Wheel bearing with controlled magnetorheological elastomer seal

Abstract

Sealing arrangement for sealing a rolling bearing (3) of a wheel bearing (1, 11) of a vehicle, wherein the rolling bearing (3) comprises a rotating inner ring (7, 17) and a stationary outer ring (4, 14), to which a radially oriented sealing carrier (12) with at least one sealing lip (19, 20) is assigned, which interacts with a cover ring (15) rotatably fixed on the inner ring (7, 17), characterized in that a ring coil (22) is assigned to the sealing carrier (12), which can be acted upon with an electric current and the sealing lip (20) consisting of a magnetorheological elastomer material can be influenced by the magnetic field generated by the current, whereby a length (S) of the sealing lip (20) can be controlled.

Description

[0001] The invention relates to a sealing arrangement for sealing an interior of a rolling bearing of a wheel bearing of a motor vehicle, wherein the rolling bearing comprises a rotating inner ring and a stationary outer ring, to which a radially oriented sealing carrier with at least one sealing lip is assigned, which is assigned to a cover ring rotatably fixed on the inner ring.

[0002] Wheel bearings for motor vehicles, designed as sealed radial rolling bearings, are known. These comprise an outer, non-rotating bearing ring and an inner, rotating bearing ring, as well as rolling elements that roll between the bearing rings and are guided in a bearing cage. To seal against moisture and contamination, these wheel bearings have a radially arranged seal on both sides between the bearing rings, axially spaced from the rolling elements. For sealing arrangements of wheel bearings with lip seals, the requirement is to create an effective and low-friction seal that prevents the ingress of dirty water into the wheel bearing and the escape of grease from the bearing. A variety of different sealing arrangements are known from the prior art.

[0003] From DE 10 2011 077 729 A1, a sealing arrangement for a wheel bearing is known, constructed as a cassette seal, comprising a carrier ring (also called a sealing disc), a cover ring, at least one sealing lip, and an elastomer-based pre-seal. The sealing lip forms a continuous, lubricating sealing contact with the cover ring. DE 10 2010 015 200 A1 describes another cassette seal with a sealing disc and a centrifugal disc, both of which are identically L-shaped. The sealing disc is associated with at least one elastic sealing lip in contact with the centrifugal disc.

[0004] According to US 4 770 425 A, the sealing arrangement includes a spring-loaded radial sealing lip, which presses the sealing lip against the counter surface.

[0005] This is intended to achieve a constant, temperature-independent position of the sealing lip in order to compensate for different coefficients of expansion between steel and sealing material.

[0006] Seals are also known that incorporate electrical or magnetic components with which the seal geometry can be changed. Such seals are disclosed in DE 10 2008 017 306 A1, DE 10 2016 223 097 A1, DE 11 2005 000 573 T5, DE 10 2012 220 987 A1, DE 10 2016 221 613 A1, DE 10 2015 222 748 A1 and EP 2 282 085 A1.

[0007] DE 10 2008 030 710 A1 discloses a cassette seal comprising several sealing lips. An axially oriented sealing lip associated with the centrifugal disc is designed such that it is supported against a sealing disc when the associated bearing is stationary or operating at low speeds. Above a defined rotational speed, the sealing lip lifts off the sealing disc in a radial direction due to centrifugal force.

[0008] The present invention is based on the objective of providing a sealing arrangement with a controllable sealing effect in order to achieve low frictional power, whereby the design ensures cost-effective series production.

[0009] This problem is solved by a sealing arrangement with the features of claim 1. Further preferred embodiments of the invention can be found in the dependent claims, the figures, and the accompanying description.

[0010] According to the invention, a ring coil is associated with the sealing carrier, which can be supplied with electric current and via which a sealing lip made of a magnetorheological elastomer material (MRE) can be influenced by the magnetic field generated by the current, whereby the length of the sealing lip can be controlled.

[0011] The adjustable length of the sealing lip allows for selective variation of the contact force. This means that the force directly influencing friction can be reduced or increased, thus advantageously maximizing sealing effectiveness. Furthermore, the adjustable sealing lip effectively prevents overpressure or underpressure inside the rolling bearing of the wheel bearing, thereby eliminating pressure differentials that often lead to detrimental, significant increases in the coefficient of friction of the seal or the sealing lip.

