Rolling bearing with sensor and drive unit

Abstract

Rolling bearing (1) with an outer ring (3) and an inner ring (2) which is rotatable relative to the outer ring (3), wherein a sensor (8) is arranged on the outer ring (3) and a measuring ring (13) which can be detected by the sensor (8) is arranged on the inner ring (2), wherein the measuring ring (13) has an electrically conductive section (15) against which a contact element (10) rests, which contact element is arranged fixedly on the outer ring (3), characterized in that the rolling bearing (1) comprises a support disk (16) on which a spring element (17) is supported in such a way that a bearing preload force can be adjusted.

Description

The invention relates to a rolling bearing having an outer ring and an inner ring rotatable with respect to the outer ring, wherein a sensor is arranged on the outer ring and a measuring ring detectable by the sensor is arranged on the inner ring, wherein the measuring ring has an electrically conductive section, on which a contact element which is arranged fixedly on the outer ring abuts. A further subject matter of the invention is a drive unit having an electric machine and a rolling bearing of this type.Rolling bearings of this type having a sensor and a measuring ring detectable by the sensor are used in drive units, for example for mounting machine shafts of electric machines, in order to monitor the rotational position of the machine shaft. In such applications, an undesired electrical voltage can occur across the rolling bearing and bearing currents caused by this voltage. If the bearing currents have a high current density, these can cause considerable damage to the rolling bearing, which can lead to premature failure of the rolling bearing and thus of the drive unit.From the publications DE 196 44 744 A1, JP 2000-266 067 A and DE 10 42 305 A, rolling bearings are known in which the inner ring and the outer ring are electrically contacted with each other. The publication DE 10 2017 130 644 A1 discloses a rolling bearing with a sensor system for detecting the angle of rotation and the speed of rotation. The documents U.S. Pat. No. 2015 / 0 162 798 A1 and DE 43 22 674 C2 are dedicated to electric machines.Rolling bearings with an optical measuring ring and a contact element are described, for example, in U.S. Pat. No. 4,259,637 A and U.S. Pat. No. 5,678,933 A. A rolling bearing with a measuring ring which has an optical standard is known from post-published DE 10 2018 117 315 A1.Against this background, the object is to extend the service life of the drive unit and to ensure the accuracy of the rotational position monitoring over the service life.To achieve the object, a rolling bearing is proposed which comprises a support disk (16) on which a spring element (17) is supported in such a way that a bearing prestressing force can be set.In the rolling bearing according to the invention, an electrical connection is produced between the outer ring and the inner ring of the rolling bearing by the contact element and the electrically conductive section of the measuring ring. This allows potential compensation to be effected which counteracts the formation of undesired electrical voltages between the inner ring and the outer ring. The risk of bearing currents having high current densities occurring can be reduced. Damage to the bearing can be avoided and the service life can be increased. The measuring ring thereby fulfils a dual function as a counterpart for the sensor and as a counterpart for the contact element. This allows a particularly compact configuration of the rolling bearing.Advantageous embodiments of the invention are the subject matter of the dependent claims.According to an advantageous embodiment, it is provided that the measuring ring has an electrically conductive coating in the electrically conductive section. A section with sufficient electrical conductivity can be provided by the coating. A further advantage of the coating is that direct contact of the contact element with a substrate of the measuring ring is not required, so that abrasion on the substrate can be avoided.In this context, it is advantageous if the coating comprises silver. By using a silver-containing coating, an increased electrical conductivity can be made possible.According to an advantageous embodiment, it is provided that the electrically conductive section of the measuring ring is formed hollow-cylindrically. This makes it possible to arrange the electrically conductive section of the measuring ring on an outer lateral surface of the inner ring. This measure facilitates the contacting of the electrically conductive section by the contact element. The contact element can be arranged running in a radial direction and be in contact with an outer lateral surface of the electrically conductive section.An advantageous embodiment provides that the measuring ring has a measuring standard. The measurement standard can be scanned by the sensor, for example in order to determine a rotational position of the inner ring relative to the outer ring. The measurement standard can be designed as a magnetic measurement standard. Such a magnetic measuring standard may comprise alternating north and south poles. Alternatively, the measurement standard can be designed as an optical measurement standard. Such an optical material measure can have adjacent regions with different optical properties, for example different reflection or absorption properties.An embodiment has proven to be advantageous in which the measuring standard is designed as an annular disk-shaped section of the measuring ring connected to the electrically conductive section. Such an annular disk-shaped section is advantageous in particular when the measuring ring is detected by a sensor spaced apart from the measuring ring in the axial direction of the rolling bearing. In this respect, the measuring ring can have an L-shaped cross section.It is preferred if the contact element is of annular configuration. An annular contact element can allow full-circumferential contacting of the electrically conductive region of the measuring ring. In this way, an electrical connection of the inner ring with the outer ring with the least resistance possible can be made possible.According to an advantageous embodiment, the contact element has a flexible contact region. Due to the flexible configuration, the contact region can deform in the event of a malposition of the inner ring with respect to the outer ring without the risk of damage to the contact element or the measuring ring.A structurally advantageous embodiment provides that the sensor is annular. Alternatively, the sensor may have the shape of a ring segment. For example, the sensor may be semi-annular or quarter-annular.The sensor is preferably a magnetic sensor, in particular a Hall sensor. A magnetic measurement body of the measurement ring can be scanned by a magnetic sensor. Alternatively, the sensor can be designed as an optical sensor. Such a configuration is advantageous when the measuring ring has an optical measuring standard.An advantageous embodiment provides that the sensor and the contact element are directly connected to the outer ring. Alternatively, it is preferred if the sensor and the contact element are connected to