Method for adjusting the preload in a bearing assembly and bearing assembly

Abstract

A method for setting a preload in a bearing assembly, the bearing assembly having at least one rolling-element bearing with at least one bearing inner ring and at least one bearing outer ring, the method including changing the preload in the bearing assembly starting from an initial value and measuring the electrical resistance between the bearing inner ring and the bearing outer ring and terminating the changing of the preload in the bearing assembly in response to a target value for the electrical resistance being reached.

Claims

1. A method for setting a preload in a bearing assembly, wherein the bearing assembly comprises at least one rolling-element bearing with at least one bearing inner ring and at least one bearing outer ring, and wherein the at least one bearing inner ring and the at least one bearing outer ring are provided with an electrical insulation so that they are electrically isolated with respect to their respective attachments, the method comprising: a) increasing the preload in the bearing assembly starting from a first initial value, or decreasing the preload in the bearing assembly starting from a second initial value, and measuring the electrical resistance between the bearing inner ring and the bearing outer ring; and b) terminating the changing of the preload in the bearing assembly in response to a target value for the electrical resistance being reached.

2. The method according to claim 1, wherein the target value for the electrical resistance is determined by a calibration measurement on the bearing assembly or on a substantially structurally identical bearing assembly, wherein the target value is defined as an electrical resistance that is present when a desired preload prevails in the bearing assembly.

3. The method according to claim 1, wherein the at least one bearing inner ring and the at least one bearing outer ring are free of the electrical insulation at at least one point.

4. The method according to claim 3, wherein the point at which the at least one bearing inner ring and the at least one bearing outer ring are kept free of electrical insulation is an end side of the at least one bearing inner ring and the at least one bearing outer ring.

5. The method according to claim 1, wherein the electrical resistance is measured while the preload in the bearing assembly is being increased or decreased.

6. The method according to claim 1 including: determining the target value by: setting a preload of a reference bearing assembly, the reference bearing assembly being substantially identical to the bearing assembly; and measuring an electrical resistance of the reference bearing assembly by measuring an electrical resistance between a first point on a bearing inner ring of the reference bearing assembly and a second point on a bearing outer ring of the reference bearing assembly.

7. A bearing assembly including a device for setting preload, wherein the bearing assembly comprises at least one rolling-element bearing including at least one bearing ring and at least one bearing outer ring, wherein the device for setting the preload comprises: a resistance meter for measuring the electrical resistance between the bearing inner ring and the bearing outer ring; an electrical connection between the resistance meter and the bearing inner ring, and an electrical connection between the resistance meter and the bearing outer ring; an adjusting possibility for the preload in the bearing assembly.

8. The bearing assembly according to claim 7, wherein the bearing inner ring and/or the bearing outer ring is provided with an electrical insulation so that the bearing inner ring and/or the bearing outer ring is electrically insulated with respect to its attachment.

9. The bearing assembly according to claim 8 wherein the bearing rings are free of the electrical insulation at at least one point.

10. The bearing assembly according to claim 9, wherein the point at which the bearing rings are kept free of electrical insulation is located at an end side of the bearing rings.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An exemplary embodiment of the invention is illustrated in the drawings.

(2) FIG. 1 shows a bearing assembly, of which one rolling-element bearing is depicted, using which a shaft is supported in a housing, and

(3) FIG. 2 schematically shows the measuring of the electrical resistance between the bearing rings for the purpose of determining the axial bearing preload.

DETAILED DESCRIPTION

(4) In FIG. 1 a bearing assembly 1 is outlined, using which a shaft 5 is supported in a housing 6. For this purpose two rolling-element bearings 2, preloaded against each other, in the form of tapered roller bearings are used, of which only one is depicted in FIG. 1; the other, not-depicted bearing is likewise a tapered roller bearing and disposed on the left in FIG. 1, so that the two bearings are positioned in back-to-back arrangement. The rolling-element bearing 2 has a bearing inner ring 3 and a bearing outer ring 4, between which rolling elements 17 are disposed.

(5) At the contact points to the attachments (shaft 5 and housing 6) the two bearing rings 3 and 4 include an electrical insulation 15 or 16. A current flow from bearing ring 3, 4 to attachment 5, 6 is thus prevented.

(6) However, on their end sides 9 or 10 the two bearing rings 3, 4 each include an uninsulated point 7 or 8 as is apparent from FIG. 2. Here the rolling-element bearing 2 is schematically depicted, wherein, however, the rolling elements 17 are symbolized as resistances with variable electrical resistance. The electrical resistance between the bearing inner ring 3 and the bearing outer ring 4 with current flow through the rolling elements 17 is variable, since it depends on the preload by which the rolling-element bearing 2 is axially preloaded (see explanation above). The higher the preload is, the more strongly the rolling elements 17 and the bearing rings 3, 4 are pressed together. The contact surfaces of the Hertzian stress are thus larger and the electrical resistance R smaller.

(7) This is presently utilized to determine the degree of the axial preload.

(8) This is particularly apparent from FIG. 2. Here it can be seen how an electrical connection 12 between the bearing inner ring 3 and a resistance meter 11 as well as an electrical connection 13 between the bearing outer ring 4 and the resistance meter 11 has been produced.

(9) Now initially a low preload value is started with (preferably with the preload zero) for setting the preload. For this purpose an adjustment means for the preload in the form of a nut 14 is initially tightened only with slight torque. The electrical resistance R is measured.

(10) It can be provided here that the bearing rings 3, 4 are free of an insulation at a plurality of points. Then the contact can be produced at a plurality of points of the respective bearing ring and an average value of the resistance can be formed. This increases the accuracy of the proposed method.

(11) In FIG. 1 the possibility is also drawn with dashed lines that alternatively or additionally the bearing outer ring 4 (the same applies to the bearing inner ring) is also contacted by its other end side and provided with a cable.

(12) However if only the contact with the outer ring 4 depicted with dashed lines is selected and the inner ring 3 is provided with a cable in the manner depicted, the current flows directly through the rolling elements 17, i.e., the current flow in this case is conducted in an improved manner through the rolling elements 17, which supports the proposed procedure.

(13) With further tightening of the nut 14 the preload increases. Thus the bearing rings and rolling elements are pressed together more strongly. The electrical resistance R thus decreases.

(14) The nut 14 is now tightened further until the electrical resistance R.sub.actual (actual value) corresponds to a prescribed target value R.sub.target, which has been obtained from a calibration measurement.

(15) Thus the desired degree of the preload can be set in a simple manner

REFERENCE NUMBER LIST

(16) 1 Bearing assembly

(17) 2 Rolling-element bearing

(18) 3 Bearing inner ring

(19) 4 Bearing outer ring

(20) 5 Attachment (shaft)

(21) 6 Attachment (housing)

(22) 7 Uninsulated point

(23) 8 Uninsulated point

(24) 9 End side

(25) 10 End side

(26) 11 Resistance meter

(27) 12 Electrical connection

(28) 13 Electrical connection

(29) 14 Adjusting possibility (nut)

(30) 15 Electrical insulation of the bearing inner ring

(31) 16 Electrical insulation of the bearing outer ring

(32) 17 Rolling element

(33) R.sub.actual Electrical resistance

(34) R.sub.target Target value for the electrical resistance