[0012] Nitrile butadiene rubber (NBR), for example, is suitable as a starting material for the magnetorheological elastomer material (MRE).

[0013] Due to the magnetically active particles located in the elastomer matrix, the length of the sealing lip can be changed by applying a magnetic field, whereby the viscoelastic or mechanical properties of the sealing lip are reversible.

[0014] Due to the ring coil integrated into the non-rotating part of the sealing assembly, the sealing lip can be extended when current is applied, as long as the magnetic field generated by the current flow is present. This increase in the sealing lip's length simultaneously results in increased overlap between the sealing lip and its support contour on the rotating cover ring of the sealing assembly.

[0015] To optimally adapt to the vehicle's operating conditions, it is advisable to apply a very low or no magnetic field to the sealing lip at high wheel bearing speeds, as the risk of dirty water ingress into the wheel bearing is low. At low speeds, there is a greater risk of dirty water ingress. Therefore, a stronger magnetic field is applied in this operating condition to ensure greater contact or overlap of the sealing lip with the mating surface.

[0016] To control the sealing lip, a magnetic circuit can be set up using an electromagnet (ring coil). Depending on the strength of the current flowing, the electromagnet can strengthen or weaken the magnetic field and, depending on its direction, also influence the direction of the magnetic field, thus increasing or decreasing the stiffness and deformation of the material.

[0017] Advantageously, the concept according to the invention, with its controllable sealing lip, offers a solution to meet the demands of automotive customers for friction-reduced wheel bearings with the aim of reducing CO2 emissions. Furthermore, the invention provides effective protection against the ingress of dirty water and prevents grease leakage from the rolling bearing. The operating principle of the controllable sealing lip differs from conventional sealing arrangements, in which a constant contact force is always applied to the sealing lips.

[0018] The activation of the ring coil, and thus the change in length of the sealing lip, can be adapted to the respective ambient conditions and / or to varying driving conditions of the associated vehicle. Advantageously, the invention compensates, for example, for temperature-related axial displacements of the seal carrier and / or the support disc, which are assigned to different components of the wheel bearing. The controllable sealing lip according to the invention therefore always ensures a predetermined, constant contact force of the sealing lip during operation.

[0019] The invention provides a sealing arrangement with a controllable sealing lip, which reduces or completely eliminates friction losses when no sealing is required due to operational requirements. Direct control over the surface pressure or the contact force of the sealing lip prevents excessively high friction, which is associated with detrimental heating and wear. Advantageously, the design of the sealing arrangement according to the invention enables cost-effective mass production.

[0020] According to an advantageous embodiment of the invention, the ring coil is controlled by a control unit located remotely from the wheel bearing, preferably a separate logic IC. Upon activation, i.e., when current is applied to the ring coil, a magnetic circuit is established, which is closed by the sealing carrier, the sealing lip, and the cover ring. The control unit, which includes a microcomputer also known as an IC (Integrated Circuit), supplies the ring coil with electric current depending on various input information or parameters of the wheel bearing and / or the vehicle, which are detected by means of sensors.

[0021] A sensor system interacting with the control unit includes at least one temperature sensor. Preferably, the sensor is positioned to reliably determine the prevailing temperature of the active material, thus ensuring a consistent contact force of the sealing lip regardless of the temperature of the magnetorheological elastomer (MRE). Furthermore, in the event of a sudden temperature change in the wheel bearing, e.g., during cooling while stationary and the associated negative pressure within the rolling bearing, the temperature sensor ensures an adjusted contact force of the sealing lip to prevent the ingress of contaminants. The sensor system associated with the control unit can also receive input signals from a speed sensor, which is preferably integrated into the wheel bearing. Alternatively, the sensor system can be arranged separately via an additional electrical interface to the wheel bearing.Furthermore, it is advisable to expand the sensor system to determine the moisture content and / or to continuously measure the axial distance between the sealing carrier and the cover ring of the sealing assembly.

[0022] According to a preferred design of the sealing arrangement, the ring coil is permanently fixed in position on the sealing carrier and enclosed in the interior of the sealing arrangement by the magnetorheological elastomer material (MRE).

