Device for pre-stressing a wheel bearing

A clamping device (1) for receiving and for the clearance-free prestressing of a wheel bearing comprises a clamping mechanism (3) which radially prestresses the wheel bearing (8) from the outside.

FIELD OF THE INVENTION

The invention relates to a device for prestressing a wheel bearing with an arbor rotating at least at times about an axis of rotation of the wheel bearing toward a clamping mechanism, wherein the clamping mechanism prestresses the wheel bearing in the device and wherein the arbor sets into rotational motion a flange, supported rotatably in an outer ring of the wheel bearing, about the rotational axis of the wheel bearing at least at those times when the wheel bearing is prestressed in the device.

BACKGROUND OF THE INVENTION

Such a device is described in DE 199 83 909 T1 wherein a wheel bearing with an axle spindle is received, which initially still has a clearance between the inner ring and the roller bodies as well as the outer ring and a flange of the wheel bearing arrangement is fixedly connected to the inner ring of the wheel bearing. For this purpose, the flange extends fixedly within a hollow cylindrical section, formed integrally on the flange, into the bore of the inner ring. The axle spindle, and consequently the outer ring, are secured on the device rotationally fixed with respect to the rotational axis of the wheel bearing. An arbor is disposed concentrically to the bearing rings and to the flange through the bore of the flange denoted in DE 199 83 909 by wheel hub.

The device exerts a clamping force on the wheel hub and on the inner ring of the wheel bearing to generate the prestress in the wheel bearing, which prestress corresponds to the conventional factory prestressing of the wheel bearing on the vehicle. After the generation of such a prestress on the inner ring, the arbor is set in rotation and then carries along the flange rotating about the axis of rotation of the wheel bearing arrangement. The flange of the wheel bearing with the wheel bearing arrangement prestressed in such a manner can now be worked with a precision corresponding to the motor vehicle operation with respect to the axial run-out or the lateral run-out deviations. However, with this solution, satisfactory per se, the danger exists that during axial prestressing of the inner ring, the weakest sites of the inner ring on the raceways will be deformed such that the closeness required for optimum roller contact in the raceways to the roller bodies is disadvantageously deformed. Simultaneously, the danger exists that the ball[s] in the axial deformation of the inner ring and during the radial prestressing of the bearing rings with respect to one another, leave markings generated by plastic deformation, which disadvantageously shorten the service life of the wheel bearing.

OBJECTS OF THE INVENTION

It is an object of the invention to provide a device according to the species, with which the above listed disadvantages are avoided.

It is another object of the invention to provide a device with which the radial run-out and the lateral run-out can be tested at the flange or at a brake disk connected with the wheel bearing arrangement under operating conditions independently of the motor vehicle. These and other objects and advantages of the invention will become obvious from the following detailed description.

THE INVENTION

The device (1,19,24) of the invention for prestressing a wheel bearing (8), comprises an arbor (2,26) rotating at least at times about a rotational axis (8a) of the wheel bearing (8) with respect to a clamping mechanism (3), wherein the clamping mechanism (3) prestresses the wheel bearing (8) in the device (1,19,24) and wherein the arbor (2,26) sets into rotational motion about the rotational axis (8a) of the wheel bearing (8), a flange (11) rotatably supported in an outer ring (8b) of the wheel bearing (8), at least at those times when the wheel bearing (8) is prestressed in the device (1,19,24), wherein the clamping mechanism (3) is disposed rotationally fixed with respect to the device (1,19,24) and for prestressing the wheel bearing (8) in the device (1,19,24) is movable from outside radially in the direction of the rotational axis (8a) against the outer ring (8b). The clamping mechanism in the device prestresses the wheel bearing from the outside radially in the direction of the rotational axis and comprises at least one clamping element movable against the outer ring as well as rotationally fixed with respect to the device. The outer ring is encompassed circumferentially by the clamping element(s). The wheel bearing is prestressed free of clearance via the outer ring and, moreover, with the same prestress as the same drive-operation ready wheel bearing mounted on the motor vehicle. Accordingly, the wheel bearing is clamped in the device with the later operational prestress. Deformations on the geometry of the raceways due to axial prestresses are avoided, since the outer ring is operationally at least partially radially constricted from the outside plastically as well as elastically in the device, in other words its diameter is decreased.

