Soichiro Kato

A Design of Crowning to Reduce Ball Passage Vibrations of a Linear Guideway Type Recirculating Linear Ball Bearing

This paper deals with a design of crowning to reduce the ball passage vibrations of a linear guideway type recirculating linear ball bearing (linear bearing) with the crowning length L C (1.2s≤L C ≤1.7s, where s is the distance between the adjacent balls in the load zone). First, a fundamental condition to reduce the ball passage vibrations is provided. Second, a design method of the crowning by applying an approximate curve (an assumed functional formula) to the control points (satisfying the fundamental condition or being the intersection of straight and crowning areas of a raceway) is presented. Third, the design procedure is explained by giving an example. In the design example the power function crowning fits the control point best. In addition, the calculated amplitude for the power function crowning is lower than those for the circular arc crowning and the crowning of the commercial linear bearing. Finally, the validity of the presented design method is confirmed experimentally.

Effects of Grease Types on Vibration and Acoustic Emission of Defective Linear-Guideway Type Recirculating Ball Bearings

In this paper, vibrations and acoustic emissions (AEs) of defective linear-guideway type recirculating ball bearings under grease lubrication were measured. The experimental results show that the vibration and AE amplitudes (the pulse amplitudes, the RMS values) of both the normal and defective bearings have a tendency to be reduced when a grease with higher base oil viscosity is used. Under the same type of grease, the RMS values of the vibrations and AE of the defective bearings increase as the defect angle increases. However, the increases of the RMS values due to increased defect angle are reduced when a grease with higher base oil viscosity is used.Copyright

Effects of Ball Groupings on Ball Passage Vibrations of a Linear Guideway Type Ball Bearing (Pitching and Yawing Ball Passage Vibrations)

The effects of ball groupings on the pitching and yawing ball passage vibrations of linear guideway type ball bearings (linear ball bearings) under low speed operation were studied. For this study, the test linear ball bearings (which can retain the ball grouping in operation) with three types of ball groupings were manufactured, and the pitching and yawing ball passage vibrations of each test linear ball bearing were measured using a laser autocollimator. Moreover, a calculation method of the ball passage vibrations for a linear ball bearing with an arbitrary ball grouping was presented. According to the presented method the ball passage vibrations for three types of ball groupings were calculated. The experimental and calculated results show that the occurrence of the pitching and yawing ball passage vibrations was affected by the ball groupings. For the occurrence, the waveforms, and the amplitude of the pitching and yawing ball passage vibrations for the ball groupings, the calculated results based on the presented method almost matched with the experimental results.Copyright

Carriage Drift in Linear-Guideway Type Roller Bearings

This study deals with carriage drift (which is the differences of the carriage displacements or angular displacements at a certain position on a rail during a forward and return process) in linear-guideway type roller bearings. First, the displacements and angular displacements of the carriage of the “nonrecirculating” linear roller and ball bearings under a reciprocating operation were measured. The experimental results showed that carriage drift (in the horizontal, vertical, yaw, and pitch directions) occurred in the roller bearing and not in the ball bearing. Next, in relationship to roller skew, the generating mechanism of carriage drift in roller bearings was examined by a multibody analysis (MBA), then the generating mechanism of carriage drift was explained. Finally, to reduce carriage drift by restricting the roller skew, an antiskewing brace (ASB) was developed.