Method for setting the preload in a bearing assembly

Abstract

A method for adjusting an axial preload in a bearing assembly that has two rolling-element bearings that are axially pressable against each other, each of the two rolling-element bearings including at least one bearing outer ring and at least one bearing inner ring and at least one row of rolling elements disposed between the at least one bearing outer ring and at least one bearing inner ring. The method includes a) driving the bearing assembly by rotating one of the bearing outer ring and the bearing inner ring while holding other bearing ring fixed and measuring the rotational speed of the circulation of the rolling elements about the bearing assembly axis or of a bearing cage about the stationary bearing ring, and b) changing the axial preload in the bearing assembly until a desired rotational speed has been obtained.

Claims

1. A method for adjusting an axial preload in a bearing assembly having an axis of rotation and comprising two rolling-element bearings configured to be axially pressable against each other, each of the two rolling-element bearings including a first ring, a second ring and a row of rolling elements disposed between the first ring and the second ring, the method comprising: providing a marking on one of a rolling element in the row of rolling elements and a cage guiding the row of rolling elements; rotating the first ring while holding the second ring fixed, with no or only a small amount of axial preload in the bearing assembly; illuminating the bearing assembly with a stroboscope lamp; after rotating the first ring, adjusting a frequency of the stroboscope lamp based on an initial angular speed of the marking about the axis of rotation of the bearing assembly; after adjusting the frequency of the stroboscope lamp, increasing the axial preload in the bearing assembly while continually illuminating the bearing assembly with the stroboscope lamp at the frequency; calculating a current angular speed of the marking based upon locations of the marking when the bearing assembly is illuminated by the stroboscope lamp such that the current angular speed of the marking is not calculated by using vibrations of the bearing assembly and no vibrations of the bearing assembly are measured; determining a change of angular speed of the marking by comparing the initial angular speed and the current angular speed; stopping the increasing of the axial preload in the bearing assembly in response to a the change of angular speed equaling a predetermined change of angular speed of the marking about the axis of rotation which corresponds to a predetermined preload.

2. The method according to claim 1, wherein the marking comprises a spot on the rolling element and/or on the cage.

3. The method according to claim 2 wherein the spot comprises reflective paint.

4. The method according to claim 1, wherein the marking is formed on an end side of the rolling element or an end side of the cage.

5. The method according to claim 1, wherein the stopping of the increasing of the axial preload occurs in response to a determination that the marking illuminated by the stroboscope lamp has a predetermined rotational speed of circulation.

6. The method according to claim 1 wherein the two rolling-element bearings are tapered roller bearings.

7. The method according to claim 1, wherein the two rolling-element bearings are angular contact ball bearings.

8. The method of according to claim 1 including determining bearing slip by comparing a theoretical angular velocity of the circulation of the rolling elements or of the cage to the current angular speed of the marking.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An exemplary embodiment of the invention is illustrated in the drawings, wherein:

(2) FIG. 1 is a front elevational view of a bearing assembly, viewed in the direction of the axis of rotation, that includes two tapered roller bearings that are pressable against each other.

(3) FIG. 2 is a radial sectional view of the bearing assembly of FIG. 1;

(4) FIG. 3 is a flowchart illustrating a preferred method of setting the preload in a bearing.

DETAILED DESCRIPTION

(5) A bearing assembly 1 is illustrated in the FIGS. 1 and 2 and includes two rolling-element bearings 2 and 3, in this embodiment, two tapered roller bearings in an O-arrangement. The bearings 2 and 3 comprise bearing outer rings 4 and 5 and bearing inner rings 6 and 7. In this embodiment, the two bearing outer rings 4 and 5 are unitary or one-piece rings.

(6) Rolling elements 8, 9, in this embodiment tapered rollers, are disposed in a known manner between the bearing outer rings 4, 5 and the bearing inner rings 6, 7. The tapered rollers 8, 9 are each guided by a cage 10, 11. The bearing rings 4, 5, 6, 7 of the bearing assembly 1 rotate about the axis of rotation a.

