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Optimization of Ball Bearing Runout for Linear Actuators

IP.com Disclosure Number: IPCOM000099434D
Original Publication Date: 1990-Jan-01
Included in the Prior Art Database: 2005-Mar-14
Document File: 2 page(s) / 68K

Publishing Venue

IBM

Related People

Taylor, MG: AUTHOR

Abstract

In a common type of linear actuator, wherein a carriage is supported on guide rails by bearings 10 consisting of balls 4 in a conventional cage type ball race, any variation in the distance between the center of the bearing and the guide rail (the 'axle' height, h, or radial runout of the bearing), can result in a tilting of the carriage. In a disk file system, where the actuator is used to move magnetic heads over the surface of a magnetic disk, and where servo information is read from a dedicated surface, the tilting results in track misregistration. This article discloses a linear actuator in which the reduction of axle height variation and, therefore, of track misregistration, is achieved by optimization of a number of bearing parameters; principally the radial play and the number of balls.

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Optimization of Ball Bearing Runout for Linear Actuators

       In a common type of linear actuator, wherein a carriage is
supported on guide rails by bearings 10 consisting of balls 4 in a
conventional cage type ball race, any variation in the distance
between the center of the bearing and the guide rail (the 'axle'
height, h, or radial runout of the bearing), can result in a tilting
of the carriage. In a disk file system, where the actuator is used to
move magnetic heads over the surface of a magnetic disk, and where
servo information is read from a dedicated surface, the tilting
results in track misregistration. This article discloses a linear
actuator in which the reduction of axle height variation and,
therefore, of track misregistration, is achieved by optimization of a
number of bearing parameters; principally the radial play and the
number of balls.

      In such a bearing system, the variation in axle height is
caused by three effects which are dependent on the positions of the
balls relative to the radial load point. In order to model these
effects, the positions to examine are when the load is in line with a
ball (Fig.  1(a)) and when the load is between two balls (Fig. 1(b)).
    The three causes of variation in axle height are:
    1.   Bending of the outer race 12 of the bearing:
    This is a load dependent effect whereby the axle height is
smaller when the load is between the two balls than when it is in
line with a ball.
    2.   Compression of the balls:
    The load on the bearing cau...