Steel bearing

Abstract

The present invention relates to a bearing assembly that provides a magnetic sensor; a shaft; and a bearing. One of the shaft and the bearing is provided with a surface having a bearing steel and including a magnetic pattern disposed thereon for indicating a rotation of the shaft relative to the bearing. The magnetic pattern is provided by the microstructure of the surface; and the sensor is arranged to sense the pattern and output a signal indicative of a rotation of the shaft relative to the bearing.

Claims

1. A bearing assembly comprising: a magnetic sensor; a shaft; and a bearing, wherein the shaft or the bearing is provided with a surface region comprising a bearing steel and including a magnetic pattern in the bearing steel of the surface region for indicating a rotation of the shaft relative to the bearing, wherein the magnetic pattern is provided by a microstructure of the bearing steel in the surface region; and the sensor is arranged to sense the pattern and output a signal indicative of a rotation of the shaft relative to the bearing.

2. The bearing assembly according to claim 1, wherein the magnetic pattern is provided by regions of increased or decreased austenite content.

3. The bearing assembly according to claim 1, wherein the magnetic pattern is provided by a regular alternation in the microstructure of said surface.

4. The bearing assembly according to claim 1, wherein the magnetic pattern is provided on the shaft or on a component of the bearing that rotates with the shaft.

5. The bearing assembly according to claim 1, wherein the surface region having a magnetic pattern further comprises at least one of alpha-ferritic and martensitic steel having regions that include austenite.

6. The bearing assembly according to claim 1, wherein the magnetic sensor is a hall-effect sensor.

7. The bearing assembly according to claim 1, wherein the surface region is provided on the shaft.

8. The bearing assembly according to claim 1, wherein the diameter of the magnetic pattern is at least 12 cm.

9. The bearing assembly according to claim 1, wherein the magnetic pattern is provided by a continuously varying concentration of austenite around the bearing steel of the surface region.

10. The method of claim 9, wherein the treating comprises: thermally treating the surface region to form austenite in portions.

11. The method of claim 10, wherein the thermally treating is conducted with a laser.

12. A bearing assembly comprising: a magnetic sensor; a shaft; and a bearing, wherein one of the shaft and the bearing is provided with a surface comprising a bearing steel and having a magnetic pattern thereon for indicating a rotation of the shaft relative to the bearing, wherein the magnetic pattern is provided by the microstructure of said surface; and the sensor is arranged to sense the pattern and output a signal indicative of a rotation of the shaft relative to the bearing, and wherein the magnetic pattern is provided by a continuously varying concentration of austenite around the surface.

13. A method of producing a bearing assembly comprising: providing a shaft and a bearing; treating a surface region of the shaft or a surface region of the bearing to produce a pattern of areas having distinct microstructures having distinct magnetic properties; and providing a magnetic sensor configured to sense the magnetic properties of the surface regions when the surface regions rotates relative to the magnetic sensor.

14. The method of claim 13, wherein the treating comprises: masking parts of a surface of the shaft or parts of a surface of the bearing, and carbon nitriding the surface of the shaft or the surface of the bearing or carburizing the surface of the shaft or the surface of the bearing.

Description

FIGURES

(1) The present invention will now be described further, by way of example, with reference to the accompany drawings in which:

(2) FIG. 1 shows a schematic of a prior art bearing 1 with a tone ring 2 and a magnetic sensor 3.

(3) FIG. 2 shows a cross-section of a prior art bearing 1 showing the off-set configuration of a tone ring 2 relative to sensors 3.

(4) FIG. 3 show cross-sectional diagrams of embodiments of the invention. In FIGS. 3A, 3B and 3C, a sensor is attached to a bearing to scan a patterned surface of a rotating shaft (3A and 3B) or a rotating cuff attached to the shaft (3C). In FIG. 3D, a sensor is attached to a shaft to scan a patterned surface of a rotating bearing component.

DETAILED DESCRIPTION OF THE INVENTION

(5) In more detail, FIG. 3A depicts a bearing assembly 100 forming a first embodiment.

(6) Bearing assembly 100 comprises: a plain bearing 110 (or a split bearing 110); a shaft 120; and a magnetic sensor 130.

(7) In the embodiment of FIG. 3A, the shaft 120 is provided with a magnetic pattern 125 on its surface, and a magnetic sensor 130 is mounted on the bearing assembly 100 to rotate with the plain bearing 110 relative to the shaft 120. Preferably, the sensor 130 is directly mounted on the plain bearing 110.

(8) The sensor 130 is mounted so that a region of the magnetic pattern 125 is exposed to the sensor 130. The sensor 130 is arranged to sense relative rotation between the shaft 120 and the plain bearing 110.

(9) The magnetic pattern 125 preferably is a regular repeating pattern around the circumference of the shaft 120. Alternatively, the magnetic pattern 125 is unique for each location around the circumference of the shaft 120. Optionally the sensor 130 outputs a unique signal for any relative rotational displacement of the shaft 120 and bearing 110. Alternatively the sensor and detection system can be calibrated to determine the location and orientation based on the measurements taken of the regular repeating pattern.

(10) Rotation of the shaft 120 relative to the sensor 130 exposes a different region of the magnetic pattern 125 to the sensor 130. The sensor 130 can thereby output a signal indicative of the rotation of the shaft 120 relative to the plain bearing 110 or of the rotational speed of the shaft 120 relative to the plain bearing 110.