the outer ring via a common holding element. The use of a common mounting element makes it possible, during the production of the rolling bearing, to mount first a unit comprising the common mounting element, the sensor, the measuring ring with measuring standard and electrically conductive section and the contact element and then to connect this unit to the outer ring.A further subject matter of the invention is a drive unit having an electric machine and a rolling bearing described above for supporting a machine shaft of the electric machine.In the drive unit, the same advantages as have already been described in connection with the rolling bearing can be achieved.According to an advantageous embodiment of the drive unit, it is provided that it comprises a transmission connected to the electric machine, wherein the rolling bearing for supporting the machine shaft is arranged on a side of the electric machine facing the transmission.An alternative, advantageous embodiment of the drive unit provides that it comprises a transmission connected to the electric machine, wherein the rolling bearing for supporting the machine shaft is arranged on a side of the electric machine facing away from the transmission.Further alternatively, it is advantageous if the drive unit comprises a transmission connected to the electric machine, wherein a first and a second rolling bearing are provided for supporting the machine shaft, wherein the first rolling bearing is arranged on a side of the electric machine facing the transmission and the second rolling bearing is arranged on a side of the electric machine facing away from the transmission.Alternatively or additionally, the advantageous configurations and features described in connection with the rolling bearing can also be used in the drive unit alone or in combination.Further advantages and details of the invention will be explained below with reference to the exemplary embodiment shown in the drawings. Shown herein: FIG. 1 shows an exemplary embodiment of a rolling bearing according to the invention in a sectional illustration; FIG. 2 shows the detail marked with the reference sign II in FIG. 1 in an enlarged illustration; and FIG. 3 shows a schematic illustration of an exemplary embodiment of a drive unit according to the invention.FIG. 1 shows a rolling bearing 1 according to an exemplary embodiment of the invention. FIG. 2 shows a detailed illustration of the detail marked with the reference symbol II. The rolling bearing 1 comprises a fixed outer ring 3 fastened to a housing 5 and an inner ring 2 rotatable with respect to the outer ring 3. A plurality of rolling bodies 4 are arranged between the outer ring 3 and the inner ring 2, which rolling bodies are designed as balls according to the exemplary embodiment. The rolling bodies can alternatively be cylindrical, conical or barrel-shaped rolling bodies. The rolling bodies 4 can be fixed in position relative to one another via a cage. The space between the outer ring 3 and the inner ring 2 is sealed by two annular sealing elements 6, 7.The rolling bearing 1 is designed in the manner of a sensor bearing and has a sensor 8 fixedly connected to the outer ring 3, by means of which sensor a measuring ring 13 arranged on the inner ring 2 in a rotationally fixed manner can be detected. A rotational position of the inner ring 2 and / or a rotational speed of the inner ring 2 can thus be determined via the sensor 8. The sensor 8 is designed as an annular sensor 8 and comprises, for example, a magnetic sensor, in particular a Hall sensor. For the electrical contacting of the sensor 8, a cable feedthrough 9 is provided, which is arranged running in a direction parallel to an axis of rotation of the rolling bearing 1.The rolling bearing 1 further comprises a support disk 16, on which a spring element 17 is supported. A bearing preload force can be set via the spring element 17. The housing 5 is covered in the axial direction by an annular cover 18.The fixed sensor 8 scans the measuring ring 13, in particular a measuring standard 14 of the measuring ring 13 facing the sensor 8, when the inner ring 2 rotates relative to the outer ring 3. The measurement scale 14 can be designed, for example, as a magnetic measurement scale. In the present exemplary embodiment, the measuring standard 14 is designed as an annular disk which is arranged in a radial plane which is perpendicular to the axis of rotation of the rolling bearing 1.The measuring ring 13 further comprises an electrically conductive section 15 connected to the measuring standard. The electrically conductive section 15 can be formed, for example, integrally with the measuring standard 14. In the exemplary embodiment, the electrically conductive section 15 is designed in the manner of a hollow cylinder which is arranged on an outer lateral surface of the inner ring 2. The electrically conductive section 15 has an electrically conductive coating, which can contain silver, for example. A contact element 10 abuts on the electrically conductive section 15 of the measuring ring 13, which contact element is arranged fixedly on the outer ring 3. This creates an electrical connection between the outer ring 3 and the inner ring 2, which leads to a potential compensation between the two rings 3, 4.The sensor 8 and the contact element 10 are connected to the outer ring 3 via a common mounting element 12. The holding element 12 has a substantially hollow cylindrical shape and can be plugged onto an annular recess of the outer ring 3. According to the exemplary embodiment, the holding element 12 has a first hollow-cylindrical region in which the contact element 10 is connected to the holding element 12 and a second hollow-cylindrical region in which the sensor 8 is connected to the holding element 12. The first and second hollow cylindrical regions have different diameters. In addition, the contact element 10 abuts the holding element 12 with an outer contour in the second hollow cylindrical region.The contact element 10 is of annular configuration. It may comprise an annular contact portion 11 which is in abutment with the measuring ring 13. This contact region 11 is preferably flexible. For example, the contact region 11 can be designed as a brush.FIG. 3 schematically shows a drive unit 20, which can be used, for example, as a traction drive of an electric vehicle or a hybrid vehicle. The drive unit 20 comprises an electric machine 21 with a machine shaft 23 and a transmission 22 coupled to the machine 21, in particular the machine shaft 23. a first rolling bearing 1 and a second rolling bearing 1' are provided for rotatably mounting the machine shaft 23. The first rolling bearing is arranged on a side of the electric machine 21 facing the transmission, and the second rolling bearing 1' is arranged on a side of the electric machine 21 facing away from the transmission. In order to reduce bearing currents and adverse effects on the transmission 22 which are thereby produced, a rolling bearing 1 which has been shown previously in FIGS. 1 and 2 and has a contact element 10 and an electrically conductive section 15 of the measuring ring 13 can be used as the first rolling bearing 1. Optionally, it can be provided that the second rolling bearing 1' is also a rolling bearing shown in FIGS. 1 and 2.

