Roller bearing ( 1 ) according to one of the preceding claims, characterized in that the burnishing layer ( 5 ) has a layer thickness of 0.5 to 2 microns. Roller bearing ( 1 ) according to one of the preceding claims, characterized in that the burnishing layer ( 5 ) on an inner peripheral surface of the outer ring ( 3 ) and / or on an outer circumferential surface of the inner ring ( 2 ) is trained. Roller bearing ( 1 ) according to one of the preceding claims, characterized in that the insulating layer ( 6 ) Comprises alumina. Roller bearing ( 1 ) according to one of the preceding claims, characterized in that the insulating layer ( 6 ) has a layer thickness of 50 to 300 microns. Roller bearing ( 1 ) according to one of the preceding claims, characterized in that the insulating layer ( 6 ) on an inner peripheral surface of the inner ring ( 2 ) and / or on an outer circumferential surface of the outer ring ( 3 ) is trained. Roller bearing ( 1 ) according to one of the preceding claims, characterized in that the inner ring ( 2 ) and / or outer ring ( 3 ) is completely coated, wherein the inner peripheral surface of the outer ring ( 3 ) and / or the outer peripheral surface of the inner ring ( 2 ) the burnishing layer ( 5 ), wherein further the remaining surface of the inner ring ( 2 ) and / or outer ring ( 3 ) the insulation layer ( 6 ) having. Electric machine comprising a rolling bearing ( 1 ) according to one of claims 1 to 8. Process for coating a component, in particular a bearing ring ( 2 . 3 ) for a rolling bearing ( 1 ) according to one of claims 1 to 8, wherein first a burnishing layer ( 5 ) and then an insulation layer ( 6 ) or first the insulation layer ( 6 ) and then the burnishing layer ( 5 ) are formed on a surface of the component.

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