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Resonance Test for Pivot Bearing Preload

IP.com Disclosure Number: IPCOM000123487D
Original Publication Date: 1998-Dec-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 2 page(s) / 71K

Publishing Venue

IBM

Related People

Prater, WL: AUTHOR [+2]

Abstract

This disclosure describes a method to accurately estimate pivot bearing preload by measuring the frequency of the first axial vibration mode.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 60% of the total text.

Resonance Test for Pivot Bearing Preload

   This disclosure describes a method to accurately estimate
pivot bearing preload by measuring the frequency of the first axial
vibration mode.

   Fig. 1 shows the actuator pivot bearing assembly,
comprised of two ball bearings (1) located at the opposite ends of
one shaft (2) and one sleeve (3).  The pivot bearing is assembled by
either adhesive bonding or press fitting the bearings to the shaft
and sleeve.  During the assembly, the ball bearings are lightly
preloaded to achieve the desired structural stiffness.  A preload
that is either too high or too low from the intended nominal would
adversely effect the bearing's running torque, vibration from
raceway/ball defects and system stiffness.

   The means to estimate the pivot bearing preload is
accomplished by measuring the frequency of the first axial vibration
mode between the shaft and sleeve.  By knowing the masses of the
moving and stationary parts of the pivot bearing, the stiffness can
be determined.  The following equation is used to calculate the axial
stiffness.
       K=<4 omega sup2 pi sup2 m sub 1 m sub 2> over
       m sub 1 + m sub 2>
  where:
         o  K is pivot axial stiffness, MN/m
         o  omega is frequency, Hz
         o  m sub 1 is mass of shaft, inner rings and screw
            glued to an accelerometer, Kg
         o  m sub 2 is mass of sleeve and outer rings, Kg

   From the calcu...