A prerequisite for the wheel bearing to be radially prestressed are inner rings of the wheel bearing which are fixed in place axially relative to the wheel bearing and axially with respect to one another and, consequently, axially immovable, if, instead of only one, two of the inner rings are set into the wheel bearing. The inner rings are axially fixed with respect to one another, for example by means of the flange section on which they are seated. For that purpose, for example, a flanged rim, also referred to as a roller rivet joint, is generated, which prestresses the inner rings axially against each other and holds these in contact together. Individual inner rings not braced with such a section, are braced, for example, by clamping bolts axially with respect to one another and fixed.

After the removal of the wheel bearing or the wheel bearing unit from the device, the outer ring resiliently rebounds again to the extent to which it had been elastically prestressed, such that the wheel bearing arrangement after the removal from the device, has again the clearance that existed initially. Intentional plastic deformations of the outer ring remain.

Two uses for the device of the invention are intended. For one, the flange on the wheel bearing unit clamped with operating stress in the device is worked by machining with a high precision of concentric running and axial running. Alternatively, it is, furthermore, also provided to work with high precision a brake disk secured on the flange of the wheel bearing arrangement. The arbor, connected torsion-tight with the wheel bearing, generates the necessary rotation of the flange. Furthermore, by means of the device of the invention, the deviations from concentric running and axial running under operating conditions of the rotating flange or of the rotating brake disk can be checked on the flange in the bearing prestressed with operating prestress with suitable measuring means. Measurements are carried out either after the machining working in the fabrication area and/or separately from the machining working in the fabrication area and/or separately from the machining working in the quality control.

The clamping element with the arbor rotating is preferably movable prestressing radially against the outer ring. The radial prestress is consequently not exerted in the static state of the bearing, but rather is only exerted onto the bearing when the inner ring rotates relative to the outer ring fixed on the device and the roller bodies roll out on the raceways. Spot-form markings through the roller bodies in the raceways of the bearing rings are consequently avoided. The running quality, and consequently the service life, of the wheel bearing arrangement is considerably increased.

Accordingly, one prerequisite is the rotating driving of the inner rings with respect to the outer ring(s) fixed on the device. The arbor, for this purpose, drives the flange and, depending on the implementation of the device, is brought to the wheel bearing arrangement axially from the sides of the end face, directed axially toward the outside away from the wheel bearing, of the flange or from a direction axially opposite thereto. Between the arbor and the flange, alternatively between the arbor and a hollow cylindrical section on the flange seated concentrically inwardly with respect to the inner rings, or between the arbor and the inner rings, is established either a form-fit or a frictional closure rotational connection. Wheel bearing arrangements for driven wheels comprise, as a rule, on the inner circumferential side on the section of the flange extending axially through the inner rings and staying the inner rings radially and axially, a splining or the like for engaging the drive.

This inner splining is preferably utilized in the working of the wheel bearings in the device of the invention for the driving by the arbor. For this purpose, the arbor is provided with an outer notching, with which the arbor engages the inner notching on the flange and via which a form-fit is established. If such a splining is omitted, all conceivable force-friction closure and further form-fit and detachable connections between the arbor and the flange or the inner ring(s) are provided.

Further implementations as well as embodiments of the invention are explained in further detail in the section “Detailed Description of the Drawing”.

