Patent ID: 11921004
Assignee: NSK LTD.
Field: Measurement (Instruments)
Classification: CPC G  F | IPC F  G

Claim 4:
5. A linear motion drive device comprising a ball screw, a linear motion table of the ball screw to be driven by the ball screw to move linearly, and an abnormality detection device configured to detect a decrease in a preload applied to the ball screw, wherein the abnormality detection device includes a vibration sensor configured to measure vibration during operation of the ball screw, a calculation processing unit configured to acquire a vibration value of a vibration signal in a specific frequency band among vibration signals measured by the vibration sensor, and an abnormality detection unit configured to determine that a decrease in the preload has occurred in the ball screw when the vibration value is less than a threshold determined based on a vibration value in an initial stage of the operation of the ball screw or during a normal operation of the ball screw,
wherein the specific frequency band is less than 10 kHz and is set based on and includes a natural frequency of the ball screw,
wherein the ball screw comprises a ball screw shaft which is rotatably supported by rolling bodies of support bearings at axial ends of the ball screw shaft,
wherein the ball screw further comprises a nut, and
wherein the vibration sensor is an acceleration sensor attached to the at least one of the nut and the linear motion table.