MONITORING DEVICE FOR ROLLING BEARINGS

Abstract: A monitoring device for a rolling bearing with rolling elements (5) positioned between two rolling races (6, 7) comprises a ring (10) with a surface facing the parts of said rolling elements (5) which are exposed between said rolling races (6, 7). The ring is substantially non-rotatable but movable towards and away from the said exposed parts of said rolling elements. The ring is pretensioned by springs (12) against the said exposed parts of said rolling elements. One or more transducers are mounted in or at the ring, or comprise the ring as a part for sensing the bearing temperature or the like.

Description: MONITORING DEVICE FOR ROLLING BEARINGS The present invention relates generally to the monitoring of rolling bearings and, more particularly, to a monitoring device for a rolling bearing with rolling elements positioned between two rolling races. The necessity for monitoring and supervising rolling bearings has been known for a long time past, and a variety of techniques have been developed to meet this necessity. The present invention aims at providing a moni- toring device which makes it possible to monitor such parameters as, for example, the bearing temperature, the wear of the rolling elements and rolling races, and the condition of the lubricating film by detection by means of transducers providing the truest possible information about these parameters. This is achieved, in accordance with the present invention, and in a monitoring device of the above- mentioned type, by means of a ring having a surface facing the exposed parts of the rolling elements be- tween the rolling races, said ring being substantially non-rotatable but movable towards and away from the said exposed parts of the rolling elements, means for pretensioning the ring against the said exposed parts of the rolling elements, and one or more trans- ducers mounted in or at the ring or comprising said ring as a part, for sensing at least one bearing condi¬ tion parameter, such as the bearing temperature. In or at the ring, one or more temperature transducers or one or more acceleration transducers may thus be mounted. The ring may also be a connecting electrode for measuring the electric impedance in a path from the ring via the lubricating film to the rolling ele¬ ments, and from there via said lubricating film to an earthed bearing race. The ring preferably -is re- 2 resiliently carried and self-centeringly mounted in an annular holder fixedly connected with one of the parts relatively movable by means of the bearing, or with a member independent of said parts. In or at the ring, a transducer detecting the passing of the rolling elements may be mounted, for example a Hall element, a coil or a permanent magnet being mounted in the ring to generate a magnetic field passing through the rolling elements. The ring may also be used as a carrier for a magnetic field generating means generating a magnetic field passing through at least one of the rolling elements, and a magnetic field detector, such as a Hall element, for detecting the magnetic field inten- sity. In this manner, the condition of the lubricating film and also the speed and any vibrations may be determined. The magnetic field is superior to an elec¬ tric field in that it is sensitive to minor distance variations in the vicinity of the magnetic field gene- rating means and relatively insensitive to the ap¬ pearance of the magnetic circuit at a distance from said means. Furthermore, to make the monitoring device accord¬ ing to the invention self-sustaining, the ring or the ring holder may be connected with an electric generator which is operated by the said parts relatively movable by means of the bearing. In order to indicate one or more bearing parameters which have been determined on the basis of the output signals of the transducer or transducers, it is also possible to provide an indicator, either on the bearing itself or spaced therefrom. The monitoring device according to the present invention thus provides for accurate sensing of, for example, the bearing temperature, the bearing vibrations and the condition of the lubricating film. Also the speed of the different bearing parts can be determined. Moreover, the monitoring device is advantageous in that it can be used on standard bearings. The same transducers and the same electronics may be used for different bearing sizes. Finally, the transducer cora- ponent can be made robust and readily exchangeable. The invention will now be described in more de¬ tail, reference being had to the accompanying drawings. Fig. 1 is an axial section of a bearing comprising one embodiment of the monitoring device according to the invention. Fig. 2 is a cross-sectional view along line II-II in Fig. 1. Figs. 3, 4 and 5 are partial cross-sectional views of a ring comprised by the de¬ vice and show the positions of several transducers therein. Fig. 6 is an equivalent circuit diagram of a variant of the monitoring device according to the in¬ vention. Fig. 1 illustrates a bearing for a shaft 1, said bearing comprising a bearing housing 2 and the rolling bearing proper with an outer bearing ring 3, an inner bearing ring 4 and rolling elements 5, in this case balls. The outer bearing ring 3 is fixedly mounted in the bearing housing 2, and the inner bearing ring 4 is fixedly mounted on the shaft 1 so that the balls 5 roll on the bearing race 6 formed by the inner side of the outer bearing ring and on the bearing race 7 formed by the outer side of the inner bearing ring 4. The ball cage of the bearing is not shown. According to the invention a holder 8 is fixedly mounted in the bearing housing 2. The holder is annular and has a throughhole for the shaft 1. The holder 8 is mounted beside the bearing 3-7 and has, in its surface facing the bearing 3-7, a circular groove 9 accommodating a ring 10. The side of the ring 10 facing the balls 5 is dished with a radius substantially corresponding to and preferably being greater than the radius of the balls 5. As will appear from Fig. 2, the grooves 9 of the holder 8 have three axial bores 11, each accommodating a helical compression spring 12. The ring 10 thus is mounted substantially non- rotatably but is movable towards and away from the exposed parts of the rolling elements 5 between the rolling races 6 and 7. The springs 12 act as preten- sioning means for the ring 10 which thus is resilient- ly urged against the said exposed parts of the balls 5. In the embodiment described above, the ring 10 thus is resiliently mounted and self-centering in relation to the balls 5 and, more particularly, is floatingly mounted in the holder 8 by means of the springs 12 distributed around the circumference of the holder. According to the invention, the ring 10 is an expedient means for mounting different transducer types. For example, and as shown in Fig. 3, there may be mounted in a ring 10 two acceleration trans¬ ducers 13 and 14 which are sensitive to axial and radial movements of the ring 10 caused by irregulari¬ ties in the balls 5 or in the rolling races 6 and 7. The acceleration transducers 13 and 14 are connect¬ ed, via lines 15 and 16, to a suitable evaluation unit which is not shown, but which may display, on an indi¬ cator also not shown, information about the bearing wear. As will appear from Fig. 4, it is also possible to mount in the ring 10 a temperature transducer 17 which, because it is mounted practically within the bearing proper, can supply, via a line 18, highly accurate information regarding the bearing temperature to a suitable calculating and indicating device. As will appear from Fig. 5, it is also possible to mount in the ring a Hall element 19 and a coil 20 with connection lines 21 and 22, respectively, or some other magnetic field generating means, such as a permanent magnet. In this case, the Hall element 19 operates as a transducer detecting the passage of the rolling elements and sensing the magnetic field generated by the coil 20, which field passes through at least one of the rolling elements 5 and changes as the rolling elements go past the transducer 19. If the ring 10, or at least its surface urged against the rolling elements 5, as indicated by dash- dot lines in Fig. 1, is made of electrically conduc¬ tive material , the remaining part of the ring con¬ sisting of electrically insulating material, the ring 10 may serve as a connecting electrode for an elec- trie current source 23, as shown in Fig. 6. By means of an ammeter 24, the current can thus be measured in a path which goes from the current source 23 to the ring 10, from the ring 10 via a lubricating film to the rolling elements 5, and from there via a second lubricating film to the rolling race of the outer and/or inner bearing ring 3 and 4, respectively. Nor¬ mally, one or both of these bearing rings 3, 4 are earthed, whereby a closed circuit can be established by earthing the other terminal of the current source. By monitoring the current intensity in this circuit, it is possible to detect breakdown in the lubricating films, and furthermore, it is possible to determine the capacitance of capacitors which are formed between the balls 5 and the ring 10 on the one hand, and the balls and the bearing races 6, 7 on the other hand, the lubricating film constituting the dielectric. In this manner, it is possible to monitor both vibra¬ tions and the lubricating film. A variety of modifications of the above-described embodiment on the monitoring device are conceivable within the scope of the invention. Thus, the surface of the ring 10 facing the balls 5 need not be dished in the manner shown, but may also be planar. Furthermore, the ring 10 may be pretensioned against the rolling elements by other means than the springs 12; for instance, it may be mounted on the inside of the resiliently mounted ring which usually is to be found on either 6 side of the rolling elements between the outer race and the inner race of closed rolling bearings. The ring holder 8 may also be connected with an electric generator (not shown) driven by the parts 1 and 2 which are mutually movable by means of the bearing and which may be provided with, for example, magnetic field varying means. The monitoring device may also be used with thrust bearings, in which case the ring may be divided into several segments.

