COATED BEARING COMPONENT AND BEARING COMPRISING SUCH A COMPONENT

Abstract

A coated bearing component comprising a metallic part and a coating deposited on the metallic part. The coating is a multi-layer coating having a sensor active layer made of a material having electrostrictive properties. The sensor active layer is directly coated on the metallic part. The bearing component can be integrated into a bearing.

Claims

1. A coated bearing component comprising a metallic part and a coating deposited on the metallic part, wherein the coating is a multi-layer coating having a sensor active layer made of a material having electrostrictive properties, wherein the sensor active layer is directly coated on the metallic part.

2. The coated bearing component according to claim 1, wherein the sensor active layer is made of aluminum nitride.

3. The coated bearing component according to claim 2, wherein the multi-layer coating comprises, successively on the sensor active layer, an electrode layer, an isolation layer and a wear layer.

4. The coated bearing component according to claim 1, wherein the multi-layer coating comprises, successively on the sensor active layer, an electrode layer, an isolation layer and a wear layer.

5. The coated bearing component according to claim 4, wherein the electrode layer is connected by a wire to a direct current (DC), while the coated bearing component is connected to a ground wire.

6. The coated bearing component according to claim 1, wherein the multi-layer coating is deposited on the metallic part using a sputtered coating method.

7. The coated bearing component according to claim 1, wherein the coating has a thickness comprised between 3 ?m and 5 ?m.

8. The coated bearing component according to claim 1, wherein the coating has a thickness that is substantially equal to 4 ?m.

9. The coated bearing component according to claim 1, wherein the sensor active layer has a usable bandwidth comprised between 20 MHz and 350 MHz.

10. A bearing comprising an inner ring and an outer ring, wherein at least a portion of at least one of the inner ring and the outer ring is a coated bearing component, wherein the coated bearing component comprises a metallic part and a coating deposited on the metallic part, wherein the coating is a multi-layer coating having a sensor active layer made of a material having electrostrictive properties, wherein the sensor active layer is directly coated on the metallic part.

11. The bearing according to claim 10, wherein at least a portion of an outer cylindrical surface of the outer ring is coated with the multi-layer coating and wherein at least the sensor active layer overlaps on a lateral surface of the outer ring.

12. The coated bearing component according to claim 10, wherein the sensor active layer is made of aluminum nitride.

13. The coated bearing component according to claim 12, wherein the multi-layer coating comprises, successively on the sensor active layer, an electrode layer, an isolation layer and a wear layer.

14. The coated bearing component according to claim 10, wherein the multi-layer coating comprises, successively on the sensor active layer, an electrode layer, an isolation layer and a wear layer.

15. The coated bearing component according to claim 14, wherein the electrode layer is connected by a wire to a direct current (DC), while the coated bearing component is connected to a ground wire.

16. The coated bearing component according to claim 10, wherein the multi-layer coating is deposited on the metallic part using a sputtered coating method.

17. The coated bearing component according to claim 10, wherein the coating has a thickness comprised between 3 ?m and 5 ?m.

18. The coated bearing component according to claim 10, wherein the coating has a thickness that is substantially equal to 4 ?m.

19. The coated bearing component according to claim 10, wherein the sensor active layer has a usable bandwidth comprised between 20 MHz and 350 MHz.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention and its advantages will be better understood by studying the detailed description of specific embodiments given by way of non-limiting examples and illustrated by the appended drawings on which:

[0030] FIG. 1 presents a schematic view of an exemplary rolling bearing in accordance with an embodiment of the invention having a coating; and

[0031] FIG. 2 presents a schematic cross section of the coating of the rolling bearing of FIG. 1.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0032] In the further description, terms outer and inner are defined with respect to the rotational axis X-X of the rolling bearing illustrated on FIG. 1, where the term inner means closer to the rotational axis X-X of the rolling bearing then term outer.