Claims

Rolling bearing (1), having an outer ring (3) and an inner ring (2) which can be rotated with respect to the outer ring (3), a sensor (8) being arranged on the outer ring (3) and a measuring ring (13) which can be detected by the sensor (8) being arranged on the inner ring (2), the measuring ring (13) having an electrically conductive section (15), against which a contact element (10) which is arranged fixedly on the outer ring (3) bears, characterized in that the rolling bearing (1) comprises a supporting disc (16), on which a spring element (17) is supported, in such a way that a bearing prestressing force can be set.Rolling bearing (1) according to Claim 1, characterized in that the measuring ring (13) has an electrically conductive coating in the electrically conductive section (15).Rolling bearing (1) according to Claim 2, characterized in that the coating comprises silver.Rolling bearing (1) according to one of the preceding claims, characterized in that the electrically conductive section (15) of the measuring ring (13) is of hollow cylindrical design.Rolling bearing (1) according to one of the preceding claims, characterized in that the measuring ring (13) has a measurement scale (14), in particular a magnetic measurement scale.Rolling bearing (1) according to one of the preceding claims, characterized in that the measurement scale (14) is designed as an annular-disc-shaped section of the measurement ring (13) connected to the electrically conductive section (15).Rolling bearing (1) according to one of the preceding claims, characterized in that the contact element (10) is of annular configuration.Rolling bearing (1) according to one of the preceding claims, characterized in that the contact element (10) has a flexible contact region (11).Rolling bearing (1) according to one of the preceding claims, characterized in that the sensor (8) is annular.Rolling bearing (1) according to one of the preceding claims, characterized in that the sensor (8) is a magnetic sensor, in particular a Hall sensor.Rolling bearing (1) according to one of the preceding claims, characterized in that the sensor (8) and the contact element (10) are connected directly to the outer ring (3) or in that the sensor (8) and the contact element (10) are connected to the outer ring (3) via a common mounting element (12).Drive unit (20) having an electric machine (21) and a rolling bearing (1) for mounting a machine shaft (23) of the electric machine according to one of the preceding claims.Drive unit (20) according to Claim 12, characterized bya transmission (22) connected to the electric machine (21), wherein the rolling bearing (1) for mounting the machine shaft (23) is arranged on a side of the electric machine (21) facing the transmission (22).Drive unit (20) according to Claim 12, characterized bya transmission (22) connected to the electric machine (21), wherein the rolling bearing (1) for mounting the machine shaft (23) is arranged on a side of the electric machine (21) facing away from the transmission (22).

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