[0023] The controllable sealing lip extending from the sealing carrier is supported in the sealed position by a radial section of the cover ring. In addition to the first controllable sealing lip, it is advantageous to provide a sealing arrangement with a second controllable sealing lip. This sealing lip, also associated with the sealing carrier, is preferably always supported by a rim of the cover ring that surrounds the inner ring.

[0024] A preferred design of the sealing arrangement comprises a seal carrier with an L-shaped cross-sectional profile and a C-shaped cover ring, which together axially define the sealing arrangement designed as a cassette seal. The seal carrier and the cover ring are each rotationally fixed to the inner ring or the outer ring via angled flanges. The cover ring, connected to the rotating inner ring of the rolling bearing, simultaneously performs the function of a centrifugal ring.

[0025] Both the sealing carrier and the cover ring are made from a formable steel sheet. To prevent corrosion, it is advisable to use a coated or corrosion-resistant steel sheet or a stainless steel sheet.

[0026] The invention is described in more detail below with reference to four figures, which relate to one embodiment. However, the invention is not limited to the embodiment shown. It shows: Fig. 1: a wheel bearing unit known from the prior art; Fig. 2: schematically in a half section a sealing arrangement with a controllable sealing lip according to the invention in an unsupported position; Fig. 3: schematically in a half section a sealing arrangement with controllable sealing lip according to the invention in the supported position; Fig. 4: the time course of an actuation of the controllable sealing lip of the sealing arrangement.

[0027] The Fig. Figure 1 shows a driven wheel bearing unit 1 of a motor vehicle (not shown), comprising a wheel hub 2 rotatably mounted relative to an outer ring 4 via a rolling bearing 3. The outer ring 4 is integrally connected to a stationary wheel carrier of a chassis suspension. At one axial end, the wheel hub 2 forms a wheel flange for mounting a wheel rim (not shown) and a brake disc. The rolling bearing 3, designed as a double-row angular contact ball bearing in an O-arrangement, is sealed on both the wheel and transmission sides by a sealing arrangement 8 to prevent the ingress of moisture and dirt and the escape of lubricant. The rolling elements 5 and 6 are assigned to an outer ring 4 and separate inner rings.The rolling elements 5 are guided on the inside of a raceway of the wheel hub 2, and the rolling elements 6 are guided on a raceway of an inner ring 7 surrounding the wheel hub 2, which is axially supported on the transmission side by a collar 9 formed by means of a rolling rivet. A toothed geometry 10 centrally integrated into the wheel hub 2 serves to accommodate a drive shaft (not shown).

[0028] In Fig. 2 and in Fig. Figure 3 shows a sealing arrangement 18 according to the invention in conjunction with the wheel bearing unit 11, of which the outer ring 14 and the inner ring 17 are also shown. The sealing arrangement 18, which forms a cassette seal, comprises an L-shaped, reinforced seal carrier 12, which is rotationally fixed to the inner side of the outer ring 14 by means of an angled flange 13. An axially spaced, also reinforced, cover ring 15 surrounds the inner ring 17 by means of an angled flange 16, which is rotationally fixed to the seal carrier 12. The seal carrier 12 is coated, at least on the side facing the cover ring 15, with a sealing material 23, in particular an elastomer, from which two sealing lips 19, 20 are formed. The sealing lip 19 is supported on the rim 16 of the cover ring 15 and the sealing lip 20 is aligned in the direction of a radial section 21 of the cover ring 15.

[0029] At least the sealing lip 20 consists of a magnetorheological elastomer material that encloses magnetically activatable particles. This allows the length S of the sealing lip 20 to be changed, in particular lengthened, when subjected to a magnetic field. A ring coil 22 is fixed radially above the sealing lip 20 on the sealing carrier 12 for applying the magnetic field. The ring coil 22 can be controlled via a control or current regulation (not shown), which lengthens the current-energized sealing lip 20. The ring coil 22 can be controlled via a control or current regulation (not shown), i.e., it can be supplied with an electric current, thereby generating a magnetic field that then acts on the sealing lip 20 and lengthens it. This establishes a magnetic circuit 24 that encloses the sealing lip 20, the section 21 of the cover ring 15, and, in some areas, the sealing carrier 12. Starting from the in Fig. In the 2 shown, non-adhering position, the sealing lip 20 is extended by the magnetic field up to the point shown in Fig. 3 shown supported position at section 21. By means of a sensor system (not shown) which is in contact with the control system, an current can be applied to the sealing lip 20 depending on different characteristic values ​​or parameters such as the rotational speed of the wheel bearing unit 11 and / or the temperature.

