On Error Torques of Squeeze-Film Cylindrical Journal Bearings

Abstract

The squeeze-film bearing has been considered for the output axis of high performance gyroscopes. Viewing this application, it is important that the parasitic torque of the bearing be very small. In the case of a squeeze-film journal bearing, parasitic torque can result from tolerance effects which disrupt rotational symmetry of the bearing. This problem has been studied by assuming ellipses for the tolerances of the journal and bearing surfaces as well as the squeeze motion, respectively. Each tolerance effect is assumed to be axially uniform. The mathematical problem is linearized with respect to each of the tolerances and the radial displacement of the journal. It was found that the parasitic torques do not depend on the radial displacement of the journal. The parasitic torques result from interactions among the three types of tolerance effects while each of the tolerances alone will not lead to any torque. Numerical estimates based on the geometry of a typical gyroscope and current fabrication practice shows such parasitic torques can seriously impair the accuracy of the gyroscope.