The invention further provides a method for the clearance-free prestress of a wheel bearing with a device of the invention. Therein, the following method steps are comprised:1) the wheel bearing is first introduced axially into the device with the outer ring against an axial stop. Between the clamping mechanism and the outer diameter of the outer ring of the wheel bearing, initially a large radial clearance is present, such that the wheel bearing with the outer ring can be introduced into the clamping mechanism axially up to the stop. On the stop, the bearing is first aligned, for which reasons preferably a three-point contact of the stop is provided.2) The clamping mechanism clamps the wheel bearing unit initially exclusively for holding it fixed in the device. The clamping forces produced by the clamping mechanism are so low that no elastic deformations of the outer ring, and consequently no changes of the bearing clearance, are generated.3) The arbor is moved to the flange before, concurrently or after the clamping-in of the outer ring into the clamping mechanism, and brought with the flange into a force-friction closure or into a form-fit closure.4) By means of the arbor, the flange is driven rotating about the rotational axis.5) The outer ring is radially deformed by means of the clamping tool with the arbor rotating and consequently with the flange rotating by constriction so far until the clamped-in bearing is clearance-free and prestressed, and optionally deformed further.6) the rotating flange or optionally the brake disk secured on the flange is worked on the prestressed bearing by machining, if necessary, and/or is tested.

DETAILED DESCRIPTION OF THE DRAWING

FIG. 1shows a front view of a device1of the invention and inFIG. 2is shown a longitudinal section through this device1. The device1is substantially formed by an arbor2rotatable relative to the device and a clamping mechanism3. The arbor2is rotationally symmetrical and provided with an axial through-bore1. An axial bolt5extends through the through-bore4and the axial bolt5is axially screwed into a drive shaft6. The drive shaft6is supported relative to the device, and therewith to a carrier7, about the rotational axis8aof a wheel bearing8in the carrier7. With respect to carrier7, the clamping mechanism3, in the form of an elastic chuck9, is fixed and the elastic chuck9comprises several clamping jaws9auniformly distributed at the circumferential side about the axis of rotation8a.

InFIG. 1, the device1is depicted without the wheel bearing and with a front plate10which front plate10is omitted in the graphic representation according toFIG. 2. As is especially evident inFIG. 1, each clamping jaw9ais separated by a gap9bfrom a circumferentially adjacent clamping jaw9a. Each gap9bis filled with an elastic material9c, for example a highly resilient elastomer. The elastic material9cis preferably vulcanized at the flank side onto the clamping jaws9bor injected into the gap9b. As is evident fromFIG. 2, the clamping jaws9aare secured on a hollow cylindrical elastic ring developed integrally in terms of material with the clamping jaws, which ring extends axially from the clamping jaws9ato the carrier7and is fixed on carrier7.

The wheel bearing8is formed of an outer ring8b, roller bodies8cin the form of balls, ball cages8d, inner rings8eand8fand a flange11. The flange11comprises a centering seat11afor a wheel rim, not shown, of a motor vehicle wheel. Flange bores11band11cas well as a hollow cylindrical section11dare developed integrally with the flange11. The inner rings8eand8fare seated concentrically and fixedly on the section11d. A flanged rim11eprestresses the inner rings8eand8faxially against one another.

An intermediate ring12is seated radially between the clamping jaws9aand the outer ring8bwhich intermediate ring is hollow cylindrically and implemented with very thin walls as well as disposed concentrically with respect to the outer ring8b. The intermediate ring is slotted in the circumferential direction of the intermediate ring12, such that between its ends12aand12b, directed at the circumferential side toward one another, a compensation gap13is developed. By using such an intermediate ring12in the clamping mechanism3, it is possible to set into the device different wheel bearings, whose outer rings vary in outer diameter in a range from zero of the wall thickness up to twofold magnitude of the wall thickness of the intermediate ring12. It is also conceivable to employ intermediate rings with greater or smaller radial wall thickness than with the wall thickness of the intermediate ring12. It is also conceivable to employ intermediate rings with greater or smaller radial wall thickness than with the wall thickness of the intermediate ring12.