[0033] Referring first to FIG. 1, which illustrates an embodiment of a rolling bearing 10 according to the invention; the bearing comprises an inner ring 12, an outer ring 14, a row of rolling elements 16 consisting, in the example illustrated, of balls, held by a cage (not shown on the Figures) between the inner ring 12 and the outer ring 14.

[0034] The inner ring 12 and the outer ring 14 are both solid and have a toroidal groove (not depicted) provided respectively on its outer cylindrical surface 12a and inner cylindrical surface 14a and forming a raceway for the rolling elements 16. The radius of curvature of the groove is slightly greater than the radius of the rolling elements 16.

[0035] The inner ring 12 and the outer ring 14 are made of metallic material.

[0036] The inner and outer rings 12, 14 may be manufactured by machining or by pressing a steel blank which is then ground and optionally lapped at the raceway in order to give the rings their geometric characteristics and its final surface finish.

[0037] As shown on the Figures, a portion of the outer cylindrical surface 14b of the outer ring 14 is coated with a multi-layer coating 20 acting as a piezoelectric sensor. The portion of the cylindrical surface 14b forms the metallic part for the coating 20.

[0038] Alternatively, it is possible to coat another component of the rolling bearing 10, for example the inner cylindrical surface of the outer ring 14, one of the cylindrical surfaces of the inner ring, the cage or any other component of the rolling bearing.

[0039] The multi-layer coating 20 comprises successive layers of a sensor active layer 22, an electrode layer 24, an isolation layer 26 and a wear layer 28.

[0040] As shown on FIG. 2, the sensor active layer 22, the electrode layer 24 and the isolation layer 26 overlap on a lateral surface 14b of the outer ring 14.

[0041] The electrode layer 24 is connected by a wire 30 to a direct current DC, while the outer ring 14 is connected to a ground wire 32.

[0042] The sensor active layer 22 is made of a material having electrostrictive properties, such as for example aluminum nitride, zinc oxide, or any other material having electrostrictive properties.

[0043] Electrostriction is a property of electrical non-conductor materials having their shape changing under application of an electrical field. Generally, electrostriction is defined as a quadratic coupling between the strain and the polarization.

[0044] The sensor active layer 22 is subjected to a direct current DC biased electrical field. Since the material of the sensor active layer is not piezoelectric, it is necessary to induce polarization with this direct current DC biased electrical field in order to obtain a pseudo-piezoelectric behavior. This pseudo-piezoelectric effect provides access to piezoelectric measuring capacities, such as vibration measurements and strain measurements without the need to control polarization growth during the service life of the rolling bearing.

[0045] The polarization is a single step in the process to build the sensor.

[0046] Conventional techniques for thin film deposition may be used for depositing the multi-layer coating 20 on the rolling bearing component, such as physical vapor deposition (PVD) process, chemical vapor deposition (CVD) process, dipping methods, casting, spray coating and/or spin coating.

[0047] Preferably, the multi-layer coating 20 is deposited on the rolling bearing component using a thin (around 4 ?m) sputtered coating method.

[0048] The sensor active layer 22 has a usable bandwidth comprised between 20 MHz and 350 MHz.

[0049] The invention is not limited to a rolling bearing and may be applied to a plain or solid bearing.

[0050] As one result of the present invention, a thin layer of a sensor active layer having electrostrictive properties is directly integrated to a component or part of the rolling bearing providing a coating acting as a pseudo-piezoelectric sensor which is low intrusive and has a high sensitivity capable of measuring strains, loads, vibrations, as well as lubricant thickness.

[0051] Furthermore, the multi-layer coating is not bonded but deposited on the rolling bearing component using particular depositing method, such that shear lag effect is avoided.

[0052] As another result of the present invention, the integration of the sensor is improved in comparison to current method which needs gluing/soldering., compensating the low sensing material performance.

[0053] Finally, the sensitivity of such multi-layer coating 20 is adjustable by adjusting the biased electrical field.