(11) FIG. 3B depicts a bearing assembly 200 forming a second embodiment.

(12) Bearing assembly 200 comprises: a bearing 210; a shaft 220; and a magnetic sensor 230.

(13) The bearing 210 may be a ball bearing or a roller bearing 210. In FIG. 3B a ball bearing is shown. The bearing 210 comprises: an outer race 211; a plurality of balls 212; and an inner race 213. The inner race 213 may be mounted on the shaft 220 and rotate therewith.

(14) In the embodiment of FIG. 3B, the shaft 220 is provided with a magnetic pattern 225 on its surface, and a magnetic sensor 230 is mounted on the outer race 211 of the bearing assembly 200 to rotate relative to the shaft 220 about the rotational axis of the shaft 220. The sensor 230 is thus arranged to sense relative rotation between the shaft 220 and the outer race 211.

(15) In FIG. 3C, the bearing 310 comprises: an outer race 311; a plurality of balls 312; and an inner race 313. The inner race 313 may be mounted on the shaft 320 and rotate therewith, and the sensor 330 is mounted on the outer race 311. The embodiment of FIG. 3C is substantially the same as that of FIG. 3B, except that the magnetic pattern 325 is not provided on the shaft 320, but on the inner race 313 of the bearing assembly 300.

(16) The embodiments described above include sensors 130 mounted on the non-rotating component and magnetic patterns formed on the rotating component. Alternative embodiments are envisaged in which the sensor 130 is mounted on the shaft 120 and the magnetic pattern is provided on the plain bearing 110. Such bearings are, however, less preferable. Preferably, such sensors 130 include a commutator or produce a wireless signal for remote reception.

(17) FIG. 3D depicts a bearing assembly 400 forming a first embodiment.

(18) Bearing assembly 400 comprises: a ball bearing 410 (or a roller bearing 410); a shaft 420; and a magnetic sensor 430.

(19) In FIG. 3D, the bearing 410 comprises: an outer race 411; a plurality of balls 412; and an inner race that may be formed integrally with the shaft 420.

(20) In the embodiment of FIG. 3D, bearing 410 is provided with a magnetic pattern 425 on its non-contact surface, and a magnetic sensor 430 is mounted on the shaft 420 to rotate with the bearing 410 relative to the shaft 420. Preferably, the sensor 430 is directly mounted on the shaft 420. In use the shaft 420 in this embodiment, unlike the previous embodiments, is preferably stationary.

(21) The sensor 430 is mounted so that a region of the magnetic pattern 425 is exposed to the sensor 430. The sensor 430 is arranged to sense relative rotation between the shaft 420 and the bearing 410.

(22) The magnetic pattern 425 may vary around the circumference of the bearing 410, but is preferably a regularly repeating pattern or array. The magnetic pattern 425 can be unique for each location around the circumference of the bearing 410 and the sensor 430 can output a unique signal for any relative rotational displacement of the shaft 420 and bearing 410. Alternatively the sensor and the related system and controller can determine the rotational displacement and/or speed from precalibration with relation to a regular repeating pattern.

(23) Rotation of the bearing 410 relative to the sensor 430 exposes a different region of the magnetic pattern 425 to the sensor 430. The sensor 430 can thereby output a signal indicative of the rotation of the bearing 410 relative to the shaft 420 or of the rotational speed of the bearing 410 relative to the shaft 420.

(24) The magnetic pattern is preferably formed by thermal laser treatment of a bearing steel surface. Using this example, different embodiments of the magnetic pattern will be described.

(25) Starting from a martensitic or alpha ferritic bearing steel surface, a thermal laser is used to heat portions of the surface of a shaft or bearing and to thereby form austenitic regions. These regions may, for example, be in the form of dots of varying location, varying size, varying depth and varying density, to thereby identify a unique portion of the surface. Due to the variance in the magnetic field that can be detected, the orientation and/or rotational speed can be determined. In one embodiment, the pattern may simply be a magnetic strip, similar to a tone ring in form, offset from the sensor to thereby produce a varying field strength measured by the sensor. In another, the extent of austenitic microstructure conversion of the surface can be varied to achieve measurable change in the concentration of the austenite in the surface and thereby a variance in the magnetic field.

(26) The magnetic pattern can alternatively be formed in other ways. For example, induction heat treatment could be used to heat portions of the surface of a shaft or bearing and to thereby form austenitic regions

(27) In other embodiments, the shaft or bearing may be heated and then quenched. A patterned mask corresponding to the magnetic pattern may be used to cover a portion of the shaft or bearing surface prior to the quenching step to form regions having varying magnetic properties.

(28) Alternatively, the shaft or bearing may be carburised or de-carburised. A patterned mask corresponding to the magnetic pattern may be used to cover a portion of the shaft or bearing surface prior to the carburisation or de-carburisation step to form regions having varying magnetic properties.

(29) The foregoing detailed description has been provided by way of explanation and illustration, and is not intended to limit the scope of the appended claims. Many variations in the presently preferred embodiments illustrated herein will be apparent to one of ordinary skill in the art, and remain within the scope of the appended claims and their equivalents.