With the forces F acting in the direction of the arrow, the clamping jaws9aclamp closed radially in the direction of the rotational axis8a. The wheel bearing8is first clamped with low forces into the device1, wherein the wheel bearing8is aligned on three of the stops14, of which only one is shown in the drawing. The arbor2is movable with the drive shaft6in the axial directions denoted by the double arrow and can therefore be brought into form-fit engagement with section11d. The form-fit closure between section11dand arbor2is established by a splining15. Axial offset between the center axis of arbor2and the rotational axis of the inner ring8eare compensated by the arbor2supported by a cardanic joint on the axial bolt via rubber-elastic compensation elements16. The arbor2is for this purpose with the cylindrical wall of the through-bore4spaced apart from the axial bolt5such that it is supported floatingly on the compensation elements16stayed on the axial bolt5.

The forces denoted by F inFIG. 2onto the clamping jaws9aare generated by at least one clamping element17of device1. In the following, different embodiments of the invention are described, in which different clamping elements are provided. According to the representation afterFIG. 3, the clamping element17is a rigid clamping ring18disposed concentrically with the clamping jaws which clamping ring18encompasses the clamping jaws9aradially on the outside as well as closed circumferentially. On the clamping ring18, an inner cone18ais developed. The clamping ring18with respect to the clamping jaws9a, and therein axially aligned with the rotational axis8a, is displaceable against the clamping jaws9aand away from the clamping jaws9a. For clamping closed the clamping mechanism3, the clamping ring18is pressed axially against the clamping jaws9aand therein is radially on the outside on the clamping jaws9aat least in sections. The possible movement directions of the clamping ring18are marked inFIG. 3by a double arrow denoted by A1. The clamping jaws9a, through contact with the inner cone18a, with the clamping ring moved is forced to yield in the direction denoted by arrow A2and to constrict the outer ring8belastically.

The clamping jaws9abrought close to one another through the clamping-closed forces circumferentially via the gap9b, compress the elastic material9c. In the elastic material9cconsequently during the prestressing of the wheel bearing8, a compression stress is present, which, after clamping-closed forces are removed, moves the clamping jaws9acircumferentially away from one another and consequently releases the wheel bearing8.

FIG. 4depicts a device19, whose structure corresponds substantially to the structure of device1. In contact on the clamping jaws20, minimally modified in comparison to the clamping jaws9aof device1, are clamping elements17in the form of stroke-movable pistons21. During the clamping into the device19and the prestressing of the wheel bearing8in the device19, an hydraulic, optionally mechanically initiated, force acts onto the piston21. The clamping jaws20yield radially elastically in the direction of the outer ring8band prestress it or constrict it. Each of the clamping jaws20is elastically fixed with respect to carrier7by means of a lever20awhich levers20aare circumferentially separated from one another by longitudinal slots20b.

FIG. 5depicts the device19with a further implementation of a clamping element17, which clamping element17is an hydraulic pressure chamber22encompassing the clamping jaws20circumferentially about the rotational axis8a. The pressure chamber22is pressurized with an hydraulic pressure fluid23. The hydraulic pressure in the pressure chamber22leads to the bulging-out of the pressure chamber22at its weakest site. The weakest site or the pressure chamber22is the thin wall (optionally also one or several radially movable pistons)22adirected radially inwardly, which bulges out radially inwardly and acts on the clamping jaws20.

FIG. 6depicts a device24partially in section. The device24comprises an hydraulic pressure chamber25as a clamping mechanism3, which chamber is filled with an hydraulic pressure fluid23. The thin wall25aof pressure chamber25bulges under pressure radially inwardly and constricts the outer ring under high pressure, such that the wheel bearing8is prestressed. The radially outer thick wall25bof pressure chamber25remains rigid even under high pressures. During the radial prestressing of the outer ring8b, flange11of wheel bearing8is connected under force-friction closure with an arbor26and rotates with it about the rotational axis8a. The force friction closure between arbor26and flange11is generated through a radial spreading open of arbor26, for which reason the arbor26comprises spreading jaws26awhich are movable radially outwardly. Via the spreading jaws, the clamping diameter of arbor26is variable, such that the arbor26is also adaptive with respect to wheel bearings with differing inner dimensions of the flange. Conceivable for these purposes are also adaptive arbors, which are provided with compensation rings, for example of rubber, which have either fixed or variable diameters.