Shaft run-out analysis by Gear-type Magnetic rotary encoder

摘要

It is difficult to use an expensive and high precision optical rotary encoder in an environment using a machine tool which cannot avoid the influence of water, oil, dust and vibration. For this reason, magnetic rotary encoders are generally used for machine tools. In particular, the gear type magnetic rotary encoder (GMR-Encoder) is a low-cost rotary encoder which makes use of magnetoresistive effect and easy to handle. Even if the gear teeth number is several hundreds, its resolution can be made high resolution by 1,000 to 10,000 times using electrical interpolation. We have been researching and developing technology to make this GMR-Encoder an angle sensor capable of outputting highly accurate angle signals. As a result, the angular accuracy of GMR-Encoder was able to reach ± 10" or less by using Self A (Self-calibratable angle device) principle. Furthermore, this GMR-Encoder not only outputs angular position information, but also makes it possible to add a function to detect the rotational shaft runout of the mounted spindle shaft. Continuous observation of changes in the amount of shaft runout is the information necessary for failure prediction and life management of machine tools. In our presentation, we introduce the structure of a Self A GMR-Encoder with high precision and runout detection function and explain the results of evaluation of its performance.