Study on cage slip for rolling bearing under speed variation conditions

The rolling bearing failure from cage slip under fast speed variation is an important issue that has drawn a wide interest. To ensure the safe operation, cage slip needs to be detected. However, due to the limit of bearing working environment of high temperature, oil mist, and small mounting space, the conventional methods such as optical fiber, ultrasound, and eddy current detection are not always feasible. This paper presents a novel method to detect cage slip based on weak magnetic detection under the speed variation. The rolling bearing, which is in the earth magnetic field, can be magnetized weakly. By the detection of the weak magnetized bearing on the earth magnetic field disturbance, the roller speed information can be obtained. This method is not affected by the bearing work environment. Then, the signal processing technology based on the ridge detection is proposed. By the speed spectrum of inner raceway, the searched path can be re-grouped. And the searched boundary is determined by assuming the roller pure rolling. Combining the searched path and the boundary, the local neighborhood of the roller rotational instantaneous frequency (IF) is determined. By finding the magnitude maximum of the local neighborhood, the roller IF can be extracted. Finally, the time-varying spectrum of the cage slip can be evaluated under the speed variation. By the comparison with the traditional optical method, it illustrates that the cage slip goes through dramatic changes under speed variation and is almost unchanged under the stabilization stage.