Claims: CLAIMS 1. Monitoring device for a rolling bearing with rolling elements (5) positioned between two rolling races (6, 7), c h a r a c t e r i s e d by a ring (10) having a surface facing the exposed parts of the rolling elements (5) between the rolling races (6, 7), said ring being substantially non-rotatable but movable towards and away from the said exposed parts of the rolling elements, means (12) for preten- sioning the ring against the said exposed parts of the rolling elements, and one or more transducers (Figs. 3-6) mounted in or at the ring or comprising said ring as a part, for sensing at least one bearing condition parameter. 2. Monitoring device as claimed in claim 1, c h a r a c t e r i s e d in that one or more tem¬ perature transducers (17) and/or one or more acce¬ leration transducers (13, 14) are mounted in or at the ring (10) . 3. Monitoring device as claimed in claim 1 or 2, c h a r a c t e r i s e d in that the said surface of the ring (10) is electrically conductive and con¬ stitutes a connnecting electrode for measuring the electric impedance in a path from said ring via a lubricating film to the bearing elements (5) and from there via a second lubricating film to an earthed bearing race (6, 7) . 4. Monitoring device as claimed in any one of claims 1-3, c h a r a c t e r i s e d in that said ring (10) is resiliently mounted and self-centering relative to said rolling elements (5). 5. Monitoring device as claimed in claim 4, c h a r a c t e r i s e d in that said ring is car¬ ried by an annular holder (8) fixedly connected with one (2) of the parts (1, 2) mutually movable by means /04138 ' 8 of said bearing, or with an element independent there¬ of. 6. Monitoring device as claimed in claim 5, c h a r a c t e r i s e d in that said ring (10) is guided in a circular groove (9) in the holder (8) and floatingly mounted therein by means of springs (12) distributed around the circumference of said holder. 7. Monitoring device as claimed in any one of claims 1-6, c h a r a c t e r i s e d in that a transducer (19), preferably a Hall element, detecting the passage of the rolling elements (5) is mounted in or at said ring (10), a means (20) being mounted in or at said ring (10) to generate a magnetic field passing through said rolling elements (5). 8. Monitoring device as claimed in claim 5 or 6, c h a r a c t e r i s e d by an electric generator which is connected to said ring holder (8) and which is operated by the parts (1, 2) mutually movable by means of the bearing. 9. Monitoring device as claimed in any one of claims 1-8, c h a r a c t e r i s e d by an indicator for indicating one or more bearing parameters based on the output signals of said transducer or trans- ducers.

Inventors: LOODBERG JAN AOKE TORSTEN, WALDERYD PER ERIK LENNART, LOODBERG, JAN, AOKE, TORSTEN, WALDERYD, PER, ERIK, LENNART
Applicants: SCANIAINVENTOR AB, AB SCANIAINVENTOR
Application year: 1985
Main classification: G01M13
IPC codes: F16C19, G01M13