(7) This construction (structure) per se is known as are conventional methods of setting a preload of such a bearing assembly. In order to set and maintain the preload a (clamping) nut (not shown) disposed concentrically with the axis of rotation a is tightened so that the two tapered roller bearings 2, 3 are pushed towards each other axially. This produces an axial (and radial) preload in the bearing assembly.

(8) In order to be able to set (adjust) the preload in a simple manner, the following steps, as illustrated in FIG. 3, are performed: A first step 20 is preferably to apply a marking 12 (and/or 12) on one end side of the rolling elements 8 (marking 12) or on the cage 10 (marking 12), with respect to one of the bearings 2, 3. The marking 12 in this case is a spot made from reflective paint. These two alternative marking locations are both illustrated in FIG. 1. The marking 12 is a spot which has been applied to one of the rolling elements 8; alternatively or in addition the cage 10 can be provided with the marking 12.

(9) The method preferably includes the step 22 of driving the bearing assembly to rotate with no or with only a minimal preload applied. In this embodiment, the bearing outer ring 4, 5 is driven while the bearing inner rings 6, 7 are stationary. The method may include the step 24 of adjusting the timing of a stroboscope lamp (not shown) such that the marking 12 stands still as the cage rolling elements 8 and cage 10 rotate in the strobe light. A plurality of rolling elements can also be provided with a marking 12, so that the standing still point can be produced even at a lower rotational speed.

(10) The method preferably includes the step 26 of slowly tightening the nut (not shown) for preloading the two tapered roller bearings 2, 3. A gap 13 is provided between the two inner rings 6, 7, so that the setting (adjusting) of a preload is possible. The result is that the rolling elements 8, 9 are subjected to a force radially and axially and are slightly compressed.

(11) This compression changes the actual effective rolling radius in the bearings 2, 3, and, consequently, with an otherwise constant driving speed of the outer ring, a change of the rotational speed or angular speed of the rolling elements 8, 9 and thus also of the cage 10, 11 about the bearing axis of rotation a takes place. The method may include a step 28 of calculating the angular speed of the rolling elements 8, 9 and/or the change of the angular speed of the rolling elements 8, 9.

(12) The frequency of the stroboscope lamp is kept constant, and thus tightening the nut causes the marking 12 or 12 to migrate under the stroboscope in the circumferential direction. The angular speed of the marking 12 or 12 is a direct and proportional measure for the preload in the bearing assembly 1.

(13) The method preferable includes the step 30 of tightening the (clamping) nut until the migrating-rotational speed of the marking 12 or 12 reaches a desired value. This desired value can be taken from the above-described characteristic curve previously determined for the bearing assembly. This produces the corresponding preload in the bearing, and preload can thus be set relatively precisely to a desired value without complex or time-consuming measures.

(14) Various modifications to the foregoing method are also possible. For example, instead of starting with little or no preload on the bearing assembly 1, the method could be performed by applying a greater than needed preload to the bearing assembly and decreasing the preload until a desired circulation speed of the marking 12 or 12 is achieved. Separately or in addition, instead of setting the frequency of the stroboscope so that the marking 12, 12 moves at a certain speed under the desired preload, the frequency of the stroboscope could be set so that the marking 12, 12 becomes stationary when the desired preload is obtained.

(15) Representative, non-limiting examples of the present invention were described above in detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Furthermore, each of the additional features and teachings disclosed above may be utilized separately or in conjunction with other features and teachings to provide improved methods for setting the preload of a bearing assembly.

(16) Moreover, combinations of features and steps disclosed in the above detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative examples of the invention. Furthermore, various features of the above-described representative examples, as well as the various independent and dependent claims below, may be combined in ways that are not specifically and explicitly enumerated in order to provide additional useful embodiments of the present teachings.

(17) All features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter, independent of the compositions of the features in the embodiments and/or the claims. In addition, all value ranges or indications of groups of entities are intended to disclose every possible intermediate value or intermediate entity for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter.

REFERENCE NUMBER LIST

(18) 1 Bearing assembly 2 Rolling-element bearing 3 Rolling-element bearing 4 Bearing outer ring 5 Bearing outer ring 6 Bearing inner ring 7 Bearing inner ring 8 Rolling element 9 Rolling element 10 Cage 11 Cage 12 Marking 12 Marking 13 Gap a Axis of rotation