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: an outer ring of a bearing, the outer ring being formed of metallic material, the outer ring having an outermost radial surface formed by an axially extending radial surface, the outer ring having an axial end defining a radially extending axial surface a coating deposited on outer ring, wherein, when the coated bearing component is viewed in cross section, the coating is a multi-layer coating comprising: a sensor active layer made of a material having electrostrictive properties, wherein the sensor active layer is positioned on the axially extending radial surface and the radially extending axial surface of the outer ring, the sensor active layer having first and second sensor layer axial ends, the second sensor layer axial end being located on the radially extending axial surface, an electrode layer located on the sensor active layer and having first and second electrode layer axial ends, the second electrode layer axial end being located along a portion of the sensor active layer that overlies the radially extending axial surface, an isolation layer having first and second isolation layer axial ends, the isolation layer being located on the electrode layer and the second isolation layer axial end being located over the axially extending radial surface, and a wear layer located on the isolation layer and having first and second wear layer axial ends, the second wear layer axial end being located over the axially extending radial surface of the outer ring, wherein the first sensor layer axial end, the first isolation layer axial end, and the first wear layer axial end each contact the axially extending radial surface of the outer ring, the isolation layer and the wear layer being configured to prevent the first electrode layer axial end from contacting the axially extending radial surface of the outer ring.

2. The coated bearing component according to claim 1, wherein a sensitivity of the coating is adjustable by adjusting a strength of the direct current biased electrical field.

3. The coated bearing component according to claim 1, 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.

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

5. The coated bearing component according to claim 1, wherein the coating has a thickness comprised between three micrometers (3 μm) and five micrometers (5 μm).

6. The coated bearing component according to claim 1, wherein the coating has a thickness that is substantially equal to four micrometers (4 μm).

7. The coated bearing component according to claim 1, wherein the sensor active layer has a usable bandwidth comprised between twenty megahertz (20 MHz) and three hundred fifty megahertz (350 MHz).

8. A coated bearing component, comprising: an outer ring of a bearing, the outer ring being formed of metallic material, the outer ring having an outermost radial surface formed by an axially extending radial surface, the outer ring having an axial end defining a radially extending axial surface a coating deposited on outer ring, wherein, when the coated bearing component is viewed in cross section, the coating is a multi-layer coating comprising: a sensor active layer made of a material having electrostrictive properties, wherein the sensor active layer is positioned on the axially extending radial surface and the radially extending axial surface of the outer ring, the sensor active layer having first and second sensor layer axial ends, the second sensor layer axial end being located on the radially extending axial surface, an electrode layer located on the sensor active layer and having first and second electrode layer axial ends, the second electrode layer axial end being located along a portion of the sensor active layer that overlies the radially extending axial surface, an isolation layer having first and second isolation layer axial ends, the isolation layer being located on the electrode layer and the second isolation layer axial end being located over the axially extending radial surface, and a wear layer located on the isolation layer and having first and second wear layer axial ends, the second wear layer axial end being located over the axially extending radial surface of the outer ring, wherein the first sensor layer axial end, the first isolation layer axial end, and the first wear layer axial end each contact the axially extending radial surface of the outer ring, the isolation layer and the wear layer being configured to prevent the first electrode layer axial end from contacting the axially extending radial surface of the outer ring, a wire connected to the electrode layer and configured to supply a direct current thereto to create a direct current DC biased electrical field, power source, wherein a sensitivity of the coating is adjustable by adjusting a strength of the direct current biased electrical field.

9. The coated bearing component according to claim 8, wherein the coated bearing component is connected to a ground wire.

10. The coated bearing component according to claim 8, wherein the multi-layer coating is deposited on the metallic part using a sputtered coating method.

11. The coated bearing component according to claim 8, wherein the coating has a thickness comprised between three micrometers (3 μm) and five micrometers (5 μm).

12. The coated bearing component according to claim 8, wherein the coating has a thickness that is substantially equal to four micrometers (4 μm).

13. The coated bearing component according to claim 8, wherein the sensor active layer has a usable bandwidth comprised between twenty megahertz (20 MHz) and three hundred fifty megahertz (350 MHz).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) 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:

(2) FIG. 1 presents a schematic view of an exemplary rolling bearing in accordance with an embodiment of the invention having a coating; and

(3) FIG. 2 presents a schematic cross section of the coating of the rolling bearing of FIG. 1.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

(4) 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”.

(5) 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.

(6) 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.

(7) The inner ring 12 and the outer ring 14 are made of metallic material.

(8) 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.

(9) 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.

(10) 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.

(11) 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.

(12) 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.

(13) 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.

(14) 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.

(15) 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.

(16) 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.

(17) The polarization is a single step in the process to build the sensor.

(18) 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.

(19) Preferably, the multi-layer coating 20 is deposited on the rolling bearing component using a thin (around 4 μm) sputtered coating method.

(20) The sensor active layer 22 has a usable bandwidth comprised between 20 MHz and 350 MHz.

(21) The invention is not limited to a rolling bearing and may be applied to a plain or solid bearing.

(22) 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.

(23) 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.

(24) 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.

(25) Finally, the sensitivity of such multi-layer coating 20 is adjustable by adjusting the biased electrical field.