[0030] The Fig.Figure 4 illustrates, using a diagram, the control logic for the sealing lip 20, which consists of magnetorheological elastomer material (MRE). The length S of the sealing lip can be changed or controlled by applying an electric current, depending on the rotational speed. The diagram shows two offset abscissas (x-axes) for time t and an ordinate (y-axis) assigned to the rotational speed n. A dotted line X, running parallel to the upper time axis t, defines a rotational speed threshold above which the contact force of the sealing lip 20 is to be changed. The area above line X corresponds to a position of the sealing lip 20 that is not in contact with the cover ring 15. Extending from line X in the direction of the time axis t, the zone begins in which the sealing lip 20 comes into contact with the cover ring 15.The lower time axis t illustrates the corresponding current supply, the control of the sealing lip 20 via the ring coil 22 by the switching cycles labeled as stages E for "On" and A for "Off". In this example, for rotational speeds below the threshold, the coil is energized, thus extending the sealing lip and bringing it into contact. If the rotational speed rises above the threshold, the current supply is switched off, the magnetic field is no longer effective, and the sealing lip returns to its shorter initial length without contact. There are only two states here: "On" and "Off"—lip touching or lip not touching. However, continuous transitions with varying contact force are also conceivable. Reference symbol list 1 wheel bearing unit 2 Wheel hub 3 rolling elements 4 outer ring 5 rolling elements 6 rolling elements 7 inner ring 8 Sealing arrangement 9th Federal State 10 Gear geometry 11 Wheel bearing unit 12 sealing carriers 13 Board 14 Outer ring 15 Cover ring 16 Board 17 inner ring 18 Sealing arrangement 19 Sealing lip 20 sealing lip Section 21 22 Ring coil 23 Sealing material 24 Magnetic circuit n rotational speed s length sealing lip t time x threshold

Claims

Sealing arrangement for sealing a rolling bearing (3) of a wheel bearing (1, 11) of a vehicle, wherein the rolling bearing (3) comprises a rotating inner ring (7, 17) and a stationary outer ring (4, 14), to which a radially oriented sealing carrier (12) with at least one sealing lip (19, 20) is assigned, which interacts with a cover ring (15) rotatably fixed on the inner ring (7, 17), characterized in that a ring coil (22) is assigned to the sealing carrier (12), which can be acted upon with an electric current and the sealing lip (20) consisting of a magnetorheological elastomer material can be influenced by the magnetic field generated by the current, whereby a length (S) of the sealing lip (20) can be controlled. Sealing arrangement according to claim 1, characterized in that the ring coil (22) is controlled via a control unit processing input information, wherein a magnetic circuit (24) extending from the ring coil (22) and including the sealing carrier (12), the sealing lip (20) and the cover ring (15) is closed. Sealing arrangement according to claim 2, characterized in that the control unit controls the ring coil (22) depending on input signals from a temperature sensor. Sealing arrangement according to claim 2, characterized in that the control unit controls the ring coil (22) depending on input signals from a speed sensor. Sealing arrangement according to one of the preceding claims, characterized in that the ring coil (22) is fixed to the sealing carrier (12) and is enclosed by the sealing material (23) towards the interior of the sealing arrangement (18). Sealing arrangement according to one of the preceding claims, characterized in that in a sealed position the controllable sealing lip (20) is supported on a radial section (21) of the cover ring (15). Sealing arrangement according to one of the preceding claims, characterized in that the sealing arrangement (18) has a second, controllably designed sealing lip (19) associated with the sealing carrier (12) and supported on the cover ring (15). Sealing arrangement according to one of the preceding claims, characterized in that the sealing carrier (12) having an L-shaped cross-sectional profile together with the C-shaped cover ring (15) axially limit the sealing arrangement (18). Sealing arrangement according to one of the preceding claims, characterized in that the sealing carrier (12) and the cover ring (15) are each rotatably connected to the inner ring (14) or the outer ring (17) via angled flanges (13, 16). Sealing arrangement according to one of the preceding claims, characterized in that the sealing carrier (12) and the cover ring (15) are made of a chipless deformable, preferably corrosion-resistant, sheet steel.

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